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Title: On the influence of polarization effects in predicting the interfacial structure and capacitance of graphene-like electrodes in ionic liquids

The electric double layer (C{sub D}) and electrode quantum (C{sub Q}) capacitances of graphene-based supercapacitors are investigated using a combined molecular dynamics and density functional theory approach. In particular, we compare an approach that includes electronic polarization to one that is polarization-free by evaluating both C{sub D} and C{sub Q} using [EMIM][BF{sub 4}] ionic liquid as a model electrolyte. Our results indicate that the inclusion of polarization effects can yield higher C{sub D} values—in this study by up to 40% around ±2 V—which we attribute primarily to the presence of charge smearing at the electrode-electrolyte interface. On the other hand, we find that the polarization-induced distortion of the electronic structure of graphene does not noticeably alter the predicted C{sub Q}. Our analysis suggests that an accurate description of the spatial charge distribution at the graphene interface due to polarization is necessary to improve our predictive capabilities, though more notably for C{sub D}. However, the conventional polarization-free approximation can serve as an efficient tool to study trends associated with both the C{sub Q} and C{sub D} at the interface of various graphene-like materials.
Authors:
; ;  [1]
  1. McKetta Department of Chemical Engineering, University of Texas, Austin, Texas 78712 (United States)
Publication Date:
OSTI Identifier:
22415844
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; APPROXIMATIONS; CAPACITANCE; CHARGE DISTRIBUTION; COMPARATIVE EVALUATIONS; DENSITY FUNCTIONAL METHOD; ELECTRODES; ELECTROLYTES; ELECTRONIC STRUCTURE; GRAPHENE; INTERFACES; MOLECULAR DYNAMICS METHOD; MOLTEN SALTS; POLARIZATION