Aspects of electron transfer processes in vanadium redox-flow batteries

The electrochemical processes in vanadium redox-flow batteries (VRFBs) include conversions of vanadium species in acidic electrolytes with total vanadium concentrations over molar range. The majority of currently available data on electrode kinetics of vanadium reactions, and on the role of electrode surface chemistry are obtained for diluted electrolyte solutions and are very controversial. In this minireview, we consider the interpretations of electrochemical kinetic data for vanadium electrode reactions and mechanistic concepts, which have been reported in the literature. Thereby, the gap between electrochemical kinetics in ""diluted"" and ""concentrated"" solutions is in the focus of the review.