Composite catalyst containing molybdenum oxide, preparation method therefor and use thereof

Abstract

Provided are a composite catalyst containing molybdenum oxide, a preparation method therefor, and a use thereof. The preparation method comprises: (1) mixing a molybdate and a ligand to obtain a mixed solution; (2) soaking nickel foam in the mixed solution, to obtain a suspension, the soaking time being not less than 1 hour; (3) performing a hydrothermal reaction and calcination. The preparation method utilizes the etching effect of molybdate on nickel foam, and immerses nickel foam in the mixed solution containing the molybdate and that ligand to cause nickel in the nickel foam to dissolve in the form of ions, which, along with molybdate ions and the ligand, grow a nickel-molybdenum complex transition layer in situ on the surface of nickel foam; by means of the hydrothermal reaction, a nickel-molybdenum-based catalyst precursor is grown on the complex transition layer, and a composite catalyst is obtained after calcination, causing the catalyst to be firmly anchored on the nickel foam substrate, thereby improving the stability and impact resistance of the catalyst, and preventing the active components in the catalyst from falling off or reducing the risk of the active components falling off from the catalyst.

Description

A composite catalyst containing molybdenum oxide and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on November 15, 2023, with application number 202311525062.X and invention name “A composite catalyst containing molybdenum oxide, its preparation method and application”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application belongs to the technical field of catalyst preparation, and specifically relates to a composite catalyst containing molybdenum oxide, a preparation method thereof, and an application thereof. Background Art

[0004] Hydrogen, a green energy source, produces only water when burned, effectively reducing air pollution and climate change. Furthermore, hydrogen's high energy density and renewability make it a promising energy storage medium. Hydrogen production through water electrolysis converts electricity into hydrogen, and then, when needed, hydrogen back into electricity, enabling efficient energy storage and utilization. In recent years, the development of water electrolysis hydrogen production technology has opened up new possibilities for the efficient production of green hydrogen.

[0005] However, the catalysts for hydrogen production by water electrolysis mostly use precious metal platinum-based catalysts, and their low stability and scarcity greatly limit the widespread application of hydrogen energy in life and production.

[0006] Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present application is to overcome the problem that the existing technology of water electrolysis hydrogen production catalysts mostly use low-stability and scarce platinum-based catalysts, thereby providing a composite catalyst containing molybdenum oxide and its preparation method and application.

[0008] To this end, this application provides the following technical solutions.

[0009] The present application provides a method for preparing a composite catalyst containing molybdenum oxide, comprising the following steps:

[0010] (1) mixing molybdate and ligand to obtain a mixed solution;

[0011] (2) soaking the nickel foam in the mixed solution to obtain a suspension; wherein the soaking time is not less than 1 hour;

[0012] (3) After hydrothermal reaction and calcination.

[0013] In step (2), the soaking temperature is 10-60°C;

[0014] Optionally, the soaking is carried out at room temperature;

[0015] Optionally, the soaking time is 1-5 hours.

[0016] The step (2) further comprises shaking and / or stirring while soaking;

[0017] Optionally, the frequency of the oscillation is 50-200 rpm.

[0018] The ligand is at least one of an oxygen-containing organic ligand, a nitrogen-containing organic ligand, and a sulfur-containing organic ligand;

[0019] Optionally, the ligand is at least one of carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, sodium alginate, polyvinyl pyrrolidone, sodium lauryl sulfate, uric acid, p-phenylenediamine, terephthalic acid, and trimesic acid.

[0020] In the step (1), the mass concentration of the ligand in the mixed solution is 3-16 g / L.

[0021] In the step (1), the mass concentration of molybdate in the mixed solution is 30-160 g / L;

[0022] Optionally, the molybdate is at least one of ammonium molybdate tetrahydrate, ammonium molybdate and ammonium phosphomolybdate.

[0023] In the step (1), the mass ratio of the molybdate to the ligand is (5-15):1.

[0024] The temperature of the hydrothermal reaction is 100-180° C., and the time is 2-12 hours.

[0025] Optionally, the calcination step comprises: heating to 350-600° C. at a heating rate of 4-10° C. / min and calcining for 0.5-8 h;

[0026] Optionally, the volume content of hydrogen in the calcination atmosphere is 4-10%.

