CN114014343B - High-activity defect-state magnesium oxide nano-sheet and preparation method and application thereof - Google Patents
High-activity defect-state magnesium oxide nano-sheet and preparation method and application thereof Download PDFInfo
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- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 title claims abstract description 102
- 239000000395 magnesium oxide Substances 0.000 title claims abstract description 101
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 title claims abstract description 101
- 239000002135 nanosheet Substances 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 230000000694 effects Effects 0.000 title claims abstract description 11
- 238000001354 calcination Methods 0.000 claims abstract description 43
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 22
- 238000004729 solvothermal method Methods 0.000 claims abstract description 20
- 230000001699 photocatalysis Effects 0.000 claims abstract description 17
- 230000007547 defect Effects 0.000 claims abstract description 14
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 12
- 239000002904 solvent Substances 0.000 claims abstract description 12
- 159000000003 magnesium salts Chemical class 0.000 claims abstract description 11
- 239000001301 oxygen Substances 0.000 claims abstract description 11
- 239000002243 precursor Substances 0.000 claims abstract description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000002060 nanoflake Substances 0.000 claims abstract description 8
- 239000002994 raw material Substances 0.000 claims abstract description 6
- WVDDGKGOMKODPV-UHFFFAOYSA-N Benzyl alcohol Chemical compound OCC1=CC=CC=C1 WVDDGKGOMKODPV-UHFFFAOYSA-N 0.000 claims description 21
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 16
- 235000019441 ethanol Nutrition 0.000 claims description 12
- 239000011777 magnesium Substances 0.000 claims description 10
- LYCAIKOWRPUZTN-UHFFFAOYSA-N ethylene glycol Natural products OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 8
- 235000019445 benzyl alcohol Nutrition 0.000 claims description 7
- 230000009467 reduction Effects 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 6
- PEDCQBHIVMGVHV-UHFFFAOYSA-N glycerol group Chemical group OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 6
- 239000003054 catalyst Substances 0.000 claims description 5
- 239000003795 chemical substances by application Substances 0.000 claims description 5
- WVDDGKGOMKODPV-ZQBYOMGUSA-N phenyl(114C)methanol Chemical compound O[14CH2]C1=CC=CC=C1 WVDDGKGOMKODPV-ZQBYOMGUSA-N 0.000 claims description 5
- 239000002244 precipitate Substances 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 claims description 4
- 229910052749 magnesium Inorganic materials 0.000 claims description 4
- 238000000227 grinding Methods 0.000 claims description 3
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims description 3
- 239000012046 mixed solvent Substances 0.000 claims description 3
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 claims description 2
- 238000005286 illumination Methods 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 150000001298 alcohols Chemical class 0.000 claims 2
- 230000010757 Reduction Activity Effects 0.000 abstract description 7
- 238000006243 chemical reaction Methods 0.000 description 10
- 230000002950 deficient Effects 0.000 description 9
- 239000013078 crystal Substances 0.000 description 7
- 239000007789 gas Substances 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- -1 polytetrafluoroethylene Polymers 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000003786 synthesis reaction Methods 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 2
- 229940091250 magnesium supplement Drugs 0.000 description 2
- MFUVDXOKPBAHMC-UHFFFAOYSA-N magnesium;dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MFUVDXOKPBAHMC-UHFFFAOYSA-N 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 239000011941 photocatalyst Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000000089 atomic force micrograph Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002090 carbon oxide Inorganic materials 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 238000009841 combustion method Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000000024 high-resolution transmission electron micrograph Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- UEGPKNKPLBYCNK-UHFFFAOYSA-L magnesium acetate Chemical group [Mg+2].CC([O-])=O.CC([O-])=O UEGPKNKPLBYCNK-UHFFFAOYSA-L 0.000 description 1
