Surface Hydroxyl-Mediated Stabilization of Cu⁺ Species in Ga-Doped Cu₂O Catalysts for Sustained CO₂ Electroreduction to Ethylene

The presence of surface hydroxyl (*OH) species plays a critical role in modulating the selectivity and stability of Cu₂O catalysts during CO₂ electroreduction to ethylene and ethanol. However, the underlying mechanism by which *OH adsorption contributes to Cu₂O stability remains poorly understood. In this study, we report the development of a Ga-doped Cu₂O (Ga-Cu₂O) catalyst, where Ga promotes the adsorption of *OH species on the catalyst surface. This enhanced *OH adsorption strengthens Cu-O interactions and improves the stability of Cu⁺ species. In situ Raman spectroscopy and theoretical calculations reveal that Ga incorporation facilitates *OH formation, which in turn increases orbital overlap between Cu 3d and O 2p orbitals. This interaction suppresses lattice oxygen leaching and contributes to the stabilization of Cu⁺. As a result, Ga-Cu₂O exhibits a stable ethylene production rate sustained for over 50 h, achieving a Faradaic efficiency (FE) for C₂H₄ of 26.4%, which is 1.4 times higher than that of pure Cu₂O. These findings offer mechanistic insights into the role of the catalyst microenvironment in Cu⁺ stabilization during CO₂RR and provide valuable guidance for the rational design of more efficient and durable CO₂ reduction catalysts.