A catalyst, a method for preparing the same, and a fuel cell

Abstract

The application discloses a catalyst, a preparation method thereof and a fuel cell, and the catalyst comprises an inner core and a shell coated on the surface of the inner core, the inner core is a composite of a PtM alloy and C, and the shell is a nitrogen-doped carbon layer, and M single atoms are distributed in the nitrogen-doped carbon layer; wherein, M is a non-noble metal. The catalyst has stable structure, rich active sites and excellent ORR catalytic activity, and the mass activity of the catalyst is superior to that of unmodified commercial platinum carbon, and the catalyst has excellent cycle stability, and the mass activity of the catalyst after being cycled at a low potential for a period of time is higher than the initial mass activity; in addition, when the catalyst is used in the fuel cell, the power density and stability of the fuel cell can be improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and relates to a catalyst, a preparation method thereof and a fuel cell. BACKGROUND

[0002] A proton exchange membrane fuel cell is a device capable of directly converting chemical energy into electrical energy, and has advantages of high energy conversion rate and clean product. In the energy conversion process, the oxygen reduction reaction (ORR) at the cathode is an important reaction process of the whole system, and the four-electron transfer process thereof needs a large reaction kinetics, which is several orders of magnitude slower than the hydrogen oxidation reaction at the anode, and thus a large amount of catalyst is needed to accelerate the reaction rate at the cathode.

[0003] Studies have shown that a noble metal platinum-based catalyst (Pt) is the most efficient ORR catalyst. At present, a carbon-supported Pt-based catalyst (Pt / C) is widely used at home and abroad to catalyze ORR and promote the slow kinetics thereof. However, due to the limited reserves and high price of Pt, the Pt / C catalyst accounts for about 50% of the cost of a fuel cell reaction stack, which limits the large-scale application of the Pt / C catalyst. In addition, in the electrocatalytic process, Pt nanoparticles usually undergo dissolution or agglomeration, resulting in poor activity and stability of the platinum-carbon catalyst, and thus modification of the commercial platinum-carbon to improve the catalytic activity and stability thereof is a research focus at present.

[0004] J. Mater. Chem. A, 2022, 10, 7399-7408 reports a method for modifying a commercial platinum-carbon with a transition metal Mn to prepare a Pt3Mn ordered alloy catalyst. The method first reduces a Mn precursor on the commercial platinum-carbon, however, the operation introduces a large amount of diphenyl ether and hexane which are toxic and irritating, and then a Pt3Mn ordered alloy / C catalyst is prepared through high-temperature heat treatment. Compared with the traditional platinum-carbon catalyst, the catalytic activity and stability of the catalyst prepared by the above method are improved to a certain extent, but the electrochemical active area thereof is small, only 44 m 2 / g Pt ; and the stability thereof is poor, and the mass activity thereof decreases by 26.5% after one thousand cycles at a low potential, which is difficult to meet the requirements of commercial application. In addition, the preparation method is complex and is not conducive to mass production.

[0005] CN111129508A discloses a transition metal-doped platinum-carbon catalyst, a preparation method and use thereof. A perfluorosulfonic acid is coated on the prepared transition metal-doped platinum-carbon catalyst to form a continuous proton-conducting surface network. Coating the perfluorosulfonic acid can significantly improve the proton transfer speed, thereby improving the current density and the service life of the membrane electrode. However, the catalytic activity of the catalyst prepared by the present application is poor, and the preparation process is complex, and a strong reducing agent and inert gas protection are required for the reaction, which is not conducive to industrialization.

[0006] CN111584888A discloses a preparation method of a silicon dioxide doped / coated platinum carbon catalyst, the Pt / C catalyst is uniformly dispersed by ultrasonic in ultrapure water to obtain a Pt / C catalyst suspension; the pH value of the Pt / C catalyst suspension is adjusted to be alkaline; under the conditions of oil bath heating and stirring, a mixture of tetraethyl orthosilicate solution and ethanol is added dropwise to react, centrifuged, washed, freeze-dried and high-temperature calcined to obtain a silicon dioxide doped / coated platinum carbon catalyst. However, the prepared catalyst cannot better improve the power density of the fuel cell when used in the fuel cell.

[0007] Therefore, it is currently an urgent problem to be solved to prepare a catalyst with high catalytic activity, good stability and better improving the power density of the fuel cell. SUMMARY

[0008] In view of the above problems existing in the prior art, the purpose of the present application is to provide a catalyst, a preparation method thereof and a fuel cell.

[0009] To achieve the above purpose, the present application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a catalyst, which comprises an inner core and a shell coated on the surface of the inner core, the inner core is a PtM alloy and C composite, and the shell is a nitrogen-doped carbon layer, and M single atoms are distributed in the nitrogen-doped carbon layer.

[0011] Wherein, M is a non-noble metal.

[0012] The catalyst in the present application has stable structure and rich active sites, the inner core of the catalyst is a PtM alloy and C composite, compared with platinum carbon, the PtM alloy and C composite has stable structure, there is strong interaction between Pt and non-noble metal M, and the addition of M can effectively change the electronic structure and stress effect of Pt, which can effectively improve the activity and cycle stability of the catalyst; in addition, the surface of the inner core is coated with a nitrogen-doped carbon layer, the nitrogen-doped carbon can effectively avoid the agglomeration of the inner core PtM alloy, and can stabilize the M single atoms; M single atoms are distributed in the nitrogen-doped carbon layer, which provides rich catalytic active sites for oxygen reduction reaction (ORR), and interacts with the inner core PtM, which can effectively improve the ORR catalytic activity.

