CN108232212B - Oxygen reduction catalyst for fuel cell fuel cell supported by hollow nano carbon spheres with nano Ag particles and preparation method and application thereof - Google Patents

Abstract

The invention discloses a preparation method of a hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst, which comprises the following steps: 1) preparing hollow carbon nanospheres; 2) dispersing the hollow carbon nanospheres into a dispersing agent, and dropwise adding oleic acid to combine carboxyl active groups on the surfaces of the hollow carbon nanospheres; 3) and (3) taking the hollow carbon nanospheres as a carrier, adding silver nitrate as a silver source, dropwise adding ethylene glycol, and reducing by using citric acid to obtain the hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst. According to the invention, silver nitrate is used as a silver source, hollow carbon nanospheres are used as a carrier, oleic acid is dripped to activate the surfaces of the carbon nanospheres, citric acid is used for reducing the silver nitrate, and ethylene glycol is dripped to refine silver particles, so that the preparation process is simple to operate, and the prepared product has uniform particles and high load.

Description

An oxygen reduction catalyst for a hollow nano carbon sphere supported nano Ag particle fuel cell and the same Its preparation method and application

technical field

The invention belongs to the technical field of fuel cell electrocatalysis, and in particular relates to an oxygen reduction catalyst for a hollow nano carbon ball supported nano Ag particle fuel cell and a preparation method and application thereof.

Background technique

With the increasing depletion of fossil energy and the pollution to the environment during use, we are required to develop clean and renewable energy as soon as possible. Fuel cell is a high-efficiency green and clean energy conversion system with great potential. It is the fourth type of power generation technology after thermal power, hydropower and nuclear power generation. It is a kind of fuel (hydrogen, natural gas, alcohol, etc.) The chemical energy of oxygen) reaction is directly converted into electrical energy through electrochemical reaction without combustion [Zhou Chonglin, Wei Xianquan, Jiang Ningning, et al. Application and Prospect of Fuel Cell, Lutianhua Technology, 2009, 4: 409-412]. Huang Youju et al have also done some in-depth research on fuel cell cathode catalysts [Huang Youju, Huang Danqing, Huang Hongliang, et al. Research Status of Fuel Cell Catalysts, Battery Industry, 2007, 01:57-60].

The cathodic oxygen reduction reaction (ORR) is an important factor limiting the performance of proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). At present, it is believed that ORR occurs mainly through two pathways, namely, the complete reduction of tetrahydrogen and four electrons to form water and the partial reduction of dihydrogen and two electrons to form hydrogen peroxide.

Nowadays, the widely used cathode catalyst for fuel cells is Pt/C catalyst, but due to the high cost of Pt electrode, low durability, lack of resources, and serious poisoning [Zhang, L.; Zhang, J.; Wilkinson, D.P.; Wang , H.J.PowerSources 2006, 156, 171.] restricts the large-scale application and commercialization of fuel cells. Therefore, there is an urgent need to develop inexpensive, durable, efficient and stable non-Pt-based cathode oxygen reduction catalysts.

Carbon materials are widely used as fuel cell catalyst supports due to their simple preparation, easy mass production, and good chemical properties and mechanical stability. Honda et al. prepared micron-sized carbon spheres from pitch for the first time [H Honda, H Kimura, Y Sanada, et al. Carbon, 1970, 8(2): 181～183], which have strong chemical and thermal stability, Due to the advantages of low density, controllable specific surface area, high compressive strength, and high chemical inertness, carbon nanospheres have broad application prospects in fuel cells, catalyst carriers, lithium-ion battery anode materials, and supercapacitor electrode materials. Du Jianping reviewed the application of nano-carbon particles in catalysts, [Du Jianping, Zhao Ruihua, Yu Feng, et al. Application and prospect of nano-carbon particles in catalysis[J].Materials Review, 2010,24(17):49- 52], Liu Yunfang has further research on the doping of carbon nanospheres, [Liu Yunfang, Chi Weidong, Liu Bo, et al. Preparation and magnetic properties of carbon nanospheres loaded with iron nanoparticles [J]. Beijing University of Chemical Technology Chinese Journal (Natural Science Edition), 2011, 38(2):58-62]. It shows that carbon nanospheres have made a lot of breakthroughs in the field of fuel cell catalysts.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a hollow nano carbon ball supported nano Ag particle fuel cell oxygen reduction catalyst and its preparation method and application. In the present invention, hollow nano carbon balls are used as carriers to provide higher specific surface area, and metallic silver particles are used as active center sites to achieve higher oxygen reduction catalytic activity. In the present invention, a series of treatments are used to increase the loading of silver particles on the hollow nano-carbon spheres to obtain a fuel cell oxygen reduction catalyst with the hollow nano-carbon spheres as carriers and the silver particles as active sites, showing the excellent oxygen reduction performance of the material. and its application in fuel cells.

