CN108940285A - A kind of preparation method and application of flexibility electrolysis water catalysis material - Google Patents

Abstract

The invention discloses a preparation method and application of a flexible electrolyzed water catalytic material, and belongs to the technical field of hydrogen production by electrolyzed water. The preparation method comprises: (1) preparing cobalt-based Prussian blue analog nanoparticles; (2) dispersing cobalt-based Prussian blue analog nanoparticles in an organic solvent, and then adding polyacrylonitrile to make a spinning solution, electrostatically Co-PBA/PAN composite nanofiber membrane is obtained by spinning; (3) Co-PBA/PAN composite nanofiber membrane is pre-oxidized, and then carbonized in an inert atmosphere to obtain the flexible electrolytic water catalyst Material. In the electrolytic water catalytic material prepared by the present invention, cobalt carbide is evenly dispersed in the porous carbon fiber, which increases the catalytic sites. At the same time, the porous carbon fiber provides the carrier of the catalytic sites and enhances the electrical conductivity, which improves the traditional powder catalytic materials. The problem of easy loss; the production method is simple, green and safe, and can realize large-area continuous production.

Description

Preparation method and application of a flexible electrolytic water catalytic material

technical field

The invention relates to the technical field of hydrogen production by electrolysis of water, in particular to a preparation method and application of a flexible electrolysis water catalytic material.

Background technique

Currently, the energy problem is one of the most serious problems facing the world today. Relying on fossil fuels for energy has a huge impact on the economy. Excessive use of fossil fuels not only pollutes the air, but also exacerbates global warming. Therefore, it is urgent to find clean and sustainable new energy sources to replace fossil fuels. Among various energy sources, efficient, clean, and renewable hydrogen is not only an energy source, but also a carrier for energy storage and transfer. Among them, hydrogen production by electrolysis of water is considered to be a very promising way to generate clean hydrogen fuels.

For hydrogen production by electrolysis of water, the key to research is to improve the activity and stability of electrocatalytic materials and reduce the overpotential of electrochemical hydrogen evolution and oxygen evolution. The noble metal platinum is recognized as the most effective hydrogen and oxygen evolution electrocatalyst so far, but due to its high preparation cost and limited resource reserves, the large-scale production of platinum as a catalyst is severely restricted. Therefore, it is of great significance to find a stable, efficient, inexpensive and environmentally friendly electrocatalytic material to improve the utilization rate of electric energy in the electrolysis water industry.

Recently, transition metals and their alloys, sulfides, carbides, etc. have aroused the interest of researchers. Transition metal sulfides, selenides, and carbides have been successfully synthesized and applied as effective cathode hydrogen evolution catalysts, especially transition Metal carbides, with their unique structures and good electrocatalytic properties, have received great attention.

For example, patent document CN105401167A discloses a novel Co ₃ Mo ₃ C electrocatalyst, the preparation method of which comprises: dissolving ammonium molybdate tetrahydrate, cobalt acetate tetrahydrate and hexamethylenetetramine in ammonia water to obtain a magenta solution in Stir and evaporate at room temperature to obtain magenta slurry, vacuum dry to obtain powder, pass inert gas, slowly heat up to 750-800°C at a rate of 5°C/min, keep warm for 2-4h, and obtain Co ₃ Mo ₃ C after natural cooling electrocatalyst. Further, the Co ₃ Mo ₃ C electrocatalyst is supported on the substrate to prepare a catalytic hydrogen evolution electrode for the electrolysis of seawater to produce hydrogen, and the substrate is selected from foamed nickel, foamed iron-nickel, titanium mesh, nickel sheet, titanium sheet or conductive glass one or more of.

At present, in the research of using nano-carbon materials as electrocatalysts, most of the carbon materials used are in the form of powder macroscopically. When the powdery catalyst is mixed and coated on the conductive carrier through the polymer binder, the electron transport resistance between the catalyst and the electrode will increase, and at the same time, some active sites of the catalyst will be covered, reducing its catalytic activity. More importantly, these powder catalysts are easy to fall off from the support during the gas release process, resulting in unstable catalytic effect. Therefore, it is an urgent problem to study macroscopic three-dimensional structure catalysts with high activity, high stability and no need for binders for hydrogen production from water electrolysis.

