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68 results on '"Hazar Guesmi"'

1. Single Metal Atoms Embedded in the Surface of Pt Nanocatalysts: The Effect of Temperature and Hydrogen Pressure

Author

Qing Wang, Beien Zhu, Frederik Tielens, and Hazar Guesmi

Subjects
single atom Pt nanocatalysts, multi-scaled reconstruction (MSR), stability, DFT, shape & surface composition prediction, reactive condition, Chemical technology, TP1-1185, Chemistry, QD1-999
Abstract

Embedding energetically stable single metal atoms in the surface of Pt nanocatalysts exposed to varied temperature (T) and hydrogen pressure (P) could open up new possibilities in selective and dynamical engineering of alloyed Pt catalysts, particularly interesting for hydrogenation reactions. In this work, an environmental segregation energy model is developed to predict the stability and the surface composition evolution of 24 Metal M-promoted Pt surfaces (with M: Cu, Ag, Au, Ni, Pd, Co, Rh and Ir) under varied T and P. Counterintuitive to expectations, the results show that the more reactive alloy component (i.e., the one forming the strongest chemical bond with the hydrogen) is not the one that segregates to the surface. Moreover, using DFT-based Multi-Scaled Reconstruction (MSR) method and by extrapolation of M-promoted Pt nanoparticles (NPs), the shape dynamics of M-Pt are investigated under the same ranges of T and P. The results show that under low hydrogen pressure and high temperature ranges, Ag and Au—single atoms (and Cu to a less extent) are energetically stable on the surface of truncated octahedral and/or cuboctahedral shaped NPs. This indicated that coinage single-atoms might be used to tune the catalytic properties of Pt surface under hydrogen media. In contrast, bulk stability within wide range of temperature and pressure is predicted for all other M-single atoms, which might act as bulk promoters. This work provides insightful guides and understandings of M-promoted Pt NPs by predicting both the evolution of the shape and the surface compositions under reaction gas condition.

Published
2022
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2. Regression Machine Learning Models Used to Predict DFT-Computed NMR Parameters of Zeolites

Author

Robin Gaumard, Dominik Dragún, Jesús N. Pedroza-Montero, Bruno Alonso, Hazar Guesmi, Irina Malkin Ondík, and Tzonka Mineva

Subjects
NMR, machine learning, zeolites, Electronic computers. Computer science, QA75.5-76.95
Abstract

Machine learning approaches can drastically decrease the computational time for the predictions of spectroscopic properties in materials, while preserving the quality of the computational approaches. We studied the performance of kernel-ridge regression (KRR) and gradient boosting regressor (GBR) models trained on the isotropic shielding values, computed with density-functional theory (DFT), in a series of different known zeolites containing out-of-frame metal cations or fluorine anion and organic structure-directing cations. The smooth overlap of atomic position descriptors were computed from the DFT-optimised Cartesian coordinates of each atoms in the zeolite crystal cells. The use of these descriptors as inputs in both machine learning regression methods led to the prediction of the DFT isotropic shielding values with mean errors within 0.6 ppm. The results showed that the GBR model scales better than the KRR model.

Published
2022
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3. Realistic Modelling of Dynamics at Nanostructured Interfaces Relevant to Heterogeneous Catalysis

Author

Kevin Rossi, Tzonka Mineva, Jean-Sebastien Filhol, Frederik Tielens, and Hazar Guesmi

Subjects
interfaces, nanochemistry, heterogeneous catalysis, theoretical chemistry, materials modelling, Chemical technology, TP1-1185, Chemistry, QD1-999
Abstract

The focus of this short review is directed towards investigations of the dynamics of nanostructured metallic heterogeneous catalysts and the evolution of interfaces during reaction—namely, the metal–gas, metal–liquid, and metal–support interfaces. Indeed, it is of considerable interest to know how a metal catalyst surface responds to gas or liquid adsorption under reaction conditions, and how its structure and catalytic properties evolve as a function of its interaction with the support. This short review aims to offer the reader a birds-eye view of state-of-the-art methods that enable more realistic simulation of dynamical phenomena at nanostructured interfaces by exploiting resource-efficient methods and/or the development of computational hardware and software.

Published
2022
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4. Interaction of Hydrogen with Au Modified by Pd and Rh in View of Electrochemical Applications

Author

Fernanda Juarez, German Soldano, Elizabeth Santos, Hazar Guesmi, Frederik Tielens, and Tzonka Mineva

Subjects
bimetallic alloy, hydrogen absorption, hydrogen adsorption, gold, DFT, Rh, Pd, dopants, Electronic computers. Computer science, QA75.5-76.95
Abstract

Hydrogen interaction with bimetallic Au(Pd) and Au(Rh) systems are studied with the density functional theory (DFT)-based periodic approach. Several bimetallic configurations with varying concentrations of Pd and Rh atoms in the under layer of a gold surface(111) were considered. The reactivity of the doped Au(111) toward hydrogen adsorption and absorption was related to the property modifications induced by the presence of metal dopants. DFT-computed quantities, such as the energy stability, the inter-atomic and inter-slab binding energies between gold and dopants, and the charge density were used to infer the similarities and differences between both Pd and Rh dopants in these model alloys. The hydrogen penetration into the surface is favored in the bimetallic slab configurations. The underlayer dopants affect the reactivity of the surface gold toward hydrogen adsorption in the systems with a dopant underlayer, covered by absorbed hydrogen up to a monolayer. This indicates a possibility to tune the gold surface properties of bimetallic electrodes by modulating the degree of hydrogen coverage of the inner dopant layer(s).

Published
2016
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6. Nanoalloy magnetic and optical properties, applications and structures: general discussion

Author

Christine M. Aikens, Damien Alloyeau, Vincenzo Amendola, Catherine Amiens, Pascal Andreazza, Joost M. Bakker, Francesca Baletto, Stephan Barcikowski, Noelia Barrabés, Michael Bowker, Fuyi Chen, Isaac T. Daniel, Wolfgang E. Ernst, Riccardo Ferrando, Piero Ferrari, Alessandro Fortunelli, Didier Grandjean, Hazar Guesmi, Graham J. Hutchings, Ewald Janssens, Robert M. Jones, Miguel Jose Yacaman, Christian Kuttner, Maria J. Lopez, Éric Marceau, Marcelo M. Mariscal, John McGrady, Christine Mottet, Jaysen Nelayah, Cameron J. Owen, Micha Polak, Jonathan Quinson, Cesare Roncaglia, Rolf Schäfer, Rasmus Svensson, Mona Treguer-Delapierre, and Yufei Zhang

Subjects
Physical and Theoretical Chemistry
Published
2023

10. Nanoalloy structures and catalysis part 2:general discussion

Author

Christine Aikens, Damien Alloyeau, Hakim Amara, Vincenzo Amendola, Catherine Amiens, Pascale Andreazza, Francesca Baletto, Stephan Barcikowski, Michael Bowker, Florent Calvo, Fuyi Chen, Emmanuel Cottancin, Wolfgang E. Ernst, Riccardo Farris, Riccardo Ferrando, Georg Daniel Förster, Alessandro Fortunelli, Alexis Front, Didier Grandjean, Hazar Guesmi, Graham J. Hutchings, Ewald Janssens, Miguel Jose Yacaman, Christian Kuttner, Éric Marceau, Marcelo M. Mariscal, Jette K. Mathiesen, John McGrady, Trang Nguyen, Pinkie Ntola, Cameron J. Owen, Charlie Paris, Micha Polak, Rasmus Svensson, Swathi Swaminathan, Mona Treguer-Delapierre, Jonathan Quinson, and Yufei Zhang

Subjects
Physical and Theoretical Chemistry
Published
2022

12. Nanoalloy structures and catalysis part 1: general discussion

Author

Damien Alloyeau, Vincenzo Amendola, Catherine Amiens, Pascal Andreazza, Joost M. Bakker, Francesca Baletto, Stephan Barcikowski, Noelia Barrabés, Michael Bowker, Fuyi Chen, Emmanuel Cottancin, Wolfgang E. Ernst, Riccardo Ferrando, Georg Daniel Förster, Alessandro Fortunelli, Didier Grandjean, Hazar Guesmi, Graham J. Hutchings, Ewald Janssens, Miguel Jose Yacaman, Christian Kuttner, Lebohang Macheli, Éric Marceau, Marcelo M. Mariscal, Jette K. Mathiesen, John McGrady, Christine Mottet, Diana Nelli, Pinkie Ntola, Cameron J. Owen, Micha Polak, Jonathan Quinson, Cesare Roncaglia, Leonid Rubinovich, Rolf Schäfer, Manoj Settem, Jeff Shield, Mzamo Shozi, Swathi Swaminathan, Štefan Vajda, and Hans-Christian Weissker

Subjects
Physical and Theoretical Chemistry
Published
2022

13. Nanostructured materials and heterogeneous catalysis : a succinct review regarding DeNox catalysis

Author

Dominique Bazin, Jelle Vekeman, Qing Wang, Xavier Deraet, Frank De Proft, Hazar Guesmi, Frederik Tielens, Chemistry, Faculty of Sciences and Bioengineering Sciences, and General Chemistry

