Sodium Chloride-Assisted Crystalline Graphitic Carbon Nitride for Efficient Photocatalytic Hydrogen Evolution

Abstract

Graphitic carbon nitride (g-C₃N₄) has attracted enormous attention as a photocatalyst due to its appropriate bandgap, high chemical stability, and visible light response. However, it is still challenging to synthesize highly crystalline g-C₃N₄, favoring the separation of photogenerated electron–hole pairs and promoting improved photocatalytic activity. Herein, we report a novel approach to achieve highly crystalline g-C₃N₄ by simply pressing sodium chloride and carbon nitride into a pellet followed by heat treatment, which is different from conventional molten salt methods. The resulting g-C₃N₄ has an optimum band structure that benefits enhanced light absorption and charge separation efficiency. The intimate contact between sodium chloride and carbon nitride in the pressed pellet facilitates the diffusion of sodium ions and increases the material's resistance to high annealing temperatures, leading to improved crystallinity. The photocurrent response of this highly crystalline material under visible light irradiation is approximately four times higher than that of its bulk counterpart, resulting in a hydrogen production rate of up to 650 μmol g⁻¹ h⁻¹ (10% TEOA). This work paves a new path in designing novel carbon nitrides with enhanced photoelectrochemical and photocatalytic performance.