Lewis acid oxide composite metal catalyst as well as preparation method and application thereof
By preparing Lewis acid oxide composite metal catalysts and utilizing the strong interaction between Lewis acid oxides and Lewis base hydroxide ions, the problem of slow kinetics in the anodic oxygen evolution reaction was solved, realizing a low-cost, high-activity catalyst, which promotes the large-scale application of carbon dioxide reduction and water electrolysis for hydrogen production.
Patent Information
- Application Number
- CN202511282825.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-09
- Publication Date
- 2025-11-18
AI Technical Summary
In existing technologies, carbon dioxide reduction and water electrolysis for hydrogen production are characterized by high energy consumption and low efficiency due to the large number of electron transfers and slow reaction kinetics in the oxygen evolution reaction at the anode. Furthermore, traditional precious metal catalysts are expensive and prone to poisoning, while non-precious metal catalysts have low reactivity, which limits their large-scale application.
A Lewis acid oxide composite metal catalyst was prepared. Through the strong interaction between Lewis acid oxide and Lewis base hydroxyl ions, hydroxyl ions in the electrolytic liquid phase were enriched in the anode microenvironment, thereby increasing the local alkalinity of the anode and improving the performance of the electrocatalytic oxygen evolution reaction and methanol oxidation reaction.
This has resulted in a low-cost, highly active catalyst that significantly improves the activity of the electrocatalytic oxygen evolution reaction and methanol oxidation reaction, promotes the large-scale application of carbon dioxide reduction and water electrolysis for hydrogen production, and enhances energy conversion efficiency.
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Figure CN120967425A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of composite metal catalyst technology, and in particular to a Lewis acid oxide composite metal catalyst, its preparation method, and its application. Background Technology
[0002] Technologies such as carbon dioxide reduction and water electrolysis for hydrogen production are key technologies for controlling carbon emissions, but their large-scale application is limited by problems such as high energy consumption and low efficiency caused by multiple electron transfers and slow reaction kinetics in the oxygen evolution reaction at the anode.
[0003] In the alkaline oxygen evolution reaction (OER), hydroxyl ions discharge at the anode. The rapid consumption of local hydroxyl ions and the slow mass transfer of bulk hydroxyl ions are the fundamental reasons for the slow reaction kinetics at high current densities. Enriching the bulk hydroxyl ion concentration and accelerating hydroxyl ion mass transfer to the anode are key to improving the performance of the OER. On the other hand, replacing the OER with methanol oxidation as the anode reaction provides a new approach to solving the above problems. Methanol is abundant and inexpensive. Thermodynamically, methanol oxidation is more favorable than the OER. Replacing the OER with methanol oxidation can reduce the anode potential and improve energy conversion efficiency. Methanol oxidation involves the nucleophilic attack of methanol by hydroxyl ions; a high local hydroxyl concentration results in high reactivity of the methanol oxidation reaction. Increasing the local hydroxyl concentration at the anode is an effective strategy to promote the methanol oxidation reaction.
[0004] Traditional precious metal catalysts, such as iridium-based and platinum-based catalysts, suffer from high costs and susceptibility to poisoning and deactivation, while non-precious metal catalysts are limited by their lower reactivity. Therefore, developing low-cost, high-activity catalysts for the oxygen evolution reaction (OER) and methanol oxidation is of great significance. This can improve energy conversion efficiency, promote the large-scale application of technologies such as carbon dioxide reduction and water electrolysis for hydrogen production, and foster the development of a green and low-carbon energy system. Summary of the Invention
[0005] The purpose of this invention is to prepare high-performance catalysts based on the requirement for high local hydroxyl concentrations in the oxygen evolution reaction (OER) and methanol oxidation reaction. These catalysts enrich hydroxyl in the electrolytic liquid phase to the anode microenvironment through the strong interaction between Lewis acid oxides and Lewis base hydroxyl ions, thereby increasing the local alkalinity of the anode and achieving the goal of improving the performance of electrocatalytic OER and methanol oxidation reactions.
[0006] To achieve the above objectives, the present invention provides a method for preparing a Lewis acid-oxide composite metal catalyst, comprising, A mixed system is obtained by adding ammonium salt, metal salt and ammonia water to a Lewis acid oxide dispersion, wherein the Lewis acid oxide can react with alkali. The mixture was subjected to a hydrothermal reaction to obtain an insoluble substance; The insoluble material was thermally reduced to obtain a Lewis acid oxide composite metal catalyst.
