Yan Zhifei, Wycisk Ryszard J, Metlay Amy S, Xiao Langqiu, Yoon Yein, Pintauro Peter N, Mallouk Thomas E
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, United States.
ACS Cent Sci. 2021 Jun 23;7(6):1028-1035. doi: 10.1021/acscentsci.1c00217. Epub 2021 May 28.
Aqueous redox flow batteries that employ organic molecules as redox couples hold great promise for mitigating the intermittency of renewable electricity through efficient, low-cost diurnal storage. However, low cell potentials and sluggish ion transport often limit the achievable power density. Here, we explore bipolar membrane (BPM)-enabled acid-base redox flow batteries in which the positive and negative electrodes operate in the alkaline and acidic electrolytes, respectively. This new configuration adds the potential arising from the pH difference across the membrane and enables an open circuit voltage of ∼1.6 V. In contrast, the same redox molecules operating at a single pH generate ∼0.9 V. Ion transport in the BPM is coupled to the water dissociation and acid-base neutralization reactions. Interestingly, experiments and numerical modeling show that both of these processes must be catalyzed in order for the battery to function efficiently. The acid-base concept provides a potentially powerful approach to increase the energy storage capacity of aqueous redox flow batteries, and insights into the catalysis of the water dissociation and neutralization reactions in BPMs may be applicable to related electrochemical energy conversion devices.
采用有机分子作为氧化还原对的水系氧化还原液流电池，在通过高效、低成本的日间储能来缓解可再生电力间歇性方面具有巨大潜力。然而，低电池电位和缓慢的离子传输常常限制了可实现的功率密度。在此，我们探索了基于双极膜（BPM）的酸碱氧化还原液流电池，其中正负极分别在碱性和酸性电解质中运行。这种新配置增加了跨膜pH差产生的电位，并实现了约1.6 V的开路电压。相比之下，在单一pH值下运行的相同氧化还原分子产生的电压约为0.9 V。双极膜中的离子传输与水的解离和酸碱中和反应相关联。有趣的是，实验和数值模拟表明，为使电池高效运行，这两个过程都必须被催化。酸碱概念为提高水系氧化还原液流电池的储能容量提供了一种潜在的有力方法，并且对双极膜中水的解离和中和反应催化作用的见解可能适用于相关的电化学能量转换装置。
