Mesoporous carbon-loaded layered platinum-based intermetallic compound as well as preparation method and application thereof

Abstract

The invention discloses a mesoporous carbon-loaded layered platinum-based intermetallic compound and a preparation method and application thereof, and relates to the technical field of electrocatalysts, the preparation method of the mesoporous carbon-loaded layered platinum-based intermetallic compound comprises the following steps: S1, dispersing platinum salt, non-noble metal salt, a surfactant and mesoporous carbon in a solvent, and drying to obtain a mesoporous carbon-loaded layered platinum-based intermetallic compound; performing high-temperature annealing to obtain a mesoporous carbon loaded platinum-based intermetallic compound; and S2, placing the mesoporous carbon-loaded platinum-based intermetallic compound prepared in the step S1 and sodium hypophosphite in the same porcelain boat in a non-contact manner, and performing high-temperature annealing to obtain the mesoporous carbon-loaded layered platinum-based intermetallic compound. According to the mesoporous carbon-loaded layered platinum-based intermetallic compound prepared by the invention, the exposure proportion and the utilization rate of platinum atoms can be remarkably improved, and the electrocatalytic activity of an alkaline hydroxide reaction is greatly improved and the durability is synchronously optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysts, and particularly relates to a mesoporous carbon-supported layered platinum-based intermetallic compound, a preparation method thereof, and uses thereof. Background Art

[0002] With the rapid consumption of global traditional energy and the aggravation of environmental pollution, hydrogen energy has become the core direction of the green energy transformation due to its zero-carbon emission characteristics. Hydrogen fuel cells generate electricity through the electrochemical reaction of hydrogen and oxygen. However, the key link - the anodic hydrogen oxidation reaction has a slow reaction rate under alkaline conditions, resulting in low overall efficiency of the battery. At present, platinum metal is widely used as the core material for catalyzing the alkaline hydrogen oxidation reaction due to its proper "adsorption-release" ability with hydrogen. However, platinum, as a rare and precious metal, is expensive and limited in reserves. The direct use of pure platinum catalysts is too costly, seriously restricting the large-scale promotion of fuel cells.

[0003] To solve the above problems, research teams at home and abroad have combined platinum with other inexpensive metals to form platinum-based intermetallic compounds with stable structures. Platinum-based intermetallic compounds can not only reduce the usage amount of platinum through ordered atomic arrangements but also improve catalytic activity and corrosion resistance. However, most of the platinum-based intermetallic compounds synthesized by existing technologies are in large particle structures, and the internal platinum atoms are "buried" by the outer-layer atoms, resulting in a large number of active sites being unable to participate in the reaction, and the platinum utilization rate being less than one-fifth of that of commercial platinum-carbon catalysts. In addition, when the existing platinum-based intermetallic compounds are used in the hydrogen oxidation catalytic reaction under alkaline conditions, the surface platinum atoms are prone to fall off or become inactivated, while the internal platinum atoms are ineffective because they cannot contact the reaction medium, causing serious waste of precious metal resources. Therefore, how to design a nanostructured catalyst that can expose surface platinum atoms and activate internal platinum sites has become a key challenge to break through the bottleneck of the alkaline hydrogen oxidation reaction. Summary of the Invention

[0004] To solve the problems of the slow reaction rate of the hydrogen oxidation reaction in an alkaline environment and the low utilization rate of platinum atoms when the existing platinum-based intermetallic compounds are used as catalysts for the hydrogen oxidation reaction, the present invention aims to provide a mesoporous carbon-supported layered platinum-based intermetallic compound, a preparation method thereof, and uses as an electrocatalyst for the alkaline hydrogen oxidation reaction.

[0005] The technical problems to be solved by the present invention are achieved by the following technical solutions:

[0006] The first object of the present invention is to provide a preparation method of a mesoporous carbon-supported layered platinum-based intermetallic compound, comprising the following steps:

[0007] S1. Dispersing a platinum salt, a non-noble metal salt, a surfactant, and mesoporous carbon in a solvent, drying, and performing high-temperature annealing to obtain a mesoporous carbon-supported platinum-based alloy;

[0008] S2. Place the above-mentioned mesoporous carbon-supported platinum-based alloy and sodium hypophosphite in the same porcelain boat without contact, and perform high-temperature annealing to obtain a mesoporous carbon-supported layered platinum-based intermetallic compound.

