CN110010904B

CN110010904B - Composite material with electrocatalytic oxygen reduction performance and preparation method and application thereof

Info

Publication number: CN110010904B
Application number: CN201910160463.7A
Authority: CN
Inventors: 于洁玫; 黄太仲; 刘宗明; 姜占坤; 齐蕾
Original assignee: University of Jinan
Current assignee: University of Jinan
Priority date: 2019-03-04
Filing date: 2019-03-04
Publication date: 2022-04-19
Anticipated expiration: 2039-03-04
Also published as: CN110010904A

Abstract

The invention discloses a composite material with electrocatalytic oxygen reduction performance and a preparation method and application thereof, belonging to the technical field of electrocatalytic materials. The metal in the composite material is uniformly attached between BN sheet layers and on the surface of the BN sheet layers, and the CNT plays a role in fixing the metal and the BN. The composite material with the electrocatalytic oxygen reduction performance provided by the invention has high-efficiency electrocatalytic oxygen reduction performance and stable cycle performance. The preparation method provided by the invention has the advantages of relatively low cost of raw materials, mild overall reaction conditions, simple post-treatment, low energy consumption and relatively low cost.

Description

Composite material with electrocatalytic oxygen reduction performance and preparation method and application thereof

Technical Field

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

Background

Energy plays a very important role in human life as the basis of social advancing power and production activities, and the development and utilization of energy greatly promote the development of world economy and human society. With the increase of the demand of modern life on energy, the energy crisis is increasingly prominent and the environmental pollution is increasingly serious. Compared with the traditional energy, the fuel cell has the obvious advantages that no harmful gas is generated in the whole process, the current situation of air pollution can be relieved, and the fuel cell is a green clean energy which is always searched.

Cathode oxygen for fuel cellThe reduction reaction is an important factor that restricts the development of fuel cells. The reversibility of the electrochemical reduction reaction of oxygen is very low, and even on some common electrocatalysts (such as Pt and Pd) with higher catalytic activity, the exchange current density of the electrochemical reduction reaction of oxygen is only 10^-9～10^-10A/cm²Therefore, the oxygen reduction reaction is always accompanied by a high overpotential, resulting in a decrease in the operating efficiency of the battery. Research on the reduction of cathode overpotential by a novel cathode catalyst and the improvement of the reduction activity of the fuel cell cathode catalyst are hot topics for improving the performance of the fuel cell. Most of the current high-efficiency catalysts for oxygen reduction reaction are rare metals with high price, so that the large-scale commercial application of the catalysts is limited. Therefore, the research and development of a high-efficiency catalyst with low cost to replace a noble metal catalyst are urgent needs of meeting the social development. In recent years, and especially in the last two years, the research on non-noble metal catalysts has been progressing in a breakthrough, and such catalysts are considered to be promising for large-scale commercial application of fuel cells.

At present, the main electrocatalyst used for the fuel cell is platinum, which has good oxygen reduction activity and durability in the fuel cell and is widely used, but because the surface of Pt is easy to combine with CO, CO can cause Pt poisoning and lose its reducibility, and platinum metal as a noble metal is precious and rare, and the utilization rate is extremely low, so that the fuel cell has high cost, and the popularization and application of the fuel cell are greatly hindered. With the continued development of power generation, there has been an increasing effort to introduce non-noble metals into the cathode catalyst field of fuel cells. Therefore, many researchers are trying to find other metal catalysts to replace the use of Pt/C to solve this problem.

Disclosure of Invention

In view of the above disadvantages of the prior art, the present invention aims to provide a composite material with electrocatalytic oxygen reduction performance, a preparation method and a use thereof, which overcome the defects of the prior art, such as high cost of a catalyst for a fuel cell, susceptibility to CO poisoning, unstable electrocatalytic oxygen reduction performance, limited application, and the like.

In order to achieve the above object or other objects, the present invention is achieved by the following aspects.

A preparation method of a composite material with electrocatalytic oxygen reduction performance comprises 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, and carrying out post-treatment after the reaction is finished to obtain a composite material;

wherein the metal salt is selected from FeCl₃·6H₂O、CoCl₂·6H₂O、NiCl₂·6H₂Any one or two of O.

