CN108232212B - Hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst and preparation method and application thereof - Google Patents

Hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst and preparation method and application thereof Download PDF

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CN108232212B
CN108232212B CN201810249976.0A CN201810249976A CN108232212B CN 108232212 B CN108232212 B CN 108232212B CN 201810249976 A CN201810249976 A CN 201810249976A CN 108232212 B CN108232212 B CN 108232212B
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hollow carbon
fuel cell
oxygen reduction
reduction catalyst
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梁栋
黄太仲
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University of Jinan
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9075—Catalytic material supported on carriers, e.g. powder carriers
    • H01M4/9083—Catalytic material supported on carriers, e.g. powder carriers on carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8825—Methods for deposition of the catalytic active composition
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9041—Metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9041—Metals or alloys
    • H01M4/905—Metals or alloys specially used in fuel cell operating at high temperature, e.g. SOFC
    • H01M4/9058—Metals or alloys specially used in fuel cell operating at high temperature, e.g. SOFC of noble metals or noble-metal based alloys
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

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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

Hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst and preparation method and application thereof
Technical Field
The invention belongs to the technical field of electrocatalysis of fuel cells, and particularly relates to a hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst, and a preparation method and application thereof.
Background
With the increasing exhaustion of fossil energy and the pollution to the environment during the use, the development of clean and renewable energy sources is required as soon as possible. The fuel cell is a high-efficiency green clean energy conversion system with great potential at present, is a fourth type of power generation technology following thermal, hydraulic and nuclear power generation, and is an electrochemical reaction device (Zhongchong forest, Wei Xian, Jiangning, etc.) which directly converts chemical energy generated by reaction of fuel (hydrogen, natural gas, alcohols, etc.) and oxidant (oxygen) into electric energy through electrochemical reaction without combustion. Fuel cell applications and prospects, lutianhua science and technology, 2009, 4: 409-412]. Some studies on fuel cell cathode catalysts have been made by chamomile et al [ chamomile, yellow-red-cyan, yellow-red-good, etc. Current research on fuel cell catalysts, Battery industry, 2007, 01:57-60 ].
The cathode Oxygen Reduction Reaction (ORR) is an important factor limiting the performance of Proton Exchange Membrane Fuel Cells (PEMFC) and Direct Methanol Fuel Cells (DMFC). At present, ORR is thought to occur mainly through two pathways, namely the complete reduction of the tetrahydrotetraelectron to water and the partial reduction of the dihydrodiielectron to hydrogen peroxide.
At present, a fuel cell cathode catalyst which is widely applied is a Pt/C catalyst, but because a Pt electrode is high in cost, low in durability, short in resource and easy to be severely poisoned [ Zhang, L.; zhang, j.; wilkinson, d.p.; wang, h.j.powersources 2006,156,171.] restricts large-scale application and commercialization of fuel cells. There is an urgent need to develop inexpensive, durable, efficient and stable non-platinum based cathodic oxygen reduction catalysts.
Carbon materials are widely used as fuel cell catalyst supports because of their simple preparation, ease of large-scale production, and good chemical and mechanical stability. Honda and the like prepare micron-sized carbon spheres from asphalt for the first time (H Honda, H Kimura, Y Sanada, et al. carbon,1970,8(2): 181-183), and the micron-sized carbon spheres have the advantages of strong chemical stability and thermal stability, low density, controllable specific surface area, high compressive strength, large chemical inertness and the like, so the micron-sized carbon spheres have wide application prospects in the aspects of fuel cells, catalyst carriers, lithium ion battery cathode materials, supercapacitor electrode materials and the like. The application of nano carbon particles in catalysis is reviewed by Dujian ping and the like, [ Dujian ping, Zhao Rui Hua, Yufeng, and the like ], the application and the prospect of nano carbon particles in catalysis [ J ] material guidance, 2010,24(17):49-52], the Liuyunfar has further research on the doping aspect of nano carbon spheres, the preparation and the magnetic performance of the carbon nanospheres loaded with nano iron particles [ J ]. Beijing university of chemical industry (Nature science edition), 2011,38(2):58-62 ]. The nano carbon spheres have made a breakthrough in the field of fuel cell catalysts.
