Enhanced nitrate removal from groundwater using a conductive spacer in flow-electrode capacitive deionization

Flow-electrode capacitive deionization(FCDI)represents a promising approach for ion separation from aqueous solutions.However,the optimization of spacer,particularly for nitrate-contaminated groundwa-ter systems,has often been overlooked.This research comprehensively investigates the influence of using a conductive(carbon cloth,CC)spacer on nitrate removal performance within FCDI system,comparing it to a non-conductive(nylon net,NN)spacer.In both CC and NN FCDI systems,it is unsurprisingly that nitrate removal efficiency improved notably with the increasing current density and hydraulic retention time(HRT).Interestingly,the specific energy consumption(SEC)for nitrate removal did not show obvious fluctuations when the current density and HRT varied in both systems.Under the auspiciously optimized process parameters,CC-FCDI attained a 20%superior nitrate removal efficiency relative to NN-FCDI,ac-companied by a notably diminished SEC for CC-FCDI,registering at a mere 28%of NN-FCDI.This great improvement can be primarily attributed to the decrement in FCDI internal resistance after using con-ductive spacer,which further confirmed by electrochemical tests such as linear sweep voltammetry(LSV)and electrochemical impedance spectroscopy(EIS).Upon prolonged continuous nitrate removal at the optimized conditions,the CC-FCDI system achieved a consistent 90%nitrate removal efficiency with a low SEC of 2.7-7.8 kWh/kg NO_(3)-N,underscoring its steady performance.Overall,this study highlights the pivotal importance of careful spacer design and optimization in realizing energy-efficient groundwater treatment via FCDI.

Enhancing capacitive deionization performance and cyclic stability of nitrogen-doped activated carbon by the electro-oxidation of anode materials

Electrode materials with high desalination capacity and long-term cyclic stability are the focus of capacitive deionization(CDI) community. Understanding the causes of performance decay in traditional carbons is crucial to design a high-performance material. Based on this, here, nitrogen-doped activated carbon(NAC) was prepared by pyrolyzing the blend of activated carbon powder(ACP) and melamine for the positive electrode of asymmetric CDI. By comparing the indicators changes such as conductivity, salt adsorption capacity, pH, and charge efficiency of the symmetrical ACP-ACP device to the asymmetric ACP-NAC device under different CDI cycles, as well as the changes of the electrochemical properties of anode and cathode materials after long-term operation, the reasons for the decline of the stability of the CDI performance were revealed. It was found that the carboxyl functional groups generated by the electro-oxidation of anode carbon materials make the anode zero-charge potential(E_(pzc)) shift positively,which results in the uneven distribution of potential windows of CDI units and affects the adsorption capacity. Furthermore, by understanding the electron density on C atoms surrounding the N atoms, we attribute the increased cyclic stability to the enhanced negativity of the charge of carbon atoms adjacent to quaternary-N and pyridinic-oxide-N.

Development of Cd-doped Co Nanoparticles Encapsulated in Graphite Shell as Novel Electrode Material for the Capacitive Deionization Technology

Because of the low energy requirement and the environmentally safe byproducts, the capacitive deionization water desalination technology has attracted the attention of many researchers. The important requirements for electrode materials are good electrical conductivity, high surface area, good chemical stability and high specific capacitance. In this study, metallic nanoparticles that are encapsulated in a graphite shell(Cd doped Co/C NPs) are introduced as the new electrode material for the capacitive deionization process because they have higher specific capacitance than the pristine carbonaceous materials. Cd doped Co/C NPs perform better than graphene and the activated carbon. The introduced nanoparticles were synthesized using a simple sol gel technique. A typical sol gel composed of cadmium acetate, cobalt acetate and poly(vinyl alcohol)was prepared based on the polycondensation property of the acetates. The physiochemical characterizations that were used confirmed that the drying, grinding and calcination in an Ar atmosphere of the prepared gel produced the Cd doped Co nanoparticles, which were encapsulated in a thin graphite layer. Overall, the present study suggests a new method to effectively use the encapsulated bimetallic nanostructures in the capacitive deionization technology.

