Size Effect of Cu Particles on Interface Formation in Cu/ZnO Catalysts for Methanol Synthesis

Abstract

Cu/ZnO/Al2O3 catalysts are extensively utilized in methanol synthesis from CO and CO2, which is a vital industrial process and a promising strategy for mitigating CO2 emissions when renewable green hydrogen is employed. Despite the considerable efforts to study CO2 hydrogenation over Cu/ZnO, understanding the structure of active sites on Cu/ZnO has remained a major challenge. We studied a series of Cu/ZnO catalysts with various Cu particle sizes and found a volcano-like pattern in methanol selectivity with respect to the Cu particle size. TEM, XPS, and TPD measurements demonstrated the migration of ZnOx species onto the Cu particle surface and showed a correlation between the ZnOx-Cu interface and methanol yield. The size of supported Cu particles affects the migration of Zn species onto Cu particle surfaces. Our study has thus explicated the role of the ZnOx-Cu interface in catalyzing CO2 hydrogenation to methanol.