[0027] When preparing a mixed solution, there is no specific requirement for the order in which the raw materials are mixed, as long as they are mixed evenly. The following methods can be used to prepare the mixed solution:

[0028] (1) dissolving molybdate and ligand in water to obtain a clear mixed solution;

[0029] (2) dissolving molybdate in water to obtain solution 1; then dissolving the ligand in water to obtain solution 2; and mixing solution 1 and solution 2 to obtain a clear mixed solution.

[0030] When preparing the composite catalyst, a ligand is added and the nickel foam is immersed in a mixed solution to obtain a suspension. This allows the nickel foam to dissolve metallic nickel and in situ generate a nickel-molybdenum complex transition layer with the molybdate ions and the ligand surface, making the connection between the catalyst and the nickel foam substrate more secure.

[0031] The present application also provides a composite catalyst containing molybdenum oxide prepared by the above method.

[0032] The present application also provides an application of the composite catalyst prepared by the above method in hydrogen production by electrolysis of water.

[0033] The technical solution of this application has the following advantages:

[0034] 1. The present application provides a method for preparing a composite catalyst containing molybdenum oxide, comprising: (1) mixing molybdate and a ligand to obtain a mixed solution; (2) soaking nickel foam in the mixed solution to obtain a suspension; wherein the soaking time is not less than 1 hour; and (3) undergoing a hydrothermal reaction and calcination. The composite catalyst prepared by this method has low cost, good stability, and high activity. The preparation method utilizes the etching effect of molybdate on nickel foam, immersing the nickel foam in a mixed solution containing molybdate and a ligand, dissolving the nickel in the nickel foam in the form of ions, and in situ growing a nickel-molybdenum complex transition layer on the surface of the nickel foam with the molybdate ions and the ligand. Through a hydrothermal reaction, a nickel-molybdenum-based catalyst precursor grows on the complex transition layer, and after calcination, a composite catalyst is obtained; the complex transition layer well connects the nickel foam substrate and the catalyst, firmly anchoring the catalyst on the nickel foam substrate, thereby improving the stability and impact resistance of the catalyst, preventing the active components in the catalyst from falling off or reducing the risk of the active components in the catalyst falling off. In addition, since the catalyst does not contain precious metals, the cost of raw materials is greatly reduced. The present invention has a simple process and mild operating conditions when preparing the catalyst. The obtained catalyst is evenly distributed, has high catalytic activity and good stability, and is easy to produce in large quantities.

[0035] In addition, when preparing the catalyst, the present application does not require the addition of an additional nickel source or precious metals such as platinum.

[0036] 2. The preparation method of the composite catalyst containing molybdenum oxide provided in the present application is to immerse the nickel foam in a mixed solution at room temperature and control the immersion time to be 1-5 hours, so as to form a nickel-molybdenum complex transition layer of appropriate thickness, further ensure the connection effect between the catalyst layer and the substrate, and effectively prevent or reduce problems such as transition etching of the substrate, brittleness and easy damage of the substrate, and influence on the subsequent preparation of the catalyst.

[0037] 3. The composite catalyst containing molybdenum oxide provided in the present application forms a catalyst layer with a sharp knife-like structure, the size of which is between 1-3 μm, and has the advantages of low cost, good stability and high activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0039] FIG1 is a scanning electron microscope image of the catalyst of Example 1 of the present application;

[0040] FIG2 is a scanning electron microscope image of the catalyst of Example 2 of the present application;

[0041] FIG3 is a scanning electron microscope image of the catalyst of Comparative Example 1 of the present application;

[0042] FIG4 is a scanning electron microscope image of the catalyst of Comparative Example 2 of the present application;

[0043] FIG5 is an X-ray powder diffraction pattern of the catalyst of Example 1 of the present application;

[0044] FIG6 is a transmission electron microscope image of the catalyst of Example 1 of the present application;

[0045] FIG7 is a graph showing the long-term performance stability of the three electrodes of the catalyst of Example 1 of the present application;

[0046] FIG8 is a linear sweep voltammetry curve of the catalysts of the examples and comparative examples of the present application. DETAILED DESCRIPTION

[0047] The following examples are provided to further better understand the present application, but are not limited to the best implementation mode described herein, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the scope of protection of the present application.

[0048] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0049] Example 1

[0050] This embodiment provides a method for preparing a composite catalyst containing molybdenum oxide, comprising the following steps:

[0051] (1) Ammonium molybdate, polyvinyl pyrrolidone and water are mixed to obtain a mixed solution, wherein the mass concentration of ammonium molybdate in the mixed solution is 33 g / L, and the mass concentration of polyvinyl pyrrolidone is 3 g / L.

