Correction to "Understanding Anomalous Gas-Phase Peak Shifts in Dip-and-Pull Ambient Pressure XPS Experiments".

[This corrects the article DOI: 10.1021/acs.jpcc.

Low-Temperature Methane Activation Reaction Pathways over Mechanochemically-Generated Ce/Cu Interfacial Sites.

Methane is a valuable resource and its valorization is an important challenge in heterogeneous catalysis. Here it is shown that CeO/CuO composite prepared by ball milling activates methane at a temperature as low as 250 °C. In contrast to conventionally prepared catalysts, the formation of partial oxidation products such as methanol and formaldehyde is also observed.

Direct and indirect role of Fe doping in NiOOH monolayer for water oxidation catalysis.

Water oxidation activity of pristine NiOOH is greatly enhanced by doping it with Fe. However, the precise role of Fe is still being debated. Using a first-principles DFT+U approach, we investigate the direct and indirect roles of Fe in enhancing the oxygen evolution reaction (OER) activity of NiOOH monolayers.

Structure and Energetics of Dye-Sensitized NiO Interfaces in Water from Ab Initio MD and Large-Scale GW Calculations.

The energy-level alignment across solvated molecule/semiconductor interfaces is a crucial property for the correct functioning of dye-sensitized photoelectrodes, where, following the absorption of solar light, a cascade of interfacial hole/electron transfer processes has to efficiently take place. In light of the difficulty of performing X-ray photoelectron spectroscopy measurements at the molecule/solvent/metal-oxide interface, being able to accurately predict the level alignment by first-principles calculations on realistic structural models would represent an important step toward the optimization of the device. In this respect, dye/NiO surfaces, employed in p-type dye-sensitized solar cells, are undoubtedly challenging for ab initio methods and, also for this reason, much less investigated than the n-type dye/TiO counterpart.

Key role of chemistry versus bias in electrocatalytic oxygen evolution.

The oxygen evolution reaction has an important role in many alternative-energy schemes because it supplies the protons and electrons required for converting renewable electricity into chemical fuels. Electrocatalysts accelerate the reaction by facilitating the required electron transfer, as well as the formation and rupture of chemical bonds. This involvement in fundamentally different processes results in complex electrochemical kinetics that can be challenging to understand and control, and that typically depends exponentially on overpotential.

Formation of a 2D Meta-stable Oxide by Differential Oxidation of AgCu Alloys.

Metal alloy catalysts can develop complex surface structures when exposed to reactive atmospheres. The structures of the resulting surfaces have intricate relationships with a myriad of factors, such as the affinity of the individual alloying elements to the components of the gas atmosphere and the bond strengths of the multitude of low-energy surface compounds that can be formed. Identifying the atomic structure of such surfaces is a prerequisite for establishing structure-property relationships, as well as for modeling such catalysts in ab initio calculations.

Understanding the electrochemical double layer at the hematite/water interface: A first principles molecular dynamics study.

Using first principles molecular dynamics simulations, we probe the electrochemical double layer formed at the interface between the hematite surface and water. We consider two terminations of the (001) surface, viz., the fully hydroxylated (OH) and the stoichiometric (FeOFe) termination.

The band structure and optical absorption of hematite (α-FeO): a first-principles GW-BSE study.

Hematite (α-Fe2O3) is a widely investigated photocatalyst material for the oxygen evolution reaction, a key step in photoelectrochemical water splitting. Having a suitable band gap for light absorption, being chemically stable and based on earth abundant elements, hematite is a promising candidate for the fabrication of devices able to split water using sunlight. What limits its performance is the high rate of bulk recombination following the optical excitation, so that few charge carriers are able to reach the surface to perform the redox reactions.

Are multiple oxygen species selective in ethylene epoxidation on silver?

The nature of the oxygen species active in ethylene epoxidation is a long-standing question. While the structure of the oxygen species that participates in total oxidation (nucleophilic oxygen) is known the atomic structure of the selective species (electrophilic oxygen) is still debated. Here, we use both and UHV X-ray Photoelectron Spectroscopy (XPS) to study the interaction of oxygen with a silver surface.

observation of reactive oxygen species forming on oxygen-evolving iridium surfaces.

Water splitting performed in acidic media relies on the exceptional performance of iridium-based materials to catalyze the oxygen evolution reaction (OER). In the present work, we use X-ray photoemission and absorption spectroscopy to resolve the long-standing debate about surface species present in iridium-based catalysts during the OER. We find that the surface of an initially metallic iridium model electrode converts into a mixed-valent, conductive iridium oxide matrix during the OER, which contains O and electrophilic O species.

Reactive oxygen species in iridium-based OER catalysts.

Tremendous effort has been devoted towards elucidating the fundamental reasons for the higher activity of hydrated amorphous Ir oxyhydroxides (IrO ) in the oxygen evolution reaction (OER) in comparison with their crystalline counterpart, rutile-type IrO, by focusing on the metal oxidation state. Here we demonstrate that, through an analogy to photosystem II, the nature of this reactive species is not solely a property of the metal but is intimately tied to the electronic structure of oxygen. We use a combination of synchrotron-based X-ray photoemission and absorption spectroscopies, calculations, and microcalorimetry to show that holes in the O 2p states in amorphous IrO give rise to a weakly bound oxygen that is extremely susceptible to nucleophilic attack, reacting stoichiometrically with CO already at room temperature.

