Insights into the Inducing Effect of Aluminum on Cu-ZnO Synergy for Methanol Steam Reforming

Methanol is considered an attractive hydrogen carrier for fuel cells via steam reforming reaction. The industrial Cu/ZnO/Al2O3 catalyst is widely used for its excellent activity in various reactions. The function of aluminum was deemed to be indispensable for catalytic activity and stability. However, the promotion mechanism of aluminum on the Cu/ZnO catalyst for methanol steam reforming reaction remains ambiguous. Herein, a series of aluminum-modified Cu/ZnO-xAl and Cu/ZnO + xAl catalysts with various loadings were fabricated. Systematic characterizations (e.g., XRD, TEM, H2-TPR, CO2-N2O titration, CO2-TPD, and XPS) prove that incorporation of Al3+ ions into the ZnO lattice remarkably boosts the activity and stability due to enhanced Cu-ZnO synergy. The properties and chemical environment of Cu NPs were comprehensively investigated, and the Cu surface areas, oxygen vacancies, and ZnOx sites were quantitatively measured. The correlation between turnover frequency and catalyst structure proves that the aluminum-induced Zn delta+ or ZnOx sites at the interface between Cu and ZnO play a dominant role in enhancing catalytic performance. This insight into Cu-ZnO synergy induced by aluminum may contribute to the design of high-performance catalysts in the future.