Carbon-coated supported metal catalyst, and preparation method and application thereof

Abstract

The application discloses a carbon-coated supported metal catalyst and a preparation method and application thereof, and belongs to the field of catalytic material preparation, and the preparation method comprises the following steps: (1) metal ion loading: uniformly dispersing carbon material and a precursor of metal ions in water, adjusting the pH value of the solution, performing ultrasonic dispersion, and then freeze-drying to obtain an unreduced precursor; (2) plasma reduction of the metal ions: placing the precursor obtained in the above step into a discharge quartz cavity of a low-pressure radio frequency inductively coupled plasma, and performing plasma discharge treatment on the precursor by introducing a discharge gas and a low-boiling-point volatile alcohol, so that the carbon-coated catalyst is finally obtained and supported on the carbon material. The carbon-coated catalyst is obtained at room temperature by the method, catalyst growth and agglomeration in the use process are avoided, and the service life of the catalyst is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of catalytic material preparation, specifically relating to a carbon-coated supported metal catalyst, its preparation method, and its application. Background Technology

[0002] Supported catalysts have broad application prospects in fuel cells, crude oil reforming and isomerization, removal of nitrogen / carbon oxides, and synthesis of natural products and pharmaceutical intermediates. Small-sized catalysts can maximize atom utilization efficiency and are an effective strategy for preparing highly active catalysts. However, small-sized catalysts have high surface energy and chemical potential, are in a metastable state thermodynamically and kinetically, and are prone to aggregation, leading to an increase in catalyst size and consequently a decrease in catalytic performance. Summary of the Invention

[0003] To address the problems mentioned in the background art, this invention uses low-boiling-point, easily volatile alcohols as a carbon source. By evaporating this organic solvent to a gaseous state, it is decomposed into carbon-containing active groups in radio frequency inductively coupled plasma, and finally a carbon layer is deposited on the catalyst surface, forming a carbon-coated core-shell structure of the catalyst. This avoids catalyst agglomeration, growth, and catalyst poisoning during use, and extends the service life of the catalyst.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing a carbon-coated supported metal catalyst includes the following steps:

[0006] Step 1, Metal ion loading: Disperse the metal ion precursor and carbon material in water, adjust the pH to 8-10, sonicate and freeze dry to obtain the metal ion loaded carbon material precursor;

[0007] Step 2, Plasma carbon coating: The precursor obtained in Step 1 is placed in a radio frequency inductively coupled plasma reaction chamber, and a mixture of discharge gas and low-boiling-point volatile alcohols is introduced. Plasma discharge treatment is carried out under low pressure to form a carbon-coated metal catalyst.

[0008] In the above technical solution, in step 1, the metal ion precursor includes at least one of platinum, palladium, copper, gold, silver, iron, ruthenium, iridium, cobalt, or nickel ions.

[0009] In the above technical solution, in step 1, the carbon material is at least one of onion carbon, carbon nanotubes, graphene, or conductive carbon black.

[0010] In the above technical solution, in step 2, the discharge gas is at least one of argon, nitrogen or ammonia.

[0011] In the above technical solution, in step 2, the low-boiling-point volatile alcohol is at least one of methanol, ethanol, and isopropanol.

[0012] In the above technical solution, in step 2, the volume ratio of alcohol to discharge gas in the mixed gas is 0.01:1 to 100:1, and the solvent is heated to 100 to 500°C and vaporized before being introduced into the reaction chamber.

[0013] In the above technical solution, in step 2, the power of the plasma discharge is 50~1000W, the processing time is 1min~120min, the gas flow rate is 5~100sccm, and the discharge pressure is 0.1Pa~300Pa.

[0014] In the above technical solution, the thickness of the graphitized carbon layer is 1~10nm.

[0015] A carbon-coated supported metal catalyst, prepared by the above method, comprises metal catalyst particles and a carbon layer coated on the surface of the metal particles, forming a core-shell structure.

[0016] Beneficial effects:

[0017] This invention discloses a carbon-coated supported metal catalyst, its preparation method, and its application. It uses a gaseous, low-boiling, volatile alcohol as the carbon source. The organic solvent is volatilized to a gaseous state and then decomposed into carbon-containing organic compounds in plasma, which are then deposited on the catalyst surface to form a carbon layer. This ultimately yields the core-shell structure of the carbon-coated catalyst in Example 1, thereby avoiding catalyst agglomeration, growth, and poisoning during use, and extending the catalyst's lifespan. Attached Figure Description

[0018] Figure 1 Transmission electron microscope image of carbon-coated PtPd / CNT.

