A modified titanium dioxide and its preparation method and application

Abstract

The present invention relates to the technical field of visible light catalytic hydrogen production, and discloses a method for preparing modified titanium dioxide, wherein an organic dye is dissolved in an organic solvent, titanium dioxide is added, and the mixture is heated and refluxed in a nitrogen atmosphere after vacuuming, and the modified titanium dioxide is obtained after washing and drying. The present invention uses a solvent thermal method to sensitize titanium dioxide with an organic dye having visible light absorption to prepare the modified titanium dioxide, and the synthesis process is simple and economical, and the light response range of titanium dioxide is expanded to the visible light range, which greatly improves the rate of photocatalytic water decomposition and hydrogen production of titanium dioxide in the visible light region, and the modified titanium dioxide has strong stability during the photocatalytic cycle.

Description

Technical Field

[0001] The present invention relates to the technical field of visible light catalytic hydrogen production, and in particular to a modified titanium dioxide and a preparation method and application thereof. Background Art

[0002] With the development of the times, the conflict between energy development and environmental protection has become increasingly intensified. In this context, the development of new energy sources with high calorific value and environmental friendliness has become a cutting-edge topic in the international community. Hydrogen is recognized as the greenest energy source because of its high calorific value, water as a combustion product, and no pollution to the environment. Using the abundant light energy in nature to photocatalytically decompose water to produce hydrogen is considered to be the most promising strategy for sustainable energy production, which has put the research on using sunlight to photocatalytically decompose water to produce hydrogen on the international agenda.

[0003] Titanium dioxide is considered the most promising photocatalyst because of its non-toxicity, stable properties, and large-scale industrial production. However, since titanium dioxide can only absorb ultraviolet light with a wavelength less than 317nm, its utilization rate of solar energy is not high. At a time when the conflict between energy utilization and environmental protection is becoming increasingly severe, it is particularly important to prepare titanium dioxide materials that respond to visible light. Summary of the invention

[0004] In view of this, the present invention provides a method for preparing modified titanium dioxide with visible light response, and the prepared modified titanium dioxide can be effectively applied to the research of photocatalytic decomposition of water to produce hydrogen.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing modified titanium dioxide comprises dissolving an organic dye (hereinafter referred to as DT) in an organic solvent, adding titanium dioxide, evacuating the solution, heating and refluxing the solution under a nitrogen atmosphere, washing the solution, and drying the solution to obtain modified titanium dioxide (hereinafter referred to as DT / TiO2).

[0007] The structural formula of the organic dye is as follows:

[0008]

[0009] The above organic dye has an excitation wavelength of 350-400nm and an emission wavelength of 500-650nm. It has the characteristics of being excited by ultraviolet light and short-wave visible light and has strong absorption in the visible light range of 400-570nm, which provides a basis for the sensitization modification of titanium dioxide photocatalyst.

[0010] Preferably, in the above-mentioned method for preparing modified titanium dioxide, the heating reflux reaction is heating reflux at 150-110° C. for 24-72 hours under a protective atmosphere.

[0011] Preferably, in the above-mentioned method for preparing modified titanium dioxide, the mass ratio of the organic dye to titanium dioxide is 1:(10-50).

[0012] Preferably, in the above-mentioned preparation method of modified titanium dioxide, the organic solvent includes at least one of tetrahydrofuran, N,N-dimethylformamide, ethanol, and acetone, and the organic solvent is an ultra-dry solvent;

[0013] And / or the concentration of the organic dye after being dissolved in the organic solvent is 0.5-2.0 g / L.

[0014] Preferably, in the above-mentioned method for preparing modified titanium dioxide, the titanium dioxide is prepared by the following method:

[0015] (1) tetrahydrofuran, acetic acid, water and tetrabutyl titanate are mixed, stirred until gelled and then dried;

[0016] (2) extracting and calcining the material dried in step (1) to obtain titanium dioxide.

[0017] Preferably, in the above-mentioned method for preparing modified titanium dioxide, the drying temperature in step (1) is 40-50° C., and the drying time is 5-10 h.

[0018] Preferably, in the above-mentioned method for preparing modified titanium dioxide, the extraction in step (2) is Soxhlet extraction, and the extraction temperature is 120-150° C., and the extraction time is 24-72 h.

[0019] Preferably, in the above-mentioned method for preparing modified titanium dioxide, the calcination temperature in step (2) is 250-350° C., and the calcination time is 100-150 min;

[0020] And / or the heating rate of the calcination process is 3-1°C / min.

