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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Proton transfer reactions and dynamics of sulfonic acid group in Nafion?
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Proton transfer reactions and dynamics of sulfonic acid group in Nafion?

机译：Nafion中的质子转移反应和磺酸基动力学

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Proton transfer reactions and dynamics of the hydrophilic group (-SO3H) in Nation? were studied at low hydration levels using the complexes formed from CF3SO3H, H3O~+ and nH2O, 1 ≤ n ≤ 3, as model systems. The equilibrium structures obtained from DFT calculations suggested at least two structural diffusion pathways at the -SO3H group namely, the "pass-through" and "pass-by" mechanisms. The former involves the protonation and deprotonation at the -SO3H group, whereas the latter the proton transfer in the adjacent Zundel complex. Analyses of the asymmetric O-H stretching frequencies (v~(OH)) of the hydrogen bond (H-bond) protons showed the threshold frequencies (v~(OH*)) of proton transfer in the range of 1700 to 2200 cm~(-1). Born-Oppenheimer Molecular Dynamics (BOMD) simulations at 350 K anticipated slightly lower threshold frequencies (v_A~(OH*,MD)), with two characteristic asymmetric O-H stretching frequencies being the spectral signatures of proton transfer in the H-bond complexes. The lower frequency (v_A~(OH,MD)) is associated with the oscillatory shuttling motion and the higher frequency (v_B~(OH,MD)) the structural diffusion motion. Comparison of the present results with BOMD simulations on protonated water clusters indicated that the -SO3H group facilitates proton transfer by reducing the vibrational energy for the interconversion between the two dynamic states (Δv_(BA)~(OH,MD)), resulting in a higher population of the H-bonds with the structural diffusion motion. One could therefore conclude that the -SO3H groups in Nation? act as active binding sites which provide appropriate structural, energetic and dynamic conditions for effective structural diffusion processes in a proton exchange membrane fuel cell (PEMFC). The present results suggested for the first time a possibility to discuss the tendency of proton transfer in H-bond using Δv_(BA)~(OH,MD) and provided theoretical bases and guidelines for the investigations of proton transfer reactions in theory and experiment.
机译：质子转移反应和亲水基团（-SO3H）的动力学在低水化水平下，使用CF3SO3H，H3O〜+和nH2O（1≤n≤3）形成的配合物作为模型系统进行了研究。从DFT计算获得的平衡结构表明-SO3H组至少有两个结构扩散途径，即“通过”和“通过”机制。前者涉及-SO3H基团的质子化和去质子化，而后者涉及相邻Zundel络合物中的质子转移。氢键（H键）质子的不对称OH拉伸频率（v〜（OH））的分析表明，质子转移的阈值频率（v〜（OH *））在1700至2200 cm〜（- 1）。 Born-Oppenheimer分子动力学（BOMD）在350 K下的模拟预期阈值频率会稍微降低（v_A〜（OH *，MD）），其中两个特征性的非对称O-H拉伸频率是质子在H键络合物中转移的光谱特征。较低的频率（v_A〜（OH，MD））与振荡穿梭运动相关，而较高的频率（v_B〜（OH，MD））与结构扩散运动相关。将当前结果与质子化水团簇上的BOMD模拟结果进行比较表明，-SO3H基团通过降低两个动态状态（Δv_（BA）〜（OH，MD））相互转换时的振动能来促进质子传递。随着结构扩散运动，氢键的数量增加。因此，可以得出结论，国家的-SO3H基团是？作为质子交换膜燃料电池（PEMFC）中有效结构扩散过程的适当结构，能量和动态条件的活性结合位点。本研究结果首次提出了利用Δv_（BA）〜（OH，MD）讨论氢键质子转移趋势的可能性，为理论和实验研究质子转移反应提供了理论基础和指导。

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