A three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst, its preparation method and application
By preparing a three-dimensional self-supported nickel-iron-based composite sheet oxygen evolution catalyst on iron foam, the problems of slow anode reaction and scarce resources of precious metal catalysts in electrolytic hydrogen production are solved, and efficient and low-cost electrolytic hydrogen production technology is achieved.
Patent Information
- Application Number
- CN202310455346.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-25
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2043-04-25
AI Technical Summary
In the existing electrolytic hydrogen production technology, the anode oxygen evolution reaction kinetics are slow and the overpotential is large, resulting in high costs and scarce precious metal catalyst resources, which limits the large-scale application of electrolytic water technology.
Using iron foam as the substrate, iron trioxide is generated by oxidation and hydrothermal reaction with a mixture of nickel chloride and sodium chloride to prepare a three-dimensional self-supported nickel-iron-based composite sheet oxygen evolution catalyst with high conductivity, high specific surface area and high porosity, and a nickel content of 0.5-1%.
Excellent catalytic performance, low cost and good stability, suitable for high current density conditions, easy to industrial production, and reduces the cost of hydrogen production by electrolyzing water.
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Figure CN116445936B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of catalysts, and particularly relates to a three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst, a preparation method thereof, and an application thereof. Background Art
[0002] Due to the development of society, the demand for energy is increasing continuously, and the resulting environmental pollution problems are becoming increasingly serious. Renewable clean energies such as wind energy, solar energy, and tidal energy will gradually replace traditional energies such as coal, oil, and natural gas. However, due to numerous natural conditions constraints, the application fields of such renewable clean energies are extremely limited. In essence, these primary energies that are not easy to store and transport can be converted into secondary energies that are easy to store and transport, such as hydrogen energy. Hydrogen energy can not only be used in chemical production processes such as ammonia synthesis and methanol production, but also is an important energy fuel, and can achieve zero emissions during use, and is a recognized clean energy. Among them, hydrogen production by electrolyzing water is an important method of hydrogen production technology. It is usually a process of decomposing water molecules into hydrogen molecules and oxygen molecules by electricity and electrolysis equipment in an alkaline electrolyte. This technology can solve the seasonal and local problems existing in clean energies such as wind energy and solar energy. Since the electrolytic water technology emerged, it has gradually matured and the water resources in nature are abundant, providing a prerequisite for the large-scale development and application of this technology. However, the oxygen evolution reaction occurring at the anode during the hydrogen production by electrolyzing water has slow kinetics and a large overpotential, resulting in a relatively high cost required for the hydrogen production by electrolyzing water technology. Therefore, it is necessary to develop highly efficient and stable catalysts to promote the electrolytic water reaction.
[0003] Most of the previously studied catalysts with relatively good catalytic performance are noble metal catalysts such as Pt-based materials and Ru / Ir oxides. However, due to the relatively small crust resources and high prices of noble metals themselves, the large-scale application of the electrolytic water technology is greatly restricted. In recent years, researchers at home and abroad have turned their attention to transition metals with rich earth reserves and good catalytic activity, and have conducted a large number of studies on the preparation of non-noble metal oxygen evolution catalysts. The currently reported non-noble metal oxygen evolution catalysts mainly include transition metal oxides, selenides, sulfides, and phosphides, etc. However, the performance of such catalysts needs to be further improved. At the same time, the preparation of such catalysts often requires relatively harsh reaction conditions, specific production equipment, and high operation techniques, making such catalysts unable to be put into large-scale industrial production. Therefore, developing inexpensive and simple preparation method non-noble metal oxygen evolution catalysts is of great significance for the large-scale application of hydrogen energy.
[0004] As one of the most abundant transition metals in the earth's crust, iron is far cheaper than nickel and cobalt. If an efficient oxygen evolution catalyst can be prepared with the main iron-based material, the production cost will be greatly reduced. However, compared with the activity of nickel-based catalysts and cobalt-based catalysts, its performance is poor. At present, a large number of high-performance oxygen evolution catalysts developed are mainly nickel-based and cobalt-based. Therefore, developing a high-performance catalyst with an iron-based main body doped with a small amount of nickel and cobalt to obtain an overpotential that is basically the same as or slightly lower than that of nickel-based catalysts can greatly reduce the cost of hydrogen production by electrolyzing water, which is of great significance for promoting the application of electrolyzed water technology and hydrogen energy. Summary of the Invention
[0005] Based on the problems existing in the above-mentioned prior art, the present invention provides a three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst, its preparation method and application, aiming to synthesize a transition metal nickel-iron-based material with high conductivity, high specific surface area and porosity using foamed metal iron as the substrate, so that it can be used as the anode oxygen evolution catalyst for hydrogen production by electrolyzing water and has excellent catalytic performance.
