CN113814408A

CN113814408A - Preparation of CuPd alloy nanocrystalline and component regulation and control method thereof

Info

Publication number: CN113814408A
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: 2021-12-21
Anticipated expiration: 2041-10-08
Also published as: CN113814408B

Abstract

The invention discloses a preparation method of CuPd alloy nanocrystalline and a component regulation method thereof, wherein the synthesis method mainly comprises the following steps: preparing soluble copper salt, adding potassium chloride powder, and stirring uniformly at a high temperature to obtain a mixture 1; dissolving palladium chloride powder in a hydrochloric acid solution, dissolving at a high temperature, and adding into the mixed solution 1; adding ascorbic acid solution, and stirring at high temperature for reaction for 5-6 hr. The component regulation and control method comprises the following steps: adjusting the dosage of hydrochloric acid and palladium chloride powder in the reaction liquid to control the atomic percentage of Cu and Pd in the alloy. The method takes water as a solvent, is carried out without gas protection, has simple operation scheme, and does not add an organic surfactant in the synthesis. The method for regulating and controlling the components provides wider space for the application of the CuPd alloy nanocrystalline.

Description

Preparation of CuPd alloy nanocrystalline and component regulation and control method thereof

Technical Field

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

Background

In recent years, the excellent application performance of the metal Pd elementary substance in the proton exchange membrane fuel attracts attention of a plurality of scholars. However, due to the high market price, further industrial application of the elemental Pd is severely restricted. The research and development of using the 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 the CuPd alloy nanocrystalline (such as important fields of electrocatalysis carbon dioxide reduction and the like).

For the nano material 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 also not suitable 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 low requirements on equipment, and becomes a mainstream means for preparing the alloy nanocrystals in recent years. The nucleation process and the internal element percentage of the nanocrystals can also be changed by simply adjusting the reaction parameters (such as reactant concentrations, molar ratios, reaction temperature and time, etc.).

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

1. the product yield is low

In the actual use of the liquid phase process, the formation of the alloy is accompanied by other reactions in addition to the co-reduction, which undoubtedly results in impurities in the product and low product yields. 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 product obtained is only forty-five percent, The cost is high, and The yield is low (Guo, Penghu, et al. "CuPd mixed-metal HKUST-1as a catalyst for aerobic alcoholic oxidation." The Journal of Physical Chemistry C122.37 (2018): 21433. sup. 21440).

2. The extraction and cleaning process is complicated

In order to obtain high purity, high specific surface area alloys, most of the preparation schemes are often carried out in an organic solvent environment. For example, Nanyang Physician, a Zhanghua group of subjects, who utilized copper acetylacetonate and palladium acetylacetonate as precursors, tri-n-octylphosphine oxide and dimethylformamide as solvents, and octadecylamine as a surfactant, produced PdCu nanoparticles at a temperature of 60 ℃ under nitrogen protection for 18 hours (Yang, Nailing, et al, "Synthesis of ultra PdCu allomaterials used as a high effective surfactants for use in Advanced Materials 29.29(2017): 1700769). These organic solvents adsorb on the sample surface, adding to 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 Quanzhou academy of faculty takes polyvinylpyrrolidone as a surfactant and formic acid as a reducing agent, and uses a direct divalent palladium salt and a copper chloride solution to prepare CuPd nano-particles by oxidation-reduction reaction at 110 ℃ (a synthesis method and application of a palladium-copper nano-catalyst reduced by formic acid [ P ]. Zhao Xiaojing, Changdong, Pandayang, 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 resulting alloy cannot be further controlled.

Disclosure of Invention

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

1) preparing a copper chloride solution by using copper chloride as a solute and deionized water as a solvent, adding potassium chloride powder, uniformly stirring by using a magnetic stirrer, and then placing in an environment at 90-100 ℃ to obtain a mixed solution 1;

2) dissolving palladium chloride powder in a 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 uniformly 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 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 beneficial effects of the implementation of the invention are as follows:

1. the obtained product has high purity and no impurities

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

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

The method takes the deionized water as the solvent, and the surfactant is not used in the whole preparation process, so that the method not only can ensure the surface cleanness of the product to the maximum extent and keep the property of the CuPd alloy, but also is beneficial to simplifying the extraction step of the later-stage product.

