Engineering Cu+/CeZrOx interfaces to promote CO2 hydrogenation to methanol

Abstract

Cu-based catalysts are widely employed for CO2 hydrogenation to methanol, which is expected as a promising process to achieving carbon neutrality. However, most Cu-based catalysts still suffer from low methanol yield with a passable CO2 conversion and lack insight into its reaction mechanism for guiding the design of catalysts. In this work, Cu+/CeZrOx interfaces are engineered by employing a series of ceria-zirconia solid solution catalysts with various Ce/Zr ratios, forming a Cu+-Ov-Ce3+ structure where Cu+ atoms are bonded to the oxygen vacancies (Ov) of ceria. Compared to Cu/CeO2 and Cu/ZrO2, the optimized catalyst (i.e., Cu0.3Ce0.3Zr0.7) exhibits a much higher mass-specific methanol formation rate (192 gMeOH/kgcat/h) at 240 °C and 3 MPa. Through a series of in-situ and ex-situ characterization, it is revealed that oxygen vacancies in solid solutions can effectively assist the activation of CO2 and tune the electronic state of copper to promote the formation of Cu+/CeZrOx interfaces, which stabilizes the key *CO intermediate, inhibits its desorption and facilitates its further hydrogenation to methanol via the reverse water–gas-shift (RWGS) + CO-Hydro pathway. Therefore, the concentration of *CO or the apparent Cu+/(Cu++Cu0) ratio could be employed as a quantitative descriptor of the methanol formation rate. This work is expected to give a deep insight into the mechanism of metal/support interfaces in CO2 hydrogenation to methanol, offering an effective strategy to develop new catalysts with high performance.