CoOx−Ag Dual-Cocatalyst Modification on the Bi4TaO8Cl0.9Br0.1 Photocatalyst for Selective CO2 Reduction in a Visible-Light-Driven Z-Scheme System Coupled with H2O Oxidation

Visible-light-driven CO2 reduction coupled with H2O oxidation is an attractive route toward artificial photosynthesis; however, its realization is often limited by inefficient charge separation in a CO2-reduction photocatalyst, sluggish interfacial charge transfer in Z-scheme systems, and insufficient CO2 activation. Herein, we report a visible-light-driven Z-scheme system in which CoOx−Ag dual-cocatalyst-modified Bi4TaO8Cl0.9Br0.1 served as the CO2-reduction photocatalyst, surface-treated WO3 as the H2O-oxidation photocatalyst, and I−/IO3− as the redox mediator. The CoOx−Ag dual cocatalysts play distinct yet cooperative roles in the Z-scheme architecture. CoOx preferentially extracts photogenerated holes and accelerates mediator oxidation, thereby promoting charge separation in Bi4TaO8Cl0.9Br0.1 and facilitating inter-photocatalyst charge transfer, whereas Ag acts as an electron-enrichment center that enhances CO2 adsorption and activation and promotes the formation of the key *COOH intermediate for selective CO production. Owing to this synergistic regulation of charge transfer and surface reaction kinetics, the optimized Z-scheme system achieved selective CO2 reduction to CO with near 100% selectivity and synchronous O2 evolution in a near-stoichiometric ratio relative to CO under visible-light irradiation. This work offers a dual-cocatalyst design strategy for efficient visible-light-driven Z-scheme CO2 reduction coupled with H2O oxidation.