CN114570344A - Transition metal monatomic catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a transition metal monatomic catalyst, which takes a transition metal monatomic as an active component, takes zirconium oxide as a carrier, and disperses the transition metal monatomic on the surface and in the zirconium oxide. The catalyst is a novel zirconia carrier anchored transition metal monoatomic photocatalyst, and has higher carbon monoxide product selectivity and generation activity when being used for preparing carbon monoxide by photocatalytic carbon dioxide reduction. The invention also discloses a preparation method and application of the catalyst.

Description

A kind of transition metal single-atom catalyst and its preparation method and application

technical field

The invention relates to the technical field of preparation of micro-nano materials. More specifically, it relates to a transition metal single-atom catalyst and its preparation method and application.

Background technique

As a bridge between homogeneous catalysts and heterogeneous catalysts, single-atom heterogeneous catalysts not only retain the characteristics of high activity and high selectivity of homogeneous catalysts for catalytic reactions, but also have the characteristics of easy separation of heterogeneous catalysts in catalytic reactions. It has become a hot field of catalyst design and represents the development direction of this field.

However, in recent years, due to the high surface energy of a single atom and its easy agglomeration in preparation and application, few reports have directly investigated the one-step preparation of oxide-anchored transition metal single-atom photocatalysts. The relatively mature examples in the prior art include carbon-nitrogen support for anchoring transition metal single atoms or metal organic framework structure support for anchoring transition metal single atoms. For example, Zhang Tierui's research group has achieved large-scale synthesis of carbon-nitrogen carrier-anchored transition metal single-atom catalysts through the coordination of phenanthroline and transition metals [Nat.Commun.2019, 10:4585]; Li Yadong's research group has passed The MOF encapsulation method has enabled the large-scale synthesis of metal-organic framework structure support-anchored transition metal single-atom catalysts [Nat. Catal. 2018, 1, 935-945]. However, the coordination mode of the single atoms of the above two supports for the synthesis of transition metal single-atom catalysts is a metal-carbon/nitrogen structure (M-C/N), which is easily destroyed by photo-generated holes and reactive oxygen species in the photocatalytic reaction. , so a large amount of sacrificial agent is required to maintain stability in practical photocatalytic applications. The solution to this problem is to develop single-atom catalysts with a metal-oxygen coordination (M-O) structure, which can substantially improve the stability of single-atom catalysts.

However, the metal oxide supports used in the prior art to synthesize transition metal single-atom catalysts with metal-oxygen coordination structures are mainly CeO ₂ , FeO _x , Al ₂ O ₃ , TiO ₂ , MgO, SiO ₂ , WO _x and ZnO. However, these carriers do not conduct photoelectrons well.

SUMMARY OF THE INVENTION

Based on the above problems, the first object of the present invention is to provide a transition metal single-atom catalyst, which uses ZrO ₂ as a carrier and has a high transition metal single-atom loading. In addition, the catalyst is a new type of photocatalyst with zirconia carrier anchoring transition metal single atoms, which is used in the application of photocatalytic reduction of carbon dioxide to prepare carbon monoxide, and has high carbon monoxide product selectivity and generation activity.

The second object of the present invention is to provide a preparation method of a transition metal single-atom catalyst. The preparation method has the advantages that it is suitable for the preparation of various transition metal single-atom catalysts, and has the advantages of low preparation temperature and large loading of the active component transition metal single-atom catalyst.

The third object of the present invention is to provide the application of a transition metal single-atom catalyst. The catalyst has high selectivity and activity.

For reaching above-mentioned first purpose, the present invention adopts following technical scheme:

A transition metal single-atom catalyst, the catalyst uses a transition metal single atom as an active component and zirconia (ZrO ₂ ) as a carrier, and the transition metal single atom is dispersed on the surface and inside of the zirconia.

In the catalyst of the present invention, the transition metal is dispersed on the surface and inside of the carrier zirconia in the form of single atoms, that is, the transition metal single-atom catalyst anchored by the zirconia. In this catalyst, single atoms of transition metals are dispersed in the defect sites of the zirconia support. As a non-reducing carrier, zirconia has high stability in light and thermal catalysis. Secondly, the oxidation state of zirconium element in zirconia is tetravalent, and the d orbital configuration is d0 configuration, which is beneficial to the conversion of ultraviolet light absorption.

