Preparation method and application of monodisperse polyacid / tiO2 nanotube photocatalytic material

Abstract

The application provides a preparation method and application of monodisperse polyacid / TiO2 nanotube photocatalytic material, and the preparation steps of the monodisperse polyacid / TiO2 nanotube photocatalytic material are as follows: (1) preparation of electrolyte: ammonium fluoride and polyacid are dispersed into ultrapure water, and ethylene glycol solution is added to form electrolyte A; (2) electrolysis: platinum wire is used as the cathode of the battery, titanium sheet is used as the anode of the battery, a direct current power supply of 60V is added, and electrolysis is carried out in the electrolyte A; (3) washing: the deposit after electrolysis is washed with ultrapure water and anhydrous ethanol, and is dried at room temperature to obtain amorphous material B; (4) calcination: the amorphous material B is placed in a muffle furnace and is calcined at 450 DEG C for 2h to obtain the monodisperse polyacid / TiO2 nanotube photocatalytic material. The application develops a convenient synthesis method, uses the in-situ anodic oxidation method to combine TiO2 nanotube and polyacid to construct a monodisperse polyacid@TiO2 nanotube coupling photocatalyst, and reduces the recombination rate of photo-generated electrons and holes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalysis, and relates to a preparation method of monodisperse polyacid / TiO2 nanotube photocatalytic material and application thereof. BACKGROUND

[0002] Energy crisis and increasingly serious environmental problems need to be solved, and the conversion and utilization of solar energy is expected to become an effective way to solve energy and environmental problems. In the past few decades, the reduction of carbon dioxide to liquid fuel by using semiconductor photocatalysis is considered to be an ideal method for converting solar energy into chemical energy. However, in the photocatalytic carbon dioxide system, water is a proton source to achieve efficient conversion of carbon dioxide to methanol, which is still challenging.

[0003] TiO2 nanotubes, as an excellent semiconductor material, have been widely concerned in the field of solar energy conversion due to their low cost, visible light response and other advantages. However, the single TiO2 has high recombination rate of photo-generated holes and electrons, large internal resistance, narrow light absorption range and other defects, which makes its photocatalytic efficiency low. Therefore, people use various strategies to explore the inhibition of electron-hole recombination, so as to improve the photocatalytic performance. Among them, more researchers improve the light absorption performance and catalytic performance of TiO2 by constructing composite materials.

[0004] Polyoxometalates (POMs) are a class of molecular clusters with clear structure, which are widely used in medicine, catalysis, material science and other fields. In recent years, POMs have been used as photocatalysts or cocatalysts for photocatalytic reduction of CO2, and have been found to have excellent activity. In addition, since POMs can donate and accept electrons, they can act as a "buffer solution" for photo-generated electrons in photo-redox reactions. Therefore, adding POMs to TiO2 semiconductors is expected to receive and store photo-generated electrons and reduce the recombination rate of photo-generated carriers.

[0005] After searching, two patent literatures related to the content of the patent were found. The Chinese patent with publication number CN116747897A provides a C, N and S co-doped TiO2 / acid etching g-C3N4 heterojunction photocatalyst. In the heterojunction photocatalyst, C, N and S co-doped TiO2 particles are deposited on the surface of the acid-etched layered g-C3N4. The heterojunction photocatalyst has two micro / nano structures, which are micron-sized particles formed by stacking of nanoscale g-C3N4 fragments formed by acid etching of layered g-C3N4, and micron-sized particles of approximately spherical shape formed by secondary agglomeration of nanoscale C, N and S co-doped TiO2 particles. The invention uses one-step hydrothermal method to prepare the heterojunction photocatalyst with excellent catalytic performance, which has excellent photocatalytic degradation activity and stable recycling degradation performance.

[0006] The Chinese patent with publication number CN116689041A provides a dye-sensitized TiO2@HOFs light-promoted catalyst and its preparation method and application, belonging to the fields of material science, environmental science and synthesis technology. The invention disperses hydrogen-bonded organic framework materials and TiO2 in deionized water and performs ultrasonic treatment, then performs rotational vortex vibration, to obtain a milky white suspension; the milky white suspension is centrifuged, and the obtained solid sample is dried to obtain a dye-sensitized TiO2@HOFs light-promoted catalyst. The invention combines HOF-TCPB-373 with TiO2 to prepare a RhB-sensitized TiO2@HOF light-promoted catalyst, which can effectively solve the problem of low sensitization efficiency in the RhB-TiO2 system and has high catalytic activity.

[0007] No patent literature has been found in the retrieval process that applies polyoxometalates to the preparation of TiO2 nanotube photocatalytic materials. Therefore, the above-mentioned literature and the technical problems and effects to be solved by the present application are obviously different. SUMMARY

[0008] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a preparation method of monodisperse polyoxometalate / TiO2 nanotube photocatalytic material. In the photocatalytic reaction, carbon dioxide is successfully reduced to liquid fuel methanol, and water is oxidized at the same time, greatly improving the utilization efficiency of solar energy and expanding new ideas for achieving carbon neutralization.

