Unraveling the Crucial Role of Electrogenerated Cu(III) on the Cu–Sb–Sn/Granular Activated Carbon Three-Dimensional Electrode for Electrocatalytic Oxidation Reactions

Constructing a three-dimensional electro-oxidation reactor (3DER) by embedding particle electrodes between the anode and cathode is an effective strategy to alleviate the mass transfer restriction of pollutants from the bulk solution to the anode surface. Yet, the synthesis of particle electrodes with outstanding electrocatalytic activity remains a major obstacle. Herein, we constructed a novel particle electrode, viz., Cu–Sb–Sn/granular activated carbon (GAC), and introduced a Cu(I)/Cu(II) redox couple into it to accelerate electron transfer. An appropriate Cu doping ratio can generate a sufficient Cu(I)/Cu(II) redox couple, thereby triggering in situ electrogeneration of Cu(III) to promote the •OH generation and the direct electron transfer (DET) pathway of tetracycline (TC), while an excessive Cu doping ratio can lead to the formation of adverse CuO with low oxygen evolution reaction (OER) potential. As a result, Cu0.02–Sb–Sn/GAC achieved a higher activity with a current efficiency of 41.1% and an energy consumption of 54.2 kW h/kg COD for the electro-oxidation removal of TC, outperforming other state-of-the-art particle electrodes in the literature. This work presents an adaptive paradigm to utilize a transition-metal-mediated redox couple to promote the generation of high-valent metal species and optimize pollutant removal from wastewater via electro-oxidation.