Facile Method for the Preparation of Water Dispersible Graphene using Sulfonated Poly(ether–ether–ketone) and Its Application as Energy Storage Materials

Kuila, Tapas,Mishra, Ananta Kumar,Khanra, Partha,Kim, Nam Hoon,Uddin, Md. Elias,Lee, Joong Hee American Chemical Society 2012 Langmuir Vol.28 No.25

<P>A simple and effective method for the preparation of water dispersible graphene using sulfonated poly(ether–ether–ketone) (SPEEK) has been described. The SPEEK macromolecules are noncovalently adsorbed on the surface of graphene through π–π interactions. The SPEEK-modified graphene (SPG) forms an aqueous dispersion that is stable for more than six months. An analysis of the ultraviolet–visible spectra shows that the aqueous dispersion of SPG obeys Beer’s law and the molar extinction coefficient has been found to be 149.03 mL mg<SUP>–1</SUP> cm<SUP>–1</SUP>. Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy analyses confirm successful reduction and surface modification of graphene. An atomic force microscopy (AFM) analysis reveals the formation of a single layer of functionalized graphene. Transmission electron microscopy results are also in good agreement with the AFM analysis and support the formation of single-layer graphene. SPG shows good electrochemical cyclic stability during cyclic voltammetry and charge/discharge process when used as a supercapacitor electrode. A specific capacitance of 476 F g<SUP>–1</SUP> at a current density of 6.6 A g<SUP>–1</SUP> is observed for SPG materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2012/langd5.2012.28.issue-25/la301469u/production/images/medium/la-2012-01469u_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la301469u'>ACS Electronic Supporting Info</A></P>

Preparation of water-dispersible graphene by facile surface modification of graphite oxide

Kuila, Tapas,Khanra, Partha,Bose, Saswata,Kim, Nam Hoon,Ku, Bon-Cheol,Moon, Bongho,Lee, Joong Hee IOP Pub 2011 Nanotechnology Vol.22 No.30

<P>Water-dispersible graphene was prepared by reacting graphite oxide and 6-amino-4-hydroxy-2-naphthalenesulfonic acid (ANS). X-ray diffraction study showed that the basal reflection (002) peak of graphite oxide was absent in the ANS-functionalized graphene (ANS-G), indicating crystal layer delamination. Ultraviolet–visible spectral data were recorded to assess the solubility of the ANS-G in water. Fourier transform infrared spectral analysis suggested the attachment of ANS molecules to the surface of graphene. Raman and x-ray photoelectron spectroscopy revealed that oxygen functionality in the graphite oxide had been removed during reduction. Atomic force microscopy found that the thickness of ANS-G in water was about 1.8 nm, much higher than that of single layer graphene. Thermal stability measurements also indicated successful removal of oxygen functionality from the graphite oxide and the attachment of thermally unstable ANS to the graphene surfaces. The electrical conductivity of ANS-G, determined by a four-point probe, was 145  S m<SUP> − 1</SUP> at room temperature. </P>

Recent advances in the efficient reduction of graphene oxide and its application as energy storage electrode materials

Kuila, Tapas,Mishra, Ananta Kumar,Khanra, Partha,Kim, Nam Hoon,Lee, Joong Hee The Royal Society of Chemistry 2013 Nanoscale Vol.5 No.1

<P>Efficient reduction of graphene oxide (GO) by chemical, thermal, electrochemical, and photo-irradiation techniques has been reviewed. Particular emphasis has been directed towards the proposed reduction mechanisms of GO by different reducing agents and techniques. The advantages of using different kinds of reducing agents on the basis of their availability, cost-effectiveness, toxicity, and easy product isolation processes have also been studied extensively. We provide a detailed description of the improvement in physiochemical properties of reduced GO (RGO) compared to pure GO. For example, the electrical conductivity and electrochemical performance of electrochemically obtained RGO are much better than those of chemically or thermally RGO materials. We provide examples of how RGO has been used as supercapacitor electrode materials. Specific capacitance of GO increases after reduction and the value has been reported to be 100-300 F g(-1). We conclude by proposing new environmentally friendly types of reducing agents that can efficiently remove oxygen functionalities from the surface of GO.</P>

One-step electrochemical synthesis of 6-amino-4-hydroxy-2-napthalene-sulfonic acid functionalized graphene for green energy storage electrode materials

Kuila, Tapas,Khanra, Partha,Kim, Nam Hoon,Choi, Sung Kuk,Yun, Hyung Joong,Lee, Joong Hee IOP Pub 2013 Nanotechnology Vol.24 No.36

