HF/H2O2 treated graphite felt as the positive electrode for vanadium redox flow battery

In order to improve the electrochemical performance of the positive graphite felt electrode in vanadium flow redox battery, a novel method is developed to effectively modify the graphite felt by combination of etching of HF and oxidation of H 2 O 2 . After the etching of HF for the graphite felt at ambient temperature, abundant oxygen-containing functional groups were further introduced on the surface of graphite felt by hydrothermal treatment using H 2 O 2 as oxidant. Benefiting from the surface etching and introduction of functional groups, mass transfer and electrode process can be improved significantly on the surface of graphite felt. VO 2+ /VO 2 + redox reaction on the graphite felt modified by HF and H 2 O 2 jointly (denote: GF-HF/H 2 O 2 ) exhibits superior electrochemical kinetics in comparison with the graphite felt modified by single HF or H 2 O 2 treatment. The cell using GF-HF/H 2 O 2 as the positive electrode was assembled and its electrochemical properties were evaluated. The increase of energy efficiency of 4.1% for GF-HF/H 2 O 2 at a current density of 50   mA   cm −2 was obtained compared with the pristine graphite felt. The cell using GF-HF/H 2 O 2 also demonstrated higher discharge capacity. Our study revealed that HF/H 2 O 2 treatment is an efficient method to enhance the electrochemical performance of graphite felt, further improving the comprehensive energy storage performance of the vanadium flow redox battery.