Fe / Ni Bimetallic MOF Composite Loaded with 1T / 2H MoS2 Heterojunction and Its Preparation Method

Abstract

The present invention provides an Fe / Ni bimetallic MOF composite material loaded with a 1T / 2H MoS2 heterojunction and a preparation method thereof. The composite material is composed of an Fe / Ni bimetallic MOF substrate and MoS2 nanoflowers densely loaded on the surface of the substrate. The MoS2 nanoflowers are formed by the orderly aggregation of multiple MoS2 nanosheets along the central axis to form a flower-like structure. When used as an electrocatalyst, the Fe / Ni bimetallic MOF composite material loaded with the 1T / 2H MoS2 heterojunction has excellent electrocatalytic performance and cycle stability under acidic conditions, a long service life, low production cost of the catalyst, and high hydrogen evolution efficiency, which can effectively solve the problems of high cost and low efficiency of the current electrocatalysts for hydrogen production.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrodes characterized by electrocatalyst materials composed of two or more catalytic elements or catalytic compounds, and particularly relates to an Fe / Ni bimetallic MOF composite material loaded with a 1T / 2H MoS2 heterojunction and a preparation method thereof. Background Art

[0002] Hydrogen, as one of the cleanest energy sources, is considered to be a perfect substitute for future carbon-based energy. Currently, hydrogen production mainly relies on photoelectric-driven water splitting, and its main problems are large external energy requirements and high energy consumption in the hydrogen production process. Rare noble metal catalysts such as Pt / C catalysts are considered to be efficient electrocatalysts for the hydrogen evolution reaction (HER). However, due to their high price, difficult development, and limited resource reserves, etc., their popularization and application as hydrogen production catalysts have been greatly restricted.

[0003] In recent years, transition metal dichalcogenides such as MoS2 have attracted extensive attention from researchers due to their large storage capacity, low cost, good chemical stability in acidic solutions, etc. Existing simulation calculations and experimental studies have proved that it has great potential for catalyzing HER. However, due to its low intrinsic conductivity, it hinders the electron transfer during the reaction process, and there is serious agglomeration between its crystal layers, resulting in a significant reduction in active sites, which limits the application of MoS2 as an electrocatalyst in hydrogen evolution.

[0004] In order to overcome these disadvantages, the present invention combines an Fe / Ni bimetallic MOF material with MoS2, significantly improving the catalytic activity of MoS2, and is expected to be popularized and applied as an efficient electrocatalyst for the hydrogen evolution reaction (HER). Summary of the Invention

[0005] In view of the above problems, the present invention provides an Fe / Ni bimetallic MOF composite material loaded with a 1T / 2H MoS2 heterojunction and a preparation method thereof. The Fe / Ni bimetallic MOF composite material loaded with a 1T / 2H MoS2 heterojunction has low cost, high catalytic hydrogen evolution efficiency, and stable performance.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] An Fe / Ni bimetallic MOF composite material loaded with a 1T / 2H MoS2 heterojunction, which is composed of an Fe / Ni bimetallic MOF substrate and MoS2 nanoflowers densely loaded on the surface of the substrate. The MoS2 nanoflowers are formed by orderly agglomeration of multiple MoS2 nanosheets along the central axis to form a flower-like structure.

[0008] According to the above scheme, the Fe / Ni bimetallic MOF substrate is obtained by agglomeration of nanoparticles with an octahedral structure, and the particle size of the nanoparticles is 150-200 nm.

[0009] According to the above scheme, the particle size of the MoS2 nanoflowers is 400-700 nm.

[0010] According to the above scheme, the MoS2 loading amount in the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction is 10-25% (mass percentage).

[0011] The present invention also provides a preparation method of the above-mentioned Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction, and the specific steps are as follows:

[0012] 1) Dissolve ferric chloride, nickel nitrate and terephthalic acid (terephthalic acid is used as the organic ligand of Fe / Ni bimetallic MOF) in N,N-dimethylformamide, then dropwise add sodium hydroxide solution (promote the ionization of the carboxyl group of terephthalic acid and increase the solubility), and continue to stir evenly, then carry out hydrothermal reaction. After the reaction is completed, centrifuge, wash and vacuum dry the product to obtain the Fe / Ni bimetallic MOF precursor;

[0013] 2) Calcinate the Fe / Ni bimetallic MOF precursor obtained in step 1) under an inert atmosphere (remove the unreacted organic ligand and convert the MOF into a stable phase), take it out after cooling, then wash and vacuum dry to obtain the Fe / Ni bimetallic MOF substrate;

[0014] 3) Ultrasonically disperse the Fe / Ni bimetallic MOF substrate obtained in step 2) in deionized water to obtain a dispersion liquid. Add sodium molybdate and thiourea to the dispersion liquid in sequence, ultrasonically disperse evenly again, and then carry out hydrothermal reaction. After the reaction is completed and cooled, centrifuge, wash and vacuum dry the product to obtain the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction.

