This presentation provides an overview of graphene, methods of preparation of graphene, important applications and its role in energy storage devices, namely, fuel cells, supercapacitors, lithium batteries and hydrogen storage

Sankara Narayanan, T S N

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Graphene: Its role in energy storage devicesT.S.N. Sankara NarayananCSIR-National Metallurgical LaboratoryMadras Centre, CSIR ComplexTaramani, Chennai-600 113E-mail: tsnsn@rediffmail.comOutline of the talk Graphene – A preamble Methods of preparation Some interesting applications Role of graphene in energy storage devices9 Fuel cells9 Supercapacitors9 Lithium ion batteries9 Hydrogen storage Concluding remarksThe Nobel Prize in Physics for 2010was awarded jointly to Andre Geim and Konstantin Novoselovfor their "groundbreaking experiments regarding the two-dimensional material graphene."Andre GeimKonstantinNovoselovAndre GeimKonstantinNovoselovGraphene - A preamble ¾ Graphene is composed of carbon, the building block of all life¾ Discovered in 2004 in its full observable and testable form¾ The new kid in the block of carbon family - basic building block for graphitic materials of all dimensions¾ single sheets of graphite ¾ a flat monolayer of carbon atoms that are tightly bonded together through covalent bond into a 2D honeycomb latticeGraphene - Mother of all graphitic formsCourtesy: A. K. Geim and K. S. Novoselov, Nature Mater., 2007, 6, 183Graphitic family: 0-dimensional fullerene, 1-dimensional carbonnanotube, 2-dimensional graphene, 3-dimensional graphiteUnzipping the Carbon nanotube to monolayer grapheneSource: Baraton et. al., Nanotechnology 22 (2011) 085601SWCNT Graphene sheet/NGPMWCNT multilayered graphene sheets/NGPGraphene – The Flat form of CNTSource: Bor Z. Jang, Wright State University and Aruna Zhamu, AngstronMaterialsCharacteristics of graphene9 thinnest possible material that is ever feasible9 Highest thermal conductivity (up to ~5,300 W/m-K), five times that of copper – faster thermal dissipation9 Electrical conductivity similar to Cu, yet its density is four time lower than Cu – lighter weight components9 Ultra-high Yong’s modulus (approximately 1,000 GPa) and highest intrinsic strength (~130 GPa)9 High specific surface area (up to~ 2,675 m2/g)9 Outstanding resistance to gas permeationSource: Ron Beech, Nanotechnology Law & Business, Spring 20119 ~200 times stronger than steel 9 "It would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap.” - Researchers at Columbia University's Fu Foundation School of Engineering9 Readily surface-functionalizable9 Dispersible in many polymers and solvents9 High loading in nanocompositesCharacteristics of grapheneSource: Ron Beech, Nanotechnology Law & Business, Spring 2011Methods of preparing graphene¾ Top-down approaches9 scotch tape stripping9 ion sputtering9 pulsed laser deposition 9 ball milling9 arc discharge¾ Bottom-up approaches9 chemical vapour deposition (CVD)9wet chemistry 9 ion implantation9 pyrolysisPeeling graphite using “Scotch tape”Source: Bor Z. Jang, Wright State University and Aruna Zhamu, AngstronMaterialsIn 2004 - Geim and Novoselov have used a tape to repeatedly peel off graphene sheets from graphite crystalsLarge scale production?Chemical vapour deposition (CVD)¾ CVD - One of the promising method of preparation of graphene¾ It involves blowing methane over thin sheets of copper¾ The carbon atoms in methane form a thin film of graphene¾ Accumulation of multilayers of carbon – unusable¾ Vacuum condition is necessarySource: Ron Beech, Nanotechnology Law & Business, Spring 20111050 °C for 15 min.10 mTorr for 10 hCarbon source - cookies, chocolate, grass, plastics, cockroaches, and dog fecesSource: RUAN ET AL. ACS Nano July 29, 20119 Chemical exfoliation9 Chemical and thermal exfoliation9 Electrochemical exfoliation These methods assume significance  ability to prepare graphene in large quantities cost-effective Exfoliation of graphiteChemical exfoliation¾ Starting