A CrN-supported Pt single-atom site catalyst, preparation and application

Abstract

The present invention discloses a CrN-supported Pt single-atom site catalyst, its preparation and application. In the present invention, a novel Pt single-atom site catalyst is prepared with CrN as the support and single-atom Pt as the active component. Among them, CrN has excellent electrical conductivity, good acid resistance and structural stability, and is an ideal support for the Pt single-atom catalyst used in the electrocatalytic oxidation reaction of hydrogen. Moreover, due to the strong interaction between Pt atoms and the large specific surface area of the prepared CrN, the atomic-level uniform distribution of Pt and the improvement of the loading amount are ensured, so that the catalyst not only has high catalytic performance but also has the ability to resist CO poisoning. The problem of particle agglomeration during the formation of CrN is effectively alleviated by the method of silica coating. This method has universality and can be used to prepare various nanomaterials of small-sized transition metal nitrides, providing conditions for improving the performance of the catalyst after loading single-atom Pt.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation. More specifically, it relates to a CrN-supported Pt single-atom site catalyst, its preparation and application. Background Art

[0002] Proton exchange membrane fuel cells are energy conversion devices with high energy conversion efficiency and environmental friendliness, and are one of the key technologies for future hydrogen energy utilization. Pt has excellent anodic hydrogen electrocatalytic oxidation reaction performance. However, the high cost of Pt and its easy deactivation due to poisoning by trace amounts of carbon monoxide (CO) gas (<10 ppm) have become bottlenecks restricting the large-scale application of fuel cells. Commercial hydrogen mainly comes from steam reforming, but CO inevitably exists in the reforming products, thus affecting the catalytic performance. Purifying low-cost crude hydrogen to meet the requirements of fuel cells will undoubtedly increase the complexity and cost of equipment. Developing catalysts with high activity, good stability and resistance to CO poisoning is another practical way to solve the above problems.

[0003] Single-atom site catalysts have an atomic utilization rate close to 100% and excellent activity, and are considered potential materials in many fields. To ensure the dispersion of single-atom Pt, the Pt loading in previously reported single-atom site Pt catalysts is usually less than 1 wt%, which will reduce the overall activity of the catalyst. In addition, as a catalyst for electrocatalytic reactions, a highly conductive support is also needed to stabilize atomically dispersed Pt. Therefore, synthesizing a highly loaded Pt single-atom site catalyst stabilized by a conductive support is challenging.

[0004] Therefore, it is of great significance to develop a new type of Pt single-atom site catalyst with good stability, high Pt loading and resistance to CO poisoning. Summary of the Invention

[0005] The first object of the present invention is to provide a CrN-supported Pt single-atom site catalyst. This catalyst has good stability and acid resistance, high Pt loading, and excellent carbon monoxide poisoning resistance.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned CrN-supported Pt single-atom site catalyst.

[0007] The third object of the present invention is to provide an application of the above-mentioned CrN-supported Pt single-atom site catalyst in the hydrogen electrocatalytic oxidation reaction.

[0008] To achieve the above first object, the technical solution provided by the present invention is as follows:

[0009] The present invention provides a CrN-supported Pt single-atom site catalyst. The catalyst uses single-atom Pt as the active component and CrN as the carrier, and the single-atom Pt is atomically dispersed on the CrN.

[0010] In the present invention, a novel CrN-supported Pt single-atom site catalyst is prepared using CrN as the carrier and atomically dispersed Pt as the active component. Among them, CrN has excellent electrical conductivity, good acid resistance, and structural stability, and is an ideal carrier for Pt single-atom catalysts used in the electrocatalytic oxidation reaction of hydrogen. Moreover, due to the strong interaction between Pt atoms and the large specific surface area of the prepared CrN, the formation tendency of Pt clusters and Pt nanoparticles is inhibited, achieving an atomic-level uniform distribution of Pt and an increase in the loading amount, making the catalyst not only have high catalytic performance but also have the ability to resist CO poisoning.

