Preparation of Cl-Doped g-C3N4 Photocatalyst and Its Photocatalytic Degradation of Rhodamine B

The increasing global demand for clean water is driving the development of advanced wastewater treatment technologies. Graphitic carbon nitride (g-C₃N₄) has emerged as an efficient photocatalyst for degrading organic pollutants, such as synthetic dyes, due to its exceptional thermo-chemical stability. However, its application is limited by an insufficient specific surface area, low photocatalytic efficiency, and an unclear degradation mechanism. In this study, we aimed to enhance g-C₃N₄ by doping it with elemental chlorine, resulting in a series of Cl-C₃N₄ photocatalysts with varying doping ratios, prepared via thermal polymerization. The photocatalytic activity of g-C₃N₄ was assessed by measuring the degradation rate of RhB. A comprehensive characterization of the Cl-C₃N₄ composites was conducted using SEM, XRD, XPS, PL, DRS, BET, EPR, and electrochemical measurements. Our results indicated that the optimized 1:2 Cl-C₃N₄ photocatalyst exhibited exceptional performance, achieving 99.93% RhB removal within 80 min of irradiation. TOC mineralization reached 91.73% after 150 min, and 88.12% removal of antibiotics was maintained after four cycles, demonstrating the excellent stability of the 1:2 Cl-C₃N₄ photocatalyst. Mechanistic investigations revealed that superoxide radicals (·O₂^-) and singlet oxygen (¹O₂) were the primary reactive oxygen species responsible for the degradation of RhB in the chlorine-doped g-C₃N₄ photocatalytic system.