(292b) Over-Limiting Current and Shock Electrochemistry in Porous Media

Salt transport in bulk electrolytes occurs by electro-diffusion and convection, but in microfluidic devices and porous media, surface conduction and electro-osmotic flow also contribute to ionic fluxes. The nonlinear coupling of bulk and interfacial transport leads to some surprising new phenomena.  In steady state, the system can sustain over-limiting current (faster than diffusion) without any hydrodynamic or chemical instability, after the propagation of a deionization shock that removes salt by surface transport. This tutorial will review the basic theory and recent experiments, as well as engineering applications to water purification (“shock electrodialysis”) and control of dendritic growth (“shock electrodeposition”).