Towards Production of a Highly Catalytic and Stable Graphene-Wrapped Graphite Felt Electrode for Vanadium Redox Flow Batteries

Abstract

Despite the appealing features of vanadium redox flow batteries as a promising energy storage solution, the polarization losses, among other factors, prevent widespread applications. The dominant contribution to these polarization losses is the sluggish (even irreversible) electron-transfer towards reactions, leading to large over-potentials (poor rate capability). In particular, the positive half-cell reaction suffers from a complex mechanism since electron- and oxygen-transfer processes are key steps towards efficient kinetics. Thus, the positive reaction calls for electrodes with a large number of active sites, faster electron transfer, and excellent electrical properties. To face this issue, a graphene-wrapped graphite felt (GO-GF) electrode was synthesized by an electrospray process as a cost-effective and straightforward way, leading to a firm control of the GO-deposited layer-by-layer. The voltage value was optimized to produce a homogeneous deposition over a GF electrode after achieving a stable Taylor cone-jet. The GO-GF electrode was investigated by cyclic voltammetry and electrochemical impedance spectroscopy in order to elucidate the electrocatalytic properties. Both analyses reflect this excellent improvement by reducing the over-potentials, improving reversibility, and enhancing collected current density. These findings confirm that the GO-GF is a promising electrode for high-performance VRFB, overcoming the performance-limiting issues in a positive half-reaction.

V2O5-Activated Graphite Felt with Enhanced Activity for Vanadium Redox Flow Battery

“…However, the poor electrochemical activity and hydrophobic properties of GF electrodes result in low kineticism in the redox reaction. Various GF electrode surface modification strategies, such as etching [12][13][14][15][16][17][18][19][20][21][22][23], functional group grafting [24][25][26][27][28][29][30], and depositing the electrocatalyst on the electrode surface [31][32][33][34][35][36][37][38], improve the performance of GF as an electrode.…”

Vanadium Oxygen Fuel Cell Utilising High Concentration Electrolyte

“…Thermal treatment in air at 400 • C and chemical treatment with H 2 SO 4 and HNO 3 developed by Skyllas-Kazacos group in the 1990s [16,17] remain the most effective, economical and easiest methods for activation of carbon-based materials. Surface modification of carbon-based electrodes with additives like WO 3 [18], W-doped Nb 2 O 5 [19], TiO 2 [20], CeO 2 [21] and ZrO 2 [22], Sb 3+ additive [23], Bismuth nanoparticles [24], N-and WO 3 - [25], graphene [26], TiN nanowires [27] have also been reported, resulting in improved battery performance.…”