[0013] The catalyst in the present application has excellent ORR catalytic activity, and its mass activity is better than that of unmodified commercial platinum carbon; in addition, the catalyst has excellent cycle stability, and its mass activity is higher than its initial mass activity after being cycled at low potential for a period of time.

[0014] Preferably, in the nitrogen-doped carbon layer, nitrogen atoms form chemical bonds with M monomers.

[0015] The advantage of nitrogen atoms forming chemical bonds with M monomers is that new active sites can be created and the dissolution of M can be effectively prevented.

[0016] Preferably, the non-noble metal comprises at least one of Fe, Co, Ni, Cu or Mn.

[0017] Preferably, the content of the inner core in the catalyst is 75wt%-95wt%, for example 75wt%, 80wt%, 85wt%, 90wt% or 95wt%, based on the total mass of the catalyst being 100wt%.

[0018] In the present application, when the content of the inner core in the catalyst is too high, the catalyst will agglomerate, which is not conducive to the exposure of active sites and is relatively high in cost; when the content of the inner core in the catalyst is too low, the catalyst has fewer active sites, which is not conducive to the catalysis of ORR.

[0019] Preferably, the content of the nitrogen-doped carbon layer in the catalyst is 5wt%-25wt%, for example 5wt%, 10wt%, 15wt%, 20wt% or 25wt%, based on the total mass of the catalyst being 100wt%.

[0020] In the present application, when the content of the nitrogen-doped carbon layer in the catalyst is too high, it is not conducive to the exposure and effective use of active sites; when the content of the nitrogen-doped carbon layer in the catalyst is too low, it is difficult to protect the inner shell PtM and improve the stability of the catalyst.

[0021] In a second aspect, the present application provides a preparation method of the catalyst according to the first aspect, the method comprising the following steps:

[0022] (1) mixing Pt / C, a salt containing M and a nitrogen-containing organic complex in a solvent, and drying to prepare a precursor material;

[0023] (2) heat-treating the precursor material of step (1) to prepare the catalyst.

[0024] In the present application, an M-nitrogen-containing organic complex formed by a salt containing M and a nitrogen-containing organic complex is introduced onto the surface of Pt / C by an adsorption method, and then a catalyst with a stable structure is prepared after heat treatment. In addition, the prepared catalyst has abundant active sites and excellent ORR catalytic activity and cycle stability.

[0025] The preparation method in the present application is simple, universal, easy to control and suitable for mass production.

[0026] Preferably, the mass ratio of the Pt / C, the M-containing salt and the nitrogen-containing organic complex in step (1) is 1: (0.001-0.5): (0.001-2), for example, “0.001-0.5” can be 0.001, 0.005, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, 0.3, 0.4 or 0.5, for example, “0.001-2” can be 0.001, 0.005, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8 or 2.0, preferably 1: (0.06-0.4): (0.5-1.5).

[0027] In the present application, too much M-containing salt will cause too much M, leading to agglomeration, which is not conducive to the formation of multiple types of active sites, and too little M-containing salt will not allow M to form stable alloy with Pt, and the number of M single-atom active sites will decrease.

[0028] In the present application, too much nitrogen-containing organic complex will cause the outer shell carbon layer to be too thick, which is not conducive to the exposure of the inner core active sites, and too little nitrogen-containing organic complex will not be conducive to the uniform dispersion of the M-containing salt, making it difficult to form M single-atom active sites.

[0029] Preferably, the M in step (1) is a non-noble metal.

[0030] Preferably, the M includes at least one of Fe, Co, Ni, Cu or Mn.

[0031] Illustratively, the M-containing salt includes, but is not limited to, at least one of a chloride salt, a nitrate salt, an acetate salt, a sulfate salt, an acetylacetone salt or a phthalocyanine salt containing M.

[0032] Preferably, the nitrogen-containing organic complex in step (1) includes at least one of phenanthroline, dopamine or aniline.

[0033] Illustratively, the solvent in step (1) includes, but is not limited to, at least one of deionized water, ultrapure water, isopropyl alcohol or ethanol.

[0034] Preferably, in step (1), the mixing of the Pt / C, the M-containing salt and the nitrogen-containing organic complex in the solvent is carried out in the following manner:

[0035] The M-containing salt and the nitrogen-containing organic complex are first mixed in the solvent, and then the Pt / C is added to form a dispersion.

[0036] In the present application, the M-containing salt and the nitrogen-containing organic complex are mixed in a solvent first, and then the Pt / C is added, which is beneficial to the preferential complexation of the M-containing salt and the nitrogen-containing organic matter and the formation of a coating structure with Pt / C.

[0037] Preferably, the drying method of step (1) comprises at least one of air drying, vacuum drying or freeze drying.

[0038] Illustratively, the drying method comprises, but is not limited to, a combination of freeze drying and vacuum drying or a combination of freeze drying and air drying.

[0039] Illustratively, the temperature of the vacuum drying comprises, but is not limited to, 40-100℃, such as 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃.

[0040] Illustratively, the time of the vacuum drying comprises, but is not limited to, 6-20h, such as 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0041] Illustratively, the time of the freeze drying comprises, but is not limited to, 20-40h, such as 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h or 40h.

[0042] Illustratively, the temperature of the air drying comprises, but is not limited to, 40-100℃, such as 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃.

[0043] Illustratively, the time of the air drying comprises, but is not limited to, 6-20h, such as 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0044] Preferably, the temperature of the heat treatment of step (2) is 300-1200℃, such as 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃ or 1200℃, preferably 500-1000℃.

