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论文类型：期刊论文

发表时间：2017-02-02

发表刊物：CHEMICAL ENGINEERING SCIENCE

收录刊物：SCIE、EI

卷号：158

页面范围：234-244

ISSN号：0009-2509

关键字：Hyfion (R); Molecular dynamics simulation; Hydrated proton; Hydrogen bonding

摘要：In polyelectrolyte membranes, hydrated protons and proton conductive channels have cooperative effect on proton conductivity, the mechanism of which is believed to involve the structure of hydrated proton being deformed to adapt the confining channel. To investigate the dependence of the structural and dynamical properties of hydrated protons in Hyfion (R) perfluorosulfonic acid membranes with various water uptake values on the channel size, a series of molecular dynamics simulations based on an all-atom force field were conducted. The water uptake dependence of the hydrated proton diffusivity determined from our simulations was consistent with the experimental results in literature, which verified the simulation systems. A probability distribution of the hydrated proton complex is proposed to characterize the confinement effect of the proton conductive channel on the hydrated proton structure in the membranes with different morphologies. By means of local structural properties and pair-potential energies, a reasonable hydrogen bond criterion was employed to characterize the structures of the hydrated proton complexes. It was found that the nanochannels confined the structure of the hydrated proton complex and that confined complexes of H9O4+, H7O3+ and H5O2+ were dominant. Weakening the confinement by increasing the channel size was beneficial for the formation of the H9O4+ complex, the probability distribution of which gradually became plateau. Thus, H9O4+ can be considered the stable structure of the confined hydrated proton complex in polymer electrolyte membranes. This work is helpful in understanding the relationship between the structure of the confined hydrated proton and the proton conductive channel. It also provides potential guidance for improving the membrane performance in fuel cell.