Preparation method of platinum-based alloy catalyst

Abstract

The invention provides a preparation method of a platinum-based alloy catalyst, and belongs to the field of alloy preparation. The invention provides a preparation method of a platinum-based alloy catalyst, which comprises the following steps: obtaining a ground state crystal structure of the platinum-based alloy catalyst by using crystal structure prediction software, and obtaining the composition of the platinum-based alloy catalyst according to the ground state crystal structure; the platinum-based alloy catalyst is obtained by mixing the corresponding metal elementary substances according to the composition and then smelting the metal elementary substances. And the ratio of the molar ratio of each metal element except platinum to platinum to the molar ratio of the corresponding metal element except platinum to platinum in the composition is independently (1.5-1.7): 1. According to the method, the ground state crystal structure of the platinum-based alloy catalyst is obtained by using crystal structure prediction software, and then the platinum-based alloy catalyst is prepared, so that the test quantity and the period length are greatly reduced when the platinum-based catalyst is prepared, and the cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of alloy preparation, and in particular to a method for preparing a platinum-based alloy catalyst. Background Art

[0002] The long-term human activities of large-scale consumption of carbon-based fuels have had a series of serious negative impacts on the global climate and environment, and have also caused human anxiety about the decreasing reserves of earth resources. With water as the only byproduct, proton exchange membrane fuel cells (PEMFCs), as an emerging green energy conversion technology, are expected to achieve zero emission, renewable and high efficiency of hydrogen energy during use.

[0003] However, the slow kinetics of the oxygen reduction reaction (ORR) in PEMFCs limits the widespread application of clean energy conversion technologies. Therefore, efficient electrocatalysts are essential for energy conversion systems. Currently, highly active platinum-based alloys are used as commercial ORR catalysts, which can effectively improve the slow kinetics in the ORR reaction.

[0004] The development of new platinum-based alloy catalysts mainly focuses on adjusting the electronic structure of the catalyst and improving the adsorption state of the catalyst to the intermediate. However, there are many orthogonal experimental variables that need to be adjusted when determining the electronic structure and improving the adsorption state, and the test volume is large and the cycle is long, which invisibly increases the time and economic cost of PEMFCs in the production process. Summary of the invention

[0005] The invention provides a method for preparing a platinum-based alloy catalyst. The platinum-based alloy catalyst prepared by the invention has low cost.

[0006] The present invention provides a method for preparing a platinum-based alloy catalyst, comprising the following steps:

[0007] Using crystal structure prediction software to obtain a ground state crystal structure of the platinum-based alloy catalyst, and obtaining the composition of the platinum-based alloy catalyst according to the ground state crystal structure;

[0008] According to the composition, corresponding metal elements are mixed and then smelted to obtain the platinum-based alloy catalyst;

[0009] The ratio of the molar ratio of each metal element other than platinum to platinum and the molar ratio of the corresponding metal element other than platinum to the platinum element in the composition is independently 1.5 to 1.7:1.

[0010] Preferably, the platinum-based alloy catalyst comprises Pt m X n or Pt m X n Y p ;

[0011] The X and Y independently include one of Li, Na, K, Ca, Al, Zn and Mg, and the X and Y are different;

[0012] m, n and p are independently natural numbers of 1 to 8.

[0013] Preferably, the platinum-based alloy catalyst includes one of Ca5Pt4, Ca5Pt2, Ca6Pt, Ca3Pt2, Ca2Pt3, CaPt5, Ca2Pt, CaPt, CaPt2, Li2Pt, Li4Pt, LiPt7, Li8Pt, LiPt, LiPt3 and Li3Pt5.

[0014] Preferably, the crystal structure of the platinum-based alloy catalyst includes one of triclinic, monoclinic, orthorhombic, hexagonal, rhombohedral, tetragonal and cubic.

[0015] Preferably, the smelting is carried out in a protective atmosphere.

[0016] Preferably, the protective atmosphere includes an argon atmosphere.

