CN102553582A - Method for preparing carbon supported Au-Pt or Au-Pd catalyst - Google Patents

Abstract

The invention relates to a method for preparing a carbon supported Au-Pt or Au-Pd catalyst by modifying Au-Pt or Au-Pd bimetal nanoparticles with microwaves, belonging to the technical field of catalytic materials. High pressure and high temperature generated by microwaves in a high-pressure reaction tank are utilized to treat an Au-Pt or Au-Pd composite nano colloid synthesized by a chemical coreduction method so as to induce the modification of the Au-Pt or Au-Pd bimetal nanoparticles; and the microwave-modified bimetal nanoparticles are deposited on the surface of the carbon support, thereby obtaining the carbon supported Au-Pt or Au-Pd catalyst with high activity. The carbon supported Au-Pt or Au-Pd catalyst has high electrocatalytic activity; the supporting rate of the Au-Pt or Au-Pd bimetal is high; the supporting amount of the Au-Pt or Au-Pd is controllable; and the method can be used for preparing the carbon supported Au-Pt or Au-Pd nano catalyst of which the mass ratio of Au-Pt or Au-Pd to carbon is 1-20%. The method provided by the invention has the advantages of low cost, simple technique and low facility request, and has wide industrial application prospects.

Description

A kind of method for preparing carbon supported gold platinum or gold palladium catalyst

the

technical field

The invention relates to a method for preparing carbon-loaded high-activity gold-platinum or gold-palladium catalysts by using microwave-modified gold-platinum or gold-palladium bimetallic nanoparticles, which belongs to the technical field of catalytic materials.

Background technique

With the rapid development of nano-preparation technology and catalytic science, some researchers have prepared bimetallic AuPt and AuPd nanoparticles with high catalytic activity from the perspective of reducing catalyst cost and improving catalyst activity and CO tolerance. Recent studies have found that the physical and chemical properties of bimetallic AuPt nanoparticles vary not only with the chemical composition of Au and Pt, but also with the microstructure of AuPt nanoparticles. For example, Zhong Chuanjian et al. (C J Zhong et al, Langmuir.2006, 22:2892) prepared a carbon-supported AuPt nanocatalyst with a mass percentage of Au of 65-85%. (Eichhorn B. et al, Advanced Fuctional Materials, 2007, 17: 3099) reported that AuPt alloy nanoparticles are more heterogeneous than AuPt nanoparticles Aggregates have more tolerance for CO; AuPt nanoparticles with small particle size can be prepared by chemical simultaneous reduction method (Chi J H et al, Journal of the electrochemical society , 2006, 153: 1812); due to Au, Pt The difference in the reduction potential of Pd and Pd leads to the difference in reduction rate. Gradient alloy (like core-shell) and phase separation structures will be formed between Au and Pt and Au and Pd. Carbon-supported Au Pt or Au Pd bimetallic catalysts need to Better catalytic activity can only be obtained by high-temperature solid-state heat treatment. However, after the catalyst is subjected to traditional high-temperature heat treatment, problems such as agglomeration and growth of nanoparticles, partial sintering, and detachment of metal nanoparticles from the surface of the carbon support will occur.

Microwave heating is internal heating, which has the characteristics of fast heating speed, uniform heating, no temperature gradient, and no hysteresis effect. At present, microwave heating is used for catalyst preparation, mainly using microwave heating to assist in the synthesis of catalysts, that is, using microwave heating to promote the reduction of metal precursors, such as Zhong Qiling et al. (ZHONG Qi Ling Acta Phys.-Chim. Sin., 2007, 23 (3) :429) Using ethylene glycol as the reducing agent, microwave heating was used to promote the reduction of chloroplatinic acid (H ₂ PtCl ₆ ) to prepare a carbon-supported catalyst with uniform distribution of platinum nanoparticles on the surface of carbon nanotubes. Utilize the high temperature and high pressure generated by microwave in the high-pressure reaction tank to directly treat the gold-platinum or gold-palladium composite nanocolloid synthesized by the chemical co-reduction method, induce the modification of gold-platinum or gold-palladium bimetallic nanoparticles in the colloid, and make gold-platinum or gold-palladium The microstructure of the bimetallic nanoparticles changes, and then the microwave-modified bimetallic nanoparticles are deposited on the surface of the carbon carrier, omitting the high-temperature heat treatment step of the catalyst, and a highly active carbon-supported bimetallic nanocatalyst can be obtained. Particle agglomeration and growth, local sintering and shedding and other problems.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a gold-platinum or gold-palladium nanoparticle modified by microwaves, and to efficiently load the modified gold-platinum or gold-palladium nanoparticle on the surface of carbon black or carbon nanotubes, A preparation method for preparing carbon-supported highly active gold-platinum or gold-palladium nano-catalysts.

