Electrode Material For Capacitive Deionization Research Articles

Constructing the quinonyl groups and structural defects in carbon for supercapacitor and capacitive deionization applications

The structural defects and oxygen-containing functional groups of carbon materials as electrode materials for supercapacitors or capacitive deionization devices are critical to their electrochemical performance. The tuning of surface oxygen-containing functional groups and carbon defects during pyrolysis is key to achieve a high performance in ion storage. Herein, quinonyl-dominant defective porous carbon is prepared by a pyrolysis and cross-linking route using lavender stem and potassium acetate as precursor. Benefiting from the presence of abundant defect and surface quinonyl groups, porous carbon shows an ultra-high specific capacitance of 401 F g−1 (1 A g−1) and a high capacitance retention of 63% at a high current density of 100 A g−1 in a KOH solution. Meanwhile, as a capacitive deionization electrode material, it also exhibited a high adsorption capacity of 25.5 mg g−1 in 500 mg L-1 NaCl solution at 1.2 V. Theoretical density functional theory (DFT) calculation demonstrates that surface quinonyl groups and carbon defects can synergistically facilitate the adsorption of K+ and Na+ during the charge/discharge process. This work provides a new perspective for understanding the role of surface oxygen-containing groups and intrinsic defects of porous carbon materials in electrochemical energy storage and desalination applications.

Metal organic framework-derived nitrogen-doped porous carbon sustained Prussian blue analogues for efficient and fast hybrid capacitive deionization

Prussian blue analogues (PBAs) are considered as exceptionally promising faradic electrode materials for next-generation capacitive deionization (CDI) electrodes due to their superior theoretical specific capacity, non-toxic property and simple preparation. However, the desalination performances of PBAs are hampered by their sluggish intrinsic kinetics and insufficient utilization of active sites. Herein, we demonstrate an advanced hybrid material constructed by anchoring nickel hexacyanoferrate (Ni-PBA) onto three-dimensional (3D) nitrogen-doped porous carbon (ZC) derived from zinc-based metal–organic frameworks (MOFs, ZIF-8) polyhedron. ZC with a 3D open structure not only provides multiple spatial supports for the in-situ growth of Ni-PBA with extraordinary redox capacity, but also features high electrical conductivity, excellent hydrophilicity and large surface area to facilitate the electron/ion transport and improve the ion accommodation. Therefore, the Ni-PBA/ZC composite electrode achieves an outstanding CDI desalination performance with an ultrahigh salt adsorption capacity (SAC) of 43.9 mg g−1 and maximum salt adsorption rate (mSAR) of 20.82 mg g−1 min−1, outperforming those of most of the recently reported MOF-derived porous carbon materials and PBAs-based materials. The strategy in this work presents a novel avenue by combining the advantages of MOF-derived porous carbon and redox-active materials for designing high-performance CDI electrode materials.

Enhanced Capacitance and Desalination Performance with Plasma‐Activated Biochar Electrodes

Derived from electric double‐layer capacitors (EDLCs), capacitive deionization (CDI) using symmetric carbon‐based electrodes is an emerging approach to purifying brackish water into drinking water. The deionization performance is mainly determined by the properties of the electrode materials. This work reports a green and efficient plasma treatment for activating raw biochar, which is subsequently used as the electrode material for both EDLCs and CDI. Oxygen plasma activation effectively modulates the surface charge, morphology, and functional groups. Biochar treated with oxygen plasma exhibits pronounced improvement in supercapacitor specific capacitance from 80 to 97.5 F g−1 and 1.2 times higher desalination capacity in comparison with the raw biochar. Plasma activation can be an effective strategy to improving the capacitance and deionization performance of biochar.

