Component-Specific Functions of Cu, Zn, and Zr in Inverse ZnZrO <sub> <i>x</i> </sub> /Cu Catalysts for CO <sub>2</sub> Hydrogenation to Methanol
Yu Gao, Erfan Shahroudi, Stefan Bouts, Yonghui Fan, Yin LI, Peeranat Chaipornchalerm, Junbu Wang, Konstantin Klementiev, Nikolay Kosinov, Emiel J. M. Hensen
Abstract
Cu-based ternary catalysts often outperform their binary counterparts in the hydrogenation of CO 2 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 ZnZrO x /Cu catalysts, which show strong promise for enhancing the synthesis of methanol from CO 2 . In situ X-ray diffraction revealed that ZrO 2 clusters effectively stabilize Cu nanoparticles against sintering during the H 2 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 H 2 reduction, partially reduced ZrO 2 facilitated CO 2 adsorption and activation. Initially dispersed Zn 2+ 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 H 2 activation on highly dispersed metallic Cu, enhanced CO 2 activation by reduced ZrO 2 clusters, and rapid formate hydrogenation facilitated by the CuZn alloy rendered inverse ZnZrO x /Cu catalysts superior in methanol formation rates as compared to inverse ZnO x /Cu, ZrO x /Cu catalysts, a commercial CuZnAl catalyst, and previously reported CuZnZr catalysts.