The present invention is achieved through the following technical solutions, and the present invention provides a preparation method of an oxygen reduction catalyst for a hollow nano-carbon ball supported nano-Ag particle fuel cell, comprising the following steps:

S101: preparation of hollow carbon nanospheres;

Hollow micro-scale carbon spheres have the advantages of strong chemical and thermal stability, low density, controllable specific surface area, high compressive strength, and high chemical inertness. Therefore, the oxygen reduction catalyst prepared with hollow nano-carbon spheres as a carrier can be used in Fuel cells, catalyst carriers, anode materials for lithium ion batteries, electrode materials for supercapacitors, etc.

S102: Disperse the hollow carbon nanospheres into a dispersant, and drop oleic acid to bind the surface of the hollow carbon nanospheres with carboxyl active groups;

Oleic acid contains carboxyl groups and has high reactivity. The hollow carbon nanospheres can be functionalized by dripping oleic acid, so that the surface of the hollow carbon nanospheres can be combined with carboxyl active groups and increase the adsorption capacity of silver ions; In the prior art, the carrier is usually pretreated with acid or alkali, so that the active component and the carrier are better combined, and the original structure of the carrier will be destroyed in the process. The activity on the surface of the carbon spheres directly reduces the silver particles to the hollow nano-carbon spheres, which not only ensures the loading capacity, but also preserves the original structure of the carrier from being damaged; It shows good activity in oxygen reduction.

S103 : using hollow carbon nanospheres as a carrier, adding a silver nitrate solution as a silver source, adding ethylene glycol dropwise, reducing with a citric acid solution, and performing post-treatment after reduction reaction to obtain a final product.

Choose silver nitrate as the silver source, silver nitrate is easy to dissolve, easy to obtain, and has strong stability, and the nitrate can be removed by washing with water in the later stage; choose citric acid solution as the reducing agent, the reduction of sodium citrate solution is not strong so that the reduction process is very mild The particle size of the reduced silver particles is smaller; ethylene glycol is selected as a dispersant, and the effect of ethylene glycol on grain refinement is good, making the silver particles more dispersed and uniform.

Using silver nitrate as the silver source, nano-silver particles can be obtained under the reduction of citric acid solution. By adding active groups to adsorb silver ions on the nano-carbon spheres, and then reducing the silver ions, the nano-silver can be successfully reduced. Particles are loaded onto nanocarbon spheres. Silver itself has better catalytic oxygen reduction performance, and nano-sized silver particles have better performance, which is due to the more exposed nano-sized silver active sites, which enhances the catalytic performance. The oxygen reduction catalyst for fuel cell fuel cells supported by hollow carbon nanospheres with nano-Ag particles has certain stability and flexibility, so its nano-thickness at the macroscopic level is expected to be more widely used in fuel cells. By adding ethylene glycol as a dispersant, the silver particles are more dispersed and uniform, and the silver particles are refined.

Preferably, in S101, the preparation of the hollow carbon nanospheres is as follows: preparing a glucose solution, pouring the glucose solution into a reaction kettle, putting it into an oven for hydrothermal reaction, obtaining a reddish-brown product, centrifugal washing, drying, and obtaining a hollow carbon nanospheres.

Glucose solution is selected as the raw material for preparing hollow carbon nanospheres. Glucose solution is easy to obtain and can achieve the expected hollow spherical porous structure; the hollow spherical porous structure prepared with glucose solution as a raw material has good uniformity in particle size and dispersion; the hollow spherical porous structure As a carrier, hollow carbon nanospheres have higher specific surface area and larger loading capacity.

