Surface structure and energetics of oxygen and CO adsorption on α-Mo2C(0 0 0 1)

Adsorption of oxygen and CO on Mo- and C-terminated α-Mo2C(0 0 0 1) has been investigated at the density functional level of theory. On the Mo-terminated surface, the most stable adsorption configuration (1) has atomic oxygen capping the threefold Mo hollow position over a second layer carbon atom (VC, C vacancy site). On the C-terminated surface, the most stable adsorption configuration (8) has atomic oxygen capping the threefold Mo hollow site over a first layer carbon atom (HC, C hollow site). For CO adsorption, the most stable configuration (17) has CO capping structure over carbon vacancy (VC) on the Mo-terminated surface, but atop of the surface carbon with the formation of ketenylidene (CCO) species on the C-terminated surface (21). Analysis of density of states reveals the metallic character of the clean and oxygen doped surfaces and the activation of the surfaces by oxygen adsorption.