Aqueous polysulfide/iodide redox flow batteries (RFBs) are an attractive candidate for scalable energy storage with highly soluble active materials, which show great potential to reduce RFB cost. However, their energy efficiency is usually limited by poor kinetics reversibility and electrochemical activity of the redox reaction of polysulfide couples on the graphite felt electrode, which hinder its further practical applications. Here, Cu₂XGeS₄ (X = Fe, Co, Ni, Cd, Mn) nanocrystals are successfully synthesized through the hot injection method, and then uniformly coated onto the surface of graphite felt as electrodes. These electrodes can successfully suppress the water splitting side reactions, especially the hydrogen evolution reaction. The ones with Cu₂CoGeS₄ nanocrystals can significantly boost electrocatalytic activities of S²⁻/S_x²⁻ redox reactions for the proper adsorbability of polysulfide, which inturn improve the charge transfer process and selectively facilitate the electro-conversion reactions of polysulfides. Furthermore, the polysulfide/iodide flow battery with GF–Cu₂CoGeS₄ generates a high energy efficiency of 77.2% at 20 mA cm⁻², a power density of 40.7 mW cm⁻² and a stable energy efficiency retention of 92% after approximately 250 continuous cycles.

中文翻译：

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用于高性能水性多硫化物/碘化物氧化还原液流电池的Cu2CoGeS4纳米晶体：选择性增强多硫化物的电催化转化

水性多硫化物/碘化物氧化还原液流电池（RFB）是具有高度可溶活性材料的可扩展能量存储的有吸引力的候选者，具有降低RFB成本的巨大潜力。然而，它们的能量效率通常受限于石墨毡电极上的多硫化物对的氧化还原反应的不良动力学可逆性和电化学活性，这阻碍了其进一步的实际应用。在此，通过热注射法成功合成了Cu ₂ XGeS ₄（X = Fe，Co，Ni，Cd，Mn）纳米晶体，然后均匀地涂覆在作为电极的石墨毡表面上。这些电极可以成功地抑制水分解副反应，特别是氢析出反应。含铜₂CoGeS ₄纳米晶体可以显着提高S ^2- / S _x ^2-氧化还原反应的电催化活性，以具有适当的多硫化物吸附能力，进而改善电荷转移过程并有选择地促进多硫化物的电转化反应。此外，具有GF-Cu ₂ CoGeS ₄的多硫化物/碘化物液流电池在20 mA cm ^-2时产生77.2％的高能量效率，在40.7 mW cm ^-2时的功率密度和大约92％的稳定能量效率保持率。 250个连续周期。