material - crystals of natural graphite ¾ Sonication in dimethyl formamide (DMF) for over 3 h ¾ DMF “dissolves” graphite - suspension of thin graphitic platelets with large proportion of monolayer graphene flakes¾ DMF wets the flakes preventing them from conglomerating¾ Centrifuge the suspension at 13,000 rpm for 10 minutes to remove thick flakes. The remaining suspension consists mostly of graphene and few-layer graphite flakes of sub-micrometer size ¾ The suspension was spray-deposited onto a preheated glass slide or spin coated ¾ These films were then annealed for 2 h in Ar (90%)-H2(10%) atmosphere at 250 °C.Source: K.S. Novoselov, The Electrochemical Society Interface, Spring 2011, p. 45Chemical and thermal exfoliation Graphite powder (40 g) is added to a mixture of concentrated HNO3 (270 ml) and H2SO4 (525 ml) with vigorous stirring to disperse the graphite powder Add 330 g potassium chlorate – slow addition to avoid the risk of explosion  Allow the reaction to proceed for 120 h at room temperature  Extract the graphite oxide (GO) powder from the solution and completely dry it at 100 C in a vacuum oven Thermal exfoliation of GO at high temperature in vacuumSource: Zhang et al., J. Mater. Chem., 2011, 21, 5392Su et al., ACS Nano, 2011, 5 (3), pp 2332–2339Source: Bor Z. Jang, Wright State University and Aruna Zhamu, AngstronMaterialsOxidation of graphite to graphene oxide and reduction to reduced graphene oxideraw graphite flakesgraphite oxide graphite oxideExfoliation of graphite flakes by chemical oxidation using 1 g of acetic anhydride, 6.2 g of Conc H2SO4 and 0.6 g K2Cr2O7Source: Saner et al., Fuel, 89 (2010) 1903-1910Exfoliation of graphite flakes by chemical oxidation using 1 g of acetic anhydride, 55 g of Conc H2SO4 and 2.1 g K2Cr2O7raw graphite flakesgraphite oxide graphite oxideSource: Saner et al., Fuel, 89 (2010) 1903-1910SEM of GO chemically oxidized using 1 g of acetic anhydride, 6.2 g of Conc H2SO4 and 0.6 g K2Cr2O7 followed by sonication for 1 h at RTSource: Saner et al., Fuel, 89 (2010) 1903-1910SEM of expanded GO chemically oxidized using 1 g of acetic anhydride, 6.2 g of Conc H2SO4 and 0.6 g K2Cr2O7 followed by sonication for 1 h at RT and thermal exfoliation at 900 °C for 15 min.Source: Saner et al., Fuel, 89 (2010) 1903-1910SEM images of graphene like nanosheetsSource: Saner et al., Fuel, 89 (2010) 1903-1910The Raman signatures for graphene and graphite employing a 514 nm laser wavelength in the Raman spectrometerSource: Ferrari et al., Phys. Rev. Lett. 97, 187401 (2006)Raman spectra recorded at 514 nm and 633 nm laser wavelengths excitation for different number of graphene layers and graphiteSource: Ferrari et al., Phys. Rev. Lett. 97, 187401 (2006)Graphene: Will it Change the Way We Live?Some interesting applicationsCourtesy: Byung Hee HONG, SKKU, South KoreaMarket size: $5-10 billion by 2013Roll-to-Roll Production of Ultra-Large-Scale Graphene FilmsSource: S. Bae et al. Nature Nanotech. 5, 574 (2010)Courtesy: Byung Hee HONG, SKKU, South KoreaCourtesy: Byung Hee HONG, SKKU, South Korea• Electronic chips – Silicon¾ Achieve more power and much smaller without increase of temperature¾ development of graphene transistors would run at much faster speeds and be able to ultimately battle the heat at a microscopic scale¾ IBM has already demonstrated a 100 GHz graphene-based transistor and stated that a 1THz processor is on the horizon¾Graphene – Will it replace silicon in transistors?Graphene – A replacement for Si?Other interesting applications9 Optoelectronic devices9 Energy storage devices9 Dye-sensitized solar cells9 Photovoltaic devices9 Neural implants - Alzheimer’s and Parkinson’s disease 9 Electrochemical sensors, Biosensors9 Sensors - oil exploration, TNT detection 9 Chemically modified electrodes9 Thinnest solid lubricant 9 Lubricant additive9 Graphene – TiO2 composite - PhotocatalystRole of graphene in energy storage devicesEnergy Density = The ability to store energyPower Density = The ability to release