Preparation method and application of three-dimensional ultrathin carbon-based composite material

Abstract

The invention belongs to the technical field of electrocatalyst material preparation, and discloses a preparation method of a Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst, which comprises the following steps: dissolving salicylic acid, cobalt chloride hexahydrate and sodium molybdate dehydrate in absolute ethyl alcohol and deionized water by a simple pyrolysis method, stirring for dissolving, drying to obtain a catalyst precursor, and preparing the Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst. And putting the catalyst precursor into a crucible, introducing inert gas into a tubular furnace for annealing treatment, and washing and drying to obtain the electrocatalyst. The prepared electrocatalyst material has a unique heterostructure, provides more active sites for reaction and accelerates the electron transfer rate, so that the electrocatalytic water decomposition performance is improved.

Description

[0001] Applicants: Jiangsu Jiangke Graphene Research Institute Co., Ltd., Jiangsu Jiangke Composite New Materials Co., Ltd., Jiangsu University; Inventors: Ren Haijun, Xu Yuanguo, Mao Huiping, Xie Meng, Xie Jimin, Yang Jinan, Zhang Mingmei.

[0002] Meng Suci Technical Field

[0003] This invention belongs to the field of electrocatalysis technology, specifically relating to a method for preparing a Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst with wide pH hydrogen evolution and alkaline water splitting. Background Technology

[0004] With industrial development, society's demand for energy is increasing, and excessive development and utilization of traditional energy sources can lead to environmental degradation. To address current energy and environmental challenges, my country has clearly proposed the goal of "peak carbon emissions and carbon neutrality." Hydrogen, as an ideal new energy source, has unique advantages. Currently, one of the most mature methods for hydrogen production is water electrolysis, a technology that is expected to become key to the widespread adoption of new energy sources.

[0005] Studies have shown that transition metal carbides have attracted widespread attention and extensive research due to their advantages such as similar d-electron structure to noble metals, good corrosion resistance, low cost, and high stability. Among them, molybdenum carbide (Mo2C) has been reported to possess excellent catalytic activity and can replace noble metals in water splitting experiments. However, high-temperature calcination of Mo2C coarsens its particles, resulting in a lower density of active sites. Furthermore, the unoccupied d orbitals of Mo in Mo2C lead to strong Mo-H bond bonding, hindering the HER process. Simultaneously, the low activity caused by the easy oxidation of Mo2C in the OER reaction also limits its overall water splitting performance. Recent studies have shown that introducing two or more transition metals (such as Ni, Co, and Fe) and bimetallic carbides (such as Co3Mo3C, Co6W6C, Fe3Mo3C, and Fe6W6C) with different activities into Mo2C can regulate the valence electron density, reduce the d-electron orbital density of Mo, increase the electron transfer rate, promote H2 desorption to accelerate HER, or regulate the morphology to expose more active sites, such as nanowires, nanotubes, and nanosheets, which can optimize the electronic structure, enhance electrical conductivity, and increase the active surface area of ​​the catalyst, thereby enhancing the overall water-splitting performance of Mo2C. Therefore, when considering Mo2C as a water-splitting catalyst, factors such as synthesis temperature, composite materials, and morphological structure must be taken into account to achieve the goal of constructing a highly efficient and stable electrocatalyst. Summary of the Invention

[0006] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing a Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst that can carry out hydrogen evolution reaction under a wide pH range.

[0007] Another objective of this invention is to provide a method for preparing a Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst capable of undergoing complete water splitting tests under alkaline conditions.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing a Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst that can undergo hydrogen evolution under a wide pH range and function as a bifunctional catalyst under alkaline conditions is disclosed, and the preparation steps are as follows:

[0010] (1) Dissolve salicylic acid, cobalt chloride hexahydrate, and sodium molybdate dihydrate in anhydrous ethanol and deionized water, and stir at a certain temperature for a certain period of time.

[0011] (2) The mixture solution was placed in an oven for drying to obtain the Mo2C / Co3Mo3C three-dimensional ultrathin carbon precursor.

[0012] (3) Grind the precursor, transfer it into a clean crucible, anneal and carbonize it under an inert gas, wash and dry the calcined material to obtain the electrocatalyst.

[0013] Preferably, in step (1), the molar contents of salicylic acid, cobalt chloride hexahydrate, and sodium molybdate dihydrate are 10%-80%, 5%-30%, and 5%-30%, respectively. The volume contents of anhydrous ethanol and deionized water are 30%-80% and 20%-80%, respectively.

[0014] Preferably, the stirring temperature in step (1) is 18-25℃ and the stirring time is 1-4h.

[0015] Preferably, the drying temperature in step (2) is 50-90℃ and the drying time is 4-36h.