Subjects
NO adsorption, NANOMETER-SCALE, General Chemical Engineering, SURFACES, IN-SITU, DeNox catalysis, DFT approach, NOBLE-METAL, Building and Construction, General Chemistry, CLOSE-PACKED TRANSITION, Metallic cluster, DENSITY-FUNCTIONAL THEORY, SYNCHROTRON-RADIATION, Chemistry, Nanoscience, BIMETALLIC CATALYSTS, RH(111) SURFACE, X-RAY, Electrical and Electronic Engineering
Abstract

In this contribution, we would like to underline the peculiar chemical properties of nanome-ter scale metallic particles. To attain this goal, we select the case of DeNox catalysis (NOx reduction to nitrogen molecule) for which such nanomaterials play a crucial role. Experimental data as well as re-cent theoretical calculation through density functional theory are used to assess the relationship be-tween the adsorption mode of NO and the behaviour of nanometre scale metallic particles. Resume. Les oxydes d'azote NOx issus des gaz d'echappement des moteurs Diesel participent a la de-terioration de l'environnement, la moitie des emissions de NO leur etant imputable. Le monoxyde d'azote provient essentiellement des reactions chimiques entre l'azote de l'air et l'oxygene qui s'eta-blissent a tres haute temperature. Le defi consiste a reduire cette emission qui doit etre selective en azote (eviter la formation de N2O ou de NO2). En ce qui concerne les catalyseurs mis en & OELIG;uvre, on en distingue trois groupes : les oxydes de metaux, les metaux nobles et les zeolites. A partir de donnees ex-perimentales obtenues sur l'adsorption du NO sur des agregats monometalliques, une relation entre les modes d'adsorption de cette molzcule (adsorption molzculaire/chimisorption) et la rzponse de l'agrzgat mztallique face a cette adsorption (croissance/dissociation) a ztz proposze. Les ztudes thzo-riques baszes sur la thzorie de la fonctionnelle de la densitz confortent cette relation. Cette contri-bution przsente l'ensemble de ces rzsultats expzrimentaux et thzoriques et tache de montrer l'aspect przdictif d'une telle relation.

Published
2022

14. Combined DRIFTS and DFT Study of CO Adsorption and Segregation Modes in Pt–Sn Nanoalloys

Author

Qing Wang, Frederic Meunier, Didier Tichit, Hazar Guesmi, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Laboratoire de Physique des Solides (LPS), and Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)

Subjects
In situ, Materials science, Infrared spectroscopy, Nanoparticle, [CHIM.CATA]Chemical Sciences/Catalysis, [CHIM.MATE]Chemical Sciences/Material chemistry, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, General Energy, Adsorption, [CHIM]Chemical Sciences, Physical chemistry, Density functional theory, Physical and Theoretical Chemistry, 0210 nano-technology
Abstract

International audience; This contribution aims at rationalizing the observations made by in situ IR spectroscopy during CO adsorption over 1.8 nm Pt-Sn nanoparticles by Density Functional Theory (DFT) calculations and describing the environment and electronic properties of surface Pt atoms modified by Sn. Pt surface enrichment upon CO exposure was observed by DRIFTS (diffuse reflectance FT-IR spectroscopy) and rationalized by the theoretical calculations, which also indicated that isolated Pt was favored over Pt pairing in a Sn-rich alloy. DFT frequency calculations allowing the fine assignment of vibrational CO spectra. The results show gradual

Published
2020

15. Parité et évaluation non-discriminatoire au CNRS

Author

Louise Jalowiecki-Duhamel, Hazar Guesmi, Jean-François Guillemoles, Kahn, Myrtil L., Paola Nava, François Ozanam, Elsje Alessandra Quadrelli, Arnaud Travert, Unité de Catalyse et Chimie du Solide - UMR 8181 (UCCS), Université d'Artois (UA)-Centrale Lille-Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut Photovoltaïque d’Ile-de-France (ITE) (IPVF), Laboratoire de chimie de coordination (LCC), Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences Moléculaires de Marseille (ISM2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique de la matière condensée (LPMC), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire catalyse et spectrochimie (LCS), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Comité Parité, Section 14, Comité National de la Recherche Scientifique CoNRS (mandature 2016-2021), Université d'Artois (UA)-Centrale Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Lille, Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Université de Caen Normandie (UNICAEN), Normandie Université (NU), Centrale Lille Institut (CLIL)-Université d'Artois (UA)-Centrale Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Lille, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
[SHS.GESTION]Humanities and Social Sciences/Business administration, JEL: J - Labor and Demographic Economics/J.J1 - Demographic Economics/J.J1.J16 - Economics of Gender • Non-labor Discrimination, [SHS.GENRE]Humanities and Social Sciences/Gender studies, JEL: L - Industrial Organization/L.L2 - Firm Objectives, Organization, and Behavior
Published
2021

16. Revealing the Dynamics of Functional Nanomaterials in Their Formation and Application Media with Liquid and Gas-phase TEM

Author

Christian Ricolleau, Jun Meng, Kinan Aliyah, Hakim Amara, Doru Constantin, Adrian Chmielewski, Guillaume Wang, Jaysen Nelayah, Hazar Guesmi, Abdelali Khelfa, Damien Alloyeau, Cyrille Hamon, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Materials science, Dynamics (mechanics), [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [CHIM.COOR]Chemical Sciences/Coordination chemistry, Nanotechnology, 02 engineering and technology, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 021001 nanoscience & nanotechnology, 0210 nano-technology, Instrumentation, ComputingMilieux_MISCELLANEOUS, Gas phase, Nanomaterials
Abstract

International audience

Published
2020

17. Support Effects Examined by a Comparative Theoretical Study of Au, Cu, and CuAu Nanoclusters on Rutile and Anatase Surfaces

Author

Mathilde Iachella, Adnene Dhouib, Francesco Di Renzo, Marwa Dhifallah, Hazar Guesmi, David Loffreda, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie - UMR5182 (LC), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Départemnt of Chemistry, University of Dammam, University of Dammam - Imam Abdulrahman Bin Faisal University, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Institut de Chimie du CNRS (INC)

Subjects
Anatase, Materials science, Energetics, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Nanoclusters, General Energy, Chemical physics, Rutile, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, 0210 nano-technology
Abstract

International audience; The role of the support anatase TiO2(100) and rutile TiO2(110) on the energetics, the shape and the charge transfer of deposited CuAu nanoclusters ( 1 nm) has been examined by using density functional theory calculations including Hubbard correction (DFT+U). Regular

Published
2019

18. Fe-Modified Pd as an Effective Multifunctional Electrocatalyst for Catalytic Oxygen Reduction and Glycerol Oxidation Reactions in Alkaline Media

Author

David Cornu, Nazym Tuleushova, Julien Cambedouzou, Mikhael Bechelany, Andrea Cassani, Qing Wang, Valerie Bonniol, Sophie Tingry, Hazar Guesmi, Yaovi Holade, Institut Européen des membranes (IEM), Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Materials science, Inorganic chemistry, Energy Engineering and Power Technology, 02 engineering and technology, [CHIM.MATE]Chemical Sciences/Material chemistry, [CHIM.CATA]Chemical Sciences/Catalysis, 010402 general chemistry, 021001 nanoscience & nanotechnology, Electrocatalyst, 7. Clean energy, 01 natural sciences, Redox, Oxygen reduction, 0104 chemical sciences, Catalysis, chemistry.chemical_compound, chemistry, Materials Chemistry, Electrochemistry, Glycerol, Chemical Engineering (miscellaneous), Electrical and Electronic Engineering, 0210 nano-technology, [CHIM.OTHE]Chemical Sciences/Other
Abstract

International audience; The development of high-performance catalytic nanomaterials is important to implement sustainable and electrochemical energy devices of alkaline fuel cells, metal–air batteries, and electrolyzers in the envisaged energy-transition scenarios. Synthesizing effective nanocatalysts as both anode materials for oxidation of glycerol (byproduct of the biodiesel industry) and cathode materials for the oxygen reduction reaction (ORR) is still a bottleneck. Herein, we report palladium-based nanomaterials whose physicochemical and electrochemical properties are tuned by the judicious choice of the support (rGO, Vulcan XC72R), the addition of a coelement (Fe), and the structure (alloy/core–shell). The bimetallic-based electrode shows a drastically enhanced electrocatalytic performance with a beneficial shifting of the onset potential, production of high currents, and good durability for both the ORR (kinetic current density jk = 2 mA cmPd–2 or 1 A mgPd–1) and glycerol oxidation (jp = 2.3 mA cmPd–2 or 1.11 A mgPd–1 at the peak), higher than those of commercial catalysts and existing literature values. The present results also provide new fundamental insights about the accurate measurement of the kinetic metrics of the ORR by employing a rotating-disk (-ring) electrode setup in alkaline electrolytes with metallic catalysts. Indeed, the anodic scanning of the electrode from a low potential to a higher one results in an ultrafast electrochemical kinetics with a positive shift of the half-wave potential of ΔE1/2,anodic/cathodic = 60 mV from the cathodic direction to the anodic one. The kinetic current density dramatically increases, jk,anodic = 19.0×, 6.9×, 3.4×, and 2.4× jk,cathodic at 950, 900, 870, and 850 mVRHE, respectively. The advantage of the synthesis methodology relies on the nonuse of organic molecules as capping agents and surfactants in order to produce bare (ligand-free) bimetallic PdFe electrocatalysts with a clean catalytic surface in a facile and straightforward way.

