Capacitive Deionization Of Saline Water Research Articles

Activated Carbon-Embedded Reduced Graphene Oxide Electrodes for Capacitive Desalination

Capacitive deionization of saline water is one of the most promising water purification technologies due to its high energy efficiency and cost-effectiveness. This study synthesizes porous carbon composites composed of reduced graphene oxide (rGO) and activated carbon (AC) with various rGO/AC ratios using a facile chemical method. Surface characterization of the rGO/AC composites shows a successful chemical reduction of GO to rGO and incorporation of AC into rGO. The optimized rGO/AC composite electrode exhibits a specific capacitance of ~243 F g<sup>−1</sup> in a 1 M NaCl solution. The galvanostatic charging-discharging test shows excellent reversible cycles, with a slight shortening in the cycle time from the ~260<sup>th</sup> to the 530<sup>th</sup> cycle. Various monovalent sodium salts (NaF, NaCl, NaBr, and NaI) and chloride salts (LiCl, NaCl, KCl, and CsCl) are deionized with the rGO/AC electrode pairs at a cell voltage of 1.3 V. Among them, NaI shows the highest specific adsorption capacity of ~22.2 mg g<sup>−1</sup>. Detailed surface characterization and electrochemical analyses are conducted.

3D graphene-supported N-doped hierarchically porous carbon for capacitive deionization of saline water

Capacitive deionization (CDI) is a promising technique for desalination of brackish water because it is highly energy-efficient and environmentally friendly.

MOF-derived nanoporous carbons with diverse tunable nanoarchitectures.

Metal-organic frameworks (MOFs), or porous coordination polymers, are crystalline porous materials formed by coordination bonding between inorganic and organic species on the basis of the self-assembly of the reacting units. The typical characteristics of MOFs, including their large specific surface areas, ultrahigh porosities and excellent thermal and chemical stabilities, as well as their great potential for chemical and structural modifications, make them excellent candidates for versatile applications. Their poor electrical conductivity, however, has meant that they have not been useful for electrochemical applications. Fortuitously, the direct carbonization of MOFs results in a rearrangement of the carbon atoms of the organic units into a network of carbon atoms, which means that the products have useful levels of conductivity. The direct carbonization of zeolitic imidazolate framework (ZIF)-type MOFs, particularly ZIF-8, has successfully widened the scope of possible applications of MOFs to include electrochemical reactions that could be used in, for example, energy storage, energy conversion, electrochemical biosensors and capacitive deionization of saline water. Here, we present the first detailed protocols for synthesizing high-quality ZIF-8 and its modified forms of hollow ZIF-8, core-shell ZIF-8@ZIF-67 and ZIF-8@mesostuctured polydopamine. Typically, ZIF-8 synthesis takes 27 h to complete, and subsequent nanoarchitecturing procedures leading to hollow ZIF-8, ZIF-8@ZIF-67 and ZIF-8@mPDA take 6, 14 and 30 h, respectively. The direct-carbonization procedure takes 12 h. The resulting nanoporous carbons are suitable for electrochemical applications, in particular as materials for supercapacitors.

Efficient and Durable Sodium, Chloride-doped Iron Oxide-Hydroxide Nanohybrid-Promoted Capacitive Deionization of Saline Water via Synergetic Pseudocapacitive Process.

Recently, the rational design and development of efficient faradaic deionization electrodes with high theoretical capacitance, natural abundance, and attractive conductivity have shown great promise for outstanding capacitive deionization (CDI)‐based desalination applications. Herein, the construction of novel FeOOH hybrid heterostructures with Na and Cl dopants (e.g., Na‐FeOOH and Cl‐FeOOH) via a robust hydrothermal strategy is reported, and an asymmetric CDI cell (Na‐FeOOH//Cl‐FeOOH) comprising Na‐FeOOH and Cl‐FeOOH working as the cathode and anode, respectively, is assembled. The multiple coupling effects of the specific structural features (e.g., enriched porosity, hierarchical pore alignment, and highly open crystalline framework), enhanced electrochemical conductivity, and optimized ion‐transfer property endow the FeOOH hybrid electrode with improved electrochemical performance. Impressively, the Na‐FeOOH//Cl‐FeOOH cell demonstrates a superior salt adsorption capacity (SACNaCl) of 35.12 mg g−1 in a 500 mg L−1 NaCl solution, a faster removal rate, and remarkable cycling stability. Moreover, the pseudocapacitive removal mechanism from the synergetic contribution of the Na‐FeOOH cathode and Cl‐FeOOH anode account for the significant desalination promotion of the Na‐FeOOH//Cl‐FeOOH cell.