3. The atomic percentages of Cu and Pd in the alloy can be adjusted.

According to the invention, the accurate control of the components in the CuPd alloy is realized by regulating and controlling the contents of hydrochloric acid and a palladium source in the mixed reaction liquid, and the method is simple and easy to realize. In addition, CuPd alloy nanocrystals with different components can meet the requirements of different performance applications.

Drawings

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

FIG. 2 is a SEM image of a sample obtained in example 1.

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

FIG. 4 is a SEM image of the sample obtained in example 2.

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

FIG. 6 is a SEM image of the sample obtained in example 3.

FIG. 7 is an X-ray diffraction pattern of a 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 and a reactant dissolving agent, and ascorbic acid as a reducing agent. The whole reaction temperature does not exceed 100 ℃. The atomic percentage of Cu and Pd in the CuPd alloy can be adjusted by regulating and controlling the content of hydrochloric acid and a palladium source in the mixed reaction liquid. In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the following examples and accompanying drawings, wherein all reagents are commercially available without further purification unless otherwise specified.

Example 1: preparation of high purity CuPd nanocrystal 1

1) Preparing 19 ml of a copper chloride solution with the concentration of 15 mmol/L by using 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 the 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) adding 6 ml of ascorbic acid with the concentration of 1.0 mol/L into the mixed solution 3, and rapidly stirring 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 blast drying oven at 60 ℃.

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

Example 2: preparation of high purity CuPd nanocrystal 2

2) dissolving 0.05 mmol of palladium chloride powder in 2.5 ml of hydrochloric acid solution with the concentration of 0.1 mol/L, and heating to 90 ℃ to dissolve the palladium chloride powder to obtain a mixed solution 2;

In contrast to example 1, example 2 compares in step 2): "5 ml of 0.1 mol/l hydrochloric acid solution" was changed to "2.5 ml of 0.1 mol/l hydrochloric acid solution". The Ph of the reaction environment rises due to the low hydrochloric acid content of 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) as compared with that in example 1. The results show that: the atomic percentage of Cu in the sample increased compared to example 1. The phenomenon is caused by that after the using amount of hydrochloric acid is reduced, the Ph value of the mixed solution is increased, the reducing performance of the reducing agent is improved, and a large amount of copper chloride is reduced to 0 valence.

Thus, it can be concluded that: the content of Cu in the CuPd alloy can be controlled by adjusting the dosage of hydrochloric acid in the reaction solution, and the atomic percentage of Cu and Pd can be regulated and controlled. As can be seen from fig. 4, the CuPd alloy product obtained in example 2 is still nanoparticulate and has enhanced aggregability.

Example 3: preparation of high purity CuPd nanocrystal 3

1) Preparing 19 ml of copper chloride solution with the concentration of 15 mmol/l by using 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 0.1 mmol of palladium chloride powder in 5 ml of hydrochloric acid solution with the concentration of 0.1 mol/L, and heating to 90 ℃ to dissolve the palladium chloride powder 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 forced air drying oven at 80 ℃.

In contrast to example 1, example 3 compares in step 2): "0.05 mmol of palladium chloride powder" was changed to "0.1 mmol of palladium chloride powder". To determine the composition of the product, we first performed X-ray diffraction tests on the samples. 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 lower angle (toward the position of the characteristic peak of elemental Pd) than that of example 1. The results show that: the atomic percentage of Pd in the CuPd alloy increases. This occurs due to the increased amount of palladium chloride.

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 using amount of the palladium salt, so that the regulation and control of the atomic percentages of Cu and Pd are realized. In order to explore the morphology of the obtained product, the product is subjected to a field emission scanning electron microscope test. As shown in fig. 6, the alloy obtained in example 3 was still in the form of aggregated particles of nano-crystals.

