Hydrogenation of CO2 to CH3OH on the Cu–ZnO–SrTiO3 Catalysts: The Electronic Metal–Support Interaction Induces Oxygen Vacancy Generation

Abstract

With the massive burning of fossil energy sources, the greenhouse effect is increasingly significant, and the reduction of the CO₂ concentration in the atmosphere is imminent. In this work, Cu–ZnO–SrTiO₃ catalysts with different Cu–Zn loadings and Cu/Zn atomic ratios were prepared by the deposition–coprecipitation method using n-type semiconductor SrTiO₃ with a perovskite structure as a support for the CO₂ hydrogenation to methanol process. In situ XPS, in situ CO–DRIFTS, electron paramagnetic resonance (EPR), and UV confirmed that electron transfer from the supports to Cu is the intrinsic nature of the electronic metal–support interaction between Cu and the supports, resulting in oxygen vacancy generation. Electron transfer is attributed to the difference in the Fermi energy levels of the metal and the supports, which in turn form Schottky–Mott junctions. EPR, CO₂-TPD, and catalytic activity illustrated that oxygen vacancies (O_v) in the supports (SrTiO₃ and ZnO) enhance the activation of CO₂. H₂-TPD demonstrated that Cu^δ− species in contact with the supports facilitate hydrogen spillover. Cu^δ−–O_v at the interface may be the active sites of catalysts. In addition, in situ XRD verified that the larger the electron transfer, the smaller the corresponding Cu particle diameter.