Preparation method and application of RE (Ni0. 8Al0. 2) 5 intermetallic compound catalyst

Abstract

The invention discloses a preparation method and application of an RE (Ni0. 8Al0. 2) 5 intermetallic compound catalyst, and the preparation method of the catalyst comprises the following steps: carrying out high-temperature melting on rare earth metal RE powder, Ni powder and Al powder in a protective atmosphere; and a product obtained after melting is subjected to ball milling, and the RE (Ni0. 8Al0. 2) 5 intermetallic compound is obtained. When the RE (Ni0. 8Al0. 2) 5 intermetallic compound catalyst is applied to a hydrogen evolution reaction, the RE (Ni0. 8Al0. 2) 5 intermetallic compound is subjected to surface activation in an alkaline solution and is loaded on a substrate. According to the intermetallic compound obtained by the method disclosed by the invention, due to the existence of a synergistic effect, the intrinsic hydrogen evolution reaction performance can be effectively improved, and the overpotential of a 30% KOH solution at room temperature under the current density of 100mA / cm < 2 > is only 133mV; after 10000 circles of CV scanning test, the HER performance of the catalyst is almost unchanged; under the current density of 200mA / cm < 2 >, hydrogen is continuously produced for 24 hours, the potential is hardly fluctuated and attenuated, and excellent hydrogen evolution catalytic performance is shown.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of an intermetallic compound, in particular to a RE (Ni 0.8 Al 0.2 )5 Preparation method and application of intermetallic compound catalysts. Background Art

[0002] Compared with the "grey hydrogen" produced by water-coal gasification, the "green hydrogen" produced by water electrolysis is considered to be an extremely promising and environmentally friendly method. However, the proportion of hydrogen produced by electrocatalytic HER in the global market is less than 5%. The reason for this phenomenon is the lack of efficient and stable electrocatalysts that can be used in industrial alkaline electrolyzers. At present, the non-precious metal catalysts used are mainly Raney nickel. Although the energy consumption of hydrogen production can be reduced to a certain extent by adjusting its electronic structure and catalyst morphology, its extent is extremely limited.

[0003] For alkaline electrolytic cells, in order to meet customers' requirements for low energy consumption, the cathode Raney nickel catalysts currently used on the market are difficult to meet customer needs, which places extremely high demands on catalyst research.

[0004] Although Raney nickel catalyst has high catalytic activity, its catalytic efficiency may be limited under certain specific reaction conditions and cannot achieve the expected effect. In an alkaline electrolyzer, when its catalytic area increases, its catalytic activity decreases significantly. In the process of hydrogen production by alkaline electrolysis of water, most of the Al components in the structure have been removed after activation of Raney nickel, so the only part of the Raney nickel catalyst that really works in the alkaline electrolyzer is porous metal nickel. First of all, porous nickel is used as the cathode material for hydrogen production in an alkaline electrolyzer, and its intrinsic activity is not high, so the catalytic performance for the hydrogen evolution reaction is not good, and the stability of the hydrogen evolution reaction of pure nickel catalyst in high temperature, high pressure and high concentration alkaline solution is poor. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a RE (Ni 0.8 Al 0.2 )5. Preparation method of intermetallic compound catalyst;

[0006] The second object of the present invention is to provide the above-mentioned RE (Ni 0.8 Al 0.2 )5Application of intermetallic compound catalysts.

[0007] Technical solution: The RE (Ni 0.8 Al 0.2 )5 A method for preparing an intermetallic compound catalyst, comprising the following steps:

[0008] (1) rare earth metal RE powder, Ni powder and Al powder are melted at high temperature under a protective atmosphere;

[0009] (2) The melted product was ball milled to obtain RE(Ni 0.8 Al 0.2 )5 intermetallic compounds;

[0010] (3) Change RE(Ni 0.8 Al 0.2 )5 The intermetallic compound is prepared by surface activation in an alkaline solution.

[0011] Wherein, in step (1), the molar ratio of the rare earth metal RE powder, Ni powder and Al powder is 1:4:1.

