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CN116393119B - Composite photocatalyst and preparation method and application thereof - Google Patents

Composite photocatalyst and preparation method and application thereof Download PDF

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CN116393119B
CN116393119B CN202310370215.1A CN202310370215A CN116393119B CN 116393119 B CN116393119 B CN 116393119B CN 202310370215 A CN202310370215 A CN 202310370215A CN 116393119 B CN116393119 B CN 116393119B
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alooh
composite photocatalyst
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raw material
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CN116393119A (en
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李宇涵
刘莉
段有雨
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Chongqing Technology and Business University
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/14—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of germanium, tin or lead
    • A—HUMAN NECESSITIES
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    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/06—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing polymers
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/39—Photocatalytic properties
    • A—HUMAN NECESSITIES
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    • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
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Abstract

The application relates to the field of photocatalytic materials, and discloses a composite photocatalyst, a preparation method and application thereof. The composite photocatalyst comprises AlOOH and ZnSn (OH) 6, wherein the AlOOH and the ZnSn (OH) 6 are compounded to form a Z-type heterojunction containing OVs modification. According to the application, by utilizing the characteristic that aluminum is easy to generate oxidation-reduction reaction in alkaline solution to generate AlOOH and the raw material reaction for preparing ZnSn (OH) 6, oxygen is extracted from a compound lattice to obtain the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst. The OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst has high separation efficiency of photogenerated carriers, good catalytic activity for removing toluene, long photocatalytic reaction aging, high stability, difficult inactivation and wide application prospect.

Description

Composite photocatalyst and preparation method and application thereof
Technical Field
The application relates to the field of photocatalytic materials, in particular to a composite photocatalyst, a preparation method and application thereof.
Background
In the prior art, the preparation of the heterojunction photocatalyst is mainly realized by a one-step hydrothermal method, and the photocatalyst modified by the method has good catalytic activity, so that research hot-dip of the heterojunction photocatalyst is initiated. The heterojunction photocatalyst is used as an efficient catalytic material in the catalytic field, the built-in electric field of the heterojunction photocatalyst greatly inhibits the recombination of photo-generated electrons and holes, and the oxidation-reduction capability of holes and electrons is improved on the basis of the single-component photocatalyst, so that the heterojunction photocatalyst is widely focused by people. In recent years, heterojunction photocatalysts are widely applied in the fields of hydrogen production by catalytic decomposition of water, CO 2 reduction, pollutant degradation and the like.
The structural characteristics of zinc hydroxystannate (ZnSn (OH) 6) determine that the material has higher photocatalytic activity and stability. However, there are still many challenges to be addressed from the commercial application level of single ZnSn (OH) 6 materials to photocatalysts, such as narrow spectral response range, low charge separation efficiency, etc. In order to solve the problems, performance optimization is mainly performed on ZnSn (OH) 6 by doping, morphology regulation, noble metal deposition and other methods. However, these modification strategies for ZnSn (OH) 6 tend to be cumbersome in steps and costly and are not suitable for large-scale industrial production. Therefore, it remains a great challenge to find a modification strategy that has simple synthesis steps, low preparation cost, and high catalytic efficiency and good stability of the obtained catalyst.
Disclosure of Invention
In view of the above, the application aims to provide a composite photocatalyst and a preparation method thereof, which have the advantages of high separation efficiency of photon-generated carriers of the composite photocatalyst, high catalytic activity for removing toluene (C 7H8), long aging time of photocatalytic reaction, high stability and difficult inactivation;
another object of the present application is to provide an application of the above composite photocatalyst in removing toluene or preparing a photocatalytic product for removing toluene;
To solve or at least partially solve the above technical problems, as a first aspect of the present application, there is provided a composite photocatalyst including AlOOH and ZnSn (OH) 6, which are composited to form a Z-type heterojunction including OVs (oxygen vacancy) modification, 6.
Optionally, the mass ratio of AlOOH to ZnSn (OH) 6 is (0.22-1.78): 1.
Optionally, the composite photocatalyst further comprises methyl cellulose, and the methyl cellulose is filled in the formed Z-shaped heterojunction gaps.
