CN113042032B - Tungsten oxide photocatalyst with efficient heterogeneous junction and preparation method and application thereof - Google Patents
Tungsten oxide photocatalyst with efficient heterogeneous junction and preparation method and application thereof Download PDFInfo
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- CN113042032B CN113042032B CN202110353962.5A CN202110353962A CN113042032B CN 113042032 B CN113042032 B CN 113042032B CN 202110353962 A CN202110353962 A CN 202110353962A CN 113042032 B CN113042032 B CN 113042032B
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- 239000011941 photocatalyst Substances 0.000 title claims abstract description 69
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 title claims abstract description 18
- 229910001930 tungsten oxide Inorganic materials 0.000 title claims abstract description 18
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 59
- 230000001699 photocatalysis Effects 0.000 claims abstract description 34
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 18
- 238000011065 in-situ storage Methods 0.000 claims abstract description 8
- 230000007704 transition Effects 0.000 claims abstract description 5
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 53
- 229910052783 alkali metal Inorganic materials 0.000 claims description 15
- -1 alkali metal tungstate Chemical class 0.000 claims description 15
- 239000007864 aqueous solution Substances 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 7
- XMVONEAAOPAGAO-UHFFFAOYSA-N sodium tungstate Chemical group [Na+].[Na+].[O-][W]([O-])(=O)=O XMVONEAAOPAGAO-UHFFFAOYSA-N 0.000 claims description 4
- AAQNGTNRWPXMPB-UHFFFAOYSA-N dipotassium;dioxido(dioxo)tungsten Chemical compound [K+].[K+].[O-][W]([O-])(=O)=O AAQNGTNRWPXMPB-UHFFFAOYSA-N 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims 2
- 230000000694 effects Effects 0.000 abstract description 11
- 238000000926 separation method Methods 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 description 18
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 15
- 239000001257 hydrogen Substances 0.000 description 15
- 229910052739 hydrogen Inorganic materials 0.000 description 15
- 239000008367 deionised water Substances 0.000 description 14
- 229910021641 deionized water Inorganic materials 0.000 description 14
- 238000012360 testing method Methods 0.000 description 13
- 238000005406 washing Methods 0.000 description 13
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 12
- 239000003054 catalyst Substances 0.000 description 12
- 238000004108 freeze drying Methods 0.000 description 12
- 239000001301 oxygen Substances 0.000 description 12
- 238000000354 decomposition reaction Methods 0.000 description 10
- 238000007146 photocatalysis Methods 0.000 description 9
- 239000002253 acid Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 238000003756 stirring Methods 0.000 description 7
- QWMFKVNJIYNWII-UHFFFAOYSA-N 5-bromo-2-(2,5-dimethylpyrrol-1-yl)pyridine Chemical compound CC1=CC=C(C)N1C1=CC=C(Br)C=N1 QWMFKVNJIYNWII-UHFFFAOYSA-N 0.000 description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical group OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 6
- 239000003795 chemical substances by application Substances 0.000 description 6
- 239000011259 mixed solution Substances 0.000 description 6
- 229910017604 nitric acid Inorganic materials 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000005070 sampling Methods 0.000 description 4
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical group [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 4
- 229910052724 xenon Inorganic materials 0.000 description 4
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 4
- 230000008021 deposition Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000012265 solid product Substances 0.000 description 3
- 206010019909 Hernia Diseases 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 238000007605 air drying Methods 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 229910001961 silver nitrate Inorganic materials 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- WUPHOULIZUERAE-UHFFFAOYSA-N 3-(oxolan-2-yl)propanoic acid Chemical compound OC(=O)CCC1CCCO1 WUPHOULIZUERAE-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 description 1
- 229910052982 molybdenum disulfide Inorganic materials 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000002074 nanoribbon Substances 0.000 description 1
- 239000003002 pH adjusting agent Substances 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
Classifications
