A CuPd-based composite material, a preparation method thereof and an application thereof

Abstract

The present invention provides a CuPd-based composite material, a preparation method thereof and an application thereof, belonging to the technical field of nanomaterials. The preparation method includes: First, dispersing carrier powder in an ethylene glycol solution to form a dispersion liquid, wherein the carrier powder is MXene or GO; Second, dissolving a Cu salt and a Pd salt in an ethylene glycol solution, and adding sodium citrate as a dispersant to obtain a mixed solution; Finally, adding the dispersion liquid to the mixed solution, after heating and reacting, performing post-treatment to obtain the CuPd-based composite material. Benefiting from the excellent electrocatalytic ammonia synthesis performance of the copper-palladium alloy, as well as the excellent electronic conductivity and surface hydrophilicity of the carrier, the composite material is expected to further improve the performance during the electrocatalytic process. In addition, the preparation method of the composite material is simple and has low cost, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of material synthesis, and relates to a CuPd-based composite material, a preparation method thereof and an application thereof. Background Art

[0002] In recent years, with the rapid development of social economy and technology, people's attention to energy and environmental issues has been continuously rising. As is well known, electrocatalysis is a promising method for future clean energy conversion technology, and the most important thing in the electrocatalytic process is the preparation of highly efficient electrocatalysts. At present, some hot materials have attracted extensive attention of researchers.

[0003] Due to its good electrical conductivity and weak hydrogen evolution ability, Cu is considered to be a highly potential electrocatalyst, which is beneficial to promoting the adsorption and conversion of active substances. However, the pure Cu electrode is prone to spontaneous oxidation loss and surface poisoning. At the same time, although single-metal catalysts are easy to obtain, their performance still has defects. To further improve the electrocatalytic performance, appropriate atoms must be introduced to form a bimetallic system. The synergistic effect of copper-palladium bimetals is beneficial to optimizing the electronic structure and reducing the reaction barrier, thus helping to improve the catalytic performance.

[0004] MXene is a new type of two-dimensional material, which is prepared by etching off the A layer in the MAX phase. It is usually represented by the chemical formula M n+1 X n T x where M represents early transition metals, X is C or N element, and T is a surface functional group (-F, -O or -OH). Thanks to its excellent electronic conductivity and surface hydrophilicity, MXene has been widely used in various fields and has also been widely reported in electrocatalysis. In addition, MXene can change the catalytic activity of the composite material by changing the electrophilicity of the active center of the supported catalyst, and can effectively improve the electrocatalytic performance of the composite material.

[0005] In addition, graphene oxide (GO) is an oxide of graphene. The increase in oxygen-containing functional groups makes its properties more active than graphene, and its properties can be improved through various reactions with oxygen-containing functional groups. As an important derivative of graphene-based materials, although the oxidation process destroys the highly conjugated structure of graphene, it still retains special surface properties and layered structure. The introduction of oxygen-containing groups not only makes graphene oxide chemically stable, but also provides surface modification active sites and a large specific surface area for the synthesis of graphene-based / graphene oxide-based materials. As a precursor and support carrier for the synthesis of graphene-based composite materials, graphene oxide is easy to functionalize and has high controllability. During the composite process with materials such as metals, metal oxides, and polymer polymers, it can provide a large specific surface area to effectively disperse and adhere the attached materials and prevent agglomeration.

[0006] Therefore, the composite materials of CuPd alloy and GO or MXene will have great potential in the field of electrocatalysis. Summary of the invention

[0007] The purpose of the present invention is to disclose a method for preparing a CuPd-based composite material. The material preparation process is simple and universal, and shows broad prospects in the field of electrocatalysis.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for preparing a CuPd-based composite material comprises: firstly, dispersing a carrier in an ethylene glycol solution to form a dispersion; secondly, dissolving a Cu salt and a Pd salt in the ethylene glycol solution, and adding sodium citrate as a dispersant to obtain a mixed solution; finally, adding the dispersion to the mixed solution, heating the mixture for reaction, and performing post-treatment to obtain a product. Specifically, the method comprises the following steps:

[0010] In the first step, at room temperature, the carrier powder is added to the ethylene glycol solution, and ultrasonic treatment is performed to obtain solution A. In each 10 mL of the ethylene glycol solution, 50 to 150 mg of the carrier powder is added, and the carrier is graphene oxide (GO) or MXene.