Thermodynamic and spectroscopic properties of oxygen on silver under an oxygen atmosphere.

We report on a combined density functional theory and the experimental study of the O1s binding energies and X-ray Absorption Near Edge Structure (XANES) of a variety of oxygen species on Ag(111) and Ag(110) surfaces. Our theoretical spectra agree with our measured results for known structures, including the p(N× 1) reconstruction of the Ag(110) surface and the p(4 × 4) reconstruction of the Ag(111) surface. Combining the O1s binding energy and XANES spectra yields unique spectroscopic fingerprints, allowing us to show that unreconstructed atomic oxygen is likely not present on either surface under equilibrium conditions at oxygen chemical potentials typical for ethylene epoxidation.

Rigid- and polarizable-ion potentials for modeling Ru-polyoxometalate catalysts for water oxidation.

This work assesses the predictive power and capabilities of classical interatomic potentials for describing the atomistic structure of a fully inorganic water-oxidation catalyst in the gas phase and in solution. We address a Ru-polyoxometalate molecule (Ru-POM) that is presently one of the most promising catalysts for water oxidation due to its efficiency and stability under reaction conditions. The Ru-POM molecule is modeled with two interatomic potentials, the rigid ion model and the shell model potentials, which are used to perform molecular dynamics simulations.

Adsorbate induced vacancy formation on silver surfaces.

The energy required to form and remove vacancies on metal surfaces mediates the rate of mass transport during a wide range of processes. These energies are known to be sensitive to environmental conditions. Here, we use electronic structure density functional theory calculations to show that the surface vacancy formation energy of silver changes markedly in the presence of adsorbed and dissolved oxygen.

Photo-driven oxidation of water on α-Fe2O3 surfaces: an ab initio study.

Adopting the theoretical scheme developed by the Nørskov group [see, for example, Nørskov et al., J. Phys.

Interface structure and reactivity of water-oxidation Ru-polyoxometalate catalysts on functionalized graphene electrodes.

We combine classical empirical potentials and density functional theory (DFT) calculations to characterize the catalyst/electrode interface of a promising device for artificial photosynthesis. This system consists of inorganic Ru-polyoxometalate (Ru-POM) molecules that are supported by a graphitic substrate functionalized with organic dendrimers. The experimental atomic-scale characterization of the active interface under working conditions is hampered by the complexity of its structure, composition, as well as by the presence of the electrolyte or solvent.

Energetics of Water Oxidation Catalyzed by Cobalt Oxide Nanoparticles: Assessing the Accuracy of DFT and DFT+U Approaches against Coupled Cluster Methods.

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.

Ag-Cu catalysts for ethylene epoxidation: selectivity and activity descriptors.

Ag-Cu alloy catalysts for ethylene epoxidation have been shown to yield higher selectivity towards ethylene oxide compared to pure Ag, the unique catalyst employed in the industrial process. Previous studies showed that under oxidizing conditions Cu forms oxide layers on top of Ag. Using first-principles atomistic simulations based on density functional theory, we investigate the reaction mechanism on the thin oxide layer structures and establish the reasons for the improved selectivity.

Water oxidation surface mechanisms replicated by a totally inorganic tetraruthenium-oxo molecular complex.

Solar-to-fuel energy conversion relies on the invention of efficient catalysts enabling water oxidation through low-energy pathways. Our aerobic life is based on this strategy, mastered by the natural Photosystem II enzyme, using a tetranuclear Mn-oxo complex as oxygen evolving center. Within artificial devices, water can be oxidized efficiently on tailored metal-oxide surfaces such as RuO2.

Atomistic structure of cobalt-phosphate nanoparticles for catalytic water oxidation.

Solar-driven water splitting is a key photochemical reaction that underpins the feasible and sustainable production of solar fuels. An amorphous cobalt-phosphate catalyst (Co-Pi) based on earth-abundant elements has been recently reported to efficiently promote water oxidation to protons and dioxygen, a main bottleneck for the overall process. The structure of this material remains largely unknown.

A first principles study of water oxidation catalyzed by a tetraruthenium-oxo core embedded in polyoxometalate ligands.

We present a computational study addressing the catalytic cycle of a recently-synthesized all-inorganic homogeneous catalyst capable to promote water oxidation with low overpotential and high turnover frequency [Sartorel et al., J. Am.

Alloy catalyst in a reactive environment: the example of ag-cu particles for ethylene epoxidation.

Combining first-principles calculations and in situ photoelectron spectroscopy, we show how the composition and structure of the surface of an alloy catalyst is affected by the temperature and pressure of the reagents. The Ag-Cu alloy, recently proposed as an improved catalyst for ethylene epoxidation, forms a thin Cu-O surface oxide, while a Ag-Cu surface alloy is found not to be stable. Several possible surface structures are identified, among which the catalyst surface is likely to dynamically evolve under reaction conditions.