Doping-engineered bifunctional oxygen electrocatalyst with Se/Fe-doped Co₃O₄/N-doped carbon nanosheets as highly efficient rechargeable zinc-air batteries

Highly efficient oxygen reduction and oxygen evolution reactions have the critical role in the practical application of zinc-air batteries. Herein, doping engineering strategy has been adopted by construction of Se/Fe-doped in Co₃O₄/N-doped carbon nanosheets (denoted as Se/Fe-Co₃O₄/N-CNs) catalyst for boosting oxygen electrocatalytic activity. The achieved Se/Fe-Co₃O₄/N-CNs catalyst presents high-performances electrocatalytic characteristics, which exhibits a small overpotential gap (0.79 V), excellent oxygen evolution reaction activity with a small overpotential of 361 mV and a low Tafel slope of 57.3 mV dec^-1 at 10 mA cm^-2 as well as excellent oxygen reduction reaction activity with a large half-wave potential of 0.8 V, also surpassing the majority of reported Co₃O₄-based electrocatalysts. The outstanding catalytic performances are benefiting from the contributions between Se/Fe doping engineering and N-doped carbon nanosheets optimizing the electronic structure of Co species, endowing more active sites, enhancing the intrinsic catalytic activity and accelerating charge transfer rate for oxygen electrocatalytic process. Particularly, the as-fabricated zinc-air batteries with Se/Fe-Co₃O₄/N-CNs as air cathode presents a high open circuit potential of 1.41 V, a prominent highly efficient peak power density of 141.3 mW cm^-2, a high specific capacity of 765.6 mAh g^-1 and energy density 861.3 Wh kg^-1 at current density of 10 mA cm^-2 as well as an excellent cycling stability, which are exceeding the commercial Pt/C-RuO₂ based zinc-air batteries. This work lays a foundation for design and development of high-performance bifunctional cobalt-based electrocatalysts for rechargeable metal-air batteries application.