Cu–Ga Interactions and Support Effects in CO₂ Hydrogenation to Methanol Catalyzed by Size-Controlled CuGa Nanoparticles Deposited on SiO₂ and ZnO

Growing environmental concerns have led to a need for the reduction of CO₂ emissions and the search for alternative fuels. The synthesis of methanol via the CO₂ hydrogenation reaction provides a promising approach for these tasks. Promoting the existing Cu-based catalysts with Ga might be an option to create more effective catalysts. Here, size-controlled bimetallic CuGa nanoparticles (NPs) supported on either SiO₂ or ZnO were synthesized to study the nature of the interaction of Cu and Ga. Operando spectroscopy and diffraction characterization methods (XPS, XAS, XRD) were employed to establish structure, chemical composition, and reactivity correlations. We find that Ga stays oxidized under the reaction conditions and segregates to the surface. For the CuGa NPs/ZnO, the dominating interaction of Cu with ZnO inhibits the promoting effect of Ga. Only on the inert SiO₂ support, the beneficial influence of Ga is visible. Furthermore, high pretreatment temperatures were found to result in a favorable Cu-Ga interaction by partially reducing Ga, which is beneficial for methanol selectivity.