[0009] Furthermore, the platinum salt includes but is not limited to at least one of chloroplatinic acid, potassium chloroplatinate, and sodium chloroplatinate.

[0010] Furthermore, the non-noble metal salt includes but is not limited to at least one of nitrates and sulfates of aluminum, gallium, and indium.

[0011] Furthermore, the surfactant is a quaternary ammonium salt surfactant, including but not limited to at least one of tetrapropylammonium chloride and tetrahexylammonium chloride.

[0012] Furthermore, the solvent is ethanol.

[0013] Furthermore, the dosage ratio of the platinum salt, non-noble metal salt, sodium hypophosphite, surfactant, and mesoporous carbon is 5 mmol: 1 mmol: 15 mmol: 50 mg: 30 mg.

[0014] In the present invention, the order of adding the platinum salt, non-noble metal salt, and surfactant into the solvent is not required, but it is necessary to fully dissolve to form a homogeneous solution. The role of the surfactant is to promote the uniform dispersion of the carbon precursor in the solution and form a stable nano-scale sol.

[0015] In step S1, the temperature of the high-temperature annealing is 500 - 700 °C, the heating rate is 1 - 5 °C / min, the holding time is 1 - 3 h, and the cooling rate is 3 - 5 °C / min.

[0016] Furthermore, the dispersion method is stirring or ultrasonic, preferably ultrasonic.

[0017] Furthermore, the porcelain boat is wrapped with tin foil paper, aiming to prevent the carrier gas from blowing the mesoporous carbon-supported platinum-based alloy outside the porcelain boat, which is beneficial to the reaction of the mesoporous carbon-supported platinum-based alloy in a phosphorus-rich atmosphere.

[0018] In step S2, the temperature of the high-temperature annealing is 300 - 500 °C, the heating rate is 1 - 5 °C / min, the holding time is 1 - 3 h, and the cooling rate is 3 - 5 °C / min.

[0019] In steps S1 and S2, the high-temperature annealing is carried out in an inert atmosphere, including argon or nitrogen.

[0020] In the present invention, high-temperature annealing can enhance the crystallization properties of the powder system and promote the uniformity of the elemental distribution of the particles.

[0021] The second objective of the present invention is to provide a mesoporous carbon-supported layered platinum-based intermetallic compound prepared by the aforementioned preparation method.

[0022] The third objective of the present invention is to provide the use of the aforementioned mesoporous carbon-supported layered platinum-based intermetallic compound as an electrocatalyst for the alkaline hydrogen oxidation reaction.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. Through the pore confinement effect of the mesoporous carbon support, the present invention effectively inhibits the aggregation and growth of nanoparticles during high-temperature treatment, and prepares catalytically active sites with uniform size; meanwhile, the highly conductive skeleton structure of the mesoporous carbon support significantly improves the electron transfer rate during the electrocatalytic process, ultimately achieving a substantial increase in the catalyst activity.

[0025] 2. The present invention utilizes the nitrogen sites formed by the quaternary ammonium salt surfactant and mesoporous carbon during the annealing process to anchor the intermetallic compound nanoparticles, restricting the migration of the intermetallic compound during the annealing process, and effectively ensuring the morphological controllability of the product.

[0026] 3. The present invention promotes the uniform loading of metal salts on the carbon support through ultrasonic dispersion to ensure the precise preparation of intermetallic compounds with specific structures after high-temperature annealing.

[0027] 4. By introducing phosphorus atoms, the present invention constructs a layered intermetallic compound structure in the platinum-based alloy particles. The phosphorus atoms are anchored in the interlayer in the form of single atoms, inhibiting the interlayer slip and enhancing the structural stability through chemical bonding; meanwhile, the layered structure exposes high-density active crystal planes, significantly increasing the exposure ratio and utilization rate of platinum atoms, ultimately achieving a substantial increase in the electrocatalytic activity and synchronous optimization of the durability.