Compared to the aforementioned CeO ₂ , FeO _x , Al ₂ O ₃ , TiO ₂ , MgO, SiO ₂ , WO _x and ZnO supports, ZrO ₂ supports have a fluorite-like structure filled with abundant Frenkel defects, i.e. crystals The structure exhibits a dipole moment that facilitates conduction of photogenerated electrons. Secondly, the ZrO ₂ carrier is qualitatively strong. Therefore, it is conducive to anchoring single atoms and maintains good charge conductivity and structural stability.

Further, based on the total weight of the catalyst as 100%, the loading amount of transition metal single atoms is 1.8-3 wt%.

Further, the transition metal single atom is selected from one or more of Zn, Ni, Fe, Co or Cu.

Further, the zirconia is a tetragonal crystal phase, a monoclinic crystal phase or a mixed crystal phase thereof. It is preferably a tetragonal crystal phase, which has a wide light absorption range and a stable zirconium-oxygen structure, which is more conducive to photocatalytic reactions.

In order to achieve above-mentioned second purpose, the present invention adopts following technical scheme:

A preparation method of transition metal single-atom catalyst, comprising the steps:

Dissolve the transition metal salt and the zirconium metal salt in the solvent and mix them evenly to obtain a clear and transparent solution;

Add alkaline solution to obtain reaction solution;

The reaction solution was stirred and reacted, and dried to obtain a crude product;

The crude product is placed in an air atmosphere, calcined, cooled to room temperature, washed and dried to obtain the transition metal single-atom catalyst.

In the preparation method of the present invention, after the transition metal salt, the zirconium metal salt and the alkaline solution are mixed, the transition metal salt and the zirconium metal salt can be dissolved and dispersed in the alkaline solution by means of stirring, ultrasonic, etc., to obtain a colloid The resulting product represents the completion of the complexation reaction.

Compared with the traditional method for preparing a metal oxide single-atom catalyst with defect site anchoring single atoms, the present invention is completed by a one-step mixing, calcining and washing route, while the traditional method often requires pre-preparing an oxide carrier, and then Defects are etched, and then the transition metal single-atom catalyst can be obtained by impregnation method. Therefore, compared with the traditional method, the synthesis process of the present invention is simple.

Further, the calcination conditions are as follows: the temperature is raised to 300-600° C. at a heating rate of 2-10° C.·min ⁻¹ , and calcined for 1-5 hours. During the heating and heating process under this condition, the colloidal product is slowly dehydrated, and the unstable components are slowly volatilized, so as to achieve the purpose of creating defects on the zirconia precursor. At the same time, this slow low-temperature heating process can also make the transition metal ions well dispersed in the colloidal product at this time. Subsequently, the colloidal product is calcined to completely remove volatile substances such as water in the components and improve the crystallinity.

Further, in the reaction solution, the mass ratio of the transition metal salt and the zirconium metal salt is 1:20-1:50.

Further, the mass concentration of the transition metal salt and the zirconium metal salt in the alkaline solution is 13-16 mg·mL ^-1 .

Further, the transition metal salt described in the present invention can be any transition metal salt that can be dispersed in an alkaline solution. The transition metal salts include, but are not limited to, one or more selected from transition metal chlorides, transition metal nitrates, transition metal acetates, and transition metal sulfates.

Further, the zirconium metal salt is selected from one or more of zirconium metal chloride, zirconium metal nitrate, zirconium metal acetate, and zirconium metal sulfate.

Further, the alkaline solution is an aqueous solution of one or more substances in NaOH, NaHCO ₃ , Na ₂ CO ₃ , (NH ₄ ) ₂ CO ₃ , preferably NaHCO ₃ , (NH ₄ ) ₂ CO ₃ aqueous solution. As a weakly alkaline substance that can be removed by thermal decomposition, it is easier to control the coordination state of metal ions in the formation of colloidal precursors.

Further, the temperature of the stirring reaction is 40-80° C., and the time is 2-8 h.

Further, the washing is 3 to 5 times of washing with dilute acid and aqueous solution.

Further, the dilute acid is selected from one or more of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid.

Further, the drying temperature is 60-90° C., and the time is 1-5 h.