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- 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
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/24—Chromium, molybdenum or tungsten
- B01J23/30—Tungsten
-
- 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
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/39—Photocatalytic properties
-
- 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
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
- B01J37/10—Heat treatment in the presence of water, e.g. steam
-
- 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
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/32—Freeze drying, i.e. lyophilisation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
- C01B13/02—Preparation of oxygen
- C01B13/0203—Preparation of oxygen from inorganic compounds
- C01B13/0207—Water
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
- C01B3/042—Decomposition of water
-
- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Combustion & Propulsion (AREA)
- Catalysts (AREA)
Abstract
The invention relates to the technical field of photocatalysts, in particular to a tungsten oxide photocatalyst with high-efficiency heterogeneous junction, and a preparation method and application thereof. The photocatalyst provided by the invention comprises WO 3 ·0.33H 2 O and in said WO 3 ·0.33H 2 m-WO of O in situ phase transition 3 Said WO 3 ·0.33H 2 O and m-WO 3 Forms a heterogeneous junction at the interface of (a). In the present invention, WO 3 ·0.33H 2 O and m-WO 3 The high-efficiency heterogeneous junction can be formed, and the separation of photo-generated electrons and holes is greatly promoted, so that the photocatalytic activity of the photocatalyst is improved; at the same time due to WO 3 ·0.33H 2 O and m-WO 3 Is as WO 3 System of WO 3 ·0.33H 2 O and m-WO 3 The energy level matching condition is easier to meet, and the two-component approximate electronic structure can enable photo-generated electrons to migrate in the heterogeneous junction more easily, so that the activity of photocatalytic water splitting is improved.
Description
Technical Field
The invention relates to the technical field of photocatalysts, in particular to a tungsten oxide photocatalyst with high-efficiency heterogeneous junction, and a preparation method and application thereof.
Background
Among the numerous methods for decomposing water to produce hydrogen energy, photocatalytic decomposition of water is widely recognized as a simple, easy-to-operate hydrogen production method. In recent years, although some photocatalysts have been disclosed, such as chinese patent CN109261215A discloses a catalyst for preparing hydrogen by photocatalytic decomposition of water, the hydrogen preparing capability of the graphene-supported metal platinum catalyst disclosed therein is at most 0.8 μmol/h, chinese patent CN111229260a discloses a catalyst for preparing hydrogen by decomposition of water under visible light, which is a hetero-structured catalyst of cadmium sulfide nano-particles and molybdenum disulfide nano-ribbons, and a preparation method thereof, and the hydrogen preparing capability of the hetero-structured catalyst IDE disclosed therein is at most 203.7 μmol/(h·g), but the photocatalysts capable of efficiently performing photocatalytic decomposition of water are not so much, mainly because: the electron and hole separation of the catalyst is difficult. In the prior art, the electron and hole pairs of the catalyst have better separation effect by methods of improving the crystallization degree of the catalyst, supporting a cocatalyst, doping modification and the like, but the improvement of the factors is limited, and the improvement of the photocatalytic activity is limited.
The tungsten oxide-based semiconductor photocatalyst has the advantages of visible light absorption, easiness in preparation and the like as a photocatalyst, but the development of the tungsten oxide-based semiconductor photocatalyst in the field of photocatalysis is limited due to the problem of high photon-generated carrier recombination probability.
Disclosure of Invention
The invention aims to provide a tungsten oxide photocatalyst with high-efficiency heterogeneous junction, a preparation method and application thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a tungsten oxide photocatalyst with high-efficiency heterogeneous junction, which comprises WO 3 ·0.33H 2 O and in said WO 3 ·0.33H 2 m-WO of O in situ phase transition 3 ，
Said WO 3 ·0.33H 2 O and m-WO 3 Forms a heterogeneous junction at the interface of (a).
Preferably, said WO 3 ·0.33H 2 O and m-WO 3 The mass ratio of (4-9): (1-6).