Atomic layer deposition of TiO_(2) on carbon-nanotubes membrane for capacitive deionization removal of chromium from water

Chromium(Cr)is a common heavy metal that has severe impacts on the ecosystem and human health.Capacitive deionization(CDI)is an environment-friendly and energy-efficient electrochemical purification technology to remove Cr from polluted water.The performance of CDI systems relies primarily on the properties of electrodes.Carbon-nanotubes(CNTs)membranes are promising candidates in creating advanced CDI electrodes and processes.However,the low electrosorption capacity and high hydrophobicity of CNTs greatly impede their applications in water systems.In this study,we employ atomic layer deposition(ALD)to deposit TiO_(2) nanoparticulates on CNTs membranes for preparing electrodes with hydrophilicity.The TiO_(2)-deposited CNTs membranes display preferable electrosorption performance and reusability in CDI processes after only 20 ALD cycles deposition.The total Cr and Cr(VI)removal efficiencies are significantly improved to 92.1%and 93.3%,respectively.This work demonstrates that ALD is a highly controllable and simple method to produce advanced CDI electrodes,and broadens the application of metal oxide/carbon composites in the electrochemical processes.

Ionic Group Derivitized Nano Porous Carbon Electrodes for Capacitive Deionization

Capacitance for electrostatic adsorption forms primarily within a Debye length of the electrode surface. Capacitive carbon electrodes were derivatized with ionic groups by means of adsorbing a surfactant in order to test the theory that attached ionic groups would exclude co-ions and increase coulombic efficiency without the need for an added charge barrier membrane. It has been discovered that capacitive electrodes surface derivatized with ionic groups become polarized and intrinsically more coulombically efficient.

Effective Modified Carbon Nanofibers as Electrodes for Capacitive Deionization Process

Carbon materials have the advantages of good electrical conductivity and excellent chemical stability, so many carbon materials have been introduced as electrodes for the capacitive deionization (CDI) process. Due to the low surface area compared to the other nanocarbonaceous materials, CNFs performance as electrode in the CDI units is comparatively low. This problem has been overcome by preparing high surface area carbon nanofibers and by creating numerous long pores on the nanofibers surface. The modified CNFs have been synthesized using low cost, high yield and facile method;electrospinning technique. Stabilization and graphitization of electrospun nanofiber mats composed of polyacrylonitrile (PAN) and poly (methyl methacrylate) (PMMA) leads form longitudinal pores CNFs. The utilized characterizations indicated that the CNFs obtained from electrospun solution having 50% PMMA have surface area of 181 m2/g which are more than the conventional CNFs. Accordingly, these nanofibers revealed salt removal efficiency of ~90% and specific capacitance of 237 F/g.

Boosting Capacitive Deionization Performance of Commercial Carbon Fibers Cloth via Structural Regulation Based on Catalytic-Etching Effect

Monolithic carbon electrodes with robust mechanical integrity and porous architecture are highly desired for capacitive deionization but remain challenging.Owing to the excellent mechanical strength and electroconductivity,commercial carbon fibers cloth demonstrates great potential as high-performance electrodes for ions storage.Despite this,its direct application on capacitive deionization is rarely reported in terms of limited pore structure and natural hydrophobicity.Herein,a powerful metal-organic framework-engaged structural regulation strategy is developed to boost the desalination properties of carbon fibers.The obtained porous carbon fibers features hierarchical porous structure and hydrophilic surface providing abundant ions-accessible sites,and continuous graphitized carbon core ensuring rapid electrons transport.The catalytic-etching mechanism involving oxidation of Co and subsequent carbonthermal reduction is proposed and highly relies on annealing temperature and holding time.When directly evaluated as a current collector-free capacitive deionization electrode,the porous carbon fibers demonstrates much superior desalination capability than pristine carbon fibers,and remarkable cyclic stability up to 20 h with negligible degeneration.Particularly,the PCF-1000 showcases the highest areal salt adsorption capacity of 0.037 mg cm^(−2) among carbon microfibers.Moreover,monolithic porous carbon fibers-carbon nanotubes with increased active sites and good structural integrity by in-situ growth of carbon nanotubes are further fabricated to enhance the desalination performance(0.051 mg cm^(−2)).This work demonstrates the great potential of carbon fibers in constructing high-efficient and robust monolithic electrode for capacitive deionization.

