anish khan abdullah m. asiri editors graphene

Carbon Nanostructures

Anish KhanMohammad JawaidBernaurdshaw NeppolianAbdullah M. Asiri Editors

Graphene Functionalization StrategiesFrom Synthesis to Applications

Carbon Nanostructures

Series Editor

Paulo Araujo, The University of Albama, Tuscaloosa, AL, USA

Editorial Board

Antonio Gomes Sousa Filho, Universidade Federal do Ceara—UFC, Fortaleza,BrazilStephen K. Doorn, Los Alamos National Laboratory—LANL, Los Alamos,NM, USAAaron D. Franklin, Electrical & Com Engg, Hudson Hall 129, Duke University,Durham, NC, USAAchim Hartschuh, Ludwig-Maximilians-Universität, München, Germany

Carbon is intimately connected to almost everything we deal with in a daily basis.Due to its outstanding properties, such as high stability at environmental conditions,different hybridizations, strong covalent bond formation and easy of compoundsformation, carbon has been a topic of scientific interest in several areas. Indeed,starting in the 19th century, chemists have devoted a whole field to studycarbon-based compounds, which is, nowadays, known as Organic Chemistry.Remarkably, the last 30 years have been witnessing an exponential advance in thescience involving carbon and carbon structures. Since the discovery of Fullerenes in1985, which was awarded the Nobel Prize in Chemistry in 1996, carbonnanostructures have been attracting a great deal of attention from the researchcommunity. This public interest dramatically increased after the publications by theIijima and Bethune groups on single-wall carbon nanotubes in 1993 and found a“new research era” with the isolation of a monolayer of carbon atoms, also calledgraphene, which conducted groundbreaking experiments demonstrating outstandingphenomena such as the Klein-Tunneling and the fractional quantum hall effect.No wonder, graphene was the object of the 2010 Nobel Prize in Physics.

The “Carbon Nanostructures” book series covers the state-of-art in the research ofnanocarbons and their applications. Topics related to carbon allotropes such asdiamond, graphite, graphene, fullerenes, metallofullerenes, solid C60, bucky onions,foams, nanotubes and nanocones, including history, theory, synthesis, chemistry& physics, Biophysics & engineering, characterization methods, properties andapplications are welcome. Within the “Carbon Nanostructures” book series, thereader will find valuable, up-to-date account of both the newer and traditional formsof carbon. This book series supports the rapid expansion of this field and is avaluable resource for students and professionals in several different areas.

Springer welcomes new book ideas from potential authors. If you are interested inpublishing your book in this series, please contact us via [email protected]

** Indexed by Scopus (2018) **

More information about this series at http://www.springer.com/series/8633

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Anish Khan • Mohammad Jawaid •

Bernaurdshaw Neppolian • Abdullah M. AsiriEditors

Graphene FunctionalizationStrategiesFrom Synthesis to Applications

123

EditorsAnish KhanChemistry Department, Faculty of ScienceKing Abdulaziz UniversityJeddah, Saudi Arabia

Center of Excellence for AdvancedMaterials ResearchKing Abdulaziz UniversityJeddah, Saudi Arabia

Mohammad JawaidLaboratory of Biocomposite TechnologyINTROPUniversiti Putra MalaysiaSelangor, Malaysia

Bernaurdshaw NeppolianEnergy and Environmental Remediation LabSRM UniversityChennai, India

Abdullah M. AsiriChemistry Department, Faculty of ScienceKing Abdulaziz UniversityJeddah, Saudi Arabia

Center of Excellence for AdvancedMaterials ResearchKing Abdulaziz UniversityJeddah, Saudi Arabia

ISSN 2191-3005 ISSN 2191-3013 (electronic)Carbon NanostructuresISBN 978-981-32-9056-3 ISBN 978-981-32-9057-0 (eBook)https://doi.org/10.1007/978-981-32-9057-0

© Springer Nature Singapore Pte Ltd. 2019This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or partof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmissionor information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodology now known or hereafter developed.The use of general descriptive names, registered names, trademarks, service marks, etc. in thispublication does not imply, even in the absence of a specific statement, that such names are exempt fromthe relevant protective laws and regulations and therefore free for general use.The publisher, the authors and the editors are safe to assume that the advice and information in thisbook are believed to be true and accurate at the date of publication. Neither the publisher nor theauthors or the editors give a warranty, expressed or implied, with respect to the material containedherein or for any errors or omissions that may have been made. The publisher remains neutral with regardto jurisdictional claims in published maps and institutional affiliations.

This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd.The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721,Singapore

https://doi.org/10.1007/978-981-32-9057-0

Dedicate this bookto hislovely and preciousDaughterAleena JawaidDr. Mohammad Jawaid

Preface

The focus of this book is about the current demand of the technology i.e. func-tionalization of grapheme oxide by graphting different entities that respond to thedifferent functionalities just like the sensitive core entities. The specialism in gra-pheme oxide functionalization inaugurated by its outstanding electrical andmechanical properties. Unlike other material, this designed material is combinedwith resins, carbon materials, nanoparticles to form a high responding functionalityas to get the interested in that particular materials. Functionalized grapheme oxidecurrently stands best among the replacement materials to conventional engineeringmaterials because of its outstanding features such as lightweight, lower cost,environmentally friendly and sustainability. The unique feature of this book is thatit presents a unified knowledge of the high-quality material on the basis of char-acterization, design, manufacture and applications.

This book will help researchers, scientists and industries to understand the needof functionalized graphene for development of safe and sustainable products fordifferent applications. The characterization of functionalized graphene plays acrucial role to find out its potentiality in different real-world application. It elabo-rates the basic characterization of functionalized graphene or graphene oxide suchas; physical, mechanical, thermal and electrical properties. Added with significantmorphological and structural properties for clear understanding of this type ofmaterials.