In order to achieve the above-mentioned third purpose, the present invention adopts following technical scheme:

The application of the transition metal single-atom catalyst described in the first object above in the photocatalytic reduction of carbon dioxide to prepare carbon monoxide.

Specifically, the chemical formula of this reaction is CO ₂ +H ₂ O=CO+H ₂ +O ₂ .

Further, the application includes the following steps:

Under the conditions of 0.01-1Mpa pressure and the presence of the catalyst, the mixture of _CO2 and water vapor is illuminated in full spectrum.

Further, the dosage of the catalyst is 0.01-1 g/0.01-0.1 L mixed gas.

The beneficial effects of the present invention are as follows:

The transition metal single-atom catalyst provided by the invention uses the transition metal single atom as the active component and the zirconia as the carrier, and is a novel photocatalyst in which the zirconia carrier anchors the transition metal single atom. The carrier of the photocatalyst is zirconia with defect sites, and the existence of defect sites provides the possibility to achieve stable single-atom anchoring of transition metals. At the same time, the transition metal single atoms anchored by defect sites are not easy to agglomerate in catalytic applications due to the strong metal-support interaction, which can greatly improve their stability in photocatalytic reactions. In the application of the transition metal single-atom photocatalyst, by virtue of the special unsaturated coordination state of the transition metal single atom, high activity and high selectivity of gas-solid reduction of carbon dioxide to carbon monoxide can be achieved. Furthermore, the use of sacrificial agents to overcome the photooxidation/photocorrosion of this catalyst is avoided due to the stability of the defect site-anchored transition metal single atoms. Therefore, the preparation method is low in cost, simple in process, and full of prospects in practical applications.

In the preparation method of the transition metal single-atom catalyst provided by the present invention, zirconium and transition metal colloid are used as precursors, and the preparation of defect site zirconia and the anchoring of transition metal single-atom on its surface are realized by a one-step method of low temperature and high temperature treatment. atom. And the preparation method is universal and can be used to prepare a variety of transition metal single-atom catalysts. Through this method, Zn single-atom catalysts, Fe single-atom catalysts, Co single-atom catalysts, Ni single-atom catalysts, and Cu single-atom catalysts are realized. preparation. In addition, the preparation method has the advantages of low cost, simple process and large-scale production.

The catalyst provided by the invention has high carbon monoxide product selectivity and generation activity in the application of photocatalytic reduction of carbon dioxide to prepare carbon monoxide.

Description of drawings

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

FIG. 1 shows the XRD pattern of the Ni single-atom catalyst obtained in Example 1 of the present invention.

FIG. 2 shows the EPR diagram of the Ni single-atom catalyst obtained in Example 1 of the present invention.

FIG. 3 shows the EPR diagram of the defective zirconia obtained in Example 1 of the present invention.

FIG. 4 shows the TEM image of the Ni single-atom catalyst obtained in Example 1 of the present invention.

FIG. 5 shows the HAADF-STEM image of the Ni single-atom catalyst obtained in Example 1 of the present invention.

FIG. 6 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalyst obtained in Example 1 of the present invention.

FIG. 7 shows the XRD patterns of the Ni single-atom catalysts synthesized in Examples 2-4.

FIG. 8 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalysts obtained in Examples 2-4 of the present invention.

FIG. 9 shows Ni single-atom XRD patterns synthesized in Example 1 and Example 5. FIG.

FIG. 10 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalyst obtained in Example 5 of the present invention.

FIG. 11 shows the XRD pattern of the single-atom catalyst synthesized in Example 6. FIG.

FIG. 12 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalysts obtained in Examples 6 and 7 of the present invention.

FIG. 13 shows the spherical aberration-corrected transmission electron microscope images of the Cu, Zn, Fe, Co single-atom catalysts obtained in Examples 8-11. 14 shows the XRD patterns of the single-atom catalysts obtained in Examples 8-11.

FIG. 15 shows the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalysts obtained in Examples 8-11 of the present invention.

FIG. 16 shows the XRD pattern of the Ni single-atom catalyst obtained in Comparative Example 1. FIG.

FIG. 17 shows the XRD pattern of the catalyst obtained in Comparative Example 2. FIG.

