Transition metal (TM)-based bimetallic spinel oxides can efficiently activate peroxymonosulfate (PMS) presumably attributed to enhanced electron transfer between TMs,b ut the existing model cannot fully explain the efficient TM redoxc ycling. Here,w ed iscover ac ritical role of TM À O covalency in governing the intrinsic catalytic activity of Co 3Àx Mn x O 4 spinel oxides.E xperimental and theoretical analysis reveals that the Co sites significantly raises the Mn valence and enlarges MnÀOc ovalency in octahedral configuration, thereby lowering the charge transfer energy to favor Mn Oh-PMS interaction. With appropriate Mn IV /Mn III ratio to balance PMS adsorption and Mn IV reduction, the Co 1.1 Mn 1.9 O 4 exhibits remarkable catalytic activities for PMS activation and pollutant degradation, outperforming all the reported TM spinel oxides.T he improved understandings on the origins of spinel oxides activity for PMS activation may inspire the development of more active and robust metal oxide catalysts.

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Transition metal (TM)-based bimetallic spinel oxides can efficiently activate peroxymonosulfate (PMS) presumably attributed to enhanced electron transfer between TMs,b ut the existing model cannot fully explain the efficient TM redoxc ycling. Here,w ed iscover ac ritical role of TM À O covalency in governing the intrinsic catalytic activity of Co 3Àx Mn x O 4 spinel oxides.E xperimental and theoretical analysis reveals that the Co sites significantly raises the Mn valence and enlarges MnÀOc ovalency in octahedral configuration, thereby lowering the charge transfer energy to favor Mn Oh-PMS interaction. With appropriate Mn IV /Mn III ratio to balance PMS adsorption and Mn IV reduction, the Co 1.1 Mn 1.9 O 4 exhibits remarkable catalytic activities for PMS activation and pollutant degradation, outperforming all the reported TM spinel oxides.T he improved understandings on the origins of spinel oxides activity for PMS activation may inspire the development of more active and robust metal oxide catalysts.