CN114570344A

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

Info

Publication number: CN114570344A
Application number: CN202011384868.8A
Authority: CN
Inventors: 张铁锐; 熊旭阳
Original assignee: Technical Institute of Physics and Chemistry of CAS
Current assignee: Technical Institute of Physics and Chemistry of CAS
Priority date: 2020-12-01
Filing date: 2020-12-01
Publication date: 2022-06-03

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

Transition metal monatomic catalyst and preparation method and application thereof

Technical Field

The invention relates to the technical field of micro-nano material preparation. More particularly, relates to a transition metal monatomic catalyst, a preparation method and application thereof.

Background

The monatomic heterogeneous catalyst is used as a bridge for communicating a homogeneous catalyst and a heterogeneous catalyst, so that the characteristics of high activity and high selectivity of the homogeneous catalyst to catalytic reaction are kept, the monatomic heterogeneous catalyst has the advantage of easy separation of the heterogeneous catalyst in the catalytic reaction, the catalyst becomes the popular field of catalyst design, and represents the development direction of the field.

However, in recent years, due to the high surface energy of single atoms and the high tendency of agglomeration in preparation and application, there are few reports on direct research on one-step preparation of oxide-anchored transition metal single-atom photocatalysts. Examples of relatively mature prior art carriers are carbon-nitrogen carrier anchored transition metal monoatomic or metal organic framework structure carrier anchored transition metal monoatomic. For example, the task group of the Zhang Fei Shao teacher realizes the large-scale synthesis of the carbon-nitrogen carrier anchored transition metal monatomic catalyst through the coordination of phenanthroline and a transition metal [ nat. Commun.2019,10:4585 ]; the Lizidona teacher topic group realizes large-scale synthesis of a transition metal monatomic catalyst anchored by a metal-organic framework structure carrier through an MOF (metal organic framework) packaging method [ nat. Catal.2018,1,935-945 ]. However, the coordination mode of the single atom of the transition metal single-atom catalyst synthesized by the two carriers is a metal-carbon/nitrogen structure (M-C/N), which is easily destroyed by photogenerated holes and active oxygen in a photocatalytic reaction, so that a large amount of sacrificial agents are needed to maintain stability in practical photocatalytic applications. The method for solving the problem is to develop the monatomic catalyst with a metal-oxygen coordination (M-O) site structure, and the stability of the monatomic catalyst can be improved essentially.

However, the prior art metal oxide support for the synthesis of transition metal monatomic catalysts of metal-oxygen coordination structure is mainly CeO₂，FeO_x，Al₂O₃，TiO₂，MgO，SiO₂，WO_xAnd ZnO. However, these supports do not conduct photoelectrons well.

Disclosure of Invention

In view of the above problems, it is a first object of the present invention to provide a transition metal monoatomic catalyst based on ZrO₂Is a carrier and has high transition metal single atom loading.In addition, 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 second purpose of the invention is to provide a preparation method of the transition metal monatomic catalyst. The preparation method has the advantages of suitability for preparation of various transition metal monoatomic catalysts, low preparation temperature and large transition metal monoatomic load of active components.

The third purpose of the invention is to provide the application of the transition metal monatomic catalyst. The catalyst has high selectivity and activity.

In order to achieve the first purpose, the invention adopts the following technical scheme:

a transition metal single atom catalyst, which takes transition metal single atom as an active component and takes zirconium oxide (ZrO) as well as₂) Is used as a carrier, and the transition metal is dispersed on the surface and in the inner part of the zirconia.

In the catalyst of the present invention, the transition metal is dispersed in the form of a single atom on the surface and inside of the zirconia as a carrier, that is, a zirconia-anchored transition metal single atom catalyst. In the catalyst, transition metal monoatomic atoms are dispersed in defect sites of a zirconia support. The zirconium oxide is used as a non-reduction carrier, and has higher stability in photocatalysis and thermocatalysis. Secondly, the oxidation state of the zirconium element in the zirconium oxide is tetravalent, and the d-orbital configuration is d0 configuration, so that the conversion of ultraviolet light absorption is facilitated.

