A metal-CNTs-TiO2 composite material and its preparation method

Abstract

This invention relates to the field of air purification materials technology, and provides a metal-CNTs-TiO2 composite material. This material has a special structure in which TiO2 is deposited inside carbon nanotubes, and noble metals are deposited on the surface of carbon nanotubes. This structure has the advantage of high catalytic efficiency in the catalytic decomposition of harmful substances such as formaldehyde in the air. This invention also provides a method for preparing the metal-CNTs-TiO2 composite material, which is simple, easy to industrialize, and can obtain the metal-CNTs-TiO2 composite material described in this invention.

Description

Technical Field

[0001] This invention relates to the field of air purification materials technology, specifically to a metal-CNTs-TiO2 composite material and its preparation method. Background Technology

[0002] With the progress of civilization, major problems such as environmental pollution and ecological damage have emerged, threatening the future survival and development of all humankind. Environmental pollution is one of the most pressing concerns for humanity this century. As awareness of indoor environmental protection continues to grow, people urgently desire a safe, comfortable, and healthy living space. However, a significant number of residences and office buildings, after haphazard renovations and decorations or due to neglect of environmental hygiene management during construction, are now severely polluted indoors.

[0003] In the field of air purification, photocatalysis is currently a popular method for decomposition. Photocatalysts (titanium dioxide) absorb light energy under specific lighting conditions, generating electron-hole pairs. These pairs react with adsorbed OH-, H2O, O2, etc., on their surface to produce free radicals. These free radicals can react with organic matter adsorbed on their surface, degrading the organic matter into environmentally friendly water and carbon dioxide. Therefore, photocatalysis can be used to degrade organic pollutants in the air. However, existing photocatalyst products have the following drawbacks:

[0004] ① Light source and illumination requirements: Photocatalysts require sufficient natural or artificial light to function, which means that in indoor environments with insufficient lighting, photocatalysts may not be able to achieve the best results.

[0005] ②Technical limitations: TiO2 photocatalysts have low utilization rates for visible light and usually need to be used in conjunction with ultraviolet light, which limits the application of photocatalysts in environments without ultraviolet light sources. Summary of the Invention

[0006] This invention provides a metal-CNTs-TiO2 composite material with a unique structure in which TiO2 is deposited inside carbon nanotubes and noble metals are deposited on the surface of the carbon nanotubes. This structure exhibits high catalytic efficiency in the catalytic decomposition of harmful substances such as formaldehyde in the air. This invention also provides a method for preparing the metal-CNTs-TiO2 composite material, which is simple, easy to industrialize, and yields the composite material described herein.

[0007] On one hand, the present invention provides a metal-CNTs-TiO2 composite material, which is composed of carbon nanotubes, TiO2 and noble metals, characterized in that TiO2 is deposited inside the carbon nanotubes and noble metals are deposited on the surface of the carbon nanotubes.

[0008] In some embodiments, the outer diameter of the carbon nanotubes is 20-80 nm.

[0009] In some embodiments, the outer diameter of the carbon nanotubes is 20-40 nm or 30-80 nm.

[0010] In some embodiments, the precious metal is selected from Au, Ag, Pt, Pd, Rh, or Ir.

[0011] In some embodiments, the precious metal is selected from Au.

[0012] In some embodiments, TiO2 is a crystal with a particle size of 10-30 nm.

[0013] In some embodiments, the mass ratio of precious metals, CNTs, and TiO2 is (1-2):1:(5-8).

[0014] On the other hand, the present invention provides a method for preparing a metal-CNTs-TiO2 composite material, characterized in that it includes:

[0015] 1) Preparation of CNTs-TiO2, including:

[0016] 1.1) Preparation of TiO2 precursor solution: The titanium source is dissolved in the first solvent to obtain a solution, and the molar ratio of titanium source to first solvent is 1:(3~20);

[0017] 1.2) Hydrothermal reaction: CNTs powder is mixed with TiO2 precursor solution at a mass ratio of 1:(25-50). The mixture is then reacted in a sealed environment at a temperature of 120-200℃ and a pressure of 2-5 atm for 1-5 hours to obtain CNTs-TiO2.

[0018] 2) Noble metal deposition: Mix a noble metal salt solution with CNTs-TiO2, add a reducing agent to deposit the metal on the surface of CNTs-TiO2, and obtain a metal-CNTs-TiO2 composite material.

