Abstract: The most commercialized redox flow battery (RFB) chemistry (vanadium RFB, VRFB) is too costly for long duration energy storage. The Ce3+/Ce4+ redox chemistry is a promising alternative to the V4+/V5+ chemistry at the RFB positive electrode because it has a higher redox potential than vanadium.

I compare the levelized cost of electricity (LCOE) and greenhouse gas emissions (GHGs) of a Ce-V RFB and a VRFB using a Life Cycle Assessment (LCA)-Technoeconomic Assessment (TEA) model. These results highlight the importance of better controlling the cerium redox kinetics and understanding the cerium charge transfer mechanism to optimize the Ce-V RFB’s economic and environmental performance. Through extended X-ray absorption fine structure spectroscopy, it is found that an inner-sphere structural change occurs as Ce4+ is reduced to Ce3+. Additionally, kinetic measurements on platinum and glassy carbon electrodes are similar and suggest that the charge transfer occurs through a simple outer-sphere, one-step electron transfer. With this information, I propose a reaction mechanism in which the electron transfer is coupled to a chemical ligand exchange step. The identification of the charge transfer mechanism allows me to identify the electrolyte as the most influential parameter on both kinetic and thermodynamic performance of the Ce3+/Ce4+ redox reaction. I suggest strategies for improving the economic and environmental performance of a Ce-V RFB based on this information. The combination of LCA-TEA modelling to identify design challenges with structural and kinetic measurements to inform the fundamental understanding of redox reactions represents a promising method of screening new chemistries for RFB applications.