Metal oxide nanotube array structure catalyst, and preparation method therefor and use thereof

Abstract

A metal oxide nanotube array structure catalyst, and a preparation method therefor and a use thereof. The preparation method comprises the following steps: cleaning and polishing a metal sheet; immersing the polished metal sheet as an anode in an electrolyte solution to construct an electrochemical system and carrying out an anodic oxidation reaction to obtain a microporous template having a nanotube structure; immersing the microporous template into a metal salt sol for impregnation; taking out the impregnated microporous template, rinsing the surface of the impregnated microporous template with deionized water, then drying the impregnated microporous template, and calcining the impregnated microporous template at a high temperature to convert the metal salt sol into a metal oxide; and dissolving the microporous template with a dissolution solution to obtain the metal oxide nanotube array structure catalyst.

Description

Metal oxide nanotube array structure catalyst and preparation method and application thereof

[0001] TECHNICAL FIELD

[0002] The present application relates to the field of biomass catalysis technology, and particularly relates to a metal oxide nanotube array structure catalyst and a preparation method and application thereof.

[0003] BACKGROUND

[0004] 5-hydroxymethylfurfural (HMF) is a biomass-derived platform molecule that can be obtained by catalytic conversion of biomass such as lignocellulose, pulp waste, and agricultural waste. This renewable production method makes HMF a sustainable energy source, which is expected to replace traditional petroleum-based materials, help reduce dependence on non-renewable resources, and reduce greenhouse gas emissions, which has a positive effect on combating climate change. At the same time, HMF is an important chemical intermediate that can be used to produce various high-value chemicals and high-performance polymer materials, such as 2,5-dimethylfuranone (DMF), dimethylol furanone (HDO), furan alcohol, and polymeric materials such as polyesters and polyethers.

[0005] Currently, the electrocatalytic method for oxidizing HMF is a research hotspot in the field, and a large number of studies have been conducted on catalysts for the oxidation of HMF to FDCA. The improvement of catalyst materials and structure is the key to improving the catalytic performance. The catalyst is prepared into a nanotube array structure, which has a high specific surface area and helps to improve the catalytic activity. More active sites are available for biomass adsorption and catalytic oxidation reaction, which can promote the key steps in the catalytic reaction and improve the selectivity and efficiency of the catalytic reaction. However, the existing nanotube array structure catalyst material preparation technology faces some problems and challenges, mainly that the main active elements such as cobalt and nickel for catalyzing HMF oxidation are difficult to directly form nanotube arrays, and the utilization rate of active substances is low, which requires the help of a nanoframe structure (such as an anodic aluminum oxide AAO) to form. The anodic aluminum oxide template has very low conductivity, and its rigid structure has low strength, which can cause the catalyst to fall off and dissolve during electrocatalysis, resulting in poor catalytic effect.

[0006] SUMMARY

[0007] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is how to improve the utilization rate, conductivity and stability of the nanotube array structure catalyst.

[0008] To solve the above technical problems, the present application provides a preparation method of a metal oxide nanotube array structure catalyst, comprising the following steps:

[0009] S1, cleaning and polishing a metal sheet;

[0010] S2. Using a polished metal sheet as the anode, an electrochemical system is constructed by immersing it in an electrolyte. The anodic oxidation reaction yields a microporous template with a nanotube structure.

[0011] S3. Immerse the microporous template in the metal salt sol;

[0012] S4. Remove the microporous template after impregnation, rinse the surface with deionized water and dry it, then calcine it at high temperature to convert the metal salt sol into metal oxide.

[0013] S5. Dissolve the microporous template with a dissolving solution to obtain a metal oxide nanotube array structure catalyst.

[0014] Furthermore, the metal salt sol is selected from one or more of cobalt salt sol, iron salt sol, nickel salt sol, and copper salt sol.

[0015] Furthermore, in step S3, the impregnation method is to first sonicate for 10-30 minutes, and then let it stand for 12-24 hours.

