CN111129511A - Nitrogen-doped carbon-supported platinum-based catalyst and preparation method and application thereof - Google Patents
Nitrogen-doped carbon-supported platinum-based catalyst and preparation method and application thereof Download PDFInfo
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- CN111129511A CN111129511A CN201911304495.6A CN201911304495A CN111129511A CN 111129511 A CN111129511 A CN 111129511A CN 201911304495 A CN201911304495 A CN 201911304495A CN 111129511 A CN111129511 A CN 111129511A
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Abstract
The invention relates to a nitrogen-doped carbon-supported platinum-based catalyst, a preparation method and application thereof. The preparation method comprises the following steps: (1) carrying out electrostatic spinning on the polymer solution to prepare a carbon material precursor; (2) carrying out heat treatment on the carbon material precursor obtained in the step (1) in a nitrogen-containing atmosphere to obtain a nitrogen-doped carbon material; (3) mixing the nitrogen-doped carbon material obtained in the step (2) with a platinum precursor solution, sequentially adding a first reducing agent and a second reducing agent to perform primary reduction and secondary reduction, separating and drying to obtain the nitrogen-doped carbon-supported platinum-based catalyst; wherein the reducibility of the first reducing agent > the reducibility of the second reducing agent. In the durability test, the catalytic performance of the catalyst is almost not attenuated after 30000 circles of accelerated durability. The preparation method not only improves the stability, durability and catalytic activity of the catalyst, but also reduces the consumption of platinum and production cost, and has higher application value.
Description
Technical Field
The invention relates to the field of new energy fuel cells, in particular to a nitrogen-doped carbon-supported platinum-based catalyst and a preparation method and application thereof.
Background
Proton Exchange Membrane Fuel Cells (PEMFCs) have the characteristics of high energy conversion efficiency, low-temperature quick start, low noise, no pollution and the like, and are considered to be very suitable for being used as power energy sources of green new energy automobiles. The proton exchange membrane fuel cell consists of catalyst, proton membrane, gas diffusion layer and bipolar plate. The principle is that hydrogen separates proton and electron from anode, proton passes through proton exchange membrane to cathode, electron reaches cathode through external circuit, and when electron reaches cathode, proton and introduced O are separated2Under the action of a cathode catalyst, combining to generate water, and specifically carrying out electrode reaction:
anode: h2→2H++2e-
Cathode: 1/2O2+2H++2e-→H2O
The overall reaction formula is: h2+1/2O2→H2O
Fuel cell technology is considered to be an ultimate goal in the development of new energy sources because fuel cells add hydrogen and reject water. However, since the ambient temperature at which the fuel cell operates is 40 to 95 ℃, it is necessary to use a noble metal Pt having high activity as a catalyst. However, due to the characteristics of less metal storage amount, high price, easy poisoning and the like, the development of a low-platinum catalyst with high activity and high durability is the focus of research at present.
CN1803292A provides a preparation method of a carbon-supported platinum-based catalyst for a fuel cell, which comprises the steps of adding a metal salt precursor, a complexing agent and an alcohol reducing agent into an organic solvent, and stirring at room temperature; adding alkaline substances, adjusting the pH value, introducing nitrogen under normal pressure for protection, heating and refluxing, or reacting in a high-pressure kettle; adding carbon carrier, stirring at room temperatureUniformly dispersing metal sol particles on a carbon carrier; adding an acidic substance, adjusting the pH value, adding secondary distilled water, and performing ultrasonic oscillation to break gel; filtering, washing the filter cake until Cl can not be detected-And (3) carrying out ion drying under vacuum, cooling and grinding to obtain the carbon-supported platinum-based catalyst for the fuel cell, which comprises Pt/C, Pt-Ru/C, Pt-Ru-Ir/C, Pt/CNT, Pt-Ru/CNTh and Pt-Ru-Ir/CNT. The method has the advantages of simple process, high recovery rate, small granularity of the active components of the catalyst to about 1nm, uniform distribution, high utilization rate of the noble metal, and high electrochemical active surface area, catalytic activity and antitoxic performance of the catalyst, but the method uses the noble metal salt and the complexing agent, thereby increasing the production cost.
CN108963282A discloses a method for preparing a fuel cell carbon-supported platinum-based catalyst by a solvothermal method, which is applied to proton exchange membrane fuel cells, including oxyhydrogen fuel cells and direct alcohol fuel cell cathode reactions, and belongs to the field of electrochemical catalytic reactions. The invention adopts a solvothermal reduction method, fully disperses a carrier carbon material in a solvent, adds a metal precursor solution while stirring, the mass percentage of active components in the prepared catalyst reaches 20-60 wt%, adjusts the pH value of the solution to be more than 9 by using an alkaline solution, and then reacts the mixed solution in a high-temperature and high-pressure sealed reaction container. And after the reaction, adjusting the pH value to be lower than 5 by using an acidic solution, and filtering, washing, drying and grinding the reaction solution to obtain the carbon-supported platinum-based electrocatalyst. The catalyst prepared by the invention has small particle size of the active component, is highly and uniformly dispersed on the carbon carrier, and has higher activity. The preparation process has the advantages of simple operation, quick reaction, less energy consumption, low cost and easy realization of large-scale industrial production, but the catalyst prepared by the method has uneven appearance and has adverse effects on the catalytic activity and the durability of the catalyst.
At present, in the common Pt/C catalyst used for the fuel cell, the Pt loading on the anode side generally needs 0.05-0.1mg/cm2The requirements of the fuel cell can be met, and the Pt loading on the cathode side needs to be 0.25-0.40mg/cm2The cost proportion of the Pt-based catalyst in the fuel cell stack is about 35-50%. Thus, the yin is loweredThe cost of the polar catalyst is crucial to reducing the cost of the overall PEMFCs, and while reducing the cost of the fuel cell catalyst, the catalytic performance, durability, and stability of the support must also be ensured.
Based on the above consideration, how to develop and prepare a catalyst which can ensure the reduction of platinum amount and high catalytic ability and can improve durability and stability becomes a problem to be solved at present.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a nitrogen-doped carbon-supported platinum-based catalyst, and a preparation method and application thereof. The method is based on an electrostatic spinning technology, the preparation of the nitrogen-doped carbon material is completed by combining high-temperature calcination heat treatment, and then a platinum precursor is reduced into nano particles to modify the surface of the nitrogen-doped carbon material in a double-reducing agent system. Compared with the traditional preparation method, under the condition of the same technical performance, the platinum consumption of the preparation method is obviously reduced, the activity of the catalyst is almost kept unchanged after the catalyst is subjected to 30000-turn accelerated durability test, and better durability and carrier stability are shown.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a carbon-supported platinum-based catalyst, comprising the steps of:
(1) carrying out electrostatic spinning on the polymer solution to prepare a carbon material precursor;
(2) carrying out heat treatment on the carbon material precursor obtained in the step (1) in a nitrogen-containing atmosphere to obtain a nitrogen-doped carbon material;
(3) mixing the nitrogen-doped carbon material obtained in the step (2) with a platinum precursor solution, sequentially adding a first reducing agent and a second reducing agent to perform primary reduction and secondary reduction, separating and drying to obtain the nitrogen-doped carbon-supported platinum-based catalyst;
wherein the reducibility of the first reducing agent > the reducibility of the second reducing agent.
