TiO2 inorganic semiconductor nanofiber aerogel as well as preparation and application thereof

Abstract

The invention relates to a TiO2 inorganic semiconductor nanofiber aerogel and preparation and application thereof, and the preparation method comprises the following steps: mixing a TiO2 semiconductor nanofiber membrane compounded with carbon with water to obtain a dispersion liquid, then adding a cross-linking agent and a catalyst to obtain a mixed liquid, then carrying out vertical directional freezing and freeze drying on the mixed liquid, and then carrying out heat treatment to obtain the TiO2 inorganic semiconductor nanofiber aerogel. The cross-linking agent comprises polyvinyl alcohol and citric acid, the mass percentage content of the dispersion liquid is 0.8%, and the mass ratio of the citric acid to the polyvinyl alcohol is 1: 1. The TiO2 inorganic semiconductor nanofiber aerogel prepared by the invention constructs a highly ordered three-dimensional porous network structure, has high catalytic activity and good stability, and can maintain rebound resilience after multiple cyclic compression tests.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterials, and in particular relates to a TiO2 inorganic semiconductor nanofiber aerogel and a preparation and application thereof. Background Art

[0002] Excessive consumption of traditional fossil fuels has led to a continuous rise in atmospheric CO2 concentrations, triggering severe problems such as frequent extreme weather events and ecosystem imbalances. Therefore, achieving CO2 emission reduction and efficient conversion and utilization has become a key area of ​​scientific research. Photothermal catalysis technology can harness solar energy, combining the advantages of photocatalysis and thermal catalysis to activate CO2 molecules and convert them into fuels or chemicals such as CO, CH4, and CH3OH. This not only mitigates the greenhouse effect but also enables resource recycling, making it an effective strategy for green CO2 emission reduction.

[0003] Traditional photothermal catalysts are semiconductor metal oxides, mostly in powder form, and suffer from low spectral utilization, difficulty in recycling, and poor catalytic activity. In recent years, graphene aerogel-loaded semiconductor metal oxide catalysts have been widely used in photocatalysis and photothermal catalysis due to their high specific surface area and three-dimensional porous structure. However, due to their mostly disordered macropore structure, wide pore size distribution, and lack of directional transmission channels, light scattering efficiency within the material is low, greatly limiting spectral utilization. Furthermore, the active components of the catalyst loaded within the macropore structure are prone to agglomeration, migration, and even detachment, seriously affecting the efficiency and stability of the photothermal catalytic reaction and hindering the large-scale application of this technology. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a TiO2 inorganic semiconductor nanofiber aerogel and its preparation and application, which overcomes the shortcomings of low spectral utilization of powder photothermal catalysts in the prior art.

[0005] The present invention provides a method for preparing TiO2 inorganic semiconductor nanofiber aerogel, comprising:

[0006] Step (1) calcining a precursor TiO2 semiconductor nanofiber membrane in an inert atmosphere to obtain a carbon-composite TiO2 semiconductor nanofiber membrane; wherein the precursor TiO2 semiconductor nanofiber membrane is obtained by electrospinning a spinning solution containing isopropyl titanate, anhydrous ethanol, acetic acid and polyvinyl pyrrolidone; the mass ratio of the isopropyl titanate, anhydrous ethanol, acetic acid and polyvinyl pyrrolidone is 0.2:3.16:2:1.5;

[0007] Step (2) mixing the carbon-composite TiO2 semiconductor nanofiber membrane with water to obtain a dispersion, and then adding a crosslinking agent and a catalyst to obtain a mixed solution; wherein the crosslinking agent component includes polyvinyl alcohol and citric acid, and the mass percentage of the dispersion is 0.8%; the mass ratio of citric acid to polyvinyl alcohol is 1:1; the mass fraction of polyvinyl alcohol relative to the dispersion is 0.4%, and the mass fraction of citric acid relative to the dispersion is 0.4%;

[0008] Step (3) vertically freezes and freeze-dries the mixed solution, and then heat treats it to obtain TiO2 inorganic semiconductor nanofiber aerogel.

[0009] In the step (1), the inert atmosphere is nitrogen; and the calcination is performed at 600° C. for 1 hour.

