阅读说明：本技术 三维有序大孔结构钽酸钠光催化制氢材料的通用合成方法 (General synthesis method of three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material ) 是由 王学文 甘蕾 张荣斌 于 2021-08-02 设计创作，主要内容包括：本发明公开了三维有序大孔结构钽酸钠光催化制氢材料的通用合成方法,涉及光催化剂技术领域,选择合适的PMMA小球作为三维有序大孔钽酸钠的模板剂,TaCl-(5)溶于无水乙醇溶液形成钽离子前聚体,前聚体均匀分布在PMMA小球缝隙中,二次浸渍引入钠离子以得到含钽离子和钠离子的球体模板剂,将此模板剂煅烧,在煅烧时,缝隙间的前聚体逐渐固化,并且结晶,随着模板剂的去除,形成三维有序大孔NaTaO～(3),以PMMA模板剂将NaTaO～(3)构建成三维有序大孔结构后,光催化剂的比表面积明显增大,反应活性位点增加,与传统水热和煅烧NaTaO～(3)的结构相比,产生氢气能力大幅提升,以PMMA为模板剂构建三维有序大孔结构后的催化剂,增加了光的吸收。(The invention discloses a general synthesis method of a three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material, and relates to the technical field of photocatalysts 5 Dissolving in absolute ethanol solution to form tantalum ion pre-polymer, uniformly distributing the pre-polymer in gaps of PMMA pellets, secondarily dipping and introducing sodium ions to obtain a spherical template agent containing tantalum ions and sodium ions, calcining the template agent, gradually solidifying the pre-polymer among the gaps during calcination, crystallizing, and forming three-dimensional ordered macroporous NaTaO along with the removal of the template agent 3 NaTaO is prepared by PMMA template agent 3 After constructing a three-dimensional ordered macroporous structureThe specific surface area of the photocatalyst is obviously increased, the reaction active sites are increased, and the method is compatible with the traditional hydrothermal method and the traditional calcined NaTaO method 3 Compared with the structure, the hydrogen generation capacity is greatly improved, and the catalyst with the three-dimensional ordered macroporous structure is constructed by taking PMMA as a template, so that the light absorption is increased.)

1. A general synthetic method of a three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material is characterized in that a proper PMMA pellet is selected as a template agent of three-dimensional ordered macroporous sodium tantalate and TaCl is selected as a template agent₅Dissolving in absolute ethanol solution to form tantalum ion pre-polymer, uniformly distributing the pre-polymer in gaps of PMMA pellets, secondarily dipping and introducing sodium ions to obtain a spherical template agent containing tantalum ions and sodium ions, calcining the template agent, gradually solidifying the pre-polymer among the gaps during calcination, crystallizing, and forming three-dimensional ordered macroporous NaTaO along with the removal of the template agent₃The method specifically comprises the following steps:

s1, selecting a proper template PMMA pellet as a template agent;

s2, taking TaCl₅Adding into absolute ethyl alcohol solution, stirring and dissolving;

s3, naturally filtering the solution obtained in the step S2 to leave a clear solution;

s4, adding the template agent obtained in the step S1 into the clear liquid obtained in the step S3, and dipping at room temperature;

s5, carrying out vacuum filtration on the standing solution to obtain a template agent with gaps containing tantalum ethoxide;

s6, placing the sample obtained in the step S5 in an ethanol solution containing sodium ions, and soaking for the second time;

s7, carrying out vacuum filtration on the standing solution to obtain a template agent with gaps containing tantalum ions and sodium ions;

s8, calcining the sample obtained in the step S7 in a nitrogen atmosphere, heating to 623K, cooling to room temperature, and taking out;

s9, placing the sample obtained in the step S8 in a muffle furnace, heating to 773K, keeping for 0.5-2h, cooling to room temperature, washing and drying to obtain the sample.

2. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material of claim 1, wherein in step S1, suitable PMMA beads are selected as a template agent for the three-dimensional ordered macroporous sodium tantalate, and PMMA is polymethylmethacrylate.

3. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material as claimed in claim 2, wherein in step S1, the template is a highly ordered PMMA bead structure.

4. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material as claimed in claim 3, wherein the size of the PMMA pellets is one or more.

5. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material of claim 1, wherein in step S2, TaCl is taken₅Adding into absolute ethanol solution, stirring and dissolving for 1-3 h.

6. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material as claimed in claim 1, wherein TaCl in step S2 is used as the material₅The dosage of the compound is 0.9-2g, and the dosage of the absolute ethyl alcohol is 10-25 mL.

7. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material as claimed in claim 1, wherein in step S4, the template agent is added to the clear solution and immersed for 2-8h at room temperature.

8. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material as claimed in claim 1, wherein in step S6, the sample obtained in S5 is placed in an ethanol solution containing sodium ions and is subjected to secondary immersion for 2-8 h.

9. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material as claimed in claim 1, wherein in step S8, the sample is calcined under nitrogen atmosphere, heated to 623K, kept for 1-4h, and taken out after being cooled to room temperature.

10. The general synthesis method of the three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material as claimed in claim 1, wherein in step S9, the sample obtained in step S8 is placed in a muffle furnace, heated to 773K, and kept for 0.5-2 h.

Technical Field

The invention relates to the technical field of photocatalysts, in particular to a general synthetic method of a three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material.

Background

With the improvement of living standard of people, the demand on green environment is higher and higher. The choice of clean energy sources is critical to the protection of the environment. Therefore, the method is urgently needed to find a clean, green and renewable energy source substitute. The hydrogen energy has the characteristics of cleanness and greenness, and has higher efficiency than fossil energy. The conversion of water into hydrogen by solar energy has a very considerable prospect. Therefore, how to efficiently convert and decompose solar energy into water to generate hydrogen is a great challenge. However, as an energy conversion method which has been studied for a long time, photocatalysis has been studied for a long time in the aspect of converting solar energy into water to generate hydrogen. The search for stable, efficient and environmentally friendly semiconductor photocatalysts has been an important goal of research. However, the problems of low specific surface area and high carrier recombination rate of semiconductor photocatalytic materials have been to hinder the step of photocatalysis from fundamental research to industrialization.

NaTaO₃Has good photocatalytic performance and thermal stability, and in addition, NaTaO₃Is a classical wide band gap semiconductor, NaTaO₃Has a conduction band potential (-0.17eV) lower than H⁺/H₂Redox potential (0eV) of NaTaO according to thermodynamic calculations₃Has great potential of photocatalytic water decomposition, however, the low surface area of the NaTaO leads to less reactive active sites and high carrier recombination rate, thereby leading to low photocatalytic performance₃The construction of a three-dimensional ordered macroporous structure is expected to improve the problems, and at present, NaTaO₃Basically has a square structure obtained by a hydrothermal method and a large-particle structure obtained by high-temperature calcination, and the low specific area and the low carrier migration efficiency of the structures limit NaTaO₃Performance of the photolysis of water to produce hydrogen, and we have found that by synthesizing NaTaO₃The three-dimensional ordered macroporous structure can effectively improve the problems and can controllably adjust the three-dimensional ordered macroporous NaTaO₃The size of the structural pore diameter.

Disclosure of Invention

In response to the deficiencies of the prior art, the present invention provides three-dimensional orderingThe general synthesis method of the macroporous sodium tantalate photocatalytic hydrogen production material improves the NaTaO₃The semiconductor catalyst has the problems of low specific surface area and high carrier recombination rate in photocatalytic water decomposition, so that the photocatalytic hydrogen production efficiency is greatly improved, and the problems in the background art are solved.

