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Using a vapor-fed anode and saline catholyte to manage ion transport in a proton exchange membrane electrolyzer
Energy & Environmental Science ( IF 32.5 ) Pub Date : 2021-10-12 , DOI: 10.1039/d1ee02265b
Ruggero Rossi 1 , Derek M. Hall 2 , Le Shi 1 , Nicholas R. Cross 3 , Christopher A. Gorski 1 , Michael A. Hickner 4 , Bruce E. Logan 1, 3
Affiliation  

Saline water represents an inexhaustible source of water for hydrogen production from electrolysis. However, direct saltwater splitting faces challenges due to chlorine evolution at the anode and the development of Nernst overpotential due to sodium ion transport competition with protons across the membrane. A new approach to minimize chlorine evolution and improve performance is proposed here by using a humidified gas stream (no liquid electrolyte) for the anode and a liquid saltwater catholyte. Charge repulsion of chloride ions by the proton exchange membrane (PEM) resulted in low chlorine generation, with anodic faradaic efficiencies for oxygen evolution of 100 ± 1% with a synthetic brackish water (50 mM NaCl, 3 g L−1) and 96 ± 2% with synthetic seawater (0.5 M NaCl, 30 g L−1). The enhanced proton transport by the electric field enabled more efficient pH control across the cell, minimizing sodium ion transport in the absence of a liquid anolyte. The vapor-fed anode configuration showed similar performance to a conventional PEM electrolyzer up to 1 A cm−2 when both anode and cathode were fed with deionized water. Much lower overpotentials could be achieved using the vapor-fed anode compared to a liquid-anolyte due to the reduced sodium ion transport through the membranes, as shown by adding NaClO4 to the electrolytes. This vapor-fed anode configuration allows for direct use of saltwater in conventional electrolyzers without additional water purification at high faradaic efficiencies.

中文翻译:

使用蒸汽馈送阳极和盐水阴极电解液来管理质子交换膜电解槽中的离子传输

盐水是电解制氢的取之不尽的水源。然而,由于阳极氯析出和钠离子传输与跨膜质子竞争导致能斯特过电位的发展,直接盐水分解面临挑战。这里提出了一种通过使用加湿气流(无液体电解质)作为阳极和液体盐水阴极电解液来减少氯析出和提高性能的新方法。质子交换膜 (PEM) 对氯离子的电荷排斥导致氯生成量低,使用合成微咸水(50 mM NaCl,3 g L -1)和 96 ± 2% 合成海水(0.5 M NaCl,30 g L -1)。电场增强的质子传输能够更有效地控制整个细胞的 pH 值,在没有液体阳极电解液的情况下最大限度地减少钠离子传输。当阳极和阴极都供给去离子水时,蒸汽供给的阳极配置表现出与传统 PEM 电解槽相似的性能高达 1 A cm -2。与液体阳极电解液相比,使用蒸汽馈电阳极可以实现低得多的过电位,因为通过膜的钠离子传输减少,如向电解质中添加 NaClO 4所示。这种蒸汽供给阳极配置允许在传统电解槽中直接使用盐水,而无需以高法拉第效率进行额外的水净化。
更新日期:2021-10-21
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