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

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 (Ov) in the supports (SrTiO3 and ZnO) enhance the activation of CO2. H2-TPD demonstrated that Cuδ− species in contact with the supports facilitate hydrogen spillover. Cuδ−–Ov 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.