Preferably, the concentration of the glucose solution is 50-60 g/L; the hydrothermal reaction conditions are hydrothermal at 160-180° C. for 10-12 hours.

Under the condition of hydrothermal reaction at 160～180℃ for 10～12h, the synthesis of hollow carbon nanospheres can be ensured without the occurrence of agglomeration, and the yield of hollow carbon nanospheres can be improved.

As a preference, in order to ensure that the washing is clean and as much as possible the product settles down, the product is washed 6 times by centrifugation at 8000 r/min, 5-10 min each time, and dried in an oven at 60-80 °C for 12 h.

Preferably, in S102, anhydrous ethanol is selected as the dispersant, and the hollow carbon nanospheres are ultrasonically dispersed in anhydrous ethanol for 1 hour, and then dripped with acid, and then continue to be ultrasonicated for 30 minutes.

Anhydrous ethanol is selected as the dispersant. Anhydrous ethanol has the characteristics of good dispersibility, easy volatility and easy handling in the later stage; the hollow nano carbon spheres are ultrasonically dispersed in anhydrous ethanol for 1 hour. First, the carbon spheres are fully dispersed, and then the acid is added for 30 minutes. It can make oleic acid adhere to the surface of carbon spheres.

Preferably, in S103, ethylene glycol is added dropwise to the mixture of the hollow carbon nanospheres and the silver nitrate solution and then ultrasonicated for 30 minutes, then the citric acid solution is added dropwise, and the ultrasonication is continued for 5-10 minutes after the addition.

Ethylene glycol and citric acid are added dropwise separately, in order to fully disperse ethylene glycol before the reduction of silver ions; citric acid solution is added dropwise to prevent the reaction from being too fast and refine the grains; ultrasonic dispersion is used. Advantages: 1. Make all reactants and additives dispersed evenly 2. Give the system an energy to promote the formation of crystal nuclei.

Preferably, in S103, the molar ratio of the added silver nitrate solution and the citric acid solution is 1:1. The two react 1:1, making the reaction sufficient without wasting reagents.

Preferably, in S103, in order to make the reduction reaction more sufficient, the reduction time using the citric acid solution is 24h, and the reduction reaction has been completed when the reaction is 24h.

Preferably, in S103, the post-processing is to centrifuge the reduction reaction product at 8000 r/min, and continue to centrifuge and wash for 5 to 6 times to fully wash the impurity ions; dry at 60 to 80 °C for 12 hours to obtain the final product.

A hollow nano-carbon ball-loaded nano-Ag particle fuel cell oxygen reduction catalyst is prepared by using the preparation method of the hollow nano-carbon ball-loaded nano-Ag particle fuel cell oxygen reduction catalyst described in any one of the above. Taking the hollow carbon nanospheres as a carrier, adding oleic acid to increase its surface active groups, adsorbing more silver ions, and then reducing it with citric acid, the nanometer silver particles are loaded on the hollow nanocarbon spheres, and the hollow nanocarbon spheres are loaded. The nano-Ag particle fuel cell oxygen reduction catalyst has good oxygen reduction performance, high electrocatalytic efficiency and large specific surface area, and has potential industrial application prospects.

An application of the hollow nano-carbon ball-loaded nano-Ag particle fuel cell oxygen reduction catalyst, the above-mentioned hollow nano-carbon ball-loaded nano-Ag particle fuel cell oxygen reduction catalyst is used to catalyze the oxygen reduction reaction of the fuel cell. The hollow nano-carbon ball-loaded nano-Ag particle fuel cell oxygen reduction catalyst prepared by the invention has good oxygen reduction performance, high electrocatalytic efficiency and large specific surface area, and has broad application prospects in fuel cell oxygen reduction.

The beneficial effects of the present invention are:

1) The advantages of the preparation method adopted in the present invention: a. Wide source of raw materials, simple and controllable method, easy operation, simple equipment and less pollution; b. The prepared hollow nano-carbon ball supported nano-Ag particle fuel cell oxygen reduction The catalyst has a large specific surface area and high electrocatalytic efficiency.