[0016] Preferably, the calcination temperature in step (3) is 350-800℃, the calcination time is 3-6h, and the calcination heating rate is 2-5℃ / min. -1 .

[0017] Preferably, the drying temperature in step (3) is 50-90℃ and the drying time is 6-24h.

[0018] The beneficial effects of this invention are:

[0019] (1) The Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst prepared by the method of the present invention has a hierarchical ordered framework of petal-shaped nanosheets, and nanoparticles of different sizes are tightly aggregated on the surface of the nanosheets, forming a unique heterostructure, which provides more active sites for the reaction.

[0020] (2) The Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst prepared by the method of the present invention has good electrochemical performance: the overpotential of the optimal catalyst in the hydrogen evolution test in alkaline solution is 86mV@10mAcm. -2 The double-layer capacitance is 98.30 mF cm. -2 The overpotential for hydrogen evolution testing in acidic solution is 102 mV @ 10 mA cm⁻¹ -2 The double-layer capacitance is 14.25 mF cm. -2 The overpotential for hydrogen evolution testing in neutral solution is 323 mV @ 10 mA cm⁻¹ -2 The double-layer capacitance is 15.70 mF cm. -2 This demonstrates the excellent hydrogen evolution performance of the material of the present invention under a wide pH range.

[0021] (3) The Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst prepared by the method of the present invention has good electrochemical performance: the overpotential of the optimal catalyst in the oxygen evolution test in alkaline solution is 336mV@10mAcm -2 This demonstrates that the material of the present invention exhibits excellent oxygen evolution performance under alkaline conditions.

[0022] (4) The Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst prepared by the method of the present invention has good electrochemical performance: the overpotential of the optimal catalyst in the total water splitting test in alkaline solution is 1.579V@10mA cm⁻¹. -2 The performance of the electrode is extremely similar to that of the Pt / C||RuO2 composition, as tested under industrial current density conditions, i.e., 1A cm⁻¹. -2 and 2A cm -2 The overpotentials at high current densities were 2.031V and 2.156V, respectively, indicating that the material of the present invention not only has good bifunctional catalytic performance under alkaline conditions, but also has the potential to be applied to industrial water splitting. Attached Figure Description

[0023] Figure 1 XRD pattern of the optimal sample prepared in this invention

[0024] Figure 2 SEM and TEM images of the optimal sample prepared in this invention.

[0025] Figure 3 Mapping diagram of the optimal sample prepared in this invention

[0026] Figure 4 The LSV diagram of hydrogen evolution of the optimal sample prepared in this invention.

[0027] Figure 5 The LSV diagram of oxygen evolution of the optimal sample prepared in this invention.

[0028] Figure 6 The LSV diagram of the optimal sample prepared in this invention for total water hydrolysis. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0030] Example 1:

[0031] The preparation method of Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst material includes the following steps:

[0032] (1) Dissolve 5 mmol of salicylic acid, 2 mmol of cobalt chloride hexahydrate and 1 mmol of sodium molybdate dihydrate in a mixture of about 20 mL of anhydrous ethanol and 20 mL of deionized water.

[0033] (2) The resulting mixture solution was stirred on a magnetic stirrer for 2 hours and then dried in an oven at 80°C for 12 hours.

[0034] (3) Grind the resulting mixture into powder and transfer it to a 10 mL clean crucible. Then, pyrolyze and anneal it at 600 °C for 3 h under an Ar atmosphere at a heating rate of 3 °C / min. -1 .

[0035] (4) The obtained sample was collected and washed three times each with anhydrous ethanol and deionized water, and then dried at 60°C for 12 hours.

[0036] Example 2:

[0037] The preparation method of Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst includes the following steps:

[0038] In order to investigate the effect of different metal ratios on the water splitting performance, the Co:Mo molar ratio in step (1) of Example 1 was controlled to be 1:1, 2:1, 2:2, etc., and the other steps were the same as in Example 1.

[0039] Example 3:

[0040] The preparation method of Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst includes the following steps:

[0041] To investigate the effect of substances obtained at different calcination temperatures on the water-splitting performance, the samples were calcined at 500℃, 550℃, and 600℃, respectively. That is, the temperature in step (3) of Example 1 was replaced with 500℃, 550℃, and 600℃, etc. The other steps were the same as in Example 1.

[0042] Figure 1 The XRD pattern of the optimal sample prepared in this invention clearly shows that the synthesized sample corresponds almost exactly to the standard card, with only a slight difference observed at the characteristic peak at 2θ = 26.1 Å; all other substances are identical. This characteristic peak is attributed to the (002) plane of graphitic carbon, which may be due to the presence of a certain amount of carbon in the sample.