Contents of the invention

The purpose of the present invention is to provide a catalytic material for hydrogen production by electrolysis of water with high activity and high stability and without binder, so as to realize the large-scale production of hydrogen production by electrolysis of water.

To achieve the above object, the present invention adopts the following technical solutions:

A method for preparing a flexible electrolytic water catalytic material, comprising the following steps:

(1) preparing cobalt-based Prussian blue analog nanoparticles;

(2) Dispersing cobalt-based Prussian blue analog nanoparticles in an organic solvent, then adding polyacrylonitrile to make a spinning solution, and electrospinning to obtain a Co-PBA/PAN composite nanofiber film;

(3) Pre-oxidize the Co-PBA/PAN composite nanofiber membrane, and then perform carbonization in an inert atmosphere to prepare the flexible electrolytic water catalytic material.

In step (1), cobalt acetate and potassium hexacyanocobaltate are used as raw materials to prepare cobalt-based Prussian blue analogue (Co-PBA) nanoparticles by chemical synthesis. Prussian blue and its analogs have good electrocatalytic properties, cobalt nanoparticles themselves also have good catalytic activity, and the Prussian blue framework structure provides a functional carbon source for the material.

The molar ratio of cobalt acetate to potassium hexacyanocobaltate is 0.15:0.08.

During the preparation process, the particle size of the nanoparticles is controlled by adding a surfactant or by adjusting the pH value of the reaction system.

The surfactant is polyvinylpyrrolidone or sodium dodecylbenzenesulfonate.

Specifically, the cobalt-based Prussian blue analog nanoparticles are prepared by chemical synthesis, and the preparation method includes: first dissolving cobalt acetate in water to prepare A solution, potassium hexacyanocobaltate, polyvinylpyrrolidone or dodecyl Sodium benzenesulfonate is dissolved in water to obtain solution B, then solution A is added to solution B while stirring, and the reaction generates cobalt-based Prussian blue analog (Co-PBA) nanoparticles.

Preferably, solution A is added to solution B at a rate of 2-3 mL/min, and the solution gradually turns from colorless to pink. After all the addition is complete, continue to stir for 10-15 minutes and let it stand for 3-4 hours.

Preferably, the mass ratio of cobalt acetate, potassium hexacyanocobaltate, polyvinylpyrrolidone or sodium dodecylbenzenesulfonate to water is 0.187-0.374:0.133-0.266:3-6:80.

The molecular weight of the polyvinylpyrrolidone is 58000.

More preferably, the mass ratio of cobalt acetate, potassium hexacyanocobaltate, PVP and deionized water is: 0.374:0.266:6:80.

In step (2), cobalt-based Prussian blue analogue (Co-PBA) nanoparticles are mixed with polyacrylonitrile (PAN), and electrospun to obtain a Co-PBA/PAN composite nanofibrous membrane, wherein the Co-PBA nanoparticles are uniformly dispersed in the fibrous membrane. After the carbonization treatment in step (3), the cobalt-based carbon nanofiber membrane in which cobalt carbide is uniformly dispersed in the porous carbon fibers is obtained, that is, the flexible electrolytic water catalytic material.

As a preference, in step (2), the organic solvent is N,N-dimethylformamide. First disperse cobalt-based Prussian blue analogue (Co-PBA) nanoparticles in N,N-dimethylformamide, add polyacrylonitrile while stirring, and continue stirring until polyacrylonitrile is completely dissolved to obtain a blue opaque viscous The thick solution is the spinning solution.

Preferably, the mass ratio of cobalt-based Prussian blue analog nanoparticles to polyacrylonitrile is 0.1-1.5:10, and the mass percentage of polyacrylonitrile in the spinning solution is 6-12%. Co-PBA nanoparticles play the main catalytic role. If the proportion is too small, the catalytic performance will be poor; if the proportion is too large, the carbon fiber will be brittle, the flexibility will be reduced, and the mechanical strength will be poor. More preferably, the mass ratio of cobalt-based Prussian blue analog nanoparticles to polyacrylonitrile is 1:10.

