Defining Surface Reactions

Electrochemical reactions that occur at the surfaces between the electrodes and the electrolyte are defined manually.

For the Air continuum, you define the reaction which occurs at the surface between the cathode and the electrolyte, Eqn. (5281).
To define the surface reactions:
  1. Expand the Continua > Air > Models node.
  2. Right-click the Electrochemical Reactions > Surface Mechanism Manager node and select New Surface Mechanism.
  3. Rename the Surface Mechanism Manager > SurfaceMechanism node to Cathodic.
  4. Right-click the Cathodic > Reacting Surface > Reactions node and select New Reaction.
  5. Rename the Reactions > Reaction 1 node to O2 + 4e- <=> 2O-2.
  6. Set up the sub-nodes of the O2 + 4e- <=> 2O-2 node as follows:
    Node Action
    Reactants
    1. Right-click and select Add Reactant > Gas Mixture > O2.
    2. Right-click and select Add Reactant > conductor-cathode: e-.
    O2 (Gas Mixture) Set Rate Exponent to 0.5.
    e- (conductor-cathode) Set Stoich. Coeff to 4.0 .
    Products Right-click and select Add Product > Mem: Electrochemical Species Mixture > O-2.
    O-2 (Mem: Electrochemical Species Mixture) Set Stoich. Coeff to 2.0.
    Properties
    Equilibrium Potential Set Select Method to Nernst From Thermodynamic Data.
    Reaction Formulation
    Butler-Volmer > Alpha A Set Value to 1.0.
    Butler-Volmer > Alpha C Set Value to 1.0.
    Specific Exchange Current
    User Specific Exchange Current
    1. Set Method to Field Function.
    2. Set Scalar Function to CathodeExchangeCurrent
For the Fuel continuum, set up the reaction that occurs at the surface between the anode and the electrolyte Eqn. (5279).
  1. Right-click the Electrochemical Reactions > Surface Mechanism Manager node and select New Surface Mechanism.
  2. Rename the Surface Mechanism Manager > SurfaceMechanism node to Anodic.
  3. Right-click the Anodic > Reacting Surface > Reactions node and select New Reaction.
  4. Rename the Reactions > Reaction 1 node to H2O + 2e- <=> H2 + O-2.
  5. Set up the sub-nodes of the H2O + 2e- <=> H2 + O-2 node as follows:
    Node Action
    Reactants
    1. Right-click and select Add Reactant > Gas Mixture > H2O.
    2. Right-click and select Add Reactant > conductor-anode: e-.
    H2O (Gas Mixture) Set Rate Exponent to 0.5.
    e- (conductor-anode) Set Stoich. Coeff to 2.0.
    Products
    1. Right-click and select Add Product > Gas Mixture > H2.
    2. Right-click and select Add Product > Mem: Electrochemical Species Mixture > O-2.
    H2 (Gas Mixture) Set Rate Exponent to 0.5.
    Properties
    Equilibrium Potential Set Method to Nernst From Thermodynamic Data.
    Reaction Formulation
    Butler-Volmer > Alpha A Set Value to 1.0.
    Butler-Volmer > Alpha C Set Value to 1.0.
    Specific Exchange Current
    User Specific Exchange Current
    1. Set Method to Field Function.
    2. Set Scalar Function to AnodeExchangeCurrent
  6. Save the simulation.