Oxygen doping and hollow structure-mediated effects to enable rapid electron transfer during photocatalytic hydrogen peroxide production

The photocatalytic production of hydrogen peroxide using solar energy is an environment-friendly solution to the energy crisis, but its low efficiency hinders its scale-up feasibility. In this work, a hollow core-shell structure OCN@In2S3 composite photocatalyst was constructed by growing In2S3 ultrathin nanosheets on the surface of O-doped hollow g-C3N4 nanospheres using a two-step hydrothermal method. The hollow structure provided a high specific surface area and enhanced light absorption. O doping increased the number of active sites, and the heterojunction promoted the rapid separation and transfer of photogenerated carriers. Under visible light irradiation, the H2O2 yield of OCN@In2S3 reached 632.5 µmol h−1 g−1, which was 5.7 times higher than that of g-C3N4 and 12.3 times that of In2S3, as well as higher than most g-C3N4-based photocatalysts. Quenching experiments and electron paramagnetic resonance spectroscopy showed that ·O2−was an intermediate product formed during photocatalytic H2O2 generation. The reaction primarily followed a two-step single-electron pathway. The Koutecky-Levich diagram confirmed that the synthesized OCN@In2S3 maintained a high two-electron ORR selectivity during the catalytic reaction (n = 1.67). The photocatalytic mechanism was elucidated by photoluminescence, electrochemical impedance spectroscopy, and ultraviolet photoelectron spectro-scopy, which confirmed that OCN@In2S3 inhibited the recombination of photogenerated carriers. This work provides a simple and attractive strategy for developing highly active energy-conversion photocatalysts.