CN103112854A - Method for synthesizing carbide/porous graphitized carbon nano compound through one-step method - Google Patents

Abstract

The invention discloses a method for synthesizing carbide/porous graphite carbon nanocomposite in one step, which relates to a method for synthesizing carbide/porous graphite carbon nanocomposite. The invention aims to solve the problems in the prior art in the preparation of the carbide/porous graphite carbon nanocomposite that the carbide particle size is large, the distribution is uneven, easy to agglomerate and the specific surface area is small. The method of the present invention is as follows: 1. dissolving the carbon source and transition metal salts in a solvent; 2. adding a pore-forming agent and a graphitization catalyst; 3. high-temperature carbonization; 4. drying after acid treatment. The invention has the advantages of simple synthesis method, small particle size of the synthesized carbide, uniform distribution and large specific surface area, little environmental pollution, low cost and simple synthesis equipment required, making it easy to realize commercialization. The invention applies to the field of energy storage and conversion.

Description

Method for one-step synthesis of carbide/porous graphitic carbon nanocomposites

technical field

The invention relates to a method for synthesizing carbide/porous graphite carbon nanocomposite.

Background technique

At present, the energy storage capacity of fossil fuels is decreasing day by day, and they release a large amount of harmful gases when they are burned. Therefore, people have begun to pay great attention to the development of new energy sources to solve energy and environmental problems. In recent years, it has been found that direct methanol Fuel cells are a new energy source that can potentially replace fossil fuels. However, because the catalysts used in the cathode and anode are noble metal catalysts, most of them are based on Pt. Its use in catalysts made it too expensive to be commercialized, and then it was found that transition metal carbides (tungsten, molybdenum, vanadium) have platinum-like properties, and their use in catalyst materials can reduce the amount of Pt used. The reduction of the cost of the catalyst makes the commercialization of the direct methanol fuel cell a reality. However, at present, the main method for preparing carbide (tungsten, molybdenum, vanadium)/porous graphitic carbon nanocomposites is: first mix and calcinate the carbon source and molecular sieve, prepare porous graphitized carbon and remove the pore-forming agent, and then The precursor of tungsten source (molybdenum source or vanadium source) is adsorbed on the surface of porous graphite carbon, and after microwave and high-temperature roasting, a composite of carbide (tungsten, molybdenum, vanadium) and porous graphite carbon is prepared. However, this preparation The synthesis process of the method is complex, and the distribution of the prepared tungsten carbide (molybdenum, vanadium) on the graphite carbon is uneven and easy to agglomerate, the particle size is large, and the specific surface area is small, thereby affecting its methanol electrooxidation performance, and it is difficult to obtain in commerce. application.

Contents of the invention

The present invention aims to solve the problem of uneven distribution of tungsten carbide, larger particle size and small specific surface area in the compound of carbide/porous graphite carbon nanometer prepared in the prior art; and provides a one-step synthesis of carbide/porous graphite carbon nanometer Composite method.

The method for the present invention's one-step synthetic carbide/porous graphite carbon nanocomposite is completed by the following steps: one, the carbon source and the transition metal salts are dissolved in a solvent with a mass ratio of 10:2, and then added Pore agent, add graphitization catalyst again, dry, obtain precursor; Wherein the mass volume ratio of carbon source and solvent is 1: (5～30), the mass volume ratio of carbon source and pore forming agent is 1: (1～10 ), the mass ratio of carbon source to graphite catalyst is 1: (0.5～5), wherein the transition metal salts are tungsten source, molybdenum source or vanadium source; 2. Under the condition of inert gas protection, the temperature rises from room temperature to 500 ~1100°C, the heating rate is 2~20°C/min, and then heat-treat the precursor in step 1 for 0.5~10 hours to obtain the pre-product; 3, grind the pre-product obtained in step 2, then acid-treat, and then use distilled water Wash until the pH is 6-8, and then dry at 60-120°C for 4-12 hours to obtain a carbide/porous graphite carbon nanocomposite, which is a one-step method for synthesizing a carbide/porous graphite carbon nanocomposite .

