Facilitation of CO2 Hydrogenation to Methanol by Spinel ZnGa2O4 in Cu-ZnO Catalysts

The hydrogenation of CO2 to methanol is an effective approach for utilizing carbon resources. Cu-ZnO-based catalysts have attracted significant attention due to their ability to activate CO2; however, improving methanol selectivity remains a challenge. In this study, the incorporation of an appropriate amount of Ga into Cu-ZnO catalysts, resulting in the formation of spinel ZnGa2O4 crystals, significantly enhances the conversion of CO2 to methanol. Ternary CuZnGa composite oxides with varying Ga contents were synthesized, and their effects on CO2 hydrogenation were investigated. The optimal Cu6Zn3Ga1 catalyst achieved a CO2 conversion rate of 13% and a methanol selectivity of 59% under reaction conditions of 240 °C, 4 MPa, and a GHSV of 7500 mL⋅gcat−1⋅h−1. In contrast, the undoped Cu6Zn4 catalyst exhibited a lower CO2 conversion of 9.8% and a methanol selectivity of 38%. Characterization results indicate that the introduction of Ga promotes the formation of oxygen vacancies, enhances CO2 activation, and facilitates electronic interactions between spinel ZnGa2O4 and Cu sites, thereby improving methanol production. Furthermore, the spinel ZnGa2O4-modified Cu catalyst demonstrated excellent stability over 90 h of continuous operation. This study presents a novel approach to designing spinel ZnGa2O4-modified Cu-ZnO-based catalysts and offers a new strategy for enhancing CO2 hydrogenation to methanol.