Preparation method of Pt nanocrystalline catalyst
Preparation of Pt nanocrystal catalysts by gel method solves the problems of uneven nanocrystal size and low catalytic activity in traditional methods, and achieves uniform size distribution and high catalytic activity of the catalyst, which is suitable for energy conversion and storage fields.
Patent Information
- Application Number
- CN202411755754.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-03
- Publication Date
- 2025-03-14
AI Technical Summary
The traditional preparation method of Pt nanocrystal catalysts has problems such as uneven nanocrystal size, poor dispersion, and low catalytic activity.
The Pt nanocrystal catalyst is prepared by gel method. By hydrolysis and polycondensation reaction of the aqueous solution containing platinum precursor at a specific temperature, a sol is formed, and then aged, dried, calcined and reduced, a Pt nanocrystal catalyst with uniform size and high catalytic activity is obtained.
The uniform size distribution, good dispersion and high catalytic activity of Pt nanocrystalline catalyst are achieved, and the stability and application performance of the catalyst are improved, which is suitable for large-scale production.
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Figure CN119608150A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of nano material preparation, and specifically relates to a method for preparing a Pt nanocrystalline catalyst. Background Art
[0002] With the rapid development of the global economy and the continuous growth of population, energy demand continues to rise, and environmental problems are becoming increasingly severe. Traditional energy utilization methods face many challenges, such as the gradual depletion of fossil energy, low energy utilization efficiency and environmental pollution. In this context, the development of efficient and clean energy conversion and storage technologies has become a top priority.
[0003] Catalysts play a vital role in the process of energy conversion and storage. For example, in fuel cells, catalysts can promote the oxidation reaction of fuels such as hydrogen or methanol and the reduction reaction of oxygen, improving energy conversion efficiency; in automobile exhaust purification, catalysts can convert harmful exhaust components into harmless substances and reduce environmental pollution; in organic synthesis reactions, efficient catalysts can increase reaction rate and selectivity, reduce energy consumption and waste emissions; in electrochemical sensors, catalysts can be used to detect various chemicals with high sensitivity, selectivity and stability.
[0004] Due to their unique physical and chemical properties, Pt nanocrystal catalysts have shown excellent performance in many catalytic fields. First, Pt nanocrystals have a high specific surface area and can provide more active sites, thereby improving catalytic activity. Secondly, nanoscale Pt crystals can regulate electronic structure and surface chemical properties to enhance selectivity for specific reactions. In addition, Pt nanocrystal catalysts also have good stability and recyclability, which is conducive to reducing costs and reducing resource waste. However, the traditional preparation method of Pt nanocrystal catalysts has problems such as uneven nanocrystal size, poor dispersibility, and low catalytic activity. Therefore, it is of great practical significance to develop an efficient preparation method for Pt nanocrystal catalysts. Summary of the invention
[0005] The purpose of the present invention is to provide a method for preparing a Pt nanocrystalline catalyst by using a gel method, which can overcome the shortcomings of traditional preparation methods and prepare a Pt nanocrystalline catalyst with uniform size, good dispersibility, high catalytic activity and stability.
[0006] The preparation method of the Pt nanocrystalline catalyst provided by the present invention comprises the following steps:
[0007] Step 1: dissolving an aqueous solution containing a platinum precursor in a solvent to form a uniform solution;
[0008] Step 2: hydrolyzing the solution of step 1 at 50-120° C., controlling the pH value of the solution in the range of 2-6 during the reaction; raising the temperature of the obtained hydrolyzate by 30-50° C. after the hydrolysis reaction, with the maximum temperature of the hydrolyzate not exceeding 150° C., and performing a polycondensation reaction to obtain a sol;
[0009] Step 3: subjecting the sol of step 2 to aging treatment to convert it into gel;
[0010] Step 4: Dry, calcine and reduce the gel of step 3 to obtain a Pt nanocrystalline catalyst.