[0011] Furthermore, the CrN-supported Pt single-atom site catalyst contains 0.68 - 2.56 wt% of Pt. Exemplarily, the catalyst contains Pt of 0.68 - 1.75 wt%, 1 - 2.56 wt%, 1.5 - 2.56 wt%, 1.75 - 2.56 wt%, 2 - 2.56 wt%, etc.

[0012] To achieve the above second object, the technical solution provided by the present invention is:

[0013] The present invention provides a method for preparing the above-mentioned CrN-supported Pt single-atom site catalyst, which is characterized by including the following steps:

[0014] Provide zinc-chromium hydrotalcite coated with silica, denoted as substance A;

[0015] Perform heat treatment on substance A and etch away the silica to obtain substance B;

[0016] Deposit single-atom Pt on substance B by atomic layer deposition to obtain the catalyst.

[0017] It should be noted that the present invention effectively alleviates the problem of particle agglomeration during the formation of CrN by coating with silica, which is beneficial to the formation of small-sized CrN and increases its specific surface area. The particle size of the CrN is 6 - 20 nm, and the specific surface area is 50 - 80 m 2 g -1 , and this method has universality and can be used to prepare various nano materials of small-sized transition metal nitrides, providing conditions for improving the catalytic performance and CO tolerance of the catalyst after loading single-atom Pt.

[0018] Furthermore, the preparation of substance A includes the following steps:

[0019] Disperse the zinc chromium hydrotalcite in a solution containing tetraethyl orthosilicate, stir for 1 - 12 h, centrifuge, and dry to obtain Substance A.

[0020] In a specific embodiment, in order to better achieve the effect of uniformly coating zinc chromium hydrotalcite nanosheets with silica, the mixed solution of the above zinc chromium hydrotalcite and tetraethyl orthosilicate can be ultrasonicated for 5 minutes before stirring.

[0021] Furthermore, the preparation of the zinc chromium hydrotalcite includes the following steps:

[0022] Drop the alkali solution into the aqueous solution containing zinc source and chromium source, stir at 60 - 80 °C for 18 - 24 h to obtain zinc chromium hydrotalcite. In the initial stage of the above preparation process of zinc chromium hydrotalcite, the addition method of the alkali solution is to drop it drop by drop into the water containing zinc source and chromium source under stirring. Among them, the zinc source is selected from one or two of zinc chloride or zinc nitrate; the chromium source is selected from one or two of chromium chloride or chromium nitrate, and the alkali solution is a mixed aqueous solution of sodium hydroxide and anhydrous sodium carbonate.

[0023] Furthermore, the preparation of Substance B includes the following steps:

[0024] Heat-treat Substance A in an NH₃ atmosphere to obtain CrN coated with silica, and then etch to remove the silica to obtain Substance B.

[0025] The preparation of CrN usually uses chromium oxide as a precursor and nitriding at a high temperature (>800 °C) in an NH₃ atmosphere. This process will inevitably lead to particle agglomeration and sintering. In the preparation method provided by the present invention, the stable silica coated on the outer layer of zinc chromium hydrotalcite nanosheets and the sacrificial template effect of zinc components can effectively slow down particle agglomeration, thereby obtaining CrN with smaller size and larger specific surface area. Due to the advantages of small size and large specific surface area of this CrN, when ensuring the atomic-level uniform distribution of single-molecule Pt, its loading amount can be further improved.

[0026] Furthermore, the heat-treatment conditions are to heat up to 1000 - 1100 °C at a heating rate of 5 °C / min in an NH₃ atmosphere, keep warm for 8 - 10 h, and then naturally cool to room temperature in an N₂ atmosphere after completion.