Published
2021

19. Mapping surface segregation of single-atom Pt dispersed in M surfaces (M = Cu, Ag, Au, Ni, Pd, Co, Rh and Ir) under hydrogen pressure at various temperatures

Author

Frederik Tielens, Beien Zhu, Hazar Guesmi, Didier Tichit, Qing Wang, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Institute of Applied Physics [Shanghai], Chinese Academy of Sciences [Beijing] (CAS), Vrije Universiteit Brussel (VUB), Chemistry, and General Chemistry

Subjects
Materials science, Hydrogen, Chemistry(all), General Physics and Astronomy, Nanoparticle, chemistry.chemical_element, 02 engineering and technology, Physics and Astronomy(all), 010402 general chemistry, 01 natural sciences, DFT, Structure stability, Catalysis, Metal, Atom, Reactivity (chemistry), Bimetallic strip, Single Atom alloys, Nano alloys, General Chemistry, Surfaces and Interfaces, [CHIM.CATA]Chemical Sciences/Catalysis, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, Surfaces, Coatings and Films, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, chemistry, visual_art, visual_art.visual_art_medium, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Physical chemistry, Density functional theory, 0210 nano-technology
Abstract

International audience; Single-atom alloys (SAAs) are emerging materials containing isolated metal atoms dispersed on host metal surfaces, exhibiting unique reactivity compared with the corresponding monometallic counterparts. However, the stability of the isolated atoms in the host metal has hardly been studied, although, metal segregation has been commonly observed in bimetallic nanoparticles under reaction conditions. In this work we focus on single-atom Pt anchored on various metallic support surfaces. Density Functional Theory (DFT) calculations coupled with environmental segregation energy analysis are performed to map the segregation trends of 22 different Pt-SAA surfaces under various hydrogen conditions. The results show the high stability of single-atom Pt in Ni, Co, Rh and Ir host metallic surfaces while no stability is predicted on Au and Ag surfaces. For Pd and Cu host supports, the single-atom Pt is found to be stable on specific surface facets and within definite temperature and pressure conditions. This work brings an important understanding of SAA systems through the prediction of of surface atomic ordering changes under operating conditions which related to the reactivity will ultimately allow the design of more efficient catalysts.

Published
2021

20. Revealing Size Dependent Structural Transitions in Supported Gold Nanoparticles in Hydrogen at Atmospheric Pressure

Author

Abdallah Nassereddine, David Loffreda, Hazar Guesmi, Jaysen Nelayah, Damien Alloyeau, Christian Ricolleau, Qing Wang, Laurent Delannoy, Catherine Louis, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie - UMR5182 (LC), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Réactivité de Surface (LRS), Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ANR-17-CE07-0031,TOTEM,Microscopie Électronique en Transmission Operando et Résolue en Temps pour la Catalyse Hétérogène(2017), Laboratoire Matériaux et Phénomènes Quantiques, Université de Paris, CNRS, Paris, F-75013 France, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), and Univ Lyon, ENS de Lyon, CNRS UMR 5182, Laboratoire de Chimie, Université Claude Bernard Lyon 1, Lyon F, 69342 France

Subjects
Materials science, Metal Nanoparticles, Nanoparticle, 02 engineering and technology, Crystal structure, Cubic crystal system, 010402 general chemistry, 01 natural sciences, Atomic units, [SPI.MAT]Engineering Sciences [physics]/Materials, Biomaterials, ETEM, Perfect crystal, General Materials Science, Particle Size, ComputingMilieux_MISCELLANEOUS, [CHIM.CATA]Chemical Sciences/Catalysis, General Chemistry, 021001 nanoscience & nanotechnology, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Atmospheric Pressure, Chemical physics, Colloidal gold, gold nanoparticles, hydrogen, size dependent restructuration, AIMD, Particle, Gold, Particle size, 0210 nano-technology, Biotechnology
Abstract

The enhancement of the catalytic activity of gold nanoparticles with their decreasing size is often attributed to the increasing proportion of low-coordinated surface sites. This correlation is based on the paradigmatic picture of working gold nanoparticles as perfect crystal forms having complete and static outer surface layers whatever their size. This picture is incomplete as catalysts can dynamically change their structure according to the reaction conditions and as such changes can be eventually size-dependent. In this work, using aberration-corrected environmental electron microscopy, size-dependent crystal structure and morphological evolution in gold nanoparticles exposed to hydrogen at atmospheric pressure, with loss of the face-centered cubic crystal structure of gold for particle size below 4 nm, are revealed for the first time. Theoretical calculations highlight the role of mobile gold atoms in the observed symmetry changes and particle reshaping in the critical size regime. An unprecedented stable surface molecular structure of hydrogenated gold decorating a highly distorted core is identified. By combining atomic scale in situ observations and modeling of nanoparticle structure under relevant reaction conditions, this work provides a fundamental understanding of the size-dependent reactivity of gold nanoparticles with a precise picture of their surface at working conditions.

Published
2021

22. Magic compositions in Pd-Au nanoalloys

Author

Hazar Guesmi, Front Alexis, Christine Mottet, Jérôme Creuze, Zhu Beien, Bernard Legrand, Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Service de recherches de métallurgie physique (SRMP), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), and Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Surface (mathematics), Icosahedral symmetry, Alloy, Monte Carlo method, 02 engineering and technology, engineering.material, 01 natural sciences, Biochemistry, Ab initio quantum chemistry methods, 0103 physical sciences, [CHIM]Chemical Sciences, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, 010306 general physics, ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], Canonical ensemble, Condensed matter physics, Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Core (optical fiber), Octahedron, Chemical physics, engineering, 0210 nano-technology
Abstract

International audience; We identified new magic compositions of Pd-Au nanolloys of simple symmetries according to the icosahedral and the cubic truncated octahedral structures. Chemically ordered structures as well as segregated ones are characterized using Monte Carlo simulations in semi-grand canonical ensemble and tightbinding semi-empirical potential fitted to ab initio calculations for the Pd-Au system. Ordering and surface (or core) segregation phenomena can be distinguished by their behavior as a function of the temperature: chemical ordering at surface or in the core disappears above a critical temperature (which is lower or equal to the bulk alloy order-disorder temperature), whereas surface/core segregation (core-shell structures) remains at high temperature, although the interfacial profile is less abrupt.

Published
2017

23. Does the S−H Bond Always Break after Adsorption of an Alkylthiol on Au(111)?

Author

Noelia B. Luque, Elizabeth Santos, Hazar Guesmi, Frederik Tielens, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Vrije Universiteit Amsterdam [Amsterdam] (VU), Laboratoire de Réactivité de Surface (LRS), Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut für Theoretische Chemie, Universität Ulm - Ulm University [Ulm, Allemagne], Instituto de Fisica Enrique Gaviola (IFEG), Universidad Nacional de Córdoba [Argentina], Spectroscopie, Modélisation, Interfaces pour L'Environnement et la Santé (LCMCP-SMiLES), Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Chemistry

Subjects
chemistry.chemical_classification, Reaction mechanism, Hydrogen bond, Organic Chemistry, Dithiol, 02 engineering and technology, General Chemistry, Activation energy, 010402 general chemistry, 021001 nanoscience & nanotechnology, Photochemistry, 01 natural sciences, Catalysis, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, chemistry.chemical_compound, Adsorption, chemistry, Chemisorption, Monolayer, 0210 nano-technology, Alkyl
Abstract

International audience; The reaction mechanism for the formation of alkyl thiol self-assembled monolayers (SAM) on Au(111) is still not clearly understood. Especially, the role of defects on the chemisorption process is an important goal to be addressed. In this work, different minimum energy reaction paths for R−SH dissociation of thiols (with long and short chains and dithiol species) adsorbed on gold adatom are calculated by using periodic density functional theory (DFT). Our results show a lower energy barrier for the RS−H bond dissociation when two thiols are adsorbed per adatom. In addition, in contrast with the formation of an adatom at the Au(111) which has been shown to depend on the alkyl chain length, the activation energy of the RS−H bond dissociation of thiols adsorbed on an adatom was shown to be independent of the alkyl chain length. The presented results and derived hypothesis support the model that thiols with long alkyl chain thiols mainly adsorb molecularly on Au(111), while for short alkyl chain thiols the S−H bond breaks. This result is explained by the fact that short-chain thiols have lower interchain interaction energies and are thus more mobile compared to the long alkyl chain thiols on the Au(111) surface. This feature enables the short chains to reach adequate geometries, driven by entropy, which could deform the Au(111) more drastically and probably pull Au atoms out from surface to form adatoms. With these results a new mechanism is proposed for the formation of alkyl chain thiols on Au(111).

