Interphase synergy of 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 proves to be highly effective for advancement of bifunctional oxygen reduction reaction/oxygen evolution reaction catalysts for advanced ZABs.