[0019] The first solvent is added to dissolve the titanium source. In order to better deposit the titanium source in the carbon nanotubes, the first solvent can be a solvent that can dissolve the titanium source. The selection of the first solvent is based on the selection of the titanium source itself and the properties of the carbon nanotubes. Specifically, it can be a hydrophilic solvent, preferably alcohol or water, or a mixture thereof, such as methanol, ethanol, water, a mixture of methanol and water, or a mixture of ethanol and water.

[0020] In some embodiments, the preparation of CNTs-TiO2 further includes carbon nanotube (CNT) pretreatment, in which the carbon nanotubes are dispersed in a second solution and then dried to obtain carbon nanotube (CNT) powder.

[0021] In some embodiments, the purpose of carbon nanotube (CNT) pretreatment is to enable the carbon nanotubes to be better dispersed for subsequent reactions. Therefore, a solvent is used, preferably a solvent that can disperse carbon nanotubes, such as a hydrophilic solvent, preferably an alcohol or water, or a mixture thereof, such as methanol, ethanol, water, a mixture of methanol and water, or a mixture of ethanol and water.

[0022] The primary solvent is to dissolve and disperse the titanium source so that it can be deposited in CNTs subsequently. Generally, a molar ratio of titanium source to primary solvent of 1:(3-20) is sufficient, and specific ratios such as 1:5, 1:10, 1:15, or 1:20 can be used.

[0023] The mass ratio of CNTs powder to TiO2 precursor solution is 1:(5-10), specifically 1:5, 1:6:1:7, 1:8, 1:9 or 1:10.

[0024] In some embodiments, the preparation of CNTs-TiO2, after the hydrothermal reaction, further includes heat treatment of CNTs-TiO2 in an inert gas at a temperature of 800–1000 °C for a time of 20–60 min.

[0025] The inert gas can be a conventional gas that has no effect on the reaction, such as nitrogen or helium.

[0026] In some embodiments, during the preparation of CNTs-TiO2, the pH of the TiO2 precursor solution is adjusted to 1-3.

[0027] pH can be adjusted using conventional pH adjusters that do not affect the reaction, such as sulfuric acid or acetic acid.

[0028] In the preferred embodiment, pH adjustment can control the nucleation and growth of TiO2.

[0029] In some embodiments, the titanium source is selected from one or more of tetrabutyl titanate (Ti(OC4H9)4), tetraisopropyl titanate (Ti(OiPr)4), isopropyl titanate, isopropoxy titanium, and titanium tetrachloride.

[0030] In some embodiments, the noble metal salt is selected from chloroaurate.

[0031] In some embodiments, the reducing agent is selected from sodium citrate, sodium borohydride, ascorbic acid, sodium bisulfite, hydrazine hydrate, or combinations thereof.

[0032] The amount of reducing agent used in this invention is related to the type of precious metal salt, the amount added, and the type of reducing agent itself. There are no special requirements for the amount used; conventional amounts used in the field are sufficient.

[0033] In some embodiments, the first solution or the second solvent is selected from: alcohol solvents (e.g., methanol, ethanol or isopropanol), water, or mixtures thereof.

[0034] Preferably, ultrapure water is used.

[0035] Beneficial effects

[0036] (1) Carbon nanotube doping can improve the absorption rate of TiO2 for visible light, expand the photoresponse range, accelerate electron transport, reduce carrier recombination, and improve catalytic efficiency. The in-situ synthesis of nano-titanium dioxide was used to control the nucleation and outward growth of nano-titanium dioxide inside carbon nanotubes, forming a short rod structure with carbon nanotubes as the matrix and titanium dioxide epitaxially. This structure can reflect incident light multiple times, thereby increasing the absorption range of light wavelength and improving photocatalytic efficiency.

[0037] (2) Surface deposition of gold particles reduces the band gap of TiO2, increases its response wavelength, and improves light utilization. A combined structure of TiO2 and noble metal is formed on the surface of TiO2, which effectively reduces the binding rate of holes and electrons and significantly enhances the catalytic efficiency of nano-TiO2 in photocatalytic reactions.

[0038] (3) Controlling the crystallinity and size of the material grains reduces the number of recombination centers inside the catalytic material. When the grain size is smaller than the diffusion length of electrons or holes, the number of charge carriers increases and the number of recombination centers decreases, which greatly improves the migration efficiency of the material and thus enhances the photocatalytic efficiency.