Published
2016

24. Predicting the Activity of Nano-Transition-Metal DeNox Catalysts

Author

Ismail Can Oğuz, Dominique Bazin, Frederik Tielens, Hazar Guesmi, Chemistry, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and Vrije Universiteit Brussel (VUB)

Subjects
Materials science, 02 engineering and technology, Electronic structure, Activation energy, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Dissociation (chemistry), 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Catalysis, General Energy, Transition metal, Chemical physics, Nano, Cluster (physics), [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, 0210 nano-technology, Adsorption energy
Abstract

International audience; With the aim of rationalizing the reactivity of transition-metal (TM) clusters, the model reaction of NO dissociation on TM 13 clusters was investigated on a set of seven TMs. The adsorption energy and the activation energy for NOdissociation were calculated for each TM and discussed within the findings of Boudart in his article “model catalysts: reductionism for understanding”. In this work, we focused on selected TM cluster calculations instead of surface science slab-type calculations, which have been performed for some TMs and focus on the electronic structure to investigate and rationalize the TM reactivity. Besides the electronic and spin properties of the TM, we discuss the reactivity trends using also qualitatively the chemical hardness and softness. We conclude that the combination of these reactivity parameters will be necessary to fine- tune TM clusters’ reactivity with the scope of multimetallic TM clusters.

Published
2019

25. High performance of PtCu@TiO 2 nanocatalysts toward methanol oxidation reaction: from synthesis to molecular picture insight

Author

Hazar Guesmi, Jenia Georgieva, Marwa Dhifallah, Tzonka Mineva, N. Dimitrova, Tzvetanka Boiadjieva-Scherzer, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Materials science, Hydrogen, General Chemical Engineering, chemistry.chemical_element, Nanoparticle, 02 engineering and technology, General Chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 7. Clean energy, Nanomaterial-based catalyst, 0104 chemical sciences, Catalysis, chemistry.chemical_compound, chemistry, Chemical engineering, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Dehydrogenation, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Methanol, 0210 nano-technology, Platinum, Bimetallic strip, ComputingMilieux_MISCELLANEOUS
Abstract

The electrocatalytic production of hydrogen from methanol dehydrogenation successfully uses platinum catalysts. However, they are expensive and Pt has the tendency to be poisoned from the intermediate compounds, formed during the methanol oxidation reaction (MOR). For these two reasons, there has been active research for alternative bi- and tri-component Pt-based catalysts. Herein, PtCu nanoparticles deposited on titania were studied and proposed to be efficient MOR catalysts. The catalyst was prepared by photo-deposition of Cu on a high-surface-area TiO2 powder support, followed by a partial galvanic displacement of the Cu deposit by platinum. The morphology and structure of the catalyst were characterized by physicochemical methods. The PtCu@TiO2 electro-catalyst has higher intrinsic catalytic activity and comparable mass specific activity for MOR in comparison with a commercial Pt/C catalyst. The experimental analyses were complemented by density functional theory-based computations. The theoretical results revealed that the most energetically favorable Pt and Cu arrangement in the supported PtCu nanoparticles was core (Cu)–shell (Pt) and/or phase-separated. The inter-atomic interactions responsible for the bimetallic cluster stabilization on titania were highlighted from the computed electronic charge distribution.

Published
2019

26. Reshaping Dynamics of Gold Nanoparticles under H

Author

Adrian, Chmielewski, Jun, Meng, Beien, Zhu, Yi, Gao, Hazar, Guesmi, Hélène, Prunier, Damien, Alloyeau, Guillaume, Wang, Catherine, Louis, Laurent, Delannoy, Pavel, Afanasiev, Christian, Ricolleau, and Jaysen, Nelayah

Abstract

Despite intensive research efforts, the nature of the active sites for O

Published
2019

27. Stability of nanostructured silver-platinum alloys

Author

Maria Ziolek, Joanna Wisniewska, Frederik Tielens, Hazar Guesmi, Chemistry, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Faculty of Chemistry, Adam Mickiewicz University in Poznań (UAM), Laboratoire de Réactivité de Surface (LRS), and Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Silver, UV–Vis, Icosahedral symmetry, XRD, Alloy, Nanoparticle, chemistry.chemical_element, 02 engineering and technology, engineering.material, 010402 general chemistry, 01 natural sciences, DFT, Ultraviolet visible spectroscopy, Cluster (physics), Materials Chemistry, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Platinum, Mechanical Engineering, Metals and Alloys, UV-Vis, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Chemical engineering, chemistry, Mechanics of Materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Slab, engineering, Density functional theory, 0210 nano-technology, Stability
Abstract

International audience; The stability of Ag-Pt systems: 13-atoms icosahedral cluster model (Ag13-nPtn) and 54-atoms (111) surface slab model (45Ag9Pt) have been systematically investigated by using Density Functional Theory within the generalized gradient approximation (DFT-GGA). Experimentally tested resistance of AgPt alloy nanoparticles supported on silica to decay upon temperature treatment (423 K-573 K in N2 flow) have shown to correlate with theoretical results. The stability of the clusters as a function of AgPt composition decreases with increasing content of Pt. The general stability trend of the AgPt alloy was maintained, in theory and experiment, for the Ag/Pt molar ratio of 1.6-5.1. Two particularly stable Ag/Pt compositions were revealed: 1.6 and 0.4. It was also found that surface location of platinum is responsible for stabilization of the Ag-Pt nanostructured alloy.

Published
2019

28. Reshaping Dynamics of Gold Nanoparticles under H 2 and O 2 at Atmospheric Pressure

Author

Pavel Afanasiev, Adrian Chmielewski, Damien Alloyeau, Christian Ricolleau, Yi Gao, Jun Meng, Hélène Prunier, Guillaume Wang, Jaysen Nelayah, Catherine Louis, Laurent Delannoy, Beien Zhu, Hazar Guesmi, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Institute of Applied Physics [Shanghai], Chinese Academy of Sciences [Beijing] (CAS), University of Chinese Academy of Sciences [Beijing] (UCAS), Laboratoire de Réactivité de Surface (LRS), Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Northeast Agricultural University, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, General Physics and Astronomy, chemistry.chemical_element, 02 engineering and technology, H2 adsorption, 010402 general chemistry, Heterogeneous catalysis, O2 adsorption, 01 natural sciences, Oxygen, DFT, multiscale structure reconstruction model, Dissociation (chemistry), Adsorption, environmental transmission electron microscopy, General Materials Science, [CHIM.COOR]Chemical Sciences/Coordination chemistry, ComputingMilieux_MISCELLANEOUS, Molecular adsorption, Atmospheric pressure, General Engineering, [CHIM.MATE]Chemical Sciences/Material chemistry, [CHIM.CATA]Chemical Sciences/Catalysis, 021001 nanoscience & nanotechnology, Nanomaterial-based catalyst, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, chemistry, 13. Climate action, Colloidal gold, Chemical physics, gold nanoparticles, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

International audience; Despite intensive research efforts, the nature of the active sites for O2 and H2 adsorption/dissociation by supported gold nanoparticles (NPs) is still an unresolved issue in heterogeneous catalysis. This stems from the absence of a clear picture of the structural evolution of Au NPs at near reaction conditions, i.e., at high pressures and high temperatures. We hereby report real-space observations of the equilibrium shapes of titania-supported Au NPs under O2 and H2 at atmospheric pressure using gas transmission electron microscopy. In situ TEM observations show instantaneous changes in the equilibrium shape of Au NPs during cooling under O2 from 400 °C to room temperature. In comparison, no instant change in equilibrium shape is observed under a H2 environment. To interpret these experimental observations, the equilibrium shape of Au NPs under O2, atomic oxygen, and H2 is predicted using a multiscale structure reconstruction model. Excellent agreement between TEM observations and theoretical modeling of Au NPs under O2 provides strong evidence for the molecular adsorption of oxygen on the Au NPs below 120 °C on specific Au facets, which are identified in this work. In the case of H2, theoretical modeling predicts no interaction with gold atoms that explain their high morphological stability under this gas. This work provides atomic structural information for the fundamental understanding of the O2 and H2 adsorption properties of Au NPs under real working conditions and shows a way to identify the active sites of heterogeneous nanocatalysts under reaction conditions by monitoring the structure reconstruction.

Published
2019

29. Equilibrium Au–Pd(100) Surface Structures under CO Pressure: Energetic Stabilities and Phase Diagrams

Author

Ismail Can Oğuz, Hazar Guesmi, Tzonka Mineva, Jérôme Creuze, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), ICMMO, Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), and Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Work (thermodynamics), Materials science, Monte Carlo method, Thermodynamics, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Condensed Matter::Materials Science, General Energy, Adsorption, Phase (matter), Monolayer, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Molecule, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, Local-density approximation, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS, Phase diagram
Abstract

In this work first-principles density-functional-theory (DFT) calculations and Monte Carlo (MC) simulations are used to study the stability of the new surface phases formed under CO gas pressure on Au–Pd (100). The segregation isotherms reveal the apparition at θCO = 0.5 monolayer (ML) of two exotic ordered phase structures over the (100) facet, depending on the CO adsorption configurations. When CO is adsorbed on bridge sites, the ordered phase is formed by Pd-CO ensembles organized in linear chains, which are separated by Au atoms forming also linear chains free of adsorbed CO molecules. When CO is adsorbed on the on-top site, a checkerboard-like stable structure appears with CO adsorbed on Pd. The phase diagrams (temperature and CO pressure) of these large surface Pd ensembles for different bulk Pd concentrations [Pdbulk] are calculated. The effect of local density approximation (LDA) and generalized gradient corrected (GGA) exchange-correlation (XC) functionals are compared. The phase diagram of the c...

