Fe3O4/Co3O4 binary oxides as bifunctional electrocatalysts for rechargeable Zn–air batteries by one-pot pyrolysis of zeolitic imidazolate frameworks

Abstract

Highly efficient bifunctional electrocatalysts towards sluggish oxygen reduction and evolution reactions (ORR and OER) are of great significance for cathode catalysis of rechargeable metal–air batteries. Herein, we report a one-pot pyrolysis strategy to construct binary transition metal oxide (TMO) interfaces on a nitrogen doped porous carbon framework (CN) for bifunctional oxygen reaction catalysis. The constructed Fe₃O₄/Co₃O₄ interfaces not only help promote the stabilization of Fe²⁺ ions, but also generate abundant oxygen vacancies on the surface of composite catalysts (Fe₃O₄/Co₃O₄-CN), which boost the intrinsic oxygen reaction activity. The Fe₃O₄/Co₃O₄-CN catalyst exhibits a bifunctional electrocatalytic performance with a significantly lowered potential difference (ΔE) of 0.68 V between the half-wave potential of the ORR (E_1/2) and the potential of the OER at a current density of 10 mA cm⁻² (E_j=10), rivaling the best performance of previously reported bifunctional TMO catalysts to the best of our knowledge. The rechargeable Zn–air battery with Fe₃O₄/Co₃O₄-CN as the cathode catalyst exhibits superior performance with an energy density of 1045.82 W h kg_Zn⁻¹ and a peak power density of 105.7 mW cm⁻², as well as excellent cycling stability (over 80 h at a current density of 10 mA cm⁻²), demonstrating our new bifunctional oxygen electrocatalyst as a promising candidate for practical energy storage applications.