[0016] Furthermore, in step S4, the high-temperature calcination conditions are as follows: the temperature is increased to 300-500°C in a muffle furnace at a rate of 50-150°C / h, held at the temperature for 4-8 hours, and then cooled to room temperature.

[0017] Furthermore, the metal sheet is aluminum foil or copper foil.

[0018] Furthermore, the electrolyte is a mixed solution of acetic acid and oxalic acid.

[0019] Furthermore, the solution is potassium hydroxide or sodium hydroxide.

[0020] Further, step S5 specifically involves attaching the microporous template after high-temperature calcination to the substrate, immersing the substrate in a dissolving solution to dissolve the microporous template, and obtaining an open hollow metal oxide nanotube array structure catalyst.

[0021] This invention first uses electrolysis to create pores on a metal sheet, then anodizes it to obtain a microporous template with a uniform and dense nanotube structure. Next, the microporous template is immersed in a metal salt sol, and the metal salt in the micropores is calcined into oxides using a muffle furnace. Finally, the microporous template is dissolved and removed to obtain a metal oxide catalyst with a hollow nanotube array.

[0022] A second aspect of this invention provides a metal oxide nanotube array structure catalyst, prepared using the method described above. This catalyst effectively constructs a three-dimensional porous structure with high specific surface area and abundant active sites. The material composition is metal oxide, exhibiting excellent conductivity and structural strength, which is beneficial for improving the electrochemical catalytic oxidation activity and stability.

[0023] The third aspect of the present application provides an application of a metal oxide nanotube array structure catalyst, the metal oxide nanotube array structure catalyst is used as an anode of an electrolytic system for electrocatalytic oxidation of 5-hydroxymethylfurfural; or, as a cathode, for hydrogen evolution of electrolytic water. The catalyst of the present application exhibits excellent HMF electrocatalytic performance, the hollow nanotube array structure makes the catalyst have a large specific surface area, improves the diffusion speed of ion migration, and improves the performance of electrochemical catalytic oxidation.

[0024] In summary, compared with the prior art, the present application has the following beneficial effects:

[0025] (1) The present application develops a simple and effective method for preparing a metal oxide nanotube array structure catalyst, which can improve the specific surface area of the catalyst, overcome the problem of low conductivity of existing nanotube catalyst materials, and improve the stability, which has important promoting significance for the development of HMF catalytic oxidation.

[0026] (2) The present application prepares the catalyst into a nanotube array structure, which helps to improve the catalytic activity due to the high specific surface area, and more active sites can improve the selectivity and efficiency of the catalyst.

[0027] (3) The preparation method of the present application is simple, can effectively construct a three-dimensional porous electrode structure, and can control the morphology and size of the array to adapt to specific reaction conditions and requirements.

[0028] BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a cross-sectional morphology diagram of the microporous template prepared in Example 1 of the present application.

[0030] Figure 2 is a surface morphology diagram of the microporous template prepared in Example 1 of the present application.

[0031] Figure 3 is a cross-sectional morphology diagram one of the cobalt tetraoxide nanotube array structure catalyst prepared in Example 1 of the present application.

[0032] Figure 4 is a cross-sectional morphology diagram two of the cobalt tetraoxide nanotube array structure catalyst prepared in Example 1 of the present application.

[0033] Figure 5 is a surface morphology diagram of the cobalt tetraoxide nanotube array structure catalyst prepared in Example 1 of the present application.

[0034] Figure 6 is an electrochemical performance diagram of the cobalt tetraoxide nanotube array structure catalyst of Example 1 of the present application.

[0035] Figure 7 is an electrochemical performance diagram of the cobalt tetraoxide nanotube array structure catalyst of Example 2 of the present application.

[0036] Figure 8 is an electrochemical performance diagram of the titanium catalyst of Comparative Example 1 of the present application.

[0037] Figure 9 is an electrochemical performance chart of a three cobalt tetraoxide nanotube array structure catalyst of the present application comparative example 2 which retains AAO.

