CN113996295A

CN113996295A - Composite catalyst and preparation method and application thereof

Info

Publication number: CN113996295A
Application number: CN202111341717.9A
Authority: CN
Inventors: 胡彦杰; 江浩; 李春忠; 季兵; 彭秋梅; 鞠杰
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2021-11-12
Filing date: 2021-11-12
Publication date: 2022-02-01

Abstract

The invention discloses a composite catalyst and a preparation method and application thereof. The composite catalyst comprises an active metal phase and an oxide matrix phase, wherein the active metal phase is dispersed and distributed on the surface of the oxide matrix phase; wherein: the active metal phase is a noble metal simple substance; the particle size of the active metal phase is 2-20 nm. The preparation method of the composite catalyst comprises the following steps: will contain NaBH₄Dripping the solution into the mixed solution C to obtain mixed solution D, and stirring for reaction to obtain the composite catalyst; wherein: the mixed liquid C comprises: an oxide matrix phase, a dispersant, a noble metal-containing salt and a solvent; the solvent may dissolve the noble metal-containing salt; in the mixed solution D, NaBH₄In a concentration of (1.0-2.5) × 10^‑4g/ml; what is needed isIn the reaction, the stirring speed is not less than 500 rpm. The invention has simple operation and is compatible with pure TiO₂Compared with the photocatalyst, the photocatalyst reduces the using amount of the catalyst and greatly improves the using efficiency of the catalyst.

Description

Composite catalyst and preparation method and application thereof

Technical Field

The invention relates to a composite catalyst and a preparation method and application thereof.

Background

With the continuous improvement of the living standard of people and the continuous acceleration of industrialized footsteps, the living environment in which people live is continuously polluted, and the health and the safety of people are threatened. For example, exhaust gas from automobiles, various petrochemical products, paints and coatings for house decoration, and some daily necessities generate compounds to pollute the environment. Therefore, the method has the advantages of controlling the emission of pollutants, purifying the environment and reducing the pollutants in the environment, and becomes the focus of attention of scientific researchers.

In the degradation of environmental pollutants, the degradation of compounds through catalytic degradation is receiving more and more attention from researchers. Researches show that the oxidation potential of hydroxyl free radical (. OH) is high, a plurality of compounds which are difficult to degrade can be degraded, the degradation rate is high, and the applicable range is wide. Researchers use nano semiconductor materials as photocatalysts in the degradation process of pollutants to convert light energy into potential energy and generate a large amount of OH, so that the pollutants are converted into water and CO₂And the degradation of pollutants is realized.

Nano semiconductor material TiO₂The catalyst has a series of characteristics of low price, no toxicity, mild reaction conditions, high catalytic activity and the like, and is one of the most promising environmental materials at present. But when TiO₂When the photocatalyst is used for degrading Volatile Organic Compounds (VOCs), the degradation efficiency is low, the stability is poor and the like due to the adhesion of an intermediate product on the surface of the catalyst.

Therefore, how to raise TiO is now on the stage₂As photocatalystsThe efficiency and the stability of catalytic degradation are still one of the technical problems to be solved in the field.

Furthermore, TiO₂The ultraviolet light can generate ozone, which belongs to one of air pollutants, but at the same time, the ozone also has strong oxidizing property, so the purpose of degrading pollutants can be achieved by reasonably utilizing the strong oxidizing property of the ozone.

At present, ion doping, noble metal deposition, semiconductor compounding, surface sensitization and complex action are generally adopted to treat TiO₂Modified to improve TiO₂Photocatalytic activity of (1). Among them, noble metal deposition is considered to be effective in enhancing TiO₂One of the methods of catalytic activity. Because the Fermi levels of the noble metal and the semiconductor material are different, when the noble metal is loaded on the semiconductor material, electrons on the photocatalytic semiconductor material move to the noble metal until the Fermi levels of the noble metal and the semiconductor material are the same, so that the recombination of electrons and holes on the photocatalytic semiconductor is effectively inhibited, and the catalytic efficiency is improved.

It has been found that noble metals such as Pt and Ag can effectively capture photogenerated electrons on a photocatalytic semiconductor, and therefore, the photocatalytic semiconductor is usually modified by supporting the noble metals such as Pt and Ag thereon.