We are highly thankful to all authors who contributed book chapters and providetheir valuable ideas and knowledge in this edited book. We attempt to gather all thescattered information of authors from diverse fields around the world (Malaysia,Jordan, USA, Turkey, India, Saudi Arabia, Bangladesh, Oman, and Sweden) in theareas of functionalized graphene nanocomposite and applications and finallycomplete this venture in a fruitful way. We greatly appreciate contributor’s com-mitment for their support to compile our ideas in reality.

vii

We are highly thankful to Springer-Nature team for their generous cooperation atevery stage of the book production.

Jeddah, Saudi Arabia Anish KhanSelangor, Malaysia Mohammad JawaidChennai, India Bernaurdshaw NeppolianJeddah, Saudi Arabia Abdullah M. Asiri

viii Preface

Acknowledgments

The financial support from Generalitat de Catalunya (Grant 2017SGR1033) and theSpanish Structures of Excellence Mariá de Maeztu Program GrantMDM-2017-0767. This work was supported by the project “Information andCommunication Technologies for a Single Digital Market in Science, Educationand Security” of the Scientific Research Center, NIS-3317.

ix

Contents

Synthesis of Metal/Metal Oxide Supported Reduced GrapheneOxide (RGO) for the Applications of Electrocatalysis andSupercapacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Lakshmanan Karuppasamy, Lakshmanan Gurusamy, Gang-Juan Leeand Jerry J. Wu

Functionalized Graphene-Metal Nanoparticles Nanohybridsas Electrochemical Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Ankita Sinha, Dhanjai, Jiping Chen and Rajeev Jain

Ultrasound-Assisted Synthesis, Exfoliation and Functionalisationof Graphene Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Dipanwita Majumdar

Sonochemically Covalent Functionalized Graphene Oxide TowardsPhotoluminescence and Nanocytotoxicity Activities . . . . . . . . . . . . . . . . 105Gopal Avashthi, Shrikant S. Maktedar and Man Singh

Functionalized Graphene/Polymer Nanofiber Compositesand Their Functional Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127Hanan Abdali and Abdellah Ajji

Graphene Functionalization and Nanopolymers . . . . . . . . . . . . . . . . . . . 157Martin Kássio Leme Silva and Ivana Cesarino

Electrochemical Detection of Dopamine in the Presence of Uric AcidUsing Graphene Oxide Modified Electrode as Highly Sensitiveand Selective Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179Buse Demirkan, Hasan Ay, Sümeyye Karakuş, Gülseren Uzun,Anish Khan and Fatih Şen

Cyclodextrin Functionalized Graphene and Its Applications . . . . . . . . . 193Li Fu

xi

Simulation Paths of Anticancer Drugs on a GrapheneOxide Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215Miroslava Nedyalkova, Julia Romanova, Joanna Stoychevaand Sergio Madurga

Graphene-Based Nanomaterials for Hydrogen Storage . . . . . . . . . . . . . 229Ayşenur Aygün, Esra Atalay, Shukria Yassin, Anish Khan and Fatih Şen

Functionalized Graphene for Drug Delivery Applications . . . . . . . . . . . 247T. K. Henna, K. P. Nivitha, V. R. Raphey, Chinnu Sabu and K. Pramod

Microwave-Assisted Modification of Graphene and Its Derivatives:Synthesis, Reduction and Exfoliation . . . . . . . . . . . . . . . . . . . . . . . . . . . 279Nitika Devi, Rajesh Kumar and Rajesh K. Singh

Graphene Functionalizations on Copper by SpectroscopicTechniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313Mehmet Gülcan, Ayşenur Aygün, Fatıma Almousa, Hakan Burhan,Anish Khan and Fatih Şen

Chemically Functionalized Penta-Graphene for Electronic DeviceApplications: Journey from Theoretical Prediction to PracticalImplementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335Kasturi Ghosh, Hafizur Rahaman and Partha Bhattacharyya

3D Graphene and Its Nanocomposites: From Synthesisto Multifunctional Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363Xin Tong, G. Zhang, Jai Prakash and Shuhui Sun

Enhanced Electrocatalytic Activity and Durability of PtRuNanoparticles Decorated on rGO Material for EthanolOxidation Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389Esra Kuyuldar, Hakan Burhan, Aysun Şavk, Buse Güven, Ceren Özdemir,Sultan Şahin, Anish Khan and Fatih Şen

xii Contents

About the Editors

Dr. Anish Khan is currently working as Assistant Professor in ChemistryDepartment, Centre of Excellence for Advanced Materials Research (CEAMR),Faculty of Science, KingAbdulaziz University, Jeddah, Saudi Arabia. Completed Ph.D. from Aligarh Muslim University, India from 2010. Completes Postdoctoral fromSchool of Chemical Sciences, University Sains Malaysia (USM) electroanalyticalchemistry in 2010). Working in the field of synthetic Biosensor, polymers composite,organic-inorganic electrically conducting nano-composites. More than 120 researcharticles, 30 book chapters 10 books published in referred international Publishers andmore than 20 international conferences/workshop. Member of American NanoSociety, Field of specialization is polymer nano composite/cation-exchanger/chemical sensor/microbiosensor/nanotechnology, application of nano materials inelectroanalytical chemistry, material chemistry, ion-exchange chromatography andelectro-analytical chemistry, dealing with the synthesis, characterization (using dif-ferent analytical techniques) and derivatization of inorganic ion-exchanger by theincorporation of electrically conducting polymers. Preparation and characterizationof hybrid nano composite materials and their applications, Polymeric inorganiccation–exchange materials, electrically conducting polymeric, materials, Compositematerial use as Sensors, Green chemistry by remediation of pollution, Heavy metalion-selective membrane electrode, Biosensor on neurotransmitter.

