离子交换膜扩散边界层厚度的测试方法比较

Comparisons on test methods of diffusion boundary layer thickness

电化学阻抗谱和线性扫描伏安法均可用来测定离子交换膜扩散边界层的厚度.本文比较了两种方法测定的扩散边界层厚度大小,并考察了不同流速和温度对阳离子交换膜和阴离子交换膜扩散边界层厚度的影响.研究发现:线性扫描伏安法的测试结果高于电化学阻抗谱法的结果,这与前者测试过程中施加电压过高使界面层发生破坏有关;随着流速的增大,电化学阻抗谱测定的扩散边界层厚度显著降低,而线性扫描伏安法的测定值基本不变,前者的测定值更接近实际值;阳离子交换膜和阴离子交换膜的扩散边界层厚度不同,且受温度的影响程度不同.研究结果对于优化离子交换膜的电化学评价技术具有重要意义.

Electrochemical impedance spectroscopy （EIS） and Linear sweep voltammetry （LSV） can be used to measure the thickness of diffusion boundary layers （DBL） in ion exchange membranes. The DBL thickness from these two methods was compared and the effects of flow rate and temperature on the DBL thickness of two ion exchange membranes were investigated. It is found that the DBL thickness measured from LSV was higher than that from EIS, which was due to the higher voltage imposed to the membrane leading to the destruction of membrane interface; when the flow rate increased, the DBL thickness decreased for EIS measurements while did not change significantly for LSV measurements, which indicated that the data from EIS was close to the real value; the DBL thickness was different for anion exchange membrane and cation exchange membrane, and the effect of temperature on them was also different. Research results are of major importance for optimization of characterization techniques on membrane transport properties of ion exchange membranes.