<P>A green approach for the one-step electrochemical synthesis of water dispersible graphene is reported. An alkaline solution of 6-amino-4-hydroxy-2-naphthalene-sulfonic acid (ANS) serves the role of electrolyte as well as surface modifier. High-purity graphite rods are used as electrodes which can be exfoliated under a constant electrical potential (∼20 V) to form ANS functionalized graphene (ANEG). The aqueous dispersion of ANEG obeyed Beer’s law at moderate concentrations, as evidenced from ultraviolet–visible spectroscopy analysis. X-ray diffraction analysis suggests complete exfoliation of graphite into graphene. Fourier transform infrared and x-ray photoelectron spectroscopy not only confirm the functionalization of graphene with ANS, but also suggest the formation of oxygen containing functional groups on the surface of ANEG. Raman spectra analysis indicates the presence of defects in ANEG as compared to pure graphite. Cyclic voltammetry and charge–discharge measurements of ANEG using three electrode systems show a specific capacitance of 115 F g<SUP>−1</SUP> at a current density of 4 A g<SUP>−1</SUP>. The ANEG electrode exhibits 93% retention in specific capacitance after 1000 charge–discharge cycles, confirming its utility as a green energy storage electrode material.</P>

Carbon-based nanostructured materials and their composites as supercapacitor electrodes

Bose, Saswata,Kuila, Tapas,Mishra, Ananta Kumar,Rajasekar, R.,Kim, Nam Hoon,Lee, Joong Hee The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.3

<p>This critical review provides an overview of current research on carbon-based nanostructured materials and their composites for use as supercapacitor electrodes. Particular emphasis has been directed towards basic principles of supercapacitors and various factors affecting their performance. The focus of the review is the detailed discussion regarding the performance and stability of carbon-based materials and their composites. Pseudo-active species, such as, conducting polymer/metal oxide have been found to exhibit pseudo-capacitive behavior and carbon-based materials demonstrate electrical double layer capacitance. Carbon-based materials, such as, graphene, carbon nanotubes, and carbon nanofibers, provide high surface area for the deposition of conducting polymer/metal oxide that facilitates the efficient ion diffusion phenomenon and contribute towards higher specific capacitance of the carbon based composite materials with excellent cyclic stability. However, further scope of research still exists from the view point of developing high energy supercapacitor devices in a cost effective and simple way. This review will be of value to researchers and emerging scientists dealing with or interested in carbon chemistry.</p> <P>Graphic Abstract</P><P>This review provides a summary of on-going researches on carbon-based nanostructured materials and their composites along with a demonstration of their performance and stability for use as supercapacitor electrodes. <img src='http://pubs.rsc.org/ej/JM/2011/c1jm14468e/c1jm14468e-ga.gif'> </P>

Facile preparation of flower-like NiCo₂O₄/three dimensional graphene foam hybrid for high performance supercapacitor electrodes

Zhang, Chunfei,Kuila, Tapas,Kim, Nam Hoon,Lee, Seung Hee,Lee, Joong Hee Elsevier 2015 Carbon Vol.89 No.-

<P><B>Abstract</B></P> <P>High quality flower-like NiCo<SUB>2</SUB>O<SUB>4</SUB> has been fabricated on three-dimensional (3D) graphene foam (GF) and used as an electrode for supercapacitors. The 3D GFs are prepared through chemical vapor deposition (CVD) followed by the electro-deposition of flower-like NiCo<SUB>2</SUB>O<SUB>4</SUB>. The NiCo<SUB>2</SUB>O<SUB>4</SUB>/3D GF nanohybrids are characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy analysis. The lack of defects in the 3D GF ensures the formation high quality graphene sheets by CVD method. The supercapacitor performances of the electrode materials are evaluated through cyclic voltammetry, charge–discharge analysis and electrochemical impedance spectroscopy. A maximum specific capacitance of 1402Fg<SUP>−1</SUP> is achieved at a current density of 1Ag<SUP>−1</SUP>. The NiCo<SUB>2</SUB>O<SUB>4</SUB>/3D GF nanohybrid-based supercapacitors exhibit long-cycle stability with a 76.6% retention in specific capacitance after 5000 cycles at a current density of 5Ag<SUP>−1</SUP>. The high electrochemical performance is attributed to the synergistic effects of the high electrical conductivity and large surface area of 3D GF along with the catalytic activity of the flower-like NiCo<SUB>2</SUB>O<SUB>4</SUB>.</P>

Carbon dot stabilized copper sulphide nanoparticles decorated graphene oxide hydrogel for high performance asymmetric supercapacitor

De, Bibekananda,Kuila, Tapas,Kim, Nam Hoon,Lee, Joong Hee Elsevier 2017 Carbon Vol.122 No.-

