Efficient charge separation at the membrane-membrane junction is key to the operation of bipolar membranes (BPMs). Beyond co-ion crossover, there is a lack of understanding of the fundamental processes that control charge separation in BPMs. Herein, we employ polyelectrolytes to investigate the factors controlling charge separation in a cell devoid of co-ion crossover. We find that mobile polymeric charges at the bipolar interface can undergo charge-pairing and quenching in a process that we term bipolar pairing. This phenomenon attenuates membrane voltages and inhibits reverse bias water dissociation kinetics, leading to large overpotential penalties exceeding 7.5 V in some cases. However, we find that a sequential approach to constructing the catalyst and ionomeric binder layers of a BPM can more effectively minimize bipolar pairing than codepositing the two as a single mixed layer. These studies expose a hitherto unknown mechanism of efficiency loss in BPMs with implications for the design of high-efficiency bipolar interfaces.

中文翻译：

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聚合物电荷的分离实现双极膜的高效运行

膜-膜连接处的有效电荷分离是双极膜 (BPM) 运行的关键。除了共离子交叉之外，人们对 BPM 中控制电荷分离的基本过程缺乏了解。在此，我们采用聚电解质来研究在没有共离子交叉的电池中控制电荷分离的因素。我们发现双极界面上的移动聚合物电荷可以在我们称之为双极配对的过程中经历电荷配对和猝灭。这种现象会减弱膜电压并抑制反向偏压水解离动力学，导致在某些情况下超过 7.5 V 的大过电位惩罚。然而，我们发现，与将两者共沉积为单个混合层相比，构建 BPM 的催化剂和离聚物粘合剂层的顺序方法可以更有效地最小化双极配对。这些研究揭示了 BPM 中迄今为止未知的效率损失机制，对高效双极接口的设计具有影响。