Preparation method and application of ultrathin two-dimensional metal oxide nanosheet catalyst
The preparation of ultra-thin two-dimensional metal oxide nanosheets is simplified by the anion exchange method, which solves the problems of complexity and difficulty in mass production of traditional methods, and achieves the effect of efficient electrocatalytic reduction of CO2 to high-value-added products.
Patent Information
- Application Number
- CN202510690486.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-27
- Publication Date
- 2025-07-18
AI Technical Summary
The preparation methods of existing two-dimensional materials are cumbersome and difficult to achieve large-scale production. The synthesis process of traditional CuO catalysts is complex, making it difficult to efficiently catalyze the electroreduction of CO2 into high-value-added products.
The simple anion exchange method is used to treat metal sulfide or selenide using H2O2 aqueous solution, replace the S-S or Se-Se bonds into O-O bonds, and convert them into two-dimensional ultra-thin CuO or SnO2 nanosheets. The preparation process is simplified by simple hydrothermal method or commercial CuS as raw materials.
The prepared ultra-thin two-dimensional metal oxide nanosheets have a larger electrochemical surface area and more active sites, which improves the efficiency and selectivity of electrocatalytic reduction of CO2 to C2+ products, and is suitable for large-scale production.
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Figure CN120330767A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalyst synthesis, and particularly relates to a preparation method of an ultrathin two-dimensional metal oxide nanosheet catalyst and its application in the electrocatalytic reduction of CO2. Background Art
[0002] Electrocatalytic CO2 reduction is an effective way to close the anthropogenic carbon cycle and achieve the "dual carbon" goal. Converting CO2 into C2H4, C2H5OH and other C 2+ products with higher energy density has higher technical and economic value and thus has attracted more attention. Among them, Cu-based catalysts can selectively convert CO2 into C2H4 and other C 2+ high-value-added reduction products at a relatively high current density, and are one of the most widely studied CO2 electroreduction catalysts. Oxide-derived Cu (OD-Cu) can better promote C-C coupling due to its numerous grain boundaries and defect sites, and thus exhibits good catalytic performance for C 2+ products, and is one of the most promising electrocatalysts for industrial application at present. At present, the preparation of CuO catalysts requires multiple processes such as oxidation treatment and high-temperature annealing, and the synthesis process is relatively complex. Two-dimensional materials have a large specific surface area, good electron transport ability due to their ultrathin structure, and can expose more active sites; in addition, the unsaturated coordination structure on their surface can often exhibit higher catalytic performance. The above advantages make two-dimensional materials widely used in the field of electrocatalytic reduction of CO2. The preparation of traditional two-dimensional materials uses the template method or the wet chemical method, which not only requires harsh reaction conditions, but also requires the participation of organic solvents and subsequent removal of templates, etc. The preparation process is cumbersome and it is difficult to achieve large-scale preparation. Summary of the Invention
[0003] Object of the Invention: Aiming at the problems existing in the prior art, the present invention provides a preparation method of an ultrathin two-dimensional metal oxide nanosheet catalyst. The present invention relates to a method for preparing ultrathin two-dimensional metal oxide (TMO) nanosheets by adopting a simple anion exchange strategy and applying it to the electrocatalytic reduction of CO2. The present invention uses a simple hydrothermal method to synthesize or commercial CuS (Cu can be replaced by other metals such as Sn, and S can be replaced by Se) as a raw material. By treating with an H2O2 aqueous solution of a certain concentration, the S-S bond in CuS can be replaced by an O-O bond, so that two-dimensional or three-dimensional CuS can be converted into two-dimensional ultrathin CuO2 nanosheets, and CuO2 is not very stable and will quickly be converted into CuO nanosheets under certain conditions.
[0004] In the present invention, the synthesis process of two-dimensional ultrathin CuO nanosheets is simple. Due to its ultrathin characteristics, more active sites can be exposed, and it has a higher electrochemical surface area, showing higher C during the electrocatalytic reduction of CO22+ Product generation performance.
