Fe-Co dual atomic doublets on N, P codoped carbon as active sites in the framework of heterostructured hollow fibers towards high-performance flexible Zn-Air battery

Dual single-atom catalysts (DSACs) with maximized atomic utilization efficiency and high catalytic activity are attractive for electrocatalytic reactions. However, their catalytic performances largely depend on the surrounding micro-environment and the efficient support, which remain a challenging issue until now. Herein, the hollow fibers which are composed of the carbon nanobubbles with N, P heteroatom codopants and Fe-Co dual atomic sites are designed and realized. The Fe-Co dual atomic sites are anchored on the N, P codoped carbon bubbles to form the FeCoN6-P-C (FeCo-NPC) configuration. The bubbles connect with each other and form the “bubble-in-rod” structure, appearing as the “BAH” fiber. The synergistic effect of Fe-Co dual centers and local electron engineering of P doping upgrade the adsorption/desorption features and boost the oxygen electrocatalytic reactions. Additionally, the highly porous and conductive framework boasts abundant active sites and thus enables the fast kinetics. Both theoretical and experimental results demonstrate the desired superior electrocatalytic activity with good stability towards the oxygen reduction/evolution reactions, which outperforms the reference samples of the counterpart catalyst without P dopant (FeCo-NC), the catalyst of single-atom Fe (Fe-NPC) and the catalyst of single-atomic Co based (Co-NPC) catalysts. On the basis of FeCo-NPC BAH cathode, the fabricated Zn-air battery achieves the high energy density and good cycling stability over 200 h. Moreover, the flexible solid-state ZAB with the polymer electrolyte and the 3D carbon matrix@Zn anode exhibits superior reliability, good durability and a wide range of adaptability over deformation and temperature. Therefore, this work not only paves a way for catalysts design, but also promotes the development of metal-air batteries for diverse electronics.