CN111408366A - A kind of preparation method of carbon-supported metal nanocluster catalyst - Google Patents

Abstract

The invention discloses a preparation method of a carbon-loaded metal nanocluster catalyst, which relates to the field of preparation of metal nanocluster catalysts and comprises the following preparation steps: 1) soaking the carbon carrier into an acid treatment solution, and then filtering and washing to prepare carbon carrier powder rich in functional groups; 2) soaking the carbon carrier powder rich in functional groups into a soluble metal salt solution, and carrying out washing and freeze drying after adsorption to prepare a metal adsorption carbon carrier material; 3) putting the metal-adsorbed carbon carrier material into volatile mercaptan vapor for fumigation treatment to prepare a mercaptan-metal-carbon carrier composite material; 4) calcining the mercaptan-metal-carbon carrier composite material in a protective atmosphere to prepare the carbon-supported metal nanocluster catalyst; according to the invention, metal ions are adsorbed on the carbon material after acid treatment, and then the metal nanocluster catalyst with the sulfur fixed on the surface is prepared by adopting a mercaptan fumigation method, wherein the metal nanoclusters of the catalyst are small in size and good in dispersity.

Description

A kind of preparation method of carbon-supported metal nanocluster catalyst

technical field

The invention relates to the field of metal cluster catalyst preparation, in particular to a preparation method of a carbon-supported metal nano-cluster catalyst.

Background technique

Metal cluster catalysts exhibit excellent catalytic performance of nano-catalyst materials by virtue of their unique surface effects, volume effects and quantum size effects, and are widely used in low-temperature catalytic carbon monoxide (CO) oxidation, fuel cell reactions, and low-temperature water-gas conversion in the chemical industry. Reactions and catalytic decomposition of nitrogen oxides (NOx), etc., are called fourth-generation catalysts. The size, morphology, atomic composition, surface environment and support of metal cluster catalysts have important effects on the catalytic performance of the catalysts.

At present, most of the metal nanocatalysts are synthesized by solution phase, in order to prevent their agglomeration during the application process, they also need to be supported on a carrier. However, there will be a large amount of surfactant on the surface of the metal nanocluster catalyst synthesized in solution phase, which will seriously hinder the improvement of its catalytic performance. However, the direct removal of the surfactant on the surface of the cluster will cause the metal nanocluster catalyst to agglomerate. , resulting in a decrease in catalytic performance.

For example, a Chinese patent document discloses "a preparation method of a metal cluster photostability catalyst and its application", its bulletin number CN109499567A, which discloses a preparation method of a metal cluster photostability catalyst and, The photostability of metal clusters can be improved by a combination strategy of surface property control and/or interface modification. However, the catalyst is synthesized in solution phase, and there are a large number of surfactants on the surface, which seriously hinders the improvement of its catalytic performance.

SUMMARY OF THE INVENTION

The present invention is to overcome the existence of a large number of surfactants on the surface of the metal nanocluster catalyst currently synthesized in solution phase, which seriously hinders the improvement of its catalytic performance. However, directly removing the surfactant on the surface of the cluster will cause metal nanocluster The cluster catalyst agglomerates, which reduces its catalytic performance. A preparation method of carbon-supported metal nanocluster catalyst is proposed.

In order to achieve the above object, the present invention adopts the following technical solutions:

A preparation method of a carbon-supported metal nanocluster catalyst, comprising the following preparation steps:

1) Soak the carbon carrier in the acid treatment solution, then filter and wash to prepare the functional group-rich carbon carrier powder;

2) soaking the functional group-rich carbon carrier powder in a soluble metal salt solution, washing and freeze-drying after adsorption, to prepare a metal-adsorbing carbon carrier material;

3) The metal-adsorbed carbon carrier material is placed in the volatilized mercaptan vapor for fumigation treatment to prepare a mercaptan-metal-carbon carrier composite material;

4) The thiol-metal-carbon support composite material is calcined under a protective atmosphere to prepare a carbon-supported metal nanocluster catalyst.

In the present invention, the carbon carrier is first soaked in an acid treatment solution for acid treatment, and the surface of the prepared functional group-rich carbon carrier powder is rich in adsorption groups of hydroxyl and carboxyl groups. After soaking in a soluble metal salt solution, the functional group-rich carbon carrier powder utilizes surface adsorption The group adsorbs metal ions, and then the metal-adsorbed carbon support material is placed in the volatilized mercaptan vapor for fumigation. At this time, the thiol molecules slowly volatilize and diffuse, and slowly form metal sulfur with the metal adsorbed by the metal-adsorbed carbon support material. The alcohol coordination compound prevents the agglomeration of metal clusters, and the thiol-metal-carbon support composite material is prepared. Finally, high temperature calcination is carried out in a protective atmosphere to reduce the metal thiol coordination compound in situ. At this time, the thiol molecule It can prevent the agglomeration of metal clusters in high-temperature reduction, and at the same time, high-temperature calcination will carbonize the thiol molecule alkyl groups, so as to obtain carbon-supported metal nanocluster catalysts with sulfur fixed on the surface. At this time, the sulfur atoms bound to the surface of metal clusters can also It forms protection for metal agglomeration and prevents the catalyst from being oxidized during storage and use, thereby improving the stability of catalyst performance.

