Reaction [n] Reference

Type

A reaction Type is specified by default, depending whether the Electrochemical Species model is selected when the electrochemical surface mechanism which contains [Reaction n] is created.

• Electrochemistry Species: Available when the Electrochemical Species model is selected. Allows you to model electrochemical reactions which simulate the transport of species.
• Electrochemistry Potential: Available when the Electrochemical Species model is not selected. Allows you to simulate electrochemical reactions without using the Electrochemical Species model, either:
  • without simulating the transport of species
  • by simulating the transport of species from the Solid Ion model in an associated solid continuum
  • by simulating the intercalation of ions into the active material in the electrode porous medium.
• Sorption : Available when the Electrochemical Species model is not selected and either the Multi-Component Liquid or Multi-Component Gas model is selected. Allows you to simulate particles from a multi-component fluid adhering to the surface of a solid (adsorption) then moving into the solid (absorption). Provides the option to select the type of sorption under the [Reaction] > Properties > Reaction Formulation node.

• The Electrochemical Species model is selected within the fluid continuum.
• The Solid Ion model and the Electrochemical Reactions model are used in a corresponding solid continuum and either the Multi-Component Gas or Multi-Component Liquid model is used in the fluid continuum, or a phase within the fluid continuum (using the Mixture Multiphase (MMP) model or the Eulerian Multiphase (EMP) model).
• The Sub-grid Particle Intercalation model is used for solid porous phases with the Concentrated Electrolyte model in the fluid continuum for the electrolyte.

[Reactants / Products]

Right-Click Actions

Add Reactant / Add Product

A [Reaction Component] sub-node appears for each reactant or product that is specified.

Electrochemical Species Mixture

Allows you to select electrochemical species that are present as reactants or products in the surface reaction. Only electrochemical species that are defined within the Electrochemical Species model or Solid Ion model are available.

Solid Mixture

Allows you to select solid species that are present as reactants or products in the surface reaction. Only solid species that are defined within the Solid Species node are available.

[H20]

Adds the specified substance as a reactant or product. Each substance that is specified in the Liquid or Multi-component Liquid model is available to select as a reaction component—including those specified in a Eulerian phase (when using the Mixture Multiphase (MMP) model or the Eulerian Multiphase (EMP) model).

e-

Adds electrons as reactants or products. Make sure that you select electrons from the correct continuum or phase to suit each reaction. The location from which the electron comes from is determined as the conductor in the reaction.

[porous phase]

Adds a porous solid phase as reactants or products. Is available only for the solid porous phases that have the Sub-grid Particle Intercalation model activated.

Refresh

Refreshes the list of reaction components that are available to select.

[Reaction Component]

Stoich.Coeff

The stoichiometric coefficient specifies the molar ratio of this reaction component in the balanced equation for that electrochemical reaction.

Rate Exponent

The rate exponent, ${\gamma }_i$ , for this reaction component, as used to calculate the specific reaction current in Eqn. (4129), Eqn. (4132), or Eqn. (4134). You can set rate exponent values for electrochemical species components that are specified in the Electrochemical Species model, or solvent species from the Liquid model or Multi-Component Liquid model. Molar concentrations of all reaction components which physically exist in the fluid domains are used to compute the electrochemical reaction current.

Reaction [n] > Properties > Double Layer Capacitance

Available for unsteady simulations only.

Models the effects of double layer capacitance at electrochemical reaction sites, which become particularly prominent during sudden changes in the operational conditions of electrochemical devices.

Method

Allows you to specify how the double layer capacitance is determined.

Method	Corresponding Child Node
None	None.
User Double Layer Capacitance Simulates the effects of double layer capacitance in electrochemical reactions during battery charge/discharge cycles.	User Double Layer Capacitance Allows you to specify the double layer capacitance, $C_{}$ in Eqn. (4138), as a scalar profile.

Reaction [n] > Properties > Equilibrium Potential

Method

Allows you to specify how the equilibrium potential, $U_{eq}$ , is determined.

Method	Corresponding Child Node
User Equilibrium Potential	User Equilibrium Potential Allows you to specify the equilibrium potential, $U_{eq}$ in Eqn. (4139), as a scalar profile.
Nernst Equilibrium Potential Only available when the Electrochemical Species model is selected—with both Reactant and Product species specified.	Nernst Standard Potential Allows you to specify the Nernst Standard Potential, $E^0$ that is used to calculate the equilibrium potential, $U_{eq}$ , in Eqn. (4139), as a scalar profile. When using the Electrochemical Reaction Heating model and specifying the Nernst standard potential as a function of temperature, make sure to specify the corresponding temperature derivative.
Nernst From Thermodynamic Data Calculates the Nernst equilibrium potential $U_{eq}$ from thermodynamic data for liquid and gaseous species according to equation Eqn. (4140). Only available when an energy model, for example Segregated Fluid Temperature model, is selected.	Nernst from Thermodynamic Data The Nernst Standard Potential, $E^0$ and the derivative of equation Eqn. (4140) with respect to temperature are calculated automatically.