Preferably, the electrospinning conditions are as follows: the inner diameter of the metal needle is 0.6-0.7 mm, the advancing speed is 0.8-1.5 mL h ^-1 , the distance between the needle tip and the receiving plate is 15-18 cm, and the voltage is 25 ~30kV, the ambient temperature is 23~30°C, and the ambient humidity is 30~40%.

The spun film prepared by electrospinning was vacuum dried at 80°C.

The average diameter of the Co-PBA/PAN composite nanofiber is 200-400nm.

Preferably, in step (3), the pre-oxidation treatment condition is: treatment at 260-280° C. for 0.5-2 hours in an air atmosphere.

Preferably, in step (3), the carbonization treatment conditions are: heating up to 700-1100° C. at a rate of 5-10° C./min, and keeping the temperature for 1-6 hours.

More preferably, the carbonization treatment condition is to raise the temperature to 1000° C. at a rate of 5° C./min and keep the temperature for 3 hours. The research results show that the electrocatalytic performance of the prepared material is the best when the carbonization temperature is 1000°C and the time is 3 hours.

As a preference, in step (3), the inert atmosphere is nitrogen or argon, and the gas flow rate is 100 sccm.

The invention also provides a flexible electrolytic water catalytic material prepared by the preparation method. The average diameter of the cobalt-based carbon nanofiber is 100-300nm, and the cobalt carbide is uniformly dispersed in the porous carbon fiber, which has excellent catalytic performance and good structural stability.

The electrolytic water catalytic material provided by the present invention is a flexible self-supporting structure, which can be directly used as a catalytic electrode for electrolytic water, and can be loaded on a conductive carrier without a binder to realize efficient hydrogen and oxygen production by electrolyzing water, effectively avoiding powder Disadvantages of catalysts in electrocatalytic applications.

The present invention also provides the application of the flexible electrolytic water catalytic material in electrolyzing water to produce hydrogen and oxygen.

The application is as follows: the flexible electrolytic water catalytic material is used as a catalytic electrode, platinum is used as an auxiliary electrode, and Ag/AgCl is used as a reference electrode; the electrolytic solution is an alkaline or acidic aqueous solution.

Preferably, the electrolyte is 1M KOH aqueous solution.

The beneficial effect that the present invention possesses:

(1) The present invention prepares cobalt-based Prussian blue analog (Co-PBA) nanoparticles by chemical synthesis, and then mixes them with polyacrylonitrile (PAN) and utilizes electrospinning to make Co-PBA/PAN composite nanofiber membranes. The electrolytic water catalytic material with a self-supporting cobalt-based carbon nanocomposite fiber structure prepared by high-temperature carbonization can be directly used as an electrolytic water catalytic electrode. The manufacturing method is simple, green and safe, and can realize large-area continuous production.

(2) In the electrolytic water catalytic material prepared by the present invention, cobalt carbide is evenly dispersed in the porous carbon fiber, which increases the catalytic sites, while the porous carbon fibers provide the carrier of the catalytic sites and enhance the electrical conductivity, which improves the traditional powder catalytic materials The problems of easy falling off and loss are suitable for large-scale industrial electrolyzed water production, and show extremely broad application prospects in the field of electrolyzed water.

Description of drawings

Figure 1 is a scanning electron microscope image of cobalt-based carbon nanocomposite fibers, and (b) is an enlarged size view of (a).

Figure 2 is the X-ray powder diffraction spectrum of Co CNFs.

Figure 3 is the photo of the prepared Co-PB/PAN nanofiber membrane and carbonization treatment, wherein (a) is the Co-PB/PAN nanofiber membrane obtained by electrospinning, and (b) is the carbon nanofiber in the bending state. Photo, with good flexibility, (c) from left to right are the Co-PB/PAN nanofiber membrane, the pretreated Co-PB/PAN nanofiber membrane and the cobalt-based carbon nanocomposite fiber obtained after high-temperature carbonization.

Fig. 4 is the electrocatalytic hydrogen evolution and oxygen evolution performance tested in 1M KOH by carbon nanocomposite fibers doped with different proportions (0%, 3%, 5% and 10%) of cobalt-based Prussian blue nanoparticles, where (a ) is the electrocatalytic hydrogen evolution HER diagram, (b) is the electrocatalytic oxygen evolution OER diagram.

