EP2560754A1 - Composite grapheno-metal oxide platelet method of preparation and applications - Google Patents
Composite grapheno-metal oxide platelet method of preparation and applicationsInfo
- Publication number
- EP2560754A1 EP2560754A1 EP10805644A EP10805644A EP2560754A1 EP 2560754 A1 EP2560754 A1 EP 2560754A1 EP 10805644 A EP10805644 A EP 10805644A EP 10805644 A EP10805644 A EP 10805644A EP 2560754 A1 EP2560754 A1 EP 2560754A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- graphene
- composite catalyst
- oxide
- metal oxide
- preparation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000002131 composite material Substances 0.000 title claims abstract description 40
- 229910044991 metal oxide Inorganic materials 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title claims abstract description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 74
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 63
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 23
- 239000003054 catalyst Substances 0.000 claims abstract description 20
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 39
- 239000000243 solution Substances 0.000 claims description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 239000000463 material Substances 0.000 claims description 15
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 12
- 239000002105 nanoparticle Substances 0.000 claims description 12
- 230000001699 photocatalysis Effects 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 11
- 230000008569 process Effects 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 8
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 claims description 7
- 230000008859 change Effects 0.000 claims description 7
- 230000002829 reductive effect Effects 0.000 claims description 6
- 229910000069 nitrogen hydride Inorganic materials 0.000 claims description 5
- 239000003638 chemical reducing agent Substances 0.000 claims description 4
- 230000009467 reduction Effects 0.000 claims description 4
- -1 KTa03 Inorganic materials 0.000 claims description 3
- 239000003795 chemical substances by application Substances 0.000 claims description 3
- 229930195733 hydrocarbon Natural products 0.000 claims description 3
- 150000002430 hydrocarbons Chemical class 0.000 claims description 3
- 239000007800 oxidant agent Substances 0.000 claims description 3
- 230000001590 oxidative effect Effects 0.000 claims description 3
- 239000002244 precipitate Substances 0.000 claims description 3
- 238000001556 precipitation Methods 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 3
- 229910021529 ammonia Inorganic materials 0.000 claims description 2
- 229910002113 barium titanate Inorganic materials 0.000 claims description 2
- 239000003637 basic solution Substances 0.000 claims description 2
- 238000001354 calcination Methods 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims description 2
- 239000011261 inert gas Substances 0.000 claims description 2
- 239000012702 metal oxide precursor Substances 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 229910052763 palladium Inorganic materials 0.000 claims description 2
- 229910052697 platinum Inorganic materials 0.000 claims description 2
- 239000000725 suspension Substances 0.000 claims description 2
- 238000005406 washing Methods 0.000 claims description 2
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 abstract description 12
- 238000003786 synthesis reaction Methods 0.000 abstract description 9
- 230000015572 biosynthetic process Effects 0.000 abstract description 7
- 239000001257 hydrogen Substances 0.000 abstract description 5
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000004065 semiconductor Substances 0.000 abstract description 4
- 230000008901 benefit Effects 0.000 abstract description 3
- 230000003197 catalytic effect Effects 0.000 abstract description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000011941 photocatalyst Substances 0.000 description 6
- 239000002041 carbon nanotube Substances 0.000 description 5
- 229910021393 carbon nanotube Inorganic materials 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 230000006798 recombination Effects 0.000 description 5
- 238000005215 recombination Methods 0.000 description 5
- 238000006722 reduction reaction Methods 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- 238000001179 sorption measurement Methods 0.000 description 4
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- 239000011324 bead Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000002086 nanomaterial Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 241000282414 Homo sapiens Species 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 230000031700 light absorption Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 150000002894 organic compounds Chemical class 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000007146 photocatalysis Methods 0.000 description 2
- 238000013033 photocatalytic degradation reaction Methods 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 241000894007 species Species 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000007669 thermal treatment Methods 0.000 description 2
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 2
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 2
- FJLUATLTXUNBOT-UHFFFAOYSA-N 1-Hexadecylamine Chemical compound CCCCCCCCCCCCCCCCN FJLUATLTXUNBOT-UHFFFAOYSA-N 0.000 description 1
- WXNZTHHGJRFXKQ-UHFFFAOYSA-N 4-chlorophenol Chemical group OC1=CC=C(Cl)C=C1 WXNZTHHGJRFXKQ-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- NIWQQYJSLXQOCI-UHFFFAOYSA-L [O--].[K+].[Ti+4].[O-]C(=O)C([O-])=O Chemical compound [O--].[K+].[Ti+4].[O-]C(=O)C([O-])=O NIWQQYJSLXQOCI-UHFFFAOYSA-L 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000003945 anionic surfactant Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000008344 brain blood flow Effects 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000013626 chemical specie Substances 0.000 description 1
- 208000037998 chronic venous disease Diseases 0.000 description 1
- 210000001072 colon Anatomy 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000011246 composite particle Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000001404 mediated effect Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000002114 nanocomposite Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- UJVRJBAUJYZFIX-UHFFFAOYSA-N nitric acid;oxozirconium Chemical compound [Zr]=O.O[N+]([O-])=O.O[N+]([O-])=O UJVRJBAUJYZFIX-UHFFFAOYSA-N 0.000 description 1
- 210000000056 organ Anatomy 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical class [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 238000001782 photodegradation Methods 0.000 description 1
- 239000003504 photosensitizing agent Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000000979 retarding effect Effects 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- DZLFLBLQUQXARW-UHFFFAOYSA-N tetrabutylammonium Chemical compound CCCC[N+](CCCC)(CCCC)CCCC DZLFLBLQUQXARW-UHFFFAOYSA-N 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 150000003609 titanium compounds Chemical class 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
Classifications
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- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
Definitions
- the invention relates to composite graphene-metal oxide materials, the method of preparation and their applications. Taking advantage of the semi-conductor properties of metal oxides, these materials have great potential to be used in organic synthesis, solar cells, solar hydrogen production and synthesis of methanol.
