Ta₂O₅-Nanoparticle-Modified Graphite Felt As a High-Performance Electrode for a Vanadium Redox Flow Battery

Abstract

To increase the electrocatalytic activity of graphite felt (GF) electrodes in vanadium redox flow batteries (VRFBs) toward the VO 2 + /VO 2+ redox couple, we prepared a stable, high catalytic activity and uniformly distributed hexagonal Ta 2 O 5 nanoparticles on the surface of GF by varying the Ta 2 O 5 content. Scanning electron microscopy (SEM) revealed the amount and distribution uniformity of the electrocatalyst on the surface of GF. It was found that the optimum amount and uniformly immobilized Ta 2 O 5 nanoparticles on the GF surface provided the active sites, enhanced hydrophilicity, and electrolyte accessibility, thus remarkably improved electrochemical performance of GF. In particular, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results showed that the Ta 2 O 5 -GF nanocomposite electrode with a weight percentage of 0.75 wt % of Ta 2 O 5 to GF exhibited the best electrochemical activity and reversibility toward the VO 2 + /VO 2+ redox reaction, when compared with the other electrodes. The corresponding energy efficiency was enhanced by ∼9% at a current density of 80 mA cm −2 , as compared with untreated GF. Furthermore, the charge−discharge stability test with a 0.75 wt % Ta 2 O 5 -GF electrode at 80 mA cm −2 showed that, after 100 cycles, there was no obvious attenuation of efficiencies signifying the best stability of Ta 2 O 5 nanoparticles, which strongly adhered on the GF surface. KEYWORDS: Vanadium redox flow batteries, Ta 2 O 5 nanoparticles, Redox couple (VO 2 + /VO 2+ )

Electrocatalysis at Electrodes for Vanadium Redox Flow Batteries

“…Ta 2 O 5 nanoparticles were deposited on graphite felt by Bayeh et al [427]. Optimum performance evidence by separated peak separation in CVs and diminished charge transfer resistance in impedance measurements were observed at 0.75 wt.% of Ta 2 O 5 .…”

Mass Transfer and Reaction Kinetic Enhanced Electrode for High‐Performance Aqueous Flow Batteries

“…One effective way to enhance the electrocatalytic activity and thereby energy efficiency and power density is to deposit precious noble metals, such as Pt, Ru, Au, Bi, and Ir, but their high cost and higher hydrogen evolution rate hinder the large‐scale commercialization . Alternatively, low‐cost metal oxides such as ZrO 2 , Mn 3 O 4 , WO 3 , TiO 2 , CeO 2, PbO 2 ,, Ta 2 O 5 , Nd 2 O 3 , and Nb 2 O 5 have also been deposited on the GF to enhance the electrocatalytic activity. However, several critical parameters like their nanosize, nonuniform distribution, structural stability in the harsh vanadium redox flow battery (VRFB) environment, and stability against dissolution severely reduce the activity of the metal oxide catalysts.…”

Characterization of Carbon Felt Electrodes for Vanadium Redox Flow Batteries: Impact of Treatment Methods

“…These include improved felt design, [10][11][12][13] compression, [14][15][16] as well as surface modifications, which either increase the surface area, [17][18][19][20][21] or introduce functional groups [22][23][24][25][26][27][28] or supporting catalysts, such as metals 29,30 or metal oxides. [31][32][33] So far, the most practical and common treatment method is a thermal treatment, where the electrode surface is oxidized in an air atmosphere for up to 30 h at 400 • C. [34][35][36] Although most publications are focusing on one carbon felt or paper type and their modification, the precursor was found to influence the catalytic activity of the electrode. Zhong et al studied the differences between Rayon and PAN based graphite electrodes with regard to electrical resistivity, pore size and surface area, as well as the interaction of surface atoms by means of X-ray photoelectron spectroscopy (XPS) and surface morphology by means of scanning electron microscopy (SEM).…”