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

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

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

when the metal salt is selected from FeCl₃·6H₂O、CoCl₂·6H₂O、NiCl₂·6H₂And when any two of the O are adopted, the molar ratio of the two metal salts is 1: 1.

that is, when the metal salt is FeCl₃·6H₂O、CoCl₂·6H₂In the case of mixtures of O, CNT, FeCl₃·6H₂O、CoCl₂·6H₂O, BN is in a molar ratio of 1: 1: 1: 1.

when the metal salt is FeCl₃·6H₂O、NiCl₂·6H₂In the case of mixtures of O, CNT, FeCl₃·6H₂O、NiCl₂·6H₂O, BN is in a molar ratio of 1: 1: 1: 1.

when the metal salt is CoCl₂·6H₂O、NiCl₂·6H₂In the case of mixtures of O, CNT, CoCl₂·6H₂O、NiCl₂·6H₂O, BN is in a molar ratio of 1: 1: 1: 1.

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

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

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

Further, the stirring in the step (2) is continued for 10min to 20min, so that the raw materials are fully dissolved and uniformly mixed.

Further, after standing the reaction system for 15-25 min in the step (3), carrying out heating reflux reaction for 6-8 h.

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

Further, after the reaction in the step (3) is finished, cooling to room temperature, and sequentially carrying out centrifugal washing on the reaction system by using distilled water and ethanol. Preferably, the washing is performed by sequentially centrifuging and washing for 3-5 times by using distilled water and ethanol. Preferably, the centrifugal speed is 8000-9000 r/min and the centrifugal time is 5-10 min during centrifugal washing.

Preferably, the drying treatment is carried out by adopting a vacuum drying oven, the drying temperature is 90 ℃, the vacuum degree is 0.08Mpa, and the drying time is 9-12 h.

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

The metal in the composite material is uniformly attached between BN sheet layers and on the surface of the BN sheet layers, and the CNT plays a role in fixing the metal and the BN.

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

In the invention, the metal simple substance is uniformly attached to the surface of the sheet layer and among the sheet layers of BN (boron nitride), and the CNT (carbon nano tube) fixes the metal and the BN like a rope to form a spherical structure with the grain diameter of 50-400 nm.

The hexagonal boron nitride adopted by the invention has a layered structure similar to graphite, the metal can be uniformly attached to the surface of the boron nitride and between the sheets, and the carbon nano tube can fix the metal and the boron nitride together like a rope to form a spherical structure, so that the conductivity of the composite material is improved.

According to the conductive BN composite material, metal ions are adsorbed between and on the surfaces of the BN sheets by utilizing the adsorption performance of BN, the metal ions are reduced into metal simple substances by utilizing ethylene glycol as a solvent and a reducing agent, the metal simple substances are attached to the surfaces of the BN sheets and between the BN sheets, the BN and the metal simple substances can be fixed by the CNT like a rope by adding the CNT, and meanwhile, the conductive performance of the composite material is improved.

In conclusion, the invention provides a composite material with electrocatalytic oxygen reduction performance, which has high-efficiency electrocatalytic oxygen reduction performance and stable cycle performance. The preparation method provided by the invention has the advantages of relatively low cost of raw materials, mild overall reaction conditions, simple post-treatment, low energy consumption and relatively low cost.

Drawings

FIG. 1 is an X-ray diffraction (XRD) pattern of the BN/Ni/CNT composite prepared in example 1;

FIG. 2 is a Transmission Electron Micrograph (TEM) of the BN/Ni/CNT composite prepared in example 1;

FIG. 3 is an X-ray diffraction (XRD) pattern of the BN/Fe/CNT composite made in example 3;

FIG. 4 is a Transmission Electron Micrograph (TEM) of the BN/Fe/CNT composite prepared in example 3;

FIG. 5 is an X-ray diffraction (XRD) pattern of the BN/Co/CNT composite made in example 5;

FIG. 6 is a Transmission Electron Micrograph (TEM) of the BN/Co/CNT composite prepared in example 5;

