A production process for a high-performance noble metal catalyst for hydrogen fuel cells

Abstract

The present invention relates to the technical field of hydrogen fuel cells, and discloses a production process of a high-performance noble metal catalyst for hydrogen fuel cells, comprising the following steps: (1) noble metal precursor; (2) carrier gradient modification; (3) nano-composite deposition; (4) high-temperature treatment; The production process of the high-performance noble metal catalyst for hydrogen fuel cells of the present invention has remarkable effects in improving the catalytic activity of the catalyst and the durability of the hydrogen fuel cell. First of all, in the present invention, a platinum source, a lanthanum source, and a zirconium source are dissolved in an organic solvent according to a specific atomic ratio, and a noble metal precursor is formed by microwave-assisted heating. Microwave heating can uniformly disperse each metal source and cause rapid reaction to form an alloy with a unique crystal structure and electronic properties. The addition of lanthanum and zirconium changes the electron cloud distribution of platinum, enhances the adsorption and activation ability of reactant molecules, reduces the activation energy of the reaction, and thus improves the catalytic activity.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen fuel cells, and specifically to a production process of a high-performance noble metal catalyst for hydrogen fuel cells. Background Art

[0002] With the increasing global demand for clean energy, hydrogen fuel cells, as an efficient and environmentally friendly energy conversion device, have received extensive attention and research. A hydrogen fuel cell is a power generation device that directly converts the chemical energy of hydrogen and oxygen into electrical energy. Its working principle is based on the oxidation reaction of hydrogen under the action of an anode catalyst, releasing electrons and protons. The electrons form an electric current through an external circuit, and the protons pass through a proton exchange membrane to reach the cathode, where they react with oxygen under the action of a cathode catalyst to generate water. The whole process does not produce greenhouse gases and pollutants, and has the advantages of high energy conversion efficiency, low noise, strong reliability, etc., and has broad application prospects in the fields of transportation, distributed power generation, portable power sources, etc.

[0003] During the working process of a hydrogen fuel cell, the catalyst plays a crucial role. The catalyst can reduce the activation energy of the reaction between hydrogen and oxygen, accelerate the electrode reaction, and thus improve the performance and efficiency of the battery. At present, noble metal catalysts, especially platinum-based catalysts, are widely used in hydrogen fuel cells due to their excellent catalytic activity and stability. Platinum-based catalysts can effectively promote the oxidation reaction of hydrogen and the reduction reaction of oxygen, enabling the battery to work at a lower overpotential, and improving the output voltage and power density of the battery.

[0004] However, the existing noble metal catalysts for hydrogen fuel cells have some obvious drawbacks. The most prominent problem is the relatively low catalytic efficiency. In traditional catalyst preparation methods, there are often problems such as a limited number of active sites of the catalyst and the inability to fully exert the catalytic activity. On the other hand, during long-term use of the catalyst, it is easy to cause a decrease in the stability of the catalyst and a gradual reduction in the catalytic efficiency.

[0005] In order to solve the problem of low catalytic efficiency of existing hydrogen fuel cell catalysts, the present invention proposes a production process of a high-performance noble metal catalyst for hydrogen fuel cells to solve the corresponding problems. Summary of the Invention

[0006] In view of the problems in the prior art, the present invention provides a production process of a high-performance noble metal catalyst for hydrogen fuel cells.

[0007] The technical solution adopted by the present invention to solve its technical problems is: a production process of a high-performance noble metal catalyst for hydrogen fuel cells, including the following steps:

[0008] (1) Noble metal precursor: Dissolve a platinum source, a lanthanum source, and a zirconium source in an organic solvent at an atomic ratio of 0.4 - 0.6:0.15 - 0.25:0.15 - 0.25, and heat it to 460 - 500 °C with the aid of microwave for 20 - 25 min to obtain the noble metal precursor;

[0009] (2) Carrier gradient modification: Use a mixed gas as plasma to perform plasma treatment on the activated carbon carrier at a power density of 70 - 130 W / cm². After the plasma treatment, first perform a liquid nitrogen quick-freezing treatment on the activated carbon carrier at -196 °C, keep it warm for 30 min, then restore it to 20 °C and keep it warm for 30 min, and then perform a gradient heating treatment from 20 °C to 110 °C, and finally restore it to room temperature to obtain the modified carrier;