The preparation method provided by the invention is characterized in that firstly, an electrostatic spinning technology is used as a support, a spinning precursor solution is prepared by adopting a polymer, a carbon material precursor such as carbon nanofiber or carbon nanosphere can be prepared in a large quantity, secondly, a high-temperature calcination heat treatment process is adopted, nitrogen atoms are doped into crystal lattices of the carbon material, a nitrogen-doped carbon nanomaterial with uniform appearance and size is obtained, and finally, platinum nanoparticles with uniform appearance and size are obtained on the nitrogen-doped carbon material under a double-reducing agent system, so that the surface modification of the carbon material is more beneficial to the exposure of active crystal faces of the platinum nanoparticles, and the nitrogen-doped carbon-supported platinum-based catalyst is obtained. The electrostatic spinning technology adopted by the preparation method has the characteristics of convenience, rapidness, low cost and capability of preparing a large amount of polymer nano materials; the preparation method reduces the consumption of platinum and the production cost on the basis of improving the stability, durability and catalytic activity of the catalyst, and has higher application value.
Preferably, the first reducing agent includes sodium borohydride and/or potassium borohydride, and may be sodium borohydride, or potassium borohydride, or a mixture of sodium borohydride and potassium borohydride.
Preferably, the second reducing agent comprises any one of ascorbic acid, formaldehyde or dimethylformamide, or a combination of at least two thereof, with typical but non-limiting combinations: ascorbic acid and dimethylformamide, formaldehyde and dimethylformamide.
Preferably, the mass ratio of the nitrogen-doped carbon material, the first reducing agent and the second reducing agent is 1 (0.5-10): 3-15, and for example, may be 1:0.5:3, 1:0.55:10, 1:0.8:5, 1:1:10, 1:3:12, 1:5:5, 1:8:3, 1:8:10, 1:10:8 or 1:10:15, and preferably is 1 (0.55-8): 3-10); if the mass ratio is less than 1:0.5:3, the precursor of the platinum cannot be completely reduced; the mass ratio is more than 1:10:15, waste is caused, the production cost is increased, and the performance of the catalyst is not optimal.
Preferably, the polymer in step (1) comprises any one of polyacrylonitrile, polyvinylpyrrolidone, polyurethane or polyimide or a combination of at least two thereof, wherein the typical but non-limiting combination is: polyacrylonitrile and polyvinylpyrrolidone, polyurethane and polyimide, and the like.
Preferably, the solvent of the polymer solution in step (1) comprises any one or a combination of at least two of ethanol, N-dimethylformamide, dimethylsulfoxide or acetone, wherein the typical but non-limiting combination is: ethanol and N, N-dimethylformamide, dimethyl sulfoxide and acetone, ethanol and acetone, N-dimethylformamide and dimethyl sulfoxide, and the like.
Preferably, the polymer solution in step (1) is heated to 60-120 ℃ during the preparation process, such as 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃ or 120 ℃.
In the present invention, the heating method in the preparation process of the polymer solution is not particularly limited, and may be an oil bath, a water bath, or the like, and any heating method commonly used by those skilled in the art is applicable to the present invention.
Preferably, the mass ratio of the polymer to the solvent in the polymer solution in the step (1) is 0.05 to 0.5:1, and for example, may be 0.05:1, 0.08:1, 0.1:1, 0.15:1, 0.2:1, 0.3:1, 0.4:1, 0.45:1, or 0.5:1, and the like, preferably 0.08 to 0.3:1, and if the mass ratio is less than 0.05:1, the structure of the carbon material precursor is discontinuous; if the mass ratio is greater than 0.5:1, spinning cannot be performed.
Preferably, the voltage of the electrostatic spinning in step (1) is 5-30kV, for example, 5kV, 5.5kV, 6kV, 8kV, 10kV, 15kV, 20kV, 25kV, 28kV or 30kV, etc., preferably 15-20 kV.
Preferably, the carbon material precursor is a nanofiber film or a nanoparticle film.
Preferably, the temperature of the heat treatment in step (2) is 500-; if the temperature is lower than 500 ℃, impurities cannot be removed; temperatures above 1200 c are likely to cause cross-linking.
Preferably, the heating mode of the heat treatment is a step-type heating, and the step-type heating can maintain the intact morphology of the material.
Preferably, the number of steps of the stepwise temperature increase is not less than 2, for example, 2, 3, 4, 5, etc., preferably 2.
Preferably, the step-wise temperature rising procedure with the step number of 2 is as follows: first raising the temperature to a temperature T1Time of heat preservation t1Then raising the temperature to the temperature T2Time of heat preservation t2。
Preferably, said temperature T1200 ℃ to 300 ℃, for example, 200 ℃, 220 ℃, 250 ℃, 280 ℃ or 300 ℃ can be used.
Preferably, said time t1Is 1.5-2.5h, for example, 1.5h, 2h or 2.5 h.
Preferably, said temperature T2The temperature is 500 ℃ to 1200 ℃, for example, 500 ℃, 550 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃ or 1200 ℃, preferably.
Preferably, said time t2Is 0.5 to 8 hours, for example, 0.5 hour, 1 hour, 1.5 hour, 3 hours, 5 hours, 7 hours or 8 hours, etc., preferably 1 to 2 hours; if the time is less than 0.5h, the shape of the crystal is not favorable; and the time is more than 8h, and the material is easy to crosslink.
Preferably, the temperature rising speed of the first stage and the second stage is 1-7 ℃/min independently, the same temperature rising speed can be used for the independent temperature rising process, and different temperature rising speeds can be adopted, such as 1 ℃/min, 2 ℃/min, 3 ℃/min, 5 ℃/min, 6 ℃/min or 7 ℃/min, and the like, preferably 2-5 ℃/min.
Preferably, the gas of the nitrogen-containing atmosphere is nitrogen and/or ammonia.
Preferably, the precursor of platinum in step (3) comprises any one of chloroplatinic acid, potassium tetrachloroplatinate, potassium hexachloroplatinate, platinum acetylacetonate, platinum nitrate or platinum tetraammine chloride, or a combination of at least two thereof, wherein the typical but non-limiting combination is: chloroplatinic acid and platinum nitrate, potassium tetrachloroplatinate and hexachloroplatinate, potassium tetrachloroplatinate and tetraammineplatinum, chloroplatinic acid and acetylacetonatoplatinate hexachloroplatinate and tetraammineplatinum, and the like.
Preferably, the mixing in step (3) is by stirring and/or sonication.
Preferably, a buffer substance is added before the first reducing agent is added in step (3).
Preferably, the buffer substance comprises any one of ammonia, ammonium carbonate, ammonium bicarbonate or urea, or a combination of at least two thereof, with a typical but non-limiting combination: ammonia and ammonium carbonate, ammonia and urea, ammonium carbonate and ammonium bicarbonate, and the like.
Preferably, the mass ratio of the nitrogen-doped carbon material to the platinum in the platinum precursor to the buffer substance is 1 (1-7): (5-20), and may be, for example, 1:1:5, 1:1.5:10, 1:1.5:17.5, 1:1.5:20, 1:2:5, 1:3:10, 1:5:5, 1:5:15, 1:6.5:5, 1:6.5:15, 1:6.5:17.5, 1:7:5, 1:7:10, 1:7:15, or 1:7:20, and preferably 1 (1.5-6.5): 5-17.5.