Exploration of the Exceptional Capacitive Deionization Performance of CoMn_(2)O_(4) Microspheres Electrode

The“battery type”inorganic electrode has been demonstrated the highly efficient sodium ion intercalation capacity for capacitive deionization.In this work,the CoMn_(2)O_(4)(CMO)microspheres with porous core-shell structure are prepared via co-precipitation and followed by annealing.The effects of annealing temperatures on the morphology,pore structure,valence state,and electrochemical behavior of CMO are explored.As electrode for capacitive deionization,the salt removal capacity and current efficiency of optimized AC||CMO device reaches up to 60.7 mg g^(−1) and 97.6%,respectively,and the capacity retention rate is 74.1%after 50 cycles.Remarkably,both the in-situ X-ray diffraction and ex-situ X-ray diffraction analysis features that the intercalation/de-intercalation of sodium ions are governed by(103)and(221)crystal planes of CMO.Accordingly,the density functional theory calculations realize that the adsorption energies of Na+onto(103)and(221)crystal planes are higher than that of any other crystal planes,manifesting the priorities in adsorption of sodium atoms.Furthermore,the X-ray photoelectron spectra of pristine and post-CMO electrode highlights that the reversible conversion of Mn^(3+)/Mn^(4+)couple is resulted from the intercalation/de-intercalation of Na^(+),while this is irreversible for Co^(3+)/Co^(2+)couple.Beyond that,the CMO electrode has been proven the selectivity removal of Na^(+) over K^(+)and Mg^(2+)in a multi-cation stream.

Synthesis and electrochemical behavior of monolayer-Ti_(3)C_(2)T_(x) for capacitive deionization

MXene materials have got great attention from researchers of environmental treatment for the great electrochemical performance.Monolayer-Ti_(3)C_(2)T_(x)(T_(x) is the surface terminal groups such as-O,-OH and/or-F species),as a typical structural MXene,always shows better chemical-physical characteristics than multilayer-Ti_(3)C_(2)T_(x).Thus,we prepared monolayer-Ti_(3)C_(2)T_(x) electrode by HF etching method and absolute ethyl alcohol intercalationdelamination treatment for capacitive deionization(CDI).The prepared monolay-Ti_(3)C_(2)T_(x) shows a higher specific surface area(235.6 m^(2)/g)and a thinner thickness(0.8 nm).Moreover,a series of systematic investigation demonstrated that monolayer-Ti_(3)C_(2)T_(x) has obvious promotional phenomenon on electrochemical properties(e.g.,mass specific capacitance increased from 52.1 F/g to 144.7 F/g).The NaCl adsorption capacity of monolayer-Ti_(3)C_(2)T_(x),is 30.7 mg/g in 1000 mg/L NaCl solution at 1.2 V.We concluded that the electro-sorption mechanism could be expressed as double electric layer and monolayer coverage by a good fitting of Langmuir isotherms and the pseudo-second-order kinetics equation.This work would provide a new strategy for the application of monolayer-Ti_(3)C_(2)T_(x) material in wastewater treatment in the future.

Adsorption properties of Ⅴ(Ⅳ) on resin-activated carbon composite electrodes in capacitive deionization

Composite electrodes prepared by cation exchange resins and activated carbon(AC)were used to adsorb Ⅴ(Ⅳ)in capacitive deionization(CDI).The electrode made of middle resin size(D860/AC M)had the largest specific surface area and mesoporous content than two other composite electrodes.Electrochemical analysis showed that D860/AC M presents higher specific capacitance and electrical double layer capacitor than the others,and significantly lower internal diffusion impedance.Thus,D860/AC M exhibits the highest adsorption capacity and rate of Ⅴ(Ⅳ)among three electrodes.The intra-particle diffusion model fits well in the initial adsorption stage,while the liquid film diffusion model is more suitable for fitting at the later stage.The pseudo-second-order kinetic model is suited for the entire adsorption process.The adsorption of Ⅴ(Ⅳ)on the composite electrode follows that of the Freundlich isotherm.Thermodynamic analysis indicates that the adsorption of Ⅴ(Ⅳ)is an exothermic process with entropy reduction,and the electric field force plays a dominant role in the CDI process.This work aims to improve our understanding of the ion adsorption behaviors and mechanisms on the composite electrodes in CDI.

Desalination Alternative Technology in Conjunction with Membrane Capacitive Deionization (MCDI): A Literature Review Article

Water and energy shortages came due to rapid population growth, living standards and rapid development in the agriculture and industrial sectors. Desalination tends to be one of the most promising water solutions;however, it is a process of intense energy. Membrane Capacitive Deionization (MCDI) has received considerable interest as a promising desalination technology, and MCDI research has increased significantly over the last 10 years. In addition, there are no guidelines for the design of Capacitive Deionization (CDI) implementation strategies for individual applications. This study, therefore;provides an alternative of CDI’s recent application developments, with emphasis placed on hybrid systems to address the technological needs of different relevant fields. The MCDI’s energy consumption is compared with the reverse osmosis literature data based on experimental data from laboratory-scale system. The study demonstrates that MCDI technology is a promising technology in the next few years with an extreme competition in water recovery, energy consumption and salt removal for reverse osmosis.

