Influence of oxygen vacancies of CeO2 on reverse water gas shift reaction

Catalytic CO2 hydrogenation on metal oxides is attractive to realize carbon neutrality initiatives. Understanding roles of oxygen vacancies of oxide-based catalysts is critical for the catalytic mechanism of CO2 hydrogenation. Herein, we used CO2 hydrogenation as model reaction on CeO2 to investigate the effects of oxygen vacancies and provided direct spectroscopic evidence for redox mechanism via in-situ DRIFTS and isotope switch experiments. A volcano-type activity curve was found for CO2 hydrogenation to CO on CeO2 upon the continuous variation of the surface defect concentration of oxygen vacancy. Kinetic analysis and ex-situ techniques indicate that surface oxygen contributes to H2 activation and oxygen vacancy accelerates the dissociation of CO2, emphasizing the unique roles of surface oxygen and oxygen vacancies, respectively. These results enrich the understanding of surface defect chemistry of CeO2 and lay an important theory foundation for design of oxide-based catalysts for hydrogenation.