Macroporous ZnO/ZnS/CdS composite spheres as efficient and stable photocatalysts for solar-driven hydrogen generation

Solar-driven hydrogen (H₂) generation utilizing photocatalysts has received extensive attention because of its potential to mitigate the global energy crisis and environmental problem. The implementation of efficient H₂ production strongly relies on stable, active, and low-cost photocatalysts. In this work, we report the designed synthesis of macroporous ZnO/ZnS/CdS composite spheres as a highly active photocatalyst for H₂ production via solar-driven water splitting. The composite spheres were synthesized by a facile solvothermal reaction paired with controllable ion-exchange processes. The resulting material exhibits superior photocatalytic activity, delivering a high H₂ production rate of ~11.37 mmol h⁻¹ g⁻¹ under light illumination (250–780 nm, with an ultraviolet light intensity of 34 mW cm⁻² and visible light intensity of 158 mW cm⁻²). Such performance enhancement can be mainly ascribed to the synergic effects of the composite structure: (1) formation of coherent ZnO/CdS and ZnS/CdS heterojunctions at nanoscale, facilitating charge separation of photoinduced electron/hole pairs, (2) highly accessible inner surface of the meso/macroporous ZnO/ZnS/CdS composites for rapid mass transfer of electrolyte, and (3) enhanced visible light scattering capability induced by their large particle size.