On the Role of Bulk Hydrogen in Carbon Dioxide Hydrogenation On Ni(111) and Ni(110) Surfaces

It has been shown experimentally that hydrogen in catalytic transition-metals (subsurface H) exhibits unique reactivity in the heterogeneous catalytic hydrogenation of hydrocarbons such as ethylene and acetylene. By using periodic self-consistent density functional theory calculations, we study the role of subsurface H in carbon dioxide (CO₂) hydrogenation on Ni(111) and Ni(110) model surfaces. CO₂ hydrogenation to useful chemicals such as formic acid by surface H in the absence or presence of subsurface H will be contrasted with reactive paths involving a more direct hydrogenation role for the latter. Insights derived could be of importance to the atomic-level understanding of the role of bulk species in heterogeneously catalyzed reactions.