The process of the present invention is simple, the carbides are evenly distributed on the graphite carbon, and the particle size is small, and because the carbon source of the present invention has a wide range of sources and is cheap, the production cost is reduced, and the environmental pollution is small, the required equipment is simple, and it is easy to implement commercialize. The product of the invention has platinum-like catalyst properties, and can resist carbon monoxide poisoning simultaneously, so it can be used as an electrode material for a direct methanol fuel cell.

Description of drawings

Fig. 1 is the low magnification transmission electron micrograph of the pure phase tungsten carbide nanoparticles of the tungsten carbide/porous graphite carbon nanocomposite prepared by the test;

Fig. 2 is the high-magnification transmission electron micrograph of the pure phase tungsten carbide nanoparticles of the tungsten carbide/porous graphite carbon nanocomposite prepared by the test;

Fig. 3 is the cyclic voltammogram of experimentally prepared tungsten carbide/porous graphite carbon nanocomposites loaded with 10%Pt and commercially available Pt/C; wherein a and c are the cyclic voltammograms of commercially available graphite carbon loaded Pt, b and d is the cyclic voltammogram of the experimentally prepared tungsten carbide/porous graphite carbon nanocomposite loaded with 10% Pt.

Detailed ways

Specific embodiment one: the method for synthesizing carbide/porous graphite carbon nanocomposites in one step in this embodiment is completed by the following steps: one, the carbon source and transition metal salts are dissolved in the mass ratio of 10:2 In solvent, then add pore forming agent, then add graphitization catalyst, dry, obtain precursor; Wherein the mass volume ratio of carbon source and solvent is 1: (5～30), the mass volume ratio of carbon source and pore forming agent is 1: (1 ~ 10), the mass ratio of carbon source and graphite catalyst is 1: (0.5 ~ 5), wherein the transition metal salts are tungsten source, molybdenum source or vanadium source; 2. Under the condition of inert gas protection, From room temperature to 500-1100°C, the temperature rise rate is 2-20°C/min, and then heat-treat the precursor in step 1 for 0.5-10 hours to obtain the pre-product; 3. Grind the pre-product obtained in step 2, and then carry out Acid treatment, and then washed with distilled water until the pH is 6-8, and then dried at 60-120°C for 4-12 hours to obtain carbide/porous graphite carbon nanocomposites, that is, to complete the one-step synthesis of carbide/porous graphite carbon nanocomposites approach.

The process of this embodiment is simple, the carbides are evenly distributed on the graphite carbon, and the particle size is small, and because the carbon source of this embodiment has a wide range of sources and is cheap, the production cost is reduced, and the environmental pollution is small, and the required equipment is simple. Ease of commercialization. The product of this embodiment has platinum-like catalyst properties and can also resist carbon monoxide poisoning, so it can be used as an electrode material for a direct methanol fuel cell.

Specific embodiment two: the difference between this embodiment and specific embodiment one is: the carbon source in step one is the extract of crops, high molecular polymer or shell extract, wherein the extract of crops is glucose, sucrose, citric acid , sucrose, fructose, maltose, oxalic acid, tartaric acid or starch; the polymer is one of polystyrene, polyacrylamide, polyfurfuryl alcohol, polyimide, polyurethane, polyglucosamine, polyvinyl acid methyl ester and polyaniline or a mixture of several of them in any ratio; the shell extract is chitosan or chitin. Other steps and parameters are the same as those in Embodiment 1.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the tungsten source in step 1 is H ₂ W ₆ O ₁₉ , H ₃ PW ₁₂ O ₄₀ , H ₃ SiW ₁₂ O ₄₀ , H ₄ W ₁₀ O ₃₂ , (NH ₄ ) ₆ W ₇ O ₂₄ , Na ₂ WO ₄ , Na ₂ W ₆ O ₁₉ , WCl ₆ , Na ₃ PW ₁₂ O ₄₀ , Na ₃ SiW ₁₂ O ₄₀ , Na ₄ W ₁₀ O ₃₂ , K ₂ W ₆ O ₁₉ , K ₃ PW ₁₂ O ₄₀ , K ₃ SiW ₁₂ O ₄₀ or K ₄ W ₁₀ O ₃₂ ; molybdenum sources are H ₂ Mo ₆ O ₁₉ , H ₃ PMo ₁₂ O ₄₀ , H ₃ SiMo ₁₂ O ₄₀ , H ₄ Mo ₁₀ O ₃₂ , (NH ₄ ) ₆ Mo ₇ O ₂₄ , Na ₂ MoO ₄ , Na ₂ Mo ₆ O ₁₉ , Na ₃ PMo ₁₂ O ₄₀ , Na ₃ SiMo ₁₂ O ₄₀ , Na ₄ Mo ₁₀ O ₃₂ , K ₂ Mo ₆ O ₁₉ , K ₃ PMo ₁₂ O ₄₀ , K ₃ SiMo ₁₂ O ₄₀ or K ₄ Mo ₁₀ O ₃₂ ; vanadium source: HVO ₃ , H ₃ VO ₄ , H ₄ V ₂ O ₇ , H ₃ V ₃ O ₉ , NaVO ₃ , NH ₄ VO ₃ , Na ₃ VO ₄ or (NH ₄ ) ₂ V ₆ O ₁₆ . Other steps and parameters are the same as those in Embodiment 1 or Embodiment 2.

