阅读说明：本技术 一种树枝状的有序介孔氧化铜纳米材料及其制备方法和应用 (Dendritic ordered mesoporous copper oxide nano material and preparation method and application thereof ) 是由 顾栋 宋述华 于 2021-08-20 设计创作，主要内容包括：本发明公开了一种树枝状的有序介孔氧化铜纳米材料及其制备方法和应用,可获得高比表面积的介孔氧化铜纳米材料。制备方法如下：通过简单的硬模板方法,将金属铜盐及正硅酸四乙酯填入至介孔二氧化硅中,通过在空气中煅烧后,用氢氧化钠将二氧化硅模板去除,即可得到树枝状的有序介孔氧化铜材料,其具有高比表面积(80m～(2)g～(-1)～150m～(2)g～(-1))和有序介孔结构等特点。本发明通过加入硅源,克服了介孔氧化铜在传统制备过程中严重晶化,结构易被破坏等缺点,可用于电催化二氧化碳还原等领域,且所有制备流程安全可靠,制备方法较为简单可控,为合成其它的介孔金属氧化物提供可行的方法。(The invention discloses a dendritic ordered mesoporous copper oxide nano material, a preparation method and application thereof, and the mesoporous copper oxide nano material with high specific surface area can be obtained. The preparation method comprises the following steps: filling metal copper salt and tetraethyl orthosilicate into mesoporous silica by a simple template hardening method, calcining in air, and removing the silica template by sodium hydroxide to obtain the dendritic ordered mesoporous copper oxide material with the mesoporous copper oxide materialHigh specific surface area (80 m) 2 g ‑1 ～150m 2 g ‑1 ) And ordered mesoporous structure. The silicon source is added, so that the defects that the mesoporous copper oxide is seriously crystallized in the traditional preparation process, the structure is easily damaged and the like are overcome, the preparation method can be used in the fields of electrocatalytic carbon dioxide reduction and the like, all preparation processes are safe and reliable, the preparation method is simpler and more controllable, and a feasible method is provided for synthesizing other mesoporous metal oxides.)

1. A preparation method of a dendritic ordered mesoporous copper oxide nano material is characterized by comprising the following steps:

1) synthesizing a mesoporous silica template with rich silicon hydroxyl on the surface by a hydrothermal method;

2) preparing an alcoholic solution of a copper salt;

3) adding tetraethyl orthosilicate into an alcoholic solution of copper salt, adding an alcoholic solution of hydrochloric acid, and fully stirring to obtain a solution A;

4) adding a mesoporous silica template with the surface rich in silicon hydroxyl into the solution A, stirring for reaction, and then drying to obtain a copper salt-silica composite;

5) transferring the copper salt-silicon dioxide compound, calcining, and removing the silicon dioxide template to obtain the dendritic ordered mesoporous copper oxide.

2. The method of claim 1, wherein: the mesoporous silica template with abundant silicon hydroxyl groups in the step 1) comprises SBA-15, MCF and KIT-6.

3. The method of claim 1, wherein: in the step 2), the copper salt comprises copper nitrate and copper sulfate; the alcohol is ethanol, wherein the dosage ratio of the copper salt to the ethanol is 1g:5-20 mL.

4. The method of claim 1, wherein: in the step 3), the hydrochloric acid alcohol solution is hydrochloric acid alcohol solution, and the concentration is 0.2-0.3M; the dosage ratio of the copper salt, tetraethyl orthosilicate and hydrochloric acid alcohol solution is 1-2g:1g:1 mL.

5. The method of claim 1, wherein: in the step 4), the dosage ratio of the mesoporous silica template with the surface rich in silicon hydroxyl groups to the solution A is 1g:20 mL.

6. The method of claim 1, wherein: in the step 4), the stirring reaction is carried out under a sealed condition, the reaction temperature is 30-80 ℃, and the stirring time is 2-4 hours; the drying reaction temperature is 50-80 ℃.

7. The method of claim 1, wherein: in the step 4), the filling ratio of tetraethyl orthosilicate and metal copper salt accounting for the pore volume of the template is 20-100%.

8. The method of claim 1, wherein: in the step 5), the calcining temperature is 300-500 ℃; the method for removing the silica template comprises the following steps: and removing the silicon dioxide template by adopting 0.5-2.0 mol/L NaOH solution at the temperature of 40-80 ℃.

9. A dendritic ordered mesoporous copper oxide nano material is characterized in that: prepared by the process of any one of claims 1 to 8.

