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

Abstract

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.