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Flexible 3D Nanoporous Graphene for Desalination and Biodecontamination of Brackish Water via Asymmetric Capacitive Deionization Ahmed Gamal El-Deen, Remko M. Boom, Hak Yong Kim, Hongwei Duan, Mary B Chan-Park, and Jae-Hwan Choi ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b08658 • Publication Date (Web): 02 Sep 2016 Downloaded from http://pubs.acs.org on September 3, 2016

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ACS Applied Materials & Interfaces

Flexible 3D Nanoporous Graphene for Desalination and Biodecontamination of Brackish Water via Asymmetric Capacitive Deionization Ahmed G. El-Deena, b, e,*, Remko M. Boomc, Hak Yong Kimd, Hongwei Duana, Mary B. Chan-Parka, b,* and Jae-Hwan Choi f,* a

School of Chemical and Biomedical Engineering, Nanyang Technological University, 62

Nanyang Drive, Singapore 637459 (Singapore) b

Centre for Antimicrobial Bioengineering, Nanyang Technological University, Singapore

637459 c

Food Process Engineering Laboratory, Agrotechnology and Food Sciences Group,

Wageningen University, The Netherlands d

BioNanosystem and Bin Fusion Department, Chonbuk National University, Jeonju 561-756,

South Korea e

Renewable Energy Science and Engineering Department, Faculty of Postgraduate Studies

for Advanced Sciences (PSAS), Beni- Suef University, Beni-Suef 62511, Egypt f

Department of Chemical Engineering, Kongju National University, 1223-24 Cheonan-daero,

Seobuk-gu, Cheonan, Chungnam 331-717, Republic of Korea

*Corresponding author. Tel.: +82 41 521 9362; fax: +82 41 521 2640. *E-mail address: [email protected]; [email protected] ; [email protected]

ACS Paragon Plus Environment


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Abstract Nanoporous graphene based materials are a promising nanostructured carbon for energy storage and electrosorption applications. We present a novel and facile strategy for fabrication of asymmetrically functionalized microporous activated graphene electrodes for high performance capacitive desalination and disinfection of brackish water. Briefly, Thiocarbohydrazide coated silica nanoparticles (SiO2-TCH) intercalated graphene sheet are used as a sacrificial material for creating mesoporous graphene followed by alkaline activation process. This fabrication procedure meets the ideal desalination pore diameter with ultrahigh specific surface area ∼ 2680 m2 g-1 of activated 3D graphene based microporous. The obtained activated graphene electrode modified by carboxymethyl cellulose (CMC) as negative charge (COO--) and disinfectant quaternary ammonium cellulose (QMC) with positively charged polyatomic ions of the structure (NR4+). Our novel asymmetric coated microporous activated 3D graphene employs non-toxic water soluble binder which increases the surface wettability and decreases the interfacial resistance moreover improvement the electrode flexibility compared with organic binders. The desalination performance of the fabricated electrodes were evaluated by carrying out single pass mode (SP-Mode) experiment under various cell potential with symmetric and asymmetric cell. The asymmetric charge coated microporous activated graphene (QC-3DAPGr) exhibits exceptional electrosorption capacity of 18.43 mg g-1 at flow rate of 20 ml/min upon applied cell potential 1.4V with initial NaCl concentration is 300 mg L-1, high charge efficiency, excellent recyclability moreover good antibacterial behavior. The present strategy provides a new avenue for producing ultra-pure water via green CDI technology. Keywords: nanoporous graphene; asymmetric capacitive deionization; water desalination; water disinfection; nanohybrid electrode.


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Introduction The provision of affordable fresh water will pose a growing challenge to the global community in coming decade1. To complicate matters, clean water sources are being degraded or overexploited, high rates of bio-contamination and population growth. Brackish water desalination is a key approach to providing clean water. Conventional desalination methods, such as thermal distillation, multistage flash distillation (MSF) and reverse osmosis (RO) have drawbacks, including high energy consumption, employment of hazardous chemicals or the need for large and costly infrastructure2. There is urgent need for green and economical technologies for water desalination. Recently, capacitive deionization (CDI) has attracted a great deal of attention as innovative desalination technology because of its high energy efficiency, low operating and maintenance cost, environmental friendliness and suitability for small-scale portable implementation 3. CDI is a promising desalination technology based on applying an external voltage between two oppositely charged carbon electrodes, the salt ions electro-adsorbed and sorted in the electric double layer on highly pours carbon electrode4. To achieve the desired desalination efficiency, the electrode materials should have high specific surface area, good electrical conductivity, robust chemical inertia, large capacitance, and high fouling resistance 5. Many carbon based materials, including activated carbon (AC)6-8, carbon aerogels

9-12

, ordered mesoporous

carbon (OMC)13-16, carbon nanofibers17-18, carbon nanotube19-22 and graphene have been employed as CDI electrode. Recently, unremitting efforts prompted for developing optimal carbon based CDI electrode including incorporated metal oxide, heterogeneous atom doped carbon and surface charge of carbon nanostructured. Anchoring of metal oxide (such as MnO2, SnO2 and ZnO) nanoparticles onto carbon increases the capacitance and charge efficiency. TiO2 nanoparticles can enhance the surface wettability due to their hydrophilicity properties

23-25

. However, carbon/metal oxide composites as CDI electrodes do not yet



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perform as well as desired. High surface area with suitable pore size distribution of electrode materials is one of the main factors for high electrosorption efficiency. Rationally designed porous carbon with high specific surface area such as Carbide-derived carbons (CDCs)

26-27

,

3D hierarchical porous carbon and nitrogen doped carbon have exhibited significant increase in desalination capacity28-29. However, there remain impediments to high desalination performance, such as limited surface wettability and electrical conductivity, reduce internal resistance, high polarization, electrode cracking as well as the “green” issue of employment of toxic organic binders30-31. Undoubtedly, the unique characteristics of graphene-based nanomaterials such as large surface area, high mechanical strength, and good adsorption. Therefore it has been the subject of much research for its potential in many applications, especially energy storage and desalination32-33. Various structured forms of graphene have been explored as promising candidates for CDI electrode. Unfortunately, the salt removal capacity didn’t achieve the expected performance due to the limited specific surface area (SSA) and electrical conductivity and low surface wettability of the chemically reduced graphene. To circumvent this problem, different approaches have been applied to suppress the graphene sheets aggregation, thus enhancing their electrical conductivity by heteroatom doped graphene lattice and alkaline activation to increase the surface area34-35 . Asymmetrical electrode configuration, such as acidic surface charge, (COO--) or (SO4--), coated cathode and pristine carbon anode demonstrates good cation selectivity and reduction of co-ion effect and also shows high desalination capacity, reaching 9.54 mg g-1 under 1.2 V with feed concentration of 400 mg/L36-37. Most recently, inverted captive deionization has been introduced as a promising technique which can enhance the salt removal efficiency to reach approximately 5.3 mg g-1 under applied voltage of 1.1 V 38


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In this study, we demonstrate; (1) an effective strategy for preparing controlled nanoporous graphene based CDI electrode material with ultrahigh specific surface area and favourable pore size distribution. (2) Novel asymmetric coated CDI electrode configurations by carboxymethyl cellulose (CMC) (COO--) and quaternary ammonium cellulose (QMC) (NR4+). We also employ an ecofriendly class of water soluble binder. A notable innovation is the use of cationic quaternized ammonium cellulose as anode coating; this enhances adsorption of anions and also promotes the killing of bacteria. The asymmetric electrode configurations shows unprecedented electrosorption capacity 18.32 mg g-1 and high charge efficiency. This strategy opens up a new way to meet CDI requirements without membranes, for energy-efficient, cost-effective desalination and green disinfection.