- graphene-Ti02 has excellent photocatalyt ic activity and can be used to degrade inorganic and organic pollutants in water and air, synthesis of organic compounds, production of hydrogen using solar cells and synthesis of methanol
- photo active semiconductor like Ti0 2 When photo active semiconductor like Ti0 2 is illuminated with photons with energy equal or larger than the band gap, electrons (e ⁇ ) are excited from the valence band into the conduction band leaving a positive hole (h + ) ; the electrons migrate to the surface of graphene preventing the direct recombination with the holes and providing an adsorption site for the species to be oxidized. The holes became then available for conducting oxidation reactions on the photocatalyst surface.
- the photocatalytic activity can be enhanced by: a) Increasing the surface area; b) Decreasing the recombination rate of the photo generated electron-hole ; c) Extend the light absorption to longer wavelengths.
- Patent EP0997191 [4] describes the preparation of TiC supported at least partially on the surface of nanoparticles of Ti02. This material was produced by CVD treatment of Ti02 with gaseous hydrocarbons and a reductant agent, the material thus produced was able to photo-oxidize formaldehyde using visible light.
- Patent US7524793B2 describes the preparation of photocatalytic Ti02 having atoms of carbon. This photocatalyst was manufactured by mixing a fine grained titanium compound with a specific area of at least 50 m2/g with an organic compound and subsequent thermal treatment at temperatures up to 350 °C. Carbon is present only on the surface of Ti02 particles, which is different from the carbon doped Ti02 described in [6] where carbon was claimed to be inserted inside Ti02 crystals.
- Carbon nanotubes have a large electron storage capacity; they can accept and store photo- excited electrons from Ti0 2 retarding the recombination of the electron-hole pair.
- carbon nanotubes provide a surface area similar to activated carbon and may enhance the photocatalytic activity acting as photosensitizer .
- Graphene have very recently attracted considerable attention as a viable and inexpensive alternative to carbon nanotubes in nanocomposite materials.
- Graphene is essentially a flattened carbon nanotube cut along its axes made of a two-dimensional crystalline sheet of carbon atoms arranged in a honeycomb lattice. It has two faces with no bulk in between, therefore reagents can attach to both graphene faces.
- the great interest of graphene is because of its ultrathin geometry (is the thinnest known material) and properties such as high charge carrier mobility, excellent thermal conductivity and high mechanical strength (the strongest ever measured) [9].
- the present invention discloses a composite material containing nanoparticles of Ti02 chemically bonded to a graphene platelet surfaces. This composite particle is in the range of micrometers in diameter and possesses no danger for the human beings like TiO nanoparticles may do.
- the invention relates the process of synthesis and use of a new composite catalyst of graphene-metal oxide. It is based on a metal oxide that is presented in amorphous, semicrystalline or crystalline and/or oxohydrate and/or hydrated form and graphene and/or reduced graphene oxide.
- the composite material is prepared by mixing an aqueous solution of graphene oxide and a solution of a metal source material dissolved in water or a water miscible solvent. After hydrolysis, the metal oxide is attached to graphene oxide by physical and/or chemical interaction. The graphene oxide can be converted into graphene by chemical reduction and/or thermal treatment under hydrogen. A change of color takes place after the reducing process.
