A molybdenum oxide electrocatalyst with complex defects of ruthenium and molybdenum, a preparation method and application thereof

Abstract

The application aims to provide a ruthenium molybdenum alloy composite defect type molybdenum oxide electrocatalyst, a preparation method and application thereof, and belongs to the technical field of electrocatalysts. The preparation method comprises the following steps: (1) adding a foamed nickel into a molybdenum salt solution, carrying out a hydrothermal reaction to obtain a Mo-O precursor, and then carrying out joule heating on the precursor to obtain a Mo / MoO x precursor; (2) soaking the Mo / MoO x precursor in a ruthenium salt solution to obtain a Ru-Mo-O precursor; and (3) carrying out joule heat pyrolysis on the Ru-Mo-O precursor under a reducing atmosphere, and obtaining the ruthenium molybdenum alloy composite defect type molybdenum oxide electrocatalyst after the pyrolysis is completed. The prepared RuMo / MoO x electrocatalyst has the advantages of uniform size and large specific surface area, and has good catalytic activity and stability, and can be used for electrocatalytic splitting of water to produce hydrogen in a full pH range.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalyst technology, specifically relating to a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen (H2) boasts high energy density and zero pollution. Due to global climate change and the energy crisis caused by the over-burning of fossil fuels, the demand for H2 is constantly increasing. Electrocatalytic water splitting is an ideal and large-scale sustainable method for producing green hydrogen, attracting widespread attention. The hydrogen evolution reaction (HER) is a key half-reaction in water splitting for hydrogen production. According to the kinetic volcano diagram, the metal oxide MoO2 is located near the top, possessing suitable metal-hydrogen bond strength, and is therefore widely used for water splitting to produce hydrogen. However, it still faces problems such as few active sites and low activity per site. To date, Pt-based and other noble metal compounds remain the most effective HER electrocatalysts, effectively optimizing the adsorption energy of intermediates, improving catalytic activity, and solving the problem of insufficient active sites. However, the high cost and scarcity of noble metal Pt catalysts hinder their large-scale application; therefore, developing noble metal catalysts with good activity and stability is an urgent need for the above-mentioned reaction. Ru is a member of the noble metal family, but its price is 10 times lower than platinum, giving it a significant price advantage. Furthermore, Ru-based materials, due to their good Ru-H bond strength and ability to reduce the hydrogen desorption barrier, can adapt to both acidic and alkaline conditions. Recent research advances have shown that Ru-based composites can provide electrocatalytic activity comparable to commercial Pt / C, indicating that Ru-based materials are excellent candidates for the HER reaction.

[0003] It has been reported that alloy formation can increase the number of active sites on the catalyst and optimize the adsorption energy of intermediates, thereby improving catalytic activity (Y. Li, LA Zhang, Y. Qin, F. Chu, Y. Kong, Y. Tao, Y. Li, Y. Bu, D. Ding, M. Liu, Crystallinity Dependence of Ruthenium Nanocatalyst toward Hydrogen Evolution Reaction, ACS Catalysis, 8 (2018) 5714-5720.). However, the reported electrocatalysts have long synthesis times and face problems such as easy sintering and oxidation. Furthermore, no electrocatalytic water splitting performance tests were conducted in alkaline and neutral electrolytes, indicating significant room for improvement in synthesis methods and other aspects. Summary of the Invention

[0004] The purpose of this invention is to provide a ruthenium-molybdenum alloy composite defective molybdenum oxide electrocatalyst, its preparation method, and its applications, to solve the problems existing in the prior art. This invention rapidly synthesizes a ruthenium-molybdenum alloy composite defective (oxygen-deficient molybdenum oxide) molybdenum oxide electrocatalyst based on the Joule heating effect. This electrocatalyst has advantages such as large active area, regular morphology, high catalytic activity, and a wide applicable range (all pH). Furthermore, the synthesis method is a rapid synthesis method, which has advantages such as time and energy saving, and the catalyst can be effectively controlled with high reproducibility.

[0005] The present invention adopts the following technical solution: A ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst, wherein the molecular formula of the electrocatalyst is RuMo / MoO x , where x = 2~3.

[0006] Furthermore, the electrocatalyst has a nanoflower structure with a diameter of 1-3 μm.

[0007] A method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst includes the following steps: The first step involves adding nickel foam to a molybdenum salt solution, performing a hydrothermal reaction, washing, and drying (vacuum drying at 50-80°C for 12 hours) to obtain the Mo-O precursor (yellow Mo-O is loaded on the nickel foam). The second step involves Joule thermal pyrolysis of the Mo-O precursor under a reducing atmosphere. After pyrolysis (Joule thermal effect), Mo / MoO is obtained. x Precursor (black Mo / MoOx loaded on nickel foam); The third step is to combine Mo / MoO x The precursor was immersed in a ruthenium salt solution, then removed and dried (vacuum drying at 50~80℃ for 12h) to obtain the Ru-Mo-O precursor (the black Ru-Mo-O was loaded on nickel foam). The fourth step involves subjecting the Ru-Mo-O precursor to Joule thermal pyrolysis under a reducing atmosphere. After pyrolysis (Joule thermal effect), the ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst is obtained.