[0010] In step (1), isopropyl titanate, anhydrous ethanol, acetic acid and polyvinyl pyrrolidone are stirred for 2 to 6 hours to obtain a spinning solution.

[0011] The process parameters of electrospinning in step (1) include: a propulsion speed of the spinning solution of 0.8-1 ml / h, a spinning distance between the spinning needle and the roller collector of 15 cm, and a pressurized electric field of 14-18 KV.

[0012] Preferably, the catalyst in step (2) is polyphosphoric acid, which promotes the cross-linking reaction.

[0013] Preferably, the mass fraction of the catalyst relative to the dispersion in step (2) is 0.2%.

[0014] The mixing in step (2) is homogeneous mixing, and the speed of the homogenizer used is 4000~5000 rpm / min and the time is 30~60 min.

[0015] After adding the cross-linking agent and catalyst in step (2), the mixture is homogenized at a speed of 4000-5000 rpm / min for 30-60 min.

[0016] In the copper mold used for vertical directional freezing in step (3), the core is composed of a polytetrafluoroethylene plastic main cavity and a copper bottom substrate. Liquid nitrogen is used as a cold source. Copper has an extremely high thermal conductivity (about 394 W / (m·K)), which can quickly conduct the energy of the external cold source to the inside of the cavity, ensuring the formation of a stable vertical temperature gradient, allowing ice crystals to vertically pass through the TiO2 fiber mixture to construct a hierarchical porous framework structure. The ice crystals are then removed by freeze-drying to obtain an uncross-linked composite nanofiber aerogel. The uncross-linked composite nanofiber aerogel is placed in an air circulation oven for heat treatment to achieve a cross-linking esterification reaction of the cross-linking agent, thereby obtaining a TiO2 inorganic semiconductor nanofiber aerogel with a hierarchical porous framework structure having stable connection points.

[0017] Preferably, the vertical directional freezing in step (3) includes directional freezing under liquid nitrogen conditions for 15 minutes.

[0018] Preferably, the freeze-drying process parameters in step (3) include: freezing temperature of -65 to -55 °C, vacuum degree of 5 to 10 Pa, and time of 3 days.

[0019] Preferably, the heat treatment in step (3) is performed at 95-105°C for 60 minutes under air circulation conditions.

[0020] For example, the heat treatment is carried out in a forced air drying oven.

[0021] The present invention provides a TiO2 inorganic semiconductor nanofiber aerogel prepared by the method. The TiO2 inorganic semiconductor nanofiber aerogel has a composite hierarchical porous framework structure with stable connection points.

[0022] The present invention provides an application of the TiO2 inorganic semiconductor nanofiber aerogel in photothermal CO2 conversion.

[0023] The TiO2 inorganic semiconductor nanofiber aerogel prepared by this invention constructs a highly ordered three-dimensional porous network structure. Its unique pore structure provides efficient diffusion channels for the reactants and products of the CO2 conversion reaction. By calcining the composite carbon semiconductor fiber material in an inert gas, the material's light absorption capacity is enhanced, enabling efficient utilization of the full spectrum of sunlight and significantly enhancing photothermal conversion capabilities. Combined with the aerogel's high porosity and low thermal conductivity, it efficiently converts absorbed light energy into heat energy and achieves uniform heat distribution within the material, providing a stable thermodynamic environment for the CO2 reduction reaction.

[0024] In addition, the present invention uses a chemical cross-linking process of polyvinyl alcohol and citric acid to make the aerogel have excellent compression resilience. At a compression distance of 20%, the compression strength reaches 1.41 kPa, giving the material excellent mechanical properties and providing a solid material foundation for the industrial application of photothermal catalytic CO2 conversion technology.

[0025] Beneficial effects

[0026] The preparation process of the invention is simple and the cost is low, and it is a convenient and efficient preparation method.

