Iron and nitrogen-doped porous carbon nanofibers derived from one-step grown non-granular metal-organic frameworks for zinc-air batteries

The development of low-cost bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for advancing Zn-air batteries (ZABs). Herein, Fe/N-doped porous carbon nanofibers (Fe/N@PCNF-2) were synthesized via a one-step strategy featuring the in-situ growth of non-granular metal-organic frameworks (MOFs) directly on electrospun nanofibers, followed by pyrolysis. The optimized Fe/N@PCNF-2 combines a conductive hierarchical porous network with abundant Fe-N x -related sites, delivering an ORR half-wave potential of 0.87 V and an OER potential of 1.55 V at 10 mA cm −2 . Density functional theory (DFT) calculations further attribute the superior bifunctional activity of Fe/N@PCNF-2 to the more balanced adsorption, conversion, and desorption of oxygen-containing intermediates on the representative Fe-N 4 /C configuration. When employed as the air-cathode catalyst, the resulting liquid ZAB displayed a high-power density of 245 mW cm −2 , a minimal charging/discharging voltage gap of 0.75 V, and outstanding cycling stability over 1500 h (4500 cycles). Impressively, a flexible ZAB incorporating the Fe/N@PCNF-2 also achieved a high-power density of 215 mW cm −2 , excellent durability over 75 h (225 cycles) and remarkable flexibility under the multi-angle bending conditions. This work provides a novel and straightforward approach for designing efficient bifunctional electrocatalysts, highlighting their promising potential for practical application.