CN107540014B - A kind of heterogeneous seed mesoporous monocrystalline rutile titanium dioxide controllable growth preparation method - Google Patents

Abstract

The invention relates to the field of preparation of heterogeneous seed mesoporous metal oxides, in particular to a preparation method for the controllable growth of heterogeneous seed mesoporous single crystal rutile titanium dioxide. This method uses titanium tetrachloride as a precursor and silica spheres containing heterogeneous seeds as a template through a wet chemical process to hydrothermally grow rutile titanium dioxide with specific crystal planes exposed, and etches the template to obtain a medium containing heterogeneous seeds. Porous single-crystal rutile titanium dioxide can realize heterogeneous seed epitaxial growth co-catalyst, which solves the problems of poor contact quality between catalyst and co-catalyst interface and low photocatalytic efficiency. Different from the traditional seed template method, the present invention puts the titanium tetrachloride precursor and the silicon dioxide template containing heterogeneous seeds into the reaction kettle, heats them, and obtains mesoporous single-crystal rutile titanium dioxide with specific crystal faces exposed after etching .

Description

A preparation method for the controllable growth of heterogeneous seed mesoporous single crystal rutile titanium dioxide

technical field

The invention relates to the field of preparation of heterogeneous seed mesoporous metal oxides, in particular to a preparation method for the controllable growth of heterogeneous seed mesoporous single crystal rutile titanium dioxide, which uses ruthenium dioxide (tin dioxide, iridium dioxide) ) heterogeneous seeds, using TiCl ₄ as precursor to hydrothermally grow mesoporous single-crystal rutile TiO ₂ with specific crystal facets.

Background technique

Due to the advantages of high stability, suitable band gap, low cost, and non-toxicity, titanium dioxide has attracted extensive attention and in-depth research as a classic photocatalytic material. In addition to being used in photocatalytic water splitting, titanium dioxide photocatalysts are also widely used in photodegradation, solar cells, photoelectrochemistry, and self-cleaning. Because the photocatalytic reaction is mainly carried out on the surface of semiconductor materials, and a certain amount of co-catalysts can use the separation of photogenerated carriers, it is the focus of research in recent years to study the deposition of co-catalysts on semiconductor materials and find ways to improve their photocatalytic efficiency. In recent years, the deposition of co-catalysts is mainly through heat sinking and optical deposition. The interfacial contact quality of co-catalysts deposited by these two methods is poor, so that the photogenerated carriers cannot be effectively separated and reacted.

Contents of the invention

The purpose of the present invention is to provide a preparation method for the controllable growth of mesoporous single-crystal rutile titanium dioxide with heterogeneous seeds, using the similarity in structure to make RuO ₂ (SnO ₂ , IrO ₂ ) as the nucleation site for TiO ₂ growth in the preparation process It can also be used as a co-catalyst in the photocatalytic reaction. This method can obtain mesoporous single-crystal rutile TiO ₂ with all exposed {111} crystal planes. The shape of the sample basically does not change when the concentration of the seed is changed.

Technical scheme of the present invention is:

A preparation method for the controllable growth of heterogeneous seed mesoporous single-crystal rutile titanium dioxide, using titanium tetrachloride hydrochloric acid solution as a precursor, commercial sodium fluoride as a crystal plane control agent, and selecting rutile-type ruthenium dioxide and Tin or iridium dioxide are used as heterogeneous seeds, the specific process is as follows:

(1) Take ruthenium chloride aqueous solution or iridium chloride aqueous solution as the seed solution, or take the ethanol solution of stannous chloride or the mixed solution of water and ethanol as the seed solution, add silica balls, and prepare the carbon dioxide containing heterogeneous seeds Silicon ball seed template;

(2) Put the precursor, sodium fluoride and silica ball seed template into the reaction kettle, the volume of the precursor is 20ml~60ml, and the mass ratio of sodium fluoride and silica ball seed template is (0.1~1) : (0.5～20), after the reaction kettle is sealed, put it into the oven for heat treatment, take out the reaction sample, wash and dry with deionized water, after etching the template, wash and dry with deionized water and ethanol respectively, to obtain { 111} facet-exposed mesoporous single-crystal rutile titania containing different heterogeneous seeds, which serve as both nucleation sites during preparation and co-catalysts during photocatalytic testing.