Compared with the CeO₂，FeO_x，Al₂O₃，TiO₂，MgO，SiO₂，WO_xAnd ZnO carrier, ZrO₂The carrier has a fluorite structure and is full of abundant Frankle defects, namely the crystal structure shows dipole moment and is beneficial to conduction of photo-generated electrons. Second, ZrO₂The carrier has strong qualitative property. It lends itself to anchoring the monoatomic atoms and maintains good charge-conducting ability and structural stability.

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

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

Further, the zirconia is in a tetragonal phase, a monoclinic phase or a mixed phase thereof. Preferably tetragonal crystal phase, wide light absorption range and stable zirconium-oxygen structure, and is more beneficial to photocatalytic reaction.

In order to achieve the second purpose, the invention adopts the following technical scheme:

a preparation method of a transition metal monatomic catalyst comprises the following steps:

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.

In the preparation method, 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 promoted to be dissolved and dispersed in the alkaline solution by stirring, ultrasonic and other modes, and a colloidal product is obtained, which represents the completion of the complex reaction.

Compared with the traditional method for preparing the metal oxide monatomic catalyst with the defect site anchored monatomic, the method is completed by a path of one-step mixing, calcining and washing, and the traditional method usually needs to prepare an oxide carrier in advance, then etches out defects and obtains the transition metal monatomic catalyst by an impregnation method. Therefore, compared with the traditional method, the synthesis process of the invention is simple.

Further, the calcination conditions are: at 2-10 ℃ per minute^-1The temperature is increased to 300-600 ℃ at the temperature increasing rate, and the calcination is carried out for 1-5 h. In the heating process under the condition, the colloidal product is slowly dehydrated and unstable components are generatedSlowly volatilizes to achieve the purpose of manufacturing defects on the zirconia precursor. Meanwhile, the slow low-temperature heating process can also enable the transition metal ions to be well dispersed in the colloid product at the moment. Then, the colloidal product is calcined to thoroughly 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 to 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 according to the present invention may be any transition metal salt that is dispersible in an alkaline solution. The transition metal salt includes, but is not limited to, one or more selected from transition metal chloride salt, transition metal nitrate salt, transition metal acetate salt, and transition metal sulfate salt.

Further, 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.

Further, the alkaline solution is NaOH and NaHCO₃、Na₂CO₃、(NH₄)₂CO₃Preferably aqueous solution of one or more of (a) and (b), preferably NaHCO₃，(NH₄)₂CO₃An aqueous solution of (a). As a weak alkaline, thermally decomposed removable alkaline substance, the coordination condition of metal ions in the formed colloidal precursor is easier to regulate.

Further, the stirring reaction is carried out at the temperature of 40-80 ℃ for 2-8 hours.

Further, the washing is carried out for 3-5 times by using 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 ℃, and the drying time is 1-5 h.

In order to achieve the third purpose, the invention adopts the following technical scheme:

use of a transition metal monatomic catalyst according to the first object above for the photocatalytic reduction of carbon dioxide to carbon monoxide.

Specifically, the chemical formula of the reaction is CO₂+H₂O＝CO+H₂+O₂。

Further, the application comprises the steps of:

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.

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

The invention has the following beneficial effects:

the transition metal monatomic catalyst provided by the invention takes a transition metal monatomic as an active component and zirconia as a carrier, and is a novel zirconia carrier anchored transition metal monatomic photocatalyst. The carrier of the photocatalyst is zirconia with defect sites, and the existence of the defect sites provides possibility for realizing stable transition metal monoatomic anchoring. Meanwhile, due to the interaction of strong metal carriers, the transition metal monoatomic layer anchored at the defect position is not easy to agglomerate in the catalytic application, so that the stability of the transition metal monoatomic layer in the photocatalytic reaction can be greatly improved. In the application of the transition metal monatomic photocatalyst, the performance of reducing gas-solid phase carbon dioxide into carbon monoxide with high activity and high selectivity can be realized by virtue of the special unsaturated coordination state of the transition metal monatomic. Furthermore, reliance on the use of sacrificial agents to overcome photo-oxidation/photo-corrosion of the catalyst is avoided due to the stability of the defect site anchored transition metal monoatomic. Therefore, the preparation method has low cost and simple process, and has a promising prospect in practical application.

