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The oxygen evolution reaction (OER) plays a crucial role in (photo)electrochemical devices that use renewable energy to produce synthetic fuels. Recent measurements on semiconducting oxides have found a power law dependence of the OER rate on surface hole density, suggesting a multihole mechanism. In this study, using transient photocurrent measurements, density functional theory simulations and microkinetic modelling, we have uncovered the origin of this behaviour in haematite. We show here that the OER rate has a third-order dependence on the surface hole density. We propose a mechanism wherein the reaction proceeds by accumulating oxidizing equivalents through a sequence of one-electron oxidations of surface hydroxy groups. The key O–O bond formation step occurs by the dissociative chemisorption of a hydroxide ion involving three oxyl sites. At variance with the case of metallic oxides, the activation energy of this step is weakly dependent on the surface hole coverage, leading to the observed power law.

Single-atom catalysts represent an essential and ever-growing family of heterogeneous catalysts. Recent studies indicate that besides the valuable catalytic properties provided by single-atom active sites, the presence of single-atom sites on the catalyst substrates may significantly influence the population of supported metal nanoparticles coexisting with metal single atoms. Treatment of ceria-based single-atom catalysts in oxidizing or reducing atmospheres was proven to provide precise experimental control of the size of the supported Pt nanoparticles, and, correspondingly, control of catalyst activity and stability. Based on dedicated surface science experiments, ab-initio calculations and kinetic Monte-Carlo simulations we demonstrate that the morphology of Pt nanoparticle population on ceria surface is a result of a competition for Pt atoms between Pt single-atom sites and Pt nanoparticles. In oxidizing atmosphere, Pt single-atom sites provide strong bonding to single Pt atoms and Pt nanoparticles shrink. In reducing atmosphere, Pt single atom sites are depopulated and Pt nanoparticles grow. We formulate a generic model of Pt redispersion and coarsening on ceria substrates. Our model provides a unified atomic-level explanation for a variety of metal nanoparticle dynamic processes observed in single-atom catalysts under stationary or alternating oxidizing/reducing atmospheres, and allows to classify the conditions when nanoparticle ensembles on single-atom catalysts substrates can be stabilized against Ostwald ripening.

CuFeO2 is a p-type semiconductor that has been recently identified as a promising photocathode material for photoelectrochemical water splitting. CuFeO2 can absorb solar light and promote the hydro...

Aims To highlight (a) trends common to all nurses on priorities attributed to interventions, and (b) whether there are profiles of nurses working in the same context who prioritize interventions in a similar way. Background The underlying prioritization of interventions leading to unfinished nursing care has been minimally investigated. Methods A 2017 pilot Q methodology study. Full-time nurses, with at least 6 months of experience in a surgical unit, were involved. Eleven nurses rated the priority given in daily practice (from -3 as the lowest to +3 as the highest) to 35 Q-sample statements representing nursing care, non-nursing and organisational interventions. Results Overall, the intervention receiving the lowest priority was 'Providing patient hygiene', while the highest was 'Answering phone calls'. In the by-person factor analysis (total variance = 60.79%), three profiles of nurses emerged, (a) 'Patient safety-oriented' (variance = 31.66%); (b) 'Nursing task-oriented' (=16.32%); and (c) 'Team process-oriented' (=12.81%). Conclusions Three profiles of nurses emerged in the same setting with significant differences both in the statistical order of priorities and in their practical implications. Implications for nursing management Understanding levels of prioritization, which are not only affected by the unit but also by sub-groups of nurses who rank priorities in a similar way, can support nurse managers in their role.

Quantitative assessment of the charge transfer phenomena in cobalt oxides and cobalt complexes is essential for the design of advanced catalytic materials. We propose a method for the evaluation of the oxidation state of cobalt oxides with mixed valence states using resonant photoemission spectroscopy. The method is based on the calculation of the resonant enhancement ratio (RER) from the heights of the resonant features associated with the Co3+ and Co2+ states. The nature of the corresponding states was corroborated by means of density functional calculations. We employed a well-ordered Co3O4(111) film to calibrate the RER with respect to the atomic Co3+/Co2+ ratio. The method was applied to monitor the reduction of a well-ordered Co3O4(111) film to CoO(111) upon annealing under exposure to isopropanol. We demonstrate that this method yields the stoichiometry of cobalt oxides at a level of accuracy that cannot be achieved when fitting the Co 2p core level spectra.

BACKGROUND To date, few studies have explored cases of implantable cardioverter defibrillator (ICD) shock delivery with the intent of understanding patients' educational and supportive needs. AIMS AND OBJECTIVES To explore patient experiences as lived before, during and after one or more shocks. DESIGN A descriptive qualitative study carried out between 2016 and 2017. METHODS Semi-structured face-to-face audio-recorded interviews were performed and analysed using a content analysis methodology. RESULTS A total of 50 patients (average age = 68.3 years; largely male = 49; 98%) were interviewed. Four themes emerged: (a) "Feeling surprised vs. alerted by the changes inside me"; (b) "Living an intense, mono-dimensional vs. living a multidimensional storm experience", (c) "Facing the event vs. being supported"; and (d) "Living a drama vs. being used to it". CONCLUSIONS Findings suggest that ICD use can trigger negative physical and emotional effects in patients. Moreover, nurses should recognize patients' educational needs according to the stage of adaptation that each patient is experiencing with the aim of tailoring appropriate supportive interventions. RELEVANCE TO CLINICAL PRACTICE Therefore, it is necessary to consider the psychological needs of patients by integrating these into clinical care at different levels (emergency department, hospital ward, home). Specific structured support aimed at helping patients overcome intense negative experiences is suggested, especially in the first stage of the adaptation process. Nurses should also ensure that appropriate education programmes with adequate follow-up interventions are offered to improve the experience of living with an ICD. In addition, patient-reported outcomes should be routinely collected from patients with an ICD.