Results and discussion A facile synthesis approach for producing graphene films with controlled hierarchical pore structure graphene is described (Scheme 1). Graphene-based electrode materials were prepared via three distinct routes. In Route 1, graphene oxide was reduced with TCH to produce 3D graphene (3DGr). In Route 2, silica nanoparticles were coated with TCH and sonicated with graphene oxide sheets to produce SiO2/TCH/graphene oxide composite which was then etched with HF to produce 3D porous graphene (3DPGr). In Route 3, the SiO2/TCH/graphene oxide composite produced as in Route 2 was soaked in NaOH (6M), filtered and then thermally activated under inert atmosphere to produce 3DAPGr. Generally, chemically reduced graphene produced using hydrazine as the reducing agent suffers from sheet aggregation and poor pore formation that leads to lower surface area than of monolayer graphene. Here, TCH was used as a novel reducing agent to fabricate 3D graphene with interconnected pore structure (as in Fig 1A). This 3D graphene displayed interconnected open pores surrounded by layers of overlapping flexible graphene sheets. The



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3D framework is formed from the crosslinking of the terminal amine of TCH with carboxylic groups on graphene oxide. The incorporation of TCH coated silica nanoparticles (NPs) (Route 2) between graphene sheets provides a sacrificial material which prevents graphene sheet aggregation. The SEM image in Fig 1B shows SiO2 NPs densely covering the graphene surface and intercalated between sheets. The NPs adhere to the nanosheets because of the strong electrostatic interaction between branched amine groups of the NP surface treatment TCH and negative surface charges of GO. Energy-dispersive X-ray spectroscopy (EDS) of this composite material (Fig. 1C) indicates the existence of C, Si and O in the corresponding area, with high concentration of SiO2. The interconnect open pores of graphene disappeared after etching of SiO2 NPs (Fig. 1D) and myriad open dead pores were created on the surface sheets with pore size corresponding to the Silica nanoparticle diameter; i.e. removing the NPs leaves behind dead pores of the same size. Alkaline thermal activation of GO-SiO2/TCH exhibits a highly porous structure, the SEM image of activated porous Graphene (3DAPGr) Fig 1E shows branched wrinkled graphene edges with high exfoliated sheets. The alkaline etching and thermal process creates the in-plane micro pores and generates large amount of edge carbon that enhance the specific capacitance compared to basal plane39-40. TEM was employed to examine the morphological differences among the various prepared forms of graphene. TEM image (Figure 2A) displays the hierarchical structure of 3DGr showing wrinkled ultrathin sheets and Fig 2B shows pores (enlarged in the inset) in the 3DPGr illustrating the importance of the functional SiO2/TCH for creating the 3D graphene based mesoporous structure. We can see numerous pores interspersed among the crumpled hierarchical graphene sheets and the inset HR-TEM images describes dual pores structured; interconnect pores between scrolled graphene nanosheets framework and intra-mesopores throughout graphene nanosheets. On the other hand, the nanoporous hierarchical graphene introduced free stacking sheets like silk veil waves as shown in Fig 2C.


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Fig. 3 shows XRD patterns of GO, 3DPGr and 3DAPGr. GO exhibits a distinct peak centered at 2θ=10.9o and no obvious graphite (002) sharp peak at 26.6o, confirming the interlayer spacing of GO owing to abundant oxygen-containing groups. After reduction with TCH, 3DGr shows characteristic GO peak disappeared while a broad (002) peak at 23.82o appears in the XRD pattern indicating reduction of oxygenated functional groups. Similarity, The 3DPGr displays the same peak position as the 3DGr but with reduced intensity due to dislocations of stacked graphene sheets. Whereas, the (002) peak of 3DAPGr is much weaker and broader than 3DPGr and 3DGr, reflecting the sheets are more sufficient exfoliation and loosely stacked. Large surface area and suitable pore diameter of porous carbon are key factors for high adsorption desorption capacity in CDI process. The N2 adsorption/desorption isotherms in Fig 4 depict the 3DGr hysteresis loop indicating presence of dominant macroporous structures that are undesirable for electrosorption. 3DPGr displays a typical IUPAC type-IV adsorption isotherm pattern with a clear hysteresis loop at a wide relative pressure range (0.4–1.0) confirming the mesoporous structure of synthesized graphene. The open dead mesopores created on the graphene sheets can attributed to etching of SiO2. The hysteresis loop of 3DAGPr implies microporous structure identical for carbon based CDI electrode. The specific surface area, total pore volume and average pore size of the synthesized porous graphene are submitted in Table 1. The 3DAPGr shows ultrahigh specific surface area of 2680 m2g-1, which is almost tenfold that of 3DPGr and twentyfold that of 3DGr.

Scheme 2 shows the non-coated and asymmetrical coated electrode configurations we explored, in which the anode and cathode are made of the same material, we explored all three types of graphene structures (Scheme 2A, i, ii, iii; in this and following discussion, 3DGr, 3DPGr and 3DAPGr using neat SBR as binder). For the symmetric CDI cell, the



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activated 3D graphene preparation is specific electrode material for all cell design. Scheme 2B, C and D represent the asymmetric coated electrode pairs of (3DAPGr and 3DAPGr/QMC denoted as Asym-Q 3DAPGr; 3DAPGr and 3DAPGr/CMC denoted as Asym-C 3DAPGr; 3DAPGr/QMC and 3DAPGr/CMC denoted as Asym-QC 3DAPGr)

The different types of 3DGr were mixed with a water-soluble binder formulations and formed into flexible electrode sheets after water evaporation. We used styrene butadiene rubber SBR as foundation of our binder formulations, the first use of this material for CDI applications. Others have shown the bonding ability and cycle stability of SBR in non-CDI applications to be the same as that of conventional PVDF41. In addition to neat SBR, the small proportion of (QMC or CMC) polymer added to SBR binder for similar charge coated electrode to decrease the concentration polarization and enhance binding ability.

