Preparation method of hexagonal-phase tungsten trioxide integrating morphology-crystalline phase-defect regulation and control, product prepared by preparation method and application of hexagonal-phase tungsten trioxide
By using solvothermal and low-temperature calcination methods to control the morphology, crystal phase, and defects of tungsten trioxide, the efficiency limitation of tungsten trioxide in visible light catalysis in existing technologies has been solved, and highly efficient photocatalytic, electrocatalytic, and thermal catalytic performance has been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-11
- Publication Date
- 2026-03-27
AI Technical Summary
Existing technologies cannot effectively control the morphology, crystal phase, and defects of tungsten trioxide, which limits its application efficiency in visible light catalysis.
By combining solvothermal method with low-temperature calcination, the ratio of sodium tungstate dihydrate and sodium chloride and the pH value are adjusted to achieve synergistic control of the morphology, crystal phase and defects of hexagonal tungsten trioxide, ensuring the introduction of appropriate oxygen vacancies while maintaining the morphology.
A hexagonal tungsten trioxide with high crystallinity, high aspect ratio and moderate oxygen vacancies was achieved, which improved its performance and stability in photocatalysis, electrocatalysis and thermocatalysis, and provided stronger light absorption and conductivity.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of material chemistry and catalysis technology, and particularly relates to a hexagonal phase tungsten trioxide preparation method integrating morphology-crystal phase-defect regulation, and a product and application thereof. BACKGROUND
[0002] Since the 1970s, semiconductor catalysts represented by titanium dioxide have gradually become a research hotspot as a key component of the catalytic system. However, the large band gap (3.2 eV) of titanium dioxide can only respond to about 4% of the ultraviolet light in the solar spectrum, which seriously limits the actual application efficiency. Therefore, it is the key to solve the energy and environmental crisis to find and design a visible light-driven, high-activity and chemically stable narrow-bandgap semiconductor catalyst.
[0003] Metal oxides attract research attention due to their unique electronic structure, adjustable oxidation state and rich active sites. Their catalytic activity is usually derived from ion vacancies caused by non-stoichiometric structure and unique metal-oxygen bond characteristics, which activate reactant molecules through electron transfer process. The band gap of tungsten trioxide (WO3) is located in the visible light region, and the theoretical visible light utilization rate can reach about 12%. Moreover, it is chemically stable and has strong anti-photo-etching ability, so it has become one of the research focuses. As a typical n-type semiconductor transition metal oxide, WO3 has a relatively narrow band gap (about 2.4-2.8 eV), excellent photoelectric properties, chemical stability, corrosion resistance, and unique acidity and redox properties. These characteristics make it have great application potential in the field of catalysis, including photocatalysis, electrocatalysis and traditional heterogeneous catalysis.
[0004] The catalytic performance of WO3 mainly depends on its microstructure, including morphology (nanosheet, nanowire, nanorod, multi-level structure, etc.), crystal phase (mainly monoclinic phase at room temperature), specific surface area, defect engineering (introduction of oxygen vacancies), etc. Therefore, developing controllable and efficient WO3 synthesis methods to realize precise regulation of its microstructure is the key to improving its catalytic performance and promoting its practical application. SUMMARY
[0005] The purpose of this section is to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments.
[0006] As one aspect of the present application, the present application provides a hexagonal phase tungsten trioxide preparation method integrating morphology-crystal phase-defect regulation, which comprises the following steps,
[0007] (1) dissolving sodium tungstate dihydrate and sodium chloride in a solvent to obtain a mixed solution, the mass ratio of sodium tungstate dihydrate to sodium chloride being 5: (1-1.2); the mass fraction of sodium tungstate dihydrate being 3-3.5%;
[0008] (2) adding hydrochloric acid dropwise to adjust pH to 0.6-0.8, and stirring;
[0009] (3) transferring the product obtained in step (2) to a high-pressure reaction kettle, and performing solvothermal reaction in a blast drying oven; after the reaction is completed, cooling to room temperature, washing, and drying;
[0010] (4) dispersing the product obtained in step (3) in a dispersant, drying, and then placing in a tube furnace to perform calcination, to obtain rod-shaped tungsten trioxide.
