Radiation-grafted anion-exchange membranes for CO 2 electroreduction cells: an unexpected effect of using a lower excess of N -methylpiperidine in their fabrication
Radiation-grafted anion-exchange membranes for CO 2 electroreduction cells: an unexpected effect of using a lower excess of N -methylpiperidine in their fabrication
复制标题
用于CO 2 电还原电池的辐射接枝阴离子交换膜：在其制造中使用较低过量的N-甲基哌啶的意想不到的效果
DOI：
10.1039/d3ta04915a
复制
发表时间：
2023
影响因子：
11.9
通讯作者：
Willson T
中科院分区：
文献类型：
--
作者：
Willson T
Giron Rodriguez等人[ACS Sustainable Chem. Eng.，2023，11，1508]先前表明，含有N-苄基-N-甲基哌啶鎓头基的辐射接枝的阴离子交换膜（MPIP-RG-AEM）有希望用于CO2电解（参见商业和其它RG-AEM类型）。为了更可持续的合成，MPIP-RG-AEM现在已经使用减少的1.1倍过量的胺试剂（历史上使用>5倍过量制备）来制造。所得到的RG-AEM有希望地具有与用传统的大量过量制备的那些相当的本体胺化水平。然而，出乎意料的是，它具有显著降低的含水量，另外两个批次显示该观察结果是可重复的（并且通过在不同实验室中使用不同技术对单个批次收集的测量结果是可重复的）。用受控的1.1过量胺制备的RG-AEM的离子电导率也较低，具有较高的活化能。太赫兹时域光谱测量显示，用1.1胺过量制备的较低吸水率的RG-AEM相对于结合水含有较少量的本体水（用不同抗衡阴离子的可重复观察）。当在CO2电解槽中测试这种RG-AEM时，这种本体水的缺乏导致水扩散系数降低，导致水管理的变化，从而显著影响原位性能。小角散射数据（X射线和中子）表明，使用1.1过量的胺的MPIP-RG-AEM制造减小了水合时无定形片层结构域的尺寸，并且这种变化被怀疑是较低的水吸收和溶胀的原因。化学上相似的AEM可能具有显著不同的水合特性，这一发现对所有离子交换膜用户和开发人员都具有潜在的重要性（超出本研究的CO2电解范围）。
Giron Rodriguez et al. [ACS Sustainable Chem. Eng., 2023, 11, 1508] previously showed that radiation-grafted anion-exchange membranes containing N-benzyl-N-methylpiperidinium headgroups (MPIP-RG-AEM) are promising for use in CO2 electrolysis (cf. commercial and other RG-AEM types). For a more sustainable synthesis, MPIP-RG-AEMs have now been fabricated using a reduced 1.1 times excess of amine reagent (historically made using >5 times excess). A resulting RG-AEM promisingly had a bulk amination level that was comparable to those made with the traditional large excess. Unexpectedly, however, it had a significantly reduced water content, with two further batches showing that this observation was repeatable (and reproducible via measurements collected on a single batch using different techniques in different labs). The ionic conductivities of the RG-AEM made with a controlled 1.1 excess of amine were also lower, with higher activation energies. Terahertz time-domain spectroscopy measurements showed that the lower water uptake RG-AEMs, made with the 1.1 amine excess, contained smaller amounts of bulk water relative to bound water (a repeatable observation with different counter-anions). This lack of bulk water, yielding reduced water diffusion coefficients, led to a change in the water management when such RG-AEMs were tested in CO2 electrolysis cells, with significantly affected in situ performances. Small angle scattering data (X-ray and neutron) indicated that MPIP-RG-AEM fabrication with the 1.1 excess of amine reduced the size of the amorphous lamella domains on hydration, and this change is suspected to be the cause of the lower water uptakes and swelling. The finding that chemically similar AEMs can have significantly different hydration properties is potentially important to all ion-exchange membrane users and developers (beyond the CO2 electrolysis scope of this study).