A novel mechanism for the oxidation reaction of VO2+ on a graphite electrode in acidic solutions

• Published in: Journal of power sources Vol. 261; pp. 212 - 220
• Main Authors: Wang, Wenjun, Fan, Xinzhuang, Liu, Jianguo, Yan, Chuanwei, Zeng, Chaoliu
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-09-2014; Elsevier
• Subjects: Applied sciences; Carbon electrodes; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Kinetic equation; Reaction mechanism; Rotating disk system; Vanadium; Reaction mechanism; Rotating disk system; Vanadium; Kinetic equation; Carbon electrodes; Vanadyl; Redox flow battery; Carbon electrode; Transition metal; Secondary cell; Acidic solution; Rotating system; Graphite; Oxidation
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2014.03.053

With the consideration of optimizing the performance of the all-vanadium redox flow battery (VRB), the oxidation reaction mechanism of VO2+ on a rotating graphite disk electrode has been investigated by potentiodynamic polarization in sulfuric acid solutions with various pH and vanadium concentrations. Furthermore, the reaction orders of VO2+ and H+ for the oxidation reaction of VO2+ have been calculated from the polarization results and compared with the theoretical results according to the possible reaction mechanisms available in the literature. However, a new oxidation reaction mechanism has been proposed to describe the oxidation of VO2+ at last, and the theoretic reaction orders of VO2+ and H+ based on the new mechanism are consistent with the experimental results when the electrochemical reaction is the rate-limited process. Moreover, a corresponding kinetic equation has been established for the oxidation reaction of VO2+ on a spectroscopically pure graphite electrode, and can be well used to predict the polarization behavior in V (IV) acidic solutions.
•The reaction orders of VO2+ and H+ for the oxidation reaction of VO2+ are calculated.•A new reaction mechanism is proposed to describe the oxidation of VO2+.•A real kinetic equation is built up for the oxidation reaction of VO2+.