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The escalating energy consumption demands in contemporary society underscore the imperative for advancing energy storage technologies. To address this challenge, the aqueous organic redox flow batteries (AORFBs) emerge as a promising technology for grid-scale energy storage due to their scalability and flexibility. Proposed in 1981, the alkaline zinc-iron flow battery (AZIFB) is a representative zinc-based flow battery with a high potential of 1.74 V and low materials costs. However, the highest reported concentration of ferro-ferricyanide couple is only 0.4 mol/L in alkaline media, resulting in a battery with low energy density. This limitation also necessitates a larger volume of electrolyte for AZIFB systems with defined capacities.The solubility of pentacyanoferrate derivatives can be easily enhanced by using hydrophilic pyridine-based ligand to break the symmetric structure of ferrocyanide. By far most published materials utilize 2,2’-bipyridine as the hydrophilic ligand or chelating ligand. While this does give a very high redox potential and excellent solubility, the structure of 2,2’-bipyridine only allows the 2 nitrogen on the bipyridine ring connecting to the same redox center, making it difficult to design a 2-electron transfer metal complex. On the contrary, another popular ligand, 4,4’-bipyrdine is often used to bridge metal centers and mediate electronic effects between paramagnetic metal ions, making it a perfect ligand for metal complexes with 2 redox centers.In this thesis, we present a novel two electron transfer organometallic catholyte bridged by 4,4’-bipyridine with high energy density and outstanding performance in AZIFBs.