[0005] Technical solution: To achieve the above object, a preparation method of an ultrathin two-dimensional metal oxide nanosheet catalyst according to the present invention includes the following steps:
[0006] (1) Disperse a metal sulfide or a metal selenide into an aqueous H2O2 solution, and mix well to obtain a precursor dispersion A;
[0007] (2) Continuously stir the precursor dispersion A until the ion exchange process is fully carried out to obtain a dispersion B;
[0008] (3) Separate the solid in the dispersion B and dry it to obtain a solid powder C;
[0009] (4) Redisperse the solid powder C into deionized water and stir to obtain a dispersion D;
[0010] (5) Separate and dry the solid in the dispersion D to obtain a two-dimensional ultrathin metal oxide catalyst.
[0011] Among them, the mass fraction of the aqueous H2O2 solution in step (1) is 1% - 10%, and 0.05 - 0.5 g of a metal sulfide or a metal selenide is added to every 50 - 200 mL of the aqueous H2O2 solution.
[0012] Among them, the metal in step (1) is Cu, Sn or Ag.
[0013] Among them, the stirring temperature condition in step (2) is 20°C - 60°C, and the stirring time is 1 - 18 h.
[0014] Among them, in step (3), the dispersion B is separated by suction filtration, and the solid cake is vacuum dried at 60 - 90°C to obtain a solid powder C.
[0015] Among them, in step (4), 0.05 - 0.5 g of the solid powder C is added to every 50 - 200 mL of deionized water; the stirring temperature condition is 50 - 90°C, and the stirring time is 3 - 12 h.
[0016] Among them, in step (5), the dispersion D is suction filtered, and the solid cake is vacuum dried at 50 - 90°C to obtain a two-dimensional ultrathin metal oxide catalyst.
[0017] The ultrathin two-dimensional metal oxide nanosheet catalyst prepared by the preparation method of the present invention.
[0018] Application of the ultrathin two-dimensional metal oxide nanosheet catalyst of the present invention in electrocatalytic reduction of CO2 to formic acid or ethylene.
[0019] Among them, the electrolytic cell used for electrocatalytic CO2 reduction is an H-type or flow-type electrolytic cell separated by an ion exchange membrane, with an Ag / AgCl electrode or a Hg / HgO electrode as the reference electrode, a Pt sheet or nickel foam as the counter electrode, and a hydrophobic carbon paper coated with an ultrathin two-dimensional metal oxide nanosheet catalyst as the working electrode. The constant potential range is -0.30V to -2.0V vs. RHE. The electrolyte is a solution of KCl, KOH or KHCO3 with a concentration of 0.1 to 3M, and the carbon dioxide gas flow rate is 10 to 50 sccm.
[0020] Preferably, the binary solid solution oxide catalyst prepared by the present invention is used for electrocatalytic reduction of CO2 to produce high-value-added chemicals such as formic acid and ethylene.
[0021] Furthermore, the solid solution oxide catalyst is used as the working electrode in a three-electrode system for constant potential electrocatalytic reduction of carbon dioxide reaction;
[0022] Among them, the ion exchange membrane is an anion or cation exchange membrane, and the carrier is a hydrophobic carbon paper coated with the catalyst;
[0023] Preferably, the preparation method of the solid solution catalyst-coated carbon paper includes the following steps:
[0024] Add a Nafion solution to a dispersion of the solid solution catalyst with a concentration of 1 to 10 mg / mL, and then spray the catalyst dispersion on the carbon paper. After drying at room temperature, the working electrode is obtained;
[0025] Among them, 100 to 600 μL of the catalyst dispersion is sprayed per square centimeter of the carbon paper; the solvent of the dispersion is isopropanol or a mixture of isopropanol and water with a ratio of 1:3 to 3:1; the volume ratio of the Nafion solution to the dispersion is 1:10 to 100; the concentration of the Nafion solution is 1 wt% to 10 wt%.
[0026] Preferably, a certain mass of hydrothermally synthesized CuS nanosheets or commercial CuS nanoparticles is added to an H2O2 aqueous solution with a certain concentration (1% to 10%), stirred for a certain time (1 to 12 h) at a certain temperature (room temperature to 60 °C), and then the treated dispersion is separated by centrifugation or filtration to obtain ultrathin two-dimensional CuO2 nanosheets. Then, it is dispersed in deionized water and reacted at a temperature of 60 - 90 °C for 6 - 24 h and separated by centrifugation or filtration to obtain ultrathin two-dimensional CuO nanosheets.
