The effect of electrode surface topography on the structure and differential capacitance of the electric double layer capacitor

Update Item Information
Title The effect of electrode surface topography on the structure and differential capacitance of the electric double layer capacitor
Publication Type thesis
School or College College of Engineering
Department Materials Science & Engineering
Author Cao, Liulei
Date 2011-08
Description Molecular dynamics simulations were conducted to study the structure and differential capacitance of the electric double layer capacitor by varying electrode topography. Studying the dependence of structure and differential capacitance (DC) on electrode potential is a central point of electric double layer (EDL) models, from the early Gouy-Chapman approximation to the more recent Kornyshev formulation or Lamperski treatment. Although the influence on DC of temperature, density, polarisability and dispersion interactions of room temperature ionic liquid (RTIL) electrolyte is becoming more understood, the effect of electrode topography on DC remains unclear and perhaps controversial. Moreover, the variability of DC results for poorly prepared polycrystalline electrodes may indicate a strong dependence of EDL structure and DC on the topography of electrode surface. In this work, we employ molecular dynamics simulations to prove that the crystallographic orientation and the surface roughness of electrode could intensely alter the shape of DC curve as a function of electrode potential, especially near the potential of zero charge (PZC). Specifically, we simulated a RTIL electrolyte, consisting of 1-ethyl-3-methyl imidazolium (EMIM+), bisfluorosulfonyl imide (FSI-), and Li+ (in a molar ratio of 24:31:7), in contact with two types of graphite electrodes: one is graphite with atomically flat basal plane and the other is graphite with edge orientation. This work demonstrates that the capacitor with atomically flat basal plan graphite generates a camel-shaped DC curve; while, the capacitor with edge orientation graphite engenders a bell-shaped DC curve. Furthermore, the capacitor with edge orientation graphite displays a significantly larger DC (almost double) than the capacitor with atomically flat basal plane graphite near PZC. Additionally, these findings coincide with the results of numerous recent experiments. Thus, we conclude that the crystallographic orientation and surface roughness will modify the EDL structure and hence, vary the DC curve of the EDLC.
Type Text
Publisher University of Utah
Subject Capacitor; Differential capacitance; Electric double layer; Surface topography; Physical chemistry; Energy; Materials science
Dissertation Institution University of Utah
Dissertation Name Master of Science
Language eng
Rights Management Copyright © Liulei Cao 2011
Format application/pdf
Format Medium application/pdf
Format Extent 4,816,797 bytes
Identifier us-etd3,53242
Source Original housed in Marriott Library Special Collections, TK7.5 2011 .C26
ARK ark:/87278/s6dr395x
Setname ir_etd
ID 194322
Reference URL https://collections.lib.utah.edu/ark:/87278/s6dr395x
Back to Search Results