Microwave-treated graphite felt as the positive electrode for all-vanadium redox flow battery

• Published in: Journal of power sources Vol. 263; pp. 104 - 109
• Main Authors: Wu, Xiaoxin, Xu, Hongfeng, Xu, Pengcheng, Shen, Yang, Lu, Lu, Shi, Jicheng, Fu, Jie, Zhao, Hong
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2014; Elsevier
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Economics; Electric batteries; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Electrochemical impedance spectroscopy; Electrodes; Exact sciences and technology; Graphite; Graphite felt; Hydroxylated-functionalization; Materials; Microwave treatment; Microwaves; Rechargeable batteries; Vanadium; Vanadium redox flow battery; Graphite felt; Vanadium redox flow battery; Microwave treatment; Hydroxylated-functionalization; Cathode; Vanadium; Redox flow battery; Transition metal; Secondary cell; Electrode material; Microwave heating; Operating conditions; Functionalization; Graphite
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2014.04.035

An environmental, economic, and highly effective method based on microwave treatment was firstly used to improve the electrochemical activity of graphite felt as the positive electrode in all vanadium redox flow battery (VRFB). The graphite felt was treated by microwave and characterized by Fourier transform infrared and scanning electron microscopy. The electrochemical performance of the prepared electrode was evaluated with cyclic voltammetry and electrochemical impedance spectroscopy. Results show that graphite felt treated by microwave for 15 min at 400 °C exhibits excellent electro-catalytic activity and reactive velocity to vanadium redox couples. The coulombic, voltage, and energy efficiency of the VRFB with as-prepared electrodes at 50 mA cm−2 are 96.9%, 75.5%, and 73.2%, respectively; these values are much higher than those of cell-assembled conventionally and thermally treated graphite felt electrodes. The microwave-treated graphite felt will carry more hydrophilic groups, such as –OH, on its defects, and rough degree of the surface which should be advantageous in facilitating the redox reaction of vanadium ions, leading to the efficient operation of a vanadium redox flow battery. Moreover, microwave treatment can be easily scaled up to treat graphite felt for VRFB in large quantities. •Graphite felt treated by microwave method works as positive electrode of VRFB firstly.•The microwave-treated graphite felt carries more hydrophilic groups on its defects.•Graphite felt treated via microwave exhibits excellent electrochemical activity.•The single cell performance is improved remarkably with the use of modified electrode.