[0045] In the present application, when the temperature of the heat treatment is high, the metal particles are prone to agglomeration and growth, reducing the number of active sites; when the temperature of the heat treatment is low, it is not conducive to the formation of PtM alloy in the core and the formation of high-graphitized carbon layer in the shell, making the structure unstable and the type of active sites reduced.

[0046] Preferably, the heat treatment in step (2) is performed for 0.5-10 hours, for example 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0047] In the present application, when the heat treatment is performed for a long time, the metal particles are prone to agglomerate and grow, reducing the number of active sites; when the heat treatment is performed for a short time, it is not conducive to the formation of PtM alloy in the core and the formation of high graphitized carbon layer in the shell, resulting in unstable structure and reduced active site types.

[0048] Preferably, the heat treatment in step (2) is performed in a protective atmosphere and / or a reducing atmosphere.

[0049] In one embodiment, the first heat treatment can be performed in a reducing atmosphere, and the second heat treatment can be performed in a protective atmosphere.

[0050] The gas in the reducing atmosphere in the present application can be a single reducing gas, or a mixture of a reducing gas and a protective gas.

[0051] The present application does not limit the type of reducing gas, which can be hydrogen, for example.

[0052] The gas in the protective atmosphere in the present application is a protective gas.

[0053] The present application does not limit the type of protective gas, which includes but is not limited to at least one of argon, nitrogen or ammonia, for example.

[0054] Preferably, the catalyst obtained in step (2) is subjected to acid pickling.

[0055] In the present application, the purpose of acid pickling is to remove impurities and metal oxides on the surface of the catalyst, expose more active sites, and avoid the influence of impurities and metal oxides on the surface of the catalyst on the proton exchange membrane.

[0056] Preferably, the acid used in the acid pickling includes at least one of hydrochloric acid, nitric acid or sulfuric acid.

[0057] The concentration of the acid is 0.1-4M, for example 0.1M, 1M, 1.5M, 2M, 2.5M, 3M, 3.5M or 4M, for example.

[0058] Preferably, the acid pickling is performed for 0.1-24 hours, for example 0.1 hour, 0.5 hour, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours.

[0059] Preferably, the temperature of the acid washing is 20-110℃, such as 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃ or 110℃.

[0060] Exemplarily, the dried catalyst after the acid washing is dried by at least one of the following drying methods, including but not limited to air drying, vacuum drying or freeze drying.

[0061] Exemplarily, the drying method includes but is not limited to a combination of freeze drying and vacuum drying or a combination of freeze drying and air drying.

[0062] Exemplarily, the temperature of the vacuum drying includes but is not limited to 40-100℃, such as 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃.

[0063] Exemplarily, the time of the vacuum drying includes but is not limited to 6-20h, such as 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0064] Exemplarily, the time of the freeze drying includes but is not limited to 20-40h, such as 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h or 40h.

[0065] Exemplarily, the temperature of the air drying includes but is not limited to 40-100℃, such as 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃.

[0066] Exemplarily, the time of the air drying includes but is not limited to 6-20h, such as 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0067] Exemplarily, the dried catalyst after the acid washing is washed with deionized water to neutral and then dried.

[0068] In a third aspect, the present application provides a fuel cell comprising the catalyst according to the first aspect of the present application.

[0069] The fuel cell prepared by using the catalyst according to the first aspect of the present application has higher power density and stability.

[0070] Compared with the prior art, the present application has the following beneficial effects:

[0071] (1) The catalyst in the present application has stable structure, rich active sites and excellent ORR catalytic activity, and the mass activity is superior to that of unmodified commercial platinum carbon, and the catalyst has excellent cycle stability, and the mass activity after cycling at low potential for a period of time is higher than the initial mass activity; in addition, when the catalyst is used in a fuel cell, the power density and stability of the fuel cell can be improved.

[0072] (2) The preparation method in the present application is simple, universal, easy to control and suitable for mass production. BRIEF DESCRIPTION OF DRAWINGS

[0073] Figure 1 Preparation flow chart of the catalyst in an embodiment of the present application;

[0074] Figure 2 Linear sweep voltammetry (LSV) test results of the catalyst in Example 1 before and after cycling;

[0075] Figure 3 LSV test results of the catalyst in Comparative Example 1 before and after cycling;

[0076] Figure 4 Performance test results of the fuel cell prepared by the catalyst in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0077] The technical solutions of the present application will be further described below in combination with the drawings and through specific embodiments.

[0078] The "room temperature" in the embodiments of the present application refers to 25℃.

[0079] In an embodiment, a preparation method of a catalyst is provided, and a preparation flow chart is shown as Figure 1 The method comprises the following steps: mixing a salt containing M, a nitrogen-containing organic complex and Pt / C, uniformly dispersing the mixture, and then preparing the catalyst by one-time drying, heat treatment, acid washing and two-time drying of the dispersion.

[0080] Example 1

[0081] The present embodiment provides a catalyst, the inner core of the catalyst is a composite of PtFe alloy and C (PtFe / C), and the outer shell is a nitrogen-doped carbon layer, and Fe monatomic atoms are dispersed in the nitrogen-doped carbon layer, and the Fe monatomic atoms form chemical bonds with nitrogen, the content of the inner core in the catalyst is 85wt% based on the total mass of the catalyst being 100wt%, and the content of the nitrogen-doped carbon layer in the catalyst is 15wt%.

