Begić Srđan, Li Hua, Atkin Rob, Hollenkamp Anthony F, Howlett Patrick C
ARC Centre of Excellence for Electromaterials Science (ACES), Institute for Frontier Materials (IFM), Deakin University Burwood Campus, 221 Burwood Hwy, Burwood, VIC 3125, Australia.
Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle, Callaghan, NSW 2308, Australia.
Phys Chem Chem Phys. 2016 Oct 26;18(42):29337-29347. doi: 10.1039/c6cp04299f.
The electrochemical systems containing zinc dicyanamide salt (Zn(dca)) in both 1-ethyl-3-methylimidazolium dicyanamide ([Cmim][dca]) and N-butyl-N-methylpyrrolidinium dicyanamide ([Cmpyr][dca]) ionic liquids (ILs) have been studied by atomic force microscopy (AFM) on a highly oriented pyrolytic graphite (HOPG) surface under different conditions and applied potentials. The results reveal the following: (1) interfacial layers exist in both ILs, even after the addition of 3 wt% water and 9 mol% Zn(dca) salt. (2) The number of layers is different for the different ILs, with the [Cmim][dca]-based samples exhibiting a much more limited interfacial structure compared to the [Cmpyr][dca] at almost all of the tested conditions. (3) For the [Cmpyr][dca]-based samples, without added zinc salt, the number of detected interfacial layers increases with negative potential. With added zinc, the [Cmpyr][dca] sample shows about the same number of layers independent of the applied potentials, namely between 5-7. Likewise, for the [Cmim][dca] samples, with the zinc added the sample shows the same number of layers at the applied potentials, but for this system only 1-2 layers are detected. And (4) the addition of Zn(dca) into the [Cmim][dca] IL does not cause a large change in the interfacial ordering, whereas the addition of the same salt into the [Cmpyr][dca] samples is marked by a stark increase in both the number and the consistency of the perceived interfacial layers. These results are significant because they show a marked difference in the interfacial nanostructure between two zinc-based electrochemical systems that were previously shown to have distinctly different electrochemical behaviour, despite their chemical similarity.
在不同条件和外加电势下，利用原子力显微镜（AFM）在高度取向热解石墨（HOPG）表面对含有双氰胺锌盐（Zn(dca)）的电化学体系进行了研究，该体系中的离子液体（ILs）分别为1-乙基-3-甲基咪唑双氰胺盐（[Cmim][dca]）和N-丁基-N-甲基吡咯烷双氰胺盐（[Cmpyr][dca]）。结果表明：（1）即使添加了3 wt%的水和9 mol%的Zn(dca)盐，两种离子液体中均存在界面层。（2）不同离子液体的层数不同，在几乎所有测试条件下，基于[Cmim][dca]的样品与基于[Cmpyr][dca]的样品相比，界面结构更为有限。（3）对于基于[Cmpyr][dca]的样品，在不添加锌盐的情况下，检测到的界面层数随负电势增加。添加锌后，[Cmpyr][dca]样品显示的层数与外加电势无关，约为5 - 7层。同样，对于基于[Cmim][dca]的样品，添加锌后在施加电势下显示相同的层数，但对于该体系仅检测到1 - 2层。并且（4）向[Cmim][dca]离子液体中添加Zn(dca)不会导致界面有序性发生大的变化，而向[Cmpyr][dca]样品中添加相同的盐则表现为所感知的界面层数和一致性都显著增加。这些结果意义重大，因为它们表明，尽管两种基于锌的电化学体系化学性质相似，但先前已证明它们具有明显不同的电化学行为，而现在发现它们的界面纳米结构存在显著差异。