Dr. Mohammad Jawaid is currently working as Senior Fellow Researcher(Associate Professor) at Biocomposite Technology Laboratory, Institute of TropicalForestry and Forest Products (INTROP), Universiti Putra Malaysia (UPM),Serdang, Selangor, Malaysia, and also has been Visiting Professor at theDepartment of Chemical Engineering, College of Engineering, King SaudUniversity, Riyadh, Saudi Arabia since June 2013. He has more than 14 years ofexperience in teaching, research, and industries. His area of research interestsincludes hybrid composites, lignocellulosic reinforced/filled polymer composites,advance materials: graphene/nanoclay/fire retardant, modification and treatment oflignocellulosic fibers and solid wood, biopolymers and biopolymers for packaging

xiii

applications, nanocomposites and nanocellulose fibers, and polymer blends. So far,he has published 34 books, 60 book chapters, more than 250 peer-reviewedinternational journal papers, and 5 published review papers under top 25 hot articlesin science direct during 2013–2018. H-index and citation in Scopus are 37 and 6179and in Google scholar, H-index and citation are 44 and 8594. He worked as guesteditor of special issues of Current Organic Synthesis and Current AnalyticalChemistry, Bentham Publishers, UK; International Journal of Polymer Science,Hindawi Publishing; Inderscience Enterprises Ltd; IOP Conference Proceeding; andis Editorial Board Member of Journal of Polymers and The Environment, Journalof Asian Science, Technology and Innovation and the Recent Innovations inChemical Engineering. Besides that, he is also reviewer of several high-impactinternational peer-reviewed journals of Elsevier, Springer, Wiley, Saga, etc.Presently, he is supervising 18 Ph.D. students (6 Ph.D. as Main Supervisor, and 12Ph.D. as Member) and 9 Master’s students (3 Master as Main Supervisor, and 6Master as Member) in the fields of hybrid composites, green composites,nanocomposites, natural fiber-reinforced composites, nanocellulose, etc. 12 Ph.D.and six master’s students graduated under his supervision in 2014–2018. He hasseveral research grants at university, national, and international levels on polymercomposites of around 3 million Malaysian ringgits (USD 700,000). He alsodelivered plenary and invited talks in international conferences related to com-posites in India, Turkey, Malaysia, Thailand, the United Kingdom, France, SaudiArabia, Egypt, and China. Besides that, he is also a member of technical com-mittees of several national and international conferences on composites andmaterial science. Recently Dr. Mohammad Jawaid received Excellent AcademicAward in Category of International Grant-Universiti Putra Malaysia-2018 and alsoExcellent Academic Staff Award in industry High Impact Network (ICAN 2019)Award. Beside that Gold Medal-Community and Industry Network (JINMShowcase) at Universiti Putra Malaysia. He also Received Publons Peer ReviewAwards 2017, and 2018 (Materials Science) and Certified Sentinel of scienceAward Receipient-2016 (Materials Science). He is also Winner of Newton-UngkuOmar Coordination Fund: UK-Malaysia Research and Innovation BridgesCompetition 2015.

Dr. Bernaurdshaw Neppolian is currently working as a Professor at SRMResearch Institute, SRM University, Kattankulathur, Chennai, India since 2012. Hehas more than 20 years of research experience in the field of photocatalysis. Heobtained his Ph.D. degree Anna University, Chennai, year 2000 and then he joinedas a Post Doctoral Researcher at Gwangju Institute of Science and Technology,South Korea for two years (2000–2002). Later, Dr. Neppolian had been awardedwith Japan Society of Promotion of Science (JSPS), prestigious fellowship to carryout research work at Osaka Prefecture University, Osaka, Japan (2002–2006).Dr. Neppolian had been awarded by KOSEF Brain Pool program to work as aResearch Professor in Gwangju Institute of Science and Technology, South Koreafor two years (2006–2008). Before joining at SRM University, he worked inDepartment of Chemistry under the Discovery Project of Australian Research

xiv About the Editors

Council, University of Melbourne, Australia for more than 3 years (2008–2011).He is author of more than 100 publications that have received around 5000 citationswith H-Index of 30 and 6 book chapters. He has been working on the preparation ofTiO2 based photocatalysts for energy and environmental remediation studiesincluding splitting of water to produce hydrogen. He is also working on advancedoxidation methods including ultrasound method for the degradation of organicpollutants. Recently, his group started working on Polymer solar cells and Directmethanol oxidation fuel cell using metallic catalysts prepared by ultrasound assistedmethod. He is currently having 4 research projects from Department of ScienceTechnology and Ministry of New and Renewable Energy, India and guided onePh.D. student, guiding 8 Ph.D. students and tranined many post and under graduatestudents. He is potential reviewer for more than 40 reputed international jour-nals inclduing Applied Catalysis B, Enery and Environmental Science, Langumir,etc. He recently received Hiyoshi Environmental Award-2015 from HiyoshiCorporation, Japan for his outstanding research in the field of environmental pro-tection in India.

Prof. Abdullah M. Asiri is Professor in Chemistry Department—Faculty ofScience—King Abdulaziz University. Ph.D. (1995) From University of WallsCollege of Cardiff, U.K. on Tribochromic compounds and their applications. Thechairman of the chemistry department, King Abdulaziz University currently andalso The Director of the center of Excellence for advanced Materials Research.Director of Education Affair Unit–Deanship of Community services. Member ofAdvisory committee for advancing materials, (National Technology Plan, KingAbdul Aziz City of Science and Technology, Riyadh, Saudi Arabia). Colorchemistry. Synthesis of novel photochromic and thermochromic systems, Synthesisof novel colorants and coloration of textiles and plastics, Molecular Modeling,Applications of organic materials into optics such as OEDS, High performanceorganic Dyes and pigments. New applications of organic photochromic compoundsin new novelty. Organic synthesis of heterocyclic compounds as precursor for dyes.Synthesis of polymers functionalized with organic dyes. Preparation of somecoating formulations for different applications. Photodynamic thereby usingOrganic Dyes and Pigments Virtual Labs and Experimental Simulations. He ismember of Editorial board of Journal of Saudi Chemical Society, Journal of KingAbdul Aziz University, Pigment and Resin Technology Journal, Organic ChemistryInsights, Libertas Academica, Recent Patents on Materials Science, BenthamScience Publishers Ltd. Beside that he has professional membership of Internationaland National Society and Professional bodies.

