Hollow CoCo-LDH loaded with Au atoms and preparation method and application thereof

Abstract

The present invention belongs to the field of semiconductor technology, and specifically relates to a hollow CoCo-LDH loaded with Au atoms, and a preparation method and application thereof. The present invention provides a hollow CoCo-LDH loaded with Au atoms (CoCo-LDH-Au), in which Au atoms are loaded on the hollow CoCo-LDH in the form of single atoms, so that the hollow CoCo-LDH has a large Au atom utilization efficiency, a clear active center and excellent photocatalytic activity.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a hollow CoCo-LDH loaded with Au atoms and a preparation method and application thereof. Background Art

[0002] Photocatalytic reduction reactions with CO2 as reactant can use solar energy to efficiently convert CO2 into high-value-added chemical products (CO and CH4). Many common semiconductor materials, such as TiO2, g-C3N4, CdS, perovskite and bismuth-based materials, have the potential to be used as photocatalysts to achieve efficient CO2 conversion. However, due to the high recombination rate of photogenerated carriers and insufficient light utilization, the current CO2 reduction efficiency is low, which limits the promotion of CO2 photocatalytic reduction technology.

[0003] Among many semiconductor photocatalysts, layered double hydroxides (LDHs) are a new type of semiconductor photocatalytic material. They have advantages such as unique layered structure and tunable metal cations in the main layer, and are widely studied in the fields of photocatalysis. However, the layered structure of LDHs is easy to stack, the specific surface area is small, the reaction active sites are covered, and the transmission distance of photogenerated electrons and holes increases, resulting in a very low photocatalytic quantum efficiency. Therefore, assembling LDHs nanosheets in a hollow structure will prevent the stacking of the sheet structure and promote the separation of photogenerated electron-hole pairs. On the other hand, loading precious metals on LDHs can effectively improve the photocatalytic activity of LDHs.

[0004] However, existing LDHs loaded with noble metals have problems such as low utilization of noble metal atoms, unclear active centers and still low photocatalytic activity. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of LDHs loaded with precious metals in the prior art, such as low utilization rate of precious metal atoms, unclear active centers and still low photocatalytic activity, thereby providing a hollow CoCo-LDH loaded with Au atoms and its preparation method and application.

[0006] To this end, the present invention provides the following technical solutions.

[0007] In a first aspect, the present invention provides a hollow CoCo-LDH loaded with Au atoms, wherein the Au atoms are loaded on the hollow CoCo-LDH in the form of single atoms.

[0008] In a second aspect, the present invention provides a method for preparing the above-mentioned hollow CoCo-LDH, comprising the following steps:

[0009] S1. Add cobalt nitrate hexahydrate to the ZIF-67 dispersion, and perform a first reaction at 70-90° C. for 20-40 min to obtain a reaction product;

[0010] S2, separating the solid in the reaction product, performing a first washing and a first drying to obtain a hollow CoCo-LDH;

[0011] S3. Take the hollow CoCo-LDH to prepare a CoCo-LDH dispersion, and add chloroauric acid to carry out a second reaction.

[0012] In an optional embodiment, in step S3, the reaction conditions of the second reaction include:

[0013] The reaction temperature is 20-30°C and the reaction time is 50-70 min.

[0014] In an optional embodiment, in step S1, the mass ratio of the ZIF-67 to the cobalt nitrate hexahydrate is 1:(2-4);

[0015] And / or, in step S3, the mass ratio of the hollow CoCo-LDH to the chloroauric acid is 1:(0.01-0.05).

[0016] In an optional embodiment, the preparation method further comprises the step of preparing the ZIF-67:

[0017] S11, weighing cobalt nitrate hexahydrate, dissolving it in water, and adding hexadecyltrimethylammonium bromide to form solution A;

[0018] S12, weigh 2-methylimidazole and dissolve it in water to form solution B;

[0019] S13, pouring the A solution into the B solution, stirring, centrifuging, washing, and drying to obtain the ZIF-67.

