A composite material with hollow nickel cobalt oxide surface-modified nano-metal particles, its preparation method and application

Abstract

This invention belongs to the field of nanocomposite materials technology, specifically relating to a hollow nickel cobalt oxide surface-modified nano-metal particles composite material, its preparation method, and its application. The hollow nickel cobalt oxide surface-modified composite material of this invention, containing palladium, nickel, iron, copper, indium, and other nano-metal particles, is a novel composite material with controllable structure, excellent performance, and good stability, exhibiting excellent performance in thermocatalytic carbon dioxide reduction. The preparation method uses inexpensive and readily available raw materials, is simple to operate, and does not require expensive equipment, thus facilitating industrial production.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite materials technology, specifically relating to a composite material with hollow nickel cobalt oxide surface-modified nano-metal particles, its preparation method, and its application. Background Technology

[0002] Energy is a crucial guarantee for driving social development and scientific and technological progress. With economic development and rapid industrialization, the massive consumption of fossil fuels has led to severely excessive atmospheric carbon dioxide levels, contributing to the greenhouse effect. Thermally driven thermocatalytic reduction of carbon dioxide into fuels or commercial chemicals is a promising strategy for meeting global energy demand while mitigating the greenhouse effect. Carbon dioxide reduction involves two parts: carbon dioxide activation and catalytic reduction. It requires active sites for carbon dioxide adsorption and activation, and thermal energy for catalytic reduction. Therefore, designing catalytic materials with highly active sites and high surface area to promote carbon dioxide reduction has become a key focus.

[0003] Supported metal catalysts, especially palladium-based catalysts, are high-performance catalytic materials for the hydrogenation reduction of carbon dioxide. By introducing different metals, such as nickel, iron, copper, and indium, to design synergistic catalytic systems, the charge distribution around the active palladium metal can be effectively adjusted. At the same time, by using nickel cobalt oxide, which has a large specific surface area and excellent thermal stability, as a support for the embedded metal species, more active metals can be loaded, thereby improving the carbon dioxide adsorption and activation capacity of the catalyst and enhancing its catalytic performance. Summary of the Invention

[0004] This invention aims to solve the problem of thermocatalytic carbon dioxide reduction to fuel or commercial chemicals. It provides a method for preparing and applying a composite material with hollow nickel cobalt oxide surface modified with nano-metal particles such as palladium, nickel, iron, copper, and indium. This composite material can support more active metals and effectively regulate the charge distribution around the active metals by utilizing intermetallic synergistic effects, thereby improving the carbon dioxide adsorption and activation capacity of the catalyst. It can be widely used in the field of thermocatalytic carbon dioxide reduction.

[0005] To address the aforementioned technical problems, this application provides the following technical solution:

[0006] This invention provides a method for preparing a composite material with hollow nickel cobalt oxide surface-modified nano-metal particles, comprising the following steps:

[0007] S11: Cobalt salt and dimethylimidazole are added to organic solvent A and mixed to obtain dodecahedral ZIF-67 nanomaterials;

[0008] S12: The dodecahedral ZIF-67 nanomaterial is dispersed in anhydrous ethanol and then ethanol containing nickel nitrate is added to etch the ZIF-67 nanomaterial into hollow nickel cobalt oxide nanomaterial. The hollow nickel cobalt oxide nanomaterial is obtained by centrifugation and washing.

[0009] S13: Dissolve the precursor in organic solvent B, drop it onto the hollow nickel cobalt oxide nanomaterial, stir and dry, and then calcine it at 300-350°C for 3-5 hours under an inert gas atmosphere to obtain the composite material of the hollow nickel cobalt oxide surface modified with nano-metal particles.

[0010] The precursor is selected from one or more of palladium acetylacetonate, nickel acetylacetonate, copper acetylacetonate, indium acetylacetonate, and iron acetylacetonate.

[0011] Preferably, the molar ratio of the cobalt salt to dimethylimidazole is 1-3:8-16.

[0012] Furthermore, the molar ratio of the cobalt salt to dimethylimidazole is 1:8.

[0013] Preferably, the cobalt salt is cobalt nitrate.

[0014] Preferably, in step S11, the concentration of cobalt salt is 0.045-0.05 mol / L.

[0015] Furthermore, in step S11, the concentration of the cobalt salt is 0.05 mol / L.