Example 4: preparation of high purity CuPd nanocrystal 4

1) Copper chloride is used as a solute, deionized water is used as a solvent, and a copper chloride solution with the volume of 38 ml and the concentration of 15 mmol/L is prepared; adding 300 mg of potassium chloride powder, uniformly stirring by using a magnetic stirrer, and then placing in a 95 ℃ environment to obtain a mixed solution 1;

2) dissolving 0.2 mmol of palladium chloride powder in 5 ml of hydrochloric acid solution with the 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) adding 13 ml of ascorbic acid with the concentration of 1.0 mol/L into the mixed solution 3, and rapidly stirring for 6 hours at 98 ℃;

5) separating the obtained product by 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 centrifugation in a forced air 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 evidence 1

The key of the technology of the invention is that: firstly, hydrochloric acid solution is utilized to pre-dissolve chloropalladate powder. In addition, a longer reaction time is also an important guarantee for the full progress of the co-reduction reaction. To demonstrate the above, we have carried out comparative example 1, with the following specific operating steps:

1) preparing a copper chloride solution with the volume of 38 ml and the concentration of 15 mmol/L by using copper chloride as a solute and deionized water as a solvent, adding 300 mg of potassium chloride powder, and stirring for 10 minutes to obtain a mixed solution 1;

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

3) adding 10 ml of palladium chloride solution with the concentration of 10 mmol/L into the mixed solution 2, and stirring and reacting for 1 hour at 95 ℃;

4) separating the obtained product by using a centrifuge, performing secondary centrifugation after ultrasonic dispersion in deionized water, dispersing the product into ethanol, performing ultrasonic treatment and secondary centrifugation, and drying the product in a forced air drying oven at 50 ℃ to obtain the final product.

To determine the composition of the resulting product, we performed X-ray diffraction tests on the samples. As can be seen from FIG. 8, in addition to the CuPd alloy, the product of comparative example 1 also contains a large amount of elemental Pd (JCPDF card number: 5-681) and cuprous chloride impurities. The above phenomenon occurs because the chloropalladate powder has a 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 amount of cupric chloride is reduced to cuprous chloride by the action of a reducing agent.

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

Comparative example 2: key technical evidence 2

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

1) copper chloride is used as a solute, deionized water is used as a solvent, a copper chloride solution with the volume of 38 ml and the concentration of 15 mmol/L is prepared, 300 mg of potassium chloride powder is added, and the mixture is stirred for 10 minutes to obtain a mixed solution 1

3) adding 10 ml of palladium chloride solution with the concentration of 10 mmol/L into the mixed solution 2, and stirring and reacting for 6 hours at room temperature;

4) separating the obtained product by using a centrifugal machine, performing secondary centrifugation after ultrasonic dispersion in deionized water, dispersing the product into ethanol, performing ultrasonic treatment and secondary centrifugation, and drying the product in a blast drying box at the temperature of 60 ℃ to obtain the final product.

To determine the composition of the resulting product, we performed X-ray diffraction tests on the samples. As shown in fig. 9, the product obtained in comparative example 2 is mainly a mixture of cuprous chloride and elemental Pd, and no CuPd alloy is generated under room temperature. Therefore, the control of the reaction temperature in the preparation process is necessary guarantee for obtaining the high-purity CuPd alloy.

Claims

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

1) preparing a 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/L, heating to 80-90 ℃, and further dissolving to obtain mixed solution 2;

4) adding an ascorbic acid solution with the concentration of 1.0 mol/L into the mixed solution 3, placing the mixture in an environment of 90-100 ℃, and quickly stirring the mixture for reaction for 5-6 hours;

5) separating the obtained product by 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 obtained powder in a forced air drying oven after secondary centrifugation.

2. The method for preparing CuPd alloy nanocrystals and adjusting the composition thereof as claimed in claim 1, wherein the method comprises the following steps:

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;

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

and 5) drying at 50-100 ℃.

3. The method for preparing CuPd alloy nanocrystals and adjusting and controlling the components thereof according to claim 1, wherein the method for adjusting and controlling the components in the alloy comprises the following steps: the content of Pd in the CuPd alloy is increased by increasing the consumption of palladium chloride; the content of Cu in the CuPd alloy is increased by reducing the consumption of hydrochloric acid in the reaction liquid; the molar ratio of the palladium chloride powder in the step 2) to the hydrochloric acid is 1: 10 to 3: 5 or more; the volume ratio of the mixed solution 2 to the mixed solution 1 in the step 3) is 1: 8 to 1: 3, or less.