[0020] In an optional embodiment, in step S11, the mass ratio of the cobalt nitrate hexahydrate to the hexadecyltrimethylammonium bromide is 1:(0.0083-0.0417);

[0021] And / or, in step S12, the mass ratio of the cobalt nitrate hexahydrate to the 2-methylimidazole is 1:(10-18).

[0022] In an optional embodiment, in step S2, the first drying conditions include: drying temperature of 70-90° C., drying time of 1.5-2.5 h;

[0023] And / or, step S3 further comprises separating the solid in the reaction product of the second reaction and performing a second washing and a second drying operation;

[0024] The second drying conditions include: drying temperature of 70-90° C., and drying time of 1.5-2.5 h.

[0025] In an optional embodiment, the solvent of the ZIF-67 dispersion is ethanol, and the solvent of the CoCo-LDH dispersion is water.

[0026] In a third aspect, the present invention provides the use of the hollow CoCo-LDH or the hollow CoCo-LDH prepared by the above preparation method in the preparation of a photocatalyst.

[0027] In a fourth aspect, the present invention provides the use of the above-mentioned hollow CoCo-LDH or the hollow CoCo-LDH prepared by the above-mentioned preparation method in photocatalytic CO2 reduction.

[0028] The technical solution of the present invention has the following advantages:

[0029] 1. The present invention provides a hollow CoCo-LDH loaded with Au atoms (CoCo-LDH-Au), wherein Au atoms are loaded on the hollow CoCo-LDH in the form of single atoms, so that the hollow CoCo-LDH has a large Au atom utilization efficiency, a clear active center and excellent photocatalytic activity.

[0030] Specifically, the experimental results show that the CoCo-LDH-Au has excellent photocatalytic CO2 reduction performance, and the CO production rate can reach up to 20.3 μmol / g / h, which is 7 times higher than that of CoCo-LDH. The study found that after CoCo-LDH is loaded with single-atom Au, it has good light absorption properties and excellent photogenerated carrier separation capabilities. In addition, the hollow material has good CO2 adsorption capacity, which provides a basis for efficient photocatalytic CO2 reduction performance.

[0031] 2. The preparation method of the hollow CoCo-LDH provided by the present invention uses a metal-organic framework (ZIF-67) as a template, uses cobalt nitrate hexahydrate to carry out an etching reaction at 70-90 ° C for 20-40 minutes to prepare a hollow CoCo-LDH, and then reacts the prepared hollow CoCo-LDH with chloroauric acid to complete the single atom loading of Au atoms on the hollow CoCo-LDH.

[0032] Specifically, when preparing the hollow CoCo-LDH, a higher etching temperature (70-90 ° C) was used to promote the etching speed, combined with a shorter etching time (20-40min), so that the above method can generate thinner sheet CoCo-LDH in a short time. Compared with thicker CoCo-LDH, thinner sheet CoCo-LDH is more likely to lose surface oxygen atoms, thereby forming a hollow CoCo-LDH with oxygen vacancies on the surface. After the hollow CoCo-LDH is contacted with chloroauric acid, the oxygen vacancies on the surface of the material have the ability to reduce, and can self-reduce Au ions to Au atoms in situ at room temperature, thereby preparing a hollow CoCo-LDH loaded with single-atom Au.

[0033] 3. In the preparation method of the hollow CoCo-LDH provided by the present invention, after the CoCo-LDH dispersion is contacted with chloroauric acid, the reaction time is controlled to be 50-70 minutes. The shorter reaction time can prevent the accumulation of Au atoms on the surface of the hollow CoCo-LDH, which is more conducive to the loading of single-atom Au.

