Preparation method and application of a multistage cobalt-manganese spinel array photo-thermal catalyst
By preparing a multi-level cobalt-manganese spinel array photothermal catalyst on a three-dimensional mesh metal support, the problem of insufficient light absorption and photothermal conversion capacity of traditional catalysts was solved, achieving a highly efficient CO preferential oxidation effect and improving the performance and lifespan of fuel cells.
Patent Information
- Application Number
- CN202310317402.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-03-29
- Publication Date
- 2025-11-04
- Estimated Expiration
- 2043-03-29
AI Technical Summary
In existing technologies, traditional powder catalysts have poor light absorption and photothermal conversion capabilities during photocatalysis or thermocatalysis, are prone to agglomeration, and have large pressure differences at high temperatures, making it difficult to effectively remove CO from hydrogen-rich gas, resulting in reduced fuel cell performance and shortened lifespan.
By preparing a multi-level cobalt-manganese spinel array photothermal catalyst on a three-dimensional mesh metal carrier and forming a nanoarray structure through hydrothermal etching, the photon transmission path and light absorption efficiency are improved, the voltage drop is reduced, and the photothermal conversion capability is enhanced.
Highly efficient photothermal catalysis was achieved at room temperature, with a CO conversion rate of over 93% and an O2 selectivity of 80%, completely removing CO from hydrogen-rich gas under low solar radiation intensity.
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Figure CN116920868B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the preparation of photo-thermal catalytic materials, in particular to a preparation technology of a multi-stage cobalt-manganese spinel array photo-thermal catalyst.
[0002] PEMFC proton exchange membrane fuel cell is a conversion device that converts chemical energy into electrical energy by using hydrogen as fuel, and the whole operation process is environmentally friendly and the chemical byproduct is water. However, the CO poisoning problem is still one of the key difficulties of hydrogen fuel cells. At present, H2 is mainly obtained from industrial reforming reaction, which inevitably leads to the generation of CO. Even after the water gas shift reaction, the concentration of CO in the hydrogen-rich gas is still as high as 2000 ppm, and the excess CO is easy to poison and deactivate the Pt electrode of the fuel cell, reduce the performance of the fuel cell and shorten the service life. The preferential catalytic oxidation method (CO-PROX) can remove the concentration of CO in the hydrogen-rich gas to below 100 ppm, and is considered to be the most economical and effective method for deep purification of trace CO in hydrogen-rich gas.
[0003] Although thermal catalytic technology plays an important role in the fields of environment, energy and chemical industry, it is difficult to carry out at room temperature and has high energy consumption, and high-performance thermal catalysts often use noble metals. Therefore, researchers have proposed photo-thermal catalytic technology, which adds heating or light irradiation on the basis of photocatalysis or thermal catalysis to achieve synergistic catalysis. This process couples light and heat together to produce a photo-thermal catalytic synergistic effect to make up for the shortcomings of single catalytic process, which can effectively improve the catalytic activity. For photo-thermal catalysis, the light absorption capacity and photo-thermal effect of the catalyst largely determine the catalytic performance. However, under the same catalyst component conditions, the light absorption capacity and photo-thermal conversion capacity of traditional powder catalysts are poor, they are easy to agglomerate at high temperature and have a large pressure drop, which is not conducive to improving the processing capacity of the catalyst. By anchoring the active substance on the metal carrier with a three-dimensional network structure and forming a monolithic catalyst with an array structure, a special refraction and scattering path is provided for photon transmission, which can prolong the contact time between photons and materials, significantly improve the light capture efficiency and absorption efficiency. In addition, the monolithic catalyst has lower pressure drop, better diffusion performance and more excellent heat transfer and thermal conductivity. Therefore, based on the above discussion, if a photo-thermal catalyst with a special array structure and strong light absorption capacity can be developed, it is expected to achieve the goal of completely removing CO in hydrogen-rich gas at a lower sunlight intensity. SUMMARY
[0004] The purpose of the present application is to solve the above-mentioned problems existing in the prior art, a method for preparing a multi-stage cobalt-manganese spinel array photo-thermal catalyst by simple hydrothermal etching treatment is proposed, and the catalyst is applied to photo-thermal catalytic preferential oxidation of CO at room temperature, and the obtained catalyst has high photo-thermal catalytic activity.
[0005] The object of the present application is achieved at least by one of the following technical solutions.
[0006] The present application provides a multi-stage cobalt-manganese spinel array photo-thermal catalyst and a preparation method.