[0082] The preparation method of the catalyst is as follows:

[0083] (1) 0.06 g of iron chloride and 0.5 g of o-phenanthroline were weighed into a reaction container, 50 mL of ethanol was added thereto to form a Fe-o-phenanthroline complex solution;

[0084] (2) The solution obtained in step (1) and 1 g of commercial platinum carbon Pt / C were mixed, placed in an ultrasonic cleaner for ultrasonic treatment for 25 min to obtain a uniformly dispersed dispersion liquid, and then transferred to a vacuum drying oven for drying at 100°C for 6 h to obtain a precursor material;

[0085] (3) The precursor material obtained in step (2) was transferred to a tube furnace, and heat-treated at 900°C for 0.5 h under nitrogen protection, and then taken out after cooling to room temperature under nitrogen protection to obtain the catalyst;

[0086] (4) The catalyst obtained in step (3) was placed in 0.1 M hydrochloric acid for acid pickling, the acid pickling time was 0.1 h, and the acid pickling temperature was 20°C, and then the product was suction filtered, washed with deionized water until neutral, and transferred to a vacuum drying oven for drying at 100°C for 6 h.

[0087] In this embodiment, the mass ratio of Pt / C, iron chloride and o-phenanthroline is 1:0.06:0.5.

[0088] Example 2

[0089] The catalyst provided in this embodiment has a PtCo alloy and C composite (PtCo / C) as the inner core and a nitrogen-doped carbon layer as the outer shell, Co monomers are dispersed in the nitrogen-doped carbon layer, and the Co monomers form chemical bonds with N. The content of the inner core in the catalyst is 95 wt%, and the content of the nitrogen-doped carbon layer in the catalyst is 5 wt% based on the total mass of the catalyst.

[0090] The preparation method of the catalyst is as follows:

[0091] (1) 0.001 g of cobalt nitrate and 0.005 g of dopamine were weighed into a reaction container, 100 mL of isopropyl alcohol was added thereto to form a Co-dopamine complex solution;

[0092] (2) The solution obtained in step (1) and 1 g of commercial platinum carbon Pt / C were mixed, placed in an ultrasonic cleaner for ultrasonic treatment for 45 min to obtain a uniformly dispersed dispersion liquid, and then transferred to a vacuum drying oven for drying at 90°C for 12 h to obtain a precursor material;

[0093] (3) The precursor material obtained in step (2) was transferred to a tube furnace, and heat-treated at 400°C for 1 h under argon protection, and then taken out after cooling to room temperature under argon protection to obtain the catalyst;

[0094] (4) The catalyst obtained in step (3) is placed in 0.1M sulfuric acid for acid washing, the acid washing time is 1h, the acid washing temperature is 30℃, then the product is suction filtered, washed with deionized water until neutral, and transferred to a vacuum oven for drying at 90℃ for 12h.

[0095] In this embodiment, the mass ratio of Pt / C, cobalt nitrate and dopamine is 1:0.001:0.005.

[0096] Example 3

[0097] This embodiment provides a catalyst, the inner core of the catalyst is a composite of PtNi alloy and C (PtNi / C), the outer shell is a nitrogen-doped carbon layer, and Ni monomers are dispersed in the nitrogen-doped carbon layer, the Ni monomers form chemical bonds with N, the content of the inner core in the catalyst is 78wt% based on the total mass of the catalyst, and the content of the nitrogen-doped carbon layer in the catalyst is 22wt%.

[0098] The preparation method of the catalyst is as follows:

[0099] (1) 0.1g of nickel acetate and 0.6g of aniline are weighed in a reaction container, 150mL of n-octanol is added thereto to form a Ni-aniline complex solution;

[0100] (2) The solution obtained in step (1) and 1g of commercial platinum Pt / C are mixed, placed in an ultrasonic cleaner for continuous ultrasonic for 60min to obtain a uniformly dispersed dispersion liquid, then transferred to a vacuum drying oven for drying at 60℃ for 14h to obtain a precursor material;

[0101] (3) The precursor material obtained in step (2) is transferred to a tube furnace, heated at 500℃ for 3h in a 3% hydrogen-97% argon (volume percentage) atmosphere, then taken out after cooling to room temperature under the protection of a 3% hydrogen-97% argon atmosphere to obtain the catalyst;

[0102] (4) The catalyst obtained in step (3) is placed in 0.1M nitric acid for acid washing, the acid washing time is 4h, the acid washing temperature is 40℃, then the product is suction filtered, washed with deionized water until neutral, and transferred to a vacuum drying oven for drying at 60℃ for 14h.

[0103] In this embodiment, the mass ratio of Pt / C, nickel acetate and aniline is 1:0.1:0.6.

[0104] Example 4

[0105] The embodiment provides a catalyst, the inner core of the catalyst is a composite (PtMn / C) of a PtMn alloy and C, the outer shell is a nitrogen-doped carbon layer, Mn monomers are dispersed in the nitrogen-doped carbon layer, the Mn monomers form chemical bonds with N, the content of the inner core in the catalyst is 77% by weight, and the content of the nitrogen-doped carbon layer in the catalyst is 23% by weight, with the total mass of the catalyst being 100% by weight.

[0106] The preparation method of the catalyst is as follows:

[0107] (1) 0.3 g of manganese acetylacetonate and 0.8 g of o-phenanthroline are weighed in a reaction container, 200 mL of acetone is added to the reaction container, and a Mn-o-phenanthroline complex solution is formed;

[0108] (2) The solution obtained in step (1) and 1 g of commercial platinum carbon Pt / C are mixed, and are continuously stirred on a magnetic stirring table for 3 h to obtain a uniformly dispersed dispersion liquid, and then the dispersion liquid is transferred to a freeze dryer for freeze drying for 20 h to obtain a precursor material;

[0109] (3) The precursor material obtained in step (2) is transferred to a tube furnace, is kept at 600 DEG C for 5 h in a 10% hydrogen-90% nitrogen (volume percentage) atmosphere, and then is taken out after being cooled to room temperature under the protection of a 10% hydrogen-90% nitrogen atmosphere to obtain the catalyst;

[0110] (4) The catalyst obtained in step (3) is placed in 1M hydrochloric acid for acid washing, the acid washing time is 6 h, the acid washing temperature is 50 DEG C, then the product is suction filtered, washed with deionized water until neutral, and transferred to a freeze dryer for freeze drying for 20 h.

