The Sb–N charge transfer bridge over Cs₃Sb₂Br₉/Sb–C₃N₄ Z-scheme heterojunction for boosting photocatalytic CO₂ reduction

Developing highly efficient heterostructural photocatalysts for direct CO₂ reduction coupled with water oxidation remains challenging, the key to which is to establish an efficient interfacial charge transport channel. Herein, we present a Cs₃Sb₂Br₉/Sb–C₃N₄ Z-scheme heterojunction prepared with an in-situ growth method based on the Sb atomic pinning effect. As revealed by the analysis of experimental and theoretical calculation results, the introduction of Sb anchors on C₃N₄ leads to the formation of an Sb–N charge transfer bridge between Cs₃Sb₂Br₉ and C₃N₄, promoting interfacial charge communication over Cs₃Sb₂Br₉/Sb–C₃N₄ heterojunction. Moreover, it can induce the heterojunction interfacial charge transfer pathway between Cs₃Sb₂Br₉ and C₃N₄ to change from type II to the type Z-scheme, enabling the change of the catalytic site from C₃N₄ to Cs₃Sb₂Br₉, thus promoting the CO₂ activation. As a result, Cs₃Sb₂Br₉/Sb–C₃N₄ achieves efficient CO₂ to CO photocatalytic conversion using water as the electron source under simulated solar light irradiation (100 mW·cm⁻²), with the yield of 198.4 µmol·g⁻¹·h⁻¹, which is nearly 3-fold and 9-fold over the counterpart synthesized catalyst without Sb anchors (Cs₃Sb₂Br₉/g–C₃N₄) and pure g–C₃N₄, respectively. This work provides a new alternative solution for the design of highly efficient heterojunction photocatalysts.