Preferably, the manner of adding the first reducing agent and the second reducing agent in step (3) is as follows:
under the condition of vigorous stirring, a first reducing agent is rapidly added, vigorous stirring is carried out for 0.5-2h at the temperature of 25-60 ℃, and then a second reducing agent is added.
The stirring temperature may be 25 ℃, 30 ℃, 35 ℃, 40 ℃, 50 ℃, 55 ℃ or 60 ℃ or the like.
The stirring time may be 0.5h, 1h, 1.5h, 2h, or the like.
Preferably, the mode of the primary reduction and the secondary reduction in the step (3) is reflux.
Preferably, the secondary reduction in step (3) is carried out in an oil bath.
Preferably, the temperature of the secondary reduction in step (3) is 80 to 150 ℃, for example, 80 ℃, 85 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃ or 150 ℃, preferably 90 to 135 ℃.
Preferably, the time for the secondary reduction in step (3) is 6-12h, such as 6h, 7h, 8h, 9h, 10h, 11h or 12 h.
Preferably, the separation in step (3) comprises any one or a combination of at least two of centrifugation, suction filtration, pressure filtration or filtration, wherein the combination is typically but not limited to: centrifuging and suction filtering, centrifuging and filter pressing.
Preferably, the solid phase obtained by said separation in step (3) is washed to neutrality.
Preferably, the temperature of the drying in the step (3) is 60-100 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃ and the like.
Preferably, the drying time in step (3) is 5-10h, for example, 5h, 5.5h, 6h, 7h, 8h, 9h, 9.5h or 10h, etc.
As a further preferable technical solution of the present invention, the method comprises the steps of:
(1) weighing polymer powder in a conical flask, adding a solvent, controlling the mass ratio of the polymer to the solvent to be 0.05-0.5:1, heating and stirring at 60-120 ℃ to prepare a spinning precursor solution, pumping the spinning precursor solution into a spinning nozzle, loading 5-30kV high pressure between the spinning nozzle and a receiver, splitting a Taylor cone formed by the polymer solution at the nozzle under the high pressure condition to form a fiber film or a particle film, and spraying the fiber film or the particle film on the receiver;
the polymer comprises any one or the combination of at least two of polyacrylonitrile, polyvinylpyrrolidone, polyurethane or polyimide;
the solvent comprises any one or the combination of at least two of ethanol, N-dimethylformamide, dimethyl sulfoxide or acetone;
(2) taking the fiber membrane or the particle membrane obtained in the step (1) down from the receiver, transferring the fiber membrane or the particle membrane into a tubular furnace, heating the fiber membrane or the particle membrane to 500-1200 ℃ at a heating rate of 1-7 ℃/min in a nitrogen-containing atmosphere, calcining the fiber membrane or the particle membrane for 0.5-8h, and then naturally cooling the fiber membrane or the particle membrane under the protection of the atmosphere to obtain a nitrogen-doped carbon material;
(3) placing the nitrogen-doped carbon material prepared in the step (2) into a round bottom flask, adding a buffer substance, uniformly dispersing under the condition of an ultrasonic homogenizer, rapidly adding a platinum precursor solution under the condition of later vigorous stirring, controlling the mass ratio of platinum and the buffer substance in the nitrogen-doped carbon material and the platinum precursor to be (0.015-0.08): (0.01-0.3): (0.1-0.8), stirring, rapidly adding a first reducing agent, vigorously stirring at 25-60 ℃ for 0.5-2h, adding a second reducing agent, and carrying out oil bath reflux at 90-135 ℃ for 6-12h, and controlling the mass ratio of the nitrogen-doped carbon material, the first reducing agent and the second reducing agent to be (0.015-0.08): (0.01-0.3): 0.1-0.5);
the buffer substance comprises any one or the combination of at least two of ammonia water, ammonium carbonate, ammonium bicarbonate or urea;
the precursor of the platinum comprises any one or the combination of at least two of chloroplatinic acid, potassium tetrachloroplatinate, potassium hexachloroplatinate, platinum acetylacetonate, platinum nitrate or tetraammineplatinum chloride;
the first reducing agent comprises sodium borohydride and/or potassium borohydride;
the second reducing agent comprises any one or the combination of at least two of ascorbic acid, formaldehyde or dimethylformamide;
(4) separating reactants in the step (3), washing a solid phase obtained by separation with deionized water to be neutral, and drying in a vacuum oven at 60-100 ℃ for 5-10h to obtain the nitrogen-doped carbon-supported platinum-based catalyst;
the separation mode comprises any one or the combination of at least two of centrifugation, suction filtration, filter pressing and filtration.
In a second aspect, the invention provides a nitrogen-doped carbon-supported platinum-based catalyst prepared by the preparation method according to the first aspect, wherein the mass fraction of platinum is 60-90% based on 100% of the mass of the catalyst.
According to the nitrogen-doped carbon-supported platinum-based catalyst provided by the invention, nitrogen atoms in a carbon substrate lattice have strong electronegativity, so that the carbon atoms in the structure have electropositivity, and thus the nitrogen-doped carbon-supported platinum-based catalyst has advantages in electron conduction; platinum nano particles are uniformly combined with a nitrogen-doped carbon substrate, the number of active crystal faces is more, the platinum amount is obviously reduced, the cooperation of the platinum nano particles and the nitrogen-doped carbon substrate enables reactants to react on the surface of the catalyst, and then internal electrons are rapidly led out, so that the electrons and holes are not easy to compound after being separated, the catalysis efficiency of the material is greatly improved, the corrosion effect of the material in the catalysis process is weakened, the activity of the catalyst is almost kept unchanged after 30000s endurance test, and better durability and stability are demonstrated.
In the present invention, the mass fraction of platinum may be 60%, 65%, 70%, 80%, 85%, 90%, or the like, based on 100% by mass of the catalyst.
Preferably, the mass fraction of nitrogen is 1-10%, for example, 1%, 2%, 3%, 5%, 8%, 10%, or the like, based on 100% of the mass of the nitrogen-doped carbon material.
In the invention, the mass fraction of nitrogen element is obtained by the element analyzer of Hitachi company.
In a third aspect, the present invention provides a fuel cell comprising a nitrogen-doped carbon-supported platinum-based catalyst as described in the second aspect above.
The fuel cell provided by the invention adopts the nitrogen-doped carbon-supported platinum-based catalyst, the catalytic activity is higher, and the electrode reaction speed is improved, so that the fuel cell can meet the requirement of high-power output; the catalyst has good stability and high durability, and the service life of the fuel cell is prolonged; compared with the prior art, the amount of platinum used for the catalyst is reduced, the cost of the fuel cell is reduced, and the industrialization process of the fuel cell is promoted.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the preparation method provided by the invention is based on electrostatic spinning, combines high-temperature calcination heat treatment to complete the preparation of the nitrogen-doped carbon material, and then combines the use of a double reducing agent to reduce a platinum precursor into nano particles to modify the surface of the nitrogen-doped carbon material, so as to obtain the nitrogen-doped carbon-supported platinum-based catalyst; the preparation method reduces the consumption of platinum and the production cost on the basis of improving the stability, durability and catalytic activity of the catalyst, and has higher application value;
(2) according to the nitrogen-doped carbon-supported platinum-based catalyst provided by the invention, the introduction of nitrogen atoms improves the electronic conductivity of the catalyst; the platinum nanoparticles are uniformly distributed, the active crystal faces are more exposed, and the platinum nanoparticles and the active crystal faces act synergistically to enable internal electrons to be rapidly led out after reactants react on the surface of the catalyst, so that the electrons and holes are not easy to combine after being separated, the catalytic efficiency of the material is greatly improved, the stability and durability of the catalyst are improved, and the mass activity of the catalyst is almost not attenuated after 30000 circles of acceleration and durability in a durability test;
(3) the fuel cell provided by the invention has longer service life and can meet the requirement of high-power output, and the peak power of the fuel cell can reach 1.8w/cm2Meanwhile, the method is easy for batch production, has low production cost, can promote the industrialization process of the fuel cell, and has wide application prospect.