[0052] (2) The nickel foam and the mixed solution were placed in an oscillator, and the nickel foam was immersed in the mixed solution and oscillated for 2 hours at a frequency of 150 rpm to obtain a white-green suspension; wherein the immersion and oscillation temperature was 25°C.

[0053] (3) The nickel foam and the white-green suspension were placed at 150°C for a hydrothermal reaction for 6 hours to obtain a catalyst precursor; the temperature was then raised to 500°C at a heating rate of 5°C / min, and the temperature was maintained at 500°C for calcination for 2 hours to obtain a composite catalyst containing molybdenum oxide; wherein the volume proportion of hydrogen in the calcination atmosphere was 5%, and the remaining gas was argon.

[0054] Example 2

[0055] This embodiment provides a method for preparing a composite catalyst containing molybdenum oxide, comprising the following steps:

[0056] (1) Ammonium molybdate, sodium lauryl sulfate and water are mixed to obtain a mixed solution, wherein the mass concentration of ammonium molybdate in the mixed solution is 100 g / L, and the mass concentration of sodium lauryl sulfate is 15 g / L.

[0057] (2) The nickel foam and the mixed solution were placed in an oscillator, and the nickel foam was immersed in the mixed solution and oscillated for 2 hours at a frequency of 150 rpm to obtain a white-green suspension; wherein the immersion temperature was 25°C.

[0058] (3) The nickel foam and the white-green suspension were subjected to a hydrothermal reaction at 150°C for 6 hours to obtain a catalyst precursor; the temperature was then increased to 500°C at a heating rate of 5°C / min and maintained at 500°C for calcination for 2 hours to obtain a composite catalyst containing molybdenum oxide; wherein the volume proportion of hydrogen in the calcination atmosphere was 5%, and the remaining gas was argon.

[0059] Comparative Example 1

[0060] This comparative example provides a method for preparing a composite catalyst, comprising the following steps:

[0061] (1) Ammonium molybdate, polyvinyl pyrrolidone and water are mixed to obtain a mixed solution, wherein the mass concentration of ammonium molybdate in the mixed solution is 33 g / L, and the mass concentration of polyvinyl pyrrolidone is 3 g / L.

[0062] (2) The nickel foam was mixed with the mixed solution and subjected to a hydrothermal reaction at 150°C for 6 h to obtain a catalyst precursor; the temperature was then increased to 500°C at a heating rate of 5°C / min and maintained at 500°C for calcination for 2 h to obtain a composite catalyst; wherein the volume proportion of hydrogen in the calcination atmosphere was 5%, and the remaining gas was argon.

[0063] Comparative Example 2

[0064] This comparative example provides a method for preparing a composite catalyst, comprising the following steps:

[0065] (1) Ammonium molybdate is mixed with water to obtain a solution, wherein the mass concentration of ammonium molybdate in the solution is 33 g / L.

[0066] (2) The nickel foam and the above solution were placed in an oscillator, and the nickel foam was immersed in the solution and oscillated for 2 hours at a frequency of 150 rpm to obtain a blue clear solution; wherein the immersion temperature was 25°C.

[0067] (3) The nickel foam and the above-mentioned blue solution were placed at 150°C for hydrothermal reaction for 6 hours to obtain a catalyst precursor; then the temperature was increased to 500°C at a heating rate of 5°C / min, and the temperature was maintained at 500°C for calcination for 2 hours to obtain a composite catalyst; wherein, the volume proportion of hydrogen in the calcination atmosphere was 5%, and the remaining gas was argon.

[0068] Test example

[0069] This test example provides performance tests of the catalysts prepared in each embodiment and comparative example, as follows:

[0070] Catalyst stability test method: Take a catalyst of approximately 1 cm x 1 cm, soak it in water, and then perform ultrasonic treatment for 3600 seconds to observe whether the catalyst falls off. The stability of the catalyst of the example and the comparative example is compared. The ultrasonic frequency is 53 kHz.

[0071] Catalyst polarization curve: A three-electrode test method was used, with the catalyst as the cathode (the catalyst was from each embodiment and comparative example), the counter electrode being a platinum mesh, and the reference electrode being a saturated calomel electrode. The measurement was performed in a glass electrolytic cell, and the electrolyte had a molar concentration of 1 mol·L -1 The potassium hydroxide solution was used to obtain a current density of 1 A·cm -2 The commercial platinum-carbon catalyst was used as the control group. Manufacturer and model: Johnson Matthey, HISPEC10000; 60% Pt.

