Preparation method and application of nickel-copper alloy nanoparticle catalyst

Abstract

The invention discloses a preparation method and application of a nickel-copper alloy nanoparticle catalyst, nickel-copper nanoparticles are prepared by adopting a high-temperature pyrolysis method, and a nickel-copper nanoparticle catalyst material can be obtained by washing, centrifuging and drying. The preparation method disclosed by the invention is simple to operate, the element proportion is adjustable, the synthesized nanoparticles are uniform in size, the nanoparticles are used as a catalyst for electro-catalytic decomposition of ammonia, and excellent catalytic activity and stability are achieved in an ammonia electro-oxidation reaction of an anode; the problem that the activity of a nickel-based electrocatalyst is reduced after surface reconstruction in an ammonia electrooxidation reaction is solved, and the efficiency of hydrogen production through ammonia decomposition is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of nanoparticle synthesis and electrocatalysis, and in particular to a method for preparing a nickel-copper alloy nanoparticle catalyst and its application in electrocatalytic ammonia decomposition. Background Art

[0002] In the field of electrocatalysis, low-cost transition metals are valued because of their abundant reserves and easy large-scale production. In particular, nickel and copper, two transition metals, are not only abundant in nature but also have easily adjustable electronic structures, and they play an important role in the synthesis of electrocatalysts.

[0003] Although traditional methods for preparing nickel-copper alloy materials can successfully prepare alloy materials, these methods are often large-sized materials and cannot effectively utilize the catalytic sites of the materials. Reducing the size of the catalyst and preparing a suitable working electrode can effectively improve the internal atomic utilization of the catalyst. Therefore, an efficient and controllable preparation method is urgently needed to synthesize nickel-copper alloy nanoparticles to improve their catalytic activity and stability in electrocatalytic reactions.

[0004] Ammonia is an important hydrogen energy carrier with the advantages of mature synthesis process, low cost, and carbon-free energy storage. However, ammonia decomposition is an endothermic reaction and usually requires high temperature (>400°C) to produce high-purity hydrogen.

[0005] This process is not only energy-intensive, but also requires a complex decomposition device. In contrast, the electrocatalytic decomposition of ammonia to produce hydrogen has emerged. As an emerging energy conversion technology, ammonia electrooxidation has received widespread attention in recent years. During the electrocatalytic process, nickel-based materials will form NiOOH, which is the key active site for ammonia electrooxidation. However, the utilization efficiency of nickel-based materials in electrocatalytic anode reactions still needs to be improved. Summary of the invention

[0006] One of the purposes of the present invention is to provide a method for preparing nickel-copper alloy nanoparticles.

[0007] A second object of the present invention is to provide a nickel-copper alloy nanoparticle catalyst.

[0008] A third object of the present invention is to provide a method for preparing copper-nickel alloy nanoparticles and its application in the field of electrocatalytic ammonia decomposition and hydrogen production.

[0009] In order to achieve the above object, the present invention first provides a method for preparing nickel-copper alloy nanoparticles, which is characterized by comprising the following steps:

[0010] Step 1: Preparation of reaction solution:

[0011] Dissolve nickel acetylacetonate and copper acetylacetonate in 10 mL of oleylamine solution and mix evenly to obtain a reaction precursor mixture;

[0012] Step 2: Dissolving the Precursor

[0013] Under nitrogen environment, heat the above solution to 50-100°C and maintain for 10-30 minutes to ensure that the reaction system is fully mixed and dissolved;

[0014] Step 3: Deoxygenation

[0015] Under vigorous stirring, add 0.5 mL of tri-n-octylphosphine to the above solution and continue stirring for 20-30 minutes to eliminate oxygen in the system;

[0016] Step 4: Heat the reaction

[0017] Then the temperature was rapidly raised to 180°C and maintained at this temperature for 4 hours to promote the alloying reaction of Ni and Cu;

[0018] Step 5: Cooling and washing

[0019] After the reaction was completed, the reaction mixture was gradually cooled to room temperature and washed and centrifuged three times with n-hexane and ethanol (volume ratio of 1:15) at a speed of 10000 rpm / min for 10 min to remove the unreacted precursor;

[0020] Step 6: Dry the product

[0021] Finally, the obtained nickel-copper nanoparticles were placed in a vacuum oven at 60° C. and dried to obtain final nickel-copper alloy nanoparticles.

[0022] Preferably, in step 1, the amount of nickel acetylacetonate added is 0.8 mmol, and the amount of copper acetylacetonate added is 0.2 mmol.