As a second aspect of the present application, there is provided a method for preparing the composite photocatalyst, comprising:
Providing a raw material for preparing ZnSn (OH) 6;
The simple substance aluminum and the raw materials for preparing ZnSn (OH) 6 are mixed and then subjected to hydrothermal reaction to generate the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst.
Optionally, the starting materials for preparing ZnSn (OH) 6 include a Zn salt starting material, a Sn salt starting material, and a starting material capable of providing OH -; the Zn salt raw material comprises one or more of hydrochloride, nitrate, sulfate, acetate or hydrate thereof, and the Sn salt raw material comprises one or more of hydrochloride, nitrate, sulfate, acetate or hydrate thereof. Further alternatively, the molar ratio of the Zn salt starting material, the Sn salt starting material, and the starting material capable of providing OH - is 1:1:6.9, based on the amount of Sn 4+、Zn2+ and OH - ion species.
Optionally, the method also comprises the step of adding a methyl cellulose raw material to participate in the hydrothermal reaction, wherein the working concentration of the methyl cellulose in the hydrothermal reaction is 0.1-0.5g/L.
Alternatively, the elemental Al accounts for 10-80% of the mass of ZnSn (OH) 6 prepared from the starting material from which ZnSn (OH) 6 is prepared.
Optionally, the temperature of the hydrothermal reaction is 100-200 ℃ and the time is 1-15h.
As a third aspect of the present application, there is provided the use of the composite photocatalyst of the present application or the composite photocatalyst prepared by the preparation method of the present application for removing toluene or preparing a toluene-removed photocatalytic product.
According to the application, by utilizing an in-situ hydrothermal synthesis method, oxygen is extracted from a compound lattice by utilizing the characteristic that aluminum is easy to generate AlOOH generated by oxidation-reduction reaction in alkaline solution and raw material reaction for preparing ZnSn (OH) 6, so as to obtain the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst. The OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst has high separation efficiency of photogenerated carriers, good catalytic activity for removing toluene, long photocatalytic reaction aging, high stability, difficult inactivation and wide application prospect.
Drawings
FIG. 1 is a flow chart of a preparation process of the composite photocatalyst of the application;
FIG. 2 shows the X-ray diffraction patterns of the products obtained in examples 1 to 4, comparative example 1 and comparative example 2; examples 1-4 are abbreviated as AZHS-10, AZHS-20, AZHS-40, AZHS-80 in this order, comparative example 1 is abbreviated as ZHS, and comparative example 2 is abbreviated as AlOOH (hereinafter);
FIG. 3 shows an X-ray diffraction pattern of the product obtained in comparative example 3;
FIG. 4 is a diagram showing a transmission electron microscope and a scanning electron microscope of the product obtained in example 2;
FIG. 5 shows X-ray photoelectron spectra of the products obtained in example 2, comparative example 1 and comparative example 2;
FIG. 6 is a schematic diagram showing the structure of an OVs-modified Z-type energy band constructed by AlOOH and ZnSn (OH) 6, which promotes interfacial charge transfer efficiency by the action of defect energy levels and built-in electric fields;
FIG. 7 is a schematic diagram showing the photocatalytic C 7H8 activity test apparatus of examples 1 to 4, comparative example 1 and comparative example 2;
FIG. 8 is a graph showing the activity test points of the photocatalytic oxidation C 7H8 of the products obtained in example 2 and comparative example 3;
FIG. 9 is a graph showing the dotted lines of the photocatalytic oxidation C 7H8 activity test (a) and the mineralization rate (b) of the products obtained in examples 1 to 4, comparative example 1 and comparative example 2 and the single long-time test (C) and ten photocatalytic oxidation C 7H8 cycle tests (d) of the products obtained in example 2.
Detailed Description
The application discloses a composite photocatalyst, a preparation method and application thereof, and a person skilled in the art can properly improve the process parameters by referring to the content of the application. It is expressly noted that all such similar substitutions and modifications will be apparent to those skilled in the art, and are deemed to be included in the present application. While the products, processes and applications of the present application have been described in terms of preferred embodiments, it will be apparent to those skilled in the relevant art that the application can be practiced and practiced with modification and alteration and combination of the products, processes and applications described herein without departing from the spirit and scope of the application. It will be apparent that the described embodiments are some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" and the like, if any, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. Meanwhile, the embodiments of the present application and features in the embodiments may be combined with each other without collision.
