Degradation of QPPO-based anion polymer electrolyte membrane at neutral pH.
Degradation of QPPO-based anion polymer electrolyte membrane at neutral pH.
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阴离子聚合物电解质膜（AEM）的化学稳定性决定了AEM水电解槽（AEMWE）的耐久性。AEM的碱性稳定性已在文献中被广泛研究。然而，AEM在接近实际AEMWE操作条件的中性pH下的降解被忽略，并且降解机理仍不清楚。研究了季铵化聚对苯醚（QPPO）基AEM在不同条件下的稳定性，包括芬顿溶液、H2 O2溶液和去离子水。原始PPO和氯甲基化PPO（ClPPO）在芬顿溶液中表现出良好的化学稳定性，仅观察到有限的重量损失，分别为2.8%和1.6%。QPPO遭受了高质量损失（29%）。此外，具有较高IEC的QPPO表现出较高的质量损失。QPPO-1（1.7 mmol g−1）的质量损失几乎是QPPO-2（1.3 mmol g−1）的两倍。IEC的降解速率与H_2O_2浓度有很强的相关性，表明反应级数在1级以上。还通过将膜浸入60 °C的DI水中10个月来进行pH中性条件下的长期氧化稳定性测试。降解试验后，膜破裂成碎片。可能的降解机理是氧或OH的四甲基自由基攻击重排叶立德上的甲基，形成连接到CH 2基团上的醛或羧基。QPPO基阴离子交换膜在去离子水中的降解。
The chemical stability of anion polymer electrolyte membranes (AEMs) determines the durability of an AEM water electrolyzer (AEMWE). The alkaline stability of AEMs has been widely investigated in the literature. However, the degradation of AEM at neutral pH closer to the practical AEMWE operating condition is neglected, and the degradation mechanism remains unclear. This paper investigated the stability of quaternized poly(p-phenylene oxide) (QPPO)-based AEMs under different conditions, including Fenton solution, H2O2 solution and DI water. The pristine PPO and chloromethylated PPO (ClPPO) showed good chemical stability in the Fenton solution, and only limited weight loss was observed, 2.8% and 1.6%, respectively. QPPO suffered a high mass loss (29%). Besides, QPPO with higher IEC showed a higher mass loss. QPPO-1 (1.7 mmol g−1) lost nearly twice as much mass as QPPO-2 (1.3 mmol g−1). A strong correlation between the degradation rate of IEC and H2O2 concentration was obtained, which implied that the reaction order is above 1. A long-term oxidative stability test at pH neutral condition was also conducted by immersing the membrane in DI at 60 °C water for 10 months. The membrane breaks into pieces after the degradation test. The possible degradation mechanism is that oxygen or OH˙ radicals attack the methyl group on the rearranged ylide, forming aldehyde or carboxyl attached to the CH2 group. The degradation of QPPO-based anion exchange membrane in DI water.
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