[0023] A nickel-copper alloy nanoparticle is prepared by the method described above in the present invention, and the nickel-copper alloy nanoparticle has the general formula of Ni x Cu y NPs, wherein the molar ratio of Ni and Cu is x:y=8:2.

[0024] Furthermore, the nickel-copper alloy nanoparticles are Ni 0.8 Cu 0.2 NPs, Ni 0.7 Cu 0.3 NPs, Ni 0.6 Cu 0.4 NPs or Ni 0.5 Cu 0.5 NPs.

[0025] Preferably, the particle size is 5 to 7 nm.

[0026] Preferably, the nickel-copper alloy nanoparticles are nearly spherical in shape.

[0027] Secondly, the present invention also provides a method for preparing a nickel-copper alloy nanoparticle electrocatalyst, comprising the following steps:

[0028] Accurately weigh 5.0 mg of the nickel-copper alloy nanoparticles obtained by the present invention, add 1 mL of N,N-dimethylformamide, 1.0 mg of carbon black and 100 μL of Nafion solution to form a uniform solution;

[0029] 8.0 μL of the mixed solution was dropped onto the surface of the glassy carbon electrode and dried to obtain the nickel-copper alloy catalytic electrode.

[0030] Finally, the present invention also provides the use of the nickel-copper alloy nanoparticle electrocatalyst prepared by the above method in ammonia electrooxidation.

[0031] The present invention provides a nickel-copper alloy catalytic electrode and a preparation method and application thereof. Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] The present invention provides a simple and convenient method for synthesizing nickel-copper alloy nanoparticles. By precisely controlling the ratio of synthetic precursors and then controlling the atomic ratio of nickel-copper alloy nanoparticles, the prepared particles are uniform in size, nearly spherical, and have abundant active sites. The synthesis method effectively avoids the interference of oxygen and ensures the purity and catalytic performance of the alloying reaction.

[0033] The present invention provides an application of a nickel-copper alloy catalytic electrode. The nickel-copper alloy catalytic electrode can not only give full play to the original nickel-based material's high efficiency in decomposing ammonia, but also can be coupled to produce green hydrogen energy, thereby improving the utilization rate of the cathode reaction. In addition, it has excellent working stability.

[0034] The nickel-copper nanoparticles prepared by the present invention can be quickly reconstructed into Ni 1-x Cu x OOH, as an active species in the ammonia electrooxidation reaction, improves the kinetics of ammonia electrooxidation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A synthetic process flow chart of nickel-copper alloy nanoparticles provided by the present invention;

[0036] Figure 2 The Ni prepared in Example 1 0.8 Cu 0.2 TEM images of NPs;

[0037] Figure 3The Ni prepared in Example 1 0.8 Cu 0.2 XRD patterns of NPs;

[0038] Figure 4 Electrochemical working cell for testing ammonia electrooxidation reaction;

[0039] Figure 5 The Ni prepared in Example 2 0.8 Cu 0.2 Comparison of CV scans of NPs in 1.0M KOH and 1.0MKOH+0.5M NH3 electrolytes, respectively.

[0040] Figure 6 The Ni prepared in Example 2 0.8 Cu 0.2 Stability test diagram of NPs in 1.0M KOH+0.5M NH3 electrolyte.

[0041] Figure 7 The Ni NPs and Cu NPs prepared in Comparative Examples 1 and 2 are 0.8 Cu 0.2 LSV scanning comparison of NPs in 1.0M KOH and 1.0M KOH+0.5M NH3 electrolytes, respectively. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0043] Example 1

[0044] Ni 0.8 Cu 0.2 NPs alloy nanoparticles synthesis, the synthesis steps are as follows:

[0045] Step 1: Follow the instructions Figure 1 Flow chart, build the required reaction device, and prepare Ni by high temperature pyrolysis 0.8 Cu 0.2 NPs.

[0046] Step 2: Accurately weigh 0.8 mmol of nickel acetylacetonate and 0.2 mmol of copper acetylacetonate and mix them in 10 mL of oleylamine solvent.

[0047] Step 3: In a nitrogen environment, heat the above solution to 80° C. and maintain it for 10 minutes until the two mixed precursors are completely dissolved.

[0048] Step 4: Add 0.5 mL of tri-n-octylphosphine to the above solution under vigorous stirring, and continue stirring for 20 minutes to eliminate oxygen in the system.

[0049] Step 5: The temperature was then rapidly raised to 180°C and maintained at this temperature for 4 hours.