Disclosure of Invention
The invention aims to provide an oxygen reduction catalyst for a hollow carbon nanosphere-loaded nano Ag particle fuel cell, and a preparation method and application thereof. The invention takes the hollow carbon nanospheres as the carrier, provides higher specific surface area, and takes the metal silver particles as the active central sites to achieve higher oxygen reduction catalytic activity. According to the invention, the loading capacity of the silver particles on the hollow carbon nanospheres is increased through a series of treatments, so that the fuel cell oxygen reduction catalyst which takes the hollow carbon nanospheres as a carrier and the silver particles as active sites is obtained, and the excellent oxygen reduction performance of the material and the application of the material in fuel cells are shown.
The invention is realized by the following technical scheme, and provides a preparation method of a hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst, which comprises the following steps:
s101: preparing hollow carbon nanospheres;
the hollow micron-sized carbon spheres have the advantages of strong chemical stability and thermal stability, low density, controllable specific surface area, high compressive strength, large chemical inertness and the like, so that the oxygen reduction catalyst prepared by taking the hollow nano-carbon spheres as a carrier can be applied to the aspects of fuel cells, catalyst carriers, lithium ion battery cathode materials, supercapacitor electrode materials and the like.
S102: 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;
the oleic acid contains carboxyl groups, the reaction activity is high, the hollow carbon nanospheres can be functionalized by using a method of dripping the oleic acid, so that the surfaces of the hollow carbon nanospheres are combined with the carboxyl active groups, and the adsorption capacity to silver ions is increased; in the prior art, the carrier is generally pretreated by acid or alkali, so that active components and the carrier are better combined, and the original structure of the carrier can be damaged in the process; the prepared material has uniform particle distribution and high load, and shows good activity in the aspect of catalyzing oxygen reduction of the fuel cell.
S103: and (3) taking the hollow carbon nanospheres as a carrier, adding a silver nitrate solution as a silver source, dropwise adding ethylene glycol, reducing by using a citric acid solution, and performing post-treatment after reduction reaction to obtain a final product.
Silver nitrate is selected as a silver source, is easy to dissolve and obtain and has strong stability, and nitrate radicals can be removed by water washing at the later stage; selecting a citric acid solution as a reducing agent, wherein the sodium citrate solution has weak reducibility so that the reduction process is very mild and the particle size of the reduced silver particles is smaller; the ethylene glycol is selected as the dispersing agent, and the effect of refining the crystal grains by the ethylene glycol is good, so that the silver particles are more dispersed and uniform.
Silver nitrate is used as a silver source, nano silver particles can be obtained under the reduction of a citric acid solution, and the nano silver particles can be successfully loaded on the nano carbon spheres by a method of adding an active group for adsorbing silver ions on the nano carbon spheres and then reducing the silver ions. The silver has better catalytic oxygen reduction performance, and the nano-silver particles have more excellent performance, because the nano-silver active sites are more exposed, the catalytic performance is enhanced. The hollow carbon nanosphere-supported nano Ag particle fuel cell oxygen reduction catalyst has certain stability and flexibility, so that the nano-scale thickness of the catalyst on a macroscopic level is expected to be more widely applied to fuel cells. The ethylene glycol is added as a dispersing agent, so that the silver particles are dispersed and uniform, and the silver particles are refined.
Preferably, in S101, the preparation of the hollow nanocarbon sphere comprises the following steps: preparing a glucose solution, pouring the glucose solution into a reaction kettle, putting the reaction kettle into an oven for hydrothermal reaction to obtain a reddish brown product, centrifuging, washing and drying to obtain the hollow carbon nanospheres.
A glucose solution is selected as a raw material for preparing the hollow carbon nanospheres, and the glucose solution is easy to obtain and can reach an expected hollow spherical porous structure; the hollow spherical porous structure prepared by taking glucose solution as a raw material has uniform particle size and good dispersibility; the hollow spherical porous structure is used as a carrier, and the hollow nano carbon spheres have higher specific surface area and larger loading capacity.
Preferably, the concentration of the glucose solution is 50-60 g/L; the hydrothermal reaction condition is hydrothermal for 10-12 h at 160-180 ℃.