Drawings
FIG. 1 is an I-V test curve for a catalyst assembled cell prepared in example 1.
Detailed Description
The following further describes the technical means of the present invention to achieve the predetermined technical effects by means of embodiments with reference to the accompanying drawings, and the embodiments of the present invention are described in detail as follows.
Example 1
In the nitrogen-doped carbon-supported platinum-based catalyst provided in this embodiment, the mass fraction of platinum is 87% based on 100% of the mass of the nitrogen-doped carbon-supported platinum-based catalyst; the mass fraction of nitrogen is 6.3% based on 100% of the mass of the nitrogen-doped carbon material;
the preparation method of the nitrogen-doped carbon-supported platinum-based catalyst comprises the following steps:
1) weighing 1g of polyacrylonitrile powder into a conical flask, adding 5mLN, N-dimethylformamide, carrying out oil bath at 60 ℃, stirring for 4 hours until the polyacrylonitrile powder is uniform, then pumping the polyacrylonitrile powder solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 15kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 5h of electrostatic spinning process, taking down the obtained fiber membrane from a receiver, transferring the fiber membrane into a tubular furnace, firstly heating to 250 ℃ at the speed of 5 ℃/min in nitrogen, keeping for 2h, continuously heating to 500 ℃ at the speed of 2 ℃/min, staying for 0.5h, and then naturally cooling under the atmosphere protection until the material is taken out for later use at room temperature;
3) weighing 0.01g of the nitrogen-doped carbon material prepared in the step 2), adding 600 mu L of concentrated ammonia water into a round-bottom flask, ultrasonically homogenizing for 10min, then rapidly adding 6.7mL of chloroplatinic acid aqueous solution with the concentration of 0.01g/mL (containing platinum content) under the condition of vigorous stirring, rapidly adding 1mL of 80mg/mL sodium borohydride aqueous solution at 25 ℃ after stirring for 20min, vigorously stirring for 2h, then adding 100.5mg of ascorbic acid into the mixture, and refluxing for 12h in an oil bath at 90 ℃;
4) and (3) collecting a reaction product in a centrifugal mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at the temperature of 80 ℃ for 6 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
The nitrogen-doped carbon-supported platinum-based catalyst prepared in example 1 was subjected to single cell preparation: weighing 0.12g of the catalyst prepared in the example 1, adding 1mL of water for soaking, adding 56mL of isopropanol and 23mL of ethanol, ultrasonically stirring for 20min, then adding 5% Nafion solution 1350ul, continuously ultrasonically stirring for 30min under the protection of nitrogen for 60min, and crushing cells for 10 min; CCM is prepared by ultrasonic spraying, the proton membrane is Goll enhanced 18um, and the anode Pt loading capacity is 0.10mg/cm2Cathode at 0.4mg/cm2The carbon paper is SGL 29BC, and the effective area of the membrane electrode is 5 multiplied by 10cm2And edge sealing is carried out on the single cell, and single cell manufacturing is carried out.
Among them, the test cell temperature was 75 ℃, the humidification temperature was 70 ℃, the relative humidity was 60% RH, the stoichiometric ratio hydrogen/air was 1.2/2.2, and the back pressure was 0.1Mpa, and the test results are shown in fig. 1, from which it can be seen that the power characteristics of the single cell prepared by example 1 are good, and the current density was up to 650mA/cm at a voltage of 0.8V, and the current density was up to 650mA/cm2When the voltage is 0.6V, the current density can reach 3000mA/cm2The peak power density is as high as 1.8W/cm2。
Example 2
In the nitrogen-doped carbon-supported platinum-based catalyst provided in this embodiment, the mass fraction of platinum is 70% based on 100% of the mass of the nitrogen-doped carbon-supported platinum-based catalyst; the mass fraction of nitrogen is 8.2% based on 100% of the mass of the nitrogen-doped carbon material;
the preparation method of the nitrogen-doped carbon-supported platinum-based catalyst comprises the following steps:
1) weighing 5g of polyvinylpyrrolidone into a conical flask, adding 50mL of ethanol, carrying out oil bath at 120 ℃ and stirring for 2h, then pumping the polyvinylpyrrolidone solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 20kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 10h of electrostatic spinning process, taking down the obtained particle film from a receiver, transferring the particle film to a tubular furnace, calcining the particle film at high temperature under the protection of nitrogen atmosphere, maintaining the material in a good shape through stepwise temperature rise, firstly raising the temperature to 250 ℃ at the speed of 2 ℃/min, keeping the temperature for 2h, continuing raising the temperature to 1200 ℃ at the speed of 2 ℃/min, staying for 8h, and then naturally lowering the temperature under the protection of atmosphere until the material is taken out for later use;
3) weighing 1g of the nitrogen-doped carbon material prepared in the step 2), adding 8.64g of ammonium carbonate and 5mL of water into a round-bottom flask, ultrasonically homogenizing for 10min, then rapidly adding 23.3mL of platinum nitrate aqueous solution with the concentration of 0.1g/mL (containing platinum content) under the condition of vigorous stirring, rapidly adding 9.7mL of 80mg/mL sodium borohydride aqueous solution at 60 ℃ after stirring for 45min, vigorously stirring for 0.5h, then adding 8.2g of ascorbic acid into the mixture, and refluxing for 6h in 135 ℃ oil bath;
4) and collecting a reaction product by a suction filtration mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at 100 ℃ for 5 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Example 3
In the nitrogen-doped carbon-supported platinum-based catalyst provided in this embodiment, the mass fraction of platinum is 60% based on 100% of the mass of the nitrogen-doped carbon-supported platinum-based catalyst; the mass fraction of nitrogen is 7% based on 100% of the mass of the nitrogen-doped carbon material;
the preparation method of the nitrogen-doped carbon-supported platinum-based catalyst comprises the following steps:
1) weighing 3.5g of polyurethane powder in a conical flask, adding 38mL of dimethyl sulfoxide, stirring for 2h at 100 ℃ in an oil bath, pumping the polyurethane solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 15kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 8 hours of electrostatic spinning process, taking down the obtained particle film from a receiver, transferring the particle film to a tubular furnace, calcining the particle film at high temperature under the protection of nitrogen atmosphere, maintaining the material in a good shape through stepwise temperature rise, firstly raising the temperature to 250 ℃ at the speed of 5 ℃/min, keeping the temperature for 2 hours, continuing raising the temperature to 900 ℃ at the speed of 2 ℃/min, staying for 2 hours, and then naturally lowering the temperature under the protection of nitrogen atmosphere until the material is taken out for later use;
3) weighing 0.8g of the nitrogen-doped carbon material prepared in the step 2), adding 13.98g of ammonium bicarbonate into a round-bottom flask, adding 5mL of water, ultrasonically homogenizing for 10min, then quickly adding 12mL of tetrammine platinum chloride aqueous solution with the concentration of 0.1g/mL (containing platinum) under the condition of vigorous stirring, stirring for 45min, quickly adding 10mL of 80mg/mL of sodium borohydride aqueous solution at 35 ℃, vigorously stirring for 0.5h, then adding 4.3g of ascorbic acid into the mixture, and refluxing for 12h in 120 ℃ oil bath;
4) and collecting a reaction product by a suction filtration mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at 100 ℃ for 8 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Example 4
