Impedance of nanocapacitors from molecular simulations to understand the dynamics of confined electrolytes

• 成果类型: Article
• 署名作者: Pireddu, Giovanni; Fairchild, Connie J.; Niblett, Samuel P.; Cox, Stephen J.; Rotenberg, Benjamin
• 署名单位: Sorbonne Universite; Centre National de la Recherche Scientifique (CNRS); University of Cambridge; Centre National de la Recherche Scientifique (CNRS); CNRS - Institute of Chemistry (INC)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-13957
• DOI: 10.1073/pnas.2318157121
• 发表日期: 2024-04-30
• 关键词: dielectric-constant; thermal agitation; aqueous-solutions; water; electrochemistry; supercapacitors; spectroscopy; origin; charge; layer

摘要

Nanoelectrochemical devices have become a promising candidate technology across various applications, including sensing and energy storage, and provide new platforms for studying fundamental properties of electrode/electrolyte interfaces. In this work, we employ constant -potential molecular dynamics simulations to investigate the impedance of gold -aqueous electrolyte nanocapacitors, exploiting a recently introduced fluctuation-dissipation relation. In particular, we relate the frequency -dependent impedance of these nanocapacitors to the complex conductivity of the bulk electrolyte in different regimes, and use this connection to design simple but accurate equivalent circuit models. We show that the electrode/electrolyte interfacial contribution is essentially capacitive and that the electrolyte response is bulk -like even when the interelectrode distance is only a few nanometers, provided that the latter is sufficiently large compared to the Debye screening length. We extensively compare our simulation results with spectroscopy experiments and predictions from analytical theories. In contrast to experiments, direct access in simulations to the ionic and solvent contributions to the polarization allows us to highlight their significant and persistent anticorrelation and to investigate the microscopic origin of the timescales observed in the impedance spectrum. This work opens avenues for the molecular interpretation of impedance measurements, and offers valuable contributions for future developments of accurate coarse -grained representations of confined electrolytes.