Introduction of electron-deficient unit in resorcinol-formaldehyde resin to construct donor–acceptor conjugated polymer for enhancing photocatalytic H2O2 production

Abstract

Photocatalytic two electron oxygen reduction reaction is considered to be a promising approach for green H₂O₂ production. Herein, for the first time, an intramolecular donor–acceptor (D–A) conjugated polymer was constructed in resorcinol-formaldehyde (RF) resin by embedding benzothiadiazole. As a typical electron deficient group, the introduction of benzothiadiazole can increase the specific surface area of RF and expose more active sites, and the hydrophobicity was also improved, thereby enhancing the affinity of RF to O₂. Owing to the potential difference between the electron donor and acceptor, the formation of a D–A conjugated polymer can provide a driving force to separate photoinduced charge, prolonging the lifetime of photogenerated charge and restraining the recombination of photogenerated electrons and holes. Furthermore, the light absorption ability of RF was enhanced after the introduction of benzothiadiazole. As expected, the catalyst (namely RF-BZ) exhibited excellent performance in photocatalytic H₂O₂ evolution, and the highest yield of H₂O₂ over RF-BZ can reach 2553.2 μmol g⁻¹. More importantly, the thermodynamic analysis based on DFT calculations revealed that the introduction of benzothiadiazole can reduce the adsorption energy of O₂ over RF, and the Gibbs free energy of the rate-determining step for the two-electron oxygen reduction reaction was also reduced to 0.28 eV from 2.05 eV. In short, the current study provides a valuable reference for future research on photocatalytic H₂O₂ production.