Nafion 1135阳离子交换膜中扩散系数
(中南大学 化学化工学院， 长沙 410083)
摘 要: 研究通过电导率测定钒离子VO2+在Nafion 1135离子交换膜中的扩散系数的方法。 采用交流阻抗技术测定含不同浓度VO2+的0.1 mol/L硫酸电解质溶液在有无膜时的阻抗值， 采用有膜时的阻抗减去无膜时阻抗值得到了不同条件下的膜阻抗。 结果表明：阻抗大小与电极距离成正比， 有膜与无膜时分别测定的阻抗与电极距离的关系曲线近似呈平行线， 与电解液组成无关； 膜阻抗随着溶液中VO2+浓度的增加而增加。 根据基于Nernst-Planck扩散对流方程的二元离子在交换膜中扩散系数与电导率的关系方程计算了钒离子VO2+在Nafion 1135离子交换膜中的扩散系数为4.5×10-12 m2/s。
关键字: 钒离子(Ⅳ); 离子交换膜； 扩散系数； 电导率； 膜阻抗
electrical conductivity measurement
（School of Chemistry and Chemical Engineering,
Central South University, Changsha 410083, China）
Abstract: The diffusion coefficient determination of VO2+ in Nafion 1135 membrane by electrical conductivity measurement was studied. The resistances of the electrolyte with different VO2+ concentrations in 0.1 mol/L vitriol solution and the solution with Nafion 1135 cation exchange membrane were measured by AC impedance technique. The membrane resistance was obtained by the difference of the resistances with and without membrane. The results show that the curves representing the relation of the membrane-solution and solution resistances with the inter-electrode distance are parallel straight lines， whatever the composition of the solution is. The membrane resistance grows with increasing VO2+ concentration. The calculated diffusion coefficient of VO2+ in Nafion 1135 cation exchange membrane is 4.5×1012 m2/s by the relation of diffusion coefficient and conductivity in bi-ionic system based on the Nernst-Plank diffusion-convection equation.
Key words: vanadium ion(Ⅳ); ion exchange membrane; diffusion coefficient; conductivity; membrane resistance