[0111] In the embodiment, the mass ratio of Pt / C, manganese acetylacetonate and o-phenanthroline is 1:0.3:0.8.

[0112] Embodiment 5

[0113] The embodiment provides a catalyst, the inner core of the catalyst is a composite (PtMn / C) of a PtMn alloy and C, the outer shell is a nitrogen-doped carbon layer, Mn monomers are dispersed in the nitrogen-doped carbon layer, the Mn monomers form chemical bonds with N, the content of the inner core in the catalyst is 77% by weight, and the content of the nitrogen-doped carbon layer in the catalyst is 23% by weight, with the total mass of the catalyst being 100% by weight.

[0114] The preparation method of the catalyst is as follows:

[0115] (1) 0.5 g of copper sulfate and 1 g of dopamine are weighed in a reaction container, 500 mL of water is added to the reaction container, and a Cu-dopamine complex solution is formed;

[0116] (2) The solution obtained in step (1) and 1 g of commercial platinum carbon Pt / C were mixed, continuously stirred on a magnetic stirrer for 5 h to obtain a uniformly dispersed dispersion liquid, which was then transferred to a freeze dryer and freeze-dried for 30 h to obtain a precursor material;

[0117] (3) The precursor material obtained in step (2) was transferred to a tube furnace, and heat-treated at 700 ℃ for 10 h in an ammonia atmosphere, and then taken out after being cooled to room temperature in an ammonia atmosphere to obtain the catalyst;

[0118] (4) The catalyst obtained in step (3) was placed in 1M sulfuric acid for acid washing, the acid washing time was 8 h, and the acid washing temperature was 60 ℃, and then the product was suction filtered, washed with deionized water until neutral, and transferred to a freeze dryer for freeze-drying for 30 h.

[0119] In this embodiment, the mass ratio of Pt / C, copper sulfate and dopamine is 1:0.5:1.

[0120] Example 6

[0121] The catalyst provided in this embodiment has a PtFeCo alloy and C composite (PtFeCo / C) as the inner core, and a nitrogen-doped carbon layer as the outer shell, wherein Fe single atoms and Co single atoms are dispersed in the nitrogen-doped carbon layer, and the Fe single atoms and the Co single atoms form chemical bonds with N, respectively. The content of the inner core in the catalyst is 75 wt%, and the content of the nitrogen-doped carbon layer in the catalyst is 25 wt% based on the total mass of the catalyst being 100 wt%.

[0122] The preparation method of the catalyst is as follows:

[0123] (1) 0.0001 g of iron phthalocyanine, 0.0009 g of cobalt chloride and 1.8 g of aniline were weighed into a reaction container, and 50 mL of ethanol was added to form a Fe-aniline complex and a Co-aniline complex solution;

[0124] (2) The solution obtained in step (1) and 1 g of commercial platinum carbon Pt / C were mixed, continuously stirred on a magnetic stirrer for 8 h to obtain a uniformly dispersed dispersion liquid, which was then transferred to a freeze dryer and freeze-dried for 40 h to obtain a precursor material;

[0125] (3) The precursor material obtained in step (2) was transferred to a tube furnace, and heat-treated at 800 ℃ for 1 h under a 3% hydrogen-97% argon (volume percentage) atmosphere, and then heat-treated at 800 ℃ for 1 h under a nitrogen atmosphere, and then taken out after being cooled to room temperature under nitrogen protection to obtain the catalyst;

[0126] (4) The catalyst obtained in step (3) is placed in 1M nitric acid for acid washing, the acid washing time is 10h, the acid washing temperature is 70℃, then the product is centrifuged, washed with ultrapure water until neutral, transferred to a freeze dryer for freeze drying for 40h.

[0127] In this embodiment, the mass ratio of the total mass of Pt / C, iron phthalocyanine and cobalt chloride to the mass of aniline is 1:0.001:1.8.

[0128] Example 7

[0129] This embodiment provides a catalyst, the inner core of the catalyst is a composite of PtFeNi alloy and C (PtFeNi / C), the outer shell is a nitrogen-doped carbon layer, Ni monomers and Fe monomers are dispersed in the nitrogen-doped carbon layer, the Ni monomers and the Fe monomers form chemical bonds with N respectively, the content of the inner core in the catalyst is 80wt% based on the total mass of the catalyst, and the content of the nitrogen-doped carbon layer in the catalyst is 20wt%.

[0130] The preparation method of the catalyst is as follows:

[0131] (1) 0.002g of iron nitrate, 0.008g of nickel chloride and 0.3g of o-phenanthroline are weighed in a reaction container, 100mL of isopropyl alcohol is added thereto to form a Fe-o-phenanthroline complex and a Ni-o-phenanthroline complex solution;

[0132] (2) The solution obtained in step (1) and 1g of commercial platinum carbon Pt / C are mixed, placed in an ultrasonic homogenizer for continuous ultrasonic for 25min to obtain a uniformly dispersed dispersion liquid, then transferred to a blast drying oven for drying at 100℃ for 8h to obtain a precursor material;

[0133] (3) The precursor material obtained in step (2) is transferred to a tube furnace, first incubated at 900℃ for 2h under an atmosphere of 10% hydrogen-90% argon (volume percentage), then incubated at 100℃ for 2h under a nitrogen atmosphere, then taken out after cooling to room temperature under the protection of nitrogen to obtain the catalyst;

[0134] (4) The catalyst obtained in step (3) is placed in 4M hydrochloric acid for acid washing, the acid washing time is 12h, the acid washing temperature is 80℃, then the product is centrifuged, washed with ultrapure water until neutral, transferred to a blast drying oven for drying at 90℃ for 8h.