[0011] As a preferred scheme of the preparation method of the hexagonal tungsten trioxide integrating morphology-crystal phase-defect regulation: in step (2), the pH is adjusted to 0.7 by adding hydrochloric acid dropwise, and the stirring time is 2-3 h.
[0012] As a preferred scheme of the preparation method of the hexagonal tungsten trioxide integrating morphology-crystal phase-defect regulation: in step (3), the temperature of the solvothermal reaction is 160-200 ℃, and the reaction time is 8-12 h.
[0013] As a preferred scheme of the preparation method of the hexagonal tungsten trioxide integrating morphology-crystal phase-defect regulation: in step (3), the temperature of the solvothermal reaction is 180 ℃, and the reaction time is 10 h.
[0014] As a preferred scheme of the preparation method of the hexagonal tungsten trioxide integrating morphology-crystal phase-defect regulation: in step (4), the dispersant comprises ethanol.
[0015] As a preferred scheme of the preparation method of the hexagonal tungsten trioxide integrating morphology-crystal phase-defect regulation: in step (4), the calcination is performed under a nitrogen atmosphere at 200-240 ℃ for 2-3 h.
[0016] As a preferred scheme of the preparation method of the hexagonal tungsten trioxide integrating morphology-crystal phase-defect regulation: in step (3), the washing and drying comprise washing with water, and the drying comprises drying at 60-70 ℃.
[0017] The application further provides the rod-shaped tungsten trioxide prepared by the preparation method of the hexagonal phase tungsten trioxide with morphology-crystal phase-defect regulation.
[0018] The application further provides application of the rod-shaped tungsten trioxide as a catalyst for photocatalysis, electrocatalysis or thermal catalysis.
[0019] The application has the following beneficial effects: the application optimizes pH value (0.7), concentration and ratio of Na2WO4.2H2O and NaCl in the solvothermal method through multi-parameter coordination, shortens nucleation induction time, reduces oxygen vacancy concentration change, realizes coordination of high crystallinity-high aspect ratio-moderate oxygen vacancy, exposes more active crystal faces, and provides an advantageous structure for catalytic application. The application realizes controllable conversion of mixed-phase WO3.0.33H2O and WO3 into stable high-purity hexagonal phase WO3 through a low-temperature calcination method after solvothermal treatment, and realizes controllable conversion of two crystal phases in the same synthesis system; compared with common chemical reduction methods for introducing oxygen vacancies, the method does not cause damage to crystal morphology, that is, oxygen vacancy regulation can be realized on the premise of maintaining morphology. The application realizes synchronous regulation of morphology, crystal phase and defect, reduces oxygen vacancy concentration fluctuation, and clearly defines its specific application in the catalytic field (WO3 has better stability, stronger conductivity and is more suitable for electrocatalysis and thermal catalysis). The synthesis method of the application has simple conditions, stable product structure, good performance repeatability, and the method of coordinated regulation of parameters can better control and optimize performance, and improve practical value. BRIEF DESCRIPTION OF DRAWINGS
[0020] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description, wherein:
[0021] Figure 1 The X-ray diffraction (XRD) spectrum of the product prepared in Example 1.
[0022] Figure 2 The X-ray diffraction (XRD) spectrum of the product prepared in Comparative Example 1.
[0023] Figure 3 The X-ray diffraction (XRD) spectrum of the product prepared in Comparative Example 2.
[0024] Figure 4 The X-ray diffraction (XRD) spectrum of the product prepared in Example 2.
[0025] Figure 5 The scanning electron microscope (SEM) image of the product prepared in Example 2.
[0026] Figure 6 High resolution transmission electron microscope (HRTEM) image of the product prepared for Example 2.
[0027] Figure 7 X-ray diffraction (XRD) pattern of the product prepared for Comparative Example 3.