In a first aspect of the application, there is provided a composite photocatalyst comprising AlOOH and ZnSn (OH) 6 polymerized to form an OVs modified Z heterojunction. According to the application, an in-situ hydrothermal synthesis method is utilized, and an ion exchange effect is generated by exogenous metal Al powder and ZnSn (OH) 6 precursor liquid under an alkaline condition, so that the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst is synthesized by reaction, the synthesis steps are simple and efficient, the obtained catalyst is stable and excellent in performance, the photocatalytic oxidation C 7H8 is long in reaction time, high in stability and not easy to deactivate.
In certain embodiments of the application, the mass ratio of AlOOH to ZnSn (OH) 6 is (0.22-1.78): 1.
In certain embodiments of the application, the composite photocatalyst further comprises methylcellulose, the methylcellulose filling the formed Z-type heterojunction voids; in still other embodiments of the present application, the mass ratio of AlOOH, znSn (OH) 6, and methylcellulose is (0.22 to 1.78): 1: (0.04-0.2), more specifically, the mass ratio of the three is 0.22:1:0.11.
In a second aspect of the present application, there is provided a method for preparing the composite photocatalyst, comprising:
Providing a raw material for preparing ZnSn (OH) 6;
The simple substance aluminum and the raw materials for preparing ZnSn (OH) 6 are mixed and then subjected to hydrothermal reaction to generate the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst.
In order to further increase the contact area of the raw materials during mixing so as to be fully contacted during reaction and improve the rate of subsequent chemical reaction, the solution of the raw materials (except for elemental aluminum) can be prepared by taking water as a solvent for mixing; meanwhile, under alkaline conditions, the oxidation-reduction reaction of elemental aluminum and water is helpful for providing precursor substances for the formation of AlOOH, so that the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst can be successfully prepared, and the specific reaction process is as follows:
2Al+2H2O+2OH-→2AlO2 -+3H2；
AlO2 -+2H2O→Al(OH)3+OH-；
Al(OH)3→AlOOH+H2O。
In certain embodiments of the application, the starting materials for preparing ZnSn (OH) 6 include Zn salt starting materials, sn salt starting materials, and starting materials capable of providing OH -; the Zn salt raw material comprises one or more of hydrochloride, nitrate, sulfate, acetate or hydrate thereof, and the Sn salt raw material comprises one or more of hydrochloride, nitrate, sulfate, acetate or hydrate thereof.
In other embodiments of the application, the Zn salt feedstock is its acetate hydrate, such as Zn (AC) 2·2H2 O; the Sn salt raw material is hydrochloride hydrate of the Sn salt raw material, such as SnCl 4·5H2 O; the raw material capable of providing OH - comprises one or more than two of alkali, ammonia water and sodium carbonate, wherein the alkali mainly comprises hydroxide, such as sodium hydroxide, potassium hydroxide and the like.
In certain embodiments of the application, the molar ratio of Zn salt starting material, sn salt starting material, and starting material capable of providing OH - is 1:1:6.9, based on the amount of Sn 4+、Zn2+ and OH - ion species.
In certain embodiments of the application, the method further comprises the step of adding a methyl cellulose raw material to participate in the hydrothermal reaction, wherein the methyl cellulose can be used as a catalyst and a forming auxiliary agent, can also be used as a matrix adhesive, can be filled in Z-type heterojunction gaps to improve the bonding strength between particles and improve the crystallinity of crystals; in still other embodiments of the application, the methylcellulose is present in a working concentration of 0.1 to 0.5g/L, such as 0.273g/L, in the hydrothermal reaction.
In certain embodiments of the application, the elemental Al comprises 10-80%, alternatively 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80% of the mass of ZnSn (OH) 6 (which may be referred to herein simply as background ZnSn (OH) 6) prepared from the starting material from which ZnSn (OH) 6 was prepared. The mass percentages of the two are controlled within a reasonable range, so that a proper amount of AlOOH is conveniently generated in the hydrothermal reaction process, and the finally prepared OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst has higher catalytic activity; if the addition amount of the simple substance Al powder is too small, alOOH of the system in the subsequent hydrothermal reaction process is too small, and the activity of the generated AlOOH/ZnSn (OH) 6 heterojunction catalyst is easy to decrease; if the addition amount of the simple substance Al powder is too large, agglomeration of the simple substance Al powder and the generated heterojunction catalyst is easy to occur, so that nanoclusters are generated, and the catalytic activity is reduced.
