CoFe ₂ O ₄ with the In‐Situ Formed Oxygen Vacancies and Co Particles as an Efficient Bifunctional Catalyst for Rechargeable Zinc‐Air Batteries

Rechargeable zinc-air batteries (RZABs) are considered as one of the most promising clean energy device due to their abundant resources, low cost and environmental friendliness. However, their energy efficiency and cycle life are far from satisfactory due to the poor activity and stability of bi-functional electrocatalyst in air cathode. In this work, an efficient bi-functional catalyst (rGO-CoFe₂O₄/Co) was derived from its precursor (rGO-CoFe₂O₄) through a simple annealing process. Electrochemical measurements prove that rGO-CoFe₂O₄/Co with the in-situ formed Co nano particles and rich oxygen vacancies appears excellent oxygen reduction reaction and oxygen evolution reaction catalytic activity compared to its counterpart. Its half-wave potential is 0.81 V (vs RHE) and the OER overpotential is only 310 mV (vs RHE). In addition, rechargeable zinc-air batteries assembled with rGO-CoFe₂O₄/Co show the highest peak power density (128.9 mW cm^-2) and cycling stability compared to rGO-CoFe₂O₄ and commercial Pt/C-RuO₂ catalysts. This work provides a simple strategy for the design of advanced bifunctional catalysts.