Ceria represents a technologically indispensable reducible catalyst support. Besides the general impact on the surface chemistry, the oxygen content of the ceria surface directly influences the dispersion of ceria-supported metal nanoparticles, and the properties of ceria-supported metal catalysts. We investigate the role of oxygen atoms on a CeO2(111) surface in supporting Pt as smallest metallic Pt clusters or, concurrently, as monodispersed Pt2+ ions. We demonstrate that the necessary condition for the formation of Pt2+ ions is the availability of lattice O or excess O atoms at surface step edges. Although Pt2+ ions can exist on partially reduced surfaces, excess O atoms are required to maximize the capacity of the surface to accommodate Pt2+ and to trigger the redispersion of metallic Pt clusters. Our study provides atomic-level understanding and control of the highest dispersions of Pt on the ceria surface for advancing the state-of-the-art Pt/ceria catalysts that are presently identified at the verge of single-atom Pt dispersion.

Objective To summarize the experience of individuals placed in quarantine during an outbreak. Design A meta‐summary and a meta‐synthesis based upon a systematic review of qualitative studies. Sample The Cumulative Index of Nursing and Allied Health Literature, MEDLINE, and Scopus databases were all searched up to April 2020. Measurements The Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines were followed; then, the methodological quality of the studies included was assessed with the Critical Appraisal Screening Programme tool for qualitative studies. Results Five studies have been included documenting the experience of 125 adult individuals. A total of 16 codes emerged: in the meta‐summary, the most and least frequent codes were “Thinking about quarantine” (80%) and “Emotional roller coaster,” “Being alert for any symptom,” “Trusting or not?,” “Knowing who brought the infection,” and “Living in a surreal world” (20%). The codes which emerged were categorized into three main themes which summarized the whole experience of being placed in quarantine: (a) “Being swamped with a thousand emotions”; (b) “Being restrained”; and (c) “Needing to be considered.” Conclusions The experience of quarantine for people is a long journey which can feel chaotic due to uncertainty about the consequences on health, work, and the future. The findings of this study can help nurses in caring for quarantined individuals by enabling them to understand people's need for educational and emotional support. Ensuring the supply of consistent information is also important to increase people's compliance.

Nanoscience and nanotechnology are broad domains of research and innovation that represent a major fi eld of activity at global level. This originates from the outstanding demonstrations obtained in the last two decades of the possibility to control the organization of matter at the scale of few atoms and molecules, to address their properties and to obtain functional systems with potential exploitation in the fields of health, environment, energy and communication. Research in nanoscience requires direct sensitivity to the atomic scale and to the fundamental time scale of the processes ruling the assembly of matter and the interactions with light, electric current, and molecules at all levels of complexity, from the gases of the atmosphere to proteins and DNA. Nanoscience therefore necessitates special research infrastructures like “atomically clean environments” for the synthesis and the assembling of nanosystems on the one hand, and advanced radiation sources for the direct analysis of their properties (Large Scale Facilities for fine analysis of matter, LSFs) and for controlling the functionalities at the relevant space and time scale of the fundamental processes on the other hand. Both these infrastructures, which require substantial investment in terms of human and financial resources, are most often not co-located and not operated in close synergy. While the European offer of LSFs is adequate, the availability of open access nanoscience centres is overall undersized, and the link to LSF is weak. This is a severe limitation for the optimal development of nanoscience and the ensuing nanotechnologies, as well as a limiting factor for a scientifi c return from the LSFs. State of the art synthesis and characterization laboratories lack the direct use of numerical modelling, fine analysis, in-situ and in-operando experiments. Advanced beamlines on synchrotron radiation sources, free electron lasers and neutron sources generally lack adequate synthesis and sample preparation and delivery tools, or atomic resolution microscopy. Numerical simulations are most often performed on model systems and are not on-line with synthesis and experimental work. The Nanoscience Foundries & Fine Analysis project (NFFA) addresses the integration of all these competences and methods by setting up a European Distributed Research Infrastructure that will co-locate 3-6 Nanoscience Centres with LSFs and thus shall offer a unique environment for advanced research by providing open access to European and international scientists. NFFA intends to play a key role in the construction of the European Research Area by creating a unique environment for the support of leading research by users from academy and institutes, by offering advanced training to young researchers and engineers and by providing an effective support to innovation projects by diverse stakeholders. This booklet summarizes the outcomes of the NFFA Design Study and outlines the strategic needs and roadmap for the implementation of the NFFA Research Infrastructure.

To understand what nursing education activities are missed in the daily life of nursing programmes, by also identifying antecedents and consequences of missed educational activities.A descriptive qualitative study according to the COnsolidated criteria for REporting Qualitative research guidelines.A purposeful sample of 32 participants with different roles (nurse educators, clinical nurses, students, and administrative personnel) and working in different settings (university, administrative, healthcare service levels) were involved in three focus groups and nine face-to-face interviews from 2019-2020. Both focus groups and face-to-face interviews were audio-recorded and transcribed verbatim. The data that emerged were thematically categorized by induction.Missed Nursing Education reflects those educational activities needed in the process of nursing education that are missed or delayed. Direct educational activities missed include clinical rotations, classroom teaching and students' overall learning experience. Indirect missed educational activities concern continuing professional development of nursing faculty members, nursing discipline development and the organizational processes of the nursing programme. As antecedents, missed nursing education is triggered by factors at the organizational, nursing faculty, and student levels. Consequences have been reported for students, nursing faculty, clinical nurses, and patients.Missed Nursing Education can be considered a multifaceted, multicausal phenomenon, with multitargeted consequences.To date, missed nursing care has only been investigated in clinical practice. However, care also permeates the relationship between nurse educators and students. Thus, at the point of 'educational care' delivery, aspects can also be omitted. Educational activities at risk of being missed or delayed affect the quality of nursing education and, in the short- and in the long- terms, also the quality of patient care. Some Missed Nursing Education antecedents can be modified by appropriate strategies that should be addressed by policy, health care and academic institutions.目的: 了解日常护理课程中错过的护理教育活动,同时明确措施该教育活动的前因后果。 设计: 根据报告定性研究指南中的综合标准开展描述性定性研究。 方法: 在2019年到2020年间,有目的地筛选32名不同职位(护士教育者、临床护士、学生和管理人员)且在不同环境(大学、行政机构、医疗服务机构)下工作的参与者,将这些参与者分为三个焦点小组,展开九次面对面访谈。焦点小组和面对面访谈内容都是通过录音和逐字转录的形式记录。相关数据应该按主题归纳和分类。 调查结果: 护理教育缺失是指护理教育过程中所需要的教育活动遭到错过或延误。错过的直接教育活动包括临床实习、课堂教学和学生的整体学习经历。错过的间接教育活动包括护理人员的持续专业发展、护理学科的发展和护理课程的组织过程。护理教育缺失是组织、护理人员和学生三个层面的因素所引发。现已对学生、护理人员、临床护士和患者所面临的后果进行报道。 结论: 护理教育缺失涉及多方面,因多个因素造成,可能造成多种后果。 影响: 截止目前,仅在临床实践中对护理教育缺失进行调查。然而,护理教育者与学生之间存在一定感情。因此,在提供“教育关怀”的同时,也可以省略部分方面。教育活动的错过或延迟可能对护理教育的质量产生影响,并且,从短期和长期来看,可能影响患者护理质量。部分护理教育缺失的前因可以通过适当的策略加以修正,此类策略应该由政策机构、卫生保健机构和学术机构制定。.