Embodiment 4: This embodiment differs from Embodiment 1 to Embodiment 3 in that: the solvent in step 1 is one of water, methanol, ethanol and isopropanol or a mixture of several of them mixed in any ratio. Other steps and parameters are the same as those in the specific embodiment 1 to 3.

Specific embodiment five: this embodiment is different from one of specific embodiments one to four in that: the pore-forming agent in step one is tetraethyl orthosilicate, silica gel, SBA-n molecular sieve, CMK-n molecular sieve, MCM-22 molecular sieve , Beta molecular sieve, USY molecular sieve, BEA/MOR co-crystal molecular sieve, MFI/MOR co-crystal molecular sieve, PS ball, zeolite, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polypropylene glycol Addition polymer with ethylene oxide, polymethylmethacrylate, polyvinylpyrrolidone, cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, sodium lauryl sulfate, Calcium acetate, calcium oxalate, calcium carbonate, ammonium carbonate, or ammonium bicarbonate. Other steps and parameters are the same as one of the specific embodiments 1 to 4.

Specific embodiment six: this embodiment is different from one of specific embodiments one to five: the graphitization catalyst in step one is nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, ferric chloride, ferrous chloride, One of ferric nitrate, ferrous nitrate, ferric sulfate, ferrous sulfate, potassium ferricyanide, potassium ferrocyanide, potassium ferrioxalate, cobalt chloride, cobalt nitrate, cobalt sulfate and cobalt acetate Several mixtures mixed in any ratio. Other steps and parameters are the same as those of Embodiments 1 to 5.

Embodiment 7: This embodiment differs from Embodiment 1 to Embodiment 6 in that the inert gas in step 2 is one of nitrogen, argon and helium or a mixture of several of them mixed in any ratio. The other steps and parameters are the same as those of Embodiments 1 to 6.

Embodiment 8: The difference between this embodiment and one of Embodiments 1 to 7 is that the heat treatment atmosphere in step 2 is nitrogen, argon, helium, methane, ethylene, carbon dioxide or carbon monoxide, and the gas flow rate is 10-200 mL/min . Other steps and parameters are the same as one of the specific embodiments 1 to 7.

Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is: the method of acid treatment in step three is: after the concentration is 0.5 ~ 5mol/L sodium hydroxide solution for 4 ~ 48h, then Reflux in 11.9mol/L hydrochloric acid or 14mol/L nitric acid solution at 70-140°C for 6-12 hours. Other steps and parameters are the same as those in Embodiments 1 to 8.

Embodiment 10: This embodiment is different from Embodiment 1 to Embodiment 9 in that the method of acid treatment in step 3 is: stirring in hydrofluoric acid with a mass concentration of 10-15% at 20-40°C 6～72h. Other steps and parameters are the same as those of Embodiments 1 to 9.

Embodiment 11: The difference between this embodiment and Embodiments 1 to 10 is that the heating rate in step 2 is 5° C./min. Other steps and parameters are the same as those in Embodiments 1 to 11.

Embodiment 12: This embodiment is different from Embodiment 1 to Embodiment 11 in that: in step 2, the room temperature is raised to 1000°C. Other steps and parameters are the same as those in Embodiments 1 to 11.