In some embodiments of the application, the raw materials can be mixed by a constant temperature magnetic stirrer, and the specific parameter setting can be 25 ℃ and 500-1000r/min.
In certain embodiments of the application, the hydrothermal reaction is at a temperature of 100-200 ℃ for a time of 1-15 hours; in other embodiments of the application, the hydrothermal reaction is carried out at a temperature of 120 to 160 ℃ for a period of 4 to 9 hours; if the reaction temperature is too high, the crystal structure of ZnSn (OH) 6 is destroyed and other substances such as Zn 2SnO4 are produced by reaction, and if the reaction temperature is too low, znSn (OH) 6 with good crystallization cannot be formed, or ZnSn (OH) 6 cannot be formed. In a hydrothermal heat preservation stage (i.e. a reaction stage), the AlOOH and ZnSn (OH) 6 are recrystallized to form a stable compound, and the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst is formed through a polymerization reaction; if the heat preservation reaction time is too long, on one hand, the crystal structure can be partially dissolved, the yield of the catalyst is reduced, and on the other hand, the synthesis cost is increased, so that the material is not beneficial to the industrial application; if the reaction time is too short, a composite photocatalyst with good crystallization cannot be formed.
In still other embodiments of the present application, the elemental aluminum and the raw materials for preparing ZnSn (OH) 6 are thoroughly mixed by a stirring device into a white suspension, and the temperature of the hydrothermal reaction is raised from room temperature to the reaction temperature.
In the heating stage of the hydrothermal reaction, temperature difference is formed inside and outside the reaction device so as to generate convection to form a supersaturated state and separate out a catalyst crystal structure, so that crystal structures of AlOOH and ZnSn (OH) 6 can be formed, and the smooth progress of the reaction of forming the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst by the polymerization reaction in the next stage is ensured; in still other embodiments of the application, the rate of temperature rise is 1-10 ℃/min, e.g., 5 ℃/min, which helps ensure that ZnSn (OH) 6 forms a regular octahedral cube crystal structure while introducing surface OVs defects, which in turn helps surface hydroxyl (-OH) accept photogenerated holes (h +) to form hydroxyl radical (. OH) active groups.
In certain embodiments of the present application, the composite photocatalyst obtained after the reaction may be subjected to further treatments such as cooling, centrifugation, washing, drying, and the like; in other embodiments of the present application, the centrifugation and washing may be performed using a high-speed centrifuge apparatus, the rotational speed may be selected to be 6000r/min, the single washing time is 3min, and the centrifugation is performed using anhydrous ethanol and distilled water alternately for 6 times.
In certain embodiments of the present application, the method further comprises a treatment of grinding the composite photocatalyst, for example, grinding in an agate mortar having an inner diameter of 80mm and a purity of 99% or more. The agate mortar with high hardness can be used for effectively and rapidly grinding a massive catalyst sample into fine powder, and impurity components on the inner wall of a container are not introduced, so that pollution to the sample caused by impurities released by the container such as a soft material when the sample is rolled is avoided, the specific surface area of the catalyst can be increased, and the subsequent adsorption reaction process of catalytic oxidation C 7H8 is facilitated.
In a third aspect of the application, the OVs modified Z-heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst is applied to catalytic oxidation for C 7H8 removal in a simulation system monitored in real time by a photoacoustic spectrometer. The result shows that the photocatalytic activity of the composite photocatalyst is obviously improved on the basis of ZnSn (OH) 6 background, and is better than the catalytic activity of AlOOH and the catalytic activity of the composite photocatalyst prepared by using other modifiers, and the aging of the single photocatalytic oxidation C 7H8 of the composite photocatalyst can reach 180 minutes without inactivation, and the stability is excellent. Based on the excellent technical effects, the application provides application of the composite photocatalyst or the composite photocatalyst prepared by the preparation method in removing toluene or preparing a photocatalytic product for removing toluene.
