Preparation method of supported noble metal catalyst based on defective carbon

Abstract

The invention discloses a preparation method of a supported noble metal catalyst based on defective carbon. The method comprises the following steps: 1) grinding and mixing a carbon material and boron oxide, adding water, uniformly stirring, and then drying and grinding to obtain a boron-carbon precursor; 2) putting the boron-carbon precursor into a tubular furnace, sintering at high temperature, cooling, grinding, washing, filtering, drying, and regrinding to obtain a defective carbon material; (3) dispersing at least one noble metal compound and a defective carbon material in a dispersing agent or a reducing agent, and loading noble metal on defective carbon to obtain a head product; and 4) filtering the initial product, and drying to obtain the noble metal / defective carbon composite catalyst. According to the method, multiple conditions can be selected, the controllability is high, the applicable preparation range is wide, single or multiple precious metal alloy supported materials can be synthesized, the proportion components are adjustable, large-scale preparation is easy, and the cost can be effectively reduced. The synthesized catalyst can be applied to various catalytic reactions or electro-catalytic reactions, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst synthesis, and particularly relates to a preparation method of a supported noble metal catalyst based on defective carbon. Background Art

[0002] As the world economy enters a period of rapid growth, the demand for various chemicals and energy is increasing day by day. Traditionally, people have obtained chemicals and energy through the conversion and utilization of various fossil fuels, such as petroleum, coal, natural gas and other resources. This process usually requires the use of various catalysts, such as noble metal-based catalysts. For the current economic development, in order to pursue sustainability, it is necessary to develop and utilize various renewable new energies, such as wind energy, water energy and solar energy. These new energies will be further converted into electrical energy, which is stored or directly used in electrocatalytic synthesis and conversion reactions, such as synthesizing various organic and inorganic chemicals (carbon monoxide, hydrogen, methane, formic acid, ammonia, etc.) or redox reactions of various organic substances to achieve the storage and release of electrical energy. These processes also require various catalysts to regulate to reduce the energy loss in the process. Among the various transition metal, noble metal and non-metal catalysts currently studied, noble metal-based catalysts have the best activity and stability and are the most widely used. However, the cost of noble metal-based catalysts is extremely high, and their large-scale use is limited. Developing atomically dispersed noble metal catalysts will help maximize the utilization rate of noble metal atoms and reduce the use cost, which is a feasible technical solution to solve the effective application of noble metal catalysts.

[0003] In various chemical and electrochemical conversion reactions mentioned above, various noble metal-based catalysts have been reported, such as alloy materials composed of single metals and multi-metals based on Au, Ir, Rh, Pt, Ru, Pd, Ag, etc. To prevent the diffusion and aggregation of atomically dispersed noble metal components during use, various carriers such as metal oxides, carbon, and polymers are required. The interaction between noble metals and carriers is beneficial to the synthesis of atomically dispersed noble metal-based composite materials. How to achieve the composite of these two through appropriate chemical methods is the key to the synthesis of atomically dispersed noble metal-based materials at present. Currently, for the synthesis of noble metal-based materials, the commonly used methods are: (1) Wet chemical synthesis method, that is, first dissolve noble metal salts and disperse the carrier into the solution, and then through steps such as drying, heat treatment, activation, or reduction, the loading of atomically dispersed metals is achieved. (2) Metal etching method, that is, first compound metal salts and organic substances, pyrolyze after drying, and then remove metal nanoparticles through acid treatment to prepare carbon-supported atomically dispersed metal materials. (3) Electrodeposition method, that is, deposit atomically dispersed metals on the substrate surface through potential control. (4) Metal-organic framework synthesis method, that is, first compound metal ions and organic ligands to form metal-organic framework compounds, and then pyrolyze to obtain single-atom materials. The above methods have their own advantages and disadvantages. Especially, most of the methods have cumbersome processes, low controllability, and expensive raw materials, which are not conducive to large-scale application. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a supported noble metal catalyst based on defective carbon. Defective carbon is synthesized by co-firing carbon materials and boron oxide, and a noble metal / defective carbon composite material is deposited on the surface of defective carbon through a reduction method, realizing its lower cost and wider application.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: A preparation method of a supported noble metal catalyst based on defective carbon, comprising the following steps: 1) Grind and mix carbon materials and boron oxide according to a mass ratio of 5:1 to 25, then add water and stir evenly, and then dry and grind to obtain a boron-carbon precursor; 2) Put the boron-carbon precursor into a tubular furnace, heat it to 500 - 1400 °C in an argon or nitrogen atmosphere, keep it warm for 10 min - 10 h, then cool it, grind the obtained material, wash, filter, dry, and then grind to obtain defective carbon materials; 3) Disperse at least one noble metal compound and defective carbon materials in a dispersant or reducing agent, and load the noble metal on the defective carbon by means of heating, ultrasonic, microwave, hydrothermal, or hydrazine hydrate reduction to obtain a primary product; 4) Filter and dry the primary product to obtain a noble metal / defective carbon composite catalyst.

