Dual-Mechanism Regulation in Photocatalytic CO₂ Reduction through Er Single-Atom Engineering: Enhancing Charge Dynamics and Molecular Activation

Photocatalytic CO2 reduction represents a promising strategy for solar-to-fuel conversion; however, challenges remain in optimizing active sites and charge carrier dynamics. In this work, we successfully constructed a rare-earth-based atomic engineering strategy to form erbium (Er) single atoms anchored on oxygen-deficient BiVO4 through hydrothermal synthesis and controlled calcination. The unique 4f electronic configuration and high coordination flexibility of the rare earth atoms optimized the band structure of the catalyst, facilitating the efficient separation and transfer of photogenerated charge carriers. Simultaneously, the atomically dispersed active sites activated the CO2 molecules via strong orbital hybridization, lowering the energy barrier for *COOH intermediate formation and enhancing CO selectivity. Density functional theory calculations and in situ characterization analysis indicated that the Er single atoms modulated local charge distribution, accelerating electron transfer to the adsorbed CO2 while stabilizing key intermediates. The optimized catalyst achieved a CO yield rate of 496.23 μmol·g–1·h–1 with 99% selectivity, representing an 11.2-fold enhancement over pristine BiVO4. This study elucidated the critical role of rare-earth single-atom sites in directing charge kinetics and molecular activation pathways, offering atomic-level insights for designing high-performance photocatalytic systems for carbon neutrality applications.