Metal-oxide interfaces and oxygen vacancies as dominant active sites in CO2 hydrogenation to methanol: Contrasting reactivity of Cu- and In-based functionalities

In this research work CuO-ZnO-ZrO₂ and In₂O₃-ZnO-ZrO₂ are used as benchmark systems to unravel the nature of active sites during CO₂ hydrogenation to methanol, as driven by metal-oxide interfaces and oxygen vacancies respectively. A combination of structural and surface techniques is applied to systematically correlate methanol formation rates with either interfacial site density or oxygen vacancy concentration. On the Cu-based catalyst the methanol rate appears as a direct function of the Cu–oxide interfacial area, with H₂ activation and spillover confirmed as essential steps by temperature programmed measurements. On the other hand, the methanol productivity on the In-based catalyst directly scales with vacancy density, with formate intermediates identified as bound exclusively to oxide sites by operando DRIFTS. These results establish clear structure–activity relationships for interface-driven and oxide-driven pathways, providing a framework for the rational design of next-generation CO₂-to-methanol catalysts.