Electrochemistry Module Updates

For users of the Electrochemistry Module, COMSOL Multiphysics® version 5.5 includes an interface for equilibrium potential calculation using the Nernst equation, concentration-dependent Butler–Volmer kinetics from chemical equations, and Chemistry interface support for electrode reactions. Read more about the electrochemistry news below.

Equilibrium Potential Calculation Using the Nernst Equation

In the Electrode Reaction and Porous Electrode Reaction features, the equilibrium potential of electrode reactions can be defined using the new Nernst Equation option, making it easier to set up thermodynamically consistent models. In physics interfaces solving for multiple concentrations, such as the Tertiary Current Distribution and Chemistry interfaces, the equilibrium potential will automatically be concentration dependent, based on the reaction stoichiometry. All models in the Application Libraries featuring Nernstian equilibrium potentials have been updated to use the new feature.

The Porous Electrode Reaction feature settings with the Equilibrium Potential section open and the Nernst equation selected. Porous Electrode Reaction feature: Equilibrium Potential Settings section for the Equilibrium Potential in the Tertiary Current Distribution, Nernst-Planck interface. The equilibrium potential will be calculated automatically from the reaction stoichiometry and species concentrations.

Concentration-Dependent Butler–Volmer Kinetics

In the Electrode Reaction and Porous Electrode Reaction features, the exchange current density of the Butler-Volmer and Linearized Butler-Volmer kinetics expressions can now be automatically defined to be concentration dependent, based on reaction stoichiometry. The option is available if the Nernst equation option is used when defining the equilibrium potential. In the Tertiary Current Distribution, Nernst-Planck interface, the options Mass action law and Lumped multistep are available for the exchange current density type. All models in the Application Libraries featuring Nernstian equilibrium potentials and concentration-dependent kinetics have been updated to use the new feature.

The Porous Electrode Reaction feature settings with the Electrode Kinetics section open and the Butler-Volmer expression type selected. Porous Electrode Reaction feature: Electrode Kinetics Settings section for the Electrode kinetics in the Tertiary Current Distribution, Nernst-Planck interface. The exchange current density will be calculated automatically from the reaction stoichiometry and species concentrations.

Chemistry Interface Support for Electrode Reactions

The Chemistry interface, added to the Electrochemistry Module in version 5.5, now features Electrode Reaction and Electrode Reaction Group features. The Chemistry interface allows for defining multiple species and electrode reactions, as well as ordinary chemical reactions. Additionally, mixture and thermodynamic properties, such as equilibrium potentials, can be calculated automatically by the Chemistry interface. Variables defined by these features, such as local current densities and equilibrium potentials, can be coupled to any other applicable physics interface.

The settings for the Electrode Reaction feature when two Chemistry interfaces are used. Electrode Reaction feature: Chemistry interfaces Two Chemistry interfaces are used in this model to define the equilibrium potentials and kinetics of the reactions in a solid oxide water electrolyzer.