[0027] The TiO2 inorganic semiconductor nanofiber aerogel prepared by the present invention constructs a highly ordered three-dimensional porous network structure, realizes full-spectrum sunlight utilization through composite carbon materials, introduces cross-linking agents to improve the strength and resilience of the TiO2 inorganic semiconductor nanofiber aerogel, has high catalytic activity and good stability, and can maintain resilience after multiple cyclic compression tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The scanning electron microscope image (a) of the carbon-composite TiO2 semiconductor nanofiber membrane of Comparative Example 5 and the scanning electron microscope image (b) of the TiO2 inorganic semiconductor nanofiber aerogel of Example 1;

[0029] Figure 2 The UV-visible diffuse reflectance spectra of Example 1 and Comparative Example 6 are shown;

[0030] Figure 3 The temperature of the sample surface changes with time under 300 W xenon lamp irradiation for Example 1 and Comparative Example 6;

[0031] Figure 4 Compression stress-strain curves of Example 1 and Comparative Examples 1-4 at 20% compression distance;

[0032] Figure 5 is the compression stress-strain curve of Example 1 in the 45-cycle compression test;

[0033] Figure 6 This is a photothermal CO2 conversion reaction performance test diagram of Example 1, Comparative Examples 1-3, and Comparative Examples 5-6;

[0034] Figure 7 Schematic diagram of vertical directional freezing in the preparation method of TiO2 inorganic semiconductor nanofiber aerogel of the present invention;

[0035] Figure 8 This is a scanning electron microscope image of the TiO2 inorganic semiconductor nanofiber aerogel of Comparative Example 4. DETAILED DESCRIPTION

[0036] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0037] The final materials obtained in the examples and comparative examples were used as samples for relevant tests.

[0038] The test standards and methods involved in the embodiments and comparative examples are as follows:

[0039] Photothermal CO2 conversion performance was tested in a closed vacuum system using 50 mg of sample as catalyst, 80 kPa of pure CO2, and 5 mL of deionized water. The 50 mg catalyst was placed on a custom tripod within the reactor to avoid direct contact with water. A 300 W xenon lamp (PLS-SXE300+, Beijing Perfect Light Technology Co., Ltd.) was used as the light source. The product (CO) was analyzed by gas chromatography (FuliGC9790II, Fuli Analytical Instruments Co., Ltd.) equipped with a flame ionization detector (FID).

[0040] Mechanical Properties: Stress-strain tests were conducted on the samples using an electronic universal testing machine (Model: Instron 5969). The testing process strictly adhered to the relevant provisions for compression testing of non-metallic materials in the GB / T 16491-2022 "Electronic Universal Testing Machine" standard. The test parameters were set as follows: a compression rate of 2 mm / min, a strain of 20% per compression cycle, and 45 cycles of compression.

[0041] Scanning electron microscopy (SEM) test: A field emission scanning electron microscope (TESCAN / MAIA3) was used to characterize the microscopic surface morphology of the samples.

[0042] UV-Visible Absorption Test: A Shimadzu UV-2600 spectrophotometer was used to analyze the light absorption properties of the samples. Pure BaSO4 was used as a reflectance standard sample for light absorption analysis.

[0043] Sample surface temperature testing: A 300 W xenon lamp (PLS-SXE300+, Beijing Perfect Light Technology Co., Ltd.) was used as the light source for irradiation testing. Simultaneously, an infrared thermal imager (UNI-T, Uni-T Technologies (China) Co., Ltd.) was used to monitor surface temperature changes in real time. The xenon lamp power was maintained at 300 W, and the irradiation time was 1 minute. Temperature data was recorded every 10 seconds to record surface temperature changes.

[0044] In the vertically oriented frozen copper mold, the core is composed of a polytetrafluoroethylene plastic main cavity and a copper bottom substrate.

[0045] Polyvinylpyrrolidone (Mw = 1300000) and citric acid were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0046] Isopropyl titanate and polyphosphoric acid were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0047] Acetic acid (99.5%) and anhydrous ethanol (99.7%) were purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0048] Polyvinyl alcohol was purchased from Anaiji (Shanghai) Pharmaceutical Chemistry Co., Ltd.