[0015] Preferably, in step 1), the mass ratio of ferric chloride to terephthalic acid is 0.2-5:1, the mass ratio of nickel nitrate to terephthalic acid is 0.1-10:1, and the mass-volume ratio of ferric chloride to N,N-dimethylformamide is 0.002-0.005 g / mL.

[0016] According to the above scheme, the sodium hydroxide solution in step 1) is an aqueous solution of sodium hydroxide, with a concentration of 0.5-3 mol / L, and the mass ratio of sodium hydroxide to terephthalic acid in the sodium hydroxide solution is 0.1-3:1.

[0017] According to the above scheme, in step 1), the hydrothermal reaction temperature is 80-140 °C, and the hydrothermal reaction time is 15-36 h.

[0018] According to the above scheme, in step 2), the calcination process conditions are as follows: heating from room temperature to 400-800 °C at a heating rate of 5-10 °C / min, and holding for 4-8 h.

[0019] According to the above scheme, in step 3), the concentration of the Fe / Ni bimetallic MOF substrate in the dispersion liquid is 0.125-1.5 mg / mL.

[0020] According to the above scheme, in step 3), the mass ratio of the Fe / Ni bimetallic MOF substrate to sodium molybdate is 1:5-15, and the mass ratio of sodium molybdate to thiourea is 0.5-3:1.

[0021] According to the above scheme, in step 3), the hydrothermal reaction temperature is 160-240 °C, and the hydrothermal reaction time is 20-36 h.

[0022] The present invention also includes the application of the above Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction as an electrocatalyst in catalytic hydrogen evolution.

[0023] The present invention selects the Fe / Ni bimetallic MOF material as the substrate, and in-situ loads MoS2 on its surface through hydrothermal reaction. The high conductivity of the metal-organic framework enables the MoS2 nanosheets to grow evenly therein. And due to the presence of iron and nickel metal elements, the formation of 1T-phase MoS2 is induced, and it coexists with 2H-phase MoS2 to form a heterojunction. The catalytic activity of HER in 2H-phase MoS2 comes from its edge, while both the edge and the basal plane of 1T-phase MoS2 are active for HER. Therefore, the presence of the 1T / 2H MoS2 heterojunction ensures the high activity of the catalyst. In addition, due to the coexistence of 1T-phase and 2H-phase in the heterojunction, the 2H-phase helps to stabilize the metastable 1T-phase, ensuring the excellent durability of the catalyst. Therefore, when used as a hydrogen evolution catalyst, the 1T / 2H MoS2 heterojunction and the Fe / Ni bimetallic MOF material can not only play a synergistic role, effectively increasing its electron transport ability, but also additionally increasing the active sites of the catalyst, thereby improving its catalytic hydrogen evolution performance.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction provided by the present invention has excellent electrocatalytic performance and cycle stability under acidic conditions, and has a long service life;

[0026] 2. The raw materials used in the preparation method of the present invention are cheap and easy to obtain, the preparation steps are simple, and it is suitable for large-scale industrial production. Description of the Drawings

[0027] Figure 1 SEM image of the Fe / Ni bimetallic MOF prepared in Comparative Example 1 of the present invention;

[0028] Figure 2 Linear sweep voltammetry (LSV) curves of the samples of Examples 1-3 and Comparative Example 1 under acidic conditions;

[0029] Figure 3 Raman spectra of the samples of Examples 1-3 and Comparative Example 1;

[0030] Figure 4 Comparison diagram of linear sweep voltammetry (LSV) curves of Example 3 before and after stability test under acidic conditions, and the inset is the i-t curve of the stability test of Example 3 under acidic conditions;

[0031] Figure 5 SEM image of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction prepared in Example 3. Detailed Description of the Invention

[0032] The preparation method of the Fe / Ni bimetallic MOF composite catalyst loaded with 1T / 2H MoS2 heterojunction provided by the present invention will be further described in detail below in conjunction with specific examples and drawings.