[0007] (1) Foam nickel is dried after acid pickling and ethanol ultrasonic treatment; manganese nitrate, cobalt nitrate, ammonium fluoride and urea are used as reaction raw materials, dissolved in deionized water, and the foam nickel is put into the mixed metal salt solution to carry out hydrothermal reaction by co-precipitation method, repeated hydrothermal reaction for several times, washed and dried to obtain a precursor;
[0008] (2) The precursor is put into a polytetrafluoroethylene reaction kettle containing a certain volume of solution, and hydrothermal etching treatment is carried out, and the multi-stage cobalt-manganese spinel array photo-thermal catalyst is obtained after drying and calcination.
[0009] Preferably, the molar ratio of cobalt nitrate to manganese nitrate in step (1) is 1:1 to 2:1;
[0010] Preferably, the hydrothermal reaction temperature in step (1) is 90-100℃, and the hydrothermal time is 12-24h;
[0011] Preferably, the number of hydrothermal reactions in step (1) is 1-3 times.
[0012] Preferably, one of the hydrothermal solutions in step (2) is deionized water.
[0013] Preferably, one of the hydrothermal solutions in step (2) is an alkaline aqueous solution, and the solute is sodium hydroxide or potassium hydroxide, and the concentration is 0.05-0.2mol / L.
[0014] Preferably, one of the hydrothermal solutions in step (2) is an ethanol aqueous solution, and the volume fraction of ethanol is 50-100%.
[0015] Preferably, the hydrothermal treatment temperature in step (2) is 100-180℃.
[0016] Preferably, the hydrothermal treatment time in step (2) is 1-4h.
[0017] Preferably, the calcination temperature in step (2) is 400-500℃, and the calcination time is 1-3h.
[0018] The multi-stage cobalt-manganese spinel array photo-thermal catalyst obtained by the above preparation method.
[0019] The present application also provides the application of the multi-stage cobalt-manganese spinel array photo-thermal catalyst obtained by the above preparation method in photo-thermal catalytic CO preferential oxidation.
[0020] Preferably, the light-thermal catalytic simulated sunlight intensity is 200-500 mW cm -2 .
[0021] Compared with the prior art, the present application has the following beneficial effects:
[0022] The multistage cobalt-manganese spinel array photo-thermal catalyst prepared by the present application has simple process, low cost, uniform product morphology, good repeatability, and high photo-thermal conversion performance. The multistage nano array improves the light absorption capacity and carrier separation efficiency to promote photocatalysis, and the high oxygen active species enhances the catalytic oxidation capacity. Compared with the powder cobalt-manganese spinel, the photo-thermal conversion capacity and molecular oxygen activation capacity are more excellent, so that the photo-thermal catalytic preferential oxidation of CO in hydrogen-rich gas is easier to carry out. When the initial concentration of CO is 1% vol, the mass space velocity is 60000 mL g -1 h -1 , the CO conversion rate reaches more than 93% and the O2 selectivity reaches more than 80% when the light is warmed to 125℃, and the preferential oxidation of trace CO in hydrogen-rich gas can be realized under the driving of simulated sunlight. BRIEF DESCRIPTION OF DRAWINGS
[0023] Figure 1 XRD spectrum of the catalyst prepared in the comparative example and examples 1-3
[0024] Figure 2 SEM image of the catalyst prepared in the comparative example
[0025] Figure 3 SEM image of the catalyst prepared in example 1
[0026] Figure 4 SEM image of the catalyst prepared in example 2
[0027] Figure 5 SEM image of the catalyst prepared in example 3
[0028] Figure 6 UV-visible-infrared diffuse reflectance spectrum of the catalyst prepared in the comparative example and examples 1-3
[0029] Figure 7 CO preferential oxidation performance diagram of the catalyst in the comparative example and examples 1-3 under light irradiation DETAILED DESCRIPTION
[0030] The present application will be described in detail below in combination with the drawings and examples.
[0031] Comparative example
[0032] (1) Mn(NO3)2.4H2O (2 mmol), Co(NO3)2.6H2O (4 mmol), NH4F (12 mmol), urea (24 mmol) were dissolved in 80 ml deionized water and stirred at room temperature until a clear solution was obtained. The solution was transferred into a polytetrafluoroethylene liner and placed in a hydrothermal reactor. The precursor was obtained by hydrothermal reaction at 95°C for 12 h. The precursor solution was centrifuged at 6000 rpm for 3 min and washed with deionized water and anhydrous ethanol three times, respectively. The precursor product was transferred into a vacuum drying oven at 80°C for 12 h to obtain a solid powder.