About the Editors xv

Synthesis of Metal/Metal OxideSupported Reduced Graphene Oxide(RGO) for the Applicationsof Electrocatalysis and Supercapacitors

Lakshmanan Karuppasamy, Lakshmanan Gurusamy,Gang-Juan Lee and Jerry J. Wu

Abstract Reduced graphene oxide (RGO), atomically thin two-dimensional car-bon nanosheets, owns outstanding chemical, electrical, material, optical, andphysical properties due to its large surface area, high electron mobility, thermalconductivity, and stability. These unique properties have made reduced grapheneoxide an ideal platform for constructing a series of RGO-based functional nano-materials. Specifically, RGO and RGO derivatives have been utilized as templatesfor the synthesis of various noble-metal/metal oxide nanocomposites. These hybridnanocomposites materials are promising alternatives to reduce the drawback ofusing only transition metal nanoparticles in various applications, such as electro-chemical energy storage and conversion technology of supercapacitors and fuelcells. The goal of this chapter is to discuss the state-of-the-art of reduced grapheneoxide-based metal and metal oxide nanocomposites with a detailed account of theirsynthesis and properties. Especially, much attention has been paid to their synthesisand a wide range of applications in various fields, such as electrochemical andelectrical fields. This chapter is presented first time with an introduction, followedby synthetic methods of RGO and RGO-based nanocomposites. Then, the appli-cation of this novel RGO/metal-metal oxide nanocomposites in fuel cells andsupercapacitors are summarized and discussed. Finally, the future research trendsand challenges of design and synthesis of RGO/metal-metal oxide nanocompositesare presented.

Keywords Reduced graphene oxide � Metal/metal oxide nanocomposites �Supercapacitors � Fuel cells � Electrochemical reaction

L. Karuppasamy � L. Gurusamy � G.-J. Lee � J. J. Wu (&)Department of Environmental Engineering and Science, Feng Chia University,Taichung 407, Taiwane-mail: [email protected]

© Springer Nature Singapore Pte Ltd. 2019A. Khan et al. (eds.), Graphene Functionalization Strategies,Carbon Nanostructures, https://doi.org/10.1007/978-981-32-9057-0_1

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1 Introduction

Graphene, a two-dimensional single atomic layer planar sheet with densely packedatomically thin layer of sp2 hybridized carbon atoms in a honeycomb crystal lattice.Since the first isolation of graphene in 2004 [1]. The appreciation of its significancewas followed by the physics noble prize in 2010. The unique and superior physicaland chemical properties of graphene, such as a large specific surface area,high-speed electron mobility, strong mechanical strength, and excellent electric andthermal conductivity, are now frequently utilized with new applications [2, 3].Chemists have taken the advantages of its unique properties by the research ongraphene and its nanocomposites, graphene oxide (GO) and reduced grapheneoxide (RGO), which have emerged as a promising new nanomaterial for a variety ofexciting applications in the fields of chemistry, physics, biology, and many otherinterdisciplinary fields, such as nanotechnology and nanomedicine. For nearly threedecades, carbonaceous materials, such as fullerenes and carbon nanotubes (CNTs),have drawn considerable attention due to their exceptional electronic andmechanical properties [4]. Specifically, after the discoveries of zero-dimensional(0-D) buckminsterfullerene [5] and shortly later one-dimensional (1-D) CNTs [6],enthusiasm in the research of carbon-based nanomaterials has increased further [7].Both fullerenes and CNTs have been proposed to be derived from 2-D graphenesheets that are viewed as key building blocks of all other graphitic carbon allotropes(Fig. 1), such as “graphite” made up of graphene sheets stacked on top of eachother (separated by an interlayer distance of 3.37 °A) [8]. “Fullerenes” and “CNTs”can be virtually made by wrapping and rolling a section of a graphene sheet [9]. Inreality, however, they are not synthesized from graphene.

Fig. 1 Graphene is atwo-dimensional buildingblock for carbonaceousmaterials of all otherdimensions and it can bewrapped up into 0-Dbuckyballs, rolled into 1-Dnanotubes or stacked into 3-Dmultilayer graphene

2 L. Karuppasamy et al.

Great contributions have been made in the synthesis of novel catalytic, magnetic,and optoelectronic properties of graphene nanocomposites based on thehybridization with nanoparticles (NPs). It can be noted that hybridizationhas provided an effective strategy for enhancing the functionality of materials [10].Particularly, due to the unique sp2 hybridization of carbon bonds present in gra-phene, it facilitates the delocalization of electrons to possess excellent electronicconduction [1]. This electronic conduction of graphene can be enhanced byincorporating various inorganic nanoparticles, including different metal and metaloxide NPs. Due to the enhanced electrical and electronic properties and the syn-ergistic effect between graphene and inorganic nanoparticles, graphene/nanoparticlecomposites offer a great potential for various applications, including energy storagesupercapacitor and energy conversion fuel cells devices [11–13]. In order to furtherenhance the properties and to broaden the applications of graphene, various metaland metal oxide NPs have been decorated on graphene. Apart from enhancing theproperties of graphene, the NPs act as a stabilizer against the aggregation ofindividual graphene sheet, which is caused by strong van der Waals interactionsbetween graphene layers [14]. Therefore, more efforts and new strategies to syn-thesize graphene-based nanocomposites are indispensable. This chapter has focusedon one of such nanocomposites, made of chemically exfoliated graphene and metaloxides. We overview and discuss their synthesis methods, structural features,electrocatalytic applications, and future perspectives.

1.1 Comparison of Energy Storage and Conversion Devices(Electrochemical Supercapacitors, Battery,and Fuel Cells)

Energy and power densities are of two main parameters of an energy storagesystem. Specific energy, expressed in watt-hours per kilogram (Wh kg−1), deter-mines how much amount of energy could be stored in the system. While thespecific power in watt per kilogram (W kg−1) indicates how the energy could beconverted. The energy and power density was compared in the electrochemicalenergy storage system, which is known as a Ragone plot as shown in Fig. 2. Thespecific energy usually decreases with the increase of specific power. The con-ventional capacitors have been considered as high-power systems, whereas fuelcells exhibited the high energy density with the combustion engine. Compared withthe conventional capacitors, electrochemical supercapacitor (ES) has the ability tostore greater amounts of energy due to high surface area carbon nanomaterialscombined with pseudocapacitive nature of nanostructured materials. In addition, ESis able to deliver more power than batteries.

