WO3-modified graphite felt for anode of vanadium redox flow batteries

초록

In this study, we investigated the addition of tungsten catalyst into the negative electrolyte (anolyte) of the vanadium redox flow batteries (VRFBs), determining the performance of the cells with respect to the small amount of the tungsten hexachloride as a precursor. The VRFBs showed an improvement in electrochemical performance clearly by the electrodeposition of tungsten or tungsten oxide as catalysts (W metal, WO3) on the anode. Modified electrode occurred as following reaction (WCl6 → WO4- → WO3 by complex reaction). The presence of tungsten allowed the ionization of tungsten in the anolyte during the cell cycle. The trade-off concentration of the tungsten precursor was determined by electrochemical analysis methods. It showed that the energy efficiency of the VRFBs was enhanced up to 3 % after adding small amount of tungsten into the anolyte. Particularly, the performance of cells in the anolyte containing tungsten catalysts was significantly enhanced at the high current rates (80 mA cm-2). In addition, the result of ICP-MS showed that permeation of the tungsten precursor did not appear through the separator during the cell cycle.