Detailed ways

In order to illustrate the present invention more clearly, the present invention will be further described below with reference to the preferred embodiments and accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not limit the protection scope of the present invention.

Example 1

A method for zirconia anchoring transition metal Ni single-atom photocatalyst, comprising the steps of:

1) take by weighing 0.53mmol nickel nitrate, 6.75mmol zirconium nitrate is added in the beaker, add 100mL deionized water, magnetically stir to completely dissolve to obtain a clear and transparent solution; when not adding nickel nitrate in this step, obtain a defective position after the preparation is completed. zirconia;

2) After the reaction is completed, take 15mmol (NH ₄ ) ₂ CO ₃ and dissolve it in 100 mL of deionized water thoroughly, then add the clear and transparent solution obtained above, and a flocculent product appears;

3) The flocculent product obtained above was continuously stirred for 5 hours under the condition of a 70°C water bath, and finally a gel-like product was obtained;

4) The gel-like product obtained above was heated to 600° C. at a heating rate of 5° C. min ⁻¹ in an air atmosphere, kept at this temperature for 2 h, and then cooled down to room temperature naturally to obtain a powdery product;

5) The powdered product obtained above was washed three times with dilute hydrochloric acid and deionized water respectively, until the washing liquid was completely colorless and transparent when poured out, centrifuged and dried in an oven at 60°C for 2 hours to obtain a Ni single-atom catalyst, It is denoted as Ni-SAC, and it can be detected by ICP-AES method that the loading amount of Ni atoms in this Ni-SAC is 1.8 wt%.

The XRD pattern of the catalyst, the EPR pattern of the defective zirconia, the EPR pattern of the catalyst, the TEM pattern, and the HAADF-STEM pattern are sequentially shown in Figures 1-5.

The catalyst is used in photocatalytic reduction of carbon dioxide to prepare carbon monoxide:

Under the pressure of 0.08Mpa, the mixture of 50mL CO ₂ and water vapor, 10mg of the above catalyst, using full solar spectrum illumination for 2h, using gas chromatography external standard method to test the yield of the obtained product, etc. FIG. 6 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalyst obtained in Example 1 of the present invention. It can be seen from the figure that the Ni single-atom catalyst obtained in Example 1 obtains CO after photocatalytic _CO reduction, the formation rate of CO is 11.8 μmol/g h, and the product selectivity of CO is 92.5% (the rest are selectivity of _H2 ).

Example 2-4

Example 1 was repeated, except that nickel nitrate was changed to nickel chloride, nickel acetate, and nickel sulfate. There is no obvious difference between the obtained Ni single-atom catalyst and the single-atom catalyst obtained in Example 1, and through the ICP-AES method, it can be detected that in the Ni-SAC, the loading amount of Ni atoms is 3wt%.

Fig. 7 is the XRD pattern of the Ni single-atom catalyst synthesized by embodiment 2-4, as can be seen from the figure, the Ni single-atom catalyst synthesized by using nickel chloride, nickel acetate, nickel sulfate all only appears the peak of zirconia , there is no peak of Ni or its compounds. This also shows that the anion species in the transition metal salt has no obvious effect on the formation of single-atom catalysts.

The catalyst prepared in Example 2-4 was used in the photocatalytic reduction of carbon dioxide to prepare carbon monoxide:

Under the pressure of 0.08Mpa, the mixture of 10mL CO ₂ and water vapor, 50mg of the above catalyst, using full solar spectrum illumination for 5h, using gas chromatography external standard method to test the yield of the obtained product, etc.

FIG. 8 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalysts obtained in Examples 2-4 of the present invention. It can be seen from the figure that the Ni single-atom catalysts obtained in Examples 2-4 obtained CO after photocatalytic _CO reduction, and the formation rates of CO were 5.2 μmol/g·h, 6.1 μmol/g·h, 3.4 μmol/g·h, respectively. μmol/g·h; the product selectivities of CO were 95.2%, 90.3%, and 98.4%, respectively (the remainder was the selectivity of _H2 ).

Example 5

Example 1 was repeated, except that the zirconium nitrate was changed to zirconium acetate, the obtained catalyst was a single-atom catalyst, and by ICP-AES method, it could be detected that in the Ni-SAC, the loading amount of Ni atoms was 2wt%.

