Understanding the Synergistic Catalysis in Hydrogenation of Carbonyl Groups on Cu-Based Catalysts
Qing‐Nan Wang, Ruizhi Duan, Zhendong Feng, Ying Zhang, Peng Luan, Zhaochi Feng, Jijie Wang, Can Li
Abstract
Understanding the synergy of Cu 0 and Cu + in hydrogenation reactions is indispensable for reasonably modulating the product distributions and improving the catalyst design. Herein, we investigated the hydrogenation of dimethyl oxalate on CeZrO x -supported Cu with varying molar ratios of n Cu + / n Cu 0 . A volcano-type correlation of structure and activity indicates that the selectivity of ethylene glycol is strongly dependent on the n Cu + / n Cu 0 ratio, arising from the matching of rates for the activation of carbonyl group-included reactants and H 2 on Cu + and Cu 0, respectively. The maximal selectivity toward ethylene glycol is achieved at a ratio of 0.15; deviating from this value leads to the favorable formation of methyl glycolate, a primary product. Results obtained from temperature-programmed surface reactions indicate that the presence of Cu + and oxygen vacancies (O V ) reduces the reaction temperature for the hydrogenation of carbonyl groups. Theoretical data show that the O V located at the copper–ceria interface induces a downward-directed adsorption configuration of the reaction intermediate adsorbed at the Cu + site, compared to the presence of an upward-directed counterpart at the Cu 0 –Cu + center. This change leads to a reduction in the kinetic barrier for the subsequent hydrogenation step, which consumes active *H species transferred from adjacent Cu 0 via a hydrogen spillover process. Manipulating the Cu valence state and oxygen vacancies via interfacial engineering offers a viable strategy for governing product distributions, serving as an inspiration for the design of selective hydrogenation catalysts.