In order to achieve the purpose, the invention provides the following technical scheme: a general synthetic method of a three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material selects proper PMMA pellets as a template agent of three-dimensional ordered macroporous sodium tantalate and TaCl₅Dissolving in absolute ethanol solution to form tantalum ion pre-polymer, uniformly distributing the pre-polymer in gaps of PMMA pellets, secondarily dipping and introducing sodium ions to obtain a spherical template agent containing tantalum ions and sodium ions, calcining the template agent, gradually solidifying the pre-polymer among the gaps during calcination, crystallizing, and forming three-dimensional ordered macroporous NaTaO along with the removal of the template agent₃The method specifically comprises the following steps:

s1, selecting a proper template PMMA pellet as a template agent;

s2, taking TaCl₅Adding into absolute ethyl alcohol solution, stirring and dissolving;

s3, naturally filtering the solution obtained in the step S2 to leave a clear solution;

s4, adding the template agent obtained in the step S1 into the clear liquid obtained in the step S3, and dipping at room temperature;

s5, carrying out vacuum filtration on the standing solution to obtain a template agent with gaps containing tantalum ethoxide;

s6, placing the sample obtained in the step S5 in an ethanol solution containing sodium ions, and soaking for the second time;

s7, carrying out vacuum filtration on the standing solution to obtain a template agent with gaps containing tantalum ions and sodium ions;

s8, calcining the sample obtained in the step S7 in a nitrogen atmosphere, heating to 623K, cooling to room temperature, and taking out;

s9, placing the sample obtained in the step S8 in a muffle furnace, heating to 773K, keeping for 0.5-2h, cooling to room temperature, washing and drying to obtain the sample.

Further optimizing the technical scheme, in the step S1, a proper PMMA pellet is selected as a template agent of the three-dimensional ordered macroporous sodium tantalate, and PMMA is polymethyl methacrylate.

In step S1, the template is a highly ordered PMMA bead structure.

Further optimizing the technical scheme, the size of the PMMA pellets is one or more.

Further optimizing the technical scheme, in the step S2, TaCl is taken₅Adding into absolute ethanol solution, stirring and dissolving for 1-3 h.

Further optimizing the technical scheme, the TaCl in the step S2₅The dosage of the compound is 0.9-2g, and the dosage of the absolute ethyl alcohol is 10-25 mL.

Further optimizing the technical scheme, in the step S4, the template agent is added into the clear solution and dipped for 2-8h at room temperature.

In step S6, the sample obtained in step S5 is placed in an ethanol solution containing sodium ions, and the sample is dipped for 2 to 8 hours.

In step S8, the sample is calcined in nitrogen atmosphere, heated to 623K, kept for 1-4h, cooled to room temperature, and taken out.

In step S9, the sample obtained in step S8 is placed in a muffle furnace, and the temperature is raised to 773K and maintained for 0.5-2 h.

The invention constructs three-dimensional ordered macroporous NaTaO by PMMA template agent at room temperature₃. In this process, TaCl₅Dissolving in absolute ethanol solution to form ethanol solution containing tantalum ions, and filling the prepolymer solution by twice impregnation to introduce sodium ions, TaCl₅Dissolving in absolute ethanol solution to form ethanol tantalum precursor, uniformly distributing the precursor in gaps of the template pellet, solidifying and crystallizing the precursor in the gaps during calcination, and removing the template agent to obtain the NaTaO with the three-dimensional ordered macroporous structure₃Formed by constructing a three-dimensional ordered macroporous structure NaTaO₃Structural improvementThe specific surface area of the photocatalytic material is reduced, and the carrier migration distance is shortened, so that the NaTaO is improved₃The hydrogen production efficiency of the decomposed water.

Compared with the prior art, the invention provides a general synthesis method of a three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material, which has the following beneficial effects:

1. the invention uses PMMA template agent to prepare NaTaO₃After the three-dimensional ordered macroporous structure is constructed, the specific surface area of the photocatalyst is obviously increased, the reaction active sites are increased, and the method is compared with the traditional hydrothermal method and the method for calcining NaTaO₃Compared with the structure, the hydrogen generation capacity is greatly improved.

2. According to the invention, the PMMA template agent is used for constructing the catalyst with the three-dimensional ordered macroporous structure, the migration distance of carriers is shortened, the service life of photogenerated carriers is obviously prolonged, and the carriers of reaction transferred to the surface of the catalyst are increased, so that the efficiency of decomposing water of the catalyst to generate hydrogen is improved.

