Enlarging the π-conjugation system of carbon nitride for boosting hydrogen peroxide generation

Heterojunction engineering of graphitic carbon nitride (CN) was considered as a facile and efficient approach to boost photocatalytic hydrogen peroxide (H2O2) generation. However, photocatalytic H2O2 generation over CN/carbon fiber (CF) heterojunction is still challenging due to the rapid transfer and recombination of photogenerated charges. To solve this problem, a novel sulfur/nitrogen-self-doped carbon fibers (CFS,N), derived from poly(2-acrylamido-2-methylpropane sulfonic) (AMPS)-grafted cellulose nanofibers as an efficient electron mediate was herein engineered onto CN skeleton (CN/CFS,N) for achieving high-performance H2O2 production. The as-synthesized CN/CFS,N nanocomposites exhibit an efficient H2O2 production rate of 1.31 mmol∙L-1∙h−1, which is 6.0 and 1.3 times higher than that of pure CN (0.22 mmol∙L-1∙h−1) and CN/CF (0.99 mmol∙L-1∙h−1), respectively, which also significantly outperforms recently-reported CN-based photocatalysts. Based on the experimental results and density functional theory (DFT) simulation, the CFS,N with S/N-doped carbon can act as an ultrafast electronic mediate for directional electron transport, which facilitates interfacial carrier transfer between CN and CFS,N. More importantly, beneficially from the interfacial electron redistribution via the π-conjugation of CFS,N, the molecular oxygen (O2) is highly activated to orderly drive sequential one-electron two-step O2-to-H2O2 conversion. This study presents a promising design of cellulose-derived carbon, which efficiently regulates the charge transfer and separation of CN-based photocatalysts for significantly enhanced H2O2 production.