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Noble metals supported on reducible oxides, like CoO_xand TiO_x, exhibit superior activity in many chemical reactions, but the origin of the increased activity is not well understood. To answer this question we studied thin films of CoO_xsupported on an Au(111) single crystal surface as a model for the CO oxidation reaction. We show that three reaction regimes exist in response to chemical and topographic restructuring of the CoO_xcatalyst as a function of reactant gas phase CO/O₂stoichiometry and temperature. Under oxygen-lean conditions and moderate temperatures (≤150 °C), partially oxidized films (CoO_x<1) containing Co⁰were found to be efficient catalysts. In contrast, stoichiometric CoO films containing only Co²⁺form carbonates in the presence of CO that poison the reaction below 300 °C. Under oxygen-rich conditions a more oxidized catalyst phase (CoO_x>1) forms containing Co³⁺species that are effective in a wide temperature range. Resonant photoemission spectroscopy (ResPES) revealed the unique role of Co³⁺sites in catalyzing the CO oxidation. Density function theory (DFT) calculations provided deeper insights into the pathway and free energy barriers for the reactions on these oxide phases. These findings in this work highlight the versatility of catalysts and their evolution to form different active phases, both topological and chemically, in response to reaction conditions exposing a new paradigm in the catalyst structure during operation.

 

Step and kink sites at Pt surfaces have crucial importance in catalysis. We employ a high dimensional neural network potential (HDNNP) trained using first-principles calculations to determine the adsorption structure of CO under ambient conditions ( T = 300 K and P = 1 atm) on these surfaces. To thoroughly explore the potential energy surface (PES), we use a modified basin hopping method. We utilize the explored PES to identify the adsorbate structures and show that under the considered conditions several low free energy structures exist. Under the considered temperature and pressure conditions, the step edge (or kink) is totally occupied by on-top CO molecules. We show that the step structure and the structure of CO molecules on the step dictate the arrangement of CO molecules on the lower terrace. On surfaces with (111) steps, like Pt(553), CO forms quasi-hexagonal structures on the terrace with the top site preferred, with on average two top site CO for one multiply bonded CO, while in contrast surfaces with (100) steps, like Pt(557), present a majority of multiply bonded CO on their terrace. Short terraced surfaces, like Pt(643), with square (100) steps that are broken by kink sites constrain the CO arrangement parallel to the step edge. Overall, this effort provides detailed analysis on the influence of the step edge structure, kink sites, and terrace width on the organization of CO molecules on non-reconstructed stepped surfaces, yielding initial structures for understanding restructuring events driven by CO at high coverages and ambient pressure. 

Copper (Cu) remains the most important metal catalyst for the carbon dioxide reduction reaction (CO₂RR) into C₂products. Due to limited evidence from in situ experiments, mechanistic studies are often performed in the framework of density functional theory (DFT), using functionals at the generalized gradient approximation (GGA) level, which have fundamental difficulties to correctly describe CO adsorption and surface stability. We employ the adiabatic connection fluctuation dissipation theorem within the random phase approximation (RPA), in combination with the linearized Poisson–Boltzmann equation to describe solvation effects, to investigate the mechanism of CO₂RR on the Cu(100) facet. Qualitatively different from the DFT‐GGA results, RPA results propose the formation of *OCCHO as the potential determining step towards C₂products. The results suggest that it is important to use more accurate methods like RPA when modeling reactions involving multiple CO‐related species like CO₂RR.

 

Copper (Cu) remains the most important metal catalyst for the carbon dioxide reduction reaction (CO₂RR) into C₂products. Due to limited evidence from in situ experiments, mechanistic studies are often performed in the framework of density functional theory (DFT), using functionals at the generalized gradient approximation (GGA) level, which have fundamental difficulties to correctly describe CO adsorption and surface stability. We employ the adiabatic connection fluctuation dissipation theorem within the random phase approximation (RPA), in combination with the linearized Poisson–Boltzmann equation to describe solvation effects, to investigate the mechanism of CO₂RR on the Cu(100) facet. Qualitatively different from the DFT‐GGA results, RPA results propose the formation of *OCCHO as the potential determining step towards C₂products. The results suggest that it is important to use more accurate methods like RPA when modeling reactions involving multiple CO‐related species like CO₂RR.