The synthesis of the hollow carbon nanospheres can be guaranteed under the hydrothermal reaction condition of hydrothermal for 10-12 h at the temperature of 160-180 ℃, the agglomeration phenomenon is avoided, and the yield of the hollow carbon nanospheres can be increased.
Preferably, in order to ensure that the product is settled as much as possible while cleaning, the product is centrifugally washed 6 times at 8000r/min for 5-10 min each time, and dried in an oven at 60-80 ℃ for 12 h.
Preferably, in S102, the dispersing agent is absolute ethyl alcohol, the hollow carbon nanospheres are ultrasonically dispersed in the absolute ethyl alcohol for 1 hour, then oleic acid is dropwise added, and then the ultrasonic treatment is continued for 30 min.
The dispersing agent is absolute ethyl alcohol which has the characteristics of good dispersibility, easy volatilization and easy later treatment; the hollow carbon nanospheres are ultrasonically dispersed in absolute ethyl alcohol for 1 hour, the carbon nanospheres are fully dispersed, and oleic acid is attached to the surfaces of the carbon nanospheres by ultrasonic treatment for 30min after the oleic acid is dropwise added.
Preferably, in S103, the mixture of the hollow carbon nanospheres and the silver nitrate solution is subjected to ultrasonic treatment for 30min after ethylene glycol is dropwise added, then a citric acid solution is dropwise added, and the ultrasonic treatment is continued for 5-10 min after the addition is finished.
The ethylene glycol and the citric acid are added in a separate dropwise manner, so that the ethylene glycol is fully dispersed before the reduction of the silver ions; the citric acid solution is selectively added dropwise to prevent the reaction from being too fast and refine grains; advantages of using ultrasonic dispersion: 1. so that all reactants and additives are uniformly dispersed 2, and an energy is given to the system to promote the formation of crystal nuclei.
Preferably, in S103, the molar ratio of the silver nitrate solution to the citric acid solution is 1: 1. the two react in a ratio of 1:1, so that the reaction is complete and no reagent is wasted.
Preferably, in S103, in order to make the reduction reaction more sufficient, the reduction time using the citric acid solution is 24 hours, and the reduction reaction is completed already at 24 hours.
Preferably, in S103, the post-treatment is to centrifugally precipitate the reduction reaction product at a rotation speed of 8000r/min, continue to centrifugally wash for 5-6 times, and fully wash out the impurity ions; and drying for 12 hours at the temperature of 60-80 ℃ to obtain the final product.
The oxygen reduction catalyst for the hollow carbon nanosphere-loaded nano Ag particle fuel cell is prepared by adopting the preparation method of the oxygen reduction catalyst for the hollow carbon nanosphere-loaded nano Ag particle fuel cell. The hollow carbon nanospheres are used as carriers, oleic acid is added to increase surface active groups of the hollow carbon nanospheres, more silver ions are adsorbed, and then the hollow carbon nanospheres are reduced by citric acid to realize the loading of nano silver particles on the hollow carbon nanospheres, so that the hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst is obtained.
The application of the hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst is to use the hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst for catalyzing the oxygen reduction reaction of a fuel cell. The hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst prepared by the invention has good oxygen reduction performance, high electrocatalysis efficiency and large specific surface area, and has wide application prospect in the aspect of fuel cell oxygen reduction.
The invention has the beneficial effects that:
1) the preparation method adopted by the invention has the advantages that: a. the raw material source is wide, the method is simple and controllable, the operation is easy, the equipment is simple, and the pollution is less; b. the prepared hollow nano carbon sphere loaded nano Ag particle fuel cell oxygen reduction catalyst has large specific surface area and high electrocatalysis efficiency.
2) The invention successfully prepares the oxygen reduction catalyst of the hollow carbon nanosphere-loaded nano Ag particle fuel cell by a simple method, and the method shows excellent oxygen reduction catalytic performance by controlling the loading of nano silver particles. The method has the advantages of cheap and easily-obtained raw materials, simple and quick operation, low energy consumption, no special requirements on equipment and little additional environmental pollution, so that the method has good application prospect in the field of fuel cells and is an efficient, low-price and environment-friendly green synthesis method.
