Density functional calculations on the hydrogenation of carbon dioxide on Fe(111) and W(111) surfaces

With quantum-chemical calculations, we investigated the hydrogenation of a CO₂ molecule on Fe(111) and W(111) surfaces using the density functional theory (DFT) with the projector-augmented wave (PAW) approach in periodic boundary condition. The structures and geometric parameters of the hydrogenation products, and the potential-energy surfaces, were calculated. It was shown that similar reaction paths for the hydrogenation of CO₂ on Fe(111) and W(111) surfaces were found but with disparate energies. The rate-controlling energy barriers from M-CO₂ (M ) Fe, W) plus H atom to form formate (HCOO) and carboxyl (COOH) on a Fe(111) surface are 0.37 and 1.69 eV, respectively, but 0.54 and 2.79 eV, respectively, on a W(111) surface. The most probable path for the hydrogenation of a CO₂ molecule on either the Fe(111) or W(111) surface is the formation of a formate-vertical structure. To understand the interaction between adsorbates and surfaces, we calculated the Bader charges and analyzed the local densities of states.