In each of the comparative experiments provided by the present application, unless otherwise specified, other experimental conditions, materials, etc. were kept consistent to allow for comparability, except for the differences noted in each group.
The following further describes a composite photocatalyst, a preparation method and application thereof.
Example 1: OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst and preparation method thereof
S1, preparing a 0.5M Zn (AC) 2·2H2 O solution, a 0.5M SnCl 4·5H2 O solution, a 2.5g/L methylcellulose solution and a 3M NaOH solution, and accurately fixing the volume by adopting a volumetric flask. The zinc acetate solution and the tin tetrachloride solution provide a Zn source and a Sn source for ZnSn (OH) 6; the methyl cellulose is used as a catalyst forming auxiliary agent and is also a matrix adhesive, and can be filled in the Z-type heterojunction gaps to improve the bonding strength among particles and the crystallinity of crystals; the sodium hydroxide solution adjusts the pH value of the reaction system, and provides proper pH value for the reaction.
S2, in order to improve the efficiency of fully mixing the raw materials, the solution prepared in S1 is quantitatively dripped into 150mL of distilled water in sequence according to the sequence of Zn (AC) 2·2H2O、SnCl4·5H2 O, naOH and methyl cellulose, and the reaction concentrations of Zn (AC) 2·2H2O、SnCl4·5H2 O, methyl cellulose and NaOH are respectively as follows: 0.011M, 0.273g/L and 0.076M, magnetically stirring to form a milky suspension, adding AlOOH precursor Al powder, wherein the mass of the background ZnSn (OH) 6 is 0.44g, the mass of the Al powder accounts for 10% of that of ZnSn (OH) 6, placing the mixed solution in an oven for hydrothermal reaction, heating to 160 ℃, adopting an oven natural heating program, and naturally cooling to room temperature after heat preservation for 6.5h, wherein the flow diagram is shown in figure 1.
S3, the sample obtained in the step S2 is a precipitate with supernatant, and the sample is centrifuged, washed and dried to obtain a block-shaped sample;
S4, grinding the bulk sample to obtain an OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst, wherein the mass ratio of AlOOH, znSn (OH) 6 to methyl cellulose is 0.22:1:0.11, grinding is helpful for increasing the specific surface area of the sample, so as to facilitate the improvement of the catalytic activity of the sample.
Example 2: OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst and preparation method thereof
The difference from example 1 is that: the mass percentage of the Al powder accounting for the mass percentage of the ZnSn (OH) 6 of the background is 20 percent.
Example 3: OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst and preparation method thereof
The difference from example 1 is that: the mass percentage of the Al powder accounting for the mass percentage of the ZnSn (OH) 6 of the background is 40 percent.
Example 4: OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst and preparation method thereof
The difference from example 1 is that: the mass percentage of Al powder accounting for the mass percentage of the ZnSn (OH) 6 of the background is 80 percent.
Comparative example 1:
The difference from example 1 is that: no Al powder was added.
Comparative example 2:
The chemical reagent company purchased analytically pure AlOOH finished product for activity test comparison.
Comparative example 3:
The difference from example 1 is that: al 2O3 with the same amount of Al element substances is used for replacing Al powder to prepare the Al 2O3/ZnSn(OH)6 heterojunction photocatalyst.
Experimental example: performance characterization experiments of different photocatalysts
A number of characterization experiments were performed using the photocatalysts of examples 1-4 and comparative examples 1-3, wherein examples 1-4 may be abbreviated as AZHS-10, AZHS-20, AZHS-40, AZHS-80 in order in some experimental results, comparative example 1 may be abbreviated as ZHS in some experimental results, comparative example 2 may be abbreviated as AlOOH in some experimental results, and comparative example 3 may be abbreviated as Al 2O3/ZnSn(OH)6 in some experimental results.
1. XRD characterization experiment
To verify the kinds of the products obtained in examples 1 to 4 and comparative examples 1, comparative example 2 and comparative example 3, XRD test was carried out on each product by using a Japanese D/Max RA-type full-automatic X-ray diffractometer (scanning rate 4 DEG. Min -1).
