Investigation of Solvent and Stirring-Assisted Morphologically Tuned CuO-ZnO-CeO ₂ Catalyst for CO ₂ Hydrogenation to Methanol

The combustion of fossil fuels and accelerated industrialization are primary sources of excessive carbon dioxide emissions and are major contributors to the greenhouse effect. As a result, converting CO₂ into value-added fuels such as methanol through hydrogenation has emerged as a promising approach for both carbon mitigation and renewable energy production. In this work, CuO/ZnO/CeO₂ catalysts with various morphologies were synthesized by using three distinct methods: solid-state heating (SSH), solvothermal (ST), and stirring-assisted double-solvent hydrothermal (SHT) synthesis protocols. Different analytical techniques, such as XRD, FE-SEM, BET, XPS, and H₂-TPR, were used to extensively characterize the catalysts. Hexagonal rods, nanowires, flakes, rectangular tubes, and bush-like distinct morphologies were observed through SEM analysis. <i>In situ</i> DRIFTS further identified key surface intermediates, including formate, dioxymethylene, and methoxy species, and confirmed that the stabilization of formate and methoxy species is critical for methanol formation. The catalytic performance was then evaluated in a bench-scale fixed-bed flow reactor. Among the synthesized catalysts, the catalyst prepared by the solvothermal method exhibited the highest methanol turnover frequency (TOF_MeOH). Overall, these results demonstrate that the synthesis method not only governs the morphology, dispersion, and specific surface area of Cu but also influences the catalytic efficiency for the hydrogenation of CO₂ to methanol.