K₃[Fe(CN)₆] and K₄[Fe(CN)₆] have been frequently applied in redox flow batteries to achieve sustainable and economical renewable energy storage. However, fundamental knowledge of the redox couple of K₃[Fe(CN)₆] and K₄[Fe(CN)₆] regarding their flow battery performance is largely underdeveloped. Herein, we present a comprehensive study on the fundamental properties and electrochemical kinetics of K₃[Fe(CN)₆] and K₄[Fe(CN)₆] in aqueous supporting electrolytes at different pH values. Particularly, the charge/discharge cycling stability of the redox couple was evaluated at different pH values using a half-cell flow battery configuration. The battery results unambiguously confirmed that the redox couple functions best at neutral or near neutral conditions. Dramatic capacity decay of the redox couple was observed in a strong alkaline KOH electrolyte (pH =14), which is due to the chemical decomposition associated with the CN^- ligand dissociation. The presented study not only advances an in-depth understanding of K₃[Fe(CN)₆] and K₄[Fe(CN)₆] regarding their flow battery applications but also highlights the challenge of acid-base side reactions of redox active molecules applied in aqueous acidic/alkaline redox flow batteries.

K ₃ [Fe（CN）₆ ]和K ₄ [Fe（CN）₆ ]经常被用于氧化还原液流电池中，以实现可持续和经济的可再生能源存储。然而，关于K ₃ [Fe（CN）₆ ]和K ₄ [Fe（CN）₆ ]的液流电池性能的氧化还原对的基础知识在很大程度上尚未得到开发。本文中，我们对K ₃ [Fe（CN）₆ ]和K ₄ [Fe（CN）₆的基本性质和电化学动力学进行了全面的研究。]在不同pH值的水性支持电解质中。尤其是，使用半电池液流电池配置在不同的pH值下评估了氧化还原对的充电/放电循环稳定性。电池结果明确证实了氧化还原电对在中性或接近中性条件下的性能最佳。在强碱性KOH电解质（pH为= 14），这是由于与CN相关联的化学分解，观察到氧化还原对的戏剧性容量衰减^-配体的解离。提出的研究不仅提高了对K ₃ [Fe（CN）₆ ]和K ₄ [Fe（CN）₆的深入理解]关于其液流电池的应用，但也强调了应用于水性酸性/碱性氧化还原液流电池的氧化还原活性分子的酸碱副反应的挑战。