CN113814408B

CN113814408B - Preparation and component regulation and control method of CuPd alloy nanocrystalline

Info

Publication number: CN113814408B
Application number: CN202111171249.5A
Authority: CN
Inventors: 刘欣美; 李雪; 杨文龙; 周雪; 李宇航; 李东平
Original assignee: Harbin University of Science and Technology
Current assignee: Harbin University of Science and Technology
Priority date: 2021-10-08
Filing date: 2021-10-08
Publication date: 2023-05-26
Anticipated expiration: 2041-10-08
Also published as: CN113814408A

Abstract

The invention discloses a preparation method and a component regulation method of CuPd alloy nanocrystalline, and the synthesis method mainly comprises the following steps: preparing soluble copper salt, adding potassium chloride powder, and uniformly stirring in a high-temperature environment to obtain a mixture 1; dissolving palladium chloride powder in hydrochloric acid solution, dissolving at high temperature, and adding into the mixed solution 1; adding ascorbic acid solution, stirring at high temperature for reaction for 5-6 hours. The component regulation and control method comprises the following steps: the atomic percentages of Cu and Pd in the alloy are controlled by adjusting the dosage of hydrochloric acid and palladium chloride powder in the reaction liquid. The method takes water as solvent, is carried out under the condition of no gas protection, has simple operation scheme and does not add organic surfactant in synthesis. The component regulation and control method provides wider space for the application of the CuPd alloy nanocrystalline.

Description

Preparation and component regulation and control method of CuPd alloy nanocrystalline

Technical Field

The invention relates to the technical field of metal nano material preparation, in particular to a preparation method and a component regulation method of CuPd alloy nanocrystalline.

Background

In recent years, the excellent application performance of the metal Pd simple substance in proton exchange membrane fuel attracts attention of a plurality of students. However, further industrial application of Pd simple substance is severely limited due to higher market price. The research and development of taking CuPd alloy nanocrystalline as a substitute can effectively reduce the use of noble metals. Meanwhile, the adjustable d-band center and the synergistic effect of the bimetal provide a wider space for the application of CuPd alloy nanocrystalline (such as the important fields of electrocatalytic carbon dioxide reduction and the like).

For nano materials with high specific surface energy, the procedures of high temperature, annealing and the like in the traditional alloy preparation are not applicable. The gas phase process is likewise unsuitable for large-scale production. This is mainly due to the high equipment requirements and low throughput of the gas phase process. Among the existing preparation methods, the liquid phase method has lower requirements on equipment, and has become the main stream means for preparing alloy nanocrystalline in recent years. The nucleation process of the nanocrystals and the percentages of the internal elements can also be changed by simply regulating the reaction parameters (such as reactant concentration, molar ratio, reaction temperature and time, etc.).

However, there are also the following problems with liquid phase preparation of CuPd alloy nanocrystals:

1. lower product yield

In the practical use of the liquid phase method, the co-reduction reaction is carried out along with other reactions to form an alloy, which clearly results in the product containing impurities and low yield of the product. Guo et al prepared CuPd alloy nanoparticles using N, N-dimethylformamide as a solvent and trimesic acid as a reducing agent. However, the yield of the resulting product was only forty-five percent, with higher costs and lower yields (Guo, penghu, et al, "CuPd mixed-metal HKUST-1as a catalyst for aerobic alcohol oxidation." The Journal of Physical Chemistry C122.37 (2018): 21433-21440).

2. The extraction and cleaning process is complex

In order to obtain high purity, high specific surface area alloys, most of the preparation schemes are often performed in an organic solvent environment. For example, the Zhang Hua subject group of south ocean engineering prepared PdCu nanoparticles (Yang, nailiang, et al, "Synthesis of ultrathin PdCu alloy nanosheets used as a highly efficient electrocatalyst for formic acid oxidation." Advanced Materials 29.29.29 (2017): 1700769) using copper acetylacetonate and palladium acetylacetonate as precursors, tri-n-octylphosphine oxide and dimethylformamide as solvents, and octadecylamine as a surfactant, under nitrogen protection at 60 degrees celsius for 18 hours. The organic solvents are adsorbed on the surface of the sample, which increases the complexity of product extraction.

