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⋅g_cat⁻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.

CO₂ hydrogenation to methanol has attracted considerable attention as a promising catalytic route for both reducing CO₂ emissions and producing valuable chemical intermediates. Among various catalysts, Cu–ZnO-based systems are the most widely studied; however, their performance remains constrained by limited methanol selectivity and stability, highlighting the need for improved catalytic strategies. In this work, liquid metal gallium (Ga) was incorporated into Cu–ZnO catalysts as an additive for CO₂ hydrogenation to methanol. Owing to its high dispersibility and fluidity, Ga helps maintain long-term catalyst stability. We investigated different introduction methods for Ga promoters and found that the physical mixing approach generated the strongest alkaline sites, thereby enhancing CO₂ activation and increasing the CO₂ conversion to methanol. Moreover, this catalyst effectively suppressed carbon deposition, further improving its stability. These findings offer new insights into the use of liquid metal Ga in CO₂ hydrogenation and provide fresh perspectives for the rational design of efficient methanol synthesis catalysts.