Wright State University CORE Scholar Special Session 5: Carbon and Oxide Based Nanostructured Materials (2011) Special Session 5 6-2011 Understanding Irreducible and Reducible Oxides as Catalysts for Carbon Nanotubes and Graphene Formation Alicja Bachmatiuk Follow this and additional works at: http://corescholar.libraries.wright.edu/ss5_2011 Part of the Physics Commons Repository Citation Bachmatiuk, A. (2011). Understanding Irreducible and Reducible Oxides as Catalysts for Carbon Nanotubes and Graphene Formation.. http://corescholar.libraries.wright.edu/ss5_2011/1 This Presentation is brought to you for free and open access by the Special Session 5 at CORE Scholar. It has been accepted for inclusion in Special Session 5: Carbon and Oxide Based Nanostructured Materials (2011) by an authorized administrator of CORE Scholar. For more information, please contact corescholar@www.libraries.wright.edu.
Understanding irreducible and reducible oxides as catalysts for carbon nanotubes and graphene formation Alicj a Bachmatiuk 1
Outline! Introduction! Histor y of sp 2 carbo n formation through oxid e catalysts! Irreducibl e an d reducibl e oxide s fo r sp 2 carbon formation! Carbothermal reduction o f SiO 2! Theoretical studies! Summary 2
sp 2 carbon allotropes 0D FULLERENES 1D CARBO N NANOTUBES 2D GRAPHENE sp 2 hybrydization Overlapping o f Sigma Bonds in a Single Graphene Layer 3
Properties of graphene and CNTs CARBO N NANOTUBES GRAPHENE Remarkably high electron mobilities a t room temperature! Young s modulus 1000-5000 GPa! Metallic or semiconducting properties! Easy to functionalize! Young s modulus 1060 GPa! semi-meta l with unique electronic properties! Easy to functionalize Graphene nanoribbons (GNR)! GNR properties depend on ribbon width and chirality 4
Application fo r electronics Conventiona l synthesis with metals FET drawbacks: New synthesis using meta l oxides - transfer required - difficulties with purification Synthesis from SiC - no transfer required - no purification needed - lo w temperature possible FETs with graphene drawbacks: - high temperature - interaction with SiC 5
Carbon nanotubes formation using meta l catalysts CNT growth catalyzed by a Ni! Metal catalyst s required (transition metals)! Metal catalyst s a re argued t o fulfil variou s roles: - Catalyti c decomposition o f carbo n feedstoc k (CVD) - Catalyti c nucleation and growth o f CNT Lin, et al., Nan o Lett., 7 (2007) 2234 Vapor-Liquid-Solid (VLS) mechanism: Drawbacks for electronic applications: - difficulties with purification - transfer required 6
Carbon nanotubes formation through oxide catalysts SWCNT from MgO, PbO 2, In 2 O 3 Carbon nanofibres from SiO 2 Rümmeli, et al., Nano Lett., 5 (2005) 1209 Bachmatiuk, et al., ACS Nano, 3 (2009) 4098 SWCNT from NPs: SiO 2, Er 2 O 3, Al 2 O 3, TiO 2 SWCNT and MWCNT from ZrO 2 Liu, et al., J. Am. Chem. Soc., 131 (2009) 2082 Huang, et al., J. Am. Chem. Soc., 131 (2009) 2094 Liu, et al., J. Am. Chem. Soc., 133 (2011) 197 Steiner, et al., J. Am. Chem. Soc., 131 (2009) 12144 7
Carbon nanotubes formation from hybrid catalysts MWCNT growth from Al 2 O 3 substrate Rümmeli, et al., J. Am. Chem. Soc., 129 (2007) 15772 Rümmeli, et al., ACS Nano, 4 (2010) 1146! Catalys t lies entirely within tube a t its base! Graphitic walls stem from the oxide support! Meta l catalys t nucleates the CNT! Oxide causes CNT growth Oxide s ar e activ e catalyst s fo r carbon nanotub e formation WH Y NOT GRAPHENE? 8
Graphene formation through oxide catalysts Graphene growth on MgO, Al 2 O 3, Ga 2 O 3, TiO 2 Graphene growth on MgO and ZrO 2 Rümmeli, et al., Chem. Mater., 4 (2007) 4105 Rümmeli, et al., ACS Nano, 4 (2010) 4206 Scott, et al., APL, 98 (2011) 073110 NO metals Graphene growth on sapphire Nanographene growth on differen t substrates 9 Hwang, et al.., J. of Cryst. Growth, 312 (2010) 3219 Zhang, et al., Nano Res., 4 (2011) 315