[0008] Furthermore, the molybdenum salt mentioned in the first step is ammonium molybdate tetrahydrate, and the concentration of the molybdenum salt solution is 0.1~0.4 mmol / L; the hydrothermal reaction temperature is 120~150℃, and the time is 3~6h.

[0009] Furthermore, the reducing atmosphere in the second step is a mixture of hydrogen and argon; the hydrogen content in the mixture is 10~50 vol.%.

[0010] Furthermore, in the second step, the Joule heating pyrolysis temperature is 600~900℃, the energizing time is 60s, and the energizing current is 9.5A.

[0011] Furthermore, the ruthenium salt solution mentioned in the third step is a ruthenium chloride solution, and the concentration of the ruthenium salt solution is 5~9 g / L; the soaking time is 2 minutes.

[0012] Furthermore, the reducing atmosphere described in the fourth step is a mixture of hydrogen and argon; the hydrogen content in the mixture is 10~50 vol.%.

[0013] Furthermore, in the fourth step, the Joule heating pyrolysis temperature is 700~1200℃, the energizing time is 3s, the energizing potential is 10V, and the energizing current is 100A.

[0014] Joule heating can not only reduce catalyst agglomeration caused by prolonged heating, but also effectively avoid changes in the physicochemical properties of the catalyst under extreme environmental conditions (such as catalyst surface oxidation caused by prolonged material preparation and reduced bonding strength between the catalyst and the support).

[0015] Application of a ruthenium-molybdenum alloy composite defective molybdenum oxide electrocatalyst in catalytic cracking for hydrogen production across the entire pH range.

[0016] The specific method of application includes: using the electrocatalyst supported on nickel foam as the working electrode and a platinum wire as the counter electrode to perform catalytic cracking to produce hydrogen across the entire pH range; the loading of the electrocatalyst on the nickel foam is 0.01~0.5 mg / cm³. 2 .

[0017] The beneficial effects of this invention are as follows: 1. The ruthenium-molybdenum alloy composite defective molybdenum oxide electrocatalyst of the present invention exhibits excellent hydrogen production performance in acidic, neutral, and alkaline solutions. Firstly, the in-situ formed RuMo nanoalloy is tightly immobilized on MoO. x The nickel foam not only forms abundant interfaces to promote electron transfer and adjust the binding energy of reaction intermediates, but also enhances the mechanical stability during the electrocatalytic reaction. Simultaneously, the rapid heating conditions endow the catalyst with abundant surface defects, increasing the specific surface area, accelerating electron transfer, and increasing active sites and unit site activity, enabling the catalyst to exhibit excellent hydrogen production performance even under non-acidic conditions. Finally, the three-dimensional morphology and excellent conductivity of the nickel foam itself provide the catalyst with a large specific surface area and rapid electron transfer performance.

[0018] 2. This invention prepares a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst via Joule thermal synthesis. This method is time-efficient, simple to operate, and highly reproducible, providing a solid technical foundation and material guarantee for large-scale application.

[0019] 3. The preparation method of this invention is characterized by its simplicity, high repeatability, rapid speed, and high efficiency. Furthermore, the composite heterostructure formed by the prepared ruthenium-molybdenum alloy and defective molybdenum oxide exhibits a nanoflower-like morphology. This three-dimensional morphology provides a large specific surface area for the catalyst, enhances its hydrophilicity, optimizes the three-phase interface during the reaction, and promotes bubble desorption. Moreover, the efficient and rapid Joule heating ensures good dispersion of the RuMo nanoparticles, which are firmly anchored to MoO. x On the surface, a strong metal-support (SMSI) effect is formed. Therefore, the synthesized catalyst has the advantages of a large active area and high activity per unit site. Simultaneously, the constituent metal atoms are uniformly distributed, exhibiting good catalytic activity; under acidic conditions, its hydrogen evolution activity is 13 mV @ 10 mA cm⁻¹. -2 Under neutral conditions, its hydrogen evolution activity is 12 mV @ 10 mA cm⁻¹. -2 Its hydrogen evolution activity is 5 mV @ 10 mA cm under alkaline conditions. -2 It can be found at 1 A•cm -2 It can operate stably for 1000 hours at a current density and can be used in the field of electrocatalytic cracking for hydrogen production across the entire pH range. Attached Figure Description

