Document Type : Research Article


Institute of Mechanics, Iranian Space Research Center, Shiraz, Iran


Traditional vanadium batteries use pure sulfuric acid as electrolyte, but H2SO4 does not absorb enough vanadium ions to make the electrolyte an efficient energy source. This study investigates the effect of hydroxylation process on electrochemical and operational properties of carbon felt electrode in VOSO4 solution with an optimized supporting electrolyte (a mixture of six parts HCl and 2.5 parts H2SO4). Carbon felt electrode was hydroxylated with mixed acids of H2SO4 and HNO3 in a stainless steel autoclave for 6 h. Then thermal treatment of electrode was performed at 400 oC for 5h. Obtained results of cyclic voltammograms showed that when the carbon felt was hydroxylated, both oxidation and reduction peak currents were increased remarkably and the peak potential separation is decreased from 356 mV to 246 mV, suggesting that the electrochemical activity and the kinetic reversibility on HCF electrode were improved compared to the pristine one. According to results of electrochemical impedance spectra, charge transfer resistance (Rct) was calculated to be 648 Ω for pristine carbon felt. The obtained Rct at hydroxylated electrode (176 Ω) shows a decrease of about 73 % in Rct. Charge-discharge profiles of two cells assembled with the pristine carbon felt (cell A), and hydroxylated carbon felt (cell B) showed that energy, voltage and coulombic efficiencies were significantly improved by using the hydroxylated electrodes inside the cell of vanadium redox flow battery.


1.     Parasuraman, A., Lim, T.M., Menictas, C. and Skyllas-Kazacos, M., "Review of material research and development for vanadium redox flow battery applications", Electrochimica Acta, Vol. 101, (2013), 27-40.

2.     Rahman, F. and Skyllas-Kazacos, M., "Vanadium redox battery: Positive half-cell electrolyte studies", Journal of Power Sources, Vol. 189, No. 2, (2009), 1212-1219.

3.     Roe, S., Menictas, C. and Skyllas-Kazacos, M., "A high energy density vanadium redox flow battery with 3 M vanadium electrolyte", Journal of The Electrochemical Society, Vol. 163, No. 1, (2016), A5023-A5028.

4.     Liu, Q., Grim, G., Papandrew, A., Turhan, A., Zawodzinski, T. A. and Mench, M. M., "High performance vanadium redox flow batteries with optimized electrode configuration and membrane selection", Journal of The Electrochemical Society, Vol. 159, No. 8, (2012), A1246-A1252.

5.     Kabir, H., Gyan, I. O. and Cheng, I. F., "Electrochemical modification of a pyrolytic graphite sheet for improved negative electrode performance in the vanadium redox flow battery", Journal of Power Sources, Vol. 342, (2017), 31-37.

6.     Wang, W. and Wang, X., "Investigation of Ir-modified carbon felt as the positive electrode of an all-vanadium redox flow battery", Electrochimica Acta, Vol. 52, No. 24, (2007), 6755-6762.

7.     Liu, T., Li, X., Xu, C. and Zhang, H., "Activated carbon fiber paper based electrodes with high electrocatalytic activity for vanadium flow batteries with improved power density", ACS Applied Materials & Interfaces, Vol. 9, No. 5, (2017), 4626-4633.

8.     Sun, B. and Skyllas-Kazacos, M., "Modification of graphite electrode materials for vanadium redox flow battery application—I. Thermal treatment", Electrochimica Acta, Vol. 37, No. 7, (1992), 1253-1260.

9.     Sun, B. and Skyllas-Kazacos, M., "Chemical modification of graphite electrode materials for vanadium redox flow battery application—part II. Acid treatments", Electrochimica Acta, Vol. 37, No. 13, (1992), 2459-2465.

10.   Noack, J. and Tübke, J., "A comparison of materials and treatment of materials for vanadium redox flow battery", ECS Transactions, Vol. 25, No. 35, (2010), 235-245.

11.   Li, X.-g., Huang, K.-l., Liu, S.-Q., Ning, T. and Chen, L.-q., "Characteristics of graphite felt electrode electrochemically oxidized for vanadium redox battery application", Transactions of Nonferrous Metals Society of China, Vol. 17, No. 1, (2007), 195-199.

12.   González, Z., Sánchez, A., Blanco, C., Granda, M., Menéndez, R. and Santamaría, R., "Enhanced performance of a Bi-modified graphite felt as the positive electrode of a vanadium redox flow battery", Electrochemistry Communications, Vol. 13, No. 12, (2011), 1379-1382.

13.   Li, L., Kim, S., Wang, W., Vijayakumar, M., Nie, Z., Chen, B., Zhang, J., Xia, G., Hu, J. and Graff, G., "A Stable Vanadium Redox‐Flow Battery with High Energy Density for Large‐Scale Energy Storage", Advanced Energy Materials, Vol. 1, No. 3, (2011), 394-400.

14.   Yue, L., Li, W., Sun, F., Zhao, L. and Xing, L., "Highly hydroxylated carbon fibres as electrode materials of all-vanadium redox flow battery", Carbon, Vol. 48, No. 11, (2010), 3079-3090.

15.   Bard, A.J. and Faulkner, L.R., "Fundamentals and applications", Electrochemical Methods, 2nd ed.; Wiley: New York, (2001).

16.   Lefrou, C., Fabry, P. and Poignet, J.-C., "Electrochemistry: the basics, with examples", Springer Science & Business Media, (2012).

17.   Conway, B. and Jerkiewicz, G., "Nature of electrosorbed H and its relation to metal dependence of catalysis in cathodic H 2 evolution", Solid State Ionics, Vol. 150, No. 1, (2002), 93-103.