Abstract:

Solar photocatalysis is a green, economical, and sustainable method for H₂O₂ synthesis, which has been regarded as the most promising alternative to the traditional anthraquinone oxidation method. However, single-component photocatalyst exhibits moderate activity owing to the limited light-harvesting range, fast charge recombination and inadequate redox capacity. Moreover, the addition of sacrificial agents is required in the reaction system. Herein, we present the development of an S-scheme heterojunction, achieved through photodepositing Bi₂O₃ nanoparticles (BO) on ionic covalent organic framework nanofiber (iCOF). The optimized photocatalyst iCOF/BO10 shows the highest H₂O₂ production performance in pure water, achieving an H₂O₂ yield of 9.76 mmol·g⁻¹·h⁻¹ with an apparent quantum yield (AQY) of 5.5% at 420 nm. This photocatalytic performance is approximately 2.2 and 5.6 times as high as that of pristine iCOF and BO, respectively. In-depth characterizations including in situ irradiated XPS, DFT-calculations, active species trapping experiments and in situ DRIFTS, reveal that the obtained sample not only facilitates charge carrier separation and enhances light absorption capability, but also maximizes the redox ability to concurrently achieve indirect 2e⁻ ORR and 4e⁻ WOR for H₂O₂ production. Additionally, the generated O₂ from the 4e⁻ WOR is capable of accelerating the reaction kinetics for H₂O₂ formation via the indirect 2e⁻ ORR pathway, enabling overall photocatalytic H₂O₂ synthesis. This work provides a new insight into creating innovative catalysts for achieving high-efficiency photosynthesis of H₂O₂.

Key words: Photocatalysis, S-scheme heterojunction, H₂O₂ production, Non-sacrificial agent, Dual channels