TiO₂By compounding with semiconductor material MnO, the separation rate of photogenerated carriers in the system can be increased, and the recombination of photogenerated electrons and holes can be inhibited₂Not only can be mixed with TiO₂The composition forms a heterostructure, and greatly improves TiO₂The catalytic activity of (3) can also be achieved by decomposing ozone generated during light irradiation and decomposing ozone to generate superoxide radical (. O) having oxidizing property₂ ^-) And further used for decomposing VOCs.

However, noble metal nanoparticles in TiO₂And the surface of the material is difficult to be uniformly distributed, so that the catalytic efficiency is low. Most of the existing methods such as high-energy mechanical ball milling method, chemical/physical vapor deposition method, chemical precipitation method, spraying method, hydrolysis method, sol-gel method and the like can not completely realize nano-scaleThe rice grains are uniformly dispersed, the grain diameter is controllable, and the production equipment is complex and difficult to industrialize.

Therefore, how to further improve the precious metal nanoparticles in TiO₂The distribution of the surface of the material is a technical problem to be solved in the field.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the TiO in the prior art₂The catalyst has the defects of low use efficiency, high use amount and uneven distribution of noble metal nano particles on the surface, and provides the noble metal-loaded composite catalyst and the preparation method and the application thereof. With pure TiO₂Photocatalyst in contrast to the noble metal-supported composite catalyst of the present invention (e.g., Pt/TiO)₂/MnO₂Photocatalyst) reduces the amount of catalyst used, greatly improving the use efficiency of the catalyst; the preparation method of the composite catalyst is simple to operate, high in yield and easy to amplify and prepare, and the particle size of the noble metal (such as Pt) is controllable.

The design idea of the invention is as follows:

the invention adjusts NaBH₄The concentration, the rotating speed and other process parameters of the catalyst, the technical effect that precious metal (such as Pt) nano particles (such as 2-3nm) are uniformly loaded on a matrix phase is achieved, and the catalytic efficiency of the catalyst is improved.

The specific method can be as follows:

oxide containing Ti (e.g. TiO)₂) And Mn-containing oxides (e.g. MnO)₂) Dispersing in medium (such as deionized water), adding dispersant (such as PVP-K30), adding salt solution containing noble metal (such as chloroplatinic acid solution) as precursor of noble metal (such as Pt), and passing through NaBH₄Reducibility of the solution, depositing a noble metal (e.g. Pt) onto the matrix phase (e.g. TiO)₂/MnO₂Composite material), and then centrifugally washed to obtain the noble metal-supported composite catalyst, such as Pt/TiO₂/MnO₂A photocatalyst.

The invention provides a composite catalyst, which comprises an active metal phase and an oxide matrix phase, wherein the active metal phase is dispersed and distributed on the surface of the oxide matrix phase; wherein:

the active metal phase is a noble metal simple substance;

the particle size of the active metal phase is 2-20 nm.

In the present invention, the noble metal simple substance may be a noble metal simple substance having catalytic activity, which is conventional in the art, such as one or more of Ir (iridium), Ru (ruthenium), Pt (platinum), Pd (palladium), and gold (Au), and further such as Pt.

In the present invention, the particle size of the active metal phase may be 2 to 3nm, for example 3 nm.

In the present invention, the oxide matrix phase may be a monovalent metal oxide containing multiple valence states, such as a Ti-containing oxide and/or a Mn-containing oxide.

Wherein the Ti-containing oxide may be TiO₂。

Wherein the Mn-containing oxide may be MnO₂。

When the Ti-containing oxide and the Mn-containing oxide are contained in the oxide matrix phase, the mass ratio of the Ti-containing oxide to the Mn-containing oxide may be 10: (0.1-2), for example 10:0.5, 10:1 or 10: 1.5.

In the present invention, the content of the active metal phase in the composite catalyst may be 0.5 to 2 wt%, for example, 1 wt%, and wt% means weight percentage.

For example, when the composite catalyst is Pt/TiO₂/MnO₂In the case of the catalyst, the content of Pt may be 0.5 to 2 wt%, for example, 1 wt%.

The invention also provides a preparation method of the composite catalyst, which comprises the following steps:

will contain NaBH₄Dripping the solution into the mixed solution C to obtain mixed solution D, and stirring for reaction to obtain the composite catalyst; wherein:

the mixed liquid C comprises: an oxide matrix phase, a dispersant, a noble metal-containing salt and a solvent; the solvent may dissolve the noble metal-containing salt;

in the mixed solution D, NaBH₄In a concentration of (1.0-2.5) × 10^-4g/ml；

In the reaction, the stirring speed is more than or equal to 500 rpm.