[0020] Figure 1 RuMo / MoO prepared in Example 1 of this invention x Temperature rise curve of the catalyst; Figure 2 RuMo / MoO prepared in Example 1 of this invention x X-ray diffraction pattern of the catalyst; Figure 3 RuMo / MoO prepared in Example 1 of this invention x Mo 3d XPS spectra of the catalyst; Figure 4 RuMo / MoO prepared in Example 1 of this invention x Ru 3p XPS spectrum of the catalyst; Figure 5 RuMo / MoO prepared in Example 1 of this invention x O1s XPS spectrum of the catalyst; Figure 6 RuMo / MoO prepared in Example 1 of this invention x Scanning electron microscope image of the catalyst; Figure 7 RuMo / MoO prepared in Example 1 of this invention x Hydrogen production performance of the catalyst in acidic solution; Figure 8 RuMo / MoO prepared in Example 1 of this invention x Hydrogen production performance of the catalyst in neutral solution; Figure 9 RuMo / MoO prepared in Example 1 of this invention x A graph showing the hydrogen production performance of the catalyst in alkaline solution. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention.

[0023] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe the methods and materials associated with those references. In the event of any conflict with any incorporated reference, the contents of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] Example 1 A method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst: (1) Under room temperature conditions, molybdate tetrahydrate was dissolved in deionized water and sonicated for 30 min to obtain a molybdate solution with a concentration of 0.10 mmol / L (colorless transparent solution).

[0028] (2) At room temperature, a piece of nickel foam with a length of 4.5 cm, a width of 3.3 cm and a thickness of 1 mm was successively immersed in 1 mol / L hydrochloric acid solution, acetone solution and deionized water, and ultrasonically cleaned for 10 min to obtain clean nickel foam.

[0029] (3) The solution prepared in step (1) and the clean nickel foam prepared in step (2) are transferred to the reactor and kept at 150°C for 6 hours. Then, the reactor is washed three times with deionized water and ethanol solution respectively, and then vacuum dried at 80°C for 12 hours to obtain a yellow Mo-O precursor.

[0030] (4) Place the Mo-O precursor flat in the center of the conductive graphite plate, then move it into the Joule heating chamber and fix both sides. Under a hydrogen / argon reducing atmosphere (hydrogen content 10 vol.%), control the current to be 9.5 A and the energizing time to be 60 s to obtain black Mo / MoO. x The precursor undergoes Joule thermal pyrolysis at a temperature of 700℃.

[0031] (5) Combine Mo / MoO x The precursor was immersed in a ruthenium chloride solution with a concentration of 9 g / L for 2 minutes, and then dried under vacuum at 80 °C for 12 h to obtain a black Ru-Mo-O precursor.

[0032] (6) Place the Ru-Mo-O precursor obtained in step (5) flat in the center of the conductive graphite plate, then move it into the Joule heating device cavity and fix both sides. Under a hydrogen / argon reducing atmosphere (hydrogen content 10 vol.%), control the energizing potential to be 10 V, the energizing current to be 100 A, and the energizing time to be 3 s. Prepare the ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst (black block RuMo / MoO) by Joule heating pyrolysis (heating temperature is about 1000 ℃, starting from room temperature and rapidly increasing to about 950 ℃, then the temperature fluctuates to a certain extent, cooling is not included in the pyrolysis process, after pyrolysis is completed, the power is turned off, and cooling to room temperature begins). x Catalyst, x=2~3).

[0033] The temperature rise curves for preparing the RuMo / MoOx catalyst are shown in the figure. Figure 1 .

[0034] from Figure 1 As can be seen from this, RuMo / MoO is prepared using the Joule heating effect. xCatalysts have a shorter processing time and are characterized by speed, energy saving, time saving, and high efficiency.

[0035] RuMo / MoO x The X-ray diffraction pattern of the catalyst is shown in the figure. Figure 2 .

[0036] from Figure 2 As can be seen from the present invention, the RuMo / MoO prepared by the present invention x The main phase of the catalyst has a molybdenum dioxide crystal structure. The RuMo alloy could not be detected because of the low Ru content.

[0037] RuMo / MoO x The Mo 3d XPS spectra of the catalyst are shown below. Figure 3 .

[0038] from Figure 3 As can be seen from this, after the precursor is rapidly heated by Joule heating, some of the Mo... 6+ Mo is produced by component reduction 5+ Mo 4+ Mo 0 This confirms MoO x The presence of oxygen vacancies also contributes to enhanced conductivity. Mo 0 The existence of the RuMo alloy has been confirmed.

[0039] RuMo / MoO x The Ru 3p XPS spectrum of the catalyst is shown below. Figure 4 .

[0040] from Figure 4 As can be seen from this, after the precursor undergoes rapid Joule heating, the 3p orbital of Ru mainly exhibits Ru... 0 This confirms the existence of the RuMo alloy.