[0009] The specific technical solution is as follows:

[0010] A preparation method of monodisperse polyoxometalate / TiO2 nanotube photocatalytic material, the steps of which are as follows:

[0011] (1) Preparation of electrolyte: disperse ammonium fluoride and polyoxometalate into ultrapure water, add ethylene glycol solution to form electrolyte A;

[0012] (2) Electrolysis: platinum wire as the cathode of the battery, titanium sheet as the anode of the battery, add a 60V direct current power source, and perform electrolysis in electrolyte A;

[0013] (3) Washing: wash the deposits after electrolysis with ultrapure water and anhydrous ethanol, dry at room temperature to obtain amorphous material B;

[0014] (4) Calcination: place the amorphous material B in a muffle furnace at 450℃ for 2h to obtain monodisperse polyoxometalate / TiO2 nanotube photocatalytic material.

[0015] Moreover, in step (1), the weight ratio of ammonium fluoride, polyoxometalate dispersion, ultrapure water and ethylene glycol is 0.5-0.6:0.1-0.3:3-4:100-150.

[0016] Moreover, in step (1), the polyacid is selected from one of PW 12 , PMo 12 , P2Mo 18 , and P2W 18 .

[0017] Moreover, in step (2), the electrolysis time is 2h.

[0018] Moreover, in step (4), the calcination temperature is 450℃, and the time is 2h.

[0019] The application also provides an application of the monodisperse polyacid / TiO2 nanotube photocatalytic material in photocatalytic reduction of carbon dioxide, which is a method of adding H2O to the monodisperse polyacid / TiO2 nanotube photocatalytic material, and performing a carbon dioxide reduction catalytic reaction under light irradiation with water as a proton source to generate methanol and oxygen.

[0020] Moreover, the ratio of the amount of H2O to the amount of monodisperse polyacid@TiO2 nanotube photocatalyst is 1-10:2 (v / w).

[0021] Moreover, the catalytic reaction temperature is 20-25℃.

[0022] Moreover, the catalytic reaction atmosphere is selected to be carbon dioxide.

[0023] Moreover, the light irradiation condition of the catalytic reaction can be realized by light irradiation of a xenon lamp with a light intensity of 100mW / cm 2 .

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] (1) The application develops a convenient synthesis method, and a monodisperse polyacid / TiO2 nanotube photocatalytic material is constructed by using an in-situ anodic oxidation method to composite TiO2 nanotubes and polyacids.

[0026] (2) The application can use a variety of polyacids (for example, PW 12 , PMo 12 , P2Mo 18 , and P2W 18The polyoxometalates are uniformly dispersed on the surface of the TiO2 nanotubes by in-situ anodic oxidation. The polyoxometalates can accept the photo-generated electrons of the TiO2 nanotubes. The conduction band potential of the TiO2 is sufficient to drive the photocatalytic reduction of carbon dioxide. Under light irradiation, the electrons in the conduction band of the TiO2 can transfer to the polyoxometalates. The photo-generated holes left on the valence band of the TiO2 can oxidize water into oxygen. The photocatalytic reduction of carbon dioxide into methanol and the oxidation of water into oxygen can be simultaneously catalyzed. No sacrificial agent is needed in the catalytic process, and the light energy can be fully and effectively utilized. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The XRD pattern of the monodisperse polyoxometalate / TiO2 nanotube photocatalytic material in Example 1 of the present application.

[0028] Figure 2 The HRTEM pattern of the monodisperse polyoxometalate / TiO2 nanotube photocatalytic material in Example 1 of the present application. DETAILED DESCRIPTION

[0029] The technical solutions of the present application are further illustrated below in combination with the drawings and specific examples.

[0030] Example 1

[0031] The present application provides a monodisperse polyoxometalate / TiO2 nanotube photocatalytic material, and a preparation method thereof, which comprises the following steps:

[0032] 1) 557.5 mg of ammonium fluoride and 200 mg of polyoxometalate (P2Mo 18 ) are dispersed into 3 mL of ultrapure water, 100 mL of ethylene glycol solution is added to form an electrolyte A;

[0033] 2) A platinum wire is used as the cathode of the battery, a titanium sheet is used as the anode of the battery, a direct current power supply of 60 V is added, and electrolysis is carried out in the electrolyte A for 2 h.

