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

Hydrogen (H 2 ) 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 H 2 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. A solvothermal method was performed to integrate highly-dispersed black NiO clusters with ZnIn 2 S 4 (ZIS) microsphere, which exhibited the highly efficient PHE and apparent quantum yield owing to the synergistic effects of increased light harvesting capability, S-scheme heterojunction and photothermal effect. • The TRPL technique can quantitatively simulate the charge carrier transport behavior during the PHE test. • Highly-dispersed NiO clusters were integrated with ZIS microspheres through the solvothermal method. • The constructed S-scheme NiO/ZIS heterojunction achieves efficient charge carrier separation. • The photothermal effect of NiO/ZIS expedites the charge transfer and improves surface reaction kinetics. • The promoted PHE activity for NiO/ZIS composites was ascribed to the synergistic effect between black NiO clusters and ZIS.