Component-Specific Functions of Cu, Zn, and Zr in Inverse ZnZrOx/Cu Catalysts for CO2 Hydrogenation to Methanol.

Cu-based ternary catalysts often outperform their binary counterparts in the hydrogenation of CO2 to methanol. Unraveling the underlying synergistic effects among multiple components remains challenging and requires comprehensive operando characterization. In this study, we present a detailed investigation into the synergistic Cu-Zn-Zr interactions in inverse ZnZrOx/Cu catalysts, which show strong promise for enhancing the synthesis of methanol from CO2. In situ X-ray diffraction revealed that ZrO2 clusters effectively stabilize Cu nanoparticles against sintering during the H2 reduction. Operando X-ray absorption spectroscopy at the Cu, Zn, and Zr K-edges demonstrated that the enhanced reducibility of Zn and Zr species arises from synergistic Cu-Zn-Zr interactions. Upon H2 reduction, partially reduced ZrO2 facilitated CO2 adsorption and activation. Initially dispersed Zn2+ species were partially transformed into the CuZn alloy, which remained stable under reaction conditions. Notably, the CuZn alloy significantly enhanced the hydrogenation of key formate reaction intermediates to methanol. Moreover, Zn incorporation in Cu inhibited methanol decomposition to CO. The combined effects of efficient H2 activation on highly dispersed metallic Cu, enhanced CO2 activation by reduced ZrO2 clusters, and rapid formate hydrogenation facilitated by the CuZn alloy rendered inverse ZnZrOx/Cu catalysts superior in methanol formation rates as compared to inverse ZnOx/Cu, ZrOx/Cu catalysts, a commercial CuZnAl catalyst, and previously reported CuZnZr catalysts.