Perspective on electrocatalysts and performance hindrances at the negative electrode in vanadium redox flow batteries
釩氧化還原流電池負極電催化劑與性能障礙之展望
📄 英文摘要
Vanadium redox flow batteries (VRFBs) are widely used in energy storage systems due to their large storage capacity and stable performance. As one of the critical components of VRFBs to provide the reaction sites for redox couples, an ideal electrode should possess excellent conductivity, electrochemical and chemical stability, good reaction kinetics, and a low price. Due to their favorable properties, carbon-based materials such as graphite felt (GF) and carbon paper (CP) are widely used as VRFB electrodes. However, these electrodes suffer from poor electrochemical activity towards VO2+/VO2+ and V2+/V3+ redox couples, caused by sluggish kinetics and high polarization, limiting the operation of VRFB at high current density. Specifically, the negative electrode is performance-limiting due to the V2+/V3+ reaction overlapping with the potential range of the hydrogen evolution reaction (HER), further hindering performance. Researchers have developed different strategies to improve the performance of VRFB electrodes towards the V2+/V3+ reaction. Here, the leading causes of capacity losses in VRFB towards the V2+/V3+ reaction, including the undesirable side reactions, such as the HER and degradation of carbon materials, are briefly reviewed. The electrochemical kinetics, the mechanism, and the role of various electrocatalysts in enhancing the V2+/V3+ redox reaction are discussed.
📄 中文摘要
釩氧化還原流電池（VRFB）因其大容量儲能與穩定性能而廣泛應用於能源儲存系統。理想之 electrode（電極）應具備優異導電性、電化學與化學穩定性、良好反應動力學，且價格實惠。石墨氈（GF）與碳紙（CP）等碳基材料因其良好特性而廣泛用作 VRFB 電極。然而，此類 electrodes 對 VO2+/VO2+ 與 V2+/V3+ 氧化還原對的電化學活性不足，受限於緩慢動力學與高度極化，阻礙 VRFB 以高電流密度運作。具體而言，負極因 V2+/V3+ 反應與氫氣產生反應（HER）電位範圍重疊而成為性能瓶頸。本展望文章簡要回顧 VRFB 中導致 V2+/V3+ 反應容量損失的主因，包括 HER 等不良副反應及碳材料的降解，並討論電催化劑提升 V2+/V3+ 氧化還原反應的電化學動力學、機制與角色。
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