Copolymerization synthesis of highly hydrophilic carbon nitride for efficient solar hydrogen production

Abstract

Polymeric carbon nitride (PCN) holds great potential in solar-to-hydrogen (H₂) production, while it usually suffers from hydrophobic and insoluble character, thus greatly limiting solar-to-H₂ production efficiency. The construction of a well-defined, highly hydrophilic interface is crucial for efficient charge carrier separation, however, it remains a challenge in synthesis. Here we report the first synthesis of high-hydrophilic PCN by copolymerizing urea with indole via a facile one-step in situ surface-amination strategy. Results reflected that the surface-amination tactic could not only ameliorate its hydrophilicity but also promote the dissociation of charge carriers and simultaneously enrich proton (H⁺) from water, therefore, improving the rapid production of H₂. As expected, the optimal surface-ammoniated sample exhibited a remarkable enhancement for the H₂ production of 55.85 μmol h⁻¹ under visible light illumination, which outperformed most reported hydrophilic PCN-based materials thus far. Surprisingly, the optimal sample also presented outstanding photoactivity under blue and green light irradiation. This work sheds light on a novel organic molecular-tailoring protocol for the preparation of hydrophilic carbon-based materials toward highly-efficient solar-to-H₂ production.