9 shows the Ni single-atom XRD patterns synthesized in Example 1 and Example 5. In the figure, for the synthesized Ni single atoms, only the peak of zirconia appears, and there is no peak of metal element or compound. This indicates that the type of zirconium salt has no significant effect on the formation of single-atom catalysts.

The catalyst prepared in Example 5 was used in the photocatalytic reduction of carbon dioxide to prepare carbon monoxide:

Under the pressure of 0.05Mpa, the mixture of 100mL CO ₂ and water vapor, 100mg of the above catalyst, and the full solar spectrum illumination for 2h were used to test the yield of the obtained product by gas chromatography external standard method.

FIG. 10 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalyst obtained in Example 5 of the present invention. It can be seen from the figure that the Ni single-atom catalyst obtained in Example 5 obtained CO after photocatalytic _CO reduction, the formation rate of CO was 9.5 μmol/g h, and the product selectivity of CO was 88.4% (the rest were selectivity of _H2 ).

Example 6-7

Example 1 was repeated, except that the addition amount of (NH ₄ ) ₂ CO ₃ was changed to 20 mmol and 30 mmol, the obtained catalysts were denoted as NiN20 and NiN30, and the two synthesized catalysts were single-atom catalysts.

FIG. 11 shows the XRD pattern of the single-atom catalyst synthesized in Example 6. FIG. There are only two broad peaks corresponding to zirconia in the figure, and no peaks of metals or their compounds appear, which indicates that the two synthesized catalysts are single-atom catalysts.

The catalysts prepared in Examples 6-7 were used in the photocatalytic reduction of carbon dioxide to prepare carbon monoxide:

Under the pressure of 0.01Mpa, the mixture of 100mL CO ₂ and water vapor, 50mg of the above catalyst, using full solar spectrum illumination for 5h, using gas chromatography external standard method to test the yield of the obtained product, etc.

FIG. 12 shows the photocatalytic carbon dioxide reduction performance diagram of the Ni single-atom catalysts obtained in Examples 6-7 of the present invention. It can be seen from the figure that the Ni single-atom catalysts obtained in Examples 6-7 obtained CO after photocatalytic _CO reduction, and the formation rates of CO were 3.2 μmol/g·h and 4.4 μmol/g·h, respectively; CO The product selectivities were 60.9% and 54.2%, respectively (the remainder was the selectivity of _H2 ).

Examples 8-11

Example 1 was repeated, except that the metal salts were changed to Cu, Zn, Fe, Co salts. The obtained catalysts are all single-atom catalysts. Specifically, the spherical aberration-corrected transmission electron microscope images of the four metal single-atom catalysts are shown in Figure 13, and the marked dark spots are metal single atoms. It can be found that the transition metals are dispersed on the surface and inside of zirconia in the form of single atoms. The corresponding XRD pattern is shown in FIG. 14 , only the peak of zirconia appears, and the peak of metal element or compound does not appear. Examples 8-11 also illustrate that the synthesis method of the transition metal single-atom catalyst has wide applicability.

The catalysts prepared in Examples 8-11 were used in photocatalytic reduction of carbon dioxide to prepare carbon monoxide:

Under the pressure of 0.08Mpa, the mixture of 40mL CO ₂ and water vapor, 10mg of the above catalyst, using full solar spectrum illumination for 4h, using gas chromatography external standard method to test the yield of the obtained product, etc.

FIG. 15 shows the photocatalytic carbon dioxide reduction performance of the Ni single-atom catalysts obtained in Examples 8-11 of the present invention. It can be seen from the figure that the Ni single-atom catalysts obtained in Examples 8-11 obtained CO after photocatalytic _CO reduction, and the formation rates of CO were 8.8 μmol/g·h, 10.4 μmol/g·h, 6.5 μmol/g·h, respectively. μmol/g·h, 9.2 μmol/g·h; the product selectivities of CO were 87.1%, 91.5%, 60.5%, 72.3%, respectively (the remainder was the selectivity of _H2 ).

Comparative Example 1

Example 1 was repeated except that the zirconium nitrate was changed to cerium nitrate. The resulting catalysts were all capable of forming single-atom catalysts. Through the ICP-AES test, its loading was only 0.5 wt%.