Prove the beneficial effect of the present invention by following test:

Test: The method for synthesizing carbide/porous graphite carbon nanocomposites in one step in this test is completed by the following steps: 1. Dissolve 2g of glucose and 0.4g of sodium tungstate in 30°C water, and then add 4mL of orthosilicic acid Ethyl ester, then add 2g of nickel chloride, dry to obtain the precursor; 2. Under the condition of inert gas protection, the temperature rises from room temperature to 1000 ° C, and the heating rate is 5 ° C / min, and then the precursor of step 1 Carry out heat treatment for 2 hours to obtain the pre-product; 3. Grind the pre-product obtained in step 2, add it to 120 mL of acetic acid with a mass concentration of 15%, stir at 25°C for 4 hours, and wash with distilled water until the pH of the washing solution is 7 , and then dried at 100° C. for 8 hours to obtain a tungsten carbide/porous graphite carbon nanocomposite, that is, a one-step method for synthesizing the carbide/porous graphite carbon nanocomposite.

The transmission electron microscope photos of the tungsten carbide/porous graphite carbon nanocomposites prepared in this test are shown in Fig. It is about 10nm and has a porous structure, which further proves that the product is a composite of tungsten carbide/porous graphite carbon, so that it can catalyze some important chemical reactions, such as methanol electrooxidation, sensitization of the counter electrode of solar cells, and hydrolysis. Hydrogen, ammonia decomposition, oxidation reactions, and hydrocarbon conversion and synthesis reactions, etc., have shown good catalytic performance. The tungsten carbide porous graphite carbon nanocomposite prepared in Experiment 1 was loaded with 10% Pt, and Fig. 3 is the tungsten carbide porous graphite carbon nanocomposite loaded with 10% Pt and the commercially available Pt/C catalyst for methanol fuel cell Cyclic voltammogram, we can see from the figure that the tungsten carbide/porous graphite carbon nanocomposite loaded with 10% Pt has a higher peak current, and can effectively inhibit the phenomenon of carbon monoxide poisoning, indicating that loaded with 10 %Pt tungsten carbide/porous graphitic carbon nanocomposites have better catalytic performance for methanol electrooxidation.

Claims (10)

