Lutetium-doped porous cuprous oxide material and preparation method thereof

Abstract

The application discloses a kind of Lanthanum-doped Porous Cuprous Oxide Material and preparation method thereof.Copper salt and Lanthanum salt are dissolved in ultrapure water according to proportion, sodium hydroxide and ascorbic acid are added in turn, and stirred and reacted, and then Lanthanum-doped Porous Cuprous Oxide Material is obtained after centrifugation, washing and drying.The obtained material has three-dimensional network foam-like morphology, the pore size is mainly distributed in the mesoporous range of 10-50 nm, and Lanthanum element is uniformly doped in the cuprous oxide lattice.The material can be used as a cathode catalyst for electrocatalytic reduction of carbon dioxide, and under the condition of total reduction current density of 700 mA / cm 2 , ethylene Faraday efficiency can reach 83%, and ethylene partial current density can reach 578 mA / cm 2 , and the electrochemical performance is excellent.

Description

Technical Field

[0001] This invention belongs to the field of inorganic nanomaterials technology, specifically relating to a lutetium-doped porous cuprous oxide material and its preparation method. Background Technology

[0002] Utilizing renewable electricity to electrochemically reduce CO2 into high-value-added chemicals or fuels is a promising carbon neutrality technology route. Among the many products of CO2 electroreduction, ethylene is highly favored due to its important role as a basic chemical feedstock.

[0003] Cuprous oxide (Cu₂O) is a p-type semiconductor material with a direct band gap of 2–2.2 eV and high carrier mobility, providing numerous copper active sites for carbon dioxide activation. However, its slow charge transfer, suboptimal electronic structure, and poor stability result in low ethylene selectivity and current densities that are insufficient for industrial applications. Therefore, improving the catalytic activity of Cu₂O is a key issue that needs to be addressed now and in the future. Summary of the Invention

[0004] One of the objectives of this invention is to provide a method for preparing lutetium-doped porous cuprous oxide materials, which has simple and controllable synthesis steps and low cost.

[0005] The second objective of this invention is to provide a lutetium-doped porous cuprous oxide material prepared by the above-mentioned method. This material, through the doping of lutetium, effectively inhibits the aggregation of cuprous oxide crystals, increases the number of active sites, and forms a rich porous structure, thereby significantly improving catalytic efficiency.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing lutetium-doped porous cuprous oxide material, comprising the following steps: (1) Weigh out copper salt and lutetium salt respectively in a molar ratio of 4-7:1, add them to ultrapure water, and stir until completely dissolved to obtain a mixed solution; the copper salt is one or more of copper nitrate, copper sulfate, copper chloride, copper acetate, and copper acetylacetonate, and the lutetium salt is one or more of lutetium chloride, lutetium sulfate, lutetium nitrate, and lutetium acetate; (2) Add sodium hydroxide to the mixed solution obtained in step (1) and stir to react; wherein the molar ratio of sodium hydroxide to copper salt is 6-12:1; (3) Add ascorbic acid to the reaction solution obtained in step (2) and continue stirring the reaction; wherein the molar ratio of ascorbic acid to copper salt is 1-5:1. (4) The precipitate obtained in step (3) is centrifuged, washed with water and dried to obtain lutetium-doped porous cuprous oxide material.

[0007] Preferably, in step (1), the copper salt is copper nitrate and the lutetium salt is lutetium nitrate, at which point the catalytic performance is optimal.

[0008] Preferably, in step (1), the molar ratio of the copper salt to the lutetium salt is 5:1.

[0009] Preferably, in step (2), the molar ratio of sodium hydroxide to copper salt is 8.5:1.

[0010] Preferably, in step (3), the molar ratio of the ascorbic acid to the copper salt is 2.7:1.

[0011] Preferably, in step (2), the stirring reaction time is 10-60 min. More preferably, the stirring reaction time is 30 min.

[0012] Preferably, in step (3), the stirring reaction time is 60-120 min. More preferably, the stirring reaction time is 90 min.

[0013] Secondly, the present invention also provides a lutetium-doped porous cuprous oxide material prepared by the above preparation method.

[0014] The material prepared by this invention exhibits a loose, continuous foam-like morphology, with particles interconnected to form a three-dimensional network structure. The pore size of the material is mainly distributed in the range of 10-50 nm, belonging to a typical mesoporous structure.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The raw materials used in this invention, such as copper salt, lutetium salt, sodium hydroxide, and ascorbic acid, are widely available, inexpensive, and have simple and controllable synthesis steps, making them suitable for large-scale production.