[0034] 4. The preparation method of hollow CoCo-LDH provided by the present invention adds hexadecyltrimethylammonium bromide when preparing ZIF-67, and controls the mass ratio of cobalt nitrate hexahydrate and hexadecyltrimethylammonium bromide to be 1:(0.0083-0.0417), so that ZIF-67 with a suitable size (about 500nm) and more reaction sites can be prepared. Experimental studies have found that if the amount of hexadecyltrimethylammonium bromide is too small, the size of ZIF-67 will be too large, which will lead to fewer reaction sites. If the amount of hexadecyltrimethylammonium bromide is too large, the size of ZIF-67 will be too small, which will lead to difficulty in separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 is the XRD pattern of ZIF-67 prepared in Example 1 of the present invention;

[0037] Figure 2 is a scanning electron microscope image (SEM) of ZIF-67 prepared in Example 1 of the present invention;

[0038] Figure 3is the XRD pattern of CoCo-LDH and CoCo-LDH-Au prepared in Example 1 of the present invention;

[0039] Figure 4 are scanning electron microscope images of CoCo-LDH and CoCo-LDH-Au prepared in Example 1 of the present invention; wherein (a) is a scanning electron microscope image of CoCo-LDH, and (b) is a scanning electron microscope image of CoCo-LDH-Au;

[0040] Figure 5 1 is a transmission electron microscope image and element distribution map of CoCo-LDH-Au prepared in Example 1 of the present invention; wherein, (a) is a transmission electron microscope image of CoCo-LDH-Au, (b) is a local enlarged view of (a), (c) is a distribution map of the Co element in CoCo-LDH-Au, and (d) is a distribution map of the Au element in CoCo-LDH-Au;

[0041] Figure 6 This is a spherical aberration electron microscope image of gold single atoms of CoCo-LDH-Au prepared in Example 1 of the present invention; wherein the circled part is a bright spot of metal atoms;

[0042] Figure 7 1 is an electron spin resonance spectrometer (ESR) test graph of CoCo-LDH and CoCo-LDH-Au prepared in Example 1 of the present invention;

[0043] Figure 8 is the UV-visible diffuse reflectance spectra (DRS) of CoCo-LDH and CoCo-LDH-Au prepared in Example 1 of the present invention;

[0044] Fig. 9 This is a photocurrent test graph of CoCo-LDH and CoCo-LDH-Au prepared in Example 1 of the present invention;

[0045] Fig.10 1 is the AC impedance diagram of CoCo-LDH and CoCo-LDH-Au prepared in Example 1 of the present invention;

[0046] Fig.11 It is a photocatalytic CO2 reduction test diagram of the sample (CoCo-LDH-Au-1) of Example 1 in Experimental Example 1 of the present invention, Experimental Example 2, Experimental Example 3 and Experimental Example 4. DETAILED DESCRIPTION

[0047] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0048] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially. Example 1

[0049] Hollow CoCo-LDH loaded with Au atoms (CoCo-LDH-Au) was prepared as follows:

[0050] (1) Weigh 0.12 g of cobalt nitrate hexahydrate and dissolve it in 20 ml of distilled water, then add 0.001 g of hexadecyltrimethylammonium bromide to form solution A; weigh 1.8 g of 2-methylimidazole (C4H6N2) and dissolve it in 20 mL of distilled water, stir to form solution B;

[0051] (2) Pour solution A into solution B and stir at room temperature (25°C) for 20 min. Then centrifuge the resulting solution and collect the purple precipitate, wash it with ethanol three times, and place it in an oven at 80°C for 2 h to obtain ZIF-67.

[0052] (3) Weigh 0.1 g of the ZIF-67 prepared in step (2) and disperse it in 30 ml of anhydrous ethanol to obtain a ZIF-67 dispersion; add 0.3 g of cobalt nitrate hexahydrate to the above dispersion, react in a constant temperature water bath at 80°C for 30 min, centrifuge to obtain a precipitate, wash it with ethanol, put it in an oven, and dry it at 80°C for 2 h to obtain CoCo-LDH;

[0053] (4) Weigh 0.1 g of the CoCo-LDH prepared in step (3) and disperse it in 30 ml of distilled water to form a CoCo-LDH dispersion; weigh 0.001 g of chloroauric acid and add it to the suspension, react at room temperature (25°C) for 60 min, centrifuge and precipitate, wash the precipitate with ethanol, and put it in an oven and dry it at 80°C for 2 h to obtain CoCo-LDH-Au.