3) The hollow nano carbon sphere loaded nano Ag particle fuel cell oxygen reduction catalyst prepared by the invention increases the loading capacity of silver particles particularly after the carbon sphere is functionalized by oleic acid, so that the catalyst has higher activity in electrochemical reaction.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is an XRD chart of the prepared hollow nanocarbon sphere (denoted as CNHS) and the fuel cell oxygen reduction catalyst with the hollow nanocarbon sphere loaded with nano Ag particles (denoted as Ag @ CNHS).
Fig. 2 is an SEM image and a TEM image of the prepared hollow nanocarbon sphere (denoted as CNHS) and the fuel cell oxygen reduction catalyst with the hollow nanocarbon sphere supporting nano Ag particles (denoted as Ag @ CNHS).
FIG. 3 shows different sweep rates (5, 10, 20, 50, 100mV s) of an Ag @ CNHS fuel cell oxygen reduction catalyst in 0.1M KOH solution-1) Cyclic voltammogram (CV curve) below.
FIG. 4 shows the different sweep rates (5, 10, 20, 50, 100mV s) of CNHS in 0.1MKOH solution-1) Cyclic voltammogram (CV curve) below.
FIG. 5 is a graph of a rotating disk of Ag @ CNHS fuel cell oxygen reduction catalyst in 0.1M KOH saturated with oxygen.
FIG. 6 is a graph of a rotating disk of CNHS in 0.1M KOH saturated with oxygen.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. 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 application belongs.
As described in the background section, the fuel cell cathode catalyst which is widely used today is the Pt/C catalyst, but the large-scale application and the commercial development of the fuel cell are severely restricted due to the high cost, low durability, resource shortage and easy poisoning of the Pt electrode. There is an urgent need to develop inexpensive, durable, efficient and stable non-platinum based cathodic oxygen reduction catalysts.
Carbon materials are widely used as fuel cell catalyst supports because of their simple preparation, ease of large-scale production, and good chemical and mechanical stability. Honda and the like firstly prepare micron-sized carbon spheres from asphalt, and have the advantages of strong chemical stability and thermal stability, low density, controllable specific surface area, high compressive strength, large chemical inertness and the like, so the nano carbon spheres have wide application prospects in the aspects of fuel cells, catalyst carriers, lithium ion battery cathode materials, supercapacitor electrode materials and the like. The application of the nano carbon particles in the catalyst is reviewed by Dujian Hei et al, and Liuyunfan has further research on the doping aspect of the nano carbon spheres, which shows that the nano carbon spheres have made a breakthrough in the field of fuel cell catalysts.
In one embodiment of the invention, the preparation method of the oxygen reduction catalyst for the hollow carbon nanosphere-supported nano Ag particle fuel cell comprises the following steps:
s101: preparing hollow carbon nanospheres;
the hollow micron-sized carbon spheres have the advantages of strong chemical stability and thermal stability, low density, controllable specific surface area, high compressive strength, large chemical inertness and the like, so that the oxygen reduction catalyst prepared by taking the hollow nano-carbon spheres as a carrier can be applied to the aspects of fuel cells, catalyst carriers, lithium ion battery cathode materials, supercapacitor electrode materials and the like.
In S101, preparing hollow nano carbon spheres, comprising the following steps: preparing a glucose solution, pouring the glucose solution into a reaction kettle, and putting the reaction kettle into an oven for hydrothermal reaction, wherein the concentration of the glucose solution is 50-60 g/L; the hydrothermal reaction condition is that the hydrothermal reaction is carried out for 10-12 hours at the temperature of 160-180 ℃; centrifugally washing and drying the reddish brown product to obtain hollow carbon nanospheres; in order to ensure that the product is settled as much as possible while the product is washed cleanly, the product is centrifugally washed for 6 times at 8000r/min, 5-10 min each time, and dried for 12h in an oven at 60-80 ℃.
A glucose solution is selected as a raw material for preparing the hollow carbon nanospheres, and the glucose solution is easy to obtain and can reach an expected hollow spherical porous structure; the hollow spherical porous structure prepared by taking glucose solution as a raw material has uniform particle size and good dispersibility; the hollow spherical porous structure is used as a carrier, and the hollow nano carbon spheres have higher specific surface area and larger loading capacity.