[0028] 5. The mesoporous carbon-supported layered platinum-based intermetallic compound of the present invention has a novel structure and controllable size and morphology; moreover, the preparation method provided by the present invention has a simple process, is easy to repeat, and can be applied industrially. Description of the Drawings

[0029] Figure 1 Transmission electron microscope images of Pt5AlP, Pt5GaP, and Pt5InP prepared in Examples 1-3;

[0030] Figure 2 X-ray diffraction patterns of Pt5AlP, Pt5GaP, and Pt5InP prepared in Examples 1-3;

[0031] Figure 3Activity comparison chart of Pt5AlP, Pt5GaP, Pt5InP prepared in Examples 1-3, Pt5Ga, Pt5Ga@P alloys prepared in Comparative Examples 1-2, and commercial platinum-carbon for electrocatalytic alkaline hydrogen oxidation reaction. Detailed implementation manners

[0032] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments and illustrations.

[0033] The mesoporous carbon in the following examples and comparative examples is Ketjenblack ECP-600JD.

[0034] Example 1

[0035] (1) Dissolve 0.05 mmol of chloroplatinic acid and 0.01 mmol of aluminum nitrate in 5 mL of ethanol, then add 50 mg of tetrahexylammonium chloride and dissolve it thoroughly to obtain a homogeneous and transparent solution.

[0036] (2) Add 30 mg of mesoporous carbon to the solution obtained in step (1), and disperse it by ultrasonic wave to obtain a homogeneous sol.

[0037] (3) Freeze-dry the sol obtained in step (2) to obtain a black powder.

[0038] (4) Place the black powder obtained in step (3) in a tubular furnace, heat it to 600 °C at a heating rate of 3 °C / min in an argon atmosphere and anneal for 2 h, and then cool it to room temperature at a cooling rate of 4 °C / min to obtain a mesoporous carbon-supported platinum-based alloy.

[0039] (5) Place the mesoporous carbon-supported platinum-based alloy obtained in step (4) and 0.75 mmol of sodium hypophosphite in the same porcelain boat without contact, wrap the porcelain boat with tin foil paper, and then place it in a tubular furnace. Heat it to 400 °C at a heating rate of 3 °C / min in an argon atmosphere and anneal for 2 h, and then cool it to room temperature at a cooling rate of 4 °C / min to obtain a mesoporous carbon-supported layered platinum-based intermetallic compound (abbreviated as Pt5AlP).

[0040] The transmission electron microscope image of Pt5AlP prepared in Example 1 is as Figure 1 shown. It can be seen from Figure 1 that Pt5AlP is nanoparticles with an average size of about 5 nm.

[0041] The X-ray diffraction pattern of Pt5AlP prepared in Example 1 is as Figure 2 shown. It can be seen from Figure 2 that the diffraction data of Pt5AlP is consistent with the standard diffraction card, thus proving that the sample is Pt5AlP.

[0042] Example 2

[0043] According to the method of Example 1, except that aluminum nitrate is replaced by gallium nitrate.

[0044] The transmission electron microscope image of Pt5GaP prepared in Example 2 is as Figure 1 shown. It can be seen from Figure 1 that Pt5GaP is nanoparticles with an average size of about 5 nm.

[0045] The X-ray diffraction pattern of Pt5GaP prepared in Example 2 is as Figure 2 shown. It can be seen from Figure 2 that the diffraction data of Pt5GaP is consistent with the standard diffraction card, thus proving that the sample is Pt5GaP.

[0046] Example 3

[0047] According to the method of Example 1, except that aluminum nitrate is replaced by indium nitrate.

[0048] The transmission electron microscope image of Pt5InP prepared in Example 3 is as Figure 1 shown. It can be seen from Figure 1 that Pt5InP is nanoparticles with an average size of about 5 nm.