3. Can not realize the regulation and control of the atomic percentages of Cu and Pd in the alloy

The spring institute of education uses polyvinylpyrrolidone as surfactant and formic acid as reducer, and the positive divalent palladium salt and cupric chloride solution are subjected to oxidation-reduction reaction at 110 ℃ to obtain CuPd nano-particles (a synthetic method and application of the palladium-copper nano-catalyst reduced by formic acid [ P ] Zhao Xiaojing, chang Yandong, pan Xiaoyang, chinese patent CN113042069A, 2021-06-29). The method realizes the preparation of the small-scale alloy nanocrystalline in the water phase environment. However, the atomic percentages of Cu and Pd in the obtained alloy cannot be further controlled.

Disclosure of Invention

The invention overcomes the defects existing in the background technology and provides a preparation method and a component regulation method of CuPd alloy nanocrystalline. The preparation of the invention can be realized under the protection of no nitrogen, and the surface of the CuPd alloy nanocrystalline has no organic molecular adsorption because no organic surfactant is added in the preparation process, so that the CuPd alloy nanocrystalline has a clean surface. The specific operation comprises the following steps:

1) Copper chloride is used as a solute, deionized water is used as a solvent, a copper chloride solution is prepared, potassium chloride powder is added, and the mixture is placed in an environment of 90-100 ℃ after being uniformly stirred by a magnetic stirrer, so as to obtain a mixed solution 1;

2) Dissolving palladium chloride powder in hydrochloric acid solution, and heating to about 80-90 ℃ to fully dissolve the palladium chloride powder to obtain a mixed solution 2;

3) Adding the mixed solution 2 into the mixed solution 1, and stirring until the mixed solution is uniform to obtain a mixed solution 3;

4) Adding 1.0 mol/L ascorbic acid solution into the mixed solution 3, and reacting for 5-6 hours under rapid stirring at 90-100 ℃;

5) Separating the obtained product by using a centrifugal machine, dispersing the product into deionized water, performing ultrasonic treatment, performing secondary centrifugation, dispersing the product into ethanol, performing ultrasonic treatment, and drying the powder after secondary centrifugation in a blast drying oven.

Correspondingly, the invention also discloses a CuPd alloy nanocrystalline with a clean surface, which is obtained by the preparation method of the CuPd alloy nanocrystalline. The implementation of the invention has the following beneficial effects:

1. the obtained product has high purity and no impurity

According to the invention, excessive hydrochloric acid solution is introduced into the reaction liquid, so that the intermediate product cuprous chloride is dissolved, and the product purity is improved. And the dissolved monovalent Cu ions are further reduced to a CuPd alloy in an acidic environment.

2. The preparation process is simple, and the energy consumption and the cost are low.

The method takes deionized water as a solvent, and does not use a surfactant in the whole preparation process, so that the method not only can ensure the surface cleaning of the product to the greatest extent and keep the self attribute of the CuPd alloy, but also is beneficial to simplifying the extraction steps of the later-stage product.

3. The atomic percentages of Cu and Pd in the alloy are adjustable.

The method realizes the accurate control of the components in the CuPd alloy by regulating and controlling the contents of hydrochloric acid and palladium sources in the mixed reaction liquid, and is simple and easy to realize. In addition, the CuPd alloy nanocrystals of different compositions will meet the requirements of different performance applications.

Drawings

FIG. 1 is an X-ray diffraction pattern of the sample obtained in example 1.

FIG. 2 is a field emission scanning electron microscope picture of the sample obtained in example 1.

FIG. 3 is an X-ray diffraction pattern of the sample obtained in example 2.

Fig. 4 is a field emission scanning electron microscope picture of the sample obtained in example 2.

FIG. 5 is an X-ray diffraction pattern of the sample obtained in example 3.

FIG. 6 is a field emission scanning electron microscope picture of the sample obtained in example 3.

FIG. 7 is an X-ray diffraction pattern of the sample obtained in example 4.

FIG. 8 is an X-ray diffraction pattern of the sample obtained in comparative example 1.