[0049] Example 1

[0050] (1) A TiO2 fiber spinning solution was prepared by mixing isopropyl titanate, anhydrous ethanol, acetic acid, and polyvinyl pyrrolidone in a mass ratio of 0.2:3.16:2:1.5 and stirring for 6 h. A precursor TiO2 semiconductor nanofiber membrane was prepared by electrospinning based on the TiO2 fiber spinning solution. During the electrospinning process, the spinning solution was fed at a speed of 1 ml / h, the spinning distance between the spinning needle and the roller collector was 15 cm, and the applied electric field was 15 kV. The precursor TiO2 semiconductor nanofiber membrane was calcined at 600 °C in a nitrogen atmosphere for 1 h to obtain a carbon-complexed TiO2 semiconductor nanofiber membrane.

[0051] (2) The carbon-composite TiO2 semiconductor nanofiber membrane was immersed in deionized water, and 15 g of a 0.8% carbon-composite TiO2 semiconductor nanofiber membrane dispersion was prepared. The mixture was homogenized at a high speed of 5000 rpm / min for 1 min. A crosslinking agent and polyphosphoric acid were added, wherein the mass fraction of polyvinyl alcohol relative to the dispersion was 0.4%, the mass fraction of citric acid relative to the dispersion was 0.4%, and the mass fraction of polyphosphoric acid relative to the dispersion was 0.2%. The mixture was then homogenized at a high speed of 5000 rpm / min for 1 h to obtain a mixed solution.

[0052] (3) The mixed solution was poured into a cylindrical mold with a diameter of 3 cm and a height of 5 cm and then vertically frozen using liquid nitrogen for 15 min. The mixture was then placed in a freeze dryer at -60±5°C and a vacuum degree of 5-10 Pa for 3 days to obtain an uncross-linked composite nanofiber aerogel.

[0053] (4) The uncrosslinked composite nanofiber aerogel was placed in an air circulation oven at 100±5°C for heat treatment for 60 min to achieve the crosslinking esterification reaction of the crosslinker and obtain a TiO2 inorganic semiconductor nanofiber aerogel with a hierarchical porous framework structure and stable connection points.

[0054] Example 1 shows high catalytic activity in the photothermal CO2 conversion to CO reaction: the CO yield can reach 379.44 μmol g in 5 hours. catalyst -1 , indicating that it has good conversion efficiency in photothermal-driven carbon emission reduction reactions.

[0055] Mechanical Strength: In compression testing, the material withstood a compressive stress of 1.41 kPa at a 20% compression distance, demonstrating a certain structural load-bearing capacity. Compression Rebound Stability: After 45 compression-rebound cycles, the material maintained its compression resilience, demonstrating excellent structural fatigue resistance and mechanical stability.

[0056] Comparative Example 1

[0057] (1) A TiO2 fiber spinning solution was prepared by mixing isopropyl titanate, anhydrous ethanol, acetic acid, and polyvinyl pyrrolidone in a mass ratio of 0.2:3.16:2:1.5 and stirring for 6 h. A precursor TiO2 semiconductor nanofiber membrane was prepared by electrospinning based on the TiO2 fiber spinning solution. During the electrospinning process, the spinning solution was fed at a speed of 1 ml / h, the spinning distance between the spinning needle and the roller collector was 15 cm, and the applied electric field was 15 KV. The precursor TiO2 semiconductor nanofiber membrane was calcined at 600 °C in a nitrogen atmosphere for 1 h to obtain a carbon-composite TiO2 semiconductor nanofiber membrane.

[0058] (2) Immerse the carbon-composite TiO2 semiconductor nanofiber membrane in deionized water, prepare 15 g of a 0.8% carbon-composite TiO2 semiconductor nanofiber membrane dispersion, and homogenize it at a high-speed homogenizer at 5000 rpm / min for 1 min. Add a crosslinker and polyphosphoric acid, wherein the mass fraction of polyvinyl alcohol relative to the dispersion is 0.4%, the mass fraction of citric acid relative to the dispersion is 0.8%, and the mass fraction of polyphosphoric acid relative to the dispersion is 0.2%. Then continue homogenizing at a high-speed homogenizer at 5000 rpm / min for 1 h to obtain a mixed solution.

[0059] (3) The mixed solution was poured into a cylindrical mold with a diameter of 3 cm and a height of 5 cm and then vertically frozen using liquid nitrogen for 15 min. The mixture was then placed in a freeze dryer at -60±5°C and a vacuum degree of 5-10 Pa for 3 days to obtain an uncross-linked composite nanofiber aerogel.

