Preparation method and application of ordered platinum-cobalt intermetallic compound catalyst

Abstract

The invention discloses a preparation method and application of an ordered platinum-cobalt intermetallic compound catalyst, and the preparation method comprises the following steps: step S1, mixing a mixture containing an acidic solution, a platinum-carbon catalyst and a small molecule coordination agent to obtain a mixed solution; s2, heating the mixed solution, adding cobalt salt, adding a reducing agent when the mixed solution is in a homogeneous state, stirring, filtering and drying to obtain a catalyst precursor; and S3, calcining the catalyst precursor in a reducing atmosphere to obtain the ordered platinum-cobalt intermetallic compound catalyst. The platinum-carbon catalyst is directly used as a carrier, and the prepared ordered platinum-cobalt intermetallic compound catalyst is high in order degree, small in particle size and high in oxygen reduction activity.

Description

Technical Field

[0001] The present application relates to a preparation method and application of an ordered platinum-cobalt intermetallic compound catalyst, belonging to the technical field of catalyst preparation. Background Art

[0002] In recent years, the global energy shortage problem has occurred frequently. Hydrogen energy has attracted widespread attention due to its abundant sources, green and low-carbon, and renewable characteristics. At present, building an efficient hydrogen energy recycling system is considered to be one of the most promising ways to achieve carbon peak and carbon neutrality goals. Fuel cells are an extremely critical link because of their many advantages such as low pollution, environmental protection, and high power density. However, the oxygen reduction reaction process at the cathode has the problem of slow reaction kinetics, which directly affects the reaction efficiency of the entire fuel cell energy device and has become a key factor restricting the large-scale commercial development of fuel cells.

[0003] The existing process synthesis methods still have problems such as low order, large particle size, and low oxygen reduction activity. Héctor D. Abruña et al. synthesized a core-shell structured Pt3Co intermetallic compound. The high temperature annealing in the synthesis process inevitably led to metal sintering. At the thermal annealing temperature of 700°C, the catalyst agglomerates significantly, and the particle size exceeds 7 nm. The mass activity of the most preferred catalyst can only reach 520 mA / mg (mass activity is a key evaluation indicator for fuel cell applications; Nature Material. 2013, 12, 81-87).

[0004] At present, the synthesis of most platinum-cobalt catalysts uses carbon black as a carrier, and then reduces the platinum salt and cobalt salt on the carrier. It usually requires the addition of excess cobalt and platinum alloying, and then undergoes high-temperature thermal annealing, air burning, pickling, secondary annealing surface reconstruction, washing and drying processes to finally complete the synthesis of ordered platinum-cobalt intermetallic compounds. This method has a complex process, poor air burning uniformity, and the overall process controllability is difficult to guarantee, which cannot be adapted to industrial-scale preparation. Summary of the invention

[0005] In view of the problems in the prior art of complex process, low catalyst order, large particle size and low oxygen reduction activity, the present invention provides a highly ordered platinum-cobalt intermetallic compound catalyst with simple process, small particle size and high activity.

[0006] According to one aspect of the present application, a method for preparing an ordered platinum-cobalt intermetallic compound catalyst is provided, the preparation method comprising the following steps: Step S1, mixing a mixture containing an acidic solution, a platinum-carbon catalyst, and a small molecule ligand to obtain a mixed solution; Step S2, heating the mixed solution and adding cobalt salt, adding a reducing agent when the mixed solution is in a homogeneous state, stirring, filtering, and drying to obtain a catalyst precursor; Step S3: calcining the catalyst precursor under a reducing atmosphere to obtain the ordered platinum-cobalt intermetallic compound catalyst.

[0007] Optionally, in step S1, the small molecule ligand is selected from at least one of cysteine, sodium thioglycolate, methionine, ethanethiol, and mercaptoethanol.

[0008] Optionally, the acidic solution is selected from at least one of hydrochloric acid, sulfuric acid, perchloric acid, nitric acid, and acetic acid solutions.

[0009] Optionally, in step S1, the mass volume ratio of the platinum-carbon catalyst to the acidic solution is 1:0.1~1:1 g / L.

[0010] Optionally, in step S1, the molar ratio of platinum metal in the platinum-carbon catalyst to the small molecule ligand is 1:0.4-1:2.

