CN110010904B - A composite material with electrocatalytic oxygen reduction performance and its preparation method and use - Google Patents

Abstract

The invention discloses a composite material with electrocatalytic oxygen reduction performance, a preparation method and application thereof, and belongs to the technical field of electrocatalytic materials. In the composite material, the metal is uniformly attached between the BN sheets and on the surface of the sheet, and the CNTs play a role in fixing the metal and BN. The invention provides a composite material with electrocatalytic oxygen reduction performance, which has efficient electrocatalytic oxygen reduction performance and stable cycle performance. The raw material cost used in the preparation method of the present invention is relatively low, the overall reaction conditions are mild, the post-processing is simple, the energy consumption is low, and the cost is low.

Description

A composite material with electrocatalytic oxygen reduction performance and its preparation method and use

technical field

The invention belongs to the technical field of electrocatalytic materials, and in particular relates to a composite material with electrocatalytic oxygen reduction performance and a preparation method and application thereof.

Background technique

Energy plays a very important role in human life as the driving force for social progress and the basis of production activities. The development and utilization of energy has greatly promoted the development of the world economy and human society. With the increasing demand for energy in modern life, the energy crisis has become increasingly prominent, and environmental pollution has become increasingly serious. Compared with traditional energy sources, the obvious advantage of fuel cells is that they do not produce harmful gases in the whole process, which can alleviate the status quo of air pollution. It is a green and clean energy we have been looking for.

The cathode oxygen reduction reaction of fuel cells is an important factor restricting the development of fuel cells. The reversibility of the electrochemical reduction of oxygen is very low. Even on some commonly used electrocatalysts with high catalytic activity (such as Pt, Pd), the exchange current density of the oxygen reduction reaction is only 10 ^-9 to 10 ^-10 A/ cm ² , therefore, the oxygen reduction reaction is always accompanied by a high overpotential, resulting in a decrease in the working efficiency of the cell. It is a hot topic to improve the performance of fuel cells to study new cathode catalysts to reduce cathode overpotential and improve the reduction activity of fuel cell cathode catalysts. Most of the current high-efficiency catalysts for the oxygen reduction reaction are expensive rare metals, which limit their large-scale commercial applications. Therefore, the research and development of low-cost and efficient catalysts to replace precious metal catalysts is an urgent need to meet social development. In recent years, especially in the last two years, breakthroughs have been made in the research of non-precious metal catalysts, which are considered to be the hope for large-scale commercial application of fuel cells.

Currently, the main electrocatalyst for fuel cells is platinum, which is widely used due to its good oxygen reduction activity and durability in fuel cells. Reducibility, and platinum metal, as a precious metal, is precious and rare, and the utilization rate is extremely low, which makes the fuel cell cost high and largely hinders the promotion and application of fuel cells. With the continuous development of electricity production, more and more efforts have been made to introduce non-precious metals into the field of cathode catalysts for fuel cells. Therefore, many researchers are trying to find other metal catalysts to replace the use of Pt/C to solve this problem.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a composite material with electrocatalytic oxygen reduction performance and its preparation method and application, which overcomes the high cost of catalysts used in fuel cells in the prior art. , easy to be poisoned by CO, unstable electrocatalytic oxygen reduction performance, limited application and other defects.

In order to achieve the above object or other objects, the present invention is achieved through the following technical solutions.

A preparation method of a composite material with electrocatalytic oxygen reduction performance, comprising the following steps:

(1) adding CNT and BN to ethylene glycol, and ultrasonically dispersing;

(2) adding metal salt and urea to the reaction system obtained in step (1) under stirring, and continuing to stir;

(3) the reaction system in the step (2) is allowed to stand and then carry out a heating and refluxing reaction, and after the reaction is completed, post-processing is carried out to obtain a composite material;

Wherein, the metal salt is selected from any one or any two of FeCl ₃ ·6H ₂ O, CoCl ₂ ·6H ₂ O, and NiCl ₂ ·6H ₂ O.

Wherein, the BN is hexagonal boron nitride obtained by general commercial means, and BN has a sheet-like structure with good electrical insulation, thermal conductivity, chemical resistance and lubricity. The particle size of BN used in the present invention is 20-700 nm.

The CNTs are carbon nanotubes obtained by general commercial means. Preferably, the particle size of the CNTs is not less than 200 nm.

Further, the molar ratio of CNT, metal salt, and BN is 1:2:1.

When the metal salt is selected from any two of FeCl ₃ ·6H ₂ O, CoCl ₂ ·6H ₂ O, and NiCl ₂ ·6H ₂ O, the molar ratio of the two metal salts is 1:1.

That is, when the metal salt is a mixture of FeCl ₃ .6H ₂ O and CoCl ₂ .6H ₂ O, the molar ratio of CNT, FeCl ₃ .6H ₂ O, CoCl ₂ .6H ₂ O, and BN is 1:1:1: 1.

