Design and synthesis of porous channel-rich carbon nanofibers for self-standing oxygen reduction reaction and hydrogen evolution reaction bifunctional catalysts in alkaline medium

Carbon-nanofiber-based (CNF-based) nonprecious catalysts and electrodes are essential components in next generation energy conversion and storage technologies. Moreover, porous architectures are highly desirable for active material embedded CNFs. Despite recent progress, controllable synthesis of porous CNFs with favorable mechanical properties is still challenging. Herein, we present a general and novel approach to prepare porous and channel-rich CNFs on a large scale through a free-surface electrospinning technique and subsequent carbonization of polyacrylonitrile (PAN)/cellulose acetate (CA) nanofibers. The resultant free-standing and flexible PAN/CA CNFs (CACNFs) possess abundant porous and channel-rich structures, which can be easily controlled by adjusting the weight ratio of PAN and CA. Based on the porous CACNFs, binder-free Fe₃C embedded Fe/N doped CACNF films are successfully prepared. Combining the porous channel-rich structures and the high electrical conductivity of the carbon fibers, abundant accessible active sites and fast mass transport pathways are generated in the carbon fibers, leading to favorable catalytic activity and superior stability for ORR (half-wave potential 12 mV more positive than that of Pt/C) and HER (overpotential 440 mV@80 mV cm⁻² and more than 100 000 s catalytic stability) in alkaline medium, demonstrating their promising potential for application in fuel cells, metal-air batteries and water splitting devices.