Preparation method and application of 1T-phase molybdenum sulfide

Abstract

The invention discloses a preparation method and application of 1T-phase molybdenum sulfide, and the method comprises the following steps: under the action of an external magnetic field, ammonium molybdate tetrahydrate and thiourea are respectively used as a molybdenum source and a sulfur source, cobalt nitrate hexahydrate is used as an initiator, and the 1T-phase molybdenum sulfide is generated in the reaction process through a one-step hydrothermal method. The 1T-phase molybdenum sulfide is used for preparing an oxygen evolution and hydrogen evolution dual-function electrode. According to the preparation method disclosed by the invention, a hydrothermal synthesis product is converted from 2H-phase molybdenum sulfide to 1T-phase molybdenum sulfide by utilizing a magnetic field and Co atoms, so that the HER and OER bifunctional catalyst with high conductivity and excellent catalytic performance is prepared. The method is simple, economical and remarkable in effect, the problem that the 1T-phase molybdenum sulfide catalyst is difficult to prepare is solved, and the method has great application value in the field of electrochemical catalysis.

Description

Technical Field

[0001] The present invention relates to the field of new energy materials and electrocatalysis, and in particular to a preparation method of 1T phase molybdenum sulfide and application thereof. Background Art

[0002] Hydrogen is a renewable, energy-dense, clean energy source. Electrochemical decomposition of water can sustainably produce high-purity, pollution-free, and easily transportable hydrogen. However, traditional Pt-based catalysts are of low abundance and high price in the earth, which limits the development of hydrogen production by electrolysis of water. 1T-phase molybdenum sulfide, as an emerging hydrogen production catalyst by electrolysis of water, perfectly solves the problems of Pt-based catalysts. Its high catalytic activity, low cost, and high abundance make it an excellent substitute for Pt-based catalysts. However, the 1T phase of molybdenum sulfide is a metastable phase. The synthesis conditions are harsh and there are still many impurities in the synthetic product, which seriously restricts the development of molybdenum sulfide in the research of hydrogen production by electrolysis of water. How to easily synthesize high 1T-phase molybdenum sulfide catalysts has become one of the problems that urgently need to be solved in the research of hydrogen production by electrolysis of water. Summary of the invention

[0003] The object of the present invention is to provide a preparation method of 1T phase molybdenum sulfide and application thereof, which not only has a simple synthesis process and low synthesis cost but also the synthesized catalyst has high catalytic activity.

[0004] In one aspect of the present invention, the present invention provides a method for preparing 1T phase molybdenum sulfide. According to an embodiment of the present invention, the method comprises the following steps: under the action of an external magnetic field, using ammonium molybdate tetrahydrate and thiourea as a molybdenum source and a sulfur source, respectively, and cobalt nitrate hexahydrate as an initiator, a one-step hydrothermal method is used to generate 1T phase molybdenum sulfide in a reaction process.

[0005] In addition, the method for preparing 1T phase molybdenum sulfide according to the above embodiment of the present invention may also have the following additional technical features:

[0006] In some embodiments of the present invention, the external magnetic field is provided by two samarium cobalt permanent magnets located on the same central axis and with positive and negative poles facing each other.

[0007] In some embodiments of the present invention, the diameter of the samarium cobalt permanent magnet is 25-35 mm, the height is 18-20 mm, and the surface magnetic field strength of the samarium cobalt permanent magnet is 0.35-0.45T.

[0008] In some embodiments of the present invention, the distance between two samarium cobalt permanent magnets is 58-62 mm.

[0009] In some embodiments of the present invention, the molar ratio of ammonium molybdate tetrahydrate, thiourea and cobalt nitrate hexahydrate is 4:28:1-5.

[0010] In some embodiments of the present invention, the concentration of the ammonium molybdate tetrahydrate is 0.010-0.020 mol / L, the concentration of the thiourea is 0.10-0.20 mol / L, and the concentration of the cobalt nitrate hexahydrate is 0.001-0.01 mol / L.