[0011] Optionally, the platinum content of the platinum-carbon catalyst is 10-50%.

[0012] Optionally, the amount of platinum supported in the platinum-carbon catalyst is independently selected from any value of 10%, 20%, 30%, 40%, 50% or a range between any two of the above.

[0013] Optionally, the platinum content of the platinum-carbon catalyst is 30-50%.

[0014] Optionally, the platinum loading in the platinum-carbon catalyst is 40%.

[0015] Optionally, the particle size of the platinum-carbon catalyst is 2.0-4.0 nm.

[0016] Optionally, the particle size of the platinum-carbon catalyst is independently selected from any value of 2.0 nm, 2.5 nm, 3.0 nm, 3.5 nm, 4.0 nm, or a range between any two of the above values.

[0017] Optionally, in step S2, the cobalt salt is selected from at least one of cobalt sulfate, cobalt carbonate, cobalt nitrate and cobalt halide.

[0018] Optionally, the molar ratio of platinum metal to the cobalt salt in the platinum-carbon catalyst is 1:0.4 to 1:2.

[0019] Optionally, the molar ratio of platinum metal to the reducing agent in the platinum-carbon catalyst is 1:2.5 to 1:20.

[0020] Optionally, in step S2, the reducing agent is selected from at least one of hydrazine hydrate, ammonia water, and potassium borohydride.

[0021] Optionally, in step S3, the reducing atmosphere is selected from one or more of a mixture of an inert gas and hydrogen or hydrogen.

[0022] The inert gas is selected from argon or nitrogen.

[0023] Optionally, in step S3, the reducing atmosphere is selected from one or more of argon-hydrogen mixed gas, nitrogen-hydrogen mixed gas, and hydrogen.

[0024] Optionally, the volume ratio of the inert gas to hydrogen in the reducing atmosphere is 9:1 to 19:1.

[0025] Optionally, the volume ratio of the inert gas to hydrogen in the reducing atmosphere is independently selected from any value of 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or a range between any two of the above.

[0026] Optionally, the volume ratio of inert gas to hydrogen in the reducing atmosphere is 19:1.

[0027] Optionally, in step S3, the calcination includes a first stage, a second stage, a third stage and a fourth stage; The heating rate of the first stage is 2-10°C / min, the temperature is 300-500°C, and the time is 0.5-1.5h; The heating rate of the second stage is 2-10°C / min, the temperature is 800-1000°C, and the time is 1-4h; The temperature of the third stage is 500-700°C and the time is 3-6 hours; The temperature of the fourth stage is 20-30°C.

[0028] According to another aspect of the present application, there is provided an ordered platinum-cobalt intermetallic compound catalyst prepared by the preparation method described above, wherein the molecular formula of the ordered platinum-cobalt intermetallic compound catalyst is Pt x Co, where x is 1 or 3; The particle size of the ordered platinum-cobalt intermetallic compound catalyst is 3.0-6.0 nm.

[0029] Optionally, the particle size of the ordered platinum-cobalt intermetallic compound catalyst is independently selected from any value of 3.0 nm, 4.0 nm, 5.0 nm, 6.0 nm, or a range between any two of the above values.

[0030] According to another aspect of the present application, there is provided an ordered platinum-cobalt intermetallic compound catalyst prepared by the preparation method described above or the use of the ordered platinum-cobalt intermetallic compound catalyst described above in a fuel cell.

[0031] The preparation method of the present invention comprises: S1: Add platinum-carbon catalyst and small molecule coordination agent to the acidic solution, increase the temperature and add cobalt salt; S2: After the solution becomes homogeneous, a reducing agent is added dropwise, and the solution is washed and dried after the reaction; S3: High temperature annealing under a reducing atmosphere to obtain an ordered platinum-cobalt intermetallic compound catalyst.

[0032] The beneficial effects of this application include: 1) Compared with the preparation method of using carbon black as a carrier to load platinum salt and cobalt salt in the existing conventional scheme, the preparation method of the ordered platinum-cobalt intermetallic compound catalyst provided in the present application is simple in process, does not require acid washing and reconstruction operation, and shortens the preparation process: using a platinum-carbon catalyst as a carrier, adding cobalt salt and small molecules with specific functional groups to an acidic solution, adding a reducing agent for reduction, and then heat-treating in a reducing atmosphere to form a small-particle platinum-cobalt intermetallic compound catalyst with a high degree of order.