10. The use of the mesoporous copper oxide nanomaterial of claim 9 in electrocatalytic carbon dioxide reduction.

Technical Field

The invention relates to the technical field of mesoporous materials, in particular to a dendritic ordered mesoporous copper oxide nano material and a preparation method and application thereof.

Background

The mesoporous metal oxide material has excellent structural performance, and has the characteristics of high specific surface area, ordered structure, adjustable aperture and morphology and the like. The high specific surface area can provide a large number of active sites for the surface interface related process, and the uniform and adjustable mesoporous aperture can be beneficial to the transmission of substances. The mesoporous channel can be used as a micro nano reactor and has a certain nano confinement effect. Therefore, the mesoporous oxide plays an important role in the fields of catalysis, energy sources and the like. Mesoporous copper oxide is a typical p-type semiconductor, and the crystal structure of the mesoporous copper oxide is a monoclinic system, and is one of nanometer semiconductor materials which are receiving attention in recent years. However, the preparation method of the ordered mesoporous copper oxide is relatively few at present, and mainly adopts a hard template method, mesoporous silicon dioxide such as SBA-15 is taken as a template, a copper source is added, the template is calcined after being fumigated in an ammonia atmosphere, and finally the template is removed. The process is relatively cumbersome and difficult to control. In the other method, mesoporous silicon dioxide is used as a primary template to synthesize an ordered mesoporous carbon material, and then the ordered mesoporous carbon material is used as a secondary template to synthesize mesoporous copper oxide. The method has complex synthesis steps and long time consumption. Therefore, how to design a simple and effective method for synthesizing ordered mesoporous copper oxide is a problem which needs to be solved urgently at present.

Disclosure of Invention

In order to solve the above-mentioned problems, the present invention aims to provide a dendritic ordered mesoporous copper oxide nanomaterial, and a preparation method and an application thereof.

The invention provides a simple and effective synthesis method, wherein novel mesoporous copper oxide is prepared by a hard template method, and the prepared mesoporous copper oxide not only has an ordered mesoscopic structure, but also grows a nano sheet similar to a tree shape on the surface, so that the mesoporous copper oxide has a large specific surface area, can fully expose a large number of active sites, and is expected to play an important role in the fields of catalysis, energy storage, conversion and the like.

The first aspect of the invention provides a preparation method of a dendritic ordered mesoporous copper oxide nano material, which comprises the following steps:

1) synthesizing a mesoporous silica template with rich silicon hydroxyl on the surface by a hydrothermal method;

2) preparing an alcoholic solution of a copper salt;

3) adding tetraethyl orthosilicate into an alcoholic solution of copper salt, adding an alcoholic solution of hydrochloric acid, and fully stirring to obtain a solution A;

4) adding a mesoporous silica template with the surface rich in silicon hydroxyl into the solution A, stirring for reaction, and then drying to obtain a copper salt-silica composite;

5) transferring the copper salt-silicon dioxide compound, calcining, and removing the silicon dioxide template to obtain the ordered mesoporous copper oxide.

Further, the mesoporous silica template with abundant silicon hydroxyl groups in the step 1) comprises SBA-15, MCF and KIT-6.

Further, SBA-15(J.Am.chem.Soc.1998,120,6024), MCF-OH (J.Am.chem.Soc.1999,121,254-255), KIT-6-OH (chem.Commun.2003,2136-2137) was prepared according to a literature reported manner. Unlike the literature, which uses high-temperature roasting to remove the block copolymer, the invention uses mild oxidation, and the specific process is as follows: adding 6-10 g of a silicon dioxide-surfactant mixture into a round-bottom flask with the volume of 1-2L, pouring 90-140 mL of concentrated nitric acid (65-68 wt%) and 30-60 mL of hydrogen peroxide (35-40 wt%) solution, refluxing for 3-5 h at 70-90 ℃, cooling, adding 500-800 mL of water into the system, filtering, washing and drying to obtain the template with the surface rich in silicon hydroxyl. The more specific process is as follows: 8.0g of the dried silica-block copolymer mixture was added to a 1L round bottom flask and 120mL of concentrated HNO was poured₃(65 wt%) and 40mL hydrogen peroxide (35 wt%), heating to 80 deg.C, refluxing and stirring for 3h, cooling, filtering, washing and drying to obtain mesoporous silica template with rich hydroxyl group on surface.

Further, in the step 2), the copper salt comprises copper nitrate and copper sulfate; the alcohol is ethanol, the dosage ratio of the copper salt to the ethanol is 1g:5-20mL, the preferred dosage ratio is 1g:10mL, and the copper salt has higher solubility in the ethanol and is beneficial to dissolving the copper salt.