Published
2018

30. The effect of Pd ensemble structure on the O

Author

Ismail-Can, Oğuz, Tzonka, Mineva, and Hazar, Guesmi

Abstract

The reactivity of various Pd ensembles on the Au-Pd(100) alloy catalyst toward CO oxidation was investigated by using density functional theory (DFT). This study was prompted by the search for efficient catalysts operating at low temperature for the CO oxidation reaction that is of primary environmental importance. To this aim, we considered Pd modified Au(100) surfaces including Pd monomers, Pd dimers, second neighboring Pd atoms, and Pd chains in a comparative study of the minimum energy reaction pathways. The effect of dispersion interactions was included in the calculations of the O

Published
2018

31. Gold nanoparticles for catalysis,Les nanoparticules d'or pour la catalyse

Author

Hazar Guesmi, Catherine Louis, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Laboratoire de Réactivité de Surface (LRS), and Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [CHIM.COOR]Chemical Sciences/Coordination chemistry, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2018

32. Welcome to the world of nanometric gold!,Bienvenue dans le monde de l'or nanométrique !

Author

Hazar Guesmi, Olivier Pluchery, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Institut des Nanosciences de Paris (INSP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), and Guesmi, Hazar

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [CHIM.COOR]Chemical Sciences/Coordination chemistry, [CHIM.COOR] Chemical Sciences/Coordination chemistry, [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2018

33. Crossover among structural motifs in Pd–Au nanoalloys

Author

C. Mottet, Hazar Guesmi, Bernard Legrand, Jérôme Creuze, Beien Zhu, Laboratoire de Réactivité de Surface (LRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Université Montpellier 2 - Sciences et Techniques (UM2)-Université Montpellier 1 (UM1)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Institut d’Électronique, de Microélectronique et de Nanotechnologie (IEMN) - UMR 8520 (IEMN), Ecole Centrale de Lille-Institut supérieur de l'électronique et du numérique (ISEN)-Université de Valenciennes et du Hainaut-Cambrésis (UVHC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF), Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Service de recherches de métallurgie physique (SRMP), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
[PHYS]Physics [physics], Range (particle radiation), Chemistry, Monte Carlo method, Crossover, General Physics and Astronomy, Nanoparticle, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, Kinetic energy, 01 natural sciences, 0104 chemical sciences, Molecular dynamics, Crystallography, Octahedron, Chemical physics, Ab initio quantum chemistry methods, Physical and Theoretical Chemistry, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS
Abstract

The crossovers among the most abundant structural motifs (icosahedra, decahedra and truncated octahedra) of Pd-Au nanoalloys have been determined theoretically in a size range between 2 and 7 nm and for three compositions equivalent to Pd3Au, PdAu and PdAu3. The chemical ordering and segregation optimisation are performed via Monte Carlo simulations using semi-empirical tight-binding potentials fitted to ab initio calculations. The chemical configurations are then quenched via molecular dynamic simulations in order to compare their energy and characterize the equilibrium structures as a function of the cluster size. For the smaller sizes (of around 300 atoms and fewer) the structures are also optimized at the electronic level within ab initio calculations in order to validate the semi-empirical potential. The predictions of the crossover sizes for the nanoalloys cannot be simply extrapolated from the crossover of the pure nanoparticles but imply stress release phenomena related to the size misfit between the two metals. Indeed, alloying extends the range of stability of the icosahedron beyond that of the pure systems and the energy differences between decahedra and truncated octahedra become asymptotic, around the sizes of 5-6 nm. Nevertheless, such equilibrium results should be modulated regarding kinetic considerations or possible gas adsorption under experimental conditions.

Published
2015

34. Characterization of molybdenum monomeric oxide species supported on hydroxylated silica: a DFT study

Author

Hazar Guesmi, Frederik Tielens, Robert Gryboś, Jarosław Handzlik, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Laboratoire de Chimie de la Matière Condensée de Paris (site Paris VI) (LCMCP (site Paris VI)), Université Pierre et Marie Curie - Paris 6 (UPMC)-Collège de France (CdF (institution))-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and Chemistry

Subjects
Inorganic chemistry, Oxide, General Physics and Astronomy, chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, Grafting, 01 natural sciences, 0104 chemical sciences, Characterization (materials science), chemistry.chemical_compound, Silanol, Monomer, chemistry, Molybdenum, Physical chemistry, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS, Nest (protein structural motif), Vicinal
Abstract

Periodic DFT calculations have been performed on molybdenum(VI) oxide species supported on the hydroxylated amorphous silica surface. The Mo grafting site has been investigated systematically for the type of silanol (geminate, vicinal, isolated or in a nest) accessible on the surface, as well as its effect on H-bond formation and stabilization, with the Mo-oxide species. Different grafting geometries, combined with different degrees of hydration of the Mo species are investigated using atomistic thermodynamics. The most stable Mo(VI) oxide species resulting from these calculations are confronted with experiment. Finally, calculated vibrational frequencies confirm the experimental evidence of the dominant presence of di grafted di-oxo Mo(VI) species on silica up to 700 K.

Published
2014

35. Theoretical insights on the effect of reactive gas on the chemical ordering of gold-based alloys

Author

Hazar Guesmi, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Reactive gas, Materials science, Under gas, Alloy, Nanotechnology, 02 engineering and technology, engineering.material, 010402 general chemistry, 01 natural sciences, Alloy surface, Catalysis, Inorganic Chemistry, Metal, Metallic materials, General Materials Science, Reactivity, Metallurgy, Structure, [CHIM.MATE]Chemical Sciences/Material chemistry, [CHIM.CATA]Chemical Sciences/Catalysis, 021001 nanoscience & nanotechnology, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, visual_art, engineering, visual_art.visual_art_medium, Gold, 0210 nano-technology
Abstract

International audience; Alloy catalysts typically operate under high pressure and high-temperature conditions, and these reactive environments may substantially influence the alloy surface composition. Theoretical studies of catalytic properties are often investigated on model systems where no account is taken for the possibility that the surface composition can be modified after the gas exposure. This is a serious drawback that may prevent reliable description of the catalyst reactivity that mainly depends on the configuration of the surface. Nowadays, modelling the equilibrium structure of metal surfaces and alloys in a reactive environment is still a barely studied subject and remains an extremely challenging task. Recent methodological advances and their applications, mainly on gold-based alloy systems, are presented and discussed in this brief overview.

Published
2013

36. Interaction of hydrogen with au modified by Pd and Rh in view of electrochemical applications

Author

Frederik Tielens, Germán Soldano, Hazar Guesmi, Fernanda Juarez, Tzonka Mineva, Elizabeth Santos, Institut für Theoretische Chemie, Universität Ulm - Ulm University [Ulm, Allemagne], Instituto de Fisica Enrique Gaviola (IFEG), Universidad Nacional de Córdoba [Argentina], Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Spectroscopie, Modélisation, Interfaces pour L'Environnement et la Santé (SMiLES), Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC), General Chemistry, and Chemistry

Subjects
Materials science, General Computer Science, Hydrogen, Inorganic chemistry, chemistry.chemical_element, 02 engineering and technology, dopants, 010402 general chemistry, Electrochemistry, bimetallic alloy, 01 natural sciences, 7. Clean energy, DFT, lcsh:QA75.5-76.95, Theoretical Computer Science, Metal, HYDROGEN ADSORPTION, purl.org/becyt/ford/1 [https], Modelling and Simulation, Monolayer, purl.org/becyt/ford/1.4 [https], Pd, Rh, Bimetallic strip, hydrogen adsorption, Dopant, Otras Ciencias Químicas, Applied Mathematics, Doping, DOPANTS, Ciencias Químicas, hydrogen absorption, gold, 021001 nanoscience & nanotechnology, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, chemistry, 13. Climate action, Modeling and Simulation, visual_art, visual_art.visual_art_medium, BIMETALLIC ALLOY, Density functional theory, lcsh:Electronic computers. Computer science, 0210 nano-technology, CIENCIAS NATURALES Y EXACTAS, Computer Science(all)
Abstract