Controlled fabrication of nitrogen-doped porous carbon foam with refined hierarchical architectures for desalination via capacitive deionization

Porous carbon materials have been regarded as a promising alternative to activated carbon for desalination via capacitive deionization (CDI) due to refined architectures and functionalities. However, it is still challenging to obtain a controlled hierarchical pore structure and considerable nitrogen-doped content by convenient method. Herein, nitrogen-doped hierarchical porous carbon foams (NHCFs) with different microstructural features, nitrogen contents and nitrogen species were successfully fabricated via a stepwise pyrolysis carbonization strategy using easily available melamine foam. Due to the synergistic effect of hierarchical porous structure and doped nitrogen, the optimized NHCF sample carbonized at 800℃ (NHCF-800) exhibited a maximum desalination capacity of 30.1 mg g−1 at the optimal operating parameters (500 mg/L NaCl solution, 1.2 V) and an excellent regeneration performance after 50 continuous adsorption–desorption cycles. Furthermore, density functional theory (DFT) was also conducted to elaborate the disparity of sodium adsorption energy among the nitrogen species for in-depth understanding, and it mainly benefits from the ascendency of the pyrrolic-N and pyridinic-N over the graphitic-N dopant. This work paves the way of rational regulation of nitrogen-doped process and hierarchical porous structure carbon as CDI electrode materials for desalination.

Platanus acerifolia (Aiton) Willd. fruit-derived nitrogen-doped porous carbon as an electrode material for the capacitive deionization of brackish water

Capacitive deionization (CDI) is a new technology for the desalination of brackish water and its performance is greatly affected by the electrode materials utilized. Biomass-derived carbons have attracted significant attention as CDI materials due to their high availability, inexpensiveness, renewability and eco-friendly characteristics. In this work, Platanus acerifolia (Aiton) Willd. fruit-derived nitrogen-doped porous carbon (sf-APAWx) is prepared through carbonization at 450 °C, followed by NaOH activation at different temperatures of 700, 800 and 900 °C. The sf-CPAW activated at 800 °C possesses a large specific surface area (3846 m2 g−1), affluent pores and a hierarchical structure; and exhibits a high specific capacitance of 138.81 F g−1, a satisfactory salt adsorption capacity of 18.05 mg g−1 and the fastest salt adsorption rate of 1.01 mg g−1 min−1. These results demonstrate the potential of sf-APAW800 as an electrode material for CDI and the sustainable use of abandoned resources.

Two-dimensional bimetallic cobalt-copper metal organic framework for improved desalination performance of capacitive deionization

Capacitive deionization (CDI) technology has recently attracted much attention due to its distinct advantages, which include energy efficiency, eco-friendly method, and simple process. Capacitive materials, such as activated carbon, carbon fiber, and carbon aerogel, have mostly been used. However, the conventional carbon-based materials still suffer limitations, such as low electrosorption capacity, slow desalination rate, and insufficient desalination capacity for high saline concentration. Herein, the 2 Dimensional-Cobalt-Copper sulfur linker-based MOF material was prepared by a solvothermal method to develop the performance of electrode material, namely 2D-CoCu sMOF. We applied the synthesized material with porous carbon material (AC) as an electrode material in the CDI desalination system. Owing to the fast and efficient electron transfer in the electrode layer and the lower interfacial resistance between electrode surface and saline electrolyte originating from the redox reactions of MOF structure, 2D − CoCu sMOF exhibited a much higher desalination performance, compared to the pristine AC. CDI experimental results showed that the salt adsorption capacity (SAC) of electrode using 2D − CoCu sMOF was significantly improved from 4.18 to 7.55 mg/g without any changes in the long-term stability test, which was over an 80% increase in desalination performance. This approach provides an effective and simple method for the preparation of MOF-based CDI electrode material, which could have potential for high-performance green technology including desalination applications.