[0016] Preferably, the mixing method is stirring for 8-24 hours.

[0017] Furthermore, the stirring time is 16 hours.

[0018] Preferably, organic solvent A is methanol and organic solvent B is chloroform.

[0019] Preferably, in step S11, the mixture is centrifuged, washed with methanol, and dried.

[0020] Preferably, in step S12, the mixing method is stirring and sonication, and the sonication time is 45-60 minutes.

[0021] Furthermore, the ultrasound duration is 45 minutes.

[0022] Preferably, in the nickel nitrate-containing ethanol, 1.5-2g of nickel nitrate is added to every 50-70mL of ethanol.

[0023] Furthermore, in the ethanol containing nickel nitrate, 1.5g of nickel nitrate is added to every 50mL of ethanol.

[0024] Preferably, the mass ratio of the dodecahedral ZIF-67 nanomaterial to anhydrous ethanol is 7-15:3-9, and the volume ratio of the anhydrous ethanol to nickel nitrate-containing ethanol is 5-11:1-2.

[0025] Furthermore, the ratio of the dodecahedral ZIF-67 nanomaterial, anhydrous ethanol, and nickel nitrate-containing ethanol is such that 7 mg of ZIF-67 is dispersed in 5 mL of anhydrous ethanol and 1 mL of nickel nitrate-containing ethanol.

[0026] Preferably, in step S13, the temperature for stirring and drying is room temperature (25±5℃).

[0027] Preferably, in step S13, the heating rate of high-temperature calcination is 2-10℃ / min.

[0028] Furthermore, in step S3, the calcination temperature is 300℃, the calcination time is 3h, and the heating rate is 2℃ / min.

[0029] Preferably, in step S3, the precursors such as palladium acetylacetone, nickel acetylacetone, copper acetylacetone, indium acetylacetone, and iron acetylacetone are modified onto hollow nickel cobalt oxide nanomaterials in combinations such as palladium-nickel, palladium-copper, palladium-iron, and palladium-indium.

[0030] Furthermore, in step S3, the composite material with palladium-nickel nanoparticles on the surface of hollow nickel cobalt oxide modified with precursors such as palladium-nickel acetylacetone, nickel acetylacetone, copper acetylacetone, indium acetylacetone, and iron acetylacetone in combination of palladium-nickel, palladium-copper, palladium-iron, and palladium-indium has the best performance.

[0031] Specifically, the preparation method of the composite material with hollow nickel cobalt oxide surface modified with nano-metal particles such as palladium, nickel, iron, copper, and indium may include the following steps:

[0032] (1) Dissolve 2.93-8.79 g of cobalt nitrate hexahydrate and 6.49-12.98 g of dimethylimidazole in 200-440 mL of methanol respectively. After mixing, stir at room temperature for 8-24 h. Finally, centrifuge the solution, wash with methanol and dry to obtain dodecahedral ZIF-67 nanomaterials.

[0033] (2) Disperse the obtained 7-15 mg dodecahedral ZIF-67 nanomaterials in 5-11 mL of anhydrous ethanol, add 1-2 mL of ethanol solution containing 30-60 mg of nickel nitrate under magnetic stirring, stir and sonicate for 45-60 min, etch the ZIF-67 nanomaterials into hollow structure nickel cobalt oxide nanomaterials, and centrifuge and wash to obtain solid product.

[0034] (3) Palladium acetylacetone, nickel acetylacetone, copper acetylacetone, indium acetylacetone, iron acetylacetone and other precursors are dissolved in chloroform. Palladium nickel, palladium copper, palladium iron, palladium indium and other combinations are added dropwise to hollow structure nickel cobalt oxide nanomaterials in proportion. The mixture is stirred and dried at room temperature. Finally, under the protection of an inert gas atmosphere, it is calcined at 300-350℃ for 3-5h at a heating rate of 2-10℃ / min to obtain palladium, nickel, iron, copper, indium / nickel cobalt oxide composite material, that is, the composite material of hollow structure nickel cobalt oxide surface modified with palladium, nickel, iron, copper, indium and other nano metal particles.

[0035] The present invention also provides a composite material of hollow nickel cobalt oxide surface-modified nano-metal particles prepared by the above preparation method.

[0036] The present invention also provides a method for thermocatalytic carbon dioxide reduction, using the above-mentioned composite material of hollow nickel cobalt oxide surface modified with nano-metal particles as a catalyst.

