CN112537783A - W18O49Modified g-C3N4Application of material in photocatalysis nitrogen fixation - Google Patents
W18O49Modified g-C3N4Application of material in photocatalysis nitrogen fixation Download PDFInfo
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 94
- 239000000463 material Substances 0.000 title claims abstract description 55
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 49
- 230000001699 photocatalysis Effects 0.000 title claims abstract description 32
- 238000007146 photocatalysis Methods 0.000 title claims abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 34
- 238000003756 stirring Methods 0.000 claims abstract description 13
- 238000002156 mixing Methods 0.000 claims abstract description 6
- 239000012298 atmosphere Substances 0.000 claims abstract description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 46
- 238000010438 heat treatment Methods 0.000 claims description 19
- 229910003091 WCl6 Inorganic materials 0.000 claims description 15
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims description 10
- 229910052724 xenon Inorganic materials 0.000 claims description 10
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 claims description 10
- 229920000877 Melamine resin Polymers 0.000 claims description 9
- 238000002360 preparation method Methods 0.000 claims description 9
- 238000000227 grinding Methods 0.000 claims description 7
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 7
- 238000010298 pulverizing process Methods 0.000 claims description 2
- 239000002131 composite material Substances 0.000 description 36
- 239000003054 catalyst Substances 0.000 description 34
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 23
- 238000006243 chemical reaction Methods 0.000 description 20
- 238000000034 method Methods 0.000 description 13
- 229910021529 ammonia Inorganic materials 0.000 description 11
- 239000000203 mixture Substances 0.000 description 11
- 239000000243 solution Substances 0.000 description 10
- 238000005286 illumination Methods 0.000 description 9
- 238000002474 experimental method Methods 0.000 description 8
- 239000003795 chemical substances by application Substances 0.000 description 7
- 238000003795 desorption Methods 0.000 description 7
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 239000000969 carrier Substances 0.000 description 4
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- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen(.) Chemical compound [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 238000006722 reduction reaction Methods 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 241000606266 Nardostachys Species 0.000 description 3
- 230000004913 activation Effects 0.000 description 3
- 238000006555 catalytic reaction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000000706 filtrate Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
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- 238000006303 photolysis reaction Methods 0.000 description 3
- 230000015843 photosynthesis, light reaction Effects 0.000 description 3
- LJCNRYVRMXRIQR-OLXYHTOASA-L potassium sodium L-tartrate Chemical compound [Na+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O LJCNRYVRMXRIQR-OLXYHTOASA-L 0.000 description 3
- 239000001476 sodium potassium tartrate Substances 0.000 description 3
- 235000011006 sodium potassium tartrate Nutrition 0.000 description 3
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- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 2
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- STZCRXQWRGQSJD-GEEYTBSJSA-M methyl orange Chemical compound [Na+].C1=CC(N(C)C)=CC=C1\N=N\C1=CC=C(S([O-])(=O)=O)C=C1 STZCRXQWRGQSJD-GEEYTBSJSA-M 0.000 description 2
- 229940012189 methyl orange Drugs 0.000 description 2
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- 239000002070 nanowire Substances 0.000 description 2
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
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- 238000010521 absorption reaction Methods 0.000 description 1
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- 239000008346 aqueous phase Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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- 150000002843 nonmetals Chemical class 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
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- HOWHQWFXSLOJEF-MGZLOUMQSA-N systemin Chemical compound NCCCC[C@H](N)C(=O)N[C@@H](CCSC)C(=O)N[C@@H](CCC(N)=O)C(=O)N[C@@H]([C@@H](C)O)C(=O)N[C@@H](CC(O)=O)C(=O)OC(=O)[C@@H]1CCCN1C(=O)[C@H]1N(C(=O)[C@H](CC(O)=O)NC(=O)[C@H](CCCN=C(N)N)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CO)NC(=O)[C@H]2N(CCC2)C(=O)[C@H]2N(CCC2)C(=O)[C@H](CCCCN)NC(=O)[C@H](CO)NC(=O)[C@H](CCC(N)=O)NC(=O)[C@@H](NC(=O)[C@H](C)N)C(C)C)CCC1 HOWHQWFXSLOJEF-MGZLOUMQSA-N 0.000 description 1
- 108010050014 systemin Proteins 0.000 description 1
- KPGXUAIFQMJJFB-UHFFFAOYSA-H tungsten hexachloride Chemical compound Cl[W](Cl)(Cl)(Cl)(Cl)Cl KPGXUAIFQMJJFB-UHFFFAOYSA-H 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
- C01C1/0411—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst characterised by the catalyst
-
- 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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B01J35/39—
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention relates to a W18O49Modified g-C3N4The application of the material in photocatalysis nitrogen fixation18O49Modified g-C3N4Mixing the materials with water, stirring for at least 0.5 hour in a dark and air atmosphere, and performing photocatalytic nitrogen fixation treatment under the irradiation of a light source; the W is18O49Modified g-C3N4The molar ratio of the material to the water is (100: 1) - (1: 10000); the W is18O49Modified g-C3N4The material comprises g-C3N4Base material, and growing the g-C3N4W on the base material18O49W is as described18O49The content of (B) is 0 to 60wt%, preferably 10 to 40 wt%.