1. the method for one-step synthetic carbide/porous graphite carbon nanocomposite is characterized in that the method for one-step synthetic carbide/porous graphite carbon nanocomposite is accomplished by following steps: one, mass ratio is 10: The carbon source and transition metal salts of 2 are dissolved in a solvent, then add a pore-forming agent, then add a graphitization catalyst, and dry to obtain a precursor; wherein the mass-volume ratio of the carbon source and the solvent is 1: (5-30), The mass volume ratio of carbon source and pore forming agent is 1: (1-10), the mass ratio of carbon source and graphite catalyst is 1: (0.5-5), and the transition metal salts are tungsten source, molybdenum source or vanadium source ; 2. Under the condition of inert gas protection, the temperature is raised from room temperature to 500-1100 °C at a heating rate of 2-20 °C/min, and then the precursor in step 1 is heat-treated for 0.5-10 hours to obtain a pre-product; 3. Grinding the pre-product obtained in step 2, then acid treatment, then washing with distilled water until the pH is 6-8, and then drying at 60-120°C for 4-12 hours to obtain carbide/porous graphite carbon nanocomposites , that is, a method for one-step synthesis of carbide/porous graphitic carbon nanocomposites. 2. the method for one-step synthetic carbide/porous graphite carbon nanocomposite according to claim 1, is characterized in that the carbon source in step 1 is the extract of crops, polymer or shell extract, wherein crops The extract is glucose, sucrose, citric acid, sucrose, fructose, maltose, oxalic acid, tartaric acid or starch; the polymer is polystyrene, polyacrylamide, polyfurfuryl alcohol, polyimide, polyurethane, polyglucosamine, poly One of methyl acrylate and polyaniline or a mixture of several of them mixed in any ratio; the shell extract is chitosan or chitin. 3. The method for one-step synthesis of carbide/porous graphitic carbon nanocomposites according to claim 1, characterized in that the tungsten source in step one is H ₂ W ₆ O ₁₉ , H ₃ PW ₁₂ O ₄₀ , H ₃ SiW ₁₂ O ₄₀ , H ₄ W ₁₀ O ₃₂ , (NH ₄ ) ₆ W ₇ O ₂₄ , Na ₂ WO ₄ , Na ₂ W ₆ O ₁₉ , WCl ₆ , Na ₃ PW ₁₂ O ₄₀ , Na ₃ SiW ₁₂ O ₄₀ , Na ₄ W ₁₀ O ₃₂ , K ₂ W ₆ O ₁₉ , K ₃ PW ₁₂ O ₄₀ , K ₃ SiW ₁₂ O ₄₀ or K ₄ W ₁₀ O ₃₂ ; molybdenum sources are H ₂ Mo ₆ O ₁₉ , H ₃ PMo ₁₂ O ₄₀ , H ₃ SiMo ₁₂ O ₄₀ , H ₄ Mo ₁₀ O ₃₂ , (NH ₄ ) ₆ Mo ₇ O ₂₄ , Na ₂ MoO ₄ , Na ₂ Mo ₆ O ₁₉ , Na ₃ PMo ₁₂ O ₄₀ , Na ₃ SiMo ₁₂ O ₄₀ , Na ₄ Mo ₁₀ O ₃₂ , K ₂ Mo ₆ O ₁₉ , K ₃ PMo ₁₂ O ₄₀ , K ₃ SiMo ₁₂ O ₄₀ or K ₄ Mo ₁₀ O ₃₂ ; vanadium sources are: HVO ₃ , H ₃ VO ₄ , H ₄ V ₂ O ₇ , H ₃ V ₃ O ₉ , NaVO ₃ , NH ₄ VO ₃ , Na ₃ VO ₄ or (NH ₄ ) ₂ V ₆ O ₁₆ . 4. the method for one-step synthetic carbide/porous graphite carbon nanocomposite according to claim 1, is characterized in that the solvent in step 1 is one or several of them in water, methyl alcohol, ethanol and Virahol A mixture mixed in any ratio. 5. the method for one-step synthetic carbide/porous graphitic carbon nanocomposite according to claim 1, is characterized in that the pore-forming agent in the step 1 is tetraethyl orthosilicate, silica gel, SBA-n molecular sieve, CMK- n molecular sieve, MCM-22 molecular sieve, Beta molecular sieve, USY molecular sieve, BEA/MOR co-crystal molecular sieve, MFI/MOR co-crystal molecular sieve, PS ball, zeolite, polyethylene oxide-polypropylene oxide-polyethylene oxide three Block copolymer, addition polymer of polypropylene glycol and ethylene oxide, polymethylmethacrylate, polyvinylpyrrolidone, cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, Sodium Lauryl Sulfate, Calcium Acetate, Calcium Oxalate, Calcium Carbonate, Ammonium Carbonate or Ammonium Bicarbonate. 6. the method for one-step synthetic carbide/porous graphite carbon nanocomposite according to claim 1, is characterized in that the graphitization catalyst in step one is nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, chloride Iron, ferrous chloride, ferric nitrate, ferrous nitrate, ferric sulfate, ferrous sulfate, potassium ferricyanide, potassium ferrocyanide, potassium ferrite trioxalate, cobalt chloride, cobalt nitrate, cobalt sulfate, and acetic acid One of cobalt or a mixture of several of them mixed in any ratio. 7. the method for one-step synthetic carbide/porous graphite carbon nanocomposite according to claim 1, is characterized in that the inert gas in step 2 is one or wherein several in nitrogen, argon and helium Mixtures in any ratio. 8. the method for one-step synthetic carbide/porous graphite carbon nanocomposite according to claim 1, is characterized in that heat treatment atmosphere is nitrogen, argon, helium, methane, ethylene, carbon dioxide or carbon monoxide in the step 2, gas The flow rate is 10-200mL/min. 9. The method for one-step synthesis of carbide/porous graphite carbon nanocomposites according to claim 1, characterized in that the acid treatment method in step 3 is: in a sodium hydroxide solution with a concentration of 0.5～5mol/L After treating for 4-48 hours, reflux in 11.9 mol/L hydrochloric acid or 14 mol/L nitric acid solution at 70-140°C for 6-12 hours. 10. The method for one-step synthesis of carbide/porous graphite carbon nanocomposites according to claim 1, characterized in that the method of acid treatment in step 3 is: under the condition of 20～40°C, at a mass concentration of 10～ Stir in 15% hydrofluoric acid for 6-72 hours.

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