The precursor is a commercial chemically pure titanium tetrachloride solution, and the diameter of the silicon dioxide spheres used is 5-250 nanometers.

The material of the reaction kettle is one of stainless steel, aluminum alloy, copper and tantalum, and the inner tank of the reaction kettle is one of polytetrafluoroethylene and high-density polyethylene.

In the described titanium tetrachloride hydrochloric acid solution, the molar concentration of hydrochloric acid is 0.05M-5M, and the molar concentration of titanium tetrachloride is 0.01M-1M; in the described ruthenium chloride aqueous solution or iridium chloride aqueous solution, the The molar concentration of ruthenium or iridium chloride is 0.001mM～0.1M; in the ethanol solution of described stannous chloride or water, ethanol mixed solution, the molar concentration of stannous chloride is 0.001mM～0.1M, ethanol and water The volume ratio is between 0 and 1.

The preparation method of the heterogeneous seed mesoporous single crystal rutile titanium dioxide controllable growth, preferably: in the titanium tetrachloride hydrochloric acid solution, the molar concentration of hydrochloric acid is 1M-5M, and the molar concentration of titanium tetrachloride is 0.01 M～0.1M; in the ruthenium chloride aqueous solution or iridium chloride aqueous solution, the molar concentration of ruthenium chloride or iridium chloride is 0.02mM～10mM; the ethanol solution of the stannous chloride or the mixture of water and ethanol In the solution, the molar concentration of stannous chloride is 1mM-30mM, and the volume ratio of ethanol to water is between 0-1.

When putting into an oven for heat treatment, the heating temperature is 100-300°C, and the heating time is 2h-48h.

When drying after cleaning with deionized water, the drying temperature is 60-100°C.

When etching the template, a NaOH aqueous solution with a molar concentration of 1M-5M is used for etching at a water bath temperature of 60-90° C. for 0.5-2 hours.

According to the preparation method for the controllable growth of mesoporous single crystal rutile titanium dioxide with heterogeneous seeds, the sample grain size of mesoporous single crystal rutile titanium dioxide prepared by heterogeneous seeds with different concentrations is 300nm-900nm, and the pore diameter is between 2 and 50 nanometers , the channel runs through the inside of the sample, and the {111} crystal plane is exposed on the surface.

In the preparation method for the controllable growth of mesoporous single-crystal rutile titanium dioxide in heterogeneous seeds, when preparing the silica ball seed template, the seed solution and the silica ball are kept in a water bath at 60-80°C for 0.5-2 hours, and then deionized water is used to Rinse, dry the silica balls after planting seeds in a heating mantle at 70-90°C, and place them in a muffle furnace at 450-550°C for 20-40 minutes.

Design idea of the present invention is as follows:

For photocatalytic reactions, the specific surface area of the sample represents the number of reactive sites to a certain extent, so it is very important to obtain porous semiconductor materials; and co-catalyst deposition is an important aspect to improve photocatalytic performance. At present, the main deposition method It is thermal deposition and photodeposition, the co-catalyst and catalyst interface contact quality obtained by these two methods is poor, which is not conducive to the separation of carriers. Therefore, mesoporous single _- crystal rutile _{TiO 2} was selected as the synthesis object during the experiment. _In the preparation process, the heterogeneous seed Process for the preparation of mesoporous single-crystal rutile _TiO2 by epitaxial growth. After hydrothermal and etching treatments, mesoporous single crystal samples containing heterogeneous seeds as cocatalysts can be obtained. When RuO2 was used as seeds, the prepared samples showed better photocatalytic _hydrogen and oxygen production performance.

Advantage of the present invention and beneficial effect are:

1. The present invention is a method for preparing mesoporous single-crystal rutile _TiO2 grown epitaxially by heterogeneous seeds, and mesoporous samples can be obtained under different seed concentrations.

