CN116065265A - A cobalt-molybdenum co-doped porous nanowire and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of transition metal catalysts, and provides a cobalt-molybdenum co-doped porous nanowire and a preparation method and application thereof. The method comprises the following steps: mixing polystyrene, molybdenum acetylacetonate, zinc chloride and N,N-dimethylamide, and performing electrospinning to obtain a fiber film co-doped with zinc and molybdenum; co-doping zinc and molybdenum The doped fiber film is acidified to obtain a sulfonated fiber film; the sulfonated fiber film, ethanol solution of pyrrole, cobalt nitrate solution and ammonium thiosulfate are mixed for polymerization to obtain zinc, cobalt, molybdenum co-doped poly Pyrrole-coated polystyrene nanowires; finally, it is carbonized to obtain cobalt-molybdenum co-doped porous nanowires. The process design of the invention is reasonable, the cost of raw materials is low, and it is suitable for large-scale production. The cobalt-molybdenum co-doped porous nanowire obtained by the preparation method of the invention has excellent hydrogen evolution performance, and the hydrogen evolution overpotential reaches 85mV in a 1.0mol/L potassium hydroxide solution.

Description

A cobalt-molybdenum co-doped porous nanowire and its preparation method and application

technical field

The invention relates to the technical field of transition metal catalysts, in particular to a cobalt-molybdenum co-doped porous nanowire and a preparation method and application thereof.

Background technique

With the development of economy and society, people's demand for energy is increasing. However, non-renewable fossil fuels are becoming exhausted day by day, and the environmental pollution problems caused by fossil fuels are also becoming more and more serious. Renewable, clean, environmentally friendly and new hydrogen energy with high energy utilization rate has gradually entered people's production and life. Among them, hydrogen production by electrolysis of water has become a new trend of next-generation energy production due to its low energy consumption, high purity of hydrogen, and ease of large-scale application. At present, platinum or platinum-based nanomaterials are the electrode materials with the best performance for hydrogen production by electrolysis of water, but their limited reserves and high prices greatly limit the industrial production of this technology. In addition, the transition metal catalysts developed at this stage have disadvantages such as poor stability, low hydrogen evolution performance, low catalyst active area, and high catalyst loading. Therefore, it is of great significance to develop a transition metal catalyst with low price, high activity, excellent stability and low loading.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a cobalt-molybdenum co-doped porous nanowire and its preparation method and application.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a method for preparing cobalt-molybdenum co-doped porous nanowires, comprising the following steps:

(1) Mix polystyrene, molybdenum acetylacetonate, zinc chloride and N,N-dimethylamide, and perform electrospinning to obtain zinc and molybdenum co-doped fiber film;

(2) zinc, molybdenum co-doped fiber film is acidified to obtain sulfonated fiber film;

(3) Mix the sulfonated fiber film, ethanol solution of pyrrole, cobalt nitrate solution and ammonium thiosulfate, and carry out a polymerization reaction to obtain zinc, cobalt, and molybdenum co-doped polypyrrole-coated polystyrene nanowires;

(4) Carbonizing polypyrrole-coated polystyrene nanowires co-doped with zinc, cobalt and molybdenum to obtain the cobalt-molybdenum co-doped porous nanowires.

Preferably, the mass volume ratio of polystyrene, molybdenum acetylacetonate, zinc chloride and N,N-dimethylamide in step (1) is 1.0-1.2g: 0.05-0.25g: 0.1-0.3g: 8 ~12mL.

Preferably, the electrospinning voltage in step (1) is 12-20 kV, the spinning distance is 10-20 cm, and the rotation speed of the roller is 350-450 r/min.

As a preference, the acidified sulfuric acid solution in step (2) has a mass fraction of 97-99%, and the mass-volume ratio of the zinc and molybdenum co-doped fiber film to the sulfuric acid solution is 1g:95-105mL;

The temperature of the acidification is 20-30° C., and the time of the acidification is 2.5-3.5 hours.

Preferably, the mass concentration of the ethanol solution of pyrrole in step (3) is 0.4-0.6 g/L, and the concentration of the cobalt nitrate solution is 0.1-0.3 mmol/L.

As preferably, the ethanol solution of pyrrole in step (3), the cobalt nitrate solution and the polystyrene in step (1) have a volume to mass ratio of 180 to 220 mL: 40 to 60 mL: 1.0 to 1.2 g, and the thiosulfuric acid The molar ratio of ammonium to pyrrole is 0.8-1.2:0.8-1.2.

Preferably, the temperature of the polymerization reaction in step (3) is 3-7° C., and the time is 22-26 hours.