Integration of pore structure modulation and B,N co-doping for enhanced capacitance deionization of biomass-derived carbon

Biomass-derived carbon has demonstrated great potentials as advanced electrode for capacitive deionization(CDI),owing to good electroconductivity,easy availability,intrinsic pores/channels.However,conventional simple pyrolysis of biomass always generates inadequate porosity with limited surface area.Moreover,biomass-derived carbon also suffers from poor wettability and single physical adsorption of ions,resulting in limited desalination performance.Herein,pore structure optimization and element co-doping are integrated on banana peels(BP)-derived carbon to construct hierarchically porous and B,N co-doped carbon with large ions-accessible surface area.A unique expansionactivation(EA)strategy is proposed to modulate the porosity and specific surface area of carbon.Furthermore,B,N co-doping could increase the ions-accessible sites with improved hydrophilicity,and promote ions adsorption.Benefitting from the synergistic effect of hierarchical porosity and B,N co-doping,the resultant electrode manifest enhanced CDI performance for NaCl with large desalination capacity(29.5 mg g^(-1)),high salt adsorption rate(6.2 mg g^(-1)min^(-1)),and versatile adsorption ability for other salts.Density functional theory reveals the enhanced deionization mechanism by pore and B,N co-doping.This work proposes a facile EA strategy for pore structure modulation of biomass-derived carbon,and demonstrates great potentials of integrating pore and heteroatoms-doping on constructing high-performance CDI electrode.

Locally Enhanced Flow and Electric Fields Through a Tip Effect for Efficient Flow‑Electrode Capacitive Deionization

Low-electrode capacitive deionization(FCDI)is an emerging desalination technology with great potential for removal and/or recycling ions from a range of waters.However,it still suffers from inefficient charge transfer and ion transport kinetics due to weak turbulence and low electric intensity in flow electrodes,both restricted by the current collectors.Herein,a new tip-array current collector(designated as T-CC)was developed to replace the conventional planar current collectors,which intensifies both the charge transfer and ion transport significantly.The effects of tip arrays on flow and electric fields were studied by both computational simulations and electrochemical impedance spectroscopy,which revealed the reduction of ion transport barrier,charge transport barrier and internal resistance.With the voltage increased from 1.0 to 1.5 and 2.0 V,the T-CC-based FCDI system(T-FCDI)exhibited average salt removal rates(ASRR)of 0.18,0.50,and 0.89μmol cm^(-2) min^(-1),respectively,which are 1.82,2.65,and 2.48 folds higher than that of the conventional serpentine current collectors,and 1.48,1.67,and 1.49 folds higher than that of the planar current collectors.Meanwhile,with the solid content in flow electrodes increased from 1 to 5 wt%,the ASRR for T-FCDI increased from 0.29 to 0.50μmol cm^(-2) min^(-1),which are 1.70 and 1.67 folds higher than that of the planar current collectors.Additionally,a salt removal efficiency of 99.89%was achieved with T-FCDI and the charge efficiency remained above 95%after 24 h of operation,thus showing its superior long-term stability.

Kinetic-Thermodynamic Promotion Engineering toward High-Density Hierarchical and Zn-Doping Activity-Enhancing ZnNiO@CF for High-Capacity Desalination