- 229940069446 magnesium acetate Drugs 0.000 description 1
- 239000011654 magnesium acetate Substances 0.000 description 1
- 235000011285 magnesium acetate Nutrition 0.000 description 1
- 229940097364 magnesium acetate tetrahydrate Drugs 0.000 description 1
- 229940050906 magnesium chloride hexahydrate Drugs 0.000 description 1
- DHRRIBDTHFBPNG-UHFFFAOYSA-L magnesium dichloride hexahydrate Chemical compound O.O.O.O.O.O.[Mg+2].[Cl-].[Cl-] DHRRIBDTHFBPNG-UHFFFAOYSA-L 0.000 description 1
- XKPKPGCRSHFTKM-UHFFFAOYSA-L magnesium;diacetate;tetrahydrate Chemical compound O.O.O.O.[Mg+2].CC([O-])=O.CC([O-])=O XKPKPGCRSHFTKM-UHFFFAOYSA-L 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000013081 microcrystal Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000007146 photocatalysis Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 230000007847 structural defect Effects 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/02—Magnesia
-
- 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
- B01J23/02—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the alkali- or alkaline earth metals or beryllium
-
- B01J35/39—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/84—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by UV- or VIS- data
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
Abstract
The invention discloses a high-activity defect-state magnesium oxide nano-sheet, and a preparation method and application thereof. The invention takes a bivalent magnesium salt as a raw material and takes organic alcohol as a solvent, firstly adopts a solvothermal method to synthesize a precursor at low temperature, and then prepares the magnesium oxide nano-sheet with controllable surface defect concentration through controlled calcination treatment. The obtained magnesium oxide nano-flake has smaller size, obvious porous characteristic, abundant surface oxygen vacancies and low coordination atoms, thus showing excellent CO 2 Capture performance and photocatalytic CO 2 Reduction activity.
Description
Technical Field
The invention belongs to CO 2 The technical fields of capturing, enriching and converting, and relates to a high-activity defect-state magnesium oxide nano-sheet, a preparation method and application thereof.
Background
Magnesium oxide MgO is a novel high-functional fine inorganic material, typical alkaline earth metal oxide, white fluffy powder and NaCl-type crystal structure, and belongs to a cubic crystal system. Since the surface thereof has abundant alkaline sites, it has been used as CO in recent years 2 Solid capture agents for gases have received considerable attention, often CO 2 The basic sites on the MgO surface are combined to be converted into carbonates, so that MgO is deactivated, and thus, the MgO needs to be regenerated and recycled through high-temperature treatment. Artificial light driven CO 2 Conversion to hydrocarbon fuels or high value chemicals is a hotspot in current research. At present, mgO is used as an important promoter to improve the CO of the composite photocatalyst 2 There have been a large number of reports on adsorption of (a) but studies on direct use as a photocatalyst to reduce carbon dioxide are rare. The reason for this is that magnesium oxide is an insulator with a forbidden band width of about 5-7eV, which essentially has extremely high energy limitations as a photocatalytic material. Teramira et al reported for the first time in 2004 that the use of H 2 Or CH (CH) 4 The gas is a reducing agent, and the magnesium oxide can catalyze and reduce CO under ultraviolet irradiation 2 To CO (J.Phys.chem.B.2004, 108:346-354.), although the reactionThe rate is extremely low, namely only 2.4 mu mol g -1 ·h -1 However, the results indicate that the defects inherent to the MgO surface are capable of inducing photocatalytic activity.