[0072] Table 1 Performance test results of catalysts in Examples and Comparative Examples

[0073] Figures 1-4 correspond to scanning electron micrographs of the catalysts of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, respectively. As can be seen from Figures 1-4, the catalysts of Examples 1-2 have a sharp knife-like structure and a uniform morphology; the catalyst of Comparative Example 1 is relatively fragmented and uneven, and the catalyst of Comparative Example 2 has numerous cracks, a spiky shape, and is uneven.

[0074] FIG5 is an X-ray powder diffraction pattern of the catalyst of Example 1. It can be seen from FIG5 that the bulk structure of the catalyst is molybdenum dioxide.

[0075] Figure 6 is a transmission electron microscope image of Example 1. From Figure 6, it can be seen that the morphology of the catalyst presents a sharp knife-like structure; its bulk structure is a molybdenum dioxide phase with metallic nickel nanoparticles attached on top.

[0076] FIG7 is a graph showing the long-term performance stability of the three-electrode catalyst of Example 1. It can be seen from the graph that the catalyst has excellent stability.

[0077] FIG8 is a linear sweep voltammetry curve of Example 1-2, Comparative Example 1-2 and the control group. It can be seen from the figure that the catalyst of Example 1-2 has excellent catalytic hydrogen release performance.

[0078] From the above results, it can be seen that the catalyst in Example 1-2 of the present application did not fall off after the end of 3600s of ultrasound, indicating that the catalyst has good stability. It further shows that the catalyst has good mechanical strength and impact resistance, which can anchor the catalyst on the foam nickel substrate, avoiding the falling off of active components or reducing the risk of the active components in the catalyst falling off.

[0079] Furthermore, the current density is 1A·cm -2 The overpotential indicates that the catalysts of Examples 1-2 of the present application have good catalytic activity. Furthermore, in Comparative Example 1, the nickel foam and the mixed solution were directly subjected to a hydrothermal reaction, and the resulting catalyst easily fell off, resulting in decreased activity. In Comparative Example 2, the ligand was removed during the preparation of the catalyst, and the resulting catalyst fell off after approximately 300 seconds of ultrasonication, resulting in lower catalytic activity than that of the present application.

[0080] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a composite catalyst containing molybdenum oxide, characterized in that: The following steps are involved: (1) mixing molybdate and ligand to obtain a mixed solution; (2) soaking the nickel foam in the mixed solution to obtain a suspension; wherein the soaking time is not less than 1 hour; (3) After hydrothermal reaction and calcination.

2. The preparation method according to claim 1, characterized in that: In step (2), the soaking temperature is 10-60° C. Preferably, the soaking is carried out at room temperature; Preferably, the soaking time is 1-5 hours.

3. The preparation method according to claim 1 or 2, characterized in that: The step (2) further comprises shaking and / or stirring while soaking; Preferably, the frequency of the oscillation is 50-200 rpm.

4. The preparation method according to any one of claims 1 to 3, characterized in that The ligand is at least one of an oxygen-containing organic ligand, a nitrogen-containing organic ligand and a sulfur-containing organic ligand; Preferably, the ligand is at least one of carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, sodium alginate, polyvinyl pyrrolidone, sodium dodecyl sulfate, uric acid, p-phenylenediamine, terephthalic acid, and trimesic acid.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In the step (1), the mass concentration of the ligand in the mixed solution is 3-16 g / L.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In the step (1), the mass concentration of molybdate in the mixed solution is 30-160 g / L; Preferably, the molybdate is at least one of ammonium molybdate tetrahydrate, ammonium molybdate and ammonium phosphomolybdate.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In the step (1), the mass ratio of the molybdate to the ligand is (5-15):

1.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The temperature of the hydrothermal reaction is 100-180°C and the time is 2-12h; Preferably, the calcination step comprises: heating to 350-600°C at a heating rate of 4-10°C / min and calcining for 0.5-8h; Preferably, the volume content of hydrogen in the calcination atmosphere is 4-10%.

9. A composite catalyst containing molybdenum oxide obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the composite catalyst prepared by the preparation method according to any one of claims 1 to 8 in hydrogen production by water electrolysis.

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