[0007] In the hydrothermal reaction, ammonia water etches Lewis acid oxides to form acid radicals; ammonium salts inhibit the dissociation of ammonia water, preventing the metal salt from forming hydroxide precipitates; free metal ions combine with acid radicals to form metal oxoacid salt precursors. During the thermal reduction process, metal particles precipitate from the precursors, simultaneously forming Lewis acid oxides, thus preventing metal particle agglomeration and preparing a composite catalyst of finely structured nano-metal particles and Lewis acid oxides.
[0008] Furthermore, the solvent for dispersing Lewis acid oxides need not be strictly limited; for example, it can be water, ethanol, acetone, etc., with water being preferred.
[0009] Furthermore, the concentrations of Lewis acid oxide, ammonium salt, metal salt, and ammonia in the mixed system are 0.5-3 g / L, 0.05-0.6 mol / L, 0.005-0.03 mol / L, and 0.08-0.3 mol / L, respectively.
[0010] Furthermore, the hydrothermal reaction is carried out at 80-220℃ for 10-48 hours.
[0011] Furthermore, the thermal reduction treatment is carried out in a reducing gas atmosphere for 1-6 hours at 500-1000℃.
[0012] Furthermore, the reducing gas can be at least one of ammonia, hydrogen, carbon monoxide, etc., with a concentration of 5%-20%, and the remaining gas is a rare gas or nitrogen.
[0013] Furthermore, the Lewis acid oxide includes at least one of silicon dioxide, aluminum oxide, and germanium dioxide.
[0014] Furthermore, the ammonium salt includes at least one of ammonium chloride, ammonium nitrate, ammonium sulfate, and ammonium acetate.
[0015] Furthermore, the mass concentration of the ammonia water is 25%-28%.
[0016] It should be noted that the type of metal salt is not strictly limited in this invention, and can be at least one of noble metal salts, transition metal salts, and rare metal salts. To reduce costs, transition metal salts are preferred, and iron, cobalt, and nickel salts are even more preferred.
[0017] The present invention also provides a Lewis acid oxide composite metal catalyst, which is prepared by the above-described preparation method.
[0018] Furthermore, metal species are modified on the surface of Lewis acid oxide, and the size of the metal species is 5-50 nm.
[0019] This invention also provides the application of the above-mentioned Lewis acid oxide composite metal catalyst in the electrocatalytic oxygen evolution reaction and methanol oxidation reaction.
[0020] Compared with the prior art, the present invention has the following beneficial effects: In the composite metal catalyst prepared by this invention, the nano-metal particles possess a high specific surface area and are uniformly distributed when combined with Lewis acid oxides, promoting the exposure of active sites. The Lewis acid oxides enhance the enrichment of hydroxide ions, significantly improving the activity of the electrocatalytic oxygen evolution reaction and methanol oxidation reaction. The raw materials used in this invention are inexpensive, the preparation method is simple, and the obtained catalyst exhibits excellent performance, making it of great application value in fields such as carbon dioxide reduction and water electrolysis for hydrogen production. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 The XRD pattern of the cobalt silicate and Co / SiO2 composite catalyst prepared in Example 1 is shown. Figure 2 A scanning electron microscope image of cobalt silicate prepared in Example 1 is shown; Figure 3 A scanning electron microscope image of the Co / SiO2 composite catalyst prepared in Example 1 is shown; Figure 4 The transmission electron microscope image of the Co / SiO2 composite catalyst prepared in Example 1 is shown. Figure 5 The electrocatalytic oxygen evolution reaction performance of the Co / SiO2 composite catalyst prepared in Example 1 is shown in the figure. Figure 6 The electrocatalytic methanol oxidation reaction performance of the Co / SiO2 composite catalyst prepared in Example 1 is shown in the figure. Detailed Implementation
[0023] The endpoints and any values of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.
[0024] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] Example 1 A method for preparing a Lewis acid oxide composite metal catalyst, comprising the following steps: Mix 64 mL isopropanol, 23.5 mL water, and 13 mL ammonia (25 wt%), add 0.6 mL tetraethyl orthosilicate, and stir magnetically at 35 °C for 1 h. Add 5 mL tetraethyl orthosilicate and continue the reaction for 2 h. Wash the product with water and dry it under vacuum to obtain SiO2 microsphere powder with a diameter of 450 nm. Weigh 0.06 g of SiO2 microsphere powder and ultrasonically disperse it in 60 mL of water to obtain a SiO2 microsphere dispersion. Then add 24 mmol NH4Cl, 0.6 mmol Co(CH3COO)2, and 0.4 mL of ammonia (25 wt%). After mixing evenly, transfer the mixture to a hydrothermal reactor and react at 100 °C for 20 h. After cooling to room temperature, wash with water and vacuum dry to obtain the cobalt silicate precursor. The cobalt silicate precursor was placed in a tube furnace and reacted at 800°C for 6 hours in a hydrogen / argon mixed atmosphere (hydrogen concentration of 5%) to obtain a Co / SiO2 composite catalyst.