Designing of a Free-Standing Flexible Symmetric Electrode Material for Capacitive Deionization and Solid-State Supercapacitors

In this work, a highly efficient free-standing flexible electrode material for capacitive deionization and supercapacitors was reported. The reported porous carbon shows a high surface area of 2070.4 m2 g–1 with a pore volume of 0.8208 cm3 g–1. The material exhibited a high specific capacitance of 357 F g–1 at 1 A g–1 in a two-electrode symmetric setup. A solid-state supercapacitor device has been fabricated with a total cell capacitance of 152.5 F g–1 at 1 A g–1 in a solid PVA/H2SO4 gel electrolyte with an energy density of 21.18 W h kg–1 at a 501.63 W kg–1power density. A long-run stability test was carried out up to 15,000 cycles at 5 A g–1 that showed capacitance retention of 99% with ∼100% Coulombic efficiency. Furthermore, the electrosorption experiment was conducted by a flow-through test by coating on commercially available cellulose thread that was employed, which shows electrosorption ability up to 16.5 mg g–1 at 1.2 V in a 500 mg L–1 NaCl solution. Complete experiments were conducted with a proper procedure, provided by scientific approaches with analytical data. Thus, the reported electrode material showed bifunctional application for energy storage and environmental remediation.

Co/Fe co-doped ZIF-8 derived hierarchically porous composites as high-performance electrode materials for Cu2+ ions capacitive deionization

Due to a threat to human life from heavy metal ions pollution, unprecedented interest has been gained in the development of water purification technologies. Here, we explore another new approach to exploit a prospective carbon material for removing copper ions from aqueous solution based on rapid and easy capacitive deionization (CDI). Reasonable carbon materials modification with ideal composition and improved morphological structure is essential to additionally optimize the capabilities of CDI. We prepared a nitrogen-rich hierarchically porous carbon composites (CoFe-NC) with uniform cobalt (Co) and iron (Fe) doped metal in carbon skeleton by a simple impregnation and pyrolysis method, derived from zeolitic imidazolate framework-8, to use as highly effective CDI electrode for copper ions removal. The addition of Fe can facilitate the uniform dispersion of metals, and enable the formation of a stable carbon cage after pyrolysis. It can sufficiently expose active sites of the electrode materials and promote interfacial charge transfer, thus improving CDI electrosorption efficiency. CoFe-NC composites electrode can achieve outstanding deionization capacity (91.31 mg g−1) in 25 mg L−1 CuSO4 solution. The carbon cage structure of CoFe-NC not only prevents aggregation of metals and avoids destruction of rich multistage pore system by pyrolysis, but also induces a faster ions transport rate. In addition, density functional theory calculations demonstrated that the co-doping of Co and Fe can remarkably increase the adsorption energies of Cu2+ ions, leading to excellent selectivity, which indicates that CoFe-NC composites can be a desired CDI electrode material.

Space stability by incorporating iron atoms into the cobalt structure enabling capacitive deionization stability possible

Exploring and designing high performance pseudocapacitance electrode materials is of great significance in enhancing the desalination performance of capacitive deionization (CDI). Transition metal cobalt is considered a prospective electrode material for CDI because of its abundance and high theoretical capacity, which can produce a higher salt removal capacity than pure capacitive materials in the CDI process. However, due to the collapse and loss of the active electrode crystal matrix, the cobalt electrode exhibits poor electrochemical performance. In this work, we used a second metal element, Fe, introduced by ion exchange pyrolysis to regulate the leaching effect and optimize the ion matching for cobalt to protect the electrode structure. In addition, the interconnected external carbon layers form a robust matrix for enhanced electrical conductivity with ion transport. Thanks to the synergistic effect of the cobalt‑iron (Co3Fe7@C) electrode structure and surface engineering, the adsorption capacity reached 72.29 mg·g−1, achieving 110 % capacity retention in 100 cycles of chlorine removal. As a result, the carbon-coated cobalt‑iron bimetallic electrode exhibits excellent dechlorination capabilities in capacity, cycle life and rate capability. This study provides a promising avenue for the design of stable electrode materials for capacitive deionization electrodes.

