Particle Size-Dependent Charge Transfer Dynamics for Boosting CO₂ Photoreduction over Ag/TiO₂ Heterojunction

Photocatalytic CO₂ reduction (PCO₂R) represents a critical pathway in renewable energy generation. Silver nanoparticles (Ag NPs) of varying sizes were deposited on TiO₂ surfaces, exhibiting size-dependent catalytic activities and selectivities due to distinct charge transfer dynamics. The integration of the particle size and Ag/TiO₂ Schottky junction density supplied ample active sites for CO₂ reduction. Modifying the size of the Ag NPs significantly enhanced the photocatalytic performance of the Ag/TiO₂ heterojunction. Notably, Ag_0.5%/TiO₂ showed a CO generation rate of 86.8 μmol g^-1 h^-1, which was 1.79 times higher than that of anatase. More importantly, Ag_3.0%/TiO₂ resulted in the highest selectivity of CH₄ (28.1%). The particle size of Ag NPs influenced the ratio of thermal electron transfer during photoexcitation and the intermediate product pathways in the CO₂ reduction process. This research provides insights and experimental foundations for particle size regulation in designing heterojunction catalysts for PCO₂R.