In the nitrogen-doped carbon-supported platinum-based catalyst provided in this embodiment, the mass fraction of platinum is 50% based on 100% of the mass of the nitrogen-doped carbon-supported platinum-based catalyst; the mass fraction of nitrogen is 1.2% based on 100% of the mass of the nitrogen-doped carbon material;
the preparation method of the nitrogen-doped carbon-supported platinum-based catalyst comprises the following steps:
1) weighing 3.5g of polyimide in a conical flask, adding 38mL of acetone, carrying out oil bath at 100 ℃ and stirring for 2h, then pumping the polyimide solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 18kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning under the voltage;
2) after 8 hours of electrostatic spinning process, taking down the obtained particle film from a receiver, transferring the particle film to a tubular furnace, calcining the particle film at high temperature under the protection of nitrogen atmosphere, maintaining the material in a good shape through stepwise temperature rise, firstly raising the temperature to 250 ℃ at the speed of 2 ℃/min, keeping the temperature for 2 hours, continuing raising the temperature to 700 ℃ at the speed of 2 ℃/min, staying for 3 hours, and then naturally lowering the temperature under the protection of nitrogen atmosphere until the material is taken out for later use;
3) weighing 0.6g of the nitrogen-doped carbon material prepared in the step 2), adding 6g of urea into a round-bottom flask, adding 7.5mL of water, ultrasonically homogenizing for 10min, then rapidly adding 6mL of potassium hexachloroplatinate aqueous solution with the concentration of 0.1g/mL (containing platinum content) under the condition of vigorous stirring, rapidly adding 8mL of 80mg/mL sodium borohydride aqueous solution at 35 ℃ after stirring for 45min, vigorously stirring for 0.5h, then adding 4.3g of ascorbic acid into the solution, and refluxing for 12h in 120 ℃ oil bath;
4) and collecting a reaction product by a suction filtration mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at 100 ℃ for 8 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Example 5
In the nitrogen-doped carbon-supported platinum-based catalyst provided in this embodiment, the mass fraction of platinum is 60% based on 100% of the mass of the nitrogen-doped carbon-supported platinum-based catalyst; the mass fraction of nitrogen is 2.1% based on 100% of the mass of the nitrogen-doped carbon material;
the preparation method of the nitrogen-doped carbon-supported platinum-based catalyst comprises the following steps:
1) weighing 4g of polyvinylpyrrolidone into a conical flask, adding 20mL of ethanol and 20mL of N, N-dimethylformamide, stirring for 2h at 120 ℃ in an oil bath, then pumping the polyvinylpyrrolidone solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 20kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 8 hours of electrostatic spinning process, taking down the obtained particle film from a receiver, transferring the particle film to a tubular furnace, calcining the particle film at high temperature under the protection of nitrogen atmosphere, maintaining the material in a good shape through stepwise temperature rise, firstly raising the temperature to 250 ℃ at the speed of 2 ℃/min, keeping the temperature for 2 hours, continuing raising the temperature to 1200 ℃ at the speed of 2 ℃/min, staying for 8 hours, and then naturally lowering the temperature under the protection of atmosphere until the material is taken out for later use;
3) weighing 1g of the nitrogen-doped carbon material prepared in the step 2), adding 4.0g of ammonium carbonate and 4.5g of ammonium bicarbonate into a round-bottom flask, adding 6mL of water, ultrasonically homogenizing for 10min, then rapidly adding 15mL of platinum nitrate aqueous solution with the concentration of 0.1g/mL (containing platinum content) under the condition of vigorous stirring, rapidly adding 10mL of 80mg/mL of sodium borohydride aqueous solution at 25 ℃ after stirring for 45min, vigorously stirring for 0.5h, then adding 4.8g of ascorbic acid into the mixture, and refluxing for 6h in an oil bath at 120 ℃;
4) and collecting a reaction product by a suction filtration mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at 100 ℃ for 5 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Example 6
In the nitrogen-doped carbon-supported platinum-based catalyst provided in this example, the mass fraction of platinum is 66.7% based on 100% of the mass of the nitrogen-doped carbon-supported platinum-based catalyst; the mass fraction of nitrogen is 8.3% based on 100% of the mass of the nitrogen-doped carbon material;
the preparation method of the nitrogen-doped carbon-supported platinum-based catalyst comprises the following steps:
1) weighing 5g of polyvinylpyrrolidone into a conical flask, adding 20mL of acetone and 20mL of dimethyl sulfoxide, carrying out oil bath at 80 ℃, stirring for 3h, then pumping polyvinylpyrrolidone solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 18kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning under the voltage;
2) after the electrostatic spinning process of 9h, taking down the obtained particle film from a receiver, transferring the particle film into a tubular furnace, calcining the particle film at high temperature under the protection of ammonia gas, maintaining the material in a good shape through stepwise temperature rise, firstly raising the temperature to 250 ℃ at the speed of 1 ℃/min, keeping the temperature for 2h, continuing raising the temperature to 1000 ℃ at the speed of 7 ℃/min, staying for 7h, and then naturally lowering the temperature under the protection of ammonia gas until the material is taken out for later use;
3) weighing 0.1g of the nitrogen-doped carbon material prepared in the step 2), adding 1g of ammonium carbonate and 1g of ammonium bicarbonate into a round-bottom flask, adding 8mL of water, ultrasonically homogenizing for 10min, then rapidly adding 2mL of platinum nitrate aqueous solution with the concentration of 0.1g/mL (containing platinum content) under the condition of vigorous stirring, stirring for 45min, rapidly adding 12.5mL of 80mg/mL of sodium borohydride aqueous solution at 25 ℃, vigorously stirring for 0.5h, then adding 1.2g of ascorbic acid into the mixture, and refluxing for 6h in 150 ℃ oil bath;
4) and (3) collecting a reaction product by a suction filtration mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at the temperature of 60 ℃ for 10 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Example 7
In the nitrogen-doped carbon-supported platinum-based catalyst provided in this embodiment, the mass fraction of platinum is 75% based on 100% of the mass of the nitrogen-doped carbon-supported platinum-based catalyst; the mass fraction of nitrogen is 5.8% based on 100% of the mass of the nitrogen-doped carbon material;
the preparation method of the nitrogen-doped carbon-supported platinum-based catalyst comprises the following steps:
1) weighing 1g of polyacrylonitrile powder into a conical flask, adding 5mLN, N-dimethylformamide, carrying out oil bath at 60 ℃, stirring for 4 hours until the polyacrylonitrile powder is uniform, then pumping the polyacrylonitrile powder solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 15kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 5h of electrostatic spinning process, taking down the obtained fiber membrane from a receiver, transferring the fiber membrane into a tubular furnace, firstly heating to 250 ℃ at the speed of 5 ℃/min in nitrogen, keeping for 2h, continuously heating to 900 ℃ at the speed of 2 ℃/min, staying for 0.5h, and then naturally cooling under the atmosphere protection until the material is taken out for later use at room temperature;