[0038] DETAILED DESCRIPTION

[0039] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0040] It should be understood that the terms described in the present application are only for describing the specific embodiments and are not intended to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or stated range and any other stated value or intermediate value within the stated range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0041] Many modifications and variations of the specific embodiments of the present application described in the specification can be made without departing from the scope or spirit of the present application, which will be apparent to those skilled in the art. Other embodiments derived from the specification of the present application will be apparent to those skilled in the art. The specification and examples of the present application are only exemplary.

[0042] The specific embodiments of the present application provide a metal oxide nanotube array structure catalyst, which has a material composition of metal oxide, good electrical conductivity and structural strength, and the catalyst has a nanotube array structure, high specific surface area and abundant active sites, and exhibits excellent HMF electrocatalytic performance and stability.

[0043] The metal oxide nanotube array structure catalyst is prepared through electrolysis, immersion, calcination and dissolution steps, and the specific preparation process is as follows:

[0044] S1, clean and polish the metal sheet. The metal sheet is aluminum foil or copper foil, which is ultrasonically cleaned in an ethanol and deionized water environment, and then electrochemically polished with a mixed solution of perchloric acid and ethanol as polishing liquid to improve the flatness and smoothness of the metal sheet.

[0045] S2, immerse the polished metal sheet as anode into an electrolyte to construct an electrochemical system and perform electrochemical reaction. The cathode in the electrochemical system is another metal sheet, and the electrolyte is a mixed solution of acetic acid and oxalic acid. The anodic oxidation reaction obtains a microporous template with a dense nanotube structure.

[0046] S3, configure a metal salt sol, which can be selected from a cobalt salt sol, an iron salt sol, a nickel salt sol, a copper salt sol, etc. The microporous template is immersed in the metal salt sol for impregnation, and the impregnation mode is to first ultrasonic for 10-30 min, and then stand for 12-24 h, so that the metal salt sol enters the pores of the microporous template.

[0047] S4, the microporous template after impregnation is taken out, washed with deionized water, and then dried and calcined at high temperature to convert the metal salt sol into a metal oxide. The high-temperature calcination condition is to heat to 300-500 ℃ at a rate of 50-150 ℃ / h in a muffle furnace, keep the temperature constant for 4-8 h, and then cool to room temperature.

[0048] S5, the microporous template is dissolved away with a dissolving solution, which is an alkali solution such as potassium hydroxide, sodium hydroxide, etc. The specific method is to paste the microporous template after high-temperature calcination on a substrate, and immerse the whole substrate in the dissolving solution, so that the microporous template can be dissolved away, and an open hollow metal oxide nanotube array structure catalyst is obtained.

[0049] The metal oxide nanotube array structure catalyst prepared by the above method has a large specific surface area, improves the diffusion speed of ion migration, and improves the performance of electrochemical catalytic oxidation, and exhibits excellent HMF electrocatalytic performance. When used for electrocatalysis, the catalyst is used as an anode of an electrolytic system, and the typical reaction condition is: current 5-30 mA, and reactant concentration 1-100 mM. The metal oxide nanotube array structure catalyst can also be used as a cathode for hydrogen evolution from water electrolysis.

[0050] The technical effects of the present application are described below in combination with specific examples. Unless otherwise specified, the raw materials in the examples of the present application are purchased through commercial channels.

[0051] Example 1

[0052] (1) Aluminum foil pretreatment: cut the aluminum foil into 15 mm*30 mm, and ultrasonic clean in ethanol and deionized water environment for 10 min respectively; take the aluminum foil as an anode, and configure a polishing solution with a volume ratio of perchloric acid to ethanol of 4:1, and perform electrochemical polishing at a voltage of 30 V.