[0028] Figure 8 UV-visible diffuse reflectance (UV-vis DRS) spectrum of the product prepared for Example 1, Example 2.
[0029] Figure 9 Photoluminescence (PL) spectrum of the product prepared for Example 1 and Example 2.
[0030] Figure 10 Transient photocurrent (TPC) spectrum of the product prepared for Example 1 and Example 2.
[0031] Figure 11 X-ray diffraction (XRD) pattern of the product prepared for Comparative Example 4.
[0032] Figure 12 X-ray diffraction (XRD) pattern of the product prepared for Comparative Example 5.
[0033] Figure 13 Transient photocurrent (TPC) spectrum of the product prepared for Comparative Example 5.
[0034] Figure 14 Transient photocurrent (TPC) spectrum of the product prepared for Comparative Example 6. DETAILED DESCRIPTION
[0035] In order to make the above objectives, features and advantages of the present application more apparent and comprehensible, the specific embodiments of the present application will be described in detail below with specific embodiments.
[0036] Example 1:
[0037] WO3·0.33H2O was synthesized by solvothermal method. 1.0 g of Na2WO4·2H2O and 0.20 g of NaCl were weighed and dissolved in 30 mL of deionized water under stirring. The pH value of the solution was adjusted to 0.70 by adding an aqueous solution of HCl (12 M). After stirring for another 2 h, the mixture was transferred to a 50 mL high-pressure reaction kettle and incubated at 180 ℃ for 10 h. After cooling, the product was washed by centrifugation with deionized water and dried at 70 ℃. The product was collected by grinding and was a light yellow powder.
[0038] Figure 1The X-ray diffraction spectrum of the product obtained in Example 1 is shown in the figure. It can be seen from the figure that the prepared WO3·0.33H2O has strong diffraction peaks at 14.1°, 18.1°, 23.0°, 27.1°, 28.1°, 28.4°, 36.6° and 36.8°. These position information respectively matches the (020), (111), (002), (022), (220), (040), (222) and (042) crystal faces of WO3·0.33H2O (JCPDS No. 87-1203). It is worth noting that the three peaks at 18.1°, 39.2° and 39.7° can be used as characteristic peaks to distinguish the hydrated and non-hydrated states. Many characteristic peaks of the hydrated state and the non-hydrated state are overlapped, so the product may be a mixed phase state of WO3·0.33H2O and WO3.
[0039] Comparative Example 1:
[0040] In the process of synthesizing WO3·0.33H2O by the solvothermal method, the influence of different pH values on the crystal phase composition of the material was explored. The pH value of the solution in the solvothermal process was adjusted to 0.4, 0.5, 0.6, 0.7 and 0.8 using concentrated hydrochloric acid. Other preparation conditions were the same as in Example 1. The X-ray diffraction spectra of the products obtained at different pH values are shown in Figure 2 from top to bottom, the pH value increases.
[0041] It can be seen from Figure 2 that from top to bottom, the relative intensity of the diffraction peaks at 14.1°, 23.0°, 27.1°, 28.1°, 28.4°, 36.6° and 36.8° gradually increases with the increase of the pH value, i.e. the decrease of the acidity, while the three peaks at 18.1°, 39.2° and 39.7° related to the hydrated state show a trend of first increasing and then decreasing.
[0042] Comparative Example 2:
[0043] The influence of temperature change on the crystal phase composition of the material in the solvothermal synthesis was studied. The temperature in the solvothermal process was set to 140℃, 160℃, 180℃ and 200℃ respectively. Other preparation conditions were the same as in Example 1. The X-ray diffraction spectra of the products obtained at different temperatures are shown in Figure 3 from top to bottom, the temperature decreases. Figure 3
[0044] It can be seen from Figure 3 that from top to bottom, the relative intensity of the diffraction peaks at 14.1°, 23.0°, 27.1°, 28.1°, 28.4°, 36.6° and 36.8° gradually increases with the increase of the pH value, i.e. the decrease of the acidity, while the three peaks at 18.1°, 39.2° and 39.7° related to the hydrated state show a trend of first increasing and then decreasing. Figure 3 As the temperature of the WO3·0.33H2O prepared from top to bottom decreases, the relative intensity of the diffraction peaks at 18.1° and 22.9° gradually decreases, while the relative intensity of the diffraction peaks at 14.1° and 50.1° gradually increases. The three peaks at 18.1°, 39.2° and 39.7° related to the hydration state show a decreasing trend as the temperature increases.
[0045] Example 2:
[0046] The WO3·0.33H2O synthesized by the solvothermal method was treated by low-temperature calcination. 0.3 g of WO3·0.33H2O prepared in Example 1 was uniformly dispersed in 30 mL of anhydrous ethanol by ultrasonic, and then the obtained dry material was ground and transferred into a quartz boat, heated to 200 ℃ for 2 h in a tube furnace under N2 atmosphere, and the product was the target WO3 product, in the form of a grayish blue powder.
[0047] Figure 4 The X-ray diffraction spectrum of the product obtained in Example 2 is shown in the figure. It can be seen that the prepared WO3 has strong diffraction peaks at positions of 13.9°, 22.7°, 24.3°, 26.8°, 28.1°, 33.5° and 36.5°. These position information respectively corresponds to the (100), (001), (110), (101), (200), (111) and (201) crystal faces of hexagonal WO3 (JCPDS No. 33-1387). The three characteristic peaks at 18.1°, 39.2° and 39.7° belonging to the hydrated phase WO3·0.33H2O are not found in this spectrum, and no other impurity peaks are observed. The material has high crystallinity, clear and pure crystal phase, and more stable structure. Figure 5 The scanning electron microscope image of WO3 prepared in Example 2 is shown in the figure. Figure 6 The high-resolution transmission electron microscope image of WO3 prepared in Example 2 is shown in the figure. Figure 5 、 6 It can be seen that the prepared WO3 is a uniform and regular rod-shaped, which is a uniform aggregate rod. The rod-shaped size is in the range of 200-500 nm in length and about 30 nm in diameter. It has clear crystal lattice fringes, and the lattice spacing in the picture is 0.316 nm and 0.391 nm, which can correspond to the (200) and (001) crystal faces of WO3. It shows that the method of solvothermal treatment followed by low-temperature calcination can complete the controllable conversion of the mixed phase state of WO3·0.33H2O and WO3 to stable hexagonal WO3, and realize the controllable conversion of the two crystal phases in the same synthesis system.
[0048] Comparative Example 3:
[0049] The effect of temperature change on the crystal phase composition of the material during low-temperature calcination treatment. The temperature during calcination was set at 160°C, 200°C and 240°C, respectively. The other preparation conditions are the same as in Example 2. The X-ray diffraction spectra of the products obtained at different temperatures are shown in Figure 7 , from top to bottom, the temperature decreases in turn.
[0050] As can be seen from Figure 7 , with the increase of temperature, the relative intensity of the diffraction peak at 22.7° of the prepared WO3 gradually weakens, while the relative intensity of the diffraction peak at 28.1° gradually increases. The three peaks at 18.1°, 39.2° and 39.7° related to the hydrated state disappear with the increase of temperature, indicating the change of the hydrated state.
[0051] In addition, in order to compare the performance of the mixed phase WO3·0.33H2O obtained in Example 1 and WO3 with the pure phase WO3 obtained in Example 2, the ultraviolet-visible diffuse reflectance (UV-vis DRS) spectra of the two products are tested as shown in Figure 8 , the photoluminescence (PL) spectra are shown in Figure 9 , and the transient photocurrent (TPC) spectra are shown in Figure 10 .