The synthesis of the hollow carbon nanospheres can be guaranteed under the hydrothermal reaction condition of hydrothermal for 10-12 h at the temperature of 160-180 ℃, the agglomeration phenomenon is avoided, and the yield of the hollow carbon nanospheres can be increased.
S102: 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;
the oleic acid contains carboxyl groups, the reaction activity is high, the hollow carbon nanospheres can be functionalized by using a method of dripping the oleic acid, so that the surfaces of the hollow carbon nanospheres are combined with the carboxyl active groups, and the adsorption capacity to silver ions is increased; in the prior art, the carrier is generally pretreated by acid or alkali, so that active components and the carrier are better combined, and the original structure of the carrier can be damaged in the process; the prepared material has uniform particle distribution and high load, and shows good activity in the aspect of catalyzing oxygen reduction of the fuel cell.
In S102, as the absolute ethyl alcohol has the characteristics of good dispersibility, volatility and easiness in later-stage treatment, the dispersant is the absolute ethyl alcohol, the hollow carbon nanospheres are ultrasonically dispersed in the absolute ethyl alcohol for 1 hour, then oleic acid is dropwise added, and then the ultrasonic treatment is continued for 30 min. The first ultrasonic treatment can fully disperse the carbon spheres, and the second ultrasonic treatment can attach the oleic acid to the surfaces of the carbon spheres.
S103: and (3) taking the hollow carbon nanospheres as a carrier, adding a silver nitrate solution as a silver source, dropwise adding ethylene glycol, reducing by using a citric acid solution, and performing post-treatment after reduction reaction to obtain a final product.
Silver nitrate is selected as a silver source, is easy to dissolve and obtain and has strong stability, and nitrate radicals can be removed by water washing at the later stage; selecting a citric acid solution as a reducing agent, wherein the sodium citrate solution has weak reducibility so that the reduction process is very mild and the particle size of the reduced silver particles is smaller; the ethylene glycol is selected as the dispersing agent, and the effect of refining the crystal grains by the ethylene glycol is good, so that the silver particles are more dispersed and uniform.
Silver nitrate is used as a silver source, nano silver particles can be obtained under the reduction of a citric acid solution, and the nano silver particles can be successfully loaded on the nano carbon spheres by a method of adding an active group for adsorbing silver ions on the nano carbon spheres and then reducing the silver ions. The silver has better catalytic oxygen reduction performance, and the nano-silver particles have more excellent performance, because the nano-silver active sites are more exposed, the catalytic performance is enhanced. The hollow carbon nanosphere-supported nano Ag particle fuel cell oxygen reduction catalyst has certain stability and flexibility, so that the nano-scale thickness of the catalyst on a macroscopic level is expected to be more widely applied to fuel cells. The ethylene glycol is added as a dispersing agent, so that the silver particles are dispersed and uniform, and the silver particles are refined.
In S103, in order to sufficiently disperse ethylene glycol before reduction of silver ions; and (3) dropwise adding ethylene glycol and citric acid in a separate dropwise manner, carrying out ultrasonic treatment for 30min after dropwise adding the ethylene glycol into the mixture of the hollow carbon nanospheres and the silver nitrate solution, dropwise adding the citric acid solution, and continuing ultrasonic treatment for 5-10 min after the dropwise adding. The citric acid solution is selectively added dropwise to prevent the reaction from being too fast and refine grains; advantages of using ultrasonic dispersion: 1. so that all reactants and additives are uniformly dispersed 2, and an energy is given to the system to promote the formation of crystal nuclei.
The molar ratio of the added silver nitrate solution to the added citric acid solution is 1: 1. the two react in a ratio of 1:1, so that the reaction is complete and no reagent is wasted. In order to make the reduction reaction more complete, the reduction time is 24 hours by using citric acid solution, and the reduction reaction is completed at 24 hours. In order to fully wash out the impurity ions, the post-treatment is to carry out centrifugal precipitation on the reduction reaction product at the rotating speed of 8000r/min, and continue centrifugal washing for 5-6 times; and drying for 12 hours at the temperature of 60-80 ℃ to obtain the final product.
