Modeling ion migration in electrochemical systems under conditions involving heterogeneous electron transfer.

by Hesan, Shirin; Abrego Tello, Miguel A.; Fritsch, Ingrid

This work uses numerical approxns. to predict the migration of ions in an electrochem. cell and their concn. distribution. A series of studies will be described with iteratively increasing complexity. They start with diffuse double-layer behavior at electrode/soln. interfaces for different electrode-pair geometries in a static soln. of different supporting electrolyte concns. A sustained current is then introduced (through faradaic processes at those electrodes) and the change in ion distribution is detd. The Nernst-Planck equation, which is solved for the mass flux of each ion (governing the diffusion and migration contributions), is combined with Poisson's equation to calc. the potential. The simulations are obtained for one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) mass transfer depending on electrode geometry. Geometries include pairs of planar electrodes facing each other and coplanar microband electrodes with decreasing length-to-gap ratios. The studies are performed utilizing COMSOL Multiphysics. The results of this work are of interest for modeling redox-MHDs (R-MHD) microfluidics, whose flow velocities and profiles depending on the distribution of ionic c.d. in an electrolyte soln. between two electrodes, that perform oxidn. and redn., and at right angles to a local magnetic flux d. provided by an external magnet.