Preferably, the heating rate of the carbonization in step (4) is 2-4°C/min, the target temperature is 850-950°C, and the holding time after reaching the target temperature is 1.5-2.5h.

The invention also provides the cobalt-molybdenum co-doped porous nanowire obtained by the preparation method.

The invention also provides the application of the cobalt-molybdenum co-doped porous nanowire in hydrogen production by electrolyzing water.

The beneficial effects of the present invention are:

The invention provides a method for preparing cobalt-molybdenum co-doped porous nanowires, comprising the following steps: mixing polystyrene, molybdenum acetylacetonate, zinc chloride and N,N-dimethylamide, performing electrospinning, Obtain zinc, molybdenum co-doped fiber film; zinc, molybdenum co-doped fiber film is acidified to obtain sulfonated fiber film; sulfonated fiber film, ethanol solution of pyrrole, cobalt nitrate solution and ammonium thiosulfate Mix and carry out polymerization reaction to obtain polypyrrole-coated polystyrene nanowires co-doped with zinc, cobalt and molybdenum; carbonize polypyrrole-coated polystyrene nanowires co-doped with zinc, cobalt and molybdenum to obtain cobalt molybdenum Co-doped porous nanowires. The process design of the invention is reasonable, the cost of raw materials is low, the shape of the finished product is easy to control, and is suitable for large-scale production. The cobalt-molybdenum co-doped porous nanowire obtained by the preparation method of the invention has excellent hydrogen evolution performance, and the hydrogen evolution overpotential reaches 85mV in a 1.0mol/L potassium hydroxide solution.

Detailed ways

The invention provides a method for preparing cobalt-molybdenum co-doped porous nanowires, comprising the following steps:

(1) Mix polystyrene, molybdenum acetylacetonate, zinc chloride and N,N-dimethylamide, and perform electrospinning to obtain zinc and molybdenum co-doped fiber film;

(2) zinc, molybdenum co-doped fiber film is acidified to obtain sulfonated fiber film;

(3) Mix the sulfonated fiber film, ethanol solution of pyrrole, cobalt nitrate solution and ammonium thiosulfate, and carry out a polymerization reaction to obtain zinc, cobalt, and molybdenum co-doped polypyrrole-coated polystyrene nanowires;

(4) Carbonizing polypyrrole-coated polystyrene nanowires co-doped with zinc, cobalt and molybdenum to obtain the cobalt-molybdenum co-doped porous nanowires.

In the present invention, the mass volume ratio of polystyrene, molybdenum acetylacetonate, zinc chloride and N,N-dimethylamide in step (1) is preferably 1.0-1.2g: 0.05-0.25g: 0.1-0.3 g: 8-12mL, more preferably 1.05-1.15g: 0.10-0.20g: 0.15-0.25g: 9-11mL, more preferably 1.07-1.13g: 0.12-0.18g: 0.17-0.23g: 9.5-10.5mL .

In the present invention, the mixing temperature in step (1) is preferably 20-30°C, more preferably 22-28°C, more preferably 24-26°C; the rotation speed is preferably 200-400r/min, more preferably 250 ~350r/min, more preferably 270~330r/min; time is preferably 4~6h, more preferably 4.5~5.5h, more preferably 4.7~5.3h.

In the present invention, the electrospinning voltage in step (1) is preferably 12-20kV, more preferably 14-18kV, more preferably 15-17kV; the spinning distance is preferably 10-20cm, more preferably 12-20cm 18cm, more preferably 14-16cm; the rotational speed of the roller is preferably 350-450r/min, more preferably 370-430r/min, more preferably 390-410r/min.

In the present invention, the acidification in step (2) is to completely immerse the zinc and molybdenum co-doped fiber film in sulfuric acid solution, and obtain the sulfonated fiber film after a certain period of time.

In the present invention, the acidified sulfuric acid solution mass fraction in step (2) is preferably 97-99%, more preferably 97.5-98.5%, more preferably 97.7-98.3%; the zinc, molybdenum co-doped fiber The mass volume ratio of the film to the sulfuric acid solution is preferably 1g:95-105mL, more preferably 1g:97-103mL, more preferably 1g:99-101mL; the acidification temperature is preferably 20-30°C, more preferably 22 ~28°C, more preferably 24~26°C; the acidification time is preferably 2.5~3.5h, more preferably 2.6~3.4h, more preferably 2.7~3.3h.