[0037] This invention uses cobalt nitrate hexahydrate and dimethylimidazole as precursors and methanol as solvent to prepare dodecahedral ZIF-67 material via a simple sol-gel method. The prepared dodecahedral ZIF-67 material is then dissolved in anhydrous ethanol, and an ethanol solution of nickel nitrate is added while stirring. The ZIF-67 nanomaterial is etched into hollow nickel cobalt oxide nanomaterials by stirring and sonication. Finally, precursors such as palladium acetylacetonate, nickel acetylacetonate, copper acetylacetonate, indium acetylacetonate, and iron acetylacetonate are dissolved in chloroform and added dropwise to the hollow nickel cobalt oxide nanomaterials in a specific ratio. The mixture is stirred and dried at room temperature, and finally calcined at high temperature under an inert gas atmosphere to obtain a composite material with hollow nickel cobalt oxide surface modified with palladium, nickel, iron, copper, and indium nanoparticles. In this method, palladium acetylacetonate is used as the palladium source and the active metal for carbon dioxide reduction. Nickel acetylacetonate, copper acetylacetonate, indium acetylacetonate, and iron acetylacetonate are used as the nickel source, iron source, copper source, and indium source, respectively. This effectively regulates the charge distribution around the active palladium metal. At the same time, nickel cobalt oxide, which has a large specific surface area and excellent thermal stability, is selected as the carrier for the embedded metal species, which can load more active metals and greatly improve the performance of thermocatalytic carbon dioxide reduction.

[0038] The technical solution of the present invention has the following advantages compared with the prior art:

[0039] 1. The method for preparing composite materials with hollow nickel cobalt oxide surface modified with nano-metal particles such as palladium, nickel, iron, copper, and indium disclosed in this invention uses low-cost and readily available raw materials, is simple to operate, and does not require expensive equipment, which is conducive to industrial production.

[0040] 2. The hollow nickel cobalt oxide composite material disclosed in this invention, which is surface-modified with nano-metal particles such as palladium, nickel, iron, copper, and indium, is a novel composite material with controllable structure, excellent performance, and good stability. It has excellent performance in thermocatalytic carbon dioxide reduction and can be used to produce formic acid by thermocatalytic carbon dioxide reduction, which is very beneficial for industrial application. Attached Figure Description

[0041] Figure 1 Here is a scanning electron microscope (SEM) image of ZIF-67 in Example 1;

[0042] Figure 2 The image shows a transmission electron microscope (TEM) image of ZIF-67 in Example 1.

[0043] Figure 3 The image shown is a scanning electron microscope (SEM) image of the hollow nickel cobalt oxide in Example 1.

[0044] Figure 4 This is a transmission electron microscope (TEM) image of the hollow nickel cobalt oxide in Example 1.

[0045] Figure 5 Here is a scanning electron microscope (SEM) image of the palladium / nickel / nickel cobalt oxide composite material from Example 1;

[0046] Figure 6 The image shows a transmission electron microscope (TEM) image of the palladium / nickel / nickel cobalt oxide composite material from Example 1.

[0047] Figure 7 The graph shows the performance of the palladium-nickel / nickel cobalt oxide composite material in Example 1 for the thermocatalytic reduction of carbon dioxide. Detailed Implementation

[0048] The present invention will be further described below with reference to the figures and specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0049] Example 1

[0050] (1) Preparation of dodecahedral ZIF-67, the specific steps are as follows:

[0051] 2.93 g of cobalt nitrate hexahydrate and 6.49 g of dimethylimidazole were dissolved in 200 mL of methanol, respectively. The mixture was stirred at room temperature for 16 h. The solution was then centrifuged, washed with methanol, and dried to obtain dodecahedral ZIF-67 nanomaterials. The SEM image of the obtained ZIF-67 is shown below. Figure 1 As shown, the TEM image is as follows Figure 2 As shown in the figure, the dodecahedral ZIF-67 was successfully prepared and is of uniform size.

