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A novel polyoxometalate-based electrode was developed by incorporating phosphotungstic acid (PWA) in nylon-6,6 nanofiber, followed by carbonization. The developed PWA-carbon nanofiber (PWA-CNF) showed the characteristics of the dual-scale porosity of micro- and mesoporous substrate with surface area of around 684 m2 g-1. The compound exhibited excellent stability in vanadium electrolyte and battery cycling. Evaluation of electrocatalytic properties toward V2+/V3+ and VO2+/VO2+ redox couples indicated promising advantages in electron transfer kinetics and increasing energy efficiency, particularly for the VO2+/VO2+ couple. Moreover, the developed electrode exhibited substantially improved energy efficiency (14% higher than that of pristine carbon felt) in the single cell vanadium redox flow battery. This outstanding performance was attributed to high surface area and abundant oxygen-containing linkages in the developed electrode.

The performance of vanadium redox flow battery (VRFB) is highly dependent on the efficiency of the membrane. Generally, anion exchange membranes and cation exchange membranes can be applied in the VRFB. In this paperwork, AMI-7001S anion exchange membrane and CMI-7000S cation exchange membranes were tested for their suitability in the VRFB application. Both of the membranes were originally used for electrocoat and water treatment system. In order to study the behavior of the membranes in the VRFB, several tests were performed. This includes VO2+ ion permeability, ionic conductivity, ion selectivity, chemical stability and single cell performance. The results obtained were compared to Nafion 117 which is a proton exchange membrane. This membrane is one of the most established membranes for VRFB. From the experiment, it can be summarized that the membranes are unsuitable to be used in VRFB. This is due to the low ion selectivity, poor chemical stability and high resistance.