The technical scheme of the present invention is: at first synthetic particle size is 3～10 nanometers gold-platinum or gold-palladium composite nano-colloid with chemical co-reduction method, and composite nano-colloid is transferred in the high-pressure reaction tank, makes the gold-platinum in the reaction tank Or gold-palladium composite nanocolloids generate high temperature and high pressure in a short period of time. After the sol is cooled, microwave-modified gold-platinum or gold-palladium composite nanoparticles are used as catalyst active components and loaded onto carbon black or carbon nanotube carriers. On the surface, a carbon-supported high-activity gold-platinum or gold-palladium catalyst with high activity is obtained. Wherein the specific preparation steps of the carbon-supported high-activity gold-platinum catalyst include as follows:

(1) In a mixed aqueous solution or ethanol solution with an Au(Ⅲ) content of 0.01-0.04wt% chloroauric acid and a Pt(Ⅳ) content of 0.01-0.04wt% chloroplatinic acid, the mass ratio of gold: platinum is 1: 0.25 to 4, then add polyvinylpyrrolidone (PVP) with a concentration of 1wt% to this solution as a protective agent, and then add a reducing agent with a concentration of 0.1wt%, wherein Au(Ⅲ): polyvinylpyrrolidone: the mass of the reducing agent The ratio is 1:2~5:0.1~0.5, the mass ratio of Pt(Ⅳ):polyvinylpyrrolidone: reducing agent is 0.25~4:2~5:0.1~0.5, and the stirring speed is 0.5 at 60~300 rpm ～1h, the reaction temperature is 10～50°C, and a gold-platinum composite colloid solution with a particle size of 3-10 nanometers is obtained;

(2) Heat the gold-platinum composite colloid solution obtained in step (1) to 100-250oC under the condition of 2-6 standard atmospheric pressure (atm) and microwave frequency of 915-2450MHz, and keep it for 1-8 minutes to obtain Microwave-treated gold-platinum composite colloid solution; using microwaves to generate high temperature and high pressure in a high-pressure reaction tank to treat gold-platinum or gold-palladium composite nano-colloids to induce modification of gold-platinum or gold-palladium bimetallic nanoparticles;

(3) Add carbon black or carbon nanotubes to the microwave-treated gold-platinum composite colloid solution obtained in step (2), keep the mass ratio of gold-platinum:carbon black at 1-30:100, and after ultrasonic treatment for 0.15h, Stir at a rate of 60-300 rpm for 2-24 hours, then filter, wash with secondary water until Cl ^- cannot be detected, and dry under vacuum at 60°C for 1-3 hours to obtain highly active carbon-supported gold platinum nanoparticles catalyst.

Au(III) means trivalent gold, Pt(IV) means tetravalent platinum, and Pd(IV) means tetravalent palladium.

The concentration of the ethanol solution in the step (1) is 50 mol % to 95 mol %.

The specific preparation method of the carbon-supported high-activity gold-palladium catalyst is the same as the preparation method of the gold-platinum catalyst, and the chloroplatinic acid solution containing Pt (Ⅳ) in step (1) is replaced with Pd ( Ⅳ) Palladium chloride solution of 0.01-0.04wt% is sufficient, and a highly active carbon-supported gold-palladium nano-catalyst is finally obtained.