Fig. 5 shows SEM images of the cross section morphology of flat and bending 3DAPGr electrode using SBR, SBR/QMC and SBR/CMC binders. SEM images of cross section flat electrodes in Fig 5A, B and C displays no creak observed on the flat surface electrode for all binder formulations. The inset optical images for the bending electrodes in Fig 5A, B and C demonstrated the higher flexibility of both SBR/CMC and SBR/CMC binder electrode compared neat SBR binder. The cross section images for SBR/QMC (Fig. 5Bi) and SBR/CMC (Fig. 5Ci) exhibit no cracking in a highly warped electrode. In contrast, the 3DAPGr electrode using SBR, Figure 5Ai that shows, the electrode cracks after bending,

Surface wettability is considered to be an important factor for enhancing the adsorption capacity. However, all carbon based electrodes, including graphene, suffer from low surface wettability because of their hydrophobicity. In this study, we coated the activated microporous graphene with carboxylic group (COO--) and quaternary group (NR4+) to increase the hydrophilicity of 3DAPGr electrode while preserving the high porosity. The


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surface wettability characteristics for the coated and uncoated electrode were evaluated by measurement of static water contact angles on the electrode surface at room temperature. Coating the electrode noticeably improved the surface wettability of 3DAPGr, the static contact angle of uncoated 3DAPGr was approximately 88.3°. On contrary, the 3DAPGr electrode coated by CMC or QMC showed highly hydrophilic behavior with 26° and 28° water contact angles respectively (SI, Fig. S3).

Electrochemical characteristics of the fabricated electrodes. Based on Electrical double layer capacitor (EDLC), CV measurements are widely applied as an effective and reliable way to determine the electrosorption ability and capacitance of electrode materials. It is noteworthy to mention that the electrochemical results were obtained under same NaCl concentration of CDI process; two working electrode, same electrode fabrication and at low ionic strength (5 mM). Fig. 6A shows CV curves of three types of symmetric electrodes, made with porous 3DGr, 3DPGr and 3DAPGr and SBR binder, at a scan rate of 5 mV/s in 5 mM NaCl. No obvious Faradaic peaks are present in the CV profiles for all materials; this reflects the adsorption of ions on the surface of porous graphene based on Coulombic interactions rather than redox reactions. The 3DAPGr trace is clearly symmetric with respect to the X axis with ideal rectangular shape, reflecting typical EDL capacitance and highly reversible capacitive process. The activated porous graphene 3DAPGr exhibits accessibility to storage ions than 3DGr and 3DPGr; the behavior of these three electrodes corresponds to the progression of surface area with preparation method shown in table 1.

Using 3DAPGr, we made three types of asymmetric coated electrodes using the two blended binder and coated formulations (Scheme 2b). Figure 6B shows, to the same scale as Figure 6A, the CV performance of the asymmetric electrodes under same conditions. The



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asymmetric cell QC-3DAPGr, exhibits the best electrochemical performance. It can be attributed to the capability of asymmetric charge coated (NR4+) and (COO--) electrode to reduce co-ion expulsion similar to role of membrane for blocking co-ions from carrying parasitic current and hence enhance the adsorption capacity of the electrode.

The specific capacitance (Cs) values have been calculated from the CV results according to Eq. (1). The specific capacitance for all fabricated electrode are presented in Figure 6C. The 3DAPGr has the highest specific capacitance amongst the three types of uncoated porous 3D graphene. Interestingly, the use of quaternary amine group (NR4+) and carboxylic group (COO-- coated 3DAPGr electrode (QC-3DAPGr) showed significant improvement in specific capacitance compared to symmetric uncoated 3DAPGr due to decreased graphene polarization and enhanced ion selectivity.

Electrochemical Impedance Spectroscopy (EIS) is a powerful diagnostic technique to determine the electrical conductivity of the electrode materials. The Nyquist profiles in fig 6D, displays all fabricated electrode materials have similar shapes, including a quasisemicircle at the high frequency and a straight spike at the low frequency region. Generally, The intercepts at the real axis (Z’) corresponding to value of equivalent series resistance (ESR) and reflect resistance from electrodes, solution, and contact resistance. As seen in the inset figure 6D, The asymmetric coated QC-3DAPGr cell at high frequency shows lower intercepts with the real axis (Z') and smallest semicircle diameter, indicating small intrinsic resistance of electrodes and low charge transfer resistance compared to all cell configurations42. Hence, the asymmetric QC-3DAPGr electrode provides ideal capacitive behaviour and lower internal resistances that can improve the desalination performance.

Prior to experiments to estimate the desalination capacity of the fabricated electrodes, all electrodes were activated by soaking in 300 mg/l NaCl solution for 15 min, under vacuum


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for to remove any air bubbles. A pair of free-standing electrodes were assembled in a prototype CDI cell in as schematic 2. The CDI cell tests were conducted in NaCl aqueous solution with concentration of 300 mg/l at different applied voltages from 0.8 to 1.6V.

The desalination efficiency of the fabricated electrode was plotted in Fig. 7A, a single pass method with NaCl aqueous solution having an initial conductivity of ~ 568 µS/cm. In the first 50 secs or so, the effluent conductivity dramatically decreases as the ions are driven onto the electrodes under imposed external cell potential (1.4V in these figures). This initial sharp decrease in conductivity indicates a rapid adsorption of the salt ions on the electrode surface. With time passes, the conductivity gradually recovers toward the adsorption equilibrium due to the electrostatic repulsion between the adsorbed ions on the surface. As shown in figure 7A, Sym-3DGr cell shows very low adsorption capacity due to low surface area with macro-porous structure; it is unsuitable for CDI. The 3DPGr exhibited slight improvement based on accumulation of ions into the created mesoporous. The 3DAPGr presented the highest adsorption/desorption performance among all obtained 3D pours graphene materials attributing to its high SAA with desirable microporous structure. The Asym QC-3DAPGr CDI cell demonstrated best desalination performance because of low concentration polarization, high hydrophilic behaviour and reduction of co-ion expulsion.

Figure 7B depicts adsorption/desorption curves for the tested materials over 4 consecutive cycles. There is no discernible change in the traces from cycle to cycle, which suggests excellent regeneration capability and chemical stability for electrode materials In addition to the electrosorption capacity and electrochemical capacitance, the cycling stability (Fig. 7C) with full regeneration is another important property of CDI electrode materials. As shown in Figure 7C, recyclability test of the asymmetric QC-Cell electrode was studied over 100 successive adsorption/desorption processes under 1.4V.There is no discernible



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systematic decline in the conductivity profile or ion removal capacity during this experiment and revealed 99.56% remaining desalination retention, indicating good chemical inertia of the asymmetric charge coated electrode.