Synthesis of Metal/Metal Oxide Supported Reduced Graphene Oxide … 3

The energy storage mechanism of ES and batteries are fundamentally different.The ES stores the charge on the surface of capacitive materials, whereas batteriesstore the charge on entire bulk of the electrodes [16, 15]. ESs, batteries, and fuelcells do not always compete with each other. The high power and high-energyresources of electrochemical capacitor have bridged the gap between capacitors andbatteries. ES also possess a number of desirable properties that make them anattractive energy storage behavior [17]. For example, the extremely reversiblecharge and discharge cycle of EDLCs were obtained in a suitable potential window.Moreover, ESs can store or release energy very quickly and can operate over a widerange of temperatures. They also have a high charge and discharge efficiency. Theenergy loss to heat during each cycle is relatively small. In addition, ESs generallydo not contain toxic materials and are much safer than batteries and fuel cells [18].

With the aforementioned advantages, ESs have become a very competitivechoice for practical applications of electric vehicles, elevators, digital cameras,mobile phones, pulse laser techniques, and uninterruptible power supplies [19]. Forinstances, it is very expensive to make frequent replacement of the batteries in thememory back-up system due to their poor cycle life. In a fuel cell or battery electricvehicles, it is difficult to meet peak load requirements of high power, like accel-erating or climbing. With the advantages of a long lifetime and high power density,ESs can solve these problems. In the coming decades, the main market targeted byESs manufacturers may be on the transportation, including hybrid electric vehiclesand metro trains [20].

Fig. 2 Schematic diagram of the Ragone plot of energy storage devices [15]


2 Synthesis of RGO and RGO-Based Metal-Metal OxideNanocomposites

2.1 Synthesis of Reduced Graphene Oxide (RGO)

A number of methods have been reported already for the synthesis of RGO that canbe mainly classified into two different categories, bottom-up approaches andtop-down approaches (Fig. 3). The bottom-up synthesis of RGO sheets is analternative to the micromechanical exfoliation of bulk graphite. For the bottom-upprocesses, RGO is synthesized by a variety of methods, such as chemical vapor

Fig. 3 Schematic representation of the methods used for the synthesis of reduced graphene oxide(RGO), which is classified into top-down and bottom-up approaches. The top-down approach iswidely used for the scalable synthesis of graphene that produces a relatively low quality ofgraphenes like material commonly known as Highly Reduced Graphene Oxide (HRGO) orgraphene in the large quantity required for the preparation of graphene-based nanocomposites


deposition (CVD) [21, 22], arc discharge [23], and epitaxial growth on SiC [24].Using CVD, RGO, and few-layer RGO have been grown on catalytic metal sur-faces from carbon-containing gases. The direct synthesis of the CVD method isused for the production of high-quality layers of RGO nanosheets with a large areaand low defect concentration, but in small quantities. However, these and othermethods revealed before unsuitable for the synthesis of RGO-based nanocompos-ites, whereas bulk quantities of RGO sheets with a modified surface structure arerequired. Therefore, for the synthesis of RGO-based nanocomposites, top-downapproaches have been used in most cases. These techniques yield low-cost bulkamounts of RGO-like sheets that albeit not defect free, and they are highly pro-cessable and can be fabricated into a variety of materials.

The manufacturing of RGO-based nanocomposites generally requires bulkquantities of homogeneously distributed RGO sheets. Therefore, the most commontop-down approach for the synthesis of RGO is the reduction of GO by thermal orchemical methods (Fig. 3). The reduction of GO is a low cost and facile techniqueto yield bulk quantities of RGO nanosheets, where those are highly processable andcan be fabricated into a variety of materials. It is now being reinvestigated andreceiving intense research interest due to its extensive use as a precursor for thelarge-scale synthesis of RGO and RGO-based materials. Hence, the application ofgraphite or graphite derivatives for the synthesis of RGO offers considerable eco-nomic advantages over bottom-up methods. Initially, GO was prepared frominexpensive graphite as a raw starting material by the cost-effective and scalablemodified Hummers method [25]. Using oxidation and exfoliation of this graphiteoxide followed by a reduction process, graphene can be achieved as highly RGO.Like graphite, GO has a layered structure, but the plane of the carbon atoms areheavily decorated by oxygen-containing functional groups, which expand theinterlayer distance and make graphite oxide hydrophilic. Exfoliated GO has onlyone or a few layers of carbon atoms like graphene. GO can be reduced to grapheneby removing the oxygen-containing functional groups with the recovery of theconjugated structure. Different reduction processes have been introduced to convertGO into graphene and different reduction processes result in different properties ofgraphene, which in turn affects the final product and also the performance of thematerial [26]. Reduced GO has chemically derived graphene, which is also referredto functionalized graphene [27], chemically modified graphene [28], RGO [29],chemically converted graphene [30], or reduced graphene [31]. For the chemicalreduction of GO, hydrazine monohydrate and dimethylhydrazine have been usedextensively as these do not react with water and have the attractive option forreducing GO in an aqueous dispersion [32–34]. Though hydrazine effectivelyremoves the oxygen functional group from GO, it also introduces heteroatomimpurities, such as N2, which form amines, hydrazones, or other similar functionalgroups covalently attached on the sheet of graphene [35]. NaBH4 has beendemonstrated as being more effective than hydrazine as a reducing agent of GO.NaBH4 is more effective at reducing the C=O group, while it has moderate effi-ciency in the reduction of epoxide and carboxylic acid [36] (Table 1).


