Center for Energy Storage Research , Korea Institute of Science and Technology (KIST) , 14-gil 5, Hwarang-ro , Seongbuk-gu, Seoul 02792 , Republic of Korea.
Division of Energy & Environmental Engineering , Korea University of Science & Technology (UST)-KIST School , 217 Gajeong-ro , Yuseong-gu, Daejeon 34113 , Republic of Korea.
ACS Appl Mater Interfaces. 2019 Jul 31;11(30):26842-26853. doi: 10.1021/acsami.9b06790. Epub 2019 Jul 16.
Histidine, inspired by vanadium bromoperoxidase enzyme, has been applied as a homogeneous electrocatalyst to the positive electrolyte of vanadium redox flow battery (VRFB) to improve the performance and stability of VRFB at elevated temperatures. The histidine-containing electrolyte is found to significantly improve the performance of VRFB in terms of thermal stability estimated by the remaining amount of VO in the electrolyte (61 vs 43% of a pristine one), energy efficiency at a high current density of 150 mA cm (78.7 vs 71.2%), and capacity retention (73.2 vs 27.7%) at 60 °C. The mechanism of the catalytic functions of histidine with the chemical species in the electrolyte has been investigated for the first time by multinuclear NMR spectroscopy and first-principles calculations. The analyzed data reveal that histidine improves the kinetics of both charge and discharge reactions through different affinity toward the reactants and products as well as suppresses the precipitation of VO by impeding the polymerization of vanadium ions. These findings are in good agreement with the improved chemical and electrochemical performance of the histidine-containing VRFB. Our results show a new type of chemical/electrochemical mechanism in the improved redox flow battery performance that may be essential in a new research arena for better performance of electrochemical systems.
组氨酸受钒溴过氧化物酶的启发，已被用作钒氧化还原流电池（VRFB）正电解质的均相电催化剂，以提高 VRFB 在高温下的性能和稳定性。研究发现，含组氨酸的电解质可显著提高 VRFB 的性能，表现在电解质中 VO 的剩余量（61%，而原始电解质为 43%）所估计的热稳定性、在 150 mA cm 的高电流密度下的能量效率（78.7%，而 71.2%），以及在 60°C 时的容量保持率（73.2%，而 27.7%）。通过多核 NMR 光谱和第一性原理计算，首次研究了组氨酸与电解质中化学物质的催化作用机制。分析数据表明，组氨酸通过对反应物和产物的不同亲和力以及阻碍钒离子聚合来抑制 VO 的沉淀，从而改善了充放电反应的动力学。这些发现与含组氨酸的 VRFB 的化学和电化学性能的提高一致。我们的研究结果表明，在改进的氧化还原流电池性能中存在一种新型的化学/电化学机制，这可能在电化学系统性能改进的新研究领域中至关重要。