2) The present invention successfully prepares an oxygen reduction catalyst for fuel cell fuel cells supported by hollow nano carbon spheres supported by nano Ag particles through a simple method, which shows excellent oxygen reduction catalytic performance by controlling the loading amount of nano silver particles. Because the raw materials used in the method are cheap and easy to obtain, the operation is simple and fast, the energy consumption is small, there is no special requirement for the equipment, and the additional environmental pollution is small, so that it has a good application prospect in the field of fuel cells. green synthesis method.

3) The oxygen reduction catalyst of the hollow nano carbon sphere supported by the nano-Ag particle fuel cell prepared by the present invention, especially after the carbon sphere is functionalized with oleic acid, the loading amount of silver particles is increased, so that it has a higher loading capacity in the electrochemical reaction. active.

Description of drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative efforts.

Figure 1 shows the XRD patterns of the prepared hollow carbon nanospheres (denoted as CNHS) and the hollow nanocarbon spheres supported nano Ag particles (denoted as Ag@CNHS) fuel cell oxygen reduction catalyst.

Figure 2 shows the SEM images and TEM images of the prepared hollow carbon nanospheres (denoted as CNHS) and the hollow nanocarbon spheres supported nano-Ag particles (denoted as Ag@CNHS) fuel cell oxygen reduction catalyst.

Figure 3 shows the cyclic voltammograms (CV curves) of Ag@CNHS fuel cell oxygen reduction catalysts at different scan rates (5, 10, 20, 50, 100 mV s ^-1 ) in 0.1 M KOH solution.

Figure 4 shows the cyclic voltammetry (CV curve) of CNHS at different scan rates (5, 10, 20, 50, 100 mV s ^-1 ) in 0.1 MKOH solution.

Figure 5 shows the spinning disk curves of the Ag@CNHS fuel cell oxygen reduction catalyst in oxygen-saturated 0.1 M KOH solution.

Figure 6 is the spinning disk curve of CNHS in oxygen-saturated 0.1 M KOH solution.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, 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 application belongs.

As introduced in the Background section, the widely used cathode catalyst for fuel cells is Pt/C catalyst. However, due to the high cost of Pt electrodes, low durability, lack of resources, and susceptibility to poisoning, the large-scale application and use of fuel cells are seriously restricted. commercial development. Therefore, there is an urgent need to develop inexpensive, durable, efficient and stable non-Pt-based cathode oxygen reduction catalysts.

Carbon materials are widely used as fuel cell catalyst supports due to their simple preparation, easy mass production, and good chemical properties and mechanical stability. Honda et al. prepared micron-scale carbon spheres from pitch for the first time, which has the advantages of strong chemical and thermal stability, low density, controllable specific surface area, high compressive strength, and high chemical inertness. Therefore, nano-carbon spheres are used in fuel cells. , catalyst carrier, lithium-ion battery anode materials, supercapacitor electrode materials and other aspects have a wide range of application prospects. Du Jianping reviewed the application of nano-carbon particles in catalysts, and Liu Yunfang conducted further research on nano-carbon sphere doping, indicating that nano-carbon spheres have made great breakthroughs in the field of fuel cell catalysts.

In one embodiment of the present invention, the preparation method of the hollow nano-carbon sphere-supported nano-Ag particle fuel cell oxygen reduction catalyst of the present invention comprises the following steps:

S101: preparation of hollow carbon nanospheres;

Hollow micro-scale carbon spheres have the advantages of strong chemical and thermal stability, low density, controllable specific surface area, high compressive strength, and high chemical inertness. Therefore, the oxygen reduction catalyst prepared with hollow nano-carbon spheres as a carrier can be used in Fuel cells, catalyst carriers, anode materials for lithium ion batteries, electrode materials for supercapacitors, etc.

In S101, the steps of preparing the hollow carbon nanospheres are as follows: preparing a glucose solution, pouring the glucose solution into a reaction kettle, and putting it into an oven for hydrothermal reaction, the concentration of the glucose solution is 50-60 g/L; The reaction conditions are hydrothermal at 160-180°C for 10-12h; after obtaining a reddish-brown product, centrifugal washing and drying to obtain hollow carbon nanospheres; in order to ensure that the washing is clean and the product settles down as much as possible, the product is subjected to 8000 r Centrifugal washing 6 times per min, 5-10 min each time, and drying in an oven at 60-80 °C for 12 h.