FIG. 7 is an X-ray diffraction (XRD) pattern of the BN/FeCo/CNT composite prepared in example 6;

FIG. 8 is a Transmission Electron Micrograph (TEM) of the BN/FeCo/CNT composite prepared in example 6;

FIG. 9 is an X-ray diffraction (XRD) pattern of the BN/FeNi/CNT composite made in example 7;

FIG. 10 is a Transmission Electron Micrograph (TEM) of the BN/FeNi/CNT composite prepared in example 7;

FIG. 11 is an X-ray diffraction (XRD) pattern of the BN/CoNi/CNT composite made in example 8;

FIG. 12 is a Transmission Electron Micrograph (TEM) of the BN/CoNi/CNT composite prepared in example 8;

FIG. 13 shows Pt/C composite material in O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 14 is a plot of cyclic voltammetry for the BN/Ni/CNT composite made in example 1 in an oxygen saturated 0.1M KOH solution with a sweep rate of 5mV s^-1；

FIG. 15 is a plot of cyclic voltammetry for the BN/Fe/CNT composite made in example 3 in 0.1M KOH solution saturated with oxygen at a scan rate of 5mV s^-1；

FIG. 16 is a plot of cyclic voltammetry for the BN/Co/CNT composite made in example 5 in 0.1M KOH saturated with oxygen at a scan rate of 5 mV/s;

FIG. 17 is a plot of cyclic voltammetry for the BN/FeCo/CNT composite made in example 6 in 0.1M KOH solution saturated with oxygen at a scan rate of 5mV s^-1；

FIG. 18 is a plot of cyclic voltammetry for the BN/FeNi/CNT composite made in example 7 in 0.1M KOH saturated with oxygen at a scan rate of 5mV s^-1；

FIG. 19 is a plot of cyclic voltammetry for the BN/CoNi/CNT composite made in example 8 in 0.1M KOH saturated with oxygen at a scan rate of 5mV s^-1；

FIG. 20 shows the results of comparative example 1 when the material is O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 21 shows the results of comparative example 2 with O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 22 shows the results of comparative example 3 when the material is at O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 23 shows the results of comparative example 5 with a material in O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 24 shows the results of comparative example 6 in which₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 25 shows the results of comparative example 7 in O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 26 shows the results of comparative example 9 in which₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 27 shows the results of comparative example 10 when the material is O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 28 shows the results of comparative example 11 with a material at O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 29 shows the results of comparative example 13 with a material in O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 30 shows the results of comparative example 14 when the material is O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 31 shows the results of comparative example 15 in which₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 32 shows the results of comparative example 17 in which₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 33 shows the results of comparative example 18 with a material at O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 34 shows the results of comparative example 19 in which₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 35 shows the results of comparative example 21 in which₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 36 shows the results of comparative example 22 in which₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 37 shows the results of comparative example 23 with a material in O₂Cyclic voltammogram in saturated 0.1M KOH solution, sweep rate: 5mV s^-1；

FIG. 38 is a graph showing the time-current curves of the BN/Ni/CNT composite and the Pt/C composite obtained in example 1;

FIG. 39 is a graph showing the time-current curves of the BN/Fe/CNT composite and the Pt/C composite obtained in example 3.

FIG. 40 is a graph showing the time-current curves of the BN/Co/CNT composite and the Pt/C composite obtained in example 5.

FIG. 41 is a time-current graph of BN/FeCo/CNT composite and Pt/C composite prepared in example 6.

FIG. 42 is a time-current graph of the BN/FeNi/CNT composite and the Pt/C composite made in example 7.

FIG. 43 is a time-current graph of the BN/CoNi/CNT composite and the Pt/C composite made in example 8.

Detailed Description

The following description of the embodiments of the present invention is provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict. It is also to be understood that the terminology used in the examples is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. Test methods in which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under conditions recommended by the respective manufacturers.

When numerical ranges are given in the examples, it is understood that both endpoints of each of the numerical ranges and any value therebetween can be selected unless the invention otherwise indicated. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs and the description of the present invention, and any methods, apparatuses, and materials similar or equivalent to those described in the examples of the present invention may be used to practice the present invention.

