Iron-chelated hydrogel-derived bifunctional oxygen electrocatalyst for high-performance rechargeable Zn–air batteries

Efficient oxygen electrocatalysts are the key elements of numerous energy storage and conversion devices, including fuel cells and metal–air batteries. In order to realize their practical applications, highly efficient and inexpensive non-noble metal-based oxygen electrocatalysts are urgently required. Herein, we report a novel iron-chelated urea-formaldehyde resin hydrogel for the synthesis of Fe-N-C electrocatalysts. This novel hydrogel is prepared using a new instantaneous (20 s) one-step scalable strategy, which theoretically ensures the atomic-level dispersion of Fe ions in the urea-formaldehyde resin, guaranteeing the microstructural homogeneity of the electrocatalyst. Consequently, the prepared electrocatalyst exhibits higher catalytic activity and durability in the oxygen reduction (ORR) and evolution (OER) reactions than the commercial Pt/C catalyst. Furthermore, the above catalyst also shows a much better performance in rechargeable Zn–air batteries, including higher power density and better cycling stability. The developed synthetic approach opens up new avenues toward the development of sustainable active electrocatalysts for electrochemical energy devices.