Materials based on regular π-stacks of planar organic radicals are intensively pursued by virtue of their technologically relevant properties. Yet, these π-stacks are commonly unstable against π-dimerization. In this computational study, we reveal that regular π-stacks of planar dithiazolyl radicals can be rendered stable, in some range of temperatures,viatwo different mechanisms. When the radicals of a π-stack are both longitudinally and latitudinally slipped with respect to each other, the corresponding regular π-stacked configuration is associated with a locally stable minimum in the potential energy surface of the system. Conversely, those regular π-stacks in which radicals are latitudinally slipped with respect to each other are stable as a result of a dynamic interconversion between two degenerate dimerized configurations. The existence of two stabilization mechanisms, which can be traced back to the bonding properties of isolated π-dimers, translates into two different ways of exploiting spin-Peierls-like transitions in switchable dithiazolyl-based materials.

The cuprous delafossite, ${\mathrm{CuFeO}}_{2}$, has received significant attention in recent years as a potential photocathode material in photoelectrochemical water-splitting cells. Presented herein is an investigation of the electronic structure of ${\mathrm{CuFeO}}_{2}$ in the framework of density functional theory. We have benchmarked three of the most popular formulations for the treatment of the electron exchange and correlation interactions, highlighting their strengths and weaknesses in predicting electronic structures compatible with the available spectroscopic measurements. Although some features are correctly reproduced by the simplest approach, which is based on the generalized gradient approximation, this fails in describing the fundamental semiconducting character of the material. The introduction of the fully self-consistent Hubbard $U$ correction in the exchange correlation functional accounts explicitly for the on-site Coulomb interaction among localized $d$ electrons, thereby opening a gap in the band structure. However, our results indicate that the $U$ correction disrupts the crystal-field splitting of the ${t}_{2g}$ and ${e}_{g}$ states, resulting in an inaccurate description of the conduction-band edge. We provide a qualitative and quantitative analysis to explain why the ${t}_{2g}$ and ${e}_{g}$ states behave differently when the Hubbard correction is switched on. We find that best practice for accurate, yet computationally viable, simulations of CFO makes use of hybrid functionals, where the fraction of exact exchange is not arbitrarily selected but tuned according to the static dielectric constant of the material. In this case, theoretical predictions are found to be in excellent agreement with experimental results.

Supported Pt nanoparticles are key components in heterogeneous catalysis for energy and environment applications that involve vapor and wet conditions. In the latter case, the reaction proceeds at the catalyst-water interface where the solvent actively participates in the reaction mechanism. In this work, ab initio molecular dynamics simulations shed light on the effects of solvation on the reactivity and electronic properties of Pt6 nanocatalysts supported by ceria (CeO2), a highly reducible oxide. The calculated trajectories show that H2O molecules spontaneously dissociate at both the supported Pt6 cluster and at the ceria surface already at T = 350 K. Water dissociation leads to hydroxylation of the ceria surface and, most importantly, to the selective decoration of the metal-oxide periphery with hydroxide ions, which are stabilized by solvent-induced electronic effects and which quickly diffuse to the interfacial Pt sites via Grotthus-like proton chains. The periphery of the metal-oxide interface is thus identified as the active region of ceria-supported Pt clusters in wet environments. Solvation is shown to drive dynamic charge transfers across the metal/oxide interface that modify the cluster charge, a key parameter of the catalyst reactivity. Fil: Szabová, Lucie. Tsukuba University. National Institute For Materials Science; Japón Fil: Camellone, Matteo Farnesi. Democritos Modeling Center For Research In Atomistic Simulation; Fil: Negreiros Ribeiro, Fábio. National Research Council-Istituto Officina dei Materiali. Democritos Modeling Center For Research In Atomistic Simulation; Italia. 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: Matolín, Vladimír. Charles University. Faculty of Mathematics and Physics; República Checa Fil: Tateyama, Yoshitaka. Tsukuba University. National Institute For Materials Science; Japón Fil: Fabris, Stefano. National Research Council-Istituto Officina dei Materiali. Democritos Modeling Center For Research In Atomistic Simulation; Italia

Single-atom catalysts represent the ultimate extreme in heterogeneous catalysis for the maximum dispersion of mononuclear catalytic metal particles on supporting surfaces. Ultralow Pt loading has been achieved on nanostructured ceria surfaces that allow for stabilizing metallic and ionic Pt sites that are anchored at surface defects. Here, we assess the chemical reactivity of these different Pt species, which are experimentally known to coexist on Pt-ceria nanocatalysts, by taking methanol oxidation as a chemical probe. Our density functional theory calculations demonstrate that Pt2+ and Pt4+ single-ion species do not promote methanol oxidation by themselves. Instead, metallic sites of supported sub-nanometer Pt particles are always required to promote the oxidation reaction. Our finding generalizes the conclusions of recent photoemission experiments in the context of H2 oxidation by ceria/Pt nanocatalysts. Moreover, the simulations predict that surface hydroxide groups may act as cocatalyst for the direct methanol oxidation to formaldehyde, thus proposing a viable strategy for catalyst design