- the composite material has improved photoactivity due to: a) the high surface area; the nanosize metal oxide particles are dispersed on both surface sides of graphene, b) reduced rate of electron hole recombination; the high mobility of electrons and high electron storage of graphene makes the exchange of electrons with the titania easier, and c) adsorption of chemical species to be photodegraded and intermediate products on the surface.
- the present invention refers to the process of preparation and application of a composite of graphene-metal oxide.
- the platelets of graphene have been proved to be effective supports for metal-oxide catalysts.
- the composite catalyst of platelets of graphene and metal oxides could be used in organic synthesis, solar cells, solar generation of hydrogen, synthesis of methanol, taking advantage of the semi-conductor properties of metal oxides or just by their catalytic properties.
- the present invention refers to a composite catalyst, the method of preparation and their applications.
- the catalyst of the present invention is composed of nanoparticles of metal oxides attached to platelets of graphene or reduced graphene-oxide .
- the platelets are composed of one layer or multiple layers.
- the thickness of the platelets of graphene is less than 1000 nm preferably between 1 to 100 nm.
- the size of the nanoparticles of metal-oxide should be between 1 to 100 nm, and the metal-oxide is amorphous, semicrystalline or crystalline and/or in the oxohydrate and/or hydrate form.
- the metal-oxide nanoparticles is selected from the group of Ti02, ZnO, Zr02, Fe203, W03, SrTi03, BaTi03, Nb205, KTa03, Sn02, Ta205, A1203, Ce02, Y203 or a mixture of them.
- the metal oxide is doped or decorated doped material is selected from the group consisting of Pt, Pd, Ni, Cu, Fe, Rh, Ru, N, C or a mixture of them; and the concentration relative to the metal-oxide is between 0.5 to 20 weight percent.
- the composite material has a surface area between 40 to 500 m2/g, preferably between 60 to 250 m2/g.
- the method of preparation of the composite material comprises : a) Preparation of a solution of graphene oxide in water ; b) Preparation of a solution of the metal-oxide precursor in a solvent miscible with water; c) Mixture of both solutions prepared previously in the desired proportion; d) Precipitation of the solution obtained in c) by addition of a basic solution preferentially ammonia; e) Reduction of the graphene oxide by adding a reductant agent, preferentially N2H4 and heating the suspension at a convenient temperature and enough time to obtain a constant change of color of graphene.
- the heating conditions can change according to the time and temperature of the process; for example, we verified that the constant change of color at temperatures higher than 30 °C for more than 2h, preferentially at 90 °C for about 12 h. ; . f) Filtration and washing of the precipitate.
- the material thus obtained can be calcinated in a non- oxidant environment which can be an inert gas, NH3, hydrocarbons, at higher than 400 °C preferentially 450 °C for 2 h.
- a non- oxidant environment which can be an inert gas, NH3, hydrocarbons, at higher than 400 °C preferentially 450 °C for 2 h.
- the reduction of the graphene oxide to graphene is total or partial; and the composition of graphene is from 0.01 wt . % to 2 wt . % and preferably between 0.1 to 1 wt . % .
- the graphene metal-oxide catalyst according to the invention displays improved photocatalytic activity than nanoparticles of Ti02. As the nanoparticles of Ti02 are attached strongly to both phases of graphene platelets; minimizes the risk of the particles to reach vital organ of living objects.
- the composite catalyst is a photocatalyst .
- H 2 S0 4 50 ml of H 2 S0 4 is added to 2 g of graphite at room temperature; the solution is cooled at 0 °C using an ice bath and then 7 g of KMn0 4 is added gradually. The mixture is heated at 35 °C and stirred for 2 h. After that, 300 ml of water is added into the mixture at 0 °C (ice bath) . Then H 2 0 2 (30%) is added until no gas is produced. The solid is filtered, washed with 250 ml of HC1 (0.1 M) and water (500 ml) . The graphene oxide is dried under vacuum at room temperature for 24 h and then triturated using a mortar.
- Example 1 Preparation of Ti02-graphene composite titanium tetrachloride (6 g) is added dropwise under strong stirring into a 4 % solution of HC1. The stirring is continued until the solution becomes clear. 7 g of the graphene oxide solution is added and the solution stirred for another 30 minutes. Then NH 3 (28-30%) is added dropwise until the pH becomes 7. In order to reduce the graphene oxide 3 g of N2H4 is added and leave to react overnight at 90 °C. The Ti02-graphene is filtered and washed with water until no chloride was detected (formation of AgCl) and dried at 90 °C overnight.
- Fig 1 shows a SEM image of the composite material, it can be seen that 10-15 nm Ti02 particles are present on the graphene platelets.
