Catechol-Formaldehyde Resin Coated CdS Core-Shell Composite as Robust Photocatalyst for Long-Term Sustainable Artificial Photosynthesis of H₂O₂

Catechol-formaldehyde resin (CFR) is very attractive for H₂O₂ production via the catalytic process. However, the H₂O₂ formation is accompanied by the oxidation of catechol groups to o-benzoquinone groups on CFR, which will cause irreversible damage to CFR and greatly limit its long-term stable catalytic activity. Herein, CdS/CFR composite photocatalyst with a core-shell structure was synthesized by hydrothermal method. The photogenerated electrons of CdS are used as a powerful driving force for the reversible redox conversion between catechol groups and o-benzoquinone groups on the CFR, which not only achieves the long-term stability of CFR-catalyzed production of H₂O₂, but also promotes the separation efficiency of photogenerated e^– and h⁺ in CdS, greatly inhibiting their recombination, so as to maintain CdS stability. The H₂O₂ yield of CdS/CFR can accumulate to 1.65 mmol·L^–1 under visible light for 6 h without sacrificial agent, which is about 3.1 and 2 times that of CdS and CFR, respectively, and CdS/CFR can persist for 10 cycles of photocatalysis (60 h). CdS/CFR also improves the yield of photocatalytic H₂O₂ by increasing the selectivity of H₂O₂ and inhibiting its decomposition. This work offers a novel tactic for expanding the application of CFR in photocatalytic generation of H₂O₂.