Capacitive deionization with asymmetric electrodes: Electrode capacitance vs electrode surface area

Laxman, Karthik; Gharibi, Laila Al; Dutta, Joydeep

doi:10.1016/j.electacta.2015.07.036

Cited by 25 publications

(10 citation statements)

References 40 publications

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“…Thermal and membrane separation processes have been applied for the production of potable water, especially in arid regions of the world, but due to its complicated operations, high energy consumption, and higher cost of installation and running the processes, the scope for further utilization is limited. , Capacitive deionization (CDI) is a relatively new technology wherein an electrical voltage is applied to improve adsorption on nanostructured high-surface-area electrodes that can potentially reduce the cost of desalination as well as secondary pollution. , During the CDI process, salt ions are electrosorbed on the electrodes upon the application of a small DC (direct current) voltage, leading to desalination of water. The adsorbed ions are released back into a bulk solution upon reversing the electric potential (regeneration of the electrodes). − For reliable scaling-up of the CDI desalination technology, it is very important to further improve the salt adsorption capacity (SAC) of the electrodes.…”

Section: Introductionmentioning

confidence: 99%

“…However, the physical adsorption of ions on the electrodes leads to the formation of an electric double-layer (EDL) limiting ion removal capacity. Generally, improving the characteristics of the carbon cloth itself, such as surface modification, leads to a moderate increase in specific surface area, which provides more surface-active sites for ion adsorption. , Controlling the porosity and coordinating the ratio of micropores and mesopores also lead to accelerating the adsorption/desorption of ions, while doping with heteroatoms introduces a pseudocapacitance, thus increasing capacitance. , A better alternative could be to combine the carbon material with other materials imbibed with pseudocapacitive characteristics. This would lead to better ion adsorption, keeping the attributes of carbon cloth electrodes like its stability and high specific capacitance and introducing the reversible redox reaction from the second material, thus improving the overall electrochemical behavior and CDI process performance. ,, …”

Section: Introductionmentioning

confidence: 99%

“…Generally, improving the characteristics of the carbon cloth itself, such as surface modification, leads to a moderate increase in specific surface area, which provides more surface-active sites for ion adsorption. 14,23 Controlling the porosity and coordinating the ratio of micropores and mesopores also lead to accelerating the adsorption/desorption of ions, while doping with heteroatoms introduces a pseudocapacitance, thus increasing capacitance. 24,25 A better alternative could be to combine the carbon material with other materials imbibed with pseudocapacitive characteristics.…”

Section: ■ Introductionmentioning

confidence: 99%

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X-Fe (X = Mn, Co, Cu) Prussian Blue Analogue-Modified Carbon Cloth Electrodes for Capacitive Deionization

Zhang

Dutta

2021

ACS Appl. Energy Mater.

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Capacitive deionization is proven to be a viable resource-efficient alternative to remove dissolved salts from water. Further improvements in electrode materials are, however, necessary to achieve a higher efficiency of water desalination. In this work, X-Fe (X = Mn, Co, Cu) Prussian blue analogues of homogeneous particle sizes were grown on electrically conducting activated carbon cloth electrodes by a simple and facile synthesis process. As two-dimensional/three-dimensional (2D/3D) nanostructured Prussian blue analogue materials present favorable electrochemical behavior and ion-exchange possibilities, they are promising for application in capacitive deionization. The modified carbon cloth electrodes exhibit higher salt adsorption capacity and better charge efficiency compared to those constructed with pristine carbon cloth. Cobalt hexacyanoferrate-modified electrodes show the most stable performance, reaching a salt adsorption capacity of 14.47 mg g–1 at 1.0 V, accompanied by the lowest energy consumption (0.389 kWh m–3). This simple strategy is expected to offer possibilities for designing and synthesizing advanced electrode materials with superior performances for application in capacitive deionization devices.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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X-Fe (X = Mn, Co, Cu) Prussian Blue Analogue-Modified Carbon Cloth Electrodes for Capacitive Deionization

Zhang

Dutta

2021

ACS Appl. Energy Mater.

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“…2 MCDI can operate without membranes in a process simply known as capacitive deionization (CDI). [3][4][5][6] However, with membranes in place, otherwise expelled co-ions during cell polarization in CDI remain confined near the electrodes, leading to the additional flux of counter-ions from the solution bulk to neutralize the trapped unbalanced charges. [7][8][9] The end result is a significant increase in the salt adsorption capability and energy efficiency of MCDI in comparison to conventional CDI.…”