3) weighing 0.025g of the nitrogen-doped carbon material prepared in the step 2), adding 550 mu L of concentrated ammonia water into a round-bottom flask, ultrasonically homogenizing for 10min, then rapidly adding 7.5mL of chloroplatinic acid aqueous solution with the concentration of 0.01g/mL (platinum content) under the condition of vigorous stirring, rapidly adding 2.5mL of 50mg/mL sodium borohydride aqueous solution at 25 ℃ after stirring for 20min, vigorously stirring for 2h, then adding 200mg of dimethylformamide into the mixture, and refluxing the oil bath at 110 ℃ for 12 h;
4) and (3) collecting a reaction product in a centrifugal mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at the temperature of 80 ℃ for 6 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Example 8
In the nitrogen-doped carbon-supported platinum-based catalyst provided in this embodiment, the mass fraction of platinum is 55% based on 100% of the mass of the nitrogen-doped carbon-supported platinum-based catalyst; the mass fraction of nitrogen is 4.2% based on 100% of the mass of the nitrogen-doped carbon material;
the preparation method of the nitrogen-doped carbon-supported platinum-based catalyst comprises the following steps:
1) weighing 1g of polyacrylonitrile powder into a conical flask, adding 5mLN, N-dimethylformamide, carrying out oil bath at 60 ℃, stirring for 4 hours until the polyacrylonitrile powder is uniform, then pumping the polyacrylonitrile powder solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 15kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 5h of electrostatic spinning process, taking down the obtained fiber membrane from a receiver, transferring the fiber membrane into a tubular furnace, firstly heating to 250 ℃ at the speed of 5 ℃/min in nitrogen, keeping for 2h, continuously heating to 1200 ℃ at the speed of 2 ℃/min, staying for 0.5h, and then naturally cooling under the atmosphere protection until the material is taken out for later use at room temperature;
3) weighing 0.18g of the nitrogen-doped carbon material prepared in the step 2), adding 2g of urea into a round-bottom flask, ultrasonically homogenizing for 10min, then rapidly adding 22mL of chloroplatinic acid aqueous solution with the concentration of 0.01g/mL (containing platinum content) under the condition of vigorous stirring, rapidly adding 8.64mL of potassium borohydride aqueous solution with the concentration of 250mg/mL at 25 ℃ after stirring for 20min, vigorously stirring for 2h, adding 220mg of formaldehyde, and refluxing for 12h in an oil bath at 80 ℃;
4) and (3) collecting a reaction product in a centrifugal mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at the temperature of 80 ℃ for 6 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Comparative example 1
Compared with example 1, the difference is that the comparative example does not add a second reducing agent, ascorbic acid, in step (3), and specifically comprises the following steps:
1) weighing 1g of polyacrylonitrile powder in a conical flask, adding 5mLN, N-dimethylformamide, stirring at 60 ℃ for 4 hours until the polyacrylonitrile powder is uniform, then pumping polyacrylonitrile solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 15kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 5 hours of electrostatic spinning process, taking down the obtained fiber membrane from a receiver, transferring the fiber membrane into a tubular furnace, calcining the fiber membrane at high temperature under the protection of nitrogen, maintaining the material in a good shape through stepwise temperature rise, firstly raising the temperature to 250 ℃ at the speed of 5 ℃/min, keeping the temperature for 2 hours, continuing raising the temperature to 500 ℃ at the speed of 2 ℃/min, staying for 0.5 hour, and then naturally cooling the fiber membrane under the protection of atmosphere until the temperature of the fiber membrane is room temperature, and taking out the fiber membrane for later use;
3) weighing 0.01g of the nitrogen-doped carbon material prepared in the step 2), adding 600 mu L of concentrated ammonia water into a round-bottom flask, ultrasonically homogenizing for 10min, then quickly adding 6.7mL of chloroplatinic acid aqueous solution with the concentration of 0.01g/mL (containing platinum content) under the condition of vigorous stirring, stirring for 20min, then quickly adding 1mL of 80mg/mL sodium borohydride aqueous solution at 25 ℃, and vigorously stirring for 2 h;
4) and (3) collecting a reaction product in a centrifugal mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at the temperature of 80 ℃ for 6 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Comparative example 2
Compared with example 1, the difference is that in the present comparative example, no first reducing agent, sodium borohydride, is added in step 3), and the method specifically comprises the following steps:
1) weighing 1g of polyacrylonitrile powder in a conical flask, adding 5mLN, N-dimethylformamide, stirring at 60 ℃ for 4 hours until the polyacrylonitrile powder is uniform, then pumping polyacrylonitrile solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 15kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 5h of electrostatic spinning process, taking down the obtained fiber membrane from a receiver, transferring the fiber membrane into a tubular furnace, firstly heating to 250 ℃ at the speed of 5 ℃/min in nitrogen, keeping for 2h, continuously heating to 500 ℃ at the speed of 2 ℃/min, staying for 0.5h, and then naturally cooling under the atmosphere protection until the material is taken out for later use at room temperature;
3) weighing 0.01g of the nitrogen-doped carbon material prepared in the step 2) into a round-bottom flask, adding 600 mu L of concentrated ammonia water, ultrasonically homogenizing for 10min, then adding 100.5mg of ascorbic acid under the condition of vigorous stirring, and refluxing in oil bath at 90 ℃ for 12 h;
4) and (3) collecting a reaction product in a centrifugal mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at the temperature of 80 ℃ for 6 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Comparative example 3
Compared with the embodiment 1, the difference is only that the temperature rising speed in the step 2) is replaced by 10 ℃/min in the comparative example, and the method specifically comprises the following steps:
1) weighing 1g of polyacrylonitrile powder in a conical flask, adding 5mLN, N-dimethylformamide, stirring at 60 ℃ for 4 hours until the polyacrylonitrile powder is uniform, then pumping polyacrylonitrile solution into a spinning nozzle, setting the distance between a spinning head and a receiver to be 20cm, loading 15kV high voltage between the spinning head and the receiver, and carrying out electrostatic spinning at the voltage;
2) after 5h of electrostatic spinning process, taking down the obtained fiber membrane from a receiver, transferring the fiber membrane into a tubular furnace, firstly heating to 250 ℃ at the speed of 10 ℃/min in nitrogen, keeping for 2h, continuously heating to 500 ℃ at the speed of 10 ℃/min, staying for 0.5h, and then naturally cooling under the atmosphere protection until the material is taken out for later use at room temperature;
3) weighing 0.01g of the nitrogen-doped carbon material prepared in the step 2), adding 600 mu L of concentrated ammonia water into a round-bottom flask, ultrasonically homogenizing for 10min, then rapidly adding 6.7mL of chloroplatinic acid aqueous solution with the concentration of 0.01g/mL (containing platinum content) under the condition of vigorous stirring, rapidly adding 1mL of 80mg/mL sodium borohydride aqueous solution at 25 ℃ after stirring for 20min, vigorously stirring for 2h, then adding 100.5mg of ascorbic acid into the mixture, and refluxing for 12h in an oil bath at 90 ℃;
4) and (3) collecting a reaction product in a centrifugal mode, washing the reaction product with deionized water until the reaction product is neutral, and drying the reaction product in a vacuum oven at the temperature of 80 ℃ for 6 hours to obtain the nitrogen-doped carbon-supported platinum-based catalyst.
