Interphase synergy of an in situ grown skeletal porous structured multiphase composite catalyst enables highly efficient and stable ORR/OER for high performance rechargeable zinc–air batteries

Abstract

Development of cost-effective, highly efficient and stable bifunctional catalysts for catalysis of oxygen reduction and evolution reactions at air positive electrodes is critical for practical applications of rechargeable zinc–air batteries (ZABs). Herein, an in situ grown skeletal porous structured binder-free homogeneous two-phase Co-based hexagonal close-packed-Co/face-centered cubic-FeCoNi (HCP-Co/FCC-FeCoNi) composite catalyst is reported. The composite catalyst, with activity enhancements arising from interphase synergy between HCP-Co and FCC-FeCoNi and highly efficient reaction environments offered by the binder-free skeletal porous structure, exhibits exceptional electrochemical performances. The HCP-Co/FCC-FeCoNi-based air electrode achieves an ultra-small potential gap at 10/100 mA cm⁻² (ΔE₁₀/ΔE₁₀₀) of 0.596/0.810 V and the HCP-Co/FCC-FeCoNi-based ZAB delivers an ultralow voltage gap of 1.644 V at 400 mA cm⁻², an extraordinarily high discharge peak power density of 423 mW cm⁻², and outstanding cycling stability of 770 h at 10 mA cm⁻², largely outperforming the (Pt/C + RuO₂)-based benchmarks. The presence of Fe significantly promotes formation of FCC-FeCoNi, the main active component of the two-phase composite catalyst, leading to ultrahigh bifunctional catalytic activities. The composition and nanostructure engineering approaches developed herein prove to be highly effective for advancement of bifunctional oxygen reduction reaction/oxygen evolution reaction catalysts for advanced ZABs.