Carbon-Nanotube-Electrolyte Interface: Quantum and Electric Double Layer Capacitance.
Carbon-Nanotube-Electrolyte Interface: Quantum and Electric Double Layer Capacitance.
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DOI：
10.1021/acsnano.8b01427
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发表时间：
2018-10-23
期刊：
影响因子：
17.1
通讯作者：
Burke PJ
中科院分区：
文献类型：
--
作者：
Li J;Pham PHQ;Zhou W;Pham TD;Burke PJ
我们对一维电子材料和电解质之间的电化学电容进行了全面的研究。与传统的平面电极相比，电极的纳米级尺寸（直径小于德拜长度并接近溶液中离子的尺寸）定性地改变了电容，我们在此测量和建模。此外，这些低维电子系统中的有限状态密度产生了与电化学电容相当的量子电容。使用电化学阻抗谱 (EIS)，我们测量了纯化 (99.9%) 的半导体纳米管网络和 10 mM 至 1 M 之间不同浓度的水性电解质 (KCl) 之间的整体平均、复数、频率相关阻抗（从 0.1 Hz 到 1 MHz）。电容的电势依赖性与纳米管网络面内电导的电势依赖性相结合，我们使用传输线模型对其进行建模，以解释面内频率依赖性阻抗以及网络和电解质之间的总界面阻抗。电容的离子强度依赖性预计有双层电容的根本原因，我们使用修改后的泊松-玻尔兹曼方程对其进行建模。这两个电容的相对贡献可以定量解耦。根据液体栅极电势从 -0.5 到 -0.7 V 的变化，我们发现每管的总电容为 0.67–1.13 fF/μm。
We present a comprehensive study of the electrochemical capacitance between a one-dimensional electronic material and an electrolyte. In contrast to a conventional, planar electrode, the nanoscale dimension of the electrode (with diameter smaller than the Debye length and approaching the size of the ions in solution) qualitatively changes the capacitance, which we measure and model herein. Furthermore, the finite density of states in these low dimensional electronic systems results in a quantum capacitance, which is comparable to the electrochemical capacitance. Using electrochemical impedance spectroscopy (EIS), we measure the ensemble average, complex, frequency dependent impedance (from 0.1 Hz to 1 MHz) between a purified (99.9%) semiconducting nanotube network and an aqueous electrolyte (KCl) at different concentrations between 10 mM and 1 M. The potential dependence of the capacitance is convoluted with the potential dependence of the in-plane conductance of the nanotube network, which we model using a transmission-line model to account for the frequency dependent in-plane impedance as well as the total interfacial impedance between the network and the electrolyte. The ionic strength dependence of the capacitance is expected to have a root cause from the double layer capacitance, which we model using a modified Poisson–Boltzmann equation. The relative contributions from those two capacitances can be quantitatively decoupled. We find a total capacitance per tube of 0.67–1.13 fF/μm according to liquid gate potential varying from −0.5 to −0.7 V.
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