[0033] 2) The ordered platinum-cobalt intermetallic compound catalyst provided in this application has a high degree of order, a small particle size, and a high oxygen reduction activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 1 is the XRD diagram of the ordered platinum-cobalt intermetallic compound catalyst in the examples and comparative examples of the present application. DETAILED DESCRIPTION

[0035] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0036] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0037] In the examples of the present application, the preparation method of the homemade platinum-carbon catalyst is prepared by the following method. The homemade platinum-carbon catalysts of Example 1, Example 3 and Example 4 are prepared by adjusting the raw material ratio in the method.

[0038] The preparation method of the homemade platinum-carbon catalyst is as follows: (1) Weigh 3.55 g of magnesium acetate tetrahydrate and dissolve it in 100 mL of ethanol. After it is completely dissolved, add 2 g of KB300 and stir for 12 h. Then evaporate the ethanol at 110 °C. After drying and grinding, place it in a tubular furnace and sinter it at 100 °C under a nitrogen atmosphere for 3 h to obtain a 25%-MgO / KB300 carrier. (2) Weigh 2 g of 25%-MgO / KB300 carrier and 80 mL of ethylene glycol solution into a 250 mL round-bottom flask and stir until the carrier is evenly dispersed in the solution; (3) Place the reaction system in (2) in an oil bath at 140°C and heat with stirring until the temperature stabilizes; (4) Use a peristaltic pump to slowly add 101 mL of 0.1 M chloroplatinic acid hexahydrate in ethylene glycol solution within 20 minutes. After the addition is complete, keep warm for 60 minutes. (5) After the reaction mixture cools down, wash the mixture with acetol and deionized water several times, and finally test the filtrate with 0.1 M silver nitrate solution until there is no chloride ion. (6) The product obtained after centrifugation was placed in a vacuum drying oven at 40 °C for 8 h to obtain a platinum-carbon catalyst.

[0039] Example 1 Step S1: Weigh 1.0 g of a homemade platinum-carbon catalyst (platinum loading of 40%, particle size of 2.0 nm) into a 500 ml round-bottom beaker, add 100 ml of hydrochloric acid (concentration 0.1 mol / L), simultaneously add a small molecule ligand and 129 mg of cysteine, and stir to evenly disperse the platinum-carbon catalyst, hydrochloric acid, and cysteine ​​raw materials to obtain a mixed solution; Step S2: The mixed solution in step S1 is placed in an oil bath, heated and continuously stirred until the temperature of the reaction solution is stabilized at 90°C, 170 mg of cobalt chloride hexahydrate is added to the reaction system, and stirring is continued for 30 min; 68.3 ml of 0.1 mol / L hydrazine hydrate as a reducing agent is added dropwise; after the addition of the reducing agent, the temperature and stirring state are maintained for 12 h; after filtering and washing, the mixture is placed in a vacuum drying oven and dried at 80°C for 12 h to obtain a catalyst precursor; Step S3: Take the catalyst precursor and spread it evenly on a high-temperature furnace porcelain boat, and anneal it at high temperature in a tubular furnace. The heat treatment atmosphere is a mixture of 5% hydrogen and 95% argon. After heating to 400°C at a rate of 2°C / min, keep it at 400°C for 1 hour, then heat it to 900°C at a rate of 2°C / min, keep it at 900°C for 2 hours, and finally cool it to 600°C and maintain it for 5 hours. After waiting for the temperature to drop to room temperature, a highly active ordered platinum-cobalt intermetallic compound catalyst is obtained.