[0012] Wherein, in step (1), the rare earth metal RE is at least one of Pr, Gd and Er.

[0013] Wherein, in step (1), the temperature of the high temperature melting is 1000-2000°C.

[0014] Wherein, in step (1), the protective atmosphere is argon.

[0015] Wherein, in step (2), the rotation speed of the ball mill is 400-500 rpm and the time is 6 hours.

[0016] Wherein, in step (3), the concentration of the alkaline solution is 20-30%; and the alkali is potassium hydroxide and / or sodium hydroxide.

[0017] The RE (Ni 0.8 Al 0.2 )5 Application of intermetallic compound catalysts in hydrogen evolution reaction.

[0018] Among them, the activated RE (Ni 0.8 Al 0.2 )5 The intermetallic compound catalyst is loaded on the substrate; the loading method is thermal spraying, specifically high-temperature thermal spraying.

[0019] Wherein, the substrate is at least one of a metal nickel mesh or a foam nickel, wherein the nickel mesh is a 46-mesh twill nickel mesh.

[0020] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0021] (1) The present invention synthesizes rare earth metal intermetallic compounds RE (Ni 0.8 Al 0.2)5 catalyst, the rare earth metal compound and Raney nickel have similar stoichiometric ratios, but the rare earth metal compound has a fixed chemical formula and crystal structure, which can better control the feed ratio. The alloy catalyst in the prior art is only a mixture of different atoms, which has a little disorder and has very limited improvement in catalytic activity. However, the metal compound prepared by the method of the present invention can effectively improve the intrinsic hydrogen evolution reaction performance due to the synergistic effect; (2) The catalyst is used in the hydrogen evolution reaction, and the catalyst has a 30% KOH solution at room temperature at 100 mA / cm 2 The overpotential of the current density is only 133mV; after 10,000 cycles of CV scanning test, the HER performance of the catalyst has almost no change; at 200mA / cm 2 The potential of the catalyst hardly fluctuates or decays for 24 hours at a current density of 1.5 wt %. This indicates excellent catalytic performance for hydrogen evolution. (3) After the catalyst surface is etched by catalytic activation technology, the catalyst has a porous structure at the physical level, similar to Raney nickel. At the atomic level, there are also a large number of vacancy defects in the crystal structure, which can further effectively improve the hydrogen evolution performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 : LSV curves of Example 1, Example 2 and Example 3;

[0023] Figure 2 1 is the LSV curve of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3;

[0024] Figure 3 LSV curves of Example 1 before and after 10,000 cycles of CV scanning test;

[0025] Figure 4 Example 1 at 200 mA / cm 2 IT curve under current density. DETAILED DESCRIPTION

[0026] The present invention is described in further detail below.

[0027] Example 1

[0028] In this embodiment, Pr(Ni 0.8 Al 0.2 )5 intermetallic compound, the specific preparation process is: first weigh a total of 1g of Pr powder, Ni powder and Al particles, the stoichiometric ratio of the three is 1:4:1; under the protection of argon, the above metal powders are melted at high temperature, the temperature is 2000℃, the time is 10 seconds; and ball milling is performed to obtain Pr(Ni 0.8 Al 0.2) 5 metal catalyst, the ball milling speed is 450 rpm, and the time is 6 hours;

[0029] The obtained Pr(Ni 0.8 Al 0.2 )5 metal catalyst for surface activation, take 5mg Pr(Ni 0.8 Al 0.2 )5 The metal catalyst is loaded on a 1*1 cm nickel mesh by high-temperature thermal spraying to obtain a catalyst with a high specific surface area, which is denoted as Pr-Ni-Alx; wherein the high-temperature thermal spraying method is a prior art.