[0135] In this embodiment, the mass ratio of the total mass of Pt / C, iron nitrate and nickel chloride to the mass of o-phenanthroline is 1:0.01:0.3.

[0136] Example 8

[0137] The embodiment provides a catalyst, the inner core of the catalyst is a composite of a PtMnFe alloy and C (PtMnFe / C), the outer shell is a nitrogen-doped carbon layer, Mn monomers and Fe monomers are dispersed in the nitrogen-doped carbon layer, the Mn monomers and the Fe monomers form chemical bonds with N respectively, and the content of the inner core in the catalyst is 77% and the content of the nitrogen-doped carbon layer in the catalyst is 23% according to the total mass of the catalyst being 100 wt%.

[0138] The preparation method of the catalyst is as follows:

[0139] (1) 0.03 g of iron acetate, 0.07 g of manganese chloride and 0.8 g of dopamine are weighed in a reaction container, 150 mL of n-octanol is added to the reaction container to form a Fe-dopamine complex and a Mn-dopamine complex solution;

[0140] (2) the solution obtained in step (1) and 1 g of commercial platinum carbon Pt / C are mixed, and are placed in an ultrasonic homogenizer for ultrasonic treatment for 60 min to obtain a uniformly dispersed dispersion liquid, and then the dispersion liquid is transferred to a blast drying oven for drying at 80 DEG C for 10 h to obtain a precursor material;

[0141] (3) the precursor material obtained in step (2) is transferred to a tube furnace, is first kept at 1000 DEG C for 3 h under a 3% hydrogen-97% nitrogen (volume percentage) atmosphere, is then kept at 1000 DEG C for 3 h under a nitrogen atmosphere, and is taken out after being cooled to room temperature under the protection of nitrogen to obtain the catalyst;

[0142] (4) the catalyst obtained in step (3) is placed in 4M sulfuric acid for acid pickling, the acid pickling time is 14 h, the acid pickling temperature is 90 DEG C, then the product is centrifuged, washed with ultrapure water until neutral, and transferred to a blast drying oven for drying at 80 DEG C for 10 h.

[0143] In the embodiment, the mass ratio of the total mass of Pt / C, iron acetate and manganese chloride to the mass of dopamine is 1:0.1:0.8.

[0144] Embodiment 9

[0145] The embodiment provides a catalyst, the inner core of the catalyst is a composite of a PtMnFe alloy and C (PtMnFe / C), the outer shell is a nitrogen-doped carbon layer, Mn monomers and Fe monomers are dispersed in the nitrogen-doped carbon layer, the Mn monomers and the Fe monomers form chemical bonds with N respectively, and the content of the inner core in the catalyst is 77% and the content of the nitrogen-doped carbon layer in the catalyst is 23% according to the total mass of the catalyst being 100 wt%.

[0146] The preparation method of the catalyst is as follows:

[0147] (1) Take 0.25 g of iron acetylacetonate, 0.25 g of copper chloride and 1 g of aniline in a reaction container, and add 200 mL of acetone thereto to form a Fe-aniline complex and a Cu-aniline complex solution;

[0148] (2) Mix the solution obtained in step (1) and 1 g of commercial platinum carbon Pt / C, first place in an ultrasonic cleaner for continuous ultrasonic for 35 min, then place on a magnetic stirring table for continuous stirring for 5 h, and then transfer to a forced air drying oven for drying at 60 °C for 12 h to obtain a precursor material;

[0149] (3) Transfer the precursor material obtained in step (2) to a tube furnace, first heat at 1100 °C for 4 h under an atmosphere of 10% hydrogen-90% nitrogen (volume percentage), then heat at 1100 °C for 4 h under a nitrogen atmosphere, and then take out after cooling to room temperature under nitrogen protection to obtain the catalyst;

[0150] (4) Place the catalyst obtained in step (3) in 4M nitric acid for acid pickling, the acid pickling time is 16 h and the acid pickling temperature is 100 °C, and then centrifuge the product, wash with ultrapure water until neutral, and transfer to a forced air drying oven for drying at 60 °C for 12 h.

[0151] In this embodiment, the mass ratio of Pt / C, iron acetylacetonate and copper chloride to aniline is 1:0.5:1.

[0152] Example 10

[0153] The catalyst provided in this embodiment has a core of a PtFeCoNi alloy and C composite (PtFeCoNi / C) and a nitrogen-doped carbon layer as a shell, and Ni monomers, Co monomers and Fe monomers are dispersed in the nitrogen-doped carbon layer, and the Ni monomers, Co monomers and Fe monomers form chemical bonds with N, respectively. The content of the core in the catalyst is 77 wt% and the content of the nitrogen-doped carbon layer in the catalyst is 23 wt% based on the total mass of the catalyst being 100 wt%.