[0033] Comparative Example 1

[0034] An Fe / Ni bimetallic MOF material without loading 1T / 2H MoS2 heterojunction, and the specific preparation method is as follows:

[0035] 1) Dissolve 0.13 g of ferric chloride, 0.1 g of nickel nitrate and 0.24 g of terephthalic acid in 40 mL of N,N-dimethylformamide. Drop 1 mL of sodium hydroxide solution with a concentration of 0.8 mol / L into the obtained solution and continue stirring for 5 min, and carry out a hydrothermal reaction at 110 °C for 22 h. After the reaction is completed, centrifuge at a speed of 5500 rpm for 25 min to collect the precipitate. Wash the precipitate with N,N-dimethylformamide and absolute ethanol three times each, and filter. Finally, vacuum dry the sample at 60 °C for 24 h to obtain an Fe / Ni bimetallic MOF precursor;

[0036] 2) Heat the Fe / Ni bimetallic MOF precursor obtained in step 1) to 700 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcine for 6 h. After cooling, take it out, wash it three times with absolute ethanol, and filter. Finally, vacuum dry the sample at 60 °C for 24 h to obtain an Fe / Ni bimetallic MOF material.

[0037] AsFigure 1 The SEM image of the Fe / Ni bimetallic MOF material prepared in this comparative example is shown. It can be seen that the Fe / Ni bimetallic MOF material is aggregated by octahedral-shaped nanoparticles, and the particle size of the nanoparticles is 150 - 200 nm.

[0038] Example 1

[0039] A Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS₂ heterojunction, and the specific preparation method is as follows:

[0040] 1) Dissolve 0.13 g of ferric chloride, 0.1 g of nickel nitrate and 0.24 g of terephthalic acid in 40 mL of N,N-dimethylformamide. Add 1 mL of sodium hydroxide solution with a concentration of 0.8 mol / L to the obtained solution and continue stirring for 5 min, and carry out hydrothermal reaction at 110 °C for 22 h. After the reaction is completed, centrifuge at a speed of 5500 rpm for 25 min to collect the precipitate. Wash the precipitate with N,N-dimethylformamide and absolute ethanol three times each, and filter. Finally, vacuum dry the sample at 60 °C for 24 h to obtain the Fe / Ni bimetallic MOF precursor;

[0041] 2) Heat the Fe / Ni bimetallic MOF precursor obtained in step 1) to 700 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcine for 6 h. Take it out after cooling, wash it three times with absolute ethanol, and filter. Finally, vacuum dry the sample at 60 °C for 24 h to obtain the Fe / Ni bimetallic MOF substrate;

[0042] 3) Add 20 mg of the Fe / Ni bimetallic MOF substrate obtained in step 2) to 40 mL of deionized water and perform ultrasonic dispersion treatment for 8 min. Then add 249 mg of sodium molybdate and 224 mg of thiourea in sequence, continue ultrasonic treatment for 25 min, and then carry out hydrothermal reaction at 210 °C for 22 h. After cooling, centrifuge the product at 3000 rpm for 25 min. Wash the obtained solid three times with deionized water and filter. Finally, vacuum dry the sample at 60 °C for 12 h to obtain the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS₂ heterojunction.

[0043] Example 2

[0044] A Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS₂ heterojunction, and the specific preparation method is as follows:

[0045] 1) Dissolve 0.13 g of ferric chloride, 0.1 g of nickel nitrate and 0.24 g of terephthalic acid in 40 mL of N,N-dimethylformamide. Dropwise add 1 mL of sodium hydroxide solution with a concentration of 0.8 mol / L to the resulting solution and continue stirring for 5 min. Then, carry out a hydrothermal reaction at 110 °C for 22 h. After the reaction, centrifuge at a speed of 5500 rpm for 25 min to collect the precipitate. Wash the precipitate with N,N-dimethylformamide and absolute ethanol three times each, and filter. Finally, vacuum dry the sample at 60 °C for 24 h to obtain the Fe / Ni bimetallic MOF precursor;

[0046] 2) Heat the Fe / Ni bimetallic MOF precursor obtained in step 1) to 700 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcine for 6 h. Take it out after cooling, wash it three times with absolute ethanol, and filter. Finally, vacuum dry the sample at 60 °C for 24 h to obtain the Fe / Ni bimetallic MOF substrate;

[0047] 3) Add 30 mg of the Fe / Ni bimetallic MOF substrate obtained in step 2) to 40 mL of deionized water and ultrasonically disperse for 8 min. Then, sequentially add 249 mg of sodium molybdate and 224 mg of thiourea, continue ultrasonic treatment for 25 min, and then carry out a hydrothermal reaction at 210 °C for 22 h. After cooling, centrifuge the product at 3000 rpm for 25 min. Wash the obtained solid three times with deionized water and filter. Finally, vacuum dry the sample at 60 °C for 12 h to obtain the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction.