The BN adopted in the embodiment of the invention is hexagonal boron nitride obtained by a common commercial means, and the particle size of the BN adopted in the invention is 20-700 nm. The CNT is a general carbon nanotube obtained by general commercial means, and preferably, the CNT has a particle size of not less than 200 nm. .

Example 1

A BN/Ni/CNT composite material, wherein metal Ni is uniformly attached between BN sheet layers and on the surface of the BN sheet layers, and CNT plays a role in fixing Ni and BN to form a spherical structure with the particle size of 100-300 nm. Wherein the molar ratio of BN, Ni and CNT is 1: 2: 1.

the preparation method comprises the following steps:

(1) adding 0.005mol of Carbon Nano Tube (CNT) and 0.005mol of Boron Nitride (BN) into 50mL of ethylene glycol, and performing ultrasonic dispersion for 30 min;

(2) adding 0.01mol NiCl under stirring₂·6H₂Continuously stirring O and 0.06mol of urea for 10min to fully dissolve the solid and uniformly mix the solution;

(3) standing for 20min, heating and refluxing the reaction system for 6h, cooling to room temperature after the reaction is finished, respectively washing the solid with redistilled water and ethanol in a centrifuging way, and respectively washing for 3 times, wherein the rotating speed of the centrifuge is 8000r/min, and the centrifuging time is 5 min. And pouring the finally obtained solid into a beaker, sealing the beaker by using a sealing film, punching a plurality of vent holes on the film, putting the beaker into a vacuum drying oven, keeping the temperature at 90 ℃ and the pressure at 0.08MPa, drying the beaker for 9 hours, cooling the beaker to room temperature after the drying is finished, and grinding the beaker to obtain the target solid composite material BN/Ni/CNT.

The obtained BN/Ni/CNT composite material is subjected to XRD and TEM characterization, and the results are shown in figures 1 and 2.

As can be seen from FIG. 1, characteristic diffraction peaks of BN, Ni and CNT are shown in the figure, and no other impurity peaks appear, thus proving that the obtained product is the BN/Ni/CNT composite material.

In FIG. 2, as can be seen from FIG. 2a, the obtained BN/Ni/CNT composite material has a spherical structure with a particle size of 100 to 300 nm. As can be seen from fig. 2b, the simple Ni is uniformly attached to the sheet layer of BN, and the CNT fixes the BN to which Ni is attached like a rope.

Example 2

The preparation method of the BN/Ni/CNT composite material in the embodiment is the same as that of the embodiment 1, and is different from the embodiment 1 in that the step (3) is heated and refluxed for 8 hours. The resulting material structure was similar to example 1.

Example 3

A BN/Fe/CNT composite material is provided, wherein metal Fe is uniformly attached between BN lamella and on the surface of the BN lamella, and CNT plays a role in fixing Fe and BN to form a spherical structure with the particle size of 100-300 nm. Wherein the molar ratio of BN, Fe and CNT is 1: 2: 1. the preparation method comprises the following steps:

(2) adding 0.01mol of FeCl while stirring₃·6H₂Continuously stirring O and 0.06mol of urea for 10min to fully dissolve the solid and uniformly mix the solution;

(3) standing for 20min, heating and refluxing the reaction system for 6h, cooling to room temperature after the reaction is finished, respectively washing the solid with redistilled water and ethanol in a centrifuging way, and respectively washing for 3 times, wherein the rotating speed of the centrifuge is 8000r/min, and the centrifuging time is 5 min. And pouring the finally obtained solid into a beaker, sealing the beaker by using a sealing film, punching a plurality of vent holes on the film, putting the beaker into a vacuum drying oven, keeping the temperature at 90 ℃ and the pressure at 0.08MPa, drying the beaker for 9 hours, cooling the beaker to room temperature after the drying is finished, and grinding the beaker to obtain the target solid composite material BN/Fe/CNT.

The obtained BN/Fe/CNT composite material is subjected to XRD and TEM characterization, and the results are shown in figures 3 and 4.

