基于电化学剥离的石墨烯复合膜电极的制备及电容去离子特性研究

Electrosorption is an efficient non-polluting desalination technology, but only can be applied in the low concentration of salt water desalination due to limitation by the low adsorption capacity and low Coulombic efficiency of the electrode material. So the fundamental way is to develop new electrode materials as well as to adjust the electrode structure to solve this practical problems. In this research, we demonstrate a simple and fast electrochemical method to exfoliate graphite into thin graphene oxide sheets, which further could be reduce and self-assembly to prepare graphene gel with controlled pore structure. Then the preparation and capacitive deionization performance of graphene gel electrode coated with ion exchange membrane are studied. In the preparation process, single-layer or few-layer graphene oxide with a large lateral size are prepared by electrochemical exfolination method under different mild aqueous aromatic ring structure acidic media, and then be reduced and assembly to acquire the graphene gel. Cation and anion exchange membranes are in situ coated on the graphene gel electrode surface to prepare the composite electrodes. The effects of some parameters including the ion exchange capacity, membrane resistance, thickness, swelling ratio, on the ion selectivity are investigated in the capacitive deionization process. The synergy mechanism between the ion-exchange membrane and graphene electrode will be revealed. The absorption-desorption microscopic model of inorganic ions on the composite electrode is established through research on electrosorption mechanism of membrane capacitive deionization module under different solution conditions. The module of membrane capacitive deionization is established, which supplies theory basis for the practical application to increase the adsorption capacity Coulombic efficiency of the electrode..

电吸附是一种高效无污染的脱盐技术，目前存在吸附容量小、库仑效率低的问题，应用受到一定限制。我们采取制备新型电极材料以及对电极结构进行调整来解决这一实际问题。本课题提出电化学剥离法制备氧化石墨烯并将其还原组装为石墨烯凝胶电极，与离子交换膜复合后，研究复合电极的电容去离子特性。采用温和的具有芳香环结构的酸盐作为阴离子插层试剂，通过石墨阳极电化学剥离制备单层、大尺寸氧化石墨烯，然后将其还原组装成三维结构石墨烯凝胶电极，并在电极表面采用流延法原位刮膜制备阴阳离子膜复合电极。通过研究复合电极在不同溶液条件下电吸附机理，阴阳离子膜的基本理化性能对离子透过选择性的影响，明确离子膜与石墨烯电极之间的协同作用机理，发现复合电极吸脱附性能的影响因素。考察不同种类阴阳离子的电吸附机理，建立复合电极上阴阳离子吸脱附的微观模型，以此优化组建实用化膜电容去离子模块，从而提高吸附容量和库仑效率。

电吸附是一种高效无污染的脱盐技术，存在吸附容量小、库仑效率低的问题，应用受到一定限制。通过制备新型石墨烯基电极材料以及对电极结构进行调整可以大幅度提高其性能。采用电化学剥离技术制备大片层氧化石墨烯（GO），约90%的GO层数低于5层，GO的边长尺寸高达200-500μm，GO的氧化程度很高，C/O比率为2.11，其中含氧碳的比率占59.37%。以GO为模板，间苯二酚，三聚氰胺，甲醛为原料制备可以常压干燥的富氮炭气凝胶材料，表面氮含量可以达到8.11 at%。富氮炭气凝胶具有较高的比电容222 F g-1，较低的ESR电阻；恒电压电吸附测试表明，随着电压增大，库仑力变大，样品的吸附量都增大，电吸附容量为16.72 mg g−1。采用反向悬浮聚合法， GO、间苯二酚、甲醛在水和环己烷形成的两相界面上反应，制备了石墨烯复合微球。实验合成了粒径均一，球形度完整的石墨烯复合微球，直径为5-10μm，壁厚约2μm，微球里层为纯的间苯二酚甲醛颗粒，外层为表面生长有间苯二酚甲醛颗粒的石墨烯片组成。微球应用于电吸附电极材料，在电压为1.6V时，吸附量高达27.76 mg/g，充电效率高达77.8-81.4%。随着电压从1.2V增加到1.6V，微球的电吸附容量从20.76mg/g增加到了33.52mg/g。将石墨烯凝胶、季铵化聚乙烯醇(QPVA)离子膜/全氟磺酸(PFSA)离子膜组装成膜碳复合电极，研究了复合电极的吸脱附应用和参数优化。电化学测试说明贴膜比涂膜有更高的电容和更低的电阻，主要原因在于膜碳结合方式上，涂膜导致碳材料孔隙被树脂填满，占据了离子迁移通道和存贮空间；对比膜碳结合方式和离子膜交联度的影响，复合装置可以在1.2 V电压，800 mg/L初始浓度获得最大的吸附效果(15.6 mg/g)和最短的脱附时间，而且吸附行为符合Lagergren假一级动力学模型。改进优化多极电容吸附脱盐装置，研究多极电容吸附的规律，具有能耗低的优点。新型石墨烯凝胶导电性高，比表面积大，其与离子交换膜组合成膜电极具有吸附量大，吸脱附速度快的优点，是一种非常有潜力的电吸附电极材料。