As shown in fig. 2, XRD diffraction peaks of OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 at 19.6 °, 22.7 °, 32.4 °, 40.0 °, 46.5 °, 52.4 ° and 57.8 ° correspond to (111), (200), (220), (222), (400), (420) and (422) planes of cubic ZnSn (OH) 6 (JCPDS file No. 73-2384), respectively; the (020), (120), (031) and (051) planes at 14.5 °, 28.2 °, 38.4 ° and 48.9 ° correspond to AlOOH (JCPDS file No. 83-2384), respectively. Apart from the characteristic peaks of these two species, no additional hetero-peaks appear, confirming that AlOOH and ZnSn (OH) 6 have formed a heterojunction structure. In addition, as the mass percent content of the Al powder increases, the intensity of the (200) peak gradually decreases and the (020) peak gradually increases, indicating that the content of AlOOH increases with the mass increase of the Al powder, and as AlOOH is composited in the ZnSn (OH) 6 system, while introducing surface OVs defects, slightly impairing the crystallinity of ZnSn (OH) 6.
In FIG. 3, al 2O3/ZnSn(OH)6 (comparative example 3) only contains characteristic peaks of two substances, namely, cubic ZnSn (OH) 6 (JCPLS fileno. 73-2384) and Al 2O3 (JCPLS fileno. 75-1862), wherein the (200) crystal faces and the (402) crystal faces are respectively the exposed faces of ZnSn (OH) 6 and Al 2O3, and no other additional impurity peaks exist, thus proving that the comparative example 3 produces an Al 2O3/ZnSn(OH)6 heterojunction photocatalyst.
2. Electron microscope characterization experiment
The present application uses a scanning electron microscope of Japanese JSM-6490 and a transmission electron microscope of Japanese JEM-2010 model to scan and transmission image example 2, including a morphological image of a sample at a field of view of 50nm and a lattice image at a field of view of 5 nm. As shown in fig. 4, a clear boundary can be found in the 50nm field of view, which proves that AlOOH forms better recombination with ZnSn (OH) 6, and clearly shows that Al element is a uniformly distributed composite system in STEM-EDS mode, and the electron microscope images of other examples are consistent with example 2.
3. X-ray photoelectron spectroscopy test
To further verify the composition and surface chemistry of the surface elements of the AlOOH and ZnSn (OH) 6 samples, the application tested example 2, comparative example 1 and comparative example 2 using X-ray photoelectron spectroscopy, and the results are shown in FIG. 5, wherein the electron binding energy of the sample of example 2 is lower than that of the sample of comparative example 1 as seen from the XPS spectrum of Sn 3d, indicating that Sn in the sample of example 2 gets electrons. Accordingly, from the XPS spectrum of Al 2p, the electron binding energy of the example 2 sample was higher than that of the comparative example 2, indicating that Al in the example 2 sample lost electrons. The presence of surface electron pathways and strong bonding of the AlOOH and ZnSn (OH) 6 samples in example 2 is illustrated to facilitate transfer of photogenerated charge while also making the formation of heterojunction with ZnSn (OH) 6 more stable. Meanwhile, it can be seen from the XPS spectrum of O1s that lattice oxygen loss is generated in example 2, so that surface OVs defects are formed, the intermediate energy level of OVs reduces the transition energy barrier of the photon-generated carriers, and the intermediate energy level serves as a recombination site of photon electron-hole pairs, so that the directional migration and efficient separation of the photon-generated carriers as shown in fig. 6 are realized.
4. Characterization experiment for photocatalytic Activity of C 7H8
In order to test the photocatalytic activity of the OVs modified Z-type heterojunction AlOOH/ZnSn (OH) 6 photocatalyst, the application provides a photocatalytic performance detection experiment, an experimental device is shown in figure 7, and the experimental method is as follows:
0.4g of the product is weighed and evenly distributed on 4 quartz glass plates, the product on each quartz glass plate is dispersed and dissolved by absolute ethyl alcohol, the quartz glass plates are evenly distributed and then are placed in an oven to be dried for 10 minutes at 60 ℃ to form a uniform thin layer sample, and then the thin layer sample is cooled to room temperature for standby. In the experiment, quartz glass sheets are put into a reaction bin to be sealed, an air generator is opened, C 7H8 gas is introduced into the reaction bin, the initial concentration of the reaction bin C 7H8 is set to be 50ppm, and after the C 7H8 gas reacts with the surface of a catalyst to reach adsorption-desorption equilibrium, a UV light source is turned on to perform photocatalysis reaction. The concentrations of C 7H8、CO2 and H 2 O in the reactor were monitored online by a photoacoustic spectrometer (ductec). Wherein the purity of the C 7H8 standard gas is 99.99%, the light source is 125W high-pressure mercury lamp (GGZ 125), the working current is 1.2A, and the working voltage is 115V.