[0006] To achieve the purpose, the present invention adopts the following technical solutions:
[0007] The present invention first provides a three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst, which is characterized in that: the oxygen evolution catalyst is obtained by first oxidizing foamed iron to generate magnetite, and then adding it to a mixed solution of nickel chloride and sodium chloride for hydrothermal reaction to generate nickel iron oxyhydroxide. The catalyst has a three-dimensional self-supporting flake array morphology, has magnetite and nickel iron oxyhydroxide, and iron, nickel and oxygen are evenly distributed, wherein the atomic percentage of nickel is 0.5-1%.
[0008] The present invention also provides a preparation method of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst, which includes the following steps:
[0009] (1) Pretreat foamed iron with hydrochloric acid, and then put it into an oven for oxidation treatment in an air atmosphere to obtain a foamed iron substrate loaded with magnetite;
[0010] (2) Add nickel chloride, sodium chloride and urea to deionized water, stir well to obtain a mixed salt solution; put the foamed iron substrate loaded with magnetite into the mixed salt solution for hydrothermal reaction; after the reaction, cool to room temperature, wash, and vacuum dry to obtain the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst.
[0011] Further, in step (1), the concentration of the hydrochloric acid used is 1-5M, preferably 1-2M.
[0012] Further, in step (1), the oxidation treatment is carried out at 50-80°C for 5-7 hours.
[0013] Further, in step (2), the molar ratio of nickel chloride, sodium chloride and urea in the mixed salt solution is 0.1 - 0.2:1:1 - 2, and the total concentration of nickel chloride and sodium chloride in the mixed salt solution is 0.05 - 0.1 mol / L.
[0014] Further, in step (2): the temperature of the hydrothermal reaction is 80 - 180 °C, preferably 100 - 140 °C; the time of the hydrothermal reaction is 10 - 24 h, preferably 10 - 14 h.
[0015] The three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared by the present invention can be used as a catalyst for the oxygen evolution reaction of the electrolytic water anode.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0017] 1. The oxygen evolution catalyst of the present invention has a porous flake structure, and has an open space, a large specific surface area and a high porosity, so that the active sites of the catalyst are fully exposed, showing extremely high oxygen evolution catalytic activity. Compared with other existing non-precious metal materials, the catalytic performance is excellent, and it can replace the relatively expensive all-nickel-based or all-cobalt-based oxygen evolution catalysts.
[0018] 2. The oxygen evolution catalyst of the present invention is grown on the iron foam by oxidation and hydrothermal reaction. The flake array is firmly combined with the iron foam substrate and is not easy to fall off under the condition of oxygen evolution at a large current density, and has excellent activity and stability.
[0019] 3. Only a little nickel element is doped in the oxygen evolution catalyst of the present invention. Compared with the all-nickel-based and all-cobalt-based catalysts, the cost of such catalysts is greatly reduced.
[0020] 4. The raw materials for preparing the oxygen evolution catalyst of the present invention have low cost, and are rich in reserves on the earth and have a wide source.
[0021] 5. The preparation method of the oxygen evolution catalyst of the present invention is simple, only involves a simple hydrothermal reaction, is convenient to operate, and is easy to be industrially produced on a large scale. Description of the Drawings
[0022] Figure 1 It is the X-ray powder diffraction curve of the iron foam substrate (i.e., the precursor after iron foam oxidation) loaded with magnetite and the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in Example 1 of the present invention.
[0023] Figure 2 It is the scanning electron microscope photograph of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in Example 1 of the present invention.
[0024] Figure 3In (a) is the transmission electron microscope image of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in Example 1 of the present invention, Figure 3 In (b-d) are the elemental surface distribution maps of energy-dispersive X-ray spectroscopy ((b) is the distribution map of Ni, (c) is the distribution map of Fe, and (d) is the distribution map of O).
[0025] Figure 4 is the Raman spectrum of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in Example 1 of the present invention.
[0026] Figure 5 In (a) and (b) are the multi-functional photoelectron spectra of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in Example 1 of the present invention.