energyHow graphene could/would help in reaching this mile stone?milestoneApplications of graphene in energy storage devices Fuel cells9 Catalyst support9 Bipolar plate Supercapacitors Electrode materials Li-ion Batteries9Anode active material9Hybrid active material9Electrode conductive additives Hydrogen storage materialSource: Bor Z. Jang, Wright State University and Aruna Zhamu, AngstronMaterialsFuel cellsRole of Graphene in fuel cells¾ Direct ethanol and direct methanol fuel cells –& high energy density& low pollutant emission& low operating temperature& ease of handling liquid ethanol/methanol fuel low electrocatalytic activity of anode/cathode  high cost of platinum (Pt)-based catalysts low DMFC power density low CO toleration short cycle life¾ Graphene – good electrical conductivity and large specific surface area – how we can use it? Water-ethylene glycol is used as the medium oxidation of graphite to graphite oxide (GO); exfoliation of GO to graphene oxide sheets by sonication in water; attachment of Pt/Pt-Ru particles on the graphene oxide sheets; chemical reduction of graphene oxide sheetsSchematic route for anchoring of Pt/Pt-Ru nanoparticles on graphene to prepare Pt/Pt-Ru-graphene nanocompositesSource: Xu et al., J. Phys. Chem. C 112, (2008) 19841-19845Pt nanoparticles supported on graphene sheets simultaneously imaged with (a) SE; (b) BSE (b); (c) STEM-BF; and (d) STEM-HAADF detectorsSource: Dong et. al., Physics and applns of graphene: Experiments, In Tech, 2011, p. 525 dimensions of Pt nanoparticles: ~ 6 to 8 nmAFM topography (a) and phase (b) images of Pt nanoparticles supported on graphene sheetsSource: Dong et. al., Physics and applns of graphene: Experiments, In Tech, 2011, p. 525 Electrocatalytic activity of graphene and Vulcan XC-72R carbon black-supported Pt nanoparticles for methanol oxidationvs. Ag/AgClPeak current density vs. scan rateScan rate: 50 mV/sCV’s (5th): 1 M CH3OH/0.5 M H2SO4Methanol oxdnRemoval of Co & residual CSource: Dong et. al., Physics and applns of graphene: Experiments, In Tech, 2011, p. 525 Electrocatalytic activity of graphene and Vulcan XC-72R carbon black-supported Pt nanoparticles for methanol oxidationPeak current density vs. scan ratevs. Ag/AgClCV’s (5th): 1 M CH3OH/0.5 M H2SO4Scan rate: 50 mV/s Methanol oxdnRemoval of Co & residual CSource: Dong et. al., Physics and applns of graphene: Experiments, In Tech, 2011, p. 525 Comparison of electrocatalytic activity of methanol oxidation ongraphene and carbon black-supported Pt and Pt-Ru nanoparticles9 Current in the forward sweep - directly proportional to the amount of methanol oxidized at the electrode9 Current in the reverse sweep - removal of CO and other residual carbon species formed on the electrode in the forward sweep.9 IF/IR -tolerance of Pt/Pt-Ru catalysts to CO and other carbonaceous species – retained even after 50 cycles – good stability9 Graphene-supported Pt/Pt-Ru nanoparticles - higher activity for methanol oxidation and a better tolerance to COSource: Dong et. al., Physics and applns of graphene: Experiments, In Tech, 2011, p. 525 Comparison of electrocatalytic activity of methanol oxidation ongraphene and carbon black-supported Pt and Pt-Ru nanoparticles9 IF/IR -tolerance of Pt/Pt-Ru catalysts to CO and other carbonaceous species – good stability9 Graphene-supported Pt/Pt-Ru nanoparticles - higher activity for ethanol oxidation and a better tolerance to COSource: Dong et. al., Physics and applns of graphene: Experiments, In Tech, 2011, p. 525 Chronoamperometric curves for graphene- and carbon black-supported Pt and Pt-Ru nanoparticles in 1 M CH3OH or CH3CH2OH/0.5 M H2SO4  The potential was 0.4 V vs. Ag/AgCl.CH3OH CH3CH2OHSource: Dong et. al., Physics and applns of graphene: Experiments, In Tech, 2011, p. 525 Current status and future prospects¾ As catalyst supports, graphene can more effectively enhance the electrocatalytic activity of Pt and Pt-Runanoparticles for the oxidation of methanol and ethanol into CO2. ¾ A next step