Other reductants used for the chemical transformation of GO to graphene includehydroquinone [41], gaseous H2 [42], alkaline solution [43, 44], and ascorbic acid[45]. Despite the chemical reagent reduction, other reduction processes were usedfor the conversion of GO to graphene, e.g., microwave irradiation [46, 47], elec-trochemical reduction [48, 49], thermal annealing [50], photocatalytic reduction[51], solvothermal reduction [52, 53], thermal deoxygenation [54], or chemicaldeoxygenation [55]. In terms of electrical conductivity, the quality of reducedgraphene is lower than that of the graphene nanosheets prepared by CVD. Theintrinsic quality of CVD graphene films makes them an excellent candidate foroptoelectronic and electronic applications. In brief, the reduction method fits betterfor the production of small graphene nanosheets. However, the CVD process ismore efficient for larger graphene nanosheets.

Table 1 Advantages and limitations of the major synthesis procedure of graphene

Syntheticprocedure

Advantages Limitations Ref.

Micromechanicalexfoliation

• Simple process• Few decades• Excellent quality ofgraphene

• Well suited forfundamental research

• Poor reproducibility• Not amenable for large scaleproduction

[37]

CVD • Large area (up to *1 cm2)• A limited number ofdefects

• Mass production• High-quality graphene

• Expensive• Poor scalability

[38]

Epitaxial growth • High quality of graphene• Few defects

• High cost• High temperature required

[37]

Colloidalsuspension

• Scalable• High volume of production• Suitable for multipurposechemical functionalization

• Significant numbers of defects [34]

Unzipping ofCNTs

• Scalable with controlledwidths and edge structures

• Better control overchemical functionalizationand edge quality

• Low yield• More expensive in respect tochemical exfoliation of graphite orgraphite oxide

[39]

Reduction of GO • Economical and faciletechnique

• Significant numbers of defects [40]


2.2 Synthesis and Architecture of NPs-RGONanocomposites

Graphene derivatives, especially GO and RGO, are good templates or supports formetal and metal oxide nanoparticle nucleation, growth, and attachment, owing to alarge number of defects and oxygen functional groups on their surfaces. Thus, for thesynthesis of graphene-nanocomposites in most cases, top-down approaches havebeen used. In another process for the synthesis of graphene-based nanocomposites,graphene or nanoparticles (NPs) could be chemically functionalized firstly and thenNPs could be conjugated to the graphene surface by covalent or noncovalentinteraction [56, 57]. Graphene is flexible and has a unique 2D sheet-like structure.These sheets can be easily used to wrap or encapsulate NPs with diameters from thenanometer to even the micrometer range. The encapsulated structure is comprised ofa single NP encapsulated by a single graphene nanosheet (Fig. 4a), whereas awrapped structure refers to the case where more than one NP is covered by multiplegraphene nanosheets (Fig. 4b). Graphene encapsulated and wrapped structures haveadvantages compared to bare NPs, including reduced NP agglomeration, as well asincreased electrical, electrochemical, and optical properties. Encapsulating NPs withgraphene increases the surface-to-volume ratio that is available for sensing [58].

Furthermore, the presence of graphene results in extremely high carrier mobility,high carrier density, and low intrinsic noise for better detection by virtue of the highsignal-to-noise ratio. In the anchored structure, electroactive NPs are anchored onthe graphene nanosheets (Fig. 4c) [59] and in the mixed structure the graphene and

Fig. 4 Schematic presentation of methods used for the formation of graphene–nanoparticles(NPs) composites and different structures of a graphene-encapsulated NPs, b graphene-wrappedNPs, c NPs anchored to graphene nanosheets, d mixed graphene–NP structures, e graphene–NPsandwich structures, and f graphene–NP layered


NPs are synthesized separately and mixed mechanically for application needs invarious fields (Fig. 4d) (though mainly used for electrode preparation in Li-ionbattery applications). In the sandwich structure, graphene was used as a template togenerate the active NP/graphene sandwich structure (Fig. 4e) [60] and in the layerstructure, graphene and NPs (Fig. 4f) were alternated. The most research effort hasbeen directed towards the quality improvement of RGO in order to ameliorate theproperties of graphene.

2.3 Synthesis of Metal/Metal Oxide NPs on ReducedGraphene Oxide

In this section, the synthetic methods of preparing metal and metal oxide NPs ongraphene are classified according to the overall strategy and the frequency of theiruse in the literature (Fig. 5), namely in situ (chemical reduction, hydrothermal andelectrochemical methods) and ex situ methods (e.g., physical mixingpre-synthesized NPs with graphene derivatives). Ex situ method involves mixing of

Fig. 5 Schematic illustration of the binding mechanisms of nanoparticles (NPs) onto HRG sheets.The NPs can be loaded onto HRG sheets in two different ways by in situ or ex situ binding. A highdensity of NPs can be achieved via in situ binding. Both HRG sheets and NPs can befunctionalized either via non-covalent p–p stacking or covalent C–C coupling reactions [10]


separate solutions of graphene nanosheets and pre-synthesized NPs. Prior to mix-ing, the NPs and/or graphene sheets are surface functionalized to enhance theprocessability of the resulting products. The conjugated graphene sheets can bereadily functionalized by non-covalent p–p stacking or covalent C–C couplingreactions. The functionalization of graphene and/or NPs significantly enhances theirsolubility and hence broadens the opportunities for the preparation ofgraphene-based composites. However, the ex situ method may suffer from lowdensity and non-uniform coverage of nanostructures by graphene sheets. Therefore,the in situ methods for the preparation of metal and metal oxide decoratedgraphene-based nanocomposites will be discussed in some detail. In the followingparagraphs, we describe the most recent methods for the synthesis ofgraphene-based metal and metal oxide nanocomposites by in situ methods, i.e. bythe simultaneous reduction of graphite oxide or graphene oxide and the respectivemetal salts.

2.3.1 In Situ Method

Wet-Chemical Method

The chemical reduction method is probably used most frequently because this easyand straightforward method can generate the graphene-based metal and metal oxidenanocomposites [61–63]. In a typical synthesis, the metal precursor (e.g., HAuCl4,K2PdCl4 or H2PtCl6) is mixed with the graphene compounds in an aqueous solutionunder a given condition and the reductant (e.g. NaBH4) is then added.

