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

Designing a catalyst that exhibits high photocatalytic hydrogen (H 2 ) evolution activity, stability, cost-effectiveness, and environmental protection poses a significant challenge. Graphitic carbon nitride (g-C 3 N 5 ) is widely utilized in the photocatalysis field due to its superior thermal stability and enhanced electronic property. Nevertheless, the practical application of g-C 3 N 5 in efficient and stable H 2 production remains challenging. In this work, we successfully synthesized K + and Cl – codoped g-C 3 N 5 (K, Cl/g-C 3 N 5 ) with the aim of boosting H 2 production. Our findings reveal that the codoping of K + and Cl – into g-C 3 N 5 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-C 3 N 5 catalyst achieved an impressive H 2 evolution rate of 3.46 mmol·g –1 ·h –1, while pristine g-C 3 N 5 showed a mere 0.34 mmol·g –1 ·h –1 . After four cycles of H 2 production experiments, the 4-K, Cl/g-C 3 N 5 sample demonstrated remarkable photocatalytic stability. Additionally, an in-depth elucidation of the enhanced photocatalytic mechanism governing H 2 evolution was provided. This work highlights a promising strategy through a dual-doping methodology for the fabrication of highly efficient g-C 3 N 5 -based photocatalysts, which significantly advances the field of photocatalytic water splitting for H 2 evolution.