2. The method of the present invention combines the seeds required in the preparation process of the mesoporous samples with the cocatalyst required for the photocatalytic reaction to obtain in-situ cocatalyst-modified mesoporous single crystal rutile TiO ₂ .

3. The heterogeneous seed mesoporous single crystal rutile TiO ₂ formed by the method of the present invention has uniform appearance and uniform pore distribution, and the particle size can be regulated by the seed concentration.

In conclusion, the preparation of mesoporous single-crystal rutile TiO ₂ with regular morphology, uniform pore size distribution and adjustable particle size by the present invention is of great importance for the synthesis of the material itself and the subsequent study of photocatalytic activity. significance. For material synthesis, different concentrations of RuCl ₃ (IrCl ₃ ) in water and different concentrations of SnCl ₂ in water and ethanol were used for the synthesis of heterogeneous seeded mesoporous single-crystal rutile TiO ₂ crystals in the present invention. For the study of photocatalytic activity of mesoporous TiO ₂ epitaxially grown by heterogeneous seeds, the contact between heterogeneous seeds as cocatalysts and TiO ₂ is at the atomic level, and there is no macroscopic interface, so the separation of carriers during the photocatalytic reaction The efficiency is higher, which leads to the difference in the ability of photocatalytic water splitting to produce hydrogen. This also leads to a deeper understanding of the way to grow co-catalysts in situ, which provides a basis for the subsequent preparation of other mesoporous oxides with heterogeneous seeds.

Description of drawings

Figure 1 SEM photos of mesoporous single crystal rutile _TiO2 under different concentrations of seeds; among them, pictures (a), (b) are samples prepared when _0.04mMolRuO2 is used as seeds, and pictures (c), (d) are 1mMol IrO ₂ Samples prepared when used as seeds, Figures (e) and (f) are samples prepared when 10mMol SnO ₂ was used as seeds.

TEM photos of mesoporous single-crystal rutile _TiO2 under different concentrations of seeds in Fig. 2; among them, figure (a), (b) are respectively 0.04mM RuO ₂ and 1mM IrO ₂ Prepare the transmission pictures of samples when making seeds, figure (c) Transmission photographs of samples prepared when seeded with 10 mMol _SnO2 . The two insets in panel (a) are the low-magnification phase and selected area diffraction pattern of mesoporous single-crystal rutile TiO ₂ obtained at the seed concentration of 0.04mM RuO ₂ , and the two insets in panel (b) are 1mM The low-magnification phase and selected area diffraction pattern of mesoporous single crystal rutile _TiO2 obtained at the seed concentration of _IrO2 . The two insets in figure (c) are respectively the mesoporous single crystal rutile TiO obtained at the seed concentration of 10mM _{SnO2 The} low magnification phase and selected area diffraction pattern of 2.

Mesoporous single crystal rutile TiO under different seeds of Fig. ₃ XRD patterns; Wherein, figure (a) is _0.04mM RuO Prepare the XRD pattern of samples when making seeds, figure (b ₎ prepare and obtain samples when making seeds for 1mM IrO Figure (c) is the XRD pattern of the sample prepared when 10mMol SnO ₂ was used as the seed; the X-axis is the diffraction angle 2θ (degrees), and the Y-axis is the intensity (au).

Figure 4 is the _N2 adsorption curve and pore size distribution diagram of mesoporous single crystal rutile _TiO2 under different seeds; wherein, figure (a) is the adsorption curve and pore size distribution diagram of the sample prepared when _0.04mM RuO2 is used as the seed (inset Represent 0.04mMRuO _The pore size distribution figure of the sample prepared under the concentration), figure (b) is 10mMol _SnO When making the seed, the adsorption curve and the pore size distribution figure of the sample prepared (wherein the inset represents the pore size distribution figure of the prepared sample under the 10mMol SnO2 concentration) . In Figure (a) and Figure (b), the X-axis is the relative pressure (P/P0), and the Y-axis is the adsorption amount (mmol/g). In the inset of Figure (a) and Figure (b), the X-axis is the pore diameter (nm), and the Y-axis is the pore volume (cm ³ /g·nm).