- Example 2 Preparation of Ti02-graphene composite Potassium titanium oxide oxalate (3 g) is dissolved in 100 ml of water and stirred until the solution becomes clear. 3 g of the graphene oxide solution is added and stirred for another 30 minutes. Then NH3 (2 M) is added dropwise until pH 7. The graphene oxide is reduced by addition of 3 g of N2H4, the reduction is carried out overnight at 90 °C. The Ti02-graphene is filtered, washed with water and dried at 90 °C overnight. Then the composite material is calcinated at 450 °C for 2 h under nitrogen with heating rate of 2°C/min.
- Example 3 Preparation of Ti02-graphene composite beads. - 1.3 g of hexadecylamine is dissolved in 150 ml of ethanol and 1 ml of KC1 (0.1 M in water) . To this solution 2 g of a solution of graphene oxide is added. Then titanium isopropoxide (4.5 g) is added dropwise under strong stirring; the solution was kept static for 24h. The precipitate is filtered and transferred into a flask. Then 3 g of N2H4 and 20 ml of water are added, the flask was closed and heated at 90 °C overnight. The composite material is calcinated at 450 °C for 2h under nitrogen with heating rate of 2°C/min. SEM images of the beads are shown in Fig 2.
- Fig 2. SEM images of the Ti02-graphene beads.
- Fig 3. Photocatalytic degradation of NO by graphene-Ti02 and P 25 Ti02. a) selectivity of conversion, b)percentage of conversion.
- Garriga i Cabo 0. Gonzalez-Diaz, J. A. Herrera-Melian, J. Perez-Pena, G. Colon, J. A. Navio; "Ti02 activation by using activated carbon as a support: Part II. Photoreactivity and FTIR study", Appl. Catal. B Environ. 44, 153-160, 2003.
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Abstract
The present invention relates to the method of preparation and applications of composite catalyst of grapheno-metal oxide. Graphene platelets demonstrated to be very convenient support for metal-oxides catalysts. In particular, grapheno-metal oxide platelets can be used advantageously in organic synthesis, solar cells, solar hydrogen production and synthesis of methanol, taking advantage of metal-oxide semi-conductor properties or just of catalytic properties.
Description
DESCRIPTION
"COMPOSITE GRAPHENO-METAL OXIDE PLATELET METHOD OF
PREPARATION AND APPLICATIONS"
Field of the invention
The invention relates to composite graphene-metal oxide materials, the method of preparation and their applications. Taking advantage of the semi-conductor properties of metal oxides, these materials have great potential to be used in organic synthesis, solar cells, solar hydrogen production and synthesis of methanol. In particular graphene-Ti02 has excellent photocatalyt ic activity and can be used to degrade inorganic and organic pollutants in water and air, synthesis of organic compounds, production of hydrogen using solar cells and synthesis of methanol
State-of-the-art
When photo active semiconductor like Ti02 is illuminated with photons with energy equal or larger than the band gap, electrons (e~) are excited from the valence band into the conduction band leaving a positive hole (h+) ; the electrons migrate to the surface of graphene preventing the direct recombination with the holes and providing an adsorption site for the species to be oxidized. The holes became then available for conducting oxidation reactions on the photocatalyst surface. The photocatalytic activity can be enhanced by: a) Increasing the surface area; b) Decreasing the recombination rate of the photo generated electron-hole ; c) Extend the light absorption to longer wavelengths.
In order to improve the photocatalytic activity, it has been proposed the addition of metals to the metal oxides. Thus, Pt was deposited on the surface of Ti02. After excitation, the electron migrates to the metal where it is trapped and the electron-hole recombination reduced [ 1 ] ; the concentration of metal should be very small, because large concentrations are detrimental for the photoactivity [1] .
Addition of activated carbon increases the photocalytic activity of Ti02 due to the adsorption on the substrate of the reactants or the intermediate species on the activated carbon [2,3] . Carbon can be also used to reduce the band gap of Ti02 allowing absorption of photons in the visible region increasing the adsorption efficiency [4-7]
Patent EP0997191 [4] describes the preparation of TiC supported at least partially on the surface of nanoparticles of Ti02. This material was produced by CVD treatment of Ti02 with gaseous hydrocarbons and a reductant agent, the material thus produced was able to photo-oxidize formaldehyde using visible light.
Khan et al . [5] prepared Ti02 modified with carbon by flame pyrolysis using metallic titanium as precursor. The pyrolysis was carried out in the presence of products of combustion (C02 and water vapor) of a flame of natural gas with controlled addition of oxygen. In this material, some atoms of oxygen of the crystalline network were replaced with carbon allowing the absorption of light at wavelengths below 535 nm. This photocatalyst was efficient for water splitting .