In order to make the technical solutions of the present application more clearly understood by those skilled in the art, 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 in the art and commercially available.
Example 1
Silver ions are reduced on the carbon spheres by a citric acid reduction method to obtain the fuel cell oxygen reduction catalyst taking silver particles as active sites and hollow nano carbon spheres as carriers.
Dissolving 4.5g of glucose into 75mL of deionized water, uniformly stirring, placing the solution into a 100mL reaction kettle, placing the reaction kettle into an oven, and keeping the hydrothermal reaction at 160-180 ℃ for 10-12 hours. Then, washing with deionized water and absolute ethyl alcohol, centrifugally washing for 6 times at 8000r/min, 5-10 min each time, and drying in an oven at 60-80 ℃ for 12h to obtain hollow carbon nanospheres; weighing 0.25g of the obtained carbon nanospheres, dispersing the carbon nanospheres into 30mL of absolute ethyl alcohol, performing ultrasonic treatment for 1 hour, dropwise adding 1-3 drops of oleic acid, and continuing performing ultrasonic treatment for 30 min; obtaining functionalized hollow nano carbon spheres; respectively weighing the components in a molar ratio of 1:1, preparing a solution by using silver nitrate (0.5g) and citric acid (0.6g is slightly excessive), firstly adding the silver nitrate solution into a functionalized hollow carbon nanosphere, dropwise adding 1-3 drops of ethylene glycol, carrying out ultrasonic treatment for 30min, dropwise adding the citric acid solution, continuing to carry out ultrasonic treatment for 5-10 min after the addition is finished, stirring the mixed liquid for 24h, then centrifuging at the rotating speed of 8000r/min to obtain a precipitate, continuing to carry out centrifugal washing for 5-6 times to obtain clean hollow carbon nanosphere-loaded nano Ag particles, and drying at the temperature of 60-80 ℃ for 12h to obtain a final product.
Fig. 1 is an X-ray diffraction pattern of the Ag @ CNHS fuel cell oxygen reduction catalyst obtained in this example and an X-ray diffraction pattern of a hollow nanocarbon sphere, and analysis by Jade software can obtain that a substance supported on the hollow nanocarbon sphere is silver particles and has a diffraction peak of carbon at 23 °.
Fig. 2 is a scanning electron microscope picture and a transmission electron microscope picture of the Ag @ CNHS fuel cell oxygen reduction catalyst and CNHS obtained in this example, the prepared CNHS is a spherical structure with a uniform particle size and a diameter of 150 to 200nm, silver particles are attached to the surface of a carbon sphere to form a core-shell structure, and the average particle size of the silver particles is 5 to 6nm, which is beneficial to the oxygen reduction reaction.
The prepared catalyst is subjected to performance test according to the following method:
modifying an oxygen reduction catalyst of the Ag @ CNHS fuel cell on an electrode. Before testing, a glassy carbon electrode (diameter 3mm) was subjected to the following steps: firstly using 50nm of Al2O3And (3) polishing the powder film, then respectively cleaning with ethanol and ultrapure water (in an ultrasonic instrument), and airing in the air. The working electrode was prepared as follows: adding 5mg of catalyst into 450 mu L of ultrapure water, adding 50 mu L of Nafion solution with the mass fraction of 5%, ultrasonically dispersing for 1 hour, taking 5 mu L of the catalyst solution on a glassy carbon electrode by using a trace liquid transfer gun, and airing in the air. The disk electrode (diameter 5mm) was rotated and subjected to the same treatment, and then 10. mu.L of the droplets were applied to the electrode surface and air-dried.