[0010] (3) Nanocomposite deposition: Mix the noble metal precursor and the modified carrier with the assistance of ultrasound at a frequency of 42 kHz, and then use freeze-drying to remove the solvent to obtain the composite;

[0011] (4) High-temperature treatment: In an inert atmosphere, raise the temperature of the composite to 950 - 1000 °C at a rate of 4 °C / min, keep it warm for 2 - 3 hours and then perform a gradient cooling, stay for 1.5 hours in the range of 160 °C - 170 °C, and then restore it to room temperature to obtain the noble metal catalyst.

[0012] As a further technical solution, the platinum source in step (1) is chloroplatinic acid, the lanthanum source is lanthanum nitrate, the zirconium source is zirconium nitrate, and the organic solvent is a mixed solution of polyethylene glycol and polyvinyl alcohol with a mass ratio of 1:2.

[0013] As a further technical solution, the microwave power of the microwave-assisted heating in step (1) is 400 W.

[0014] As a further technical solution, the time for treating the activated carbon carrier with plasma in step (2) is 15 - 18 minutes.

[0015] As a further technical solution, the rate of gradient heating in step (2) is 4 - 4.5 °C / min.

[0016] As a further technical solution, the modified carrier and the noble metal precursor in step (3) are mixed at a mass ratio of 2.2 - 2.8:1.

[0017] As a further technical solution, the time for ultrasonic-assisted mixing in step (3) is 25 - 30 minutes, and the ultrasonic frequency is 40 kHz.

[0018] As a further technical solution, in the step (4), the inert atmosphere is nitrogen or argon, and the gas purity is not less than 99.95%.

[0019] As a further technical solution, in the step (4), the rate of gradient cooling is 8 °C / min.

[0020] Advantages of the present invention:

[0021] The production process of the high-performance noble metal catalyst for hydrogen fuel cells of the present invention has remarkable effects in improving the catalytic activity of the catalyst and the durability of the hydrogen fuel cell. First of all, in the present invention, a platinum source, a lanthanum source, and a zirconium source are dissolved in an organic solvent according to a specific atomic ratio, and a noble metal precursor is formed by microwave-assisted heating. Microwave heating can evenly disperse and quickly react the metal sources to form an alloy with a unique crystal structure and electronic properties. The addition of lanthanum and zirconium changes the electron cloud distribution of platinum, enhances the adsorption and activation ability of reactant molecules, reduces the activation energy of the reaction, and thus improves the catalytic activity. Then, the support is modified: The activated carbon support is treated with plasma, introducing abundant surface functional groups, increasing the interaction between the support and the noble metal, and facilitating the uniform loading of the noble metal. Liquid nitrogen quick-freezing and gradient heating treatment make the support form a hierarchical pore structure. The mesoporous structure provides a fast diffusion channel for reactants and products, increases the contact opportunity between active sites and reactants, and further improves the catalytic efficiency. Subsequent ultrasonic-assisted mixing evenly disperses the noble metal precursor on the modified support. During the freeze-drying process to remove the solvent, particle agglomeration is avoided, the size of platinum particles is effectively controlled, the number of active sites is increased, and the catalytic activity is improved. Finally, high-temperature treatment in an inert atmosphere further orders the alloy, forms a stable crystal structure, enhances the activity and stability of the catalyst. Gradient cooling and staying in a specific temperature range help control crystal growth and defect formation, optimize the microstructure of the catalyst, and improve the catalytic performance.

[0022] The catalyst structure alloyed by the specific method of the present invention improves the anti-poisoning ability and anti-oxidation ability of the catalyst, and reduces the activity attenuation of the catalyst during use.

[0023] At the same time, the hierarchical pore structure and surface functional groups of the support enhance the binding force between the support and the noble metal, prevent the migration and agglomeration of noble metal particles during the operation of the battery, and extend the service life of the catalyst.