In the present invention, after the acidification of step (2), it is preferred to wash the obtained sulfonated fiber film, and then carry out subsequent procedures; the washing is deionized water washing and absolute ethanol washing carried out alternately, so The number of said alternation is preferably greater than or equal to 3 times, more preferably greater than or equal to 4 times, more preferably greater than or equal to 5 times.

In the present invention, the mass concentration of the ethanol solution of pyrrole described in step (3) is preferably 0.4～0.6g/L, more preferably 0.45～0.55g/L, more preferably 0.47～0.53g/L; The concentration of the cobalt solution is preferably 0.1-0.3 mmol/L, more preferably 0.15-0.25 mmol/L, more preferably 0.17-0.23 mmol/L.

In the present invention, the volume to mass ratio of the ethanol solution of pyrrole in step (3), cobalt nitrate solution and polystyrene in step (1) is preferably 180-220mL: 40-60mL: 1.0-1.2g, more preferably 190-210mL: 45-55mL: 1.05-1.15g, more preferably 195-205mL: 47-53mL: 1.07-1.13g; the molar ratio of ammonium thiosulfate to pyrrole is preferably 0.8-1.2: 0.8-1.2 , more preferably 0.85-1.15:0.85-1.15, more preferably 0.9-1.1:0.9-1.1.

In the present invention, the mixing described in step (3) specifically includes the following steps:

(a) soaking the sulfonated fiber film in pyrrole alcohol solution to obtain the first mixed solution;

(b) adding the cobalt nitrate solution into the first mixed solution, and obtaining the second mixed solution after standing;

(c) Ammonium thiosulfate is added into the second mixed solution to carry out subsequent polymerization reaction.

In the present invention, the soaking temperature in step (a) is preferably 3-7°C, more preferably 4-6°C, more preferably 4.5-5.5°C; the time is preferably 22-26h, more preferably 23-25h , more preferably 23.5-24.5h.

In the present invention, the standing temperature in step (b) is preferably 3-7°C, more preferably 4-6°C, more preferably 4.5-5.5°C; the time is preferably 22-26h, more preferably 23-5°C 25h, more preferably 23.5-24.5h.

In the present invention, the temperature of the polymerization reaction in step (3) is preferably 3 to 7°C, more preferably 4 to 6°C, more preferably 4.5 to 5.5°C; the time is preferably 22 to 26h, more preferably 23 to 5.5°C 25h, more preferably 23.5-24.5h.

In the present invention, after the polymerization reaction in step (3), the obtained zinc, cobalt, and molybdenum co-doped polypyrrole-coated polystyrene nanowires are suction-filtered with ethanol, and N,N-dimethyl Soak in amide (DMF) and then carbonize.

In the present invention, new DMF solution needs to be replaced in the soaking process, and the interval time of said replacement is preferably 7～9h, more preferably 7.5～8.5h, more preferably 7.7～8.3h; the volume of DMF solution used once The mass ratio to the polystyrene in step (1) is preferably 130-170mL: 1.0-1.2g, more preferably 140-160mL: 1.05-1.15g, more preferably 145-155mL: 1.07-1.13g; The total soaking time is preferably 22-26 hours, more preferably 23-25 hours, more preferably 23.5-24.5 hours.

In the present invention, the function of soaking in DMF is to dissolve part of polystyrene, so that polystyrene can be decomposed to produce pores at high temperature, and zinc ions are melted and volatilized at high temperature to obtain a microporous structure.

In the present invention, the heating rate of the carbonization in step (4) is preferably 2-4°C/min, more preferably 2.5-3.5°C/min, more preferably 2.7-3.3°C/min; the target temperature is preferably 850- 950°C, more preferably 860-940°C, more preferably 870-930°C; the holding time after reaching the target temperature is preferably 1.5-2.5h, more preferably 1.7-2.3h, more preferably 1.9-2.1h.

The invention also provides the cobalt-molybdenum co-doped porous nanowire obtained by the preparation method.

The invention also provides the application of the cobalt-molybdenum co-doped porous nanowire in hydrogen production by electrolyzing water.

The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be interpreted as limiting the protection scope of the present invention.