[0050] Step 6: After the reaction is completed, the reaction mixture is gradually cooled to room temperature, and washed with n-hexane and ethanol (volume ratio of 1:15) and centrifuged three times at a speed of 10000 r / min for 10 min.

[0051] Step 7: Dry the obtained nickel-copper nanoparticles in a vacuum oven at 60°C to obtain the final nickel-copper alloy nanoparticles. Figure 2 and attached Figure 3 For Ni 0.8 Cu 0.2 SEM and XRD of NPs.

[0052] Example 2

[0053] Ni 0.7 Cu 0.3 NPs alloy nanoparticles synthesis, the synthesis steps are as follows:

[0054] Step 1: Build the same reaction apparatus as above to prepare Ni 0.7 Cu 0.3 NPs.

[0055] Step 2: Accurately weigh 0.7 mmol of nickel acetylacetonate and 0.3 mmol of copper acetylacetonate and mix them in 10 mL of oleylamine solvent.

[0056] Step 3: In a nitrogen environment, heat the above solution to 50° C. and maintain it for 30 minutes until the two mixed precursors are completely dissolved.

[0057] Step 4: Add 0.5 mL of tri-n-octylphosphine to the above solution under vigorous stirring, and continue stirring for 30 minutes to eliminate oxygen in the system.

[0058] Step 5: The temperature was then rapidly raised to 180°C and maintained at this temperature for 4 hours.

[0059] Step 6: After the reaction is completed, the reaction mixture is gradually cooled to room temperature, and washed with n-hexane and ethanol (volume ratio of 1:15) and centrifuged three times at a speed of 10000 r / min for 10 min.

[0060] Step 7: Dry the obtained nickel-copper nanoparticles in a vacuum oven at 60°C to obtain the final Ni 0.7 Cu 0.3 NPs.

[0061] Example 3

[0062] Ni 0.6 Cu 0.4 NPs alloy nanoparticles synthesis, the synthesis steps are as follows:

[0063] Step 1: Build the same reaction apparatus as above to prepare Ni 0.6 Cu 0.4 NPs.

[0064] Step 2: Accurately weigh 0.6 mmol of nickel acetylacetonate and 0.4 mmol of copper acetylacetonate and mix them in 10 mL of oleylamine solvent.

[0065] Step 3: In a nitrogen environment, heat the above solution to 100° C. and maintain it for 15 minutes until the two mixed precursors are completely dissolved.

[0066] Step 4: Add 0.5 mL of tri-n-octylphosphine to the above solution under vigorous stirring, and continue stirring for 20 minutes to eliminate oxygen in the system.

[0067] Step 5: The temperature was then rapidly raised to 180°C and maintained at this temperature for 4 hours.

[0068] Step 6: After the reaction is completed, the reaction mixture is gradually cooled to room temperature, and washed with n-hexane and ethanol (volume ratio of 1:15) and centrifuged three times at a speed of 10000 r / min for 10 min.

[0069] Step 7: Dry the obtained nickel-copper nanoparticles in a vacuum oven at 60°C to obtain the final Ni 0.6 Cu 0.4 NPs.

[0070] Example 4

[0071] Ni 0.5 Cu 0.5 NPs alloy nanoparticles synthesis, the synthesis steps are as follows:

[0072] Step 1: Build the same reaction apparatus as above to prepare Ni 0.5 Cu 0.5 NPs.

[0073] Step 2: Accurately weigh 0.5 mmol of nickel acetylacetonate and 0.5 mmol of copper acetylacetonate and mix them in 10 mL of oleylamine solvent.

[0074] Step 3: In a nitrogen environment, heat the above solution to 70° C. and maintain it for 30 minutes until the two mixed precursors are completely dissolved.

[0075] Step 4: Add 0.5 mL of tri-n-octylphosphine to the above solution under vigorous stirring, and continue stirring for 25 minutes to eliminate oxygen in the system.

[0076] Step 5: The temperature was then rapidly raised to 180°C and maintained at this temperature for 4 hours.

[0077] Step 6: After the reaction is completed, the reaction mixture is gradually cooled to room temperature, and washed with n-hexane and ethanol (volume ratio of 1:15) and centrifuged three times at a speed of 10000 r / min for 10 min.

[0078] Step 7: Dry the obtained nickel-copper nanoparticles in a vacuum oven at 60°C to obtain the final Ni 0.5 Cu 0.5 NPs.

[0079] Example 5

[0080] Ammonia electrooxidation reaction performance test. 0.8 Cu 0.8 Taking NPs as an example, the test steps are as follows:

[0081] Step 1: Weigh 5.0 mg Ni 0.8 Cu 0.2 NPs, add 1 mL of N,N-dimethylformamide and sonicate for 10 min, add 1.0 mg of carbon black and sonicate for 10 min, and add 100 μL of Nafion solution and sonicate for 30 min.

