Ion distribution in electrified micropores and its role in the anomalous enhancement of capacitance.
The distribution of K+ ions in electrified slit-shaped micropores with pore widths ranging from 9.36 to 14.7 A was studied using molecular dynamics simulations. We show that, in slit pores with pore widths between 10 and 14.7 A, the K+ ion distribution differs qualitatively from that described by classical electrical double-layer (EDL) theories in that fully hydrated K+ ions accumulate primarily in the central plane of the slit pores. This phenomenon disappears when the pore width is narrower than 10 A. Ion hydration and water-water interactions, which are rarely considered in prior EDL theories for micropores, are found to be responsible for this behavior. On the basis of these results, we have developed a new sandwich capacitance model to describe the capacitance of the EDLs formed by K+ ions enclosed in slit-shaped micropores. This model is capable of predicting the anomalous enhancement of capacitance experimentally observed in micropores.
Feng
Guang
G
College of Engineering & Science, Clemson University, Clemson, South Carolina 29634-0921, USA.
Qiao
Rui
R
Huang
Jingsong
J
Sumpter
Bobby G
BG
Meunier
Vincent
V
D025802:Electric Capacitance; D004560:Electricity; D004573:Electrolytes / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D016062:Porosity; D011188:Potassium / Q000737:chemistry*; D055672:Static Electricity; D014867:Water / Q000737:chemistry
D004573:Electrolytes; D014867:Water; D011188:Potassium