[0016] (2) In this invention, lutetium, a rare earth metal, is introduced to dope cuprous oxide. Lutium has a large atomic radius, which can effectively inhibit the aggregation of cuprous oxide nanoparticles. At the same time, lutetium and cuprous oxide can synergistically catalyze CO2, which significantly improves the activity of ethylene.

[0017] (3) The lutetium-doped porous cuprous oxide material prepared by the present invention has a rich porous structure, which provides a large number of active sites for carbon dioxide reduction. At the same time, the porous structure is conducive to the diffusion of reaction substrates and the release of products, thereby improving catalytic efficiency.

[0018] (4) The lutetium-doped porous cuprous oxide material prepared by the present invention has excellent ethylene activity, with an ethylene Faradaic efficiency of up to 83% and an ethylene current density of up to 578 mA / cm². Its electrochemical performance is significantly better than that of the prior art. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the lutetium-doped porous cuprous oxide material prepared in Example 1 of the present invention.

[0020] Figure 2 This is a pore size distribution diagram of the lutetium-doped porous cuprous oxide material prepared in Example 1 of the present invention.

[0021] Figure 3 This is the CO2 adsorption isotherm of the lutetium-doped porous cuprous oxide material prepared in Example 1 of the present invention.

[0022] Figure 4 The X-ray diffraction patterns are those of the lutetium-doped porous cuprous oxide material prepared in Example 1 of the present invention and the pure-phase porous cuprous oxide material prepared in Comparative Example 1.

[0023] Figure 5 The figures show the ethylene Faraday efficiency of the lutetium-doped porous cuprous oxide materials prepared in Examples 1-5 of this invention and the pure-phase porous cuprous oxide material prepared in Comparative Example 1 under different reduction current densities.

[0024] Figure 6 The figures show the ethylene current density of the lutetium-doped porous cuprous oxide materials prepared in Examples 1-5 of this invention and the pure-phase porous cuprous oxide material prepared in Comparative Example 1 under different reduction current densities. Detailed Implementation

[0025] To further illustrate the technical means adopted in this invention and its beneficial effects, specific embodiments and accompanying drawings are described below. These embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of this invention, but do not limit the invention in any way.

[0026] Example 1 Weigh 1 mmol of copper nitrate and 0.2 mmol of lutetium nitrate, add them to 200 mL of ultrapure water, and stir until completely dissolved. Then add 8.5 mmol of sodium hydroxide and stir at room temperature for 30 min. Then add 2.7 mmol of ascorbic acid and continue stirring at room temperature for 90 min. Centrifuge the mixture and wash it three times with water. Place the obtained solid in an oven and dry it at 80 °C for 24 h to obtain lutetium-doped porous cuprous oxide material.

[0027] Figure 1 This is a scanning electron microscope (SEM) image of the lutetium-doped porous cuprous oxide material prepared in Example 1. The image clearly shows that the material exhibits a loose, continuous foam-like morphology, with particles interconnected to form a three-dimensional network structure. This unique skeletal structure facilitates thorough electrolyte wetting and rapid escape of gaseous products.

[0028] Figure 2This is a pore size distribution diagram of the lutetium-doped porous cuprous oxide material prepared in Example 1. Figure 2 It can be seen that the pore size of the material is mainly distributed in the range of 10-50 nm, which is a typical mesoporous structure. This mesoporous-dominated pore size distribution not only provides a larger specific surface area to expose more active sites, but also facilitates the rapid diffusion of CO2 molecules into the pores and the timely release of ethylene, thereby significantly improving the mass transfer efficiency and overall reaction rate of electrocatalytic CO2 reduction.

[0029] Figure 3 This is the CO2 adsorption isotherm of the lutetium-doped porous cuprous oxide material prepared in Example 1. The material adsorbs 7.65 cm⁻¹ of CO2 under ambient temperature and pressure conditions. 3 / g, which indicates that the porous structure of the material is conducive to the adsorption of CO2, and thus can provide sufficient reaction substrate for catalytic reaction.

[0030] Example 2 Weigh 1.4 mmol of copper nitrate and 0.2 mmol of lutetium nitrate, add them to 200 mL of ultrapure water, and stir until completely dissolved; then add 8.5 mmol of sodium hydroxide and stir for 30 min; then add 2.7 mmol of ascorbic acid and continue stirring for 90 min. Centrifuge the mixture and wash it three times with water. Place the resulting solid in an oven and dry for 24 h to obtain lutetium-doped porous cuprous oxide material.

