Unraveling the behavior of the individual ionic activity coefficients on the basis of the balance of ion-ion and ion-water interactions.
Unraveling the behavior of the individual ionic activity coefficients on the basis of the balance of ion-ion and ion-water interactions.
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DOI：
10.1021/jp509445k
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发表时间：
2014-09
期刊：
影响因子：
--
通讯作者：
M. Valiskó;D. Boda
中科院分区：
文献类型：
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作者：
M. Valiskó;D. Boda
我们使用基于离子-离子（II）和离子-水（IW）相互作用的竞争的理论研究了纯1：1和2：1电解质的单个活度系数（Alzheze等人，J. Chem.Phys.2010，133，154507）。II项计算巨正则Monte Carlo模拟的基础上的隐式溶剂模型的电解质使用硬球离子与Pauling半径。IW项计算的基础上，玻恩的治疗溶剂化使用实验水合自由能。这两个术语通过电解质的浓度依赖性介电常数耦合。我们表明，该理论可以提供有价值的洞察个人活度系数的非单调浓度依赖性。我们将我们的理论预测与含有离子特定电极的电化学电池测量的实验数据进行比较。我们发现2：1电解质的一致性良好，而1：1系统的准确性较差。这种精度偏差的原因是，在2：1的情况下，两个竞争项（II和IW）要大得多，导致相对误差较小。阳离子和阴离子的过量化学势的差异由两种离子的性质的不对称性决定：电荷、半径和水合自由能。
We investigate the individual activity coefficients of pure 1:1 and 2:1 electrolytes using our theory that is based on the competition of ion-ion (II) and ion-water (IW) interactions (Vincze et al. J. Chem. Phys. 2010, 133, 154507). The II term is computed from grand canonical Monte Carlo simulations on the basis of the implicit solvent model of electrolytes using hard sphere ions with Pauling radii. The IW term is computed on the basis of Born's treatment of solvation using experimental hydration free energies. The two terms are coupled through the concentration-dependent dielectric constant of the electrolyte. We show that the theory can provide valuable insight into the nonmonotonic concentration dependence of individual activity coefficients. We compare our theoretical predictions against experimental data measured by electrochemical cells containing ion-specific electrodes. We find good agreement for 2:1 electrolytes, while the accuracy is worse for 1:1 systems. This deviation in accuracy is explained by the fact that the two competing terms (II and IW) are much larger in the 2:1 case, resulting in smaller relative errors. The difference of the excess chemical potentials of cations and anions is determined by asymmetries in the properties of the two ions: charge, radius, and hydration free energies.