[0027] The present invention prepares a metal oxide catalyst with a two-dimensional ultrathin structure by a simple anion exchange method. By treating with an aqueous H2O2 solution of a certain concentration, the S-S bond (or Se-Se bond) in commercial (or simple hydrothermal synthesis) metal sulfide (or selenide) can be replaced by an O-O bond, so that two-dimensional or three-dimensional MS x or MSe x particles can be transformed into two-dimensional ultrathin MO2 nanosheets, and then will be quickly transformed into two-dimensional MO x nanosheets under certain conditions. The synthesis process of the two-dimensional ultrathin MO x nanosheets is simple. Due to its ultrathin characteristics, more active sites can be exposed, and it has a higher electrochemically active surface area, showing higher C 2+ product generation performance during the electrocatalytic reduction of CO2. The nanocatalyst prepared by the present invention has a large specific surface area and many defect sites, which is beneficial to the adsorption of reactants and intermediates. During the preparation process of the ion exchange method in the present invention, the material ratio, the concentration of the aqueous H2O2 solution, the reaction time, etc. are all crucial.
[0028] Advantages: Compared with the prior art, the present invention has the following advantages:
[0029] (1) The present invention provides a simple method for preparing a two-dimensional ultrathin metal oxide nanosheet catalyst, which only needs to use a dilute aqueous H2O2 solution, and prepares a two-dimensional metal oxide electrocatalyst by an anion exchange - chemical bond cleavage method. The process operation is simple, the result is highly repeatable, and it is suitable for large-scale preparation;
[0030] (2) The two-dimensional ultrathin metal oxide nanosheets prepared by the present invention have a larger electrochemically specific surface area, can expose more unsaturated coordination sites and defect sites, and promote the directional generation of CO2 into high-value reduction products; compared with the catalysts prepared by traditional methods, the nanosheet catalyst has higher target product selectivity.
[0031] (3) By the anion exchange - chemical bond cleavage method, the present invention exfoliates two-dimensional or three-dimensional metal sulfide (selenide) into two-dimensional ultrathin metal peroxide, and then transforms it into two-dimensional metal oxide. This two-dimensional material shows good electrocatalytic reduction performance of CO2 to C 2+ product.
[0032] (4) The strategy for preparing ultrathin two-dimensional metal oxide nanosheets by anion exchange provided by the present invention can be extended to other electrocatalytic fields, such as electrocatalytic fields related to water electrolysis, fuel cells, etc., providing effective ideas and references for the development of efficient electrocatalysts. Description of the Drawings
[0033] Figure 1Transmission electron microscopy (TEM) image of the two-dimensional CuO nanosheet catalyst prepared in Example 1;
[0034] Figure 2 Transmission electron microscopy (TEM) image of the two-dimensional SnO2 nanosheet catalyst prepared in Example 2;
[0035] Figure 3 Powder XRD diffraction pattern of the sample catalysts of Example 1 and Example 2;
[0036] Figure 4 Scanning electron microscopy (SEM) images of the samples of Comparative Example 1 and Comparative Example 2;
[0037] Figure 5 Faraday efficiency bar chart of electrocatalytic reduction of carbon dioxide to C by the sample catalyst of Example 1 and the comparative sample at different potentials 2+ ;
[0038] Figure 6 Faraday efficiency bar chart of electrocatalytic reduction of carbon dioxide to C by the two-dimensional CuO nanosheet catalyst prepared with different H2O2 treatment times at different potentials 2+ ;
[0039] Figure 7 Faraday efficiency bar chart of electrocatalytic reduction of carbon dioxide to C by the two-dimensional CuO nanosheet catalyst prepared with different H2O2 concentrations at different potentials 2+ ;
[0040] Figure 8 Faraday efficiency bar chart of electrocatalytic reduction of carbon dioxide to C by the two-dimensional CuO nanosheet catalyst prepared with different CuS addition amounts at different potentials 2+ ; Detailed implementation manners
[0041] The present invention will be further described below in conjunction with specific embodiments, which are only used to explain the present invention and should not be construed as a limitation to the present invention. Those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the present invention, and the scope of the present invention is defined by the claims and their equivalents.
