Preparation and optimization of Ag nanoparticle-decorated porous carbon fibers from electrospun water-soluble lignin precursors as efficient bifunctional cathodes for rechargeable zinc-air batteries

Lignin has attracted significant attention for its complicated structures and potential to produce high-value carbon materials from low-cost waste. The present work demonstrates successful water-based electrospinning of lignin-based carbon fiber (LCFs) precursors, despite challenges posed by high lignin content. The diameters of precursor fibers decreased as lignin content increased. After carbonization, porous carbon fibers with an average diameter of 72 ± 27 nm were successfully fabricated. Such CFs exhibited a high specific surface area. When loaded with Ag nanoparticles, LCFs-Ag exhibited remarkable electrocatalytic performance, including an oxygen reduction reaction (ORR) half-wave potential of 0.85 V and an oxygen evolution reaction (OER) overpotential of 0.382 V at 10 mA cm −2 . This performance is on par with Pt/C and IrO 2 . Rechargeable liquid zinc-air batteries (LZABs) assembled with LCFs-Ag yielded an open-circuit voltage of 1.50 V, a peak power density of 135.9 mW cm −2 , and cycling stability of over 400 h, outperforming LZABs with a Pt/C + IrO 2 cathode under identical experimental conditions. The present work highlights that water-based electrospinning of lignin can be used to convert waste into a valuable resource, producing carbon fibers with excellent electrocatalytic properties for rechargeable zinc-air battery applications.