Structure Preferred Spinel Ferrite on Polypyrrole Derived N-Doped Carbon Nanofibers as Bifunctional Electrocatalyst for Zn-Air Battery

Abstract

The explorationof noble metal free bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is very important for Zn-air batteries (ZABs). Spinel ferrites are famous bifunctional ORR/OER electrocatalysts. Herein, to further improve their ORR and OER activities, we anchor CoFe₂O₄ on N-doped carbon nanofibers (NCNF) derived from polypyrrole (PPy) and obtain CoFe₂O₄ loaded NCNF (CoFe₂O₄@NCNF). In its structure, CoFe₂O₄ particles with small size distribute evenly on NCNF. The combination of CoFe₂O₄ and NCNF generates excellent ORR activity with typical four-electron character in both alkaline and neutral electrolyte. In OER, the activity of CoFe₂O₄@NCNF is also excellent. A rechargeable ZAB is constructed with CoFe₂O₄@NCNF as cathode material. The specific capacity and energy density of this ZAB reach 807.4 mAh g⁻¹ and 963.6 Wh kg⁻¹ at 10 mA cm⁻², respectively. ZAB can keep stable after continuous charge/discharge test for 120 h. This work not only provides an efficient and low cost cathode material for ZABs, but also clarifies the structure-activity relationship in ORR/OER for spinel ferrites.