[0042] The experimental methods in the following examples are all conventional methods unless otherwise specified. The test materials used in the following examples are all purchased from conventional biochemical reagent companies unless otherwise specified.
[0043] Example 1
[0044] Step 1: Synthesize CuS nanosheets by hydrothermal method. First, dissolve 241.6 mg of the precursor salt copper nitrate in 60 mL of water, dissolve 80 mg of NaOH in 10 mL of water, and add it dropwise to the above copper nitrate solution to make it completely precipitate. Then, add 482 mg of the sulfur source Na2S·9H2O to the above dispersion under continuous stirring, transfer it to a hydrothermal reactor, and react at 180 °C for 12 h to obtain CuS nanosheets. Accurately weigh 50 mg of the CuS nanosheets synthesized by hydrothermal method and disperse them in 200 mL of an aqueous solution of 3% H2O2 by mass to form precursor dispersion A;
[0045] Step 2: Continuously stir precursor dispersion A at room temperature for 3 h until the ion exchange process is fully carried out to obtain dispersion B;
[0046] Step 3: Filter and separate dispersion B, and perform vacuum overnight drying on the solid cake at 60 °C to obtain solid powder C;
[0047] Step 4: Accurately weigh 50 mg of solid powder C and redisperse it in 100 mL of deionized water, and continuously stir and react at 60 °C for 12 h to obtain dispersion D;
[0048] Step 5: Filter and separate dispersion D, and perform vacuum overnight drying on the solid cake at 60 °C to obtain a two-dimensional ultrathin CuO catalyst.
[0049] Figure 1 Fig. is the TEM image of the two-dimensional CuO nanosheet catalyst prepared in Example 1. It can be seen from the figure that CuO is a nanosheet structure, and the lighter color indicates its very thin thickness. The ultrathin two-dimensional sheet structure endows it with a large specific surface area and more defect sites.
[0050] Figure 3 a is the XRD pattern of the sample prepared in Example 1. Only the diffraction peaks of CuO are shown in the figure, indicating that CuO nanosheets have been successfully prepared.
[0051] Example 2
[0052] Step 1: Accurately weigh 50 mg of hydrothermally synthesized SnS2 nanosheets (the synthesis method is the same as that in Example 1, except that copper nitrate is replaced with tin chloride) and disperse them in a beaker containing 200 mL of 3% H2O2 aqueous solution to form precursor dispersion A;
[0053] Step 2: Continuously stir precursor dispersion A at room temperature for 12 h until the ion exchange process is fully carried out to obtain dispersion B;
[0054] Step 3: Filter and separate dispersion B, and perform vacuum overnight drying on the solid cake at 60 °C to obtain solid powder C;
[0055] Step 4: Accurately weigh 50 mg of solid powder C and redisperse it in 100 mL of deionized water. Continuously stir and react at 60 °C for 8 h to obtain dispersion D.
[0056] Step 5: Perform suction filtration separation on dispersion D. Vacuum dry the solid cake overnight at 80 °C to obtain the two-dimensional ultrathin SnO₂ catalyst.
[0057] Figure 2 It is the TEM image of the two-dimensional SnO₂ nanosheet catalyst prepared in Example 2. It can be seen from the figure that it is composed of two-dimensional nanosheets. The lighter color indicates its ultrathin thickness, which can expose a larger electrochemical specific surface area and more defect sites.
[0058] Figure 3 b is the XRD pattern of the sample prepared in Example 2. Only the diffraction peaks of SnO₂ are shown in the figure, indicating that SnO₂ nanosheets have been successfully prepared.