[0017] Preferably, the smelting method is electric current smelting.

[0018] Preferably, the current of the current smelting is an intermittent current, the magnitude of the intermittent current is 50-60A, and the intermittent time is 0.5-1.5s;

[0019] The current smelting time is 3 to 7 minutes.

[0020] Preferably, after the smelting, the process further comprises: cooling the obtained melt to obtain the platinum-based alloy catalyst.

[0021] Preferably, obtaining the ground state crystal structure of the platinum-based alloy catalyst using crystal structure prediction software comprises the following steps:

[0022] (1) Determine the element type of the platinum-based alloy catalyst, then use crystal structure prediction software to generate a primary crystal structure, and then use first-principles calculation software to optimize the primary crystal structure to obtain the energy value of the crystal structure;

[0023] (2) feeding back the energy value to the crystal structure prediction software for generating the next generation crystal structure;

[0024] (3) Repeating steps (1) to (2) until no lower energy crystal structure is generated for thirty consecutive generations, thereby obtaining the ground state crystal structure of the platinum-based alloy catalyst.

[0025] The present invention first uses crystal structure prediction software to obtain the ground state crystal structure of the platinum-based alloy catalyst, and then prepares the platinum-based alloy catalyst, so that the test amount and cycle length when preparing the platinum-based catalyst are greatly reduced, and the cost is reduced. In addition, in the preparation process of the platinum-based alloy catalyst, the metal element will volatilize at high temperature, resulting in the metal element ratio in the finished crystal being lower than the theoretical value. The present invention makes the molar ratio of each metal element other than platinum in the preparation raw material to platinum and the molar ratio of the metal element to the platinum element in the platinum-based alloy catalyst be 1.5 to 1.7:1, which is higher than the theoretical value, and can ensure that the prepared structure is consistent with the structure of the platinum-based alloy catalyst. Compared with the preparation method of the traditional platinum-based alloy catalyst, the present invention directly uses the smelting method to prepare the new structure generated by the crystal structure prediction in one step, which increases the probability of structural synthesis and shortens the synthesis process. At the same time, the method has no waste liquid / gas discharge, and is an environmentally friendly method.

[0026] The crystal structure prediction software obtains the composition of the platinum-based alloy catalyst and combines it with arc melting to achieve the one-step preparation of low-platinum-loaded alloy catalysts. This overcomes the shortcomings of conventional orthogonal experiments, such as many variables, large test volume, long cycle, and unclear target product structure composition.

[0027] First, the ground state structure of alloy catalysts with different platinum contents was obtained through crystal structure prediction, and then the performance of alloy catalysts with different platinum contents was obtained through simulation calculation. Finally, the target platinum-based alloy catalyst was prepared in one step by arc melting. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flow chart for predicting crystal structure for an embodiment;

[0029] Figure 2 A schematic diagram of the device used in the embodiment;

[0030] Figure 3 is the predicted Ca x Pt y Crystal structure diagram;

[0031] Figure 4 is a schematic diagram of the structure of CaPt5;

[0032] Figure 5 To predict the XRD and crystal structure of the prepared CaPt5, simulated XRD of the CaPt5 crystal structure was obtained;

[0033] Figure 6 SEM and ESD images of the prepared CaPt5;

[0034] Figure 7 Energy spectrum of the prepared CaPt5 alloy;

[0035] Figure 8is a schematic diagram of the structure of CaPt2;

[0036] Fig. 9 The XRD and crystal structure prediction of CaPt2 prepared in Example 2 obtains the simulated XRD of the CaPt2 crystal structure;

[0037] Fig.10 SEM and ESD of the prepared CaPt2;

[0038] Fig.11 Simulated XRD of other Ca-Pt intermetallic compounds obtained for crystal structure prediction;

[0039] Fig.12 is the predicted Li x Pt y Crystal structure diagram;

[0040] Fig.13 Schematic diagram of the structure of Li2Pt;