In the preparation method of the transition metal monatomic catalyst, zirconium and transition metal jelly are used as precursors, and the preparation of defect site zirconium oxide and the anchoring of transition metal monatomics on the surface of the defect site zirconium oxide are realized by a low-temperature and high-temperature treatment one-step method. The preparation method has universality and can be used for preparing various transition metal monoatomic catalysts, and the preparation of Zn monoatomic catalysts, Fe monoatomic catalysts, Co monoatomic catalysts, Ni monoatomic catalysts and Cu monoatomic catalysts is realized through the method. In addition, the preparation method has low cost and simple process and can be used for large-scale production.

The catalyst provided by the invention has higher selectivity and generation activity of carbon monoxide products in the application of preparing carbon monoxide by photocatalytic carbon dioxide reduction.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Fig. 1 shows an XRD spectrum of the Ni monatomic catalyst obtained in example 1 of the present invention.

FIG. 2 shows an EPR diagram of a Ni monatomic catalyst obtained in example 1 of the invention.

FIG. 3 shows an EPR chart of a defective site zirconia obtained in example 1 of the present invention.

Fig. 4 shows a TEM image of the Ni monatomic catalyst obtained in example 1 of the present invention.

FIG. 5 shows the HAADF-STEM diagram of the Ni monatomic catalyst obtained in example 1 of the present invention.

Fig. 6 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni monatomic catalyst obtained in example 1 of the present invention.

Fig. 7 shows XRD patterns of Ni monatomic catalysts synthesized in examples 2 to 4.

FIG. 8 is a graph showing the photocatalytic carbon dioxide reduction performance of Ni monatomic catalysts obtained in examples 2 to 4 of the present invention.

Fig. 9 shows the Ni monoatomic XRD patterns synthesized in example 1 and example 5.

Fig. 10 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni monatomic catalyst obtained in example 5 of the present invention.

Fig. 11 shows an XRD pattern of the monatomic catalyst synthesized in example 6.

Fig. 12 is a graph showing photocatalytic carbon dioxide reduction performance of Ni monatomic catalysts obtained in examples 6 and 7 of the present invention.

FIG. 13 is a transmission electron micrograph showing spherical aberration corrections of the Cu, Zn, Fe and Co monatomic catalysts obtained in examples 8 to 11. FIG. 14 shows XRD patterns of the monatomic catalysts obtained in examples 8 to 11.

FIG. 15 is a graph showing the photocatalytic carbon dioxide reduction performance of Ni monatomic catalysts obtained in examples 8 to 11 of the present invention.

Fig. 16 shows an XRD pattern of the Ni monatomic catalyst obtained in comparative example 1.

Fig. 17 shows an XRD pattern of the catalyst obtained in comparative example 2.

Detailed Description

In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. Similar components in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

Example 1

A method for anchoring transition metal Ni monatomic photocatalyst by zirconia comprises the following steps:

1) weighing 0.53mmol of nickel nitrate and 6.75mmol of zirconium nitrate, adding into a beaker, adding 100mL of deionized water, and magnetically stirring until the nickel nitrate and the zirconium nitrate are completely dissolved to obtain a clear and transparent solution; in the step, zirconium oxide with defect sites is obtained after the preparation is finished without adding nickel nitrate;

2) after the reaction was complete, 15mmol (NH) was weighed₄)₂CO₃Dissolving the mixture in 100mL of deionized water completely, and then adding the obtained clear and transparent solution to generate a flocculent product;

3) continuously stirring the obtained flocculent product for 5 hours under the condition of 70 ℃ water bath to finally obtain a gelatinous product;

4) the obtained gel product is processed at 5 deg.C/min in air atmosphere^-1Raising the temperature to 600 ℃ at the heating rate, keeping the temperature for 2 hours, and naturally cooling to room temperature to obtain a powdery product;

5) and (3) washing the obtained powdery product respectively with dilute hydrochloric acid and deionized water for three times until the washing liquid is completely colorless and transparent when poured out, centrifuging and drying in a 60 ℃ oven for 2 hours to obtain the Ni single-atom catalyst, which is marked as Ni-SAC, wherein the load of Ni atoms in the Ni-SAC is 1.8 wt% by an ICP-AES method.

The XRD spectrum, EPR pattern of defect site zirconia, EPR pattern, TEM pattern and HAADF-STEM pattern of the catalyst are shown in the following figures 1-5.

