First-principles study of CO₂ hydrogenation on Cd-doped ZrO₂: Insights into the heterolytic dissociation of H₂

Cd-doped ZrO2 catalyst has been found to have high selectivity and activity for CO2 hydrogenation to methanol. In this work, density functional theory calculations were carried out to investigate the microscopic mechanism of the reaction. The results show that Cd doping effectively promotes the generation of oxygen vacancies, which significantly activate the CO2 with stable adsorption configurations. Compared with CO2, gaseous H-2 adsorption is more difficult, and it is mainly dissociated and adsorbed on the surface as [H-Cd-H-O]* or [H-Zr-H-O]* compact ion pairs, with [H-Cd-H-O]* having the lower energy barrier. The reaction pathways of CO2 to methanol has been investigated, revealing the formate path as the dominated pathway via HCOO* to H2COO* and to H3CO*. The hydrogen anions, H-Cd* and H-Zr*, significantly reduce the energy barriers of the reaction.