[0041] Fig.14 The XRD and crystal structure prediction of Li2Pt prepared in Example 3 obtained the simulated XRD of the Li2Pt crystal structure;

[0042] Fig.15 It is a schematic diagram of the structure of LiPt3;

[0043] Fig.16 The XRD and crystal structure prediction of LiPt3 prepared in Example 4 is used to obtain the simulated XRD of the LiPt3 crystal structure;

[0044] Fig.17 Simulated XRD of other Li-Pt intermetallic compounds obtained for crystal structure prediction. DETAILED DESCRIPTION

[0045] The present invention provides a method for preparing a platinum-based alloy catalyst, comprising the following steps:

[0046] Using crystal structure prediction software to obtain a ground state crystal structure of the platinum-based alloy catalyst, and obtaining the composition of the platinum-based alloy catalyst according to the ground state crystal structure;

[0047] According to the composition, corresponding metal elements are mixed and then smelted to obtain the platinum-based alloy catalyst;

[0048] The ratio of the molar ratio of each metal element other than platinum to platinum and the molar ratio of the corresponding metal element other than platinum to the platinum element in the composition is independently 1.5 to 1.7:1.

[0049] In the present invention, the ground state crystal structure of the platinum-based alloy catalyst is obtained using crystal structure prediction software, preferably including the following steps:

[0050] (1) Determine the element type of the platinum-based alloy catalyst, then use crystal structure prediction software to generate a primary crystal structure, and then use first-principles calculation software to optimize the primary crystal structure to obtain the energy value of the crystal structure;

[0051] (2) The energy value is fed back to the crystal structure prediction software to generate the next generation crystal structure;

[0052] (3) Repeat steps (1) to (2) until no lower energy crystal structure is generated for thirty consecutive generations, thereby obtaining the ground state crystal structure of the platinum-based alloy catalyst.

[0053] In the present invention, the crystal structure prediction software preferably includes Calypso or USPEX, and the first principle calculation software includes VASP, ABINIT or WIEN2K.

[0054] The present invention has no special limitation on the steps (1) to (3), and any method known to those skilled in the art can be used. Specifically, taking USPEX as an example: x M y The structure is searched for all components, with x:y ranging from 1:0 to 0:1. The space group of the structure search is limited to the range of 2 to 230, and the number of atoms in the primitive cell is limited to the range of 1 to 20. The first generation of structures is 200, generated by topological and random structure generators. Each subsequent generation of 100 structures is based on the calculated structures of the previous generation, generated by genetic algorithms (50%), topological machines (20%), mutations (10%), and randomness (10%). The convergence criterion is that no lower energy structure is generated after 30 consecutive repeated calculations.

[0055] In the present invention, the platinum-based alloy catalyst preferably comprises Pt m X n or Pt m X n Y p ; X and Y preferably independently include one of Li, Na, K, Ca, Al, Zn and Mg; X and Y are different; M, n and p are preferably independently natural numbers of 1 to 8.

[0056] In the present invention, the platinum-based alloy catalyst preferably includes Ca5Pt4, Ca5Pt2, Ca6Pt, Ca3Pt2, Ca2Pt3, CaPt5, Ca2Pt, CaPt, CaPt2, Li2Pt, Li4Pt, LiPt7, Li8Pt, LiPt, LiPt3, and Li3Pt5.

[0057] In the present invention, the crystal structure of the platinum-based alloy catalyst preferably includes one or more of triclinic, monoclinic, orthorhombic, hexagonal, rhombohedral, tetragonal and cubic.

[0058] In the present invention, the molar ratio of each metal element other than platinum to platinum and the molar ratio of the corresponding metal element other than platinum in the composition to the platinum element are independently 1.5 to 1.7:1. In specific embodiments of the present invention, they can be 1.5:1, 1.6:1 or 1.7:1.