The invention provides a preparation method of a tungsten oxide photocatalyst with a high-efficiency heterogeneous junction, which comprises the following steps:
mixing alkali metal tungstate with water, and performing a first hydrothermal reaction on the obtained alkali metal tungstate aqueous solution to obtain WO 3 ·0.33H 2 O；
The WO is applied to 3 ·0.33H 2 Mixing O with water to obtain WO 3 ·0.33H 2 And carrying out a second hydrothermal reaction on the O aqueous solution to obtain the photocatalyst.
Preferably, the alkali metal tungstate is sodium tungstate or potassium tungstate.
Preferably, the mass concentration of the alkali metal tungstate aqueous solution is 0.01-0.03 g/mL.
Preferably, the pH value of the first hydrothermal reaction and the second hydrothermal reaction is independently 0.5-1.5.
Preferably, the temperature of the first hydrothermal reaction and the second hydrothermal reaction is 180-200 ℃ independently.
Preferably, the time of the first hydrothermal reaction is 3-6 h, and the time of the second hydrothermal reaction is 1-48 h.
The invention provides the tungsten oxide photocatalyst with the high-efficiency heterogeneous junction in the technical scheme or the application of the tungsten oxide photocatalyst with the high-efficiency heterogeneous junction obtained by the preparation method in the technical scheme in photocatalytic water decomposition.
Preferably, the mass concentration of the photocatalyst in the photocatalytic water splitting system is 0.001-0.005 g/mL.
The invention provides a tungsten oxide photocatalyst with high-efficiency heterogeneous junction, which comprises WO 3 ·0.33H 2 O and in said WO 3 ·0.33H 2 m-WO of O in situ phase transition 3 Said WO 3 ·0.33H 2 O and m-WO 3 Forms a heterogeneous junction at the interface of (a). In the present invention, the WO 3 ·0.33H 2 O is an orthogonal phase, the conduction band position is-0.53 eV, the valence band position is 2.67eV, the m-WO 3 For monoclinic phase, the conduction band position is-0.03 eV, the valence band position is 2.77eV, WO 3 ·0.33H 2 O and m-WO 3 Is suitable for the position of conduction band and valence band, can form high-efficiency heterogeneous junction, WO 3 ·0.33H 2 O and m-WO 3 The construction of a junction in the formed heterogeneous junction greatly promotes the separation of photo-generated electrons and holes, thereby improving the photocatalytic activity of the photocatalyst; at the same time due to WO 3 ·0.33H 2 O and m-WO 3 Is as WO 3 System of WO 3 ·0.33H 2 O and m-WO 3 The energy level matching condition is easier to be satisfied, and the two-component approximate electronic structure can lead the photo-generated electrons to be more easily transported in the heterogeneous junction, thereby remarkably improving WO 3 ·0.33H 2 Photo-generated electrons in O and m-WO 3 The separation efficiency of the medium-light generated holes is improved, thereby improving the activity of photocatalytic water splitting. According to the results of the examples, the photocatalyst provided by the invention has the hydrogen production rate of 0.3-0.7 mu mol/h and the oxygen production rate of 6.8-7.7 mu mol/h when water is decomposed by photocatalysis.
The invention also provides a preparation method of the photocatalyst, which is characterized in that the photocatalyst is prepared by a hydrothermal reaction in WO 3 ·0.33H 2 O in situ phase transformation to m-WO 3 The preparation method is simple and easy to implement.
Drawings
FIG. 1 is an XRD pattern of the photocatalyst described in example 3;
FIG. 2 is a graph showing the component ratios of the photocatalysts of examples 1 to 3 and comparative examples 1 to 2;
FIG. 3 is a graph showing the activity of hydrogen production of the photocatalysts of examples 1 to 3 and comparative examples 1 to 2;
FIG. 4 is a graph showing the oxygen generating activity test of the photocatalysts of examples 1 to 3 and comparative examples 1 to 2.