FIG. 9 is an X-ray diffraction pattern of the sample obtained in comparative example 2.

Detailed Description

The method takes deionized water as a solvent, preferably copper chloride and palladium chloride as precursors, hydrochloric acid as a pH regulator, a dissolving agent of reactants and ascorbic acid as a reducing agent. The whole reaction temperature is not more than 100 ℃. By regulating and controlling the contents of hydrochloric acid and palladium sources in the mixed reaction liquid, the atomic percentage of Cu and Pd in the CuPd alloy can be regulated. For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following examples and drawings, wherein the reagents used are commercially available without further purification unless otherwise specified.

Example 1: preparation of high purity CuPd nanocrystalline 1

1) Preparing 19 ml of copper chloride solution with the concentration of 15 mmol/L by taking copper chloride as a solute and deionized water as a solvent, adding 150 mg of potassium chloride, uniformly stirring by using a magnetic stirrer, and then placing at 95 ℃ to obtain a mixed solution 1;

2) Dissolving 0.05 mmol of palladium chloride powder in 5 ml of hydrochloric acid solution with concentration of 0.1 mol/L, and heating to 85 ℃ to dissolve the palladium chloride powder to obtain a mixed solution 2;

3) Adding the mixed solution 2 into the mixed solution 1, and stirring for 15 minutes at 95 ℃ to obtain a mixed solution 3;

4) 6 ml of ascorbic acid with the concentration of 1.0 mol/L is added into the mixed solution 3, and the mixture is rapidly stirred for 5 hours at 95 ℃;

5) Separating the obtained product by using a centrifugal machine, dispersing the product into deionized water, performing ultrasonic treatment, performing secondary centrifugation, dispersing the product into ethanol, performing ultrasonic treatment, and drying the powder after secondary centrifugation in a 60 ℃ blast drying oven.

To determine the composition of the product, we first performed X-ray diffraction on the sample, as shown in FIG. 1, and the X-ray diffraction pattern of the obtained sample corresponds to the standard diffraction card JCPDS 48-1551 of CuPd. The obtained product is CuPd alloy nanocrystalline with high purity. As can be seen from the sem pictures of fig. 2 in the description of the drawings: the obtained CuPd alloy nanocrystalline is nano particles. The diameter is about 40-60 nanometers.

Example 2: preparation of high purity CuPd nanocrystalline 2

2) 0.05 mmol of palladium chloride powder is dissolved in 2.5 ml of hydrochloric acid solution with the concentration of 0.1 mol/L, and the solution is heated to 90 ℃ to be dissolved, so as to obtain a mixed solution 2;

In comparison to example 1, example 2 compares in step 2): "5 ml of a hydrochloric acid solution having a concentration of 0.1 mol/l" is changed to "2.5 ml of a hydrochloric acid solution having a concentration of 0.1 mol/l". The Ph of the reaction environment increases due to the lower content of hydrochloric acid in the solution. The sample diffraction peak of example 2 is located between elemental Cu and elemental Pd. As shown in fig. 3, the diffraction peak position of the product obtained in example 2 was shifted to a high diffraction angle (toward the characteristic peak position of elemental Cu) compared with that in example 1. The results show that: the atomic percent increase in Cu in the sample was increased over example 1. The above phenomenon is caused by the fact that after the consumption of the hydrochloric acid is reduced, the Ph value of the mixed solution is improved, the reduction performance of the reducing agent is improved, and a large amount of copper chloride is reduced to be 0 price.

Thus, it can be concluded that: the Cu content in the CuPd alloy can be controlled by adjusting the consumption of hydrochloric acid in the reaction liquid, so that the regulation and control of the atomic percentages of Cu and Pd are realized. From fig. 4, the CuPd alloy product obtained in example 2 remains nanoparticulate and has enhanced aggregation.