[0059] In the present invention, the smelting is carried out in a protective atmosphere; the smelting method is preferably electric current smelting; the current of the electric current smelting is preferably intermittent current, and the size of the intermittent current is preferably 50-60A. In a specific embodiment of the present invention, the size of the intermittent current can be 50A, 51A, 52A, 53A, 54A, 55A, 56A, 57A, 58A, 59A or 60A; the intermittent time is preferably 0.5-1.5s. In a specific embodiment of the present invention, the intermittent time can be 0.5s, 1s or 1.5s; the time of the electric current smelting is preferably 5-7min, and the electric current smelting is preferably carried out in a protective atmosphere.

[0060] After the smelting, the process further comprises: cooling the obtained melt to obtain the platinum-based alloy catalyst. In the present invention, the cooling method is natural cooling.

[0061] The present invention also provides a device used in the preparation method described in the above technical solution, comprising an arc melting furnace 5;

[0062] A circulating cooling water tank 1, a device for containing protective gas 3 and a vacuum pump 5 connected to the arc melting furnace;

[0063] An arc melting furnace controller 2 controls the arc melting furnace 5 .

[0064] In the present invention, the method for using the device comprises the following steps:

[0065] (1) Platinum powder and other metal elements are mixed evenly and placed in a crucible of an arc melting furnace 5;

[0066] (2) Use a vacuum pump to evacuate the arc melting furnace cavity to a vacuum state, and then use argon gas to pressurize the cavity to normal pressure, and repeat this step three times;

[0067] (3) Open the circulating cooling water tank to provide cooling water for the high-temperature arc melting furnace;

[0068] (4) Turn on the controller of the arc melting furnace, adjust the current to a level that can melt the material, align the electrode with the material in the clamp pot, and use intermittent current to stimulate the synthesis reaction between the platinum powder and other metal elements.

[0069] The preparation method of the platinum-based alloy catalyst provided by the present invention is described in detail below in conjunction with the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0070] Figure 1 A flow chart for predicting crystal structure for an embodiment;

[0071] Figure 2 This is a schematic diagram of the device used in the embodiment, and the device model is MSM20-7 metal smelting suction casting furnace.

[0072] Simulation:

[0073] Ca x Pt y The crystal structure was searched for all components, with x:y ranging from 1:0 to 0:1. The space group of the crystal structure search was limited to 2-230, and the number of atoms in the primitive cell was limited to 1-20. The first generation of crystal structures was generated in 200 numbers, which were generated by the topological and random crystal structure generator.

[0074] Each subsequent generation of 100 crystal structures is based on the calculated crystal structures of the previous generation and is generated by genetic algorithms (50%), topological machines (20%), mutations (10%), and randomness (10%). The convergence criterion is that no crystal structure with lower energy is generated after 30 consecutive repetitions of calculation. The final predicted Ca x Pt y The crystal structure is shown in 3. x Pt y The lattice parameters and atomic positions are shown in Table 1.

[0075] Table 1. Ca x Pt y Lattice parameters and atomic positions

[0076]

[0077]

[0078] Example 1

[0079] Preparation and characterization of CaPt5

[0080] The target alloy CaPt5 belongs to the hexagonal system, and the space group is P6 / mmm. The structural diagram of CaPt5 is shown in Figure 4 shown.

[0081] (1) Platinum powder and metal Ca powder are mixed evenly and placed in a crucible of an arc melting furnace;

[0082] (2) To prevent air from participating in the reaction during arc melting, the arc melting furnace needs to be purged. Use a vacuum pump to evacuate the arc melting furnace cavity to a vacuum state, and then use argon gas to pressurize the cavity to normal pressure. Repeat this step three times;

[0083] (3) Open the circulating cooling water tank to provide cooling water for the high-temperature arc melting furnace;

[0084] (4) Turn on the controller of the arc melting furnace, adjust the current to a level that can melt the material, aim the electrode at the material in the clamp pot, and use intermittent current (to avoid excessive temperature and excessive volatilization of active metals, the interval time is 1 second) to stimulate the synthesis reaction of platinum metal and metal Ca for 5 minutes;

[0085] (5) In order to ensure that platinum metal and metal Ca fully react to form the target alloy catalyst, the arc melting furnace needs to be left to stand for 3 minutes and then cooled to room temperature to obtain CaPt5.

