Atomic Fe-N-x Coupled Open-Mesoporous Carbon Nanofibers for Efficient and Bioadaptable Oxygen Electrode in Mg-Air Batteries

The recently emerging metal-air batteries equipped with advanced oxygen electrodes have provided enormous opportunities to develop the next generation of wearable and bio-adaptable power sources. Theoretically, neutral electrolyte-based Mg-air batteries possess potential advantages in electronics and biomedical applications over the other metal-air counterparts, especially the alkaline-based Zn-air batteries. However, the rational design of advanced oxygen electrode for Mg-air batteries with high discharge voltage and capacity under neutral conditions still remains a major challenge. Inspired by fibrous string structures of bufo-spawn, it is reported here that the scalable synthesis of atomic Fe-N-x coupled open-mesoporous N-doped-carbon nanofibers (OM-NCNF-FeNx) as advanced oxygen electrode for Mg-air batteries. The fabricated OM-NCNF-FeNx electrodes present manifold advantages, including open-mesoporous and interconnected structures, 3D hierarchically porous networks, good bio-adaptability, homogeneously coupled atomic Fe-N-x sites, and high oxygen electrocatalytic performances. Most importantly, the assembled Mg-air batteries with neutral electrolytes reveal high open-circuit voltage, stable discharge voltage plateaus, high capacity, long operating life, and good flexibility. Overall, the discovery on fabricating atomic OM-NCNF-FeNx electrode will not only create new pathways for achieving flexible, wearable, and bio-adaptable power sources, but also take a step towards the scale-up production of advanced nanofibrous carbon electrodes for a broad range of applications.