Surface engineered nickel sites immobilization in exfoliated graphitic carbon nitride for highly efficient photocatalytic degradation of 2,4 dichlorophenol

•Novel Ni@CN nanostructure was fabricated to degrade 2,4-DCP.•A rapid degradation kinetics of 2,4-DCP (kobs = 0.114 min-1) was observed under visible light.•The exceptional photocatalytic degradation of 2,4-DCP> 4-BP> 4-CP was recorded.•Highly reactive ·OH, ·O2, and 1O2, were identified. The fabrication and homogenous distribution of Ni nanoparticles on ultrathin two-dimensional carbon nitride (g-C3N4CN) can achieve the complete mineralization of 2,4 dichlorophenol (2,4-DCP) under visible light irradiation (420 nm). The newly synthesized Ni@CN nanostructure was characterized using various techniques, including XRD, TEM, SEM-EDS elemental mapping, and FT-IR. The Ni@CN nanostructure was used to photodegrade 4-BP, 4-CP, and 2,4-DCP under visible light. The Ni@CN nanostructure exhibited remarkable efficiency in the photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP), 4-bromophenol (4-BP), and 4-chlorophenol (4-CP), with reaction rates of 0.114, 0.110, and 0.0352 min-1, respectively. Notably, the catalyst demonstrated superior stability and reusability, maintaining its effectiveness over five repeated cycles of 2,4-DCP degradation. Meanwhile, site-selective Ni doping could generate a hybrid band gap to extend the application of visible light, which can catalyze the dominant production of 1O2 and boost the generation of other highly reactive ROS, including ·OH and ·O2, which were identified by free-radical scavenging tests and further screened by ESR measurements. This study provides a significantly efficient visible-light-active single-atom Ni@CN catalyst for photocatalytic degradation of phenolic compounds. [Display omitted]