[0040] Example 2 Step S1: weigh 1.0 g of a commercial TKK platinum-carbon catalyst (platinum loading of 50%, particle size of 2.0 nm) into a 500 ml round-bottom beaker, add 100 ml of dilute sulfuric acid (concentration 0.05 mol / L), simultaneously add a small molecule ligand, 153 mg of sodium thioglycolate, and disperse the TKK platinum-carbon catalyst, sulfuric acid, and sodium thioglycolate raw materials uniformly by stirring to obtain a mixed solution; Step S2: The mixed solution in step S1 is placed in an oil bath, heated and continuously stirred until the temperature of the reaction solution is stabilized at 90°C, 213 mg of cobalt chloride hexahydrate is added to the reaction system, and stirring is continued for 30 minutes; 17.1 ml of 0.5 mol / L hydrazine hydrate as a reducing agent is added dropwise; after the addition is completed, the temperature and stirring state are maintained for 12 hours; after filtering and washing, the mixture is placed in a vacuum drying oven and dried at 80°C for 12 hours to obtain a catalyst precursor; Step S3: Take the catalyst precursor and spread it evenly on a high-temperature furnace porcelain boat, and anneal it at high temperature in a tubular furnace. The heat treatment atmosphere is a mixture of 5% hydrogen and 95% argon. After heating to 300°C at a rate of 5°C / min, keep it at 300°C for 1.5h, then heat it to 800°C at a rate of 4°C / min, keep it at 800°C for 2.5h, and finally cool it to 600°C and maintain it for 6h. After waiting for the temperature to drop to room temperature, a highly active ordered platinum-cobalt intermetallic compound catalyst is obtained.

[0041] Example 3 Step S1: 1.0 g of a self-made platinum-carbon catalyst (platinum loading of 40%, particle size of 4.0 nm) was weighed into a 500 ml round-bottom beaker, 100 ml of nitric acid (concentration of 0.1 mol / L) was added, and a small molecule ligand and 157 mg of methionine were added simultaneously, and the self-made platinum-carbon catalyst, nitric acid and methionine were evenly dispersed by stirring to obtain a mixed solution; Step S2: The mixed solution in step S1 is placed in an oil bath, heated and continuously stirred until the temperature of the reaction solution is stabilized at 75°C, 205 mg of cobalt nitrate hexahydrate is added to the reaction system, and stirring is continued for 60 minutes; 34.0 ml of potassium borohydride with a concentration of 0.2 mol / L as a reducing agent is added dropwise; after the addition of the reducing agent, the temperature and stirring state are maintained for 6 hours; after filtering and washing, the mixture is placed in a vacuum drying oven and dried at 80°C for 12 hours to obtain a catalyst precursor; Step S3: Take the dried catalyst precursor and place it in a tubular furnace for high-temperature annealing. The heat treatment atmosphere is a mixture of 10% hydrogen and 90% argon. Heat to 500°C at a rate of 5°C / min, maintain at 500°C for 0.5h, then heat to 1000°C at a rate of 10°C / min for 1.5h, and finally cool to 500°C and maintain for 6h. When the temperature drops to room temperature, a highly active ordered platinum-cobalt intermetallic compound catalyst is obtained.

[0042] Example 4 Step S1: weigh 1.0 g of a homemade platinum-carbon catalyst (platinum loading of 30%, particle size of 2.5 nm) into a 500 ml round-bottom beaker, add 100 ml of acetic acid (concentration of 0.1 mol / L), simultaneously add a small molecule ligand, 193 mg of mercaptoethanol, and disperse the homemade platinum-carbon catalyst, acetic acid, and mercaptoethanol uniformly by stirring to obtain a mixed solution; Step S2: The reaction system in step S1 is placed in an oil bath and heated with continuous stirring until the temperature of the reaction liquid is stabilized at 90°C, 195 mg of cobalt carbonate is added to the reaction system, and stirring is continued for 60 min; 75 ml of 0.2 mol / L ammonia water as a reducing agent is added dropwise; after the addition of the reducing agent, the temperature and stirring state are maintained for 12 h; after filtering and washing, the mixture is placed in a vacuum drying oven at 80°C for 12 h to obtain a catalyst precursor; Step S3: Take out the dried catalyst precursor and spread it evenly on a high-temperature furnace porcelain boat, anneal it at high temperature in a tubular furnace, and the heat treatment atmosphere is a nitrogen-hydrogen mixture with a hydrogen content of 5%; heat it to 400°C at a rate of 10°C / min, keep it at 400°C for 0.5 h, then heat it to 900°C at a rate of 2°C / min, keep it at 900°C for 4 h, and finally cool it to 700°C and maintain it for 3 h. The temperature is then reduced to room temperature to obtain a highly active ordered platinum-cobalt intermetallic compound catalyst.