Despite the promising potential of transition metal oxides(TMOs)as capacitive deionization(CDI)electrodes,the actual capacity of TMOs electrodes for sodium storage is significantly lower than the theoretical capacity,posing a major obstacle.Herein,we prepared the kinetically favorable Zn_(x)Ni_(1−x)O electrode in situ growth on carbon felt(Zn_(x)Ni_(1−x)O@CF)through constraining the rate of OH^(−)generation in the hydrothermal method.Zn_(x)Ni_(1−x)O@CF exhibited a high-density hierarchical nanosheet structure with three-dimensional open pores,benefitting the ion transport/electron transfer.And tuning the moderate amount of redox-inert Zn-doping can enhance surface electroactive sites,actual activity of redox-active Ni species,and lower adsorption energy,promoting the adsorption kinetic and thermodynamic of the Zn_(0.2)Ni_(0.8)O@CF.Benefitting from the kinetic-thermodynamic facilitation mechanism,Zn_(0.2)Ni_(0.8)O@CF achieved ultrahigh desalination capacity(128.9 mgNaCl g^(-1)),ultra-low energy consumption(0.164 kW h kgNaCl^(-1)),high salt removal rate(1.21 mgNaCl g^(-1) min^(-1)),and good cyclability.The thermodynamic facilitation and Na^(+)intercalation mechanism of Zn_(0.2)Ni_(0.8)O@CF are identified by the density functional theory calculations and electrochemical quartz crystal microbalance with dissipation monitoring,respectively.This research provides new insights into controlling electrochemically favorable morphology and demonstrates that Zn-doping,which is redox-inert,is essential for enhancing the electrochemical performance of CDI electrodes.

A novel flow electrode capacitive deionization device with spindle-shaped desalting chamber

Flow-electrode capacitive deionization(FCDI)is an innovative technology in which an intermediate chamber plays an important role in the desalination process.However,relatively few studies have been conducted on the structures of these intermediate chambers.In this study,we propose a novel flow-electrode capacitive deionization device with a spindle-shaped inlet chamber(S-FCDI).The desalination rate of the S-FCDI under optimal operating conditions was 36%higher than that of the FCDI device with a conventional rectangular chamber(R-FCDI).The spindle-shaped chamber transferred 1.2μmol more ions than the rectangular chamber,based on energy per joule.Additionally,we performed a detailed analysis of different inlet chamber shapes using computational fluid dynamics software.We concluded that S-FCDI has a relatively low flow resistance and almost no stagnation zone.This provides unique insights into the development of intermediate chambers.This study may contribute to the improvement of the desalination performance in industrial applications of FCDI.

Hierarchically porous biochar derived from aerobic granular sludge for high-performance membrane capacitive deionization

Membrane capacitive deionization(MCDI)is a cost-effective desalination technique known for its low energy consumption.The performance of MCDI cells relies on the properties of electrode materials.Activated carbon is the most widely used electrode material.However,the capacitive carbon available on the market is often expensive.Here,we developed hierarchically porous biochar by combining carbonization and activation processes,using easily acquired aerobic granular sludge(AGS)from biological sewage treatment plants as a precursor.The biochar had a specific surface area of 1822.07 m^(2)g^(-1),with a micropore area ratio of 58.65%and a micropore volume of 0.576 cm3 g^(-1).The MCDI cell employing the biochar as electrodes demonstrated a specific adsorption capacity of 34.35 mg g^(-1),comparable to commercially available activated carbon electrodes.Our study presents a green and sustainable approach for preparing highly efficient,hierarchically porous biochar from AGS,offering great potential for enhanced performance in MCDI applications.

A confinement strategy to in-situ prepare a peanut-like N-doped, C-wrapped TiO_(2) electrode with an enhanced desalination capacity and rate for capacitive deionization

Capacitive deionization(CDI)technology has been considered a promising desalination technique,especially for brackish water,because of its relatively low energy consumption,facile operation,and easy regeneration of electrodes.However,the desalination capacity,cost,fabrication method,electrochemical stability,and environmental unfriendliness of the electrodes have restricted the practical application of the CDI technique.Herein,we reported the one-step in situ preparation of nitrogen-doped and carbon-decorated MXene-derived TiO_(2)(termed N-TiO_(2−x)/C)through the confinement-growth strategy.The small particle size(∼25 nm)and uniform distribution of a peanut-like N-TiO_(2−x)/C material could be ascribed to the confined growth space created by the nanoporous structure of melamine foam.The defects produced by N doping provide an enhanced electrical conductivity and more adsorption sites,while wrapping with a carbon shell layer increases the conductivity and offers protection for N-TiO_(2−x) to achieve an excellent electrochemical stability.The prepared N-TiO_(2−x)/C electrode is hydrophilic due to the abundant oxygen-containing functional groups(e.g.,C-O,N-Ti-O,-NO_(x),and-OH)and exhibits a high salt removal capacity(33.4 mg·g^(−1)),desalination rate(1.5 mg·g^(−1)·min^(−1)),and remarkable cycling stability(without declining after 100 cycles),which might be ascribed to the synergistic effects of the short ion diffusion path,more active adsorption sites,enhanced conductivity,pseudocapacitive behavior,and protection of the carbon shell layer.This work provides a confined-growth strategy to develop MXene-derived oxide electrodes for electrochemical desalination.