[0049] The X-ray diffraction pattern of Pt5InP prepared in Example 3 is as Figure 2 shown. It can be seen from Figure 2 that the diffraction data of Pt5InP is consistent with the standard diffraction card, thus proving that the sample is Pt5InP.

[0050] Example 4

[0051] According to the method of Example 1, except that chloroplatinic acid is replaced by potassium chloroplatinate.

[0052] Example 5

[0053] According to the method of Example 1, except that aluminum nitrate is replaced by aluminum sulfate.

[0054] Example 6

[0055] According to the method of Example 1, except that the annealing conditions in step (4) are changed, that is: heating to 500 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and annealing for 3 h, and then cooling to room temperature at a cooling rate of 3 °C / min.

[0056] Example 7

[0057] According to the method of Example 1, except that the annealing conditions in step (5) were changed, that is: heated to 300 °C at a heating rate of 2 °C / min in a nitrogen atmosphere and annealed for 3 h, and then cooled to room temperature at a cooling rate of 5 °C / min.

[0058] Comparative Example 1

[0059] According to the method of Example 2, except that sodium hypophosphite was not added.

[0060] (1) Dissolve 0.05 mmol of chloroplatinic acid and 0.01 mmol of gallium nitrate in 5 mL of ethanol, then add 50 mg of tetrahexylammonium chloride and dissolve it thoroughly to obtain a homogeneous transparent solution.

[0061] (2) Add 30 mg of mesoporous carbon to the solution obtained in step (1) and disperse it by ultrasonic treatment to obtain a homogeneous sol.

[0062] (3) Lyophilize the sol obtained in step (2) to obtain a black powder.

[0063] (4) Place the black powder obtained in step (3) in a tube furnace, heat it to 600 °C at a heating rate of 3 °C / min in an argon atmosphere and anneal for 2 h, and then cool it to room temperature at a cooling rate of 4 °C / min to obtain a platinum-based alloy supported on mesoporous carbon.

[0064] (5) Place the platinum-based alloy supported on mesoporous carbon obtained in step (4) in a tube furnace, heat it to 400 °C at a heating rate of 3 °C / min in an argon atmosphere and anneal for 2 h, and then cool it to room temperature at a cooling rate of 4 °C / min to obtain a platinum-based alloy supported on mesoporous carbon (abbreviated as Pt5Ga).

[0065] Comparative Example 2

[0066] According to the method of Example 2, except that tetrahexylammonium chloride was not added.

[0067] (1) Dissolve 0.05 mmol of chloroplatinic acid and 0.01 mmol of gallium nitrate in 5 mL of ethanol and dissolve it thoroughly to obtain a homogeneous transparent solution.

[0068] (2) Add 30 mg of mesoporous carbon to the solution obtained in step (1) and disperse it by ultrasonic treatment to obtain a homogeneous sol.

[0069] (3) Lyophilize the sol obtained in step (2) to obtain a black powder.

[0070] (4) Place the black powder obtained in step (3) in a tube furnace, heat it to 600 °C at a heating rate of 3 °C / min in an argon atmosphere and anneal for 2 h, and then cool it to room temperature at a cooling rate of 4 °C / min to obtain a platinum-based alloy supported on mesoporous carbon.

[0071] (5) The platinum-based alloy supported on mesoporous carbon obtained in step (4) and 0.75 mmol of sodium hypophosphite are placed in the same porcelain boat without contact, and the porcelain boat is wrapped with tin foil paper, and then placed in a tube furnace. It is heated to 400 °C at a heating rate of 3 °C / min in an argon atmosphere and annealed for 2 h, and then cooled to room temperature at a cooling rate of 4 °C / min to obtain a platinum-based alloy supported on mesoporous carbon (abbreviated as Pt5Ga@P alloy).