[0052] As can be seen from Figure 8 , the WO3·0.33H2O prepared in Example 1 and the WO3 prepared in Example 2 are light yellow and gray blue respectively, which also corresponds to the light absorption ability shown in the spectra. The absorption edge of WO3 has a red shift compared with that of WO3·0.33H2O, and the absorption intensity increases as a whole, indicating that WO3 has stronger light absorption performance. In addition, the change of the absorption tail at 450 nm is also different, which also indicates that the WO3 obtained after the treatment in Example 2 has obvious oxygen vacancy, which makes the absorption tail move up obviously, which is due to the light absorption effect caused by the surface oxygen defects of WO3.
[0053] Generally speaking, the photoluminescence performance of photocatalyst is closely related to the recombination of photo-carriers, that is, the greater the photoluminescence intensity, the more the recombination of photo-carriers. As can be seen from Figure 9 , compared with pure WO3·0.33H2O, the photoluminescence intensity of WO3 is obviously reduced, indicating that the optimization of crystal phase and the construction of oxygen vacancy of WO3 play a positive role in the separation of photo-carriers. It is further verified that the WO3 prepared in Example 2 can more effectively promote the separation of photo-carriers and thus participate in the catalytic reaction.
[0054] Considering the actual application in the field of electrocatalysis, we measured the transient photocurrent (TPC) spectra of the two products. As can be seen from Figure 10It can be seen that, compared with pure WO3·0.33H2O, WO3 has more obvious photocurrent response signal, and the result corresponds to the optimized crystal phase (non-hydrated phase: hexagonal close-packed structure, WO6 octahedron is closely connected, no water molecules between layers, the structure is dense, hydrated phase: layered structure, water molecules are embedded between layers, forming W-O-H-O-W bridge, which weakens the interlayer interaction).
[0055] Comparative Example 4:
[0056] The sodium tungstate and sodium chloride ratio (molar ratio about 1:1.1, 1.0 g Na2WO4·2H2O and 0.20 g NaCl) of Example 1 of the application is used, except that the pH value is different, the rest of the conditions are the same as Example 1, and the pH value is set to 1.5. As shown in Figure 11 Compared with the XRD spectrum with a pH value of 0.7, when the pH value is 1.5, the diffraction peak intensity of the hexagonal hydrated WO3 in the spectrum near 18° is reduced, and no diffraction peak of the hexagonal hydrated WO3 near 40° is found. In addition, a new split low peak appears between 23°-24°, which belongs to monoclinic WO3, that is, the product obtained when the pH is 1.5 is a mixture of monoclinic and hexagonal phases. Higher pH value will slow down the nucleation rate of the product, make isotropic growth, and increase the size, which is not conducive to the exposure of active sites in the reaction.
[0057] Comparative Example 5:
[0058] 1.0 g Na2WO4·2H2O and 0.35 g NaCl are weighed, and the rest of the conditions are the same as Example 1. The diffraction peak intensity of the hexagonal hydrated WO3 in the spectrum near 18° is stronger, the characteristic peak (JCPDS 33-1387) of h-WO3 is dominant, the crystallinity and crystal type are more sharp, and the crystallinity is improved. Through transient photocurrent test, it can be concluded that the crystallinity is enhanced, the product size is increased, the carrier transport performance is limited, which is not conducive to the catalytic reaction, see Figure 12 and Figure 13 .
[0059] Comparative Example 6:
[0060] First, WO3·0.33H2O with different pH values is synthesized according to the method of Example 1, and then it is treated by low-temperature calcination according to the method of Example 2. When Example 1 is synthesized, the pH is set to 0.4, 0.7 and 1.5 respectively. The product sample is calcined to remove the crystallization water and converted into anhydrous WO3 with more complete crystallinity, and the nitrogen atmosphere introduces appropriate oxygen vacancies, which greatly improves the performance from improving charge transport and increasing carrier concentration respectively. As shown in the transient photocurrent spectrum ( Figure 14) as shown: for the sample of PH = 0.4, more structural defects may have been generated under strong acidity, which are difficult to completely repair by calcination and more excess oxygen vacancies are introduced, which aggravate charge recombination. For the sample of PH = 0.7, the initial crystallization is good, the morphology is relatively optimal, and the oxygen vacancies are moderate, and calcination improves the crystallinity and increases the oxygen vacancies. For the sample of PH = 1.5, the photocurrent signal is weak due to the mixed phase state and large size.
