Proton-conducting polymers play a pivotal role in clean energy technologies and various industrial applications, with a significant emphasis on enhancing energy efficiency and minimizing environmental impact. Sulfonated polyether ether ketone (SPEEK), which is renowned for its proton conductivity, has emerged as a key material in electrochemical processes, notably in proton exchange membrane (PEM) fuel cells. This study investigated the proton conductivity and dielectric behavior of SPEEK electrolytes at varying degree of sulfonation (DS) of 65% and 80%, correlating these properties with free volume profiles determined by positron annihilation lifetime spectroscopy (PALS). The SPEEK-65 and SPEEK-80 electrolytes were prepared via a controlled sulfonation process and characterized by FTIR, TGA, and SEM analyses. Proton conductivity and dielectric measurements were conducted at temperatures ranging from 300 to 370 K and frequencies ranging from 20 Hz to 1 MHz. The results revealed that SPEEK-80 exhibited a maximum proton conductivity of 3.4 × 10−2 S/m at 300 K and 1 MHz, which was significantly greater than the 4.38 × 10−3 S/m observed for SPEEK-65 under the same conditions. PALS analysis demonstrated a notable increase in free volume with increasing DS, with SPEEK-80 showing a higher o-Ps lifetime and intensity, indicating larger free volume sizes and fractions. These findings underscore the critical interplay between DS, free volume, and proton conductivity, offering insights into optimizing SPEEK-based electrolytes for advanced electrochemical applications.

中文翻译：

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磺化聚醚醚酮电解质中质子电导率与自由体积的相关性：正电子湮没寿命谱研究


质子导电聚合物在清洁能源技术和各种工业应用中发挥着关键作用，特别强调提高能源效率和最大限度地减少对环境的影响。磺化聚醚醚酮 （SPEEK） 以其质子导电性而闻名，已成为电化学过程中的关键材料，尤其是在质子交换膜 （PEM） 燃料电池中。本研究研究了 SPEEK 电解质在不同 65% 和 80% 磺化程度 （DS） 下的质子电导率和介电行为，将这些特性与正电子湮没寿命谱 （PALS） 确定的自由体积分布相关联。SPEEK-65 和 SPEEK-80 电解液通过受控磺化工艺制备，并通过 FTIR、TGA 和 SEM 分析表征。质子电导率和介电测量在 300 至 370 K 的温度范围内进行，频率范围为 20 Hz 至 1 MHz。结果表明，SPEEK-80 在 300 K 和 1 MHz 时表现出 3.4 × 10−2 S/m 的最大质子电导率，显著大于在相同条件下观察到的 SPEEK-65 的 4.38 × 10−3 S/m。PALS 分析表明，随着 DS 的增加，游离体积显著增加，SPEEK-80 显示出更高的 o-Ps 寿命和强度，表明游离体积大小和馏分更大。这些发现强调了 DS、自由体积和质子电导率之间的关键相互作用，为优化基于 SPEEK 的电解质用于高级电化学应用提供了见解。