[0154] The preparation method of the catalyst is as follows:

[0155] (1) Take 0.1 g of iron sulfate, 0.1 g of cobalt phthalocyanine, 0.1 g of nickel phthalocyanine and 0.8 g of o-phenanthroline in a reaction container, and add 200 mL of water thereto to form a Fe-o-phenanthroline complex, a Co-o-phenanthroline complex and a Ni-o-phenanthroline complex solution;

[0156] (2) The solution obtained in step (1) was mixed with 1 g of commercial platinum carbon Pt / C, and the mixture was first placed in an ultrasonic cleaning machine for continuous ultrasonication for 10 min, and then placed on a magnetic stirring table for continuous stirring for 10 h to obtain a uniformly dispersed dispersion, and then transferred to a blast drying oven at 40° C. and dried for 15 h to obtain a precursor material;

[0157] (3) transferring the precursor material obtained in step (2) into a tube furnace, first keeping the temperature at 1200° C. for 5 h under an ammonia atmosphere, then keeping the temperature at 1200° C. for 5 h under an argon atmosphere, and then taking out the catalyst after cooling it to room temperature under argon protection;

[0158] (4) The catalyst obtained in step (3) was placed in 1M nitric acid for pickling for 24 hours at a temperature of 110°C. The product was then filtered, rinsed with deionized water until neutral, and transferred to a forced air drying oven at 40°C for drying for 15 hours.

[0159] In this embodiment, the mass ratio of the total mass of Pt / C, ferric sulfate, cobalt phthalocyanine and nickel phthalocyanine to o-phenanthroline is 1:0.3:0.8.

[0160] Example 11

[0161] Compared with Example 1, the only difference is that the temperature of the heat treatment in step (3) is 300°C.

[0162] Example 12

[0163] Compared with Example 8, the only difference is that the temperature of the heat treatment in step (3) is 1200°C.

[0164] Example 13

[0165] Compared with Example 3, the only difference is that the mass ratio of Pt / C, nickel acetate and aniline is 1:0.05:0.6.

[0166] Example 14

[0167] Compared with Example 4, the only difference is that the mass ratio of Pt / C, manganese acetylacetonate and o-phenanthroline is 1:0.5:0.8.

[0168] Example 15

[0169] Compared with Example 1, the only difference is that the mass ratio of Pt / C, ferric chloride and o-phenanthroline is 1:0.06:0.4

[0170] Example 16

[0171] Compared with Example 4, the only difference is that the mass ratio of Pt / C, manganese acetylacetonate and o-phenanthroline is 1:0.3:1.8.

[0172] Comparative Example 1

[0173] Comparative Example 1 is commercial platinum carbon Pt / C.

[0174] Comparative Example 2

[0175] Compared with Example 1, the only difference is that no phenanthroline is added in step (1).

[0176] Comparative Example 3

[0177] Compared with Example 1, the only difference is that ferric chloride is not added in step (1).

[0178] Performance testing:

[0179] The catalysts in Examples 1-16 and Comparative Examples 1-3 were subjected to LSV tests. The test parameters were set as follows: scanning voltage of 0.05-1.05V, scanning rate of 5mV / s, rotation speed of 1600 rpm, and oxygen flow. 20mg of the catalyst to be tested was weighed, 5mL of ethanol and 4.9mL of water were added, and ultrasonication was performed for 20min. Then, 0.1mL of a 5% perfluorosulfonic acid solution was added, and ultrasonication was continued for 40min. 10uL of the dispersed slurry was dropped onto the glassy carbon electrode tip, the area of ​​which was 0.196cm 2 The initial mass activity test results at 0.9 V are shown in Table 1.

[0180] Table 1

[0181]

[0182]

[0183] It can be seen from Table 1 that the catalysts prepared in the examples of the present invention have a higher initial mass activity. The mass activity of the catalyst in Example 1 is twice that of the catalyst in Comparative Example 1.

[0184] The LSV test results of the catalyst in Example 1 before and after the cycle are as follows: Figure 2 As shown, the calculated initial mass activity of the catalyst in Example 1 at 0.9 V before cycling was 508 mA / mg. After 30,000 cycles in the voltage range of 0.6-0.95 V, its initial mass activity at 0.9 V was 809 mA / mg, 1.6 times its initial mass activity. This shows that after the cycling test, the mass activity of the catalyst in Example 1 increased significantly, indicating that the catalyst prepared in Example 1 has excellent catalytic performance and durability.

[0185] The LSV test results of the catalyst in Comparative Example 1 before and after the cycle are as follows: Figure 3As shown, the catalyst in Comparative Example 1 was calculated to have an initial mass activity of 259 mA / mg at 0.9 V. After 30,000 cycles in the voltage range of 0.6-0.95 V, its initial mass activity at 0.9 V was 135 mA / mg, and the mass activity decayed by 47.7% (the U.S. Department of Energy's target requirement is less than 40%). This shows that the catalyst in Example 1 has significant advantages over unmodified commercial platinum carbon (Pt / C) in both catalytic activity and stability.

[0186] The performance of the fuel cells prepared using the catalysts in Example 1 and Comparative Example 1 was tested:

[0187] (1) Preparation of fuel cell: Weigh 0.2 g of the catalyst to be tested, add 1 mL of water to soak it, then add 49 mL of isopropanol and 49 mL of ethanol, ultrasonicate for 20 min, then add 1000 μL of 5% perfluorosulfonic acid solution, continue ultrasonicate for 30 min, and stir for 120 min; use ultrasonic spraying device to evenly spray the slurry on carbon paper; the Pt loading of cathode and anode is 0.1 mg Pt / cm 2 When the catalyst in Example 1 was tested, the anode of the fuel cell was commercial Pt / C and the cathode was the catalyst in Example 1. When the catalyst in Comparative Example 1 was tested, both the anode and cathode of the fuel cell were commercial Pt / C.