Further, in the step 3), the hydrochloric acid alcohol solution is a mixed solution of hydrochloric acid and ethanol, and the concentration is 0.2-0.3M, wherein the preferred concentration is 0.2M.

Further, in the step 3), the dosage ratio of the copper salt, the tetraethyl orthosilicate and the hydrochloric acid alcohol solution is 1-2g:1g:1 mL. Preferably, the dosage ratio of the copper salt, tetraethyl orthosilicate and the hydrochloric acid alcohol solution is 1g:1g:1 mL.

Further, in the step 4), the dosage ratio of the mesoporous silica template with the surface rich in silicon hydroxyl groups to the solution A is 1g:20 mL.

Further, in the step 4), the stirring reaction is carried out under a sealed condition, the reaction temperature is 30-80 ℃, and the stirring time is 2-4 hours; the drying reaction temperature is 50-80 ℃.

Further, in the step 4), the filling ratio of tetraethyl orthosilicate and copper salt together in the pore volume of the template is 20-100%. The preferred pore volume filling ratio is 30 to 80%.

Further, in the step 5), the calcining temperature is 300-500 ℃; the method for removing the silica template comprises the following steps: and removing the silicon dioxide template by adopting 0.5-2.0 mol/L NaOH solution at the temperature of 40-80 ℃.

The second aspect of the invention provides the dendritic ordered mesoporous copper oxide nano material prepared by the method of the first aspect, and the specific surface area of the prepared ordered mesoporous copper oxide nano material is 80m² g^-1～150m² g^-1。

The third aspect of the invention provides an application of the dendritic ordered mesoporous copper oxide nanomaterial described in the second aspect in electrocatalytic carbon dioxide reduction.

The invention has the following beneficial effects:

1) the invention takes mesoporous silicon dioxide as a template, and avoids the problems of serious crystallization, unstable structure and the like of a copper source in the high-temperature calcination process by adding tetraethyl orthosilicate and utilizing the interaction between the tetraethyl orthosilicate and the copper source.

2) According to the invention, the tetraethyl orthosilicate is added into the alcoholic solution of the copper salt, and then the alcoholic solution of the hydrochloric acid is added, so that the hydrolysis of the tetraethyl orthosilicate can be effectively regulated and controlled, and the interaction between the tetraethyl orthosilicate and the copper ions is enhanced.

3) NaOH can react with silicon dioxide and copper oxide at the same time, the structure of mesoporous copper oxide is accurately regulated and controlled in the process of removing silicon dioxide, dendritic nanosheets grow on the surface of the mesoporous copper oxide, and the special structure can fully expose a large number of active sites.

4) The prepared dendritic mesoporous copper oxide has an ordered structure, a higher specific surface area and a special surface structure, can be used for electrocatalytic carbon dioxide reduction, and has high catalytic efficiency.

5) The synthesis method is relatively simple and controllable, and has a wide application prospect.

Drawings

FIG. 1 is an SEM image of dendritic mesoporous copper oxide prepared in example 1;

FIG. 2 is a TEM image of the dendritic mesoporous copper oxide prepared in example 1;

figure 3 is a graph of the results of testing the electrocatalytic redox of the dendritic mesoporous copper oxide prepared in example 1, (a) the total current density at different potentials, and (b) the faradaic efficiency of the product at different potentials.

Detailed Description

In order to more clearly illustrate the problems to be solved by the present invention, the following further describes the specific implementation steps of the present invention with reference to the attached drawings. The content of the invention is not limited to this at all.

Example 1

1) Preparation of mesoporous silica SBA-15: taking 20.0g of block copolymer P123, adding 650mL of deionized water and 100mL of concentrated hydrochloric acid (37 wt%), stirring in a 38 ℃ water bath for 2h, adding 41.6g of tetraethyl orthosilicate, stirring at 38 ℃ for 24h, transferring to a hydrothermal kettle after stirring, carrying out hydrothermal treatment at 110 ℃ for 24h, cooling, carrying out suction filtration, and drying at 50 ℃ to obtain white powder. 8.0g of white powder was dispersed in 120mL of concentrated HNO₃(65 wt%) and 40ml of hydrogen peroxide (35 wt%) solution, heating to 80 ℃ and refluxing for 3h, and finally filtering, washing and drying to obtain the mesoporous silica template rich in silicon hydroxyl.