[0043] Comparative Example 1 Step S1: weigh 1.0 g of a homemade platinum-carbon catalyst (same as in Example 1, with a platinum loading of 40% and a particle size of 2.0 nm) into a 500 ml round-bottom beaker, add 100 ml of hydrochloric acid (concentration 0.1 mol / L), and disperse the platinum-carbon catalyst and the hydrochloric acid raw material uniformly by stirring to obtain a mixed solution; Step S2: The mixed solution in step S1 is placed in an oil bath, heated and continuously stirred until the temperature of the reaction solution is stabilized at 90°C, 170 mg of cobalt chloride hexahydrate is added to the reaction system, and stirring is continued for 30 min; 68.3 ml of 0.1 mol / L hydrazine hydrate as a reducing agent is added dropwise; after the addition of the reducing agent, the temperature and stirring state are maintained for 12 h; after filtering and washing, the mixture is placed in a vacuum drying oven and dried at 80°C for 12 h to obtain a catalyst precursor; Step S3: Take the catalyst precursor and spread it evenly on a high-temperature furnace porcelain boat, and anneal it at high temperature in a tubular furnace. The heat treatment atmosphere is a mixture of 5% hydrogen and 95% argon. After heating to 400°C at a rate of 2°C / min, keep it at 400°C for 1 hour, then heat it to 900°C at a rate of 2°C / min, keep it at 900°C for 2 hours, and finally cool it to 600°C and maintain it for 5 hours. After waiting for the temperature to drop to room temperature, a highly active ordered platinum-cobalt intermetallic compound catalyst is obtained.

[0044] Comparative Example 2 Step S1: weigh 1.0 g of a homemade platinum-carbon catalyst (same as in Example 1, with a platinum loading of 40% and a particle size of 2.0 nm) into a 500 ml round-bottom beaker, add 100 ml of hydrochloric acid (concentration 0.1 mol / L), and simultaneously add 160 mg of 2,2'-bipyridine, and disperse the platinum-carbon catalyst, hydrochloric acid, and 2,2'-bipyridine raw materials uniformly by stirring to obtain a mixed solution; Step S2: The mixed solution in step S1 is placed in an oil bath, heated and continuously stirred until the temperature of the reaction solution is stabilized at 90°C, 170 mg of cobalt chloride hexahydrate is added to the reaction system, and stirring is continued for 30 min; 68.3 ml of 0.1 mol / L hydrazine hydrate as a reducing agent is added dropwise; after the addition of the reducing agent, the temperature and stirring state are maintained for 12 h; after filtering and washing, the mixture is placed in a vacuum drying oven and dried at 80°C for 12 h to obtain a catalyst precursor; Step S3: Take the catalyst precursor and spread it evenly on a high-temperature furnace porcelain boat, and anneal it at high temperature in a tubular furnace. The heat treatment atmosphere is a mixture of 5% hydrogen and 95% argon. After heating to 400°C at a rate of 2°C / min, keep it at 400°C for 1 hour, then heat it to 900°C at a rate of 2°C / min, keep it at 900°C for 2 hours, and finally cool it to 600°C and maintain it for 5 hours. After waiting for the temperature to drop to room temperature, a highly active ordered platinum-cobalt intermetallic compound catalyst is obtained.

[0045] Comparative Example 3 Step S1: weigh 0.6 g of carbon powder into a 500 ml round-bottom beaker, dissolve 1.05 g of chloroplatinic acid in 100 ml of deionized water, stir evenly and slowly add to the round-bottom beaker, then add 124 mg of cysteine, stir until evenly dispersed, and obtain a mixed solution; Step S2: The reaction system in step S1 is placed in an oil bath and heated with continuous stirring until the temperature of the reaction liquid is stabilized at 90°C, 244 mg of cobalt chloride hexahydrate is added to the reaction system, and stirring is continued for 30 min; 35 ml of 0.1 mol / L hydrazine hydrate as a reducing agent is added dropwise; after the addition of the reducing agent, the temperature and stirring state are maintained for 12 h; after filtering and washing, the mixture is placed in a vacuum drying oven at 80°C for 12 h to obtain a catalyst precursor; Step S3: Take the catalyst precursor and spread it evenly on a high-temperature furnace porcelain boat, and anneal it at high temperature in a tubular furnace. The heat treatment atmosphere is a mixture of 5% hydrogen and 95% argon. After heating to 400°C at a rate of 2°C / min, keep it at 400°C for 1 hour, then heat it to 900°C at a rate of 2°C / min, keep it at 900°C for 2 hours, and finally cool it to 600°C and maintain it for 5 hours, waiting for the temperature to drop to room temperature to obtain a highly active ordered platinum-cobalt intermetallic compound catalyst.