Synergetic pseudocapacitive sodium capture for efficient saline water desalination by iron oxide Hydroxide-Decorated palladium nanoparticle anchored 3D flowerlike molybdenum sulfide

Capacitive deionization (CDI)-based saline water desalination presents an admirable alternative for sustainable freshwater production. However, the lack of robust electrode materials impedes its wide application. Herein, a three-dimension (3D) heterostructured iron oxide-hydroxide-incorporated palladium nanoparticle-anchored molybdenum disulphide (FeOOH/Pd/MoS2) hybrid constructed by the two-step spontaneous interfacial redox reactions is reported as efficient Faradaic CDI electrode materials for desalination application. The FeOOH/Pd/MoS2 hybrid electrode delivers a superior desalination capacity of 41.1 mg g−1 in a 500 mg L-1 NaCl solution, along with impressive cycling stability and a high capacitive contribution of 80 % at a rate of 1 mV s−1. The synergetic pseudocapacitive removal process is thoroughly clarified by ex-situ XPS characterizations. Experimental analysis and density functional theory calculations reveal that the bi-component participation of FeOOH and Pd can efficiently tailor the electronic structure of MoS2, leading to the reinforcing electronic conductivity toward the promoted Na+ capture feature. Moreover, the hybrid electrode manifests outstanding removal efficiencies up to 91.25 % for diverse heavy metal ions (i.e., Pb2+, Cd2+, Cu2+, Ni2+, and Cr3+), demonstrating its great prospects for low-concentration wastewater purification. This work supplies an ingenious avenue for the rational design of heterostructured MoS2 Faradaic electrodes for advanced CDI desalination.

Silkworm cocoon waste-derived nitrogen-doped hierarchical porous carbon as robust electrode materials for efficient capacitive desalination

Capacitive deionization (CDI) has potential in desalination applications. However, developing a cost-effective and environmental-friendly CDI electrode is still challenging. Here, we report the synthesis of a tailored nitrogen-doped hierarchical porous carbon (NPC) derived from the waste silkworm cocoon and its promising use as a CDI electrode for desalination applications. Results show that both the graphitic N contents and defects (from ID/IG values) within NPC-x regulated the intrinsic resistance and conductivity of NPC-x electrodes, thus giving graphitic N contents and defects-dependent CDI desalination performance. The optimized NPC-1.5 electrode exhibited an electrosorption capacity of 22.19 mg g−1 with an average desalination rate of 1.1 mg g−1 min−1 (100 mg L−1 of NaCl solution, an applied voltage of 1.2 V, and a flow rate of 40 mL min−1). Such desalination performance is superior to the commonly reported activated carbon and other porous carbon electrodes under similar desalination conditions. Moreover, the optimized electrode can still maintain 97 % of its initial electrosorption capacity even after 50 cycles, indicating its outstanding reusability in the desalination application. This work shows a promising CDI electrode material of silkworm cocoon waste-derived porous carbon with highly efficient desalination performance, which will spark more efforts in the development of resource utilization-oriented desalination technologies.

Evaluation of the Specific Capacitance of High-Entropy Oxide-Based Electrode Materials in View of Their Use for Water Desalination via Capacitive Method

Water pollution and scarcity are serious concerns for the growing world population. To meet the ever-pressing demand of fresh water, a variety of desalting techniques of seawater have been developed. Due to its environmental friendliness, high efficiency, easy regeneration of the electrodes, ambient operating pressure, and low operating potential suitable for the use in remote areas, the capacitive deionization (CDI) method is one of the most sustainable among them. This work focuses on the preparation of high-entropy oxides (HEOs) and carbon/HEO composites and the evaluation of their specific capacitance in view of their possible use as CDI electrode materials. CrMnFeCoNi-HEO, having spinel structure (sHEO), is obtained in the form of nanoparticles (NPs) and nanofibers (NFs) by the sol–gel method and electrospinning, respectively. Composite NFs with embedded sHEO NPs or MgCoNiCuZn-HEO NPs with rock-salt structure (rHEO) are also produced. In the 5–100 mV s−1 scan rate range, the specific capacitance improves in the order C/rHEO NFs (8–32 F g−1) ≅ sHEO NPs (9–32 F g−1) < sHEO NFs (8–43 F g−1) < C/sHEO NFs (12–66 F g−1). The highest capacitance is obtained when the beneficial contributions of the carbon matrix and smaller-sized HEO NPs are synergistically coupled.

