In Situ Pore-Making and Heteroatom Doping of Carbon Nanofibers Electrode for High Performance Vanadium Redox Flow Battery

Abstract

Electrochemical performance of the electrospun carbon nanofibers (ECNFs) electrode for all vanadium redox flow battery (VRFB) is significantly enhanced by introducing urea into the precursor solution and the subsequent thermal treatment. A novel N, O dual-doped carbon nanofibers with a series of micronanometer multiscale pores on the surface can be easily obtained by the in situ thermolysis processes of urea, which endows the electrode larger surface area, better wettability and improved electroactive sites. The electrochemical results demonstrate that the N, O co-doping ECNFs with multiscale pores shows reduced charge transfer resistance and diffusion resistance for vanadium ions redox reactions, which should be attributed to the synergy of the larger effective surface area and better electrocatalytic activity. The VRFB equipped with the novel carbon nanofibers electrode delivers a 84.6% increase of the discharge capacity and 17% amplification of the energy efficiency compared with the pristine ECNFs at 150 mA cm−2. This simple method to construct electrodes with N, O dual-doped and micronanometer multiscale pores also paves the way to finely regulating the internal microstructure and composition of the electrodes in a variety of energy storage systems.

Green and Affordable Manufacturing Method for Multi-Scale Porous Carbon Nanofibers and Its Application in Vanadium Redox Flow Battery

“…A series of hydrophilic modifiers, such as CeO 2 , 27 TiO 2 , 28 NiO, 29 CoO 30 and etc., have been introduced into the electrode surface to improve the hydrophilic properties, and result in an improved electrochemical surface area (ECSA) and electrocatalytic activity of the electrode. In addition, various etching agents have been applied to form etch pits on the fiber surface under higher temperature, such as KOH, 31 CO 2 , 32 NH 3 , 33 urea 34 and etc. Compared to other methods, pore-making on carbon fiber surface is easier, more efficient and low cost, which is very suitable for large-scale production.…”