3D hierarchical porous N-doped carbon quantum dots/vanadium nitride hybrid microflowers as a superior electrode material toward high-performance asymmetric capacitive deionization

3D hierarchical porous NCQDs/VN hybrid microflowers were first demonstrated as an advanced electrode for an asymmetric capacitive deionization of saline water.

Trace-Fe-Enhanced Capacitive Deionization of Saline Water by Boosting Electron Transfer of Electro-Adsorption Sites.

Capacitive deionization (CDI) is a promising water purification technology. However, the current ion adsorption capacity of CDI electrode materials is still an issue, which cannot meet the rapid demand of clean water from saline water. Herein, trace-Fe-enhanced removal of ions from saline water via CDI is presented. The ion adsorption capacity of CDI electrodes is up to 36.25 mg g-1 in a 500 mg L-1 NaCl media at 1.2 V together with stable regeneration property. In situ Raman and ex situ XPS measurements unravel the removal mechanism of ions from saline water, and the reinforced adsorption of ions is due to the introduction of trace Fe boosting electron transfer of electro-adsorption sites during the CDI process. This work presents a promising solution to highly efficient capacitive deionization for saline water.

Enhanced capacitive deionization of saline water using N-doped rod-like porous carbon derived from dual-ligand metal–organic frameworks

Enhanced capacitive deionization of saline water has been demonstrated by using N-doped rod-like porous carbon derived from dual-ligand metal–organic frameworks.

Fabrication of an antimony doped tin oxide-graphene nanocomposite for highly effective capacitive deionization of saline water.

In this study, antimony doped tin oxide loaded reduced graphene oxide (ATO–RGO) nanocomposites were synthesized via a facile hydrothermal approach. As a typical N-type semiconductor, the ATO in the composite can enhance the conductivity between graphene sheets, thus improving the specific capacitance and electrosorption performance. Under the optimal conditions, the largest surface area was 445.2 m2 g−1 when the mass content of ATO in the nanocomposite was 20 wt%. The synthesized optimal ATO–RGO electrode displayed excellent specific capacity (158.2 F g−1) and outstanding electrosorptive capacity (8.63 mg g−1) in sodium chloride solution, which were much higher than the corresponding results of pristine graphene (74.3 F g−1 and 3.98 mg g−1). At the same applied voltage, electrosorption capacity and charge efficiency of the ATO–RGO (20 wt%) material were better than those of reported carbon materials in recent years.

Permselective ion electrosorption of subnanometer pores at high molar strength enables capacitive deionization of saline water

Small carbon pores below 1 nm become increasingly ionophobic which enables the more and more permselective charge storage and perspectives for capacitive deionization with porous carbons even at high molar strength.

Efficient Capacitive Deionization of Saline Water by an Integrated Tin disulfide Nanosheet@Graphite Paper Electrode via an in Situ Growth Strategy

Capacitive deionization (CDI) is a promising desalination method to address the water resource crisis. However, widely used CDI electrodes mostly rely on carbonaceous nanomaterials and highly compl...

Capacitive Deionization of Saline Water by Using MoS2-Graphene Hybrid Electrodes with High Volumetric Adsorption Capacity.