Graphene synthesis by surface diffusion MgO, cyclohexane, 875 C ZrO 2, acetylene, 480 C MgO, acetylene, 325 C Irreducible oxides Step site nucleation and growth! Low temperatures ( < 500 C), smal l nano-islands Rümmeli, et al., Chem. Mater., 4 (2007) 4105 Rümmeli, et al., ACS Nano, 4 (2010) 4206 Scott, et al., APL, 98 (2011) 073110! Reaction stops once nano-crystals are encapsulated! Graphene layers roo t into step sites 10
Theoretica l studies of surface diffusion C 2 H 2 adsorption sites on MgO (100) Dissociation Energy (ev) 1.0 0.5 0.0-0.5-1.0 A B C D E F Adsorption site! C 2 H 2 adsorption on surface is weak! C 2 H 2 adsorption a t step site is stronger! Step sites play very importan t role C diff. barrie r ca. 0.38 ev H diff. barrie r ca. 0.20 ev Scott, et al., APL, 98 (2011) 073110 In collaboration with T U Dresden 11
Possible growth route! Hydrogen diffuses, Carbon remains 12 Adv. Mater., (2011) accepted
Temperature influence on graphene domain size Sapphire substrates C3H8, 1350 C C2H5OH, 850 C 2 nm 2 nm D 5 G G/D ratio Intensity (arb. units) 6 850 o C 2D 4 3 2 1 0 1200 1400 1600 2600 2800 Raman shift (cm-1) 750 3000! Low temperature smaller domains 950 1150 1350 1550 Temperature ( C) 1750 more defects 13 Hwang, J. of Cryst. Growt h, 312 (2010 ) 3219 In collaboration with Cornell University
sp 2 carbon formation from oxide catalysts Irreducible oxides (MgO, Al 2 O 3, ZrO 2, TiO 2, Ga 2 O 3?, SiO 2?) Reducible oxides (SiO 2 ) Steiner, et al., J. Am. Chem. Soc., 131 (2009) 12144 Scott, et al., APL, 98 (2011) 073110 Bachmatiuk, et al., ACS Nano, 3 (2009) 4098 Bachmatiuk, et al., Carbon, 48 (2010) 3175 Bachmatiuk, et al., J. Appl. Phys, 109, (2011) 094317! No zirconium or zirconium carbide is observed! No silicon or silicon carbide is observed 14
Carbothermal reduction GOAL: Formation o f sp 2 carbon via carbothermal reduction o f Si x O y 3 C + SiO SiC 2(s) (s) (g) + 2CO endothermi c process (below 1000 C) C + SiO2(s) SiO (g) + CO (g) 2 C + SiO (g) SiC (s) + CO (g)! SiC results from the direct reduction of SiO by solid carbon 15
Carbotherma l reduction! Stacked-cup CNTs are formed by precipitation! SiC particles are presen t a t roots! Oxide particles are reduced during the process! Loca l EDS o f the particles shows only S i & C SiC (111) cubic Reducible oxide Bachmatiuk, et al., ACS Nano, 3 (2009) 4098 16 Bachmatiuk, et al., Carbon, 48 (2010) 3175
Spectroscopic study! SiC and O x Si-H y are observed SiC SiC Bachmatiuk, et al., ACS Nano, 3 (2009) 4098! No silicon or silicon carbide is observed 17 Bachmatiuk, et al., Carbon, 48 (2010) 3175
Proposed mechanism! SiO 2 is reduced via a carbotherma l reaction forming SiC! SiC particles coalescence and then the carbon nanofibres grow by precipitation Bachmatiuk, et al., ACS Nano, 3 (2009) 4098 18
Theoretica l studies of carbotherma l reduction Carbothermal reduction of SiO 2 in presence of CH 4! Formation of SiC occurs on the surface/subsurface layers of the SiO 2 nanoparticle Page, et al., J. Am. Chem. Soc., 133 (2011) 621 19
Graphene synthesis by bulk diffusion! sp 2 carbon formation via a precipitation mechanism from Si x O y 20
Graphene synthesis by bulk diffusion! Formation of graphene at 1000 C from SiO early steps! Where and how is the graphene formed? FIB cross-sectional studies 21
Evidence fo r SiC formation G λ= 442 nm its] D arb. u n ity SiC [Si o annealed @C, SiO at 1000 C Intens @C, SiO @C 600 1200 1800 2400 3000-1 Raman shift [cm ] Normalized intensity C1s SiC grazing angle 0 5 15 45 85 Normalized i nten sit y Si2p SiC grazing angle 0 5 15 45 85 282 284 286 288 290 100 102 104 106 108 In collaboration with AFRL Binding energy [ev] Binding energy [ev] 22
Summary! Oxides are alternative systems for growth of sp 2 carbon! Two different routes are possible! Step sites are crucial for graphene growth (irreducible oxides)! Precipitation process occurs (reducible oxides)! Domain size depends on the process temperature! Low temperature synthesis (<500 C) is possible 23
Ma rk H. Rümmeli Joh n Boeckl Howar d Smith Scott Dudley Michae l Spencer Jeonghyun Hwang Andrew Scott Rafae l Mendes Felix Börrnert Jamie Warner Imad Ibrahi m Bernd Büchner Thank you for your attention! 24