(48g) Metal Single-Atom Catalysts Driven Heterogeneous Electro-Fenton Technology for Fast Elimination of Refractory Contaminants

Fenton reaction represents the promising technology to tackle severe water environment pollution issues via super-active ·OH production, due to the high reaction rate, non-toxic reagents, and environmentally friendly process. However, it suffers from the low atomic efficiency, poor pH adaptability, and catalyst non-reusability in a homogeneous or heterogeneous system. Herein, metal single-atom catalysis is introduced to drive heterogeneous electro-Fenton for ·OH evolution utilizing earth-abundant oxygen and water as raw materials. An iron single-atom settled by defective three-dimensional porous carbon (FeSA/3DPC) with unique unsaturated coordination is designed to tune multi-electron oxygen reduction processes, enabling O₂-to-·OH conversion. The isolation feature of iron atoms and the unique unsaturated coordination are identified via atom resolved scanning transmission electron microscopy and extended X-ray absorption fine structure analysis. The prepared FeSA/3DPC catalyst can dramatically catalyze O₂ or H₂O₂ into ·OH in circumneutral solution, delivering almost two-orders of magnitude higher mass activity in ·OH productivity compared to nanoparticular iron oxide catalyst. The FeSA/3DPC electro-Fenton system exhibits fast elimination of refractory toxic pollutants(sulfamethoxazole, nitrobenzene, etc), surpassing nanoparticular iron oxides in kinetic rate by 59 times or homogeneous Fenton by 10 times under similar experimental conditions. The remarkable enhanced mass activity of FeSA/3DPC in catalyzing O₂/H₂O₂ to ·OH is mainly contributed by the synergistic effects of the maximized catalysis of single-atom iron and unique unsaturated coordination regulation, as demonstrated experimentally and theoretically. Furthermore, cobalt single-atom is additionally introduced to accelerate the preliminary step of O₂ reductive H₂O₂ formation, cooperatively working with high H₂O₂ active iron single-atom for fast ·OH production. Benefiting from the dual-atom effect, the ·OH productivity is significantly raised by 7.7 times compared with the iron single-atom catalyst. The dual-atom electro-Fenton system is capable of eliminating COD of actual refinery wastewater with a lower electricity consumption of 11.1 kWh kg^-1 COD^-1 compared with electrooxidation or homogeneous electro-Fenton technology. These metal single-atom catalytic systems are demonstrated to be pH-universal, long-term stable, and well recyclable for pollutants elimination from water. It addresses the issues of low activity and catalyst disability that are typically suffered in heterogeneous Fenton or homogeneous electro-Fenton catalysis. It is prospective to integrate renewable electricity with freely available air and water for green and sustainable wastewater purification or other potential applications.