[0011] Step 2: Preparation of products

[0012] 2.1) At room temperature, Cu salt and Pd salt are added to ethylene glycol solution, sodium citrate is added as a dispersant, and stirred to dissolve to obtain a mixed solution B. The molar ratio of the Cu salt to the Pd salt is in the range of (9-1):1.

[0013] 2.2) Add solution A to mixed solution B, stir evenly, adjust the pH to 9-11 with KOH ethylene glycol solution, stir at room temperature for 30 minutes, re-measure the pH value to ensure that the pH value is stable. Then increase the temperature to 120-170°C, heat the reaction for 4-8 hours, centrifuge, wash, and vacuum dry to obtain the product.

[0014] Furthermore, the ultrasonic time in the first step is 0.5 to 1.0 hour.

[0015] Furthermore, in the second step, the Cu salt may be CuCl2, and the Pd salt may be PdCl2.

[0016] Furthermore, the amount of sodium citrate added in the second step is: 200-300 mg of sodium citrate is added to every 50 mL of ethylene glycol solution.

[0017] Furthermore, the vacuum drying in the second step is carried out at a temperature of 60 to 70° C. and for a time of 10 to 12 hours.

[0018] A CuPd-based composite material, which is prepared by the above preparation method. According to different carriers, the products are CuPd@MXene composite material or CuPd@GO composite material respectively. The CuPd@MXene composite material has an accordion-like layered structure, and the CuPd alloy is relatively uniformly loaded on the surface and between the layers of MXene. The CuPd@GO composite material has a two-dimensional sheet-like structure, and the CuPd alloy is relatively uniformly loaded on the surface and between the layers of GO.

[0019] An application of a CuPd-based composite material, which is used as an electrocatalyst for electrocatalytic nitrogen reduction reaction and nitrate reduction reaction, and can efficiently convert N2, nitrate and nitrogen oxides into NH3 under environmental conditions. Specifically: at an overpotential of -0.4V vs. RHE, the ammonia production rate of the CuPd@GO composite material can reach 1.62mg h -1 cm -2 , and can reach a Faraday efficiency of 38.2%; the ammonia production rate of the CuPd@MXene composite material can reach 0.86mg h -1 cm -2 , and can reach a Faraday efficiency of 48.2%.

[0020] The innovation analysis of the present invention is as follows: Metal nanoparticles have various special properties, such as large specific surface area, adjustable particle size, etc., so they exhibit unique physical properties and high chemical activity, and are widely used in related fields such as catalysis, photoelectric conversion, dye cells and electrochemical sensing. Due to the high surface energy of metal nanoparticles, they are prone to aggregation, which will affect their catalytic performance and stability. Dispersing metal nanoparticles on a suitable carrier is an effective way to overcome the aggregation phenomenon of nanoparticles, so as to fully exert their activity. MXene has an accordion-like multi-layer structure, with an intrinsic nano-structure, excellent mechanical properties and electrical conductivity, and an outstanding specific surface area and hydrophilicity, which can provide more active sites for metal particles and has become a potential high-performance catalyst carrier. As an important derivative of graphene-based materials, although the oxidation process destroys the highly conjugated structure of graphene, it still maintains special surface properties and layered structure. The introduction of oxygen-containing groups not only makes graphene oxide have chemical stability, but also provides surface modification active sites and a large specific surface area for the synthesis of graphene-based / graphene oxide-based materials. As a precursor and support carrier for the synthesis of graphene-based composite materials, graphene oxide is easy to functionalize and has high controllability. In the process of compounding with materials such as metals, metal oxides, and polymer polymers, it can provide a large specific surface area to effectively disperse and adhere the materials, prevent aggregation, and improve the utilization rate and catalytic performance of metal particles.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The preparation process of the present invention is simple, mild and universal, has no special requirements for equipment, and is suitable for large-scale production. The CuPd-based composite material prepared by this method has a stable structure and excellent electrocatalytic performance when applied to the electrocatalytic synthesis of ammonia reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the scanning electron microscope image of CuPd@GO obtained in Example 1.

[0024] Figure 2 It is the X-ray diffraction pattern of CuPd@GO obtained in Example 1.

[0025] Figure 3 It is the linear sweep voltammogram of CuPd@GO obtained in Example 1.