[0046] Particle size test: The ordered platinum-cobalt intermetallic compound catalyst samples of Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to X-ray diffraction test to obtain X-ray diffraction patterns (XRD), and the data shown in Table 1 were obtained: Table 1 Average particle size obtained by XRD pattern fitting Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Average particle size (nm) 3.5 4.8 5.1 4.1 16.8 14.9 8.1 The XRD pattern fitting shows that the XRD patterns of the platinum-cobalt catalysts obtained in Examples 1 to 4 and Comparative Example 1 are as follows: Figure 1 The results show that the small molecule ligand added in Examples 1 to 4 greatly reduces the average particle size of the obtained platinum-cobalt intermetallic compound (Table 1). The main reason is that the thiol group of cysteine ​​can coordinate with the platinum atom, and the carboxyl group can bind to the free cobalt ion. This shows that the specific functional groups of the small molecules anchor the cobalt atoms on the platinum atoms before reduction, thereby reducing the energy barrier of the reduction process and fixing the distribution of cobalt. Therefore, after the initial heat treatment atomic rearrangement, there is a certain degree of order, which makes it difficult to agglomerate and grow in the subsequent annealing process, and the average particle size of the finally obtained intermetallic compound is smaller.

[0047] At the same time, the small molecule ligand used in Comparative Example 2 has no specific functional group, and the prepared platinum-cobalt intermetallic compound is not completely converted and the particle size cannot be controlled, which further confirms the above viewpoint.

[0048] Quality Activity Test: The ordered platinum-cobalt intermetallic compound catalyst samples of Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to linear voltammetry tests to obtain linear voltammetry curves. The specific test conditions were based on the national standard (GB / T 20042.4-2009). The brief test conditions are as follows: 1. The working electrode is a graphite electrode, the reference electrode is a saturated calomel electrode, the counter electrode is a carbon rod, and the electrolyte solution is a 0.1 M HClO4 aqueous solution.

[0049] 2. The scanning range is -0.3 V to 0.8 V, the scanning speed is: 10 mV / sec (LSV), and the rotation rate is: 1600 rpm (RDE).

[0050] 3. Ink preparation: Weigh 1.4 mg of the catalyst and prepare a solution with a ratio of isopropanol: water: Nafion = 7.9:2:0.1. Disperse evenly in an ultrasonic ice bath below 20°C.

[0051] 4. Take 10 uL and drop it onto the working electrode. Wait for it to dry naturally before testing.

[0052] The test results of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 2: Table 2 Mass activity test results Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 MA (mA / mg) 649.0 633.4 562.8 575.5 206.2 155.5 405.6 The XRD patterns of the platinum-cobalt catalysts obtained in Examples 1 to 4 and Comparative Example 1 are as follows: Figure 1 The results show that the small molecule ligand added in Examples 1 to 4 greatly reduces the average particle size of the obtained platinum-cobalt intermetallic compound (Table 1). The main reason is that the thiol group of cysteine ​​can coordinate with the platinum atom, and the hydroxyl group can bind to the free cobalt ion. This shows that the specific functional group of the small molecule anchors the cobalt atom on the platinum atom before reduction, thereby reducing the energy barrier of the reduction process and fixing the distribution of cobalt. Therefore, after the initial heat treatment atomic rearrangement, there is a certain degree of order, which makes it difficult to agglomerate and grow in the subsequent annealing process, and the average particle size of the obtained intermetallic compound is small. At the same time, the small molecule ligand used in Comparative Example 2 has no specific functional group, and the conversion of the prepared platinum-cobalt intermetallic compound is not complete and the particle size cannot be controlled, which further proves the above view.

[0053] Experimental Example 4 precisely controls the atomic ratio of platinum and cobalt. Compared with Experimental Example 1, the obtained ordered intermetallic compound is transformed from Pt3Co to PtCo, and no cobalt element remains. No subsequent acid washing and reconstruction step is required, which simplifies the preparation process. Compared with Comparative Example 3, which directly uses chloroplatinic acid as the raw material, the platinum and cobalt are not precisely positioned, resulting in uncontrollable nucleation of the platinum-cobalt intermetallic compound synthesized in Comparative Example 3 and a large particle size. This shows the effectiveness of the strategy for precise control of platinum and cobalt by the site-specific bridging effect of small molecules on a platinum-carbon catalyst substrate proposed in the present invention, thereby realizing the controllable preparation of platinum-cobalt alloy state.