MgO belongs to ion crystals, and physical and chemical properties and electronic structures of the surfaces of the MgO can be optimized through regulation and control of surface defects and low coordination atoms, so that research on defective magnesium oxide becomes a focus of attention of vast students. At present, the synthesis method of the defect magnesium oxide mainly comprises a solvothermal method, a two-dimensional template method, a solution combustion method and a condensation reflux method. For example, using magnesium band as magnesium source, solvothermal synthesis of Mg (OH) - (OCH) 3 ) The precursor is calcined at a high temperature in an auxiliary mode to prepare MgO nano-sheets with exposed crystal faces (111), but the proportion of water and solvent is required to be strictly controlled in the synthesis process, argon Ar is used for purging for 10min, ar is then pressurized to 10bar, the operation is complex, and the synthesis conditions are harsh (Angew. Chem,2006,118, 7435-7439); with ultra-thin Mg (OH) 2 Synthesizing single crystal MgO (111) nano-sheet by using nano-sheet as template, firstly synthesizing MgCO by coprecipitation method 3 .3H 2 Calcining in air atmosphere to prepare MgO nano particles with high surface area, and then hydrolyzing the MgO nano particles to generate Mg (OH) 2 Ultrathin nanosheets, finally heating Mg (OH) under dynamic high vacuum 2 The ultrathin nano-sheet is dehydrated and decomposed under the topology conversion condition, so that gram-scale preparation (111) direction oriented ultrathin single-crystal MgO nano-sheet is realized, but the reaction process is complex and the condition is harsh, and MgO polycrystalline nano-sheet or octahedral microcrystal (Angew.chem.int.ed., 2020,60, 3254-3260) is easy to form. Hao et al prepared MgO with exposed (111) crystal face containing surface oxygen vacancies in one step by constructing a reducing atmosphere during the combustion reaction, and although the operation was simple, the size of the synthesized MgO nano-sheet was 270-325nm, and the agglomeration was severe (ACS appl. Mater. Interfaces,2017,9, 12687-12693.). Therefore, the development of the preparation process of the defect-state magnesium oxide nano-sheet, which is convenient to operate, low in cost and mild in reaction condition, still has a challenging problem. The invention adopts a solvothermal method to synthesize a precursor at low temperature, and then obtains the magnesium oxide nano-sheet with controllable surface defect concentration through controlled calcination treatment, and the aqueous dispersion of the defect-state magnesium oxide has extremely high CO 2 Capturing and photocatalytic reduction of CO 2 To CO activity.
Disclosure of Invention
The invention aims to provide a high-activity defect-state magnesium oxide nano-sheet, and a preparation method and application thereof.
In order to solve the technical problems, the invention adopts the technical scheme that:
the magnesium oxide nano-flake has a microporous structure and has lattice defects, and oxygen vacancies and low coordination atoms exist on the surface of the magnesium oxide.
According to the scheme, the thickness of the magnesium oxide nano-sheet is 7-9nm, and the size is 20-50nm.
The preparation method of the high-activity defect-state magnesium oxide nano sheet comprises the following main synthesis steps: the magnesium oxide with controllable surface defect concentration is prepared by taking a divalent magnesium salt as a raw material, taking benzyl alcohol diluted by an organic alcohol solvent as a solvent, performing solvothermal reaction, and controlling calcination.
According to the scheme, the solvothermal reaction temperature is 150-200 ℃ and the reaction time is 10-14h.
According to the scheme, the bivalent magnesium salt is Mg (Ac) 2 ·4H 2 O,MgC 2 O 4 ·2H 2 O,MgCl 2 ·6H 2 O,MgSO 4 ·7H 2 O,Mg(NO 3 ) 2 ·6H 2 Magnesium salt such as O, and the above divalent magnesium salt is used by drying to remove adsorbed water. The drying condition is that the drying is carried out for 4 hours at 100 ℃. The divalent magnesium salt is preferably magnesium acetate.
According to the scheme, the solvent for the solvothermal reaction is a mixed solvent consisting of alcohol and benzyl alcohol, wherein the alcohol is one or more selected from absolute methanol, absolute ethanol and glycol, and the volume ratio of the alcohol to the benzyl alcohol is preferably 1-15: 1.
according to the scheme, the calcination is secondary calcination, the first calcination is air atmosphere calcination, the calcination temperature is 450-800 ℃, and the calcination is carried out for 4-7h, wherein the calcination atmosphere is air; the second calcination is inert atmosphere calcination, the calcination temperature is 500-700 ℃, and the calcination is carried out for 2-4 hours, wherein the inert atmosphere is N 2 Or an Ar atmosphere.
According to the scheme, after the solvothermal reaction is finished, naturally cooling to room temperature, centrifuging to obtain precipitate, repeatedly washing with absolute ethyl alcohol, drying to obtain a precursor, grinding and calcining to prepare the defect-state magnesium oxide.