Preferably, the carbon carrier in step 1) includes one or more of activated carbon, conductive carbon black, carbon paper, carbon cloth, and graphene.

The carbon support is a graphitized carbon material.

Preferably, the acid treatment solution in step 1) includes piranha solution; the mass ratio of the carbon carrier and the acid treatment solution is 0.5-3.5:100; the soaking time is 10-48h; during the filtration and washing, use Wash with deionized water until the pH of the final filtrate is between 6-7.

Under this ratio, the effect of carbon support acid treatment is better.

Preferably, in step 2) the soluble metal salt solution includes one or more mixed solutions of Pt salt, Au salt, Ru salt, Rh salt, Fe salt, Co salt, Ni salt, Pd salt, and Ag salt; the The soluble metal salt solution is 0.005-5 mol/L.

Preferably, in step 2), the ratio of the functional group-rich carbon carrier powder to the soluble metal salt solution is 0.1-3.5:100; when soaking, the temperature is kept at 25-99° C. for 5-20 hours.

Under the condition of this ratio, the adsorption effect of the functional group-rich carbon carrier powder is better.

Preferably, the fumigation treatment in step 3) is fumigation at 10-220° C. for 5-100 hours in a closed vacuum environment or an inert gas environment.

Preferably, in the step 3), the mercaptan includes methyl mercaptan, ethane mercaptan, octane mercaptan, cyclohexane mercaptan, cyclopentane mercaptan, n-dodecane mercaptan, 2-propyl mercaptan, heptyl thiol One or more of alcohol, phenylethanethiol and butanethiol.

Preferably, the calcination in step 4) is to raise the temperature to 300-700° C. at a heating rate of 5-10° C./min, and keep calcined for 1-4 hours.

Therefore, the present invention has the following beneficial effects: the present invention adsorbs metal ions on the carbon material after acid treatment, and then adopts the method of mercaptan fumigation to prepare a metal nanocluster catalyst with fixed sulfur on the surface, and the metal nanocluster of the catalyst is prepared. The cluster size is small and the dispersion is good, which can effectively improve the utilization rate of metals and reduce the usage of metals in fuel cells.

Description of drawings

FIG. 1 is a TEM image of the carbon-supported metal nanocluster catalyst in Example 1 of the present invention.

FIG. 2 is an STEM image of the carbon-supported metal nanocluster catalyst in Example 1 of the present invention under dark field.

3 is the XRD pattern of the carbon-supported metal nanocluster catalyst in Example 1 of the present invention.

4 is a graph showing the comparison of the ORR catalytic performance of the carbon-supported metal nanocluster catalyst of Example 1 of the present invention and the Johon Matthey type commercial 20% Pt/C catalyst under the same test conditions.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Embodiment 1: a preparation method of carbon-supported metal nanocluster catalyst, comprising the following preparation steps:

1) Soak 2g of conductive carbon black powder into 70mL of piranha solution for 20h, then use deionized water to filter and wash until the pH of the final filtrate is 7, and prepare functional group-rich carbon carrier powder;

2) Immerse 0.5 g of functional group-rich carbon carrier powder into 20 mL of 0.05 mol/L chloroplatinic acid solution, keep at 40 °C for 10 h, and freeze-dry after adsorption to prepare a metal-adsorbed carbon carrier material;

3) The metal-adsorbed carbon support material was placed in an argon atmosphere, and fumigated with n-dodecanethiol molecules at 50 °C for 10 h to prepare a thiol-metal-carbon support composite material;

4) The thiol-metal-carbon support composite material was heated to 400 °C at a heating rate of 5 °C/min in an argon atmosphere, and calcined for 1 h to prepare a carbon-supported metal nanocluster catalyst.

Embodiment 2: a preparation method of carbon-supported metal nanocluster catalyst, comprising the following preparation steps:

1) Soak 3.5g of activated carbon into 100mL of piranha solution for 48h, then filter and wash with deionized water until the pH of the final filtrate is 6, to prepare functional group-rich carbon carrier powder;

2) Immerse the functional group-rich carbon carrier powder in a 5 mol/L ferric chloride solution, keep at 25 °C for 20 hours, and freeze-dry it after adsorption to prepare a metal-adsorbed carbon carrier material;

3) The metal-adsorbed carbon support material was placed in an argon atmosphere, and fumigated with methyl mercaptan molecules at 10 °C for 100 h to prepare a thiol-metal-carbon support composite material;

4) The thiol-metal-carbon support composite material was heated to 700 °C at a heating rate of 10 °C/min in an argon atmosphere, and calcined for 2 h to prepare a carbon-supported metal nanocluster catalyst.