As can be seen from FIG. 3, characteristic diffraction peaks of BN, Fe and CNT are shown in the graph, and no other impurity peaks appear, which proves that the obtained product is the BN/Fe/CNT composite material.

In FIG. 4, as can be seen from FIG. 4a, the obtained BN/Fe/CNT composite material has a spherical structure with a particle size of 100 to 300 nm. As can be seen from fig. 4b, the Fe simple substance is uniformly attached to the sheet of BN, and the CNT fixes the BN to which Fe is attached like a rope.

Example 4

The preparation method of the BN/Fe/CNT composite material in the embodiment is the same as that of the embodiment 3, and is different from the embodiment 3 in that the step (3) is heated and refluxed for 8 hours. The resulting material structure was similar to example 3.

Example 5

A BN/Co/CNT composite material is characterized in that metal Co is uniformly attached between BN lamella and on the surface of the BN lamella, the CNT plays a role in fixing Co and BN to form a spherical structure with the particle size of 100-200 nm, and the particle size of a Co simple substance is 1-5 nm. Wherein the molar ratio of BN, Co and CNT is 1: 2: 1. the preparation method comprises the following steps:

(2) 0.01mol of CoCl was added with stirring₂·6H₂Continuously stirring O and 0.06mol of urea for 10min to fully dissolve the solid and uniformly mix the solution;

(3) standing for 20min, heating and refluxing the reaction system for 6h, cooling to room temperature after the reaction is finished, respectively washing the solid with redistilled water and ethanol in a centrifuging way, and respectively washing for 3 times, wherein the rotating speed of the centrifuge is 8000r/min, and the centrifuging time is 5 min. And pouring the finally obtained solid into a beaker, sealing the beaker by using a sealing film, punching a plurality of vent holes on the film, putting the beaker into a vacuum drying oven, keeping the temperature at 90 ℃ and the pressure at 0.08MPa, drying the beaker for 9 hours, cooling the beaker to room temperature after the drying is finished, and grinding the beaker to obtain the target solid composite material BN/Co/CNT.

The obtained BN/Co/CNT composite material is subjected to XRD and TEM characterization, and the results are shown in FIGS. 5 and 6.

As can be seen from FIG. 5, characteristic diffraction peaks of BN, Co and CNT are shown in the graph, and no other impurity peaks appear, thus proving that the obtained product is the BN/Co/CNT composite material.

In FIG. 6, as can be seen from FIG. 6a, the resulting BN/Co/CNT composite material has a spherical structure with a particle size of 200 nm. As can be seen in fig. 6b, the simple substance Co is uniformly attached to the sheet of BN, and the CNT fixes the BN to which Co is attached like a rope.

Example 6

A BN/FeCo/CNT composite material is characterized in that metal Fe and metal Co are uniformly attached between BN lamella and on the surface of the BN lamella, and the metal Fe, the metal Co and the metal BN are fixed by the metal CNT to form a spherical structure with the particle size of 100-400 nm. Wherein the molar ratio of BN, Fe, Co to CNT is 1: 1: 1: 1. the preparation method comprises the following steps:

(2) adding 0.005mol FeCl under stirring₃·6H₂O、0.005mol CoCl₂·6H₂Continuously stirring O and 0.06mol of urea for 10min to fully dissolve the solid and uniformly mix the solution;

(3) standing for 20min, heating and refluxing the reaction system for 6h, cooling to room temperature after the reaction is finished, respectively washing the solid with redistilled water and ethanol in a centrifuging way, and respectively washing for 3 times, wherein the rotating speed of the centrifuge is 8000r/min, and the centrifuging time is 5 min. And pouring the finally obtained solid into a beaker, sealing the beaker by using a sealing film, punching a plurality of vent holes on the film, putting the beaker into a vacuum drying oven, keeping the temperature at 90 ℃ and the pressure at 0.08MPa, drying the beaker for 9 hours, cooling the beaker to room temperature after the drying is finished, and grinding the beaker 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.

As can be seen from FIG. 7, characteristic diffraction peaks of BN, Fe, Co and CNT are all shown in the graph, and no other impurity peaks appear, thus proving that the obtained product is the BN/FeCo/CNT composite material.