Hydrogen interaction with bimetallic Au(Pd) and Au(Rh) systems are studied with the density functional theory (DFT)-based periodic approach. Several bimetallic configurations with varying concentrations of Pd and Rh atoms in the under layer of a gold surface(111) were considered. The reactivity of the doped Au(111) toward hydrogen adsorption and absorption was related to the property modifications induced by the presence of metal dopants. DFT-computed quantities, such as the energy stability, the inter-atomic and inter-slab binding energies between gold and dopants, and the charge density were used to infer the similarities and differences between both Pd and Rh dopants in these model alloys. The hydrogen penetration into the surface is favored in the bimetallic slab configurations. The underlayer dopants affect the reactivity of the surface gold toward hydrogen adsorption in the systems with a dopant underlayer, covered by absorbed hydrogen up to a monolayer. This indicates a possibility to tune the gold surface properties of bimetallic electrodes by modulating the degree of hydrogen coverage of the inner dopant layer(s) Fil: Juarez, Maria Fernanda. Universidad de Ulm; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Soldano, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Universidad de Ulm; Alemania Fil: Santos, Elizabeth del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina Fil: Guesmi, Hazar. Institut Charles Gerhardt Montpellier; Francia Fil: Tielens, Frederik. Universite de Paris I Pantheon - Sorbonne; Francia Fil: Mineva, Tzonka. Institut Charles Gerhardt Montpellier; Francia

Published
2016

37. First-principles study of Au–Cu alloy surface changes induced by gas adsorption of CO, NO, or O2

Author

Sarah Aldulaijan, Marwa Dhifallah, Hazar Guesmi, Francesco Di Renzo, Adnene Dhouib, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Unité de recherche environnement, catalyse et analyse des procédés, Université de Gabès, Université de Gabès, Départemnt of Chemistry, University of Dammam, University of Dammam - Imam Abdulrahman Bin Faisal University, GENCI (Grand Equipement National de Calcul Intensif] [CCRT/CINES/IDRIS] allocation 2016 [Grant No. x2016087369], and Research Center, Scientific Research Deanship, University of Dammam, KSA, Award No. 2015208

Subjects
Materials science, Alloy, General Physics and Astronomy, chemistry.chemical_element, 02 engineering and technology, Electronic structure, engineering.material, 010402 general chemistry, 01 natural sciences, Metal, Adsorption, Ab initio quantum chemistry methods, Computational chemistry, Molecule, [CHIM]Chemical Sciences, Physical and Theoretical Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, [CHIM.CATA]Chemical Sciences/Catalysis, 021001 nanoscience & nanotechnology, Copper, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, chemistry, Chemical engineering, visual_art, engineering, visual_art.visual_art_medium, Density functional theory, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], 0210 nano-technology
Abstract

International audience; The surface composition of bimetallics can be strongly altered by adsorbing molecules where the metal with the strongest interaction with the adsorbate segregates into the surface. To investigate the effect of reactive gas on the surface composition of Au–Cu alloy, we examined by means of density functional theory to study the segregation behavior of copper in gold matrices. The adsorption mechanisms of CO, NO, and O2 gas molecules on gold, copper, and gold-copper low index (111), (100), and (110) surfaces were analyzed from energetic and electronic points of view. Our results show a strong segregation of Cu toward the (110) surface in the presence of all adsorbed molecules. Interestingly, the Cu segregation toward the (111) and (100) surface could occur only inthe presence of CO and at a lower extent in the presence of NO. The analysis of the electronic structure highlights the different binding characters of adsorbates inducing the Cu segregation.

Published
2016

38. Characterization of tungsten monomeric oxide species supported on hydroxylated silica; a DFT study

Author

Robert Grybos, Jarosław Handzlik, Hazar Guesmi, Frederik Tielens, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Jerzy Haber Institute of Catalysis and Surface Chemistry, Polska Akademia Nauk = Polish Academy of Sciences (PAN), Faculty of Chemical Engineering and Technology, Cracow University of Technology, Spectroscopie, Modélisation, Interfaces pour L'Environnement et la Santé (SMiLES), Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC), Chemistry, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
General Chemical Engineering, Inorganic chemistry, Oxide, chemistry.chemical_element, 02 engineering and technology, General Chemistry, Tungsten, equipment and supplies, 010402 general chemistry, 021001 nanoscience & nanotechnology, Grafting, 01 natural sciences, Oxygen, 0104 chemical sciences, Amorphous solid, chemistry.chemical_compound, Silanol, Monomer, chemistry, Group (periodic table), [CHIM]Chemical Sciences, 0210 nano-technology
Abstract

International audience; A DFT based characterization of tungsten oxide supported on amorphous hydroxylated silica is presented. The different molecular organizations are investigated on the surface topology and tungsten oxygen coordination. The presence of mono- and di-grafted species is discussed and rationalized, using an atomistic thermodynamic approach. The presence of W[double bond, length as m-dash]O groups are preferred over W–OH groups and the grafting coordination is dominated by the degree of hydration of the silica surface. At room temperature di-oxo digrafted and mono-oxo-tetragrafted species are in competition regulated by the ambient degree of hydration which also affects the silanol density of the silica support. A comparison between tungsten and the other group VI elements confirms a greater chemical difference with Cr than with Mo.

Published
2016

39. CO Adsorption-Induced Surface Segregation and Formation of Pd Chains on AuPd(100) Alloy: Density Functional Theory Based Ising Model and Monte Carlo Simulations

Author

Jérôme Creuze, Hazar Guesmi, Beien Zhu, Bernard Legrand, C. Mottet, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Service de recherches de métallurgie physique (SRMP), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)

Subjects
Alloy, Monte Carlo method, Thermodynamics, 02 engineering and technology, engineering.material, 010402 general chemistry, 01 natural sciences, Adsorption, Molecule, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, Saturation (magnetic), ComputingMilieux_MISCELLANEOUS, Canonical ensemble, Condensed matter physics, Chemistry, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, General Energy, engineering, Ising model, Density functional theory, 0210 nano-technology
Abstract

In order to study how adsorption of CO molecules changes the surface composition of AuPd alloys, we develop a theoretical methodology which is able to take this effect into account. An Ising model based on density functional theory calculations is derived to define interatomic potentials that describe metal–metal, metal–CO, and CO–CO interactions. Then, through the use of Monte Carlo simulations within the semi-grand canonical ensemble, the effect of adsorption-induced segregation for the AuPd(100) surface is well-reproduced for different temperatures and CO pressures. Segregation isotherms identify a Pd surface enrichment for low CO pressures, and CO surface saturation is reached at an intermediate coverage of θ = 0.5 ML. Furthermore, Pd chains induced by an ordering of adsorbed CO molecules appear at low temperature and intermediate CO pressures. These chains are the result of a competitive effect between CO–CO repulsions and metal–CO interactions.

Published
2016

40. A combined experimental and theoretical study of the simultaneous occupation of SIa and SI′ sites in fully dehydrated K–LSX

Author

Habiba Nouali, Jean-Louis Paillaud, Hazar Guesmi, and Pascale Massiani

Subjects
Hexagonal prism, Chemistry, Rietveld refinement, 02 engineering and technology, General Chemistry, Faujasite, engineering.material, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, 0104 chemical sciences, Ion, Crystallography, Mechanics of Materials, engineering, General Materials Science, Density functional theory, 0210 nano-technology, Zeolite, Single crystal, Powder diffraction
Abstract

In the case of fully potassium exchanged X and LSX faujasites, it was reported from a single crystal X-ray study on zeolite X and preliminary powder X-ray diffraction (PXRD) study on zeolite LSX that K+ ions can be found concomitantly in both sites I and I′ with partial or full occupancy of site I inside the hexagonal prism depending on the Si/Al ratio of the matrix. Such experimental observation of a simultaneous occupancy of adjacent SI and SI′ sites in fully exchanged and dehydrated K–LSX was next supported by a theoretical study using the Mott-Littleton approach and a set of formally charged parameters to describe the zeolite. Here, the more appropriate Density Functional Theory (DFT) has been applied to identify the sitting, coordination, environment and properties of the exchanged cations, DFT being indeed recognized as a very successful tool to study the interactions of cations with their environment in zeolites. This approach has been associated to new experimental knowledge gained from argon adsorption measurements and a reinvestigation of the K–LSX structure from Rietveld refinement, to provide an accurate description of not solely the most favorable K+ locations inside the hexagonal prisms of fully exchanged K–LSX, but also of the bonding scheme of all exchanged K+ ions with respect both to each other and to the zeolitic framework. To understand further the origin of the particular sitting of K+ ions in faujasite, calculations have been also performed on Na–LSX, taken as a reference system. Thus, a critical K+–K+ distance was determined from which the charges of potassium cations become equivalent and therefore induces the stability of the system.

Published
2012

41. Investigation of finite-size effects in chemical bonding of AuPd nanoalloys

Author

Beien Zhu, Ismail Can Oğuz, Hazar Guesmi, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Chemistry, Coordination number, General Physics and Astronomy, Nanoclusters, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Chemical bond, Ab initio quantum chemistry methods, Chemical physics, Computational chemistry, Molecular vibration, Atom, Molecule, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, Bimetallic strip, ComputingMilieux_MISCELLANEOUS
Abstract

In this paper, the size-dependent changes in energetic, vibrational, and electronic properties of C-O gas molecule interacting with surface Pd atom of a variety of AuPd nanoalloy structures are investigated by means of first principles calculations. The variation in C-O adsorption energies, C-O vibration frequencies (nu(C-O)), and Pd d-bond centers (epsilon(d)) on a series of non-supported Aun-1-Pd-1 nanoparticles (with n varying from 13 to 147) and on two semi-finite surfaces are inspected with cluster size. We demonstrate for the first time that, with small AuPd bimetallic three-dimensional clusters as TOh(38), one can reach cluster size convergence even for such a sensitive observable as the adsorption energy on a metal surface. Indeed, the results show that the adsorbate-induced perturbation is extremely local and it only concerns the isolated Pd interacting with the reactive gas molecule. Except for 13 atom clusters, in which molecular behaviour is predominant, no finite-size effects are observed for surface Pd atom substituted in AuPd free nanoclusters above 38 atoms. (C) 2015 AIP Publishing LLC.