Reactions of reduced cerium oxide CeOx with water are fundamental processes omnipresent in ceria-based catalysis. Using thin epitaxial films of ordered CeOx, we investigate the influence of oxygen vacancy concentration and coordination on the oxidation of CeOx by water. Upon changing the CeOx stoichiometry from CeO2 to Ce2O3, we observe a transition from a slow surface reaction to a productive H2-evolving CeOx oxidation with reaction yields exceeding the surface capacity and indicating the participation of bulk OH species. Both the experiments and the ab initio calculations associate the effective oxidation of highly reduced CeOx by water to the next-nearest-neighbor oxygen vacancies present in the bixbyite c-Ce2O3 phase. Next-nearest-neighbor oxygen vacancies allow for the effective incorporation of water in the bulk via formation of OH- groups. Our study illustrates that the coordination of oxygen vacancies in CeOx represents an important parameter to be considered in understanding and improving the reactivity of ceria-based catalysts.

CuFeO2 has been recently identified as a promising photocathode material for photoelectrochemical water splitting cells. In spite of the first encouraging results, improvements in the catalytic activity and charge separation are required and an adequate theoretical characterization is currently not available to complement experimental results. We present a first-principles investigation of the bulk properties of CuFeO2, focusing in particular on its stability in air and in an aqueous environment. Here, we show that while the material is in a metastable phase in air at ambient conditions, the electrochemical environment strongly stabilizes it. In fact, at conditions of applied bias and pH used in the experiments, the material operates within its region of thermodynamic stability, thus explaining its remarkable resistance to corrosion. We investigated the formation energy of native point defects in the stability region, predicting a small formation energy for an antisite defect, which could be detrimental for the performance of CuFeO2 as a photocathode, since defect states lying inside the gap may favor the electron-hole recombination.

The efficiency of chemical reactions on surfaces is traditionally related to their lattice structures. The periodic out-of-plane lattice distortions of supported two-dimensional layers offer an alternative strategy to surface functionalization, scarcely investigated so far. Here, we show that the variable buckling geometry of a GdAu2 Moiré overlayer supported on the Au(111) surface exposes specific single-atom sites that control the dehydrogenation process of phthalocyanine (H2-PC) molecules, limiting their reactivity to about 1/3 of the monolayer. The lattice mismatch between the substrate and the alloy layer leads to the previously reported outward displacement of distinct Gd sites. We show that these atomic sites promote the selective dehydrogenation of H2-PC molecules., This project has received funding from the EU-H2020 research and innovation program (grant number 654360) having benefitted from the access provided by Istituto Officina dei Materiali in Trieste (Italy) within the framework of the NFFA Transnational Access Activity. L.V., A.B., and A.C. acknowledge the economic support of the Spanish Ministry of Economy, Industry and Competitiveness (grant number MAT2016-78293-C6-5-R) and Prof. S. Modesti for his help with the electronics. A.B. acknowledges Vicerrectorado de Investigacion of the University of the Basque Country (UPV/ EHU) for the PhD fellowship (2016)

The electronic metal-substrate interaction plays an important role in the surface reactions on supported metal nanoparticles. We study the interaction between rhodium clusters and cerium oxide substrate having various stoichiometries, CeOx (2.00 > x > 1.67), by means of photoelectron spectroscopy. Our results show that rhodium deposited on substrates with stoichiometry of 2.00 > x > 1.93 induces reduction of cerium oxide. On the other hand, cerium oxide with a higher degree of reduction (1.93 > x > 1.67) becomes partially oxidized after the Rh deposition. Density functional theory simulations of Rh adatom adsorbed on the CeO2(111) surface and on an oxygen vacancy at the CeOx(111) surface show that there is a charge transfer between rhodium and cerium oxide substrate. While Rh adsorption on the CeO2(111) surface leads to electron depletion at the Rh adatom and cerium oxide reduction, Rh adsorption on the oxygen vacancy at CeOx(111) leads to electron accumulation about the Rh adatom and partial oxidation of cerium oxide. The results clearly demonstrate that the electronic metal-substrate interaction occurs on Rh/CeOx systems and strongly depends on the stoichiometry of cerium oxide. These findings could be beneficial for designing catalysts with specific properties.

Heterogeneous reactions at the surfaces of mineral dusts represent a key process in the formation of atmospheric aerosols. To quantify the rate of aerosol formation in climate modeling as well as combat hazardous aerosols, a deep understanding of the mechanisms of these reactions is essential. In the present work, density functional theory calculations, including a Hubbard-like +

Heterogeneous reactions at the surfaces of mineral dusts represent a key process in the formation of atmospheric aerosols. To quantify the rate of aerosol formation in climate modeling as well as combat hazardous aerosols, a deep understanding of the mechanisms of these reactions is essential. In the present work, density functional theory calculations, including a Hubbard-like +U correction, were employed to elucidate the reaction between SO2 and the hematite(0001) surface. Three reaction conditions are considered: dry, wet, and aerobic. In the absence of water and oxygen, adsorption energies of SO2 on the clean Fe-O-3-Fe-termination were found to be about -0.8 to -1.0 eV and resulted in the formation of an adsorbed SO3-like species. The addition of water leads to surface hydroxylation and has little effect on promoting the SO2 adsorption. Under such circumstances, an HSO3-like species was formed with a smaller adsorption energy of about -0.5 eV. By contrast, the presence of molecular oxygen enhances the SO-2 adsorption significantly as the two species combine to form sulfate SO42-, with adsorption energies of -1.31 to -1.64 eV. The calculated vibrational frequencies of the adsorbate species provide insight into the surface bonding and a useful spectral fingerprinting for experimental measurements. These results elucidate the atomistic mechanism of the reaction between SO2 and hematite and highlight the important role of atmospheric O-2 in the formation of sulfates. Published by AIP Publishing.