The reducing agent used in the synthesis of gold-platinum or gold-palladium composite nanocolloids in the step (2) is sodium borohydride, potassium borohydride (KBH ₄ ), formaldehyde, paraformaldehyde, sodium thiosulfate, ethanol, ethylene glycol , citric acid, glucose, and hydrazine hydrate, all of which are commercially available.

The carrier of the catalyst is carbon black or multi-walled carbon nanotubes, and the active component is gold-platinum or gold-palladium composite nanoparticles modified by microwaves.

The carbon black is commercially available Vulcan XC-72 carbon black, the carbon nanotubes are commercially available multi-walled carbon nanotubes, and the diameter of the carbon tubes is 20-60 nanometers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                            

Compared with the prior art, the present invention has the following advantages or positive effects:

1. The activity of the catalyst is high: the gold-platinum or gold-palladium compound synthesized by the chemical co-reduction method is treated by microwave high temperature and high pressure

Nano-colloid, which changes the microstructure of gold-platinum or gold-palladium composite nanoparticles as the active component of the catalyst, and greatly improves the catalytic activity of the carbon-supported catalyst;

2. Controllable loading: can prepare carbon-supported gold-platinum or gold-palladium nanocatalysts with a mass ratio of gold-platinum or gold-palladium to carbon in the range of 1-20%;

3. The cost of the method is low, the process is simple, the requirements for equipment are low, and the method has good industrial application prospects.

Description of drawings

FIG. 1 is a TEM image of gold-platinum composite nanoparticles prepared in Example 1 of the present invention loaded with multi-walled carbon nanotubes after microwave treatment.

Detailed ways

The present invention will be further described below with embodiment.

Embodiment 1: The specific preparation steps of carbon-supported high-activity gold-platinum catalyst include as follows:

(1) In the mixed aqueous solution of Au(Ⅲ) content of 0.01wt% chloroauric acid and Pt(Ⅳ) content of 0.01wt% chloroplatinic acid, the mass ratio of gold: platinum is 1:0.25, and then in this solution Add polyvinylpyrrolidone (PVP) with a concentration of 1wt% as a protective agent, and then add sodium borohydride with a concentration of 0.1wt%, wherein the mass ratio of Au(Ⅲ):polyvinylpyrrolidone: sodium borohydride is 1:2: 0.1, Pt(Ⅳ): The mass ratio of polyvinylpyrrolidone: sodium borohydride is 0.25:2:0.1, stir at a speed of 60 rpm for 1 hour, and the reaction temperature is 10°C to obtain gold and platinum with a particle size of 3 to 10 nanometers Composite colloid solution (as shown in Figure 1);

(2) Heat the gold-platinum composite colloid solution obtained in step (1) to 100oC at 2 standard atmospheric pressure (atm) and a microwave frequency of 2450MHz, and keep it for 8 minutes to obtain microwave-treated gold-platinum composite colloid solution;

(3) Add Vulcan XC-72 carbon black to the microwave-treated gold-platinum composite colloid solution obtained in step (2), keep the mass ratio of gold-platinum:carbon black at 1:100, and after ultrasonic treatment for 0.15h, at 60 Stir at the speed of rev/min for 24 hours, then filter, wash with secondary water until Cl ^- cannot be detected, and dry under vacuum at 60°C for 2 hours to obtain a highly active gold-platinum:carbon black mass ratio of 1:100 Carbon-supported gold-platinum nanocatalysts.

Example 2

The specific preparation steps of the carbon-supported high-activity gold-platinum catalyst include as follows:

(1) In the mixed aqueous solution with Au(Ⅲ) content of 0.03wt% chloroauric acid and Pt(Ⅳ) content of 0.02wt% chloroplatinic acid, the mass ratio of gold: platinum is 1:2, and then in this solution Add polyvinylpyrrolidone (PVP) with a concentration of 1wt% as a protective agent, and then add potassium borohydride with a concentration of 0.1wt%, wherein the mass ratio of Au(Ⅲ): polyvinylpyrrolidone: potassium borohydride is 1:4: 0.2, Pt (Ⅳ): polyvinylpyrrolidone: potassium borohydride mass ratio is 2:4:0.2, stirred at 100 rpm for 0.8h, the reaction temperature is 40°C, and the particle size is 3-8 nanometer gold Platinum complex colloidal solution;

