COF/In2S3 S‐Scheme Photocatalyst with Enhanced Light Absorption and H2O2‐Production Activity and fs‐TA Investigation

Abstract Photocatalytic hydrogen peroxide (H2O2) synthesis from water and O2 is an economical, eco‐friendly, and sustainable route for H2O2 production. However, single‐component photocatalysts are subjected to limited light‐harvesting range, fast carrier recombination, and weak redox power. To promote photogenerated carrier separation and enhance redox abilities, an organic/inorganic S‐scheme photocatalyst is fabricated by in situ growing In2S3 nanosheets on a covalent organic framwork (COF) substrate for efficient H2O2 production in pure water. Interestingly, compared to unitary COF and In2S3, the COF/In2S3 S‐scheme photocatalysts exhibit significantly larger light‐harvesting range and stronger visible‐light absorption. Partial density of state calculation, X‐ray photoelectron spectroscopy, and femtosecond transient absorption spectroscopy reveal that the coordination between In2S3 and COF induces the formation of mid‐gap hybrid energy levels, leading to smaller energy gaps and broadened absorption. Combining electron spin resonance spectroscopy, radical‐trapping experiments, and isotope labeling experiments, three pathways for H2O2 formation are identified. Benefited from expanded light‐absorption range, enhanced carrier separation, strong redox power, and multichannel H2O2 formation, the optimal composite shows an impressive H2O2‐production rate of 5713.2 µmol g−1 h−1 in pure water. This work exemplifies an effective strategy to ameliorate COF‐based photocatalysts by building S‐scheme heterojunctions and provides molecular‐level insights into their impact on energy level modulation.