[0060] (4) The uncrosslinked composite nanofiber aerogel was placed in an air circulation oven at 100±5°C for heat treatment for 60 min to achieve the crosslinking esterification reaction of the crosslinker and obtain a TiO2 inorganic semiconductor nanofiber aerogel with a hierarchical porous framework structure and stable connection points.

[0061] Comparative Example 1: In the photothermal CO2 to CO conversion reaction, the CO yield can reach 298.17 μmol g in 5 hours. catalyst -1Mechanical strength: In the compression test, when the compression distance is 20%, the material can withstand a compressive stress of 0.92 kPa.

[0062] Comparative Example 2

[0063] (1) A TiO2 fiber spinning solution was prepared by mixing isopropyl titanate, anhydrous ethanol, acetic acid, and polyvinyl pyrrolidone in a mass ratio of 0.2:3.16:2:1.5 and stirring for 6 h. A precursor TiO2 semiconductor nanofiber membrane was prepared by electrospinning based on the TiO2 fiber spinning solution. During the electrospinning process, the spinning solution was fed at a speed of 1 ml / h, the spinning distance between the spinning needle and the roller collector was 15 cm, and the applied electric field was 15 KV. The precursor TiO2 semiconductor nanofiber membrane was calcined at 600 °C in a nitrogen atmosphere for 1 h to obtain a carbon-composite TiO2 semiconductor nanofiber membrane.

[0064] (2) The carbon-composite TiO2 semiconductor nanofiber membrane was immersed in deionized water, and 15 g of a 0.8% carbon-composite TiO2 semiconductor nanofiber membrane dispersion was prepared. The mixture was homogenized at a high speed of 5000 rpm / min for 1 min. A crosslinking agent and polyphosphoric acid were added, wherein the mass fraction of polyvinyl alcohol relative to the dispersion was 0.6%, the mass fraction of citric acid relative to the dispersion was 0.6%, and the mass fraction of polyphosphoric acid relative to the dispersion was 0.2%. The mixture was then homogenized at a high speed of 5000 rpm / min for 1 h to obtain a mixed solution.

[0065] (3) The mixed solution was poured into a cylindrical mold with a diameter of 3 cm and a height of 5 cm and then vertically frozen using liquid nitrogen for 15 min. The mixture was then placed in a freeze dryer at -60±5°C and a vacuum degree of 5-10 Pa for 3 days to obtain an uncross-linked composite nanofiber aerogel.

[0066] (4) The uncrosslinked composite nanofiber aerogel was placed in an air circulation oven at 100±5°C for heat treatment for 60 min to achieve the crosslinking esterification reaction of the crosslinker and obtain a TiO2 inorganic semiconductor nanofiber aerogel with a hierarchical porous framework structure and stable connection points.

[0067] Comparative Example 2: In the photothermal CO2 to CO conversion reaction, the CO yield can reach 175.76 μmol g in 5 hours. catalyst -1 Mechanical strength: In the compression test, when the compression distance is 20%, the material can withstand a compressive stress of 0.31 kPa.

[0068] Comparative Example 3

[0069] (1) A TiO2 fiber spinning solution was prepared by mixing isopropyl titanate, anhydrous ethanol, acetic acid, and polyvinyl pyrrolidone in a mass ratio of 0.2:3.16:2:1.5 and stirring for 6 h. A precursor TiO2 semiconductor nanofiber membrane was prepared by electrospinning based on the TiO2 fiber spinning solution. During the electrospinning process, the spinning solution was fed at a speed of 1 ml / h, the spinning distance between the spinning needle and the roller collector was 15 cm, and the applied electric field was 15 KV. The precursor TiO2 semiconductor nanofiber membrane was calcined at 600 °C in a nitrogen atmosphere for 1 h to obtain a carbon-composite TiO2 semiconductor nanofiber membrane.