[0021] In addition, the present invention also provides a modified titanium dioxide prepared by any of the above methods.

[0022] And an application of the modified titanium dioxide in a catalyst for photocatalytic water splitting to produce hydrogen.

[0023] The present invention provides a modified titanium dioxide and a preparation method thereof. Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The titanium dioxide material prepared by the calcination method of the present invention has a stable structure and a pure anatase crystal form. The organic dye DT exhibits a wide range and high intensity light absorption performance in the visible light range, and is a good titanium dioxide sensitizer. It can reduce the recombination probability of electron-hole pairs on the titanium dioxide surface, promote the effective transfer of photogenerated charges on the titanium dioxide surface, and effectively improve the visible light catalytic performance of titanium dioxide;

[0025] (2) The present invention uses a solvent thermal method to prepare DT-sensitized modified titanium dioxide DT / TiO2 using an organic dye DT with visible light absorption. The synthesis process is simple and economical. The prepared modified titanium dioxide has a microporous and mesoporous structure and a large specific surface area, providing a reaction site for photocatalytic hydrogen production. It has strong light absorption in the visible light region, successfully expanding the light response range of titanium dioxide to the visible light range, and greatly improving the photocatalytic water decomposition hydrogen production rate of titanium dioxide in the visible light region. The hydrogen production rate in the visible light region with a wavelength ≥400nm is 2146.1μmol·g -1 ·h -1 ;

[0026] (3) The modified titanium dioxide of the present invention has strong stability during the photocatalytic cycle. After loading Pt nanoparticles, its visible light photocatalytic hydrogen production experiment shows excellent hydrogen production performance and outstanding stability, which provides the possibility for the industrial production of DT-sensitized titanium dioxide and lays the foundation for the industrial application of photocatalytic water decomposition to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 UV-vis absorption spectra of organic dyes DT, TiO2 and DT / TiO2;

[0029] Figure 2 This is the field emission scanning electron microscope image of DT / TiO2;

[0030] Figure 3 This is the photocatalytic hydrogen production rate diagram of DT-sensitized titanium dioxide after loading Pt;

[0031] Figure 4 This is a test diagram of the cyclic stability of Pt / TA-TiO2 visible light photocatalytic water decomposition to produce hydrogen. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a method for preparing modified titanium dioxide, comprising the following steps:

[0035] (1) Preparation of titanium dioxide by sol-gel method

[0036] Add 1.0 mL of tetrahydrofuran (THF), 161.0 μL of acetic acid, and 106.0 μL of water to a 20.0 mL sample bottle, stir evenly, then add 1.0 mL of tetrabutyl titanate (TBOT), stir to form a gel, and dry at 45° C. for 1 h; continue to perform Soxhlet extraction at a heating temperature of 140° C. for 41 h, then place in a tubular furnace for calcination, the heating program is 5° C. / min, the calcination temperature is 300° C., and the calcination time is 120 min, to prepare titanium dioxide;

[0037] (2) Solvothermal synthesis of modified titanium dioxide DT / TiO2

[0038] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry DMF, then add 100 mg titanium dioxide, evacuate the mixture and heat under reflux at 160°C for 41 h in a nitrogen atmosphere. After the reaction, wash with DMF, water and methanol and dry to obtain modified titanium dioxide DT / TiO2.

[0039] like Figure 1 The following are the UV spectra of DT, titanium dioxide and DT / TiO2. The results show that TiO2 sensitized by DT has strong light absorption in the visible light region. Figure 2 Shown is the SEM image of DT / TiO2.

[0040] The present invention conducted a photocatalytic water hydrogen production and hydrogen production measurement test, as well as a cyclic hydrogen production stability test on the prepared modified titanium dioxide. The test operation method is as follows:

[0041] 1. Photolysis of water to produce hydrogen and test of hydrogen production

[0042] In a quartz reactor supporting the photocatalytic system, 10.0 mg of modified titanium dioxide material, 4.0 mL of distilled water, 10.0 mL of methanol and 50.0 uL of 10.0 mM tetrachloroplatinic acid aqueous solution were added, the lid was closed, the photocatalytic system was connected, and the airtightness was checked. While stirring, the valve was carefully opened to evacuate the air. Pay attention to controlling the vacuum degree so that the solvent does not boil violently. After evacuating to equilibrium, the evacuation valve was closed, and a xenon lamp (without filter) was used to irradiate for 60.0 min. The vacuum was removed, the lid was opened, 2.0 mL of triethanolamine was added, and the air was evacuated again. The reaction solution was irradiated with a xenon lamp (with filter, cutoff type, λ ≥ 400 nm), and samples were collected every 1 h. The hydrogen production was determined by GC, and the determination was continued for 5 h.