When the metal salt is a mixture of FeCl ₃ ·6H ₂ O and NiCl ₂ ·6H ₂ O, the molar ratio of CNT, FeCl ₃ ·6H ₂ O, NiCl ₂ ·6H ₂ O and BN is 1:1:1:1.

When the metal salt is a mixture of CoCl ₂ ·6H ₂ O and NiCl ₂ ·6H ₂ O, the molar ratio of CNT, CoCl ₂ ·6H ₂ O, NiCl ₂ ·6H ₂ O and BN is 1:1:1:1.

Further, the molar ratio of metal salt to urea is 1:(6-10).

Further, in the present invention, ethylene glycol is used as a solvent, and the added amount is excessive. Preferably, the amount of ethylene glycol required for 1 mol of CNT should not be less than 4L. More preferably, the molar volume ratio of CNT to ethylene glycol is 1 mol:10L.

Further, in step (1), the ultrasonic dispersion time is 30min-60min; the BN and CNT in the system are fully contacted.

Further, in step (2), stirring is continued for 10 to 20 minutes, so that each raw material is fully dissolved and uniformly mixed.

Further, in step (3), the reaction system is allowed to stand for 15 to 25 minutes, and then the heating and reflux reaction is performed, and the reaction time is 6 hours to 8 hours.

Further, the post-treatment in step (3) includes washing and drying.

Further, in step (3), after the reaction is completed, it is cooled to room temperature, and the reaction system is centrifuged and washed with distilled water and ethanol in turn. Preferably, distilled water and ethanol are used for centrifugal washing 3 to 5 times in sequence. Preferably, during centrifugal washing, the centrifugal speed is 8000-9000 r/min, and the centrifugal time is 5-10 min.

Preferably, during the drying process, a vacuum drying oven is used, the drying temperature is 90° C., the vacuum degree is 0.08 Mpa, and the drying time is 9-12 hours.

The present invention also provides a composite material with electrocatalytic oxygen reduction performance prepared by the above-mentioned preparation method.

In the composite material, the metal is uniformly attached between the BN sheets and on the surface of the sheet, and the CNTs play a role in fixing the metal and BN.

The third aspect of the present invention also provides a use of the composite material prepared by the above preparation method as a catalyst in a fuel cell.

In the present invention, the metal element is uniformly attached to the lamellar surface of BN (boron nitride) and between the lamellae, while CNT (carbon nanotube) fixes the metal and BN like a rope to form a particle size of 50-400 nm. spherical structure in between.

The hexagonal boron nitride used in the present invention has a layered structure similar to graphite, the addition of metal can be more uniformly attached to the surface of the boron nitride and between the sheets, and the addition of carbon nanotubes can be like a rope. The boron nitride is held together to form a spherical structure while improving the electrical conductivity of the composite.

In the present invention, the adsorption performance of BN is used to adsorb metal ions between and on the surface of the BN sheets, and ethylene glycol is used as a solvent and a reducing agent to reduce the metal ions into metal elements, so that the metal elements are attached to the BN sheets. Between the surface and the lamellae, the addition of CNTs can make CNTs like ropes to fix BN and metal elements, and at the same time increase the electrical conductivity of the composites.

In conclusion, the present invention provides a composite material with electrocatalytic oxygen reduction performance, which has high electrocatalytic oxygen reduction performance and stable cycle performance. The raw material cost used in the preparation method of the present invention is relatively low, the overall reaction conditions are mild, the post-processing is simple, the energy consumption is low, and the cost is low.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) pattern of the BN/Ni/CNT composite material prepared in Example 1;

Fig. 2 is the transmission electron microscope spectrum (TEM) of the BN/Ni/CNT composite material prepared in Example 1;

3 is the X-ray diffraction (XRD) pattern of the BN/Fe/CNT composite material prepared in Example 3;

Fig. 4 is the transmission electron microscope spectrum (TEM) of the BN/Fe/CNT composite material prepared in Example 3;

5 is the X-ray diffraction (XRD) pattern of the BN/Co/CNT composite material prepared in Example 5;

Fig. 6 is the transmission electron microscope spectrum (TEM) of the BN/Co/CNT composite material prepared in Example 5;

7 is the X-ray diffraction (XRD) pattern of the BN/FeCo/CNT composite material prepared in Example 6;

8 is the transmission electron microscope (TEM) of the BN/FeCo/CNT composite material prepared in Example 6;

9 is the X-ray diffraction (XRD) pattern of the BN/FeNi/CNT composite material prepared in Example 7;

10 is the transmission electron microscope (TEM) of the BN/FeNi/CNT composite material prepared in Example 7;

11 is the X-ray diffraction (XRD) pattern of the BN/CoNi/CNT composite material prepared in Example 8;

12 is the transmission electron microscope (TEM) of the BN/CoNi/CNT composite material prepared in Example 8;

Figure 13 is the cyclic voltammetry curve of Pt/C composite in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

14 is a cyclic voltammogram of the BN/Ni/CNT composite prepared in Example 1 in an oxygen-saturated 0.1M KOH solution, where the scan rate is 5mV s ⁻¹ ;

15 is a cyclic voltammetry diagram of the BN/Fe/CNT composite prepared in Example 3 in an oxygen-saturated 0.1M KOH solution, where the scan rate is 5mV s ⁻¹ ;

16 is a cyclic voltammetry diagram of the BN/Co/CNT composite prepared in Example 5 in an oxygen-saturated 0.1M KOH solution, where the scan rate is 5mV/s;

17 is a cyclic voltammetry diagram of the BN/FeCo/CNT composite prepared in Example 6 in an oxygen-saturated 0.1M KOH solution, wherein the scan rate is 5mV s ⁻¹ ;

18 is a cyclic voltammogram of the BN/FeNi/CNT composite prepared in Example 7 in an oxygen-saturated 0.1M KOH solution, where the scan rate is 5mV s ⁻¹ ;

19 is a cyclic voltammetry diagram of the BN/CoNi/CNT composite prepared in Example 8 in an oxygen-saturated 0.1M KOH solution, wherein the scan rate is 5mV s ⁻¹ ;

Figure 20 is the cyclic voltammetry curve of the material obtained in Comparative Example 1 in 0.1M KOH solution saturated with O ₂ , scan rate: 5mV s ^-1 ;

Figure 21 is the cyclic voltammetry curve of the material obtained in Comparative Example 2 in 0.1M KOH solution saturated with O ₂ , scan rate: 5mV s ^-1 ;

Figure 22 is the cyclic voltammetry curve of the material obtained in Comparative Example 3 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 23 is the cyclic voltammetry curve of the material obtained in Comparative Example 5 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 24 is the cyclic voltammetry curve of the material obtained in Comparative Example 6 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 25 is the cyclic voltammetry curve of the material obtained in Comparative Example 7 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 26 is the cyclic voltammetry curve of the material obtained in Comparative Example 9 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 27 is the cyclic voltammetry curve of the material obtained in Comparative Example 10 in 0.1M KOH solution saturated with O ₂ , scan rate: 5mV s ^-1 ;

Figure 28 is the cyclic voltammetry curve of the material obtained in Comparative Example 11 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 29 is the cyclic voltammetry curve of the material obtained in Comparative Example 13 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 30 is the cyclic voltammetry curve of the material obtained in Comparative Example 14 in 0.1M KOH solution saturated with O ₂ , scan rate: 5mV s ^-1 ;

Figure 31 is the cyclic voltammetry curve of the material obtained in Comparative Example 15 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 32 is the cyclic voltammetry curve of the material obtained in Comparative Example 17 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 33 is the cyclic voltammetry curve of the material obtained in Comparative Example 18 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 34 is the cyclic voltammetry curve of the material obtained in Comparative Example 19 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 35 is the cyclic voltammetry curve of the material obtained in Comparative Example 21 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

Figure 36 is the cyclic voltammetry curve of the material obtained in Comparative Example 22 in 0.1M KOH solution saturated with O ₂ , scan rate: 5mV s ^-1 ;

Figure 37 is the cyclic voltammetry curve of the material obtained in Comparative Example 23 in O ₂ saturated 0.1M KOH solution, scan rate: 5mV s ^-1 ;

38 is a time-current curve diagram of the BN/Ni/CNT composite material and the Pt/C composite material prepared in Example 1;

FIG. 39 is a time-current curve diagram of the BN/Fe/CNT composite material and the Pt/C composite material prepared in Example 3. FIG.

FIG. 40 is a time-current curve diagram of the BN/Co/CNT composite material and the Pt/C composite material prepared in Example 5. FIG.

FIG. 41 is a time-current curve diagram of the BN/FeCo/CNT composite material and the Pt/C composite material prepared in Example 6. FIG.

FIG. 42 is a time-current curve diagram of the BN/FeNi/CNT composite material and the Pt/C composite material prepared in Example 7. FIG.

FIG. 43 is a time-current curve diagram of the BN/CoNi/CNT composite material and the Pt/C composite material prepared in Example 8. FIG.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

It should be noted that the following embodiments and features in the embodiments may be combined with each other under the condition of no conflict. It should also be understood that the terms used in the embodiments of the present invention are for describing specific specific embodiments, rather than for limiting the protection scope of the present invention. In the following examples, the test methods without specific conditions are usually in accordance with conventional conditions or in accordance with the conditions suggested by various manufacturers.

When numerical ranges are given in the examples, it is to be understood that, unless otherwise indicated herein, both endpoints of each numerical range and any number between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention and those skilled in the art have mastered the prior art and the description of the present invention, and can also use the methods, equipment, and materials described in the embodiments of the present invention. Any methods, devices and materials similar or equivalent to those of the prior art can be used to implement the present invention.

The BN used in the embodiments of the present invention is hexagonal boron nitride obtained by common commercial means, and the particle size of the BN used in the present invention is 20-700 nm. CNTs are ordinary carbon nanotubes obtained by general commercial means, and preferably, the particle size of the CNTs is not less than 200 nm. .

Example 1

The utility model relates to a BN/Ni/CNT composite material. Metal Ni is uniformly attached between BN sheets and on the surface of the sheets, and CNTs play a role in fixing Ni and BN to form a spherical structure with a particle size of 100-300 nm. Among them, the molar ratio of BN, Ni and CNT is 1:2:1.

Its preparation method comprises the following steps:

(1) Add 0.005mol carbon nanotube (CNT) and 0.005mol boron nitride (BN) to 50 mL of ethylene glycol, and ultrasonically disperse for 30 min;

(2) under stirring, add 0.01mol NiCl ₂ ·6H ₂ O, 0.06mol urea, continue stirring for 10min, fully dissolve the solid and mix the solution uniformly;

(3) After standing for 20min, the reaction system was heated and refluxed for 6h. After the reaction was completed, it was cooled to room temperature, and the solids were centrifuged and washed with secondary distilled water and ethanol, respectively, and washed 3 times, wherein the rotating speed of the centrifuge was 8000r/min , the centrifugation time was 5 min. Pour the final obtained solid into a beaker, seal it with parafilm, poke several ventilation holes on the film, put it in a vacuum drying oven, keep the temperature of 90 ° C, the pressure of 0.08Mpa, dry for 9 hours, and the drying is over. After cooling to room temperature, grinding to obtain the target solid composite material BN/Ni/CNT.

The obtained BN/Ni/CNT composites were characterized by XRD and TEM, and the results are shown in Figure 1 and Figure 2.

It can be seen from Figure 1 that there are characteristic diffraction peaks of BN, Ni and CNT in the figure, and no other impurity peaks appear, which proves that the obtained product is a BN/Ni/CNT composite material.

In Fig. 2 and Fig. 2a, it can be seen that the obtained BN/Ni/CNT composite material has a spherical structure with a particle size of 100-300 nm. It can be seen from Figure 2b that the Ni element is uniformly attached to the BN sheet, and the CNTs fix the Ni-attached BN like a rope.

Example 2

In this example, the preparation method of the BN/Ni/CNT composite material is the same as that in Example 1, and the difference from Example 1 is that the step (3) is heated and refluxed for 8 hours. The structure of the obtained material is similar to that of Example 1.

Example 3

The utility model relates to a BN/Fe/CNT composite material. Metal Fe is uniformly attached between BN sheets and on the surface of the sheets, and CNTs fix Fe and BN to form a spherical structure with a particle size of 100-300 nm. Among them, the molar ratio of BN, Fe and CNT is 1:2:1. Its preparation method comprises the following steps:

(1) Add 0.005mol carbon nanotube (CNT) and 0.005mol boron nitride (BN) to 50 mL of ethylene glycol, and ultrasonically disperse for 30 min;

(2) adding 0.01mol FeCl ₃ ·6H ₂ O and 0.06mol urea under stirring, and continuing to stir for 10min to fully dissolve the solid and mix the solution uniformly;

(3) After standing for 20min, the reaction system was heated and refluxed for 6h. After the reaction was completed, it was cooled to room temperature, and the solids were centrifuged and washed with secondary distilled water and ethanol, respectively, and washed 3 times, wherein the rotating speed of the centrifuge was 8000r/min , the centrifugation time was 5 min. Pour the final obtained solid into a beaker, seal it with parafilm, poke several ventilation holes on the film, put it in a vacuum drying oven, keep the temperature of 90 ° C, the pressure of 0.08Mpa, dry for 9 hours, and the drying is over. After cooling to room temperature, grinding to obtain the target solid composite material BN/Fe/CNT.

The obtained BN/Fe/CNT composites were characterized by XRD and TEM, and the results are shown in Fig. 3 and Fig. 4 .

It can be seen from Figure 3 that there are characteristic diffraction peaks of BN, Fe and CNT in the figure, and no other impurity peaks appear, which proves that the obtained product is a BN/Fe/CNT composite material.

In Fig. 4 and Fig. 4a, it can be seen that the obtained BN/Fe/CNT composite material has a spherical structure with a particle size of 100-300 nm. It can be seen from Figure 4b that the Fe element is uniformly attached to the BN sheet, and the CNTs fix the Fe-attached BN like a rope.

Example 4

In this example, the preparation method of the BN/Fe/CNT composite material is the same as that in Example 3, and the difference from Example 3 is that the step (3) is heated and refluxed for 8 hours. The structure of the obtained material is similar to that of Example 3.

Example 5

A BN/Co/CNT composite material, the metallic Co is uniformly attached between the BN sheets and on the surface of the sheet, and the CNTs play a role in fixing Co and BN, forming a spherical structure with a particle size of 100-200 nm, and the particle size of the Co element In 1 ~ 5nm. Among them, the molar ratio of BN, Co and CNT is 1:2:1. Its preparation method comprises the following steps:

(1) Add 0.005mol carbon nanotube (CNT) and 0.005mol boron nitride (BN) to 50 mL of ethylene glycol, and ultrasonically disperse for 30 min;

(2) under stirring, add 0.01mol CoCl ₂ ·6H ₂ O, 0.06mol urea, continue stirring for 10min, fully dissolve the solid and mix the solution uniformly;

(3) After standing for 20min, the reaction system was heated and refluxed for 6h. After the reaction was completed, it was cooled to room temperature, and the solids were centrifuged and washed with secondary distilled water and ethanol, respectively, and washed 3 times, wherein the rotating speed of the centrifuge was 8000r/min , the centrifugation time was 5 min. Pour the final obtained solid into a beaker, seal it with parafilm, poke several ventilation holes on the film, put it in a vacuum drying oven, keep the temperature of 90 ° C, the pressure of 0.08Mpa, dry for 9 hours, and the drying is over. After cooling to room temperature and grinding, the target solid composite material BN/Co/CNT was obtained.

The obtained BN/Co/CNT composites were characterized by XRD and TEM, and the results are shown in Figure 5 and Figure 6 .

It can be seen from Figure 5 that there are characteristic diffraction peaks of BN, Co and CNT in the figure, and no other impurity peaks appear, which proves that the obtained product is a BN/Co/CNT composite material.

In Fig. 6 and Fig. 6a, it can be seen that the obtained BN/Co/CNT composite material has a spherical structure with a particle size of 200 nm. It can be seen from Figure 6b that the Co element is uniformly attached to the BN sheet, and the CNTs fix the Co-attached BN like a rope.

Example 6

The utility model relates to a BN/FeCo/CNT composite material. Metal Fe and Co are uniformly attached between BN sheets and on the surface of the sheets. CNTs play a role in fixing Fe, Co and BN to form a spherical structure with a particle size of 100-400 nm. Among them, the molar ratio of BN, Fe, Co and CNT is 1:1:1:1. Its preparation method comprises the following steps:

(1) Add 0.005mol carbon nanotube (CNT) and 0.005mol boron nitride (BN) to 50 mL of ethylene glycol, and ultrasonically disperse for 30 min;

(2) under stirring, add 0.005mol FeCl ₃ ·6H ₂ O, 0.005mol CoCl ₂ ·6H ₂ O, 0.06mol urea, continue stirring for 10min, fully dissolve the solid and mix the solution uniformly;

(3) After standing for 20min, the reaction system was heated and refluxed for 6h. After the reaction was completed, it was cooled to room temperature, and the solids were centrifuged and washed with secondary distilled water and ethanol, respectively, and washed 3 times, wherein the rotating speed of the centrifuge was 8000r/min , the centrifugation time was 5 min. Pour the final obtained solid into a beaker, seal it with parafilm, poke several ventilation holes on the film, put it in a vacuum drying oven, keep the temperature of 90 ° C, the pressure of 0.08Mpa, dry for 9 hours, and the drying is over. After cooling to room temperature, grinding to obtain the target solid composite material BN/FeCo/CNT.

The obtained BN/FeCo/CNT composite material was characterized by XRD and TEM, and the results are shown in Fig. 7 and Fig. 8 .

It can be seen from Figure 7 that there are characteristic diffraction peaks of BN, Fe, Co and CNT in the figure, and no other impurity peaks appear, which proves that the obtained product is a BN/FeCo/CNT composite material.

In Fig. 8 and Fig. 8a, it can be seen that the obtained BN/FeCo/CNT composite material has a spherical structure with a particle size of 100-400 nm. It can be seen from Figure 8b that Fe and Co elements are uniformly attached between the BN lamellae and on the surface of the lamellae, and the CNTs are like ropes to fix the BN with Fe and Co attached.

Example 7

The utility model relates to a BN/FeNi/CNT composite material. Metal Fe and Ni are uniformly attached between BN sheets and on the surface of the sheets, and CNTs fix Fe, Ni and BN to form a spherical structure with a particle size of 100-200 nm. Among them, the molar ratio of BN, Fe, Ni and CNT is 1:1:1:1. Its preparation method comprises the following steps:

(1) Add 0.005mol carbon nanotube (CNT) and 0.005mol boron nitride (BN) to 50 mL of ethylene glycol, and ultrasonically disperse for 30 min;

(2) continue to add 0.005mol FeCl ₃ ·6H ₂ O, 0.005mol NiCl ₂ ·6H ₂ O, 0.06mol urea under stirring, continue stirring for 10min, fully dissolve the solid and mix the solution uniformly;

(3) After standing for 20min, the reaction system was heated and refluxed for 6h. After the reaction was completed, it was cooled to room temperature, and the solids were centrifuged and washed with secondary distilled water and ethanol, respectively, and washed 3 times, wherein the rotating speed of the centrifuge was 8000r/min , the centrifugation time was 5 min. Pour the final obtained solid into a beaker, seal it with parafilm, poke several ventilation holes on the film, put it in a vacuum drying oven, keep the temperature of 90 ° C, the pressure of 0.08Mpa, dry for 9 hours, and the drying is over. After cooling to room temperature and grinding, the target solid composite material BN/FeNi/CNT was obtained.

The obtained BN/FeNi/CNT composite material was characterized by XRD and TEM, and the results are shown in Fig. 9 and Fig. 10 .

It can be seen from Figure 9 that there are characteristic diffraction peaks of BN, Fe, Ni and CNT in the figure, and no other impurity peaks appear, which proves that the obtained product is a BN/FeNi/CNT composite material.

In Fig. 10 and Fig. 10a, it can be seen that the obtained BN/FeNi/CNT composite material has a spherical structure with a particle size of 100-200 nm. It can be seen from Fig. 10b that Fe and Ni are uniformly attached between the lamellae of BN and on the surface of the lamellae, and the CNTs fix the BN attached with Fe and Ni like a rope.

Example 8

The utility model relates to a BN/CoNi/CNT composite material. Metal Co and Ni are uniformly attached between BN sheets and on the surface of the sheets, and CNTs fix Co, Ni and BN to form a spherical structure with a particle size of 50-100 nm. Among them, the molar ratio of BN, Co, Ni and CNT is 1:1:1:1. Its preparation method comprises the following steps:

(1) Add 0.005mol carbon nanotube (CNT) and 0.005mol boron nitride (BN) to 50 mL of ethylene glycol, and ultrasonically disperse for 30 min;

(2) continue to add 0.005mol CoCl ₂ ·6H ₂ O, 0.005mol NiCl ₂ ·6H ₂ O, 0.06mol urea under stirring, continue stirring for 10min, fully dissolve the solid and mix the solution uniformly;

(3) After standing for 20min, the reaction system was heated and refluxed for 6h. After the reaction was completed, it was cooled to room temperature, and the solids were centrifuged and washed with secondary distilled water and ethanol, respectively, and washed 3 times, wherein the rotating speed of the centrifuge was 8000r/min , the centrifugation time was 5 min. Pour the final obtained solid into a beaker, seal it with parafilm, poke several ventilation holes on the film, put it in a vacuum drying oven, keep the temperature of 90 ° C, the pressure of 0.08Mpa, dry for 9 hours, and the drying is over. After cooling to room temperature, grinding to obtain the target solid composite material BN/CoNi/CNT.

The obtained BN/CoNi/CNT composite material was characterized by XRD and TEM, and the results are shown in Fig. 11 and Fig. 12 .

It can be seen from Figure 11 that there are characteristic diffraction peaks of BN, Co, Ni and CNT in the figure, and no other impurity peaks appear, which proves that the obtained product is a BN/CoNi/CNT composite material.

In Fig. 12 and Fig. 12a, it can be seen that the obtained BN/CoNi/CNT composite material has a spherical structure with a particle size of 50-100 nm. It can be seen from Figure 12b that Co and Ni are uniformly attached between the lamellae of BN and on the surface of the lamellae, and CNTs fix the BN attached with Co and Ni like a rope.

Comparative Example 1

In this example, a preparation method similar to that of Example 1 was adopted, but different from Example 1, in this example, water was added as a solvent, ethylene glycol was used as a reducing agent, and the addition amounts of water and ethylene glycol were each 25ml.

Comparative Example 2

In this example, a preparation method similar to that of Example 1 is adopted, and what is different from Example 1 is that this example does not add urea.

Comparative Example 3

In this example, a preparation method similar to that of Example 1 is adopted, and what is different from Example 1 is that NiCl ₂ ·6H ₂ O and urea are replaced with NiSO ₄ ·6H ₂ O in this example.

Comparative Example 4

In this example, a preparation method similar to that of Example 1 is adopted, and the difference from Example 1 is that the amount of urea added in this example is 0.01 mol.

Comparative Example 5

In this example, a preparation method similar to that of Example 3 was adopted, but different from Example 3, in this example, water was added as a solvent, ethylene glycol was used as a reducing agent, and the addition amounts of water and ethylene glycol were each 25ml.

Comparative Example 6

This example adopts the preparation method similar to Example 3, and is different from Example 3 in that urea is not added in this example.

Comparative Example 7

In this example, a preparation method similar to that of Example 3 is adopted, and what is different from Example 3 is that FeCl ₃ ·6H ₂ O and urea are replaced by Fe ₂ (SO ₄ ) ₃ in this example.

Comparative Example 8

In this example, a preparation method similar to that of Example 3 is adopted, and the difference from Example 3 is that the amount of urea added in this example is 0.01 mol.

Comparative Example 9

In this example, a preparation method similar to that of Example 5 was adopted, but different from Example 5, in this example, water was added as a solvent, ethylene glycol was used as a reducing agent, and the addition amounts of water and ethylene glycol were each 25ml.

Comparative Example 10

This example adopts the preparation method similar to Example 5, and is different from Example 5 in that urea is not added in this example.

Comparative Example 11

In this example, a preparation method similar to that of Example 5 is adopted, and what is different from Example 5 is that CoCl ₂ ·6H ₂ O and urea are replaced with CoSO ₄ ·7H ₂ O in this example.

Comparative Example 12

In this example, the preparation method similar to Example 5 is adopted, and the difference from Example 5 is that the amount of urea added in this example is 0.02 mol.

Comparative Example 13

In this example, a preparation method similar to that of Example 6 was adopted, but different from Example 6, in this example, water was added as a solvent, ethylene glycol was used as a reducing agent, and the addition amounts of water and ethylene glycol were each 25ml.

Comparative Example 14

This example adopts the preparation method similar to Example 6, and is different from Example 6 in that urea is not added in this example.

Comparative Example 15

In this example, a preparation method similar to that of Example 6 is adopted, but different from Example 6, in this example, FeCl ₃ ·6H ₂ O and CoCl ₂ ·6H ₂ O are replaced by CoSO ₄ ·7H ₂ O and Fe ₂ (SO ₄ ) ₃ , and no urea was added.

Comparative Example 16

In this example, a preparation method similar to that of Example 6 is adopted, and the difference from Example 6 is that the amount of urea added in this example is 0.01 mol.

Comparative Example 17

In this example, a preparation method similar to Example 7 was adopted, but different from Example 7, in this example, water was added as a solvent, ethylene glycol was used as a reducing agent, and the addition amounts of water and ethylene glycol were each 25ml.

Comparative Example 18

This example adopts the preparation method similar to Example 7, and is different from Example 7 in that urea is not added in this example.

Comparative Example 19

In this example, the preparation method similar to Example 7 is adopted, but different from Example 7, in this example, FeCl ₃ ·6H ₂ O and NiCl ₂ ·6H ₂ O are replaced by NiSO ₄ ·6H ₂ O and Fe ₂ (SO ₄ ) ₃ , and no urea was added.

Comparative Example 20

In this example, a preparation method similar to that of Example 7 is adopted, and the difference from Example 7 is that the amount of urea added in this example is 0.01 mol.

Comparative Example 21

In this example, a preparation method similar to that of Example 8 was adopted, but different from Example 8, in this example, water was added as a solvent, ethylene glycol was used as a reducing agent, and the addition amounts of water and ethylene glycol were each 25ml.

Comparative Example 22

This example adopts the preparation method similar to Example 8, and is different from Example 8 in that urea is not added in this example.

Comparative Example 23

In this example, a preparation method similar to that of Example 8 is adopted, but different from Example 8, in this example, CoCl ₂ ·6H ₂ O and NiCl ₂ ·6H ₂ O are replaced by NiSO ₄ ·6H ₂ O and CoSO ₄ • _7H2O , and no urea added.

Comparative Example 24

In this example, a preparation method similar to that of Example 8 is adopted, and the difference from Example 8 is that the amount of urea added in this example is 0.01 mol.

Experimental example

Electrocatalytic oxygen reduction performance

1. The composite materials obtained in Example 1, Example 3, Example 5 to Example 8, and commercial Pt/C composite materials (purchased by general commercial means) were respectively tested for the corresponding electrochemical properties. The instrument used for chemical testing was the CHI 760E electrochemical workstation of Shanghai Chenhua Company. The electrochemical measurement used a three-electrode system, with platinum wire as the counter electrode, saturated calomel electrode (SCE) as the reference electrode, and glassy carbon electrode as the working electrode. The test was carried out at room temperature with Hg/Hg ₂ Cl ₂ as the reference electrode in 0.1 mol L ^-1 KOH solution, the scan rate was 5 mV s ^-1 , and the amount of catalyst on the glassy carbon working electrode was 0.073 mg.

Specifically, before the start of each oxygen reduction reaction, the electrolyte solution was saturated with N ₂ and scanned from 0.2 V to −0.8 V at a scan rate of 5 mVs ⁻¹ for 20 cycles to ensure the stability of the current-voltage signal. The electrolyte solution was passed into O ₂ for at least 30min and then the electrochemical performance was tested. Scan the working electrode for at least 20 cycles before data recording.

