WIAS Preprint No. 2057, (2014)

Modeling of electrochemical double layers in thermodynamic non-equilibrium



Authors

  • Dreyer, Wolfgang
  • Guhlke, Clemens
  • Müller, Rüdiger
    ORCID: 0000-0003-2643-722X

2010 Mathematics Subject Classification

  • 35Q35 76T30 35C20

2008 Physics and Astronomy Classification Scheme

  • 82.45.Gj 82.45.Fk

Keywords

  • thermodynamics, electrode-electrolyte interface, double-layer, asymptotic analysis

Abstract

We consider the contact between an electrolyte and a solid electrode. At first we formulate a thermodynamic consistent model that resolves boundary layers at interfaces. The model includes charge transport, diffusion, chemical reactions, viscosity, elasticity and polarization under isothermal conditions. There is a coupling between these phenomena that particularly involves the local pressure in the electrolyte. Therefore the momentum balance is of major importance for the correct description of the layers. The width of the boundary layers is typically very small compared to the macroscopic dimensions of the system. In a second step we thus apply the method of asymptotic analysis to derive a simpler reduced model that does not resolve the boundary layers but instead incorporates the electrochemical properties of the layers into a set of new boundary conditions. For a metal-electrolyte interface, we derive a qualitative description of the double layer capacitance without the need to resolve space charge layers.

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