According to the scheme, air calcination is carried out, natural cooling is carried out to room temperature, grinding is carried out, magnesium oxide powder is obtained, and secondary calcination is carried out under inert atmosphere.
Providing a method for reducing CO by photocatalysis 2 The method comprises the steps of taking the high-activity defect-state magnesium oxide nano-flake as a catalyst, adding water and an organic sacrificial agent in a certain proportion, and then introducing CO 2 Light irradiation for photocatalytic reduction of CO 2 。
According to the scheme, the illumination wavelength is 190nm-780nm.
According to the scheme, the sacrificial agent is glycerol, glycol, ethanol, methanol, triethanolamine, ethanolamine or diethanolamine.
The invention takes the bivalent magnesium salt as a raw material, takes benzyl alcohol as a solvent, preferably takes alcohol and benzyl alcohol as a mixed solvent, and prepares the magnesium oxide nano-sheet through solvothermal reaction. The obtained magnesium oxide nano-sheet has a microporous structure and has lattice defects, and oxygen vacancies and low coordination atoms exist on the surface of the magnesium oxide. The preparation method does not need adding water or high pressure, only uses organic alcohol as solvent, and has simple and controllable process.
The invention has the beneficial effects that:
the preparation method provided by the invention is simple and convenient to operate, high-pressure is not needed, the synthesis yield is high, the price is low, and the raw materials are cheap.
The magnesium oxide nano-sheet provided by the invention has smaller size, obvious porous characteristic, abundant surface oxygen vacancies and low coordination atoms, thus showing excellent CO 2 Capture performance and photocatalytic CO 2 Reduction activity.
Description of the drawings:
fig. 1: example 2 defective magnesium oxide (MgO) 1-x ) Is an X-ray diffraction pattern of (2).
Fig. 2: example 2 defective magnesium oxide (MgO) 1-x ) A TEM image and a HRTEM image of (a).
Fig. 3: example 2 defective magnesium oxide (MgO) 1-x ) AFM of (a).
Fig. 4: example 2 defective magnesium oxide (MgO) 1-x ) Magnesium oxide MgO treated by secondary calcination 1-x -N 2 And a commercial MgO ultraviolet-visible diffuse reflection spectrum.
Fig. 5: example 2 defective magnesium oxide (MgO) 1-x ) Magnesium oxide MgO treated by secondary calcination 1-x -N 2 Photocatalytic CO of commercial MgO 2 Reduction activity map.
Detailed Description
Example 1
4.0617g of magnesium chloride hexahydrate is weighed, dried for 4 hours at 100 ℃, then placed into a 50mL beaker, added with 20mL of absolute methanol and 12.2mL of benzyl alcohol, magnetically stirred and completely dispersed, and the dispersion is transferred into a polytetrafluoroethylene lining and heated for 14 hours in a reaction kettle at 150 ℃ for solvothermal reaction; and after the solvothermal reaction is finished, naturally cooling the reaction kettle to room temperature, centrifuging to obtain a precipitate, repeatedly washing with absolute ethyl alcohol, drying at 70 ℃, taking a white sample as a precursor, placing the grinded precursor into a muffle furnace, and calcining at 450 ℃ in an air atmosphere for 4 hours to obtain the defect-state magnesium oxide. Paving the powder of ground defective magnesium oxide in a small ark, placing in a tube furnace, introducing N 2 Calcining at 600 ℃ for 2 hours to obtain the magnesium oxide subjected to secondary calcination treatment.
