The Electroanalysis Interface
The Electroanalysis (elan) interface (), found under the Electrochemistry branch () when adding a physics interface, has the equations, boundary conditions, and rate expression terms for modeling mass transport of diluted species in electrolytes using the diffusion-convection equation, solving for electroactive species concentration(s). The physics interface contains tailor-made functionality for modeling cyclic voltammetry and electrochemical impedance spectroscopy.
Use this physics interface to model electroanalytical problems with electrolyte solutions containing a large quantity of inert “supporting” electrolyte. Ohmic loss is assumed to be negligible.
The settings for this physics interface can be chosen so as to simulate chemical species transport through diffusion (Fick’s law), migration (when coupled to an electric field — electrokinetic flow), and convection (when coupled to fluid flow).
The physics interface supports simulation of transport by convection and diffusion in 1D, 2D, and 3D as well as for axisymmetric components in 1D and 2D. The default dependent variables are the molar concentrations, c1 and c2, of the two electroactive species in a redox couple.
Note that most of the physics interface settings are the same as for The Transport of Diluted Species Interface.
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Introduction to Electrochemistry Modeling
Settings
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is elan.
Out-of-Plane Thickness
For 2D components, the Thickness field (default value: 1 m) defines a parameter for the thickness of the geometry perpendicular to the two-dimensional cross section. The value of this parameter is used, among other things, to automatically calculate the total current from the current density vector. The analogy is valid for other fluxes.
Cross Sectional Area
For 1D components, the Cross sectional area field (default value: 1 m2) defines a parameter for the area of the geometry perpendicular to the 1D component. The value of this parameter is used, among other things, to automatically calculate the total current from the current density vector. The analogy is valid for other fluxes.
Transport Mechanisms
Diffusion is always included. By default, the Convection and Migration in electric field check boxes are not selected under Additional transport mechanisms.
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Selecting the Convection check box enables the addition of the Inflow and Outflow boundary nodes.
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Selecting the Migration in electric field check box activates the migration transport of ionic species in the Transport Properties node. Since supporting electrolytes of high conductivity are usually used in electroanalytical problems, migrative effects are usually negligible.
The physics interface has one tailor-made study type, see Cyclic Voltammetry in the COMSOL Multiphysics Reference Manual.
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Theory for the Electroanalysis Interface
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Domain, Boundary, and Pair Nodes for the Electroanalysis Interface
In the COMSOL Multiphysics Reference Manual see Table 2-3 for links to common sections and Table 2-4 to common feature nodes. You can also search for information: press F1 to open the Help window or Ctrl+F1 to open the Documentation window.