Modulated Carbon Nitride Donor−Acceptor Structures Promote Spatial Charge Separation for Improved Solar-Driven Hydrogen Generation

Abstract

Graphitic carbon nitride (g-C3N4) holds great potential for photocatalytic hydrogen evolution, yet suffers from insufficient light harvesting, fast charge recombination, and low surface area. In this work, nitro-functionalized worm-like chain carbon nitride with benzene ring domains (CCNB) was rationally fabricated via copolymerization of melamine and p-nitrobenzoic acid. Systematic characterizations and density functional theory (DFT) calculations demonstrate that benzene rings coupled with electron-withdrawing nitro groups exert a synergistic effect on interfacial charge transport, wherein the π-electron delocalization is extended by the benzene structure while the nitro functional group acts as an effective driver for electron transfer. Meanwhile, the introduction of nitro groups and benzene ring effectively narrows the band gap of CCNB, strengthening its optical absorption capacity. Consequently, the optimal CCNB-0.15 sample exhibits an outstanding photocatalytic hydrogen evolution rate of 2312 μmol·g−1·h−1, which is 10.9 times higher than that of pristine g-C3N4. This study provides a feasible dual-modification strategy coupling benzene ring and surface nitro functionalization to surmount the inherent drawbacks of bulk g-C3N4, offering a pathway for designing high-performance carbon nitride-based photocatalysts toward efficient solar hydrogen production.