Highly efficient and stable 3D Ni(OH)2/CdS/ZnIn2S4/TiO2 heterojunction under solar light: Effect of an improved TiO2/FTO interface and cocatalyst

- Highly efficient and stable Ni(OH)2/CdS/ZnIn2S4/TiO2 photoanode was synthesized.
- Annealing improves the FTO and TiO2 interface for efficient electron transport.
- Cocatalyst stabilizes photoelectrode through hole trapping.
- The simultaneous counter-directed electron-hole transfer is well proposed.

A simple and effective strategy was used to fundamentally improve the performance of a heterostructured Ni(OH)2/CdS/ZnIn2S4/TiO2 photoanode. TiO2 nanorods grown hydrothermally on fluorine-doped tin oxide (FTO) and annealed at 500 °C yielded an optimal photocurrent density of ~988 μA cm-2 at 0.1 V vs. Ag/AgCl under simulated illumination conditions. The annealing process minimized the defects in TiO2 and assisted in the formation of close contacts between the FTO and TiO2 nanorods, which allowed for efficient electron transport. The stepwise introduction of ZnIn2S4 and CdS on annealed TiO2 enhanced absorption in the visible range and electron/hole separation in CdS/ZnIn2S4/TiO2. Additionally, the Ni(OH)2 cocatalyst functioned in hole trapping and improved the stability of the photoelectrode through timely consumption of the photogenerated charges, particularly the holes.

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