Description
Technical Field
The invention relates to a W18O49Modified g-C3N4The material is applied to the field of photocatalysis nitrogen fixation.
Background
N2As a raw material for ammonia synthesis, N is abundant in earth2The molecule is nonpolar, the nitrogen-nitrogen triple bond has 945kJ/mol of bond energy, and the first bond dissociation energy is high, the nucleophilicity to proton is weak, and the reduction is extremely difficult. At present, the artificial nitrogen fixation is mainly carried out by a haber method, the reaction conditions are harsh, the artificial nitrogen fixation needs to be carried out at high temperature and high pressure, the energy consumption is high, and simultaneously, a large amount of CO is accompanied2And (5) discharging. Therefore, from the viewpoint of cost control and environmental protection, it is of great significance to study artificial nitrogen fixation under mild conditions. In recent years, scientists find that the solar energy is used as a driving force in the nitrogen fixation reaction process to replace the harsh conditions of high temperature and high pressure in the haber reaction, but the efficiency of the catalytic reaction is far lower than the expectation of people. Therefore, the development of a high-efficiency, environment-friendly and mild-technical photocatalytic material is attracting more and more attention.
The existing photocatalysis nitrogen fixation technology has a plurality of difficulties: 1) catalyst pair N due to limited surface defects2The adsorption activation amount of (A) is insufficient; 2) the photon-generated carriers are easy to recombine; 3) the oxidation capability to water is weak and protons required for the nitrogen fixation reaction cannot be provided. g-C3N4The material is a newly grown organic semiconductor material and has wide application in the field of photocatalysis. But due to C3N4The photogenerated carriers are easy to recombine, and have limited surface defects and poorer water oxidation capability. At present, researchers improve the g-C through various means (such as constructing a semiconductor heterojunction, loading noble metals, doping metals or nonmetals, adding sacrificial agents and the like)3N4Utilization of photogenerated carriers of, for N2Adsorption activation ability and water oxidation ability. However, the photocatalytic nitrogen fixation cannot get rid of organic capture agents or sacrificial agents (such as ethanol and the like), and the production cost is high and the energy consumption is large.
Disclosure of Invention
Aiming at the current generalHigh-temperature high-pressure large-amount CO existing in the Huber method ammonia synthesis technology2The invention aims to provide a W with large energy consumption18O49Modified g-C3N4The application of the material in photocatalysis nitrogen fixation18O49Modified g-C3N4Mixing the materials with water, magnetically stirring for at least 0.5 hour in a dark and air atmosphere, and performing photocatalytic nitrogen fixation treatment under the irradiation of a light source; the W is18O49Modified g-C3N4The molar ratio of the material to the water is (100: 1) - (1: 10000); the W is18O49Modified g-C3N4The material comprises g-C3N4Base material, and growing the g-C3N4W on the base material18O49W is as described18O49The content of (B) is 0 to 60wt%, preferably 10 to 40 wt%.