Graphene oxide electrode for unusual water softening in capacitive deionization

With the depleting freshwater resources and increasing demand for potable water, brackish water sources are potential sources for obtaining potable water due to their availability and low salt concentration. Various technologies are employed to treat the brackish water among which the Capacitive deionization (CDI) is an energy-efficient technique to achieve this due to its high regeneration and reuse capability, low voltage requirement, no pressure requirement, and scalability. The major bottlenecks in this pursuit involve limited desalination capacities and high costs. Here, we demonstrate the use of graphene oxide (GO) as an efficient and inexpensive electrode material for CDI. The hydrophilic nature of GO enables the interaction of hydrolyzed ions in water with the GO surface and reduces electrode-water resistance. The oxygen-containing groups in GO store pseudo charge making it useful for CDI. GO electrodes show a desalination capacity of ∼ 230 mg/g, which is the highest among all carbon-based materials at a high flow rate of ∼ 720 ml/min for 1000 ppm sodium chloride feed solution operating at a cell potential of 1 V. The salt adsorption capacity of GO increases with increasing ionic charges as Na+ < Mg2+ < Fe3+. Excellent recyclability and complete regeneration of electrodes along with high salt adsorption capacity underline the potential of GO electrodes to achieve high capacity, high rate, and efficient CDI.

Spinel LiMn2O4 as a Capacitive Deionization Electrode Material with High Desalination Capacity: Experiment and Simulation.

Capacitive deionization (CDI) is a newly developed desalination technology with low energy consumption and environmental friendliness. The surface area restricts the desalination capacities of traditional carbon-based CDI electrodes while battery materials emerge as CDI electrodes with high performances due to the larger electrochemical capacities, but suffer limited production of materials. LiMn2O4 is a massively-produced lithium-ion battery material with a stable spinel structure and a high theoretical specific capacity of 148 mAh·g-1, revealing a promising candidate for CDI electrode. Herein, we employed spinel LiMn2O4 as the cathode and activated carbon as the anode in the CDI cell with an anion exchange membrane to limit the movement of cations, thus, the lithium ions released from LiMn2O4 would attract the chloride ions and trigger the desalination process of the other side of the membrane. An ultrahigh deionization capacity of 159.49 mg·g-1 was obtained at 1.0 V with an initial salinity of 20 mM. The desalination capacity of the CDI cell at 1.0 V with 10 mM initial NaCl concentration was 91.04 mg·g-1, higher than that of the system with only carbon electrodes with and without the ion exchange membrane (39.88 mg·g-1 and 7.84 mg·g-1, respectively). In addition, the desalination results and mechanisms were further verified with the simulation of COMSOL Multiphysics.

Large gap cobalt‑vanadium oxide structure encapsulated in porous carbon for high performance capacitive deionization

The application of traditional electrode materials for high-performance capacitive deionization (CDI) has been persistently limited by their low charge-storage capacities and slow salt removal rates. In order to improve the electrochemical performance, cobalt‑vanadium coated porous carbon gradient hollow spheres (Co3V2O8@C) with large internal spacing, and high pore structure was prepared in this paper to improve the ion mobility. The structure with the following characteristics: (1) Co3V2O8@C with a reversible ionic insertion/de-insertion and good electrical conductivity; (2) the increased lattice spacing effectively mitigates volume expansion during prolonged cycling; (3) it increases the utilization rate of the active center inside the electrode material and shows high electrochemical adsorption capacity by being applied to capacitive deionization. When applied to CDI, Co3V2O8@C has top CDI performance compared to the currently reported cobalt-based electrode materials. The holding capacities for different ions (Cl−, SO42−, NO3−, and Na+) were 160, 161, 244, and 69 mg·g−1 with good cycling stability after 100 h. Our research provides a reasonable pathway for building the structure of high-capacity cobalt-based electrodes and further promoting the development of high-performance CDI electrode materials.