Figure 5 shows the electrocatalytic hydrogen evolution and oxygen evolution performance of cobalt-based carbon nanocomposite fibers as catalytic electrodes in 1M KOH and 0.5MH ₂ SO ₄ , where (a) is the electrocatalytic hydrogen evolution HER diagram, and (b) is the electrocatalytic hydrogen evolution HER diagram. Oxygen OER diagram.

Detailed ways

The present invention is specifically described and further illustrated below in conjunction with specific embodiments, the purpose of which is to better understand the technical connotation of the present invention, but the protection scope of the present invention is not limited to the following implementation scope.

The reagents used in the examples are analytical reagents, and the experimental water is secondary deionized water.

Example 1

1. Preparation of Co-PBA nanoparticles

The preparation of cobalt-like Prussian blue particles (Co-PBA) includes two steps of synthesis and purification.

Accurately weigh 0.15 mmol of cobalt acetate and dissolve in 40 ml of water to obtain A solution. At the same time, 0.08 mmol of potassium hexacyanocobaltate was accurately weighed and dissolved in 40 ml of water, and PVP was added while stirring to obtain solution B. Slowly add solution A to solution B while stirring (about 10 minutes after the addition), the solution gradually changes from colorless to pink, and continue stirring for 10 minutes after all the addition is completed. The above mixture was left to stand for 4 hours, immediately washed with water and ethanol by centrifugation for several times to remove residual impurities, and then freeze-dried for future use.

2. Preparation of Co-PB/PAN nanofiber membrane

Accurately weigh 0.584g of the above-mentioned nanoparticles and disperse them in 52mL DMF, add 5.84g of PAN (Co-PBA nanoparticles: PAN=10%) while stirring, and continue stirring for 12h. After the PAN is completely dissolved, a blue opaque viscous shape is obtained. The solution is the spinning solution.

Take 50ml of the above-mentioned spinning solution and put them into five 10ml syringes respectively, select metal needles with an inner diameter of 0.6mm, and advance at a speed of 1.0mL h ^-1 for the preparation of nanofibers. The distance between the needle tip and the receiving plate is 15cm, the voltage is 25.0kV, the ambient temperature is 23-30°C, and the ambient humidity is 30-40%. Then the prepared spun membrane was dried and stored in a vacuum oven at 80°C.

3. Preparation of Co-based carbon nanofiber membrane

The above-mentioned nanofiber membrane was cut into pieces, sandwiched between graphite sheets and placed in a corundum boat. First, it was pre-oxidized in air at 5°C/min to 280°C for 2 hours, and then heated in a nitrogen atmosphere tube furnace at the same rate. Rate heat treatment at 1000°C, heat preservation for 3 hours, and finally cooling to room temperature under the protection of nitrogen to obtain a flexible self-supporting cobalt-based carbon nanocomposite fiber structure electrolysis of water to produce hydrogen and oxygen electrocatalytic materials.

4. Co-based carbon nanofibers for water electrolysis

Directly use the self-supporting cobalt-based carbon nanocomposite fiber as the catalytic working electrode, platinum as the counter electrode, Ag/AgCl as the reference electrode, and 1M KOH solution as the electrolyte for three-electrode electrocatalytic testing.

In the cobalt-based carbon nanocomposite fibers prepared in this example (morphological structure as shown in Figures 1 and 2), one-dimensional Co nanoparticles are doped into the three-dimensional conductive network of the carbon skeleton, which promotes electron transfer and mass transfer, increasing At the same time, the porous carbon fiber provides the carrier of the catalytic sites and enhances the electrical conductivity. And the production method is simple, green and safe, the prepared fiber membrane is flexible and bendable (as shown in Figure 3(b)), and can realize large-area continuous production (as shown in Figure 3(a)), suitable for large Large-scale industrial electrolyzed water production has shown a very broad application prospect in the field of electrolyzed water.