Performance evaluation of the nitrogen-doped carbon-supported platinum-based catalyst:
the nitrogen-doped carbon-supported platinum-based catalysts prepared in examples 1 to 8 and comparative examples 1 to 3 were subjected to a quality activity test and a durability test on a rotating disk electrode by the following test methods:
quality activity test method: and carrying out LSV test on the material in 0.1M perchloric acid solution, setting a voltage window to be 0.05-1.03V, sweeping speed to be 5mV/s, and sampling point interval to be 1 mV. After obtaining the LSV curve, the mass activity (m) was calculated using the following formulaA)：
Wherein j iskThe current density (mA/cm) was set to 0.9V2) (ii) a j is the limiting current density (mA/cm)2)；LptThe loading amount of platinum (mg) is adopted, and the loading amount of Pt dripped from the glassy carbon electrode tip is 0.005 mg; s is the area of the glassy carbon electrode and is 0.196cm2。
30000 circles Activity test method: the material was subjected to an accelerated CV test in a 0.1M perchloric acid solution at a voltage of 0.6-1.2V, oxygen saturation, a sweep rate of 200mV/s, and a cycle number of 30000 cycles. Mass activity decay was calculated by testing LSV curves before and after 30000 cycles of testing.
The test results are shown in table 1.
TABLE 1
Note: mA/mg in the tablept@0.90V represents the mass activity of the catalyst at a voltage of 0.9V.
The following points can be seen from table 1:
(1) it can be seen from the comprehensive examples 1-8 that in the examples 1-8, the nitrogen-doped carbon material is prepared by adopting electrostatic spinning combined with high-temperature heat treatment, and then the nitrogen-doped carbon supported platinum-based catalyst is prepared by adopting a dual-reducing agent system for reduction, wherein the initial mass activity of the catalyst is 266-302mA/mgpt@0.90V, and the mass activity after 30000 circles is 257-pt@0.90V, thus demonstrating that the nitrogen-doped carbon-supported platinum-based catalysts prepared in examples 1-8 have higher mass activity and better durability;
(2) general examples 1 andas can be seen in comparative example 1, in example 1, sodium borohydride and ascorbic acid are sequentially adopted to prepare the nitrogen-doped carbon-supported platinum-based catalyst through reduction, and the mass activity is 285mA/mgpt@0.90V, and the mass activity after 30000 circles of accelerated durability is 261mA/mgpt@0.90V, the mass activity of which is attenuated by 8 percent, compared with the mass activity of the catalyst obtained in the comparative example 1, which is obtained by only adopting sodium borohydride to reduce and obtain the nitrogen-doped carbon-supported platinum-based catalyst, the mass activity of the catalyst obtained in the comparative example 1 is 185mA/mgpt@0.90V, and the mass activity after 30000 circles of accelerated durability is 98mA/mgpt@0.90V, mass activity of which decays by 47%; the initial mass activity of the catalyst prepared in example 1 is 1.5 times that of comparative example 2, and the mass activity after 30000 cycles is 2.66 times that of comparative example 2, thereby showing that the performance of the nitrogen-doped carbon-supported platinum-based catalyst prepared in example 1 by reduction using sodium borohydride and ascorbic acid is superior to that of the nitrogen-doped carbon-supported platinum-based catalyst prepared in comparative example 1 by reduction using only sodium borohydride;
(3) as can be seen from the combination of example 1 and comparative example 2, in example 1, the nitrogen-doped carbon-supported platinum-based catalyst is prepared by sequentially reducing sodium borohydride and ascorbic acid, and compared with the nitrogen-doped carbon-supported platinum-based catalyst prepared by reducing only ascorbic acid in comparative example 2, the initial mass activity of the catalyst prepared in comparative example 2 is 155mA/mgpt@0.90V, and the mass activity after 30000 circles of accelerated durability is 73mA/mgpt@0.90V, with a mass activity decay of 53%; the initial mass activity of the catalyst prepared in example 1 is 1.84 times that of comparative example 2, and the mass activity after 30000 circles is 3.58 times that of comparative example 2, thereby showing that the performance of the nitrogen-doped carbon-supported platinum-based catalyst prepared in example 1 by reduction with sodium borohydride and ascorbic acid is superior to the performance of the nitrogen-doped carbon-supported platinum-based catalyst prepared in comparative example 2 by reduction with ascorbic acid only;
(4) it can be seen from the combination of example 1 and comparative example 3 that in example 1, the temperature is raised to 250 ℃ at a rate of 5 ℃/min, then raised to 500 ℃ at a rate of 2 ℃/min, and compared with comparative example 3, the temperature is raised to 250 ℃ at a rate of 10 ℃/min, then raised to 500 ℃ at a rate of 10 ℃/min, the initial mass activity of the catalyst obtained in comparative example 3 is 135mA/mgpt@0.90V, and the mass activity after 30000 circles of accelerated durability is 62mA/mgpt@0.90V, mass activity decay thereofDecreasing by 54 percent; the initial mass activity of the catalyst prepared in example 1 was 2.11 times that of comparative example 3, and the mass activity after 30000 cycles was 4.21 times that of comparative example 3, thus demonstrating that the performance of the catalyst prepared in example 1 using a stepwise low temperature rise rate for preparing the nitrogen-doped carbon-supported platinum-based catalyst is superior to the performance of the catalyst prepared in comparative example 3 using a stepwise high temperature rise rate for obtaining the nitrogen-doped carbon-supported platinum-based catalyst.
In summary, the preparation method provided by the invention is based on the electrostatic spinning technology, completes the preparation of the nitrogen-doped carbon material by combining with the high-temperature calcination heat treatment, and reduces the platinum precursor into the nano particles to modify the surface of the nitrogen-doped carbon material by combining with the use of the dual reducing agents, so as to obtain the nitrogen-doped carbon-supported platinum-based catalyst. The introduction of nitrogen atoms increases the electronic conductivity of the catalyst; the platinum nanoparticles are uniformly distributed, the active crystal faces are more exposed, and the platinum nanoparticles and the active crystal faces act synergistically to enable reactants to react on the surface of the catalyst, so that internal electrons are rapidly led out, the electrons and holes are not easy to combine after being separated, the catalytic efficiency of the material is greatly improved, the stability and durability of the catalyst are improved, the mass activity is attenuated by about 8% after 30000 circles, the service life of a fuel cell containing the catalyst is long, the requirement of high-power output can be met, and the application value is high.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A preparation method of a nitrogen-doped carbon-supported platinum-based catalyst is characterized by comprising the following steps:
(1) carrying out electrostatic spinning on the polymer solution to prepare a carbon material precursor;
(2) carrying out heat treatment on the carbon material precursor obtained in the step (1) in a nitrogen-containing atmosphere to obtain a nitrogen-doped carbon material;
(3) mixing the nitrogen-doped carbon material obtained in the step (2) with a platinum precursor solution, sequentially adding a first reducing agent and a second reducing agent to perform primary reduction and secondary reduction, separating and drying to obtain the nitrogen-doped carbon-supported platinum-based catalyst;
wherein the reducibility of the first reducing agent > the reducibility of the second reducing agent.