(2) Heat the gold-platinum composite colloid solution obtained in step (1) to 200oC at 3 standard atmospheric pressure (atm) and a microwave frequency of 2000MHz, and keep it for 1min to obtain microwave-treated gold-platinum composite colloid solution;

(3) Add multi-walled carbon nanotubes (carbon tubes with a diameter of 20 to 60 nanometers) into the microwave-treated gold-platinum composite colloid solution obtained in step (2), keeping the mass ratio of gold-platinum:carbon black at 1: 10. After ultrasonic treatment for 0.15h, stir at 100 rpm for 12h, then filter, wash with secondary water until Cl ^- cannot be detected, and dry under vacuum at 60°C for 1h to obtain gold platinum: carbon black A highly active carbon-supported gold-platinum nanocatalyst with a mass ratio of 1:10.

Example 3

The specific preparation steps of the carbon-supported high-activity gold-platinum catalyst include as follows:

(1) In a mixed ethanol solution (95% concentration) with Au(III) content of 0.04wt% chloroauric acid and Pt(IV) content of 0.01wt% chloroplatinic acid, the mass ratio of gold: platinum is 1: 4. Then add polyvinylpyrrolidone (PVP) with a concentration of 1wt% to this solution as a protective agent, and then add formaldehyde with a concentration of 0.1wt%, wherein the mass ratio of Au(III): polyvinylpyrrolidone: formaldehyde is 1: 5:0.5, Pt (Ⅳ): polyvinylpyrrolidone: formaldehyde mass ratio is 4:5:0.5, stirred at a speed of 300 rpm for 0.8h, the reaction temperature is 40°C, and the particle size is 3-7 nanometer gold Platinum complex colloidal solution;

(2) Heat the gold-platinum composite colloid solution obtained in step (1) to 250oC under the condition of 6 standard atmospheric pressure (atm) and a microwave frequency of 915MHz, and keep it for 6min to obtain microwave-treated gold-platinum composite colloid solution;

(3) Add multi-walled carbon nanotubes (carbon tubes with a diameter of 20 to 60 nanometers) into the microwave-treated gold-platinum composite colloid solution obtained in step (2), keeping the mass ratio of gold-platinum:carbon black at 3: 10. After ultrasonic treatment for 0.15h, stir at 300 rpm for 2h, then filter, wash with secondary water until Cl ^- cannot be detected, and dry under vacuum at 60°C for 3h to obtain gold platinum: carbon black A highly active carbon-supported gold-platinum nanocatalyst with a mass ratio of 3:10.

Example 4:

The specific preparation steps of the carbon-supported high-activity gold-palladium catalyst include as follows:

(1) In a mixed ethanol solution (80% concentration) with Au(Ⅲ) content of 0.02wt% chloroauric acid and Pt(Ⅳ) content of 0.01wt% chloropalladic acid, the mass ratio of gold: palladium is 1: 4. Then add polyvinylpyrrolidone (PVP) with a concentration of 1wt% to this solution as a protective agent, and then add paraformaldehyde with a concentration of 0.1wt%, wherein Au(Ⅲ): polyvinylpyrrolidone: the mass of paraformaldehyde The ratio is 1:3:0.5, the mass ratio of Pt(Ⅳ):polyvinylpyrrolidone:paraformaldehyde is 4:3:0.5, stirred at a speed of 100 rpm for 0.8h, and the reaction temperature is 30°C to obtain the particle size It is a 3-10 nanometer gold-palladium composite colloidal solution;

(2) Heat the gold-palladium composite colloid solution obtained in step (1) to 190oC at 4 standard atmospheric pressure (atm) and a microwave frequency of 1950MHz, and keep it for 7min to obtain microwave-treated gold-palladium composite colloid solution;

(3) Add multi-walled carbon nanotubes (carbon tubes with a diameter of 20 to 60 nanometers) into the microwave-treated gold-palladium composite colloid solution obtained in step (2), keeping the mass ratio of gold-platinum:carbon black at 1: 50. After ultrasonic treatment for 0.15h, stir at 300 rpm for 2h, then filter, wash with secondary water until Cl ^- cannot be detected, and dry at 60°C for 3h under vacuum to obtain gold palladium: carbon black A highly active carbon-supported gold-palladium nanocatalyst with a mass ratio of 1:50.

