Titanium suboxide powder material and method of preparation

Abstract

The application discloses a kind of titanium suboxide powder materials and preparation method, belong to solar energy photo-thermal conversion material technical field, the preparation method of titanium suboxide powder material provided by the present application includes: S1.preparation precursor powder, S2.SiO2 is coated, S3.hydrogen reduction, S4.SiO2 is removed, first by specific preparation method preparation obtains the dispersed TiO2 precursor powder with nanosheet structure, subsequently in combination with specific SiO2 coating method, SiO2 microspheres are coated on the surface of TiO2 precursor powder, under hydrogen atmosphere 1000 DEG C~1050 DEG C is kept for 3~6h, and reduction is obtained SiO2 coated λ-Ti3O5 powder, finally remove SiO2 coating, and prepare single-phase λ-Ti3O5 nano-powder material, since hydrogen reduction sintering temperature is low, nano-powder does not occur agglomeration, sintering grows, still keep as dispersed uniform nano-powder structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar light-heat conversion materials, and particularly relates to a titanium suboxide powder material and a preparation method. BACKGROUND

[0002] Solar-driven interfacial water evaporation has attracted much attention in seawater desalination and wastewater treatment due to its low cost and environmental friendliness. However, the efficiency of solar evaporators is limited by the large amount of heat loss during the evaporation process. In order to improve the evaporation efficiency of solar evaporators, researchers have devoted to developing solar light-heat conversion materials with high absorption rate. Semiconductor materials have excellent light absorption characteristics and light-heat conversion capacity, and are currently very promising light-heat conversion materials. Titanium suboxide (TiO n O 2n-1 n≥3) as an oxygen-deficient rutile crystal, forms oxygen vacancies every n layers through lattice shearing on the basis of TiO2, which is conducive to the full capture and utilization of sunlight, thereby improving the light-heat conversion efficiency. Among them, λ-Ti3O5 as a metallic semiconductor has a narrower band gap than other titanium suboxides such as Ti4O7, which is more conducive to improving the solar light-heat conversion efficiency.

[0003] Since Ti3O5 includes five similar crystal structures of α, β, γ, δ and λ phases, it is very difficult to prepare single-phase λ-Ti3O5 powder material, and λ-Ti3O5 is a room-temperature metastable phase and needs to exist in the form of nanostructure at room temperature. At present, the preparation of λ-Ti3O5 nano-powder material mainly adopts sol-gel method and thermal reduction method. Cai et al. disclosed a PEG-assisted sol-gel method for synthesizing nano λ-Ti3O5 (Synthesis of nanoscale lambda-Ti3O5 via a PEG assisted sol-gel method, Y. Cai et al., Journal of Alloys and Compounds, 2020), however, the high-temperature calcination of PEG inevitably causes carbon residue, resulting in the decline of the photo-thermal conversion performance of λ-Ti3O5. Liu Gang et al. disclosed the preparation of λ-Ti3O5 powder (Research on the preparation of λ-Ti3O5 powder and its optical storage performance, Liu Gang et al., Journal of Inorganic Materials, 2013), using silica-coated nano-TiO2 powder (rutile type) as raw material, the silica coating plays a protective role on the powder, making TiO2 not easy to agglomerate, and inhibiting the growth of TiO2 particles, and λ-Ti3O5 powder with single-phase composition can be synthesized by hydrogen reduction at 1150℃ for 1h, however, due to the high sintering temperature of 1150℃, the particle powder is obviously connected, aggregated and sintered, and the silica-coated TiO2 rod-shaped nano-powder is reduced to obtain micrometer-level λ-Ti3O5 powder. Therefore, there is an urgent need to provide a new preparation method of titanium suboxide powder material, which can prepare single-phase λ-Ti3O5 nano-powder material. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of titanium suboxide powder material, which can prepare single-phase λ-Ti3O5 nano-powder material.

[0005] In order to achieve the above purpose, the present application provides the following technical solutions:

[0006] In the first aspect, the present application provides a preparation method of titanium suboxide powder material, comprising the following steps:

[0007] S1. Preparation of precursor powder, adding hydrofluoric acid and butyl titanate in a reaction container, the volume ratio of hydrofluoric acid and butyl titanate is 4-10:18-30, after stirring uniformly, the temperature is raised to 180-280℃ and reacted for 18-36h, and the reaction product is washed by centrifugation and dried to prepare the precursor powder;

[0008] S2. Coating SiO2, the precursor powder is added to a mixed solution of anhydrous ethanol and deionized water, and after being uniformly dispersed by ultrasonic, ammonia water and tetraethyl orthosilicate are added, the volume ratio of ammonia water to tetraethyl orthosilicate is 2-5:4-8, after ultrasonic reaction for 2-6 hours, the reaction product is cleaned by centrifugation and dried to prepare the SiO2-coated powder;

[0009] S3. Hydrogen reduction, the SiO2-coated powder is heated to 1000-1050 DEG C under a hydrogen atmosphere and kept for 3-6 hours to prepare a reduced SiO2-coated powder;

[0010] S4. Removing SiO2, the reduced SiO2-coated powder is added to a 0.2-0.6 mol / L NaOH solution, stirred for 2-4 hours, cleaned and dried to prepare a titanium suboxide powder material, and the titanium suboxide powder material is a single-phase λ-Ti3O5 nanometer powder material.