will be the exploration of a facile and efficient method to synthesize graphene-supported Pt and Pt-Ru nanoparticles with controlled properties:& formation of nanoparticles on defined locations& the density of nanoparticles located on graphene sheets& the size of nanoparticles, and the size and thickness of graphene sheetsSource: Dong et. al., Physics and applns of graphene: Experiments, In Tech, 2011, p. 525 Role of graphene in fuel cells¾ Platinum - one of the best catalysts for the electrochemical oxygen reduction reaction (ORR) – Fuel cells  Expensive  Exhibit time-dependent drift due to the poisoning deactivation of the Pt surface with carbon monoxide¾ Nitrogen-doped graphene - metal-free electrode& Offers enhanced electro-catalytic activity& long-term operation stability& tolerance to crossover effect than Pt for ORR oxygen reduction via a four-electron pathway in alkaline solutions producing water as a productSource: Qu et al., ACS Nano 4 (2010) 1321¾ In proton exchange membrane fuel cells (PEMFCs) Pt based electro-catalysts are widely used as anode and cathode electrocatalysts for hydrogen oxidation and for ORR, respectively.¾ Graphene nanosheets (GNS) and nitrogen doped-GNSscan serve as the catalyst support for Pt nanoparticles for ORRs in PEMFCs.¾ Nitrogen doping  creates defects, which could act as anchoring sites for the deposition of Pt nanoparticles increase the electrical conductivity improve carbon-catalyst bindingSource: Jafri et al., J. Mater. Chem., 20 (2010) 7114Role of graphene in fuel cellsSupercapacitorsSupercapacitors – A preamble There has been an ever increasing demand for  environmentally friendly high-performance energy-storage systems Supercapacitors - high power capability, long cyclic life (> 100 000 cycles), low maintenance, and fast dynamics of charge propagation Application in portable electronic devices, electric vehicles and hybrid electric vehicles (HEVs) – Suitable? Most of the commercially available supercapacitor products have a specific energy density < 10 Wh/kg, which is 3 to 15 times lower than batteries How to increase the energy performance of supercapacitors to be close to or even beyond that of batteries?Schematic diagrams of an electrochemical double layer type capacitorcharged (left) and discharged (right) statesSource: Prasant N Kumta et. al., The Electrochemical Society Interface • Fall 2010, p.57Cathode and Anode: AC; Electrolyte: H2SO4Mechanism of energy storage in supercapacitors¾ The mechanism by which a supercapacitor stores energy is, in principal, based on two types of capacitive behaviors: the electrical double layer (EDL) capacitance from pure electrostatic charge accumulation at the electrode-electrolyte interface and the pseudo-capacitance due to fast and reversible surface redox processes at characteristic potentials¾ These two mechanisms can function simultaneously, depending on the nature of the electrode materialImportant requirements of electrode materials for supercapacitors9 Good electrical conductivity9 High surface area9 Chemical and mechanical stability Currently used electrode materials – Activated carbon – low cost, easy process¾Capacitance: 50-130 F/g¾ Pores are too small for electrolyte entry– Other forms of carbon– Carbon nanotube– Transition metal oxides – RuO2, MnO2, NiO– Conducting polymers – PANI, PPY, Supercapacitor¾ The performance of a supercapacitor is evaluated on the basis of the following criteria: ♥ power density substantially greater than batteries with acceptably high energy densities (> 10 Wh/kg)♥ an excellent cycle ability (> 100 times of batteries)♥ fast charge-discharge processes (within seconds)♥ low self-discharging♥ safe operation; and ♥ low costCathode and anode: Graphene + 10% PTFEElectrolyte: 30% KOHSeparator: Polypropylene filmCurrent collectors: Ni foamGraphene based materials for supercapacitorsSource: Wang et al., J. Phys. Chem. C 2009, 113, 13103–13107Specific capacitance of 205 F/g; Energy density of 28.5 Wh/kg: Power density of 10 