Deciphering potential-dependent oxygen reduction kinetics in spinel manganese ferrite
Junxiang Wang1, Zhaoyi Jiang1, Jingwen Wei1
1China-UK Low Carbon College, Shanghai Jiao Tong University, Shanghai 200240, China. yezhou_lcc@sjtu.edu.cn.
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Accurate evaluation of oxygen reduction reaction (ORR) catalysts, especially transition metal oxides, requires careful control of testing parameters. Here, we report a potential-window-dependent ORR activity for spinel manganese ferrite (MnFe2O4). The ORR activity exhibits a volcano-shaped dependence on the lower potential limit during cathodic scans. Combined experimental analysis and joint density-functional theory (JDFT) calculations reveal that changes in surface Mn site density, Mn oxidation state, irreversible Fe segregation, and potential-dependent reaction free energies contribute to this behavior. Our findings highlight that sweeping potential windows can critically influence ORR performance and must be carefully optimized for the accurate assessment of transition metal oxide catalysts.
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