[0082] Step 2: Take 8.0 μL of the mixed solution and drop it on the surface of the glassy carbon electrode and dry it to obtain the nickel-copper alloy catalyst.

[0083] Step 3: Follow the instructions Figure 4 The device shown, Ni 0.8 Cu 0.2 NPs were used as the working electrode, Hg / HgO was used as the reference electrode, a carbon rod was used as the counter electrode, and a mixed solution of 1.0 M KOH and 1.0 M KOH+0.5 M NH3 was used as the electrode solution to construct an electrolytic cell with a three-electrode system.

[0084] Step 4: Apply voltage to the working electrode (1.0-1.7 V vs. RHE), Ni 0.8 Cu 0.8 NPs showed a high current density in the ammonia electrooxidation reaction. Figure 5 For you 0.8 Cu0.2 Comparison of CV scans of NPs.

[0085] Step 5: Apply 10 mA cm to the working electrode. -2 The constant current of Ni 0.8 Cu 0.8 NPs showed good stability in ammonia electrooxidation reaction. Figure 5 For you 0.8 Cu 0.2 Stability test diagram of NPs.

[0086] The ammonia electro-oxidation reaction performance of the nickel-copper alloy nanoparticles obtained in Examples 2-4 of the present invention also has the same technical effect, and the particle size of the nanoparticles can be controlled at 5 to 7 nm.

[0087] Comparative Example 1

[0088] The synthesis of Ni NPs alloy nanoparticles (without copper) and the test of ammonia electrooxidation performance are as follows:

[0089] Step 1: Build the same reaction device as above to prepare nickel nanoparticles.

[0090] Step 2: Accurately weigh 1 mmol of nickel acetylacetonate and mix it in 10 mL of oleylamine solvent.

[0091] Step 3: In a nitrogen environment, heat the above solution to 80° C. and maintain it for 10 minutes until the precursor is completely dissolved.

[0092] Step 4: Add 0.5 mL of tri-n-octylphosphine to the above solution under vigorous stirring and continue stirring for 20 minutes to eliminate oxygen in the system and ensure that the oxygen concentration in the solution is reduced to the minimum.

[0093] Step 5: The temperature was then rapidly raised to 235°C and maintained at this temperature for 30 min.

[0094] Step 6: After the reaction is completed, the reaction mixture is gradually cooled to room temperature, and washed with n-hexane and ethanol (volume ratio of 1:15) and centrifuged three times at a speed of 10000 r / min for 10 min.

[0095] Step 7: The obtained nickel-copper nanoparticles were placed in a vacuum oven at 60°C and dried to obtain the final Ni NPs.

[0096] Step 8: Weigh 5.0 mg Ni NPs, add 1 mL N,N-dimethylformamide and sonicate for 10 min, add 1.0 mg carbon black and sonicate for 10 min, and add 100 μL Nafion solution and sonicate for 30 min.

[0097] Step 9: Take 8.0 μL of the mixed solution and drop it on the surface of the glassy carbon electrode and dry it to obtain the nickel-copper alloy catalyst.

[0098] Step 10: Ni NPs is used as the working electrode. A voltage (1.0-1.7 V vs. RHE) is applied to the working electrode. Figure 6 This is a scanning comparison diagram of LSV of nickel nanoparticles in ammonia electrooxidation reaction.

[0099] Comparative Example 2

[0100] CuNPs alloy nanoparticle synthesis (nickel-free) and ammonia electrooxidation performance testing, the steps are as follows:

[0101] Step 1: Build the same reaction device as above to prepare copper nanoparticles.

[0102] Step 2: Accurately weigh 1 mmol of copper acetylacetonate and mix it in 10 mL of oleylamine solvent.

[0103] Step 3: In a nitrogen environment, heat the above solution to 80° C. and maintain it for 10 minutes until the precursor is completely dissolved.

[0104] Step 4: Add 0.5 mL of tri-n-octylphosphine to the above solution under vigorous stirring, and continue stirring for 20 minutes to eliminate oxygen in the system.

[0105] Step 5: The temperature was then rapidly raised to 180°C and maintained at this temperature for 4 hours.

[0106] Step 6: After the reaction is completed, the reaction mixture is gradually cooled to room temperature, and washed with n-hexane and ethanol (volume ratio of 1:15) and centrifuged three times at a speed of 10000 r / min for 10 min.