Resumen del trabajo presentado a la International Conference on Nanoscience + Technology (ICN+T), celebrada en Brno (Czech Republic) del 22 al 27 de julio de 2018., Tuning the electronic properties of two-dimensional (2D) layers is a current focus of interdisciplinary research. Here, we show that the electronic properties of a surface- supported 2-dimensional (2D) layer structure can spontaneously self-texturize at nanoscale. Specifically, we have characterized the 2D layer GdAu2 forming a mismatched interface on Au(111). We demonstrate that the variable adsorption stacking configurations causes local structural relaxation processes which result in a spatially modulated layer-buckling. This is sufficient to periodically open, at the Fermi level, an energy gap of ~0.5 eV at well-defined stacking configurations on an otherwise metallic layer. Additionally, this out-of-plane displacement of the Gd atoms patterns the character of the hybridized Gd-d states and shifts the center of mass of the Gd 4f multiplet proportionally to the lattice distortion. These findings demonstrate the close correlation between the electronic properties of the 2D-layer and its planarity. We demonstrate that the resulting template shows different chemical reactivity which may find important applications. We will compare the properties of the 2D-layer of GdAu2/Au(111) with the previously reported GdAg2/Ag(111).

Nanostructured Pt–CeO 2 films with low Pt loading show high activity and stability as anode catalysts in proton-exchange membrane fuel cells. Under electrochemical conditions, the noble metal in the catalyst films can be reversibly converted between two chemical states, an atomically dispersed Pt 2 + species and subnanometer Pt particles. The nature of these states and the mechanism of their interconversion have been investigated combining surface science and electrochemical experiments. The local structure of the Pt 2 + species, their stability, and reactivity were studied by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy under ultrahigh vacuum conditions in combination with density functional modeling. We employed surface science-based model systems of different complexity to probe the reactivity of the atomically dispersed Pt 2 + species in the absence of other species such as Pt 4 + , metallic Pt, or oxygen vacancies. It was found that the conversion of Pt 2 + to subnanometer Pt particles is triggered by a redox coupling with Ce 3 + centers generated through the formation of oxygen vacancies or by charge transfer between the metal and the support. These findings characterize the Pt–CeO 2 material as a structurally highly dynamic catalyst which attains its high stability from the ability to adapt to the changes in the operation conditions.

We present QMMMW, a new program aimed at performing Quantum Mechanics/Molecular Mechanics (QM/MM) molecular dynamics. The package operates as a wrapper that patches PWscf code included in the QUANTUM ESPRESSO distribution and LAMMPS Molecular Dynamics Simulator. It is designed with a paradigm based on three guidelines: (i) minimal amount of modifications on the parent codes, (ii) flexibility and computational efficiency of the communication layer and (iii) accuracy of the Hamiltonian describing the interaction between the QM and MM subsystems. These three features are seldom present simultaneously in other implementations of QMMM. The QMMMW project is hosted by qe-forge at (http://qe-forge.org/gf/project/qmmmw/). Program summary Program title: QMMMW Catalogue identifier: AEWS_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEWS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 7544822 No. of bytes in distributed program, including test data, etc.: 121657035 Distribution format: tar.gz Programming language: Python, C and Fortran95. Computer: All Linux based workstations and parallel supercomputers. Operating system: GNU/Linux. Classification: 3, 7.7, 16.1, 23. Nature of problem: Calculation of the hybrid quantum mechanics/molecular mechanics of molecular systems. Solution method: With the current patches QMMMW allows the performance of QM/MM simulations with mechanical coupling (i.e. classical point charge based, QM and the MM system interacts electrostatically only at the classical level.) and electrostatic coupling according to the scheme proposed by Laio, VandeVondele and Rothlisberger, J. Chem Phys. 116, 6941 (2002). Restrictions: Only coded for orthorhombic cell. The interactions coupling QM and MM degrees of freedom cannot be bonded. The QM region can only be modeled with PWscf. Unusual features: Minimal amount of modifications to the parent codes. Flexibility and computational efficiency of the communication layer. Accuracy of the Hamiltonian describing the interaction between the QM and MM subsystems. Additional comments: Relevant versions of QUANTUM ESPRESSO and LAMMPS are included in the distribution file and in the number of lines and number of bytes shown. 11111 The distribution file for this program is over 121 Mbytes and therefore is not delivered directly when download or Email is requested. Instead a html file giving details of how the program can be obtained is sent. 11111 Running time: From a few minutes for small molecules on serial machines up to many hours on multiple processors for complex nanosystems with hundreds of atoms. (C) 2015 Elsevier B.V. All rights reserved.

The chemistry of several catalytic processes can be controlled by tuning metaloxide interfaces, as demonstrated by fundamental studies on inverse model catalysts. We investigate the effects of the metaloxide interface on the surface reactivity of ceria (CeO2) thin films supported by a copper metal surface. Our density functional theory (DFT+U) calculations reveal that the interface has impact on the surface water adsorption and dissociation when the thickness of the ceria film is below approximate to 9 angstrom. On thinner films, the energetics of adsorption and dissociation display a significant variation, which arises from a combination of thickness and interface-proximity effects, and which we rationalize in terms of charge-density response at the adsorbate-oxide and oxide-metal interfaces. The adsorption energy is maximized for film thicknesses of 5.5 angstrom (corresponding to two OCeO trilayers), while thinner films affect primarily the relative stability between molecular, semidissociated, and dissociated water adsorption. These results provide useful insights into the effect of low-dimensional ceria species in Cu/CeO2 catalysts.

