This example demonstrates how you can model phenomena defined in different dimensions (2D and 1D in this example) in a fully coupled manner using COMSOL Multiphysics.
In this particular case, the model involves a small parallel-plate reactor with a catalytic surface. Similar applications where surface processes are of critical importance include biochip devices and a semiconductor components.
When modeling chemical reactions the reaction rates are commonly functions of the concentrations of the reactants in the phase that transports the chemicals. However, for surface reactions it is also necessary to account for the surface concentrations of the active sites and surface adsorbed species. The mass balances in the bulk of the reactor must therefore be coupled to the mass balances for species, present only at the surface of the device.