TiN Bridged All-Solid Z-Scheme CNNS/TiN/TiO_2−x Heterojunction by a Facile In Situ Reduction Strategy for Enhanced Photocatalytic Hydrogen Evolution

Proper interfacial electron mediators greatly influence the charge transfer efficiency of Z-scheme photocatalytic system. TiN bridged all-solid Z-scheme CNNS/TiN/TiO_2−x heterojunction composites are prepared by a facile in situ reduction strategy for highly promoted photocatalytic hydrogen evolution driven by visible light. The reduction process not only creates oxygen vacancies in TiO₂ but also reduces partial TiO₂ to TiN. Oxygen defected TiO_2−x permits TiO₂ visible light absorption capacity. Fermi level equilibrium forms internal electric fields at the interfaces to drive the charge transfer. Meanwhile, TiN electrons mediator connects the conduction band of TiO_2−x and the valance band of CNNS, which is advantageous for the transfer of photoelectrons from the conduction band of TiO_2−x to the valance band of CNNS. Compared with pure carbon nitride (CN), TiO₂, and even composites CN/TiO₂ without TiN, CNNS/TiN/TiO_2−x shows a remarkably enhanced visible light catalytic hydrogen evolution performance of 1230 μmol g⁻¹ h⁻¹, about 95 times than that of pure CN. The dramatically boosted photocatalytic activity is attributed to the extra visible light absorption capacity of TiO_2−x and convenient electron transfer between CNNS and TiO_2−x through TiN electrons mediator.