In the present invention, W18O49Modified g-C3N4Material (W)18O49a/HU-CNS hybrid catalyst or W18O49a/CNB composite catalyst) can be used for photocatalytic nitrogen fixation, and the ultrathin porous HU-CNS nanosheets or CNB nanosheets can accelerate the migration rate of surface carriers; w18O49The heterojunction with HU-CNS or CNB can accelerate the transmission rate of interface carrier. The ultrathin porous HU-CNS nano-sheet and CNB nano-sheet can provide N2The reaction site of (1). W18O49The oxygen vacancies at the surface may also provide N2The activation site of (2) to accelerate the nitrogen fixation rate. And, W18O49The photogenerated holes can migrate to HU-CNS to increase the oxidizing capacity to water and provide more protons for the nitrogen fixation reaction. Based on this, W in the present invention18O49Modified g-C3N4Material (W)18O49a/HU-CNS hybrid catalyst or W18O49/CNB composite catalyst) with good light absorption capacity and high carrier separation efficiency, and can enhance the N-component2So that efficient nitrogen fixation efficiency can be achieved. At the same time, in the reaction process,only water is used as a proton source, and an organic solvent which is toxic to the environment does not need to be introduced, so that the pollution to the environment is greatly reduced, and the environment friendliness of the reaction is improved. Compared with the Haber method which needs a large amount of energy consumption and has harsh reaction conditions, the catalytic reaction of the invention can realize higher yield and save energy under the condition of normal temperature and normal pressure illumination. According to the photocatalytic nitrogen fixation method, higher nitrogen fixation efficiency (136.8 mu M g) is realized under the condition of simulated solar illumination-1h-1) Provides a new idea for the industrial catalytic synthesis of ammonia.
Preferably, W is18O49Modified g-C3N4The ratio of the material to water is (0.01-5) g: (10-100) ml.
Preferably, the stirring time is 0.5-8 hours.
Preferably, the light source is sunlight or xenon lamp light; the power of the xenon lamp light is 100-500W.
Preferably, the irradiation time is 1 to 100 hours.
Preferably, W is18O49Modified g-C3N4The preparation method of the material comprises the following steps: g to C3N4Adding into WCl6In the ethanol solution, carrying out hydrothermal reaction for 12-36 hours at 100-200 ℃ to obtain W18O49Modified g-C3N4Material (W)18O49a/CNB composite catalyst); the WCl6The mass of the ethanol is 1-10 g, and the volume of the ethanol is 10-100 ml; the g to C3N4The mass of (b) is 0.1 to 1 g.
Preferably, W is18O49Modified g-C3N4The preparation method of the material comprises the following steps:
(1) g to C3N4Keeping the temperature at 500-600 ℃ for 1-10 hours to obtain the ultrathin porous g-C3N4；
(2) The obtained ultrathin porous g-C3N4Adding into WCl6In the ethanol solution, carrying out hydrothermal reaction for 12-36 hours at 100-200 ℃ to obtain W18O49Modified g-C3N4Material (W)18O49a/HU-CNS hybrid catalyst); the WCl6The mass of the ethanol is 1-10 g, and the volume of the ethanol is 10-100 ml; the ultra-thin porous g-C3N4The mass of (b) is 0.1 to 1 g.
Further, preferably, the g-C is obtained by heat-treating melamine at 400 to 500 ℃ for 1 to 10 hours, and then grinding and pulverizing the melamine3N4(ii) a The heat treatment system comprises: the temperature is raised to 400-500 ℃ at 1-10 ℃, then the temperature is preserved for 1-10 hours, and then the temperature is raised to 500-600 ℃ at 1-10 ℃ and the temperature is preserved for 1-10 hours.
Compared with the prior art, the invention has the following beneficial effects:
(1) w obtained by the present invention18O49a/HU-CNS composite photocatalytic material or W18O49the/HU-CNS composite catalyst has higher photocatalytic nitrogen fixation activity. The material can generate 136.8 mu mol/g ammonia nitrogen in pure water under the simulated solar illumination, and is the higher efficiency of photocatalysis nitrogen fixation in pure water under the solar energy condition reported at home and abroad at present. Under the same conditions, the system such as the Fe-Al co-loaded 3D graphene can only generate 25.3 mu mol/g ammonia nitrogen. Therefore, the composite material obtained by the invention has the advantage of high-efficiency nitrogen fixation under natural conditions, and has wide application prospect;
(2)W18O49a/HU-CNS composite photocatalytic material or W18O49The preparation method of the/HU-CNS composite catalyst does not need special equipment and harsh conditions, has simple process and strong controllability, is easy to realize large-scale production and has practicability;
(3) in the invention, g-C3N4For the matrix material, ultra-thin porous g-C by hydrothermal method is preferred3N4(HU-CNS) or g-C3N4Surface growth W of18O49Preparation of W18O49the/HU-CNS complex, which achieves a high nitrogen fixation efficiency in pure water under xenon lamp illumination without any added sacrificial agent (136.8 mu M g)-1h-1)；