Capacitive deionization (CDI) has received wide attention as an emerging water treatment technology because of its low energy consumption, low cost, and high efficiency. However, the conventional carbon electrode materials for CDI have low densities, which occupy large volumes and are disadvantageous for use in limited space (e.g., in household or on offshore platforms). In order to miniaturize the CDI device, it is quite urgent to develop high volumetric adsorption capacity (VAC) electrode materials. To overcome this issue, we rationally designed and originally developed high VAC MoS2-graphene hybrid electrodes for CDI. It is interesting that MoS2-graphene hybrid electrode has a much higher NaCl VAC of 14.3 mg/cm3 with a gravimetric adsorption capacity of 19.4 mg/g. It has been demonstrated that the adsorption capacity is significantly enhanced because of the rapid ion transport of MoS2 and high electrical conductivity of graphene. In situ Raman spectra and high-angle annular dark-field scanning transmission electron microscopy tests demonstrated a favorable Faradaic reaction, which was crucial to enhancing the NaCl VAC of the MoS2-graphene hybrid electrode. This work opens a new avenue for miniaturizing future CDI devices.

An integrated large-scale and vertically aligned Co(OH)2 nanosheet@graphite paper electrode for high performance capacitive deionization of saline water

Capacitive deionization (CDI) based on the principle of electrochemical double layers has emerged as a prospective water treatment technology to challenge the water scarcity. Herein, a novel integrated CDI electrode comprised of large-scale and vertically aligned Co(OH)2 nanosheets on the GP matrix (Co(OH)2@GP) has been prepared successfully via a facile hydrothermal strategy for the first time. The texture analyses such as TEM, SEM, XPS, XRD and N2 adsorption indicated that well-grown and interconnected Co(OH)2 nanosheets on the GP matrix ensured the electrode a high specific surface area (207.62 m2/g) and superior open pore network. The electrochemical performance investigated by the CV, EIS and GC techniques revealed that the Co(OH)2@GP electrode combing the merits of Co(OH)2 nanomaterial and GP efficiently obtained the amazing specific capacitance of 411.02 F/g, good electric conductivity and favourable cyclability. Moreover, the CDI behaviour of Co(OH)2@GP electrode evaluated by the batch mode experiments in the 300 mg/L of NaCl solution demonstrated an ultrahigh salt removal capacity of 48.21 mg/g and excellent regeneration ability. The highly simplified electrode processing, free binder and outstanding CDI performance render the Co(OH)2@GP electrode a promising candidate in the highly efficient CDI application.

Capacitive deionization of saline water using graphene nanosphere decorated N-doped layered mesoporous carbon frameworks

Capacitive deionization (CDI) is an alternative water purification technology.

Maxing Out Water Desalination with MXenes

In this issue of Joule, Guoxiu Wang, Yury Gogotsi, and collaborators design and synthesize highly porous MXene electrodes that are resistant to nanosheet restacking and deliver high electroadsorption capacity for capacitive deionization (CDI) of saline water. In CDI cells constructed with aerogel-like Ti3C2Tx MXene electrodes, an adsorption capacity of 118 mg/cm3 (45 mg/g) was achieved in a 10,000 mg/L salt solution, more than one order of magnitude greater than carbon-based electrode materials.

Porous Cryo-Dried MXene for Efficient Capacitive Deionization

Summary Aerogel-like, porous Ti 3 C 2 T x MXene architecture electrode displayed a high electroadsorption capacity for capacitive deionization of saline water. A vacuum freeze-drying process was employed to prevent the restacking of MXene nanosheets due to van der Waals forces, leading to the formation of a porous structure with a large specific surface area. When applied as electrode materials for capacitive deionization, porous MXene demonstrated a high specific capacitance of 156 F/g and a volumetric capacitance of 410 F/cm 3 in 1 M sodium chloride (NaCl) electrolyte. The porous Ti 3 C 2 T x MXene electrodes can deliver a high electroadsorption capacity of 118 mg/cm 3 (45 mg/g) in 10,000 mg/L NaCl solution (applied voltage: 1.2 V) and excellent cycling stability (up to 60 cycles) in comparison with the restacked MXene and activated carbon electrodes, indicating its promising potential for desalination applications.