[0039] Terminology Explanation

[0040] Certain embodiments of the present invention will now be described in detail. The present invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials described herein can be used to practice the present invention. The present invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0041] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0042] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0044] In the following content, all figures disclosed herein, whether or not they use words such as "approximately" or "about," are approximate values. The value of each figure may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%, etc. Whenever a figure with a value of N is disclosed, any figure with a value of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction. Attached Figure Description

[0045] Figure 1 The structure diagram of the photocatalyst prepared in Example 1 is shown.

[0046] Figure 2 The structure diagram of the photocatalyst prepared in Example 2 is shown.

[0047] Figure 3 The structure diagram of the photocatalyst prepared in Example 3 is shown.

[0048] Figure 4 The structure diagram of the photocatalyst prepared for Comparative Example 1 is shown.

[0049] Figure 5 This is an example of a system for testing the decomposition of harmful gases. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0051] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0052] Example 1

[0053] S1: Preparation of CNTs-TiO2:

[0054] (1) Carbon nanotubes (CNTs) (outer diameter 20-40 nm) and a mixture of ultrapure water and ethanol were added to the reactor, dispersed by ultrasonication, filtered by vacuum filtration, and then dried in an oven at 80-100℃ for later use. The mass fraction ratio of CNTs to the mixture was 1:50; the mass fraction ratio of water to ethanol was 3:7.

[0055] (2) TiO2 precursor solution: Tetrabutyl titanate (Ti(OC4H9)4), an organic compound of titanium, is used as the titanium source and dissolved in an appropriate ethanol solvent. The molar ratio of titanium source to ethanol is 1:(3~20), and in this example it is 1:10.

[0056] (3) Adjust the pH of the TiO2 precursor solution: Add acetic acid to adjust the pH of the solution to ≈2, which facilitates the control of TiO2 nucleation and growth.

[0057] (4) Hydrothermal reaction: The CNTs powder (1) and the TiO2 precursor solution (3) were placed in a high-pressure reactor, and the temperature was set to 160℃ and the pressure to 3 atm (atmospheric pressure). The reaction was carried out in a closed environment. The reaction time was about 2 hours. The mass ratio of the CNTs powder (1) to the TiO2 precursor solution (3) was 1:35.

[0058] (5) Cooling and separation: After the reaction is complete, the autoclave is cooled to room temperature, then the autoclave is opened and filtered to obtain the carbon nanotube product with deposited titanium dioxide.

[0059] (6) Washing, drying, and calcination: The product was washed with ethanol solvent to remove residual reactants and byproducts, then filtered, dried, and heat-treated at 900℃ for 30 min under a nitrogen atmosphere to improve the crystallinity of CNTs-TiO2. Dry CNTs-TiO2 nanopowder A was obtained.

[0060] S2: Preparation of Au-CNTs-TiO2:

[0061] A solvent, water was used here, was added to the reactor. 1g of CNTs-TiO2 nanopowder A prepared in S1 was added and dispersed thoroughly. 15g of a 2% diluted chloroaurate solution was added and stirred until homogeneous. Finally, 0.2g of sodium citrate and 0.3g of sodium borate were added, and the mixture was stirred at room temperature. After gold particles were deposited on the surface of the CNTs-TiO2 nanopowder, the mixture was filtered, and the filtered solid was dried to obtain Au-CNTs-TiO2 photocatalyst A. The structure is as follows... Figure 1 TiO2 is deposited inside the carbon nanotubes, while Au is deposited on the outside of the carbon nanotubes.

[0062] Example 2

[0063] S1: Preparation of CNTs-TiO2:

[0064] (1) Carbon nanotubes (CNTs) (outer diameter 30-80 nm) and a mixture of ultrapure water and ethanol were added separately to a reactor, ultrasonically dispersed, and then dried in an oven at 80-100℃ for later use. The mass fraction ratio of CNTs to the mixture was 1:50; the mass fraction ratio of water to ethanol was 3:7.

[0065] (2) TiO2 precursor solution: Tetrabutyl titanate (Ti(OC4H9)4), an organic compound of titanium, is used as the titanium source and dissolved in an appropriate ethanol solvent. The molar ratio of titanium source to ethanol is 1:(3~20), and in this example it is 1:10.

[0066] (3) Adjust the pH of the TiO2 precursor solution: Add acetic acid to adjust the pH of the solution to ≈2, which facilitates the control of TiO2 nucleation and growth.