Electrochemical test results show that: under alkaline conditions, the starting site of electrocatalytic hydrogen production (HER) is 70-100mV, and the potential is 290-300mV when the current density is 10mAcm ^-2 (as shown in Figure 4) ; The starting point of electrocatalytic oxygen evolution (OER) is 1.24-1.30V, and the potential is 1.52-1.60V when the current density is 10mAcm ^-2 .

Example 2

Referring to the method of Example 1, the proportion of Co-PB doped in the nanofiber was changed (the proportions of Co-PB and PAN were respectively 0%, 3% and 5%), and other conditions remained unchanged.

The experimental results show that doping the cobalt-based Prussian blue analog nanoparticles in the nanofibers promotes electron transfer and mass transfer, increases the catalytic sites, and is beneficial to improve the electrocatalytic performance. The experimental results are shown in Figure 4.

Example 3

Referring to the method of Example 1, the above-mentioned Co-based carbon nanocomposite fiber was used as the catalytic working electrode, platinum was used as the counter electrode, Ag/AgCl was used as the reference electrode, and 0.5M sulfuric acid solution was used as the electrolyte for three-electrode electrocatalytic testing.

The experimental results show that the catalyst has good electrocatalytic performance in electrolysis of water under both acidic and alkaline conditions, and the electrocatalytic hydrogen production performance under alkaline conditions is better than that under acidic conditions, and the electrocatalytic oxygen production performance under acidic conditions is better than that under acidic conditions. Better than under acidic conditions, the experimental results are shown in Figure 5.

Claims (10)

1. a kind of preparation method of flexibility electrolysis water catalysis material, which comprises the following steps:

(1) the Prussian blue similar object nanoparticle of cobalt-based is prepared；

(2) it disperses the Prussian blue similar object nanoparticle of cobalt-based in organic solvent, adds polyacrylonitrile and spinning solution is made, Co-PBA/PAN composite nano-fiber membrane is made in electrostatic spinning；

(3) pre-oxidation treatment is carried out to Co-PBA/PAN composite nano-fiber membrane, then carries out carbonization treatment in an inert atmosphere, made Obtain the flexible electrolysis water catalysis material.

2. preparation method as described in claim 1, which is characterized in that in step (1), it is general to prepare cobalt-based using chemical synthesis Shandong scholar's indigo plant analog nanoparticle, preparation method, comprising: first by cobalt acetate obtained solution A soluble in water, six cyano cobalt acid Potassium, polyvinylpyrrolidone or neopelex is soluble in water obtains B solution, then solution A is added while stirring Into B solution, reaction generates the Prussian blue similar object nanoparticle of cobalt-based.

3. preparation method as described in claim 1, which is characterized in that in step (2), the Prussian blue similar object nanoparticle of cobalt-based The mass ratio of son and polyacrylonitrile is 0.1~1.5:10, and the mass percent of polyacrylonitrile is 6~12% in spinning solution.

4. preparation method as described in claim 1, which is characterized in that the condition of the electrostatic spinning are as follows: metal needle Internal diameter is 0.6~0.7mm, and fltting speed is 0.8~1.5mL h^-1, the distance between needle point and receiver board are 15~18cm, electricity Pressure is 25~30kV, and environment temperature is 23~30 DEG C, and ambient humidity is 30~40%.

5. preparation method as described in claim 1, which is characterized in that in step (3), the condition of pre-oxidation treatment are as follows: air 260~280 DEG C of 0.5~2h of processing under atmosphere.

6. preparation method as described in claim 1, which is characterized in that in step (3), the condition of carbonization treatment are as follows: with 5~10 DEG C/min is warming up to 700~1100 DEG C, keep the temperature 1~6h.

7. preparation method as described in claim 1, which is characterized in that in step (3), the inert atmosphere is nitrogen or argon Gas, gas flow rate 100sccm.

8. a kind of flexibility electrolysis water catalysis material as made from claim 1-7 described in any item preparation methods.

9. application of the flexibility electrolysis water catalysis material as claimed in claim 8 in water electrolysis hydrogen production oxygen.

10. application as claimed in claim 9, which is characterized in that the flexible electrolysis water catalysis material as catalysis electrode, Platinum is auxiliary electrode, and Ag/AgCl is reference electrode；Electrolyte is alkalinity or acidic aqueous solution.