[0024] In summary, the production process of the present invention significantly improves the catalytic activity of the catalyst and the durability of the hydrogen fuel cell through the synergistic effect of each step. Detailed implementation manners

[0025] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0026] Example 1

[0027] A production process for a high-performance noble metal catalyst for hydrogen fuel cells includes the following steps:

[0028] (1) Preparation of noble metal precursor

[0029] Dissolve chloroplatinic acid, lanthanum nitrate, and zirconium nitrate in a mixed solution of polyethylene glycol and polyvinyl alcohol with a mass ratio of 1:2 according to an atomic ratio of 0.4:0.15:0.15. Under the condition of a microwave power of 400 W, perform microwave-assisted heating, heat the mixed solution to 460 °C, and maintain it for 20 min to obtain the noble metal precursor.

[0030] (2) Carrier gradient modification

[0031] Use a mixed gas as plasma, perform plasma treatment on the activated carbon carrier at a power density of 70 W / cm² for 15 minutes; perform a liquid nitrogen quick-freezing treatment at -196 °C on the activated carbon carrier after plasma treatment and keep it warm for 30 min, then restore it to 20 °C and keep it warm for 30 min; perform a gradient heating treatment from 20 °C to 110 °C at a rate of 4 °C / min, and finally restore it to room temperature to obtain the modified carrier.

[0032] (3) Nano-composite deposition

[0033] Mix the modified carrier and the noble metal precursor according to a mass ratio of 2.2:1, and perform ultrasonic-assisted mixing for 25 minutes under the condition of an ultrasonic frequency of 40 kHz. After mixing is completed, use freeze-drying technology to remove the solvent to obtain a composite.

[0034] (4) High-temperature treatment

[0035] Place the composite in an inert atmosphere composed of nitrogen with a purity of not less than 99.95%, raise the temperature to 950 °C at a rate of 4 °C / min, and keep it warm for 2 hours. Then perform gradient cooling, with a cooling rate of 8 °C / min, stay in the 160 °C interval for 1.5 hours, and finally restore it to room temperature to obtain a high-performance noble metal catalyst for hydrogen fuel cells.

[0036] Example 2

[0037] A production process of a high-performance noble metal catalyst for hydrogen fuel cells, comprising the following steps:

[0038] (1) Preparation of noble metal precursor

[0039] Dissolve chloroplatinic acid, lanthanum nitrate, and zirconium nitrate in a mixed solution of polyethylene glycol and polyvinyl alcohol with a mass ratio of 1:2 according to an atomic ratio of 0.5:0.2:0.2. Carry out microwave-assisted heating under the condition of a microwave power of 400 W, heat the mixed solution to 470 °C, and maintain it for 22 min to obtain the noble metal precursor.

[0040] (2) Carrier gradient modification

[0041] Use The mixed gas as plasma, perform plasma treatment on the activated carbon carrier at a power density of 90 W / cm² for 16 minutes; perform liquid nitrogen quick-freezing treatment at -196 °C on the activated carbon carrier after plasma treatment, and keep it warm for 30 min, then restore it to 20 °C and keep it warm for 30 min; perform gradient heating treatment from 20 °C to 110 °C at a rate of 4.2 °C / min, and finally restore it to room temperature to obtain the modified carrier.

[0042] (3) Nano-composite deposition

[0043] Mix the modified carrier and the noble metal precursor according to a mass ratio of 2.4:1, and perform ultrasonic-assisted mixing for 26 minutes under the condition of an ultrasonic frequency of 40 kHz. After mixing is completed, use freeze-drying technology to remove the solvent to obtain the composite.

[0044] (4) High-temperature treatment

[0045] Place the composite in an inert atmosphere composed of argon with a purity of not less than 99.95%, raise the temperature to 960 °C at a rate of 4 °C / min, and keep it warm for 2.2 hours. Then perform gradient cooling, with a cooling rate of 8 °C / min, stay in the 162 °C interval for 1.5 hours, and finally restore it to room temperature to obtain the high-performance noble metal catalyst for hydrogen fuel cells.