[0027] Figure 6 is the oxygen evolution polarization curve of the oxygen evolution catalysts prepared in Example 1 of the present invention and Comparative Example 1, Comparative Example 2, and Comparative Example 3.
[0028] Figure 7 is the oxygen evolution polarization curve of the oxygen evolution catalysts prepared in Example 1 of the present invention and Comparative Example 4, Comparative Example 5, Comparative Example 6, Comparative Example 7, and Comparative Example 8.
[0029] Figure 8 is the stability curve of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in Example 1 of the present invention.
[0030] Figure 9 is the scanning electron microscope photograph of the oxygen evolution catalyst prepared in Comparative Example 3, where (a) and (b) correspond to different magnifications. Detailed implementation manners
[0031] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. The methods are conventional methods unless otherwise specified. The raw materials can be obtained from public commercial channels unless otherwise specified.
[0032] Example 1
[0033] Step 1: First, soak 4 cm -2 of iron foam in 1 M hydrochloric acid for 30 minutes, and then put it into a mixed solution of ethanol and deionized water with a volume ratio of 1:1 for ultrasonic cleaning for 10 minutes. Put the treated iron foam into an oven and oxidize it at 60 °C for 6 h in an air atmosphere to obtain an iron foam substrate loaded with magnetite.
[0034] Step 2: Add 0.3 mmol of nickel chloride, 2 mmol of sodium chloride, and 2 mmol of urea into 30 mL of deionized water, stir for 30 minutes to make them fully and evenly mixed, and then let it react at room temperature for 1 hour; transfer this colorless solution into a 40 mL polytetrafluoroethylene reaction kettle, and then add the iron foam substrate loaded with iron oxide to the reaction kettle, and carry out hydrothermal reaction at 120 °C for 12 h. After the reaction, wait for the reaction kettle to cool to room temperature, take it out and rinse it repeatedly with deionized water until the washing liquid becomes clear, and then dry it overnight in a vacuum drying oven at 60 °C to obtain a three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst.
[0035] The X-ray powder diffraction curve of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in this example is as Figure 1 shown. As can be seen from the figure, in addition to the diffraction peaks of the iron foam substrate, there are also diffraction peaks of iron oxide and nickel iron oxyhydroxide in the catalyst prepared in this example, indicating that the catalyst prepared in this example is a flake oxygen evolution catalyst composed of iron oxide and nickel iron oxyhydroxide.
[0036] The scanning electron microscope photograph of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in this example is as Figure 2 shown. It can be seen that the obtained oxygen evolution catalyst has a regular three-dimensional flake morphology.
[0037] Figure 3 (a) in Figure 3 is the transmission electron microscope image of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst prepared in this example, Figure 3 (b-d) in
[0038] are the elemental surface distribution maps of energy-dispersive X-ray spectroscopy ((b) is the distribution map of Ni, (c) is the distribution map of Fe, and (d) is the distribution map of O). From Figure 4 shown. It can be seen from -1 (b-d) in -1 that nickel, iron, and oxygen are evenly distributed in the catalyst, and the atomic percentages of nickel, iron, and oxygen are 0.97%, 28.07%, and 70.97% respectively.
[0039] The Raman spectrum of the three-dimensional nickel-iron-based composite flake oxygen evolution catalyst prepared in this example is as Figure 5 shown. In the figure, the peaks at 479 cm Figure 5 (a) in Figure 5As shown in (b) of , the peaks at 856 eV and 862 eV respectively correspond to the characteristic peaks of trivalent nickel, which are the peaks of trivalent nickel in nickel iron oxyhydroxide.
[0040] From the above data, it can be seen that the catalyst prepared in this example is a three-dimensional self-supporting nickel-iron-based composite flake structure with iron foam as the substrate.
[0041] Comparative Example 1
[0042] Directly use iron foam as the electrolytic water anode catalyst.
[0043] Comparative Example 2
[0044] Use the iron foam substrate loaded with magnetite prepared in Step 1 of Example 1 as the electrolytic water anode catalyst.
[0045] Comparative Example 3
[0046] Replace nickel chloride in Step 2 of Example 1 with an equal amount of cobalt chloride to prepare a flaky oxygen evolution catalyst composed of magnetite and cobalt oxyhydroxide. The catalyst obtained in this example is basically a flaky structure, but the structure is uneven.