[0054] Figure 1: is the XRD pattern of ZIF-67 prepared in this embodiment. It can be seen that the diffraction peak of the sample prepared in this embodiment is consistent with the diffraction peak of ZIF-67, and no other impurity peaks appear, indicating that ZIF-67 is successfully synthesized in this embodiment. At the same time, the sharp peaks indicate good crystallinity.

[0055] Figure 2 The SEM image of ZIF-67 prepared in this example is shown in Figure 2. In order to further study the micromorphology of ZIF-67, a scanning electron microscope was used to characterize the micromorphology of ZIF-67. Figure 2 As can be seen from the figure, ZIF-67 is a cubic structure with a smooth surface and a size of about 500 nm.

[0056] Figure 3 The XRD patterns of CoCo-LDH and CoCo-LDH-Au prepared in this example are shown in the figure. 2+ After etching, the original diffraction peak of ZIF-67 disappeared, and some other characteristic peaks appeared, indicating that ZIF-67 was transformed into other substances. According to the position of the characteristic peaks in the figure, it is consistent with the characteristic peaks of CoCo-LDH reported in the literature. 2+ After etching, ZIF-67 was successfully converted into CoCo-LDH. After reacting with chloroauric acid, the intensity of the diffraction peak of CoCo-LDH decreased, indicating that CoCo-LDH interacted with gold, but no other characteristic peaks appeared, indicating that no gold nanoparticles were formed after loading gold.

[0057] Figure 4 The scanning electron micrographs of CoCo-LDH and CoCo-LDH-Au prepared in this example are shown in Figure 1, where (a) is the scanning electron micrograph of CoCo-LDH and (b) is the scanning electron micrograph of CoCo-LDH-Au. 2+ After etching, the material changed from a smooth cube to a cube composed of nanosheets. The overall morphology of the material did not change after loading with gold, and it still maintained a cubic structure composed of nanosheets.

[0058] Figure 5 The transmission electron microscope image and element distribution map of CoCo-LDH-Au prepared in this embodiment, wherein (a) is a transmission electron microscope image of CoCo-LDH-Au, (b) is a local enlarged view of (a), (c) is a distribution map of the Co element in CoCo-LDH-Au, and (d) is a distribution map of the Au element in CoCo-LDH-Au. It can be seen from the figure that the CoCo-LDH-Au prepared in this embodiment is a hollow structure composed of a large number of lamellar structures, which is consistent with the SEM test results.

[0059] Figure 6 This is a spherical aberration electron microscope image of the gold single atom of CoCo-LDH-Au prepared in this example. From the image, it can be seen that the bright spots of metal atoms at the atomic level are evenly distributed and have a high density, indicating that the gold single atoms have been successfully loaded.

[0060] Figure 7 The electron spin resonance spectrometer (ESR) test diagram of CoCo-LDH and CoCo-LDH-Au prepared in this embodiment shows that there is a strong signal peak for CoCo-LDH, indicating that CoCo-LDH contains abundant oxygen vacancies. After loading gold, the signal peak intensity of oxygen vacancies is significantly reduced, indicating that the oxygen vacancies contained in CoCo-LDH are reducible. Through its own reducing ability, single-atom gold is loaded on CoCo-LDH. This method avoids the conditions of high-temperature calcination or reducing atmosphere (H2) in traditional methods, and provides a safe and efficient new method for the construction of single atoms.