Detailed ways

In the specific implementation process, the preparation method for the controllable growth of heterogeneous seed mesoporous single crystal rutile TiO ₂ of the present invention, first of all, the preparation process of the seed template: the aqueous solution of RuCl ₃ .xH ₂ O with a certain concentration is used as the seed solution, and the above-mentioned Add a certain amount of silica spheres (3g to 25g) to 50mL solution, bathe in 70°C water for 1h, rinse with a large amount of deionized water, dry the silica spheres after planting seeds in a heating mantle at 80°C, and place Heat in a muffle furnace (2°C/min up to 500°C, hold for 30min). TiO ₂ precursor solution preparation process: Slowly drop TiCl ₄ into hydrochloric acid, add a certain amount of water to make a certain concentration of TiCl ₄ hydrochloric acid aqueous solution, and an ice-water bath is required during the solution preparation process. Next is the preparation of heterogeneous seed mesoporous single crystal _TiO2 : take a certain amount of silica spherical seed template (500mg ~ 5g) and put it into a polytetrafluoroethylene liner containing the precursor solution, and put it in an oven at a certain temperature Heat water for a certain period of time. After the inner tank is cooled, collect the silica ball seed template, wash it with a large amount of deionized water, dry it in a heating mantle at 80°C, collect it, put it in a water bath with a certain concentration of NaOH solution at a certain temperature for 1 hour, and inscribe Etch the silica ball seed template, centrifuge to collect the mesoporous TiO ₂ sample, wash with deionized water and ethanol for 2 to 3 times, collect and dry the sample. At the same time, heterogeneous seeds can also choose SnO ₂ or IrO ₂ , and the preparation process is similar to the above, except that the seed solution is an aqueous solution of IrCl ₃ .xH ₂ O, or the seed solution is an ethanol solution of SnCl ₂ or a mixed solution of water and ethanol. Among them, the specific features are:

1. The TiCl ₄ used in the reaction is a commercially pure solution, and the silica ball seed template is a small SiO ₂ ball with a diameter of about 50 nm.

2. The material of the reaction kettle is one of stainless steel, aluminum alloy, copper and tantalum, and the inner tank is one of polytetrafluoroethylene and high-density polyethylene.

3. The concentration of the seed solution: for the RuCl ₃ .xH ₂ O aqueous solution or IrCl ₃ .xH ₂ O aqueous solution, the concentration is 0.02mM-10mM; for the SnCl ₂ solution, the concentration is 1mM-30mM, the water in the SnCl ₂ solution The volume ratio to ethanol is between 0 and 1.

4. In the process of etching the template, the molar concentration of the NaOH aqueous solution used is 1M-5M, and the temperature of the water bath is 60-90°C.

5. When putting into an oven for heat treatment, the heating temperature is 100-300°C, and the heating time is 2h-48h.

6. When drying after cleaning with deionized water, the drying temperature is 60-100°C.

7. When RuO ₂ is used as the seed, mesoporous single crystal rutile TiO ₂ can be obtained at different concentrations. The size of the sample is between 500nm and 900nm. There are differences; similarly, when using SnO ₂ or IrO ₂ as seeds, mesoporous single crystal rutile TiO ₂ with similar morphology can be obtained.

The present invention will be described in detail below in conjunction with examples.

Example

In this example, the preparation of mesoporous single-crystal rutile TiO ₂ with RuO ₂ as heterogeneous seeds is taken as an example:

Seed template preparation process: Take 3g of close-packed SiO ₂ ball template and put it into 50mL RuCl ₃ aqueous solution with a molar concentration of 0.04mM. ℃ drying in a heating mantle; after that, place in a muffle furnace at 500 ℃ for 30 minutes to obtain a silica ball seed template containing heterogeneous seeds.