[0059] Example 3
[0060] The specific method for electrocatalytic reduction of carbon dioxide to high-value products using a two-dimensional metal oxide catalyst is as follows:
[0061] In an H-type electrolytic cell separated by a cation exchange membrane, an electrocatalytic reduction of carbon dioxide reaction is carried out in a three-electrode system with an Ag / AgCl electrode as the reference electrode, a Pt sheet as the counter electrode, and a 2 cm × 0.5 cm carbon paper sprayed with 1.2 mg of the solid solution catalyst as the working electrode. The preparation method of the working electrode is as follows: Take 10 mg of the two-dimensional ultrathin CuO catalyst prepared in Example 1 above and disperse it in 5 mL of isopropanol. Add 10 μL of 5 wt% Nafion solution. Subsequently, use an airbrush to spray the catalyst dispersion onto a 2 cm × 0.5 cm carbon paper in 3 times, 200 μL each time. After air drying at room temperature, the working electrode is obtained. In the electroreduction test, 0.1 M KCl solution is used as the electrolyte, and a constant potential reduction test is carried out under the condition of continuously introducing pure carbon dioxide with a flow rate of 30 mL / min. The range of the constant potential is -1.0 V to -2.0 V vs. RHE.
[0062] Example 4
[0063] Example 4 adopts the method of Example 3, except that the catalyst is replaced with the two-dimensional ultrathin SnO₂ catalyst prepared in Example 2.
[0064] Example 5
[0065] Example 5 The method of Example 3 was adopted, except that the electrolyte was replaced with a 1 M KOH or KHCO3 solution, the electrolytic cell was a flow-through electrolytic cell, the reference electrode was a Hg / HgO electrode, and the ion exchange membrane was an anion exchange membrane.
[0066] Comparative Example 1
[0067] CuO nanosheets were synthesized by a hydrothermal method: First, 362.4 mg of copper nitrate was dissolved in 30 mL of water, and 30 mL of 3 M NaOH solution was added dropwise. Then it was transferred to a 100 mL hydrothermal autoclave and reacted at 100 °C for 12 h. After that, it was filtered by suction and dried in vacuum to obtain CuO nanosheets.
[0068] Comparative Example 2
[0069] SnO2 nanosheets were synthesized by a hydrothermal method: First, 350.6 mg of tin chloride was dissolved in 50 mL of water, and 30 mL of 0.4 M NaOH solution was added dropwise. Then it was transferred to a 100 mL hydrothermal autoclave and reacted at 180 °C for 12 h. After that, it was filtered by suction and dried in vacuum to obtain SnO2 nanosheets.
[0070] The scanning electron microscope images of the CuO and SnO2 nanosheets prepared by the hydrothermal method are shown in Figure 4 Figures a and 4b respectively. It can be seen from the figures that compared with the nanosheets prepared by the H2O2 exfoliation method in Examples 1 and 2, they have a larger thickness, which is not conducive to exposing more active sites.
[0071] Example 6
[0072] The samples of Example 1 and Comparative Example 1 were electrocatalytically reduced for carbon dioxide to C 2+ The Faraday efficiency of the product changes with the applied potential. As Figure 5 shown, by comparison, it can be found that the ultrathin two-dimensional CuO nanosheets in Example 1 showed a higher C 2+ Faraday efficiency of the product within a wide electrochemical window (-1.0 to -1.8 V vs. RHE), indicating that it can better convert CO2 into high-value-added C 2+ products. The main reason is that the two-dimensional ultrathin CuO nanosheets obtained after the anion exchange process have a higher electrochemically specific surface area and more defect sites and unsaturated sites, which are beneficial to the adsorption process of CO2 reduction intermediates, and at the same time prove that the catalyst prepared by the present invention has a higher C 2+ product selectivity.
[0073] Example 7
[0074] Prepare the two-dimensional ultrathin CuO catalyst according to the method of Example 1, except that the precursor dispersion A is continuously stirred at 500 revolutions per minute at room temperature for 1 h, 3 h, or 5 h until the ion exchange process is fully carried out to obtain dispersion B. Electro-catalytically reduce carbon dioxide to C according to the method of Example 3 2+ The Faradaic efficiency of the product varies with the applied potential, as Figure 6 shown. It is found that the CuO nanosheets obtained by treatment for 3 h have the best performance. Too short stirring time will result in incomplete ion exchange, and CuS is not completely converted to CuO2. Too long stirring time will damage the lamellar structure and reduce the performance.