Example 1

Add 1.12g polystyrene, 0.15g molybdenum acetylacetonate, and 0.2g zinc chloride to 10mL N,N-dimethylamide, stir at 300r/min at 25°C for 5h, and then subject the resulting mixed solution to static electricity. Spinning, the setting voltage is 15kV, the spinning distance is 15cm, and the roller speed is 400r/min to prepare a zinc and molybdenum co-doped fiber film; the zinc and molybdenum co-doped fiber film is immersed in a mass fraction of 98% in sulfuric acid solution (the mass volume ratio of zinc, molybdenum co-doped fiber film to sulfuric acid solution is 1g:100mL), acidified at 25°C for 3h to obtain sulfonated fiber film; then the obtained sulfonated fiber film was alternately Wash with deionized water and absolute ethanol (alternately for 3 times); after washing, immerse the fiber film in 200mL pyrrole ethanol solution with a mass concentration of 0.5g/L, soak at 5°C for 24h, and then add 50mL concentration 0.2mmol/L cobalt nitrate solution, then let it stand at 5°C for 24h, and finally add ammonium thiosulfate (the molar ratio of ammonium thiosulfate to pyrrole is 1:1) to the mixed solution, and carry out at 5°C Polymerization for 24 hours to obtain zinc, cobalt, and molybdenum co-doped polypyrrole-coated polystyrene nanowires; the obtained nanowires are suction-filtered with ethanol, and then soaked in DMF solution (new DMF solution needs to be replaced during the soaking process) , the replacement interval is 8h, the volume of a single DMF is 150mL, and the total soaking time is 24h), to obtain a small amount of polystyrene nanowires coated with zinc, cobalt, and molybdenum co-doped polypyrrole; The heating rate of °C/min was raised to 900 °C for carbonization, and kept at 900 °C for 2 hours to obtain the cobalt-molybdenum co-doped porous nanowires.

The cobalt-molybdenum co-doped porous nanowires prepared in this example were tested for hydrogen evolution performance, and the hydrogen evolution overpotential in 1.0 mol/L potassium hydroxide solution was 85 mV, which has excellent hydrogen evolution performance.

Example 2

Add 1.16g of polystyrene, 0.17g of molybdenum acetylacetonate, and 0.22g of zinc chloride into 11mL of N,N-dimethylamide, stir at 350r/min for 5.3h at 26°C, and then carry out the mixed solution obtained Electrospinning, the setting voltage is 17kV, the spinning distance is 16cm, the roller speed is 420r/min, and the zinc and molybdenum co-doped fiber film is prepared; the zinc and molybdenum co-doped fiber film is immersed in a mass fraction of 98.5 % sulfuric acid solution (the mass volume ratio of zinc, molybdenum co-doped fiber film and sulfuric acid solution is 1g: 102mL), acidified at 26°C for 2.6h to obtain a sulfonated fiber film; then the obtained sulfonated fiber The film was alternately washed with deionized water and absolute ethanol (the number of alternations was 4 times); after washing, the fiber film was immersed in 205 mL of pyrrole alcohol solution with a mass concentration of 0.55 g/L, soaked at 4 ° C for 23 h, and then added 52mL of cobalt nitrate solution with a concentration of 0.22mmol/L, and then let it stand at 4°C for 23h, and finally add ammonium thiosulfate (the molar ratio of ammonium thiosulfate to pyrrole is 0.95:1) to the mixed solution, at 4°C Carry out the polymerization reaction under 23h to obtain zinc, cobalt, molybdenum co-doped polypyrrole-coated polystyrene nanowires; the obtained nanowires are suction-filtered with ethanol, and then soaked in DMF solution (new ones need to be replaced during the soaking process). DMF solution, the interval time of changing is 8.5h, and the volume of single DMF is 155mL, and total soaking time is 25.5h), obtains zinc, cobalt, molybdenum co-doped polypyrrole coats a small amount of polystyrene nanowires; finally It was heated to 920° C. for carbonization at a heating rate of 4° C./min, and kept at 920° C. for 2.1 hours to obtain the cobalt-molybdenum co-doped porous nanowire.

The cobalt-molybdenum co-doped porous nanowire prepared in this example was tested for hydrogen evolution performance, and its hydrogen evolution overpotential in 1.0 mol/L potassium hydroxide solution was 81 mV.

