P.M. (Maarten) Biesheuvel Wageningen, the Netherlands Wetsus, Leeuwarden, the Netherlands - - - - + + + + Porouselectrode Porouselectrode - - - - - - - + + + + + + + -------- + + + + + + + + Capacitive Porous Electrodes
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P.M. (Maarten) BiesheuvelWageningen, the NetherlandsWetsus, Leeuwarden, the Netherlands
non-faradaic=capacitive
Capacitive Deionization
Porous electrode
Porous electrode- --
-
---
+ + +
++
++
- - - - - - - -
+ + + + + + + +
Porous electrode
Porous electrode- --
-
---
+ + +
++
++
- - - - - - - -
+ + + + + + + +
Capacitive Porous Electrodes
Capacitive Deionization
non-faradaic=capacitive
Capacitive Deionization
Porous electrode
Porous electrode- --
-
---
+ + +
++
++
- - - - - - - -
+ + + + + + + +
Porous electrode
Porous electrode- --
-
---
+ + +
++
++
- - - - - - - -
+ + + + + + + +
Capacitive Deionization
(CDI)Supercapacitors
Static Flow-throughnon-faradaic=capacitive
Capacitive Deionization
Porous electrode
Porous electrode- --
-
---
+ + +
++
++
- - - - - - - -
+ + + + + + + +
Porous electrode
Porous electrode- --
-
---
+ + +
++
++
- - - - - - - -
+ + + + + + + +
3
A close relative …
“Capacitive Deionization” – Web of Science
(Membrane) Capacitive Deionization
with ion-exchange membranes
without ion-exchange membranes
Porous electrode
Porous electrode
Capacitive Deionization
- ----- -+ + + + + + +
- - - - - - - -
+ + + + + + + +
Adsorption
Vcell
6
macroporenanopore
++
+ +++
+
-
ci(x,t)f(x,t)
f1(t)Stern layer,DfSt
-
-
- --
-
-
Dfd+
Capacitive Deionization
Porous electrode
Porous electrode- ----- -
+ + + + + + +- - - - - - - -
+ + + + + + + +
Releaseshort-circuit
7
macroporenanopore
++
+ +++
+
-
ci(x,t)f(x,t)
f1(t)Stern layer,DfSt
-
-
- --
-
-
Dfd+
Models for the Electrical Double Layer
Salt adsorption and Charge in Microporous Carbons
Equilibrium, @ Vcell=1.2 V
New system designs
FreshwaterFreshwater
Flowable electrodes
Desalination with Wires
FreshwaterFreshwater
Results published in: Porada, S., B.B. Sales, H.V.M. Hamelers, and P.M. Biesheuvel (2012) The Journal of Physical Chemistry Letters 3: 1613-1618
Desalination with Wires
Ion transport phenomena in realistic systems:
Instead of “Na+ Cl-” also H+ OH- HCO3- etc.
Three examples for amphoteric ionic systems
e.g., CO32-HCO3
- H2CO3
Capacitive Deionization
Current-induced membrane discharge
CO2 energy
CDI – pH effects
Example 2. Overlimiting current in Ion-exchange membranes
water in membrane pores membrane discharge
Example 2. Overlimiting current in Ion-exchange membranes
Current Induced Membrane Discharge
Example 3. “CO2 energy” from power plant off-gas
AEM CEM
H+HCO3
-
Anode Cathode
RNH3+
RNHCOO-
CO2-flushed
e-
270 µm 270 µm200 µm40 µm 40 µm
OH-
CO32-
H2CO3
--
-
-
++++
++
++
++++
++
+
++
+
-
-
--
--
Flow channel
PCE PCE
-
-
AEM CEM
H+HCO3
-
Anode Cathode
RNH3+
RNHCOO-
CO2-flushed
e-
270 µm 270 µm200 µm40 µm 40 µm
OH-
CO32-
H2CO3
--
-
-
++++
++
++
++++
++
+
++
+
-
-
--
--
Flow channel
PCE PCEAEM CEM
H+HCO3
-
Anode Cathode
RNH3+
RNHCOO-
CO2-flushed
e-
270 µm 270 µm200 µm40 µm 40 µm
OH-
CO32-
H2CO3
--
-
-
++++
++
++
++++
++
+
++
+
-
-
--
--
Flow channel
PCE PCE
-
-
Modeling of ion transport in amphoteric systems
e.g., CO32- + H+ HCO3
-
JOH-(aq)
JNH3(g)
JH+(aq)
JNH4+(aq)
Advantages of fast ion equilibration
• By addition of balances, for each “group” such as for CO2/HCO3
-/CO32-, only one balance per group remains
• and, all dummy parameters R disappear !
• very elegant to include now reactions at solid surfaces, or evaporation
liquid gasJNH3(aq)
Thank you !
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