During the synthesis, the metal precursor is reduced to its metallic form, wherethere are three primary steps: reduction, nucleation, and NP growth, and meanwhilethe graphene derivative are also reduced. In this method, GO is the most frequentlyused graphene compound because the surface functional groups of GO not onlyafford solubility in water [64–66], but also they stabilize NPs. In a typical case,Hutchings’ group adopted this method for preparing GO-stabilized Au–Pd NPs(AuPd–GO) using a “ligand-free” chemical reduction method [67]. GO wasintroduced into a mixed aqueous solution of HAuCl4 and PdCl2 and the metalprecursors were reduced using NaBH4, without the addition of a surfactant, to formAuPd NPs stabilized solely by GO (AuPd–GO) (Fig. 6). Due to the broad AuPd NPsize distribution (1–7 nm) and GO stacking, however, AuPd NPs/GO exhibitedworse conversion even than PVA-stabilized AuPd/GO counterpart in thesolvent-free oxidation of alcohols with molecular oxygen. In order to overcomethese problems, the authors then immobilized the TiO2 NPs, which efficientlyinhibited stacking of GO layers, promoted the diffusion of alcohols and oxygenmolecules between adjacent GO sheets, and therefore improved the surface catalyticactive sites exposure and significantly enhanced the catalytic activity.


Microwave-Irradiation (MWI) Method

MWI is also widely applied for the synthesis of graphene-based nanocomposites.Particularly, the preparation of graphene/metal nanoparticle (NP) composites bysimultaneous (in situ) reduction of various metal salts and GO is highly effective. Inthe case of microwave-assisted reduction to prepare metal-metal oxide/graphenecomposites, the microwaves caused local dielectric heating of a metal salt solution,thereby resulting in the reduction. The advantage of microwave irradiation-assistedreduction is the uniform and rapid heating that reduces the barriers to the reduction,nucleation, ion incorporation, and NP growth [68, 69]. Thus, in this way, the NPsare obtained with ultrafine NP size and narrow size distribution. For instance,Chen’s group reported the microwave-assisted synthesis of CuNPs/GO in thepresence of EG (Fig. 7), yielding GO-decorated CuNPs with a 4.1–5.4 nm size thatdepends on the Cu contents [69]. MWI has attracted much attention due to its easeof processing and scalable production. Moreover, owing to the rapid and uniformheating, MWI prevents the aggregation of graphene layers. A major drawback is thedifficulty in controlling the size, uniformity, and surface distribution of NPs onRGO surfaces.

Fig. 6 Preparation of GO-stabilized Au–Pd NPs on TiO2 (AuPd–GO/TiO2) using “ligand-free”co-reduction and subsequent sol-immobilization method [67]


Hydrothermal Method

Hydrothermal and solvothermal reduction processes have been applied for thesynthesis of graphene-based metal and metal oxide nanocomposites. It is alow-cost, facile, and template less approach. It generally involves a chemicalreaction occurring in a solvent at high temperature above the solvent boiling pointand under high pressure in the presence or absence of reducing agent. The NP size,morphology, and crystallinity are tuned upon by adjusting the temperature, pres-sure, nature of the solvent, and eventually the presence and nature of the reducingagent. Meanwhile, the graphene derivative may also undergo a reduction process toRGO. Moreover, in most of the case, this method allows the synthesis of metal andmetal oxide/graphene nanohybrids in one-step. Hydrothermal reactions are some-times carried out in the absence of reducing agent, but a solvent such as water [70]is necessary. This method is eventually associated with the subsequent annealingtreatment to modify the NP morphology. On the other hand, the solvent (EG [71,72], formic acid [73], EtOH, or DMF) also serves as the reducing agent.

In a typical synthesis procedure [71], the pre-synthesized 3D graphene (3DG)was mixed with Pd(acac)2 and Co(acac)2 in the presence of EG under stirring. Themixed solution was placed in a Teflon-sealed autoclave and maintained at 260 °Cfor 10 h under high-purity argon protection followed by centrifugation, washing,and oven-drying at 70 °C to obtain the Pd6Co/3DG catalyst. The resulting Pd6Co/3DG has a narrow size of Pd6Co NPs of 5.2 nm that was uniformly distributed onthe 3DG, showing a much higher formic acid electro-oxidation activity, the largerpeak current density and better stability than Pd/3DG, Pd/C and commercial Pd–Ccounterparts (Fig. 8). Similarly, Zhang and co-workers reported a facile andcost-effective strategy to synthesize ultrafine Pd NPs supported on N and Sdual-doped graphene (NS-G) nanosheets for both direct formic acid fuel cell anddirect methanol fuel cell [72]. The NS-G was first prepared by the incorporation ofN and S atoms into graphene frameworks via a thermal treatment process, followed

Fig. 7 Microwave synthesis process for GO hybrids decorated with CuNPs [69]


by the controlled growth of PdNPs on it through a hydrothermal process. The PdNPs were obtained with an ultrasmall size of 4.6 nm benefiting from thepre-synthesized NS-G sheets that provided sufficient anchoring sites.

Sonochemical Method

The ultrasonic wave irradiation method provides a remarkably facile and versatileroute to fabricate various metal nano-architectures in a very short period of time, inwhich the ultrasonic wave produces various distinctive properties by acousticcavitation, such as bubbles formation, growth, and implosive the collapse of bub-bles in the liquid, which can be well utilized to achieve excellent quality of novelmetal nano dendrites with narrower size distribution, larger surface area, and amuch smaller size [74]. Nevertheless, limited articles are available on the devel-opment of novel metal nano dendrite structures by ultrasonic irradiation for the useas in DEFC. Herein, we have reported a facile one-pot synthesis of Au nanodendrites with branched architectures of RGO nanosheets by sonochemical irradi-ation method (Fig. 9). The important advantages of this novel method to synthesizeAu nano dendrites on RGO nanosheets consist of the following: (1) the Au nanoseeds are formed at very short interval of ultrasonic wave irradiation, which can beeither act as a catalyst to further growth of Au nano dendrites structures, (2) the sizeand shape of Au nano dendrites can be easily controlled by ultrasonic irradiationtime, concentration of surfactant and reducing agent, and (3) the as obtained Au

Fig. 8 One-pot hydrothermal process synthesis of a Pd6Co/3DG catalyst and its application informic acid oxidation [71]


nano dendrites with “clean” surfaces on RGO nanosheets can be directly utilized asthe electrocatalyst towards ethanol oxidation and oxygen reduction in alkalinemedium without further pretreatment.