[0026] Example 2 A method for preparing a Lewis acid oxide composite metal catalyst, comprising the following steps: Mix 64 mL isopropanol, 23.5 mL water, and 13 mL ammonia (25 wt%), add 0.6 mL tetraethyl orthosilicate, and stir magnetically at 35 °C for 1 h. Add 5 mL tetraethyl orthosilicate and continue the reaction for 2 h. Wash the product with water and dry it under vacuum to obtain SiO2 microsphere powder with a diameter of 450 nm. Weigh 0.06 g of SiO2 microsphere powder and ultrasonically disperse it in 60 mL of water to obtain a SiO2 microsphere dispersion. Then add 24 mmol NH4Cl, 1.2 mmol Co(CH3COO)2, and 0.8 mL of ammonia (25 wt%). After mixing evenly, transfer the mixture to a hydrothermal reactor and react at 140 °C for 10 h. After cooling to room temperature, wash with water and vacuum dry to obtain the nickel silicate precursor. The cobalt silicate precursor was placed in a tube furnace and reacted at 800°C for 6 hours in a hydrogen / argon mixed atmosphere (hydrogen concentration of 5%) to obtain a Ni / SiO2 composite catalyst.
[0027] Example 3 A method for preparing a Lewis acid oxide composite metal catalyst, comprising the following steps: Weigh 0.12 g of Al2O3 powder (0.4 μm, Aladdin chemical reagent), ultrasonically disperse it in 60 mL of water to obtain an Al2O3 dispersion, then add 12 mmol NH4Cl, 1.2 mmol CoSO4, and 0.4 mL ammonia (25 wt%), mix well, transfer to a hydrothermal reactor, react at 100 °C for 12 h, cool to room temperature, wash with water, and vacuum dry to obtain the cobalt aluminate precursor; The cobalt silicate precursor was placed in a tube furnace and reacted at 500°C for 3 hours in a hydrogen / argon mixed atmosphere (hydrogen concentration of 5%) to obtain the Co / Al2O3 composite catalyst.
[0028] Example 4 A method for preparing a Lewis acid oxide composite metal catalyst, comprising the following steps: Weigh 0.06 g of Al2O3 powder (0.4 μm, Aladdin chemical reagent), ultrasonically disperse it in 60 mL of water to obtain an Al2O3 dispersion, then add 24 mmol NH4Cl, 0.6 mmol Fe(CH3COO)2, and 0.4 mL ammonia (25 wt%), mix well, transfer to a hydrothermal reactor, react at 100 °C for 48 h, cool to room temperature, wash with water, and vacuum dry to obtain the ferric aluminate precursor; The cobalt silicate precursor was placed in a tube furnace and reacted at 500°C for 3 hours in a hydrogen / argon mixed atmosphere (hydrogen concentration of 5%) to obtain the Fe / Al2O3 composite catalyst.
[0029] Example 5 A method for preparing a Lewis acid oxide composite metal catalyst, comprising the following steps: Weigh 0.15 g of GeO2 powder (200 mesh, Aladdin chemical reagent), ultrasonically disperse it in 60 mL of water to obtain a GeO2 dispersion, then add 12 mmol NH4Cl, 1.2 mmol Co(NO3)2, and 1.2 mL ammonia (25 wt%), mix well, transfer to a hydrothermal reactor, react at 180 °C for 10 h, cool to room temperature, wash with water, and vacuum dry to obtain the cobalt germanate precursor; The cobalt germanate precursor was placed in a tube furnace and reacted at 800°C for 6 hours in a hydrogen / argon mixed atmosphere (hydrogen concentration of 10%) to obtain the Co / GeO2 composite catalyst.