The catalyst is used for preparing carbon monoxide by photocatalytic carbon dioxide reduction:

50mL of CO was added under a pressure of 0.08MPa₂And the mixed gas of water vapor and 10mg of the catalyst are subjected to full solar spectrum illumination for 2 hours, and the yield and the like of the obtained product are tested by a gas chromatography external standard method. Fig. 6 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni monatomic catalyst obtained in example 1 of the present invention. As can be seen from the figure, the Ni monatomic catalyst obtained in example 1 is used for photocatalytic CO₂After reduction, CO is obtained, the generation rate of the CO is 11.8 mu mol/g.h, and the product selectivity of the CO is 92.5 percent (the rest is H)₂Selectivity of (ii).

Examples 2 to 4

Example 1 was repeated with the only difference that nickel nitrate was changed to nickel chloride, nickel acetate, nickel sulfate. The obtained Ni monatomic catalyst was not significantly different from the monatomic catalyst obtained in example 1, and it was found that the Ni atom-supporting amount was 3% by weight in the Ni-SAC by the ICP-AES method.

FIG. 7 is an XRD pattern of Ni monatomic catalysts synthesized in examples 2 to 4, from which it can be seen that Ni monatomic catalysts synthesized using nickel chloride, nickel acetate, and nickel sulfate all showed only a zirconia peak and did not show a peak of Ni or its compound. This also indicates that the anionic species in the transition metal salt has no significant effect on the formation of the monatomic catalyst.

The catalysts prepared in examples 2 to 4 were used in the photocatalytic reduction of carbon dioxide to carbon monoxide:

under a pressure of 0.08MPa, 10mL of CO₂Mixed gas of water vapor and 50mg of the catalyst, and is irradiated by full solar spectrum lightAnd 5h, testing the yield and the like of the obtained product by adopting a gas chromatography external standard method.

FIG. 8 is a graph showing the photocatalytic carbon dioxide reduction performance of Ni monatomic catalysts obtained in examples 2 to 4 of the present invention. As can be seen from the figure, the Ni monatomic catalysts obtained in examples 2 to 4 were used in the photocatalysis of CO₂CO is obtained after reduction, and the generation rates of the CO are respectively 5.2 mu mol/g.h, 6.1 mu mol/g.h and 3.4 mu mol/g.h; the product selectivities of CO were 95.2%, 90.3%, 98.4%, respectively (balance H)₂Selectivity of (ii).

Example 5

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

Fig. 9 shows the XRD patterns of Ni monoatomic atoms synthesized in example 1 and example 5. In the figure, the synthesized Ni single atoms only have the zirconium oxide peak, and no metal simple substance or compound peak is appeared. This indicates that the zirconium salt type has no significant effect on the formation of the monatomic catalyst.

The catalyst prepared in example 5 was used in the photocatalytic carbon dioxide reduction to carbon monoxide:

under 0.05MPa, 100mL of CO was added₂And the mixed gas of water vapor and 100mg of the catalyst are subjected to full-solar spectrum illumination for 2 hours, and the yield and the like of the obtained product are tested by a gas chromatography external standard method.

Fig. 10 is a graph showing the photocatalytic carbon dioxide reduction performance of the Ni monatomic catalyst obtained in example 5 of the present invention. As can be seen from the figure, the Ni monatomic catalyst obtained in example 5 is used for photocatalytic CO₂After reduction, CO is obtained, the generation rate of the CO is 9.5 mu mol/g.h, and the product selectivity of the CO is 88.4 percent (the balance is H)₂Selectivity of (ii).

Examples 6 to 7

Example 1 was repeated with the only difference that (NH)₄)₂CO₃The addition was changed to 20mmol and 30mmol, the resulting catalysts were designated as NiN20 and NiN30, both catalysts synthesizedIs a single atom catalyst.

Fig. 11 shows an XRD pattern of the monatomic catalyst synthesized in example 6. Only two broad peaks corresponding to zirconia appear in the figure, and no peaks of the metal or its compound appear, indicating that both catalysts synthesized are monatomic catalysts.

