Apparent surface rate constants in diffusion problems - Flux constriction effects

The impact of surface inhomogeneities on diffusion kinetics in solids is investigated by assuming that the exchange of the diffusing species takes place at active spots or stripes only. Finite element simulations are analyzed on the basis of analytical approximations. Such lateral inhomogeneities lead to an apparent surface rate constant even in cases in which the local surface kinetics at the active spots is infinitely first. The influence of geometric parameters (e.g., size and distance between the active sites) as well as control parameters such as the temperature on the apparent surface rate constant is investigated. (C) 2000 The Electrochemical Society. All rights reserved.