A highly solubility and stability of hydroxyl-ferrocene as catholyte in neutral aqueous organic redox flow battery

Neutral aqueous organic redox flow batteries (AORFBs) are increasingly recognized for their potential to enhance power grid operations, primarily due to their safety, modular design, and scalability. However, the widespread application of AORFBs still faces significant challenges, particularly in the design and preparation of stable catholyte molecules. To address these challenges, this study reports water-soluble and low-permeability ferrocene catholyte materials, FcNOH and FcN(OH)₂ (hydroxyl ferrocene), with solubilities reaching 2.1 M and 1.6 M, respectively. Combined with a Dex-Vi (Dextrosil-Viologen) as anolyte, the battery demonstrated exceptional stability. Notably, the 1.5 M FcNOH/Dex-Vi-based AORFB demonstrates a capacity retention of 99.76 % over 75 cycles, while the 1.0 M FcN(OH)₂/Dex-Vi-based AORFB maintains 99.36 % of its capacity after 50 cycles. This study not only revealed the electrochemical behavior and charge-discharge properties of FcNOH and FcN(OH)₂ in AORFB systems but also contributes significant insights toward developing more stable and efficient AORFB technologies.