Unsaturated cobalt-nitrogen atomic sites in necklace-like hairy fibers towards highly efficient oxygen electrocatalysis for flexible Zn-Air battery

Exploration of single-atom catalysts (SACs) with high activity and efficient utilization efficiency holds great promise in the field of electrocatalysis. However, it is still a challenge to rationally design the SACs due to their properties are greatly influenced by the local electron environment and the effective substrate. Herein, we synchronously realized the modulation of unsaturated cobalt-nitrogen atomic sites (CoN3) and uniformly archoring them on the carbon-nanotube assembled necklace-like fiber (NLF). The unsaturated cobalt-nitrogen atomic sites with asymmetric structure favor the adsorption/desorption features and promote the electrocatalytic reactions of oxygen. Meanwhile, the hairy NLF fiber with the highly conductive and porous matrix guarantees the active sites accessibility and fast kinetics. In addition, the unique necklace-like configuration endows good mechanical strength and high reliability for the CoN3 NLF fiber. Both density functional theoretical (DFT) calculation and the experimental results reveal its superior catalytic properties and good reliability in the oxygen electrocatalytic reactions. Moreover, the finite element analysis (FEA) and the corresponding tests further certify its high pliability and good robustness. Based on the CoN3 NLF fiber air cathode, the aqueous Zn-air battery (ZAB) delivers a high power density (306 mW cm(-2)) and outstanding cycling stability over 300 h. Furthermore, all-solid-state ZAB based on the freestanding CoN3 NLF air cathode shows considerable flexibility and superior reliability over a wide range of temperatures (-20 similar to 25 degrees C). Therefore, this work provides an effective catalyst design for the development of metal-air batteries for diverse applications.