[0046] Example 3

[0047] A production process of a high-performance noble metal catalyst for hydrogen fuel cells, comprising the following steps:

[0048] (1) Preparation of noble metal precursor

[0049] Dissolve chloroplatinic acid, lanthanum nitrate, and zirconium nitrate in a mixed solution of polyethylene glycol and polyvinyl alcohol with a mass ratio of 1:2 according to an atomic ratio of 0.55:0.22:0.22. Under the condition of a microwave power of 400 W, perform microwave-assisted heating to heat the mixed solution to 490 °C and maintain it for 24 min to obtain a noble metal precursor.

[0050] (2) Carrier gradient modification

[0051] Use A mixed gas as plasma to perform plasma treatment on the activated carbon carrier at a power density of 110 W / cm² for 17 minutes; perform a liquid nitrogen quick-freezing treatment at -196 °C on the activated carbon carrier after plasma treatment and keep it warm for 30 min, then restore it to 20 °C and keep it warm for 30 min; perform a gradient heating treatment by heating from 20 °C to 110 °C at a rate of 4.4 °C / min, and finally restore it to room temperature to obtain a modified carrier.

[0052] (3) Nano-composite deposition

[0053] Mix the modified carrier and the noble metal precursor according to a mass ratio of 2.6:1, and perform ultrasonic-assisted mixing for 28 minutes under the condition of an ultrasonic frequency of 40 kHz. After mixing, use freeze-drying technology to remove the solvent to obtain a composite.

[0054] (4) High-temperature treatment

[0055] Place the composite in an inert atmosphere composed of nitrogen with a purity of not less than 99.95%, raise the temperature to 980 °C at a rate of 4 °C / min, and keep it warm for 2.8 hours. Then perform gradient cooling, with a cooling rate of 8 °C / min, stay in the 168 °C interval for 1.5 hours, and finally restore it to room temperature to obtain a high-performance noble metal catalyst for hydrogen fuel cells.

[0056] Example 4

[0057] A production process of a high-performance noble metal catalyst for hydrogen fuel cells, comprising the following steps:

[0058] (1) Preparation of noble metal precursor

[0059] Dissolve chloroplatinic acid, lanthanum nitrate, and zirconium nitrate in a mixed solution of polyethylene glycol and polyvinyl alcohol with a mass ratio of 1:2 according to an atomic ratio of 0.6:0.25:0.25. Under the condition of a microwave power of 400 W, perform microwave-assisted heating to heat the mixed solution to 500 °C and maintain it for 25 min to obtain a noble metal precursor.

[0060] (2) Carrier gradient modification

[0061] Use The mixed gas, as a plasma, was used to perform plasma treatment on the activated carbon support at a power density of 130 W / cm² for 18 minutes. The plasma-treated activated carbon support was quickly frozen with liquid nitrogen at -196 °C and kept at this temperature for 30 min, and then restored to 20 °C and kept at this temperature for 30 min. The temperature was raised from 20 °C to 110 °C at a rate of 4.5 °C / min for gradient temperature increase treatment, and finally restored to room temperature to obtain a modified support.

[0062] (3)Nano-composite deposition

[0063] The modified support and the noble metal precursor were mixed at a mass ratio of 2.8:1 and ultrasonically assisted for 30 minutes under the condition of an ultrasonic frequency of 40 kHz. After mixing, the solvent was removed by freeze-drying technology to obtain a composite.

[0064] (4)High-temperature treatment

[0065] The composite was placed in an inert atmosphere composed of argon with a purity of not less than 99.95%. The temperature was raised to 1000 °C at a rate of 4 °C / min and kept at this temperature for 3 hours. Then gradient cooling was carried out at a cooling rate of 8 °C / min, staying for 1.5 hours in the 170 °C range, and finally restored to room temperature to obtain a high-performance noble metal catalyst for hydrogen fuel cells.

[0066] Comparative example 1:

[0067] The difference from Example 1 was that no treatment was performed on the activated carbon support.

[0068] Comparative example 2:

[0069] The difference from Example 1 was that no plasma treatment was performed on the activated carbon support.

[0070] Test

[0071] Oxygen reduction reaction (ORR) activity test

[0072] Test method:

[0073] Electrode preparation: The catalysts of the examples and comparative examples were prepared into rotating ring-disk electrodes (RRDE) of the same specification.

