Graphene-based hybrid nanoporous materials for efficient CO2 adsorption Dr. Theodore Tsoufis NCSR Demokritos, Institute of Nanoscience & Nanotechnology, Athens, Greece |1 Introduction … 2 • Production of Graphene by Scotch tape method (starting from Graphite) Graphite Graphene Substrate • NOT suitable for large-scale applications Nobel prize in Physics 2010 Graphene Oxide (GO)…. Graphite Oxidative Treatment Graphite • Chemically inert • Practically insoluble in water and most common solvents 3 Graphene Oxide Graphene Oxide • Highly hydrophilic due to the introduction of the oxygen containing groups • Exhibits solubility in a wide range of solvents (H2O, CH3OH, CH3CH2OH etc) • GREAT potential for WET CHEMISTRY Graphene Oxide (GO) Epoxy groups • Ring opening reactions (nucleophilic substitution with amines) 4 Carboxylic groups • Activation using e.g. SOCl2 • Attachment of nucleophilic reagents e.g amines Non-covalent functionalization Through π-π interactions between graphene and suitable derivatives of polyaromatic molecules (pyrene-amine, anthrecene-amine), Wan der Waals interactions etc. GO-based hybrids 5 Tsoufis et al, Carbon (2013) 59, 100 Naphthalene Amine Aniline Enzymes Chemically Funct. GO Enzymes Bioresource Technology (2012) 115, 164. "Graphite oxide and aromatic amines: Size matters”, Submitted at Angewandte Chemie Concept of intercalation Graphene Oxide Intercalation compound Graphene Oxide 6 Graphene-based intercalation compounds • Inrcement of GO inter-layer distance (by demand) • Interlayer space accessible to molecules (especially gas mol.) • Development of graphenebased nano-porous materials PolyEthyleneImine (PEI) • PEI belongs to polymers family. 7 the Dendritic • PEI Hyperbranched polymer easily prepared, contains primary, secondary and tertiary amine groups. • Cost effective, available in large quantities (industrial scale). • Applications: Bio-medical, Detergents, adhesives, water treatment agents and cosmetics, paper industry Intercalation of PEI into GO 8 • Low molecular weight PEI (MW: 1.300, 2.000 and 5.000 Da) • Lower MW Lower size of hyperbranched PEI structure Smaller size of PEI allows the accommodation of the polymer within the interlayer space of GO, preserving the parallel arrangement of the GO sheets + NH 3 H NH 3 N H2 NH- NH T. Tsoufis et al, Chemistry A European Journal, 2014, 26, 8129-8137. N NH2 HN 2 N -H 2 2 NH 2 NH NH 2 NH - + N NH 2 H 2 2 H2 N -H NH NH 2 NH N NH 2 NH 2 H2 N Graphite Oxide + NH 3 H2 N NH 3 NH 2 2 NH2 NH NH 2 2 PEI NH 2 NH • Facile, bulk synthesis of final hybrids without the aid of any coupling agent (direct grafting of PEI at GO framework) + GO-PEI Hybrids (XRD) Effect of PEI loading Effect of PEI size GO+PEI 1.300 samples 7.3 Å Graphene Oxide (GO) 14.7 Å GO+PEI 1.300 GO+PEI 2.000 Weight ratio GO:PEI 1:0.5 Intensity (a.u.) 11.4 Å Intensity (a.u.) 9 GO:PEI 1:3 18.0 Å GO:PEI 1:10 GO+PEI 5.000 4 6 8 10 12 14 16 18 2 Theta Clear trend: Higher PEI mol. weight Further shifting of the d001 peak at lower 2θ values “Swelling” of GO sheets along the c-axis due to increment of interlayer distance 4 6 8 10 12 14 16 2 Theta For a given PEI (MW=1.300) it was studied the effect of different GOPEI weight loadings (1:0.5, 1:3, 1:10) to the basal spacing of the resulting GO-PEI hybrids. T. Tsoufis et al, Chemistry A European Journal, 2014, 26, 8129-8137. GO-PEI Hybrids (XPS analysis) C 1s PEI Intensity (a.u) GO-PEI C 1s GO C-O 286.0 eV 23% Intensity (a.u.) O 1s (a) C=O 287.5 eV 47% N 1s C-C 285 eV 20% C(O)O 288.8 eV 10% C-O, C-N 286.0 eV 46% C=O 287.5 eV 24% Intensity (a.u.) C 1s (b) GOPEI C-C 285 eV 21% C(O)OH 288.8 eV 9% GO 294 292 290 288 286 284 282 280 294 292 Binding Energy (eV) 250 300 350 400 450 500 550 600 650 290 288 286 284 282 Binding Energy (eV) Amine groups 400.4 eV N 1s 700 Binding Energy (eV) + Amide groups 399.3 eV NH3 Intensity (a.u.) 200 10 401.7 eV GO- PEI Successful covalent attachment of PEI at GO framework PEI 406 404 402 400 398 396 394 Binding Energy (eV) T. Tsoufis et al, Chemistry A European Journal, 2014, 26, 8129-8137. 280 GO-PEI Hybrids (TEM, SEM) GO (Ref) EDX GO-PEI-1.300 T. Tsoufis et al, Chemistry A European Jourl, 2014, 26, 8129-8137. 