Hydrogen assisted oxygen desorption from the V₂O₅(010) surface

Abstract

Vanadium oxide surfaces are well known to play an active role as catalysts in hydrocarbon oxidation reactions where oxygen from different surface sites participates in the reaction. Due to the ubiquity of hydrogen in these systems, reaction steps involving (temporary) hydrogenation are possible and may influence the overall reaction scheme. This work examines structural and energetic consequences of hydrogen interacting with different oxygen sites at the V₂O₅(010) surface where the local surface environment is modeled by embedded clusters. The electronic structure and equilibrium geometries of the clusters are obtained by density functional theory (DFT) using gradient corrected functionals (RPBE) for exchange and correlation. Hydrogen is found to stabilize preferentially near oxygen sites forming surface OH and H₂O species with binding energies of 0.5–2.3 eV per H atom depending on the site and species. Hydrogen adsorption weakens the binding of the surface oxygen with its vanadium neighbors considerably where the weakening is larger for H₂O than for OH formation as evidenced by bond order analyses and results of the binding energetics. Thus, the studies suggest strongly that the presence of hydrogen at the oxide surface facilitates oxygen removal and, therefore, contributes to the enhanced yield of oxygenated products near vanadia based surfaces.