SIMULATION OF THE IMPEDANCE OF 2-DIMENSIONAL POROUS-ELECTRODES

The frequency response of porous electrodes has been investigated using a two-dimensional random-walk algorithm. For simple geometries the values obtained for the characteristic constant-phase-angle exponent is in good agreement with theoretical expectations. The random-walk approach has also been used to study the response of more complex disorderly geometries. In general, the simulation results can be understood in terms of the growth of the "active length" (that part of the electrode-electrolyte interface that participates in the transport process) as the sticking probability or frequency is decreased. The constant-phase-angle exponent-eta is given by eta = 1-nu(y), where the exponent nu(y) describes how the penetration of random walkers into the uniformly porous structure grows with time (number of steps in the walk).