Electrochemical and Kinetic Analysis of Manganese Electrolytes for Redox Flow Batteries

Abstract

The hybrid hydrogen-manganese redox flow battery (H2-Mn RFB) is a promising and sustainable electrochemical system for long-duration energy storage. One strong reason is the excellent features of manganese, such as low cost, abundance, environmental friendliness, and relatively high standard potential (+1.51 V). Nevertheless, the electrochemical and kinetic parameters of manganese electrolytes have not been studied in detail for flow batteries. In the present work, the kinetics of the Mn2+/Mn3+ redox species in an electrolyte composed of 1M TiOSO4 and 1M MnSO4 in 3M H2SO4 were studied on carbon paper electrodes. The kinetic analysis of manganese redox species (Mn2+/Mn3+) in the presence of TiO2+ was performed using cyclic voltammetry and electrochemical impedance spectroscopy techniques within the H2-Mn RFB set-up. The results were compared to reference redox species vanadium (VO2+/VO2 +) within H2-V RFB system. The results showed that the heterogeneous electron transfer rate constant (8.6 × 10−7 cm s−1) of manganese is comparable to that of vanadium (4.8 × 10−6 cm s−1), with less than an order of magnitude difference between them.