[0011] In the above step 1, the platinum-containing precursor is selected from any one or more of chloroplatinic acid, ammonium chloroplatinate, and dinitrosodiammineplatinum. These precursors can provide platinum elements in subsequent reactions and have good solubility and stability.
[0012] In the above step 1, the solvent is any one of water, ethanol and isopropanol. These solvents can be fully mixed with the platinum-containing precursor to form a uniform solution, and can play a good dispersing and stabilizing role in subsequent reactions.
[0013] In the above step 2, the platinum-containing precursor undergoes a hydrolysis reaction in the solution to form a metal hydroxide or a hydrated oxide, and sodium hydroxide is added during the hydrolysis reaction to control the pH value of the solution to be in the range of 2 to 6. The hydrolysis product further undergoes a polycondensation reaction to form a sol. During the polycondensation reaction, the metal ions are connected to form a three-dimensional network structure through the formation of chemical bonds. Preferably, the solution of step 1 is hydrolyzed at 60 to 90°C, and the pH value of the solution is controlled to be in the range of 2 to 6 during the reaction; after the hydrolysis reaction is completed, the temperature of the obtained hydrolyzate is increased by 20 to 30°C, and the maximum temperature of the hydrolyzate does not exceed 120°C, and a polycondensation reaction is performed to obtain a sol. It is further preferred that the hydrolysis reaction time is 2 to 8 hours, and the polycondensation reaction time is 20 to 100 hours.
[0014] In the above step 3, during the aging process, the colloidal particles in the sol gradually aggregate and grow to form a gel with a three-dimensional network structure. Preferably, the aging treatment temperature is 30-90°C, the humidity is 40%-90%, and the time is 30-120 hours.
[0015] In the above step 4, the gel is dried to remove the solvent therein. The drying method is any one of natural drying, oven drying or freeze drying.
[0016] In the above step 4, the dried gel is calcined to remove the organic components therein and crystallize the Pt nanocrystals. The calcination temperature is preferably 300-800° C. and the calcination time is 2-10 hours.
[0017] In the above step 4, the calcined gel is subjected to reduction treatment to reduce the oxidized platinum in the Pt nanocrystals to metallic platinum, further improving its catalytic activity. The reduction method is hydrogen reduction, preferably the reduction temperature is 300-600° C., and the reduction time is 2-6 hours.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] 1. The present invention utilizes a gel method to prepare a Pt nanocrystalline catalyst, and the reaction conditions are mild and easy to control, and the size and morphology of the nanocrystals can be precisely controlled. The prepared Pt nanocrystalline catalyst has a uniform size distribution and good dispersibility, can provide more active sites, and improves the catalytic activity. The catalyst has high crystallinity and good stability, can maintain good catalytic performance in different application environments, and has a longer life. The method is suitable for large-scale production and has high economic benefits and application value.
[0020] 2. The Pt nanocrystalline catalyst prepared by the present invention has broad application prospects in the fields of fuel cells, automobile exhaust, organic synthesis, electrochemical sensors, etc. In the application of proton exchange membrane fuel cells and direct methanol fuel cells, the Pt nanocrystalline catalyst can promote the oxidation reaction of hydrogen or methanol and the reduction reaction of oxygen. Its high catalytic activity can improve the performance and efficiency of fuel cells, reduce costs, and enhance the stability and durability of fuel cells. In the application of automobile exhaust purification, it synergizes with other precious metal catalysts to convert harmful gases such as carbon monoxide, hydrocarbons and nitrogen oxides in automobile exhaust into harmless carbon dioxide, nitrogen and water. The efficient Pt nanocrystalline catalyst can reduce the ignition temperature, improve the purification efficiency, and reduce the amount of precious metals. In organic synthesis reactions such as hydrogenation reactions, oxidation reactions, coupling reactions, etc., Pt nanocrystalline catalysts can increase the reaction rate and selectivity, reduce the generation of by-products, and improve the purity and yield of products. Its good dispersibility and high catalytic activity can reduce the harshness of reaction conditions and save energy and resources. Application in electrochemical sensors for detecting various chemicals, such as hydrogen, oxygen, glucose, formaldehyde, etc., Pt nanocrystal catalysts can improve the sensitivity, selectivity and stability of sensors, providing powerful tools for environmental monitoring, biomedical testing and other fields. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is the SEM spectrum of the Pt nanocrystalline catalyst prepared in Example 1.
