Department of Applied Physics, Faculty of Science, University of Granada, 18071 Granada, Spain.
Phys Chem Chem Phys. 2023 Mar 29;25(13):9482-9491. doi: 10.1039/d2cp05682h.
Recently, the need for obtaining, reusing, or purifying water has become a crucial issue. The capacitive deionization (CDI) method, which is based on the electric double layer (EDL) concept, can be applied to ion adsorption from an aqueous solution. This process is carried out by applying a potential difference to highly porous electrodes while pumping salty solution between them, partially removing the ions present in the solution and keeping them in the surface of the electrodes. The use of coated carbon electrodes with one polyelectrolyte layer, turning them into "soft electrodes" (SEs), has been proved to improve the efficiency of the system with respect to its original configuration. In this work, we investigate the effect on the ion adsorption and the efficiency of the process when implementing the coating technique known as layer-by-layer (LbL) on the electrode. This consists in successively coating the electrode surfaces with polyelectrolyte layers, alternating their charge polarity in each step. We tested the effect of the number of layers deposited, as well as the impact of this technique by using different carbons. We found that the second polyelectrolyte layer adheres more than the first layer, serving as a support or seed when it is not dense and uniformly distributed. In contrast, if the first layer is well adhered, a third layer is needed to observe improvements in adsorption and process efficiency. The adsorption of the polymer layers depends in any instance on the porosity of the carbon.
最近，获取、再利用或净化水的需求已成为一个关键问题。基于双电层（EDL）概念的电容去离子（CDI）方法可应用于从水溶液中吸附离子。该过程通过在高多孔电极上施加电势差并在它们之间泵送咸溶液来进行，部分去除溶液中存在的离子并将其保留在电极表面。使用带有一层聚电解质的涂覆碳电极，将其变成“软电极”（SE），已被证明可提高系统相对于原始配置的效率。在这项工作中，我们研究了当在电极上实施称为层层（LbL）的涂层技术时，对离子吸附和过程效率的影响。这包括通过交替每一步的电荷极性，依次用聚电解质层涂覆电极表面。我们测试了沉积的层数的影响，以及使用不同碳时这种技术的影响。我们发现，第二层聚电解质的附着性比第一层强，在其不致密且分布不均匀时作为支撑或种子。相比之下，如果第一层附着良好，则需要第三层才能观察到吸附和过程效率的提高。聚合物层的吸附在任何情况下都取决于碳的孔隙率。
