硫酸交联壳聚糖膜质子传导行为的研究

制备了硫酸交联壳聚糖膜, 通过研究其质子传导性能、力学性能、化学成分及结构变化, 分析了硫酸与壳聚糖分子间的交联方式, 并对质子传导机理进行了解析. 结果表明, 硫酸交联可显著改善壳聚糖膜的质子传导能力与力学性能, 这种改善作用在交联6 h后趋于稳定, 交联6 h后的壳聚糖湿膜在室温下时质子传导率为0.0472 S? cm^－1, 比未交联的壳聚糖膜提高5倍左右. 硫酸交联壳聚糖膜中的质子传导率与温度的关系符合Arrhenius定律, 质子传导激活能为18 kJ/mol, 其传导机制应属于Grotthus机制. 硫酸对提高壳聚糖膜的质子传导能力主要有两方面的作用: (1) H₂SO₄可使壳聚糖分子中NH₂质子化形成NH₃^＋. (2) 处于两个氨基之间的SO₄^2－在质子传递过程中起离子桥梁作用, 参与以水分子为载体的质子传导过程, 从而减小质子传导的阻力, 提高了质子传导率.

Investigation on Proton Conductivity Behavior of Sulfuric Acid Crosslinked Chitosan Membrane

The sulfuric acid crosslinked chitosan membrane was prepared for fuel cells. The proton conductivity, mechanical performance, infrared spectroscopy and elemental analysis were investigated. The interaction between sulfuric acid and the chitosan membrane was analyzed. Proton conductivity and mechanical performance were clearly enhanced by interaction, reaching a steady level after 6 h crosslinking. The 6 h crosslinked chitosan membrane showed the high proton conductivity of 0.0472 S?cm^－1 at room temperature under fully hydrated conditions, a 5-fold increase compared to the non-crosslinked chitosan membrane. And the mechanism for the proton conductivity of the crosslinked chitosan membrane was proposed. The relationship between conductivity and temperature accords with the law of Arrhenius and the activation energy of the proton conductivity in the crosslinked chitosan membranes is 18 kJ/mol corresponding to Grotthus mechanism. The contribution of the sulfuric acid to the proton conductivity improvement in the crosslinked chitosan membranes is as follows: the amino groups in the chitosan were pro-tonated efficiently by sulfuric acid; SO₄^2－ located between the amino groups, and acted as the ionic bridge in the process of the proton conduction.