In another paper [6], carbon was introduced in the structure of Ti02 by hydrolysis of titanium tetrachloride with tetrabutylammonium followed by the calcinations of one hour at 400 °C. The resultant dark brown material was 5 times more photoactive in the decomposition of 4- chlorophenol than Ti02 doped with nitrogen. In this case, the used of tetrabutylammoniumn in the precipitation
process, produced relatively homogenous doped Ti02 particles .
Patent US7524793B2 describes the preparation of photocatalytic Ti02 having atoms of carbon. This photocatalyst was manufactured by mixing a fine grained titanium compound with a specific area of at least 50 m2/g with an organic compound and subsequent thermal treatment at temperatures up to 350 °C. Carbon is present only on the surface of Ti02 particles, which is different from the carbon doped Ti02 described in [6] where carbon was claimed to be inserted inside Ti02 crystals.
On the other hand, it was recently observed that the photocatalytic activity of Ti02 can be improved by adding carbon nanotubes [8] . Carbon nanotubes have a large electron storage capacity; they can accept and store photo- excited electrons from Ti02 retarding the recombination of the electron-hole pair. In addition, carbon nanotubes provide a surface area similar to activated carbon and may enhance the photocatalytic activity acting as photosensitizer .
Graphene have very recently attracted considerable attention as a viable and inexpensive alternative to carbon nanotubes in nanocomposite materials. Graphene is essentially a flattened carbon nanotube cut along its axes made of a two-dimensional crystalline sheet of carbon atoms arranged in a honeycomb lattice. It has two faces with no bulk in between, therefore reagents can attach to both graphene faces. The great interest of graphene is because of its ultrathin geometry (is the thinnest known material) and properties such as high charge carrier mobility, excellent thermal conductivity and high mechanical strength (the strongest ever measured) [9].
It was described the use of self-organized hybrid nanostructures of graphene-Ti02 to increase the charge- discharge ratio of lithium batteries [10] . The increase in efficiency was attributed to the increase of the electric
conductivity of the graphene-Ti02 electrodes. A determinant step in the preparation of the material was the development of an anionic surfactant mediated growth of self-assembled metal oxide-graphene hybrid nanostructures.
It is been discussed if single nanoparticles of Ti02 are harmful for the human beings as they can penetrate even into the brain blood circulation. The present invention discloses a composite material containing nanoparticles of Ti02 chemically bonded to a graphene platelet surfaces. This composite particle is in the range of micrometers in diameter and possesses no danger for the human beings like TiO nanoparticles may do.
Description
The invention relates the process of synthesis and use of a new composite catalyst of graphene-metal oxide. It is based on a metal oxide that is presented in amorphous, semicrystalline or crystalline and/or oxohydrate and/or hydrated form and graphene and/or reduced graphene oxide.
The composite material is prepared by mixing an aqueous solution of graphene oxide and a solution of a metal source material dissolved in water or a water miscible solvent. After hydrolysis, the metal oxide is attached to graphene oxide by physical and/or chemical interaction. The graphene oxide can be converted into graphene by chemical reduction and/or thermal treatment under hydrogen. A change of color takes place after the reducing process. The composite material has improved photoactivity due to: a) the high surface area; the nanosize metal oxide particles are dispersed on both surface sides of graphene, b) reduced rate of electron hole recombination; the high mobility of electrons and high electron storage of graphene makes the exchange of electrons with the titania easier, and c) adsorption of chemical species to be photodegraded and intermediate products on the surface.
Summary of the invention
The present invention refers to the process of preparation and application of a composite of graphene-metal oxide. The platelets of graphene have been proved to be effective supports for metal-oxide catalysts. In particular, the composite catalyst of platelets of graphene and metal oxides could be used in organic synthesis, solar cells, solar generation of hydrogen, synthesis of methanol, taking advantage of the semi-conductor properties of metal oxides or just by their catalytic properties.
The present invention refers to a composite catalyst, the method of preparation and their applications.
The catalyst of the present invention is composed of nanoparticles of metal oxides attached to platelets of graphene or reduced graphene-oxide . The platelets are composed of one layer or multiple layers.
In a preferred embodiment, the thickness of the platelets of graphene is less than 1000 nm preferably between 1 to 100 nm.
In a more preferential embodiment the size of the nanoparticles of metal-oxide should be between 1 to 100 nm, and the metal-oxide is amorphous, semicrystalline or crystalline and/or in the oxohydrate and/or hydrate form.
In a preferential embodiment, the metal-oxide nanoparticles is selected from the group of Ti02, ZnO, Zr02, Fe203, W03, SrTi03, BaTi03, Nb205, KTa03, Sn02, Ta205, A1203, Ce02, Y203 or a mixture of them.