[0067] (4) Hydrothermal reaction: The CNTs powder (1) and the TiO2 precursor solution (3) were placed in a high-pressure reactor, and the temperature was set to 160℃ and the pressure to 3 atm (atmospheric pressure). The reaction was carried out in a closed environment. The reaction time was about 2 hours. The mass ratio of the CNTs powder (1) to the TiO2 precursor solution (3) was 1:35.

[0068] (5) Cooling and separation: After the reaction is complete, the autoclave is cooled to room temperature, then the autoclave is opened and filtered to obtain the carbon nanotube product with deposited titanium dioxide.

[0069] (6) Washing, drying, and calcination: The product was washed with ethanol solvent to remove residual reactants and byproducts, then filtered, dried, and heat-treated at 900℃ for 30 min under a nitrogen atmosphere to improve the crystallinity of CNTs-TiO2. Dry CNTs-TiO2 nanopowder B was obtained.

[0070] S2: Preparation of Au-CNTs-TiO2:

[0071] Water was added to the reactor, followed by 1g of CNTs-TiO2 nanoparticles B prepared in S1, and the mixture was thoroughly dispersed. 15g of a 2% diluted chloroaurate solution was added and stirred until homogeneous. Finally, 0.2g of sodium citrate and 0.3g of sodium borate were added, and the mixture was stirred at room temperature. After gold particles were deposited on the surface of the CNTs-TiO2 nanoparticles, the mixture was filtered and dried to obtain Au-CNTs-TiO2 photocatalyst B. The structure is as follows... Figure 2 TiO2 is deposited inside the carbon nanotubes, while Au is deposited on the outside of the carbon nanotubes.

[0072] Example 3

[0073] S1: Preparation of CNTs-TiO2:

[0074] (1) Carbon nanotubes (CNTs) (outer diameter 20-40 nm) and a mixture of ultrapure water and ethanol were added separately to a reactor, ultrasonically dispersed, and then dried in an oven at 80-100℃ for later use. The mass fraction ratio of CNTs to the mixture was 1:50; the mass fraction ratio of water to ethanol was 3:7.

[0075] (2) TiO2 precursor solution: Tetrabutyl titanate (Ti(OC4H9)4), an organic compound of titanium, is used as the titanium source and dissolved in an appropriate ethanol solvent. The molar ratio of titanium source to ethanol is 1:(3~20), and in this example it is 1:10.

[0076] (3) Adjust the pH of the TiO2 precursor solution: Add acetic acid to adjust the pH of the solution to ≈2, which facilitates the control of TiO2 nucleation and growth.

[0077] (4) Hydrothermal reaction: The CNTs powder (1) and the TiO2 precursor solution (3) were placed in a high-pressure reactor, and the temperature was set to 160℃ and the pressure to 3 atm (atmospheric pressure). The reaction was carried out in a closed environment. The reaction time was about 1 hour. The mass ratio of the CNTs powder (1) to the TiO2 precursor solution (3) was 1:35.

[0078] (5) Cooling and separation: After the reaction is complete, the autoclave is cooled to room temperature, then the autoclave is opened and filtered to obtain the carbon nanotube product with deposited titanium dioxide.

[0079] (6) Washing, drying, and calcination: The product was washed with ethanol solvent to remove residual reactants and byproducts, then filtered, dried, and heat-treated at 900℃ for 30 min under a nitrogen atmosphere to improve the crystallinity of CNTs-TiO2. Dry CNTs-TiO2 nanopowder C was obtained.

[0080] S2: Preparation of Au-CNTs-TiO2:

[0081] Water was added to the reactor, followed by 1g of CNTs-TiO2 nanopowder C prepared in S1, and the mixture was thoroughly dispersed. 15g of a 2% diluted chloroaurate solution was added and stirred until homogeneous. Finally, 0.2g of sodium citrate and 0.3g of sodium borate were added, and the mixture was stirred at room temperature. After gold particles were deposited on the surface of the CNTs-TiO2 nanopowder, the mixture was filtered and dried to obtain Au-CNTs-TiO2 photocatalyst C. The structure is as follows... Figure 3 TiO2 is deposited inside the carbon nanotubes, while Au is deposited on the outside of the carbon nanotubes.

[0082] Example 4

[0083] S1: Preparation of CNTs-TiO2:

[0084] Dry CNTs-TiO2 nanopowder A was obtained according to Example 1.

