A RE(Ni 0.8 Al 0.2 )5 Preparation method and application of intermetallic compound catalyst

Abstract

The present invention discloses a RE (Ni 0.8 Al 0.2 )5 Preparation method and application of intermetallic compound catalyst, the preparation method of the catalyst is: rare earth metal RE powder, Ni powder and Al powder are melted at high temperature under protective atmosphere; the product obtained after melting is ball milled to obtain RE (Ni 0.8 Al 0.2 )5 intermetallic compound. RE(Ni 0.8 Al 0.2 )5 intermetallic compound catalyst is used in hydrogen evolution reaction, RE(Ni 0.8 Al 0.2 )5 The intermetallic compound is surface activated in an alkaline solution and loaded on a substrate. The intermetallic compound obtained by the method of the present invention can effectively improve the intrinsic hydrogen evolution reaction performance due to the existence of synergistic effect. At room temperature, in a 30% KOH solution at 100mA / 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 showed almost no fluctuation and attenuation when hydrogen was produced continuously for 24 hours at a current density of 1.5 wt %. This showed excellent hydrogen evolution catalytic performance.

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 to 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, the 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 alkaline electrolyzers, when its catalytic area increases, its catalytic activity decreases significantly. In the process of hydrogen production by alkaline electrolysis of water, after activation, most of the Al components in the structure of Raney nickel have been removed, so the only real role of Raney nickel catalyst in the alkaline electrolyzer is porous metal nickel. First of all, using only porous nickel as the cathode material for hydrogen production in alkaline electrolyzers has low intrinsic activity, so the catalytic performance for 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. The preparation method of the intermetallic compound catalyst comprises 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 surface activated in an alkaline solution to obtain the product.

[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 ball milling speed 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, and 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 at room temperature in 30% KOH solution at 100mA / 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 under a current density of 100 nm, showing excellent hydrogen evolution catalytic performance. (3) After the catalyst surface is etched by catalytic activation technology, the present invention has a porous structure at the physical level, similar to Raney nickel, and a large number of vacancy defects in the crystal structure at the atomic level, 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 For 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 as follows: 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 catalysts for surface activation, take 5mg Pr(Ni 0.8 Al 0.2 )5 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 recorded 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, with a stoichiometric ratio of 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. After drying, 5 mg of the catalyst was loaded on a 1*1 cm nickel mesh by high-temperature thermal spraying and 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, with a stoichiometric ratio of 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. After drying, 5 mg of the catalyst was loaded on a 1*1 cm nickel mesh by high-temperature thermal spraying and recorded as Er-Ni-Alx.

[0036] Comparative Example 1

[0037] 5 mg of Raney nickel catalyst was weighed and loaded onto a 1*1 cm nickel mesh, surface activated in a 30% KOH solution, and dried 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 in 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 the mixture at a speed of 450rpm for 6 hours to obtain the PrNi5 metal catalyst; performing surface activation in a 30% KOH solution, and then 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, with a stoichiometric ratio of 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 1*1 cm nickel mesh to prepare.

[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 and 3, diffraction peaks appeared at around 30.6°, 36.2°, 42.0°, 43°, 45.5°, 48.1° and 59.5° in the XRD spectra. 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 hexagonal P6 / MMM space group. Moreover, 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, and 3 and the electrode in Comparative Examples 1, 2, and 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, the crystal structure, that is, the effect of crystal size on hydrogen evolution performance is first optimized through Examples 1, 2, and 3. 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 133mV, while Examples 2, 3 and Comparative Examples 1, 2, 3 require overpotentials of 214mV, 267mV, 320mV, 157mV and 186mV respectively to reach 100mA / cm 2 current density.

[0046] By comparing Examples 1, 2, and 3, it was found that Pr-Ni-Alx with larger unit cell parameters had better catalytic activity, which also conformed to the law of lanthanide contraction, confirming that lanthanide contraction can effectively adjust hydrogen evolution performance. Secondly, by comparing Example 1 and Comparative Example 3, it was proved that surface activation technology can also effectively increase the electrochemical specific surface area to improve the electrochemical performance of hydrogen evolution. Thirdly, the comparison between Example 1 and Comparative Example 2 proves that metal Al provides the possibility of surface activation technology, effectively increases its electrochemical surface area, and improves the hydrogen evolution reaction performance. 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 Figure 1, in addition to the electrochemical performance test, the Pr-Ni-Alx catalyst prepared in Example 1 was also subjected to stability characterization. After 10,000 cycles of CV scanning test, the HER performance of the catalyst remained almost unchanged. And in order to measure its ability to continuously produce hydrogen, as shown in Figure 1, Figure 4 As shown, the catalyst is at 200 mA / cm 2 The potential of the catalyst showed almost no fluctuation or attenuation when hydrogen was produced continuously for 24 hours at a current density of 100 nm. This test proves that the prepared Pr-Ni-Alx catalyst has good application prospects in the 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) melting rare earth metal RE powder, Ni powder and Al powder at high temperature under a protective atmosphere; the rare earth metal RE is at least one of Pr, Gd and Er; the molar ratio of the rare earth metal RE powder, Ni powder and Al powder is 1:4:1; the temperature of the high temperature melting is 1000-2000°C; (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 surface activated in an alkaline solution to obtain the product.

2. 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%.

3. 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.

4. 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 h.

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

6. RE (Ni according to claim 5 0.8 Al 0.2 )5. Application 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 supported on a substrate.

7. RE (Ni according to claim 6 0.8 Al 0.2 )5. Application of an intermetallic compound catalyst in a hydrogen evolution reaction, characterized in that: The substrate is a metal nickel mesh and / or foam nickel.

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