Designed 2D/2D F-doped TiO₂@ZnIn₂S₄ heterojunction for efficient photo-utilization hydrogen generation

Comprehending the catalytic reaction implementation for heterostructure photocatalysts is crucial by scrutinizing the spatial separation and transfer process of photoexcited charges at nanoscale junctions. Herein, we fabricated the F-doped TiO₂/ZnIn₂S₄-based S-scheme heterostructure using a direct liquid-assembly method. The optimum hydrogen evolution rate (HER) of ∼ 1.58 mmol g^-1h^-1 was acquired for 30-F₃T@ZIS, which was about 15 and 2 times superior to the pristine F-doped TiO₂ and ZnIn₂S₄, respectively. The interaction between F-doped TiO₂ and ZnIn₂S₄ facilitated the charge transfer from ZIS to F₃T which was confirmed through XPS. UV-vis spectroscopy and Mott-Schottky validated that F-doped TiO₂ and ZnIn₂S₄ retain the suitable energy band alignment for the S-scheme heterostructure. In situ, KPFM and EPR analysis revealed that F-doped TiO₂ and ZnIn₂S₄ possess a spontaneous photoelectrochemical response, and their junction significantly improves the internal electric field by separating photoexcited charge carriers. This work provides a conclusive experimental and theoretical validation for an internal electric field and charge flow direction in non-noble-metal-based heterostructure photocatalysts.