According to Eq. (3), the electrosorption capacities were calculated and plotted versus cell potential in Fig. 7D. The Sym-3DAPGr cell demonstrated significant improvement in adsorption/desorption capacity compared symmetrical non-coated CDI cell (Sym-3DGr and Sym-3DPGr cell) at all the applied voltages. After coating the 3DAPGr electrode with (COO) Or (NR4+) group, both of the Asym C-3DAPGr cell and Asym Q-3DAPGr cell provided higher electrosorption capacity than non-coated (Sym-3DAPGr) cell. Owing to the intrinsic improvement in electrochemical performance and surface wettability aforementioned, the Asym QC-3DAPGr CDI cell exhibits highest electrosorption capacity of all introduced CDI cell.

Charge efficiency (Λ) (i.e., the ratio of equilibrium salt adsorption over charge), is an effective way to illustrate the double layer formed at the interface between the surface electrode materials and solution. The Charge efficiency has been calculated according to Eq. (4).The measured charge efficiencies for the tested materials is shown versus voltage in Fig 7E. The charge efficiency of QC-3DAPGr (0.87) is more than 4 times that of 3DGr (0.22). This is attributed to rational design of graphene with many embedded pores and asymmetric charge coating, which facilitates ion diffusion and low contact resistance. Generally, the maximum charge efficiency reported for membrane capacitive deionization is around 0.9– 0.95 and for CDI using microporous activated carbon is ≥ 0.843. The charge efficiency of QC3DAPGr (0.87) is competitive with that of other approaches.

Our strategy not only achieves high desalination performance and meets the requirements of CDI electrode but also possess a novel capability for in situ disinfection


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through coating the anode surface with a polymer which, due to its strong quaternary charge (NR4+), has good antimicrobial properties. Based on contact-active killing of microbes by cationic polymers, the QMC coating electrode in QC-3DAPGr cell kills microbes on contact by physical disruption of the anionic microbe cytoplasmic membrane44-46. Figure 8A shows the killing efficiency for Asym QC-3DAPGr cell under batch mode process during continues charging step for 5 min. during the first 30 sec, no live E. coli was detected at the effluent solution despite the high injection of E. coli concertation is 104 CFU ml-1. With the time going on, the electrode the disinfection performance slightly decrease which can reach to 98.55% killing (i.e., ∼ 1.9 log reduction) at end of first cycle without further reaeration. Of note is that the killing efficiency of the AsymQC-3DAPGr cell in fig 8B shows high regeneration performance and retains the disinfection capacity at 1.9 log reduction over 6h , reflecting the high NR4+ density and effective charging stability of antimicrobial QMC coated electrode.

Our Asym-QC-3DAPGr CDI cell exhibits superior electrosorption capacity (23.17 mg g-1) and charge efficiency 0.85 under high flow rate of 10 ml/min compared to others inverted and asymmetric CDI technique (highest reported are 20 mg g-1, 0.68 and 8.67 flow rate respectively, Table 2) and has good antimicrobial performance.

Conclusions We have introduced a facile and effective approach to produce asymmetric coated nanoporous graphene based CDI electrodes for high desalination and disinfection performance. Firstly, we have successfully enhanced surface area and controlled porous graphene architecture through incorporation of surface-treated nanoparticles and thermal activation. The surface area of graphene based electrode improved from 115 m2/g for 3DGr to m2/g 223 for 3DPGr to 2680 m2/g for 3DAPGr. The average pore diameter decreased from



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22 nm to 1.8 nm. Secondly, we devised a charged electrode coating using carboxylic group (COO--) and quaternary amine (NR4+) (incorporated into non-toxic water-soluble binder) for high electrosorption capacity and good energy efficient CDI process. The improvement of electrochemical capacitance and surface wettability behavior are key factors for high CDI desalination performance. The asymmetric coated activated porous graphene (QC-3DAPGr) demonstrated noticeably improved electrochemical capacitance, ~200% that of the symmetric uncoated cell. The desalination performance was investigated for all electrode formulations using single pass method. The asymmetric single-side coated electrode, with (COO--) on the cathode, (C-3DAPGr) or (NR4+) on the anode, Q-3DAPGr) performed significantly better than the CDI cell with symmetrical uncoated 3DAPGr in electrosorption performance and charge efficiency, due to reduction of co-ion expulsion. The asymmetric coated (QC3DAPGr) cell performed best of all, with exceptional electrosorption capacity, 18.43 mg g-1, and charge efficiency of 0.87. In addition, the anode coating we employed. The cationic antimicrobial polymer (NR4+), imparts good microbe-killing properties to the CDI cell. The disinfection performance achieved 98.55% killing of E-coli through the (QC-3DAPGr) cell. The proposed asymmetric QC-3DAPGr shows superior desalination performance, cycling stability, disinfection capacity and charge efficiency. These proposed electrode materials present a new approach for high desalination and good bio-decontamination performance with energy efficiency for CDI process. Experimental Materials and Methods Natural graphite fine powder, hydrogen peroxide solution

30 % (w/w) in H2O,

thiocarbohydrazide 98% and carboxymethylcellulose sodium salt, average Mw ~90,000, were purchased from Sigma Aldrich. Commercial grade styrene-butadiene rubber (SBR) was obtained from Zeon, Japan. All chemicals were used without further purification.


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Synthesis of 3D graphene ((3DGr). Graphene oxide (GO) was synthesized from natural graphite powder using the modified Hummers’ method47. 300 mg of TCH added to 100 ml of GO dispersion (4mg/ml) sonicated for 10 min then heated for 12 h at 90 °C without stirring. The obtained monolithic 3D graphene flashed by nitrogen and freeze for 12 h under – 800C to full solidified then transferred into vacuum freeze-drying for 48h. Synthesis of 3D mesoporous graphene (3DPGr). A template-free approach to create mesoporous graphene has been to use SiO2 NPs with diameter around 25nm as a sacrificial material to inhibit graphene stacking. To prepare thiocarbohydrazide-coated Silica, the 100 mg of silica nanoparticles sonicated for 2h in 20 ml in DMF of TCH (20 mg/ml) then collected and washed by cold water. The obtained (SiO2TCH) NPs incorporated into Graphene oxide (GO) solution and sonicated for 2h then the uniformly suspension mixture was heated at 90 0C for 12 h without stirring. The obtained 3DGr-SiO2 composite soaked overnight into 50 ml HF to remove the SiO2 NPs intercalated graphene then washed several time with distilled water and dried at 80oC under vacuum oven. Fabrication of 3D activated microporous graphene (3DAPGr). The obtained 3DGr-SiO2 cake was stirred in 6M of NaOH overnight and refluxed for 24h at 120oC then separated by low-pressure vacuum filtration. The resulting alkaline cake was soaked in DI H2O for 12 h to remove the sodium silicate then filtered and dried in a vacuum oven at 80oC for 12h. The dried product was calcined under argon atmosphere at 3C/min to 700C and kept 5h at 700oC. The activated microporous graphene was then washed several times DI H2O till pH 7 and dried at 80oC in a vacuum oven.