[0026] Figure 4 It is the electrocatalytic ammonia synthesis performance diagram of CuPd@GO obtained in Example 1.

[0027] Figure 5 It is the scanning electron microscope image of CuPd@MXene obtained in Example 4.

[0028] Figure 6 It is the X-ray diffraction pattern of CuPd@MXene obtained in Example 4.

[0029] Figure 7 It is the linear sweep voltammogram of CuPd@MXene obtained in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that all the following embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0031] Example 1

[0032] A. Take a clean beaker, add 20 mL of ethylene glycol solution, and then weigh 0.3 g of GO into the beaker and ultrasonicate for 0.5 hour to obtain a homogeneous dispersion. Then, at room temperature, add 72 mg of CuCl2 and 76 mg of PdCl2 (molar ratio 1:1) to another beaker containing ethylene glycol solution (50 mL), and add 200 mg of sodium citrate as a dispersant and stir to dissolve. Finally, mix the above two solutions, adjust the pH to 9 with KOH ethylene glycol solution, and stir at room temperature for 30 min.

[0033] B. Take a clean three-necked flask, pour the mixed solution obtained in step A into the three-necked flask, and stir and react at 160 °C in an oil bath for 6 h. Finally, perform suction filtration and washing, repeating three times. And vacuum dry at 60 °C for 12 hours to obtain CuPd@GO.

[0034] Through Figure 1 、 Figure 2 The morphology diagram and X-ray diffraction diagram of the CuPd@GO composite material can be obtained respectively. It can be seen from the figure that the copper-palladium alloy and the carrier GO are successfully synthesized, and the copper-palladium metal particles are evenly distributed on the surface and between the layers of GO, greatly improving the contact area and activity of the catalyst.

[0035] Figure 3 、 Figure 4 is the performance diagram of the CuPd@GO composite material in the electrochemical synthesis of ammonia. It can be seen from the figure that the ammonia production rate of this catalyst can reach 1.62 mg h -1 cm -2 at the potential of -0.4 V vs. RHE, and the Faraday efficiency can reach 38.2%.

[0036] Example 2

[0037] A preparation method of a CuPd@GO composite material, comprising the following steps:

[0038] A. Take a clean beaker, add 20 mL of ethylene glycol solution, and then weigh 0.3 g of GO into the beaker and ultrasonicate for 1 hour until a homogeneous dispersion is obtained. Then, at room temperature, add 131.3 mg of CuCl2 and 15.18 mg of PdCl2 (molar ratio 9:1) to another beaker containing ethylene glycol solution (50 mL), and add 250 mg of sodium citrate as a dispersant and stir to dissolve. Finally, mix the above two solutions, adjust the pH to 10 with KOH ethylene glycol solution, and stir at room temperature for 30 min.

[0039] B. Take a clean three-necked flask, pour the mixed solution obtained in step A into the three-necked flask, and stir and react at 120 °C in an oil bath for 8 h. Finally, perform suction filtration and washing, repeating three times. And vacuum dry at 60 °C for 12 hours to obtain CuPd@GO.

[0040] The structure and performance of the CuPd@GO catalyst obtained in this example are as follows: The catalyst structure is a two-dimensional flaky structure, and the metal agglomerates, but it still has the catalytic performance for ammonia synthesis. The ammonia production rate of this catalyst can reach 1.58 mg h -1 cm -2 at the potential of -0.4 V vs. RHE, and the Faraday efficiency can reach 39.7%.

[0041] Example 3

[0042] A preparation method of a CuPd@GO composite material, comprising the following steps:

[0043] A. Take a clean beaker, add 20 mL of ethylene glycol solution, and then weigh 0.3 g of GO into the beaker. Ultrasonic for 0.5 hour until a homogeneous dispersion is obtained. Then, at room temperature, add 72 mg of CuCl2 and 76 mg of PdCl2 (molar ratio 1:1) to another beaker containing ethylene glycol solution (50 mL), and add 280 mg of sodium citrate as a dispersant, and stir to dissolve. Finally, mix the above two solutions, adjust the pH to 7 with a KOH ethylene glycol solution, and stir at room temperature for 30 min.