Review on 2D MXene and graphene electrodes in capacitive deionization

The development of the electrochemical desalination technique for saline water by the capacitive deionization (CDI) process is progressing with ever-increasing interest. In the CDI technology, the saline water flows through the spacer sandwiched between the pair of electrodes, and the ions are captured and stored within electric double layers (EDLs) when a voltage between 0.5–2.0 V is applied. When the voltage is reversed or removed, adsorbed ions are released, and electrodes are regenerated. Carbon materials-based electrodes show effective, but limited electrosorption capacity as the ions are removed based on the EDL mechanism only. There is a demand for new advanced materials that can enhance the electrosorption performance of the CDI. The improvement can be achieved by involving other electrosorption mechanisms such as redox pseudocapacitance and intercalation pseudocapacitance mechanisms. Graphene is a 2D nanosheet material, it has a laminar structure and can be stacked up to form slip shape pores in the electrode and allow easy ion motions than other random porous materials. Graphene can also be prepared into a 3D graphene sponge as an interconnected framework. MXene is a new group of materials made of 2D transition metal nitrides, carbides, and carbonitrides. It has exhibited a significant pseudocapacitance behavior, outpacing the energy storage capacity of many other capacitive materials, particularly when normalizing to the electrode’s volume. This review discusses (1) the recent advances in graphene materials and their limitation for enhanced desalination performance and (2) the state-of-the-art art developments of MXene as an emerging material for CDI. • The recent advances and limitations of graphene and MXene as CDI electrodes. • Redox and ion intercalation pseudocapacitance mechanisms are employed in CDI. • Graphene nanosheets and 3D sponges have a laminar structure allowing easy ion motion. • MXene has exhibited an outstanding pseudocapacitance behaviour behavior as electrodes. • The state-of-the-art developments of MXene as an emerging CDI electrode materials.

Linking macroscopic surface morphology of activated carbon fibres and electrosorption performance: An electrochemical impedance spectroscopy and capacitive deionization study

Activated carbon fibres (ACFs) are successful electrode materials for capacitive deionization (CDI) owing to their excellent electrochemical properties and commercial availability, for example, with knitted or woven morphology patterns. However, the lack of a common and effective analytical framework to analyse the performance of ACFs is hindering further progress in the area. This study establishes an electrochemical impedance-based method to detect and investigate the electrochemical properties of ACF materials without destroying their original weaving patterns. Five commercial ACFs with two distinct patterns and similar specific surface areas were investigated. Data from electrochemical impedance spectroscopy (EIS) are compared to the desalination performance and energy consumption of the ACFs in a CDI cell. The weaving pattern played a role in the electrochemical properties and desalination performance. The volume-salt adsorption capacities in CDI were related to the volume-specific capacities in EIS, however, there was no significant difference between knitted and woven materials. Linked to EIS features, knitted ACFs consume less energy than woven ACFs for removing the same amount of NaCl from water. These results provide ACF researchers with a new, effective, and readily available approach for measuring the electrochemical performance of ACF materials via EIS.