[0070] (2) The carbon-composite TiO2 semiconductor nanofiber membrane was immersed in deionized water, and 15 g of a 0.8% carbon-composite TiO2 semiconductor nanofiber membrane dispersion was prepared. The mixture was homogenized at a high-speed homogenizer at 5000 rpm / min for 1 min. A crosslinker and polyphosphoric acid were added, wherein the mass fraction of polyvinyl alcohol relative to the dispersion was 0.6%, the mass fraction of citric acid relative to the dispersion was 1.2%, and the mass fraction of polyphosphoric acid relative to the dispersion was 0.2%. The mixture was then homogenized at a high-speed homogenizer at 5000 rpm / min for 1 h to obtain a mixed solution.

[0071] (3) The mixed solution was poured into a cylindrical mold with a diameter of 3 cm and a height of 5 cm and then vertically frozen using liquid nitrogen for 15 min. The mixture was then placed in a freeze dryer at -60±5°C and a vacuum degree of 5-10 Pa for 3 days to obtain an uncross-linked composite nanofiber aerogel.

[0072] (4) The uncrosslinked composite nanofiber aerogel was placed in an air circulation oven at 100±5°C for heat treatment for 60 min to achieve the crosslinking esterification reaction of the crosslinker and obtain a TiO2 inorganic semiconductor nanofiber aerogel with a hierarchical porous framework structure and stable connection points.

[0073] Comparative Example 3: In the photothermal CO2 to CO conversion reaction, the CO yield can reach 298.17 μmol g in 5 hours. catalyst -1 Mechanical strength: In the compression test, when the compression distance is 20%, the material can withstand a compressive stress of 0.33 kPa.

[0074] Comparative Example 4

[0075] (1) A TiO2 fiber spinning solution was prepared by mixing isopropyl titanate, anhydrous ethanol, acetic acid, and polyvinyl pyrrolidone in a mass ratio of 0.2:3.16:2:1.5 and stirring for 6 h. A precursor TiO2 semiconductor nanofiber membrane was prepared by electrospinning based on the TiO2 fiber spinning solution. During the electrospinning process, the spinning solution was fed at a speed of 1 ml / h, the spinning distance between the spinning needle and the roller collector was 15 cm, and the applied electric field was 15 kV. The precursor TiO2 semiconductor nanofiber membrane was calcined at 600 °C in nitrogen for 1 h to obtain a carbon-composite TiO2 semiconductor nanofiber membrane.

[0076] (2) The carbon-composite TiO2 semiconductor nanofiber membrane was immersed in deionized water, and 15 g of a 0.4% carbon-composite TiO2 semiconductor nanofiber membrane dispersion was prepared. The mixture was homogenized at a high speed of 5000 rpm / min for 1 min. A crosslinking agent and polyphosphoric acid were added, wherein the mass fraction of polyvinyl alcohol relative to the dispersion was 0.4%, the mass fraction of citric acid relative to the dispersion was 0.4%, and the mass fraction of polyphosphoric acid relative to the dispersion was 0.2%. The mixture was then homogenized at a high speed of 5000 rpm / min for 1 h to obtain a mixed solution.

[0077] (3) The mixed solution was poured into a cylindrical mold with a diameter of 3 cm and a height of 5 cm and then vertically frozen using liquid nitrogen for 15 min. The mixture was then placed in a freeze dryer at -60±5°C and a vacuum degree of 5-10 Pa for 3 days to obtain an uncross-linked composite nanofiber aerogel.

[0078] (4) The uncrosslinked composite nanofiber aerogel was placed in an air circulation oven at 100±5°C for heat treatment for 60 min to achieve the crosslinking esterification reaction of the crosslinking agent and obtain an incomplete morphology of TiO2 inorganic semiconductor nanofiber aerogel. Figure 8 As shown in the figure, the fiber aerogel has a reduced proportion of TiO2 fiber membrane base material, resulting in a lack of sufficient fiber support to form the aerogel wall during the aerogel preparation process, the structure collapses, and the fiber surface is covered by the cross-linking agent.

[0079] Mechanical strength of Comparative Example 4: In the compression test, when the compression distance is 20%, the material can withstand a compressive stress of 0.86 kPa. However, it does not have compression resilience.