[0052] (2) The specific steps for preparing hollow nickel cobalt oxide nanomaterials are as follows:

[0053] 7 mg of dodecahedral ZIF-67 nanomaterials were dispersed in 5 mL of anhydrous ethanol. 1 mL of an ethanol solution containing 30 mg of nickel nitrate was added under magnetic stirring. The mixture was stirred and sonicated for 45 min to etch the ZIF-67 nanomaterials into hollow nickel cobalt oxide nanomaterials. The solid product was obtained by centrifugation and washing. The SEM image of the obtained hollow nickel cobalt oxide nanomaterials is shown below. Figure 3 As shown, the TEM image is as follows Figure 4 As shown in the figure, hollow nickel cobalt oxide nanomaterials were successfully prepared and are uniform in size.

[0054] (3) The preparation of the composite material of hollow nickel cobalt oxide surface modified with palladium and nickel nanoparticles is as follows: Palladium acetylacetone and nickel acetylacetone precursors are dissolved in chloroform and added dropwise to the hollow nickel cobalt oxide nanomaterials in a specific ratio. The mixture is stirred and dried at room temperature, and finally calcined at 300℃ for 3 hours under an inert gas atmosphere at a heating rate of 2℃ / min to obtain the palladium / nickel / nickel cobalt oxide composite material, i.e., the composite material of hollow nickel cobalt oxide surface modified with palladium and nickel nanoparticles. The SEM image of the obtained palladium / nickel / nickel cobalt oxide composite material is shown below. Figure 5 As shown, the TEM image is as follows Figure 6 As shown in the figure, the palladium / nickel / nickel cobalt oxide composite material was successfully prepared and is of uniform size.

[0055] Example 2

[0056] (1) Preparation of dodecahedral ZIF-67, the specific steps are as follows:

[0057] 5.86 g of cobalt nitrate hexahydrate and 12.98 g of dimethylimidazole were dissolved in 400 mL of methanol, respectively. After mixing, the mixture was stirred at room temperature for 8 h. Finally, the solution was centrifuged, washed with methanol, and dried to obtain dodecahedral ZIF-67 nanomaterials.

[0058] (2) The specific steps for preparing hollow nickel cobalt oxide nanomaterials are as follows:

[0059] 14 mg of dodecahedral ZIF-67 nanomaterials were dispersed in 10 mL of anhydrous ethanol. 2 mL of an ethanol solution containing 60 mg of nickel nitrate was added under magnetic stirring. The mixture was stirred and sonicated for 45 min to etch the ZIF-67 nanomaterials into hollow nickel cobalt oxide nanomaterials. The solid product was obtained by centrifugation and washing.

[0060] (3) The preparation of composite materials with hollow nickel cobalt oxide surface modified with palladium and iron nanoparticles, the specific steps are as follows:

[0061] Palladium acetylacetone and iron acetylacetone precursors were dissolved in chloroform and added dropwise to hollow nickel cobalt oxide nanomaterials in a certain proportion. The mixture was stirred and dried at room temperature, and finally calcined at 300°C for 3 hours under an inert gas atmosphere at a heating rate of 2°C / min to obtain a palladium / iron / nickel cobalt oxide composite material, namely the composite material of palladium and iron nano-metal particles modified on the surface of hollow nickel cobalt oxide.

[0062] Example 3

[0063] (1) Preparation of dodecahedral ZIF-67, the specific steps are as follows:

[0064] 2.93 g of cobalt nitrate hexahydrate and 6.49 g of dimethylimidazole were dissolved in 220 mL of methanol, respectively. After mixing, the mixture was stirred at room temperature for 24 hours. Finally, the solution was centrifuged, washed with methanol, and dried to obtain dodecahedral ZIF-67 nanomaterials.

[0065] (2) The specific steps for preparing hollow nickel cobalt oxide nanomaterials are as follows:

[0066] 14 mg of dodecahedral ZIF-67 nanomaterials were dispersed in 10 mL of anhydrous ethanol. 2 mL of an ethanol solution containing 60 mg of nickel nitrate was added under magnetic stirring. The mixture was stirred and sonicated for 60 min to etch the ZIF-67 nanomaterials into hollow nickel cobalt oxide nanomaterials. The solid product was obtained by centrifugation and washing.

[0067] (3) The preparation of composite materials with hollow nickel cobalt oxide surface modified with palladium and copper nanoparticles, the specific steps are as follows:

[0068] Palladium acetylacetone and copper acetylacetone precursors were dissolved in chloroform and added dropwise to hollow nickel cobalt oxide nanomaterials in a certain proportion. The mixture was stirred and dried at room temperature, and finally calcined at 350°C for 5 hours under an inert gas atmosphere at a heating rate of 10°C / min to obtain a palladium / copper / nickel cobalt oxide composite material, namely the composite material of palladium and copper nanoparticles modified on the surface of hollow nickel cobalt oxide.