[0006] Further, the carbon material described in step 1) is a water-absorbing resin, starch, cellulose, etc.

[0007] Further, the washing in step 2) uses one or more of deionized water, ethanol, hydrochloric acid, and potassium hydroxide solution.

[0008] Further, the mass ratio of the noble metal compound to the defective carbon material in step 3) is 1-25:100.

[0009] Further, the noble metal compound in step 3) is one or more of chlorides, hydrochlorides, acetylacetonates, and nitrates containing Au, Ir, Rh, Pt, Ru, Pd, Ag, etc.

[0010] Further, the dispersant in step 3) is one or more of ethylene glycol, hydrazine hydrate, ethanol, and water.

[0011] Further, the reducing agent in step 3) is one or more of ethylene glycol, sodium borohydride, hydrazine hydrate, and ascorbic acid.

[0012] Further, the washing in step 4) is to wash the primary product 3-5 times with deionized water.

[0013] The present invention adopts the above technical solutions. After high-temperature sintering of the carbon material and boron oxide, through the reduction deposition process, noble metals are dispersed on the surface of defective carbon to prepare a noble metal / defective carbon composite catalyst. This material can achieve higher activity under the same noble metal loading. In the catalyst, the size of the noble metal component dispersed on the carbon surface is less than 10 nm, and the substrate defective carbon can have different nano or microstructures. The synthesis method adopted by the present invention has strong universality and is suitable for synthesizing various noble metal nanoparticles dispersed and deposited on defective carbon, with excellent performance and stability.

[0014] Compared with the prior art, the present invention has the following advantages: (1) The preparation process of the existing method is complex and cumbersome, and the equipment requirements are high. The synthesis method of the present invention is simple, adopts pyrolytic boron carbide treatment and reduction processes such as microwave, has low requirements for equipment conditions, high efficiency, and is conducive to large-scale production.

[0015] (2) The raw materials of the existing method are expensive. For example, when using metal-organic framework synthesis and metal etching methods, expensive organic ligands or organic substances are required to prepare the carbon carrier. The synthesis materials of the present invention are ordinary carbon materials, boron oxide, and noble metal compounds. Among them, the ordinary carbon materials and boron oxide are inexpensive, and the usage amount of the noble metal compound can be controlled, greatly reducing the actual synthesis cost.

[0016] (3) During the existing process of synthesizing noble metal-loaded catalysts, the synthesis control conditions are relatively strict and demanding, with poor controllability. For example, the electrodeposition method requires strict control of the potential and solution state. The control process of the present invention is simple and reliable. Through in-situ reduction deposition on the carbon surface defects, it is easy to disperse noble metals on the surface of defective carbon (size < 10 nm).

[0017] (4)The existing synthesis methods are only applicable to obtaining the loading of one noble metal or transition metal. The present invention is suitable for obtaining the loading of multiple noble metals and composite metals, with wide applicability.

[0018] (5)The noble metal / defective carbon composite catalyst obtained by the present invention can effectively improve the atomic utilization rate of various existing noble metal-based materials, and is an improved approach for noble metal materials with very broad application prospects.

[0019] (6)The supported noble metal catalyst synthesized by the present invention can be applied to various types of catalytic reactions or electrocatalytic reactions, such as hydrogen evolution reaction and hydrazine oxidation reaction, etc., achieving better performance than commercial noble metals, and having broad application prospects. Description of the Drawings

[0020] Figure 1 is a low-magnification transmission electron microscope (TEM) image of id-Pt / DC.

[0021] Figure 2 is the hydrogen evolution performance of id-Pt / DC, Pt / C, DC, C, and Com.Pt / C in 1 M KOH solution. Detailed Embodiments

[0022] The technical solutions of the present invention will be further described below in conjunction with the drawings and embodiments. Example 1

[0023] Preparation, physical and electrochemical characterization of noble metal Pt-loaded defective carbon composite material (id-Pt / DC) (1)Take 5 g of water-absorbing resin and boron oxide respectively, put them into a mortar, grind and mix evenly. Pour the ground powder into a 300 ml beaker, add 50 ml of deionized water, stir quickly and evenly, and dry at 100 °C in a blast drying oven and then grind.

[0024] (2)Load the ground powder into a porcelain boat, put it into a tubular furnace, and under the protection of an argon atmosphere, heat it to 1100 °C at a heating rate of 10 °C·min -1 , keep it warm for 1 hour, and then naturally cool to room temperature. Grind the sample, add deionized water, ultrasonically wash for 10 minutes, filter, and then dry in vacuum at 60 °C, and grind to obtain defective carbon powder DC.

[0025] (3) Take 43 mg of defective carbon powder DC, add 50 ml of ethylene glycol, and then add 3 ml of chloroplatinic acid with a concentration of 18.4 mM. After stirring evenly, ultrasonicate for 1 hour. Pour all the sonicated liquid into a flask, place it in a microwave oven, insert a condenser tube, connect the condensed water, microwave for 90 seconds, filter, wash five times with 20 ml of deionized water, and dry in a blast drying oven at 60 °C to obtain the composite material id-Pt / DC.