[0044] B. Take a clean three-necked flask, pour the mixed solution obtained in step A into the three-necked flask, and stir and react at 140 °C in an oil bath for 8 h. Finally, perform suction filtration and washing, repeating three times. And vacuum dry at 70 °C for 10 hours to obtain CuPd@GO.

[0045] The structure and performance of the CuPd@GO catalyst obtained in this example are as follows: The obtained catalyst is used for nitrogen reduction and nitrate reduction to synthesize ammonia, showing relatively high activity and stability. The ammonia production rate of this catalyst can reach 1.75 mg h -1 cm -2 -1, and can reach a Faraday efficiency of 43.2%.

[0046] Example 4

[0047] A preparation method of a CuPd@MXene composite material, comprising the following steps:

[0048] A. Take a clean beaker, add 20 mL of ethylene glycol solution, and then weigh 0.3 g of MXene into the beaker. Ultrasonic for 1 hour until a homogeneous dispersion is obtained. Then, at room temperature, add 72 mg of CuCl2 and 76 mg of PdCl2 (molar ratio 1:1) to another beaker containing ethylene glycol solution (50 mL), and add 250 mg of sodium citrate as a dispersant, and stir to dissolve. Finally, mix the above two solutions, adjust the pH to 10 with a KOH ethylene glycol solution, and stir at room temperature for 30 min.

[0049] B. Take a clean three-necked flask, pour the mixed solution obtained in step A into the three-necked flask, and stir and react at 170 °C in an oil bath for 6 h. Finally, perform suction filtration and washing, repeating three times. And vacuum dry at 70 °C for 12 hours to obtain CuPd@MXene.

[0050] The structure and properties of the CuPd@MXene catalyst obtained in this example are as follows: The obtained catalyst is used for nitrogen reduction to synthesize ammonia, showing high activity and stability.

[0051] By Figure 5 , Figure 6 the morphology diagram and X-ray diffraction pattern of the CuPd@MXene composite material can be obtained respectively. It can be seen from the figure that the catalyst is accordion-shaped, and the nano metal particles are loaded on the surface and interlayer of MXene.

[0052] Figure 7 Figure -2 .

[0053] Example 5

[0054] A preparation method of a CuPd@GO composite material includes the following steps:

[0055] A. Take a clean beaker, add 20 mL of ethylene glycol solution, and then weigh 0.3 g of GO into the beaker and ultrasonicate for 0.5 hour until a homogeneous dispersion is obtained. Then, at room temperature, add 87.56 mg of CuCl2 and 60.71 mg of PdCl2 (molar ratio 6:4) to another beaker containing ethylene glycol solution (50 mL), and add 300 mg of sodium citrate as a dispersant and stir to dissolve. Finally, mix the above two solutions, adjust the pH to 11 with KOH ethylene glycol solution, and stir at room temperature for 30 min.

[0056] B. Take a clean three-necked flask, pour the mixed solution obtained in step A into the three-necked flask, and stir and react at 140 °C in an oil bath for 12 h. Finally, perform suction filtration and washing three times. And vacuum dry at 60 °C for 12 hours to obtain CuPd@GO.

[0057] The structure and properties of the CuPd@GO catalyst obtained in this example are as follows: The obtained catalyst is used for nitrogen reduction and nitrate reduction to synthesize ammonia, showing high activity and stability. The ammonia production rate of this catalyst can reach 0.95 mg h -1 cm -2 , and can reach a Faraday efficiency of 33.8%.

[0058] Example 6

[0059] A preparation method of a CuPd@MXene composite material includes the following steps:

[0060] A. Take a clean beaker, add 20 mL of ethylene glycol solution, and then weigh 0.2 g of MXene into the beaker. Sonicate for 0.5 hour until a homogeneous dispersion is obtained. Then, at room temperature, add 116.7 mg of CuCl2 and 30.36 mg of PdCl2 (molar ratio 8:2) to another beaker containing ethylene glycol solution (50 mL), and add 300 mg of sodium citrate as a dispersant. Stir to dissolve. Finally, mix the above two solutions, adjust the pH to 10 with KOH ethylene glycol solution, and stir at room temperature for 30 min.

[0061] B. Take a clean three-necked flask, pour the mixed solution obtained in step A into the three-necked flask, and stir and react at 160 °C in an oil bath for 12 h. Finally, perform suction filtration and washing, repeating three times. And vacuum dry at 60 °C for 10 hours to obtain CuPd@MXene.