[0019] Figure 2 Comparison of HER cycle performance of PtPd / CNT before and after carbon coating. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] Example 1:

[0022] 40 mg of multi-walled carbon nanotubes were mixed evenly with deionized water, and then 10 ml of a 20 g / L mixed solution of chloroplatinic acid and chloropalladic acid was added dropwise. After sonication for 30 min, the mixture was freeze-dried to obtain a precursor of chloroplatinic acid and chloropalladic acid supported on multi-walled carbon nanotubes. The precursor was placed in a quartz cavity of inductively coupled plasma, and ethanol gas was heated to 300 °C. Nitrogen gas was introduced at 50 sccm and evaporated ethanol gas at 5 sccm. The discharge power was 300 W, the discharge time was 20 min, and the gas pressure was 15 Pa. This method for preparing carbon-coated supported metal catalysts was finally obtained.

[0023] Experimental results:

[0024] Figure 1 The image shows a transmission electron microscope image of the PtPd catalyst (PtPd / CNT) supported on multi-walled carbon nanotubes prepared in Example 1. It can be observed that the PtPd nanoparticles are wrapped by a carbon layer with a thickness of about 5 nm.

[0025] Figure 2 The figure shows the HER performance of PtPd / CNTs with a 5 nm carbon layer and PtPd / CNTs without a carbon layer prepared in Example 1. The figure shows the HER performance at a current density of 20 mA cm⁻¹. -2 At this point, the hydrogen evolution potentials of the two are -0.12V and -0.13V, respectively. After 30,000 cycles, the hydrogen evolution potentials of the two are -0.14V and -0.18V, respectively. The hydrogen evolution overpotentials of carbon-coated PtPd / CNT and uncoated PtPd / CNT increased by 0.02V and 0.05V, respectively, showing excellent cycling performance.

[0026] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a carbon-coated supported metal catalyst, characterized in that, Includes the following steps: Step 1, Metal ion loading: Disperse the metal ion precursor and carbon material in water, adjust the pH to 8-10, sonicate and freeze dry to obtain the metal ion loaded carbon material precursor; Step 2, Plasma carbon coating: The precursor obtained in Step 1 is placed in a radio frequency inductively coupled plasma reaction chamber, and discharge gas and low-boiling-point volatile alcohols are introduced. Plasma discharge treatment is carried out under low pressure to form a carbon-coated metal catalyst.

2. The method for preparing a carbon-coated supported metal catalyst according to claim 1, characterized in that, In step 1, the metal ion precursor includes at least one of platinum, palladium, copper, gold, silver, iron, ruthenium, iridium, cobalt, or nickel ions.

3. The method for preparing a carbon-coated supported metal catalyst according to claim 1, characterized in that, In step 1, the carbon material is at least one of onion carbon, carbon nanotubes, graphene, or conductive carbon black.

4. The method for preparing a carbon-coated supported metal catalyst according to claim 1, characterized in that, In step 2, the discharge gas is at least one of argon, nitrogen, or ammonia.

5. The method for preparing a carbon-coated supported metal catalyst according to claim 1, characterized in that, In step 2, the low-boiling-point volatile alcohol is at least one of methanol, ethanol, and isopropanol.

6. The method for preparing a carbon-coated supported metal catalyst according to claim 1, characterized in that, In step 2, the volume ratio of alcohol to discharge gas in the mixed gas is 0.01:1 to 100:1, and the solvent is heated to 100 to 500°C and vaporized before being introduced into the reaction chamber.

7. The method for preparing a carbon-coated supported metal catalyst according to claim 1, characterized in that, In step 2, the power of the plasma discharge is 50~1000W, the processing time is 1min~120min, the gas flow rate is 5~100sccm, and the discharge pressure is 0.1Pa~300Pa.

8. The method for preparing a carbon-coated supported metal catalyst according to claim 1, characterized in that, The thickness of the carbon layer is 1~10 nm.

9. A carbon-coated supported metal catalyst, characterized in that, Prepared by the method described in any one of claims 1-8, comprising metal catalyst particles and a carbon layer coated on the surface of the metal particles, forming a core-shell structure.

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