Zinc-assisted synthesis of polymer framework-based atomically dispersed bimetal catalysts for efficient oxygen electrocatalysis in rechargeable zinc-air batteries

The development of atomically dispersed metal catalysts has garnered significant attention for their potential in catalysing the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in various electrochemical energy devices such as metal-air batteries and fuel cells. However, achieving atomically dispersed metal catalysts with high selectivity and long-term stability remains a substantial challenge. Herein, an efficient iron‑cobalt-based oxygen bifunctional electrocatalyst, FeCoN-PDF-T2-2, is synthesised by carbonising the precursor of metal-incorporated phloroglucinol-dicyandiamide-formaldehyde polymer frameworks (PDF) and obtained atomically dispersed active sites with suitable textural properties. The FeCoN-PDF-T2-2 catalyst exhibits the half-wave potential (E1/2) of 0.85 V for ORR, Ej=10 value of 1.60 V for the OER, and excellent electrochemical stability after 10,000 potential cycles with negligible loss in E1/2. Scanning transmission electron microscopy (STEM) assessment confirms the atomically dispersed metal sites in the carbon matrix. Accordingly, the assembled rechargeable zinc-air battery (RZAB) with FeCoN-PDF-T2–2 as air-electrode delivered a peak power density of 258 mW cm−2 and long-term stability. The findings from this work are poised to provide insight and directives for the development of atomically dispersed dual-metal catalysts derived from polymer frameworks via a simple synthesis route, facilitating their eventual commercialisation in various energy storage applications.