Here, we show that the electronic properties of a surface-supported 2-dimensional (2D) layer structure can self-texturize at nanoscale. The local electronic properties are determined by structural relaxation processes through variable adsorption stacking configurations. We demonstrate that the spatially modulated layer-buckling, which arises from the lattice mismatch and the layer/substrate coupling at the GdAu

The concept of single atom catalysis offers maximum noble metal efficiency for the development of low-cost catalytic materials. Among possible applications are catalytic materials for proton exchange membrane fuel cells. In the present review, recent efforts towards the fabrication of single atom catalysts on nanostructured ceria and their reactivity are discussed in the prospect of their employment as anode catalysts. The remarkable performance and the durability of the ceria-based anode catalysts with ultra-low Pt loading result from the interplay between two states associated with supported atomically dispersed Pt and sub-nanometer Pt particles. The occurrence of these two states is a consequence of strong interactions between Pt and nanostructured ceria that yield atomically dispersed species under oxidizing conditions and sub-nanometer Pt particles under reducing conditions. The square-planar arrangement of four O atoms on {100} nanoterraces has been identified as the key structural element on the surface of the nanostructured ceria where Pt is anchored in the form of Pt2+ species. The conversion of Pt2+ species to sub-nanometer Pt particles is triggered by a redox process involving Ce3+ centers. The latter emerge due to either oxygen vacancies or adsorption of reducing agents. The unique properties of the sub-nanometer Pt particles arise from metal-support interactions involving charge transfer, structural flexibility, and spillover phenomena. The abundance of specific adsorption sites similar to those on {100} nanoterraces determines the ideal (maximum) Pt loading in Pt-CeOx films that still allows reversible switching between the atomically dispersed Pt and sub-nanometer particles yielding high activity and durability during fuel cell operation.

We study subnanometer (sub-nm) Pt clusters supported by highly reducible oxide surfaces and establish the role of cluster morphology in the thermodynamics and kinetics of surface processes relevant for reactivity, namely cluster mobility, reverse oxygen spillover, and oxygen vacancy formation. The relationships between cluster morphology and reactivity are rarely considered in computational studies because of the large domain and complexity of the potential energy surface, particularly in the presence of strong metalsupport interaction. Global optimization algorithms together with Hubbard-corrected density functional theory calculations (DFT+U) are used to identify the stable and metastable morphologies of Pt3Pt6 clusters supported on pristine and defective CeO2(111) surfaces. Our systematic exploration for these sub-nm Pt particles shows that the charge of the supported cluster, its bonding to the substrate, and the degree of ceria reduction depend on the metal/oxide interface area and on the cluster morphology. Concerning reaction thermodynamics and kinetics, the use of global optimization methods leads to very different results as compared to usual minimization procedures. By allowing for morphology changes during reaction, the energetics of reverse O spillover changes from highly endothermic to exothermic and leads to new minimum-energy reaction and diffusion mechanisms. The diffusion kinetics predicts clusters as small as Pt6 to be resistant to sintering on ceria surfaces. The relevance of these findings for larger metal clusters and for supporting oxide nanoparticles is discussed as well as their connection with the recent literature.

Some of the most promising catalysts for water oxidation rely on crystalline and amorphous cobalt oxide nanoparticles. Density functional theory (DFT) calculations are routinely used to study the electronic and atomic structures of these materials as well as the thermodynamics and mechanisms of the electrochemical oxygen evolution reaction. The accuracy of these theoretical predictions has never been compared to high-level quantum chemistry methods. We perform coupled cluster (CC) quantum chemistry calculations on model cobalt oxide surface sites and use them to benchmark the accuracy of the most popular exchange and correlation functionals. Hybrid B3LYP and PBE0 functionals lead to fair agreement with the CC energies, while standard gradient-corrected functionals show important discrepancies. The inclusion of on-site electronic repulsion (DFT +U) substantially improves the calculated electronic and structural properties, but no value of the U parameter reproduces the CC results. We discuss the implications of these findings for amorphous cobalt phosphate nanoparticles, showing that the reactivity of these catalysts is not altered by surface phosphate groups.

Density functional theory (DFT) calculations are used to identify correlations among reactivity, structural stability, cohesion, size, and morphology of small Au clusters supported on stoichiometric and defective CeO2(111) surfaces. Molecular adsorption significantly affects the cluster morphology and in some cases induces cluster dissociation into smaller particles and deactivation. We present a thermodynamic rationalization of these effects and identify Au-3 as the smallest stable nanoparticle that can sustain catalytic cycles for CO oxidation without incurring structural/morphological changes that jeopardize its reactivity. The proposed Mars van Krevelen reaction pathway displays a low activation energy, which we explain in terms of the cluster fluxionality and of labile CO2 intermediates at the Au/ceria interface. These findings shed light on the importance of duster dynamics during reaction and provide key guidelines for engineering more efficient metal-oxide interfaces in catalysis.

Supramolecular nanostructures with tunable dimensionalities are fabricated by deposition of benzene-carboxylic acids on the Cu(110) surface. By tailoring the number and position of the functional moieties, the structure of the final molecular assemblies can be rationally modified ranging from isolated one-dimensional chains to compact two-dimensional islands. Molecular units are chosen that can assemble through metal-organic and electrostatic interactions. The hierarchy between these intermolecular forces guarantees that a primary organization level, constituted by metal-organic polymeric chains, is developed by all molecular units while the secondary interchain interactions can be arbitrarily adjusted. Scanning tunneling microscopy, density functional theory calculations, and kinetic Monte Carlo simulations are used to characterize and rationalize the experimental findings. © 2013 American Chemical Society.

Wet conditions in heterogeneous catalysis can substantially improve the rate Of surface reactions by assisting the,diffusion of reaction intermediates between surface reaction sites. The atomistic mechanisms underpinning this accelerated mass transfer are, however, concealed by the complexity of the dynamic water/solid interface. Here we employ ab intio molecular dynamics simulations to disclose the fast diffusion of protons and. hydroxide species along the interface between water and ceria) a catalytically important, highly reducible oxide. Up to 20% of the interfacial water molecules are shown to dissociate at room temperature via proton transfer to surface 0 atoms, leading: to partial surface hydroxylation and to a local increase of hydroxide species in the surface solvation layer. A water-mediated Grotthus-like mechanism is shown to activate the fast and long-range proton diffusion at the water/oxide interface. We demonstrate the catalytic importance of this dynamic process for water dissociation at ceria-supported Pt nanoparticles, where the solvent accelerates the spillover of ad-species between oxide and metal sites.