[0033] (2) The MCO powder was calcined in a muffle furnace at 400°C for 2 h in an air atmosphere at a heating rate of 5°C / min to obtain the catalyst, which was labeled as MCO.
[0034] Example 1
[0035] (1) The pure foam nickel was obtained by acid washing and ethanol ultrasonic treatment followed by drying. Mn(NO3)2.4H2O (2 mmol), Co(NO3)2.6H2O (4 mmol), NH4F (12 mmol), urea (24 mmol) were dissolved in 80 ml deionized water and stirred at room temperature until a clear solution was obtained. The solution was transferred into a polytetrafluoroethylene liner and the foam nickel was added. The reactor was placed in a 95°C oven for 12 h hydrothermal reaction, and then the hydrothermal step was repeated to obtain the MCO@NF precursor.
[0036] (2) The MCO@NF precursor was placed in a polytetrafluoroethylene liner containing deionized water and placed in a hydrothermal reactor. The post-treatment was carried out by hydrothermal treatment at 150°C for 2.5 h. After ethanol washing, the product was transferred into a vacuum drying oven at 80°C for 12 h. Finally, the product was calcined in a muffle furnace at 400°C for 2 h in an air atmosphere at a heating rate of 5°C / min to obtain the monolithic catalyst, which was labeled as MCO@NF-1.
[0037] Example 2
[0038] The application example is different from Example 1 only in that the hydrothermal solvent is an alkaline aqueous solution of the same volume, and the solute is sodium hydroxide or potassium hydroxide with a concentration of 0.1 mol / L. The other processes are the same as those of Example 1, which will not be repeated here. The catalyst prepared in this example is labeled as MCO@NF-2.
[0039] Example 3
[0040] The application example is different from Example 1 only in that the hydrothermal solvent is an ethanol aqueous solution of the same volume, and the volume fraction of ethanol in the ethanol aqueous solution is 99%. The other processes are the same as those of Example 1, which will not be repeated here. The catalyst prepared in this example is labeled as MCO@NF-3.
[0041] The XRD patterns of the catalysts prepared in the comparative examples and Examples 1-3 are as follows: Figure 1 As shown in the figure, the diffraction peaks in the XRD patterns of the comparative examples and Examples 1-3 show no significant changes and conform to the standard PDF card for cubic MnCo2O4 spinel. SEM images of the catalysts prepared in the comparative examples and Examples 1-3 are shown below. Figures 2 to 5 As shown, from Figure 2 It can be seen that the powdered cobalt-manganese spinel catalyst MCO, used as a control sample, is a blocky sample composed of relatively large particles; from Figure 3 It can be seen that the cobalt-manganese spinel catalyst MCO@NF-1 prepared by hydrothermal etching has a hierarchical morphology combining nanoneedles and nanospheres, and exhibits a spherical nanoarray dispersed from the center outwards; from Figure 4 It can be seen that the monolithic cobalt-manganese spinel oxide catalyst MCO@NF-2 prepared by alkaline aqueous solution hydrothermal etching has a hexagonal hierarchical morphology with a dense exterior and porous interior; from Figure 5 It can be seen that the cobalt-manganese spinel catalyst MCO@NF-3 prepared by ethanol solvothermal recrystallization has a multi-level morphology combining nanoneedles and nanospheres, and also has an external dense hexagonal structure.
[0042] The UV-Vis-IR diffuse reflectance spectra of the catalysts prepared in comparative examples and Examples 1-3 are shown below. Figure 6 As shown, the photothermal catalyst of the multi-stage cobalt-manganese spinel array has a significantly higher light absorption capacity than that of the powder catalyst, especially in the ultraviolet and visible light bands.