[0080] Comparative Example 5

[0081] A TiO2 fiber spinning solution was prepared by mixing isopropyl titanate, anhydrous ethanol, acetic acid, and polyvinyl pyrrolidone in a mass ratio of 0.2:3.16:2:1.5 and stirring for 6 hours. A TiO2 semiconductor nanofiber membrane precursor was prepared by electrospinning from this solution. During the electrospinning process, the spinning solution was fed at a rate of 1 ml / h, the spinning distance between the spinning needle and the roller collector was 15 cm, and the applied electric field was 15 kV. The carbon-complexed TiO2 semiconductor nanofiber membrane was then calcined at 600°C in a nitrogen atmosphere for 1 hour.

[0082] Comparative Example 5: The carbon-composite TiO2 semiconductor nanofiber membrane has a CO yield of 15 μmol g in the photothermal CO2 to CO conversion reaction for 5 hours. catalyst -1 .

[0083] Comparative Example 6

[0084] (1) A TiO2 fiber spinning solution was prepared by mixing isopropyl titanate, anhydrous ethanol, acetic acid, and polyvinyl pyrrolidone in a mass ratio of 0.2:3.16:2:1.5 and stirring for 6 h. A TiO2 semiconductor nanofiber membrane precursor was prepared by electrospinning based on the TiO2 fiber spinning solution. During the electrospinning process, the spinning solution was fed at a speed of 1 ml / h, the spinning distance between the spinning needle and the roller collector was 15 cm, and the applied electric field was 15 kV. The TiO2 semiconductor nanofiber membrane precursor was calcined at 600 °C in air for 1 h to obtain a TiO2 semiconductor nanofiber membrane.

[0085] (2) The TiO2 semiconductor nanofiber membrane was immersed in deionized water, and 15 g of a 0.8% TiO2 semiconductor nanofiber membrane dispersion was prepared. The mixture was homogenized at a high speed of 5000 rpm / min for 1 min. A crosslinker and polyphosphoric acid were added, wherein the mass fraction of polyvinyl alcohol relative to the dispersion was 0.4%, the mass fraction of citric acid relative to the dispersion was 0.4%, and the mass fraction of polyphosphoric acid relative to the dispersion was 0.2%. The mixture was then homogenized at a high speed of 5000 rpm / min for 1 h to obtain a mixed solution.

[0086] (3) The mixed solution was poured into a cylindrical mold with a diameter of 3 cm and a height of 5 cm and then vertically frozen using liquid nitrogen for 15 min. The mixture was then placed in a freeze dryer at -60 ± 5 °C and a vacuum degree of 5-10 Pa for 3 days to obtain an uncrosslinked composite nanofiber aerogel.

[0087] (4) The uncrosslinked composite nanofiber aerogel was placed in an air circulation oven at 100±5°C for heat treatment for 60 min to achieve the crosslinking esterification reaction of the crosslinker and obtain TiO2 inorganic semiconductor nanofiber aerogel without carbon element.

[0088] Comparative Example 6: In the photothermal CO2 conversion reaction to CO, the CO yield can reach 8 μmol g in 5 hours. catalyst -1 .

[0089] like Figure 1 Figure a shows a scanning electron microscope image of the carbon-composite TiO2 semiconductor nanofiber membrane of Comparative Example 5, with a fiber diameter of 400-900 nm. Figure 1 Figure b is a scanning electron microscope image of the TiO2 inorganic semiconductor nanofiber aerogel prepared in Example 1. The image shows that the TiO2 inorganic semiconductor nanofiber aerogel prepared in Example 1 has a composite hierarchical porous framework structure, with the nanofibers tightly bound together by the crosslinking agent. The TiO2 inorganic semiconductor nanofiber aerogel prepared in Example 1 has a relatively ordered three-dimensional spatial structure.

[0090] like Figure 2 Shown are the UV-visible diffuse reflectance spectra of Example 1 and Comparative Example 6. The figures show that the material calcined in air absorbs light only in the UV region, while the sample from Example 1 exhibits full-spectrum absorption. This demonstrates that the TiO2 inorganic semiconductor nanofiber aerogel prepared in Example 1 can utilize the full spectrum of sunlight.

[0091] like Figure 3 The figure shows the surface temperature changes over time for Example 1 and Comparative Example 6 under 300 W xenon lamp irradiation. The figure shows that the surface temperature of the sample treated in air stabilizes around 100°C, while the surface temperature of the sample treated in N2 stabilizes around 160°C, indicating that the TiO2 inorganic semiconductor nanofiber aerogel material prepared in Example 1 has better photothermal conversion performance.