Example 3

Add 1.06g of polystyrene, 0.08g of molybdenum acetylacetonate, and 0.17g of zinc chloride into 9mL of N,N-dimethylamide, stir at 250r/min for 4.5h at 23°C, and then carry out the mixed solution obtained Electrospinning, the set voltage is 14kV, the spinning distance is 12cm, and the roller speed is 350r/min to prepare a zinc and molybdenum co-doped fiber film; the zinc and molybdenum co-doped fiber film is immersed in a mass fraction of 97 % sulfuric acid solution (the mass volume ratio of zinc, molybdenum co-doped fiber film and sulfuric acid solution is 1g:97mL), acidified at 23°C for 3.3h to obtain a sulfonated fiber film; then the obtained sulfonated fiber The film was alternately washed with deionized water and absolute ethanol (the number of alternations was 3 times); after washing, the fiber film was immersed in 195 mL of pyrrole alcohol solution with a mass concentration of 0.46 g/L, soaked at 6 °C for 25 h, and then added 45mL of cobalt nitrate solution with a concentration of 0.18mmol/L, then let it stand at 6°C for 23h, and finally add ammonium thiosulfate (the molar ratio of ammonium thiosulfate to pyrrole is 1.1:1) to the mixed solution, at 6°C Carry out the polymerization reaction under 24h to obtain zinc, cobalt, molybdenum co-doped polypyrrole-coated polystyrene nanowires; the obtained nanowires are suction-filtered with ethanol, and then soaked in DMF solution (new ones need to be replaced during the soaking process). DMF solution, the interval time of changing is 7.5h, and the volume of single DMF is 150mL, and total soaking time is 22.5h), obtains zinc, cobalt, molybdenum co-doped polypyrrole coats a small amount of polystyrene nanowires; finally It was heated to 880° C. for carbonization at a heating rate of 2.5° C./min, and kept at 880° C. for 1.8 hours to obtain the cobalt-molybdenum co-doped porous nanowire.

The cobalt-molybdenum co-doped porous nanowires prepared in this example were tested for hydrogen evolution performance, and the hydrogen evolution overpotential in 1.0 mol/L potassium hydroxide solution was 83 mV.

It can be seen from the above examples that the preparation method provided by the present invention has reasonable design of each process, low cost of raw materials, and is suitable for large-scale production. The cobalt-molybdenum co-doped porous nanowire obtained by the preparation method of the invention has excellent hydrogen evolution performance, and the hydrogen evolution overpotential reaches 85mV in a 1.0mol/L potassium hydroxide solution.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A method for preparing cobalt-molybdenum co-doped porous nanowires, characterized in that, comprising the following steps: (1) Mix polystyrene, molybdenum acetylacetonate, zinc chloride and N,N-dimethylamide, and perform electrospinning to obtain zinc and molybdenum co-doped fiber film; (2) zinc, molybdenum co-doped fiber film is acidified to obtain sulfonated fiber film; (3) Mix the sulfonated fiber film, ethanol solution of pyrrole, cobalt nitrate solution and ammonium thiosulfate, and carry out a polymerization reaction to obtain zinc, cobalt, and molybdenum co-doped polypyrrole-coated polystyrene nanowires; (4) Carbonizing polypyrrole-coated polystyrene nanowires co-doped with zinc, cobalt and molybdenum to obtain the cobalt-molybdenum co-doped porous nanowires. 2. the preparation method as claimed in claim 1 is characterized in that, the mass volume ratio of polystyrene, molybdenum acetylacetonate, zinc chloride and N,N-dimethylamide described in step (1) is 1.0～1.2 g: 0.05-0.25g: 0.1-0.3g: 8-12mL. 3. The preparation method according to claim 2, characterized in that the electrospinning voltage in step (1) is 12-20 kV, the spinning distance is 10-20 cm, and the roller speed is 350-450 r/min. 4. The preparation method according to any one of claims 1 to 3, characterized in that, the acidified sulfuric acid solution mass fraction of step (2) is 97 to 99%, and the zinc, molybdenum co-doped fiber film The mass volume ratio of sulfuric acid solution is 1g:95~105mL; The temperature of the acidification is 20-30° C., and the time of the acidification is 2.5-3.5 hours. 5. preparation method as claimed in claim 4 is characterized in that, the mass concentration of the ethanol solution of pyrrole described in step (3) is 0.4～0.6g/L, and the concentration of described cobalt nitrate solution is 0.1～0.3mmol/L L. 6. The preparation method according to claim 5, wherein the volume to mass ratio of the ethanol solution of pyrrole in step (3), the cobalt nitrate solution and the polystyrene in step (1) is 180 to 220 mL: 40 ～60mL: 1.0～1.2g, the molar ratio of the ammonium thiosulfate to pyrrole is 0.8～1.2:0.8～1.2. 7. The preparation method according to claim 5 or 6, characterized in that the temperature of the polymerization reaction in step (3) is 3-7° C., and the time is 22-26 hours. 8. The preparation method according to claim 7, wherein the heating rate of the carbonization in step (4) is 2 to 4° C./min, the target temperature is 850 to 950° C., and the holding time after reaching the target temperature is 1.5～2.5h. 9. The cobalt-molybdenum co-doped porous nanowire obtained by the preparation method described in any one of claims 1-8. 10. The application of the cobalt-molybdenum co-doped porous nanowire according to claim 9 in hydrogen production by electrolysis of water.