Embodiment 3: a preparation method of carbon-supported metal nanocluster catalyst, comprising the following preparation steps:

1) Soak 0.5 g of graphene in 100 mL of piranha solution for 10 hours, then filter and wash with deionized water until the pH of the final filtrate is 6.5, to prepare functional group-rich carbon carrier powder;

2) Immerse the functional group-rich carbon carrier powder in 0.005 mol/L silver nitrate solution, keep at 99 °C for 5 h, and freeze-dry after adsorption to prepare a metal-adsorbed carbon carrier material;

3) The metal-adsorbed carbon support material is placed in a closed vacuum environment or an inert gas environment, and fumigated with cyclohexanethiol molecules at 220 °C for 5 hours to prepare a thiol-metal-carbon support composite material;

4) The thiol-metal-carbon support composite material was heated to 300 °C at a heating rate of 7 °C/min in an argon atmosphere, and calcined for 4 h to prepare a carbon-supported metal nanocluster catalyst.

The carbon-supported metal nanocluster catalyst prepared in Example 1 was characterized, and the results are shown in the figure.

Example 1 The TEM and dark field STEM of the carbon-supported metal nanocluster catalyst are shown in Figure 1 and Figure 2, respectively. From the TEM pattern in Figure 1, it can be seen that the carbon support is composed of graphitized carbon spheres with a size of 20-80 nm. ; and in the high-power dark-field STEM (as shown in Figure 2), the bright spots of metal nanoclusters loaded on the carbon support can be seen, and the size of the metal nanoclusters is between 0.1-2 nm and the dispersion is very good. .

Example 1 The XRD pattern of the carbon-supported metal nanocluster catalyst is shown in Figure 3, and no XRD characteristic peaks of Pt metal are found in the figure, indicating that the size of the Pt particles is very small.

It was determined that the loading amount of Pt in Example 1 was 12.5%, and the ORR catalytic performance was compared with that of the Johon Matthey type commercial 20% Pt/C catalyst. The results are shown in the figure. As can be seen from the figure, the limiting current density of the carbon-supported metal nanocluster catalyst in Example 1 reaches 5.35 mA·cm ⁻² , and the limiting current density of the commercial 20% Pt/C catalyst tested under the same conditions is 5.52 mA·cm ⁻² ; Converting it into the mass activity of Pt, the activity of the carbon-supported metal nanocluster catalyst in Example 1 is 1.55 times that of the Johon Matthey-type commercial 20% Pt/C catalyst. It is obvious that the improved Pt utilization compared with the commercial catalyst can be used. Effectively reduce the amount of Pt used in fuel cells.

Claims (8)

1. A preparation method of a carbon-supported metal nanocluster catalyst is characterized by comprising the following preparation steps:

1) soaking the carbon carrier into an acid treatment solution, and then filtering and washing to prepare carbon carrier powder rich in functional groups;

2) soaking the carbon carrier powder rich in functional groups into a soluble metal salt solution, and carrying out washing and freeze drying after adsorption to prepare a metal adsorption carbon carrier material;

3) putting the metal-adsorbed carbon carrier material into volatile mercaptan vapor for fumigation treatment to prepare a mercaptan-metal-carbon carrier composite material;

4) and calcining the mercaptan-metal-carbon carrier composite material under a protective atmosphere to prepare the carbon-supported metal nanocluster catalyst.

2. The method of claim 1, wherein the carbon support of step 1) comprises one or more of activated carbon, conductive carbon black, carbon paper, carbon cloth, and grapheme carbon material.

3. The method for preparing a carbon-supported metal nanocluster catalyst as recited in claim 1, wherein said acid treatment liquid of step 1) includes a piranha solution; the mass ratio of the carbon carrier powder to the acid treatment solution is 0.5-3.5: 100; the soaking time is 10-48 h; in the filtration washing, the filtrate is washed with deionized water until the pH of the final filtrate is between 6 and 7.

4. The method for preparing a carbon-supported metal nanocluster catalyst as recited in claim 1, wherein said soluble metal salt solution of step 2) comprises one or more mixed solution of Pt salt, Au salt, Ru salt, Rh salt, Fe salt, Co salt, Ni salt, Pd salt, Ag salt, and said soluble metal salt solution is 0.005-5 mol/L.

5. The method for preparing a carbon-supported metal nanocluster catalyst as recited in claim 1, wherein said step 2) is performed by mixing said functional group-rich carbon support powder with a soluble metal salt solution in a ratio of 0.1-3.5: 100; the soaking is carried out at 25-99 deg.C for 5-20 h.

6. The method for preparing a carbon-supported metal nanocluster catalyst according to claim 1, wherein the fumigating treatment in step 3) is carried out in a closed vacuum environment or an inert gas environment at 10-220 ℃ for 5-100 h.

7. The method for preparing a carbon-supported metal nanocluster catalyst as recited in claim 1, wherein said thiol of said step 3) comprises one or more of methyl mercaptan, ethyl mercaptan, octyl mercaptan, cyclohexyl mercaptan, cyclopentyl mercaptan, n-dodecyl mercaptan, 2-propyl mercaptan, heptyl mercaptan, phenethyl mercaptan, and butyl mercaptan.

8. The method for preparing a carbon-supported metal nanocluster catalyst as recited in claim 1, wherein the calcination in step 4) is performed by heating to 300-700 ℃ at a heating rate of 5-10 ℃/min, and maintaining the temperature for 1-4 h.

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