Nafion 1135陽離子交換膜中擴散系數(shù)
(中南大學 化學化工學院， 長沙 410083)
摘 要: 研究通過電導率測定釩離子VO2+在Nafion 1135離子交換膜中的擴散系數(shù)的方法。 采用交流阻抗技術測定含不同濃度VO2+的0.1 mol/L硫酸電解質(zhì)溶液在有無膜時的阻抗值， 采用有膜時的阻抗減去無膜時阻抗值得到了不同條件下的膜阻抗。 結果表明：阻抗大小與電極距離成正比， 有膜與無膜時分別測定的阻抗與電極距離的關系曲線近似呈平行線， 與電解液組成無關； 膜阻抗隨著溶液中VO2+濃度的增加而增加。 根據(jù)基于Nernst-Planck擴散對流方程的二元離子在交換膜中擴散系數(shù)與電導率的關系方程計算了釩離子VO2+在Nafion 1135離子交換膜中的擴散系數(shù)為4.5×10-12 m2/s。
關鍵字: 釩離子(Ⅳ); 離子交換膜； 擴散系數(shù)； 電導率； 膜阻抗
electrical conductivity measurement
LI Xiao-gang, WANG Xian
（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