2) Preparing the dendritic ordered mesoporous copper oxide: 0.6g of copper nitrate was dissolved in 10mL of ethanol, 0.5g of tetraethyl orthosilicate and 0.5mL of a hydrochloric acid alcohol solution (0.2M) were added, 0.5g of SBA-15 was added, and the mixture was stirred in a water bath at 50 ℃ for 2 hours under sealed conditions. The container was then opened and baked in an oven at 70 ℃ for 4 h. Then taking out and transferring to a muffle furnace for calcining, and keeping the temperature at 300 ℃ for 5 h. And finally, removing the silicon dioxide template by using 2mol/L NaOH solution at 70 ℃, and obtaining the dendritic ordered mesoporous copper oxide material after centrifugation, washing and drying.

From fig. 1 and fig. 2, it can be seen that mesoporous copper oxide prepared by using mesoporous SBA-15 as a template has a similar morphology to that of the template, and a large number of dendritic nanosheet structures grow on the surface, which indicates that mesoporous copper oxide with a special structure is successfully prepared.

The specific surface area of the ordered mesoporous copper oxide material prepared in the test example 1 is 146m² g^-1。

Example 2

The preparation method is the same as example 1, except that the template is MCF, and the dosage ratio of the copper salt, tetraethyl orthosilicate and the hydrochloric acid alcohol solution is 1g:1g:1 mL.

The preparation method of MCF comprises the following steps:

20.0g of block copolymer P123 and 0.23g of NH were taken₄And F, adding 650mL of deionized water, 100mL of concentrated hydrochloric acid (37%) and 20.0g of 1,3, 5-trimethylbenzene, stirring in a 38 ℃ water bath for 2 hours, adding 41.6g of tetraethyl orthosilicate, stirring at 38 ℃ for 24 hours, transferring the mixture into a hydrothermal kettle after stirring, carrying out hydrothermal reaction at 110 ℃ for 24 hours, cooling, carrying out suction filtration, and drying at 50 ℃ to obtain white powder. 8.0g of white powder was dispersed in 120mL of concentrated HNO₃(65 wt%) and 40ml hydrogen peroxide (35 wt%) solution, heating to 80 deg.C and refluxing for 3h, and finally filtering, washing and drying to obtain the mesoporous MCF template rich in silicon hydroxyl.

The specific surface area of the ordered mesoporous copper oxide material prepared in the test example 2 is 82m² g^-1。

Example 3

The preparation method is the same as example 1, except that the template is KIT-6, and the dosage ratio of the copper salt, tetraethyl orthosilicate and hydrochloric acid alcohol solution is 1g:1g:1 mL.

The preparation method of KIT-6 comprises the following steps:

taking 20.0g of block copolymer P123, adding 720mL of deionized water, 31.5mL of concentrated hydrochloric acid (37 wt%) and 20.0g of 1-butanol, stirring in a 35 ℃ water bath for 1h, adding 43.0g of tetraethyl orthosilicate, stirring at 35 ℃ for 24h, transferring the mixture into a hydrothermal kettle after stirring, carrying out hydrothermal treatment at 110 ℃ for 24h, cooling, carrying out suction filtration, and drying at 50 ℃ to obtain white powder. 8.0g of white powder was dispersed in 120mL of concentrated HNO₃(65 wt%) and 40ml of hydrogen peroxide (35 wt%) solution, heating to 80 ℃, refluxing for 3h, and finally filtering, washing and drying to obtain the mesoporous KIT-6 template rich in silicon hydroxyl.

The specific surface area of the ordered mesoporous copper oxide material prepared in the test example 3 is 106m² g^-1。

Application example 1

The mesoporous copper oxide prepared in the embodiment 1 is applied to electrocatalytic carbon dioxide reduction, and the specific implementation process comprises the following steps: ultrasonically dispersing the catalyst into a mixed solution of ethanol and Nafion, uniformly coating the mixed solution on a carbon electrode, and drying the carbon electrode under an infrared baking lamp for later use. The electrocatalytic carbon dioxide reduction process is carried out in a three-electrode H-shaped glass electrolytic cell, and the electrolyte is 0.5M KHCO₃The solution, Ag/AgCl electrode as reference electrode, platinum sheet as counter electrode, and the two tanks are connected by proton exchange membrane. Before the test is started, CO is continuously introduced into the electrolyte₂Gas, starting the test after it reaches saturation, CO during the test₂The introduction was continued. The products were analyzed by gas chromatography and the faradaic efficiency of each product was calculated. As can be seen from fig. 3(a), the current density exhibits a higher value with the change of the potential, indicating that the material has higher electrocatalytic activity; as can be seen from FIG. 3(b), the faradaic efficiency of ethylene is as high as 60% at a potential of-0.8V to-0.9V, which indicates that the prepared mesoporous copper oxide has excellent ethylene selectivity in the electrocatalytic carbon dioxide reduction process.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention.