Estimation of Limiting Current Density

In order to derive the limiting current density, let us equate the net mass transfer rate of a reactant gas given by Equation 6.102 and the gas consumption rate based on the current density as follows  

Equation 6.127 can also be used to estimate the reactant gas concentration 

Notice that in situations where net mass transfer resistance is controlled by the diffusion resistance in the electrode-gas diffusion layer only, the reactant gas concentration at the reaction surface is given as 

Equating 6.127 for the current density as a function of reactant gas concentration 

Equation 6.80 shows that the current density depends directly on the reactant gas concentration in the channel as well as the reactant gas concentration at the electrode-electrolyte interface. The current density increases with higher gas concentration, Q in the channel and lower concentration, Q i, at the reaction surface. For a given electrode-gas diffusion layer and gas channel design with a fixed Q value, the maximum current density or the 

---