[0030] Example 2

[0031] A Gd(Ni 0.8 Al 0.2 )5 metal catalyst preparation method, comprising the following steps: weighing a total of 1g of Gd powder, Ni powder and Al particles, the stoichiometric ratio of which is 1:4:1, melting the above metal powders at a high temperature of 2000°C for 10 seconds under argon protection; and ball milling to obtain Gd(Ni 0.8 Al 0.2 ) 5 metal catalyst, the ball milling speed is 450 rpm, and the time is 6 hours;

[0032] The surface was activated in a 30% KOH solution, and after drying, 5 mg of the catalyst was loaded on a 1*1 cm nickel mesh by high-temperature thermal spraying, which was recorded as Gd-Ni-Alx.

[0033] Example 3

[0034] A kind of Er(Ni 0.8 Al 0.2 )5 metal catalyst preparation method, comprising the following steps: weighing a total of 1g of Er powder, Ni powder and Al particles, the stoichiometric ratio of which is 1:4:1, melting the above metal powders at a high temperature of 2000°C for 10 seconds under argon protection; and ball milling to obtain Er(Ni 0.8 Al 0.2 ) 5 metal catalyst, the ball milling speed is 450 rpm, and the time is 6 hours;

[0035] The surface was activated in a 30% KOH solution, and after drying, 5 mg of the catalyst was loaded on a 1*1 cm nickel mesh by high-temperature thermal spraying, which was recorded as Er-Ni-Alx.

[0036] Comparative Example 1

[0037] 5 mg of Raney nickel catalyst was weighed and loaded on a 1*1 cm nickel mesh, and surface activated in a 30% KOH solution. After drying, the mixture was used as Comparative Example 1.

[0038] Comparative Example 2

[0039] A preparation method of a PrNi5 metal catalyst comprises the following steps: weighing a total of 1g of Pr powder and Ni powder with a stoichiometric ratio of 1:5, melting the metal powders at a high temperature of 2000°C for 10 seconds under argon protection, and ball milling to obtain a PrNi5 metal catalyst with a ball milling speed of 450rpm for 6 hours, performing surface activation in a 30% KOH solution, and loading 5mg of the catalyst on a 1*1cm nickel mesh to obtain the catalyst.

[0040] Comparative Example 3

[0041] A Pr(Ni 0.8 Al 0.2 )5 metal catalyst preparation method, comprising the following steps: weighing a total of 1g of Pr powder, Ni powder and Al particles, the stoichiometric ratio of which is 1:4:1, melting the above metal powders at high temperature under argon protection, and ball milling to obtain Pr(Ni 0.8 Al 0.2 )5 metal catalyst, take 5 mg of catalyst and load it on a 1*1 cm nickel mesh.

[0042] First, the crystal structure and composition of the synthesized samples of the catalyst materials prepared above were analyzed by X-ray diffraction (XRD). For Examples 1, 2, 3 and Comparative Examples 2, 3, diffraction peaks appeared at around 30.6°, 36.2°, 42.0°, 43°, 45.5°, 48.1° and 59.5° in the XRD spectra, and this group of diffraction peaks was completely consistent with the ICSD#646226 standard card, confirming that the synthesized samples were pure phase and belonged to the P6 / MMM space group of the hexagonal system, and after surface activation, their crystal structure did not collapse or undergo phase change.

[0043] After confirming that the synthesized sample is pure phase, it is tested under a three-electrode system. The working electrode is the catalyst electrode prepared in Examples 1, 2, 3 and the electrode in Comparative Examples 1, 2, 3. The counter electrode is a carbon rod. The reference electrode is a Hg / HgO electrode. The test is carried out in a 30% KOH solution at a scan rate of 5 mV / s.

[0044] In the present invention, firstly, the crystal structure, that is, the effect of crystal size on hydrogen evolution performance is optimized through Examples 1, 2, and 3, and the effect of surface defect technology on hydrogen evolution performance is optimized through Example 1 and Comparative Examples 2 and 3, and Comparative Example 1 is added for comparison.

[0045] After electrochemical performance test characterization, such as Figure 1 , 2As shown, Example 1 exhibits excellent hydrogen evolution catalytic activity, which is 100 mA / cm 2 The overpotential of the current density is only 133 mV, while Examples 2, 3 and Comparative Examples 1, 2, 3 require overpotentials of 214 mV, 267 mV, 320 mV, 157 mV and 186 mV respectively to reach 100 mA / cm 2 of current density.

