New App: Electrochemical Impedance Spectroscopy
Electrochemical impedance spectroscopy (EIS) is a common technique in electroanalysis. It is used to study the harmonic response of an electrochemical system. A small, sinusoidal variation is applied to the potential at the working electrode, and the resulting current is analyzed in the frequency domain.
The real and imaginary components of the impedance give information about the kinetic and mass transport properties of the cell, as well as the surface properties through the double layer capacitance.
The purpose of theElectrochemical Impedance Spectroscopy analysis app is to understand EIS, Nyquist, and Bode plots. The app lets you vary the bulk concentration, diffusion coefficient, exchange current density, double layer capacitance, and the maximum and minimum frequency.
New App: Cyclic Voltammetry
Cyclic voltammetry is a common analytical technique for investigating electrochemical systems. In this method, the potential difference between a working electrode and a reference electrode is swept linearly in time from a start potential to a vertex potential, and back again. The current-voltage waveform, called a voltammogram, provides information about the reactivity and mass transport properties of an electrolyte.
The purpose of the app is to demonstrate and simulate the use of cyclic voltammetry. You can vary the bulk concentration of both species, transport properties, kinetic parameters, and the settings of the cyclic voltammeter.
Thin Insulating Layer in the Primary, Secondary, and Tertiary Current Distribution Interfaces
Thin insulating sheets are commonly inserted in the electrolytes of various types of electrochemical cells. For example, they may be used for optimizing the current distribution in a corrosion protection application or for optimizing the local deposition rate in a deposition bath. The new Thin Insulating Layer feature can be used to model a thin insulating sheet located on an internal boundary in an electrolyte domain. The node can be used as an alternative to drawing the actual insulating domain in the model geometry, significantly reducing meshing time – especially in 3D models.
Redesigned Deformed Geometry Interfaces
To increase flexibility for electrode deposition and dissolution, all of the Current Distribution interfaces now feature the possibility to directly model the deposition and dissolution of electrode species. This is facilitated by predefined multiphysics nodes that are introduced to handle the coupling between a deposition or dissolution velocity and the geometry deformation.
In a related functionality update, The Electrodeposition/Corrosion, Deformed Geometry interfaces have been redesigned. Upon choosing an Electrodeposition/Corrosion, Deformed Geometry interface in the Select Physics menu, an individual Current Distribution interface and a separate Deformed Geometry interface are added to the model together with two multiphysics coupling nodes: Non-Deforming Boundary and Deforming Electrode Surface.
Models created prior to COMSOL Multiphysics version 5.2 using an Electrodeposition/Corrosion interface will not be affected by the change.
Two separate physics interfaces, together with two tailor-made multiphysics coupling features, are now added when choosing an Electrodeposition, Deformed Geometry or a Corrosion, Deformed Geometry entry in the Select Physics window.
Compensating for Tube Volumes in the Current Distribution on Edges, BEM Interface
It is now possible to include the effect of the volume of tubes by specifying a radius when using edge elements and the boundary element method (BEM). This functionality is available in the electrolyte charge transfer equations in the Current Distribution on Edges, BEM interface.
The volume compensation of the cylindrical trusses in an oil platform structure is enabled by a check box in the Edge Radius node.
New Tutorial: Diffuse Double Layer
At the electrode-electrolyte interface, there is a thin layer of space charge, called the diffuse double layer. In this region, electroneutrality does not hold. The double layer may be of interest when modeling devices such as electrochemical supercapacitors and nanoelectrodes.
The Diffuse Double Layer tutorial shows you how to couple the Nernst-Planck equations to the Poisson equation in order to describe a diffuse double layer according to the Gouy-Chapman-Stern model.
The simulation app extends the simple example by including two electrodes. It also considers Faradaic (charge transfer) electrode reactions. An additional equation is solved to ensure overall conservation of charge.