[0027] Furthermore, the etching conditions are: soak in an aqueous solution of strong acid or strong base for 1 - 2 h, then wash with distilled water and ethanol, and dry; among them, the mass fraction of the aqueous solution of strong acid or strong base is 5 - 60%; preferably, the strong acid is selected from hydrofluoric acid; preferably, the strong base is selected from sodium hydroxide or potassium hydroxide; preferably, the drying temperature is 40 - 80 °C and the time is 2 - 24 h.

[0028] Furthermore, in the atomic layer deposition method, a closed cavity is used as the reactor for atomic layer deposition. Trimethyl(methylcyclopentadienyl)platinum, ozone, and high-purity nitrogen gas (99.999%) are used as the Pt source, oxidant, and carrier gas respectively to deposit Pt on the substance B. Trimethyl(methylcyclopentadienyl)platinum is heated to 60 - 70 °C to provide a suitable vapor pressure, and the pulse is 0.7 - 1 s. The Pt loading is regulated by changing the number of cycles of cyclic deposition. In the present invention, the number of cycles of cyclic deposition is controlled within 2 - 10 complete cycles to ensure the dispersion of single-atom Pt in the catalyst.

[0029] To achieve the above third objective, the present invention provides an application of the Pt single-atom site catalyst supported by CrN as described above in the hydrogen electrocatalytic oxidation reaction.

[0030] The beneficial effects of the present invention are as follows:

[0031] In the present invention, a novel CrN-supported Pt single-atom site catalyst is prepared with CrN as the carrier and single-atom Pt as the active component. Among them, CrN has excellent electrical conductivity, good acid resistance, and structural stability, and is an ideal carrier for the Pt single-atom catalyst in the hydrogen electrocatalytic oxidation reaction. Moreover, due to the strong interaction between Pt atoms and the large specific surface area of the prepared CrN, the formation tendency of Pt clusters and Pt nanoparticles is inhibited, realizing the atomic-level uniform distribution of Pt and the improvement of the loading amount, making the Pt single-atom site catalyst not only have high catalytic performance but also have the ability to resist CO poisoning.

[0032] In the preparation method of the Pt single-atom site catalyst provided by the present invention, the problem of particle agglomeration during the formation of CrN is effectively alleviated by the method of silica coating. This method has universality and can be used to prepare various nanomaterials of small-sized transition metal nitrides, providing conditions for realizing the excellent performance of the catalyst after loading single-atom Pt. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The following further elaborates on the specific embodiments of the present invention in conjunction with the drawings.

[0034] Figure 1 Shows the powder diffraction (XRD) pattern of the catalyst obtained in Example 1.

[0035] Figure 2 Shows the transmission electron microscopy (TEM) image of the catalyst obtained in Example 1.

[0036] Figure 3 Shows the aberration-corrected transmission electron microscopy (HAADF-STEM) image of the catalyst obtained in Example 1.

[0037] Figure 4 Show the TEM images of the catalyst obtained in Example 2.

[0038] Figure 5 Show the XRD patterns of the catalysts obtained in Example 3 and Example 4.

[0039] Figure 6 Show the TEM images of the catalyst obtained in Comparative Example 1.

[0040] Figure 7 Show the TEM images of the catalyst obtained in Comparative Example 2.

[0041] Figure 8 Show the TEM images of the catalysts obtained in Example 5 and Example 6.

[0042] Figure 9 Show the HAADF-STEM images of the catalyst obtained in Example 7.

[0043] Figure 10 Show the XRD patterns of the catalyst obtained in Comparative Example 3.

[0044] Figure 11 Show the TEM images of the catalyst obtained in Comparative Example 4.

[0045] Figure 12 Show the TEM images of the catalyst obtained in Comparative Example 5.

[0046] Figure 13 Show the hydrogen electrocatalytic oxidation reaction activity images of the catalyst obtained in Example 1 in 0.1 M HClO4 solution.

[0047] Figure 14 Show the hydrogen electrocatalytic oxidation reaction stability images of the catalyst obtained in Example 1 in 0.1 M HClO4 solution.