(4) In the invention, the reactant for fixing nitrogen by photocatalysis is water, and any toxic and harmful organic solvent is not required to be introduced, so that the pollution to the environment can be greatly reduced, and the environment friendliness of the reaction is improved;
(5) in the present invention W18O49The mechanism of photocatalysis and nitrogen fixation of the/HU-CNS composite photocatalytic material is as follows: g-C3N4To W18O49Conduction band of for N2Reduction of (2) W18O49The valence band hole of (B) is transferred to g-C3N4Valence band of for H2And (4) oxidizing O. Although it is in the range of g-C3N4-W18O49The composite photocatalyst has the same mechanism for degrading methyl orange and photolyzing water to produce hydrogen: g-C3N4-W18O49Composite material accelerates g-C3N4The surface electron-hole separation mechanism is the same, the migration direction is the same, and the reaction mechanism is similar, namely g-C3N4And W18O49The photocatalytic reaction efficiency is improved due to a certain coordination effect, the two catalysts can be reused to a certain extent, and the catalysts cannot be completely reused due to different oxidation-reduction reaction potentials of the photolysis water hydrogen production reaction and the nitrogen fixation reaction. But the photoproduction hole plays a leading role in the degradation reaction of methyl orange, and the photoproduction electron plays a leading role in the photocatalytic nitrogen fixation and the hydrogen production reaction by photolysis; the photolysis water and the photocatalytic nitrogen fixation reaction have different transferred electron numbers and different oxidation-reduction potential values.
Drawings
FIG. 1A is a diagram of a synthesis W according to the present invention18O49XRD pattern of the/HU-CNS composite photocatalytic material;
FIG. 1B is a diagram of synthesis of W according to the present invention18O49[ W ] HU-CNS composite photocatalytic material18O49Content 30 wt.%);
FIG. 1C is a diagram of synthesis of W according to the present invention18O49[ W ] HU-CNS composite photocatalytic material18O49Content 30 wt.%) TEM image (monoclinic phase W in the box18O49(010) Lattice spacing of the facets is 0.367 nm);
FIG. 2 shows the ratios prepared in example 1 used in the present inventionW18O49Nitrogen fixation efficiency schematic of/HU-CNS composite catalyst;
FIG. 3 shows 30-W prepared in example 2 used in the present invention18O49Nitrogen fixation efficiency profile of the/HU-CNS catalyst increasing over time;
FIG. 4 shows 30-W prepared in example 3 used in the present invention18O49/HU-CNS composite catalyst and 30-W18O49Nitrogen fixation efficiency of the/CNB composite catalyst is shown schematically.
Detailed Description
The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.
In this disclosure, W is selected for18O49Modified g-C3N4The material is used as a catalyst for carrying out photocatalysis nitrogen fixation, and can realize higher nitrogen fixation efficiency in pure water (water without any additive). The method is simple and feasible, clean and efficient (no organic solvent toxic to the environment needs to be introduced), free of any oxidant and additive (such as a catalyst, a sacrificial agent and the like), low in energy consumption, energy-saving, environment-friendly and easy to industrialize, and is a mild catalysis method. In the present invention, W18O49Modified g-C3N4The material is a nano powder composed of two-dimensional layered material and comprises g-C3N4Base material, and growing the g-C3N4W on the base material18O49W is as described18O49The content of (B) is 0 to 60wt%, preferably 10 to 40 wt%. Wherein W18O49The length of the glass is 0.1 to 10 μm, the diameter is 1 to 10nm, and the length-diameter ratio is 100 to 1000.
g-C3N4And (4) preparing a base material. Heat treating melamine at 400-500 ℃ for 1-10 hours, and grinding and crushing to obtain the g-C3N4(CNB) as g-C3N4A base material. The heat treatment schedule includes: the temperature is raised to 400-500 ℃ at 1-10 ℃, then the temperature is preserved for 1-10 hours, and then the temperature is raised to 500-600 ℃ at 1-10 ℃ and the temperature is preserved for 1-10 hours. Or furtherg-C3N4Heat treating in air at 1-10 deg.c for 1-10 hr to obtain ultrathin porous g-C3N4(HU-CNS) as g-C3N4A base material.
Addition of CNB to WCl6In the ethanol solution, hydrothermal reaction is carried out for 12 to 36 hours at the temperature of 100 to 200 ℃, and the ultra-fine W grows on the surface of the ethanol solution18O49Nanowires to give W18O49a/CNB composite catalyst. The WCl6The mass of (b) may be 1 to 10 g. The volume of the ethanol can be 10-100 ml. The g to C3N4The mass of (b) may be 0.1 to 1 g.
