Active-Site Interactions in a Synergistic Porous Structured Fe Nanoparticle-Carbon Electrocatalyst for Enhanced Redox...

In practical applications, zinc-air batteries (ZABs) require high-performance, durable, and cost-effective electrocatalysts for the critical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Here, we describe a reflux synthesis method of constructing a porous catalyst by introducing turmeric yellow into extremely porous bio-carbon (PC) materials that contain iron nanoparticles (Fe NPs); these catalysts are known as Fe NPs@PC. These catalysts have become a significant substitute for high-performance cathodes in ZABs because their electrochemical properties can improve ORR performance. In addition to enhancing conductivity, the OER/ORR bifunctional active sites must be balanced by optimizing the Fe-C and Fe-Fe interactions within the active site. X-ray absorption analysis and density functional theory confirmed that strong iron-carbon interactions promote OER (η ₁₀ = 320 mV) and ORR (E _1/2 = 0.786 V) activity and exhibit a smaller potential gap of 0.764 V of Fe NPs@PC-700 catalyst. The impact of this redox activity enhances the high-power density (219 mW cm^-2) and long-term charge-discharge cycle stability (85 h@3 mA cm^-2) of ZABs. This work charts a viable route for the assembly of practical ZABs by regulating bifunctional electrocatalysts via appropriate modification of active sites.