In the present invention, the noble metal in the noble metal-containing salt may be a noble metal having catalytic activity, which is conventional in the art, such as one or more of Ir (iridium), Ru (ruthenium), Pt (platinum), Pd (palladium), and gold (Au), and further such as Pt.

In the present invention, the noble metal-containing salt may be a Pt-containing salt, such as chloroplatinic acid.

Wherein the Ti-containing oxide may be TiO₂。

Wherein the Mn-containing oxide may be MnO₂。

In the present invention, the particle size of the oxide matrix phase may be 40 to 100 nm.

In the present invention, the dispersant may be a dispersant commonly used in liquid phase reduction, such as PVP-K30 (one of polyvinylpyrrolidone products, K value 30).

In the present invention, the solvent may be selected according to the kind of the noble metal-containing salt, and for example, when the noble metal-containing salt is chloroplatinic acid, the solvent may be water. The water may be deionized water.

In the present invention, the dropping rate may be a dropping rate which is conventional for the liquid-phase reduction reaction, for example, 1 to 10ml/min, and further for example, 5 ml/min.

In the present invention, the concentration of the oxide matrix phase in the mixed solution D may be 0.0001 to 0.05g/ml, for example, 0.023077g/ml or 0.001154 g/ml.

When the oxide matrix phase contains a Ti-containing oxide, the concentration of the Ti-containing oxide in the mixed solution D may be 0.01 to 0.05g/ml, for example 0.023077 g/ml.

When the oxide matrix phase contains an oxide containing Mn, the concentration of the oxide containing Mn in the mixed liquid D may be 0.0001 to 0.01g/ml, for example 0.001154 g/ml.

In the present invention, the concentration of the dispersant in the mixed solution D may be (1.0 to 2.0) × 10^-5g/ml, e.g. 1.43 x 10^-5g/ml。

In the present invention, the concentration of the noble metal in the mixed solution D may be 0.0001 to 0.001g/ml, for example 0.0002308 g/ml.

In the present invention, in the mixed solution D, NaBH is added₄Can be (2.0-2.5) × 10^-4g/ml, for example 0.0002248 g/ml.

In the present invention, the NaBH is₄In solution, the NaBH₄The concentration of (b) can be adjusted according to the volume of the mixed solution C, for example, when the volume of the mixed solution C is 433.335ml, the NaBH is used₄May be 7.61 x 10^-4g/ml。

In the present invention, the NaBH is₄In solution, NaBH₄The concentration of (B) may be 0.01 to 10mol/L, for example 0.02 mol/L.

In the present invention, the rotation speed of stirring in the reaction can be 500-1000rpm, such as 800-1000rpm, and further such as 500rpm, 800rpm or 1000 rpm.

In the present invention, the stirring time in the reaction may be adjusted according to the volume of the mixed solution D, and for example, when the volume of the mixed solution D is 433.335ml, the stirring time may be 2 hours.

In the invention, the mixed solution C can be prepared by mixing a solution containing a noble metal salt with the mixed solution B; the mixed liquid B is a mixed liquid of the oxide matrix phase (for example, the Ti-containing oxide and the Mn-containing oxide), the dispersant, and the solvent.

Wherein the mixed solution C can be prepared by mixing chloroplatinic acid aqueous solution and the mixed solution B; the mixed liquid B is TiO₂Powder, MnO₂Powder, PVP-K30 and solvent.

Wherein the concentration of the noble metal in the noble metal-containing salt in the solution of the noble metal-containing salt may be 0.001-0.1g/ml, such as 0.01875 g/ml.

Wherein the mixed solution B can be prepared by mixing the mixed solution A with a solution containing the dispersant; the mixed liquid a is a mixed liquid of the oxide matrix phase (for example, the Ti-containing oxide and the Mn-containing oxide) and the solvent.

The mixed solution B can be prepared by mixing the mixed solution A with a PVP-K30 solution; the mixed solution A is TiO₂Powder, MnO₂A mixture of the powder and a solvent.