Detailed Description
The invention provides a tungsten oxide photocatalyst with high-efficiency heterogeneous junction, which comprises WO 3 ·0.33H 2 O and in said WO 3 ·0.33H 2 m-WO of O in situ phase transition 3 Said WO 3 ·0.33H 2 O and m-WO 3 Forms a heterogeneous junction at the interface of (a).
The photocatalyst provided by the invention comprises WO 3 ·0.33H 2 O, said WO 3 ·0.33H 2 The O conduction band position is-0.53 eV, and the valence band position is 2.67eV; the book is provided withThe photocatalyst provided by the invention comprises m-WO 3 Said m-WO 3 The conduction band position of (2) is-0.03 eV, and the valence band position is 2.77eV; in the present invention, the WO 3 ·0.33H 2 O and m-WO 3 The heterogeneous junction of the photocatalyst is constructed to greatly promote the separation of photo-generated electrons and holes of the photocatalyst, thereby improving the photocatalytic activity of the photocatalyst.
The invention relates to WO in the photocatalyst 3 ·0.33H 2 O and m-WO 3 No particular requirement is imposed on the mass ratio of (A) to (B), in the present invention, the WO 3 ·0.33H 2 O and m-WO 3 The mass ratio of (2) is preferably (4-9): (1 to 6), more preferably (4.5 to 7): (2-5), most preferably (5-6): (3-4).
The invention provides a preparation method of a tungsten oxide photocatalyst with a high-efficiency heterogeneous junction, which comprises the following steps:
mixing alkali metal tungstate with water, and performing a first hydrothermal reaction on the obtained alkali metal tungstate aqueous solution to obtain WO 3 ·0.33H 2 O；
The WO is applied to 3 ·0.33H 2 Mixing O with water to obtain WO 3 ·0.33H 2 And carrying out a second hydrothermal reaction on the O aqueous solution to obtain the photocatalyst.
In the present invention, the raw materials used are commercially available products well known to those skilled in the art unless otherwise specified.
The invention mixes alkali metal tungstate with water, and the obtained alkali metal tungstate aqueous solution is subjected to a first hydrothermal reaction to obtain WO 3 ·0.33H 2 O; in the present invention, the alkali metal tungstate is preferably sodium tungstate or potassium tungstate, more preferably sodium tungstate, and most preferably sodium tungstate dihydrate; the mass concentration of the alkali metal tungstate aqueous solution is preferably 0.01-0.03 g/mL, more preferably 0.015-0.025 g/mL.
In the present invention, the pH of the first hydrothermal reaction is preferably 0.5 to 1.5, more preferably 0.8 to 1.2, and the pH of the first hydrothermal reaction is preferably adjusted by a pH adjuster, which preferably includes a strong acid, which preferably includes nitric acid or hydrochloric acid, and the mass concentration of the strong acid is 10 to 30%.
In the present invention, the temperature of the first hydrothermal reaction is preferably 180 to 200 ℃, more preferably 180 ℃; the time of the first hydrothermal reaction is preferably 3 to 6 hours, more preferably 4 to 5 hours.
In the present invention, the first hydrothermal reaction is preferably performed in a forced air drying oven, and the present invention is not limited in particular to the specific embodiment of the first hydrothermal reaction, and may be performed by a process well known to those skilled in the art.
In the present invention, the alkali metal tungstate is first reacted by first hydrothermal reaction to form H 2 WO 4 ，H 2 WO 4 Continuing to react with water to form water and an oxide WO 3 ·0.33H 2 O。
The invention obtains water and oxide WO by controlling the pH value, the hydrothermal time and the hydrothermal reaction temperature in the first hydrothermal reaction process 3 ·0.33H 2 O。
The invention preferably provides for the post-treatment of the solid product of the first hydrothermal reaction to give the WO 3 ·0.33H 2 O, in the present invention, the post-treatment preferably includes sequentially: washing and drying, wherein in the invention, the washing solvent is preferably a mixed solution of ethanol and strong acid, and the mass ratio of the ethanol to the strong acid is preferably 200mL: the protection range of the strong acid is preferably the same as that of the above-mentioned type of strong acid used for the pH adjustment, and is not described in detail herein, and in the present invention, the number of times of washing is preferably 3 to 5 times, more preferably 4 times. The solid product after washing is preferably dried, and in the present invention, the drying is preferably freeze-drying, the temperature of the freeze-drying is preferably-50 to-60 ℃, and the time of the freeze-drying is preferably 10 to 30 hours, more preferably 12 to 20 hours.