Example 3: preparation of high purity CuPd nanocrystals 3

1) Preparing 19 ml of copper chloride solution with concentration of 15 mmol/L by taking copper chloride as solute and deionized water as solvent; 150 mg of potassium chloride is added, and the mixture is stirred uniformly by a magnetic stirrer and then placed at 95 ℃ to obtain a mixed solution 1;

2) Dissolving 0.1 mmol of palladium chloride powder in 5 ml of hydrochloric acid solution with concentration of 0.1 mol/L, and heating to 90 ℃ to dissolve the solution to obtain a mixed solution 2;

5) Separating the obtained product by using a centrifugal machine, dispersing the product into deionized water, performing ultrasonic treatment, performing secondary centrifugation, dispersing the product into ethanol, performing ultrasonic treatment, and drying the powder after secondary centrifugation in a 80 ℃ blast drying oven.

In comparison to example 1, example 3 compares in step 2): "0.05 mmol of palladium chloride powder" is changed to "0.1 mmol of palladium chloride powder". To determine the composition of the product, we first performed an X-ray diffraction test on the sample. As a result, as shown in FIG. 5, the angle of the diffraction peak of the product obtained in example 3 was shifted to a low angle (toward the position of the characteristic peak of elemental Pd) as compared with example 1. The results show that: the atomic percentage of Pd in the CuPd alloy increases. The above phenomenon is caused by the increase of the palladium chloride dosage.

Thus, we can derive: in the process of preparing the CuPd alloy nanocrystalline, the percentage of Pd atoms in the CuPd alloy can be increased by increasing the use amount of palladium salt, so that the regulation and control of the percentage of Cu and Pd atoms are realized. To explore the morphology of the resulting product, we performed field emission scanning electron microscopy tests on the product. As shown in fig. 6, example 3 gave the alloy as granular nanocrystals, which remained as aggregated particles.

Example 4: preparation of high purity CuPd nanocrystalline 4

1) Preparing a copper chloride solution with a volume of 38 milliliters and a concentration of 15 millimoles per liter by taking copper chloride as a solute and deionized water as a solvent; adding 300 mg of potassium chloride powder, uniformly stirring by using a magnetic stirrer, and then placing in an environment of 95 ℃ to obtain a mixed solution 1;

2) Dissolving 0.2 mmol of palladium chloride powder in 5 ml of hydrochloric acid solution with concentration of 0.1 mol/L, and heating to 85 ℃ to dissolve the palladium chloride powder to obtain a mixed solution 2;

3) Adding the mixed solution 2 into the mixed solution 1, and stirring for 15 minutes to obtain a mixed solution 3;

4) 13 ml of ascorbic acid with the concentration of 1.0 mol/L is added into the mixed solution 3, and the mixture is rapidly stirred for 6 hours at 98 ℃;

5) Separating the obtained product by using a centrifugal machine, dispersing into deionized water, performing ultrasonic treatment, performing secondary centrifugation, dispersing into ethanol again, performing ultrasonic treatment, and drying the centrifuged powder in a blast drying oven at 80 ℃.

To determine the composition of the resulting product, we performed X-ray diffraction on the sample. As shown in fig. 7, the diffraction peak of the obtained product is located between the elemental Cu and the elemental Pd, and is a high-purity CuPd alloy.

Comparative example 1: key technical demonstration 1

The key of the technology of the invention is as follows: the chloropalladate powder is pre-dissolved by hydrochloric acid solution. In addition, a longer reaction time is also an important guarantee that the co-reduction reaction is sufficiently carried out. To demonstrate the above, we performed comparative example 1, the specific procedure is as follows:

1) Using copper chloride as a solute and deionized water as a solvent, preparing a copper chloride solution with a volume of 38 milliliters and a concentration of 15 millimoles per liter, adding 300 milligrams of potassium chloride powder, and stirring for 10 minutes to obtain a mixed solution 1;

2) Adding 12 ml of ascorbic acid solution with the concentration of 1.0 mol/L into the mixed solution 1, and stirring for 15 minutes to obtain a mixed solution 2;

3) 10 ml of palladium chloride solution with the concentration of 10 mmol/L is added into the mixed solution 2, and the mixture is stirred and reacted for 1 hour at the temperature of 95 ℃;

4) Separating the obtained product by a centrifugal machine, dispersing the product in deionized water by ultrasonic, centrifuging the product for the second time, dispersing the product in ethanol by ultrasonic, centrifuging the product again, and drying the product in a blast drying oven at 50 ℃ to obtain the final product.

