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3 results on '"Kolade Oyekan"'

1. Dominant role of OH

Author

Maria Isabel, Mendoza Diaz, Andrea, Balocchi, Kolade, Oyekan, Kui, Tan, William G, Vandenberghe, Alain, Esteve, and Carole, Rossi

Abstract

Anatase/rutile constituting TiO

Published
2022

2. Dominant role of OH − and Ti 3+ defects on the electronic structure of TiO 2 thin films for water splitting

Author

Maria Isabel Mendoza Diaz, Andrea Balocchi, Kolade Oyekan, Kui Tan, William G. Vandenberghe, Alain Esteve, Carole Rossi, Équipe Nano-ingénierie et intégration des oxydes métalliques et de leurs interfaces (LAAS-NEO), Laboratoire d'analyse et d'architecture des systèmes (LAAS), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT), Nanomagnétisme (LPCNO), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-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)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Texas at Dallas [Richardson] (UT Dallas), and The authors acknowledge the financial support from theEuropean Research Council (H2020 Excellent Science)Researcher Award (Grant No. 832889 – PyroSafe) and from theFEDER/Occitanie Region (Grant H2VERT/HYPHY). This work wasalso supported by the LAAS-CNRS technology platform, amember of the Renatech network. The authors also thank Dr.Hicham Jabraoui from LAAS, University of Toulouse for his helpin doing GC experiments.

Subjects
Inorganic Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, [CHIM.INOR]Chemical Sciences/Inorganic chemistry
Abstract

International audience; Anatase/rutile consituted TiO2 thin films were prepared by sputter-deposition, and the influence of post-annealing step with a narrow window at 200 °C, revealed a gaining factor of 5 in the H2 production. An in-depth analysis of the photocatalytic performance revealed the dominant role of intermediate states, rather than the hetero-crystalline nature and mesoscale structure. Structural, chemical and optical investigations based on scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, UV-visible spectroscopy and photoluminescence supported by ab-initio calculation, correlated the H2 production with the dual presence of OH − and Ti 3+ defects in the form of titanium interstitial atoms. In addition, steady-state photoluminescence measurements determined the chemically active role of ethanol, commonly used as a hole scavenger, into inducing deep hole traps upon dissociation on the surface. These results give new directions for the design of TiO2 based photocatalytic systems for light-driven H2 production through water splitting, guided by a detailed description of defects present on the electronic structure and their chemical identification.

Published
2022

3. A First-Principles Study on the Electronic, Thermodynamic and Dielectric Properties of Monolayer Ca(OH)2 and Mg(OH)2

Author

William Vandenberghe, Kolade Oyekan, and Mehrdad Rostami Osanloo

Subjects
General Chemical Engineering, General Materials Science, 2D dielectric materials, 2D van der Waals dielectrics, 2D dielectrics with TMD channels, 2D heterostructures for FETs, (OH)2/HfS2 heterobilayer, Mg(OH)2/W2 heterobilayer
Abstract

We perform first-principles calculations to explore the electronic, thermodynamic and dielectric properties of two-dimensional (2D) layered, alkaline-earth hydroxides Ca(OH)2 and Mg(OH)2. We calculate the lattice parameters, exfoliation energies and phonon spectra of monolayers and also investigate the thermal properties of these monolayers, such as the Helmholtz free energy, heat capacity at constant volume and entropy as a function of temperature. We employ Density Functional Perturbation Theory (DFPT) to calculate the in-plane and out-of-plane static dielectric constant of the bulk and monolayer samples. We compute the bandgap and electron affinity values using the HSE06 functional and estimate the leakage current density of transistors with monolayer Ca(OH)2 and Mg(OH)2 as dielectrics when combined with HfS2 and WS2, respectively. Our results show that bilayer Mg(OH)2 (EOT∼0.60 nm) with a lower solubility in water offers higher out-of-plane dielectric constants and lower leakage currents than does bilayer Ca(OH)2 (EOT∼0.56 nm). Additionally, the out-of-plane dielectric constant, leakage current and EOT of Mg(OH)2 outperform bilayer h-BN. We verify the applicability of Anderson’s rule and conclude that bilayers of Ca(OH)2 and Mg(OH)2, respectively, paired with lattice-matched monolayer HfS2 and WS2, are effective structural combinations that could lead to the development of innovative multi-functional Field Effect Transistors (FETs).

Published
2022

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