In other preferential embodiment, the metal oxide is doped or decorated doped material is selected from the group consisting of Pt, Pd, Ni, Cu, Fe, Rh, Ru, N, C or a mixture of them; and the concentration relative to the metal-oxide is between 0.5 to 20 weight percent.
The composite material has a surface area between 40 to 500 m2/g, preferably between 60 to 250 m2/g.
The method of preparation of the composite material comprises : a) Preparation of a solution of graphene oxide in water ; b) Preparation of a solution of the metal-oxide precursor in a solvent miscible with water; c) Mixture of both solutions prepared previously in the desired proportion; d) Precipitation of the solution obtained in c) by addition of a basic solution preferentially ammonia; e) Reduction of the graphene oxide by adding a reductant agent, preferentially N2H4 and heating the suspension at a convenient temperature and enough time to obtain a constant change of color of graphene. The heating conditions can change according to the time and temperature of the process; for example, we verified that the constant change of color at temperatures higher than 30 °C for more than 2h, preferentially at 90 °C for about 12 h. ; . f) Filtration and washing of the precipitate.
The material thus obtained can be calcinated in a non- oxidant environment which can be an inert gas, NH3, hydrocarbons, at higher than 400 °C preferentially 450 °C for 2 h.
In a preferential embodiment, the reduction of the graphene oxide to graphene is total or partial; and the composition of graphene is from 0.01 wt . % to 2 wt . % and preferably between 0.1 to 1 wt . % .
The graphene metal-oxide catalyst according to the invention, displays improved photocatalytic activity than nanoparticles of Ti02. As the nanoparticles of Ti02 are
attached strongly to both phases of graphene platelets; minimizes the risk of the particles to reach vital organ of living objects.
In an even more preferential embodiment, the composite catalyst is a photocatalyst .
Examples
The present invention will now be described in greater detail with reference to the following examples. The examples are for illustrative purposes only and are not intended to limit the scope of the invention.
Example of preparation of graphene oxide
50 ml of H2S04 is added to 2 g of graphite at room temperature; the solution is cooled at 0 °C using an ice bath and then 7 g of KMn04 is added gradually. The mixture is heated at 35 °C and stirred for 2 h. After that, 300 ml of water is added into the mixture at 0 °C (ice bath) . Then H202 (30%) is added until no gas is produced. The solid is filtered, washed with 250 ml of HC1 (0.1 M) and water (500 ml) . The graphene oxide is dried under vacuum at room temperature for 24 h and then triturated using a mortar.
Example of the preparation of the solution of graphene oxide .
75 mg of graphene oxide and 100 ml of water is sonicated using an ultrasonic bath for 7 h. The insoluble graphene is separated by centrifugation at 12000 rpm for 10 minutes.
Examples of preparation of the composite material .
Example 1. Preparation of Ti02-graphene composite titanium tetrachloride (6 g) is added dropwise under strong stirring into a 4 % solution of HC1. The stirring is continued until the solution becomes clear. 7 g of the graphene oxide solution is added and the solution stirred for another 30 minutes. Then NH3 (28-30%) is added dropwise until the pH becomes 7. In order to reduce the graphene oxide 3 g of N2H4 is added and leave to react overnight at 90 °C. The Ti02-graphene is filtered and washed with water until no chloride was detected (formation of AgCl) and dried at 90 °C overnight. Then the composite material was calcinated at 450 °C for 2h under nitrogen with heating rate of 2°C/min. Fig 1 shows a SEM image of the composite material, it can be seen that 10-15 nm Ti02 particles are present on the graphene platelets.
Example 2. Preparation of Ti02-graphene composite Potassium titanium oxide oxalate (3 g) is dissolved in 100 ml of water and stirred until the solution becomes clear. 3 g of the graphene oxide solution is added and stirred for another 30 minutes. Then NH3 (2 M) is added dropwise until pH 7. The graphene oxide is reduced by addition of 3 g of N2H4, the reduction is carried out overnight at 90 °C. The Ti02-graphene is filtered, washed with water and dried at 90 °C overnight. Then the composite material is calcinated at 450 °C for 2 h under nitrogen with heating rate of 2°C/min.
Example 3. Preparation of Ti02-graphene composite beads. - 1.3 g of hexadecylamine is dissolved in 150 ml of ethanol and 1 ml of KC1 (0.1 M in water) . To this solution 2 g of a solution of graphene oxide is added. Then titanium isopropoxide (4.5 g) is added dropwise under strong stirring; the solution was kept static for 24h. The precipitate is filtered and transferred into a flask. Then 3 g of N2H4 and 20 ml of water are added, the flask was closed and heated at 90 °C overnight. The composite material is calcinated at 450 °C for 2h under nitrogen with
heating rate of 2°C/min. SEM images of the beads are shown in Fig 2.