Capacitive deionization of saline water using sandwich-like nitrogen-doped graphene composites via a self-assembling strategy

Capacitive deionization of saline water using sandwich-like nitrogen-doped graphene composites via a self-assembling strategy has been demonstrated.

Plasma Treated Active Carbon for Capacitive Deionization of Saline Water

The plasma treatment on commercial active carbon (AC) was carried out in a capacitively coupled plasma system using Ar + 10% O2 at pressure of 4.0 Torr. The RF plasma power ranged from 50 W to 100 W and the processing time was 10 min. The carbon film electrode was fabricated by electrophoretic deposition. Micro-Raman spectroscopy revealed the highly increased disorder of sp2 C lattice for the AC treated at 75 W. An electrosorption capacity of 6.15 mg/g was recorded for the carbon treated at 75 W in a 0.1 mM NaCl solution when 1.5 V was applied for 5 hours, while the capacity of the untreated AC was 1.01 mg/g. The plasma treatment led to 5.09 times increase in the absorption capacity. The jump of electrosorption capacity by plasma treatment was consistent with the Raman spectra and electrochemical double layer capacitance. This work demonstrated that plasma treatment was a potentially efficient approach to activating biochar to serve as electrode material for capacitive deionization (CDI).

Chemically exfoliated MoS2 for capacitive deionization of saline water

Capacitive deionization (CDI) is a promising technology for removal of ions from saline water upon applying a voltage between two electrodes. In this work, chemically exfoliated MoS2 (ce-MoS2) has been explored as electrode material for CDI. The ce-MoS2 nanosheets demonstrate a good cycling stability, high ion quality removal capacity of 8.81mg/g, and ion volume removal capacity of 16.51mg/cm3 at 1.2V applied voltage in 400mM NaCl solution. Comparison with that of carbon materials and bulk MoS2, the ce-MoS2 nanosheets remain good removal capacity even at a low concentration of 50mM salt. These results suggest that ce-MoS2 can be a promising candidate for CDI. The sound performance of ce-MoS2 in CDI can be attributed to the unique two-dimensional (2D) thin sheet structure of 1T phase. The large layer-to-layer space and sound electric conductivity help ion intercalation and ion transportation, and the abundant negative charges on the surface of ce-MoS2 sheets enhance the electrostatic attraction of ion.

A novel method for metal oxide deposition on carbon aerogels with potential application in capacitive deionization of saline water

Carbon aerogels doped with manganese or iron oxides were prepared by the resorcinol-formaldehyde method as potential electrodes for the capacitive deionization of sodium chloride from saline water. The solution containing the metal precursors was mixed with the hydrogel before the supercritical drying step ensuring a highly homogeneous dispersion of the nanometric metal oxides as determined by X-ray diffraction and electron microscopy. XPS spectra revealed the increased contribution of hydroxyl and carboxylic groups after the activation process. Also, an enhanced metal oxidation at the outer particle surface was observed. Nitrogen isotherms have revealed a decrease of the pore volume in doped samples ascribed to the partial blocking of the pore structure by the embedded nanometric metal oxide particles.Capacitance values as large as 99 F/g and 91 F/g were respectively recorded for CAGDFeAct and CAGDMnAct by cyclic voltammetry. The large capacitance detected for the iron containing activated aerogel was confirmed by deionization experiments. An electrosorption capacity of 0.133mmol/g was recorded for CAGDFeAct in a 0.025M NaCl solution when 1.5V were applied during the charge period. The study of the kinetic response of the electrodes showed a poor behavior for CAGDMnAct and was correlated to the partial blocking of pore structure exerted by the embedded nanometric metal oxide particles.

Three‐Dimensional Graphene/Metal Oxide Nanoparticle Hybrids for High‐Performance Capacitive Deionization of Saline Water

A novel and general method is proposed to construct three-dimensional graphene/metal oxide nanoparticle hybrids. For the first time, it is demonstrated that this graphene-based composite with open pore structures can be used as the high-performance capacitive deionization (CDI) electrode materials, which outperform currently reported materials. This work will offer a promising way to develop highly effective CDI electrode materials.