[0022] Figure 2 This is the SEM spectrum of the Pt nanocrystalline catalyst prepared in Example 2.
[0023] Figure 3This is the SEM spectrum of the Pt nanocrystalline catalyst prepared in Example 3.
[0024] Figure 4 This is the SEM spectrum of the Pt nanocrystalline catalyst prepared in Example 4.
[0025] Figure 5 This is the SEM spectrum of the Pt catalyst prepared in Comparative Example 1. DETAILED DESCRIPTION
[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.
[0027] Example 1
[0028] Step 1: Dissolve 20 mL of 0.1 g / mL chloroplatinic acid aqueous solution in 100 mL of ethanol to form a uniform solution.
[0029] Step 2: The solution of step 1 is subjected to a hydrolysis reaction at 60°C, with a stirring speed of 200 rpm and a hydrolysis reaction time of 2 hours. During the reaction, a 2% sodium hydroxide aqueous solution is added to control the pH value of the solution to 2; after the hydrolysis reaction is completed, the temperature of the obtained hydrolyzate is increased to 80°C for a condensation reaction, with a stirring speed of 150 rpm and a condensation reaction time of 24 hours to obtain a sol.
[0030] Step 3: The sol of step 2 is aged for 48 hours at a temperature of 40° C. and a humidity of 60% to convert it into a gel.
[0031] Step 4: After freeze-drying the gel from step 3, place it in a muffle furnace and bake it at 400°C for 4 hours in an air atmosphere, and then place it in a tubular furnace and reduce it at 300°C for 2 hours in a hydrogen atmosphere to obtain a Pt nanocrystalline catalyst. Figure 1 It can be seen that the obtained Pt nanocrystalline catalyst has a uniform particle size distribution and an average particle size of 9 nm, which indicates that it has high stability and is more advantageous for scaling up its process.
[0032] Application test: The prepared Pt nanocrystal catalyst was applied to proton exchange membrane fuel cells to test its catalytic performance in the oxidation reaction of hydrogen and the reduction reaction of oxygen. The results showed that the catalyst can significantly improve the performance and efficiency of fuel cells.
[0033] Example 2
[0034] Step 1: Dissolve 10 mL of 0.1 g / mL ammonium chloroplatinate aqueous solution in 150 mL of pure water to form a uniform solution.
[0035] Step 2: The solution of step 1 is hydrolyzed at 70°C, the stirring speed is 250rpm, the hydrolysis reaction time is 4h, and a 2% sodium hydroxide aqueous solution is added during the reaction to control the pH value of the solution to 3; after the hydrolysis reaction is completed, the temperature of the obtained hydrolyzate is increased to 90°C for condensation reaction, the stirring speed is 200rpm, and the condensation reaction time is 36h to obtain a sol.
[0036] Step 3: The sol of step 2 is aged for 72 hours at a temperature of 50° C. and a humidity of 70% to convert it into a gel.
[0037] Step 4: After drying the gel in step 3 at 150°C in an oven for 4 hours, place it in a muffle furnace and bake it at 500°C in an air atmosphere for 6 hours, and then place it in a tubular furnace and reduce it at 350°C in a hydrogen atmosphere for 2 hours to obtain a Pt nanocrystalline catalyst. Figure 2 It can be seen that the obtained Pt nanocrystalline catalyst has a uniform particle size distribution and good dispersion between particles, and the average particle size is 6 nm.
[0038] Application test: The prepared Pt nanocrystal catalyst was used in conjunction with other precious metal catalysts in automobile exhaust purification devices to test its conversion effect on harmful gases in automobile exhaust. The results showed that the catalyst can effectively convert harmful gases in automobile exhaust into harmless substances.