Fig. 8 and 9 are graphs of the activity profile of photocatalytic C 7H8 and single and multiple cycle stability tests during the experimental procedure. As shown in fig. 8, it can be seen that the photocatalytic oxidation C 7H8 of example 2 was significantly higher than that of comparative example 3 at 30min before the lamp was turned on, and the trend of example 2 higher than that of comparative example 3 was maintained as the light irradiation time was prolonged. As shown in fig. 9a, it can be seen that the photocatalytic oxidation C 7H8 activities of examples 1 to 4 are all greater than that of the single catalyst (comparative example 1 and comparative example 2), and the activities of the examples are enhanced and then weakened with increasing Al powder addition, and the activities of the example 2 are up to 95.5%, which is a significant improvement over the catalytic activities of the comparative example 1 and comparative example 2. The amount of CO 2 produced was proportional to the activity, and the highest amount of CO 2 produced in example 2, i.e. the highest mineralization rate, achieved the deep oxidation of C 7H8 (fig. 9 b), all of which indicated that the photocatalytic activity of the OVs-modified Z heterojunction AlOOH/ZnSn (OH) 6 photocatalyst prepared by this method was improved. In addition, the aging of C 7H8 by single photocatalytic oxidation of AZHS-20 (example 2) can reach 180min, the catalytic removal efficiency is excellent and stable (figure 9C), and the activity of 10-cycle test carried out on the catalyst is almost unchanged (figure 9 d), namely, the OVs-modified Z-type heterojunction AlOOH/ZnSn (OH) 6 photocatalyst prepared by the method has good stability.
The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A composite photocatalyst comprising AlOOH and ZnSn (OH) 6, wherein AlOOH and ZnSn (OH) 6 are combined to form an oxygen-containing vacancy-modified Z-type heterojunction.
2. The composite photocatalyst according to claim 1, wherein the mass ratio of AlOOH and ZnSn (OH) 6 is (0.22-1.78): 1.
3. The composite photocatalyst of claim 1, further comprising methylcellulose filled in the formed Z-type heterojunction voids.
4. The method for preparing the composite photocatalyst according to claim 1, comprising:
Providing a raw material for preparing ZnSn (OH) 6;
The simple substance aluminum and the raw materials for preparing ZnSn (OH) 6 are mixed and then generate the Z-type heterojunction AlOOH/ZnSn (OH) 6 composite photocatalyst modified by oxygen vacancies through hydrothermal reaction.
5. The preparation method according to claim 4, wherein the raw materials for preparing ZnSn (OH) 6 include a Zn salt raw material, a Sn salt raw material, and a raw material capable of providing OH -; the Zn salt raw material comprises one or more of hydrochloride, nitrate, sulfate, acetate or hydrate thereof, and the Sn salt raw material comprises one or more of hydrochloride, nitrate, sulfate, acetate or hydrate thereof.
6. The method according to claim 5, wherein the molar ratio of the Zn salt starting material, the Sn salt starting material, and the starting material capable of providing OH - is 1:1:6.9 in terms of Sn 4+、Zn2+ and OH - ion species.
7. The method according to claim 4 or 5, further comprising adding a methylcellulose raw material to participate in the hydrothermal reaction, wherein the working concentration of the methylcellulose in the hydrothermal reaction is 0.1-0.5g/L.
8. The preparation method according to claim 4, wherein the elemental Al accounts for 10-80% of the mass of ZnSn (OH) 6 prepared from the raw material for preparing ZnSn (OH) 6.
9. The method according to claim 4, wherein the hydrothermal reaction is carried out at a temperature of 100 to 200℃for a time of 1 to 15 hours.
10. Use of a composite photocatalyst according to any one of claims 1 to 3 or a composite photocatalyst prepared by the preparation method according to any one of claims 4 to 9 for removing toluene or preparing a toluene-removed photocatalytic product.
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