3. According to the invention, PMMA is used as a template agent to construct the catalyst with a three-dimensional ordered macroporous structure, so that the light absorption is increased, and the efficiency of hydrogen generation by photocatalytic decomposition of water is greatly improved.

4. According to the invention, PMMA is used as a template agent to construct the catalyst with a three-dimensional ordered macroporous structure, and the catalyst structure obtains a highly ordered pore structure, so that the gas molecule release efficiency is improved, and the photocatalytic reaction is facilitated.

Drawings

FIG. 1 is a schematic flow chart of a general synthetic method of a three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material provided by the invention;

FIG. 2 is a three-dimensional ordered macroporous NaTaO obtained by PMMA template₃XRD spectrum compared to (PDF #25-0863) card;

FIG. 3 is a three-dimensional ordered macroporous NaTaO obtained by PMMA template₃SEM picture of (1);

FIG. 4 shows a three-dimensional ordered macroporous NaTaO₃A TEM image of (B);

FIG. 5 shows a three-dimensionally ordered macroporous NaTaO structure using a mercury lamp as a light source without adding a sacrificial agent₃Hydrothermal NaTaO₃And calcining NaTaO₃And (5) comparing hydrogen production performance.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.

Example (b):

referring to fig. 1, the invention discloses a general synthesis method of a three-dimensional ordered macroporous structure sodium tantalate photocatalytic hydrogen production material, and a proper PMMA pellet is selected as a template agent of three-dimensional ordered macroporous sodium tantalate, TaCl₅Dissolving in absolute ethanol solution to form tantalum ion pre-polymer, uniformly distributing the pre-polymer in gaps of PMMA pellets, secondarily dipping and introducing sodium ions to obtain a spherical template agent containing tantalum ions and sodium ions, calcining the template agent, gradually solidifying the pre-polymer among the gaps during calcination, crystallizing, and forming three-dimensional ordered macroporous NaTaO along with the removal of the template agent₃The method specifically comprises the following steps:

s1, selecting a proper template PMMA pellet as a template agent;

s2, taking TaCl₅Adding into absolute ethyl alcohol solution, stirring and dissolving;

s3, naturally filtering the solution obtained in the step S2 to leave a clear solution;

s4, adding the template agent obtained in the step S1 into the clear liquid obtained in the step S3, and dipping at room temperature;

s5, carrying out vacuum filtration on the standing solution to obtain a template agent with gaps containing tantalum ethoxide;

s6, placing the sample obtained in the step S5 in an ethanol solution containing sodium ions, and soaking for the second time;

s7, carrying out vacuum filtration on the standing solution to obtain a template agent with gaps containing tantalum ions and sodium ions;

s8, calcining the sample obtained in the step S7 in a nitrogen atmosphere, heating to 623K, cooling to room temperature, and taking out;

s9, placing the sample obtained in the step S8 in a muffle furnace, heating to 773K, keeping for 0.5-2h, cooling to room temperature, washing and drying to obtain the sample.

As a specific optimization scheme of this embodiment, in step S1, a suitable PMMA bead is selected as a template agent of the three-dimensional ordered macroporous sodium tantalate, and PMMA is polymethyl methacrylate.

As a specific optimization scheme of this embodiment, in step S1, the template is a highly ordered PMMA bead structure.

As a specific optimization scheme of the embodiment, the size of the PMMA pellets is one or more.

As a specific optimization scheme of this embodiment, in step S2, TaCl is taken₅Adding into absolute ethanol solution, stirring and dissolving for 1-3 h.

As a specific optimization scheme of this embodiment, TaCl in step S2 is used₅The dosage of the compound is 0.9-2g, and the dosage of the absolute ethyl alcohol is 10-25 mL.

As a specific optimization scheme of this embodiment, in step S4, the template is added to the clear solution and immersed at room temperature for 2-8 h.