[0072] An electrochemical test was carried out under a standard three-electrode system using a CHI 760E electrochemical workstation (Shanghai Zhenhua Instrument Co., Ltd.) with a rotating disk. Weigh 2 mg of the products prepared in the above examples and comparative examples respectively and ultrasonically disperse them in 1 mL of a mixed solution (containing 970 μL of ethanol and 30 μL of Nafion solution) to obtain ink. 10 μL of the ink was evenly coated on a glassy carbon electrode (5 mm in diameter), dried to obtain a working electrode. A silver / silver chloride electrode was used as the reference electrode and graphite as the counter electrode. The obtained three electrodes were first subjected to 20 cyclic voltammetry (CV) tests at a scanning rate of 20 mV / s in a hydrogen-saturated 0.1 M potassium hydroxide (KOH) solution, and then a stable linear sweep voltammetry (LSV) curve was recorded at a scanning rate of 5 mV / s in a 0.1 M KOH solution. All potentials were calibrated with a reversible hydrogen electrode (RHE), that is, E(RHE) = E(vs. Ag / AgCl) + 0.197 V + 0.0592 × pH.

[0073] Figure 3 Comparison diagram of the electrocatalytic activity of Pt5AlP, Pt5GaP, Pt5InP prepared in Examples 1-3, Pt5Ga, Pt5Ga@P alloys prepared in Comparative Examples 1-2, and commercial platinum carbon (20 wt%, purchased from Umicore) for the alkaline hydrogen oxidation reaction. From Figure 3 It can be seen that when reaching the same overpotential, using the layered platinum-based intermetallic compound supported on mesoporous carbon prepared in Examples 1-3 as the active material of the working electrode can make the assembled three-electrode have a higher current density, indicating that the layered platinum-based intermetallic compound supported on mesoporous carbon described in the present invention has better electrocatalytic activity for the alkaline hydrogen oxidation reaction than commercial platinum carbon.

[0074] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of mesoporous carbon-supported layered platinum-based intermetallic compound, characterized in that, Comprising the following steps: S1. Disperse a platinum salt, a non-noble metal salt, a surfactant and mesoporous carbon in a solvent, dry, and perform high-temperature annealing to obtain a platinum-based alloy supported on mesoporous carbon; S2. Place the platinum-based alloy supported on mesoporous carbon and sodium hypophosphite in the same porcelain boat without contact, and perform high-temperature annealing to obtain a layered platinum-based intermetallic compound supported on mesoporous carbon.

2. The preparation method according to claim 1, characterized in that: The platinum salt is at least one of chloroplatinic acid, potassium chloroplatinate, and sodium chloroplatinate; Preferably, the non-noble metal salt is at least one of nitrates and sulfates of aluminum, gallium, and indium; Preferably, the solvent is ethanol.

3. The preparation method according to claim 2, characterized in that: The surfactant is a quaternary ammonium salt surfactant.

4. The preparation method according to claim 1, characterized in that: The dosage ratio of the platinum salt, non-noble metal salt, sodium hypophosphite, surfactant, and mesoporous carbon is 5 mmol: 1 mmol: 15 mmol: 50 mg: 30 mg.

5. The preparation method according to claim 1, characterized in that: In step S1, the temperature of the high-temperature annealing is 500-700 °C, the heating rate is 1-5 °C / min, the heat preservation time is 1-3 h, and the cooling rate is 3-5 °C / min.

6. The preparation method according to claim 1, wherein: The porcelain boat is wrapped with tin foil.

7. The preparation method according to claim 1, characterized in that: In step S2, the temperature of the high-temperature annealing is 300-500 °C, the heating rate is 1-5 °C / min, the heat preservation time is 1-3 h, and the cooling rate is 3-5 °C / min.

8. The preparation method according to claim 1, characterized in that: In steps S1 and S2, the high-temperature annealing is carried out in an inert atmosphere; preferably, the inert atmosphere is argon or nitrogen.

9. A layered platinum-based intermetallic compound supported on mesoporous carbon prepared by the preparation method according to any one of claims 1-8.

10. Use of the layered platinum-based intermetallic compound supported on mesoporous carbon according to claim 9 as an electrocatalyst for the alkaline hydrogen oxidation reaction.

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