Development of new ferrocene pseudo-peptide and quaternary ammonium structured catholytes for aqueous organic redox flow batteries

Energy is the foundation of sustainable development, and while global energy demand continues to grow, a large portion of this demand is met by fossil fuels. The depletion of fossil fuels and the growing carbon footprint have underscored the importance of renewable energy sources. However, the intermittent nature of renewables has emphasized the need for efficient energy storage technologies. In this context, transition metal-based redox flow batteries (RFB) have emerged as a leading solution, with vanadium-based RFBs being widely used. However, the high cost and toxic effects of vanadium have necessitated the search for alternatives. Organic redox flow batteries (ORFBs) offer a promising solution by using redox-active organic molecules instead of toxic metal ions. Although no commercially available ORFBs exist yet, research on aqueous ORFBs is rapidly progressing. Despite the availability of many successful anolyte materials in aqueous ORFBs, the number of catholyte molecules is limited—primarily including ferrocene, TEMPO, benzoquinone, and radical dianions. While ferrocene derivatives are promising due to their structural tunability, their low water solubility and the affinity of iron for water leading to degradation over time remain significant challenges. In this thesis, the design, synthesis, and characterization of new water-soluble 1,4-disubstituted-1,2,3-triazole ferrocene salts featuring pseudo-peptide and quaternary ammonium salt structures have been carried out, with the goal of developing novel catholyte materials for aqueous ORFBs.