[0074] Test conditions: Using an O2-saturated 0.1 M KOH electrolyte solution, cyclic voltammetry scanning was carried out at a rotation speed of 1600 rpm in the voltage range of 0.6 - 1.0 V to measure the half-wave potential :

[0075] : Reflecting the ORR kinetic activity of the catalyst, the lower the voltage, the higher the activity

[0076] Table 1

[0077]

[0078] As can be seen from Table 1, the noble metal catalyst for hydrogen fuel cells prepared by the present invention has high catalytic performance.

[0079] Fuel cell durability test

[0080] Single cell assembly: The catalysts of the examples and comparative examples were assembled with a proton exchange membrane and a gas diffusion layer into a membrane electrode assembly (MEA).

[0081] Test conditions: In an H2 / O2 (1:1) atmosphere, it was operated at a constant voltage of 0.6V, the current density was gradually increased to 0.8 A / cm², and the performance degradation was evaluated after 30,000 cycles.

[0082] Activity retention rate: The ratio of the current density at 0.6V after cycling to the initial value:

[0083] Table 2

[0084] Activity retention rate % Example 1 88.2 Example 2 88.3 Example 3 88.6 Example 4 88.9 Comparative Example 1 63.5 Comparative Example 2 75.7

[0085] As can be seen from Table 2, the noble metal catalyst for hydrogen fuel cells prepared by the present invention can improve the durability of hydrogen fuel cells.

[0086] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-performance hydrogen fuel cell precious metal catalyst production process, characterized in that: The following steps are involved: (1) Precious metal precursor: Platinum source, lanthanum source and zirconium source are dissolved in an organic solvent at an atomic ratio of 0.4-0.6:0.15-0.25:0.15-0.25, and heated to 460-500°C with the aid of microwaves for 20-25 minutes to obtain a precious metal precursor; (2) Carrier gradient modification: using The mixed gas is used as plasma to treat the activated carbon carrier with a power density of 70-130W / cm². After the plasma treatment, the activated carbon carrier is firstly subjected to liquid nitrogen quick freezing treatment at -196°C, kept warm for 30 minutes, then restored to 20°C, kept warm for 30 minutes, and then subjected to gradient temperature increase treatment from 20°C to 110°C, and finally returned to room temperature to obtain a modified carrier; (3) Nanocomposite deposition: The noble metal precursor and the modified support are mixed under the assistance of ultrasound at a frequency of 42 kHz, and then the solvent is removed by freeze drying to obtain a composite; (4) High temperature treatment: In an inert atmosphere, the temperature of the composite is raised to 950-1000°C at a rate of 4°C / min, kept at this temperature for 2-3 hours, then gradually cooled, kept at 160-170°C for 1.5 hours, and then returned to room temperature to obtain a precious metal catalyst.

2. The production process according to claim 1, characterized in that: The platinum source in step (1) is chloroplatinic acid, the lanthanum source is lanthanum nitrate, the zirconium source is zirconium nitrate, and the organic solvent is a mixed solution of polyethylene glycol and polyvinyl alcohol in a mass ratio of 1:

2.

3. The production process according to claim 1, characterized in that: The microwave power of the microwave-assisted heating in step (1) is 400W.

4. The production process according to claim 1, characterized in that: The time for treating the activated carbon carrier with plasma in step (2) is 15-18 minutes.

5. The production process according to claim 1, characterized in that: The rate of the gradient heating in step (2) is 4-4.5°C / min.

6. The production process according to claim 1, characterized in that: The modified carrier in step (3) is mixed with the noble metal precursor at a mass ratio of 2.2-2.8:

1.

7. The production process according to claim 1, characterized in that: The time of ultrasonic-assisted mixing in step (3) is 25-30 minutes, and the ultrasonic frequency is 40 kHz.

8. The production process according to claim 1, characterized in that: In step (4), the inert atmosphere is nitrogen or argon, and the gas purity is not less than 99.95%.

9. The production process according to claim 1, characterized in that: The gradient cooling rate in step (4) is 8°C / min.

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