Investigation of adsorption/desorption behavior of Cr(Ⅵ) at the presence of inorganic and organic substance in membrane capacitive deionization(MCDI)

The adsorption and desorption behavior of Cr(Ⅵ) in membrane capacitive deionization(MCDI) was investigated systematically in the presence of bovine serum albumin(BSA) and KCl with different concentrations, respectively. Results revealed that Cr(Ⅵ) absorption was enhanced and the adsorption amount for Cr(Ⅵ) increased from 155.7 to 190.8 mg/g when KCl concentration increased from 100 to 200 mg/L in the adsorption process, which was attributed to the stronger driving force. However, the adsorption amount sharply decreased to 90.2 mg/g when KCl concentration reached up to 1000 mg/L suggesting the negative effect for Cr(Ⅵ) removal that high KCl concentration had. As for the effect of BSA on ion adsorption, the amount for Cr(Ⅵ) significantly declined to 78.3 mg/g and p H was found to be an important factor contributing to this significant reduction. Then, the desorption performance was also conducted and it was obtained that the presence of KCl had negligible effect on Cr(Ⅵ) desorption, while promoted by the addition of BSA. The incomplete desorption was obtained and the residual chromium ions onto the electrode after desorption was detected via energy-dispersive X-ray spectroscopy(EDS). Based on above analysis, the enhanced removal mechanism for Cr(Ⅵ) in MCDI was found to be consisted of ion adsorption onto electrode surface, the redox reaction of Cr(Ⅵ) into Cr(III)and precipitation, which was demonstrated by X-ray photoelectron spectroscopy(XPS) and scanning electron microscope(SEM).

Nitrogen-enriched micro-mesoporous carbon derived from polymers organic frameworks for high-performance capacitive deionization

Nitrogenization is an effective method for improving the capacitive deionization(CDI)performance of porous carbon materials.In particular,polymer organic frameworks with heteroatom doping,containing an ordered pore structure and excellent electrochemical stability,are ideal precursors for carbon materials for high-performance CDI.In this study,a nitrogen-enriched micro-mesoporous carbon(NMC)electrode was fabricated by carbonizing a Schiff base network-1 at 500,600,and 700℃.Scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray diffraction,N_(2) adsorption-desorption,the contact angle of water,cyclic voltammetry,and electrochemical impedance spectroscopy were used to characterize the morphological structure,wettability,Brunauer–Emmett–Teller surface areas,and electrochemical performance of the NMCs.The results showed that the NMC carbonized at 600℃ achieved the best specific capacitance(152.33 F/g),as well as a high electrosorption capacity(25.53 mg/g)because of its chemical composition(15.57%N)and surface area(312 m^(2)/g).These findings prove that NMC is viable as an electrode material for desalination by high-performance CDI applications.

Tailoring interlayer spacing in MXene cathodes to boost the desalination performance of hybrid capacitive deionization systems

Capacitive deionization(CDI)is a promising technology to satisfy the global need for fresh water,since it can be both economical and sustainable.While two-dimensional transition metal carbides/nitrides(MXenes)exhibit great characteristics for use as CDI electrode materials,their tightly spaced layered structure renders intercalation inefficiency.In this study,the interlayer distance of MXenes is precisely modulated by inserting different quantity of one-dimensional bacterial fibers(BC),forming freestanding MXene/BC composite electrodes.Among the studied samples,MXene/BC-33%electrode with the interlayer spacing of 15.2Åcan achieve an optimized tradeoff among various desalination performance metrics and indicators.The salt adsorption capacity(SAC),the average salt adsorption rate(ASAR),the energy normalized adsorbed salt(ENAS),and the thermodynamic energy efficiency(TEE)of the MXene/BC-33%electrode are improved by 24%,46%,13%,and 66%respectively compared with those of pure MXene electrode.While the insertion of BC improves the ion diffusion pathways and facilitates the intercalation kinetics,the desalination performance decreases when the insertion amount of BC exceeds 40%.This is attributed to the overlarge resistance of the composite and the resulting increased energy consumption.This study reveals the desalination performance tradeoffs of MXene-based electrodes with different interlayer distances and also sheds light on the fundamental ion storage mechanisms of intercalation materials in a CDI desalination system.