[0048] Figure 15 Show the anti-CO poisoning performance images of the catalyst obtained in Example 1 in 0.1 M HClO4 solution.

[0049] Figure 16 Show the anti-CO poisoning performance images of the catalyst obtained in Comparative Example 5 in 0.1 M HClO4 solution. Detailed implementation manners

[0050] To illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and the accompanying drawings. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0051] In the present invention, the preparation method is a conventional method unless otherwise specified. The raw materials used can be obtained from public commercial channels unless otherwise specified.

[0052] Example 1

[0053] 1) Weigh 11.88 g of zinc nitrate hexahydrate, 8.00 g of chromium nitrate nonahydrate, and 780 mg of cetyltrimethylammonium bromide and dissolve them in 30 mL of deionized water to form solution A. Then, ultrasonically dissolve 10.6 g of anhydrous sodium carbonate and 4.8 g of sodium hydroxide in 40 mL of deionized water to form solution B. Solution B is added dropwise to solution A under stirring, and then aged in an oil bath at 60 °C for 18 h to form zinc-chromium hydrotalcite.

[0054] 2) Disperse the above zinc-chromium hydrotalcite completely by ultrasound in 400 mL of aqueous solution containing 780 mg of cetyltrimethylammonium bromide, then inject 7.5 mL of tetraethyl orthosilicate solution, ultrasonicate for 5 minutes, and then stir for 8 h. After stirring, centrifuge and dry to obtain zinc-chromium hydrotalcite coated with silica.

[0055] 3) Heat-treat the zinc-chromium hydrotalcite coated with silica at 1000 °C in an NH3 atmosphere for 8 hours and cool to room temperature in an N2 atmosphere. Then, etch the SiO2 shell with a 10% by mass hydrofluoric acid solution, wash with distilled water 3 times, and dry to obtain CrN with an average particle size of 8.6 nm and a specific surface area of 75.7 m 2 g -1 ².

[0056] 4) Deposit single-atom Pt on the surface of CrN by atomic layer deposition: Use a closed cavity as the reactor for atomic layer deposition, and use trimethyl(methylcyclopentadienyl)platinum, ozone, and high-purity nitrogen (99.999%) as the Pt source, oxidant, and carrier gas, respectively. Trimethyl(methylcyclopentadienyl)platinum is heated to 60 °C, with a pulse of 0.7 s and 5 cycles, to obtain the final product Pt single-atom site catalyst (named Pt1 / CrN), where Pt accounts for 1.75 wt% of the mass of the catalyst.

[0057] Figure 1 XRD pattern of Pt1 / CrN prepared in Example 1.

[0058] Figure 2 TEM image of Pt1 / CrN prepared in Example 1.

[0059] Figure 3 HAADF-STEM image of Pt1 / CrN prepared in Example 1.

[0060] From Figure 1It can be seen that only the diffraction peaks of CrN appear in the XRD pattern of the synthesized Pt1 / CrN, and no characteristic diffraction peaks of Pt nanoparticles are observed. The TEM image shows no obvious Pt nanoparticles, which proves the formation of single-atom Pt. Figure 3 The HAADF-STEM image of Figure 3 further proves the existence of single atoms, and the single-atom Pt is uniformly dispersed on the surface of CrN.

[0061] Example 2

[0062] Repeat Example 1, except that zinc nitrate hexahydrate and chromium nitrate nonahydrate are replaced with zinc chloride and chromium chloride, respectively. The addition amount of zinc chloride is 5.44 g, and the addition amount of chromium chloride is 5.33 g. As can be seen from Figure 4 the TEM image of the final product, the types of zinc and chromium sources have no effect on the morphology of the product, and a Pt single-atom site catalyst supported on small-sized CrN can still be obtained.

