Identification of the Reduction Reaction Mechanism of V³⁺ on a Graphite Electrode in Acidic Solutions

Abstract

The oxidation and reduction reaction mechanisms of the VO2 +/VO2+ redox couple have been studied to better understand the electrode reaction processes and further optimize the battery performance of vanadium flow battery (VFB) in our previous work. However, it is found that the negative electrode process of VFB plays a more important role in the improvement of the overall battery performance as research continues. Hence, the reduction reaction mechanism of V3+ in acidic solutions has been investigated systematacially in this work. Potentiodynamic polarization combined with rotating disk electrode have been applied to calculate the reaction orders (m) and the electron transfer number (n) of the reduction reaction of V3+. The results of this work demonstrated that the reduction reaction of V3+ is a single electron transfer step and H+ keeps out of the electrochemical reaction. Furthermore, the kinetic equation for the reduction reaction of V3+ has been established, and the theoretic polarization curve based on the established kinetic equation is well consistent with the experimental result, indicating an accurate prediction of the polarization behavior in V3+ acidic solutions.

Simple-Synthesized Sulfonated Ferrocene Ammonium for Aqueous Redox Flow Batteries

“…All-vanadium RFBs are the most investigated systems. Some researchers investigated the redox mechanism of vanadium-based flow battery materials and modified the electrode surface with inorganic materials to assemble batteries with high energy density and high efficiency. − Others have made great efforts in the membrane and carbon felt of vanadium liquid flow batteries and obtained good results. − However, their application is limited due to relatively low earth abundance, high cost, side reactions, cross-contamination, and corrosive electrolytes that are dangerous and strongly acidic. − Considering these problems, it is extremely important to find a novel flow battery system with low cost, environmental friendliness, high energy density, and excellent electrochemical kinetic characteristics . In the past few years, the electrochemical performance of various redox flow batteries ranging from aqueous to nonaqueous has been extensively studied .…”

In Situ Pore-Making and Heteroatom Doping of Carbon Nanofibers Electrode for High Performance Vanadium Redox Flow Battery

“…[1][2][3] As one of the most advanced RFBs, all vanadium redox flow battery (VRFB) applies the electrochemical redox reactions of vanadium ions with different valence states to realize the energy conversion, which effectively eliminates the cross contamination between the electroactive ions in positive and negative sides. [4][5][6][7] However, the relatively lower energy and power densities hindered the commercialization of VRFB. Increasing vanadium ions concentration in the electrolyte is an effective way to improve the energy density, 8 while enhancing the active area and electrocatalytic activity of the electrodes may improve the power density effectively.…”