H2 Dissociation on H Precovered Ni(111) Surfaces: Coverage Dependence, Lattice Motion, and Arrangement Effects

Abstract

Hydrogen molecule dissociation on metal surfaces is a prototype reaction to study the gas–surface interaction. The dissociation rate constants of H2 on H atom precovered Ni(111) surfaces are calculated using the quantum instanton method in full dimensionality. Four different arrangements of the preadsorbed H and the dissociated H2, in which the preadsorbed H is located at the nearest (H2/H1–Ni(111)), second-nearest (H2/H2–Ni(111)), third-nearest (H2/H3–Ni(111)), and fourth-nearest (H2/H4–Ni(111)) neighbor sites of the bridge site where the H2 is dissociated, are considered. Compared to the dissociation rates of H2 on a clean Ni(111) surface (H2/Ni(111)), the dissociation rates of H2/H1–Ni(111) are much smaller. For instance, the former is 5.22 times larger than the latter at 300 K. This is because there is a strong repulsive interaction between the preadsorbed H and H2, which hinders the dissociation of H2. The dissociation rates of the four arrangements increase in the order of H2/H1–Ni(111), H2/H2–Ni(11...