Effects of UV‐Induced Structural Changes in Graphitic Carbon Nitride on Photocatalytic Degradation of Organic Dyes in Water

Graphitic carbon nitride (g‐C 3 N 4 ) is a promising visible‐light‐driven photocatalyst that can be applied in various fields. However, its intrinsically low photocatalytic efficiency limits practical applications. In this study, g‐C 3 N 4 was structurally modified by ultraviolet (UV) irradiation to improve its photocatalytic performance. Both pristine and UV‐irradiated g‐C 3 N 4 photocatalysts were characterized by X‐ray diffractometry, X‐ray photoelectron spectroscopy, X‐ray absorption near‐edge structure spectroscopy, electron spin resonance spectroscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, and nitrogen adsorption measurement. The photocatalytic efficiency was evaluated by measuring the decomposition rate of rhodamine B (RhB) in water. Our results demonstrated that short‐term UV irradiation for 45 min caused the elimination of pyridinic nitrogen (the N abundance ratio changed from 74 to 67 mol% after UV irradiation), leading to the formation of surface‐deficient sites and new defects in the band structure, which could accelerate the photocatalytic RhB decomposition (the rate constant increased by 1.23 times after UV irradiation). Prolonged UV irradiation resulted in destructive structural changes involving the elimination of carbon, which negatively affected the photocatalytic reactivity due to a decreased number of reactive sites, reduced specific surface area, and increased electron–hole recombination. Therefore, appropriate UV irradiation conditions should be adopted to improve the photocatalytic performance of g‐C 3 N 4 .