[0011] In some embodiments of the present invention, the ammonium molybdate tetrahydrate and thiourea need to be stirred for 45-60 minutes before adding the cobalt nitrate hexahydrate.

[0012] In some embodiments of the present invention, the temperature of the hydrothermal method is about 180-220° C., and the time is 18-24 hours.

[0013] In some embodiments of the present invention, after the 1T phase molybdenum sulfide is obtained, it is washed with deionized water and anhydrous ethanol and then dried.

[0014] In another aspect of the present invention, the present invention provides an application of 1T phase molybdenum sulfide. According to an embodiment of the present invention, the 1T phase molybdenum sulfide prepared by the preparation method of 1T phase molybdenum sulfide is used to prepare a dual-functional electrode for oxygen and hydrogen evolution.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The present invention adds a new reaction condition, a magnetic field, to the conventional hydrothermal reaction, so that the product transforms from the 2H phase to the 1T phase.

[0017] (2) The 1T phase conversion rate of the present invention is high and has good stability.

[0018] (3) The 1T-phase molybdenum sulfide synthesized in the present invention has high catalytic activity, high conductivity and excellent catalytic performance, and is a dual-functional catalyst for HER (electrocatalyst hydrogen evolution reaction) and OER (oxygen evolution reaction).

[0019] (4) The present invention has low material cost, is environmentally friendly, has a simple and easy-to-operate preparation process, and has strong feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The XRD diffraction patterns of Example 1 and Comparative Example 1 of the present invention are as follows:

[0021] Figure 2 It is the Raman spectrum of Example 1 of the present invention and Comparative Example 1;

[0022] Figure 3 is a scanning electron microscope photograph of 1T phase molybdenum sulfide of Example 1 of the present invention;

[0023] Figure 4 is the XRD diffraction pattern of 1T phase molybdenum sulfide synthesized in Example 2-5 of the present invention;

[0024] Figure 5 The HER polarization curves of Example 1 and Comparative Example 1 are obtained in the application examples of the present invention when 1 mol / L KOH is used as the electrolyte and a three-electrode system is adopted;

[0025] Figure 6 The OER polarization curves of Example 1 and Comparative Example 1 are obtained when 1 mol / L KOH is used as electrolyte and a three-electrode system is adopted in the application examples of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] A method for preparing 1T phase molybdenum sulfide comprises the following steps:

[0029] (1) Construction of an external magnetic field environment, embedding a cylindrical high-temperature resistant samarium cobalt magnet with a diameter of 30 mm and a height of 20 mm into a polytetrafluoroethylene shell. The polytetrafluoroethylene shell is a cylinder with an outer diameter of 57.2 mm and a height of 30 mm, and has a cylindrical pit with an inner diameter of 30 mm and a depth of 20 mm at the bottom that is coaxial with the polytetrafluoroethylene shell. There are two polytetrafluoroethylene shells, one with the N pole of the magnet outside and the other with the S pole outside. The reactor liner is 54 mm high and 57.2 mm in diameter. The reactor shell is assembled in the form of a three-layer stack of polytetrafluoroethylene shell, reactor liner, and polytetrafluoroethylene shell, where the side of the polytetrafluoroethylene shell containing the magnet is in contact with the reactor liner.

[0030] (2) Preparation of reaction precursors: 30 ml of solvent water, 0.5 mmol of ammonium molybdate tetrahydrate and 3.5 mmol of thiourea, respectively. After stirring for 1 hour using a magnetic stirrer, 0.25 mmol of cobalt nitrate hexahydrate was added and stirred for another 40 minutes.

[0031] (3) The reaction precursors were placed in a reaction vessel, assembled and reacted at 200 degrees Celsius for 22 hours.

[0032] (4) After the reaction is completed, the suspension in the reactor is taken out and placed in a centrifuge tube, which is centrifuged at 6000 r / min for 3 min using a high-speed centrifuge, then rinsed three times with ethanol and deionized water alternately, and finally dried in a vacuum oven at 60 degrees Celsius.