FIG. 16 shows the XRD pattern of the Ni single-atom catalyst obtained in Comparative Example 1 of the present invention. It can be seen that only the peak of cerium oxide appears, and there is no peak of Ni metal element or compound.

Comparative Example 2

Example 1 was repeated except that the zirconium nitrate was changed to titanium tetrachloride. The resulting catalysts were all capable of forming single-atom catalysts.

FIG. 17 shows the XRD pattern of the Ni single-atom catalyst obtained in Comparative Example 1 of the present invention. It can be seen that only the peak of titanium oxide appears, and there is no peak of Ni metal element or compound.

Comparative Example 3

Example 6 was repeated, except that the temperature increase rate in step 4) was changed to 1°C·min ⁻¹ , and the other conditions remained unchanged to prepare a catalyst.

The catalyst was used in the photocatalytic reduction of carbon dioxide to prepare carbon monoxide using the application conditions as in Example 6. The results showed that the formation rate of CO was 2.7 μmol/g·h, and the product selectivity of CO was 50.1% (the rest was _H2 optional).

Comparative Example 4

Example 6 was repeated, except that the temperature increase rate in step 4) was changed to 12°C·min ⁻¹ , and the other conditions remained unchanged to prepare the catalyst.

The catalyst was used in the photocatalytic reduction of carbon dioxide to prepare carbon monoxide using the application conditions as in Example 6. The results showed that the formation rate of CO was 2.6 μmol/g·h, and the product selectivity of CO was 51.3% (the rest was _H2 optional).

Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the embodiments of the present invention. Changes or changes in other different forms cannot be exhausted here, and all obvious changes or changes derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims (10)

1. The transition metal monatomic catalyst is characterized in that a transition metal monatomic is used as an active component of the catalyst, zirconia is used as a carrier, and the transition metal monatomic is dispersed on the surface and in the interior of the zirconia.

2. The transition metal monatomic catalyst of claim 1, wherein the transition metal monatomic loading is 1.8 to 3 wt% based on the total weight of the catalyst taken as 100%.

3. The transition metal monatomic catalyst of claim 1, wherein said transition metal monatomic is selected from one or more of Zn, Ni, Fe, Co, or Cu.

4. The transition metal monatomic catalyst of claim 1, wherein the zirconia is in a tetragonal phase, a monoclinic phase, or a mixed phase thereof.

5. A process for preparing a transition metal monatomic catalyst according to any one of claims 1 to 4, which comprises the steps of:

dissolving transition metal salt and zirconium metal salt in a solvent, and uniformly mixing to obtain a clear and transparent solution;

adding an alkaline solution to obtain a reaction solution;

stirring the reaction solution for reaction, and drying to obtain a crude product;

and placing the crude product in an air atmosphere, calcining, cooling to room temperature, washing and drying to obtain the transition metal monatomic catalyst.

6. The method according to claim 5, wherein the calcination is carried out under the following conditions: at a temperature of 2-10 ℃ min^-1The temperature is increased to 300-600 ℃ at the temperature increasing rate, and the calcination is carried out for 1-5 h.

7. The preparation method according to claim 5, wherein the mass ratio of the transition metal salt to the zirconium metal salt in the reaction solution is 1:20 to 1: 50;

preferably, the mass concentration of the transition metal salt and the zirconium metal salt in the alkaline solution is 13-16 mg-mL^-1；

Preferably, the transition metal salt is selected from one or more of transition metal chloride salt, transition metal nitrate, transition metal acetate and transition metal sulfate;

preferably, the zirconium metal salt is selected from one or more of zirconium metal chloride salt, zirconium metal nitrate, zirconium metal acetate and zirconium metal sulfate;

preferably, the alkaline solution is NaOH or NaHCO₃、Na₂CO₃、(NH₄)₂CO₃An aqueous solution of one or more of the substances in (a).

8. The preparation method according to claim 5, wherein the stirring reaction is carried out at a temperature of 40-80 ℃ for 2-8 h.

9. Use of a transition metal monatomic catalyst according to any one of claims 1 to 4, for photocatalytic carbon dioxide reduction to produce carbon monoxide.

10. The application according to claim 9, characterized in that it comprises the following steps:

under the conditions of 0.01-1MPa pressure and the presence of the catalyst, the full spectrum illumination of CO₂And a mixture of water vapor.

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