Comprehensive enhancement of photocatalytic H2O2 generation and antibacterial efficacy on carbon nitride through a straightforward polydopamine coating strategy

Carbon nitride (CN) has garnered considerable interest for its potential in photocatalytic H2O2 production. However, several obstacles need to be overcome to further improve its efficiency. These challenges include a narrow light absorption range, facile recombination of photogenerated electron-hole (e(-)/h(+)) pairs, and a dearth of requisite oxygen reduction active sites for the selective production of H2O2. Herein, a straightforward strategy involving the in-situ growth of polydopamine (PDA) on the surface of CN to fabricate a CN@PDA composite is proposed to simultaneously solve these problems. As a result, the optimally prepared composite material CN@PDA-10 exhibits an obviously improved (4.5 times) H2O2 production efficiency (578.7 mu mol<middle dot>g(-)(1)<middle dot>h(-)(1)) under visible light irradiation (>400 nm) compared to the original CN (128.7 mu mol<middle dot>g(-)(1)<middle dot>h(-)(1)). This improvement can be attributed to the encompass of numerous functional groups in PDA, such as catechols and amines that severing as active sites, the high electrical conductivity caused by its pi-pi structure, and the near-infrared light response resulting from the its narrow bandgap characteristics. Further investigation through active species trapping experiments, ESR, and rotating disk electrode (RDE) test results reveal that a stepwise single-electron pathway is the predominant mechanism in the CN@PDA-10-driven photocatalytic reduction of O-2 to H2O2 process. Additionally, to maximize the utilization of the in-situ generated H2O2, Escherichia coli is selected as the target bacteria for evaluating the bactericidal activity of CN@PDA-10. This work presents a practical approach to improve the photocatalytic H2O2 production performance using CN-based materials, and the successful application of the in-situ generated H2O2 in environmental remediation efforts.