In the mixed solution A, the concentration of the oxide matrix phase can be 0.01-0.1g/ml, such as 0.0525g/ml, 0.055g/ml or 0.0575 g/ml.

When the oxide matrix phase contains a Ti-containing oxide, the Ti-containing oxide (for example, TiO) is contained in the mixed solution A₂) The concentration of (B) may be 0.01-0.1g/ml, for example 0.05 g/ml.

When an oxide containing Mn is contained in the oxide matrix phase, the oxide containing Mn (e.g., MnO) is contained in the mixed solution A₂) May be in a concentration of 0.5-10mg/ml, such as 2.5-7.5mg/ml, further such as 2.5mg/ml, 5.0mg/ml or 7.5 mg/ml.

In a preferred embodiment of the present invention, the preparation method of the composite catalyst comprises the steps of:

step (1): adding TiO into the mixture₂Powder and MnO₂Mixing the powder and the solvent, and stirring to obtain a mixed solution A;

step (2): mixing the PVP-K30 solution with the mixed solution A, and continuously stirring to obtain mixed solution B;

and (3): mixing the chloroplatinic acid solution with the mixed solution B, and continuously stirring to obtain a mixed solution C;

and (4): reacting NaBH₄Dripping the solution into the mixed solution C, and continuously stirring to obtain a mixed solution D; after the reaction is completed, centrifuging and washing the product to obtain Pt/TiO₂/MnO₂A catalyst.

Wherein, in the step (1), the solvent may be deionized water.

Wherein in the step (1), the mixed solution A is compared with TiO₂，MnO₂The mass fraction of (B) may be 5-20 wt%, for example 5 wt%, 10 wt% or 15 wt%.

Wherein in the step (1), the TiO in the mixed solution A₂The concentration of the powder may be 0.01-0.1g/ml, for example 0.05 g/ml.

Wherein, in the step (1), the MnO is added to the mixed solution A₂The concentration of the powder may be 0.5-10mg/ml, such as 2.5-7.5mg/ml, further such as 2.5mg/ml, 5.0mg/ml or 7.5 mg/ml.

Wherein, in the step (2), the concentration of PVP-K30 in the PVP-K30 solution can be (4-8) × 10^-5g/ml, e.g. 6.2 x 10^-5g/ml。

In the step (3), the concentration of Pt in the chloroplatinic acid solution may be 0.01-0.1g/ml, for example, 0.01875 g/ml.

Wherein, in the step (4), the NaBH is added₄In solution, NaBH₄The concentration of (B) may be 0.01 to 10mol/L, for example 0.02 mol/L.

Wherein, in the step (4), the NaBH is added₄The dropping rate of the solution may be 1-10ml/min, for example 5 ml/min.

The invention also provides a composite catalyst prepared by the method.

Wherein the composite catalyst can be Pt/TiO₂/MnO₂A catalyst.

The invention also provides an application of the composite catalyst as a photocatalyst with ozone synergistic effect.

The application can be the application as a photocatalyst in the aspects of environmental pollution treatment, VOCs removal and the like.

Wherein, the application can be the application as VOCs degrading agent.

Wherein, the application is generally carried out under ultraviolet irradiation.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows:

(1) the method has the advantages of simple operation, high yield, easy amplification and preparation, controllable Pt particle size and uniform distribution.

(2) With pure TiO₂Photocatalyst in contrast, the noble metal-supported composite catalyst of the present invention (e.g., Pt-supported TiO)₂/MnO₂Photocatalyst) reduces the amount of catalyst used, greatly improves the use efficiency of the catalyst.

Drawings

FIG. 1 is a transmission electron micrograph of the composite photocatalyst obtained in example 2.

Figure 2 is an XRD pattern of the composite photocatalyst obtained in example 2.

FIG. 3 is TiO₂And the performance chart of the example 1, 2 and 3 for photocatalytic degradation of toluene under ultraviolet light.

FIG. 4 is a transmission electron micrograph of the composite photocatalyst obtained in comparative example 1.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

In the following examples and comparative examples, TiO₂And MnO₂The particle size of (A) is 40-100 nm.

Example 1

Step 1: 10g of TiO are weighed₂And 0.5g of MnO₂200ml of deionized water was added, and the mixture was stirred and dispersed by mechanical stirring at 1000rpm for 10 min.

