Performance Enhancement in Redox Flow Batteries Using Bismuth Based Catalyst

Abstract

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.