Ultra-thin porous g-C3N4Adding into WCl6In the ethanol solution, hydrothermal reaction is carried out for 12 to 36 hours at the temperature of 100 to 200 ℃, and the ultra-fine W grows on the surface of the ethanol solution18O49Nanowires to give W18O49a/HU-CNS hybrid catalyst; the WCl6The mass of (b) may be 1 to 10 g. The volume of the ethanol can be 10-100 ml. Ultrathin porous g-C3N4The mass of (b) may be 0.1 to 1 g.
As a W18O49A preparation method and a detailed example of the/HU-CNS composite catalyst comprise the following steps:
(1) weighing a certain amount of melamine (15-150 g), placing the melamine in an alumina crucible, transferring the melamine into a muffle furnace, heating to 500 ℃ at a heating rate of 2 ℃/min, preserving heat for 2h, heating to 520 ℃ at a heating rate of 10 ℃/min, preserving heat for 2h, cooling, washing and drying to obtain a bulk phase g-C3N4(CNB)；
(2) Grinding a certain amount of CNB (1-10 g) obtained in the step (1), uniformly dispersing the CNB on an alumina crucible cover, placing the CNB in a muffle furnace, heating to 520 ℃ at a heating rate of 2 ℃/min, keeping the temperature for 6h, cooling and washing to obtain the ultrathin porous g-C3N4(HU-CNS)；
(3) A certain amount (1-10 g) of WCl6Dissolving in an ethanol solution (10-100 ml), stirring, and ultrasonically dispersing uniformly;
(4) dispersing the HU-CNS (0.1-1 g) obtained in the step (2) in the WCl obtained in the step (3)6Placing the mixture in an ethanol solution, heating the mixture for 24 hours at 180 ℃, cooling and washing the mixture to obtain W18O49a/HU-CNS hybrid catalyst.
In one embodiment of the present invention, W is18O49Modified g-C3N4Material (W)18O49a/HU-CNS hybrid catalyst or W18O49a/CNB composite catalyst) is used for obtaining ammonia through photocatalysis in an aqueous solution reaction system. Specifically, the above W is18O49a/HU-CNS hybrid catalyst or W18O49Mixing the/CNB composite catalyst with water, stirring for more than half an hour in the dark to reach N2The adsorption and desorption are balanced. Wherein, the W18O49a/HU-CNS hybrid catalyst or W18O49The mol ratio of the/CNB composite catalyst to water is 100: 1-1: 10000. For example, 0.01 to 5g of surface-modified g-C3N4Mixing with 10-100 mL of water. Stirring in dark for a certain time to reach adsorption and desorption equilibrium, for example, the stirring time can be 0.5-8 hours. At the most reach N2After the adsorption and desorption are balanced, the light energy excitation source (light source) is used for exciting the N in the air2And water as reactant, under the condition of normal temperature and normal pressure light irradiation to make photocatalysis nitrogen fixation, and it has no need of adding any sacrificial agent, only utilizes the electron produced by material self-body to reduce N2The holes deoxidize water to obtain protons with good feasibility, and finally realize the purpose of removing N in the air2Reduction to NH3。
In alternative embodiments, the light source may be sunlight or simulated sunlight. For example, the light source can be a xenon lamp light with a power of 100-500W, preferably 500W. The illumination energy (light source intensity or power) can be adjusted, and the illumination time can also be adjusted, for example, 1 to 100 hours. In the invention, the photocatalysis nitrogen fixation process is a normal temperature and normal pressure process, and heating and pressurizing are not needed, so that the energy consumption can be reduced, and the environmental friendliness of the reaction is improved.
In the invention, the photocatalysis nitrogen fixation process is carried out in air atmosphere. As an example, W may be18O49Mixing the/HU-CNS composite catalyst with water, and placing the mixture in a reaction systemIn the reactor, stirring was carried out in the dark.
Test of ammonia production:
the product from the test was sampled and tested for ammonia production. As an example, for example, 5mL of liquid is taken every 1h, placed in a colorimetric tube, diluted to 50mL, added with a Nassner reagent to perform a color reaction, and then measured with an ultraviolet spectrophotometer.