[0107] Step 7: The obtained copper nanoparticles were placed in a vacuum oven at 60° C. to dry to obtain the final Cu NPs.

[0108] Step 8: Weigh 5.0 mg Ni NPs, add 1 mL N,N-dimethylformamide and sonicate for 10 min, add 1.0 mg carbon black and sonicate for 10 min, and add 100 μL Nafion solution and sonicate for 30 min.

[0109] Step 9: Take 8.0 μL of the mixed solution and drop it on the surface of the glassy carbon electrode and dry it to obtain the nickel-copper alloy catalyst.

[0110] Step 10: CuNPs is used as the working electrode, and a voltage (1.0-1.7 V vs. RHE) is applied to the working electrode. Figure 6 This is a scanning comparison diagram of LSV of copper nanoparticles in ammonia electro-oxidation reaction.

[0111] The present invention provides a highly efficient method for synthesizing nickel-copper alloy nanoparticles, which is simple and easy to implement and has a strong application prospect. The method can reduce the size of the catalyst to 5-7 nm, and prepare a series of nickel-copper alloy nanoparticles with different atomic ratios by adjusting the ratio of nickel-copper precursors, and optimize the electronic structure of the copper-nickel alloy to further improve the catalytic performance of ammonia electrooxidation reaction. Compared with Ni NPs and CuNPs, the nickel-copper alloy nanoparticles prepared by the present invention have a current density of ammonia voltage reaction increased by 2-3 times.

[0112] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing nickel-copper alloy nanoparticles, characterized in that: The following steps are involved: Step 1: Preparation of reaction solution: Dissolve nickel acetylacetonate and copper acetylacetonate in 10 mL of oleylamine solution and mix evenly to obtain a reaction precursor mixture; Step 2: Dissolving the Precursor Under nitrogen environment, heat the above solution to 50-100°C and maintain for 10-30 minutes to ensure that the reaction system is fully mixed and dissolved; Step 3: Deoxygenation Under vigorous stirring, add 0.5 mL of tri-n-octylphosphine to the above solution and continue stirring for 20-30 minutes to eliminate oxygen in the system; Step 4: Heat the reaction Then the temperature was rapidly raised to 180°C and maintained at this temperature for 4 hours to promote the alloying reaction of Ni and Cu; Step 5: Cooling and washing After the reaction was completed, the reaction mixture was gradually cooled to room temperature and washed with n-hexane and ethanol by centrifugation for 3 times at a speed of 10000 rpm / min for 10 min to remove the unreacted precursor; wherein the volume ratio of n-hexane to ethanol was 1:15; Step 6: Dry the product Finally, the obtained nickel-copper nanoparticles were placed in a vacuum oven at 60° C. and dried to obtain final nickel-copper alloy nanoparticles.

2. The method for preparing nickel-copper alloy nanoparticles according to claim 1, characterized in that: In step 1, the amount of nickel acetylacetonate added is 0.8-0.5 mmol, and the amount of copper acetylacetonate added is 0.2-0.5 mmol.

3. A nickel-copper alloy nanoparticle, characterized in that: Prepared by the method of claim 1 or 2, the nickel-copper alloy nanoparticles are generally Ni x Cu y NPs, wherein the molar ratio of Ni and Cu is x:y=8:

2.

4. The nickel-copper alloy nanoparticles according to claim 3, characterized in that: The nickel-copper alloy nanoparticles are Ni 0.8 Cu 0.2 NPs, Ni 0.7 Cu 0.3 NPs, Ni 0.6 Cu 0.4 NPs or Ni 0.5 Cu 0.5 NPs.

5. The nickel-copper alloy nanoparticles according to claim 3 or 4, characterized in that: The particle size is 5 to 7 nm.

6. The nickel-copper alloy nanoparticles according to claim 3 or 4, characterized in that: The nickel-copper composite nanoparticles are nearly spherical in shape.

7. A method for preparing a nickel-copper alloy nanoparticle electrocatalyst, characterized in that: The following steps are involved: Step 1: accurately weigh 5.0 mg of the nickel-copper alloy nanoparticles according to claim 4, add 1 mL of N,N-dimethylformamide, 1.0 mg of carbon black and 100 μL of Nafion solution to form a uniform solution; Step 2: Take 8.0 μL of the mixed solution and drop it on the surface of the glassy carbon electrode and dry it to obtain the nickel-copper alloy catalytic electrode.

8. Use of the nickel-copper alloy nanoparticle electrocatalyst according to claim 7 in ammonia electrooxidation.

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