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Ion transport mechanisms in bipolar membranes for (photo)electrochemical water splitting†
Sustainable Energy & Fuels ( IF 5.6 ) Pub Date : 2018-06-14 00:00:00 , DOI: 10.1039/c8se00118a
David A. Vermaas 1, 2, 3, 4, 5 , Sandra Wiegman 1, 2, 3, 4 , Tetsuro Nagaki 1, 2, 3, 4 , Wilson A. Smith 1, 2, 3, 4
Affiliation  

Bipolar membranes (BPMs) have attracted growing interest in electrochemical and photoelectrochemical systems, as they allow the unique ability to pair two different electrolytes which can be optimized for their respective oxidation and reduction reactions. Understanding the membrane voltage at a non-extreme pH gradient (ΔpH < 14) is an important step towards practical applications for electrochemical conversions, as many (photo-)electrodes and catalysts can only operate efficiently in a limited pH range. To obtain a better understanding of the individual effects that determine the BPM voltage, a complete series of experiments measuring the actual BPM voltage as a function of the pH, salt type/concentration, flow rate and current density is needed. In this paper, we present experimental results of voltage–current relations for a BPM using 16 different pH differences, 4 concentrations, 7 flow rates and permeation of 6 different ionic species. The results show that both ion cross-over and local diffusion boundary layers play important roles in the BPM voltage. We also show that the supporting electrolyte composition plays an important role, even more important than the pH itself, which is an important parameter to realize practical application of BPMs in electrochemical cells.

中文翻译:

双极膜中的离子传输机理,用于(光)电化学水分解

双极膜(BPM)在电化学和光电化学系统中引起了越来越多的兴趣,因为它们具有将两种不同的电解质配对的独特能力,这些电解质可以针对各自的氧化和还原反应进行优化。了解非极端pH梯度(ΔpH<14)下的膜电压是电化学转化实际应用的重要一步,因为许多(光)电极和催化剂只能在有限的pH范围内有效运行。为了更好地了解确定BPM电压的各个效应,需要进行一系列完整的实验,测量实际BPM电压随pH,盐类型/浓度,流速和电流密度的变化。在本文中,我们介绍了BPM使用16种不同的pH差异,4种浓度,7种流速和6种不同离子种类的渗透的电压-电流关系的实验结果。结果表明,离子穿越和局部扩散边界层均在BPM电压中起重要作用。我们还表明,支持电解质组合物起着重要作用,甚至比pH本身更重要,这是实现BPM在电化学电池中实际应用的重要参数。
更新日期:2018-06-14
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