[0034] 3) After electrolysis, washing is carried out with an appropriate amount of ultrapure water and anhydrous ethanol, and drying is carried out at room temperature. An amorphous material B is obtained;

[0035] 4) The amorphous material B is calcined in a muffle furnace at 450 ℃ for 2 h to obtain a composite nanomaterial (labeled as monodisperse polyoxometalate / TiO2 nanotube photocatalytic material)

[0036] Structure characterization:

[0037] The monodisperse polyoxometalate / TiO2 nanotube photocatalytic material obtained in step 4 is subjected to structure characterization, and the results are as follows:

[0038] The polyoxometalate is uniformly dispersed on the surface of the TiO2 nanotubes by in-situ anodic oxidation. The polyoxometalate can accept the photo-generated electrons of the TiO2 nanotubes. The conduction band potential of the TiO2 is sufficient to drive the photocatalytic reduction of carbon dioxide. Under light irradiation, the electrons in the conduction band of the TiO2 can transfer to the polyoxometalates. The photo-generated holes left on the valence band of the TiO2 can oxidize water into oxygen. The photocatalytic reduction of carbon dioxide into methanol and the oxidation of water into oxygen can be simultaneously catalyzed. No sacrificial agent is needed in the catalytic process, and the light energy can be fully and effectively utilized. Figure 1The XRD diagram of the monodisperse polyoxometalate / TiO2 nanotube photocatalytic material shows that only the diffraction peak of TiO2 appears, which proves the synthesis of the TiO2 nanotube material.

[0039] Meanwhile, P2Mo 18 The HRTEM diagram of the TiO2 is shown in Figure 2. Figure 2 As shown in Figure 2, the TiO2 nanotube material has a uniform diameter of about 10 nm. Figure 2 As shown in Figure 3, the monodisperse polyoxometalate / TiO2 nanotube photocatalytic material has a uniform diameter of about 10 nm.

[0040] In summary, the polyoxometalate can be successfully grown on the TiO2 nanotube and uniformly distributed.

[0041] Example 2

[0042] The monodisperse polyoxometalate / TiO2 nanotube photocatalytic material prepared above is applied to photocatalytic reduction of CO2 to generate methanol, and water is oxidized to oxygen at the same time. The specific method is as follows:

[0043] 2mg of the monodisperse polyoxometalate / TiO2 nanotube photocatalytic material and 5mL of H2O are added to a 16mL quartz tube. After sealing, the mixture is bubbled with carbon dioxide for 20min, and then irradiated under a 300W Xe lamp to perform a catalytic reaction, and the reaction time is 10h. During the reaction, gas chromatography (GC-2014) is used to qualitatively and quantitatively measure the released methanol and oxygen, the methanol yield is 21μmol·g -1 ·h -1 , and the oxygen yield is 30μmol·g -1 ·h -1 .

[0044] The monodisperse polyoxometalate / TiO2 nanotube photocatalytic material is used for photocatalytic reduction of CO2 to prepare CH3OH. The POM@TiO2 has good catalytic activity for the reaction of photocatalytic reduction of CO2 to prepare CH3OH. For pure TiO2, the electron and hole recombine too fast, which is not conducive to the photocatalytic reduction of carbon dioxide.

[0045] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, and all shall be included in the protection scope of the present application.

Claims

1. An application of a monodisperse polyacid / TiO2 nanotube photocatalytic material in the photocatalytic reduction of carbon dioxide, characterized in that: H2O is added to a monodisperse polyacid / TiO2 nanotube photocatalytic material, and a carbon dioxide reduction catalytic reaction is carried out under light irradiation using water as a proton source to produce methanol and oxygen. The preparation method of the monodisperse polyacid / TiO2 nanotube photocatalytic material is as follows: (1) Preparation of electrolyte: Ammonium fluoride and polyoxometalate are dispersed in ultrapure water, and ethylene glycol solution is added to form electrolyte A. The polyoxometalate is a polyoxometalate selected from PW 12 PMo 12 P2Mo 18 With P2W 18 The ammonium fluoride, polyacid, ultrapure water, and ethylene glycol are in the following weight ratio: (0.5~0.6):(0.1~0.3):(3~4):(100~150). (2) Electrolysis: Platinum wire is used as the cathode of the battery, titanium sheet is used as the anode of the battery, and a 60 V DC power supply is applied to carry out electrolysis in electrolyte A for 2 hours; (3) Washing: The electrolyzed deposits were washed with ultrapure water and anhydrous ethanol and dried at room temperature to obtain amorphous material B; (4) Calcination: Amorphous material B was calcined in a muffle furnace at 450 °C for 2 h to obtain monodisperse polyacid / TiO2 nanotube photocatalytic material.

2. The application according to claim 1, characterized in that: The volume-to-mass ratio of H2O to monodisperse polyacid / TiO2 nanotube photocatalytic material is (1-10) mL: 2 mg.

3. The application according to claim 1, characterized in that: The catalytic reaction temperature is 20–25°C.

4. The application according to claim 1, characterized in that: The catalytic reaction was irradiated with a light intensity of 100 mW / cm². 2 The xenon lamp is realized.

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