Step 2: 0.0062g of PVP-K30 is weighed and dissolved in 100ml of deionized water, the solution is added into the system in the step 1, the rotating speed is set to 1000rpm, and the stirring is continued for 10 min.

And step 3: 5.335ml of chloroplatinic acid aqueous solution (the concentration of Pt in the chloroplatinic acid is 1.875g/100ml) is measured and added dropwise into the system in the step 2, the rotating speed is set to be 1000rpm, and the stirring is continued for 10 min.

And 4, step 4: 0.0974g of NaBH was weighed out₄Using 128ml of deionized water (NaBH)₄0.02mol/L) was added dropwise to the system of step 3 at a dropping rate of 5ml/min, the rotational speed was set to 1000rpm, and stirring was continued for 2 hours. In the system of step 4:

TiO₂：0.023077g/ml，MnO₂：0.001154g/ml，PVP-K30：1.43*10^-5g/ml, Pt in chloroplatinic acid: 0.0002308g/ml, NaBH₄：0.0002248g/ml。

And 5: and (4) centrifugally washing the solution obtained by the reaction in the step (4), preparing the obtained photocatalyst into a 10 wt% solution, loading the solution on a catalytic plate, and testing the solution on a machine.

In the centrifugally washed catalyst in step 5, the content of Pt was 1.0 wt%.

Example 2

MnO in this embodiment₂In an amount of 1.0g, the remainder of the procedure and Pt/TiO described in example 1₂/MnO₂The preparation method of the photocatalyst is completely the same.

Example 3

MnO in this embodiment₂In an amount of 1.5g, the remainder of the procedure and Pt/TiO described in example 1₂/MnO₂The preparation method of the photocatalyst is completely the same.

Comparative example 1

Steps 1 to 3 were the same as in example 1;

and 4, step 4: 0.0974g of NaBH was weighed out₄The system of step 3 was directly mixed (non-dropwise mixed) with 128ml of deionized water solution at 1000rpm, and stirring was continued for 2 hours.

As shown in fig. 4, in the composite catalyst of comparative example 1, Pt was agglomerated and dispersed unevenly.

Comparative example 2

Step 1: 10g of TiO are weighed₂And 1.0g of MnO₂200ml of deionized water was added, and the mixture was stirred and dispersed by mechanical stirring at 1000rpm for 10 min.

Step 2: weighing 0.0062g of PVP-K30, dissolving in 100ml of deionized water, adding the solution into the system in the step 1, setting the rotating speed to be 1000rpm, and continuing stirring for 10min to obtain TiO₂/MnO₂-10 composite catalyst.

Comparative example 3

And 4, step 4: 0.0974g of NaBH was weighed out₄Using 64ml of deionized water (NaBH)₄0.04mol/L) was added dropwise to the system of step 3 at a dropping rate of 5ml/min, the rotational speed was set to 1000rpm, and stirring was continued for 2 hours.

The rest of the procedure was the same as in example 2.

In the system of step 4:

TiO₂：0.027076g/ml，MnO₂：0.001354g/ml，PVP-K30：1.68*10^-5g/ml, Pt in chloroplatinic acid: 0.0002708g/ml, NaBH₄：0.0002637g/ml。

Comparative example 4

And 4, step 4: 0.0974g of NaBH was weighed out₄Using 32ml of deionized water (NaBH)₄Was 0.08mol/L), the solution was added dropwise to the system of step 3 at a dropping rate of 5ml/min, the rotational speed was set to 1000rpm, and stirring was continued for 2 hours.

The rest of the procedure was the same as in example 2.

In the system of step 4:

TiO₂：0.02964g/ml，MnO₂：0.001482g/ml，PVP-K30：1.84*10^-5g/ml, Pt in chloroplatinic acid: 0.0002965g/ml, NaBH₄：0.0002887g/ml。

NaBH in step 4 of example 2, comparative example 3, comparative example 4₄The concentrations of the solutions are shown in table 1 below.

TABLE 1

Numbering	NaBH₄Concentration of (2)	Whether Pt is uniformly dispersed in the catalyst or not
			Comparative example 3	0.04mol/L	Unevenness of
Comparative example 4	0.08mol/L	Is not too uniform
			Example 2	0.02mol/L	Uniformity

In table 1 above: the dispersion of Pt was observed by transmission electron microscopy.