[0039] Example 3
[0040] Step 1: Dissolve 50 mL of 0.02 g / mL dinitrodiammine platinum aqueous solution in 50 mL of isopropanol to form a homogeneous solution.
[0041] Step 2: The solution of step 1 is subjected to a hydrolysis reaction at 80°C, with a stirring speed of 300 rpm and a hydrolysis reaction time of 4 hours. During the reaction, a sodium hydroxide aqueous solution with a mass concentration of 2% is added to control the pH value of the solution to 4; after the hydrolysis reaction is completed, the temperature of the obtained hydrolyzate is increased to 100°C for a condensation reaction, with a stirring speed of 250 rpm and a condensation reaction time of 48 hours to obtain a sol.
[0042] Step 3: The sol of step 2 is aged at a temperature of 60° C. and a humidity of 80% for 96 hours to convert it into a gel.
[0043] Step 4: After the gel of step 3 is dried naturally for 8 hours, it is placed in a muffle furnace and calcined at 600°C for 8 hours in an air atmosphere, and then placed in a tubular furnace and reduced at 400°C for 4 hours in a hydrogen atmosphere to obtain a Pt nanocrystalline catalyst. Figure 3 It can be seen that the obtained Pt nanocrystalline catalyst has strong adsorption capacity, and the large pore particle size is tightly wrapped around the small pore particle size, indicating that it has high activity, and its average particle size is 7nm.
[0044] Application test: The prepared Pt nanocrystalline catalyst was applied to hydrogenation reaction to test its effect on reaction rate and selectivity. The results showed that the catalyst can significantly improve reaction rate and selectivity, reduce by-product generation, and improve product purity and yield.
[0045] Example 4
[0046] Step 1: Dissolve 50 mL of 0.01 g / mL chloroplatinic acid aqueous solution and 50 mL of 0.02 g / mL ammonium chloroplatinate aqueous solution in 100 mL of ethanol to form a uniform solution.
[0047] Step 2: The solution of step 1 is subjected to a hydrolysis reaction at 90°C, with a stirring speed of 400 rpm and a hydrolysis reaction time of 8 hours. During the reaction, a sodium hydroxide aqueous solution with a mass concentration of 2% is added to control the pH value of the solution to 5; after the hydrolysis reaction is completed, the temperature of the obtained hydrolyzate is increased to 120°C for a condensation reaction, with a stirring speed of 300 rpm and a condensation reaction time of 96 hours to obtain a sol.
[0048] Step 3: The sol of step 2 is aged at a temperature of 70° C. and a humidity of 50% for 96 hours to convert it into a gel.
[0049] Step 4: After the gel of step 3 is dried naturally for 6 hours, it is placed in a muffle furnace and calcined at 700°C for 9 hours in an air atmosphere, and then placed in a tubular furnace and reduced at 500°C for 4 hours in a hydrogen atmosphere to obtain a Pt nanocrystalline catalyst. Figure 4 It can be seen that the average particle size of the obtained Pt nanocrystalline catalyst is 4 nm. Although there are many binding points on its surface, there are very few binding points in the small pores, which shows that it is a selective adsorption with high selectivity.
[0050] Application test: The prepared Pt nanocrystal catalyst was applied to electrochemical sensors to detect various chemical substances. The results showed that the catalyst can accurately and quickly detect various chemical substances, and has higher selectivity and better stability than ordinary catalysts.
[0051] Comparative Example 1
[0052] Step 1: Weigh 20 g of activated carbon, wash it repeatedly with deionized water, and bake the washed activated carbon in an oven at 100° C. for 12 hours to remove moisture to obtain pretreated activated carbon.
[0053] Step 2: Dissolve 50 mL of 0.01 g / mL chloroplatinic acid aqueous solution in 100 mL of pure water to form a uniform solution, and add 50 mL of ethanol to the solution to increase the permeability of the solution.
[0054] Step 3: Immerse the activated carbon pretreated in step 1 in the solution obtained in step 2 and stir on a magnetic stirrer for 24 hours to allow the activated carbon to fully absorb chloroplatinic acid.
