Decomposition of H ₂ O on clean and oxygen-covered Au (1 0 0) surface: A DFT study

Employing density functional theory (DFT) together with periodic slab models, the adsorption and dehydrogenation of H ₂ O on clean and oxygen-covered Au (1 0 0) have been investigated systematically. On the basis of the theoretical analysis, the favorable adsorption sites and stable configurations of all species were clarified. H ₂ O was predicted to adsorb weakly on the top, bridge, hollow sites, with the top site preferred. Whereas OH and atomic O prefer to adsorb on the hollow site and H occupies the bridge site. What's more, this work displayed the optimum configurations for the relevant co-adsorption groups. The results elucidated that co-adsorption is apt to impair the interaction of adsorbate-substrate due to the joining of oxygen atom except for H ₂ O molecule. Eventually, the interrelated transition states and activation energies were calculated to explore the dehydrogenation mechanism of H ₂ O. A feasible mechanism on oxygen pre-covered surfaces for complete dehydrogenation of H ₂ O was also presented. It was illuminated that atomic oxygen could diminish the barrier energy substantially of the first dissociation step and play a pivotal role in the decomposition of H ₂ O molecule.