In the invention, a proper composite catalyst is prepared by design, and N in the air is mixed under the illumination of sunlight or simulated sunlight after the mixture is balanced in absorption and desorption2Reduction to NH3The method can enable light energy to act on a large amount of catalysts without adding any sacrificial agent, and has a very good application prospect as a novel environment-friendly and energy-saving nitrogen fixation method. In the invention, protons required by the reaction are only from water, and no other oxidant or auxiliary agent is needed to be added, and no noble metal is needed to be used; reduces energy consumption and environmental pollution.
The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art in light of the foregoing description are intended to be included within the scope of the invention. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.
Example 1: modifying W in different proportions18O49The HU-CNS material(s) in aqueous phase:
(1) weighing a certain amount of melamine (5g), placing the melamine in an alumina crucible, transferring the melamine into a muffle furnace, heating to 500 ℃ at a heating rate of 2 ℃/min, preserving heat for 2h, heating to 520 ℃ at a heating rate of 10 ℃/min, preserving heat for 2h, cooling and washing to obtain a bulk phase g-C3N4(CNB)；
(2) A certain amount of bulk CNB (1.5g) was weighed and ground, and uniformly dispersed on an alumina crucible coverPlacing the mixture in a muffle furnace, heating to 520 ℃ at a heating rate of 2 ℃/min, keeping the temperature for 6 hours, cooling and washing to obtain the ultrathin porous g-C3N4(HU-CNS)；
(3) A certain amount of WCl6(0.1g) is dissolved in ethanol (10ml) solution, stirred and dispersed evenly by ultrasonic; HU-CNS (0g, 0.513g, 0.228g, 0.133g, 0.086g) was dispersed in WCl6Placing the mixture in an ethanol solution, heating the mixture for 24 hours at 180 ℃, and then cooling, washing and drying the mixture to obtain W18O49The catalyst is 100-W for each HU-CNS composite catalyst18O49、10wt％-W18O49/HU-CNS、20wt％-W18O49/HU-CNS、30wt％-W18O49/HU-CNS、40wt％-W18O49/HU-CNS；
(4) Subjecting the obtained W to18O49After fully grinding the/HU-CNS composite catalyst, adding 0.05g of powder into 200mL of water, placing the mixture into a 600mL reactor, placing the reactor in an open system (air atmosphere) in a dark place on a magnetic device, stirring the mixture for 0.5 hour, and carrying out N2Adsorption and desorption balance experiment;
(5) turning on a xenon lamp, and illuminating for 1h under the illumination of simulated solar light source light (xenon lamp light, 300W);
(6) and (3) carrying out suction filtration, putting 50mL of filtrate into a colorimetric tube, adding 1mL of sodium potassium tartrate and 1mL of a Nardostachys reagent, shaking up, standing for 10-15 min, and detecting the yield of ammonia by using an ultraviolet spectrophotometer when the color development is stable.
Synthetic surface-modified g-C3N4XRD and TEM of the material are shown in FIGS. 1A-1C, indicating successful synthesis of the composite material.
The nitrogen fixation efficiency obtained in the experiment is shown in FIG. 2, HU-CNS, 10-W18O49/HU-CNS、20-W18O49/HU-CNS、30-W18O49/HU-CNS、40-W18O49/HU-CNS、100-W18O49The nitrogen fixation yield in pure water was 0. mu. mol/h/g (g-C)3N4The nitrogen fixation performance in pure water is close to 0), 28.1 mu mol/h/g, 69.6 mu mol/h/g, 136.8 mu mol/h/g, 86.7 mu mol/h/g and 35.2 mu mol/h/g, wherein the nitrogen fixation performance is 30-W18O49The nitrogen fixation performance of the/HU-CNS is the best.
Example 2: w18O4930-W with optimum ratio/HU-CNS18O49HU-CNS sustained nitrogen fixation experiment
(1) Preparation of 30-W18O49the/HU-CNS composite (same as example 1);
(2) the obtained 30-W18O49After fully grinding the/HU-CNS composite material, adding 0.05g of powder into 200mL of water, placing the powder into a 600mL reactor, stirring the powder for 0.5h in the open system in the dark, and carrying out an absorption-desorption balance experiment;
(3) turning on a xenon lamp, and illuminating for 1h under the illumination of a simulated solar light source;
(4) and (3) carrying out suction filtration, putting 50mL of filtrate into a colorimetric tube, adding 1mL of sodium potassium tartrate and 1mL of a Nardostachys reagent, shaking up, standing for 10-15 min, and detecting the yield of ammonia by using an ultraviolet spectrophotometer when the color development is stable.