[0047] Comparative Example 4
[0048] Based on Step 2 of Example 1, add molybdenum chloride in the same proportion as nickel chloride, that is, replace "0.3 mmol nickel chloride, 2 mmol sodium chloride" in Step 2 with "0.3 mmol nickel chloride, 0.3 mmol molybdenum chloride, 2 mmol sodium chloride". The overpotential of the prepared composite material is significantly greater than that of Example 1.
[0049] Comparative Example 5
[0050] Replace nickel chloride in Step 2 of Example 1 with an equal amount of molybdenum chloride to prepare a flaky oxygen evolution catalyst composed of magnetite and molybdenum oxyhydroxide. The overpotential of the catalyst obtained in this example is significantly greater than that of Example 1.
[0051] Comparative Example 6
[0052] Replace nickel chloride in Step 2 of Example 1 with an equal amount of copper chloride to prepare a flaky oxygen evolution catalyst composed of magnetite and copper hydroxide. The oxygen evolution activity of the catalyst obtained in this example is insufficient and the overpotential is large.
[0053] Comparative Example 7
[0054] Change the amount of nickel chloride in Step 2 of Example 1 from 0.3 mmol to 0.6 mmol, doubling the nickel content, but the change in its overpotential is not obvious.
[0055] Comparative Example 8
[0056] Change the hydrothermal reaction temperature in step 2 of Example 1 from 120 °C to 80 °C, and change the reaction time to 24 h. Under the conditions of this comparative example, the performance of the obtained catalyst deteriorates.
[0057] Use the oxygen evolution catalysts prepared in each example and comparative example as the anode catalyst for electrolyzing water. The polarization curves of the oxygen evolution experiments are as Figure 6 and Figure 7 shown. The specific test method is as follows: directly cut the catalyst into an electrode with a size of 0.25 cm -2 and measure the experimental polarization curve in a 1 mol / L potassium hydroxide solution. The scanning rate of the curve is 5 mV / s, and the polarization curve is obtained after 85% IR correction. It can be seen that the catalyst prepared in the above Example 1 has an overpotential of 0.073 and 0.193 volts when the current density reaches 10 and 100 mA·cm -2 respectively in the oxygen evolution experiment.
[0058] Table 1 is a comparison table of the overpotentials of Example 1 and Comparative Examples 2-8 at current densities of 10 and 100 mA·cm -2 .
[0059] Table 1
[0060]
[0061] Perform a stability performance test on the catalyst obtained in Example 1. The specific experimental method is as follows: make the catalyst obtained in Example 1 into an electrode with an area of 0.25 cm 2 and measure the chronopotentiometry curve in a 1 mol / L potassium hydroxide solution. The results are as Figure 8 shown. After continuously measuring for 30 h at a constant current density of 100 mA·cm -2 , the overpotential basically does not change, indicating that the catalyst has excellent stability and is expected to achieve mass industrial production.
[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A three-dimensional self-supported nickel-iron-based composite flaky oxygen evolution catalyst, characterized in that: The oxygen evolution catalyst is obtained by first oxidizing iron foam to generate magnetite, and then adding it to a mixed solution of nickel chloride and sodium chloride for hydrothermal reaction to generate nickel iron oxyhydroxide.
2. The preparation method of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst according to claim 1, characterized in that, It includes the following steps: (1) After pretreating iron foam with hydrochloric acid, place it in an oven for oxidation treatment in an air atmosphere to obtain an iron foam substrate loaded with magnetite. (2) Add nickel chloride, sodium chloride, and urea to deionized water, stir well to obtain a mixed salt solution; place the iron foam substrate loaded with magnetite into the mixed salt solution for hydrothermal reaction; after the reaction, cool to room temperature, wash, and dry in vacuum to obtain the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst.
3. The preparation method according to claim 2, characterized in that: In step (1), the concentration of the hydrochloric acid used is 1-5M.
4. The preparation method according to claim 2, characterized in that: In step (1), the temperature of the oxidation treatment is 50-80°C, and the time is 5-7h.
5. The preparation method according to claim 2, characterized in that: In step (2), the molar ratio of nickel chloride, sodium chloride, and urea in the mixed salt solution is 0.1-0.2:1:1-2, and the total concentration of nickel chloride and sodium chloride in the mixed salt solution is 0.05-0.1mol / L.
6. The preparation method according to claim 2, wherein: In step (2), the temperature of the hydrothermal reaction is 80-180°C, and the time is 10-24h.
7. Application of the three-dimensional self-supporting nickel-iron-based composite flake oxygen evolution catalyst according to claim 1 in the anodic oxygen evolution reaction of water electrolysis.