In FIG. 8, as can be seen from FIG. 8a, the obtained BN/FeCo/CNT composite material has a spherical structure with a particle size of 100 to 400 nm. As shown in fig. 8b, Fe and Co are uniformly adhered to the inter-lamellar and surface of the BN lamellae, and the CNT fixes the BN to which Fe and Co are adhered like a rope.

Example 7

A BN/FeNi/CNT composite material is characterized in that metal Fe and Ni are uniformly attached between BN sheet layers and on the surfaces of the BN sheet layers, and the CNT plays a role in fixing Fe, Ni and BN to form a spherical structure with the particle size of 100-200 nm. Wherein the molar ratio of BN, Fe, Ni to CNT is 1: 1: 1: 1. the preparation method comprises the following steps:

(2) continuously adding 0.005mol of FeCl while stirring₃·6H₂O、0.005mol NiCl₂·6H₂Continuously stirring O and 0.06mol of urea for 10min to fully dissolve the solid and uniformly mix the solution;

(3) standing for 20min, heating and refluxing the reaction system for 6h, cooling to room temperature after the reaction is finished, respectively washing the solid with redistilled water and ethanol in a centrifuging way, and respectively washing for 3 times, wherein the rotating speed of the centrifuge is 8000r/min, and the centrifuging time is 5 min. And pouring the finally obtained solid into a beaker, sealing the beaker by using a sealing film, punching a plurality of vent holes on the film, putting the beaker into a vacuum drying oven, keeping the temperature at 90 ℃ and the pressure at 0.08MPa, drying the beaker for 9 hours, cooling the beaker to room temperature after the drying is finished, and grinding the beaker to obtain the target solid composite material BN/FeNi/CNT.

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

As can be seen from FIG. 9, the characteristic diffraction peaks of BN, Fe, Ni and CNT are all shown in the figure, and no other impurity peaks appear, thus proving that the obtained product is the BN/FeNi/CNT composite material.

In FIG. 10, as can be seen from FIG. 10a, the obtained BN/FeNi/CNT composite material has a spherical structure with a particle size of 100 to 200 nm. As can be seen from fig. 10b, Fe and Ni are uniformly adhered to the inter-lamellar and surface of the BN lamellae, and the CNT fixes the BN with Fe and Ni adhered thereto like a rope.

Example 8

A BN/CoNi/CNT composite material is characterized in that metal Co and metal Ni are uniformly attached between BN sheet layers and on the surfaces of the BN sheet layers, and the metal Co and the metal Ni are fixed by the metal CNT to form a spherical structure with the particle size of 50-100 nm. Wherein the molar ratio of BN, Co, Ni to CNT is 1: 1: 1: 1. the preparation method comprises the following steps:

(2) 0.005mol of CoCl was added with stirring₂·6H₂O、0.005mol NiCl₂·6H₂Continuously stirring O and 0.06mol of urea for 10min to fully dissolve the solid and uniformly mix the solution;

(3) standing for 20min, heating and refluxing the reaction system for 6h, cooling to room temperature after the reaction is finished, respectively washing the solid with redistilled water and ethanol in a centrifuging way, and respectively washing for 3 times, wherein the rotating speed of the centrifuge is 8000r/min, and the centrifuging time is 5 min. And pouring the finally obtained solid into a beaker, sealing the beaker by using a sealing film, punching a plurality of vent holes on the film, putting the beaker into a vacuum drying oven, keeping the temperature at 90 ℃ and the pressure at 0.08MPa, drying the beaker for 9 hours, cooling the beaker to room temperature after the drying is finished, and grinding the beaker 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 12.

As can be seen from FIG. 11, the characteristic diffraction peaks of BN, Co, Ni and CNT are all shown in the figure, and no other impurity peaks appear, thus proving that the obtained product is the BN/CoNi/CNT composite material.

In FIG. 12, as can be seen from FIG. 12a, the obtained BN/CoNi/CNT composite material has a spherical structure with a particle size of 50 to 100 nm. As can be seen from fig. 12b, the simple substances of Co and Ni are uniformly adhered between and on the surfaces of the lamellae of BN, and the CNT fixes the BN adhered with Co and Ni like a rope.