[0063] Examples 3 - 4

[0064] Repeat Example 1, except that the aging time during the synthesis of zinc-chromium hydrotalcite is changed to 20 h and 24 h. Figure 5 In the XRD of the final product, only the diffraction peaks of CrN appear, and no diffraction peaks of Pt nanoparticles are observed, indicating that the length of the aging time does not affect the composition of the final product.

[0065] Comparative Example 1

[0066] Repeat Example 1, except that the temperature of NH3 heat treatment is changed to 1100 °C. As can be seen from Figure 6 the TEM image of the final product, the morphology of the final product hardly changes after increasing the heat treatment temperature, and a Pt single-atom site catalyst supported on CrN can still be formed.

[0067] Comparative Example 2

[0068] Repeat Example 1, except that the heat treatment time is changed to 10 h. Figure 7 In the TEM image of the final product, the morphology is almost the same as that of Pt1 / CrN, indicating that extending the heat treatment time can also obtain a Pt single-atom site catalyst supported on small-sized CrN.

[0069] Examples 5 - 6

[0070] Repeat Example 1, except that the 10% hydrofluoric acid solution by mass is replaced with a 2 M sodium hydroxide or potassium hydroxide solution. Figure 8 The TEM image of the final product is shown, indicating that the type of etchant has no effect on the morphology of the final product, and the silica can be completely etched.

[0071] Example 7

[0072] Repeat Example 1, except that the number of cycles in the atomic layer deposition process is changed to 2 cycles, and the other conditions remain unchanged, to prepare a catalyst. Figure 9 The HAADF-STEM image of the obtained catalyst is shown, indicating that reducing the number of cycles to 2 cycles can still form a Pt single-atom site catalyst supported on CrN.

[0073] Comparative Example 3

[0074] Repeat Example 1, except that the heat treatment temperature is changed to 800 °C. From Figure 10 the XRD pattern of the prepared catalyst, it can be seen that under the heat treatment conditions of 800 °C, the zinc-chromium hydrotalcite is not completely nitrided to CrN, and the XRD pattern contains characteristic diffraction peaks of both CrN and zinc chromate.

[0075] Comparative Example 4

[0076] Repeat Example 1, except that the CrN support used in the atomic layer deposition is replaced with commercial carbon black (Ketjenblack EC-300J, specific surface area is 793 m 2 g -1 ). Figure 11 The TEM image of the prepared catalyst is shown. It can be clearly seen that the Pt supported on the commercial carbon black exists in the form of nanoparticles and single atoms, indicating that CrN has an advantage in fixing and dispersing Pt single atoms.

[0077] Comparative Example 5

[0078] Platinum nanoparticles supported on a CrN support were synthesized by the ethylene glycol reduction method. Specifically, 40 mg of CrN was first dispersed in a mixed solution of 27 mL of ethylene glycol and 13.5 mL of deionized water and sonicated for 15 minutes. Subsequently, 6 μL of an aqueous solution of chloroplatinic acid (1 g mL -1 ) was added to the above solution and stirred at room temperature for 18 hours. After completion, the above mixed system was placed in an oil bath preheated to 120 °C and refluxed for 2 hours. After cooling to room temperature, centrifuged, and then the sediment was washed 4 times with deionized water and once with ethanol, and finally dried at 60 °C. Figure 12 The TEM image of the obtained product is shown, and obvious spherical Pt nanoparticles can be seen.

[0079] Example 8

[0080] An application of a Pt single-atom site catalyst supported on CrN in the electrocatalytic oxidation reaction of hydrogen includes the following steps:

[0081] 1) Take 5 mg of the catalyst obtained in Example 1 and 2 mg of commercial carbon black and dissolve them in 1 mL of a mixed solution of isopropanol, distilled water, and Nafion solution (wherein the mixed solution includes 390 μL of isopropanol, 600 μL of distilled water, and 10 μL of Nafion), and ultrasonicate for 0.5 hours to form a uniform slurry.