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

under 0.01MPa, 100mL of CO₂And the mixed gas of water vapor and 50mg of the catalyst are subjected to full solar spectrum illumination for 5 hours, and the yield and the like of the obtained product are tested by a gas chromatography external standard method.

FIG. 12 is a graph showing the photocatalytic carbon dioxide reduction performance of Ni monatomic catalysts obtained in examples 6 to 7 of the present invention. As can be seen from the figure, the Ni monatomic catalysts obtained in examples 6 to 7 are used for photocatalytic CO₂CO is obtained after reduction, and the generation rates of the CO are respectively 3.2 mu mol/g.h and 4.4 mu mol/g.h; the product selectivity of CO was 60.9%, 54.2%, respectively (balance H)₂Selectivity of (ii).

Examples 8 to 11

Example 1 was repeated, with the only difference that the metal salts were changed to Cu, Zn, Fe, Co salts. The obtained catalyst is a single atom catalyst. Specifically, the spherical aberration corrected transmission electron micrographs of these 4 metal monoatomic catalysts are shown in fig. 13, with the dark spots marked with metal monoatomic atoms. It can be found that the transition metal is dispersed in the form of a single atom on the surface and inside of the zirconia. The corresponding XRD pattern is shown in FIG. 14, and only the zirconium oxide peak appears, and no metal simple substance or compound peak appears. Examples 8-11 also illustrate the wide versatility of the transition metal monatomic catalyst synthesis process.

The catalysts prepared in examples 8 to 11 were used in the photocatalytic reduction of carbon dioxide to carbon monoxide:

40mL of CO was added under a pressure of 0.08MPa₂And the mixed gas of water vapor and 10mg of the catalyst are subjected to full-solar spectrum illumination for 4 hours, and the yield and the like of the obtained product are tested by a gas chromatography external standard method.

FIG. 15 is a graph showing the photocatalytic carbon dioxide reduction performance of Ni monatomic catalysts obtained in examples 8 to 11 of the present invention. As can be seen from the figure, the Ni monatomic catalysts obtained in examples 8 to 11 are used for photocatalytic CO₂CO is obtained after reduction, and the generation rates of the CO are respectively 8.8 mu mol/g.h, 10.4 mu mol/g.h, 6.5 mu mol/g.h and 9.2 mu mol/g.h; the product selectivities of CO were 87.1%, 91.5%, 60.5%, 72.3%, respectively (balance H)₂Selectivity of (ii).

Comparative example 1

Example 1 was repeated with the only difference that zirconium nitrate was changed to cerium nitrate. The resulting catalysts are all capable of forming monatomic catalysts. The loading was only 0.5 wt% as determined by ICP-AES testing.

Fig. 16 shows an XRD pattern of the Ni monatomic catalyst obtained in comparative example 1 of the present invention. It can be seen that only the peak of cerium oxide appears, and no peak of the Ni metal simple substance or compound appears.

Comparative example 2

Example 1 was repeated with the only difference that zirconium nitrate was changed to titanium tetrachloride. The resulting catalysts are all capable of forming monatomic catalysts.

Fig. 17 shows an XRD pattern of the Ni monatomic catalyst obtained in comparative example 1 of the present invention. It can be seen that only the peak of titanium oxide appears, and no peak of the Ni metal simple substance or compound appears.

Comparative example 3

Example 6 was repeated except that the temperature increase rate in step 4) was changed to 1 ℃ min^-1And the rest conditions are unchanged, and the catalyst is prepared.

The catalyst was used in the photocatalytic carbon dioxide reduction to carbon monoxide using the application conditions as in example 6, with the result that: the formation rate of CO was 2.7. mu. mol/g.h, and the product selectivity of CO was 50.1% (the remainder being H)₂Selectivity of (ii).

Comparative example 4

Example 6 was repeated, except that the temperature increase rate in step 4) was changed to 12 ℃ min^-1And the rest conditions are unchanged, and the catalyst is prepared.

By following the actual implementationApplication conditions of example 6 the catalyst was used in the photocatalytic reduction of carbon dioxide to carbon monoxide, with the result that: the formation rate of CO was 2.6. mu. mol/g.h, and the product selectivity of CO was 51.3% (the remainder being H)₂Selectivity of (ii).

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.

Claims

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:

adding an alkaline solution to obtain a reaction solution;

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: