Electrochemical and Kinetic Analysis of Manganese Electrolytes for Redox Flow Batteries

The hybrid hydrogen-manganese redox flow battery (H 2 -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 Mn 2+ /Mn 3+ redox species in an electrolyte composed of 1M TiOSO 4 and 1M MnSO 4 in 3M H 2 SO 4 were studied on carbon paper electrodes. The kinetic analysis of manganese redox species (Mn 2+ /Mn 3+ ) in the presence of TiO 2+ was performed using cyclic voltammetry and electrochemical impedance spectroscopy techniques within the H 2 -Mn RFB set-up. The results were compared to reference redox species vanadium (VO 2+ /VO 2 + ) within H 2 -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.