[0082] 2) Take 10 μL of the above slurry and drop it onto a rotating disk electrode, and dry it at room temperature until a uniform thin film is formed. Then, it is tested in a solution of 0.1 mol L -1 HClO4 saturated with hydrogen, and the test voltage range is 0 - 0.6 V (relative to the standard hydrogen electrode). The test results are as Figure 13 , and the synthesized Pt single-atom site catalyst shows excellent electrocatalytic oxidation performance for hydrogen, and its limiting current can reach 3.02 mA cm -2 . The kinetic current density at an overpotential of 20 mV is normalized to the mass of Pt to obtain the mass activity. The mass activity of Pt1 / CrN is 2228 A g Pt -1 .

[0083] Example 9

[0084] A method for applying a Pt single-atom site catalyst supported on CrN in the electrocatalytic oxidation reaction of hydrogen, comprising the following steps:

[0085] 1) Take 5 mg of the catalyst obtained in Example 1 and 2 mg of commercial carbon black and dissolve them in 1 mL of a mixed solution of isopropanol, distilled water, and Nafion solution (wherein the mixed solution includes 390 μL of isopropanol, 600 μL of distilled water, and 10 μL of Nafion), and ultrasonicate for 0.5 hours to form a uniform slurry. Subsequently, take 10 μL of the slurry and drop it onto a rotating disk electrode, and dry it until a uniform thin film is formed.

[0086] 2) Insert the rotating disk electrode coated with the catalyst into a 0.1 M HClO4 solution saturated with hydrogen for chronoamperometry testing. The voltage of the working electrode is maintained at 0.1 V (relative to the standard hydrogen electrode) for 20000 seconds, and the rotation speed is 1600 rpm. From Figure 14 the test results, it can be seen that during the chronoamperometry testing, the current can remain stable, demonstrating the excellent stability of the Pt single-atom site catalyst in the hydrogen oxidation reaction.

[0087] Example 10

[0088] A method for applying a Pt single-atom site catalyst supported on CrN in the electrocatalytic oxidation reaction of hydrogen, comprising the following steps:

[0089] 1) Take 5 mg of the sample catalyst obtained in Example 1 and 2 mg of commercial carbon black and dissolve them in 1 mL of a mixed solution of isopropanol, distilled water, and Nafion solution (wherein, the mixed solution includes 390 μL of isopropanol, 600 μL of distilled water, and 10 μL of Nafion), and ultrasonicate for 0.5 hour to form a homogeneous slurry. Subsequently, take 10 μL of the slurry and drop it onto a rotating disk electrode, and dry it until a uniform thin film is formed.

[0090] 2) Pass hydrogen gas containing 1000 ppm CO gas into 0.1 M HClO4 solution to form a saturated solution. Subsequently, place the above rotating disk electrode into the solution as a working electrode for testing. The voltage range of the test is 0 - 0.6 V (relative to the standard hydrogen electrode), and the rotation speed is 1600 rpm. Figure 15 The linear sweep voltammogram of the Pt single - atom site catalyst in a CO / H2 mixed gas containing 1000 ppm CO is shown. The catalyst still has good hydrogen oxidation reaction performance, verifying that the Pt single - atom site catalyst supported by CrN has excellent CO - poisoning resistance.

[0091] Comparative Example 6

[0092] Repeat Example 10, with the only difference being that the catalyst obtained in Example 1 is replaced with the catalyst obtained in Comparative Example 5. Figure 16 The linear sweep voltammogram of the catalyst obtained in Comparative Example 5 in a CO / H2 mixed gas containing 1000 ppm CO is shown. It is found that the Pt nanoparticle catalyst supported by CrN has almost no hydrogen oxidation performance in the presence of 1000 ppm CO gas, indicating that replacing single - atom Pt with Pt nanoparticles significantly reduces its CO - poisoning resistance compared to the Pt single - atom site catalyst.

