Highly active Fe-N4 sites confined in ordered carbon nanotube arrays as self-supporting cathode catalyst for oxygen conversion

To develop low-cost and efficient oxygen reduction reaction (ORR) electrocatalysts, single-atom catalysts (SACs) have attracted great attention to become vital to the applications of zinc-air batteries (ZABs) because of their high catalytic activity. The development of integrated SACs as self-supporting electrodes is crucial for ZABs to overcome the drawback of powder catalysts requiring binder. Herein, an integrated atomically dispersed FeSA/NC catalyst was obtained by pyrolysis of Fe-containing ZIF-8 on fir wood-derived carbon. The atomically dispersed Fe-N4 is an efficient catalytic active site for ORR. The self-supported ordered porous structure and continuous conductive network of the catalyst provide favorable conditions for the rapid mass/electron transfer. FeSA/NC catalyst demonstrates a positive half-wave potential of 0.90 V in 0.1 M KOH electrolyte and 0.80 V in acidic solution. The outstanding ORR activity outperforms those of commercial Pt/C and most reported M-N-C (M=Fe, Co, Ni, etc.) catalysts. A quasi-solid-state ZAB using the FeSA/NC in cathode shows an excellent peak power density of 77 mW cm–2 at 121 mA cm–2. The performance in quasi-solid-state batteries exceeds that of most other catalysts. This work provides a new path to the catalytically active carbon via design of self-supporting SACs, and a clear demonstration of prospects in quasi-solid-state energy devices.