Investigation of the Electrical Double Layer with a Graphene Electrode by the Grand Canonical Monte Carlo Simulation

Abstract

Structural and thermodynamic properties of the electric double layer with a graphene electrode are investigated by the grand canonical Monte Carlo simulations. The nonelectrostatic carbon–ion and ion–ion interactions are described by the Lennard-Jones potential. The results (the ion singlet distribution functions, the mean electrostatic potential, the integral, and the differential capacitance) for an explicit corpuscular structure are compared with those obtained for the structureless carbon sheet and hard surface electrodes. Simulations are carried out for 1.0 mol/dm3 1:1 electrolyte at T = 298.15 K and εr = 78.5 in the range of the electrode surface charge density from −0.9 to +0.9 C/m2. The surface density of carbon atoms in graphene is 5.03066 × 1019 m–2. The singlet distribution functions of ions show that the ion adsorption at the carbon electrodes is evidently stronger than that at the hard surface electrode. The profiles of the mean electrostatic potential near the positively charged carbon electrodes have a minimum that is characteristic of divalent anions near a hard surface electrode. For both carbon electrodes, the integral and differential capacitance curves have the bell shape with a broad maximum, while the curve for the hard surface electrode has a camel-like shape with two humps. The difference between the graphene and structureless carbon electrodes is manifested mainly in capacitance. In the range of a small magnitude of electrode charges, the capacitance results for the graphene electrode are smaller than those for the structureless carbon electrode.

Molecular dynamics simulations of the electric double layer capacitance of graphene electrodes in mono-valent aqueous electrolytes

“…Indeed, it is not until very recently do we start to understand many of the anomalous phenomena associated with the formation of EDL particularly in small nano-sized pores, for example the drastically increased capacitance and the distortion of ion solvation shell in pores below 2 nm, to name a few [1,2]. Although the structure and property of EDLs on metal and carbon-based electrode have been widely studied via the various numeric simulation (i.e., continuum modeling [3], classic MD simulation [4][5][6], grand canonical Monte Carlo [7,8], and classic density functional theory [9]), many questions remain to be explored such as the effect of ion size, degree of ion hydration, dielectric constant of solvents [10][11][12][13][14][15], the potential-dependent EDL structure, and the "bell" or "U" shaped differential capacitance [16,17]. A comprehensive understanding of the EDL structure and its dependence on various ion type and different charging conditions remains vacant.…”

Measuring the Capacitance at Few- and Many-Layered Graphene Electrodes in Aqueous Acidic Solutions

“…Of interest is a recent theoretical account that alludes to strong ion adsorption at carbon surfaces being an important factor on the capacitance behavior. 23 A feature of which may be responsible for the dissimilar shaped potential−capacitance plots in Figure 3 and the distinctly different pzc for perchlorate and sulfate solutions.…”

Mechanisms of Porous Carbon‐based Supercapacitors

“…Molecular simulation technologies, such as MD and MC, have become powerful tools for understanding the electrochemical behavior of supercapacitors [95,137, 138] . Monte Carlo simulations are based on ion movement statistics, sampling statistics for the number of anions/cations, ion pairs, and potential energy in the study system, as well as determining the thermodynamic characteristics of the system.…”