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 sur-rounding 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 electro-catalytic 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 elec-trocatalytic 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.