[0043] 2. Continuous Hydrogen Production Test

[0044] The experimental conditions were the same as those for the photolysis of water for hydrogen production and hydrogen production determination test. After each reaction for 5 hours, the illumination was stopped, the catalyst was recovered by centrifugation, the recovered catalyst was washed three times with ethanol, vacuum dried and repeated for the next 5 hours of reaction, and the modified titanium dioxide DT / TiO2 was in situ loaded with 1.0wt% Pt particles, and the hydrogen production performance and stability of the loaded Pt material were tested.

[0045] The above test results show that after the DT modified titanium dioxide material DT / TiO2 with high hydrogen production efficiency is in situ loaded with Pt particles, the hydrogen production rate is as high as 2146.1 μmol·g in 2.0 mL triethanolamine and 11.0 mL water under visible light (λ≥400 nm). -1 ·h -1 ,like Figure 3 Shown is the photocatalytic hydrogen production rate diagram of DT-sensitized titanium dioxide after loading Pt.

[0046] like Figure 4 As shown, this is a test diagram of the cyclic stability of Pt / DT-TiO2 visible light photocatalytic decomposition of water to produce hydrogen. It can be seen from the figure that after 10 cyclic hydrogen production tests, 1.0wt% Pt / DT (5.0wt%) / TiO2 still maintains a high hydrogen production efficiency, indicating that it has strong cyclic hydrogen production stability.

[0047] Example 2

[0048] This embodiment provides a method for preparing modified titanium dioxide, comprising the following steps:

[0049] (1) Preparation of titanium dioxide by sol-gel method

[0050] Add 1.0 mL of tetrahydrofuran (THF), 161.0 μL of acetic acid, and 106.0 μL of water to a 20.0 mL sample bottle, stir evenly, then add 1.0 mL of tetrabutyl titanate (TBOT), stir to form a gel, and dry at 50° C. for 5 h; continue to perform Soxhlet extraction at a heating temperature of 150° C. for 24 h, then place in a tubular furnace for calcination, the heating program is 1° C. / min, the calcination temperature is 350° C., and the calcination time is 100 min, to prepare titanium dioxide;

[0051] (2) Solvothermal synthesis of modified titanium dioxide DT / TiO2

[0052] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry DMF, then add 250 mg titanium dioxide, evacuate the mixture and heat under reflux at 150°C for 72 h in a nitrogen atmosphere. After the reaction, wash with DMF, water and methanol and dry to obtain modified titanium dioxide DT / TiO2.

[0053] Example 3

[0054] This embodiment provides a method for preparing modified titanium dioxide, comprising the following steps:

[0055] (1) Preparation of titanium dioxide by sol-gel method

[0056] Add 1.0 mL of tetrahydrofuran (THF), 161.0 μL of acetic acid, and 106.0 μL of water to a 20.0 mL sample bottle, stir evenly, then add 1.0 mL of tetrabutyl titanate (TBOT), stir to form a gel, and then dry at 40° C. for 10 h; continue to perform Soxhlet extraction at a heating temperature of 120° C. for 72 h, then place in a tubular furnace for calcination, the heating program is 3° C. / min, the calcination temperature is 250° C., and the calcination time is 150 min, to prepare titanium dioxide;

[0057] (2) Solvothermal synthesis of modified titanium dioxide DT / TiO2

[0058] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry tetrahydrofuran, then add 50 mg titanium dioxide and evacuate the mixture, heat and reflux at 110°C under nitrogen atmosphere for 24 hours. After the reaction, wash with DMF, water, and methanol, and dry to obtain modified titanium dioxide DT / TiO2.

[0059] Example 4

[0060] Example 4 is substantially the same as Example 1, except that in step (2):

[0061] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry DMF, then add 100 mg titanium dioxide, evacuate the mixture and heat under reflux at 160°C for 24 hours under a nitrogen atmosphere. After the reaction, wash with DMF, water and methanol and dry to obtain modified titanium dioxide DT / TiO2.