Obtaining WO 3 ·0.33H 2 After O, the invention leads to WO 3 ·0.33H 2 Mixing O with water to obtain WO 3 ·0.33H 2 O aqueous solution for the second timeCarrying out hydrothermal reaction to obtain the photocatalyst; in the present invention, the WO 3 ·0.33H 2 The mass concentration of the O aqueous solution is preferably 0.012 to 0.05g/mL, more preferably 0.02 to 0.03g/mL; in the present invention, the water is preferably deionized water.
In the present invention, the pH value of the second hydrothermal reaction is preferably the same as the protection range of the pH value of the first hydrothermal reaction, and will not be described herein.
In the present invention, the temperature of the second hydrothermal reaction is preferably 180 to 200 ℃, more preferably 200 ℃; the time of the second hydrothermal reaction is preferably 1 to 18 hours, more preferably 12 to 24 hours.
In the present invention, the WO 3 ·0.33H 2 O generates m-WO through in-situ phase change during the second hydrothermal reaction 3 The photocatalyst is obtained by controlling the pH value and the hydrothermal reaction temperature in the second hydrothermal reaction process, and the m-WO is obtained 3 And (3) phase (C). In the present invention, m-WO in the photocatalyst 3 The content of the phase is positively correlated with the time of the second hydrothermal reaction, and the m-WO in the photocatalyst increases with the increase of the time of the second hydrothermal reaction 3 The content of the phase becomes large.
In the present invention, the second hydrothermal reaction is preferably performed in a forced air drying oven, and the specific embodiment of the second hydrothermal reaction is not particularly limited and may be performed by a process well known to those skilled in the art.
In the present invention, the solid product of the second hydrothermal reaction is preferably subjected to a post-treatment to obtain the photocatalyst, and in the present invention, the protection range of the post-treatment is preferably the same as that of the post-treatment of the first hydrothermal reaction, and will not be described herein.
The heterogeneous junction m-WO formed by the photocatalyst prepared by the preparation method provided by the invention 3 Is prepared from WO 3 ·0.33H 2 O is formed by in-situ phase transformation, so that WO 3 ·0.33H 2 O and m-WO 3 More easily meets the condition of energy level matching, and remarkably improves WO 3 ·0.33H 2 Photo-generated electrons in O and m-WO 3 Holes are generated by medium lightThe separation efficiency is improved, thereby improving the activity of photocatalytic water splitting.
The invention provides the tungsten oxide photocatalyst with the high-efficiency heterogeneous junction in the technical scheme or the application of the tungsten oxide photocatalyst with the high-efficiency heterogeneous junction obtained by the preparation method in the technical scheme in photocatalytic water decomposition.
In the present invention, the mass concentration of the photocatalyst in the photocatalytic water splitting system is preferably 0.001 to 0.005g/mL, more preferably 0.002 to 0.004g/mL; in the invention, the light source of the photocatalytic water splitting system is preferably a hernia lamp, and the power of the hernia lamp is preferably 300W; in the present invention, the photocatalytic water splitting system preferably includes a photocatalytic water splitting hydrogen production system or a photocatalytic water splitting oxygen production system.
