Insights into novel indium catalyst to kW scale low cost, high cycle stability of iron-chromium redox flow battery

Iron-chromium flow batteries (ICRFBs) have emerged as an ideal large-scale energy storage device with broad application prospects in recent years. Enhancement of the Cr3+/Cr2+ redox reaction activity and inhibition of the hydrogen evolution side reaction (HER) are essential for the development of ICRFBs and require a novel catalyst design. However, elucidating the underlying mechanisms for modulating catalyst behaviors remains an unresolved challenge. Here, we show a novel precisely controlled preparation of a novel thermal-treated carbon cloth electrode with a uniform deposit of low-cost indium catalyst particles. The density functional theory analysis reveals the In catalyst has a significant adsorption effect on the reactants and improves the redox reaction activity of Cr3+/Cr2+. Moreover, H+ is more easily absorbed on the surface of the catalyst with a high migration energy barrier, thereby inhibiting the occurrence of HER. The assembled ICRFBs have an energy efficiency of 85.23% at 140 mA/cm2, and this method minimizes the electrodeposition process and cleans the last obstacle for industry long cycle operation requirements. The ICRFBs exhibit exceptional long-term stability with an energy efficiency decay rate of 0.011% per cycle at 1000 cycles, the lowest ICRFBs reported so far. Therefore, this study provides a promising strategy for developing ICRFBs with low costs and long cycle life.