[0033] Figure 1This is the XRD spectrum of the 1T phase molybdenum disulfide of Example 1. The (002) crystal plane diffraction peak is located at 14°, belonging to the 1T phase.

[0034] Figure 2 The Raman spectra of Example 1 and Comparative Example 1 are shown in Figure 1. The two diffraction peaks of Comparative Example 1 are located at 378 cm -1 and 404cm -1 , which is 2H phase; while in Example 1, J1, J2, J3, E belonging to 1T phase molybdenum sulfide appeared 1g The diffraction peak indicates that the crystal phase of Example 1 is 1T phase.

[0035] Figure 3 This is a scanning electron microscope photograph of the 1T phase molybdenum sulfide of Example 1, which is in the shape of flower-shaped nanospheres. The diameter of a single sphere is about 500 nm, and different nanospheres are clustered together.

[0036] Example 2

[0037] This embodiment is basically the same as embodiment 1, with the only difference being that in step (2), the concentrations of ammonium molybdate tetrahydrate and thiourea are 0.5 mmol and 3.5 mmol respectively, and after stirring for 1 hour using a magnetic stirrer, 0.10 mmol of cobalt nitrate hexahydrate is added and stirred for another 40 minutes.

[0038] Example 3

[0039] This embodiment is substantially the same as embodiment 1, with the only difference being that in step (2), the concentrations of ammonium molybdate tetrahydrate and thiourea are 0.5 mmol and 3.5 mmol, respectively, and after stirring for 1 hour using a magnetic stirrer, 0.40 mmol of cobalt nitrate hexahydrate is added and stirred for another 40 minutes.

[0040] Example 4

[0041] This example is basically the same as Example 1, with the only difference being that in step (2), the concentrations of ammonium molybdate tetrahydrate and thiourea are 0.5 mmol and 3.5 mmol, respectively, and after stirring for 1 hour using a magnetic stirrer, 0.60 mmol of cobalt nitrate hexahydrate is added and stirred for another 40 minutes.

[0042] Example 5

[0043] This embodiment is basically the same as embodiment 1, with the only difference being that in step (2), the concentrations of ammonium molybdate tetrahydrate and thiourea are 0.5 mmol and 3.5 mmol, respectively, and after stirring for 1 hour using a magnetic stirrer, 0.80 mmol of cobalt nitrate hexahydrate is added and stirred for another 40 minutes.

[0044] Figure 4The XRD patterns of Examples 2-5 show that all Examples have a certain degree of diffraction peaks of 1T phase molybdenum sulfide, but as more cobalt nitrate is added to Liuhe water, the amount of molybdenum oxide gradually increases.

[0045] Comparative Example 1

[0046] A method for preparing 2H phase molybdenum sulfide comprises the following steps:

[0047] (1) Preparation of reaction precursors: 30 ml of solvent water, 0.5 mmol of ammonium molybdate tetrahydrate and 3.5 mmol of thiourea, respectively. After stirring for 1 hour using a magnetic stirrer, 0.25 mmol of cobalt nitrate hexahydrate was added and stirred for another 40 minutes.

[0048] (2) The reaction precursors were placed in a reaction vessel, assembled and reacted at 200 degrees Celsius for 22 hours.

[0049] (3) After the reaction is completed, the suspension in the reactor is taken out and placed in a centrifuge tube, which is centrifuged at 6000 r / min for 3 min using a high-speed centrifuge, then rinsed three times alternately with ethanol and deionized water, and finally dried in a vacuum oven at 60 degrees Celsius.

[0050] Depend on Figure 1 It can be seen that the XRD spectrum of Example 1 has two diffraction peaks at 9° and 17.8°, which belong to the (002) and (004) diffraction peaks of the 1T phase respectively, while the diffraction peak of (002) of Comparative Example 1 at 14° proves to be the 2H phase.

