Adsorption, Dissociation, and Hydrogenation of CO2 on WC(0001) and WC-Co Alloy Surfaces Investigated with Theoretical Calculations

We applied periodic density functional theory to investigate the adsorption of CO2 on WC(0001) and various WC-Co alloy surfaces and discuss the reaction trend of dissociation of CO2 and hydrogenation on these surfaces. We employed an electron localization function (ELF) to investigate the effect of electron localization or delocalization on various WC-Co alloy surfaces with a varied Co coverage; the partial-delocalization surfaces (WC-Co (0.25 ML) surface) exhibit the largest energy of adsorption of CO2 (-1.61 eV) on all calculated surfaces. When we increased the Co ratio to form a WC-2Co (0.50 ML) surface, the activation energy for the dissociation CO2 -> CO+O decreased to 0.57 eV. The energy of CO2 hydrogenation to form formate (CO2+H -> HCOO) decreases with Co coverage due to increased electron delocalization.