[0054] As can be seen from Table 2, the performance of the small-particle ordered platinum-cobalt intermetallic compound oxide prepared by this strategy is much higher than that of the catalyst obtained in Comparative Example 1, and its mass activity can reach 649.0 mA / mg, which has a very excellent catalytic effect.

[0055] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing an ordered platinum-cobalt intermetallic compound catalyst, characterized in that: The preparation method comprises the following steps: Step S1, mixing a mixture containing an acidic solution, a platinum-carbon catalyst, and a small molecule ligand to obtain a mixed solution; Step S2, heating the mixed solution and adding cobalt salt, adding a reducing agent when the mixed solution is in a homogeneous state, stirring, filtering, and drying to obtain a catalyst precursor; Step S3: calcining the catalyst precursor under a reducing atmosphere to obtain the ordered platinum-cobalt intermetallic compound catalyst.

2. The preparation method according to claim 1, characterized in that: In step S1, the small molecule ligand is selected from at least one of cysteine, sodium thioglycolate, methionine, ethanethiol, and mercaptoethanol; Preferably, the acidic solution is selected from at least one of hydrochloric acid, sulfuric acid, perchloric acid, nitric acid, and acetic acid solutions; Preferably, in step S1, the mass volume ratio of the platinum-carbon catalyst to the acidic solution is 1:0.1-1:1 g / L; Preferably, in step S1, the molar ratio of platinum metal in the platinum-carbon catalyst to the small molecule ligand is 1:0.4-1:

2.

3. The preparation method according to claim 1, characterized in that: The platinum loading in the platinum-carbon catalyst is 10-50%; Preferably, the platinum loading in the platinum-carbon catalyst is 30-50%; Preferably, the platinum loading in the platinum-carbon catalyst is 40%; Preferably, the particle size of the platinum-carbon catalyst is 2.0-4.0 nm.

4. The preparation method according to claim 1, characterized in that: In step S2, the cobalt salt is selected from at least one of cobalt sulfate, cobalt carbonate, cobalt nitrate and cobalt halide.

5. The preparation method according to claim 1, characterized in that: The molar ratio of platinum metal to cobalt salt in the platinum-carbon catalyst is 1:0.4-1:2; Preferably, the molar ratio of platinum metal to the reducing agent in the platinum-carbon catalyst is 1:2.5-1:

20.

6. The preparation method according to claim 1, characterized in that: In step S2, the reducing agent is selected from at least one of hydrazine hydrate, ammonia water, and potassium borohydride.

7. The preparation method according to claim 1, characterized in that: In step S3, the reducing atmosphere is selected from one or more of a mixture of an inert gas and hydrogen or hydrogen; the inert gas is selected from argon or nitrogen; Preferably, the volume ratio of the inert gas to hydrogen in the reducing atmosphere is 9:1 to 19:1; Preferably, the volume ratio of the inert gas to hydrogen in the reducing atmosphere is 19:

1.

8. The preparation method according to claim 1, characterized in that: In the step S3, the calcination includes a first stage, a second stage, a third stage and a fourth stage; The heating rate of the first stage is 2-10°C / min, the temperature is 300-500°C, and the time is 0.5-1.5h; The heating rate of the second stage is 2-10°C / min, the temperature is 800-1000°C, and the time is 1-4h; The temperature of the third stage is 500-700°C and the time is 3-6 hours; The temperature of the fourth stage is 20-30°C.

9. The ordered platinum-cobalt intermetallic compound catalyst prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The molecular formula of the ordered platinum-cobalt intermetallic compound catalyst is Pt x Co, where x is 1 or 3; The particle size of the ordered platinum-cobalt intermetallic compound catalyst is 3.0-6.0 nm.

10. Use of the ordered platinum-cobalt intermetallic compound catalyst prepared by the preparation method according to any one of claims 1 to 8 or the ordered platinum-cobalt intermetallic compound catalyst according to claim 9 in a fuel cell.

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