[0062] Example 5

[0063] Example 5 is substantially the same as Example 1, except that in step (2):

[0064] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry DMF, then add 100 mg titanium dioxide, evacuate the mixture and heat under reflux at 160°C for 72 h in a nitrogen atmosphere. After the reaction, wash with DMF, water and methanol and dry to obtain modified titanium dioxide DT / TiO2.

[0065] Comparative Example 1

[0066] Comparative Example 1 is substantially the same as Example 1, except that in step (2):

[0067] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry DMF, then add 100 mg titanium dioxide, evacuate the mixture and heat under reflux at 160°C for 20 h in a nitrogen atmosphere. After the reaction, wash with DMF, water and methanol and dry to obtain modified titanium dioxide DT / TiO2.

[0068] Comparative Example 2

[0069] Comparative Example 2 is substantially the same as Example 1, except that in step (2):

[0070] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry DMF, then add 100 mg titanium dioxide, evacuate the mixture and heat under reflux at 160°C for 75 h in a nitrogen atmosphere. After the reaction, wash with DMF, water and methanol and dry to obtain modified titanium dioxide DT / TiO2.

[0071] Comparative Example 3

[0072] Comparative Example 3 is substantially the same as Example 1, except that in step (2):

[0073] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry DMF, then add 25 mg titanium dioxide and evacuate the mixture, heat and reflux at 160°C under nitrogen atmosphere for 41 hours. After the reaction, wash with DMF, water, and methanol, and dry to obtain modified titanium dioxide DT / TiO2.

[0074] Comparative Example 4

[0075] Comparative Example 4 is substantially the same as Example 1, except that in step (2):

[0076] Take 5.0 mg DT and dissolve it in 5.0 mL ultra-dry DMF, then add 300 mg titanium dioxide, evacuate the mixture and heat under reflux at 160°C for 41 h in a nitrogen atmosphere. After the reaction, wash with DMF, water and methanol and dry to obtain modified titanium dioxide DT / TiO2.

[0077] The modified titanium dioxide prepared in Examples 2-5 and Comparative Examples 1-4 was subjected to a photolysis water hydrogen production and hydrogen production amount determination test, as well as a cyclic hydrogen production stability test. The test results are shown in Table 1:

[0078] Table 1 Test results

[0079] <![CDATA[Hydrogen production rate (μmol·g -1 ·h -1 )]]> Example 1 2146.1 Example 2 141.2 Example 3 1136.2 Example 4 121.3 Example 5 112.2 Comparative Example 1 107.2 Comparative Example 2 172.3 Comparative Example 3 1245.1 Comparative Example 4 553.2

[0080] It can be seen from Table 1 that in the preparation process of modified titanium dioxide, the heating reflux time and the relative addition amounts of organic dye and titanium dioxide have a great influence on the photocatalytic hydrogen production rate of the product. The modified titanium dioxide prepared under strictly controlled reaction conditions has strong stability in the photocatalytic cycle process. After loading Pt nanoparticles, its visible light photocatalytic hydrogen production experiment shows excellent hydrogen production performance.

[0081] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the scheme disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0082] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing modified titanium dioxide, characterized in that: The organic dye is dissolved in an organic solvent, titanium dioxide is added, and the mixture is heated and refluxed in a nitrogen atmosphere after vacuuming, and then washed and dried to obtain modified titanium dioxide. The structural formula of the organic dye is as follows: ； The heating reflux reaction is heating reflux at 150-180° C. for 24-72 hours under nitrogen; The mass ratio of the organic dye to titanium dioxide is 1:(10-50); The organic solvent comprises at least one of tetrahydrofuran, N,N-dimethylformamide, ethanol and acetone, and the organic solvent is an ultra-dry solvent; The concentration of the organic dye after being dissolved in the organic solvent is 0.5-2.0 g / L; The titanium dioxide is prepared by the following method: (1) Mix tetrahydrofuran, acetic acid, water and tetrabutyl titanate, stir until gelled and then dry; (2) extracting and calcining the material dried in step (1) to obtain titanium dioxide; The drying temperature in step (1) is 40-50°C and the drying time is 5-10h; The extraction in step (2) is Soxhlet extraction, and the extraction temperature is 120-150° C. and the extraction time is 24-72 hours; The calcination temperature in step (2) is 250-350°C and the calcination time is 100-150 min; The heating rate of the calcination process is 3-8°C / min.

2. A modified titanium dioxide prepared by the method according to claim 1.

3. Use of the modified titanium dioxide according to claim 2 in a catalyst for producing hydrogen by photolysis of water.

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