Theoretical method for simulation of potential swing and double layer capacitance in electrolytes containing different cations

• A new numerical method to describe the electrical double layer properties in different electrolytes.
• Both the electric potential swing and the electrode potential depend on the difference between cation and anion radii.
• The capacitance of Stern's layer controls the total capacitance of the electric double layer.

This paper aims to describe potential swings on electrodes in different electrolytes by simple but accurate theoretical method. The electric double layer capacitance was considered for spherical nanoelectrodes operating in acetonitrile-based electrolytes. The model allows determining the potential swings via accounting for the finite ion size and the influence of the local electric field on the electrolyte dielectric permittivity. It is also possible to determine the thickness of Stern and diffuse layers. A series of acetonitrile solutions of the BF4− salts of Li, Na, K, Rb, Cs and [(CH3)4N]+BF4− were examined in a systematic study. In this study we investigate the potential swings dependence of the size of the solvation sphere around ions. It is shown that this solvation sphere significantly affects the total specific capacitance of the electrolytes under consideration. As simulating parameters of electric double layers under high concentrations we used the finite size of ions covered by solvation sphere, the chemical composition of electrolytes, and surface potential. Results of this study can be widely used to design electrochemical devices (e.g. electrodes and electrolytes for electrochemical sensors and electric energy storage devices) for novel technologies.

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