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Graphene -based nanocomposite photocatalyst

Graphene -based nanocomposite photocatalyst. Paper review. 1. UV-assisted Photocatalytic reduction of graphene oxide ( april , 2008). Photoelectron → -OH@TiO2 → -COOH@GO -COOH dissociation: GO → GR G-TiO 2 carboxylate linkage is stable under irradiation

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Graphene -based nanocomposite photocatalyst

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  1. Graphene-based nanocompositephotocatalyst

  2. Paper review 1. UV-assisted Photocatalytic reduction of graphene oxide (april, 2008) Photoelectron → -OH@TiO2 → -COOH@GO -COOH dissociation: GO → GR G-TiO2 carboxylate linkage is stable under irradiation Dispersibility maintained by surface TiO2 after reduction Trapped electron@TiO2 (650nm) degraded by GO addition ↓ without GO with GO Immediate decay: submicrosecond electron transfer ↑ Transient decay of trapped electrons in TiO2recorded following 308 nm laser pulse excitation

  3. Paper review 2. Anchoring Semiconductor and Metal Nanoparticles on a Two-Dimensional Catalyst (october, 2009) Same photoreduction step Electrons are stored on graphene surface (double layer charging) Electron transfer to Ag+: Ag NP formation ~410nm absorption: SPR of Ag NP Is increased by AgNO3 addition in TiO2-GO under irradiation ← Confirming Ag-Ti separation Ag is reduced on GR, not on TiO2 ←

  4. Paper review 3. P25-Graphene Composite Photocatalyst (october, 2009) • Nanocompositie by hydrothermal route • Superheated H2O become acidic: • H2O + H2O → H3O+ + OH- • Providing H+ to GO: Reducing GO to GR • High loading of P25 NPs • Repairing sp2bondings of G (High temperature, high pressure) • P25 NPs are concentrated on edge and wrinkle • (interaction between -OH at P25 surface and –COOH at graphene edge) FTIR 1600 cm-1 : Skeletal vibration of GR (confirming reduction) 1726 cm-1 : C=O stretching (P25-GR combination) 798 cm-1: Ti-O-C bonding ← P25-GR chemical bonding

  5. Paper review 3. P25-Graphene Composite Photocatalyst (october, 2009) Degradation of Methylene blue with P25-graphene 2) Increased adsorptivity Noncovalent adsorption: π-π stacking between MB-GR 3) Efficient charge separation & transfer Smaller semicircle in Nyquist plot: decreased surface charge transfer resistance 1) Extended absorption edge

  6. Paper review 4. Process development (TiO2-GR contact) 1) TiO2 is grown on graphene (TiCl3 precursor) Reduction with PVP, 90ºC, AP (May, 2010, CIAC) ← Full coverage on GR basal plane 2) TiO2 is grown with Ti(OBu)4 precursor Hydrothermal reduction (July, 2010, Stanford University) ← Rhodamine B degradation

  7. Paper review 4. Process development (TiO2-GR contact) 3) TiO2 is grown on graphene (TiF4precursor) Hydrothermal reduction (June, 2011, Fuzhou University) ← Benzyl alcohol oxidation ← Metal hydroxide – GO interaction (A) Epoxy group – Hydrogen bonding (B) Hydroxyl group – M-O-C via condensation

  8. Paper review 5. Crystallographic relationship ZnO-GR nanocomposite (July, 2010) – No XRD data or TEM crystal facet data CdS-GR nanocomposite (March, 2011) ← Crystallinity is increased with graphene addition ← Polycrystalline (111) (220) (311) facets are favored ※ Hexagonal structure of RGO is not perfect

  9. Paper review 6. Visible-light photocatalyst RGO(Photocatalytic)-BiVO4 (July, 2010, University of New South Wales) RGO(Hydrotherma)-Bi2WO6 (Sep, 2010, Shanhai Institute of Ceramics) RGO(Hydrazine)-Bi2Mo6 (Jan, 2011, Tsinghua University) RGO(Photocatalytic)-Sr2Ta2O7:N (Sep, 2010, University of Queensland) RGO(Hydrothermal)-ZnFe2O4 (Jan, 2011, Nanjing University of Science and Technology) RGO(Hydrothermal)-InNbO4 (Fer, 2011, Dalian University of Technology) Anion doping Doping N, S, P, C into wide bandgap semiconductor Oxide with narrow bandgap MO6 octahedron full band Expand VB: narrow bandgap ← Cubic TiO2, Bandgap ~2 eV

  10. Paper review 7. Visible-light photocatalyst (Surface plasmon resonance) SPR of Ag: Absorption wavelength at 425nm Photoreduction by Visible light instead UV Degradation of MO (Another publication) ↓ Raman spectra Increased G:D ratio : more sp2 bonding ↓ C1s XPS (Before) → Ag/AgBr/GO Ag/AgCl/GO without GR with GR C1s XPS (After) →

  11. Paper review 8. Grapheneoxide as semiconductor Graphene oxide: Bandgap ~ 2.43 eV ← Reduction of Resazurin(RZ) into Resofurin(RF) ※ Defect sites in GO can act as trapping center: Hinder the recombination process ← GO/TiO2p/n junction ※ Carrier type of GO is dependent to starting solution p-type: GOT-A, GOT-B, GOT-C n-type: GOT-D, GOT-E

  12. Paper review 9. Graphene-based nanocomposite processing ← Self-assembly at liquid-liquid junction ← TEM image of GO-TiO2 NR ※ Nanorods: slightly better activity over P25 Developed to gram-scale production (another publication) OLA Stirring Water ← Macro-mesoporous TiO2-GR nanocomposite Macropore/mesopore by P123 BCP template (During calcination)

  13. Paper review 9. Graphene-based nanocomposite processing Template-free mesoporous TiO2 TiO2 growth in Ti(SO4)2/H2SO4 solution Single-crystal like mesoporous TiO2 Possible mechanism: Oriented attachment of primary particles ← Increased dark adsorption (By increased surface area) a) TO/GS b) reference TO c) GR d) P25

  14. Paper review 9. Graphene-based nanocomposite processing Filtered GR/P25 composite by vacuum co-filtration GO SRGO SEG G Filter paper D ← Significantly higher I(G)/I(D) High quality graphene Acetaldehyde degredatoin: Enhanced photocatalytic activity (Better charge transfer) →

  15. Paper review 9. Graphene-based nanocomposite processing Using expandable graphite to form nanocomposite - Graphene with less defects Thermally exfoliated EG TiO2/GR nanocomposite • Other methods • Microwave • Sonochemical • Ionic-liquid assisted

  16. Paper review 10. Application - Water splitting by graphenenanocompositephotocatalyst ← Eosin Y-sensitized graphene 1) Hydrogen bonding at GR edge 2) π-π interaction ← Z-scheme photocatalyst SrTio3:Rh – Wide bandgap, electron excited from Rh donor level

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