Transport and Reaction in Catalyst Layers

Continuity equations including all species and processes are discussed in [50]. A number of simplifications lead to the following set of equations 

as well as the flux densities of protons, (z), liquid water, f (z), and 

The electrochemical source term, (z), accounts for the effectiveness factor 

The oxygen partial pressure is related to the oxygen concentration via the ideal gas law, Pq (z) = RTc (z). The cathodic overpotential is the (positive) 

In addition to the conservation laws, a locally valid condition of mechanical equilibrium is needed. Here it is assumed that local pore filling is controlled by capillary equilibrium corresponding to the Laplace equation. 

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