11 GO-PEI Hybrids 3 -1 N2 Volume adsoebed (STP) (cm g ) GO-PEI-1.300 40 30 Adsorption Desorption 20 10 0 0.0 0.2 0.4 0.6 P/P0 12 Recorded isotherm is typical of type II Multi-layer adsorption and presence of macropores at high relative pressures, while the initial part of the isotherm (low relative pressures) revealed low volume microporosity. Furthermore, a H3 hysteresis loop is pronounced indicating slit pores. 60 50 (BET) 0.8 1.0 GO-PEI-1.300 BET surface area = 118 m2/g >>> BET surface area of pristine GO (10 m2/g) The intercalated PEI increased the interlayer distance between the neiboghring, 2D GO sheets rendering the previously (before intercalation) unreachable surface area, accessible to gas molecules. T. Tsoufis et al, Chemistry A European Journal, 2014, 26, 8129-8137. Poly(propylene imine) dendrimer (DAB) 13 • DAB belongs to the dendritic polymers family (highly branched symmetrical macromolecules of nano-sized dimensions consisting of a central core, repeating units and terminal functional groups). • DAB is highly ordered hyperbranched macromolecule of low polydispersity, exhibiting a welldefined number of active functional groups distributed along their branches and periphery T. Tsoufis et al, Submitted in Chemical Communications, Under review GO-DAB Hybrids 14 • Low molecular weight DAB (MW: DAB4=300, DAB8=741 and DAB16=1622 Da) • Lower MW Lower size of dendritic DAB structure Smaller size of DAB allows the accommodation of the polymer within the interlayer space of GO, preserving the parallel arrangement of the GO sheets • Facile, bulk synthesis of final hybrids without the aid of any coupling agent (direct grafting of DAB at GO framework) H 2N NH 2 N N N N NH2 H2 N NH 2 H 2N N N NH2 H 2N N H 2N NH 2 N N N N N H 2N N N NH 2 H2N H 2N NH 2 N N N N N H 2N N NH2 N N N N NH2 H 2N H 2N N NH 2 N N NH2 NH 2 N NH2 H 2N N NH 2 N N N NH2 N H2N NH 2 H 2N N H 2N H2N H 2N NH2 N N H2 N NH 2 H2N H 2N N H 2N NH 2 NH 2 H2 N H 2N N NH2 N N N N NH 2 H 2N N T. Tsoufis et al, Submitted in Chemical Communications, Under review N NH 2 H2N NH2 H2 N N NH 2 H 2N N N H 2N N N N N NH 2 H 2N NH 2 N NH2 H2N NH2 N N N N NH2 N NH 2 H2N N N N N H 2N N H 2N NH2 N NH 2 H 2N Graphite Oxide N N NH2 N N H 2N NH2 N NH 2 N H 2N NH 2 H 2N N H 2N H2 N NH2 H2 N NH 2 NH 2 GO-DAB Hybrids 15 XPS spectra XRD patterns GO-DAB16 Au 4p d001= 15.8 A O 1s N 1s 500 400 Au 4d C 1s GO-DAB Intensity (a.u.) GO-DAB8 d001= 13.6 A GO GO-DAB4 DAB d001= 8.3 A 900 Pristine GO 800 700 600 Amine N 1s 4 6 8 10 12 14 16 18 o 2 Theta ( ) Shifting of the d001 peak at lower 2θ values Systematic increment of GO interlayer distance after intercalation of DAB molecules of increasing MW GO+DAB8 Intensity (a.u.) 2 300 200 Binding Energy (eV) Protonated Amine Amide GO DAB8 410 408 406 404 402 400 398 Binding Energy (eV) T. Tsoufis et al, Submitted in Chemical Communications, Under review 396 Successful covalent grafting of DAB at GO GO-DAB (CO2 adsorption @Dry) GO-DAB8@310 K GO-DAB8@298 K GO (Ref)@298 K CO2 adsorption (dry conditions) GO> GO+DAB Misleading GO: 1.25 mmol/g @ 298K, 1.04 @ 310K GO+DAB: 0.64 mmol/g @298K, 0.82 @310K GO (Ref)@310 K CO2 adsorption at GO-DAB had NOT reached equilibrium T. Tsoufis et al, Submitted in Chemical Communications, Under review 16 GO-DAB Hybrids (CO2 adsorption) 17 Simulating Flue gas conditions ( Higher Temperature, Humidity) GO Dry GO Wet, P/Po= 0.03 P/Po= 0.13 P/Po= 0.35 GO-DAB8 Dry GO-DAB8 Wet, P/Po=0.03 P/Po=0.13 P/Po=0.35 GO-DAB8 Dry @310 K GO-DAB8 Wet @310 K P/Po=0.35 Wet GO-DAB8: 2 mmol/g (P/Po=0.35) CO2 adsorp. : x3 times increase comp. to GO-DAB8 dry Faster kinetics (x3 times at 50% loading, x6 times at 80% loading) T. Tsoufis et al, Submitted in Chemical Communications, Under review Summary Successful incorporation of PEI into the interlayer distance of GO Successful incorporation of DAB into the interlayer distance of GO Intercalated GO-DAB and GO-PEI hybrids Finely tuned interlayer distance by choosing different MW and/or loading of dendritic polymers The interlayer galleries between the single GO sheets expanded PEI and DAB dendrimers cross-linked the parallel aligned GO sheets The chemical micro-enviroment within the galleries was enhanced by the presence of the amine-rich dendritic polymer chemical groups Very promising CO2 adsorption capacity 18 Acknowledgements EU-funded projects 19
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