[0085] S2: Preparation of platinum-CNTs-TiO2:

[0086] Water was added to a reactor, followed by 1g of CNTs-TiO2 nanopowder A prepared in step S1, and the mixture was thoroughly dispersed. 15g of diluted chloroplatinic acid was added and stirred until homogeneous. Finally, 0.2g of sodium citrate and 0.3g of sodium borate were added, and the mixture was stirred at room temperature. After gold particles were deposited on the surface of the CNTs-TiO2 nanopowder, the mixture was filtered, and the solidified material was dried to obtain platinum-CNTs-TiO2 photocatalyst A1. Electron microscopy revealed that platinum-CNTs-TiO2 photocatalyst A1 possessed the same structure as Au-CNTs-TiO2 photocatalyst A.

[0087] Example 5

[0088] S1: Preparation of CNTs-TiO2:

[0089] (1) TiO2 precursor solution: Tetrabutyl titanate (Ti(OC4H9)4), an organic compound of titanium, is used as the titanium source and dissolved in an appropriate ethanol solvent. The molar ratio of titanium source to ethanol is 1:(3~20), and in this example it is 1:10.

[0090] (2) Hydrothermal reaction: CNT powder and the adjusted TiO2 precursor solution were placed in a high-pressure reactor, and the temperature was set to 160℃ and the pressure to 3 atm (atmospheric pressure). The reaction was carried out in a closed environment. The reaction time was about 2 hours. The mass ratio of (1) CNT powder to (3) adjusted TiO2 precursor solution was 1:35.

[0091] (3) Cooling and separation: After the reaction was completed, the autoclave was cooled to room temperature, and then the autoclave was opened and filtered to obtain the deposited titanium dioxide nanotube product. Electron microscopy showed that TiO2 was deposited inside the carbon nanotubes.

[0092] S2: Preparation of Au-CNTs-TiO2:

[0093] Au-CNTs-TiO2 photocatalyst A2 was prepared according to the S2Au-CNTs-TiO2 preparation method in Example 1. Electron microscopy revealed that Au-CNTs-TiO2 photocatalyst A2 also exhibits TiO2 deposition inside the carbon nanotubes and noble metal deposition on the surface of the carbon nanotubes.

[0094] Comparative Example 1

[0095] S1: Preparation of CNTs-TiO2:

[0096] (1) TiO2 precursor solution: Tetrabutyl titanate (Ti(OC4H9)4), an organic compound of titanium, was used as the titanium source and dissolved in an appropriate ethanol solvent. The molar ratio of titanium source to ethanol was 1:(3~20), and the comparative example was 1:10.

[0097] (2) Adjusting the pH of the TiO2 precursor solution: Adding acetic acid adjusts the pH of the solution to approximately 2, which facilitates the control of TiO2 nucleation and growth.

[0098] (3) Hydrothermal reaction: The TiO2 precursor solution prepared in (2) was placed in a high-pressure reactor, and the temperature was set to 160℃ and the pressure to 3 atm (atmospheric pressure). The reaction was carried out in a closed environment. The reaction time was about 2 hours.

[0099] (4) Carbon nanotubes (CNTs) (outer diameter 20-40 nm) and a mixture of ultrapure water and ethanol are added separately to the reactor, ultrasonically dispersed, and then dried in an oven at 80-100℃ for later use. The mass fraction ratio of CNTs to the mixture is 1:50; the mass fraction ratio of water to ethanol is 3:7.

[0100] (5) Add the dried CNTs powder of (4) to the solution of (3), wherein the mass ratio of CNTs powder to the TiO2 precursor solution adjusted in (2) is 1:35.

[0101] (6) Cooling and separation: After the reaction is complete, cool the autoclave to room temperature, then open the autoclave and take out the product.

[0102] (7) Washing, drying, and calcination: The product was washed with ethanol solvent to remove residual reactants and byproducts, then filtered, dried, and heat-treated at 900℃ for 30 min under a nitrogen atmosphere to improve the crystallinity of CNTs-TiO2. Dry CNTs-TiO2 nanopowder D was obtained.

[0103] S2: Preparation of Au-CNTs-TiO2:

[0104] Water was added to a reactor, followed by 1g of CNTs-TiO2 nanopowder D, which was then fully dispersed. 15g of a 2% diluted chloroaurate solution was added and stirred until homogeneous. Finally, 0.2g of sodium citrate and 0.3g of sodium borate were added, and the mixture was stirred at room temperature until gold particles were deposited on the surface of the CNTs-TiO2 nanopowder. The powder was then dried to obtain Au-CNTs-TiO2 photocatalyst D. The structure is as follows: Figure 4 Both TiO2 and Au are deposited on the outside of the carbon nanotubes.