Example 4-1 and example 4-2

The rotation speed of the stirring in step 4 is shown in Table 2 below, and the rest of the procedure is the same as in example 2.

TABLE 2

In table 2 above: the dispersion of Pt was observed by transmission electron microscopy.

Effect example 1

(1) Topography analysis

FIG. 1 is a transmission electron micrograph of the composite photocatalyst obtained in example 2; figure 2 is an XRD pattern of the composite photocatalyst obtained in example 2.

As can be seen from FIGS. 1 and 2, nano-sized Pt particles, TiO, were produced₂、MnO₂And Pt is uniformly dispersed, and the particle size of the Pt is about 3 nm.

Further, as can be seen from the high-power transmission electron microscope image under the dark field of the composite photocatalyst obtained in example 2 and the spatial distribution characterization image (Mapping image) of the elements Ti, Mn, and Pt, the three elements are uniformly mixed together, and Pt is in a nanometer level and is uniformly distributed.

(2) Photocatalytic performance

The method for degrading toluene by photocatalysis comprises the following steps: 3g of the catalyst (composite catalyst in examples 1, 2 and 3, composite catalyst in comparative example 2, pure TiO) was weighed out₂(purchased from winning CORPORATION, model P25) was uniformly coated on a foamed nickel plate, which was placed in an ultraviolet light catalytic box and irradiated with ultraviolet light having a wavelength of 185nm through a 100mg/m hole³The residence time of the toluene in the ultraviolet light catalytic box is about 26 s. The concentration of toluene was measured at the outlet by chromatography and the degradation rate was calculated.

The calculation method comprises the following steps: the toluene degradation rate (toluene inlet concentration-toluene outlet concentration)/toluene inlet concentration.

See table 3, fig. 3 for specific results.

TABLE 3

(3) The catalytic performances of the composite catalysts in example 2, example 4-1, example 4-2, comparative example 3 and comparative example 4 were compared. The specific method comprises the following steps:

3g of the catalyst (example 2, example 4-1, example 4-2),Composite catalyst of comparative example 3 and comparative example 4) was uniformly coated on the foamed nickel, and the foamed nickel plate was placed in an ultraviolet light catalytic chamber, to which 100mg/m of the catalyst was passed under ultraviolet light irradiation of 185nm wavelength³The residence time of the toluene in the ultraviolet light catalytic box is about 26 s. The concentration of toluene was measured at the outlet by chromatography and the degradation rate was calculated.

See table 4 for specific results.

TABLE 4

Group of	Example 2	Example 4-1	Example 4 to 2	Comparative example 3	Comparative example 4
						Toluene degradation rate of 1h	95.80％	89.45％	93.19％	85.12％	89.19％
2h toluene degradation rate	96.73％	89.69％	92.87％	85.76％	89.24％
						3h toluene degradation rate	96.05％	90.13％	92.54％	84.98％	88.93％
4h toluene degradation rate	95.70％	89.88％	93.56％	84.73％	88.31％
						Toluene degradation rate of 5h	95.71％	90.56％	93.72％	85.09％	89.15％
6h toluene degradation rate	95.45％	90.87％	92.82％	85.18％	88.56％
						Toluene degradation rate of 7h	95.59％	90.46％	92.61％	84.63％	88.99％
Toluene degradation rate of 8h	95.32％	89.97％	93.15％	84.21％	89.49％

Claims

1. The composite catalyst is characterized by comprising an active metal phase and an oxide matrix phase, wherein the active metal phase is dispersed on the surface of the oxide matrix phase; wherein:

the active metal phase is a noble metal simple substance;

the particle size of the active metal phase is 2-20 nm.

2. The composite catalyst of claim 1, wherein the composite catalyst satisfies one or more of the following conditions:

the simple substance of the noble metal is one or more of Ir, Ru, Pt, Pd and gold, such as Pt;

② the particle size of the active metal phase is 2-3nm, e.g. 3 nm;

③ the oxide matrix phase is an oxide containing Ti and/or an oxide containing Mn; wherein:

the Ti-containing oxide may be TiO₂The Mn-containing oxide may be MnO₂；

When the Ti-containing oxide and the Mn-containing oxide are contained in the oxide matrix phase, the mass ratio of the Ti-containing oxide to the Mn-containing oxide may be 10: (0.1-2), e.g., 10:0.5, 10:1, or 10: 1.5;

and in said composite catalyst, the content of said active metal phase is 0.5-2 wt%, for example 1 wt%.

