N/S‐Doped Hierarchical Porous Bamboo Carbon Fibers with Ultra‐Large Surface Area and Highly Exposed Active Sites for Flexible Zinc‐Air Battery^†

Abstract

Comprehensive Summary Facile mass transport channel and accessible active sites are crucial for binder‐free air electrode catalysts in rechargeable flexible zinc‐air battery (ZAB). Herein, a ZnS/NH 3 dual‐assisted pyrolysis strategy is proposed to prepare N/S‐doped hierarchical porous bamboo carbon cloth (HP‐NS‐BCC) as binder‐free air electrode catalyst for ZAB. BCC fabric with abundant micropores is firstly used as flexible carbon support to facilitate the heteroatom‐doping and construct the hierarchical porous structure. ZnS nanospheres and NH 3 activization together facilitate the electronic modulation of carbon matrix by N/S‐doping and optimize the macro/meso/micropores structure of carbon fibers. Benefiting from the highly‐exposed N/S‐induced sites with enhanced intrinsic activity, the optimized mass transport of biocarbon fibers, as well as the ultra‐large specific surface area of 2436.1 m 2 ·g –1 , the resultant HP‐NS‐BCC catalyst exhibits improved kinetics for oxygen reduction/evolution reaction. When applied to rechargeable aqueous ZABs, it achieves a significant peak power density of 249.1 mW·cm −2 . As binder‐free air electrode catalyst, the flexible ZAB also displays stable cycling over 500 cycles with a minimal voltage gap of 0.42 V, showcasing promising applications in flexible electronic devices.