[0061] Figure 8 The UV-visible diffuse reflectance spectra (DRS) of CoCo-LDH and CoCo-LDH-Au prepared in this embodiment. For photocatalysts, the enhancement of light absorption capacity is the basis for improving photocatalytic performance. In order to study the light absorption of the material after loading single-atom gold, the UV-visible diffuse reflectance spectra (DRS) of the material were tested. As can be seen from the figure, CoCo-LDH has light absorption capacity in both ultraviolet and visible light, which is stronger than the traditional TiO2 light absorption capacity. More noteworthy is that after loading single gold atoms, the light absorption capacity of CoCo-LDH-Au is significantly enhanced, indicating that it may have better photocatalytic activity, and there is no peak of Au nanoparticles (at 430 nm), which also indicates that single gold atoms are formed.

[0062] Fig. 9 These are the photocurrent test graphs of CoCo-LDH and CoCo-LDH-Au prepared in this example. Fig.10 The AC impedance diagram of CoCo-LDH and CoCo-LDH-Au prepared in this example. In order to study the effect of single gold atoms on the carrier separation efficiency in CoCo-LDH, the photocurrent test of CoCo-LDH and CoCo-LDH-Au prepared in this example was carried out using an electrochemical workstation. Fig. 9It can be seen from the figure that after loading single gold atoms, the photocurrent intensity of CoCo-LDH-Au is significantly enhanced. The stronger the photocurrent intensity, the higher the carrier separation efficiency of the material. Therefore, after loading single gold atoms, the separation efficiency of photogenerated electron-hole pairs of semiconductor materials is significantly improved, indicating that more electrons and holes will participate in the redox reaction, improving the photocatalytic efficiency. Further AC impedance testing shows that after loading single gold atoms, the impedance ring radius of the material is significantly reduced. Fig.10 This indicates that the migration resistance of the carriers is reduced, and it is easier for them to migrate to the surface of the material and react with the CO2 adsorbed on the surface of the material. Example 2

[0063] CoCo-LDH-Au was prepared according to the method of Example 1, except that the amount of chloroauric acid added in step (4) of this example was 0.003 g. Example 3

[0064] CoCo-LDH-Au was prepared according to the method of Example 1, except that the amount of chloroauric acid added in step (4) of this example was 0.005 g. Example 4

[0065] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (3) of this example, the reaction temperature after adding cobalt nitrate hexahydrate was 70° C. and the reaction time was 40 min. Example 5

[0066] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (3) of this example, the reaction temperature after adding cobalt nitrate hexahydrate was 90° C. and the reaction time was 20 min. Example 6

[0067] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (4) of this example, the reaction time after adding chloroauric acid was 50 min. Example 7

[0068] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (4) of this example, the reaction time after adding chloroauric acid was 70 min. Example 8

[0069] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (3) of this example, the amount of cobalt nitrate hexahydrate used was 0.2 g. Example 9

[0070] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (3) of this example, the amount of cobalt nitrate hexahydrate used was 0.4 g.

[0071] Comparative Example 1

[0072] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (3) of this example, the reaction temperature after adding cobalt nitrate hexahydrate was room temperature and the reaction time was 10 h.

[0073] Comparative Example 2

[0074] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (3) of this example, the reaction temperature after adding cobalt nitrate hexahydrate was 80° C. and the reaction time was 10 h.

[0075] Comparative Example 3

[0076] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (3) of this example, the reaction temperature after adding cobalt nitrate hexahydrate was room temperature and the reaction time was 30 min.

[0077] Comparative Example 4

[0078] CoCo-LDH-Au was prepared according to the method of Example 1, except that in step (4) of this example, the reaction time after adding chloroauric acid was 10 h.

[0079] Experimental Example 1

[0080] The CoCo-LDH-Au prepared in Examples 1-9 were numbered CoCo-LDH-Au-(1-9), and the CoCo-LDH-Au prepared in Comparative Examples 1-4 were numbered CoCo-LDH-Au-(D1-D4) respectively. A photocatalytic CO2 reduction experiment was carried out according to the following method. The experiment was carried out in a closed stainless steel reactor using a 300W xenon lamp as the light source.

