All-solid-state direct Z-scheme NiTiO3/Cd0.5Zn0.5S heterostructures for photocatalytic hydrogen evolution with visible light

Abstract

The construction of NiTiO₃/Cd_0.5Zn_0.5S heterostructures is presented as all-solid-state direct Z-scheme photocatalysts for the efficient and stable hydrogen production under visible light. The NiTiO₃/Cd_0.5Zn_0.5S hybrids are assembled by growing Cd_0.5Zn_0.5S nanoparticles on the surface of NiTiO₃ nanorods via a co-precipitation and hydrothermal coupled method. The compositional and structural features of the NiTiO₃/Cd_0.5Zn_0.5S composites are fully disclosed via diverse physicochemical characterizations. The NiTiO₃/Cd_0.5Zn_0.5S heterostructures are revealed to effectively capture the optical spectrum in the visible region as well as enhance the transfer and separation of photogenerated charge carriers through the Z-schematic pathway. Consequently, the optimized NiTiO₃/Cd_0.5Zn_0.5S photocatalyst shows a high H₂ production rate of 1058 μmol h⁻¹ (26.45 mmol h⁻¹ g⁻¹), which is independent of any cocatalysts (such as Pt), together with a high apparent quantum yield (AQY) of 34% under monochromatic light irradiation at 420 nm. Besides, the NiTiO₃/Cd_0.5Zn_0.5S composites also exhibit a high stability for the H₂ evolution photocatalysis mainly due to the fact that the Z-schematic charge separation and migration can enable the efficient consumption of light-induced holes of Cd_0.5Zn_0.5S to prevent the photocorrosion effect. Finally, a possible photocatalytic H₂ evolution mechanism over the Z-schematic NiTiO₃/Cd_0.5Zn_0.5S heterostructures is also presented based on the results of the band structures, density functional theory (DFT) calculations and electron spin resonance (ESR) tests.