[0030] Test case The cobalt silicate precursor and Co / SiO2 composite catalyst prepared in Example 1 were tested by XRD, and the results are as follows: Figure 1 As shown, after heat treatment in a reducing gas atmosphere, cobalt species were successfully reduced to elemental cobalt, while SiO2 remained in an amorphous state. The microstructures of the cobalt silicate precursor and the Co / SiO2 composite catalyst prepared in Example 1 were observed using scanning electron microscopy, as shown in the figures below. Figure 2 and Figure 3 As shown, cobalt silicate is uniformly distributed with consistent particle size and no obvious agglomeration. After heat treatment in a reducing gas atmosphere, elemental cobalt is uniformly modified on the SiO2 surface. The microstructure of the Co / SiO2 composite catalyst was also observed using transmission electron microscopy, as shown below. Figure 4 As shown, this further verifies that elemental cobalt is uniformly modified on the SiO2 surface.
[0031] The Co / SiO2 composite catalyst prepared in Example 1 was loaded onto a nickel foam substrate as the working electrode, a self-made reversible hydrogen electrode (RHE) was used as the reference electrode, and a graphite rod was used as the counter electrode for catalytic performance testing. A commercial IrO2 catalyst was used as a control sample, with both Co / SiO2 and IrO2 loadings of 2 mg / cm³. 2 The electrolyte for the oxygen evolution reaction was a 1 mol / L potassium hydroxide solution; the electrolyte for the methanol oxidation reaction was a mixed solution of 1 mol / L potassium hydroxide and 1 mol / L methanol. The test results for the oxygen evolution reaction and the methanol oxidation reaction are as follows: Figure 5 and Figure 6 As shown, the Co / SiO2 composite catalyst exhibits significantly better oxygen evolution reaction (OER) and methanol oxidation (MCO) activity than the commercial IrO2 catalyst. This is because the composite metal catalyst prepared in this invention features nano-metal particles with a high specific surface area, which are uniformly distributed when combined with Lewis acid oxides, promoting the exposure of active sites. The Lewis acid oxides enhance the enrichment of hydroxide ions, significantly improving the electrocatalytic activity of OER and MCO.
[0032] Similarly, the Ni / SiO2, Co / Al2O3, Fe / Al2O3, and Co / GeO2 composite catalysts prepared in Examples 2-5 were characterized in structure and morphology, verifying that the metal elemental particles in the composite catalysts were uniformly modified on the surface of Lewis acid oxides. The performance of the above four composite catalysts was tested using the same method, and they all achieved excellent catalytic performance in the oxygen evolution reaction and methanol oxidation reaction. These results confirm the versatility of the catalysts proposed in this invention, their preparation methods, and their applications across different types of Lewis acid oxides and metals.
[0033] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a Lewis acid oxide composite metal catalyst, characterized in that, include, A mixed system is obtained by adding ammonium salt, metal salt and ammonia water to a Lewis acid oxide dispersion, wherein the Lewis acid oxide can react with alkali. The mixture was subjected to a hydrothermal reaction to obtain an insoluble substance; The insoluble material was thermally reduced to obtain a Lewis acid oxide composite metal catalyst.
2. The preparation method of the Lewis acid oxide composite metal catalyst according to claim 1, characterized in that, The concentrations of Lewis acid oxide, ammonium salt, metal salt, and ammonia in the mixed system are 0.5-3 g / L, 0.05-0.6 mol / L, 0.005-0.03 mol / L, and 0.08-0.3 mol / L, respectively.
3. The preparation method of the Lewis acid oxide composite metal catalyst according to claim 1, characterized in that, The hydrothermal reaction is carried out at 80-220℃ for 10-48 hours.
4. The preparation method of the Lewis acid oxide composite metal catalyst according to claim 1, characterized in that, The thermal reduction treatment is carried out in a reducing gas atmosphere at 500-1000℃ for 1-6 hours.
5. The method for preparing the Lewis acid oxide composite metal catalyst according to claim 1, characterized in that, The Lewis acid oxide includes at least one of silicon dioxide, aluminum oxide, and germanium dioxide.
6. The method for preparing the Lewis acid oxide composite metal catalyst according to claim 1, characterized in that, The ammonium salt includes at least one of ammonium chloride, ammonium nitrate, ammonium sulfate, and ammonium acetate.
7. The method for preparing the Lewis acid oxide composite metal catalyst according to claim 1, characterized in that, The mass concentration of the ammonia water is 25%-28%.
8. A Lewis acid oxide composite metal catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.
9. The Lewis acid oxide composite metal catalyst according to claim 8, characterized in that, Metal particles are applied to the surface of Lewis acid oxide, and the size of the metal particles is 5-50 nm.
10. The application of the Lewis acid oxide composite metal catalyst as described in claim 8 in the electrocatalytic oxygen evolution reaction and methanol oxidation reaction.