[0011] Optionally, in step S1, the volume ratio of the hydrofluoric acid to the butyl titanate is 5-8:20-30, and after being uniformly stirred, the temperature is raised to 180-220 DEG C and reacted for 18-30 hours.

[0012] Optionally, in step S2, the mass-volume ratio of the precursor powder to the mixed solution, ammonia water and tetraethyl orthosilicate is 0.3-0.8 g:130-180 mL:2-5 mL:4-8 mL.

[0013] Optionally, in step S1, the precursor powder is a pure-phase anatase TiO2, and TiO2 grows preferentially along (200) and (211) crystal planes.

[0014] Optionally, in step S1, the precursor powder has a nanosheet structure, the nanosheet structure is uniformly dispersed, and the particle size in the length direction is 80-110 nm and the particle size in the thickness direction is 5-15 nm.

[0015] Optionally, in step S2, the SiO2-coated powder is amorphous SiO2-coated TiO2, the SiO2-coated powder has a microsphere combination structure, a plurality of SiO2 microspheres are combined on the surface of TiO2 to form a microsphere combination particle, the particle size of the SiO2 microsphere is 120-200 nm, and the particle size of the microsphere combination particle is 300-900 nm.

[0016] Optionally, in step S4, the titanium suboxide powder material has a nanosheet structure, the nanosheet structure is uniformly dispersed, and the particle size in the length direction is 100-150 nm and the particle size in the thickness direction is 8-15 nm.

[0017] Optionally, in step S4, the specific surface area of the prepared titanium suboxide powder material reaches 131.3 m 2 g -1 .

[0018] Optionally, in step S4, the solar light absorption rate of the prepared titanium suboxide powder material reaches 92.2%, the light-heat conversion efficiency reaches 91.7%, and the evaporation rate reaches 1.79 kg m -2 h -1 .

[0019] In the second aspect, the application provides a titanium suboxide powder material prepared by the above-mentioned preparation method of a titanium suboxide powder material.

[0020] In summary, the application has at least one of the following beneficial effects:

[0021] 1. The application provides a preparation method of a titanium suboxide powder material, which comprises the following steps: first, preparing a dispersed TiO2 precursor powder with a nanosheet structure by a specific preparation method; then, coating the TiO2 precursor powder with SiO2 microspheres by a specific SiO2 coating method; reducing the SiO2-coated TiO2 precursor powder at 1000-1050°C for 3-6 h in a hydrogen atmosphere to obtain a SiO2-coated λ-Ti3O5 powder; and finally, removing the SiO2 coating layer to prepare a single-phase λ-Ti3O5 nanometer powder material. Since the hydrogen reduction sintering temperature is low, the nanometer powder does not agglomerate or sinter and grow, and still maintains a dispersed and uniform nanometer powder structure.

[0022] 2. The application provides a preparation method of a titanium suboxide powder material, which comprises the following steps: first, preparing a TiO2 precursor powder with a sheet-like nanometer structure by a specific preparation method; then, coating the TiO2 precursor powder with SiO2 microspheres by a specific SiO2 coating method; and finally, removing the SiO2 coating layer to prepare a single-phase λ-Ti3O5 nanometer powder material. The length of the TiO2 precursor powder is 80-110 nm, the thickness is 5-15 nm, the TiO2 is anatase TiO2, and the TiO2 grows preferentially along the (200) and (211) crystal planes. The TiO2 is dispersed uniformly, the SiO2 microspheres are combined with the TiO2 on specific crystal planes, have low interface binding energy, are conducive to promoting the reduction reaction between hydrogen and TiO2, thereby reducing the reduction temperature, and are conducive to removing the SiO2 microspheres without introducing other impurities, thereby preparing a pure-phase λ-Ti3O5 nanometer powder material.

[0023] 3.The application provides a preparation method of titanium suboxide powder, which can prepare flaky single-phase lambda-Ti3O5 nanopowder material, wherein the particle size of the nanopowder material in the length direction is 100-150 nm, the particle size of the nanopowder material in the thickness direction is 8-15 nm, and the nanopowder material is uniformly dispersed; the uniformly dispersed nanopowder material has a large specific surface area, which is conducive to promoting the absorption of sunlight; in addition, the nanoparticle size of the lambda-Ti3O5 has a narrower band gap, thereby promoting the photo-thermal conversion and further improving the photo-thermal conversion efficiency; in the subsequent examples, the specific surface area of the titanium suboxide powder measured by the BET method can be as high as 131.3 m 2 g -1 , the sunlight absorption rate can reach 92.2%, the photo-thermal conversion efficiency reaches 91.7%, and the evaporation rate reaches 1.79 kg m -2 h -1 . BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 (a) XRD and (b) SEM of the precursor powder sample of Example 1.