In the present invention, the photocatalytic water splitting hydrogen production system preferably comprises a photocatalyst, a cocatalyst, a sacrificial agent and water, wherein the water is preferably deionized water; in the invention, the promoter is preferably elemental platinum or chloroplatinic acid, and in the invention, the mass and water volume ratio of the promoter is preferably (0.3-0.6) g: in the present invention, the sacrificial agent is preferably methanol, and the volume ratio of the sacrificial agent to water is preferably (1-2): 10.
in the present invention, the photocatalytic water splitting oxygen generating system preferably includes a photocatalyst, a sacrificial agent and water, and the water is preferably deionized water; in the present invention, the sacrificial agent is preferably silver nitrate, and the mass concentration of the sacrificial agent is preferably 0.001 to 0.002g/mL.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
0.9896g of sodium tungstate dihydrate and 50mL of deionized water are mixed with stirring until all of them are dissolvedAfter decomposition, HNO with mass concentration of 20% is added dropwise 3 The pH value of the mixed system is 0.5, and the mixed system is subjected to hydrothermal reaction at 180 ℃ for 4 hours, and EtOH-HNO is used 3 Washing the mixture (volume: 100. Mu.L, wherein the nitric acid concentration is 0.05% by volume) 4 times, and freeze-drying at-55deg.C for 16h to obtain WO 3 ·0.33H 2 O。
Will be 0.62g of WO 3 ·0.33H 2 O and 50mL deionized water are mixed until all the components are dissolved, and HNO is added dropwise 3 The pH value of the mixed system is 1, the mixed system is subjected to hydrothermal reaction for 4 hours at 200 ℃, and EtOH-HNO is used 3 Washing the mixed solution for 4 times, and freeze-drying at-55deg.C for 16 hr to obtain the photocatalyst, which is named as WOO-1, WO in NWO-1 3 ·0.33H 2 O and m-WO 3 The mass ratio of (3) is 87:13.
example 2
0.9896g of sodium tungstate dihydrate and 50mL of deionized water are mixed to be completely dissolved under stirring, and HNO with the mass concentration of 20% is added dropwise 3 The pH value of the mixed system is 1.5, and the mixed system is subjected to hydrothermal reaction at 180 ℃ for 4 hours, and EtOH-HNO is used 3 Washing the mixture (volume: 100. Mu.L, wherein the nitric acid concentration is 0.05% by volume) 4 times, and freeze-drying at-55deg.C for 16h to obtain WO 3 ·0.33H 2 O。
Will be 0.62g of WO 3 ·0.33H 2 O and 50mL deionized water are mixed until all the components are dissolved, and HNO is added dropwise 3 The pH value of the mixed system is 1, and the mixed system is subjected to hydrothermal reaction at 200 ℃ for 8 hours, and EtOH-HNO is used 3 Washing the mixed solution for 4 times, and freeze-drying at-55deg.C for 16h to obtain the photocatalyst, which is named as NWO-2, WO in NWO-2 3 ·0.33H 2 O and m-WO 3 The mass ratio of (1): 19.
example 3
0.9896g of sodium tungstate dihydrate and 50mL of deionized water are mixed to be completely dissolved under stirring, and HNO with the mass concentration of 20% is added dropwise 3 The pH value of the mixed system is 1, the mixed system is subjected to hydrothermal reaction at 180 ℃ for 4 hours, and EtOH-HNO is used 3 Washing the mixture (volume: 100. Mu.L, wherein the nitric acid concentration is 0.05% by volume) 4 times, and freeze-drying at-55deg.C for 16h to obtain WO 3 ·0.33H 2 O。
Will be 0.62g of WO 3 ·0.33H 2 O and 50mL deionized water are mixed until all the components are dissolved, and HNO is added dropwise 3 The pH value of the mixed system is 1, and the mixed system is subjected to hydrothermal reaction at 200 ℃ for 12 hours, and EtOH-HNO is used 3 Washing the mixed solution for 4 times, and freeze-drying at-55deg.C for 16h to obtain the photocatalyst, which is named as NWO-3, WO in NWO-3 3 ·0.33H 2 O and m-WO 3 The mass ratio of (2) is 41:59.