Capacitive removal of Pb ions via electrosorption on novel willow biochar–manganese dioxide composites

ABSTRACT Biochar derived from lignocellulosic biomass has been used as a low-cost adsorbent in wastewater treatment applications. Due to its rich porous structure and good electrical conductivity, biochar can be used as a cost-effective electrode material for capacitive deionization of water. In this work, willow biochar was prepared through carbonization of shrub willow chips, activated with potassium hydroxide, and loaded with manganese dioxide (WBC-K-MnO2 nanocomposite). The prepared materials were used to electrochemically adsorb Pb2+ from aqueous solutions. Under the applied potential of 1.0 V, the WBC-K-MnO2 electrode exhibited a high Pb2+ specific electrosorption capacity (23.3 mg/g) as compared to raw willow biochar (4.0 mg/g) and activated willow biochar (9.2 mg/g). KOH activation followed by MnO2 loading on the surface of raw biochar enhanced its BET surface area (178.7 m2/g) and mesoporous volume ratio (42.1%). Moreover, the WBC-K-MnO2 nanocomposite exhibited the highest specific capacitance value of 234.3 F/g at a scan rate of 5 mV/s. The electrosorption isotherms and kinetic data were well explained by the Freundlich and pseudo-second order models, respectively. The WBC-K-MnO2 electrode demonstrated excellent reusability with a Pb2+ electrosorption efficiency of 76.3% after 15 cycles. Thus, the WBC-K-MnO2 nanocomposite can serve as a promising candidate for capacitive deionization of heavy metal contaminated water.

Enhanced capacitive deionization properties of activated carbon doped with carbon nanotube-bridged molybdenum disulfide

The shortage of freshwater supplies has restricted societal development. Capacitive deionization (CDI) is an emerging technology for desalination of seawater or brackish water, the performance of which is highly dependent on electrode materials. In this work, a molybdenum disulfide/carbon nanotube composite (CNTs-b-MoS2) with high capacitance was successfully synthesized using a hydrothermal method. The composite exhibited a specific capacitance of 112.79 F g−1. To reduce costs and determine the practicality of using CNTs-b-MoS2 for CDI, we combined activated carbon (AC) with CNTs-b-MoS2 as a CDI electrode. The research demonstrated that after doping with 5% (mass ratio) CNTs-b-MoS2, the specific capacitance and electrosorption capacity of AC were significantly improved and the maximum desalination capacity of CNTs-b-MoS2/AC reached 8.19 mg g−1. The low dosage of CNTs-b-MoS2 combined with the high specific surface area of AC avoided the shortcomings of CNTs-b-MoS2, namely low specific surface area and high cost. Moreover, the outstanding conductivity of CNTs-b-MoS2 improved the conductivity and enhanced the adsorption capacity of AC, giving CNTs-b-MoS2/AC potential as an advanced, low-cost CDI electrode material.

Enhanced electrochemical and capacitive deionization performances of single-layer graphene oxide/nitrogen-doped porous carbon/activated carbon fiber composite electrodes

Capacitive deionization (CDI) is an electrosorption desalination technology based on electrode charge surface, where CDI electrode materials play important roles in efficient desalination processes. This study created and manufactured innovative single-layer graphene oxide (SGO), nitrogen-doped porous carbon (NPC), and activated carbon fiber (ACF) composites to produce SGO/NPC/ACF electrode materials with electrochemical and CDI performances. The SGO/NPC/ACF electrode combined the stability of NPC with the high conductivity of SGO to yield enhanced electrochemical and CDI activities. The samples have been characterized using XRD, SEM, and XPS. The electrochemical performance was tested by cyclic voltammetry and electrochemical impedance spectroscopy methods. As a result, SGO/NPC/ACF showed a high specific capacitance of 323.08 F g−1. The specific surface area of SGO/NPC/ACF is 1154.91 m2 g−1. The salt adsorption capacity (SAC) of the SGO/NPC/ACF composite electrode is 16.25 mg g−1, which is about 1.5 times (10.70 mg g−1) that of the ACF electrode. After fifty adsorption/desorption treatments, the SAC retention of the SGO/NPC/ACF electrode is 1.6 times higher than that of ACF. Our work also provides a theoretical basis for the efficient development of green carbon-based composites. Therefore, the SGO/NPC/ACF electrode has good cycle stability and reproducibility, which is expected to become a practical CDI electrode material for desalination.