Gradient graphitic carbon rings induce successive built-in electric field for photo-Fenton-like reaction

The heterojunction with matched energy band enables efficient peroxymonosulfate (PMS)-based photo-Fentonlike reaction. Nevertheless, the rapid photogenerated charge separation and transfer has been challenging. Herein, we precisely constructed an efficient heterogeneous photo-Fenton-like reactor with successive built-in electric field by gradient doping of coplanar graphitic carbon rings (Cgra) into cobalt tungstate/graphitic carbon nitride (CoWO4/GD-CN) heterostructure. The as-prepared CoWO4/GD-CN exhibited remarkable enhancement with a tetracycline hydrochloride degradation rate constant (0.776 min-1) higher than that of CoWO4/CN (0.507 min-1). Theoretical and experimental results demonstrated that the successive built-in electric field enhanced by gradient-doped coplanar Cgra ring accelerated photogenerated electrons transfer from the innermost to the outmost layer of CoWO4/GD-CN. This transfer drove Co(III)/Co(II) conversion for accelerated PMS activation, leading to enhanced degradation reactivity. CoWO4/GD-CN had excellent degradability towards representative contaminants, including carbamazepine (1.0 min-1), 4-chlorophenol (0.920 min-1), sulfamethoxazole (0.90 min-1), bisphenol A (0.933 min-1), atrazine (0.829 min-1), ciprofloxacin (0.589 min-1) and norfloxacin (0.617 min-1) in CoWO4/GD-CN/PMS/vis system, respectively. This work provided a novel insight into the gradient-dope modulated photo-Fenton-like reaction and guided the design of efficient photo-Fenton-like reactor.