[0025] Figure 2 (a) XRD, (b) SEM, (c) EDS Ti element area scan and (d) EDS Si element area scan of the SiO2-coated powder sample of Example 1.

[0026] Figure 3 (a) XRD and (b) SEM of the reduced powder sample of Example 1 coated with SiO2.

[0027] Figure 4 (a) XRD, (b) SEM and (c) nitrogen isothermal adsorption-desorption curve of the final powder sample of Example 1.

[0028] Figure 5 (a) XRD and (b) SEM of the final powder sample of Example 2.

[0029] Figure 6 (a) XRD, (b) SEM and (c) nitrogen isothermal adsorption-desorption curve of the reduced powder sample of Comparative Example 1.

[0030] Figure 7 (a) sunlight absorption rate and (b) photo-thermal conversion capacity comparison chart of the flaky lambda-Ti3O5 and lambda-Ti3O5 respectively prepared in Example 1 and Comparative Example 1.

[0031] Figure 8 Comparison chart of the evaporation performance of the flaky lambda-Ti3O5 and lambda-Ti3O5 respectively prepared in Example 1 and Comparative Example 1 as photo-thermal conversion materials of the evaporator.

[0032] Figure 9 (a) XRD, (b) SEM of the coated SiO2reduced powder sample of Comparative Example 2.

[0033] Figure 10 XRD of the final powder sample of Comparative Example 3.

[0034] Figure 11 XRD of the final powder sample of Comparative Example 4.

[0035] Figure 12 SEM image of the precursor powder sample of Comparative Example 5. DETAILED DESCRIPTION

[0036] The present application provides a titanium suboxide powder material and a preparation method. In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0037] When the semiconductor material is used as a solar light-heat conversion material, the essence of light-heat conversion is electron transition, therefore, the band gap structure is the core to measure the light-heat conversion capacity of the semiconductor material. In order to make the sunlight be fully captured and utilized, the semiconductor is required to have a narrow band gap, and the narrower the band gap width, the less energy required for the electron transition, and the more easily the electron-hole pairs are formed under the irradiation of sunlight. The energy of the excited hole-electron pairs mainly exists in the form of heat, therefore, the band gap width determines the light-heat conversion capacity. Among them, λ-Ti3O5 as a metallic semiconductor has a narrower band gap width than other titanium suboxides such as Ti4O7, and is more conducive to improving the solar absorption rate and the light-heat conversion efficiency. λ-Ti3O5 needs to exist in a nano structure at room temperature to remain stable, and the existing hydrogen hot reduction method combined with silicon oxide coating has a certain effect on inhibiting the growth of powder particles. However, in order to obtain pure phase λ-Ti3O5, the reduction temperature of the hydrogen hot reduction method is as high as 1150°C or above, which causes the powder to still agglomerate, sinter and grow, making it very difficult to prepare a dispersed nano λ-Ti3O5 powder with a pure phase. The inventors have found through long-term research that by a specific method, a TiO2 precursor powder with a specific microstructure and orientation is prepared, the TiO2 precursor powder is a uniformly dispersed nano sheet-shaped powder, the particle size in the length direction is 80-110 nm, the particle size in the thickness direction is 5-15 nm, and the growth is preferentially oriented along the (200) and (211) crystal planes. In the subsequent specific SiO2 coating process, the specific crystal planes of the SiO2 microspheres and the TiO2 precursor powder are combined, which has a low interface bonding energy, is conducive to promoting the reduction reaction of hydrogen and TiO2, thereby reducing the reduction temperature to 1000-1050°C, avoiding the agglomeration, sintering and growth of the powder during the reduction process, and in the subsequent specific SiO2 removal process, due to the low bonding energy state, it is beneficial to remove SiO2, and only 0.2-0.6 mol / L of NaOH solution is required at room temperature to completely remove the SiO2 coating layer without introducing other impurities, thereby preparing a uniformly dispersed nano λ-Ti3O5 powder. The λ-Ti3O5 powder is a nano sheet-shaped powder, the particle size in the length direction is 100-150 nm, and the particle size in the thickness direction is 8-15 nm. The specific microstructure of the λ-Ti3O5 powder has a high specific surface area, is conducive to reducing the sunlight reflection and increasing the sunlight absorption, has better hydrophilicity, can ensure that the light absorption layer has sufficient water for evaporation, has a narrower band gap width, and therefore the electron transition is easier, and has a higher light-heat conversion capacity. The present application is obtained on the basis of the research.

[0038] Specifically, the present application provides a preparation method of a titanium suboxide powder material, comprising the following steps:

[0039] S1. Preparation of precursor powder, adding hydrofluoric acid and butyl titanate in a reaction vessel, the volume ratio of hydrofluoric acid and butyl titanate is 4-10:18-30, after stirring uniformly, heating to 180-280℃ for 18-36h, the reaction product is washed by centrifugation and dried to prepare the precursor powder. Preferably, the volume ratio of hydrofluoric acid and butyl titanate is 5-8:20-30; preferably, the reaction temperature is 180-220℃, more preferably, the reaction temperature is 190-210℃; preferably, the reaction time is 18-30h, more preferably, the reaction time is 20-26h.