Example 2
4.2845g of magnesium acetate tetrahydrate is weighed, dried for 4 hours at 100 ℃, then placed into a 50mL beaker, added with 30mL of absolute methanol and 2.2mL of benzyl alcohol, magnetically stirred and completely dispersed, and the dispersion is transferred into a polytetrafluoroethylene lining and heated for 12 hours in a 180 ℃ reaction kettle for solvothermal reaction; after the solvothermal reaction is finished, naturally cooling the reaction kettle to room temperature, centrifuging to obtain precipitate, repeatedly washing with absolute ethyl alcohol, drying at 70 ℃, taking a white sample as a precursor, placing the grinded precursor into a muffle furnace, calcining at 500 ℃ in an air atmosphere for 6 hours to obtain defect-state magnesium oxide, and marking as MgO 1-x . Paving the powder of ground defective magnesium oxide in a small ark, placing in a tube furnace, introducing N 2 Calcining at 500 ℃ for 3 hours to obtain secondary calcinationTreated magnesia, let N 2 The product calcined at 500℃for 3h was designated MgO 1-x -N 2 The method comprises the steps of carrying out a first treatment on the surface of the N is led to 2 The product calcined at 700℃for 3 hours was designated MgO 1-x -N 2- 700。
Example 3
5.1226g of magnesium nitrate hexahydrate is weighed, dried for 4 hours at the temperature of 100 ℃, then placed into a 50mL beaker, added with 28mL of absolute methanol and 4.2mL of benzyl alcohol, magnetically stirred and completely dispersed, and the dispersion is transferred into a polytetrafluoroethylene lining and heated for 10 hours in a reaction kettle at the temperature of 180 ℃ for solvothermal reaction; and after the solvothermal reaction is finished, naturally cooling the reaction kettle to room temperature, centrifuging to obtain a precipitate, repeatedly washing with absolute ethyl alcohol, drying at 70 ℃, taking a white sample as a precursor, placing the grinded precursor into a muffle furnace, and calcining at 600 ℃ in an air atmosphere for 4 hours to obtain the defect-state magnesium oxide. Paving the powder of ground defective magnesium oxide in a small ark, placing in a tube furnace, introducing N 2 Calcining at 700 ℃ for 3 hours to obtain the magnesium oxide subjected to secondary calcination treatment.
FIG. 1 shows MgO 1-x X-ray diffraction pattern (XRD pattern) of (C), wherein diffraction peaks and lattice parameters are as follows PDF card of face centered cubic MgO (JCPCDS No. 45-0946) is matched.
FIGS. 2A and 2B show MgO 1-x TEM image of the nano-sheet, the diameter size of the nano-sheet is 20-50nm, and the nano-sheet has obvious micropore structure. A large number of lattice defects are visible in fig. 2C, which illustrates MgO 1-x Contains a large number of structural defects.
FIG. 3 shows MgO 1-x AFM image of nanoflakes, thickness of nanoflakes 7-9nm.
FIG. 4 shows MgO 1-x 、MgO 1-x -N 2 And the ultraviolet-visible diffuse reflection spectrum of commercial MgO. The strong absorption peak at 205nm corresponds to the absorption of pentadentate oxygen. Defect magnesium oxide MgO 1-x The peak at 270nm corresponds to the tridentate oxygen ionO 3c -due to the presence of a large number of surface oxygen vacancy clusters it shows a strong and continuous absorption throughout the UV-Vis region and the optical response is significantly larger than commercial MgO. This indicates that MgO was prepared 1-x Has abundant surface oxygen vacancies and low coordination atoms. Further calcining the MgO obtained 1-x -N 2 The tridentate oxygen ions are significantly stronger than the photoresponse caused by the pentadentate cations. This indicates MgO 1-x At N 2 Atomic rearrangement occurs in the atmosphere treatment.
Specific application
Photocatalytic CO 2 And (3) reduction:
the carbon oxide photocatalytic reduction experiments were performed in a 400mL closed reactor, the cover of which was highly light transmitting quartz glass. To prevent uv exposure, the outside of the reactor was covered with aluminum foil. The 300W xenon lamp provided a light source and the catalyst performance was tested under full light. Before the photocatalytic test, 5mg of catalyst was weighed into a reactor and 150mL of solution (deionized water and TEOA,10% TEOA) was added to disperse the catalyst, TEOA was used as an electron donor, and CO was introduced under dark conditions 2 The gas is injected into the gas chromatograph GC for 30min, then the light source is turned on, the wavelength range is 320-780nm, 1mL of the gas is taken from the reactor every 1h, and the FID detector is used for detecting the products CO and CH 4 Judging the product according to the dead time.
