Anion-exclusion carbon electrodes for energy storage and conversion by capacitive mixing

Capacitive mixing is a newly emerging technique for the production of renewable energy from the controlled mixing of river water and seawater. Energy extraction is provided by the potential rise in electrodes held in a fixed charge, as a response to the concentration change. Therefore, electrodes that exhibit high potential variation as a response to concentration change (negative rise for the cation-capturing electrode and vice versa) are highly desirable. In this work, electrodes that can accommodate mostly cations within their porous structure are discussed. In accordance to the modified Donnan (mD) model of the electrical double layer, it is expected that such electrodes will display the highest potential change as a response to concentration change (while being held with a fixed charge). Using appropriate selective activated carbon electrodes, high potential rise, around 50 mV, was observed as a response to concentration change, when the concentration of NaCl solutions was changed from 1M to 10^-1 M and from 10^-1 M to 10^-2 M. Such a capability of potential rise of selective electrodes can serve as a good basis for energy extraction by capacitive mixing.