The yield of ammonia obtained in the experiment is shown in FIG. 3, 30-W18O49The nitrogen fixation performance of the/HU-CNS composite catalyst is linearly increased along with the change of time.
Example 3
Comparison of g to C3N4Heat treated (HU-CNS) and not heat treated g-C3N4W of (CNB)18O49Nitrogen fixation performance experiment of the/CNB composite material.
(1) Preparation of 30 wt% -W18O49HU-CNS and 30% -W18O49the/CNB composite (same as example 1);
(2) the obtained 30-W18O49(HU-CNS) composites and 30-W18O49After fully grinding the/CNB composite material, respectively adding 0.05g of powder into 200mL of water, placing the powder into a 600mL reactor, wherein the reactor is an open system, placing the reactor on a magnetic stirrer in a dark place, stirring for 0.5h, and carrying out an absorption-desorption balance experiment;
(3) turning on a xenon lamp, and illuminating for 1h under the illumination of a simulated solar light source;
(4) and (3) carrying out suction filtration, putting 50mL of filtrate into a colorimetric tube, adding 1mL of sodium potassium tartrate and 1mL of a Nardostachys reagent, shaking up, standing for 10-15 min, and detecting the yield of ammonia by using an ultraviolet spectrophotometer when the color development is stable.
The yield of ammonia obtained in the experiment is shown in FIG. 4, 30-W18O49(HU-CNS) composites and 30-W18O49NH of/CNB composite3Yields of 121.6. mu. mol/h/g and 136.8. mu. mol/h/g, respectively, further indicating heat treatment g-C3N4Can improve nitrogen fixation performance.
Claims (8)
1. W18O49Modified g-C3N4The application of the material in photocatalysis nitrogen fixation is characterized in that W is added18O49Modified g-C3N4Mixing the materials with water, stirring for at least 0.5 hour in a dark and air atmosphere, and performing photocatalytic nitrogen fixation treatment under the irradiation of a light source; the W is18O49Modified g-C3N4The molar ratio of the material to the water is (100: 1) - (1: 10000); the W is18O49Modified g-C3N4The material comprises g-C3N4Base material, and growing the g-C3N4W on the base material18O49W is as described18O49The content of (B) is 0 to 60wt%, preferably 10 to 40 wt%.
2. Use according to claim 1, wherein W is18O49Modified g-C3N4The ratio of the material to water is (0.01-5) g: (10-100) ml.
3. Use according to claim 1 or 2, wherein the stirring time is 0.5 to 8 hours.
4. The use according to any one of claims 1 to 3, wherein the light source is sunlight, or xenon light; the power of the xenon lamp light is 100-500W.
5. Use according to any one of claims 1 to 4, wherein the irradiation time is from 1 to 100 hours.
6. Use according to any one of claims 1 to 5, wherein W is18O49Modified g-C3N4The preparation method of the material comprises the following steps: g to C3N4Adding into WCl6In the ethanol solution, carrying out hydrothermal reaction for 12-36 hours at 100-200 ℃ to obtain W18O49Modified g-C3N4A material; the WCl6The mass of the ethanol is 1-10 g, and the volume of the ethanol is 10-100 ml; the g to C3N4The mass of (b) is 0.1 to 1 g.
7. Use according to any one of claims 1 to 5, characterized in that W is18O49Modified g-C3N4The preparation method of the material comprises the following steps:
(1) g to C3N4Keeping the temperature at 500-600 ℃ for 1-10 hours to obtain the ultrathin porous g-C3N4；
(2) The obtained ultrathin porous g-C3N4Adding into WCl6In the ethanol solution, carrying out hydrothermal reaction for 12-36 hours at 100-200 ℃ to obtain W18O49Modified g-C3N4A material; the WCl6The mass of the ethanol is 1-10 g, and the volume of the ethanol is 10-100 ml; the ultra-thin porous g-C3N4The mass of (b) is 0.1 to 1 g.
8. The use according to claim 6 or 7, characterized in that the g-C is obtained by heat-treating melamine at 400-500 ℃ for 1-10 hours, followed by grinding and pulverization3N4(ii) a Preferably, the schedule of heat treatment comprises: the temperature is raised to 400-500 ℃ at 1-10 ℃, then the temperature is preserved for 1-10 hours, and then the temperature is raised to 500-600 ℃ at 1-10 ℃ and the temperature is preserved for 1-10 hours.
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