Ioffe Institute, Polytechnicheskaya 26, 194021 St. Petersburg, Russia.
Int J Mol Sci. 2024 Sep 19;25(18):10083. doi: 10.3390/ijms251810083.
The time dynamics of charge accumulation at the electrochemical interface between graphene and water is important for supercapacitors, batteries, and chemical and biological sensors. By using impedance spectroscopy, we have found that measured capacitance (C) at this interface with the gate voltage V ≈ 0.1 V follows approximate laws CT and CT (T is V period) in frequency ranges (1000-50,000) Hz and (0.02-300) Hz, respectively. In the first range, this dependence demonstrates that the interfacial capacitance (C) is only partially charged during the charging period. The observed weaker frequency dependence of the measured capacitance (C) at frequencies below 300 Hz is primarily determined by the molecular relaxation of the double-layer capacitance (C) and by the graphene quantum capacitance (C), and it also implies that C is mostly charged. We have also found a voltage dependence of C below 10 Hz, which is likely related to the voltage dependence of C. The observation of this effect only at low frequencies indicates that C relaxation time is much longer than is typical for electron processes, probably due to Dirac cone reconstruction from graphene electrons with increased effective mass as a result of their quasichemical bonding with interfacial molecular charges.
在石墨烯和水之间的电化学界面上，电荷积累的时间动态对于超级电容器、电池、化学和生物传感器都非常重要。通过使用阻抗谱，我们发现，在栅极电压 V ≈ 0.1 V 的情况下，该界面处的测量电容（C）在频率范围（1000-50,000）Hz 和（0.02-300）Hz 内分别遵循近似规律 CT 和 CT（T 是 V 周期）。在第一个范围内，这种依赖性表明，在充电期间，界面电容（C）仅部分充电。在低于 300 Hz 的频率下，测量电容（C）的观察到的较弱频率依赖性主要由双电层电容（C）的分子弛豫和石墨烯量子电容（C）决定，这也意味着 C 主要是充电的。我们还发现了在低于 10 Hz 的电压下 C 的电压依赖性，这可能与 C 的电压依赖性有关。这种效应仅在低频下观察到，表明 C 的弛豫时间比电子过程的典型时间长得多，这可能是由于狄拉克锥由于界面分子电荷的准化学结合而导致的石墨烯电子有效质量增加，从而发生重建。