[0048] Example 3

[0049] A Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction, and the specific preparation method is as follows:

[0050] 1) Dissolve 0.13 g of ferric chloride, 0.1 g of nickel nitrate and 0.24 g of terephthalic acid in 40 mL of N,N-dimethylformamide. Dropwise add 1 mL of sodium hydroxide solution with a concentration of 0.8 mol / L to the resulting solution and continue stirring for 5 min. Then, carry out a hydrothermal reaction at 110 °C for 22 h. After the reaction, centrifuge at a speed of 5500 rpm for 25 min to collect the precipitate. Wash the precipitate with N,N-dimethylformamide and absolute ethanol three times each, and filter. Finally, vacuum dry the sample at 60 °C for 24 h to obtain the Fe / Ni bimetallic MOF precursor;

[0051] 2) The Fe / Ni bimetallic MOF precursor obtained in step 1) was heated to 700 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined for 6 h. After cooling, it was taken out, washed 3 times with absolute ethanol, and filtered. Finally, the sample was vacuum dried at 60 °C for 24 h to obtain the Fe / Ni bimetallic MOF substrate;

[0052] 3) 40 mg of the Fe / Ni bimetallic MOF substrate obtained in step 2) was added to 40 mL of deionized water and ultrasonically dispersed for 8 min. Then, 249 mg of sodium molybdate and 224 mg of thiourea were added in sequence, and ultrasonic treatment was continued for 25 min. Then, hydrothermal reaction was carried out at 210 °C for 22 h. After cooling, the product was centrifuged at 3000 rpm for 25 min. The obtained solid was washed 3 times with deionized water and filtered. Finally, the sample was vacuum dried at 60 °C for 12 h to obtain the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction.

[0053] According to the EDS energy spectrum, the MoS2 loading in the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction obtained in this example was 20.69 wt%.

[0054] The Fe / Ni bimetallic MOF composite materials loaded with 1T / 2H heterojunction prepared in Examples 1-3 and the Fe / Ni bimetallic MOF material prepared in Comparative Example 1 were respectively placed in an ethanol solvent and ultrasonically treated for 30 min. The obtained dispersion was coated on the surface of a glassy carbon electrode and dried. Then, a layer of Nafion solution was coated on the surface of the glassy carbon electrode to obtain a hydrogen evolution working electrode. Using 0.5 mol / L sulfuric acid solution as the electrolyte, a saturated calomel electrode as the reference electrode, and a platinum electrode as the counter electrode, electrochemical hydrogen evolution tests were carried out on a CHI760E electrochemical workstation. The test results are shown in Table 1 below:

[0055] Table 1

[0056] Project <![CDATA[Current density (mA / cm 2 )]]> Hydrogen evolution overpotential (mV) Example 1 10 290 Example 2 10 260 Example 3 10 200 Comparative Example 1 2 350

[0057] As Figure 2 shown are the linear sweep voltammetry (LSV) curves of the Fe / Ni bimetallic MOF composite materials loaded with 1T / 2H heterojunction prepared in Examples 1-3 and the Fe / Ni bimetallic MOF material prepared in Comparative Example 1 under the above test conditions. It can be seen that at a current density of 10 mA / cm 2 the hydrogen evolution overpotentials of the Fe / Ni bimetallic MOF composite materials loaded with 1T / 2H heterojunction prepared in Examples 1-3 were 290 mV, 160 mV, and 200 mV respectively, while the maximum current density that the Fe / Ni bimetallic MOF material prepared in Comparative Example 1 could reach was only 2 mA / cm 2, and the hydrogen evolution overpotential is relatively high (350 mV). Through comparison, it is proved that the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction can greatly improve the activity of the catalyst. In addition, as Figure 4 shown is the comparison diagram of linear sweep voltammetry (LSV) curves before and after constant electrolysis for 24 h at an overpotential of 200 mV of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction prepared in Example 3 under the above acidic conditions. The inset is the i-t curve of the stability test of the composite material in Example 3 under this acidic condition. It can be seen that the current density remains unchanged before and after constant electrolysis for 24 h of the composite material in Example 3, proving that the composite material has excellent durability.