Published
2015

42. Surface segregation in AuPd alloys: Ab initio analysis of the driving forces

Author

Hazar Guesmi, Beien Zhu, Christine Mottet, Jérôme Creuze, Bernard Legrand, Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Réactivité de Surface (LRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Service de recherches de métallurgie physique (SRMP), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)

Subjects
Surface (mathematics), Enthalpy, Ab initio, Thermodynamics, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Ab initio quantum chemistry methods, Computational chemistry, Materials Chemistry, [CHIM]Chemical Sciences, Coupling, Chemistry, Segregation, Surfaces and Interfaces, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Combined approach, 0104 chemical sciences, Surfaces, Coatings and Films, Ising model, Gold, Ab initio calculations, 0210 nano-technology, Size difference, Palladium
Abstract

International audience; In order to determine the energetic driving forces for surface segregation in AuPd alloys, we use a combined approach coupling ab initio calculations and an analysis via an effective Ising model. Previously, this approach has been used successfully in the framework of N-body interatomic potentials to study the surface segregation in both semi-infinite alloys and nanoparticles, allowing one to determine the relative contributions of the different elementary driving forces. Here, we go beyond the use of N-body interatomic potentials by using ab initio calculations to evaluate the segregation enthalpy and the effective pair interactions, the contribution due to the size difference between the constituants being still obtained by N-body interatomic potentials. We show that the decomposition of the segregation enthalpy into its different elementary contributions is still valid at this level of description. This allows us to analyze the segregation driving forces in the two infinite dilute limits of the Au–Pd system, for both (100) and (111) surfaces. Finally, between the two infinite dilute limits, we find that our results are consistent with existing experimental data.

Published
2015

43. On the relationship between the basicity of a surface and its ability to catalyze transesterification in liquid and gas phases: the case of MgO

Author

Guillaume Laugel, Damien Cornu, Hazar Guesmi, Jean-Marc Krafft, Hélène Lauron-Pernot, Laboratoire de Réactivité de Surface (LRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Models, Molecular, Reaction mechanism, Surface Properties, Inorganic chemistry, Ethyl acetate, Carbonates, General Physics and Astronomy, Infrared spectroscopy, 02 engineering and technology, Acetates, Alkenes, 010402 general chemistry, Hydroxylation, 01 natural sciences, Catalysis, chemistry.chemical_compound, Adsorption, Isomerism, Hydroxides, [CHIM]Chemical Sciences, Physical and Theoretical Chemistry, [PHYS]Physics [physics], Esterification, Chemistry, Methanol, Transesterification, Carbon Dioxide, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Gases, 0210 nano-technology, Magnesium Oxide, Isomerization
Abstract

International audience; Gas or liquid phase transesterification reactions are used in the field of biomass valorization to transform some platform molecules into valuable products. Basic heterogeneous catalysts are often claimed for these applications but the role of basicity in the reaction mechanism depending on the operating conditions is still under debate. In order to compare the catalyst properties necessary to perform a transesterification reaction both in liquid and gas phases, ethyl acetate and methanol, which can be easily processed both in these two phases, were chosen as reactants. The catalyst studied is MgO, known for its basic properties and its ability to perform the reaction. By means of appropriate thermal treatments, different kinds of MgO surfaces, with different coverages of natural adsorbates (carbonates and hydroxyls groups), can be prepared and characterized by means of CO2 adsorption followed by IR spectroscopy and hept-1-ene isomerization model reaction. New results on the basicity of the natural MgO surface (covered by carbonate and hydroxyl groups) are first given and discussed. The catalytic behavior in the transesterification reaction is then determined as a function of the adsorbate coverage. It is shown that the transesterification activity in the liquid phase is directly correlated with the kinetic basicity of the surface in agreement with the mechanism already proposed in the literature. On the reverse, no direct correlation with the basicity of the surface was established with the transesterification activity in the gas phase. A very high activity, in the gas phase, was observed and discussed for the natural surface pre-treated at 623 K. Preliminary DFT modeling of ester adsorption and methanol adsorption capacity determination were performed to investigate plausible reaction routes.

Published
2015

44. Density Functional Study of Pd13 Magnetic Isomers in Gas-Phase and on (100)-TiO2 Anatase

Author

Oussama Gantassi, Hazar Guesmi, Chemseddine Menakbi, Tzonka Mineva, Najoua Derbel, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Anatase, Materials science, Spin states, Icosahedral symmetry, Molecular physics, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, General Energy, Cluster (physics), Particle, Periodic boundary conditions, Density functional theory, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, Atomic physics, Ground state, ComputingMilieux_MISCELLANEOUS
Abstract

A systematic study on the magnetic property variations of Pd13 particles as a function of particle sizes and structures, and of Pd13 interactions with the (100) TiO2 anatase surface, was carried out with standard density functional theory (DFT) based method with periodic boundary conditions. The biplanar Pd13 structure with the spin state quintet is obtained to be the ground state in the gas-phase and on the anatase surface, being more stable than the compact icosahedral configuration by 0.067 and 0.865 eV, respectively. The preferred particle nucleation on the anatase surface is that with the largest possible contacts between Pd13 and the oxide surface oxygens. The supported Pd13 particles are better stabilized by 0.3 eV compared to the isolated ones. The profiles of the relative energies as a function of the spin state reveal that the Pd13 magnetic isomers, belonging to the same cluster topology, become closer in energy and nearly degenerate on the anatase surface compared to their gas-phase counterpart...

Published
2015

45. Catalytic properties of Au electrodes modified by an underlayer of Pd

Author

Germán Soldano, Elizabeth Santos, Hazar Guesmi, M.F. Juarez, Frederik Tielens, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Instituto de Fisica Enrique Gaviola (IFEG), Universidad Nacional de Córdoba [Argentina], Institut für Theoretische Chemie, Universität Ulm - Ulm University [Ulm, Allemagne], Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)

Subjects
Hydrogen, Inorganic chemistry, ELECTRONIC STRUCTURE, chemistry.chemical_element, Electrocatalyst, 7. Clean energy, Catalysis, Monolayer, Materials Chemistry, Reactivity (chemistry), [CHIM.COOR]Chemical Sciences/Coordination chemistry, Surface layer, DENSITY FUNCTIONAL THEORY, Bimetallic strip, GOLD-PALLADIUM ALLOYS, Otras Ciencias Químicas, Ciencias Químicas, Surfaces and Interfaces, Condensed Matter Physics, Surfaces, Coatings and Films, HYDROGEN ADSORPTION-ABSORPTION-STORAGE, chemistry, Chemical engineering, ELECTROCATALYSIS, Density functional theory, CIENCIAS NATURALES Y EXACTAS
Abstract

Bimetallic catalysts have manifold technological applications; their reactivity can greatly exceed that of the original single metals. In this work, we investigate an ideal model-system consisting of a complete monolayer of Pd underneath the surface of Au(111). First, we investigate the stability of this system, and then its interaction with hydrogen. We analyze in detail the energetics and the electronic interactions for the Volmer step of the hydrogen evolution reaction (HER), and the further absorption below the surface layer of gold. We combine Density Functional Theory based on computational techniques with the theory of electrocatalysis. Fil: Juarez, Maria Fernanda. Universitat Ulm; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Soldano, Germán. Universitat Ulm; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Guesmi, Hazar. Institut Charles Gerhardt Montpellier; Francia Fil: Tielens, Frederik. Universite Pierre et Marie Curie; Francia Fil: Santos, Elizabeth del Carmen. Universitat Ulm; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina

Published
2015

46. Density functional theory study of CO-induced segregation in gold-based alloys

Author

Myriam Sansa, Adnene Dhouib, Hazar Guesmi, Université de Carthage - University of Carthage, Université de Tunis El Manar (UTM), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), European Project: 909407,EC:FP7:PEOPLE,FP7-PEOPLE-2009-IIF,NANOALLOY(2013), and Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, SURFACE SEGREGATION, INITIO MOLECULAR-DYNAMICS, General Physics and Astronomy, CATALYSTS, DFT, transition metals, ACTIVATION, Adsorption, HYDROGEN-PEROXIDE, Transition metal, Impurity, NANOPARTICLES, Physical and Theoretical Chemistry, Facet, Chemical composition, Gold alloys, reactive gas, SPECTROSCOPY, PALLADIUM, Metallurgy, gold-based alloys, [CHIM.MATE]Chemical Sciences/Material chemistry, Crystallography, AU, PD, CO adsorption, Density functional theory
Abstract

International audience; This paper reports a systematic study of the effect of CO gas on the chemical composition at the surface of gold-based alloys. Using DFT periodic calculations in presence of adsorbed CO the segregation behavior of group 9-10-11 transition metals (Ag, Cu, Pt, Pd, Ni, Ir, Rh, Co) substituted in semi-infinite gold surfaces is investigated. Although, CO is found to be more strongly adsorbed on (100) than on the (111) surface, the segregation of M impurities is found to be more pronounced on the (111) surface. The results reveal two competitive effects: the effect of M on CO and the effect of CO on M. Thus, on one hand, if M exists on the (100) gold facet, CO would be strongly adsorbed on it. But if M is initially located in the bulk, it would segregate to the (111) facet instead of the (100) in order to bind to CO.

