Boosting H2O2 production over carboxymethyl cellulose modified g-C3N4 via hydrogen-bonding-assisted charge transfer

Photocatalytic H2O2 synthesis (PHS) via solar-driven process has emerged as a coveted orientation in the future low-carbon industry. However, the performance of conventional graphitic carbon nitride (g-C3N4) is still constrained by the poor charge transfer and inefficient oxygen reduction reaction (ORR). Cellulose, as its low cost and eco-friendly properties, can serve as a green electron mediate to promote PHS through hydrogen bonds. Nevertheless, the effect of hydrogen bond strength on photocatalytic activity has not been thoroughly explored. Herein, we report a facile method to boost photocatalytic H2O2 generation by modifying g-C3N4 with carboxymethyl cellulose (CMC) of different substitution degrees (DS = 1.2, CMCH; DS = 0.7, CMCL) via multiple hydrogen bonds. The photocatalytic H2O2 production rate of the CN/CMCL composite catalyst was up to 35.7 μmol·L-1·h−1, which was approximately 3.5 times than that of the pristine g-C3N4. Experimental characterization and density functional theory (DFT) calculations demonstrated that both CMCH and CMCL can act as electron mediates, and CMCL possesses a stronger interaction of hydrogen bonds with g-C3N4. As a result, CN/CMCL exhibits superior charge transfer efficiency, thus promoting the two-step single-electron ORR for PHS. This research significantly contributes to the understanding of the hydrogen bond theory over PHS and sheds light on the potential applications of biomass materials containing rich hydroxyl groups significantly enhancing photocatalytic performance.