FIG. 3 shows the oxygen saturation of 0.1 mol.L of the oxygen reduction catalyst of the Ag @ CNHS fuel cell of this example-1Cyclic voltammograms in KOH solution at different sweep rates. During scanning, the Ag @ CNHS begins to generate a peak near-0.3V, the peak position is-0.3V to-0.5V, and the peak value of the current density is-0.5 mAcm-2。
FIG. 4 shows the CNHS of this example at 0.1 mol. L saturated with oxygen-1Cyclic voltammograms in KOH solution at different sweep rates. During scanning, CNHS begins to generate peak around-0.3V, the peak position is-0.3V to-0.45V, and the peak value of current density is-0.25 mAcm-2。
FIG. 5 shows the oxygen saturation of 0.1 mol.L of the oxygen reduction catalyst of the Ag @ CNHS fuel cell of this example-1The current density of the rotating disk curve in the KOH solution is increased along with the increase of the rotating speed, the oxygen reduction process is controlled by diffusion, and the number n of transferred electrons at-0.45, -0.5, -0.55 and-0.6V of the catalyst Ag @ CNHS is calculated to be 3.71, 3.73, 3.74 and 3.77 respectively.
FIG. 6 shows the present embodiment0.1 mol. L of CNHS saturated in oxygen-1The number of transferred electrons n at-0.45, -0.5, -0.55, -0.6V for CNHS was calculated to be 2.29, 2.32, 2.35, respectively, for the curve of the rotating disk in KOH solution.
The specific conditions are as follows: performing electrochemical property test with CHI 760d electrochemical workstation (Shanghai Chenghua apparatus Co., Ltd.), coating the prepared catalyst on glassy carbon electrode as working electrode, and collecting Hg/Hg2Cl2Electrodes and Pt electrodes were used as reference and auxiliary electrodes and tested in 0.1M potassium hydroxide solution to give cyclic voltammograms (CV plots).
Of course, the above description is not limited to the above examples, and the undescribed technical features of the present invention can be implemented by or using the prior art, and will not be described herein again; the above embodiments and drawings are only for illustrating the technical solutions of the present invention and not for limiting the present invention, and the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that changes, modifications, additions or substitutions within the spirit and scope of the present invention may be made by those skilled in the art without departing from the spirit of the present invention, and shall also fall within the scope of the claims of the present invention.

Claims (5)

1. A preparation method of a hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst is characterized by comprising the following steps: the method comprises the following steps:
s101: preparing hollow carbon nanospheres: preparing hollow carbon nanospheres by taking a glucose solution as a raw material and utilizing a hydrothermal reaction; the concentration of the glucose solution is 50-60 g/L; the hydrothermal reaction condition is that the hydrothermal reaction is carried out for 10-12 hours at the temperature of 160-180 ℃;
s102: 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;
s103: taking a hollow carbon nanosphere as a carrier, dropwise adding ethylene glycol into a mixture of the hollow carbon nanosphere and a silver nitrate solution, and performing ultrasonic treatment for 30min, wherein the molar ratio of the added silver nitrate solution to the added citric acid solution is 1: 1; and dropwise adding a citric acid solution, continuing performing ultrasonic treatment for 5-10 min after the addition is finished, reducing for 24h by using the citric acid solution, and performing post-treatment after the reduction reaction to obtain a final product.
2. The preparation method of the hollow carbon nanosphere-supported nano Ag particle fuel cell oxygen reduction catalyst according to claim 1, characterized in that: in S102, anhydrous ethanol is selected as a dispersing agent, oleic acid is dropwise added after the hollow carbon nanospheres are ultrasonically dispersed in the anhydrous ethanol for 1 hour, and then the ultrasonic treatment is continued for 30 min.
3. The preparation method of the hollow carbon nanosphere-supported nano Ag particle fuel cell oxygen reduction catalyst according to claim 1, characterized in that: and S103, carrying out post-treatment, namely carrying out centrifugal precipitation on the reduction reaction product at the rotating speed of 8000r/min, continuously carrying out centrifugal washing for 5-6 times, and drying for 12 hours at the temperature of 60-80 ℃ to obtain the final product.
4. An oxygen reduction catalyst of a hollow carbon nanosphere-loaded nano Ag particle fuel cell is characterized in that: the preparation method of the hollow carbon nanosphere-loaded nano Ag particle fuel cell oxygen reduction catalyst according to any one of claims 1 to 3.
5. The application of the oxygen reduction catalyst of the hollow carbon nanosphere-loaded nano Ag particle fuel cell is characterized in that: the hollow nanocarbon sphere-supported nano Ag particle fuel cell oxygen reduction catalyst of claim 4 is used for catalyzing oxygen reduction reaction of a fuel cell.
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