Published
2014

47. How Surface Hydroxyls Enhance MgO Reactivity in Basic Catalysis: The Case of Methylbutynol Conversion

Author

Françoise Delbecq, Hazar Guesmi, Hugo Petitjean, Guylène Costentin, Philippe Sautet, Hélène Lauron-Pernot, David Loffreda, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Laboratoire de Réactivité de Surface (LRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie - UMR5182 (LC), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Institut de Chimie du CNRS (INC), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
MBOH, water, MgO, Alcohol, 02 engineering and technology, Activation energy, 010402 general chemistry, Photochemistry, 01 natural sciences, Dissociative adsorption, DFT, Catalysis, basic catalyst, Chemical kinetics, chemistry.chemical_compound, Molecule, Reactivity (chemistry), alcohol, General Chemistry, 021001 nanoscience & nanotechnology, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, chemistry, hydroxyl, 0210 nano-technology
Abstract

International audience; This combined experimental and theoretical study aims at understanding why surface hydroxyl groups may enhance catalytic reactivity of MgO surfaces in basic catalysis, whereas hydroxyls are weakly deprotonating groups. We investigated that reactivity enhancement in the catalytic conversion of 2-methyl-but-3-yn-2-ol (MBOH). Reaction kinetics was experimentally determined on partially hydroxylated MgO: active sites were saturated with the reactant and catalyzed its conversion with an activation energy of 85 kJ·mol–1. Reaction pathways were calculated over fully hydroxylated, partially hydroxylated, and dehydroxylated MgO surfaces by means of first-principles simulations. To highlight the effect of reactant coverage, we also calculated the reaction pathway on MgO precovered with MBOH molecules. The results show that the surface OH groups generated by dissociative adsorption of water induce a lowering in the activation energy barriers when they keep a bare Mg2+-O2– pair available in the vicinity for MBOH to adsorb and react. Interestingly, OH groups do not directly interact with MBOH converting on the surface, but they modify the basic properties of the vicinal bare Mg2+-O2– pair on which MBOH adsorbs and converts. A similar effect is predicted when MBOH converts on a bare Mg2+-O2– pair in the vicinity of a second adsorbed MBOH molecule. The beneficial effect of coadsorbates on the reactivity of active sites is analyzed by means of a thermodynamic model and an electronic structure analysis.

Published
2014

48. Influence of natural adsorbates of magnesium oxide on its reactivity in basic catalysis

Author

Guylène Costentin, Hazar Guesmi, Hugo Petitjean, Hélène Lauron-Pernot, Jean-Marc Krafft, Damien Cornu, Laboratoire de Réactivité de Surface (LRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Models, Molecular, Surface Properties, Inorganic chemistry, Carbonates, Molecular Conformation, General Physics and Astronomy, chemistry.chemical_element, Alkenes, 010402 general chemistry, Heterogeneous catalysis, Hydroxylation, 01 natural sciences, Catalysis, chemistry.chemical_compound, Adsorption, Hydroxides, Reactivity (chemistry), Physical and Theoretical Chemistry, chemistry.chemical_classification, 010405 organic chemistry, Chemistry, Magnesium, Alkene, [CHIM.CATA]Chemical Sciences/Catalysis, Carbon Dioxide, Hydrogen-Ion Concentration, 0104 chemical sciences, Alcohols, Magnesium Oxide, Isomerization
Abstract

International audience; Solid materials possessing basic properties are naturally covered by carbonates and hydroxyl groups. Those natural adsorbates modify their chemical reactivity. This article aims to specifically evidence the role of surface carbonates and hydroxyls in basic heterogeneous catalysis on MgO. It compares the catalytic behaviors of hydroxylated or carbonated MgO surfaces for two types of reactions: one alkene isomerization and one alcohol conversion (hept-1-ene isomerization and 2-methyl-3-butyn-2-ol conversion). Catalysis experiments showed that carbon dioxide adsorption poisons the catalyst surface and the DRIFT-DFT combination showed that the nature of active sites in the two reactions differs. On the reverse, partial hydroxylation of the surface enhances activity for both reactions. Interestingly hept-1-ene isomerization gives a volcano curve for the conversion as a function of hydroxyl coverage. Calculations of the electronic structure of magnesium oxide surfaces show that neither Lewis basicity nor Brønsted basicity of the surface defects (steps for example) are enhanced by hydroxylation. Meanwhile CO2 adsorption followed by IR spectroscopy shows that (110) and (111) unstable planes are strongly basic and are stabilized by partial surface hydroxylation. These results could explain the volcano curve obtained for the evolution of alkene isomerisation as a function of hydroxyl coverage.

Published
2013

49. Evidence of Pd segregation and stabilization at edges of AuPd nano-clusters in the presence of CO: A combined DFT and DRIFTS study

Author

Bernard Legrand, Jérôme Creuze, Laurent Delannoy, Gode Thrimurthulu, Beien Zhu, Christine Mottet, Hazar Guesmi, Catherine Louis, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Réactivité de Surface (LRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Institut d’Électronique, de Microélectronique et de Nanotechnologie (IEMN) - UMR 8520 (IEMN), Ecole Centrale de Lille-Institut supérieur de l'électronique et du numérique (ISEN)-Université de Valenciennes et du Hainaut-Cambrésis (UVHC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF), HPC resources of [CCRT/CINES/IDRIS] under the allocation 2012 [x2012086395] made by GENCI, Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Service de recherches de métallurgie physique (SRMP), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Université Montpellier 2 - Sciences et Techniques (UM2)-Université Montpellier 1 (UM1)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM), and Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)

Subjects
AuPd, Diffuse reflectance infrared fourier transform, Alloy, Analytical chemistry, Nanoparticle, 02 engineering and technology, Electronic structure, engineering.material, 010402 general chemistry, 01 natural sciences, DFT, Catalysis, Nanoalloy, Adsorption, Physical and Theoretical Chemistry, Bimetallic strip, Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, [CHIM.CATA]Chemical Sciences/Catalysis, 021001 nanoscience & nanotechnology, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, DRIFTS, engineering, Physical chemistry, CO adsorption, Density functional theory, 0210 nano-technology
Abstract

International audience; Combined Density Functional Theory (DFT) calculations and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) were performed to study the distribution of Pd atoms in bimetallic AuPd nanoparticles in the presence of adsorbed CO. Compared to vacuum condition, the results showed evidence of Pd surface enrichment where both Pd monomers and Pd dimers could exist. The energetic stability calculated for several alloy configurations evidenced the preference of Pd to occupy under-coordinated edge sites in the presence of CO gas. Moreover, the calculation of the vibrational frequencies of adsorbed CO for the first time allowed the fine assignment of the complex experimental DRIFTS bands of CO interacting with the bimetallic nanoparticles and their evolution with time exposure. Electronic structure analysis shows preponderant π-back-donation from under-coordinated Pd to CO inducing strong bonding on edge sites.

Published
2013

50. How does CO capture process on microporous NaY zeolites? A FTIR and DFT combined study

Author

O. Cairon, Hazar Guesmi, Laboratoire de Chimie Structurale, Université de Pau et des Pays de l'Adour (UPPA), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Laboratoire de Réactivité de Surface (LRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Chemistry, Stereochemistry, General Physics and Astronomy, Infrared spectroscopy, 02 engineering and technology, Microporous material, [CHIM.CATA]Chemical Sciences/Catalysis, Faujasite, engineering.material, 010402 general chemistry, 021001 nanoscience & nanotechnology, Molecular sieve, 01 natural sciences, 0104 chemical sciences, Adsorption, engineering, Molecule, Physical chemistry, Gas separation, Physical and Theoretical Chemistry, 0210 nano-technology, Zeolite
Abstract

International audience; Reliable experimental IR and theoretical approaches, both investigating CO adsorption on NaY faujasites, are supporting that CO capture occurs through the completion of the vacant coordination of Na+ cations located in the accessible SII sites. As a result, carbonyl adsorbed species are formed by the capture of one, two or three CO molecules and are experimentally discernable by their respective IR positions that are down-shifted by an average 11-12 cm−1 value for each captured CO molecule. DFT analysis is proposed for comparison and reproduces well the observed experimental shift of the νCO positions of the different polycarbonyls of interest. In addition, the effect of Si or Al composition surrounding the SII Na+ cation is investigated and results suggest that polycarbonyls that are formed might be in connection with the acidic strength of the cationic sites. This combined study completes and improves the understanding of the complex issue of CO adsorption at 80 K widely used as a model to explain how physical adsorption takes place in NaY faujasites working as an efficient industrial adsorbent in gas separation or gas purification processes.

Published
2012

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