Glucose solution is selected as the raw material for preparing hollow carbon nanospheres. Glucose solution is easy to obtain and can achieve the expected hollow spherical porous structure; the hollow spherical porous structure prepared with glucose solution as a raw material has good uniformity in particle size and dispersion; the hollow spherical porous structure As a carrier, hollow carbon nanospheres have higher specific surface area and larger loading capacity.

Under the condition of hydrothermal reaction at 160～180℃ for 10～12h, the synthesis of hollow carbon nanospheres can be ensured without the occurrence of agglomeration, and the yield of hollow carbon nanospheres can be improved.

S102: Disperse the hollow carbon nanospheres into a dispersant, and drop oleic acid to bind the surface of the hollow carbon nanospheres with carboxyl active groups;

Oleic acid contains carboxyl groups and has high reactivity. The hollow carbon nanospheres can be functionalized by dripping oleic acid, so that the surface of the hollow carbon nanospheres can be combined with carboxyl active groups and increase the adsorption capacity of silver ions; In the prior art, the carrier is usually pretreated with acid or alkali, so that the active component and the carrier are better combined, and the original structure of the carrier will be destroyed in the process. The activity on the surface of the carbon spheres directly reduces the silver particles to the hollow nano-carbon spheres, which not only ensures the loading capacity, but also preserves the original structure of the carrier from being damaged; It shows good activity in oxygen reduction.

In S102, since anhydrous ethanol has the characteristics of good dispersibility, volatility, and easy handling in the later stage, anhydrous ethanol is selected as the dispersant, and the hollow carbon nanospheres are ultrasonically dispersed in anhydrous ethanol for 1 hour, and then add acid, and then continue to ultrasonic for 30min. The first sonication makes the carbon spheres fully dispersed, and the second sonication can make the oleic acid adhere to the surface of the carbon spheres.

S103 : using hollow carbon nanospheres as a carrier, adding a silver nitrate solution as a silver source, adding ethylene glycol dropwise, reducing with a citric acid solution, and performing post-treatment after reduction reaction to obtain a final product.

Choose silver nitrate as the silver source, silver nitrate is easy to dissolve, easy to obtain, and has strong stability, and the nitrate can be removed by washing with water in the later stage; choose citric acid solution as the reducing agent, the reduction of sodium citrate solution is not strong so that the reduction process is very mild The particle size of the reduced silver particles is smaller; ethylene glycol is selected as a dispersant, and the effect of ethylene glycol on grain refinement is good, making the silver particles more dispersed and uniform.

Using silver nitrate as the silver source, nano-silver particles can be obtained under the reduction of citric acid solution. By adding active groups to adsorb silver ions on the nano-carbon spheres, and then reducing the silver ions, the nano-silver can be successfully reduced. Particles are loaded onto nanocarbon spheres. Silver itself has better catalytic oxygen reduction performance, and nano-sized silver particles have better performance, which is due to the exposure of more nano-sized silver active sites, which enhances the catalytic performance. The oxygen reduction catalyst for fuel cell fuel cells supported by hollow carbon nanospheres with nano-Ag particles has certain stability and flexibility, so its nano-thickness at the macroscopic level is expected to be more widely used in fuel cells. By adding ethylene glycol as a dispersant, the silver particles are more dispersed and uniform, and the silver particles are refined.

In S103, in order to fully disperse ethylene glycol before the reduction of silver ions; ethylene glycol and citric acid were added dropwise separately, and ethylene glycol was added dropwise to the mixture of hollow nano carbon spheres and silver nitrate solution, and then sonicated for 30 min, and then sonicated for 30 min. Add the citric acid solution dropwise, and continue to sonicate for 5 to 10 minutes after the addition. The citric acid solution is added dropwise to prevent the reaction from being too fast and to refine the crystal grains; the advantages of using ultrasonic dispersion: 1. Make all reactants and additives dispersed evenly; 2. Give the system an energy to promote the formation of crystal nuclei.

The molar ratio of the added silver nitrate solution and the citric acid solution is 1:1. The two react 1:1, making the reaction sufficient without wasting reagents. In order to make the reduction reaction more sufficient, the reduction time using the citric acid solution is 24h, and the reduction reaction has been completed when the reaction is 24h. In order to fully wash the impurity ions, the post-treatment is to centrifuge the reduction reaction product at 8000 r/min, and continue to centrifuge and wash for 5 to 6 times; dry at 60 to 80 °C for 12 hours to obtain the final product.

