DIFFUSION LAYER

"A thin liquid boundary layer at the surface of an electrode that is immobile. This is part of a rather simplified and not strictly correct model (originally proposed by the early electrochemist Nernst, and is often called the ""nernstian hypothesis"") that works surprisingly well in most cases. The electrolyte solution is divided into three distinct parts: the bulk solution and the two diffusion layers at the surfaces of the electrodes. The bulk solution is assumed to be so well stirred that the concentration of all species is uniform throughout. In this region, mass transport occurs only through convection. While in the diffusion layers mass transport occurs only through diffusion. Charge transport occurs through electromigration everywhere. The thickness of the diffusion layer can vary typically between the order of 0.01 centimeter in a stagnant solution and the order of 0.0001 centimeter in very well-stirred solution. (The diffusion layer is not to be confused with the diffuse layer.) "