Comparative example 1

In this example, a similar production method to that of example 1 was employed, and in this example, water was added as a solvent, ethylene glycol was added as a reducing agent, and the amounts of water and ethylene glycol added were each 25ml, unlike example 1.

Comparative example 2

In this example, a similar preparation as in example 1 was used, but in contrast to example 1, no urea was added.

Comparative example 3

In this example, a similar preparation method to that of example 1 was adopted, and unlike example 1, NiCl was added to the mixture in this example₂·6H₂Replacement of O and Urea by NiSO₄·6H₂O。

Comparative example 4

In this example, a similar production method to that of example 1 was used, and unlike example 1, the amount of urea added in this example was 0.01 mol.

Comparative example 5

In this example, a similar production method to that of example 3 was employed, and in this example, water was added as a solvent, ethylene glycol was added as a reducing agent, and the amounts of water and ethylene glycol added were each 25ml, unlike example 3.

Comparative example 6

This example uses a similar preparation as example 3, but differs from example 3 in that no urea is added.

Comparative example 7

In this example, a similar preparation method to that of example 3 was adopted, and unlike example 3, FeCl was added to the solution₃·6H₂Replacement of O and Urea by Fe₂(SO₄)₃。

Comparative example 8

In this example, a similar production method to that of example 3 was used, and unlike example 3, the amount of urea added in this example was 0.01 mol.

Comparative example 9

In this example, a similar production method to that of example 5 was employed, and in this example, water was added as a solvent, ethylene glycol was added as a reducing agent, and the amounts of water and ethylene glycol added were each 25ml, unlike example 5.

Comparative example 10

This example uses a similar preparation as example 5, but differs from example 5 in that no urea is added.

Comparative example 11

A similar preparation method to that of example 5 was employed in this example, and unlike example 5, CoCl was added to this example₂·6H₂Replacement of O and Urea by CoSO₄·7H₂O。

Comparative example 12

In this example, a similar production method to that of example 5 was used, and unlike example 5, the amount of urea added in this example was 0.02 mol.

Comparative example 13

In this example, a similar production method to that of example 6 was employed, and in this example, water was added as a solvent, ethylene glycol was added as a reducing agent, and the amounts of water and ethylene glycol added were each 25ml, unlike example 6.

Comparative example 14

This example uses a similar preparation as example 6, but differs from example 6 in that no urea is added.

Comparative example 15

In this example, a similar preparation method to that of example 6 was adopted, and unlike example 6, FeCl was added to the solution₃·6H₂O and CoCl₂·6H₂Changing O to CoSO₄·7H₂O and Fe₂(SO₄)₃And no urea is added.

Comparative example 16

In this example, a similar production method to that of example 6 was used, and unlike example 6, the amount of urea added in this example was 0.01 mol.

Comparative example 17

In this example, a similar production method to that of example 7 was employed, and in this example, water was added as a solvent, ethylene glycol was added as a reducing agent, and the amounts of water and ethylene glycol added were each 25ml, unlike example 7.

Comparative example 18

This example uses a similar procedure to that used in example 7, except that in example 7, no urea was added.

Comparative example 19

A similar preparation method to that of example 7 was adopted in this example, and unlike example 7, FeCl was added to the solution₃·6H₂O and NiCl₂·6H₂Changing O into NiSO₄·6H₂O and Fe₂(SO₄)₃And no urea is added.

Comparative example 20

In this example, a similar production method to that of example 7 was used, and unlike example 7, the amount of urea added in this example was 0.01 mol.

Comparative example 21

In this example, a similar production method to that of example 8 was employed, and in this example, water was added as a solvent, ethylene glycol was added as a reducing agent, and the amounts of water and ethylene glycol added were each 25ml, unlike example 8.

Comparative example 22

This example uses a similar preparation as example 8, but differs from example 8 in that no urea is added.

Comparative example 23

In this example, a similar production method to that of example 8 was used, and unlike example 8, CoCl was added to the reaction mixture₂·6H₂O and NiCl₂·6H₂Changing O into NiSO₄·6H₂O and CoSO₄·7H₂O, and no urea is added.