FIG. 4 shows MgO 1-x 、MgO 1-x -N 2 Photocatalytic CO of commercial MgO 2 Reduction activity map. Under the condition of using triethanolamine as electron donor, the total time is Guan Guangzhao h, mgO 1-x Catalytic CO 2 Reduction to CO and CH 4 CO and CH 4 The yields of (2) were 228. Mu. Mol. G, respectively -1 ·h -1 And 20. Mu. Mol.g -1 ·h -1 Photocatalytic CO higher than commercial MgO and MgO reported so far 2 Reduction activity. N (N) 2 Atmosphere secondary calcined sample MgO 1-x -N 2 Is (are) photocatalytic CO 2 The reduction activity is further improved.
TABLE 1 MgO 1-x Photocatalytic CO 2 Reduction Activity literature comparison
Claims (10)
1. A high-activity defect-state magnesium oxide nano-sheet is characterized in that: the magnesium oxide nano-sheet has a microporous structure and has lattice defects, and the surface of the magnesium oxide has rich oxygen vacancies and low coordination atoms, and the magnesium oxide with controllable surface defect concentration is prepared by using a bivalent magnesium salt as a raw material and benzyl alcohol diluted by an organic alcohol solvent as a solvent for solvothermal reaction and controlled calcination.
2. The magnesium oxide nanoflakes of claim 1, wherein: the thickness of the magnesium oxide nano-flake is 7-9nm, and the size is 20-50nm.
3. The method for preparing the high-activity defect-state magnesium oxide nano-sheet according to claim 1, wherein the method comprises the following steps: the magnesium oxide with controllable surface defect concentration is prepared by taking a divalent magnesium salt as a raw material, taking benzyl alcohol diluted by an organic alcohol solvent as a solvent, performing solvothermal reaction, and controlling calcination.
4. A method of preparation according to claim 3, characterized in that: the solvothermal reaction temperature is 150-200 ℃ and the reaction time is 10-14h.
5. A method of preparation according to claim 3, characterized in that: the bivalent magnesium salt is Mg (Ac) 2 ·4H 2 O,MgC 2 O 4 ·2H 2 O,MgCl 2 ·6H 2 O,MgSO 4 ·7H 2 O or Mg (NO) 3 ) 2 ·6H 2 O, the magnesium salt is dried to remove adsorbed water when in use.
6. A method of preparation according to claim 3, characterized in that: the solvent for the solvothermal reaction is a mixed solvent composed of one or more alcohols selected from absolute methanol, absolute ethanol and glycol and benzyl alcohol, and the volume ratio of the alcohols to the benzyl alcohol is 1-15: 1.
7. a method of preparation according to claim 3, characterized in that: the calcination is secondary calcination, the first calcination is air atmosphere calcination, the calcination temperature is 450-800 ℃, the calcination time is 4-7h, and the calcination atmosphere is air; the second calcination is inert atmosphere calcination, the calcination temperature is 500-700 ℃, and the calcination is carried out for 2-4 hours, wherein the inert atmosphere is N 2 Or an Ar atmosphere.
8. A method of preparation according to claim 3, characterized in that: and after the solvothermal reaction is finished, naturally cooling to room temperature, centrifuging to obtain precipitate, repeatedly washing with absolute ethyl alcohol, drying to obtain a precursor, grinding, and calcining to prepare the defect-state magnesium oxide.
9. Photocatalytic reduction of CO 2 Is characterized in that: the high-activity defect magnesium oxide nano flake as a catalyst, water and a certain proportion of organic sacrificial agent are added, and then CO is introduced 2 Light irradiation for photocatalytic reduction of CO 2 。
10. The method according to claim 9, wherein: the illumination wavelength is 190-780nm; the sacrificial agent is glycerol, ethylene glycol, ethanol, methanol, triethanolamine, ethanolamine or diethanolamine.
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