[0086] The molar ratio of Pt to Ca in the raw materials is 2.93:1, the arc melting current is 55A, and the time is 5 minutes.

[0087] Figure 5 The simulated XRD of the CaPt5 crystal structure was obtained to predict the XRD and crystal structure of the prepared CaPt5.

[0088] Depend on Figure 5 It can be seen that the main peaks in the XRD spectrum match, indicating that the experiment successfully prepared the CaPt5 crystal structure with a space group of P6 / mmm.

[0089] Figure 6 SEM and ESD of prepared CaPt5.

[0090] Depend on Figure 6 It can be seen that the CaPt5 obtained by arc melting has a uniform crystal structure and the distribution of calcium and platinum elements is consistent.

[0091] The energy spectrum of the prepared CaPt5 alloy is as follows Figure 7 And as shown in Table 2.

[0092] Table 2 Element distribution of CaPt5 alloy

[0093]

[0094] Depend on Figure 7 As can be seen from Table 2, the atomic ratio of calcium to platinum is nearly 1:5, which proves the uniformity of the prepared alloy.

[0095] Example 2

[0096] Preparation and characterization of CaPt2

[0097] The target alloy CaPt2 belongs to the trigonal system, and the space group is Fd-3m. The structural diagram of CaPt2 is shown in Figure 8 shown.

[0098] The difference from Example 1 is:

[0099] The molar ratio of raw materials Pt and Ca is 1.33:1, and CaPt2 is obtained.

[0100] Fig. 9 The simulated XRD of the CaPt2 crystal structure was obtained to predict the XRD and crystal structure of the prepared CaPt2.

[0101] Depend on Fig. 9 It can be seen that the present invention successfully prepared the CaPt2 crystal structure with the space group Fd-3m.

[0102] Fig.10 SEM and ESD of the prepared CaPt2.

[0103] Depend on Fig.10 It can be seen that the CaPt2 crystal structure produced by arc melting is uniform, and the distribution of calcium and platinum elements is consistent.

[0104] The simulated XRD patterns of other Ca-Pt intermetallic compounds obtained by crystal structure prediction are as follows: Fig.11 As shown, it provides a reference for subsequent experimental preparation.

[0105] Simulation:

[0106] Opposite x Pt y The crystal structure was searched for all components, with x:y ranging from 1:0 to 0:1. The space group for the crystal structure search was limited to the range of 2-230. The number of atoms in the primitive cell was limited to the range of 1-20. The first generation of crystal structures produced 200 structures, which were generated by topological and random crystal structure generators. Each subsequent generation of 100 crystal structures was based on the calculated crystal structures of the previous generation, generated by genetic algorithms (50%), topological machines (20%), mutations (10%), randomness (10%), etc. The convergence criterion was that no crystal structure with lower energy was generated after 30 consecutive repeated calculations. The final predicted crystal structure is shown in 12, and the LixPty lattice parameters and atomic positions are shown in Table 3.

[0107] Table 3. Li-Pt intermetallic compound lattice parameters and atomic positions

[0108]

[0109]

[0110] Example 3

[0111] The target alloy Li2Pt belongs to the hexagonal system, the space group is P-3m1, and the structural diagram of Li2Pt is as follows: Fig.13 shown.

[0112] The difference from Example 1 is:

[0113] The molar ratio of raw material Pt to Li is 0.33:1, and Li2Pt is obtained;

[0114] Fig.14 The XRD and crystal structure prediction of Li2Pt prepared in Example 3 obtained the simulated XRD of the Li2Pt crystal structure;

[0115] Depend on Fig.14 It can be seen that the XRD of the prepared Li2Pt is consistent with the simulated XRD of the Li2Pt crystal structure predicted by the crystal structure, indicating that the experiment successfully prepared the Li2Pt crystal structure with a space group of P-3m1.

