Diffusion with general boundary conditions in electrochemical systems

We define a reflective–transmissive coefficient to characterize the boundary conditions of real electrochemical systems with a diffusion flux of charged species. For these systems we obtain from a generalized diffusion equation, for processes with a non-vanishing relaxation time, a generalized Warburg-like impedance for a finite length diffusion with general boundary conditions. The influence of the reflective–transmissive coefficient on the generalized Warburg impedance is studied and related to the reduction and corrosion nature of the interface. We also interpret this impedance in terms of a general transmission line.