A CNT-connection strategy of coupling ZnS and a CoFe alloy in ORR/OER catalysts of rechargeable zinc–air batteries

Abstract

The CNT-connection strategy was proposed to address the challenge of coupling diverse oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) active sites, which was critical for enhancing catalyst performance in rechargeable zinc–air batteries (ZABs). Through this strategy, a composite catalyst (FeCo-S/Z8-NC) was synthesized by integrating ZnS, a CoFe alloy and defective carbon planes via CNTs. Most active sites in FeCo-S/Z8-NC were encapsulated by CNTs, forming a protective shell that improved stability. FeCo-S/Z8-NC exhibited excellent bifunctional catalytic activity (ORR: E_1/2 = 0.86 V, OER: E_j=10 = 1.52 V), which outperformed the commercial Pt/C + RuO₂ catalyst. When applied in ZABs, it delivered a high open-circuit voltage of 1.56 V, remarkable long-term charge–discharge stability (270 h), and outstanding power densities across a wide temperature range (−10 °C: 114.52 mW cm⁻², 25 °C: 162.82 mW cm⁻², and 60 °C: 229.49 mW cm⁻²). This work provided a feasible approach for developing efficient, low-cost and eco-friendly ORR/OER catalysts, promoting the sustainable application of ZABs.