Polarized electrode for flow-through capacitive deionization

A fluid flow through capacitor cell comprising:

• (a) at least two capacitor electrodes having a surface area for electrostatic adsorption and desorption of ions and comprising a pore structure such that each said capacitor electrode is a porous capacitor electrode having a pore volume having pore surfaces;
• (b) a flow channel for the passage of an ionic fluid having a pH, said flow channel in ionic communication with said two capacitor electrodes;
• (c) fluid in said flow channel;
• (d) at least one ionic group attached to the surface of the pore volume of each said porous capacitor electrode, wherein a first said porous capacitor electrode having a first pore volume comprises cationic groups attached within 25 nanometers of the surface of said first pore volume, said cationic groups having a pKa that is at least one pKa unit higher than said fluid pH;
• and
• (e) wherein a second porous capacitor electrode having a second pore volume comprises anionic groups attached within 25 nanometers of the surface of said second pore volume, said anionic groups having a pKa that is at least one pKa unit lower than said fluid pH,
• wherein at least a portion of the first pore volume is occupied by a double layer and constitutes a majority proportion of total first pore volume and wherein at least a portion of the second pore volume is occupied by a double layer and constitutes a majority proportion of total second pore volume and the cationic groups are within the double layer of the first pore volume and the anionic groups are within the double layer of the second pore volume.

A method of making an electrode capacitor assembly comprising:

• (a) providing at least two capacitor electrodes comprising a pore structure such that each said capacitor electrode is a porous capacitor electrode having a pore volume, said pore volume having a surface for electrostatic adsorption and desorption of counter-ions and said pore volume comprising more than 30% of micropores, mesopores, or a combination or micropores and mesopores;
• (b) configuring a flow channel between the at least two capacitor electrodes for passage of an ionic fluid so that, in operation, said flow channel is in ionic communication with said two capacitor electrodes;
• and
• (c) attaching at least one ionic group within 25 nanometers of the surface of the pore volume of each said porous capacitor electrode, whereby a first said porous capacitor electrode having a first pore volume is an anion-permeable electrode comprising cationic groups attached within 25 nanometers of the surface of said first pore volume and whereby a second porous capacitor electrode having a second pore volume is a cation-permeable electrode comprising anionic groups within 25 nanometers of the surface of said second pore volume.

An electrode capacitor assembly comprising:

• (a) at least two capacitor electrodes comprising a pore structure such that each said capacitor electrode is a porous capacitor electrode having a pore volume, said pore volume having a surface for electrostatic adsorption and desorption of counter-ions, and said pore volume comprising more than 30% micropores, mesopores, or a combination of micropores and mesopores;
• (b) a flow channel for passage of an ionic fluid, wherein, in operation, said flow channel is in ionic communication with said two capacitor electrodes;
• and
• (c) at least one ionic group attached to the surface of the pore volume of each said porous capacitor electrode, whereby a first said porous capacitor electrode having a first pore volume is an anion-permeable electrode comprising cationic groups attached to the surface of said first pore volume and, in operation, excluding cationic co-ions from said first electrode, and whereby a second porous capacitor electrode having a second pore volume is a cation-permeable electrode comprising anionic groups attached to said second pore volume and, in operation, excluding anionic co-ions from said second electrode;
• and
• (d) fluid in said flow channel, wherein said fluid has a pH, and wherein the cationic groups within the first pore volume have a pKa, and wherein the anionic groups within the second pore volume have a pKa.