2. The production method according to claim 1, wherein the first reducing agent comprises sodium borohydride and/or potassium borohydride;
preferably, the second reducing agent comprises any one of ascorbic acid, formaldehyde or dimethylformamide or a combination of at least two thereof;
preferably, the mass ratio of the nitrogen-doped carbon material, the first reducing agent and the second reducing agent is 1 (0.5-10) to (3-15), preferably 1 (0.55-8) to (3-10).
3. The preparation method according to claim 1, wherein the polymer in step (1) comprises any one or a combination of at least two of polyacrylonitrile, polyvinylpyrrolidone, polyurethane or polyimide;
preferably, the solvent of the polymer solution in the step (1) comprises any one or a combination of at least two of ethanol, N-dimethylformamide, dimethyl sulfoxide or acetone;
preferably, the polymer solution in step (1) is heated to 60-120 ℃ during the formulation process;
preferably, the mass ratio of the polymer to the solvent in the polymer solution in the step (1) is 0.05-0.5:1, preferably 0.08-0.3: 1.
4. The production method according to claim 1, wherein the voltage of the electrospinning in the step (1) is 5 to 30kV, preferably 15 to 20 kV;
preferably, the carbon material precursor is a nanofiber film or a nanoparticle film.
5. The preparation method according to claim 1, wherein the temperature of the heat treatment in step (2) is 500-1200 ℃, preferably 600-900 ℃;
preferably, the heating mode of the heat treatment is a step-type heating;
preferably, the step number of the step-type temperature rise is more than or equal to 2, and preferably is 2;
preferably, the step-wise temperature rising procedure with the step number of 2 is as follows: first stage heating to temperature T1Time of heat preservation t1In the second stage, the temperature is raised to the temperature T2Time of heat preservation t2；
Preferably, said temperature T1200 ℃ and 300 ℃;
preferably, said time t1Is 1.5 to 2.5 hours;
preferably, said temperature T2500 ℃ and 1200 ℃;
preferably, said time t2Is 0.5 to 8 hours, preferably 1 to 2 hours;
preferably, the temperature rising speed of the first stage and the second stage is 1-7 ℃/min independently, preferably 2-5 ℃/min;
preferably, the gas of the nitrogen-containing atmosphere is nitrogen and/or ammonia.
6. The production method according to claim 1, wherein the precursor of platinum in step (3) comprises any one or a combination of at least two of chloroplatinic acid, potassium tetrachloroplatinate, potassium hexachloroplatinate, platinum acetylacetonate, platinum nitrate and tetraammineplatinum chloride;
preferably, the mixing in step (3) is performed by stirring and/or ultrasound;
preferably, a buffer substance is added before the first reducing agent is added in step (3);
preferably, the buffer substance comprises any one of ammonia, ammonium carbonate, ammonium bicarbonate or urea or a combination of at least two of the two;
preferably, the mass ratio of the nitrogen-doped carbon material to the platinum in the platinum precursor to the buffer substance is 1 (1-7): 5-20, preferably 1 (1.5-6.5): 5-17.5.
7. The production method according to claim 1, wherein the first reducing agent and the second reducing agent are added in step (3) in the following manner:
rapidly adding a first reducing agent under the condition of vigorous stirring, vigorously stirring for 0.5-2h at the temperature of 25-60 ℃, and then adding a second reducing agent;
preferably, the mode of the primary reduction and the secondary reduction in the step (3) is reflux;
preferably, the secondary reduction in step (3) is carried out in an oil bath;
preferably, the temperature of the secondary reduction in step (3) is 80-150 ℃, preferably 90-135 ℃;
preferably, the time for the secondary reduction in the step (3) is 6-12 h;
preferably, the separation mode in the step (3) comprises any one or combination of at least two of centrifugation, suction filtration, pressure filtration or filtration;
preferably, the solid phase obtained by the separation in step (3) is washed to neutrality;
preferably, the drying temperature in the step (3) is 60-100 ℃;
preferably, the drying time in the step (3) is 5-10 h.
8. The method for preparing a polymer according to any one of claims 1 to 7, comprising the steps of:
(1) weighing polymer powder in a conical flask, adding a solvent, controlling the mass ratio of the polymer to the solvent to be 0.05-0.5:1, heating and stirring at 60-120 ℃ to prepare a spinning precursor solution, pumping the spinning precursor solution into a spinning nozzle, loading 5-30kV high pressure between the spinning nozzle and a receiver, splitting a Taylor cone formed by the polymer solution at the nozzle under the high pressure condition to form a nano fiber film or a nano particle film, and spraying the nano fiber film or the nano particle film on the receiver;
the polymer comprises any one or the combination of at least two of polyacrylonitrile, polyvinylpyrrolidone, polyurethane or polyimide;
the solvent comprises any one or the combination of at least two of ethanol, N-dimethylformamide, dimethyl sulfoxide or acetone;
(2) taking the nanofiber membrane or the nanoparticle membrane obtained in the step (1) down from the receiver, transferring the nanofiber membrane or the nanoparticle membrane into a tubular furnace, heating the nanofiber membrane or the nanoparticle membrane to 500-1200 ℃ at a heating rate of 1-10 ℃/min in a nitrogen-containing atmosphere, calcining the nanofiber membrane or the nanoparticle membrane for 0.5-8h, and then naturally cooling the nanofiber membrane or the nanoparticle membrane under the protection of the atmosphere to obtain a nitrogen-doped carbon material;
(3) placing the nitrogen-doped carbon material prepared in the step (2) into a round-bottom flask, adding a buffer substance, uniformly dispersing under the condition of an ultrasonic homogenizer, rapidly adding a platinum precursor solution under the condition of later vigorous stirring, controlling the mass ratio of platinum and the buffer substance in the nitrogen-doped carbon material and the platinum precursor to be 1 (1-7) to (5-20), stirring, rapidly adding a first reducing agent, vigorously stirring at 25-60 ℃ for 0.5-2h, adding a second reducing agent, and carrying out oil bath reflux at 90-135 ℃ for 6-12h, and controlling the mass ratio of the nitrogen-doped carbon material, the first reducing agent and the second reducing agent to be 1 (0.5-10) to (3-15);
the buffer substance comprises any one or the combination of at least two of ammonia water, ammonium carbonate, ammonium bicarbonate or urea;
the precursor of the platinum comprises any one or the combination of at least two of chloroplatinic acid, potassium tetrachloroplatinate, potassium hexachloroplatinate, platinum acetylacetonate, platinum nitrate or tetraammineplatinum chloride;
the first reducing agent comprises sodium borohydride and/or potassium borohydride;
the second reducing agent comprises any one or the combination of at least two of ascorbic acid, formaldehyde or dimethylformamide;
(4) separating reactants in the step (3), washing a solid phase obtained by separation with deionized water to be neutral, and drying in a vacuum oven at 60-100 ℃ for 5-10h to obtain the nitrogen-doped carbon-supported platinum-based catalyst;
the separation mode comprises any one or the combination of at least two of centrifugation, suction filtration, filter pressing and filtration.
9. The nitrogen-doped carbon-supported platinum-based catalyst prepared by the preparation method according to any one of claims 1 to 8, wherein the mass fraction of platinum is 60 to 90% based on 100% by mass of the catalyst;
preferably, the mass fraction of nitrogen is 1-10% based on 100% of the mass of the nitrogen-doped carbon material.
10. A fuel cell comprising the nitrogen-doped carbon-supported platinum-based catalyst according to claim 9.
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