Reaction [n] > Properties > Equilibrium Potential T Derivative

Method

Allows you to specify the temperature derivative of the equilibrium potential, $U_{eq}$ which is used to compute the reversible heat contribution in Eqn. (4143).

Method	Corresponding Child Node
User Equilibrium Potential T Derivative	User Equilibrium Potential T Derivative Allows you to specify the equilibrium potential temperature derivative, $\frac{d{U}_{eq}}{dT}$ , as a scalar profile.
Nernst Equilibrium Potential T Derivative Available when the Equilibrium Potential property, Select Method , is set to Nernst Equilibrium Potential.	Nernst Standard Potential T Derivative Allows you to specify the Nernst standard potential temperature derivative, $\frac{d{E}^0}{dT}$ , that is used to calculate $\frac{d{U}_{eq}}{dT}$ in Eqn. (4143). For example, at the cathode (Eqn. (352)) and anode (Eqn. (351)) in solid oxide fuel cells.
Nernst From Thermodynamics Data T Derivative Available when the Equilibrium Potential property, Select Method , is set to Nernst From Thermodynamic Data.	None.

Reaction [n] > Properties > Equilibrium Concentration Constant

Allows you to account for the solubility of the sorbed species—the higher the value, the greater the solubility.

Appears when both:

• the Type property is set to Sorption under the Reactions > Reaction [n] node
• the Method is set to Springer or Wu-Li-Berg under the Reaction Formulation node.

Method	Corresponding Child Node
User Specific Equilibrium Concentration Constant	User Specific Equilibrium Concentration Constant Sets the User Specific Equilibrium Concentration Constant, $\xi$ in Eqn. (4168).

Reaction [n] > Properties > Reaction Formulation

The property that appears here depends upon the option that is selected for the Type property that is set under the Reactions > Reaction [n] node.

Method

Available when the Type property is set to Electrochemistry Potential or Electrochemistry Species under the Reactions > Reaction [n] node.

Allows you to specify how the specific reaction current is calculated.

The sub-nodes that appear depend on whether the electrons are specified as reactants or products.

Method	Corresponding Child Node
Butler-Volmer When this method is selected, the boundary conditions at the interface between the metal and the electrolyte are set automatically. However, you can adjust the boundary conditions manually if necessary.	Butler-Volmer Allows you to specify scalar values for the apparent anodic charge transfer coefficient, ${\alpha }_a$ , for the anodic current that is directed from the solid towards the liquid, and apparent cathodic charge transfer coefficient, ${\alpha }_c$ , for the cathodic current that is directed from the liquid towards the solid. These values are used in Eqn. (4128). Using the Butler-Volmer method without the Electrochemical Species model means that the specific reaction current is calculated without considering the concentrations of the electrochemical species—only the anodic and cathodic current are accounted for. Using the Butler-Volmer method with the Electrochemical Species model means that the specific reaction current is calculated using the molar concentrations of electrochemical species as well as the anodic and cathodic currents. The Butler-Volmer equation Eqn. (4128) combines Tafel equations Eqn. (4132) for both anodic and cathodic reactions which occur when reactions are reversible.
Tabular Selecting this method removes the Properties > Equilibrium Potential and Properties > Specific Exchange Current nodes.	Current Voltage Characteristic Provides the Tabular Polarization Curve sub-node which allows you to select a previously imported table for the Tabular Polarization Curve. You set the specific electric current and equilibrium potential in the Tabular Polarization Curve Properties. In contrast to other reaction formulation methods, the tabular polarization curve method lets you import arbitrary forms of polarization curves. You can import the tabular polarization curve by right-clicking the Tools > Tables node, choosing New Table > File Table, and selecting the appropriate file. The imported table then becomes available to select within the Tabular Polarization Curve properties. The boundary conditions are then available to specify at the interface between the reacting surface and the electrolyte. When modeling corrosion, Simcenter STAR-CCM+ uses the polarization curves to calculate the corrosion potential for each metal when the current is zero. Therefore, the tabular data must include positive and negative values for current along with the corresponding monatonically increasing potential values.
Tafel You can use the Tafel method for reactions that exhibit considerable currents in only one direction—either anodic or cathodic. Small apparent transfer coefficients or reactions operating solely in either positive or negative surface overpotential can cause one-directional current. The options that are available when selecting the Tafel method depend on whether the electrons are specified as reactants or products.	Tafel Appears when electrons are not registered as reactants or products. Allows you to set the Reaction Direction. Anodic specifies the direction of the reaction current as anodic—from the solid towards the liquid. Cathodic specifies the direction of the reaction current as cathodic—from the liquid towards the solid. A Tafel > Alpha sub-node also appears which allows you to specify a value for the apparent charge transfer coefficient. Alpha Appears when electrons are registered as reactants or products. Allows you to specify a scalar value for the apparent charge transfer coefficient. The direction of the current is determined from settings within the Electrochemical Species model.
Tafel Slope (log 10) Creates a Properties > Specific Exchange Current Y-Intercept (log10) sibling node.	Tafel Slope (log 10) Appears when electrons are not registered as reactants or products. Allows you to set the Reaction Direction. Anodic specifies the direction of the reaction current as anodic—from the solid towards the liquid. Cathodic specifies the direction of the reaction current as cathodic—from the liquid towards the solid. A Tafel Slope (log10) > Beta (log10) sub-node also appears which allows you to specify a combined term $\beta$ for the combined anodic or cathodic apparent transfer coefficients in the Tafel equation. Since the direction of the current is determined from settings within the Tafel Slope (log10) node, the $\beta$ value that you set for the effective transfer coefficient is expected to be positive. Beta Appears when electrons are registered as reactants or products. Allows you to specify a term $\beta$ for the anodic or cathodic apparent transfer coefficients in the Tafel equation.
Transport Limited Tafel Slope (log 10) Creates a Properties > Specific Exchange Current Y-Intercept (log10) sibling node.	Transport Limited Tafel Slope (log10) Provides two sub-nodes: Beta (log10) allows you to specify a combined term $\beta$ as a scalar profile for the combined anodic or cathodic apparent transfer coefficients in the Tafel equation. You can also approximate effects that are not initially accounted for in the simulation setup. Since the direction of the current is determined from settings within the Electrochemical Species model, this value that you set for the effective transfer coefficient is expected to be positive. Limiting Current allows you to approximate effects that are not initially accounted for in the simulation setup by limiting the specific reaction current. For example, in the case of buried structures [826], you can approximate effects such as oxygen starvation. You can specify the limiting current, $j_{\lim }$ , using a scalar profile. The limiting current is assumed to be a positive quantity, regardless of if the reaction is anodic or cathodic. This option allows you to specify a combined term $\beta$ for the combined anodic or cathodic apparent transfer coefficients in the Tafel equation.