[0092] like Figure 4 The compressive stress-strain curves at 20% compression distance are shown for Example 1 and Comparative Examples 1-4. It can be seen from the figure that Example 1 has good mechanical properties, can withstand a compressive stress of 1.41 kPa at a compression distance of 20%, and can recover well.

[0093] like Figure 5 The figure shows the compressive stress-strain curve of Example 1 during 45 fatigue tests (compression distance 20%). After 45 compression-recovery cycles, plastic deformation was only 9.1%. This demonstrates that the TiO2 inorganic semiconductor nanofiber aerogel material prepared in Example 1 can be reused multiple times.

[0094] like Figure 6 The photocatalytic CO2 conversion performance test diagram of Example 1 and Comparative Examples 1-3 and Comparative Examples 5-6 is shown. It can be seen from the figure that the yield of photothermal CO2 conversion to CO in Example 1 can reach 379.44 μmol g within 5 h. catalyst -1 , which is much higher than other comparative materials, indicating that the TiO2 inorganic semiconductor nanofiber aerogel in Example 1 has excellent photothermal CO2 conversion performance.

[0095] like Figure 7 This is a schematic diagram of vertical directional freezing in the preparation method of TiO2 inorganic semiconductor nanofiber aerogel of the present invention. As can be seen from the figure, vertical directional freezing is used to allow ice crystals to grow vertically to construct a composite hierarchical porous framework structure.

Claims

1. A method for preparing TiO2 inorganic semiconductor nanofiber aerogel, characterized in that: include: Step (1) calcining a precursor TiO2 semiconductor nanofiber membrane in an inert atmosphere to obtain a carbon-composite TiO2 semiconductor nanofiber membrane; wherein the precursor TiO2 semiconductor nanofiber membrane is obtained by electrospinning a spinning solution containing isopropyl titanate, anhydrous ethanol, acetic acid and polyvinyl pyrrolidone; the mass ratio of the isopropyl titanate, anhydrous ethanol, acetic acid and polyvinyl pyrrolidone is 0.2:3.16:2:1.5; Step (2) mixing the carbon-composite TiO2 semiconductor nanofiber membrane with water to obtain a dispersion, and then adding a crosslinking agent and a catalyst to obtain a mixed solution; wherein the crosslinking agent component includes polyvinyl alcohol and citric acid, and the mass percentage of the dispersion is 0.8%; the mass ratio of citric acid to polyvinyl alcohol is 1:1; the mass fraction of polyvinyl alcohol relative to the dispersion is 0.4%, and the mass fraction of citric acid relative to the dispersion is 0.4%; Step (3) vertically freezes and freeze-dries the mixed solution, and then heat treats it to obtain TiO2 inorganic semiconductor nanofiber aerogel.

2. The preparation method according to claim 1, characterized in that In the step (1), the inert atmosphere is nitrogen; and the calcination is performed at 600° C. for 1 hour.

3. The preparation method according to claim 1, characterized in that The catalyst in step (2) is polyphosphoric acid.

4. The preparation method according to claim 1, characterized in that In the step (2), the mass fraction of the catalyst relative to the dispersion is 0.2%.

5. The preparation method according to claim 1, characterized in that: The vertical directional freezing in step (3) includes directional freezing under liquid nitrogen conditions for 15 minutes.

6. The preparation method according to claim 1, characterized in that: The freeze-drying process parameters in step (3) include: freezing temperature of -65 ~ -55 °C, vacuum degree of 5 ~ 10 Pa, and time of 3 days.

7. The preparation method according to claim 1, characterized in that: The heat treatment in step (3) is performed at 95-105°C for 60 min under air circulation conditions.

8. A TiO2 inorganic semiconductor nanofiber aerogel, characterized in that: The TiO2 inorganic semiconductor nanofiber aerogel is prepared by the method according to any one of claims 1 to 7.

9. An application of the TiO2 inorganic semiconductor nanofiber aerogel according to claim 8, characterized in that: Application of the TiO2 inorganic semiconductor nanofiber aerogel in photothermal CO2 conversion.

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