Ce(IV)/Ce(III) redox cycle triggers hydroxyl radical production on the CeOx/carbon black flow-anode for electro-oxidation of acetaminophen

Abstract

Electrochemically active materials can effectively alleviate mass transfer restriction by adding them as flow-anodes into the electrochemical reactor. However, conventional flow-anode materials display a low •OH yield. Here, a novel flow-anode, CeOx/carbon black (CB), demonstrates superior electrocatalytic degradation efficiency of organic pollutants. The acetaminophen degradation kinetic constant of CeOx/CB was calculated to be 2.3–2.9 times higher than that of CB. CeOx/CB achieved a higher current efficiency of 66.4 % and relatively lower energy consumption of 157.8 kWh/kg COD compared with other GAC or γ-Al2O3-based flow-anodes. The mechanistic analyses demonstrated that rapid electron transfer, strong water adsorption, and low reaction energy barrier of CeOx/CB actuated efficient •OH generation. Moreover, Ce(IV)/Ce(III) redox cycle crucially acted as an “electron porter” to accelerate the electron transfer from adsorbed H2O molecules to CB substrate directionally in the electro-oxidation process. This work provides a feasible manner for the development of flow-anodes utilizing the advantage of the Ce(IV)/Ce(III) redox cycle.