Mechanistic insights into the use of oxide nanoparticles coated asymmetric electrodes for capacitive deionization

Han, Linchen; Karthikeyan, K.; Anderson, Marc A.; Wouters, Jesse J.; Gregory, Kelvin B.

doi:10.1016/j.electacta.2012.11.069

Cited by 93 publications

(41 citation statements)

References 42 publications

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“…The actual charge efficiency is always higher than the observed value due to the involvement of inevitable faradaic reactions. Our calculations are regarded robust enough to reflect the actual Stern layer voltage, since other studies 27,33 have shown that the faradaic current is relatively negligible as nonfaradaic current is dominant at low potential and in high surface area systems. Faradaic processes are inevitable when proton and Cl − ions are present.…”

Section: Journal Of the Electrochemical Society 162 (12) E282-e288 (mentioning

confidence: 99%

“…Therefore, the electrosorption capacity is determined by the volume (porosity) of the micropores and the energy barrier. The microporosity-based electrosorption theory is critical in analyzing energy consumption during CDI.z E-mail: kkarthikeyan@wisc.edu Although significant progress has been made recently in the development of diverse electrode materials, 13,[19][20][21][22][23][24][25][26][27] theoretical models, [16][17][18] water treatment and desalination devices, 28-30 only very few studies address the issue of energy consumption during CDI. The role of electrode materials in electrosorption and energy consumption is not completely understood and, more importantly, the impact of operational conditions on energy consumption has not been rigorously evaluated when nanoscale porous electrode is applied.…”

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confidence: 99%

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Energy Consumption and Recovery in Capacitive Deionization Using Nanoporous Activated Carbon Electrodes

Han

Karthikeyan

Gregory

2015

J. Electrochem. Soc.

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Capacitive deionization (CDI) is an emerging desalination technology which utilizes porous electrodes to remove ions in water by electrosorption. Similar to electric capacitors, energy is stored and released during charging and discharging cycles, respectively. In this study, a nanoporous activated carbon coupled flow-through CDI device was used to evaluate energy consumption and recovery under various operational conditions by charging and discharging the cell at a constant current, respectively. Results indicated that the charging/discharging current, salt concentration and water flow rate were major factors impacting electrosorption and energy consumption, by changing the structure of the electrical double layer (EDL) and how ion transport occurs between the interface and bulk solution. A porosity-based EDL theory was applied to explain the experimental observations. Between 30 and 45% of the energy consumed during charging could be recovered depending on operational conditions, although thermodynamically more than 98% of the total energy should be recoverable. Results indicated that overpotential and faradaic reactions induced irreversible energy are the major reasons for gaps in observed energy losses. Energy consumption for reducing the salinity of brackish water from 32.7 to 5.5 mM by our device could be as low as 0.85 kWh/m 3 under most optimized conditions (dependent on materials used and cell configuration). The energy consumption can be dramatically reduced by employing more electron-conductive and Faradaic-resistant electrode materials. Increasing demand for freshwater is driving the need for energyefficient and cost-effective technologies to generate potable water from unconventional sources such as brackish water.1 Due to its simplicity and reliability, capacitive deionization (CDI) has attracted a growing interest for water desalination.1-7 Capacitive deionization utilizes highly porous electrodes to remove charged ions in water by electrosorption (Figure 1). During charging, an electric voltage is applied and ions are driven to oppositely charged electrodes by electrostatic force and entrapped at the electrode-water interface by the formation of an electric double layer (EDL). After removing the ions, the electric voltage is removed or reversed to discharge and regenerate the electrodes. Ions return to solution and the concentrated brine is discarded. Desalination is realized by means of consecutive charging/discharging cycles to separate influent water into freshwater and brine (concentrate) streams.Energy consumption is a major factor driving the synthesis of new CDI electrode materials. Energy-efficient CDI devices are required for up-scaling the process and for broader adoption of this technology for potable or agricultural water treatment. An important feature of CDI is that part of the energy consumed during charging can be recovered during discharging, a process similar to charge/discharge in electric capacitors.6,8 CDI could become more cost competitive compared with well-established desa...

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Section: Journal Of the Electrochemical Society 162 (12) E282-e288 (mentioning

confidence: 99%

mentioning

confidence: 99%

Energy Consumption and Recovery in Capacitive Deionization Using Nanoporous Activated Carbon Electrodes

Han

Karthikeyan

Gregory

2015

J. Electrochem. Soc.

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“…The choice of electrode material and material morphology are extremely important for the CDI technology [15][16][17][18][19]. Various techniques have been developed for the fabrication of electrodes for efficient CDI devices [20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Influence of chemical structure of dyes on capacitive dye removal from solutions

Shi

Zhitomirsky

2015

Electrochimica Acta

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“…The two steps of salt adsorption (charging) and desorption (discharge) constitute one full CDI cycle. Charge efficiency Λ describes the ratio of salt adsorption (desorption) over the charge transfer [107,109,116,[122][123][124]. The charge efficiency differs between materials and depends on the voltage applied during charging, V ch , and salt concentration [49].…”

Section: Introductionmentioning

confidence: 99%

“…Alternative designs use carbon electrode wires [80], flowable electrode slurries [7,[72][73][74]76] or flow-through electrodes [112]. In addition, electrodes can be chemically modified [88,113], nanoparticles can be incorporated [114][115][116], ion-selective coatings can be applied [117,118], or ionexchange membranes can be placed in front of the electrodes in a modification called Membrane Capacitive Deionization, or MCDI [27,28,35,71,102,[119][120][121].…”

Section: Introductionmentioning

confidence: 99%

Desalination with porous electrodes : Mechanisms of ion transport and adsorption

Dykstra¹

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Mechanistic insights into the use of oxide nanoparticles coated asymmetric electrodes for capacitive deionization

Cited by 93 publications

References 42 publications

Energy Consumption and Recovery in Capacitive Deionization Using Nanoporous Activated Carbon Electrodes

Energy Consumption and Recovery in Capacitive Deionization Using Nanoporous Activated Carbon Electrodes

Influence of chemical structure of dyes on capacitive dye removal from solutions

Desalination with porous electrodes : Mechanisms of ion transport and adsorption

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