Influence of Cu doping on surface oxygen vacancy stability and water activation mechanisms on the anatase TiO2 (101) surface

This study utilizes first-principles calculations based on density functional theory (DFT) to systematically investigate the influence of Cu doping on surface oxygen vacancy stability and water activation mechanisms on the anatase TiO 2 (101) surface. Our results demonstrate that Cu substitution is energetically most favorable at the five-coordinated titanium sites. The Cu dopant not only significantly reduces the formation energy of adjacent oxygen vacancies but also reverses the relative stability of subsurface and surface oxygen vacancies. Furthermore, Cu doping effectively eliminates the diffusion barrier for oxygen vacancy migration from the subsurface to the surface layer. Regarding water interactions, the dual-defect site (Cu and surface oxygen vacancy) attenuates water binding affinity and fundamentally shifts the preferred dissociation mechanism from Path I to Path II. Electronic structure analysis reveals that intense Cu 3 d –O 2 p hybridization leads to the bifurcation of states into low-energy bonding states and antibonding states that are pulled toward the Fermi level. The subsequent occupancy of these antibonding states exerts a destabilizing effect that moderates the adsorption strength. This electronic modulation prevents active-site poisoning by facilitating the facile desorption of water-related species, thermodynamically promoting the release of active surface sites for continuous turnover. These findings provide a theoretical foundation for the rational design of doped metal-oxide catalysts with optimized kinetics and cycling stability.