mentioning

confidence: 99%

Anion Exchange Membrane Capacitive Deionization Cells

Omosebi

Gao

Holubowitch

et al. 2017

J. Electrochem. Soc.

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The electrochemical response of capacitive deionization (CDI) employing a single anion exchange membrane (AEM-CDI) is contrasted to conventional two-membrane CDI (MCDI) formed with complementary anion and cation exchange membranes. Pristine activated carbon cloth electrodes that possess native positive surface charge in solution were used as both anode (positive electrode) and cathode (negative electrode) in these cells. In a separate set of tests to investigate the impact of surface charge modification on deionization responses, the single and dual membrane cells were formed with asymmetric electrodes (AEM-aCDI and aMCDI) consisting of nitric acid oxidized electrodes that possess negative surface charge as the cathode material, while pristine carbon cloth was retained as the anode material. Operating at 1.2 V, salt adsorption capacities are ∼1.3, 9.9, and 16.6, and 17.3 mg NaCl g −1 electrode for the AEM-CDI, MCDI, AEM-aCDI, and aMCDI, respectively. The diminished performance of AEM-CDI is attributed to charge expulsion and enhanced parasitic electrochemical reactions at the unprotected cathode that reduce the charge efficiency. In contrast, for AEM-aCDI, a treated cathode enhances surface charge effects to match aMCDI performance with half the membrane requirement. Membrane capacitive deionization (MCDI) is an emerging water treatment technology that offers energy savings in comparison to incumbent pressure and heat driven desalination technologies when treating low to brackish level salt concentration streams.1 MCDI shares similarities with electrodialysis (ED) in that they both use complementary cation and anion selective membranes to remove dissolved ionic content with applied DC electric fields. Unlike ED, which relies on electrochemical reactions and field-driven charge diffusion facilitated by large potentials, MCDI electrostatically stores ions in electrical double-layers (EDLs) formed in highly porous electrically conductive materials, typically made of carbon (Fig. 1a). A primarily capacitive rather than charge-transfer mechanism allows the use of comparatively lower potentials with concomitant cost savings. Nonetheless, the high cost associated with membranes can still be prohibitive in terms of device commercialization. 2 MCDI can operate without membranes in a process simply known as capacitive deionization (CDI).3-6 However, with membranes in place, otherwise expelled co-ions during cell polarization in CDI remain confined near the electrodes, leading to the additional flux of counter-ions from the solution bulk to neutralize the trapped unbalanced charges.7-9 The end result is a significant increase in the salt adsorption capability and energy efficiency of MCDI in comparison to conventional CDI. Once the electrodes are saturated, the system is depolarized to create a concentrated waste stream by reducing the applied potential, shorting the electrodes, or reversing the potential. In addition to suppressing ion repulsion, the membranes also mitigate faradaic currents from electroactive species and...

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“…When a potential difference is abruptly induced between the pore material and the solution, ions will rapidly begin to electroadsorb on the electrodes by migrating to the micropores because of the induced electric field, cations adsorbing on the anodes, and vice versa. The exact performance varies between electrodes; however, such porous electrodes hold around m ads = 10 mg salt per gram of electrode [25,[29][30][31], while the effective specific surface area is around A = 1000 m 2 /g [22,32,33]. To put this in perspective, let us consider the fraction of the projected area of adsorbed ions to the total electrode area, denoted by η (Equation (1)).…”

Section: From Physics To Modelmentioning

confidence: 99%

Basis and Prospects of Combining Electroadsorption Modeling Approaches for Capacitive Deionization

Nordstrand

Dutta

2020

Physics

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Electrically driven adsorption, electroadsorption, is at the core of technologies for water desalination, energy production, and energy storage using electrolytic capacitors. Modeling can be crucial for understanding and optimizing these devices, and hence different approaches have been taken to develop multiple models, which have been applied to explain capacitive deionization (CDI) device performances for water desalination. Herein, we first discuss the underlying physics of electroadsorption and explain the fundamental similarities between the suggested models. Three CDI models, namely, the more widely used modified Donnan (mD) model, the Randles circuit model, and the recently proposed dynamic Langmuir (DL) model, are compared in terms of modeling approaches. Crucially, the common physical foundation of the models allows them to be improved by incorporating elements and simulation tools from the other models. As a proof of concept, the performance of the Randles circuit is significantly improved by incorporating a modeling element from the mD model and an implementation tool from the DL model (charge-dependent capacitance and system identification, respectively). These principles are accurately validated using data from reports in the literature showing significant prospects in combining modeling elements and tools to properly describe the results obtained in these experiments.

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Capacitive deionization with asymmetric electrodes: Electrode capacitance vs electrode surface area

Cited by 25 publications

References 40 publications

X-Fe (X = Mn, Co, Cu) Prussian Blue Analogue-Modified Carbon Cloth Electrodes for Capacitive Deionization

X-Fe (X = Mn, Co, Cu) Prussian Blue Analogue-Modified Carbon Cloth Electrodes for Capacitive Deionization

Anion Exchange Membrane Capacitive Deionization Cells

Basis and Prospects of Combining Electroadsorption Modeling Approaches for Capacitive Deionization

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