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Synthesis of antimicrobial quaterinarized charge (QMC) coating material. The cationic disinfectant coating material (NR4+) using Quaternized ammonium cellulose (QMC), specifically 2-hydroxypropyl trimethylammonium cellulose), was synthesized as previously described[25]. Briefly, cellulose was dissolved in NaOH/urea aqueous solution, the obtained solution was stored in a precooled to -10 °C for 0.5 h then stirred for 5 min at room temp, the fully transparent layer of cellulose of the resulting solution collected by centrifugation. The (Glycidyl trimethylammonium chloride, GTAC was added drop to CA solution and the mixture was stirred at 25 °C for 24 h. The product was neutralized, dialyzed and collected by freeze-drying. Electrode fabrication Electrodes were prepared using the following procedure; typically, one of the porous graphene materials (90 wt.%) and a water-soluble binder (10%), one of SBR, SBR/CMC and SBR/QMC (3:1 ratio), binder were mixed in a planetary centrifugal mixer (AR-100, THINKY Co., Japan) at 20,000 rpm for 20 min to produce completely homogeneous slurry . The obtained slurry was flattened with automatic rolling machine under suitable pressure to produce a film with thickness around 120 ± 15 µm which was then dried under vacuum for 24h at 120oC. The obtained long sheet electrode was cut into square 10 × 10 cm2 pieces, with a 10mm exit hole in the middle of one electrode. The cell plumbing was configured so that influent passed from the edge of the cell to the centre through a 120 µm thick non-conductive spacer (EX31-071/80 PW, NBC Meshtec Inc., Japan).The final mass of active materials for both 100 cm2 CDI electrodes equal to 1.14g; i.e. 5.7mg/cm2.


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Net charge asymmetric surface coating To activate the electrodes with a net negative surface charge the obtained electrode with SBR/CMC binder was immersed into 1% CMC solution for 12h with gentle stirring then washed several times and dried overnight room temp. Similarly, the positive net charge electrode SBR/QMC was coated with 1% of antimicrobial QMC solution. Electrochemical characterization of the fabricated electrodes. To measure the electrochemical performance, Circular samples like coin were cut with fixed diameter of 0.9 cm2 diameter from electrode sheets of all formulations. Cyclic voltammetry (CV) was carried out in 5mM NaCl at the scan rate 5mV/s over the potential range -0.5 to 0.5 V in an electrochemical cell with a two working electrode similar to actual salt concentration applied for CDI system. This system was controlled using an electrochemical station (Shanghai Chenhua, CHI760D). The specific capacitance was calculated from CV process data according to the equation 48

=

∗

(1)

Where SC is the specific capacitance (F/g), is the average current (A), υ is the applied voltage scan rate (V/s), and m is the mass of the active materials (g). Electrochemical impedance spectroscopy (EIS) measurements were also characterized with a CH Instruments electrochemical analyzer, model CHI 660D. The symmetrical and asymmetrical electrode are mentioned above using two-compartment coin cell. The amplitude of the alternating voltage was 5 mV around the equilibrium potential (0 V); the data were collected in the frequency range from 10 mHz to 100 Hz. CDI system was investigated using single-pass mode for desalination and batch mode for disinfection. A large scale of square self-standing CDI electrodes (10×10 cm) were



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Page 18 of 38

assembled on graphite foil as current collector and separated by nylon spacer. A continuous flow rate of 20 mL min -1 was passed between two parallel electrodes using a peristaltic pump throughout this experiment whereas the applied cell potential was controlled by high power type Potentiostat/Galvanostat WPG100HP and the obtained current recorded simultaneously. The salt removal capacity can be measured form the change in concentration of the inlet and outflow solution. During CDI process, the salt removal efficiency %() and the electrosorption capacity (Q, mg g-1) of the CDI electrodes were determined from equations (2) and (3):49

=1−

= Where

× 100

(2)

(

(3)

(mg/L) is the initial influent NaCl concentration, is the average NaCl

concentration of the effluent and V (L) is the total volume saline solution during charging step, and M (g) represents the total mass of the electrodes. The Charge efficiency (Λ) is computed from the following equations27, 50:

=

∗

; # = $ %&

(4)

Where F is the Faraday constant (96485 C mol−1), ' is the salt removal capacity (mol g−1) and the electrode charge storage Σ (C g−1) is calculated by integration of the corresponding current with time.


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Supporting information Detailed information about XPS survey for the fabricated porous graphene and the surface wettability investigation, FTIR chart, more CDI profiles of the asymmetric 3D graphene electrode at different flow rate and current changes with input voltage during the operation of the CDI unit can be found as supporting information. This material is available free of charge via the Internet at http://pubs.acs.org/.

Acknowledgment. Part of this work was funded and supported by a Singapore MOE Tier 3 grant (MOE2013-T3-1-002), a Singapore MOH Industry Alignment Fund (NMRC/MOHIAFCAT2/003/2014), and a NTU iFood Grant.



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Scheme 1 Schematic illustration of the fabricated highly nanoporous graphene.


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A

B C

E

D

Figure 1. SEM images of hierarchical macro porous 3D graphene electrode (A), SiO2 nanoparticles anchored 3DGr and the corresponding EDX spectra of materials compositions (B, C), hierarchical mesoporous 3DPGr after etching SiO2 nanoparticles and activated hierarchical nanoporous 3DAPGr electrode materials (D, E).



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B

A

10 nm

C

Figure 2. TEM images of 3DGr (A), 3DPGr electrode and the inset is the HR-TEM for interconnect-mesoporous graphene after etching SiO2 nanoparticles (B) and activated hierarchical porous 3DAPGr (C).


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Figure 3. XRD for the synthesized electrode materials.

Figure 4. (A) Nitrogen adsorption–desorption isotherms of the prepared materials.