Comparative example 24

In this example, a similar production method to that of example 8 was used, and unlike example 8, the amount of urea added in this example was 0.01 mol.

Examples of the experiments

Electrocatalytic oxygen reduction performance

1. The composite materials obtained in example 1, example 3, example 5 to example 8, and the commercial Pt/C composite material (generally commercially available) were respectively subjected to corresponding electrochemical performance tests using an apparatus of electrochemical workstation type CHI 760E of shanghai chenhua corporation. The electrochemical test adopts a three-electrode system, takes a platinum wire as a counter electrode, takes a Saturated Calomel Electrode (SCE) as a reference electrode and takes a glassy carbon electrode as a working electrode. When tested, the concentration is 0.1mol L^-1In KOH solution in Hg/Hg₂Cl₂As a reference electrode, at room temperature, at a scan rate of 5mV s^-1The amount of catalyst on the glassy carbon working electrode was 0.073 mg.

Specifically, the electrolyte solution was treated with N before each oxygen reduction reaction was started₂Saturation from 0.2V to-0.8V at 5mV s^-1The scan rate of (2) is swept for 20 cycles to ensure stability of the current-voltage signal. The electrolyte solution is pumped with O₂And performing the electrochemical performance test at least for 30 min. The working electrode was scanned at least 20 cycles before data was recorded.

The test results are shown in FIGS. 13-19, where FIG. 13 shows a commercial Pt/C composite in O₂Cyclic voltammetry curves in saturated 0.1M KOH solutions, it can be seen from the figure that the composites obtained in examples 1, 3, 5 to 8 have good electrocatalytic oxygen reduction performance in oxygen-saturated 0.1M KOH solutions, and the initial oxygen reduction potential is close to that of commercial Pt/C composites. Further comparison shows that the electrocatalytic oxygen reduction performance of the BN/CoNi/CNT composite material in example 8 is obviously improved compared with the performance of the composite materials in examples 1 and 5, the electrocatalytic oxygen reduction performance of the BN/FeNi/CNT composite material in example 7 is obviously improved compared with the performance of the composite materials in examples 1 and 3, and the electrocatalytic oxygen reduction performance of the BN/FeCo/CNT composite material in example 6 is obviously improved compared with the performance of the composite materials in examples 3 and 5, which are both shown in that the initial oxygen reduction potential and the peak current density are both obviously improved; therefore, the composite material of the invention has better synergistic effect due to the composition of BN, CNT and two metal simple substances when two metals are adopted,the electrocatalytic oxygen reduction performance is obviously improved and is obviously higher than the composition of BN, CNT and any metal material.

2. The electrochemical performance tests of the example 2, the example 4 and the comparative examples 1 to 24 are carried out according to the same operation, and the results show that the test results of the example 2 and the example 4 are similar to the test results of the example 1 and have better electrocatalytic oxygen reduction performance.

And the test results of comparative examples 1 to 3, 5 to 7, 9 to 11, 13 to 15, 17 to 19, and 21 to 23 are shown in fig. 20 to 37, respectively, and do not have electrocatalytic oxygen reduction performance.

Comparative examples 4, 8, 12, 16, 20, 24, although having some electrocatalytic oxygen reduction performance, were significantly weaker than examples 1, 3, 5, 6, 7, 8 and the performance was unstable.

Stability of performance

The composites obtained in examples 1, 3, 5, 6, 7, 8 were tested at constant voltage with respect to their corresponding time-current profiles, respectively, in comparison with the existing conventional Pt/C composite (generally commercially available).

The test results are shown in fig. 38 to 43, and it can be seen from the graphs that the current density of the composite material prepared by the embodiment of the invention hardly changes after 18000 seconds of circulation; under the same conditions, the reduction of the cycling stability of the commercial Pt/C composite material is obvious, so that the composite material prepared by the embodiment of the invention has better stability.

In conclusion, the composite material provided by the invention has higher electrocatalytic oxygen reduction performance and higher cycle stability, and has higher utilization value compared with a commercial Pt/C composite material.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

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

(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.