The test results are shown in Figure 13 to Figure 19, wherein Figure 13 is the cyclic voltammetry curve of commercial Pt/C composites in O ₂ saturated 0.1MKOH solution. It can be seen from the figures that Example 1 and Example 1 3. The composites obtained in Examples 5 to 8 have good electrocatalytic oxygen reduction performance in oxygen-saturated 0.1M KOH solution, and their initial oxygen reduction potentials are close to those of commercial Pt/C composites. Further comparison can be found that the electrocatalytic oxygen reduction performance of the BN/CoNi/CNT composite material of Example 8 is significantly improved than that of the composite materials in Examples 1 and 5, and the BN/FeNi/CNT composite material of Example 7 is significantly improved. Compared with the composite materials in Examples 1 and 3, the electrocatalytic oxygen reduction performance of the BN/FeCo/CNT composite material in Example 6 is significantly higher than that of the composite materials in Examples 3 and 5. The performances are obviously improved, both in the initial oxygen reduction potential and the peak current density; it can be proved that in the composite material of the present invention, when two metals are used, due to BN, CNT and the two metals The composite of simple substances has a good synergistic effect, and its electrocatalytic oxygen reduction performance is significantly improved, which is significantly higher than that of BN, CNT and any metal material.

2. The electrochemical performance test of Example 2, Example 4 and Comparative Example 1 to Comparative Example 24 is also carried out according to the above-mentioned operation. The results show that the test results of Example 2 and Example 4 are similar to those of Example 1, and have better performance. electrocatalytic oxygen reduction performance.

The test results of Comparative Examples 1 to 3, Comparative Examples 5-7, Comparative Examples 9-11, Comparative Examples 13-15, Comparative Examples 17-19, and Comparative Examples 21-23 are shown in Figure 20 to Figure 37, respectively. , all have no electrocatalytic oxygen reduction performance.

Although Comparative Examples 4, 8, 12, 16, 20, and 24 have certain electrocatalytic oxygen reduction performance, they are obviously weaker than Examples 1, 3, 5, 6, 7, and 8 and their performance is unstable.

performance stability

The composite materials obtained in Examples 1, 3, 5, 6, 7, and 8 and the existing conventional Pt/C composite materials (commercially available) were tested under constant voltage for their corresponding time-current curves respectively. picture.

The test results are shown in Figures 38 to 43. It can be seen from the figures that the current density of the composite material prepared in the embodiment of the present invention has almost no change after 18000 seconds of cycling; under the same conditions, the commercial Pt/C composite material has no change. There is a relatively obvious decrease in cycle stability, from which it can be seen that the stability of the composite material prepared in the embodiment of the present invention is better.

To sum up, the composite material provided by the present invention has high electrocatalytic oxygen reduction performance and high cycle stability, and is more valuable than commercial Pt/C composite materials.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (7)

1. A preparation method of a composite material with electrocatalytic oxygen reduction performance is characterized by comprising the following steps:

(1) adding CNT and BN into ethylene glycol, and performing ultrasonic dispersion treatment;

(2) adding metal salt and urea into the reaction system obtained in the step (1) under stirring, and continuing stirring;

(3) standing the reaction system in the step (2), then carrying out heating reflux reaction, carrying out post-treatment after the reaction is finished to obtain a composite material, and washing and drying the post-treatment;

wherein the molar ratio of the metal salt to the urea is 1: (6-10) the metal salt is FeCl₃·6H₂O、CoCl₂·6H₂O、NiCl₂·6H₂Any one or two of O;

the particle size of the BN is 20-700 nm; the particle size of the CNT is not less than 200 nm;

the prepared composite material comprises the following components: the metal is uniformly attached to the surface of the BN sheet layers and among the BN sheet layers, and the CNT plays a role in fixing the metal and the BN to form a spherical structure with the grain diameter of 50-400 nm.

2. The method according to claim 1, wherein the ultrasonic dispersion time in the step (1) is 30 to 60 min.

3. The method according to claim 1, wherein the stirring in the step (2) is continued for 10 to 20 min.

4. The preparation method according to claim 1, wherein the reaction system is allowed to stand for 15 to 25min in the step (3), and then is subjected to a heating reflux reaction for 6 to 8 hours.

5. A composite material having electrocatalytic oxygen reduction properties, obtainable by a process according to any one of claims 1 to 4.

6. The composite material of claim 5, wherein the metal in the composite material is uniformly attached between BN sheets and on the surfaces of the BN sheets, and the CNT plays a role in fixing the metal and the BN to form a spherical structure with the particle size of 50-400 nm.

7. Use of the composite material prepared by the preparation method according to any one of claims 1 to 4 as a catalyst in a fuel cell.

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