Example 4. Preparation of Zr02-graphene composite. -
6.3 g of zirconylnitrate is dissolved in 100 ml of water and stirred until the solution becomes clear. 4.2 g of graphene oxide solution is added and the solution stirred for another 30 minutes. Then NH3 (2M) is added dropwise until the pH becomes 7. In order to reduce the graphene oxide 3 g of N2H4 is added and leave to reacted overnight at 90 °C. The Zr02-graphene is filtered and dried at 90 °C overnight. Then the composite material is calcinated at 450 °C for 2h under nitrogen with heating rate of 2°C/min.
Photocatalytic activity
The photocatalytic activity of the composite material was compared with the commercially available P-25 Ti02 by the photodegradat ion of NO. Figure 3a clearly shows that the percentage of conversion of the Ti02-graphene material is much higher than P25. The conversion obtained with the Ti02-graphene photocatalyst is almost constant more than 90 %. However, P25 conversion has a long unsteady state period of time and reaches a much smaller steady state conversion, 63 % for the same operating conditions. Similarly, the selectivity (percentage of NO converted to N02 ~ and N03 ~) in the composite material is much higher than in P25 (Fig 3 b) .
Description of the Figures
Fig 1 - SEM image of Ti02-graphene composite.
Fig 2.- SEM images of the Ti02-graphene beads.
Fig 3.- Photocatalytic degradation of NO by graphene-Ti02 and P 25 Ti02. a) selectivity of conversion, b)percentage of conversion.
References
1. Amy L. Linsebigler, Guangquan Lu, and John T. Yates, Jr;
"Photocatalysis on Ti02 Surfaces: Principles, Mechanisms, and Selected Results", Chem. Rev. 95, 735- 758, 1995.
2. Juan Matosa, Jorge Laine, Jean-Marie Herrmann, "Synergy effect in the photocatalytic degradation of phenol on a suspended mixture of titania and activated carbon"; Appl. Catal. B: Environ. 18, 281-291, 1998.
3. J. Arana, J. M. Dona-Rodriguez, E. Tello Rendon, C.
Garriga i Cabo, 0. Gonzalez-Diaz, J. A. Herrera-Melian, J. Perez-Pena, G. Colon, J. A. Navio; "Ti02 activation by using activated carbon as a support: Part II. Photoreactivity and FTIR study", Appl. Catal. B Environ. 44, 153-160, 2003.
4. Sugiyama, Kazuo, "Photocatalyst having visible light activity and uses thereof" EP0997191, 2000.
5. S. U.M.Khan, M. Al-Shahry, W. B. Ingler Jr. Efficient photochemical water splitting by chemically modified n- Ti02, Science 297, 2243-2245, 2002
6. S. Sakthivel, H. Kisch, Dayloght photocatalysis by carbon-modified titanium dioxide, Angew. Chem. Int. Ed. 42, 4908-4911, 2003
7. J. Orth-Gerber, H. Kisch, S. Shanmugasundaram; Titanium dioxide photocatalyst containing carbon and method for its production; US 7524793 B2, 2009
8. K. Woan, C. Pyrgiotakis, W. Sigmund, "Photocatalytic Carbon-Nanotube-Ti02 composites" Adv. Mater. 21,1-7,
2009
9. A.K. Geim, "Graphene: Status and Prospects"; Science, 234, 2009, 1530.
10. D. Wang, D. Choi, J. Li, Z. Yang, R. Kou, D. Hu, C. Wang, L. Saraf, J. Zhang, I. A., J. Liu. Self-assembled Ti02-graphene hybrid nanostructures for enhanced Li-Ion Insertion; ACS Nano, 3 907-914, 2009
Claims
Claims
1 - A composite catalyst comprising nanoparticles of metal oxide attached to graphene or reduced graphene oxide platelets, where the metal oxide is doped or decorated and the decorating or doping material has a concentration relative to the metal-oxide is between 0.5 wt . % to 20 wt . % .
2 - Composite catalyst according to claim 1 wherein the graphene platelets are composed of single of multiple layers of graphene.
3 - Composite catalyst according to claims 1 - 2 wherein the thickness of the graphene platelets are less than 500 nm.
4 - Composite catalyst according to claim 3 wherein the thickness of the graphene platelets is between 0.4 and 50 nm.
5 - Composite catalyst according to claim 1 wherein the nanoparticles of metal oxide are between 1 to 100 nm.