Method

Available when the Type property is set to Sorption under the Reactions > Reaction [n] node.

All sorption methods are intended for reactions which have only one reactant gas species and one product species (electrons are considered a species).

Method	Corresponding Child Node
Henry Uses the Henry method to simulate the sorption process.	Henry Sets Henry's constant $He$ in Eqn. (4172).
Springer Only available when using the Multi-Component Gas model. Uses the Springer method [836] to simulate the sorption process.	Springer Provides the following subnodes which allow you to specify the coefficients that are used to calculate the dimensionless water content at equilibrium in Eqn. (4170): Equilibrium Water Content Coefficient, A Equilibrium Water Content Coefficient, B Equilibrium Water Content Coefficient, C Equilibrium Water Content Coefficient, D
Wu-Li-Berg Only available when using the Multi-Component Gas model. Uses the Wu Li Berg method [838] to simulate the sorption process.	Wu-Li-Berg

Reaction [n] > Properties > Sorption Rate Constant

The rate at which the sorption reaction occurs.

Appears when the Type property is set to Sorption under the Reactions > Reaction [n] node.

Method	Corresponding Child Node
User Specific Rate Constant	User Specific Rate Constant Sets the User Specific Rate Constant, $r_{surf,0}$ in Eqn. (4165).

Reaction [n] > Properties > Specific Exchange Current

This node is available when the Reaction Formulation method is set to Butler-Volmer or Tafel.

Properties

Method

Corresponding Child Node

User Specific Exchange Current

User Specific Exchange Current Allows you to set the specific exchange current, $j_0$ in Eqn. (4129) or Eqn. (4132), as a scalar profile. The specific exchange current does not include the effects of species concentrations when computing the electric current that the electrochemical reaction generates. Since the direction of the current is determined from the reaction set-up, this value is expected to be positive.

注	You can define the exchange current density $j_0$ using the field function: j_0=j_0,ref*prod(1/pow(c_i,ref, rate_exponent)) where rate_exponent is ${\gamma }_i$ .

Reaction [n] > Properties > Specific Exchange Current Y-Intercept (log10)

Method	Corresponding Child Node
User Specific Exchange Current Y-Intercept (log10)	User Specific Exchange Current Y-Intercept (log10) Allows you to specify the y-intercept of the common logarithm of the specific exchange current, ${\log }_{10}\left(j_0\right)$ in Eqn. (4135), as a scalar profile.

Reaction [n] > Properties > Vacancy Rate Exponent

Method	Corresponding Child Node
Vacancy Rate Exponent	Vacancy Rate Exponent Allows you to specify the vacancy rate exponent for calculating the activity term, ${\gamma }_i^{vac}$ in Eqn. (4142), as a scalar profile.