[0040] S2. Coating SiO2, adding the precursor powder into a mixed solution of anhydrous ethanol and deionized water, after ultrasonic dispersion, adding ammonia and tetraethyl orthosilicate, the volume ratio of ammonia and tetraethyl orthosilicate is 2-5:4-8, after ultrasonic reaction for 2-6h, the reaction product is washed by centrifugation and dried to prepare the SiO2-coated powder. Preferably, the mass volume ratio of the precursor powder and the mixed solution, ammonia and tetraethyl orthosilicate is 0.3-0.8g:130-180mL:2-5mL:4-8mL, more preferably, 0.4-0.6g:140-160mL:3-4mL:5-7mL; preferably, the ultrasonic reaction time is 3-5h.

[0041] S3. Hydrogen reduction, heating the SiO2-coated powder to 1000-1050℃ under hydrogen atmosphere for 3-6h to prepare the SiO2-coated reduced powder. Preferably, the reaction temperature is 1020-1050℃; the reaction time is 3-5h; preferably, the hydrogen flow is 500-700mL / min. -1 .

[0042] S4. Removing SiO2, adding the SiO2-coated reduced powder into 0.2-0.6mol / L NaOH solution, stirring for 2-4h, then washing and drying to prepare the titanium suboxide powder material, which is a single-phase λ-Ti3O5 nanometer powder material. Preferably, adding into 0.2-0.5mol / L NaOH solution for stirring reaction; preferably, the stirring reaction time is 2-3h; preferably, the stirring reaction speed is 600-900r / min.

[0043] In some embodiments of the present application, in step S1, the precursor powder is pure-phase anatase TiO2, and TiO2 grows preferentially along (200) and (211) crystal planes; the precursor powder is a nanosheet structure, the nanosheet structure is uniformly dispersed, and the length direction particle size is 80-110nm, and the thickness direction particle size is 5-15nm.

[0044] In some embodiments of the present application, in step S2, the SiO2-coated powder is amorphous SiO2-coated TiO2, the SiO2-coated powder is a microsphere combination structure, and a plurality of SiO2microspheres are combined on the surface of TiO2to form a microsphere combination particle, the particle size of the SiO2microspheres is 120 nm to 200 nm, and the particle size of the microsphere combination particle is 300 nm to 900 nm.

[0045] In some embodiments of the present application, in step S4, the titanium suboxide powder material has a nanosheet structure, the nanosheet structure is uniformly dispersed, the particle size in the length direction is 100 to 150 nm, and the particle size in the thickness direction is 8 to 15 nm; the specific surface area of the titanium suboxide powder material reaches 131.3 m2 / g. 2 g -1 ; the solar light absorption rate of the prepared titanium suboxide powder material reaches 92.2%, the photo-thermal conversion efficiency reaches 91.7%, and the evaporation rate reaches 1.79 kg m -2 h -1 .

[0046] The present application is further described in detail below with reference to the examples.

[0047] Example 1

[0048] The present embodiment provides a preparation method of a titanium suboxide powder material, which specifically comprises the following steps:

[0049] S1. Preparation of a precursor powder, hydrogen fluoride (AR, 40 wt.%) and tetrabutyl titanate (AR) are added into a 50 mL polytetrafluoroethylene reactor inner container in a volume ratio of 5 mL:20 mL, and stirred uniformly at room temperature; the polytetrafluoroethylene reactor containing the sample is placed in a muffle furnace, heated to 200°C at an air atmosphere and a heating rate of 10°C / min, and then cooled to room temperature after being kept at 200°C for 24 h; the white precipitate of the polytetrafluoroethylene reactor is washed by centrifugation with deionized water and anhydrous ethanol, respectively, repeated for three times, and then dried to obtain a precursor powder sample.

[0050] The phase structure of the precursor powder sample is characterized by an X-ray diffractometer (XRD), and the XRD pattern of the precursor powder sample of Example 1 is shown in Figure 1 (a). Figure 1 As can be seen from (a), the characteristic diffraction peaks of the prepared precursor powder sample match the standard card of anatase TiO2, indicating that the phase structure of the precursor powder sample prepared in Example 1 is anatase TiO2, and the relative intensity of the characteristic diffraction peaks (200) and (211) is obviously higher than that of the standard card, indicating that the precursor powder sample grows along the (200) and (211) crystal planes.

[0051] The microstructure of the precursor powder sample of the sample was characterized by scanning electron microscopy (SEM), and the SEM image of the precursor powder sample of Example 1 is shown in Figure 1 (b), from Figure 1 As can be seen from (b), the precursor powder sample of Example 1 has a nanosheet structure, and the nanosheet structure is uniformly dispersed, with a particle size of 80-110 nm in the length direction and a particle size of 5-15 nm in the thickness direction.

