Direct Z-Scheme TiO₂/NiS Core–Shell Hybrid Nanofibers with Enhanced Photocatalytic H₂-Production Activity

Photocatalytic water splitting to generate hydrogen (H 2 ) is a sustainable approach for solving the current energy crisis. A novel TiO 2 /NiS core–shell nanohybrid was fabricated where few-layer NiS nanoplates were deposited on TiO 2 skeletons via electrospinning and hydrothermal methods. The NiS nanoplates with a thickness of ca. 28 nm stood vertically and uniformly upon the TiO 2 nanofibers, guaranteeing intimate contact for charge transfer. XPS analysis and DFT calculation imply that the electrons in NiS would transfer to TiO 2 upon hybridization, which creates a built-in electric field at the interfaces and thus facilitates the separation of useful electron and hole upon photoexcitation. In-situ XPS analysis directly proved that the photoexcited electrons in TiO 2 migrated to NiS under UV–visible light irradiation, suggesting that a direct Z-scheme heterojunction was formed in the NiS/TiO 2 hybrid. This direct Z-scheme mechanism greatly promotes the separation of useful electron–hole pairs and fosters efficient H 2 production. The hybrid nanofibers unveiled a high H 2 -production rate of 655 μmol h –1 g –1, which was 14.6-fold of pristine TiO 2 nanofibers. Isotope ( 4 D 2 O) tracer test confirmed that H 2 was produced from water, rather than from any H-containing contaminants. This work provides an alternative approach to rationally design and synthesize TiO 2 -based photocatalysts with direct Z-scheme pathways toward high-efficiency photogeneration of H 2 .