Propagating reaction fronts in an ionic autocatalytic system: The effects of electric field intensity and ionic strength

An ionic chemical system which has two components, A+ and B+, reacting with a quadratic autocatalytic rate law and two further, nonreacting components C− and D+ is considered. The system is shown to be characterized by the dimensionless parameters δB, I and d0 representing the ratio of the diffusion coefficients of B+ and A+, the (constant) applied electric current and the ionic strength of the system (the initial concentration of D+), respectively. The travelling wave equations for this system are discussed first, and parameter ranges identified where forward-propagating kinetic waves can exist. These are then seen, from numerical integrations of the original initial-value problem, to be the long time structures, when this is the case. When this is not the case, qualitatively different behaviour is observed depending on whether δb > 1 or δB <1, the form of which is dependent on the size and direction of the applied electric field as well as on the ionic strength. This is described in detail and shown to agree with previous studies for d0 = 0 and do large.