Quantum dynamics of water dissociation on a Cu/Ni(111) bimetallic alloy surface: A nine-dimensional model

Abstract

The dissociative chemisorption of water on a Cu/Ni(111) bimetallic alloy surface was investigated using a combined neural-network potential energy surface and quantum dynamics approach. A full-dimensional (9D) PES was constructed and validated, enabling efficient seven-dimensional (7D) quantum wave packet calculations. Approximate 9D dissociation probabilities were obtained by site-averaging the 7D, site-specific results. The Cu monolayer is under 3.2% compressive strain, leading to a higher barrier height of 1.20 eV on Cu/Ni(111) than on pure Cu(111) (1.08 eV) and, consequently, to lower dissociation probabilities. The more reactive subsurface Ni atom induces a distinct site reactivity order (hcp > fcc > bridge > top). Strong mode specificity was observed, where vibrational excitations of the symmetric stretching, asymmetric stretching, and bending modes of H2O were found to be more efficacious than increasing the translational energy in promoting the reaction, with the asymmetric stretching mode providing the greatest enhancement and the bending mode the smallest. This mode-specific behavior aligns with earlier findings for water dissociation on pure Cu(111) and Ni(111) surfaces.