kW/kgElectrochemical performanceSource: Wang et al., J. Phys. Chem. C 2009, 113, 13103–13107Source: Cheng et al., Carbon, 49 (2011) 2917Graphene and nanostructured MnO2 composite electrodes for supercapacitorsAnode: pure graphene; Cathode: MnO2-coated grapheneElectrolyte: 1 M KCl; Separator: Polypropylene filmCurrent collector: high purity TiExcellent capacitive behavior & low contact resistanceCapacitance:150 F/g; Max. storage energy: 5.2 Wh/kgGraphene/PANI hybrid material for supercapacitors• in situ polymerization-reduction/dedoping-redoping process • A high specific capacitance of 1126 F/g with a retention life of 84% after 1000 cyclesethylene glycolcomponents. Polypyrole/Graphene nanocomposites for supercapacitorsElectrochemical properties of GR, PPy, PPy/GO, PPy/GR 0.5 M Na2SO4C.D: 1 A/gscan rate: 5 mV/sPolypyrole/Graphene nanocomposites for supercapacitorsGraphene based supercapacitor materialsLithium batteriesGraphene as a conductive additive Si - highest Li storage capacity (4,200 mAh/g) During charge/discharge cycles High volume expansion/shrinkage (320-380%) Pulverization of Si particle or thin film; Fragmented particles lose contact with the conductive additive and current collector - significant capacity decaySource: Bor Z. Jang, Wright State University and Aruna Zhamu, AngstronMaterialsPerformance - Graphene vs. Carbon Increased electrode conductivity due to a percolated graphene network; Dimensional confinement of active material particles by the surrounding graphene sheets limits the volume expansion upon lithium insertion; SnO2 – graphene nanocomposite form a stable 3D architecture. Graphene sheets prevent aggregation of nanoparticles during Li charge/discharge process.Source: Bor Z. Jang, Wright State University and Aruna Zhamu, AngstronMaterialsGraphene composite – anode active material for Lithium ion batteries• Aruna Zhamu and Bor Z. Jang, US Patent Appl. No. 11/982,672 (11/05/2007)• SnO2 and Co3O4 coated graphene nanosheets can be used as an anode materials in Li ion batteriesSource: Bor Z. Jang, Wright State University and Aruna Zhamu, AngstronMaterialsSynthesis of the Sn/graphene nanocomposite with a 3D architectureGraphene-Sn composite as anode active materials for Li ion batteries Graphene oxide nanosheet – Dispersed in deionized water by ultrasonication Addition of SnCl2.2H2O and citric acid Purge with Argon Addition of NaBH4 to reduce Sn2+ to Sn and graphene oxide nanosheets to graphene nanosheets The mixture was stirred at 0 °C (ice bath) for 3 h Filtration, washing in DI-water, drying in vacuum at 40 °C To improve the crystallinity - annealed at 200 °C for 15 h in Ar atmosphereSource: Wang et. Al.,  J. Mater. Chem., 2009, 19, 8378–8384FESEM image of Sn/graphene nanocompositeSource: Wang et. Al.,  J. Mater. Chem., 2009, 19, 8378–8384Cyclic voltammograms of the Sn/graphene electrodeSource: Wang et. Al.,  J. Mater. Chem., 2009, 19, 8378–8384Charge/discharge profiles of Sn/graphene electrode in lithium-ion cellsSource: Wang et. Al.,  J. Mater. Chem., 2009, 19, 8378–8384Hydrogen storageLayered graphene oxide framework (GOF) for H2 storage¾ GOF - Stacking up of oxidized graphene sheets like a  multilevel parking lot can accumulate H2 in greater quantities¾ GO layers are connected by boron carboxylic molecules - link the GO layers with one another and also maintain space between them ¾ GOFs can hold at least a hundred times more H2 than ordinary graphene oxide ¾ GOFs might be used both to store hydrogen and to release it when it is needed -fundamental requirement in fuel cell applicationsSource: National Institute of Standards and Technology (NIST) and Univ. PennsylvaniaA graphene-oxide framework (GOF) connected by boron-carboxylic “pillars”20042011In the coming years?Graphene – Yesterday – Today and TomorrowThank you

Graphene - Its role in energy storage devices

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Graphene - Its role in energy storage devices

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