You Wei, Ganley Jacob M, Ernst Brian G, Peltier Cheyenne R, Ko Hsin-Yu, DiStasio Robert A, Knowles Robert R, Coates Geoffrey W
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University Ithaca NY 14853 USA.
Department of Chemistry, Princeton University Princeton NJ 08544 USA.
Chem Sci. 2021 Feb 1;12(11):3898-3910. doi: 10.1039/d0sc05789d.
Alkaline anion exchange membranes (AAEMs) with high hydroxide conductivity and good alkaline stability are essential for the development of anion exchange membrane fuel cells to generate clean energy by converting renewable fuels to electricity. Polyethylene-based AAEMs with excellent properties can be prepared sequential ring-opening metathesis polymerization (ROMP) and hydrogenation of cyclooctene derivatives. However, one of the major limitations of this approach is the complicated multi-step synthesis of functionalized cyclooctene monomers. Herein, we report that piperidinium-functionalized cyclooctene monomers can be easily prepared the photocatalytic hydroamination of cyclooctadiene with piperidine in a one-pot, two-step process to produce high-performance AAEMs. Possible alkaline-degradation pathways of the resultant polymers were analyzed using spectroscopic analysis and dispersion-inclusive hybrid density functional theory (DFT) calculations. Quite interestingly, our theoretical calculations indicate that local backbone morphology-which can potentially change the Hofmann elimination reaction rate constant by more than four orders of magnitude-is another important consideration in the rational design of stable high-performance AAEMs.
具有高氢氧根传导率和良好碱性稳定性的碱性阴离子交换膜(AAEMs)对于阴离子交换膜燃料电池的发展至关重要,该电池可通过将可再生燃料转化为电能来产生清洁能源。具有优异性能的聚乙烯基AAEMs可通过环辛烯衍生物的顺序开环易位聚合(ROMP)和氢化反应制备。然而,这种方法的主要局限性之一是功能化环辛烯单体的多步合成过程复杂。在此,我们报道了哌啶鎓功能化的环辛烯单体可以通过环辛二烯与哌啶的光催化氢胺化反应在一锅两步法中轻松制备,从而生产出高性能的AAEMs。使用光谱分析和包含色散的杂化密度泛函理论(DFT)计算分析了所得聚合物可能的碱性降解途径。非常有趣的是,我们的理论计算表明,局部主链形态——它可能会使霍夫曼消除反应速率常数改变超过四个数量级——是合理设计稳定的高性能AAEMs时的另一个重要考虑因素。