title: The tail effect on the shape of an electrical double layer differential capacitance curve.
abstract: The differential capacitance curve for the double layer formed by an electrolyte dissolved in a solvent is commonly believed to be parabolic-like with a minimum at low electrolyte charge concentration and low electrode surface charge density, and independent of electrolyte concentration at high electrolyte concentrations and high electrode charge and would be, in the absence of solvent effects, featureless at these latter conditions. This is the prediction of the popular Gouy-Chapman-Stern theory. In contrast, for an ionic liquid this curve can have a single or a double hump (or a bell or camel shape). Fedorov et al. [Electrochem. Commun. 12, 296 (2010)]10.1016/j.elecom.2009.12.019 have related these humps, particularly the double hump, to the neutral tails of ions in many ionic liquids. Evidence presented here shows, however, that such humps are general features of the differential capacitance of a double layer, whether it be formed by ions with or without a neutral tail. The presence of a double or single hump results from the magnitude of the electrolyte charge concentration. For both spherical ions or non-spherical ions consisting of charged heads and neutral tails, the shape of the differential capacitance transforms continuously from a double hump to a single hump as the electrolyte concentration is increased.
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602-5700, USA.
authors: Douglas
authors: D
authors: Henderson
authors: Department of Physical Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland.
authors: Stanisław
authors: S
authors: Lamperski
authors: Laboratory of Theoretical Physics, Department of Physics, University of Puerto Rico, San Juan, Puerto Rico 00931-3343, USA.
authors: Lutful
authors: L
authors: Bari Bhuiyan
authors: Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521-0425, USA.
authors: Jianzhong
authors: J
authors: Wu