[0053] (2) Oxidation to prepare a porous aluminum oxide film (AAO): take the polished aluminum foil as an anode, and take a tantalum sheet as a cathode, immerse into an electrolyte with a volume ratio of V 乙酸 :V 0.3M 草酸 =1:2 in a salt ice water environment, and perform electrochemical oxidation to obtain a microporous template with a dense nanotube structure, and the cross-sectional and surface morphological characteristics are shown in FIG. 1 and FIG. 2.

[0054] (3) Preparation of cobalt oxalate sol: 14.5 g of polyethylene glycol was weighed as a surfactant and added to 30 ml of 0.2 mol / L cobalt oxalate solution, and 0.1 mol / L NaOH solution was added dropwise until the ink green sol state.

[0055] (4) Microporous template immersion: the microporous template with a dense nanotube structure was immersed into the cobalt oxalate sol, and after ultrasonic treatment for 15 min, it was placed for 24 h.

[0056] (5) High-temperature calcination: the microporous template after immersion was taken out, the gel attached to the surface was washed with deionized water, and then dried, and then heated to 400°C at a rate of 100°C / h in a muffle furnace, kept at a constant temperature for 6 h, and then slowly cooled to room temperature, and the cobalt oxalate was converted into cobalt trioxide.

[0057] (6) Microporous template dissolution: an adhesive was prepared by mixing ethanol and 5% Nafion solution, and the microporous template after calcination was pasted on a titanium plate and dried at 60°C for 30 min. A 1 mol / L KOH solution was prepared, and the titanium plate with the microporous template was immersed in the KOH solution to dissolve the aluminum oxide film, and an open cobalt trioxide nanotube array structure catalyst was obtained on the titanium plate. The cross-sectional micro-morphology of the array is shown in Figures 3 and 4, and the surface micro-morphology characteristics are shown in Figure 5.

[0058] The catalyst prepared in this example was cut to the required electrode size (5*30mm), and its electrochemical performance was tested by adding 10mM, 50mM, and 100mM HMF in 1 mol / L KOH electrolyte environment, and the results are shown in Figure 6, which showed good conductivity and electrocatalytic performance.

[0059] Example 2

[0060] The difference between this example and Example 1 is that the metal salt sol is iron sol, the immersion method is first ultrasonic treatment for 20 min and then standing for 18 h, and the high-temperature calcination condition is heating to 500°C at a rate of 50°C / h in a muffle furnace, keeping at a constant temperature for 4 h, and then cooling to room temperature, to prepare a three-iron oxide nanotube array structure catalyst. Its electrochemical performance was tested by adding 10mM, 50mM, and 100mM HMF in 1 mol / L KOH electrolyte environment, and the results are shown in Figure 7, which showed a slight decrease in conductivity and electrocatalytic performance compared to Example 1.

[0061] Example 3

[0062] The difference between this example and Example 1 is that the metal salt sol is nickel sol, the immersion method is first ultrasonic treatment for 10 min and then standing for 20 h, and the high-temperature calcination condition is heating to 300°C at a rate of 100°C / h in a muffle furnace, keeping at a constant temperature for 8 h, and then cooling to room temperature, to prepare a nickel oxide nanotube array structure catalyst. Its electrochemical performance was tested, which showed a slight decrease compared to Example 1.

[0063] Example 4

[0064] The difference between this example and Example 1 is that the metal salt sol is copper sol, the dipping method is first ultrasonic for 30 min, then standing for 12 h, and the high-temperature calcination condition is heating to 450℃ at 150℃ / h in a muffle furnace, standing for 6 h, and then cooling to room temperature. The copper oxide nanotube array structure catalyst is prepared, and its electrochemical performance is tested. The electrochemical performance is obviously decreased compared with Example 1, but is better than that of Example 2.

[0065] Example 5

[0066] The difference between this example and Example 1 is that the metal sheet is copper foil, and other process steps are the same as those of Example 1. The cobalt tetroxide nanotube array structure catalyst is prepared, and its electrochemical performance is tested. The electrochemical performance is basically the same as that of Example 1.

