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Abstract Bimetallic cobalt‐based spinel is sparking much interest, most notably for its excellent bifunctional performance. However, the effect of Fe 3+ doping in Co 3 O 4 spinel remains poorly understood, mainly because the surface state of a catalyst is difficult to characterize. Herein, a bifunctional oxygen electrode composed of spinel Co 2 FeO 4 /(Co 0.72 Fe 0.28 ) Td (Co 1.28 Fe 0.72 ) Oct O 4 nanoparticles grown on N‐doped carbon nanotubes (NCNTs) is designed, which exhibits superior performance to state‐of‐the‐art noble metal catalysts. Theoretical calculations and magnetic measurements reveal that the introduction of Fe 3+ ions into the Co 3 O 4 network causes delocalization of the Co 3d electrons and spin‐state transition. Fe 3+ ions can effectively activate adjacent Co 3+ ions under the action of both spin and charge effect, resulting in the enhanced intrinsic oxygen catalytic activity of the hybrid spinel Co 2 FeO 4 . This work provides not only a promising bifunctional electrode for zinc–air batteries, but also offers a new insight to understand the Co‐Fe spinel oxides for oxygen electrocatalysis.
Wang et al. (2019) studied this question.