As a specific optimization scheme of this embodiment, in step S6, the sample obtained in S5 is placed in an ethanol solution containing sodium ions, and is immersed for a second time for 2-8 h.

As a specific optimization scheme of the embodiment, in the step S8, the sample is calcined under a nitrogen atmosphere, heated to 623K, kept for 1-4h, cooled to room temperature and then taken out.

In the specific optimization scheme of this embodiment, in step S9, the sample obtained in S8 is placed in a muffle furnace, heated to 773K, and kept for 0.5-2 h.

The invention constructs three-dimensional ordered macroporous NaTaO by PMMA template agent at room temperature₃. In this process, TaCl₅Dissolving in absolute ethanol solution to form ethanol solution containing tantalum ions, and introducing sodium ions by secondary impregnation to obtain prepolymerGeneral synthetic method for solution filling, TaCl₅Dissolving in absolute ethanol solution to form ethanol tantalum precursor, uniformly distributing the precursor in gaps of the template pellet, solidifying and crystallizing the precursor in the gaps during calcination, and removing the template agent to obtain the NaTaO with the three-dimensional ordered macroporous structure₃Formed by constructing a three-dimensional ordered macroporous structure NaTaO₃The structure improves the specific surface area of the photocatalytic material and shortens the migration distance of carriers, thereby improving the NaTaO₃The hydrogen production efficiency of the decomposed water.

The first embodiment is as follows:

firstly, TaCl is taken₅(0.6g) adding the mixture into an absolute ethyl alcohol (10mL) solution, stirring and dissolving, filtering to remove impurities, then adding a PMMA template with the particle size of 200nm into the filtrate, standing for 7h, and carrying out vacuum filtration to obtain the template agent with gaps containing tantalum ethoxide. And soaking the template in an ethanol solution containing sodium ions for 5 hours, and performing vacuum filtration to obtain the template agent with gaps containing tantalum ions and sodium ions. Then, in a tube furnace, under nitrogen atmosphere, the temperature was raised to 623K and maintained for 2 hours, and the tube furnace was taken out after being cooled to room temperature. It was next placed in a muffle furnace, warmed to 773K, and held for 1 h. Obtaining the NaTaO with the three-dimensional ordered macroporous structure₃。

Example two:

firstly, TaCl is taken₅(0.7g) adding the mixture into an absolute ethyl alcohol (11mL) solution, stirring and dissolving, filtering to remove impurities, adding a 220nm PMMA template into the filtrate, standing for 7h, and carrying out vacuum filtration to obtain the template agent with gaps containing tantalum ethoxide. And soaking the template agent in an ethanol solution containing sodium ions for 6 hours, and performing vacuum filtration to obtain the template agent with gaps containing tantalum ions and sodium ions. Then, in a tube furnace, under nitrogen atmosphere, the temperature was raised to 623K and maintained for 2 hours, and the tube furnace was taken out after being cooled to room temperature. It was next placed in a muffle furnace, warmed to 773K, and held for 1 h. Obtaining the NaTaO with the three-dimensional ordered macroporous structure₃。

Example three:

firstly, TaCl is taken₅(0.8g) adding into absolute ethyl alcohol (11mL), stirring for dissolving, filtering to remove impurities, adding PMMA template of 220nm into the filtrate, standing for 6h, and vacuum filtering to obtain the final productTo a template containing tantalum ethoxide in the gap. And soaking the template in an ethanol solution containing sodium ions for 5 hours, and performing vacuum filtration to obtain the template agent with gaps containing tantalum ions and sodium ions. Then, in a tube furnace, under nitrogen atmosphere, the temperature was raised to 623K and maintained for 2 hours, and the tube furnace was taken out after being cooled to room temperature. It was next placed in a muffle furnace, warmed to 773K, and held for 1 h. Obtaining the NaTaO with the three-dimensional ordered macroporous structure₃。

