LAUSR

The inherent disadvantages of untreated carbon felt (pristine-CF) still restrict the vanadium redox flow battery (VRFB) from further improving in electrochemical performances. To solve this problem, the carbon felt (CF) decorated with bismuth hydrogen edetate (Bi(HEDTA)) complex was synthesized and studied as anode for VRFB. The cyclic voltammetry curve reflects the great improvement in electrochemical reversibility by reducing the peak potential difference from 0.73 to 0.50 V. Electrochemical impedance spectrum shows the better charge transfer process by reducing the charge transfer resistance from 7.14 to 1.13 Ω. The VRFB assembled by the CF modified with Bi(HEDTA) exhibits an energy efficiency of 66.25% at a current density of 160 mA cm−2, which is 11.76% higher than that of the pristine system. Moreover, the mechanism of Bi(HEDTA) involved in the anodic half-reaction of VRFB has been put forward. The results demonstrate that not only the metal but also the ligand of the complex are significant for improving the electrochemical activity of the reaction towards V3+/V2+ redox couple. In more detail, the oxygen-containing functional groups in the ligand could increase the wettability of the CF as well as act as the active sites, and the metal could decrease the evolution of hydrogen at the same time. Therefore, the effective combination of the respective functions of ligand and metal, makes Bi(HEDTA) a feasible ornament of the CF for VRFB.