[0041] RuMo / MoO x The O1s XPS spectrum of the catalyst is shown below. Figure 5 .

[0042] from Figure 5 From this, we can see that RuMo / MoO x The catalyst's O1s exhibits a large number of O defects, confirming the presence of MoO. x The presence of oxygen vacancies.

[0043] RuMo / MoO x Scanning electron microscope image of the catalyst is shown below. Figure 6 .

[0044] from Figure 6 As can be seen from the above, the RuMo / MoO prepared in this embodiment... xThe catalyst has a nanoflower structure with a diameter of approximately 1-3 μm.

[0045] Example 2 Same as Example 1, except that when preparing the Mo-O precursor, the nickel foam is replaced with hydrophilic carbon paper.

[0046] Example 3 Same as Example 1, except that in the preparation of RuMo / MoO x At that time, the hydrogen-argon mixture was replaced with argon gas.

[0047] Comparative Example 1 Same as Example 1, except that in the preparation of Mo / MoO x In the precursor stage, Joule heating pyrolysis is replaced with conventional tubular furnace heating pyrolysis.

[0048] Comparative Example 2 Same as Example 1, except that in the preparation of Mo / MoO x Precursors and RuMo / MoO x When using catalysts, Joule heating pyrolysis is replaced with conventional tubular furnace heating pyrolysis.

[0049] Comparative Example 3 Same as Example 1, except that in the preparation of RuMo / MoO x When using a catalyst, Joule heating pyrolysis is replaced with conventional tubular furnace heating pyrolysis.

[0050] Example of effect 1 RuMo / MoO x Electrocatalyst for water cracking to produce hydrogen (1) Combine RuMo / MoO x The electrocatalyst was supported on nickel foam, and then cut into sheets 1.5 cm long, 1 cm wide, and 1 mm thick to serve as the working electrode; a mercury / mercuric oxide (calomel) electrode served as the reference electrode; and a platinum wire electrode served as the counter electrode. RuMo / MoO x The electrocatalyst loading on nickel foam was 0.4 mg / cm³. 2 .

[0051] (2) The electrolytes used in the tests were acidic solution (0.5M H2SO4), neutral solution (1M PBS) and alkaline solution (1M KOH).

[0052] The electrocatalytic performance results of the RuMo / MoOx catalyst are shown in Table 1 and Figures 7-9 .

[0053] Table 1 RuMo / MoO x Electrocatalytic performance of catalysts from Figure 7 , Figure 8 , Figure 9 The performance graphs of RuMo / MoO in acidic, neutral, and alkaline solutions show that... x The catalyst exhibits excellent electrocatalytic activity across the entire pH range.

[0054] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst, wherein the electrocatalyst has the molecular formula RuMo / MoO. x ,in, x=2~3, the electrocatalyst has a nanoflower structure with a diameter of 1-3 μm; the electrocatalyst is used for catalytic cracking to produce hydrogen across the entire pH range; characterized in that the preparation method includes the following steps: The first step is to add nickel foam to a molybdenum salt solution and carry out a hydrothermal reaction to obtain the Mo-O precursor; The second step involves Joule heating the Mo-O precursor under a reducing atmosphere. After pyrolysis, Mo / MoO is obtained. x Precursor; The third step is to combine Mo / MoO x The precursor was immersed in a ruthenium salt solution to obtain the Ru-Mo-O precursor; The fourth step involves Joule heating of the Ru-Mo-O precursor under a reducing atmosphere. After pyrolysis, the ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst is obtained.

2. The method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst according to claim 1, characterized in that: The molybdenum salt mentioned in the first step is ammonium molybdate tetrahydrate, and the concentration of the molybdenum salt solution is 0.1~0.4 mmol / L; the hydrothermal reaction temperature is 120~150℃, and the time is 3~6h.

3. The method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst according to claim 1, characterized in that: The reducing atmosphere described in the second step is a mixture of hydrogen and argon; the hydrogen content in the mixture is 10~50 vol.%.

4. The method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst according to claim 1, characterized in that: The Joule pyrolysis temperature in the second step is 600~900℃, the energizing time is 60s, and the energizing current is 9.5A.

5. The method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst according to claim 1, characterized in that: The ruthenium salt solution mentioned in the third step is a ruthenium chloride solution with a concentration of 5~9 g / L; the soaking time is 2 minutes.

6. The method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst according to claim 1, characterized in that: The reducing atmosphere described in step four is a mixture of hydrogen and argon; the hydrogen content in the mixture is 10~50 vol.%.

7. The method for preparing a ruthenium-molybdenum alloy composite defect-type molybdenum oxide electrocatalyst according to claim 1, characterized in that: The Joule pyrolysis temperature in step four is 700~1200℃, the energizing time is 3s, the energizing potential is 10V, and the energizing current is 100A.

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