CoO x −Ag Dual-Cocatalyst Modification on the Bi ₄ TaO ₈ Cl 0.9 Br 0.1 Photocatalyst for Selective CO ₂ Reduction in a Visible-Light-Driven Z-Scheme System Coupled with H ₂ O Oxidation

Visible-light-driven CO 2 reduction coupled with H 2 O oxidation is an attractive route toward artificial photosynthesis; however, its realization is often limited by inefficient charge separation in a CO 2 -reduction photocatalyst, sluggish interfacial charge transfer in Z-scheme systems, and insufficient CO 2 activation. Herein, we report a visible-light-driven Z-scheme system in which CoO x −Ag dual-cocatalyst-modified Bi 4 TaO 8 Cl 0.9 Br 0.1 served as the CO 2 -reduction photocatalyst, surface-treated WO 3 as the H 2 O-oxidation photocatalyst, and I − /IO 3 − as the redox mediator. The CoO x −Ag dual cocatalysts play distinct yet cooperative roles in the Z-scheme architecture. CoO x preferentially extracts photogenerated holes and accelerates mediator oxidation, thereby promoting charge separation in Bi 4 TaO 8 Cl 0.9 Br 0.1 and facilitating inter-photocatalyst charge transfer, whereas Ag acts as an electron-enrichment center that enhances CO 2 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 CO 2 reduction to CO with near 100% selectivity and synchronous O 2 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 CO 2 reduction coupled with H 2 O oxidation.