[0031] Example 3 Weigh 0.8 mmol of copper nitrate and 0.2 mmol of lutetium nitrate, add them to 200 mL of ultrapure water, and stir until completely dissolved; then add 8.5 mmol of sodium hydroxide and stir for 30 min; then add 2.7 mmol of ascorbic acid and continue stirring for 90 min. Centrifuge the mixture and wash it three times with water. Place the obtained solid in an oven and dry for 24 h to obtain lutetium-doped porous cuprous oxide material.

[0032] Example 4 Weigh 1 mmol of copper nitrate and 0.2 mmol of lutetium nitrate, add them to 200 mL of ultrapure water, and stir until completely dissolved; then add 10 mmol of sodium hydroxide and stir for 30 min; then add 2.7 mmol of ascorbic acid and continue stirring for 90 min. Centrifuge the mixture and wash it three times with water. Place the obtained solid in an oven and dry for 24 h to obtain lutetium-doped porous cuprous oxide material.

[0033] Example 5 Weigh 1 mmol of copper nitrate and 0.2 mmol of lutetium nitrate, add them to 200 mL of ultrapure water, and stir until completely dissolved; then add 8.5 mmol of sodium hydroxide and stir for 30 min; then add 5 mmol of ascorbic acid and continue stirring for 90 min. Centrifuge the mixture and wash it three times with water. Place the obtained solid in an oven and dry for 24 h to obtain lutetium-doped porous cuprous oxide material.

[0034] Comparative Example 1 Weigh 1 mmol of copper nitrate and add it to 200 mL of ultrapure water, stirring until completely dissolved. Then add 8.5 mmol of sodium hydroxide and stir for 30 min. Next, add 2.7 mmol of ascorbic acid and continue stirring for 90 min. Centrifuge the mixture and wash it three times with water. Place the resulting solid in an oven and dry for 24 h to obtain pure-phase porous cuprous oxide material.

[0035] Figure 4 The X-ray diffraction patterns are shown for the lutetium-doped porous cuprous oxide material prepared in Example 1 and the pure-phase porous cuprous oxide material prepared in Comparative Example 1. Both Example 1 and Comparative Example 1 exhibit significant characteristic diffraction peaks at 29.5°, 36.5°, 42.3°, and 61.4°, corresponding to the (110), (111), (200), and (220) crystal planes of cuprous oxide, respectively. The peak intensities of the diffraction peaks of each crystal plane in Example 1 are weaker than those in Comparative Example 1, indicating that lutetium has been successfully incorporated into the cuprous oxide lattice. The larger atomic radius of lutetium inhibits the aggregation of cuprous oxide crystals; therefore, the crystallinity of the cuprous oxide crystal in Example 1 is reduced.

[0036] The catalytic performance of the porous cuprous oxide materials prepared in Examples 1-5 and Comparative Example 1 was tested, and the specific steps are as follows: Weigh 10 mg of the prepared material into a sample tube, then add 480 μL of isopropanol and 20 μL of perfluorosulfonic acid-polytetrafluoroethylene copolymer. Sonicate for 30 min to form a well-dispersed mixed solution. Then, drop the solution onto the surface of the gas diffusion layer (1 cm² area). 2 The electrode was prepared by air-drying. A platinum sheet and an Ag / AgCl electrode were used as the counter electrode and reference electrode, respectively, and the electrolyte was a 1 mol / L potassium hydroxide solution.

[0037] Figure 5 This diagram shows the ethylene Faraday efficiency of the porous cuprous oxide materials prepared in Examples 1-5 and Comparative Example 1 under different reduction current densities. Figure 5 It can be seen that the ethylene Faraday efficiency of all lutetium-doped samples (Examples 1-5) is significantly higher than that of the undoped Comparative Example 1, indicating that the introduction of lutetium effectively improves the selectivity of ethylene.

[0038] Among them, Example 1 (copper to lutetium molar ratio 5:1, sodium hydroxide to copper salt molar ratio 8.5:1, ascorbic acid to copper salt molar ratio 2.7:1) exhibited the best ethylene selectivity at 700 mA / cm². 2 The ethylene Faradaic efficiency reached 83% at the total reduction current density. The ethylene Faradaic efficiencies of Examples 2 (copper to lutetium molar ratio 7:1) and 3 (copper to lutetium molar ratio 4:1) were both lower than that of Example 1, with maximum efficiencies of approximately 71% and 68%, respectively, indicating that excessively high or low copper-lutetium ratios weaken the lutetium regulation effect. The ethylene Faradaic efficiency of Example 4 (sodium hydroxide to copper salt molar ratio 10:1) was approximately 75%, slightly lower than that of Example 1, indicating that increased alkali dosage may lead to localized over-precipitation, affecting the distribution of active sites. The ethylene Faradaic efficiency of Example 5 (ascorbic acid to copper salt molar ratio 5:1) was approximately 61%, indicating that excessive reducing agent may have altered the Cu... + The local chemical environment of the active sites adversely affects the CC coupling process, thereby reducing ethylene selectivity. The highest ethylene Faradaic efficiency of Comparative Example 1 (pure phase cuprous oxide) was only 45%, indicating that the ethylene activity of the undoped sample was low.

