Highly Efficient Hydroxyl Radicals Production Boosted by the Atomically Dispersed Fe and Co Sites for Heterogeneous Electro- Fenton Oxidation

The heterogeneous electro-Fenton (hetero-e-Fen-ton)-coupled electrocatalytic oxygen reduction reaction (ORR) is regarded as a promising strategy for middotOH production by simultaneously driving two-electron ORR toward H2O2 and stepped activating the as-generated H2O2 to middotOH. However, the high-efficiency electrogeneration of middotOH remains challengeable, as it is difficult to synchronously obtain efficient catalysis of both reaction steps above on one catalytic site. In this work, we propose a dual-atomic-site catalyst (CoFe DAC) to cooperatively catalyze middotOH electrogeneration, where the atomically dispersed Co sites are assigned to enhance O2 reduction to H2O2 intermediates and Fe sites are responsible for activation of the as-generated H2O2 to middotOH. The CoFe DAC delivers a higher middotOH production rate of 2.4 mmol L-1 min-1 gcat -1 than the single-site catalyst Co-NC (0.8 mmol L-1 min-1 gcat -1) and Fe-NC (1.0 mmol L-1 min-1 gcat -1). Significantly, the CoFe DAC hetero-e-Fenton process is demonstrated to be more energy-efficient for actual coking wastewater treatment with an energy consumption of 19.0 kWh kg-1 COD-1 than other electrochemical technologies that reported values of 29.7 similar to 68.0 kW h kg-1 COD-1. This study shows the attractive advantages of efficiency and sustainability for middotOH electrogeneration, which should have fresh inspiration for the development of new-generation wastewater treatment technology.