Zhou Xuechen, Shi Le, Taylor Rachel F, Xie Chenghan, Bian Bin, Picioreanu Cristian, Logan Bruce E
Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, P. R. China.
Environ Sci Technol. 2023 Oct 3;57(39):14569-14578. doi: 10.1021/acs.est.3c04768. Epub 2023 Sep 18.
Low-cost polyamide thin-film composite (TFC) membranes are being explored as alternatives to cation exchange membranes for seawater electrolysis. An optimal membrane should have a low electrical resistance to minimize applied potentials needed for water electrolysis and be able to block chloride ions present in a seawater catholyte from reaching the anode. The largest energy loss associated with a TFC membrane was the Nernstian overpotential of 0.74 V (equivalent to 37 Ω cm at 20 mA cm), derived from the pH difference between the anolyte and catholyte and not the membrane ohmic overpotential. Based on analysis using electrochemical impedance spectroscopy, the pristine TFC membrane contributed only 5.00 Ω cm to the ohmic resistance. Removing the polyester support layer reduced the resistance by 79% to only 1.04 Ω cm, without altering the salt ion transport between the electrolytes. Enlarging the pore size (∼5 times) in the polyamide active layer minimally impacted counterion transport across the membrane during electrolysis, but it increased the total concentration of chloride transported by 60%. Overall, this study suggests that TFC membranes with thinner but mechanically strong supporting layers and size-selective active layers should reduce energy consumption and the potential for chlorine generation for seawater electrolyzers.
低成本聚酰胺薄膜复合（TFC）膜正被探索作为海水电解阳离子交换膜的替代品。理想的膜应具有低电阻，以尽量减少水电解所需的外加电位，并能够阻止海水阴极电解液中存在的氯离子到达阳极。与TFC膜相关的最大能量损失是能斯特过电位0.74 V（相当于在20 mA/cm²时为37 Ω·cm），这是由阳极电解液和阴极电解液之间的pH差异引起的，而非膜的欧姆过电位。基于电化学阻抗谱分析，原始TFC膜对欧姆电阻的贡献仅为5.00 Ω·cm。去除聚酯支撑层可将电阻降低79%，至仅1.04 Ω·cm，同时不改变电解质之间的盐离子传输。在聚酰胺活性层中扩大孔径（约5倍）对电解过程中抗衡离子跨膜传输的影响最小，但使传输的氯离子总浓度增加了60%。总体而言，本研究表明，具有更薄但机械强度高的支撑层和尺寸选择性活性层的TFC膜应能降低海水电解槽的能耗和产氯可能性。