Prepare TiCl ₄ precursor: slowly drop 1.64mL of TiCl ₄ into 292mL of 37wt% concentrated hydrochloric acid (ice-water bath), then add deionized water to 1L, and mix well.

Preparation of mesoporous samples: Take 40 mL of the above precursor solution, put it into a polytetrafluoroethylene liner, add 80 mg of NaF as a shape control agent, add 500 mg of silica ball seed template, and seal the above polytetrafluoroethylene liner Put it into a stainless steel jacket, and heat it in an oven to 200°C for 12h. After cooling to room temperature, the template particles in the PTFE lining were rinsed with deionized water, dried at 80°C, put into 100mL NaOH solution with a molar concentration of 2M, kept in a water bath at 80°C for 1h, and the template was etched . After the etching is completed, wash with deionized water and ethanol by centrifugation for 2 to 3 times, and dry to collect samples.

The process of preparing mesoporous single-crystal rutile _TiO2 with _IrO2 or _SnO2 as seeds is similar.

Figure 1 shows the SEM photo of mesoporous single crystal rutile TiO ₂ prepared with RuO ₂ , IrO ₂ , and SnO ₂ as seeds, showing that the sample has a porous structure, and the grain size of the single crystal rutile TiO ₂ sample is between 400nm and 900nm.

Figure 2 shows the TEM photo of mesoporous single crystal rutile TiO ₂ prepared with RuO ₂ , IrO ₂ , and SnO ₂ as seeds. The diffraction spots indicate that the sample is a single crystal structure. The topography shows that the pore structure runs through the inside of the sample. The {111} crystal plane is exposed.

Figure 3 shows the XRD spectrum of mesoporous single crystal rutile TiO ₂ prepared with RuO ₂ , IrO ₂ , and SnO ₂ as seeds, indicating that the sample is in the rutile phase.

Figure 4 shows the N ₂ isotherm adsorption curve and pore size distribution curve of mesoporous single-crystal rutile TiO ₂ prepared with RuO ₂ and SnO ₂ as seeds, indicating that the sample contains a rich pore structure, and the pore size distribution shows that the pore size of the sample is about 50 nm and 2 Silica ball seed templates are consistent in size.

The results of the examples show that the present invention uses titanium tetrachloride as a precursor through a wet chemical process, and silica spheres containing heterogeneous seeds as a template, hydrothermally grows rutile titanium dioxide with specific crystal plane exposure, and after etching the template, obtains rutile titanium dioxide containing The mesoporous single-crystal rutile titanium dioxide with heterogeneous seeds can realize the epitaxial growth of co-catalysts on heterogeneous seeds, which solves the problems of poor interface contact quality between catalysts and co-catalysts and low photocatalytic efficiency. Different from the traditional seed template method, the present invention puts the titanium tetrachloride precursor and the silicon dioxide template containing heterogeneous seeds into the reaction kettle, heats them, and obtains mesoporous single-crystal rutile titanium dioxide with specific crystal faces exposed after etching .

Claims (9)