[0069] Effect Evaluation 1

[0070] The specific steps for testing the thermocatalytic carbon dioxide reduction performance under heating conditions are as follows:

[0071] The thermocatalytic carbon dioxide reduction activity of the palladium / nickel / cobalt oxide composite material obtained in Example 1 was evaluated using a magnetically heated stirrer. 10 mg of the palladium / nickel / cobalt oxide composite catalyst obtained in Example 1 was dispersed in 20 mL of ultrapure water containing 1.68 g of sodium bicarbonate by ultrasonic dispersion. The dispersion was then transferred to a magnetically heated stirrer and sealed. Air was removed from the system using an inert gas. Afterward, a carbon dioxide / hydrogen mixture of 1-3 MPa was injected into the reactor, and the reaction was heated to 40-100 °C for 1 h. The yield of formic acid was determined by ion chromatography and analysis based on standards. Figure 7 This is a performance graph of the palladium / nickel / nickel cobalt oxide composite material for the thermocatalytic reduction of carbon dioxide in Example 1. Figure 7 It is known that the palladium / nickel / nickel cobalt oxide composite material has excellent thermocatalytic carbon dioxide reduction performance, with the optimal catalyst achieving a formic acid production efficiency of 187.07 mol%. FA mol Pd -1 h -1 This composite material not only has excellent performance and good stability, but also has a simple preparation process, low raw material price, and is easy to industrialize.

[0072] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for the thermocatalytic reduction of carbon dioxide to formic acid, characterized in that, A composite material with hollow nickel cobalt oxide surface-modified with nano-metal particles is used as a catalyst. The preparation method of the composite material includes the following steps: S11: Cobalt salt and dimethylimidazole are added to organic solvent A and mixed to obtain dodecahedral ZIF-67 nanomaterials; S12: The dodecahedral ZIF-67 nanomaterial is dispersed in anhydrous ethanol and then ethanol containing nickel nitrate is added. After centrifugation and washing, hollow nickel cobalt oxide nanomaterial is obtained. S13: Dissolve the precursor in organic solvent B, drop it onto the hollow nickel cobalt oxide nanomaterial, stir and dry, and then calcine it at 300-350℃ for 3-5 h in an inert gas atmosphere to obtain a composite material of hollow nickel cobalt oxide surface-modified nano-metal particles; the precursor is selected from palladium acetylacetonate and one or more of nickel acetylacetonate, copper acetylacetonate, indium acetylacetonate and iron acetylacetonate.

2. The method for producing formic acid by thermocatalytic reduction of carbon dioxide as described in claim 1, characterized in that, In step S11, the molar ratio of cobalt salt to dimethylimidazole is 1-3:8-16.

3. The method for producing formic acid by thermocatalytic reduction of carbon dioxide as described in claim 1, characterized in that, In step S11, the cobalt salt is cobalt nitrate.

4. The method for producing formic acid by thermocatalytic reduction of carbon dioxide as described in claim 1, characterized in that, In step S11, the concentration of cobalt salt is 0.045-0.05 mol / L.

5. The method for producing formic acid by thermocatalytic reduction of carbon dioxide as described in claim 1, characterized in that, In steps S11 and S13, organic solvent A is methanol and organic solvent B is chloroform.

6. The method for producing formic acid by thermocatalytic reduction of carbon dioxide as described in claim 1, characterized in that, In step S11, the mixture is centrifuged, washed with methanol, and dried.

7. The method for producing formic acid by thermocatalytic reduction of carbon dioxide as described in claim 1, characterized in that, In step S12, 1.5-2 g of nickel nitrate is added to every 50-70 mL of ethanol containing nickel nitrate.

8. The method for producing formic acid by thermocatalytic reduction of carbon dioxide as described in claim 1, characterized in that, In step S12, the mass ratio of dodecahedral ZIF-67 nanomaterial to anhydrous ethanol is 7-15:3-9, and the volume ratio of anhydrous ethanol to nickel nitrate-containing ethanol is 5-11:1-2.

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