[0051] Application Examples

[0052] 1. Preparation of electrodes

[0053] (1) Wash and dry the carbon paper with alcohol and deionized water;

[0054] (2) The 1T phase molybdenum sulfide powder prepared in Example 1 (10 mg), deionized water (900 μL) and Nafion solution (100 μL) were ultrasonically treated for 30 min to prepare a catalyst slurry;

[0055] (3) The catalyst slurry was evenly coated on the cleaned carbon paper with a loading of 1 mg / cm 2 , and then dried at room temperature overnight to obtain the electrode.

[0056] 2. Preparation of electrolyte

[0057] Weigh a certain mass of potassium hydroxide and dilute it with water to prepare an aqueous solution with a concentration of 1 mol / L.

[0058] 3. Assemble the test device

[0059] A silver chloride electrode was used as a reference electrode, a graphite rod was used as a counter electrode, the electrode loaded with 1T phase molybdenum sulfide powder prepared in step 1 was used as a working electrode, and the potassium hydroxide solution prepared in step 2 was used as an electrolyte solution.

[0060] Comparative Example 1 was also tested under the above conditions. The HER and OER tests were performed using an electrochemical workstation three-electrode system. The results are as follows Figure 5 and Figure 6 shown.

[0061] Figure 5 The HER performance of Example 1 and Comparative Example 1 is tested. The HER performance of Example 1 is tested at 10 mA / cm 2 The overpotential is 99 mV, which is better than 150 mV of Comparative Example 1, proving that Example 1 has better HER catalytic performance.

[0062] Figure 6 The OER performance test of Example 1 and Comparative Example 1 is shown in Figure 1. 2 The overpotential is 320 mV, which is better than 370 mV of comparative example 1. The starting potential of embodiment 1 is also lower than comparative example 1, which proves that embodiment 1 has better OER catalytic performance.

[0063] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing 1T phase molybdenum sulfide, characterized in that: The following steps are involved: Under the action of an external magnetic field, 1T phase molybdenum sulfide is generated in the reaction process through a one-step hydrothermal method with ammonium molybdate tetrahydrate and thiourea as molybdenum source and sulfur source respectively and cobalt nitrate hexahydrate as initiator.

2. The method for preparing 1T phase molybdenum sulfide according to claim 1, characterized in that: The external magnetic field is provided by two samarium cobalt permanent magnets located on the same central axis with positive and negative poles facing each other.

3. The method for preparing 1T phase molybdenum sulfide according to claim 2, characterized in that: The diameter of the samarium cobalt permanent magnet is 25-30 mm, the height is 18-20 mm, and the surface magnetic field strength of the samarium cobalt permanent magnet is 0.35-0.45 T.

4. The method for preparing 1T phase molybdenum sulfide according to claim 2, characterized in that: The distance between the two samarium cobalt permanent magnets is 58-62 mm.

5. The method for preparing 1T phase molybdenum sulfide according to claim 1, characterized in that: The molar ratio of the ammonium molybdate tetrahydrate, thiourea and cobalt nitrate hexahydrate is 4:28:1-5.

6. The method for preparing 1T phase molybdenum sulfide according to claim 1, characterized in that: The concentration of the ammonium molybdate tetrahydrate is 0.010-0.020 mol / L, the concentration of the thiourea is 0.10-0.20 mol / L, and the concentration of the cobalt nitrate hexahydrate is 0.001-0.01 mol / L.

7. The method for preparing 1T phase molybdenum sulfide according to claim 1, characterized in that: The ammonium molybdate tetrahydrate and thiourea need to be stirred for 45-60 minutes before adding cobalt nitrate hexahydrate.

8. The method for preparing 1T phase molybdenum sulfide according to claim 1, characterized in that: The temperature of the hydrothermal method is 180-220° C. and the time is 18-24 hours.

9. The method for preparing 1T phase molybdenum sulfide according to claim 1, characterized in that: After obtaining the 1T phase molybdenum sulfide, it is washed with deionized water and anhydrous ethanol, and then dried.

10. An application of 1T phase molybdenum sulfide, characterized in that: The 1T phase molybdenum sulfide prepared by the preparation method of 1T phase molybdenum sulfide according to any one of claims 1 to 9 is used to prepare a dual-functional electrode for oxygen and hydrogen evolution.

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