  Capacitive deionization (CDI) is a technology in which water is desalinated
by ion electrosorption into the electric double layers (EDLs) of charging
porous electrodes. In recent years significant advances have been made in
modeling the charge and salt dynamics in a CDI cell, but the possible effect of
surface transport within diffuse EDLs on these dynamics has not been
investigated. We here present theory which includes surface transport in
describing the dynamics of a charging CDI cell. Through our numerical solution
to the presented models, the possible effect of surface transport on the CDI
process is elucidated. While at some model conditions surface transport
enhances the rate of CDI cell charging, counter-intuitively this additional
transport pathway is found to slow down cell charging at other model
conditions.