[0043] Figure 2 The SEM and TEM images of the optimal sample prepared in this invention clearly show that the synthesized sample exhibits a hierarchical ordered framework with a petal-like nanosheet structure, and nanoparticles of different sizes are tightly aggregated on the surface of the nanosheets.

[0044] Figure 3 The mapping diagram shows the optimal sample prepared according to the present invention. It can be clearly seen from the diagram that the four elements Mo, Co, C and O are evenly distributed in the synthesized sample.

[0045] Figure 4 The LSV diagram for hydrogen evolution of the optimal sample prepared in this invention clearly shows that the synthesized sample exhibits good overpotential in hydrogen evolution tests conducted in alkaline, acidic, and neutral solutions, with values ​​of η, respectively. 10 =86mV, η 10 =102mV and η 10 =323mV.

[0046] Figure 5 The figure shows the LSV (Lead Potential Variation) of the oxygen evolution of the optimal sample prepared in this invention. It is clear from the figure that the overpotential of the synthesized sample in the oxygen evolution test in alkaline solution is 336 mV @ 10 mA cm⁻¹. -2 .

[0047] Figure 6 The image shows the LSV (Laser Potential Variation) of the optimal sample prepared in this invention during water hydrolysis. It is clear from the image that the overpotential of the synthesized sample in the water hydrolysis test in alkaline solution is 1.579 V @ 10 mA cm⁻¹. -2 , in 1A cm -2 and 2A cm -2The overpotentials at high current densities were 2.031V and 2.156V, respectively, indicating that the material of the present invention not only has good bifunctional catalytic performance under alkaline conditions, but also has the potential to be applied to industrial water splitting production.

[0048] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. An electrocatalyst with a Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure, characterized in that, The Mo2C / Co3Mo3C / three-dimensional ultrathin carbon composite catalyst exhibits a hierarchical ordered framework with a petal-like structure, where nanoparticles of different sizes are tightly aggregated on the surface of the petal-like three-dimensional ultrathin carbon nanosheets. The electrocatalyst underwent hydrogen evolution tests in acidic and neutral solutions, as well as hydrogen evolution and oxygen evolution tests and total water splitting tests in alkaline solutions. The most superior catalyst exhibited the lowest overpotential in the hydrogen evolution tests in alkaline, acidic, and neutral solutions, with values ​​of η, respectively. 10 =86mV, η 10 =102mV and η 10 =323mV, and the oxygen evolution overpotential in alkaline solution is 336mV@10mA cm⁻¹. -2 In the total water splitting test, the optimal catalyst exhibited very similar electrode performance to the Pt / C||RuO2 composition, demonstrating the excellent bifunctional catalytic performance of this catalyst material.

2. A method for preparing a Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure electrocatalyst, characterized in that, Includes the following steps: (1) Preparation of Mo2C / Co3Mo3C / three-dimensional ultrathin carbon precursor Nanocomposite materials were prepared by a simple pyrolysis method. Salicylic acid, cobalt chloride hexahydrate, and sodium molybdate dihydrate were dissolved in anhydrous ethanol and deionized water. The mixture was stirred and dissolved on a magnetic stirrer and then dried in an oven to obtain the precursor of the electrocatalyst. (2) Precursor annealing and carbonization treatment The precursor was ground and transferred to a clean crucible, where it was annealed and carbonized under an inert gas atmosphere. The calcined material was then washed and dried to obtain the electrocatalyst.

3. The method for preparing an electrocatalyst according to claim 2Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure, characterized in that, In step (1), the molar contents of salicylic acid, cobalt chloride hexahydrate, and sodium molybdate dihydrate are 10%-80%, 5%-30%, and 5%-30%, respectively. The volume contents of anhydrous ethanol and deionized water are 30%-80% and 20%-80%, respectively.

4. The method for preparing an electrocatalyst according to claim 2Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure, characterized in that, The stirring temperature in step (1) is 18-25℃ and the stirring time is 1-4h.

5. A method for preparing an electrocatalyst according to claim 2Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure, characterized in that, The drying temperature in step (1) is 50-90℃ and the drying time is 4-36h.

6. A method for preparing an electrocatalyst according to claim 2Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure, characterized in that, The calcination temperature in step (2) is 350-800℃, the calcination time is 3-6h, and the heating rate is 2-5℃ / min. -1 .

7. A method for preparing an electrocatalyst according to claim 2Mo2C / Co3Mo3C / petal-shaped three-dimensional ultrathin carbon heterostructure, characterized in that, The drying temperature in step (2) is 50-90℃ and the drying time is 6-24h.

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