表面修饰模式对Nafion离子选择性影响及在VRFB中的应用

本文采用壳聚糖-磷钨酸层对Nafion膜表面分别进行单面和双面修饰改性，研究了修饰模式对Nafion膜钒离子渗透率、电导率及离子选择性的影响. 结果表明，单面、双面修饰改性均会使Nafion膜的钒离子渗透率显著降低，最高降幅分别达到89.9% (单面修饰) 和92.7% (双面修饰)；单面、双面修饰改性均会使Nafion膜的电导率下降，但存在明显差异，在相同修饰厚度条件下，双面修饰改性对Nafion膜电导率的影响比单面修饰改性更小。因此，双面修饰复合膜展示出了比单面修饰复合膜更高的离子选择性，并且在修饰层厚度为17 μm时达到最大值（1.12×10⁵ S?min?cm^-3）. 基于优化的双面修饰Nafion膜的全钒液流电池，在充放电流密度30 mA?cm^-2 时，库伦效率和能量效率分别达到93.5%和 80.7%, 并且在测试时间内展示出良好的循环稳定性.

Effects of surface modification modes on proton-over-vanadium ion selectivity of Nafion®membrane for application in vanadium redox flow battery

The effect of surface modification modes on proton-over-vanadium ion selectivity was studied by spin-coating chitosan-Phosphotungstic Acid (PWA) as a single or double layer on Nafion membrane surface. To suppress the vanadium ions permeation through the Nafion? membrane in a vanadium redox flow battery (VRFB), the single surface-modified Nafion membrane (Nafion/chitosan-PWA)S and double surface-modified Nafion membrane (Nafion/chitosan-PWA)D demonstrated a 89.9% and 92.7% reduction of vanadium ion permeability in comparison with pristine Nafion, respectively. The (Nafion/chitosan-PWA)D exhibited betterhigher selectivity between proton and vanadium ions than the (Nafion/chitosan-PWA)S at the same layer thickness. Furthermore, the columbic efficiency for the VRFB single cell based on the (Nafion/chitosan-PWA)D at an optimized thickness was 93.5% and the energy efficiency was 80.7% at a charge-discharge current density of 30 mA·cm-2, which wereas higher than the (Nafion/chitosan-PWA)S and pristine Nafion membrane. The modified membranes also possessed adequate chemical stability in the VRFB during charge-discharge cycling measurements.