The effect of graphite felt treatment using iron-triethanolamine as etching precursor on the performance of vanadium redox flow battery

In this study, to improve the performance of vanadium redox flow battery (VRFB), Fe-triethanolamine (Fe(TEA)) is used as a precursor of carbon etching to form two-scale mesoporous structure on graphite felt (GF) electrode. Specifically, large-scale mesopores (~0.5 μm) and small-scale mesopores (~10 nm) are produced on the fibers of GF electrode (Fe(TEA)-TGF). With the mesopores, the specific surface area and the number of active site of GF electrode are significantly increased, and the overvoltage sacrificed on GF electrode is reduced. When the performances of VRFBs using the treated GF electrodes are measured, energy efficiency (EE) of VRFB using Fe(TEA)-TGF is 86.1%, which is 8.2% and 2.6% higher than that of VRFBs using pristine GF (79.6%) and TGF (83.9%) at 80 mA cm⁻². In addition, in a long-term test of VRFB performed at a high current density of 200 mA cm⁻², VRFB using Fe(TEA)-TGF shows the improved performances with voltage efficiency and EE of 69.5% and 68.0%. Based on that, this is proved that Fe(TEA)-TGF can be used to improve the performances of VRFB even at high current density ranges.