Example four:

firstly, TaCl is taken₅(0.7g) adding the mixture into an absolute ethyl alcohol (10mL) solution, stirring and dissolving, filtering to remove impurities, then adding a PMMA template with the particle size of 200nm into the filtrate, standing for 6h, and carrying out vacuum filtration to obtain the template agent with gaps containing tantalum ethoxide. And soaking the template in an ethanol solution containing sodium ions for 4 hours, and performing vacuum filtration to obtain the template agent with gaps containing tantalum ions and sodium ions. Then, the temperature was raised to 623K in a tube furnace under nitrogen atmosphere, and the temperature was maintained for 3 hours, and the tube furnace was taken out after being cooled to room temperature. It was next placed in a muffle furnace, warmed to 773K, and held for 1 h. Obtaining the NaTaO with the three-dimensional ordered macroporous structure₃。

Example five:

firstly, TaCl is taken₅(0.7g) adding the mixture into an absolute ethyl alcohol (10mL) solution, stirring and dissolving, filtering to remove impurities, adding a PMMA template with the particle size of 250nm into the filtrate, standing for 5 hours, and carrying out vacuum filtration to obtain the template agent with gaps containing tantalum ethoxide. And soaking the template agent in an ethanol solution containing sodium ions for 6 hours, and performing vacuum filtration to obtain the template agent with gaps containing tantalum ions and sodium ions. Then, in a tube furnace, under nitrogen atmosphere, the temperature was raised to 623K and maintained for 2 hours, and the tube furnace was taken out after being cooled to room temperature. It was next placed in a muffle furnace, warmed to 773K, and held for 0.5 h. Obtaining the NaTaO with the three-dimensional ordered macroporous structure₃

The morphology and structure, and properties of the product obtained in the comparative example are shown in FIGS. 1-5.

As can be seen from FIG. 2, the three-dimensional ordered macroporous NaTaO structure obtained by using PMMA template₃Compared with (PDF #25-0863) card, the peak shape is consistent, and the three-dimensional ordered macroporous structure NaTaO is shown₃Is pure phase Ta₂O₅。

As can be seen from FIG. 3, the three-dimensional ordered macroporous structure NaTaO₃Highly ordered, three-dimensionally ordered macroporous NaTaO₃Successfully constructed three-dimensional ordered macroporous structure NaTaO of low-magnification SEM picture₃High porosity and integrity are maintained.

As can be seen from FIG. 4, the three-dimensional ordered macroporous structure NaTaO₃Has clear penetrating macroporous structure.

As can be seen from FIG. 5, the three-dimensional ordered macroporous structure NaTaO₃The performance of the generated hydrogen is better than that of hydrothermal NaTaO₃(H-NaTaO₃) And calcining NaTaO₃(C-NaTaO₃). Shows that the introduction of the three-dimensional ordered network structure greatly improves NaTaO₃The performance of (c).

The results of the examples show that the three-dimensional ordered macroporous NaTaO prepared by the invention₃Has excellent photodecomposition water performance.

The invention has the beneficial effects that:

1. the invention uses PMMA template agent to prepare NaTaO₃After the three-dimensional ordered macroporous structure is constructed, the specific surface area of the photocatalyst is obviously increased, the reaction active sites are increased, and the method is compared with the traditional hydrothermal method and the method for calcining NaTaO₃Compared with the structure, the hydrogen generation capacity is greatly improved.

2. According to the invention, the PMMA template agent is used for constructing the catalyst with the three-dimensional ordered macroporous structure, the migration distance of carriers is shortened, the service life of photogenerated carriers is obviously prolonged, and the carriers of reaction transferred to the surface of the catalyst are increased, so that the efficiency of decomposing water of the catalyst to generate hydrogen is improved.

3. According to the invention, PMMA is used as a template agent to construct the catalyst with a three-dimensional ordered macroporous structure, so that the light absorption is increased, and the efficiency of hydrogen generation by photocatalytic decomposition of water is greatly improved.

4. According to the invention, PMMA is used as a template agent to construct the catalyst with a three-dimensional ordered macroporous structure, and the catalyst structure obtains a highly ordered pore structure, so that the gas molecule release efficiency is improved, and the photocatalytic reaction is facilitated.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.