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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Modeling the Influence of Low Concentrations of Water on the Thermodynamics, Electron Transfer Kinetics, and Diffusivity of the [Ru(CN)(6)](4-/3-) Process in Propylene Carbonate
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Modeling the Influence of Low Concentrations of Water on the Thermodynamics, Electron Transfer Kinetics, and Diffusivity of the [Ru(CN)(6)](4-/3-) Process in Propylene Carbonate

机译：丙烯碳酸亚丙酯中[Ru（CN）（6）（4- / 3-）法的热力学，电子转移动力学和扩散性的影响模拟水的影响

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Addition of low concentrations of water to an aprotic solvent can lead to large changes in the thermodynamics of some electrode processes. In contrast, the impact of water addition on the electrode kinetics of such systems has yet to be established. Herein, direct current and Fourier transformed alternating current voltammetric studies were undertaken at a glassy carbon electrode to investigate changes in the thermodynamics, kinetics, and diffusivity of the [Ru(CN)(6)](4-/3-) process in propylene carbonate (PC, 0.10 M n-Bu4NPF6) that occur on addition of up to 1.87 M water and in fully aqueous 0.10 M KCl electrolyte media. The formal reversible potential (E-f(0)) for the [Ru(CN)(6)](4-/3-) couple is -0.66 V versus Fc(0/+) (Fc = ferrocene) in PC and shifts substantially in the positive direction by similar to 0.35 V in the presence of 1.87 M water, and it is established to be 1.0 V more positive in fully aqueous media. In comparison, E-f(0) for the Fc(0/+) process only changes by similar to 20 mV versus a Pt quasi reference electrode in the presence of 1.87 M water, emphasizing the impact of charge and structure on the thermodynamics. Modeling the water-induced shift in E-f(0) in terms of solvent interaction implies that transfer of approximately four water molecules in the secondary coordination sphere accompanies the oxidation of [Ru(CN)(6)](4-) to [Ru(CN)(6)](3-). Despite the implied large level of solvent rearrangement, the heterogeneous electron transfer rate constant only increases from 1.81 x 10(-2) cm s(-1) in "dry" PC to 3.38 x 10(-2) cm s(-1) on addition of 1.87 M water to PC. An increase in diffusivity of [Ru(CN)(6)](4-) was observed but is not evident in the Fc(0/+) process under the same conditions; hence, it is probably not simply due to the small decrease in viscosity that occurs on addition of low concentrations of water. Some, but not all, aspects of the kinetics are in qualitative agreement with Marcus theory predictions.
机译：向非质子溶剂添加低浓度的水可以导致一些电极工艺的热力学变化。相比之下，尚未建立这种系统的电极动力学对​​水的影响。在此，在玻璃碳电极下进行直流和傅里叶变换的交流伏安法研究，以研究[Ru（CN）（6）]（4- / 3-）丙烯中的热力学，动力学和扩散性的变化碳酸酯（PC，0.10米N-BU4NPF6），其在加入高达1.87米的水和完全水溶液0.10M KCl电解质介质中发生。 [Ru（CN）（6）]（4- / 3-）夫妇的正式可逆电位（EF（0））是-0.66V与Fc（0 / +）（Fc =二甲苯）在PC中，并大大移位在阳性方向上，在1.87米水中类似于0.35V，在完全水性介质中建立至1.0V更阳性。相比之下，Fc（0 / +）过程的E-F（0）仅在存在1.87米的水中相似的20mV与Pt准参考电极相似，强调电荷和结构对热力学的影响。在溶剂相互作用方面建模EF（0）中的水诱导的换档意味着在二级协调球中的约四水分子的转移伴随着[Ru（CN）（6）]（4-）的氧化至[Ru（ CN）（6）]（3-）。尽管暗示了大量的溶剂重新排列，但异构电子传递速率恒定仅从“干”PC中的1.81×10（-2）cm s（-1）增加到3.38×10（-2）cm s（-1）加入1.87米的PC。观察[Ru（CN）（6）]（4-）的扩散性的增加，但在相同条件下的Fc（0 / +）过程中不明显;因此，由于添加低浓度的水，因此可能不仅仅是由于发生的粘度的小降低。其中一些，但不是全部，动力学的各个方面都与马库斯理论预测的定性协议。

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