[0058] Figure 3 The Raman spectra of the Fe / Ni bimetallic MOF composite materials loaded with 1T / 2H heterojunctions prepared in Examples 1-3 and the Fe / Ni bimetallic MOF material prepared in Comparative Example 1 are shown. By comparison, it can be seen that the Fe / Ni bimetallic MOF composite materials loaded with 1T / 2H heterojunctions prepared in Examples 1-3 have a high content of 1T-phase MoS2, indicating the existence of 1T / 2H heterojunctions in MoS2.

[0059] Figure 5 The SEM image of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction prepared in Example 3 is shown. It can be seen from the figure that MoS2 nanoflowers formed by the orderly aggregation of MoS2 nanosheets along the central axis are densely distributed on the surface of the Fe / Ni bimetallic MOF substrate, and the diameter of the MoS2 nanoflowers is 400-700 nm.

Claims

1. A Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction, characterized in that It consists of a Fe / Ni bimetallic MOF substrate and MoS2 nanoflowers densely loaded on the surface of the substrate. The MoS2 nanoflowers are formed by the orderly aggregation of multiple MoS2 nanosheets along the central axis to form a flower-like structure.

2. The Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to claim 1, characterized in that The Fe / Ni bimetallic MOF substrate is obtained by the aggregation of nanoparticles with an octahedral structure, and the particle size of the nanoparticles is 150-200 nm.

3. The Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to claim 1, characterized in that The particle size of the MoS2 nanoflowers is 400-700 nm.

4. The Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to claim 1, characterized in that In the Fe / Ni bimetallic MOF composite loaded with 1T / 2H MoS2 heterojunction, the MoS2 loading is 10-25% by mass percentage.

5. A preparation method of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to any one of claims 1-4, characterized in that The specific steps are as follows: 1) Dissolve ferric chloride, nickel nitrate and terephthalic acid in N,N-dimethylformamide, then add sodium hydroxide solution and continue to stir evenly, and then carry out hydrothermal reaction. After the reaction is completed, centrifuge, wash and vacuum dry the product to obtain a Fe / Ni bimetallic MOF precursor; 2) Calcinate the Fe / Ni bimetallic MOF precursor obtained in step 1) under an inert atmosphere, take it out after cooling, and then wash and vacuum dry it to obtain a Fe / Ni bimetallic MOF substrate; 3) Ultrasonically disperse the Fe / Ni bimetallic MOF substrate obtained in step 2) in deionized water to obtain a dispersion. Add sodium molybdate and thiourea to the dispersion in sequence, ultrasonically disperse it evenly again and then carry out hydrothermal reaction. After the reaction is completed and cooled, centrifuge, wash and vacuum dry the product to obtain a Fe / Ni bimetallic MOF composite loaded with 1T / 2H MoS2 heterojunction.

6. The preparation method of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to claim 5, characterized in that In step 1), the mass ratio of ferric chloride to terephthalic acid is 0.2-5:1, the mass ratio of nickel nitrate to terephthalic acid is 0.1-10:1, and the mass-volume ratio of ferric chloride to N,N-dimethylformamide is 0.002-0.005 g / mL; the sodium hydroxide solution in step 1) is an aqueous solution of sodium hydroxide with a concentration of 0.5-3 mol / L, and the mass ratio of sodium hydroxide to terephthalic acid in the sodium hydroxide solution is 0.1-3:

1.

7. The preparation method of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to claim 5, characterized in that In step 1), the hydrothermal reaction temperature is 80-140 °C, and the hydrothermal reaction time is 15-36 h.

8. The preparation method of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to claim 5, characterized in that In step 2), the calcination process conditions are: heat up from room temperature to 400-800 °C at a heating rate of 5-10 °C / min, and keep the temperature for 4-8 h.

9. The preparation method of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to claim 5, characterized in that In step 3), the concentration of the Fe / Ni bimetallic MOF substrate in the dispersion is 0.125-1.5 mg / mL; the mass ratio of the Fe / Ni bimetallic MOF substrate to sodium molybdate in step 3) is 1:5-15, and the mass ratio of sodium molybdate to thiourea is 0.5-3:1; the hydrothermal reaction temperature in step 3) is 160-240 °C, and the hydrothermal reaction time is 20-36 h.

10. Application of the Fe / Ni bimetallic MOF composite material loaded with 1T / 2H MoS2 heterojunction according to any one of claims 1-4 as an electrocatalyst in catalytic hydrogen evolution.

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