Electrochemical impedance spectra for the complete equivalent circuit of diffusion and reaction under steady-state recombination current

We have analyzed the impedance model for diffusion and reaction in non-equilibrium steady-state, when large diffusion current flows in a thin film either due to homogeneous reaction or heterogeneous charge-transfer in a nanoporous film (photoelectrochemical solar cells). Besides the standard diffusion resistance, transport in non-equilibrium conditions introduces a current generator in the transmission line equivalent circuit, which is due to an inhomogeneous conductivity. Numerical simulation of impedance spectra shows that the effect of the current generator is rather large when the diffusion length is shorter than the film thickness.