[0039] The above results indicate that the preferred preparation parameters of the present invention (Example 1) can maximize the synergistic effect of lutetium doping and obtain the best ethylene selectivity.

[0040] Figure 6 This is a partial current density diagram of ethylene in the lutetium-doped porous cuprous oxide materials prepared in Examples 1-5 and Comparative Example 1 of the present invention under different reduction current densities. Figure 6 It can be seen that the ethylene fractional current density of all samples increases with the increase of the reduction current density, with Example 1 showing the highest increase at 700 mA / cm². 2 The maximum value is reached at the total reduction current density, specifically at the ethylene portion current density of 578 mA / cm². 2 This is significantly higher than in other embodiments and comparative examples.

[0041] The excellent ethylene current density in Example 1 is attributed to its porous structure (mesopores with pore sizes of 10-50 nm) and suitable lutetium doping level. The porous structure provides a high specific surface area and fast mass transfer channels, which is beneficial for CO2 diffusion and ethylene release; the synergistic catalysis of lutetium and cuprous oxide enhances the rate of electrocatalytic reduction of CO2 to ethylene. The maximum ethylene current densities in Examples 2-5 are 489, 428, 525, and 356 mA / cm², respectively. 2 All were significantly higher than the 212 mA / cm of Comparative Example 1. 2 The lowest current density was observed in Comparative Example 1, attributed to insufficient activity of active sites due to the lack of lutetium doping and severe hydrogen evolution competition.

[0042] comprehensive Figure 5 and Figure 6 The lutetium-doped porous cuprous oxide material prepared in Example 1 of this invention exhibits both high ethylene selectivity (83%) and high ethylene partial current density (578 mA / cm²). 2 It exhibits excellent electrocatalytic reduction performance of carbon dioxide to ethylene.

[0043] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a lutetium-doped porous cuprous oxide material, characterized in that, Includes the following steps: (1) Weigh out copper salt and lutetium salt respectively in a molar ratio of 4-7:1, add them to ultrapure water, and stir until completely dissolved to obtain a mixed solution; the copper salt is one or more of copper nitrate, copper sulfate, copper chloride, copper acetate, and copper acetylacetonate, and the lutetium salt is one or more of lutetium chloride, lutetium sulfate, lutetium nitrate, and lutetium acetate; (2) Add sodium hydroxide to the mixed solution obtained in step (1) and stir to react; wherein the molar ratio of sodium hydroxide to copper salt is 6-12:1; (3) Add ascorbic acid to the reaction solution obtained in step (2) and continue stirring the reaction; wherein the molar ratio of ascorbic acid to copper salt is 1-5:1; (4) The precipitate obtained in step (3) is centrifuged, washed with water and dried to obtain lutetium-doped porous cuprous oxide material.

2. The method for preparing a lutetium-doped porous cuprous oxide material according to claim 1, characterized in that, In step (1), the copper salt is copper nitrate and the lutetium salt is lutetium nitrate.

3. The method for preparing a lutetium-doped porous cuprous oxide material according to claim 1, characterized in that, In step (1), the molar ratio of the copper salt to the lutetium salt is 5:

1.

4. The method for preparing a lutetium-doped porous cuprous oxide material according to claim 1, characterized in that, In step (2), the molar ratio of sodium hydroxide to copper salt is 8.5:

1.

5. The method for preparing a lutetium-doped porous cuprous oxide material according to claim 1, characterized in that, In step (3), the molar ratio of ascorbic acid to copper salt is 2.7:

1.

6. The method for preparing a lutetium-doped porous cuprous oxide material according to claim 1, characterized in that, In step (2), the stirring reaction time is 10-60 min.

7. The method for preparing a lutetium-doped porous cuprous oxide material according to claim 1, characterized in that, In step (3), the stirring reaction time is 60-120 min.

8. A lutetium-doped porous cuprous oxide material prepared by the preparation method according to any one of claims 1 to 7.

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