[0052] S2. Coating SiO2, the precursor powder sample prepared in step S1 was added to a mixed solution of anhydrous ethanol and deionized water, the volume mixing ratio of anhydrous ethanol to deionized water was 1:1, and after being uniformly dispersed by ultrasonic at room temperature, ammonia (AR, 25-28 wt.%) and tetraethyl orthosilicate (AR) were added, the mass-volume ratio of the precursor powder to the mixed solution, ammonia and tetraethyl orthosilicate was 0.5 g:150 mL:3.6 mL:6 mL, and the reaction was carried out by ultrasonic at room temperature for 4 h; after the reaction was completed, the obtained suspension was centrifuged and washed with deionized water and anhydrous ethanol to remove excess reactants, and after being repeated three times, a powder sample coated with SiO2 was obtained by drying.

[0053] The phase structure of the powder sample coated with SiO2 was characterized by X-ray diffractometer (XRD), and the XRD pattern of the powder sample coated with SiO2 of Example 1 is shown in Figure 2 (a), from Figure 2 As can be seen from (a), the characteristic diffraction peak of the prepared powder sample coated with SiO2 is consistent with Figure 1 (a), indicating that the TiO2 in the powder sample coated with SiO2 prepared in Example 1 has not changed, and still maintains anatase TiO2, and the (200) and (211) crystal faces have preferred orientation, and no characteristic diffraction peak of SiO2 is detected, indicating that SiO2 is coated on the surface of TiO2 in an amorphous structure.

[0054] The microstructure and element distribution of the precursor powder sample of the sample were characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and the SEM image of the powder sample coated with SiO2 of Example 1 is shown in Figure 2 (b), from Figure 2 As can be seen from (b), the powder sample coated with SiO2 of Example 1 has a microsphere combination structure, and multiple SiO2 microspheres are combined on the surface of TiO2 to form microsphere combination particles, the particle size of the SiO2 microspheres is 120-200 nm, and the particle size of the microsphere combination particles is 300-900 nm. Figure 2 (c) and 2(d) are the distribution diagrams of Ti and Si elements of the powder sample coated with SiO2 of Example 1, respectively, fromFigure 2 (c) and 2(d) can be seen that the Ti element and Si element are uniformly distributed, and the SiO2 uniformly coats the surface of the TiO2.

[0055] S3. Hydrogen reduction, the coated SiO2 powder sample prepared in step S2 is put into a tube furnace, and the temperature is increased to 1050°C at a heating rate of 10°C / min in a hydrogen atmosphere, the hydrogen flow is 600 mL / min -1 , after holding for 4h, the furnace is cooled to room temperature, and a reduced powder sample coated with SiO2 is prepared.

[0056] The phase structure of the reduced powder sample coated with SiO2 is characterized by an X-ray diffractometer (XRD), and the XRD pattern of the reduced powder sample coated with SiO2 of Example 1 is shown in Figure 3 (a), from Figure 3 (a) can be seen that the phase structure of the prepared reduced powder sample coated with SiO2 is single-phase λ-Ti3O5, and no other impurities are detected, indicating that the TiO2 is reduced to pure-phase λ-Ti3O5, and no characteristic diffraction peak of SiO2 is detected, indicating that SiO2 is coated on the surface of λ-Ti3O5 in an amorphous structure.

[0057] The micro-morphology of the sample is characterized by a scanning electron microscope (SEM), and the SEM image of the reduced powder sample coated with SiO2 of Example 1 is shown in Figure 3 (b), from Figure 3 (b) can be seen that the reduced powder sample coated with SiO2 of Example 1 is consistent with Figure 2 (b), and the powder does not agglomerate, sinter or grow during the reduction process, and still maintains the microsphere combination structure, multiple SiO2 microspheres are combined on the surface of λ-Ti3O5 to form microsphere combination particles, the particle size of the SiO2 microspheres is 120nm-200nm, and the particle size of the microsphere combination particles is 300nm-900nm.

[0058] S4. Removing SiO2, the reduced powder sample coated with SiO2 prepared in step S3 is added to a 0.25mol / L NaOH solution, and stirred at room temperature at a stirring speed of 600r / min, after stirring for 2.5h, the excess NaOH is removed by washing with deionized water, and then dried to prepare a final powder sample.

[0059] The phase structure of the final powder sample is characterized by an X-ray diffractometer (XRD), and the XRD pattern of the final powder sample of Example 1 is shown in Figure 4 (a), from Figure 4 (a) can be seen that the phase structure of the prepared final powder sample is consistent withFigure 3 (a) consistent, cleaning the process of removing the SiO2coating layer without introducing other impurities, remain single-phase λ-Ti3O5.

[0060] The phase structure of the final powder sample was characterized by scanning electron microscopy (SEM). The SEM image of the final powder sample of Example 1 is shown in Figure 4 (b) from Figure 4 As can be seen from (b), the final powder sample of Example 1 still maintains a nanosheet structure, and the nanosheet structure is uniformly dispersed, with a particle size of 100-150 nm in the length direction and a particle size of 8-15 nm in the thickness direction.

[0061] The specific surface area of the final powder sample was determined by BET. The nitrogen adsorption isotherm of the final powder sample of Example 1 is shown in Figure 4 (c), the specific surface area of the final powder sample of Example 1 was measured to be 131.3 m 2 g -1 .

[0062] Example 2

[0063] The difference between Example 2 and Example 1 is that in step S3. hydrogen reduction, the SiO2coated powder sample prepared in step S2 is placed in a tube furnace, and the temperature is increased to 1000℃ at a heating rate of 10℃ / min in a hydrogen atmosphere, with a hydrogen flow rate of 600mL / min -1 , and after holding for 4h, the furnace is cooled to room temperature to prepare a SiO2coated reduced powder sample; the remaining preparation steps are the same as those of Example 1 to prepare a final powder sample.

[0064] The same characterization test method as in Example 1 was used for testing, and the XRD pattern of the final powder sample of Example 2 is shown in Figure 5 (a) from Figure 5 As can be seen from (a), the phase structure of the final powder sample prepared in Example 2 is single-phase λ-Ti3O5; the microstructure of the final powder sample prepared in Example 2 is shown in Figure 5 (b) from Figure 5 As can be seen from (b), the final powder sample of Example 2 is a nanosheet structure, and the nanosheet structure is uniformly dispersed, with a particle size of 100-150 nm in the length direction and a particle size of 8-15 nm in the thickness direction.

[0065] Example 3

[0066] Example 3 differs from Example 1 in that step S4. The SiO2-coated reduced powder sample prepared in step S3 is added to a 0.5 mol / L NaOH solution, stirred at room temperature at a stirring speed of 600 r / min, and after stirring for 2.5 h, the excess NaOH is removed by washing with deionized water, and the final powder sample is prepared by drying; the remaining preparation steps are the same as in Example 1. The same test method as in Example 1 is used for testing, and it is found that the phase structure of the final powder sample of Example 3 is a single-phase λ-Ti3O5; it is found that the final powder sample prepared in Example 3 has a nanosheet structure, the nanosheet structure is uniformly dispersed, the particle size in the length direction is 100-150 nm, and the particle size in the thickness direction is 8-15 nm.

[0067] Example 4

[0068] Example 4 differs from Example 1 in that step S1. A precursor is prepared by adding hydrofluoric acid (AR, 40 wt.%) and butyl titanate (AR) into a 50 mL PTFE reaction kettle inner container at a volume ratio of 8 mL:30 mL, and stirring uniformly at room temperature; the PTFE reaction kettle containing the sample is placed in a muffle furnace, heated to 180°C at a heating rate of 10°C / min under an air atmosphere, and after holding for 28 h, the furnace is cooled to room temperature; the white precipitate in the PTFE reaction kettle is washed by centrifugation with deionized water and anhydrous ethanol, respectively, repeated three times, and the precursor powder sample is obtained by drying; the remaining preparation steps are the same as in Example 1, and the final powder sample is prepared. The same test method as in Example 1 is used for testing, and it is found that the phase structure of the final powder sample of Example 4 is a single-phase λ-Ti3O5; it is found that the final powder sample prepared in Example 4 has a nanosheet structure, the nanosheet structure is uniformly dispersed, the particle size in the length direction is 100-150 nm, and the particle size in the thickness direction is 8-15 nm.

[0069] Comparative Example 1

[0070] Comparative Example 1 provides a method for preparing a titanium suboxide powder material, specifically comprising the following steps:

[0071] S1. A precursor is prepared by adding hydrofluoric acid (AR, 40 wt.%) and butyl titanate (AR) into a 50 mL PTFE reaction kettle inner container at a volume ratio of 5 mL:20 mL, and stirring uniformly at room temperature; the PTFE reaction kettle containing the sample is placed in a muffle furnace, heated to 200°C at a heating rate of 10°C / min under an air atmosphere, and after holding for 24 h, the furnace is cooled to room temperature; the white precipitate in the PTFE reaction kettle is washed by centrifugation with deionized water and anhydrous ethanol, respectively, repeated three times, and the precursor powder sample is obtained by drying.

[0072] S2'. Hydrogen reduction, the precursor powder sample prepared in step S1 was put into a tube furnace, and the temperature was increased to 1050℃ at a heating rate of 10℃ / min in a hydrogen atmosphere, the hydrogen flow rate was 600 mL / min -1 After holding for 4h, the furnace was cooled to room temperature to prepare a reduced powder sample.

[0073] The same characterization test method as in Example 1 was used for testing, and the XRD pattern of the reduced powder sample of Comparative Example 1 was measured as shown in Figure 6 (a), from which Figure 6 (a) can be seen, the phase structure of the prepared reduced powder sample is single-phase λ-Ti3O5, and no other impurities are detected, indicating that the TiO2 is reduced to obtain pure-phase λ-Ti3O5; the SEM image of the reduced powder sample of Comparative Example 1 is shown in Figure 6 (b), from which Figure 6 (b) can be seen, the powder of Comparative Example 1 agglomerates and sinter during the reduction process, and the prepared reduced powder sample has a dispersed particle structure, and the particle size of the particle structure is 200-800 nm.

[0074] The average absorption rate of the final powder sample sheet-like λ-Ti3O5 of Example 1 and the reduced powder sample λ-Ti3O5 of Comparative Example 1 to sunlight in the wavelength range of 200-2500 nm was measured by UV-visible near-infrared test, and the light-heat conversion efficiency of the material was calculated by temperature measurement method, and the test results are shown in Figure 7 (a). From Figure 7 (a) can be seen, the sunlight absorption rate of the reduced powder sample λ-Ti3O5 of Comparative Example 1 is 90.4%, while the sunlight absorption rate of the final powder sample sheet-like λ-Ti3O5 of Example 1 is 92.2%, and Example 1 is obviously better than Comparative Example 1. From Figure 7 (b) can be seen, the sheet-like λ-Ti3O5 is raised to a higher temperature in a shorter time under the same light conditions. The heat used for the temperature rise of the material after absorbing sunlight was calculated by a thermal formula, and the light-heat conversion efficiency of the reduced powder sample λ-Ti3O5 of Comparative Example 1 was 89.4%, and the light-heat conversion efficiency of the final powder sample sheet-like λ-Ti3O5 of Example 1 was 91.7%, and Example 1 was obviously better than Comparative Example 1. Under light and dark conditions, the water evaporation rate of the evaporation system using the final powder sample sheet-like λ-Ti3O5 of Example 1 and the reduced powder sample λ-Ti3O5 of Comparative Example 1 as light-absorbing materials was tested, respectively, and the same measurement was also performed on the water evaporation system without light-absorbing materials, to exclude the influence of natural water evaporation, Figure 8From the mass change curve, it can be seen that under dark conditions, different titanium suboxides and pure water all maintain a low evaporation rate, while under 1 sun irradiation, the evaporation rate of the evaporation system with the addition of titanium suboxide powder is significantly improved compared with pure water, and the mass of pure water decreases linearly, indicating that the evaporation system can maintain stability during the evaporation process. To further quantitatively illustrate the improvement effect of each titanium suboxide material on the evaporation rate, the evaporation rate u in the following formula is calculated Figure 8

[0075]

[0076] wherein u represents the evaporation rate, Δm represents the mass change of pure water in the evaporation system within a certain time, A represents the area for evaporation, and t represents the evaporation time. The evaporation rates of the reduced powder sample λ-Ti3O5 of Comparative Example 1 and the final powder sample sheet-shaped λ-Ti3O5 of Example 1 are 1.70 kg m -2 h -1 and 1.79 kg m -2 h -1 respectively, and Example 1 is obviously superior to Comparative Example 1.

[0077] Comparative Example 2

[0078] The difference between Comparative Example 2 and Example 1 is that in step S3. hydrogen reduction, the SiO2-coated powder sample prepared in step S2 is placed in a tube furnace, and the temperature is increased to 1100℃ at a heating rate of 10℃ / min in a hydrogen atmosphere, the hydrogen flow rate is 600 mL min -1 , and after 4h of heat preservation, the furnace is cooled to room temperature to prepare a SiO2-coated reduced powder sample.

[0079] The SiO2-coated reduced powder sample of step S3 of Comparative Example 2 is tested by using the same characterization test method as Example 1, and the test results are shown in Figure 9 From Figure 9 (a), it can be seen that the XRD pattern of the SiO2-coated reduced powder sample appears SiO2 characteristic peaks, indicating that SiO2 crystallization occurs during the reduction process; from Figure 9 (b), it can be seen that the powder agglomerates and sintering grows during the reduction process.

[0080] Comparative Example 3

[0081] ​The difference between Comparative Example 3 and Example 1 is that in step S4, removing SiO2, the reduced powder sample coated with SiO2 prepared in step S3 is added to a 0.25 mol / L NaOH solution and stirred at 60°C with a stirring speed of 600 r / min for 2.5 h. After stirring, excess NaOH is removed by washing with deionized water and then dried to obtain the final powder sample. The remaining preparation steps are the same as in Example 1.

[0082] The final powder sample from step S4 of Comparative Example 3 was tested using the same characterization and testing methods as in Example 1. The test results are as follows: Figure 10 As shown, from Figure 10 As can be seen from the data, in addition to λ-Ti3O5, the impurity phase TiO2 was detected in the final powder sample.

[0083] Comparative Example 4

[0084] The difference between Comparative Example 4 and Example 1 is that in step S4, SiO2 is removed. The reduced powder sample coated with SiO2 prepared in step S3 is added to a 1 mol / L NaOH solution and stirred at room temperature at a stirring speed of 600 r / min for 2.5 h. After stirring, excess NaOH is removed by washing with deionized water and then dried to obtain the final powder sample. The remaining preparation steps are the same as in Example 1.

[0085] The final powder sample from step S4 of Comparative Example 4 was tested using the same characterization and testing methods as in Example 1. The test results are as follows: Figure 11 As shown, from Figure 11 As can be seen from the data, TiO2 and Ti7O were detected in the final powder sample. 13 .

[0086] Comparative Example 5

[0087] The difference between Comparative Example 5 and Example 1 is that in step S1, the precursor powder is prepared by adding 2.5 mL of deionized water and 2.5 mL of hydrofluoric acid (AR, 40 wt.%) mixed solution and 20 mL of tetrabutyl titanate (AR) to a 50 mL polytetrafluoroethylene reactor liner and stirring evenly at room temperature; the polytetrafluoroethylene reactor containing the sample is placed in a muffle furnace and heated to 200°C at a heating rate of 10°C / min under an air atmosphere, and then kept at that temperature for 24 h before being cooled to room temperature with the furnace; the white precipitate in the polytetrafluoroethylene reactor is centrifuged and washed with deionized water and anhydrous ethanol respectively, and the process is repeated three times before drying to obtain the precursor powder sample.

[0088] The precursor powder sample from step S1 of Comparative Example 5 was tested using the same characterization and testing methods as in Example 1. The test results are as follows: Figure 12 As shown, from Figure 12As can be seen, the precursor powder sample is a nanoparticle structure, the particle size of the nanoparticle structure is 20-200 nm, and the nanoparticle agglomeration is serious.

[0089] The above-described embodiments are only preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Any equivalent substitutions or transformations made by those skilled in the art on the basis of the present application are within the protection scope of the present application. The protection scope of the present application is subject to the claims.

Claims

1. A method of producing a titanium suboxide powder material, characterized by, The method comprises the following steps: S1. Preparing a precursor powder, adding hydrofluoric acid and butyl titanate in a reaction container, the volume ratio of the hydrofluoric acid and the butyl titanate being 4-10:18-30, stirring uniformly, and then heating to 180-280℃ for 18-36h, and then centrifuging and drying the reaction product to obtain the precursor powder; the precursor powder has a nanosheet structure, the nanosheet structure is uniformly dispersed, the length direction particle size is 80-110nm, and the thickness direction particle size is 5-15nm; the precursor powder is pure phase anatase TiO2, and TiO2 grows along the (200) and (211) crystal planes in a preferred orientation; S2. Coating SiO2, adding the precursor powder into a mixed solution of anhydrous ethanol and deionized water, ultrasonic dispersion, then adding ammonia and tetraethyl orthosilicate, the volume ratio of the ammonia and the tetraethyl orthosilicate being 2-5:4-8, ultrasonic reaction for 2-6h, and then centrifuging and drying the reaction product to obtain the SiO2-coated powder; S3. Hydrogen reduction, heating the SiO2-coated powder to 1000-1050℃ in a hydrogen atmosphere for 3-6h to obtain the SiO2-coated reduced powder; S4. Removing SiO2, adding the SiO2-coated reduced powder into a 0.2-0.6mol / L NaOH solution, stirring for 2-4h, and then washing and drying to obtain the titanium suboxide powder material, which is a single-phase λ-Ti3O5 nanometer powder material; the titanium suboxide powder material has a nanosheet structure, the nanosheet structure is uniformly dispersed, the length direction particle size is 100-150nm, and the thickness direction particle size is 8-15nm.

2. The method for preparing the sub-titanium oxide powder material according to claim 1, characterized in that, In step S1, the volume ratio of the hydrofluoric acid and the butyl titanate is 5-8:20-30, and the stirring is uniform, and then heating to 180-220℃ for 18-30h.

3. The method of producing a titanium suboxide powder material according to claim 1 or 2, characterized by, In step S2, the mass volume ratio of the precursor powder and the mixed solution, the ammonia, and the tetraethyl orthosilicate is 0.3-0.8g:130-180mL:2-5mL:4-8mL.

4. The method for preparing the titanium suboxide powder material according to claim 1, characterized in that, In step S2, the SiO2-coated powder is amorphous SiO2-coated TiO2, the SiO2-coated powder has a microsphere combination structure, a plurality of SiO2 microspheres are combined on the surface of TiO2 to form a microsphere combination particle, the particle size of the SiO2 microspheres is 120-200nm, and the particle size of the microsphere combination particle is 300-900nm.

5. The method of claim 1, wherein In step S4, the specific surface area of the prepared titanium suboxide powder material reaches 131.3 m 2 g -1 .

6. The method of claim 1, wherein the titanium suboxide powder material is prepared by the steps of: In step S4, the solar light absorption rate of the prepared titanium suboxide powder material reaches 92.2%, the light-heat conversion efficiency reaches 91.7%, and the evaporation rate reaches 1.79 kg m -2 h -1 .

7. A titanium suboxide powder material prepared by the method for preparing the titanium suboxide powder material according to any one of claims 1-6.

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