We conduct first-principles calculations to study oxygen diffusion On the graphene surface as a function of temperature up to 3000 K. The minimum energy migration path and the corresponding activation energy are determined by the nudged elastic band method with explicit inclusion of thermal electronic excitations. Below 1000 K the activation energy for epoxy oxygen to migrate remains close to its room temperature value (0.72 eV). Above 1000 K the activation energy decreases neat linearly with temperature, from 0.70 eV at 1000 K to 0.47 eV at 3000 K. We show that this reduction originates from thermal electronic excitations. In particular, the effect is determined by the large contrasts in the electronic structures of the initial and transition states: the transition state exhibits much larger electronic density of states near the Fermi level and is more susceptible to thermal electronic excitations. The reduction in activation energy leads to appreciable enhancement in the diffusivity of oxygen adatoms. A moderate decrease in the vibrational prefactor, also caused by thermal electronic excitations, does not alter this trend. These findings may facilitate future works to accurately describe the dynamics of O adatoms on graphene at high T, which are critical for determining surface thermodynamic properties such as equilibrium coverage.

The reactivity of atomically dispersed Pt(2+) species on the surface of nanostructured CeO2 films and the mechanism of H2 activation on these sites have been investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy in combination with density functional calculations. Isolated Pt(2+) sites are found to be inactive towards H2 dissociation due to high activation energy required for H-H bond scission. Trace amounts of metallic Pt are necessary to initiate H2 dissociation on Pt-CeO2 films. H2 dissociation triggers the reduction of Ce(4+) cations which, in turn, is coupled with the reduction of Pt(2+) species. The mechanism of Pt(2+) reduction involves reverse oxygen spillover and formation of oxygen vacancies on Pt-CeO2 films. Our calculations suggest the existence of a threshold concentration of oxygen vacancies associated with the onset of Pt(2+) reduction.

The electronic properties and surface structures of K-doped graphene supported on Ir(111) are characterized as a function of temperature and coverage by combining low-energy electron diffraction, angle-resolved photoemission spectroscopy, and density functional theory (DFT) calculations. Deposition of K on graphene at room temperature (RT) yields a stable $(\ensuremath{\surd}3\ifmmode\times\else\texttimes\fi{}\ensuremath{\surd}3)$ R30\ifmmode^\circ\else\textdegree\fi{} surface structure having an intrinsic electron doping that shifts the graphene Dirac point by ${E}_{D}=1.30\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$ below the Fermi level. Keeping the graphene substrate at 80 K during deposition generates instead a $(2\ifmmode\times\else\texttimes\fi{}2)$ phase, which is stable until full monolayer coverage. Further deposition of K followed by RT annealing develops a double-layer K-doped graphene that effectively doubles the K coverage and the related charge transfer, as well as maximizing the doping level $({E}_{D}=1.61\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$. The measured electron doping and the surface reconstructions are rationalized by DFT calculations. These indicate a large thermodynamic driving force for K intercalation below the graphene layer. The electron doping and Dirac point shifts calculated for the different structures are in agreement with the experimental measurements. In particular, the ${\mathrm{K}}_{4s}$ bands are shown to be sensitive to both the K intercalation and periodicity and are therefore suggested as a fingerprint for the location and ordering of the K dopants.

Water splitting is at the basis of artificial photosynthesis for solar energy conversion into chemical fuels. While the oxidation of water to molecular oxygen and the reduction of protons to molecular hydrogen are typically promoted by different catalysts, the Ru(II)-pincer complex recently synthesized by Kohl et al. [Science2009, 324, 74] has been shown to promote both the thermal driven formation of H2 and the UV–vis driven evolution of O2. Here, we investigate, through density functional theory calculations, a portion of the catalytic cycle, focusing on the formation of hydrogen. We adopt an explicit description of the solvent and employ metadynamics coupled with the Car–Parrinello method to study the reaction mechanism and determine the activation free energies. Our simulations predict a novel catalytic cycle, which has considerably lower activation energies than earlier proposals and which does not involve the sequential aromatization–dearomatization of the PNN ligand of the complex. This work clearl...

The structural patterns formed by molecular self-assembly at surfaces are usually controlled by the relative strengths of the intermolecular and molecule-substrate interactions. An additional steering effect is present when the substrate can easily reconstruct upon molecular adsorption, which therefore drives a self-templating effect on the metal support. This is here demonstrated for the model case of Fephthalocyanine molecules adsorbed on the Au(110) surface. Scanning tunneling microscopy shows that molecular adsorption promotes a local (1 x 5) surface reconstruction, which drives the assembly of molecular chains along the [1 (1) over bar0] direction. The order and periodicity of the molecular assemblies are determined with low energy electron diffraction patterns. Density functional theory calculations reveal the energetic origins of the molecule-driven substrate reconstruction. Since the function of molecular overlayers at surfaces is strongly correlated to their structure, these results have implications in the design of new metal/molecular interfaces.

We identify mechanisms and surface precursors for the nucleation and growth of extended defects on oxidized graphene. Density functional theory calculations show that the formation of surface structures capable to initiate the unzipping and cracking of the oxidized C network is strongly influenced by the constraint of the graphitic lattice on the surface functional groups. Accounting for this effect on the preferential spatial patterning of O adsorbates allows us to revise and extend the current models of graphene oxidative unzipping and cutting. We find that these processes are rate limited by O diffusion and driven by the local strain induced by the O adspecies. Adsorbate mobility is ultimately recognized as a key factor to control and to prevent the C-network breakdown during thermal processing of oxidized graphene.

The reduction of graphene oxide surfaces yielding molecular CO/CO2 is studied from first principles using density functional theory. We find that this reaction can proceed exothermically only from surface precursors containing more oxygen atoms than strictly needed to produce CO/CO2 in the gas phase. The calculations show that the lowest-energy configurations of multiple O adsorbates do not involve clustering of epoxy groups (the stable form of O adatoms on graphitic surfaces) but always contain lactone groups either in lactone−ether or in ether−lactone−ether form. We identify these lowest-energy structures as the main reaction precursors. The O adatoms near the lactone group catalyze its gasification to CO/CO2 by reducing the activation energy from above 1.8 eV (from an isolated lactone) to below 0.6 eV (from a lactone−ether). In addition, the residual O adatoms left behind after the lactone gasification minimize the energy of the graphitic products by saturating the dangling bonds of the resulting defec...