Table 1: Textural characteristics of 3DGr, 3DPGr and 3DAPGr material electrodes

2

-1

3

-1

Sample

S B ET (m g )

V t otal (cm g )

Average Pore size (nm)

3DGr

116

0.275

22.1

3DPGr

223

0.517

5.1

3DAPGr

2680

1.167

1.76



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

A) i

A) ii

B

C

Page 24 of 38

A) iii

D

Scheme 2. Schematic diagram for all CDI cells assembled by symmetrical normal CDI using graphene based electrode materials (Ai:Aiii) and asymmetrical charge coated electrode pairs; (B) Asym Q-3DAPGr; (C) Asym Q-3DAPGr; (D) Asym QC-3DAPGr CDI cell.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


A

Ai

Bi

B

Ci

C

Figure 5. SEM images of flat and bending cross section of cracked electrodes 3DAPGr electrode (A, Ai) using neat SBR as binder, flexible Q-3DAPGr electrode and cross section of bending electrode (B, Bi) using SBR/QMC coated and cross section of flexible C-3DAPGr electrode SBR/CMC coated (C, Ci), the inset is optical image for the rolled electrodes.



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A

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B

D

C

Figure 6. (A) Cyclic voltammetry profiles of the fabricated porous graphene electrodes at a scan rate of 5 mV/s and NaCl concentrations of 5mM, (B) CV curves for asymmetrical coated of 3DAPGr electrode, (C) the specific capacitance for the fabricated electrode materials, (D) Nyquist plot for the fabricated electrode materials and the inset chart shows the magnified high frequency region.


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B

A

D C

E

Figure 7. (A) desalination plot for the synthesized electrode materials at 1.4 V with flow rate of 20mL/min (B) regeneration profiles for the introduced electrode material, (C) cycling stability test and desalination retention for Asym QC-3DAPGr over 100 cycles under same operational conditions and (D, E) electrosorption capacity and charge efficiency versus voltages for all fabricated electrode materials.



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A

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B

Figure 8. (A) Disinfection performance of the E.Coli with104 CFU mL-1 via Asym QC3DAPGr CDI Cell under 2V at flow rate of 5 ml/min and (B) Decontamination recyclability for each 5 min disinfection/regeneration over 30 cycles.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Materials

Initial NaCl concentrat ion (mg/L)

Electrosorption capacity(mg/g) &Flow rate (ml/min)

Cell potential (V)

Charge efficiency

Operational mode

Reference

Microporous carbon

250

5.3 & 20

1.1

0.53

I-CDI

38

Sulfonated G- CNF

100

9.54 & 5

1.6

0.43

SP– Asym MCDI

36

AC-QPVP

500

20.6 & 8.67

1.2

0.68

Asym-CDI

51

GrC

500

13.1

1.2

-

BM –CDI

52

NDC-Cs-900

300

15.0 & 7.5

1.2

0.85

SP-CDI

53

Graphene Aerogel/TiO2

250

9.9

1.2

-

BM -CDI

54

CDC

290

14.9

1.4

0.79

SP -CDI

27

ZnO/ACC

1000

7.7 & 3

1.6

0.78

BM -CDI

55

NPCS1000

500

13.71

1.2

0.49

BM -CDI

48

Activated 3D graphene

60

11.86

2

-

BM -CDI

56

ACF-HNO3

500

12.8 & 8.67

1.2

0.74

BM-Asym CDI

37

3DGHPC

60

6.18 & 20

1.2

-

BM -CDI

57

3DGr

300

2.17 & 20

1.4

0.24

SP-CDI

The present work

3DPGr

300

8.97 & 20

1.4

0.69

SP- CDI

The present work

3DAPGr

300

14.32 & 20

1.4

0.82

SP-CDI

The present work

Asym QC3DAPGr

300

23.17 & 10

1.4

0.85

SP- Asym CDI

The present work

Asym QC3DAPGr

300

18.43 & 20

1.4

0.87

SP- Asym CDI

The present work

Asym QC3DAPGr

300

14.08 & 30

1.4

0.84

SP- Asym CDI

The present work



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Table 2. Comparison of electrosorption capacity of different electrode materials recently published under various operational CDI techniques. SP: single-pass; BM: batch model; I-CDI inverted; Asym-CDI asymmetric.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1.

Shannon, M. A.; Bohn, P. W.; Elimelech, M.; Georgiadis, J. G.; Marinas, B. J.;

Mayes, A. M. Science and Technology for Water Purification in the Coming Decades. Nature 2008, 452, 301-310. 2.

Elimelech, M.; Phillip, W. A. The Future of Seawater Desalination: Energy,

Technology, and the Environment. Science 2011, 333, 712-717. 3.

Anderson, M. A.; Cudero, A. L.; Palma, J. Capacitive Deionization as an

Electrochemical Means of Saving Energy and Delivering Clean Water. Comparison to Present Desalination Practices: Will It Compete? Electrochimica Acta 2010, 55, 3845-3856. 4.

Porada, S.; Zhao, R.; Van Der Wal, A.; Presser, V.; Biesheuvel, P. Review on the

Science and Technology of Water Desalination by Capacitive Deionization. Progress in

Materials Science 2013, 58, 1388-1442. 5.

Welgemoed, T.; Schutte, C. Capacitive Deionization Technology™: An Alternative

Desalination Solution. Desalination 2005, 183, 327-340. 6.

Kim, J.-S.; Choi, J.-H. Fabrication and Characterization of a Carbon Electrode Coated

with Cation-Exchange Polymer for the Membrane Capacitive Deionization Applications.

Journal of membrane science 2010, 355, 85-90. 7.

Kim, Y.-J.; Choi, J.-H. Selective Removal of Nitrate Ion Using a Novel Composite

Carbon Electrode in Capacitive Deionization. Water Res. 2012, 46, 6033-6039. 8.

Choi, J.-H. Fabrication of a Carbon Electrode Using Activated Carbon Powder and

Application to the Capacitive Deionization Process. Sep. Purif. Technol. 2010, 70, 362-366. 9.

Zou, L.; Morris, G.; Qi, D. Using Activated Carbon Electrode in Electrosorptive

Deionisation of Brackish Water. Desalination 2008, 225, 329-340. 10.

Jung, H.-H.; Hwang, S.-W.; Hyun, S.-H.; Lee, K.-H.; Kim, G.-T. Capacitive

Deionization Characteristics of Nanostructured Carbon Aerogel Electrodes Synthesized Via Ambient Drying. Desalination 2007, 216, 377-385.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

11.

Page 32 of 38

Farmer, J. C.; Fix, D. V.; Mack, G. V.; Pekala, R. W.; Poco, J. F. Capacitive

Deionization of Nacl and Nano3 Solutions with Carbon Aerogel Electrodes. J. Electrochem.

Soc. 1996, 143, 159-169. 12.

Xu, P.; Drewes, J. E.; Heil, D.; Wang, G. Treatment of Brackish Produced Water

Using Carbon Aerogel-Based Capacitive Deionization Technology. Water Res. 2008, 42, 2605-2617. 13.

Tsouris, C.; Mayes, R.; Kiggans, J.; Sharma, K.; Yiacoumi, S.; DePaoli, D.; Dai, S.

Mesoporous Carbon for Capacitive Deionization of Saline Water. Environmental Science &

Technology 2011, 45, 10243-10249. 14.