[0062] The structure and performance of the CuPd@MXene catalyst obtained in this example are as follows: When the obtained catalyst is used for nitrogen reduction to synthesize ammonia, it exhibits high activity and stability. The ammonia production rate of this catalyst can reach 0.75 mg h-1 cm-2 at a potential of -0.4 V vs. RHE, and the Faraday efficiency can reach 23.2%.

[0063] Example 7

[0064] A preparation method of a CuPd@MXene composite material, comprising the following steps:

[0065] A. Take a clean beaker, add 20 mL of ethylene glycol solution, and then weigh 0.1 g of MXene into the beaker. Sonicate for 0.5 hour until a homogeneous dispersion is obtained. Then, at room temperature, add 116.7 mg of CuCl2 and 30.36 mg of PdCl2 (molar ratio 8:2) to another beaker containing ethylene glycol solution (50 mL), and add 250 mg of sodium citrate as a dispersant. Stir to dissolve. Finally, mix the above two solutions, adjust the pH to 11 with KOH ethylene glycol solution, and stir at room temperature for 30 min.

[0066] B. Take a clean three-necked flask, pour the mixed solution obtained in step A into the three-necked flask, and stir and react at 120 °C in an oil bath for 6 h. Finally, perform suction filtration and washing, repeating three times. And vacuum dry at 60 °C for 12 hours to obtain CuPd@MXene.

[0067] The structure and performance of the CuPd@MXene catalyst obtained in this example are as follows: When the obtained catalyst is used for nitrogen reduction to synthesize ammonia, it exhibits high activity and stability. The ammonia production rate of this catalyst can reach 0.88 mg h -1 cm-2 , and can achieve a Faraday efficiency of 38.3%.

[0068] The above-described embodiments only represent the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention patent. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. Application of a CuPd-based composite material, characterized in that, The described CuPd-based composite material is used as an electrocatalyst for the electrocatalytic nitrogen reduction reaction and the nitrate reduction reaction, and can efficiently convert N2, nitrate or nitrogen oxides into NH3 under ambient conditions; the preparation method of the described CuPd-based composite material is as follows: First, disperse the carrier powder in an ethylene glycol solution to form a dispersion; Second, dissolve the Cu salt and Pd salt in the ethylene glycol solution, and add sodium citrate as a dispersant to obtain a mixed solution; Finally, add the dispersion to the mixed solution, and after heating and reacting, perform post-treatment to obtain the product; including the following steps: In the first step, at room temperature, add the carrier powder to the ethylene glycol solution and ultrasonically obtain solution A; among which, for every 10 mL of the ethylene glycol solution, 50-150 mg of the carrier powder is correspondingly added, and the carrier is graphene oxide or MXene; In the second step, prepare the product 2.1) At room temperature, add the Cu salt and Pd salt to the ethylene glycol solution, and add sodium citrate as a dispersant, and stir and dissolve to obtain a mixed solution B; the molar ratio of the Cu salt to the Pd salt is (9-1):1; 2.2) Add solution A to mixed solution B, stir evenly, adjust the pH to 9-11, and continue to stir the mixed solution at room temperature, raise the temperature to 120-170 °C, carry out a heating reaction for 4-8 h, and after the reaction, centrifuge, wash, and vacuum dry to obtain the product; the described composite material has an accordion-like hierarchical structure or a two-dimensional layered structure, and the CuPd alloy is loaded on the surface and between the layers of the carrier.

2. The application of a CuPd-based composite material according to claim 1, wherein The ultrasonic time in the first step is 0.5-1.0 hour.

3. The application of a CuPd-based composite material according to claim 1, characterized in that, In the second step, the Cu salt is selected as CuCl2 and the Pd salt is selected as PdCl2.

4. The application of a CuPd-based composite material according to claim 1, characterized in that, In step 2.1), the addition amount of sodium citrate is 200-300 mg of sodium citrate added to every 50 mL of the ethylene glycol solution.

5. Use of a CuPd-based composite material according to claim 1, characterized in that, In step 2.2), the stirring time is 30 min.

6. The application of a CuPd-based composite material according to claim 1, characterized in that, In the second step, the temperature of the vacuum drying is 60-70 °C and the time is 10-12 hours.

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