The defect chemistry and electronic structure of NiO/CeO(2) solid solutions are studied by means of DFT+U calculations in the limit of low Ni doping. We consider four representative solid solutions in which the Ni atoms are present as substitutional and interstitial point defects in bulk crystalline CeO(2), both in its stoichiometric form and in the presence of O vacancies. In all cases, Ni-doping significantly enhances the O buffering effect of ceria, controlled by O vacancy formation, but the actual microscopic mechanisms are different depending on the specific type and charge state of the point defects. The oxidation state of the Ni dopant is shown to univocally characterize the type of defect, whether interstitial (Ni(+)) or substitutional (Ni(2+)). Interstitial NO defects result from a charge redistribution between the Ni and Ce cations that leads to the formation of characteristic Ni(+)-Ce(3+) defect complexes. O release via vacancy formation in these interstitial solid solutions proceeds similarly as in pure CeO(2), i.e., is mediated by electron localization processes reducing two Ce(4+) ions to Ce(3+). Quite differently, substitutional Ni(2+) point defects yield unsaturated O 2p valence bands and the appearance of unoccupied gap states spatially localized on the O atoms neighboring the Ni defect. Consequently, O vacancy formation in substitutional solid solutions does not lead to reduction of Ce ions but to quenching of these gap states. Ab initio thermodynamics predict the substitutional solid solutions to be more stable than the interstitial ones by more than 2.4 eV over a wide range of pressures and temperatures. We demonstrate that these conclusions are robust with respect to the specific choice of the Hubbard U parameters accounting for the on-site electron Coulomb interaction on the Ni and Ce sites.

An open superstructure: A Pd/CeO2 catalyst prepared by solution combustion synthesis is three to five times more active for CH4 combustion than the best conventional palladium-based systems. The catalyst contains an ordered, stable Pd-O-Ce surface superstructure (see picture; cyan arrow is a square-planar Pd site, red arrow is an undercoordinated O atom) and is an example of ultra-highly dispersed, stable PdO within an oxide carrier.

Density functional theory calculations that account for the on-site Coulomb interaction via a Hubbard term (DFT+U) reveal the mechanisms for the oxidation of CO catalyzed by isolated Au atoms as well as small clusters in Au/CeO(2) catalysts. Ceria (111) surfaces containing positively charged Au ions, either as supported Au(+) adatoms or as substitutional Au(3+) ions, are shown to activate molecular CO and to catalyze its oxidation to CO(2). In the case of supported single Au(+) adatoms, the limiting rate for the CO oxidation is determined by the adsorbate spillover from the adatom to the oxide support. The reaction then proceeds with the CO oxidation via lattice oxygen and O vacancy formation. These vacancies are shown to readily attract the supported Au(+) adatoms and to turn them into negatively charged Au(delta-) adspecies that deactivate the catalyst, preventing further CO adsorption. Au(3+) ions dispersed into the ceria lattice as substitutional point defects can instead sustain a full catalytic cycle consisting of three individual steps maintaining their activity along the reaction process: Au cations in Au(x)Ce(1-x)O(2) systems promote multiple oxidations of CO without any activation energy via formation of surface O vacancies. Molecular oxygen adsorbs at these vacancies and forms O adspecies that then catalyze the oxidation of molecular CO, closing the catalytic cycle and recovering the stoichiometric Au(x)Ce(1-x)O(2) system. The interplay between the reversible Ce(4+)/Ce(3+) and Au(3+)/Au(+) reductions underpins the high catalytic activity of dispersed Au atoms into the ceria substrate. It is shown that the positive oxidation state of the substitutional Au ions is retained along the catalytic cycle, thus preventing the deactivation of Au(x)Ce(1-x)O(2) catalysts in operation conditions. Finally, although a single Au(+) adatom bound to an O vacancy is shown to deactivate during CO oxidation, the calculations predict that the reactivity of gold nanoparticles nucleated at O vacancies can be recovered for cluster sizes as small as Au(2).

The initial oxidation stages of perfect and defective graphitic surfaces exposed to atomic oxygen have been studied with a combined high-resolution photoemission spectroscopy (HR-PES) and density functional theory (DFT) computational approach. The resulting oxygen-containing surface functional groups are identified by analyzing the multicomponent C 1s and O 1s core level spectra that are then interpreted on the basis of DFT calculations. In the initial oxidation stage, epoxy groups are formed on perfect graphene, whereas the preferential adsorption of the O atoms on the vacancies of the defective surfaces results in structures containing pairs of oxygen atoms in ether and carbonyl (semiquinone) configurations. The formation of these functional groups is preceded by metastable structures consisting of single O atoms occupying single C vacancies.

The hydroxylation of oxide surfaces driven by molecular H2 dissociation plays a cen- tral role in a wide range of catalytic redox reactions. The high reducibility and oxygen storage capacity of ceria (CeO2) surfaces account for its extensive use as active catalyst support in these redox reactions. By means of ab-initio molecular dynamics simulations, we investigate the hydroxylation and reduction of ceria surfaces and demonstrate the so-far unrecognized effects of atomic thermal fluctuations into the mechanism and kinet- ics of H2 dissociation. The reaction free-energy hypersurface is sampled and mapped at finite temperature by combining Hubbard-U density functional theory (DFT+U), ab-initio molecular dynamics, metadynamics, and umbrella sampling methods. Our molecular dynamics simulations show that the explicit inclusion of thermal fluctuations into the reaction thermodynamics alters the mechanism of H2 dissociation, changes the nature of the rate-limiting transition state, and decreases the activation temperatures by more than 25%. The results are discussed in the context of kinetic measurementsand provide novel insight into the hydroxylation and reduction steps that control the catalytic activity and selectivity of ceria surfaces.