K⁺ and Cl^– Codoped g-C₃N₅ as a Catalyst for the Photocatalytic Hydrogen Evolution

Designing a catalyst that exhibits high photocatalytic hydrogen (H2) evolution activity, stability, cost-effectiveness, and environmental protection poses a significant challenge. Graphitic carbon nitride (g-C3N5) is widely utilized in the photocatalysis field due to its superior thermal stability and enhanced electronic property. Nevertheless, the practical application of g-C3N5 in efficient and stable H2 production remains challenging. In this work, we successfully synthesized K+ and Cl– codoped g-C3N5 (K, Cl/g-C3N5) with the aim of boosting H2 production. Our findings reveal that the codoping of K+ and Cl– into g-C3N5 effectively modulates its energy band structure, enhances visible light absorption, and suppresses the recombination rate of photogenerated carriers. When irradiated with visible light in the presence of triethanolamine (TEOA) as a sacrificial agent, the 4-K, Cl/g-C3N5 catalyst achieved an impressive H2 evolution rate of 3.46 mmol·g–1·h–1, while pristine g-C3N5 showed a mere 0.34 mmol·g–1·h–1. After four cycles of H2 production experiments, the 4-K, Cl/g-C3N5 sample demonstrated remarkable photocatalytic stability. Additionally, an in-depth elucidation of the enhanced photocatalytic mechanism governing H2 evolution was provided. This work highlights a promising strategy through a dual-doping methodology for the fabrication of highly efficient g-C3N5-based photocatalysts, which significantly advances the field of photocatalytic water splitting for H2 evolution.