Self-regenerative Co2+/Co3+ mediation in Co-doped CdIn2S4 superstructures enables efficient sacrificial-agent-free H2O2 photogeneration

Photocatalytic H₂O₂ production suffers from severe charge recombination and sacrificial agent dependency. Hydrangea-like Co-doped CdIn₂S₄ superstructures (Co/CIS (HD)) synthesized via hydrothermal method exhibit hierarchical porous architecture that enhances light harvesting and reactant diffusion. Atomic Co doping introduces mixed-valence Co²⁺/Co³⁺ species, reducing the work function from 6.287 to 5.896 eV and extending carrier lifetime. The dual-valent system establishes a self-regenerative redox cycle where Co³⁺ mediates photogenerated electron transfer for O₂ activation while Co²⁺ scavenges holes to suppress recombination and photocorrosion. Without sacrificial agents, the optimized 6.5-Co/CIS (HD) achieves an exceptional H₂O₂ production rate of 1952 μmol g⁻¹ h⁻¹ under visible light, 6.33 times higher than pristine CdIn₂S₄. The catalyst maintains structural stability over five cycles due to dynamic Co²⁺/Co³⁺ regeneration. This work provides a strategic design for efficient photocatalytic H₂O₂ synthesis via synergistic morphological and electronic engineering.