Summary
Carbon felt co‐doped with nitrogen and phosphorus is suggested as an electrode for catalytically enhancing the redox reaction of the VO2+/VO2+ redox couple. N and P can be simultaneously incorporated with the carbon felt via a one‐step facile synthesis method using aniline and triphenylphosphine as the N and P sources. Successful co‐doping is confirmed using energy‐dispersive spectroscopy and X‐ray photoelectron spectroscopy analyses. The electrochemical activity of the proposed carbon felt electrode toward the VO2+/VO2+ redox reaction is significantly enhanced when compared to those of carbon felt electrodes doped with only nitrogen or phosphorus, owing to the synergetic effect of the N, P co‐doping. The all‐vanadium redox flow battery (VRFB) assembled with the N, P co‐doped carbon felt (NPCF) electrode exhibits a highly stable cyclic performance accompanied by considerably improved energy efficiencies of 84.94% and 84.33% in the 1st and 50th cycles, respectively. In addition, the cell employing the NPCF electrode exhibits an energy efficiency of 79.1%, approximately 11% higher than that of bare carbon felt (BCF: 68.1%), at a high current density of 100 mA cm−2. This improvement is mainly attributed to abundant electrochemical active sites for the oxidation and reduction of vanadium ions provided by the N and P functional groups formed on the carbon felt via our proposed treatment. These mitigate electrochemical polarization and accelerate the redox reaction.
Slow reaction rates of vanadium (V), iron (Fe), chrome (Cr) redox couples are a bottleneck to address for enhancing performance of vanadium and Fe-Cr redox flow battery (VRFB and Fe-Cr RFB) system. For promoting their reaction rates, new catalytic materials based on Bismuth (Bi) are suggested in this study. Reaction reversibility as well as catalytic activity of the catalysts is investigated using cyclic voltammogram (CV) and the results are compared with those of other catalysts. Performances and long term stabilities of VRFB and Fe-Cr RFB using Bi-based catalysts are evaluated by repetitive and cyclic measurements of charge-discharge step. Especially, energy efficiency (EE) and capacity loss rate are mainly inspected to determine superiority of the VRFB and Fe-Cr RFB. Their crystal structure, specific surface area and catalyst morphology are measured by chemical characterizations. The new Bi-based catalysts show high peak current ratio, small peak potential difference and high electron transfer rate constant, confirming that in both catalytic activity and reaction reversibility facets, the Bi-based catalysts play an important role. In terms of charge-discharge curves, VRFB and Fe-Cr RFB including new catalysts indicate high EE, low overpotential and low internal resistance. The results are attributed to role of Bi that activates Fe2+/Fe3
+, Cr2+/Cr3
+ and V4+/V5
+ redox reactions. Indeed, adoption of the Bi-based catalysts lead to improvement in performances and long term stabilities of VRFB and Fe-Cr RFB.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.