In a typical preparation of Au-RGO nano dendrites (Fig. 9), firstly 80 mg ofgraphene oxide (GO) was dispersed in 40 ml DI water (2 mg mL−1) for 10 min byultrasonication and centrifuged at 10,000 rpm for 15 min. The dispersion andultrasonication followed by centrifugation of this step repeated 4 times to endorsethe discard of unwanted impurities from graphene oxide nanosheets and the finalprecipitate of graphene oxide nanosheets was dissolved in 20 mL DI waters forfurther use. Secondly, the fabrication of Au nano dendrites on RGO nanosheets wasdone by ultrasonic irradiation method (Ti-horn, 20 kHz, and 100 W cm−2) in Aratmosphere for 45 min (55 s on, 5 s off mode) (synthesis scheme as shown inFig. 8). The aqueous solution containing 40 mL of 0.2 M CTAB, 1.92 mL of3.0 mM AgNO3, 40 mL of 1 mM HAuCl4 (Au(III)), and 1 mL of 0.1 M ascorbicacid with 10 min of vigorous stirring and keep aside at room temperature for 7 hwithout disturbing. After 7 h, the resultant solution mixture followed by adding10 mL GO suspension was purged with 60 mL min−1 Ar for 20 min and thenirradiated with the ultrasonic horn for 45 min (ultrasonic bath maintained at 25 °Cby a water circulating system). The final product of Au-RGO nano dendrites wascollected carefully and washed with absolute ethanol and water by several cyclesfor the removal of unreacted substrates. Finally, the composite was dried in vacuumair at 60 °C for 24 h.

Fig. 9 Sonochemical method for synthesis of an Au/RGO catalyst and its application inelectrocatalytic ethanol oxidation fuel cells [75]


Electrochemical Deposition Method

Chemical synthesis methods have been widely applied for the fabrication offlower-like PtPd nanostructures. However, these methods suffer from some obsta-cles, which make the procedure complicated and limit the pervasive application.For example, nanoflowers adhesion on the substrate normally restricted to weakphysical or chemical interaction and the surfactants and organic compounds, whichusually used in chemical methods, can inhibit the catalytic activity of the resultednanostructures [76]. However, the electrodeposition method is attractive forachieving high-quality films because of its simple operation, no additional purifi-cation step, implementation in low cost, operation in ambient temperature, and noneed to various chemical reagents [77]. Besides, the size, morphology, and dis-persion of the resulted catalyst nanostructures can be controlled to some extent bythe selection of precursor concentration, additives, potential or current density, andso on. In this method, a simple and one-step procedure is employed by keeping theelectrode potential at −0.20 V within 300 s at the room temperature to generate thePtPd with a nanoflower structure. In the next step, the modified electrode wasremoved and rinsed with double distilled water. The prepared electrode in this stepis notified as PtPd-NFs/Cu2O-NSs/RGO. In the following, for comparison theconventional PtPd-NPs deposited on Cu2O-NPs/RGO were prepared by a similarmethod as stated above in a solution consisting of 0.002 M of PtCl2 and PdCl2 (1:1ratio) and 0.1 M KCl. After that, the electrode was taken out and again rinsedthoroughly with double distilled water. The prepared electrode in this step isnotified as PtPd-NPs/Cu2O-NPs/rGO. To better illustrate the electrode modificationprocess, basic steps in electrochemical deposition procedure of Cu2O and PtPd withdifferent structures are schematically shown in Fig. 10.

3 Application of RGO-Based Metal/Metal OxideNanocomposites

The development of alternative strategies for the production of clean energy is oneof the biggest challenges for the scientific community. Due to the increasing globalwarming, air pollution, and growing environmental concerns, the efforts directingtoward the development of energy storage and energy conversion devices with highenergy densities and power densities have increased tremendously. Graphene-basedmetallic nanocomposites have gained immense popularity in the field of electro-chemical energy storage and conversion [79]. Because of their physicochemicalproperties, such as high thermal and chemical stability, large surface area, excellentelectrical conductivity, and superior thermal and mechanical properties,graphene-based materials have been exploited as electrode materials in electricalenergy storage devices. Additionally, their broad potential range and rich surfacechemistry have allowed customizing the properties of storage/conversion devices


[80–82]. Therefore, graphene-based metallic, bimetallic, and metal oxidenanocomposites have found wide applications in the field of electrochemistry (fuelcells, supercapacitors), photochemistry, and organochemistry (Fig. 11). The mostdistinguished applications of graphene-based metal/metal oxides in electrochem-istry have a long reputation in this area [83]. Indeed excellent electrochemicalproperties have been disclosed for graphene and its derivatives [84, 85]. Thedeposition of inorganic nanomaterials, especially metal/metal oxides, onto grapheneform interesting metal/metal oxides-graphene nanohybrids, which are expected topresent new and intriguing electrochemical properties due to the excellent catalyticactivities of metal/metal oxides nanoparticles.

3.1 Electrocatalyst

Electrocatalysis is a special field in electrochemistry that speeds up the rate of anelectrochemical reaction occurring on electrode surfaces or at liquid/solid inter-faces. There are various types of electrochemical reactions involved in different

(a)

(b) (c)

Fig. 10 Electrochemical deposition method for synthesis of a PtPd-NFs/Cu2O-NSs/RGO catalystand its application in electrocatalytic methanol oxidation fuel cells [78]


anish khan abdullah m. asiri editors graphene

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