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

[Display omitted] • A novel flow-anode, CeO x /CB, was introduced in electro-oxidation. • Ce(IV)/Ce(III) redox cycle accelerated the electron transfer directionally. • The loading of CeO x actuated efficient •OH generation. • Acetaminophen degradation rate was 2.3–2.9 times higher than the control. • CeO x /CB achieved high current efficiency and low energy consumption. 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, CeO x /carbon black (CB), demonstrates superior electrocatalytic degradation efficiency of organic pollutants. The acetaminophen degradation kinetic constant of CeO x /CB was calculated to be 2.3–2.9 times higher than that of CB. CeO x /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-Al 2 O 3 -based flow-anodes. The mechanistic analyses demonstrated that rapid electron transfer, strong water adsorption, and low reaction energy barrier of CeO x /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 H 2 O 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. [ABSTRACT FROM AUTHOR]