[0188] (2) Test conditions: Test temperature is 80℃, anode pressure is 150kPa abs H2 gas, cathode uses 150kPa abs The gas flow rates of O2 gas, anode and cathode were 500 sccm and 2000 sccm respectively, the relative humidity was 100%, and the test voltage range was 0.3-1V.

[0189] The test results are as follows Figure 4 As stated by Figure 4 It can be seen that the catalyst in Example 1 has good power characteristics in the fuel cell, with a peak power density of up to 1864.7 mW / cm 2 , which is higher than commercial Pt / C.

[0190] analyze:

[0191] It can be seen from the data of the examples that the catalyst prepared by the present invention has high mass activity and good cycle stability, and when used in a fuel cell, it can improve the power density and stability of the fuel cell.

[0192] It can be seen from the data of Examples 1 and 11 as well as Examples 8 and 12 that the temperature of heat treatment has an important influence on the performance of the catalyst of the present invention, and higher or lower heat treatment temperature will affect the performance of the catalyst.

[0193] From the data of Example 3 and Example 13, Example 4 and Example 14, Example 1 and Example 15, and Example 4 and Example 16, it can be seen that the amount of the metal salt containing M and the nitrogen-containing organic complex in the process for preparing the catalyst according to the present application has an important influence on the performance of the catalyst prepared, and only when the amount of Pt / C, the metal salt containing M and the nitrogen-containing organic complex is within a certain range, can a catalyst with high mass activity and good cycle stability be prepared.

[0194] From the data of Example 1 and Comparative Example 1, it can be seen that compared with the commercial Pt / C catalyst, the catalyst according to the present application has higher mass activity and better cycle stability.

[0195] From the data of Example 1 and Comparative Examples 2-3, it can be seen that only when the Pt / C is modified with both the metal salt containing M and the nitrogen-containing organic complex, can a catalyst with high mass activity and good cycle stability be prepared.

[0196] The applicant declares that the detailed method of the present application is illustrated by the above examples, but the present application is not limited to the above detailed method, i.e. it does not mean that the present application must rely on the above detailed method to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific methods, etc. all fall within the protection scope and disclosure scope of the present application.

Claims

1. A catalyst, characterized in that The catalyst comprises a core and a shell coated on the surface of the core, wherein the core is a composite of a PtM alloy and C, and the shell is a nitrogen-doped carbon layer, wherein M single atoms are distributed in the nitrogen-doped carbon layer; in the nitrogen-doped carbon layer, nitrogen atoms form chemical bonds with M single atoms; Wherein, M is a non-precious metal; Based on the total mass of the catalyst being 100 wt%, the content of the core in the catalyst is 75 wt%-95 wt%; Based on the total mass of the catalyst being 100 wt%, the content of the nitrogen-doped carbon layer in the catalyst is 5 wt%-25 wt%; The catalyst is prepared by the following method, which comprises the following steps: (1) Pt / C, a salt containing M, and a nitrogen-containing organic complex are mixed in a solvent, and dried to obtain a precursor material; in step (1), the mixing of Pt / C, a salt containing M, and a nitrogen-containing organic complex in a solvent is carried out in the following manner: first, the salt containing M and the nitrogen-containing organic complex are mixed in a solvent, and then Pt / C is added to form a dispersion; (2) The catalyst is prepared by heat treating the precursor material in step (1).

2. The catalyst according to claim 1, characterized in that The non-noble metal includes at least one of Fe, Co, Ni, Cu or Mn.

3. A method for preparing the catalyst according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) Pt / C, a salt containing M, and a nitrogen-containing organic complex are mixed in a solvent and dried to obtain a precursor material; (2) The catalyst is prepared by heat treating the precursor material in step (1).

4. The preparation method according to claim 3, characterized in that The mass ratio of Pt / C, M-containing salt and nitrogen-containing organic complex in step (1) is 1:(0.001-0.5):(0.001-2).

5. The preparation method according to claim 4, characterized in that The mass ratio of Pt / C, M-containing salt and nitrogen-containing organic complex in step (1) is 1:(0.06-0.4):(0.5-1.5).

6. The preparation method according to claim 3, characterized in that In step (1), M is a non-precious metal.

7. The preparation method according to claim 6, characterized in that The M includes at least one of Fe, Co, Ni, Cu or Mn.

8. The preparation method according to claim 3, characterized in that The nitrogen-containing organic complex in step (1) includes at least one of o-phenanthroline, dopamine or aniline.

9. The preparation method according to claim 3, characterized in that The drying method in step (1) includes at least one of air drying, vacuum drying or freeze drying.

10. The preparation method according to claim 3, characterized in that The temperature of the heat treatment in step (2) is 300-1200°C.

11. The preparation method according to claim 10, characterized in that: The temperature of the heat treatment in step (2) is 500-1000°C.

12. The preparation method according to claim 3, characterized in that The heat treatment time in step (2) is 0.5-10h.

13. The preparation method according to claim 3, characterized in that The atmosphere of the heat treatment in step (2) is a protective atmosphere and / or a reducing atmosphere.

14. The preparation method according to claim 3, characterized in that The catalyst obtained in step (2) is acid washed.

15. The preparation method according to claim 14, characterized in that The acid used in the pickling comprises at least one of hydrochloric acid, nitric acid or sulfuric acid.

16. The preparation method according to claim 14, characterized in that The pickling time is 0.1-24h.

17. The preparation method according to claim 14, characterized in that The pickling temperature is 20-110°C.

18. A fuel cell, characterized in that: The fuel cell comprises the catalyst according to claim 1 or 2.

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