MULTIPLICITY IN IONIC MEMBRANES WITH NEGATIVE STOICHIOMETRIC DIFFUSIVITY

Negative polarization resistance can be induced by a negative ionic co nductance in membranes. In an electrochemical cell, where an ionic mem brane coats the electrode, the existence of multiple steady states, i. e. multiple current densities for a given applied voltage, is analyzed as being caused by the opposing effects of potential on charge transf er and on diffusion in the case of an anion being reduced or a cation being oxidized. The effects of diffusivity, concentration, supporting electrolyte, and fixed space charge on the conductance in the ionic me mbranes are also studied. An inverse concentration gradient may form a s a result of the interaction between the ionic migration and the stoi chiometric flux according to the reaction kinetics. (C) 1995 Academic Press Limited