[0105] Test and verification of photocatalytic decomposition effect

[0106] Test system:

[0107] Such as Figure 5 The test equipment system. Reliability testing of the test equipment system: at 1m... 3 1 μL of toluene, the source of the contaminant, was placed in an opaque container. A circulating fan was turned on to purge the container for 10 minutes to ensure complete evaporation of the toluene. The concentration was then measured using a detection device and found to be 10.2 mg / m³. 3 10mg / m 3 10.10 mg / m 3 This proves that the medicine and container are reliable.

[0108] Test method:

[0109] In 1m 3 Place 1 μL of formaldehyde, the source of pollution, in an opaque container. Use different sample boards and light sources (such as UV lamps or lamps of different color temperatures). Figure 5 The testing system was used, with the circulating fan running for 10 minutes to ensure complete formaldehyde evaporation. A PPM-400ST high-precision formaldehyde analyzer was used to test the concentration, and the data was recorded. Test results using ultraviolet lamps as the light source are shown in Table 1, and test results using fluorescent lamps are shown in Table 2.

[0110] Table 1: Formaldehyde Decomposition Test (Ultraviolet Lamp as Light Source)

[0111]

[0112] Table 2: Formaldehyde Decomposition Test (Fluorescent Lamp as Light Source)

[0113]

[0114] In summary, using a photocatalyst with the structure described in this invention for air purification results in faster and more thorough decomposition of formaldehyde, a harmful substance.

[0115] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A method for preparing a metal-CNTs-TiO2 composite material, characterized in that, include: 1) Preparation of CNTs-TiO2, including: 1.1) Preparation of TiO2 precursor solution: The titanium source is dissolved in the first solvent to obtain a solution, and the molar ratio of titanium source to first solvent is 1:(3~20); 1.2) Hydrothermal reaction: CNTs powder and TiO2 precursor solution are mixed with a mass ratio of CNTs powder to TiO2 precursor solution of 1:(25-50). The mixture is reacted in a closed system at a temperature of 120~200℃ and a pressure of 2-5 atm for 1-5 hours to obtain CNTs-TiO2. 2) Noble metal deposition: A noble metal salt solution is mixed with CNTs-TiO2, and a reducing agent is added to deposit the metal onto the surface of CNTs-TiO2 to obtain a metal-CNTs-TiO2 composite material; The metal-CNTs-TiO2 composite material is composed of carbon nanotubes, TiO2 and noble metals, with TiO2 deposited inside the carbon nanotubes and noble metals deposited on the surface of the carbon nanotubes. The precious metals are selected from Au, Ag, Pt, Pd, Rh, or Ir; In the preparation of CNTs-TiO2, after the hydrothermal reaction, the CNTs-TiO2 is further subjected to heat treatment in an inert gas at a temperature of 800~1000 ℃ for a time of 20-60 min. In the preparation of CNTs-TiO2, the pH of the TiO2 precursor solution is adjusted to 1~3.

2. The preparation method according to claim 1, characterized in that, The outer diameter of carbon nanotubes is 20-80 nm.

3. The preparation method according to claim 1, characterized in that, TiO2 is a crystal with a particle size of 10-30 nm.

4. The preparation method according to any one of claims 1-3, characterized in that, The mass ratio of precious metals, CNTs, and TiO2 is (1~2):1:(5~8).

5. The preparation method according to claim 1, characterized in that, The titanium source is selected from one or more of tetrabutyl titanate, tetraisopropyl titanate, isopropyl titanate, titanium isopropoxy, and titanium tetrachloride. The noble metal salt is selected from: chloroaurate.

6. The preparation method according to claim 1, characterized in that, The reducing agent is selected from sodium citrate, sodium borohydride, ascorbic acid, sodium bisulfite, hydrazine hydrate, or a combination thereof.

7. The preparation method according to claim 1, characterized in that, The first solvent is selected from alcohol solvents, water, or mixtures thereof.

8. The preparation method according to claim 1, characterized in that, The preparation of CNTs-TiO2 also includes carbon nanotube CNTs pretreatment, in which carbon nanotube CNTs are dispersed in a second solvent and then dried to obtain carbon nanotube CNTs powder.

9. The preparation method according to claim 8, characterized in that, The second solvent is selected from: alcohol solvents, water, or mixtures thereof.

10. The preparation method according to any one of claims 7 or 9, characterized in that, The alcohol solvent is methanol, ethanol, or isopropanol.

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