Self-integrated black NiO clusters with ZnIn2S4 microspheres for photothermal-assisted hydrogen evolution by S-scheme electron transfer mechanism

Abstract

Hydrogen (H₂) production technology utilizing solar energy is an essential strategy for questing carbon-neutral, but designing the optimal heterostructured photocatalysts is one of the great challenges. To date, the self-integration of highly-dispersed black NiO clusters with ZIS microspheres was successfully achieved during the solvothermal process. These constructed NiO/ZIS S-scheme heterostructured composites could provide more active for photocatalytic H₂ evolution (PHE) under visible light. The optimal 2-NiO/ZIS showed the best PHE rate of 2474.0 μmol g⁻¹ h⁻¹, highest apparent quantum yield (AQY) value of 36.67 % and excellent structural stability. Furthermore, NiO/ZIS composites also exhibited the high PHE rates in natural seawater. The charge separation behaviors of the catalyst were systematically evaluated using advanced spectroscopic characterization techniques, specifically in-situ XPS, time-resolved photoluminescence (TRPL) tested in water and transient absorption spectroscopy (TAS). The experimental analysis and theoretical calculation results elucidated the S-scheme charge transfer mechanism for NiO/ZIS. The promoted PHE activity was ascribed to the combined effect between black NiO clusters and ZIS, which enhanced light harvesting ability, accelerated charge carrier transportation and separation, remained high redox ability, and improved surface reaction kinetics. This study offers the insights into constructing S-scheme heterostructured composites with photothermal effect.