Hydroxide Solvation and Transport in Anion Exchange Membranes

被引:241
作者
Chen, Chen [1 ,2 ,3 ]
Tse, Ying-Lung Steve [1 ,2 ,6 ]
Lindberg, Gerrick E. [4 ]
Knight, Chris [5 ]
Voth, Gregory A. [1 ,2 ]
机构
[1] Univ Chicago, Inst Biophys Dynam, James Franck Inst, Dept Chem, Chicago, IL 60637 USA
[2] Univ Chicago, Computat Inst, Chicago, IL 60637 USA
[3] Wuhan Univ, Coll Chem & Mol Sci, Hubei Key Lab Electrochem Power Sources, Wuhan 430072, Peoples R China
[4] No Arizona Univ, Dept Chem & Biochem, Flagstaff, AZ 86011 USA
[5] Argonne Natl Lab, Leadership Comp Facil, 9700 S Cass Ave, Argonne, IL 60439 USA
[6] Chinese Univ Hong Kong, Dept Chem, Shatin, Hong Kong, Peoples R China
基金
中国国家自然科学基金;
关键词
PERFLUOROSULFONIC ACID MEMBRANES; POLYMER ELECTROLYTE MEMBRANES; FUEL-CELL APPLICATIONS; PROTON TRANSPORT; MOLECULAR-DYNAMICS; HYDRATED PROTON; BIOMOLECULAR SYSTEMS; COMPUTER-SIMULATION; NAFION; MECHANISM;
D O I
10.1021/jacs.5b11951
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Understanding hydroxide solvation and transport in anion exchange membranes (AEMs) can provide important insight into the design principles of these new membranes. To accurately model hydroxide solvation and transport, we developed a new multiscale reactive molecular dynamics model for hydroxide in aqueous solution, which was then subsequently modified for an AEM material. With this model, we investigated the hydroxide solvation structure and transport mechanism in the membrane. We found that a relatively even separation of the rigid side chains produces a continuous overlapping region for hydroxide transport that is made up of the first hydration shell of the tethered cationic groups. Our results show that hydroxide has a significant preference for this overlapping region, transporting through it and between the AEM side chains with substantial contributions from both vehicular (standard diffusion) and Grotthuss (proton hopping) mechanisms. Comparison of the AEM with common proton exchange membranes (PEMs) showed that the excess charge is less delocalized in the AEM than the PEMs, which is correlated with a higher free energy barrier for proton transfer reactions. The vehicular mechanism also contributes considerably more than the Grotthuss mechanism for hydroxide transport in the AEM, while our previous studies of PEM systems showed a larger contribution from the Grotthuss mechanism than the vehicular mechanism for proton transport. The activation energy barrier for hydroxide diffusion in the AEM is greater than that for proton diffusion in PEMs, implying a more significant enhancement of ion transport in the AEM at elevated temperatures.
引用
收藏
页码:991 / 1000
页数:10
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