[0081] 3 mg of CoCo-LDH prepared in Example 1 and CoCo-LDH-Au prepared in Examples 1-9 and Comparative Examples 1-4 were weighed respectively, ultrasonically dispersed in water, uniformly coated on quartz glass, and placed in an oven to dry. 2.5 ml of water was added to the bottom of the reactor to provide protons, and the quartz glass coated with the catalyst was placed in the above-mentioned reactor containing water. After placement, the reactor was evacuated, then filled with CO2 gas, and the pumping operation was repeated 3 times. After the pumping operation was completed, the reactor was placed in a dark environment overnight to ensure that CO2 was completely adsorbed. The light source was placed above the reactor, and the reaction temperature in the reactor was controlled at 30 ° C through a constant temperature water circulation system. After a certain period of illumination, the gas in the 1 ml reactor was extracted at intervals (1h, 2h, 3h, 4h after the start of illumination), and the CO production was detected by gas chromatography (GC-9560). The test results are shown in Table 1.

[0082] Table 1 CO production in the reactor

[0083]

[0084] It can be seen from Table 1 that:

[0085] (1) Compared with CoCo-LDH, the photocatalytic activity of CoCo-LDH-Au-(1-9) was significantly improved after loading with single gold atoms, which indicates that the addition of single gold atoms plays a crucial role in improving the photocatalytic performance of the material;

[0086] (2) Compared with CoCo-LDH-Au-1, the photocatalytic activities of CoCo-LDH-Au-D1, CoCo-LDH-Au-D2, CoCo-LDH-Au-D3 and CoCo-LDH-Au-D4 were significantly reduced, indicating that lowering the etching temperature, prolonging the etching time or prolonging the oxidation time of Au ions would destroy the loading results of single-atom Au to a certain extent. Specifically, lowering the etching temperature and prolonging the etching time would cause the thickness of the sheet-like CoCo-LDH to become thicker, which would make it difficult to generate oxygen vacancies and load single-atom Au; prolonging the oxidation time of Au ions would cause the accumulation of Au atoms, thereby destroying the loading results of single-atom Au.

[0087] Experimental Example 2

[0088] Add 2.5 ml of water to the bottom of the reactor to provide protons, and place a piece of quartz glass in the reactor filled with water. After placement, evacuate the reactor and then fill it with CO2 gas, repeating the pumping and flushing operation 3 times. After completing the pumping and flushing operation, place the reactor in a dark environment overnight to ensure that CO2 is completely adsorbed. Place the light source above the reactor, and use a constant temperature water circulation system to ensure that the reaction temperature in the reactor is controlled at 30°C. After a certain period of illumination, extract 1 ml of the gas in the reactor at regular intervals, and use gas chromatography (GC-9560) for analysis to detect gas phase products.

[0089] Experimental Example 3

[0090] Weigh 3 mg of the CoCo-LDH-Au photocatalyst prepared in Example 1, ultrasonically disperse it in water, evenly coat it on quartz glass, and put it in an oven to dry. Add 2.5 ml of water to the bottom of the reactor to provide protons, and place the quartz glass coated with the catalyst in the above-mentioned reactor containing water. After placement, evacuate the reactor, then fill it with CO2 gas, and repeat the pumping and flushing operation 3 times. After completing the pumping and flushing operation, place the reactor in a dark environment overnight to ensure that CO2 is completely adsorbed. Through a constant temperature water circulation system, ensure that the reaction temperature in the reactor is controlled at 30 ° C. After a certain period of light exposure, extract the gas in 1 ml of the reactor at intervals, and use gas chromatography (GC-9560) for analysis to detect gas phase products.

