Black phosphorus/Bi19Br3S27 van der Waals heterojunctions ensure the supply of activated hydrogen for effective CO2 photoreduction

Photocatalytic CO 2 reduction (PCC) into solar fuels has been identified as a green avenue for carbon emission reduction. The reactions are usually restricted by the competitive hydrogen production reactions so that the acquisition and utilization of activated hydrogen (H*) in photocatalytic CO 2 reduction are hard to guarantee. Herein, heterojunction engineering, regarding amendatory H* supply and balancing hydrogen production reactions simultaneously, for enhancing PCC is achieved by fabricating black phosphorus (BP) nanosheets supported on Bi 19 Br 3 S 27 nanorods (BP/BBS). Density functional theory calculations united with experimental researches confirm the charge transfer conforms to S-scheme mechanism, which guarantee the efficient separation of photogenerated carriers to facilitate CO 2 photoreduction. Free energy analysis reveals the formation of BP/BBS heterojunction changes the active sites from BBS to BP, which decrease the rate-limiting H* formation step from 1.94 (on BBS) to 1.13 eV (BP/BBS heterojunction), ensuring the supply of activated H* for PCC. We found that the heat of the PCC is conducive to dominant protonation of CO 2 not H* desorption, which can greatly improve the reduction efficiency of CO 2 . As a result, the optimized BP/BBS heterojunction achieves an enhanced generation rate of solar fuels in liquid or gas-solid phase system with CO generation rate of 395.7 and 35.4 μmol g −1 catalyst , respectively. This work provides an efficient strategy to achieve the supply of activated H* for PCC and other photochemical process. • The S-scheme BP/Bi 19 Br 3 S 27 heterojunction were fabricated for UV–vis–NIR light-driven photocatalytic CO 2 reduction. • Van der Waals heterojunction accelerated the separation and migration of photogenerated carriers. • The Van der Waals heterojunction revealed enhanced photocatalytic activity for CO 2 reduction. • The formation of BP/BBS heterojunction decreases the rate-limiting H* formation step, ensuring the supply of activated H*. • The photocatalytic mechanism was unveiled based on the experiments and DFT calculations.