6 - Composite catalyst according to claims 1 and 5 wherein the nanoparticles of metal oxide is selected from the group of Ti02, ZnO, Zr02, Fe203, W03, SrTi03, BaTi03, Nb205, KTa03 , Sn02, Ta205, A1203, Y203, Ce02 or a mixture of them.
7 - Composite catalyst according to claims 1, 5-6 wherein the metal oxide is amorphous, semicrystalline or crystalline .
8 - Composite catalyst according to claims 1, 5-7 wherein the metal oxide is in the oxohydrate and/or hydrate form.
9 - Composite catalyst according to claim 1 wherein the doping or decorating material is selected from the group consisting of Pt, Pd, Ni, Cu, Fe, Rh, Ru, N, C or a mixture of them.
10 - Composite catalyst according to claims 1-9 wherein the surface area is between 40 and 500 m2/g, preferably between 60 and 250 m2/g.
11 - A process for preparation of the composite material described in claims 1-10 comprising the following steps: a) Preparation of a solution of graphene oxide in water ; b) Preparation of a solution of the metal-oxide precursor in a solvent miscible with water; c) Mixture of both solutions prepared previously in the desired proportion; d) Precipitation of the solution obtained in c) by addition of a basic solution preferentially ammonia; e) Reduction of the graphene oxide by addition of a reductant agent, preferentially N2H4 and heating the suspension at a convenient temperature and enough time to obtain a constant change of color of graphene. The heating conditions can change according to the time and temperature of the process; for example, we verified that the constant change of color at temperatures higher than 30 °C for more than 2h, preferentially at 90 °C for about 12 h; f) Filtration and washing of the precipitate.
12 - Process according to claim 11 comprising an additional step of calcinations under non-oxidant atmosphere.
13 - Process according to claim 12 wherein the non-oxidant atmosphere is an inert gas, NH3, N2H4 or hydrocarbons at more than 400 °C, preferably at 450 °C for 2 h.
14 - Process according to claims 11-13 wherein the composition of graphene is between 0.01 wt . % to 2 wt . % and preferably between 0.1 wt . % to 1 wt . % .
15 - Composite catalyst described in claims 1-10 and obtained by the processes of preparation described in claims 11-14 wherein it has photocatalytic activity.
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CN103382362A (en) * | 2013-08-06 | 2013-11-06 | 大连海事大学 | Polyurethane composite coating with antifouling performance and preparation method thereof |
CN108043468A (en) * | 2017-12-12 | 2018-05-18 | 成都育芽科技有限公司 | A kind of vehicle maintenance service environmentally protective catalyst and preparation method thereof |
CN108311140A (en) * | 2018-03-21 | 2018-07-24 | 长春理工大学 | A kind of preparation method of the optic catalytic composite material of palladium modification |
CN108568295A (en) * | 2017-03-07 | 2018-09-25 | 中国科学院上海硅酸盐研究所 | A kind of inkstone shape ZnO/ graphene complex photochemical catalysts and preparation method thereof |
CN113477241A (en) * | 2021-09-07 | 2021-10-08 | 华南理工大学 | Ternary composite photocatalyst and preparation method and application thereof |
US11629417B2 (en) | 2020-03-12 | 2023-04-18 | Honda Motor Co., Ltd. | Noble metal free catalyst for hydrogen generation |
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2010
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Cited By (8)
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CN103382362A (en) * | 2013-08-06 | 2013-11-06 | 大连海事大学 | Polyurethane composite coating with antifouling performance and preparation method thereof |
CN103382362B (en) * | 2013-08-06 | 2016-01-13 | 大连海事大学 | A kind of polyurethane Composite Coating with antifouling property and preparation method thereof |
CN108568295A (en) * | 2017-03-07 | 2018-09-25 | 中国科学院上海硅酸盐研究所 | A kind of inkstone shape ZnO/ graphene complex photochemical catalysts and preparation method thereof |
CN108043468A (en) * | 2017-12-12 | 2018-05-18 | 成都育芽科技有限公司 | A kind of vehicle maintenance service environmentally protective catalyst and preparation method thereof |
CN108311140A (en) * | 2018-03-21 | 2018-07-24 | 长春理工大学 | A kind of preparation method of the optic catalytic composite material of palladium modification |
US11629417B2 (en) | 2020-03-12 | 2023-04-18 | Honda Motor Co., Ltd. | Noble metal free catalyst for hydrogen generation |
CN113477241A (en) * | 2021-09-07 | 2021-10-08 | 华南理工大学 | Ternary composite photocatalyst and preparation method and application thereof |
CN113477241B (en) * | 2021-09-07 | 2021-12-17 | 华南理工大学 | Ternary composite photocatalyst and preparation method and application thereof |
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