In order to enable those skilled in the art to understand the technical solutions of the present application more clearly, the technical solutions of the present application will be described in detail below with reference to specific embodiments.

The test materials used in the examples of the present invention are all conventional test materials in the art, and can be purchased through commercial channels.

Example 1

Silver ions are reduced on carbon spheres by a citric acid reduction method to obtain a fuel cell oxygen reduction catalyst with silver particles as active sites and hollow nano carbon spheres as carriers.

Take 4.5g of glucose, dissolve it in 75mL of deionized water and stir evenly, put the solution in a 100mL reaction kettle, put it in an oven, and keep the water heat at 160-180°C for 10-12 hours. Then, washed with deionized water and absolute ethanol, washed 6 times by centrifugation at 8000 r/min, 5-10 min each time, and dried in an oven at 60-80 °C for 12 h to obtain hollow carbon nanospheres; the obtained carbon nanospheres were weighed Take 0.25 g, disperse it into 30 mL of absolute ethanol, ultrasonicate for 1 h and add 1 to 3 drops of oleic acid dropwise, and continue to ultrasonic for 30 min; obtain functionalized hollow carbon nanospheres; respectively weigh silver nitrate with a molar ratio of 1:1 ( 0.5g) and citric acid (0.6g is slightly excessive) to prepare a solution, first add the silver nitrate solution to the functionalized hollow carbon nanospheres, add 1 to 3 drops of ethylene glycol dropwise, sonicate for 30min, add the citric acid solution dropwise, After adding, continue to sonicate for 5-10min, stir the mixed liquid for 24h, then centrifuge at 8000r/min to obtain a precipitate, and continue to centrifuge and wash 5-6 times to obtain clean hollow nano-carbon balls loaded with nano-Ag particles, at 60-80 The final product was obtained by drying at °C for 12 h.

Fig. 1 is the X-ray diffraction pattern of the Ag@CNHS fuel cell oxygen reduction catalyst obtained in the present embodiment, and the X-ray diffraction pattern of the hollow carbon nanospheres. After analysis by Jade software, it can be obtained that the material loaded on the hollow carbon nanospheres is silver particles , and has a carbon diffraction peak at 23°.

2 is a scanning electron microscope image and a transmission electron microscope image of the Ag@CNHS fuel cell oxygen reduction catalyst and CNHS obtained in this example. The obtained CNHS has a spherical structure with a uniform particle size of 150-200 nm, and silver particles are attached to carbon A core-shell structure is formed on the surface of the sphere, and the average particle size of the silver particles is 5-6 nm, which is beneficial to the oxygen reduction reaction.

The obtained catalyst was tested for performance as follows:

Modification of Ag@CNHS fuel cell oxygen reduction catalyst onto electrodes. Before the test, the glassy carbon electrode (diameter 3mm) was processed by the following steps: firstly polished with 50nm Al ₂ O ₃ powder film, then washed with ethanol and ultrapure water respectively (in an ultrasonic instrument), and dried in air. The preparation of the working electrode is as follows: take 5 mg of catalyst and add 450 μL of ultrapure water, add 50 μL of Nafion solution with a mass fraction of 5%, ultrasonically disperse for 1 hour, and use a micropipette to take 5 μL of the above catalyst solution on the glassy carbon electrode, and in the air Dry in medium. The rotating disk electrode (5 mm in diameter) was treated in the same way, and then 10 μL was dropped on the electrode surface and dried in the air.

Figure 3 shows the cyclic voltammetry curves of the Ag@CNHS fuel cell oxygen reduction catalyst of the present embodiment in an oxygen-saturated 0.1 mol·L ^-1 KOH solution at different scan rates. During scanning, Ag@CNHS began to peak around -0.3V, the peak position was -0.3V to -0.5V, and the peak current density was -0.5mAcm ^-2 .

Figure 4 shows the cyclic voltammetry curves of the CNHS of the present example in an oxygen-saturated 0.1 mol·L ^-1 KOH solution at different scan rates. During scanning, CNHS began to peak around -0.3V, the peak position was -0.3V to -0.45V, and the peak current density was -0.25mAcm ^-2 .

