One-step In-situ Synthesis of Vacancy-rich CoFe₂O₄@Defective Graphene Hybrids as Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries

Developing efficient catalysts toward both oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) is the core task for rechargeable metal-air batteries. Although integration of two active components should be an effective method to produce the bifunctional catalysts in principle, traditional techniques still can not attain fine tunable surface structure during material-hybridization process. Herein, we present a facile short-time in-situ argon(Ar) plasma strategy to fabricate a high-performance bifunctional hybrid catalyst of vacancy-rich CoFe₂O₄ synergized with defective graphene(r-CoFe₂O₄@DG). Reflected by the low voltage gap of 0.79 V in two half-reaction measurements, the striking capability to catalyze ORR/OER endows it excellent and durable performance in rechargeable Zn-air batteries, with a maximum power density of 155.2 mW/cm² and robust stability(up to 60 h). Further experimental and theoretical studies validate its remarkable bifunctional energetics root from plasma-induced surface vacancy defects and interfacial charge polarization between DG and CoFe₂O₄. This work offers more opportunities for reliable clean energy systems by rational interfacial and defect engineering on catalyst design.