[0067] Example 6

[0068] The difference between this example and Example 1 is that the metal sheet is copper foil, and the metal salt sol is nickel sol. The dipping method is first ultrasonic for 10 min, then standing for 20 h, and the high-temperature calcination condition is heating to 300℃ at 100℃ / h in a muffle furnace, standing for 8 h, and then cooling to room temperature. The nickel oxide nanotube array structure catalyst is prepared, and its electrochemical performance is tested. The electrochemical performance is basically the same as that of Example 3.

[0069] Comparative Example 1

[0070] Titanium plate is used as a comparative example, and the titanium plate is cut to the required electrode size (5*30 mm). In the 1 mol / L KOH electrolyte environment, 10 mM, 50 mM and 100 mM HMF are added in batches, and the electrochemical performance is tested. The results are shown in FIG. 8, and the electrochemical performance is poor.

[0071] Comparative Example 2

[0072] The metal oxide Co nanotube array structure retaining AAO is used as a comparative example, and the difference from Example 1 is that 0.1M Na2SO4 electrolyte is configured in step (6), which will not dissolve the aluminum oxide film. The cobalt tetroxide nanotube array structure catalyst retaining AAO is catalyzed in different concentrations of HMF, and the results are shown in FIG. 9. Due to its extremely low conductivity, the electrochemical performance is very poor.

[0073] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited to this. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present disclosure.

Claims

1. A method for preparing a catalyst with a metal oxide nanotube array structure, characterized in that, Includes the following steps: S1. Clean and polish the metal sheet; S2. Using a polished metal sheet as the anode, an electrochemical system is constructed by immersing it in an electrolyte. The anodic oxidation reaction yields a microporous template with a nanotube structure. S3. Immerse the microporous template in the metal salt sol; S4. Remove the microporous template after impregnation, rinse the surface with deionized water and dry it, then calcine it at high temperature to convert the metal salt sol into metal oxide. S5. Dissolve the microporous template with a dissolving solution to obtain a metal oxide nanotube array structure catalyst.

2. The method for preparing the metal oxide nanotube array structure catalyst according to claim 1, characterized in that, The metal salt sol is selected from one or more of cobalt salt sol, iron salt sol, nickel salt sol, and copper salt sol.

3. The method for preparing the metal oxide nanotube array structure catalyst according to claim 1, characterized in that, In step S3, the impregnation method is to first sonicate for 10-30 minutes, and then let it stand for 12-24 hours.

4. The method for preparing the metal oxide nanotube array structure catalyst according to claim 1, characterized in that, In step S4, the high-temperature calcination conditions are as follows: the temperature is raised to 300-500°C in a muffle furnace at a rate of 50-150°C / h, held at the temperature for 4-8 hours, and then cooled to room temperature.

5. The method for preparing the metal oxide nanotube array structure catalyst according to claim 1, characterized in that, The metal sheet is aluminum foil or copper foil.

6. The method for preparing the metal oxide nanotube array structure catalyst according to claim 1, characterized in that, The electrolyte is a mixed solution of acetic acid and oxalic acid.

7. The method for preparing the metal oxide nanotube array structure catalyst according to claim 1, characterized in that, The solution is potassium hydroxide or sodium hydroxide.

8. The method for preparing the metal oxide nanotube array structure catalyst according to any one of claims 1-7, characterized in that, Specifically, step S5 involves attaching a microporous template, which has been calcined at high temperature, to a substrate, immersing the substrate in a dissolving solution to dissolve the microporous template, and obtaining an open hollow metal oxide nanotube array structure catalyst.

9. A catalyst with a metal oxide nanotube array structure, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of a metal oxide nanotube array structure catalyst as described in claim 9, characterized in that, The aforementioned metal oxide nanotube array structure catalyst was used as the anode in an electrolysis system for the electrocatalytic oxidation of 5-hydroxymethylfurfural. Alternatively, it can be used as a cathode for hydrogen evolution through water electrolysis.

Images