[0091] Experimental Example 4

[0092] Weigh 3 mg of the CoCo-LDH-Au photocatalyst prepared in Example 1, ultrasonically disperse it in water, evenly coat it on quartz glass, and put it in an oven to dry. Add 2.5 ml of water to the bottom of the reactor to provide protons, and place the quartz glass coated with the catalyst in the above-mentioned reactor filled with water. After the placement is completed, the reactor is evacuated, then filled with Ar gas, and the pumping operation is repeated 3 times. After the pumping operation is completed, the reactor is placed in a dark environment. The light source is placed above the reactor, and the reaction temperature in the reactor is controlled at 30°C through a constant temperature water circulation system. After a certain period of illumination, the gas in 1 ml of the reactor is extracted at intervals, and gas chromatography (GC-9560) is used for analysis to detect gas phase products.

[0093] Fig.11 These are the photocatalytic CO2 reduction test diagrams of the sample (CoCo-LDH-Au-1) of Example 1 in Experimental Example 1, Experimental Example 2, Experimental Example 3 and Experimental Example 4.

[0094] In order to explore the source of the reduction products, a comparative experiment under controlled conditions was conducted. Fig.11It can be seen that no CO is generated without catalysis, indicating that the catalyst plays a key role in the reduction process. No CO is generated in the dark or under argon conditions, indicating that both light and CO2 are key factors in the reaction, and that CO comes from CO2.

[0095] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for preparing a hollow CoCo-LDH loaded with Au atoms, characterized in that: The Au atom is loaded on the hollow CoCo-LDH in the form of a single atom, and the preparation method comprises the following steps: S1. Add cobalt nitrate hexahydrate to the ZIF-67 dispersion, and perform a first reaction at 70-90° C. for 20-40 min to obtain a reaction product; the mass ratio of the ZIF-67 to the cobalt nitrate hexahydrate is 1:(2-4); S2, separating the solid in the reaction product, performing a first washing and a first drying to obtain a hollow CoCo-LDH; S3, taking the hollow CoCo-LDH to prepare a CoCo-LDH dispersion, and adding chloroauric acid to carry out a second reaction; The preparation method further comprises the step of preparing the ZIF-67: S11, weighing cobalt nitrate hexahydrate, dissolving it in water, and adding hexadecyltrimethylammonium bromide to form solution A; S12, weigh 2-methylimidazole and dissolve it in water to form solution B; S13, pouring the A solution into the B solution, stirring, centrifuging, washing, and drying to obtain the ZIF-67.

2. The preparation method according to claim 1, characterized in that: In step S3, the reaction conditions of the second reaction include: The reaction temperature is 20-30°C and the reaction time is 50-70 min.

3. The preparation method according to claim 1, characterized in that: In step S3, the mass ratio of the hollow CoCo-LDH to the chloroauric acid is 1:(0.01-0.05).

4. The preparation method according to claim 1, characterized in that: In step S11, the mass ratio of the cobalt nitrate hexahydrate to the hexadecyltrimethylammonium bromide is 1:(0.0083-0.0417); And / or, in step S12, the mass ratio of the cobalt nitrate hexahydrate to the 2-methylimidazole is 1:(10-18).

5. The preparation method according to claim 1, characterized in that In step S2, the first drying conditions include: drying temperature of 70-90°C and drying time of 1.5-2.5 h; And / or, step S3 further comprises separating the solid in the reaction product of the second reaction and performing a second washing and a second drying operation; The second drying conditions include: drying temperature of 70-90° C., and drying time of 1.5-2.5 h.

6. The preparation method according to claim 1, characterized in that: The solvent of the ZIF-67 dispersion is ethanol, and the solvent of the CoCo-LDH dispersion is water.

7. Use of the hollow CoCo-LDH prepared by the preparation method according to any one of claims 1 to 6 in the preparation of photocatalysts.

8. Use of the hollow CoCo-LDH prepared by the preparation method according to any one of claims 1 to 6 in photocatalytic CO2 reduction.

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