1. A preparation method for the controllable growth of mesoporous single crystal rutile titanium dioxide in heterogeneous seeds, characterized in that, using titanium tetrachloride hydrochloric acid solution as a precursor, commercial sodium fluoride as a crystal plane control agent, and selecting the same rutile type Ruthenium dioxide, tin dioxide or iridium dioxide are used as heterogeneous seeds, and the rutile structure of ruthenium dioxide, tin dioxide or iridium dioxide is used, and the lattice constants are similar, and the epitaxial growth of heterogeneous seeds is designed to prepare mesoporous single cells. Crystal rutile TiO ₂ , the specific process is as follows: (1) Take ruthenium chloride aqueous solution or iridium chloride aqueous solution as the seed solution, or take the ethanol solution of stannous chloride or the mixed solution of water and ethanol as the seed solution, add silica balls, and prepare the carbon dioxide containing heterogeneous seeds Silicon ball seed template; (2) Put the precursor, sodium fluoride and silica ball seed template into the reaction kettle, the volume of the precursor is 20ml~60ml, and the mass ratio of sodium fluoride and silica ball seed template is (0.1~1) : (0.5～20), after the reaction kettle is sealed, put it into the oven for heat treatment, take out the reaction sample, wash and dry with deionized water, after etching the template, wash and dry with deionized water and ethanol respectively, to obtain { 111} Mesoporous single-crystal rutile TiO with exposed crystal facets containing different heterogeneous seeds, which serve as both nucleation sites during preparation and co-catalysts during photocatalytic testing; In the described titanium tetrachloride hydrochloric acid solution, the molar concentration of hydrochloric acid is 0.05M-5M, and the molar concentration of titanium tetrachloride is 0.01M-1M; in the described ruthenium chloride aqueous solution or iridium chloride aqueous solution, the The molar concentration of ruthenium or iridium chloride is 0.001mM～0.1M; in the ethanol solution of described stannous chloride or water, ethanol mixed solution, the molar concentration of stannous chloride is 0.001mM～0.1M, ethanol and water The volume ratio is between 0 and 1. 2. according to the preparation method of the controllable growth of heterogeneous seed mesoporous single crystal rutile titanium dioxide according to claim 1, it is characterized in that, described precursor is commercial chemical pure titanium tetrachloride solution, and used silicon dioxide sphere diameter 5 to 250 nanometers. 3. according to the heterogeneous seed mesoporous single crystal rutile titanium dioxide controllable growth preparation method according to claim 1, it is characterized in that, the material of described reactor is a kind of of stainless steel, aluminum alloy, copper and tantalum, and the reactor The liner is one of polytetrafluoroethylene and high-density polyethylene. 4. According to the preparation method of heterogeneous seed mesoporous single crystal rutile titanium dioxide controllable growth according to claim 1, it is characterized in that, preferably: in the described titanium tetrachloride hydrochloric acid solution, the molar concentration of hydrochloric acid is 1M～5M , the molar concentration of titanium tetrachloride is 0.01M～0.1M; In the described ruthenium chloride aqueous solution or iridium chloride aqueous solution, the molar concentration of ruthenium chloride or iridium chloride is 0.02mM～10mM; In the ethanol solution of stannous or the mixed solution of water and ethanol, the molar concentration of stannous chloride is 1mM～30mM, and the volume ratio of ethanol to water is between 0～1. 5. The preparation method for the controllable growth of mesoporous single-crystal rutile titanium dioxide in heterogeneous seeds according to claim 1, characterized in that, when putting into an oven for heat treatment, the heating temperature is 100-300°C, and the heating time is 2h ~48h. 6. The method for preparing heterogeneous seeded mesoporous single-crystal rutile titanium dioxide with controlled growth according to claim 1, characterized in that, when said washing with deionized water and then drying, the drying temperature is 60-100°C. 7. According to the preparation method for the controllable growth of heterogeneous seed mesoporous single crystal rutile titanium dioxide according to claim 1, it is characterized in that, when the template is etched, the molar concentration of the NaOH aqueous solution is 1M to 5M, and the temperature of the water bath is Etching at 60-90°C for 0.5-2h. 8. According to the preparation method for the controllable growth of mesoporous single crystal rutile titanium dioxide with heterogeneous seeds according to claim 1, it is characterized in that the sample grain size of the mesoporous single crystal rutile titanium dioxide prepared by heterogeneous seeds with different concentrations is 300nm～ 900nm, the pore diameter is between 2 and 50 nanometers, the channel runs through the inside of the sample, and the {111} crystal plane is exposed on the surface. 9. The preparation method for the controllable growth of mesoporous single-crystal rutile titanium dioxide in heterogeneous seeds according to claim 1, characterized in that, when preparing the silica ball seed template, the seed solution and the silica ball are placed in a 60-80°C water bath Keep warm for 0.5-2 hours, then rinse with deionized water, dry the silica balls after planting seeds in a heating mantle at 70-90°C, and place them in a muffle furnace at 450-550°C for 20-40 minutes.