<P>A three-dimensional (3-D) porous structure was designed based on carbon dot (CD)-supported copper sulphide (CuS)-decorated graphene oxide (GO) hydrogel for using in a high-performance asymmetric supercapacitor device to improve the specific capacitance, cyclic stability and energy density of CuS as well as GO based supercapacitors. CD coated CuS (CuS@ CD) decorated GO hydrogels (CuS@ CD-GOH) were prepared by a simple hydrothermal reaction at 180 degrees C and optimized through different spectroscopic, diffraction, microscopic and electrochemical analyses. CD acted as a stabilizer for the CuS nanoparticles and help to bind strongly CuS nanoparticles with GO inside the 3-D hydrogel structure. The CuS@ CD-GOH exhibited high specific capacitance of 920 F g(-1) at a current density of 1 A g(-1). The optimal CuS@ CD-GOH was used as a positive electrode for the fabrication of asymmetric supercapacitor along with reduced GO as the negative electrode, which delivered the highest energy density up to 28 W h kg(-1) along with long cycling life and retains up to 90% specific capacitance after 5000 cycles. The results are excellent in comparison to the reported CuS and composite GO hydrogel based supercapacitors. Thus, this work will provide a new insight of CuS and GO based composite 3-D structures for supercapacitor applications. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Tin-Powder Mediated Facile Route for the Reduction of Graphene Oxide

Kim, Nam Hoon,Kuila, Tapas,Zhang, Chun Fei,Lee, Joong Hee Trans Tech Publications, Ltd. 2013 Advanced materials research Vol.747 No.-

<P>A facile approach for the reduction of graphene oxide (GO) using of Tin (Sn) powder and dilute hydrochloric acid at room temperature (RT) and at 50 °C upto 0.5-3 h has been reported. The as-prepared high quality crystalline graphene has been characterized using various analytical techniques. The rate of reduction scales with the reaction time for both RT and 50 °C as evidenced from electrical conductivity data. The graphene samples reduced at RT shows high electrical conductivity value due to the presence of un-reacted Sn-particles. resulting the enhancement in the However, the graphene prepared at 50 °C shows low electrical conductivity in comparison to the room temperature reduced graphene. XPS elemental analysis is in good agreement with this observation.</P>

Electrochemically Preparation of Functionalized Graphene Using Sodium Dodecyl Benzene Sulfonate (SDBS)

Joo, Eun Hye,Kuila, Tapas,Kim, Nam Hoon,Lee, Joong Hee,Kim, Seon A.,Park, Eu Gene,Lee, Un Hyeung Trans Tech Publications, Ltd. 2013 Advanced materials research Vol.747 No.-

<P>Preparation of functionalized graphene by electrochemical exfoliation of graphite rod using sodium dodecyl benzene sulfonate (SDBS) is reported. SDBS solution has been used as the electrolyte as well as functional groups. SDBD is an anionic surfactant which helps to provide uniform dispersion in water and prevents the π-π π-π stacking as well. XRD result indicates the formation of graphene whereas; the functionalization of graphene was confirmed through the FT-IR spectrum, which shows presence of peaks corresponding to SO3<SUP>-</SUP>. UV-vis spectroscopy demonstrates the dispersibility of SDBS-functionalized graphene, and peaks of SDBS and graphene appeared at 225 nm and 260nm, respectively. Raman spectroscopy show ID/IGIDIG ratio is < 1. It means that defects of SDBS-functionalized graphene are reduced.</P>

Recent advances in graphene and its metal-oxide hybrid nanostructures for lithium-ion batteries

Srivastava, Manish,Singh, Jay,Kuila, Tapas,Layek, Rama K.,Kim, Nam Hoon,Lee, Joong Hee The Royal Society of Chemistry 2015 Nanoscale Vol.7 No.11

<P>Today, one of the major challenges is to provide green and powerful energy sources for a cleaner environment. Rechargeable lithium-ion batteries (LIBs) are promising candidates for energy storage devices, and have attracted considerable attention due to their high energy density, rapid response, and relatively low self-discharge rate. The performance of LIBs greatly depends on the electrode materials; therefore, attention has been focused on designing a variety of electrode materials. Graphene is a two-dimensional carbon nanostructure, which has a high specific surface area and high electrical conductivity. Thus, various studies have been performed to design graphene-based electrode materials by exploiting these properties. Metal-oxide nanoparticles anchored on graphene surfaces in a hybrid form have been used to increase the efficiency of electrode materials. This review highlights the recent progress in graphene and graphene-based metal-oxide hybrids for use as electrode materials in LIBs. In particular, emphasis has been placed on the synthesis methods, structural properties, and synergetic effects of metal-oxide/graphene hybrids towards producing enhanced electrochemical response. The use of hybrid materials has shown significant improvement in the performance of electrodes.</P>