[0043] The catalytic performance of the catalysts prepared in the comparative examples and Examples 1-3 was evaluated for the photothermal CO preferential oxidation reaction. The reaction conditions were as follows: 500 mg of catalyst (100 mg of active material, 400 mg of nickel foam substrate) was placed in a cylindrical quartz reactor, and a Xe lamp simulating sunlight (illuminance of 250 mW / cm²) was used. -1 The feed gas was introduced from the upper side wall of the reactor, with a total gas flow rate of 100 sccm. The feed gas composition was 25% H2 + 0.5% O2 + 0.5% CO and equilibrium gas argon. Results obtained under illumination are as follows... Figure 7 As shown. From Figure 7 It can be seen that the MCO@NF-1, MCO@NF-2, and MCO@NF-3 catalysts prepared in Examples 1-3 all exhibited significantly higher CO conversion rates than the MCO powder catalysts in the comparative examples; among them, MCO@NF-1 achieved a CO conversion rate of 250 mW / cm³. -1 Under simulated sunlight, the surface temperature can reach over 116.7 degrees Celsius, and the CO conversion rate can reach over 93%; MCO@NF-2 at 250 mW / cm²-1 The surface temperature under simulated sunlight irradiation can reach above 109.8 degrees Celsius, and the CO conversion rate reaches 89%; the MCO@NF-3 under 250 mW cm -1 The surface temperature under simulated sunlight irradiation can reach above 107.4 degrees Celsius, and the CO conversion rate reaches 78%.
[0044] Example 4
[0045] The only difference between Example 1 and this example is that the molar ratio of manganese nitrate and cobalt nitrate in step (1) is 1:1 (Mn(NO3)2·4H2O (3 mmol), Co(NO3)2·6H2O (3 mmol)), and the other processes are the same as Example 1, which will not be repeated here. The conversion rate of the catalyst prepared in this example (the test conditions are the same as the light irradiation test conditions of catalyst MCO@NF-1) is 85% under light irradiation of 110.0°C.
[0046] Example 5
[0047] The only difference between Example 1 and this example is that the number of repeated hydrothermal treatments in step (1) is 3, and the other processes are the same as Example 1, which will not be repeated here. The conversion rate of the catalyst prepared in this example (the test conditions are the same as the light irradiation test conditions of catalyst MCO@NF-1) is 87% under light irradiation of 111.5°C.
[0048] Example 6
[0049] The only difference between Example 1 and this example is that the hydrothermal post-treatment time in step (2) is 1h, and the other processes are the same as Example 1, which will not be repeated here. The conversion rate of the catalyst prepared in this example (the test conditions are the same as the light irradiation test conditions of catalyst MCO@NF-1) is 85% under light irradiation of 110.0°C.
[0050] Example 7
[0051] The only difference between Example 1 and this example is that the hydrothermal post-treatment temperature in step (2) is 120°C, and the other processes are the same as Example 1, which will not be repeated here. The conversion rate of the catalyst prepared in this example (the test conditions are the same as the light irradiation test conditions of catalyst MCO@NF-1) is 91% under light irradiation of 115.2°C.
[0052] The above describes specific embodiments of the present application. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or changes within the scope of the claims, which does not affect the essential content of the present application.
Claims
1. A method for preparing a multi-stage cobalt-manganese spinel array photothermal catalyst, characterized in that, Includes the following steps: (1) The nickel foam is dried after being pickled and ultrasonically treated with ethanol; Using manganese nitrate, cobalt nitrate, ammonium fluoride, and urea as reactants, dissolved in deionized water, clean foamed nickel was placed in the mixed metal salt solution for a co-precipitation hydrothermal reaction. The hydrothermal reaction was repeated several times, and the precursor was obtained after washing and drying. (2) The precursor is placed in a polytetrafluoroethylene reactor containing a solution and subjected to hydrothermal etching treatment. After drying and calcination, the multi-stage cobalt manganese spinel array photothermal catalyst is obtained. The hydrothermal etching solution mentioned in step (2) includes one of water, an alkaline aqueous solution and an ethanol solution, wherein the solute in the alkaline aqueous solution is sodium hydroxide or potassium hydroxide, and the concentration is 0.05-0.2 mol / L; wherein the volume fraction of ethanol in the ethanol aqueous solution is 50-100%. The hydrothermal etching process in step (2) is performed at a temperature of 100–180 °C for 1–4 h. The roasting temperature in step (2) is 400-500 °C and the time is 1-3 h.
2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of cobalt nitrate to manganese nitrate is 1:1 to 2:
1.
3. The preparation method according to claim 1, characterized in that, In step (1), the hydrothermal process is repeated 1 to 3 times.
4. The multi-stage cobalt-manganese spinel array photothermal catalyst prepared by the preparation method according to any one of claims 1-3.
5. The application of the multi-stage cobalt-manganese spinel array photothermal catalyst of claim 4 in the preferential oxidation of trace amounts of CO in hydrogen-rich gas.