Effects of alloying on mode-selectivity in H2O dissociation on Cu/Ni bimetallic surfaces.

The influence of alloying on mode-selectivity in H2O dissociation on Cu/Ni bimetallic surfaces has been studied using a fully quantum approach based on reaction path Hamiltonian. Both the metal alloy catalyst surface and the normal modes of H2O impact the chemical reactivity of H2O dissociation. A combination of these two different factors will enhance their influence reasonably. Among all the bimetallic surfaces, one monolayer (Ni4_Cu(111)) and 12 monolayer of Ni on Cu surface (Ni2_Cu(111)) show lowest barrier to the dissociation. Excitation of bending mode and symmetric stretching mode enhances the reactivity remarkably due to a significant decrease in their frequencies near the transition state in the vibrational adiabatic approximation. In the presence of non-adiabatic coupling between the modes, asymmetric stretching also shows similar enhancement in reactivity to that of symmetric stretching for all the systems. Inclusion of lattice motion using a sudden model enhances the dissociation probability at surface temperature 300 K and at lower incident energy, compared to that of the static surface approximation. The mode selective behaviour of H2O molecules is almost similar on all the Cu- and Ni-based surfaces. The excitation of symmetric stretching vibration by one quantum is shown to have largest efficacy for promoting reactions for all the systems. Overall, the dissociation probabilities for all the systems are enhanced by vibrational excitation of normal modes and become more significant with the non-adiabatic coupling effect.