Electrocatalytic Generation and Spectroscopic Investigation of Reactive Oxygen Species in Alkaline Media
XUE Yu-dong1, 2, ZHENG Shi-li1*, ZHANG Yi1, JIN Wei1*
1. National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：Liquid oxidation techniques by sub-molten salt media for the effective extraction of amphoteric metal from refractory minerals have been developed. An innovative synergistic process by electrochemical oxidation and reactive oxygen species (ROS) intensify was further proposed. In the present study, the mechanism of ROS formation and conversion in the electrocatalytic process was systematically revealed by UV-Vis spectra and electron spin resonance (ESR) measurement. The reactive species were in-situ generated by two-electron oxygen reduction reaction (ORR) at the cathode surface. The ·OH was produced from the self-induced reaction between amphoteric metal ions and HO-2, which was beneficial for the oxidation dissolution process and considered as an alkaline electrochemical advanced oxidation process. The catalytic oxidation process of low-valance amphoteric metal oxides (Cr2O3 and V2O3) by ROS was illustrated by UV-Vis spectra. Furthermore, V2O3 was more easily dissolved than Cr2O3 with the presence of ROS according to the thermodynamic data of standard free energy change. The ·OH in the electrochemical system was detected by the ESR technique. The ESR signal of ·OH catalyzed by V2O3 was more remarkable than that of Cr2O3. The quenching experiment result proved that ·OH with high standard oxidation potential played a promoting role in the liquid oxidation process. The present investigation provides further standing for the electrochemical oxidative dissolution in alkaline media.
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