[0116] Example 4

[0117] The target alloy LiPt3 belongs to the orthorhombic system, and the space group is Cmmm. The structural diagram of LiPt3 is shown in Fig.15 shown.

[0118] The difference from Example 1 is:

[0119] The molar ratio of raw materials Pt and Li is 1.77:1, and LiPt3 is obtained.

[0120] Fig.16 The XRD and crystal structure prediction of LiPt3 prepared in Example 4 is used to obtain the simulated XRD of the LiPt3 crystal structure;

[0121] Depend on Fig.16 It can be seen that the experimental XRD of the target intermetallic compound is consistent with the simulated XRD of the LiPt3 crystal structure predicted by the crystal structure, indicating that the experiment successfully prepared the LiPt3 crystal structure with the space group P-3m1.

[0122] The simulated XRD patterns of other Li-Pt intermetallic compounds obtained by crystal structure prediction are as follows: Fig.17 As shown, it provides a reference for subsequent experimental preparation.

[0123] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a platinum-based alloy catalyst, characterized in that: The following steps are involved: Using crystal structure prediction software to obtain a ground state crystal structure of the platinum-based alloy catalyst, and obtaining the composition of the platinum-based alloy catalyst according to the ground state crystal structure; According to the composition, corresponding metal elements are mixed and then smelted to obtain the platinum-based alloy catalyst; The ratio of the molar ratio of each metal element other than platinum to platinum and the molar ratio of the corresponding metal element other than platinum to the platinum element in the composition is independently 1.5 to 1.7:

1.

2. The preparation method according to claim 1, characterized in that: The platinum-based alloy catalyst includes Pt m X n or Pt m X n Y p ; The X and Y independently include one of Li, Na, K, Ca, Al, Zn and Mg, and the X and Y are different; m, n and p are independently natural numbers of 1 to 8.

3. The preparation method according to claim 1 or 2, characterized in that: The platinum-based alloy catalyst includes one of Ca5Pt4, Ca5Pt2, Ca6Pt, Ca3Pt2, Ca2Pt3, CaPt5, Ca2Pt, CaPt, CaPt2, Li2Pt, Li4Pt, LiPt7, Li8Pt, LiPt, LiPt3 and Li3Pt5.

4. The preparation method according to claim 1 or 2, characterized in that: The crystal structure of the platinum-based alloy catalyst includes one of triclinic, monoclinic, orthorhombic, hexagonal, rhombohedral, tetragonal and cubic.

5. The preparation method according to claim 1, characterized in that: The smelting is carried out in a protective atmosphere.

6. The preparation method according to claim 5, characterized in that: The protective atmosphere includes an argon atmosphere.

7. The preparation method according to claim 5, characterized in that: The smelting method is electric current smelting.

8. The preparation method according to claim 7, characterized in that: The current of the current smelting is an intermittent current, the magnitude of the intermittent current is 50-60A, and the intermittent time is 0.5-1.5s; The current smelting time is 3 to 7 minutes.

9. The preparation method according to claim 1 or 8, characterized in that: After the smelting, the method further comprises: cooling the obtained melt to obtain the platinum-based alloy catalyst.

10. The preparation method according to claim 1, characterized in that: The ground state crystal structure of the platinum-based alloy catalyst is obtained using crystal structure prediction software, including the following steps: (1) Determine the element type of the platinum-based alloy catalyst, then use crystal structure prediction software to generate a primary crystal structure, and then use first-principles calculation software to optimize the primary crystal structure to obtain the energy value of the crystal structure; (2) feeding back the energy value to the crystal structure prediction software for generating the next generation crystal structure; (3) Repeat steps (1) to (2) until no lower energy crystal structure is generated for thirty consecutive generations, thereby obtaining the ground state crystal structure of the platinum-based alloy catalyst.

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