3. The preparation method of the composite catalyst is characterized by comprising the following steps of: will contain NaBH₄Dripping the solution into the mixed solution C to obtain mixed solution D, and stirring for reaction to obtain the composite catalyst; wherein:

in the mixed solution D, NaBH₄In a concentration of (1.0-2.5) × 10^-4g/ml；

In the reaction, the stirring speed is more than or equal to 500 rpm.

4. The method for preparing the composite catalyst according to claim 3, wherein the method for preparing the composite catalyst satisfies one or more of the following conditions:

the noble metal in the noble metal-containing salt is one or more of Ir, Ru, Pt, Pd and gold, such as Pt; alternatively, the noble metal-containing salt is a Pt-containing salt, such as chloroplatinic acid;

the oxide matrix phase is an oxide containing Ti and/or an oxide containing Mn; wherein:

the Ti-containing oxide may be TiO₂The Mn-containing oxide may be MnO₂；

When the oxide matrix phase contains a Ti-containing oxide, the concentration of the Ti-containing oxide in the mixed solution D may be 0.01 to 0.05g/ml, for example 0.023077 g/ml;

when the oxide matrix phase contains an Mn-containing oxide, the concentration of the Mn-containing oxide in the mixed liquid D may be 0.0001 to 0.01g/ml, for example 0.001154 g/ml;

③ the particle size of the oxide matrix phase is 40-100 nm;

fourthly, the dispersant is PVP-K30;

the solvent is water;

and the dropping speed is 1-10ml/min, such as 5 ml/min.

5. The method for preparing the composite catalyst according to claim 3, wherein the method for preparing the composite catalyst satisfies one or more of the following conditions:

in the mixed solution D, the concentration of the oxide matrix phase is 0.0001-0.05g/ml, such as 0.023077g/ml or 0.001154 g/ml;

② in the mixed solution D, the concentration of the dispersant is (1.0-2.0) × 10^-5g/ml, e.g. 1.43 x 10^-5g/ml；

③ in the mixed solution D, the concentration of the noble metal in the noble metal-containing salt is 0.0001-0.001g/ml, such as 0.0002308 g/ml;

fourthly, in the mixed solution D, the NaBH₄The concentration of (2.0-2.5) × 10^-4g/ml, for example 0.0002248 g/ml;

and in the reaction, the rotation speed of stirring is 500-1000rpm, such as 800-1000rpm, and further such as 500rpm, 800rpm or 1000 rpm.

6. The method for producing the composite catalyst according to claim 4 or 5, wherein the mixed solution C is produced by mixing a solution containing a noble metal salt with the mixed solution B; the mixed solution B is a mixed solution of the oxide matrix phase, the dispersant and the solvent;

the concentration of the noble metal in the noble metal-containing salt in the solution of the noble metal-containing salt may be 0.001-0.1g/ml, for example 0.01875 g/ml;

the mixed solution B can be prepared by mixing the mixed solution A with a solution containing the dispersant; the mixed liquid A is a mixed liquid of the oxide matrix phase and the solvent.

7. The method for preparing the composite catalyst according to claim 6, wherein the concentration of the oxide matrix phase in the mixed solution A is 0.01 to 0.1g/ml, for example, 0.0525g/ml, 0.055g/ml or 0.0575 g/ml;

alternatively, when the oxide matrix phase contains a Ti-containing oxide, the concentration of the Ti-containing oxide in the mixed solution a is 0.01 to 0.1g/ml, for example, 0.05 g/ml;

alternatively, when an oxide containing Mn is contained in the oxide matrix phase, the concentration of the oxide containing Mn in the mixed solution A is 0.5 to 10mg/ml, for example, 2.5 to 7.5mg/ml, and further, for example, 2.5mg/ml, 5.0mg/ml or 7.5 mg/ml.

8. The method for preparing the composite catalyst according to claim 4, comprising the steps of:

9. A composite catalyst produced by the method for producing a composite catalyst according to any one of claims 3 to 8;

wherein the composite catalyst can be Pt/TiO₂/MnO₂A catalyst.

10. Use of the composite catalyst according to any one of claims 1, 2 and 9 as a photocatalyst having ozone synergy; the application may be as a VOCs degrader.