[0046] By comparing Examples 1, 2 and 3, it is found that Pr-Ni-Alx with a larger unit cell parameter has a better catalytic activity, which is also in line with the law of lanthanide contraction, proving that the hydrogen evolution performance can be effectively adjusted by lanthanide contraction. Secondly, by comparing Example 1 and Comparative Example 3, it is proved that the electrochemical specific surface area can also be effectively increased by surface activation technology to improve the electrochemical performance of hydrogen evolution. Secondly, by comparing Example 1 with Comparative Example 2, it is proved that metal Al provides the possibility of surface activation technology, effectively increases its electrochemical surface area, and improves the performance of hydrogen evolution reaction. Finally, compared with Comparative Example 1, the intermetallic compound can more effectively exert the synergistic effect of the metal to improve its electrochemical performance.

[0047] like Figure 3 As shown, in addition to the electrochemical performance test, the Pr-Ni-Alx catalyst prepared in Example 1 was also characterized for stability. After 10,000 cycles of CV scanning test, the HER performance of the catalyst was almost unchanged. And in order to measure its ability to continuously produce hydrogen, as shown in Figure 4 As shown, the catalyst is 2 The potential showed almost no fluctuation and decay when hydrogen was produced continuously for 24 hours at a current density of . This test proved that the prepared Pr-Ni-Alx catalyst has good application prospects in hydrogen evolution reaction in alkaline electrolyzers.

Claims

1. A RE (Ni 0.8 Al 0.2 )5 A method for preparing an intermetallic compound catalyst, characterized in that: The following steps are involved: (1) rare earth metal RE powder, Ni powder and Al powder are melted at high temperature under a protective atmosphere; (2) The melted product was ball milled to obtain RE(Ni 0.8 Al 0.2 )5 intermetallic compounds; (3) Change RE(Ni 0.8 Al 0.2 )5 The intermetallic compound is prepared by surface activation in an alkaline solution.

2. The RE (Ni according to claim 1 0.8 Al 0.2 )5 A method for preparing an intermetallic compound catalyst, characterized in that: In step (1), the rare earth metal RE is at least one of Pr, Gd and Er.

3. The RE (Ni according to claim 1 0.8 Al 0.2 )5 A method for preparing an intermetallic compound catalyst, characterized in that: In step (1), the molar ratio of the rare earth metal RE powder, Ni powder and Al powder is 1:4:

1.

4. The RE (Ni according to claim 1 0.8 Al 0.2 )5 A method for preparing an intermetallic compound catalyst, characterized in that: In step (3), the concentration of the alkaline solution is 20-30%.

5. The RE (Ni according to claim 1 0.8 Al 0.2 )5 A method for preparing an intermetallic compound catalyst, characterized in that: In step (3), the base is potassium hydroxide and / or sodium hydroxide.

6. The RE (Ni according to claim 1 0.8 Al 0.2 )5 A method for preparing an intermetallic compound catalyst, characterized in that: In step (2), the ball milling speed is 400-600 rpm and the time is 4-6 hours.

7. The RE (Ni according to claim 1 0.8 Al 0.2 )5 A method for preparing an intermetallic compound catalyst, characterized in that: In step (1), the temperature of the high temperature melting is 1000-2000°C.

8. A RE (Ni) prepared by the method of claim 1 0.8 Al 0.2 )5 Application of intermetallic compound catalysts in hydrogen evolution reaction.

9. The RE (Ni according to claim 8 0.8 Al 0.2 )5 Use of an intermetallic compound catalyst in a hydrogen evolution reaction, characterized in that: The activated RE(Ni 0.8 Al 0.2 )5 The intermetallic compound catalyst is loaded on a substrate.

10. The RE (Ni according to claim 9 0.8 Al 0.2 )5 Use of an intermetallic compound catalyst in a hydrogen evolution reaction, characterized in that: The substrate is a metal nickel mesh and / or foamed nickel.

Images