[0055] Step 4: Take out the Pt-containing activated carbon impregnated in step 3 and dry it in an oven at 80°C for 12 hours.
[0056] Step 5: Dissolve 2.0 g of sodium borohydride in 50 mL of pure water, add the Pt-containing activated carbon dried in step 4 to the obtained sodium borohydride aqueous solution, and stir at room temperature for 2 h.
[0057] Step 6: Wash the catalyst reduced in step 5 with pure water and ethanol for multiple times, and dry the washed catalyst in an oven at 60°C to obtain a Pt catalyst. Figure 5 It can be seen that the size distribution of the obtained Pt nanocrystalline catalyst is uneven, and the pore size is relatively dispersed, with poor dispersion. The average particle size is 18 nm. Too large a particle size will weaken its adsorption and reduce its activity.
[0058] Application test: The prepared Pt nanocrystal catalyst was applied to proton exchange membrane fuel cells to test its catalytic performance in hydrogen oxidation and oxygen reduction reactions. The results showed that the catalyst could not significantly improve the performance and efficiency of the fuel cell, and the catalyst activity was unstable.
Claims
1. A method for preparing a Pt nanocrystalline catalyst, characterized in that: The preparation method comprises the following steps: Step 1: dissolving an aqueous solution containing a platinum precursor in a solvent to form a uniform solution; Step 2: hydrolyzing the solution of step 1 at 50-120° C., controlling the pH value of the solution in the range of 2-6 during the reaction; raising the temperature of the obtained hydrolyzate by 20-50° C. after the hydrolysis reaction, with the maximum temperature of the hydrolyzate not exceeding 150° C., and performing a polycondensation reaction to obtain a sol; Step 3: subjecting the sol of step 2 to aging treatment to convert it into gel; Step 4: Dry, calcine and reduce the gel from step 3 to obtain a Pt nanocrystalline catalyst.
2. The method for preparing a Pt nanocrystalline catalyst according to claim 1, characterized in that: In step 1, the platinum-containing precursor is selected from any one or more of chloroplatinic acid, ammonium chloroplatinate, and dinitrosodiammineplatinum.
3. The method for preparing a Pt nanocrystalline catalyst according to claim 1, characterized in that: In step 1, the solvent is any one of water, ethanol and isopropanol.
4. The method for preparing a Pt nanocrystalline catalyst according to claim 1, characterized in that: In step 2, the solution of step 1 is subjected to a hydrolysis reaction at 60 to 90° C., and the pH value of the solution is controlled within a range of 2 to 6 during the reaction; after the hydrolysis reaction is completed, the temperature of the obtained hydrolyzate is increased by 20 to 30° C., and the maximum temperature of the hydrolyzate does not exceed 120° C., and a condensation reaction is carried out to obtain a sol.
5. The method for preparing a Pt nanocrystalline catalyst according to claim 1 or 4, characterized in that: In step 2, sodium hydroxide is added during the hydrolysis reaction to control the pH value of the solution to be in the range of 2 to 6.
6. The method for preparing a Pt nanocrystalline catalyst according to claim 1 or 4, characterized in that: In step 2, the hydrolysis reaction time is 2 to 8 hours.
7. The method for preparing a Pt nanocrystalline catalyst according to claim 1 or 4, characterized in that: In step 2, the polycondensation reaction time is 20 to 100 hours.
8. The method for preparing a Pt nanocrystalline catalyst according to claim 1, characterized in that: The aging treatment has a temperature of 30 to 90° C., a humidity of 40% to 90%, and a time of 30 to 120 hours.
9. The method for preparing a Pt nanocrystalline catalyst according to claim 1, characterized in that: The calcination temperature is 300-800° C. and the calcination time is 2-10 hours.
10. The method for preparing a Pt nanocrystalline catalyst according to claim 1, characterized in that: The reduction is hydrogen reduction, the reduction temperature is 300-600° C., and the reduction time is 2-6 hours.