Sustainable Fe and Cu Sites Double Redox Cycle Boosting Fenton-like Degradation of Organic Pollutants

Single-atom catalysts (SACs) show excellent activity and selectivity in Fenton-like reactions due to the atomically dispersed and homogeneous active sites. However, the sluggish redox kinetics of single-atom sites cause poor stability and durability. Herein, a graphitic carbon nitride-supported Fe and Cu dual-site catalyst with N₄-Fe-Cu-N₃ configuration (FeCu-CN) was designed and prepared, which promotes H₂O₂ activity through a sustainable dual-metal redox cycle and shows excellent pollutant degradation performance. The optimized FeCu-CN efficiently activates H₂O₂ to degrade sulfamethoxazole, with 23 and 4 times higher rates than Fe-CN and Cu-CN, respectively. Experimental and density functional theory (DFT) calculations indicate that the Cu site of FeCu-CN optimizes the electronic structure of Fe site and provides electrons to facilitate the Fe(III)/Fe(II) cycle. The reduction of Cu(II) by H₂O₂ and •O₂^- could promote the Cu(II)/Cu(I) cycle, maintaining the catalytic activation stability of FeCu-CN. Moreover, the synergistic effect of Fe and Cu sites in FeCu-CN promotes the adsorption of H₂O₂ and reduces the dissociation energy barrier of H₂O₂. The FeCu/H₂O₂ system exhibits strong resilience to changes in pH (from 3.18 to 9.35) and the coexisting substances. In continuous flow experiments, it also shows a long-term degradation effect on water pollutants. The FeCu-CN/H₂O₂ system has excellent anti-interference ability and application potential. This study develops a strategy for a persistent dual-metal synergistic redox cycle, providing new mechanistic insights for designing Fenton-like catalysts in efficient and environmentally friendly wastewater treatment.