Activating spinel CoMn2O4 supported on CNT via Zn substitution for bifunctional oxygen electrocatalysis

Efficient and stable electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have vital technical significance in the field of fuel cells and water splitting. Trimetallic spinel oxides are generated when Zn is introduced to partially replace Co of spinel CoMn2O4, resulting in a considerable increase in electrocatalytic ORR/OER activity. Combined with physical characterization and density functional theory (DFT) calculation, it is proved that the incorporation of Zn plays a critical role in regulating the lattice strain and valence states of Mn/Co on the surface and optimizing the electrocatalytic activity. Zn partial substitution efficiently narrows the band gap, and optimizes the binding strength between the active center and the reaction intermediate. When the doped amount of Zn is 0.2, the electrochemical activity of ORR (E1/2 = 0.81 V) and OER (η10 = 312 mV) are optimum. Cation substitution appears to be a potential method for enhancing the bifunctional catalytic activity of Co-Mn based spinel oxides for ORR and OER. This research contributes to the development and design of highly efficient bifunctional oxygen catalysts.