[0075] Example 8
[0076] Prepare the two-dimensional ultrathin CuO catalyst according to the method of Example 1, except that aqueous H2O2 solutions with mass fractions of 1.5%, 3%, and 4.5% are used, and the precursor dispersion A is continuously stirred at room temperature for 3 h until the ion exchange process is fully carried out to obtain dispersion B. Electro-catalytically reduce carbon dioxide to C according to the method of Example 3 2+ The Faradaic efficiency of the product varies with the applied potential, as Figure 7 shown. It is found that the CuO nanosheets obtained when the treatment concentration is 3% have the best performance.
[0077] Example 9
[0078] Prepare the two-dimensional ultrathin CuO catalyst according to the method of Example 1, except that 30 mg, 50 mg, and 80 mg of CuS powder are weighed and treated respectively. Electro-catalytically reduce carbon dioxide to C according to the method of Example 3 2+ The Faradaic efficiency of the product varies with the applied potential, as Figure 8 shown. It is found that the CuO nanosheets obtained when the input amount of CuS is 50 mg have the best performance.
Claims
1. A preparation method of an ultra-thin two-dimensional metal oxide nanosheet catalyst, characterized in that, It includes the following steps: (1)Disperse a metal sulfide or a metal selenide into an aqueous H2O2 solution with a certain concentration, and mix well to obtain a precursor dispersion A; (2)Continuously stir the precursor dispersion A until the ion exchange process is fully carried out to obtain a dispersion B; (3)Separate the solid in the dispersion B and dry it to obtain a solid powder C; (4)Redisperse the solid powder C into deionized water, and stir and react to obtain a dispersion D; (5)Separate and dry the solid in the dispersion D to obtain a two-dimensional ultrathin metal oxide catalyst.
2. The preparation method of the ultra-thin two-dimensional metal oxide nanosheet catalyst according to claim 1, wherein, The mass fraction of the aqueous H2O2 solution described in step (1) is 1% - 10%, and 0.05 - 0.5 g of the metal sulfide or the metal selenide is added to every 50 - 200 mL of the aqueous H2O2 solution.
3. The preparation method of the ultra-thin two-dimensional metal oxide nanosheet catalyst according to claim 1, characterized in that, The metal described in step (1) is preferably Cu, Sn or Ag.
4. The preparation method of the ultra-thin two-dimensional metal oxide nanosheet catalyst according to claim 1, characterized in that, The stirring temperature condition in step (2) is 20°C - 60°C, and the stirring time is 1 - 18 h.
5. The preparation method of the ultrathin two-dimensional metal oxide nanosheet catalyst according to claim 1, characterized in that, In step (3), the dispersion B is separated by suction filtration, and the solid cake is vacuum dried at 60 - 90°C to obtain a solid powder C.
6. The preparation method of the ultra-thin two-dimensional metal oxide nanosheet catalyst according to claim 1, characterized in that, In step (4), 0.05 - 0.5 g of the solid powder C is added to every 50 - 200 mL of deionized water; the reaction temperature condition is 50 - 90°C, and the stirring time is 3 - 12 h.
7. The preparation method of the ultrathin two-dimensional metal oxide nanosheet catalyst according to claim 1, characterized in that, In step (5), the dispersion D is filtered by suction, and the solid cake is vacuum dried at 50 - 90°C to obtain a two-dimensional ultrathin metal oxide catalyst.
8. An ultrathin two-dimensional metal oxide nanosheet catalyst prepared by the preparation method described in claim 1.
9. An application of the ultrathin two-dimensional metal oxide nanosheet catalyst described in claim 8 in electrocatalytic reduction of CO2 to formic acid or ethylene.
10. The application according to claim 9, characterized in that, The electrolytic cell used for the electrocatalytic reduction of CO2 is an ion-exchange membrane-separated H-type or flow-type electrolytic cell, with an Ag / AgCl electrode or a Hg / HgO electrode as the reference electrode, a Pt sheet or a nickel foam as the counter electrode, and a hydrophobic carbon paper coated with an ultrathin two-dimensional metal oxide nanosheet catalyst as the working electrode. The constant potential range is -0.30V - -2.0V vs. RHE. The electrolyte is a solution of KCl, KOH or KHCO3 with a concentration of 0.1 - 3 M, and the carbon dioxide gas flow rate is 10 - 50 sccm.