Enhancing photocatalytic CO2 reduction via S-scheme heterojunctions with tuned band structure and enhanced built-in electric field

Inhibiting photogenerated electron-hole recombination to enhance interfacial electron transfer is crucial for improving photocatalytic CO₂ reduction. Three heterojunction photocatalysts (SiW 11 Co@TiO 2 , SiW 11 Ni@TiO 2 and SiW 11 Cu@TiO 2 ) were prepared via solvothermal self-assembly. Through UV–vis–DRS, Mott-Schottky analysis and radical trapping experiments, we determined that SiW 11 Co@TiO 2 forms a type-I heterojunction while SiW 11 Ni@TiO 2 and SiW 11 Cu@TiO 2 form S-scheme heterojunctions with superior catalytic activity. UPS analysis revealed that the work function difference between SiW 11 Cu and TiO 2 (1.30 eV) exceeds that of SiW 11 Ni and TiO 2 (1.08 eV), correlating with enhanced EPR signals and faster interfacial electron transfer for SiW 11 Cu@TiO 2 . SiW 11 Cu@TiO 2 achieved optimal CO 2 reduction performance with CO and CH 4 yields of 84.12 and 12.32 μmol·g −1 ·h −1 , respectively, representing 1.38 times higher electron yield than SiW 11 Ni@TiO 2 . This work demonstrates that modulating energy band positions to construct S-scheme heterojunctions with enhanced built-in electric fields provides an effective strategy for designing high-performance CO₂ photocatalysts.