comparative example 1
0.9896g of sodium tungstate dihydrate and 50mL of deionized water are mixed to be completely dissolved under stirring, and HNO with the mass concentration of 20% is added dropwise 3 The pH value of the mixed system is 0.5, and the mixed system is subjected to hydrothermal reaction at 180 ℃ for 4 hours, and EtOH-HNO is used 3 Washing the mixed solution (volume is 200mL:100 mu L, wherein the volume concentration of nitric acid is 0.05%) for 4 times, and freeze-drying at-55 ℃ for 16h to obtain the photocatalyst, which is named as NWO-4, WO in NWO-4 3 ·0.33H 2 O and m-WO 3 The mass ratio is 100:0.
comparative example 2
0.9896g of sodium tungstate dihydrate and 50mL of deionized water are mixed to be completely dissolved under stirring, and HNO with the mass concentration of 20% is added dropwise 3 The pH value of the mixed system is 0.5, and the mixed system is subjected to hydrothermal reaction at 180 ℃ for 4 hours, and EtOH-HNO is used 3 Washing the mixture (volume: 100. Mu.L, wherein the nitric acid concentration is 0.05% by volume) 4 times, and freeze-drying at-55deg.C for 16h to obtain WO 3 ·0.33H 2 O。
Will be 0.62g of WO 3 ·0.33H 2 O and 50mL deionized water are mixed until all the components are dissolved, and HNO is added dropwise 3 The pH value of the mixed system is 1, and the mixed system is subjected to hydrothermal reaction at 200 ℃ for 48 hours, and EtOH-HNO is used 3 Washing the mixed solution for 4 times, and freeze-drying at-55deg.C for 16h to obtain the photocatalyst, which is named as NWO-5, WO in NWO-5 3 ·0.33H 2 O and m-WO 3 The mass ratio of (2) is 0:100.
test example 1
The photocatalyst described in example 3 was subjected to XRD testing, and the test results are shown in fig. 1. Diffraction angle of 14 DEG,Peaks at 18 °, 27 °, 36 ° and 49 ° appear as WO 3 ·0.33H 2 Characteristic peaks of O, and WO 3 ·0.33H 2 The O standard card (PDF#72-0199) is consistent; peaks appearing at diffraction angles of 23 °, 34 °, 39 ° and 48 ° are m-WO 3 Characteristic peaks, and m-WO 3 Standard card (PDF # 71-2141) was identical, indicating that example 3 successfully produced WO 3 ·0.33H 2 O and m-WO 3 Is a heterogeneous junction photocatalyst. Said WO 3 ·0.33H 2 The O conduction band position is-0.53 eV, and the valence band position is 2.67eV; the photocatalyst provided by the invention comprises m-WO 3 Said m-WO 3 The conduction band position of (2) is-0.03 eV and the valence band position is 2.77eV.
Application example 1
The photocatalysts prepared in examples 1 to 3 and comparative examples 1 to 2 were subjected to catalytic activity test:
hydrogen production activity test: 0.1g of the photocatalyst and 90mL of deionized water were placed in a reactor, and mixed under stirring to form a suspension, and 50. Mu.L of chloroplatinic acid (concentration: 10mg/mL, in terms of Pt) and 10mL of methanol were sequentially added. And (3) connecting the reactor into a photocatalysis test system, vacuumizing for 20min to remove dissolved oxygen contained in water, starting a xenon lamp for irradiation, and carrying out photocatalysis decomposition water reaction under the irradiation of a 300W xenon lamp light source. And (3) firstly carrying out a light deposition reaction in the first 2 hours after the lamp is turned on, removing the light source after the light deposition is finished, vacuumizing for 5 minutes to remove gas generated by the light deposition reaction in the photocatalysis test circulation system, then moving back to the light source to carry out a photocatalysis water decomposition reaction, starting timing from the moment, sampling 1 time every 1 hour, and sampling to 4 hours after starting timing. The hydrogen-generating activity was demonstrated by a gas chromatograph coupled to a photocatalytic test system.