Figure 5 shows the rotating disk curve of the Ag@CNHS fuel cell oxygen reduction catalyst of the present embodiment in an oxygen-saturated 0.1 mol·L ^-1 KOH solution. The current density increases with the increase of the rotational speed. It can be seen that the oxygen reduction process is as follows: Controlled by diffusion, the calculated numbers n of electrons transferred at −0.45, −0.5, −0.55, and −0.6 V for the catalyst Ag@CNHS are 3.71, 3.73, 3.74, and 3.77, respectively.

Fig. 6 is the rotating disk curve of CNHS of this embodiment in an oxygen-saturated 0.1 mol·L ^-1 KOH solution, and it is calculated that the number n of electrons transferred for CNHS at -0.45, -0.5, -0.55, -0.6V were 2.29, 2.32, 2.32, 2.35, respectively.

The specific conditions are as follows: the electrochemical properties were tested with a CHI 760d electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.), and the prepared catalysts were coated on glassy carbon electrodes as working electrodes, Hg/Hg ₂ Cl ₂ electrodes and Pt electrodes Used as reference electrode and auxiliary electrode, the cyclic voltammogram (CV diagram) was obtained by testing in 0.1M potassium hydroxide solution.

Of course, the above description is not limited to the above examples, and the undescribed technical features of the present invention can be realized by or using the existing technology, and will not be repeated here; the above embodiments and drawings are only used to illustrate the technical solutions of the present invention, not It is a limitation of the present invention. The present invention is described in detail with reference to the preferred embodiments. Those of ordinary skill in the art should understand that changes, modifications, The additions or substitutions do not depart from the spirit of the present invention, and should also belong to the protection scope of the claims of the present invention.

Claims (5)

1. a preparation method of a hollow nanometer carbon ball loaded nanometer Ag particle fuel cell oxygen reduction catalyst, is characterized in that: comprise the steps: S101: Preparation of hollow carbon nanospheres: using glucose solution as raw material to prepare hollow carbon nanospheres by hydrothermal reaction; the concentration of the glucose solution is 50-60 g/L; ~12h; S102: dispersing the hollow carbon nanospheres in a dispersant, dripping oil with acid, so that the surface of the hollow carbon nanospheres binds carboxyl active groups; S103: using the hollow carbon nanospheres as a carrier, adding ethylene glycol dropwise to the mixture of the hollow carbon nanospheres and the silver nitrate solution and then ultrasonicating for 30 minutes, the molar ratio of the added silver nitrate solution and the citric acid solution is 1:1; then Add the citric acid solution dropwise, continue to ultrasonic for 5-10 min after the addition, use the citric acid solution to reduce the time for 24 hours, and carry out post-treatment after the reduction reaction to obtain the final product. 2. the preparation method of a kind of hollow nano carbon sphere supporting nano Ag particle fuel cell oxygen reduction catalyst according to claim 1, it is characterized in that: in S102, dispersant selects dehydrated alcohol, and hollow nano carbon sphere is in dehydrated alcohol After 1 hour of medium ultrasonic dispersion, drop oleic acid, and then continue to ultrasonic for 30 min. 3. the preparation method of a kind of hollow nanometer carbon ball supporting nanometer Ag particle fuel cell oxygen reduction catalyst according to claim 1, it is characterized in that: in S103, after-treatment is to centrifugal precipitation of reduction reaction product at 8000r/min rotating speed , continue to centrifuge and wash for 5 to 6 times, and dry at 60 to 80 °C for 12 h to obtain the final product. 4. A hollow nano-carbon sphere supported nano-Ag particle fuel cell oxygen reduction catalyst, characterized in that: the preparation of the hollow nano-carbon sphere-supported nano-Ag particle fuel cell oxygen reduction catalyst as claimed in any one of claims 1 to 3 method prepared. 5. the application of a hollow nanometer carbon ball-loaded nano-Ag particle fuel cell oxygen reduction catalyst, characterized in that: the hollow nano-carbon ball-loaded nano-Ag particle fuel cell oxygen reduction catalyst as claimed in claim 4 is used for the catalytic fuel cell oxygen reduction catalyst. oxygen reduction reaction.

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