作者:Vincenzo Tricoli、Gabriele Orsini、Martina Anselmi
DOI:10.1039/c2cp41027c
日期:——
A class of protic ionic-compounds were prepared by Brønsted acid–base reaction of imidazole or benzimidazole with one of the following acids: trifluoromethanesulfonic, nonafluorobutanesulfonic, para-toluenesulfonic and trifluoroacetic. Except those based on trifluoroacetic acid, all prepared compounds are thermally stable up to at least 270 °C. They are solid up to temperatures between 134 and 220 °C, depending on their constituent acid and base. A simple physico-mathematical model of ion motion in the lattice was developed and implemented to correctly interpret frequency-dependent electrical response of these materials, particularly in the solid state, and investigate their ion-conducting behavior as a function of temperature. These ionic compounds display sensible ionic conductivity up to ca. 5 × 10−4 and 5 × 10−2 S cm−1 in the solid and molten state, respectively, under fully anhydrous conditions. The presence of absorbed water, after brief exposure to an ambient atmosphere, enhances conduction properties remarkably. Conductivity values up to 10−3 and 10−1 S cm−1 were registered, respectively, in the solid and molten state, after short exposure to (humid) ambient air. It is argued how absorbed water molecules may remove protons from (ImH)+ or (BImH)+ groups, thereby enabling a chain mechanism of proton-hopping through non-protonated Im or BIm sites. It is discussed how these results and methods may inspire designing protic ionic-materials at the solid-state, with enhanced proton conduction even under fully-anhydrous conditions.
通过咪唑或苯并咪唑与以下酸之一:三氟甲磺酸、九氟丁磺酸、对甲苯磺酸和三氟乙酸的布朗斯台德酸碱反应,制备了一系列质子型离子化合物。除基于三氟乙酸的化合物外,所有制备的化合物在至少270°C温度下均具有热稳定性。它们的固态温度范围为134至220°C,具体取决于所组成的酸和碱。开发并实施了一个简单的物理数学模型来解释这些材料在固态下频率依赖的电响应,并研究它们的离子导电行为随温度的变化。这些离子化合物在完全无水的条件下,分别在固态和熔融状态下显示出高达约5×10⁻⁴和5×10⁻² S/cm的合理离子电导率。短暂暴露于环境气氛后,吸附的水显著增强了传导性能。在短暂暴露于(湿润的)环境空气中后,分别在固态和熔融状态下记录到了高达10⁻³和10⁻¹ S/cm的电导率值。据推测,吸附的水分子可能从(ImH)⁺或(BImH)⁺基团中去除质子,从而通过非质子化的Im或BIm位点实现质子跳跃的链式机制。讨论了这些结果和方法如何启发在固态下设计具有增强质子传导性的质子型离子材料,即使在完全无水的条件下。