Peng, Z.; Zhang, D.; Shi, L.; Yan, T.; Yuan, S.; Li, H.; Gao, R.; Fang, J. Comparative

Electroadsorption Study of Mesoporous Carbon Electrodes with Various Pore Structures. The

Journal of Physical Chemistry C 2011, 115, 17068-17076. 15.

Wen, X.; Zhang, D.; Shi, L.; Yan, T.; Wang, H.; Zhang, J. Three-Dimensional

Hierarchical Porous Carbon with a Bimodal Pore Arrangement for Capacitive Deionization.

J. Mater. Chem. 2012, 22, 23835-23844. 16.

Peng,

Z.;

Zhang,

D.;

Yan,

T.;

Zhang,

J.;

Shi,

L.

Three-Dimensional

Micro/Mesoporous Carbon Composites with Carbon Nanotube Networks for Capacitive Deionization. Appl. Surf. Sci. 2013, 282, 965-973. 17.

El Deen, A.; Khalil, K.; Barakat, N.; Yong, K. H. Development of Multi-Channels

Carbon Nanofibers as Effective Electrosorpitive Electrodes for Capacitive Deionization Process. J. Mater. Chem. A 2013, 1, 11001-11010. 18.

El-Deen, A. G.; Barakat, N. A.; Khalil, K. A.; Kim, H. Y. Hollow Carbon Nanofibers

as an Effective Electrode for Brackish Water Desalination Using the Capacitive Deionization Process. New J. Chem. 2014, 38, 198-205.


Page 33 of 38

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


19.

Liu, Y.; Li, H.; Nie, C.; Pan, L.; Sun, Z. Carbon Nanotube and Carbon Nanofiber

Composite Films Grown on Different Graphite Substrate for Capacitive Deionization.

Desalination and Water Treatment 2013, 1-7. 20.

Zhang, D. S.; Yan, T. T.; Shi, L. Y.; Peng, Z.; Wen, X. R.; Zhang, J. P. Enhanced

Capacitive Deionization Performance of Graphene/Carbon Nanotube Composites. Journal of

Materials Chemistry 2012, 22, 14696-14704. 21.

Li, H.; Gao, Y.; Pan, L.; Zhang, Y.; Chen, Y.; Sun, Z. Electrosorptive Desalination by

Carbon Nanotubes and Nanofibres Electrodes and Ion-Exchange Membranes. Water Res. 2008, 42, 4923-4928. 22.

Zhang, D.; Shi, L.; Fang, J.; Dai, K.; Li, X. Preparation and Desalination Performance

of Multiwall Carbon Nanotubes. Mater. Chem. Phys. 2006, 97, 415-419. 23.

El-Deen, A. G.; Choi, J.-H.; Kim, C. S.; Khalil, K. A.; Almajid, A. A.; Barakat, N. A.

Tio 2 Nanorod-Intercalated Reduced Graphene Oxide as High Performance Electrode Material for Membrane Capacitive Deionization. Desalination 2015, 361, 53-64. 24.

El-Deen, A. G.; Barakat, N. A.; Kim, H. Y. Graphene Wrapped Mno 2-

Nanostructures as Effective and Stable Electrode Materials for Capacitive Deionization Desalination Technology. Desalination 2014, 344, 289-298. 25.

Laxman, K.; Myint, M. T. Z.; Bourdoucen, H.; Dutta, J. Enhancement in Ion

Adsorption Rate and Desalination Efficiency in a Capacitive Deionization Cell through Improved Electric Field Distribution Using Electrodes Composed of Activated Carbon Cloth Coated with Zinc Oxide Nanorods. ACS applied materials & interfaces 2014, 6, 1011310120. 26.

Porada, S.; Borchardt, L.; Oschatz, M.; Bryjak, M.; Atchison, J.; Keesman, K.;

Kaskel, S.; Biesheuvel, P.; Presser, V. Direct Prediction of the Desalination Performance of



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Porous Carbon Electrodes for Capacitive Deionization. Energy & Environmental Science 2013, 6, 3700-3712. 27.

Porada, S.; Weinstein, L.; Dash, R.; Van Der Wal, A.; Bryjak, M.; Gogotsi, Y.;

Biesheuvel, P. Water Desalination Using Capacitive Deionization with Microporous Carbon Electrodes. ACS applied materials & interfaces 2012, 4, 1194-1199. 28.

Xu, X.; Sun, Z.; Chua, D. H.; Pan, L. Novel Nitrogen Doped Graphene Sponge with

Ultrahigh Capacitive Deionization Performance. Scientific reports 2015, 5, 1-9. 29.

Wen, X. R.; Zhang, D. S.; Shi, L. Y.; Yan, T. T.; Wang, H.; Zhang, J. P. Three-

Dimensional Hierarchical Porous Carbon with a Bimodal Pore Arrangement for Capacitive Deionization. Journal of Materials Chemistry 2012, 22, 23835-23844. 30.

Park, B.-H.; Choi, J.-H. Improvement in the Capacitance of a Carbon Electrode

Prepared Using Water-Soluble Polymer Binder for a Capacitive Deionization Application.

Electrochimica Acta 2010, 55, 2888-2893. 31.

Park, B.-H.; Kim, Y.-J.; Park, J.-S.; Choi, J. Capacitive Deionization Using a Carbon

Electrode Prepared with Water-Soluble Poly (Vinyl Alcohol) Binder. Journal of Industrial

and Engineering Chemistry 2011, 17, 717-722. 32.

Shao, Y.; El-Kady, M. F.; Wang, L. J.; Zhang, Q.; Li, Y.; Wang, H.; Mousavi, M. F.;

Kaner, R. B. Graphene-Based Materials for Flexible Supercapacitors. Chemical Society

Reviews 2015, 44, 3639-3665. 33.

Goh, P.; Ismail, A. Graphene-Based Nanomaterial: The State-of-the-Art Material for

Cutting Edge Desalination Technology. Desalination 2015, 356, 115-128. 34.

Yang, Z. Y.; Jin, L. J.; Lu, G. Q.; Xiao, Q. Q.; Zhang, Y. X.; Jing, L.; Zhang, X. X.;

Yan, Y. M.; Sun, K. N. Sponge‐Templated Preparation of High Surface Area Graphene with Ultrahigh Capacitive Deionization Performance. Advanced Functional Materials 2014, 24, 3917-3925.


Page 34 of 38

Page 35 of 38

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


35.

Xu, X. T.; Liu, Y.; Lu, T.; Sun, Z.; Chua, D. H. C.; Pan, L. K. Rational Design and

Fabrication of Graphene/Carbon Nanotubes Hybrid Sponge for High-Performance Capacitive Deionization. Journal of Materials Chemistry A 2015, 3, 13418-13425. 36.