Oxygen production activity test: 0.1g of photocatalyst and 100ml of deionized water were placed in a reactor, and mixed under stirring to form a suspension, and 0.1699g of silver nitrate was added. And (3) connecting the reactor into a photocatalysis test system, vacuumizing for 20min to remove dissolved oxygen contained in water, starting a xenon lamp for irradiation, and carrying out photocatalysis decomposition water reaction under the irradiation of a 300W xenon lamp light source. Starting to time after turning on the lamp, sampling 1 time every 1h, and sampling to 4h after starting to time. The oxygen generating activity was demonstrated by a gas chromatograph coupled to a photocatalytic test system.
The test results are shown in FIG. 3, and the data from FIG. 3 are shown in Table 1. As can be seen from FIG. 3 and Table 1, the photocatalyst provided by the present invention is a photocatalyst having WO formed 3 ·0.33H 2 O and m-WO 3 The interfacial heterogeneous junction of (2) greatly promotes the separation of photo-generated electrons and holes of the catalyst, thereby improving the photo-catalytic activity of the photocatalyst, the hydrogen production rate is 0.3-0.7 mu mol/h, the oxygen production rate is 6.8-7.7 mu mol/h when water is decomposed by photocatalysis, and the catalyst prepared in comparative example 1 is only WO 3 ·0.33H 2 O, hydrogen production rate of 0.02. Mu. Mol/h, oxygen production rate of 3.7. Mu. Mol/h, catalyst prepared in comparative example 2 was m-WO only 3 The hydrogen production rate was 0. Mu. Mol/h and the oxygen production rate was 6.2. Mu. Mol/h, which were lower than the catalyst products obtained in examples 1 to 3.
TABLE 1 Hydrogen and oxygen production Activity of different photocatalysts
| Sequence number | H 2 Production Rate mu mol/h | O 2 Production Rate mu mol/h |
| NWO-1 | 0.7 | 6.8 |
| NWO-2 | 0.5 | 7.7 |
| NWO-3 | 0.3 | 7.5 |
| NWO-4 | 0.02 | 3.7 |
| NWO-5 | 0 | 6.2 |
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (8)
1. The preparation method of the tungsten oxide photocatalyst with the high-efficiency heterogeneous junction is characterized by comprising the following steps of:
mixing alkali metal tungstate with water, and performing a first hydrothermal reaction on the obtained alkali metal tungstate aqueous solution to obtain WO 3 ·0.33H 2 O；
The WO is applied to 3 ·0.33H 2 Mixing O with water to obtain WO 3 ·0.33H 2 Carrying out a second hydrothermal reaction on the O aqueous solution to obtain the photocatalyst; said photocatalyst comprises WO 3 ·0.33H 2 O and in said WO 3 ·0.33H 2 m-WO of O in situ phase transition 3 Said WO 3 ·0.33H 2 O and m-WO 3 Forming a heterogeneous junction at the interface of (2); said WO 3 ·0.33H 2 O and m-WO 3 The mass ratio of (1): 19.
2. the method of claim 1, wherein the alkali metal tungstate is sodium tungstate or potassium tungstate.
3. The preparation method according to claim 1 or 2, wherein the mass concentration of the alkali metal tungstate aqueous solution is 0.01-0.03 g/mL.
4. The method according to claim 1, wherein the pH of the first hydrothermal reaction and the second hydrothermal reaction are independently 0.5 to 1.5.
5. The method according to claim 1, wherein the first hydrothermal reaction and the second hydrothermal reaction are carried out at 180-200 ℃ independently.
6. The method according to claim 1, wherein the first hydrothermal reaction time is 3 to 6 hours and the second hydrothermal reaction time is 1 to 48 hours.
7. The method of any one of claims 1 to 6, wherein the tungsten oxide photocatalyst with high-efficiency heterogeneous junction is used for photocatalytic water splitting.
8. The use according to claim 7, wherein the mass concentration of the photocatalyst in the photocatalytic water splitting system is 0.001-0.005 g/mL.
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