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Emerging investigator series: local pH effects on carbon oxidation in capacitive deionization architectures
Environmental Science: Water Research & Technology ( IF 3.5 ) Pub Date : 2021-3-19 , DOI: 10.1039/d1ew00005e James Landon 1, 2 , Xin Gao 1 , Ayokunle Omosebi 1 , Kunlei Liu 1, 3
Environmental Science: Water Research & Technology ( IF 3.5 ) Pub Date : 2021-3-19 , DOI: 10.1039/d1ew00005e James Landon 1, 2 , Xin Gao 1 , Ayokunle Omosebi 1 , Kunlei Liu 1, 3
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In this work, the effect of pH and potential is examined for the oxidation of carbon cloth electrodes used in capacitive deionization (CDI) processes. The degree of oxidation of the electrode surface, examined using the electrode's potential of zero charge (Epzc) and measured using chronoamperometry and cyclic voltammetry, is found to be strongly correlated to the pH of the solution at the interface. Local pH measurements are examined at anodes and cathodes in full CDI and membrane-assisted capacitive deionization (MCDI) cells at cell voltages ranging from 0.3–1.2 V. The cathode is shown to be basic under charging potentials while the anode is found to be acidic. This local pH is found to be highly transient during charging and discharging in CDI cells while the pH is found to be relatively static in the MCDI cells, maintaining a basic pH at the cathode and an acidic pH at the anode even when the cell is discharged. Ion exchange membranes (IEM) are found to have two functions: (1) limiting co-ion expulsion that results from specific ion adsorption and (2) limiting the effects of parasitic Faradaic reactions on the separation process by stabilizing the local pH thereby mitigating dissolved oxygen reduction at the cathode and lessening carbon oxidation at the anode. Performance comparisons including the salt adsorption capacity and charge efficiency are also compared for these systems.
中文翻译：
新兴研究者系列：局部pH对电容去离子体系结构中碳氧化的影响
在这项工作中，检查了pH和电势对电容性去离子（CDI）工艺中使用的碳布电极氧化的影响。电极表面的氧化程度，使用电极的零电荷电势（E pzc并使用计时电流法和循环伏安法进行测量，发现与界面处溶液的pH值密切相关。在完整的CDI和膜辅助电容去离子（MCDI）电池中，在0.3-1.2 V的电池电压下，检查阳极和阴极的局部pH测量。在充电电位下，显示阴极为碱性，而发现阳极为酸性。发现该局部pH在CDI电池的充电和放电过程中是高度瞬态的，而发现该pH在MCDI电池中是相对静态的，即使在电池放电后也能保持阴极的碱性pH和阳极的酸性pH。 。发现离子交换膜（IEM）具有两个功能：（1）通过稳定局部pH值来限制因特定离子吸附而引起的共离子排出，以及（2）通过稳定局部pH值来限制寄生法拉第反应对分离过程的影响，从而减轻阴极处的溶解氧还原并减少阳极处的碳氧化。还比较了这些系统的性能比较，包括盐吸附容量和电荷效率。
更新日期：2021-03-23
中文翻译：
新兴研究者系列：局部pH对电容去离子体系结构中碳氧化的影响
在这项工作中，检查了pH和电势对电容性去离子（CDI）工艺中使用的碳布电极氧化的影响。电极表面的氧化程度，使用电极的零电荷电势（E pzc并使用计时电流法和循环伏安法进行测量，发现与界面处溶液的pH值密切相关。在完整的CDI和膜辅助电容去离子（MCDI）电池中，在0.3-1.2 V的电池电压下，检查阳极和阴极的局部pH测量。在充电电位下，显示阴极为碱性，而发现阳极为酸性。发现该局部pH在CDI电池的充电和放电过程中是高度瞬态的，而发现该pH在MCDI电池中是相对静态的，即使在电池放电后也能保持阴极的碱性pH和阳极的酸性pH。 。发现离子交换膜（IEM）具有两个功能：（1）通过稳定局部pH值来限制因特定离子吸附而引起的共离子排出，以及（2）通过稳定局部pH值来限制寄生法拉第反应对分离过程的影响，从而减轻阴极处的溶解氧还原并减少阳极处的碳氧化。还比较了这些系统的性能比较，包括盐吸附容量和电荷效率。
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