Example 5:

The specific preparation steps of the carbon-supported high-activity gold-palladium catalyst include as follows:

(1) In a mixed ethanol solution (50% concentration) with Au(Ⅲ) content of 0.03wt% chloroauric acid and Pt(Ⅳ) content of 0.02wt% chloropalladic acid, the mass ratio of gold: palladium is 1: 4. Then add polyvinylpyrrolidone (PVP) with a concentration of 1wt% to this solution as a protective agent, and then add a concentration of 0.1wt% sodium sulfide, wherein Au (Ⅲ): polyvinylpyrrolidone: the quality of sodium sulfide The ratio is 1:4:0.2, the mass ratio of Pt(Ⅳ):polyvinylpyrrolidone:sodium sulfate sulfate is 4:4:0.2, stirred at a speed of 100 rpm for 0.8h, and the reaction temperature is 40°C to obtain the particle size It is a 3-8 nanometer gold-palladium composite colloidal solution;

(2) Heat the gold-palladium composite colloid solution obtained in step (1) to 200oC at 3 standard atmospheric pressure (atm) and a microwave frequency of 2000MHz, and keep it for 1min to obtain microwave-treated gold-palladium composite colloid solution;

(3) Add multi-walled carbon nanotubes (carbon tubes with a diameter of 20 to 60 nanometers) into the microwave-treated gold-platinum composite colloid solution obtained in step (2), keeping the mass ratio of gold-palladium:carbon black at 1: 10. After ultrasonic treatment for 0.15h, stir at 100 rpm for 12h, then filter, wash with secondary water until Cl ^- cannot be detected, and dry under vacuum at 60°C for 1h to obtain gold palladium: carbon black A highly active carbon-supported gold-palladium nanocatalyst with a mass ratio of 1:10.

Example 6

The specific preparation steps of the carbon-supported high-activity gold-palladium catalyst include as follows:

(1) In a mixed ethanol solution (60% concentration) with Au(Ⅲ) content of 0.02wt% chloroauric acid and Pt(Ⅳ) content of 0.04wt% chloropalladium acid, the mass ratio of gold: palladium is 1: 4. Then add polyvinylpyrrolidone (PVP) with a concentration of 1wt% to this solution as a protective agent, and then add ethanol with a concentration of 0.1wt%, wherein the mass ratio of Au(Ⅲ):polyvinylpyrrolidone:ethanol is 1: 4:0.2, Pt(Ⅳ):polyvinylpyrrolidone:ethanol with a mass ratio of 4:4:0.2, stirred at a speed of 100 rpm for 0.8h, and a reaction temperature of 40°C to obtain gold particles with a particle size of 3 to 8 nanometers Palladium complex colloidal solution;

(2) Heat the gold-palladium composite colloid solution obtained in step (1) to 200oC at 3 standard atmospheric pressure (atm) and a microwave frequency of 2000MHz, and keep it for 1min to obtain microwave-treated gold-palladium composite colloid solution;

(3) Add Vulcan XC-72 carbon black to the microwave-treated gold-platinum composite colloid solution obtained in step (2), keep the mass ratio of gold-palladium: carbon black at 1:10, and after ultrasonic treatment for 0.15h, at 100 Stir at a speed of rpm for 12 hours, then filter, wash with secondary water until Cl ^- cannot be detected, and dry at 60°C for 1 hour under vacuum to obtain a highly active gold-palladium:carbon black mass ratio of 1:10 Carbon-supported gold-palladium nanocatalysts.

Embodiment 7:

The specific preparation steps of the carbon-supported high-activity gold-platinum catalyst in this example are the same as in Example 1, except that the oxidant in step (1) is ethylene glycol.

Embodiment 8:

The specific preparation steps of the carbon-supported high-activity gold-platinum catalyst in this example are the same as those in Example 2, except that the oxidizing agent in step (1) is citric acid.