[0093] Obviously, the above - mentioned embodiments of the present invention are merely examples for clearly explaining the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, based on the above description, other different forms of changes or variations can be made. It is impossible to list all the implementation manners here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A CrN-supported Pt single-atom site catalyst, characterized in that, The catalyst uses single-atom Pt as the active component and CrN as the carrier, and the single-atom Pt is atomically dispersed on CrN; The Pt single-atom site catalyst is prepared according to the following steps: Provide zinc-chromium hydrotalcite coated with silica, denoted as substance A; Heat-treat substance A and etch away silica to obtain substance B; Deposit single-atom Pt on substance B by atomic layer deposition to obtain the product; The preparation of substance B includes the following steps: Heat-treat substance A in an NH3 atmosphere to obtain CrN coated with silica, and then etch away silica to obtain substance B.

2. The CrN-supported Pt single-atom site catalyst according to claim 1, wherein The catalyst contains 0.68 - 2.56 wt% of Pt.

3. A method for preparing a CrN-supported Pt single-atom site catalyst as described in claim 1 or 2, characterized in that, Including the following steps: Provide zinc-chromium hydrotalcite coated with silica, denoted as substance A; Heat-treat substance A and etch away silica to obtain substance B; Deposit single-atom Pt on substance B by atomic layer deposition to obtain the product; The preparation of substance B includes the following steps: Heat-treat substance A in an NH3 atmosphere to obtain CrN coated with silica, and then etch away silica to obtain substance B.

4. The preparation method according to claim 3, wherein The preparation of substance A includes the following steps: Disperse the zinc-chromium hydrotalcite in a solution containing tetraethyl orthosilicate, stir for 1 - 12 h, centrifuge, and dry to obtain substance A.

5. The preparation method according to claim 3, characterized in that, The preparation of the zinc-chromium hydrotalcite includes the following steps: Drop the alkali solution into the aqueous solution containing zinc source and chromium source, stir at 60 - 80 °C for 18 - 24 h to obtain zinc-chromium hydrotalcite.

6. The preparation method according to claim 5, characterized in that, The zinc source is selected from one or two of zinc chloride or zinc nitrate; the chromium source is selected from one or two of chromium chloride or chromium nitrate; the alkali solution is a mixed aqueous solution of sodium hydroxide and anhydrous sodium carbonate.

7. The preparation method according to claim 3, characterized in that, The heat-treatment conditions are: heat up to 1000 - 1100 °C at a heating rate of 5 °C / min in an NH3 atmosphere, hold for 8 - 10 h, and then naturally cool to room temperature in an N2 atmosphere after completion.

8. The preparation method according to claim 3, characterized in that, The etching conditions are: soak in an aqueous solution of strong acid or strong base for 1 - 2 h, then wash with distilled water and ethanol, and dry.

9. The preparation method according to claim 8, wherein The mass fraction of the aqueous solution of strong acid or strong base is 5 - 60%.

10. The preparation method according to claim 8, characterized in that, The strong acid is selected from hydrofluoric acid.

11. The preparation method according to claim 8, wherein The strong base is selected from sodium hydroxide or potassium hydroxide.

12. The preparation method according to claim 8, wherein The drying temperature is 40 - 80 °C and the time is 2 - 24 h.

13. The preparation method according to claim 3, characterized in that, The steps of atomic layer deposition include: Use trimethyl(methylcyclopentadienyl)platinum, ozone, and high-purity nitrogen as the Pt source, oxidant, and carrier gas respectively to deposit Pt on substance B.

14. The preparation method according to claim 13, wherein, In atomic layer deposition, set the heating temperature to 60 - 70 °C, the pulse of trimethyl(methylcyclopentadienyl)platinum to 0.7 - 1 s, and the number of complete cycles of cyclic deposition to 2 - 10.

15. Application of the CrN-supported Pt single-atom site catalyst as described in claim 1 or 2 in the electrocatalytic oxidation reaction of hydrogen.

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