Dual-site synergy on Cu/Al2O3-CeO2-Ov: Localized vacancies enable water-assisted hydrogen supply and electron-rich interface promotes methanol synthesis

Water accumulation is a major byproduct of CO 2 hydrogenation to methanol and can deactivate catalysts by competitive adsorption and thermodynamic hindrance. Engineered oxygen vacancies in the catalyst enable the in situ dissociation of accumulated water into surface hydroxyls and reactive hydrogen species, which directly participate in CO 2 hydrogenation. This mitigates deactivation and harnesses the byproduct as an auxiliary hydrogen source, thereby converting a bottleneck into a promoter. This study, based on density functional theory (DFT), investigates the geometric and electronic structures of interfacial and surface oxygen vacancies on the Cu/Al 2 O 3 -CeO 2 -Ov, elucidating the mechanism by which oxygen vacancy geometry and electronic configuration influence CO 2 conversion and H 2 O dissociation. The results show that interfacial oxygen vacancies enable CO 2 hydrogenation to methanol proceeding predominantly via the RWGS + CO* pathway, whereas surface vacancies exhibit localized electronic states that promote spontaneous H 2 O dissociation. The generated H* species then migrate via reverse spillover to Cu clusters, providing an additional hydrogen source for methanol synthesis. Meanwhile, surface oxygen vacancies are regenerated via the CO* + O* → CO 2 * path, sustaining a synergistic catalytic cycle. This work reveals the crucial role of the spatial distribution of oxygen vacancies in determining the differentiation of catalytic functions, providing new insights into the design of bifunctional Cu/Al 2 O 3 -CeO 2 -Ov catalysts.