Embodiment 9:

The specific preparation steps of the carbon-supported high-activity gold-platinum catalyst in this example are the same as those in Example 3, except that the oxidant in step (1) is glucose.

Example 10:

The specific preparation steps of the carbon-supported high-activity gold-platinum catalyst in this example are the same as in Example 5, except that the oxidizing agent in step (1) is hydrazine hydrate.

Claims (6)

1. one kind prepares the method that carbon carries high activity gold platinum or golden palladium catalyst, it is characterized in that carbon carries the concrete preparation process process of high activity gold platinum catalyst as follows:

(1) be that 0.01～0.04wt% gold chloride and Pt (IV) content are in the mixed aqueous solution or ethanolic solution of 0.01～0.04wt% chloroplatinic acid at Au (III) content; Gold: the mass ratio of platinum is 1:0.25～4; The polyvinylpyrrolidone that in this solution, adds concentration then and be 1wt% is cooked protective agent; Add the reducing agent that concentration is 0.1wt% again; Au (III) wherein: polyvinylpyrrolidone: the mass ratio of reducing agent is 1:2～5:0.1～0.5, Pt (IV): polyvinylpyrrolidone: the mass ratio of reducing agent is 0.25～4:2～5:0.1～0.5, stirs 0.5～1h by 60～300 rev/mins speed; Reaction temperature is 10～50 ℃, and obtaining particle size is the golden platinum composite colloid solution of 3 ~ 10 nanometers;

(2) with the golden platinum composite colloid solution of step (1) gained at 2～6 standard atmospheric pressures, microwave frequency is under the condition of 915～2450MHz temperature to be heated to 100～250oC, keeps handling 1～8min, obtains the golden platinum composite colloid solution that microwave treatment is crossed;

(3) carbon black or CNT being joined the microwave treatment that step (2) obtains crosses in the golden platinum composite colloid solution; Keep golden platinum: the mass ratio of carbon black is 1～30:100; Behind the ultrasonic Treatment 0.15h; Under 60～300 rev/mins speed, stir 2～24h, filter then, spend secondary water washing and wash to detecting Cl ^-, dry 1～3h obtains high-activity carbon and carries golden platinum nano catalyst under 60 ℃ of vacuum conditions.

2. prepare the method that carbon carries high activity gold platinum or golden palladium catalyst according to claims 1 are described; It is characterized in that: the concrete preparation method that said carbon carries high activity gold palladium catalyst is identical with the preparation method of golden platinum catalyst; With the Pt (IV) that contains in the step (1) is that the platinum acid chloride solution of 0.01～0.04wt% is changed to that to contain Pd (IV) be that the palladium chloride solution of 0.01～0.04wt% gets final product, and finally obtains high-activity carbon and carries golden palladium nanocatalyst.

3. prepare the method that carbon carries high activity gold platinum or golden palladium catalyst according to claims 1 are described, it is characterized in that: the concentration of ethanolic solution is 50 mol%～95 mol % in the said step (1).

4. the method for carrying high activity gold platinum or golden palladium catalyst according to the described microwave modification gold platinum of claims 1 or golden palladium bimetal nano particle preparation carbon is characterized in that: in the said step (1) synthetic golden platinum or the employed reducing agent of golden palladium composite Nano colloid be in sodium borohydride, potassium borohydride, formaldehyde, paraformaldehyde, sodium thiosulfate, ethanol, ethylene glycol, citric acid, glucose, the hydrazine hydrate any one.

5. prepare the method that carbon carries high activity gold platinum or golden palladium catalyst according to claims 1 are described, it is characterized in that: the carrier of said catalyst is carbon black or multi-walled carbon nano-tubes, and active component is through the golden platinum of microwave modification or golden palladium composite nanoparticle.

6. prepare the method that carbon carries high activity gold platinum or golden palladium catalyst according to claims 1 are described, it is characterized in that: said carbon black is commercially available Vulcan XC-72 carbon black, and CNT is commercially available multi-walled carbon nano-tubes, and carbon pipe caliber is 20～60 nanometers.

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