To determine the composition of the resulting product, we performed an X-ray diffraction test on the sample. As can be seen from FIG. 8, in the product of comparative example 1, in addition to the CuPd alloy, a large amount of elemental Pd (JCDF card number: 5-681) and cuprous chloride impurity were present. The above phenomenon occurs because the palladium chloride powder has low solubility in water, and cannot be uniformly dispersed in the mixed solution 2, and is reduced to an alloy together with copper chloride. In contrast, an excess of cupric chloride is reduced to cuprous chloride by the action of the reducing agent.

From this we can conclude that: the pre-dissolution operation of the palladium precursor by using the hydrochloric acid solution can ensure the output of the high-purity CuPd alloy. In addition, the excessive hydrochloric acid can also play a role in dissolving the by-product cuprous chloride, so that the purity of the product is improved.

Comparative example 2: key technical demonstration 2

In the invention, the preparation environment at 90-100 ℃ is an important precondition for ensuring co-reduction of two precursors and production of CuPd alloy. To demonstrate this point, we performed comparative example 2, with the following procedure:

1) Copper chloride is used as solute, deionized water is used as solvent, 38 ml of copper chloride solution with the concentration of 15 mmol/L is prepared, 300 mg of potassium chloride powder is added, and stirring is carried out for 10 minutes, thus obtaining mixed solution 1

3) 10 ml of palladium chloride solution with the concentration of 10 mmol/L is added into the mixed solution 2, and the mixture is stirred and reacted for 6 hours at room temperature;

4) Separating the obtained product by using a centrifugal machine, dispersing the product in deionized water by using ultrasonic waves, centrifuging the product for the second time, dispersing the product into ethanol by using ultrasonic waves, centrifuging the product again, and drying the product in a blast drying oven at 60 ℃ to obtain the final product.

To determine the composition of the resulting product, we performed an X-ray diffraction test on the sample. As shown in fig. 9, the product obtained in comparative example 2 was mainly a mixture of cuprous chloride and elemental Pd in room temperature environment, and no CuPd alloy was formed. From this, it was demonstrated that the control of the reaction temperature in the preparation process of the present invention is a necessary guarantee for obtaining a high-purity CuPd alloy.

Claims

1. A preparation method and a component regulation method of CuPd alloy nanocrystalline are characterized by comprising the following specific operation steps:

1) Preparing soluble copper salt solution by taking deionized water as a solvent, adding a certain amount of potassium chloride powder, uniformly stirring, and placing in an environment of 90-100 ℃ to obtain a mixed solution 1;

2) Dissolving palladium chloride powder in hydrochloric acid solution with the concentration of 0.1 mol/liter, heating to 80-90 ℃ and further dissolving to obtain mixed solution 2;

4) Adding 1.0 mol/L ascorbic acid solution into the mixed solution 3, placing the mixed solution in an environment of 90-100 ℃ and rapidly stirring for reacting for 5-6 hours;

5) Separating the obtained product by using a centrifugal machine, dispersing the product into deionized water, performing ultrasonic treatment, performing secondary centrifugation, dispersing the product into ethanol, performing ultrasonic treatment, and drying the powder obtained after secondary centrifugation in a blast drying oven;

the soluble copper salt in the step 1) is preferably a copper chloride solution, and the molar ratio of the added potassium chloride to the soluble copper salt is 3:1-8: 1;

step 4) adding the molar ratio of the ascorbic acid solution to Cu salt in the mixed solution 3 is 19:1-24: 1;

step 5) drying temperature is preferably 50-100 ℃;

the method for regulating and controlling the components in the alloy comprises the following steps: the content of Pd in the CuPd alloy is increased by increasing the use level of palladium chloride; the Cu content in the CuPd alloy is increased by reducing the use amount of hydrochloric acid in the reaction liquid; the molar ratio of the palladium chloride powder to the hydrochloric acid in the step 2) is 1:10 to 3: 5; the volume ratio of the mixed solution 2 to the mixed solution 1 in the step 3) is 1:8 to 1: 3.