Qian, B.; Wang, G.; Ling, Z.; Dong, Q.; Wu, T.; Zhang, X.; Qiu, J. Sulfonated

Graphene as Cation‐Selective Coating: A New Strategy for High‐Performance Membrane Capacitive Deionization. Advanced Materials Interfaces 2015, 2. 37.

Wu, T.; Wang, G.; Dong, Q.; Qian, B.; Meng, Y.; Qiu, J. Asymmetric Capacitive

Deionization Utilizing Nitric Acid Treated Activated Carbon Fiber as the Cathode.

Electrochimica Acta 2015, 176, 426-433. 38.

Gao, X.; Omosebi, A.; Landon, J.; Liu, K. Enhanced Salt Removal in an Inverted

Capacitive Deionization Cell Using Amine Modified Microporous Carbon Cathodes.

Environmental science & technology 2015, 49, 10920-10926. 39.

Randin, J. P.; Yeager, E. Differential Capacitance Study of Stress‐Annealed Pyrolytic

Graphite Electrodes. Journal of the Electrochemical Society 1971, 118, 711-714. 40.

Lillo-Ródenas, M.; Cazorla-Amorós, D.; Linares-Solano, A. Understanding Chemical

Reactions between Carbons and Naoh and Koh: An Insight into the Chemical Activation Mechanism. Carbon 2003, 41, 267-275. 41.

Buqa, H.; Holzapfel, M.; Krumeich, F.; Veit, C.; Novák, P. Study of Styrene

Butadiene Rubber and Sodium Methyl Cellulose as Binder for Negative Electrodes in Lithium-Ion Batteries. Journal of Power Sources 2006, 161, 617-622. 42.

Wang, H.; Shi, L.; Yan, T.; Zhang, J.; Zhong, Q.; Zhang, D. Design of Graphene-

Coated Hollow Mesoporous Carbon Spheres as High Performance Electrodes for Capacitive Deionization. Journal of Materials Chemistry A 2014, 2, 4739-4750.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

43.

Zhao, R.; Biesheuvel, P. M.; van der Wal, A. Energy Consumption and Constant

Current Operation in Membrane Capacitive Deionization. Energy & Environmental Science 2012, 5, 9520-9527. 44.

Hancock, R. E.; Sahl, H.-G. Antimicrobial and Host-Defense Peptides as New Anti-

Infective Therapeutic Strategies. Nature biotechnology 2006, 24, 1551-1557. 45.

Wang, Y.; El-Deen, A. G.; Li, P.; Oh, B. H.; Guo, Z.; Khin, M. M.; Vikhe, Y. S.;

Wang, J.; Hu, R. G.; Boom, R. M. High-Performance Capacitive Deionization Disinfection of Water with Graphene Oxide-Graft-Quaternized Chitosan Nanohybrid Electrode Coating. ACS

nano 2015, 9, 10142-10157. 46.

Yao, C.; Li, X.; Neoh, K.; Shi, Z.; Kang, E. Surface Modification and Antibacterial

Activity of Electrospun Polyurethane Fibrous Membranes with Quaternary Ammonium Moieties. Journal of Membrane Science 2008, 320, 259-267. 47.

Marcano, D. C.; Kosynkin, D. V.; Berlin, J. M.; Sinitskii, A.; Sun, Z.; Slesarev, A.;

Alemany, L. B.; Lu, W.; Tour, J. M. Improved Synthesis of Graphene Oxide. ACS nano 2010, 4, 4806-4814. 48.

Liu, Y.; Chen, T.; Lu, T.; Sun, Z.; Chua, D. H.; Pan, L. Nitrogen-Doped Porous

Carbon Spheres for Highly Efficient Capacitive Deionization. Electrochimica Acta 2015,

158, 403-409. 49.

El-Deen, A. G.; Choi, J.-H.; Khalil, K. A.; Almajid, A. A.; Barakat, N. A. A Tio 2

Nanofiber/Activated Carbon Composite as a Novel Effective Electrode Material for Capacitive Deionization of Brackish Water. RSC Advances 2014, 4, 64634-64642. 50.

Liu, Y.; Lu, T.; Sun, Z.; Chua, D. H.; Pan, L. Ultra-Thin Carbon Nanofiber Networks

Derived from Bacterial Cellulose for Capacitive Deionization. Journal of Materials

Chemistry A 2015, 3, 8693-8700.


Page 36 of 38

Page 37 of 38

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


51.

Wu, T.; Wang, G.; Zhan, F.; Dong, Q.; Ren, Q.; Wang, J.; Qiu, J. Surface-Treated

Carbon Electrodes with Modified Potential of Zero Charge for Capacitive Deionization.

Water research 2016, 93, 30-37. 52.

Pugazhenthiran, N.; Sen Gupta, S.; Prabhath, A.; Manikandan, M.; Swathy, J. R.;

Raman, V. K.; Pradeep, T. Cellulose Derived Graphenic Fibers for Capacitive Desalination of Brackish Water. ACS applied materials & interfaces 2015, 7, 20156-20163. 53.

Porada, S.; Schipper, F.; Aslan, M.; Antonietti, M.; Presser, V.; Fellinger, T. P.

Capacitive Deionization Using Biomass‐Based Microporous Salt‐Templated Heteroatom‐ Doped Carbons. ChemSusChem 2015, 8, 1867-1874. 54.

Yin, H.; Zhao, S.; Wan, J.; Tang, H.; Chang, L.; He, L.; Zhao, H.; Gao, Y.; Tang, Z.

Three‐Dimensional Graphene/Metal Oxide Nanoparticle Hybrids for High‐Performance Capacitive Deionization of Saline Water. Advanced Materials 2013, 25, 6270-6276. 55.

Laxman, K.; Myint, M. T. Z.; Khan, R.; Pervez, T.; Dutta, J. Improved Desalination

by Zinc Oxide Nanorod Induced Electric Field Enhancement in Capacitive Deionization of Brackish Water. Desalination 2015, 359, 64-70. 56.

Li, Z.; Song, B.; Wu, Z.; Lin, Z.; Yao, Y.; Moon, K.-S.; Wong, C. 3d Porous

Graphene with Ultrahigh Surface Area for Microscale Capacitive Deionization. Nano Energy 2015, 11, 711-718. 57.

Wen, X.; Zhang, D.; Yan, T.; Zhang, J.; Shi, L. Three-Dimensional Graphene-Based

Hierarchically Porous Carbon Composites Prepared by a Dual-Template Strategy for Capacitive Deionization. Journal of Materials Chemistry A 2013, 1, 12334-12344.



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Flexible nanoporous graphene based asymmetric capacitive deionization electtrode 135x131mm (300 x 300 DPI)


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