[0026] The low-magnification transmission electron microscope of the obtained composite material id-Pt / DC is as Figure 1 shown. In id-Pt / DC, carbon exhibits high defects and low graphitization. Platinum is successfully loaded on defective carbon (DC) in the form of nanoparticles, and the platinum atoms at the grain boundaries of adjacent platinum nanoparticles are disordered.

[0027] If boron oxide is not added in step 1) of the above method, carbon powder C is obtained by grinding in step 2), and Pt / C is obtained in step 3). Figure 2 are the hydrogen evolution performances of id-Pt / DC, Pt / C, DC, C, and Com.Pt / C in 1 M KOH solution. Among them, Com.Pt / C is commercial platinum carbon (JM), that is, the platinum carbon catalyst purchased from the market.

[0028] As Figure 2 shown, compared with Com.Pt / C, id-Pt / DC has better hydrogen evolution performance in alkaline electrolyzed water under the same noble metal loading. At a current of 10 mA cm -2 , its overpotential is only 20.3 mV, and the hydrogen evolution performances of DC and C in alkaline electrolyzed water are very poor, excluding the influence of the performances of DC and C. Example 2

[0029] Preparation and physical and electrochemical characterization of noble metal Ru / defective carbon composite material (RuO x / C) (1) Take 5 g of starch and boron oxide respectively and put them into a mortar for grinding and mixing evenly. Pour the ground powder into a 300 ml beaker, add 50 ml of deionized water, stir evenly quickly, dry in a blast drying oven at 100 °C and then grind to obtain a boron-carbon precursor.

[0030] (2) Load the boron-carbon precursor into a porcelain boat and place it in a tube furnace. Under the protection of an argon atmosphere, heat it to 1000 °C at a heating rate of 10 °C·min -1 , keep it warm for 1 hour, and then cool it naturally to room temperature. Grind the sample, add deionized water and ultrasonically wash for 10 minutes, filter, and vacuum dry the obtained sample at 60 °C and grind to obtain defective carbon powder C-1000.

[0031] (3) Take 53 mg of defective carbon powder C-1000, add 50 ml of water, and then add 0.5 ml of ruthenium chloride with a concentration of 106 mM. After stirring evenly, slowly drip a solution of 1 ml of hydrazine hydrate dispersed in 9 ml of water, stir for 1 hour, filter, wash five times with 20 ml of deionized water, and dry in a forced-air drying oven at 60 °C to obtain RuO x / C.

[0032] The composite material has better hydrazine oxidation performance than Com.Pt / C in an alkaline solution of 1 M KOH + 0.5 M hydrazine hydrate at a lower noble metal loading.

Claims

1. A method for preparing a supported noble metal catalyst based on defective carbon, characterized in that: The following steps are involved: 1) Grind and mix the carbon material and boron oxide in a mass ratio of 5:1-25, add water and stir evenly, then dry and grind to obtain a boron-carbon precursor; 2) Place the boron-carbon precursor in a tube furnace, heat it to 500-1400°C in an argon or nitrogen atmosphere, keep it warm for 10 min-10 h, then cool it, grind the obtained material, wash, filter, dry it, and grind it again to obtain a defective carbon material; 3) dispersing at least one noble metal compound and a defective carbon material in a dispersant or a reducing agent, and loading the noble metal on the defective carbon by heating, ultrasound, microwave, hydrothermal or hydrazine hydrate reduction to obtain a primary product; 4) The initial product is filtered and dried to obtain a noble metal / defective carbon composite catalyst.

2. The method for preparing a supported noble metal catalyst based on defective carbon according to claim 1, characterized in that: The carbon material in step 1) is water-absorbing resin, starch or cellulose.

3. The method for preparing a supported noble metal catalyst based on defective carbon according to claim 1, characterized in that: The washing in step 2) uses one or more liquids selected from deionized water, ethanol, hydrochloric acid, and potassium hydroxide solution.

4. The method for preparing a supported noble metal catalyst based on defective carbon according to claim 1, characterized in that: The mass ratio of the noble metal compound to the defective carbon material in step 3) is 1-25:

100.

5. The method for preparing a supported noble metal catalyst based on defective carbon according to claim 1, characterized in that: Step 3) The noble metal compound is one or more of chlorides, hydrochlorides, acetylacetonates, and nitrates of Au, Ir, Rh, Pt, Ru, Pd, Ag, etc.

6. The method for preparing a supported noble metal catalyst based on defective carbon according to claim 1, characterized in that: Step 3) The dispersant is one or more of ethylene glycol, hydrazine hydrate, ethanol and water.

7. The method for preparing a supported noble metal catalyst based on defective carbon according to claim 1, characterized in that: Step 3) The reducing agent is one or more of ethylene glycol, sodium borohydride, hydrazine hydrate, and ascorbic acid.

8. The method for preparing a defective carbon-based supported noble metal catalyst according to claim 1, characterized in that: The washing in step 4) is to wash the primary product 3 to 5 times with deionized water.

Images