The effect of lead-based catalyst in-situ electrodeposition on the performance of iron-chromium redox flow batteries

Abstract

The performance of iron-chromium redox flow batteries is significantly influenced by the electrochemical activity of chromium and iron ions, with a particular emphasis on the reactivity of chromium. However, the impact of the chemical properties of chromium ions on the efficiency of electrochemical reactions remains largely unexplored. In this study, we introduced PbCl₂ into the electrolyte and achieved in-situ electrodeposition of the lead-based catalyst. Our findings indicate that the incorporation of lead ions effectively enhances the chromium half-reaction while inhibiting hydrogen evolution. Experimental analyses and molecular dynamics simulations reveal that PbCl₂ does not significantly affect the electrochemical performance of the electrolyte, its influence is mainly due to the electrochemical deposition on the electrode surface. The observed performance improvement is ascribed to the combined effects of Pb and Pb(ClO₃)₂, which catalyze the redox reaction of Cr³⁺/Cr²⁺. In situ differential electrochemical mass spectrometry monitoring of the hydrogen evolution signal demonstrates a clear inhibition of the hydrogen evolution reaction. Notably, the addition of 40 ​mM ​Pb²⁺ significantly reduces the overpotential of the reaction, allowing the energy efficiency of the battery to reach 83.90% at a current density of 140 ​mA/cm², which represents a 5.68% increase compared to the original electrolyte (78.22%). Furthermore, this configuration enables long-term stable operation over 400 cycles. This research presents an innovative approach to enhancing the performance of iron-chromium redox flow batteries, characterized by its simplicity and cost-effectiveness.