Abstract A model for a porous or particulate bed electrode reactor is presented. The model consists of nonlinear second-order ordinary differential equations, a one-dimensional Poisson equation, describing the effect of the electric field on this system, and a one-dimensional diffusion-reaction equation describing the concentration variation associated with diffusion. The model accounts for mass transport and heterogeneous electrochemical reaction. The solution of this model is by the approximate Adomian polynomial method and is used to determine lateral distributions of concentration, overpotential and current density, overall cell polarisation and effectiveness factors, and to simulate the effects of important system and operating parameters, i.e. local diffusion rates and mass transport coefficients.