Doping-engineered bifunctional oxygen electrocatalyst with Se/Fe-doped CoO/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 CoO/N-doped carbon nanosheets (denoted as Se/Fe-CoO/N-CNs) catalyst for boosting oxygen electrocatalytic activity. The achieved Se/Fe-CoO/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 at 10 mA cm as well as excellent oxygen reduction reaction activity with a large half-wave potential of 0.8 V, also surpassing the majority of reported CoO-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-CoO/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, a high specific capacity of 765.6 mAh g and energy density 861.3 Wh kg at current density of 10 mA cm as well as an excellent cycling stability, which are exceeding the commercial Pt/C-RuO 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.