Atomic Fe–Nx Coupled Open‐Mesoporous Carbon Nanofibers for Efficient and Bioadaptable Oxygen Electrode in Mg–Air Batteries

Abstract 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‐FeN x ) as advanced oxygen electrode for Mg–air batteries. The fabricated OM‐NCNF‐FeN x 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‐FeN x 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.