Controllable growth on Nano-graphite-supported ZrO2-MnOx bimetallic oxides for electrocatalytic antibiotics degradation: boosting mechanism of Mn3+/Mn4+ redox cycle

Abstract

Antibiotic contamination has become one of the most pressing problems in the field of water purification. Using Nano-graphite (Nano-G) as carbon carrier, ZrO2-MnOx/Nano-G composite electrode with high catalytic activity was prepared by hot pressing method based on MnOx/Nano-G prepared by sol-gel method. The results show that the ZrO2-MnOx/Nano-G electrode reduces charge transfer resistance while improving surface oxygen desorption ability. MnOx can catalyze the two-electron reduction of O2 to produce H2O2, which can then be converted to ·OH and ·O2-. Thereafter, the results of free radical capture experiments confirmed that ·O2- played a significant role in the electrocatalytic degradation of tetracycline hydrochloride (TC) by a ZrO2-MnOx/Nano-G composite electrode. Furthermore, the abundant hydroxyl group on the surface of Nano-G and ZrO2 particles can be used as an active site for catalyzing the Mn3+/Mn4+ redox reaction, resulting in the generation of more free radicals. The high efficiency electrocatalytic degradation of TC was achieved through the synergistic action of the three. Under optimal reaction conditions, the degradation rate of TC reached 93% after 120 min of electrolysis. ZrO2-MnOx/Nano-G displayed good stability following 10 cycles of degradation experiments. Finally, the potential TC degradation pathway was investigated using liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT), and the degradation mechanism was clarified.

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ORCID for Yongqiang Liu: orcid.org/0000-0001-9688-1786

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