[0061] In summary, the present application optimizes the pH value (0.7), the concentration and ratio of Na2WO4·2H2O and NaCl in the solvothermal method through multi-parameter coordination, shortens the nucleation induction time, reduces the oxygen vacancy concentration, realizes the coordination of "high crystallinity-high aspect ratio-moderate oxygen vacancy", exposes more active crystal faces, and provides an advantage structure for catalytic applications. The present application realizes the controllable conversion of the mixed phase state of WO3·0.33H2O and WO3 into stable high-purity hexagonal WO3 by low-temperature calcination after solvothermal synthesis, realizes the controllable conversion of two crystal phases in the same synthesis system, and realizes the oxygen vacancy regulation without destroying the crystal morphology compared with the common chemical reduction method. The present application realizes the synchronous regulation of morphology, crystal phase and defects, reduces the oxygen vacancy concentration fluctuation, and clearly defines its specific application in the catalytic field (WO3 has better stability and stronger conductivity in electrocatalysis and thermal catalysis fields, and is more suitable). The synthesis method of the present application has simple conditions, stable product structure, good performance repeatability, and the coordinated regulation method of parameters can better control and optimize the performance, and improve the practical value.
[0062] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be included in the scope of the claims of the present application.
Claims
1. A method for preparing hexagonal tungsten trioxide integrating morphology-phase-defect control, characterized in that: Includes the following steps, (1) Dissolve sodium tungstate dihydrate and sodium chloride in a solvent to obtain a mixed solution, wherein the mass ratio of sodium tungstate dihydrate to sodium chloride is 5:(1~1.2); and the mass fraction of sodium tungstate dihydrate is 3~3.5%. (2) Add hydrochloric acid dropwise to adjust the pH to 0.6-0.8, and stir; (3) Transfer the product obtained in step (2) to a high-pressure reactor and carry out a solvothermal reaction in a forced-air drying oven. After the reaction is completed, cool to room temperature, wash, and dry. (4) Disperse the product obtained in step (3) in a dispersant, dry it and place it in a tube furnace for calcination to obtain rod-shaped tungsten trioxide.
2. The method for preparing hexagonal tungsten trioxide integrating morphology-phase-defect control according to claim 1, characterized in that: In step (2), hydrochloric acid is added dropwise to adjust the pH to 0.7, and the stirring time is 2-3 hours.
3. The method for preparing hexagonal tungsten trioxide integrating morphology-phase-defect control according to claim 1 or 2, characterized in that: In step (3), the temperature of the solvothermal reaction is 160-200 °C and the reaction time is 8-12 h.
4. The method for preparing hexagonal tungsten trioxide integrating morphology-phase-defect control according to claim 1 or 2, characterized in that: In step (3), the temperature of the solvothermal reaction is 180 °C and the reaction time is 10 h.
5. The method for preparing hexagonal tungsten trioxide integrating morphology-phase-defect control according to claim 1 or 2, characterized in that: In step (4), the dispersant includes ethanol.
6. The method for preparing hexagonal tungsten trioxide integrating morphology-phase-defect control according to claim 1 or 2, characterized in that: In step (4), the calcination is carried out in a nitrogen atmosphere at 200-240 °C for 2-3 h.
7. The method for preparing hexagonal tungsten trioxide integrating morphology-phase-defect control according to claim 1 or 2, characterized in that: In step (3), the washing and drying include washing with water and drying at 60-70 °C.
8. The rod-shaped tungsten trioxide prepared by the hexagonal phase tungsten trioxide preparation method integrating morphology-phase-defect control according to claim 1 is characterized in that: The tungsten trioxide has a highly crystalline hexagonal phase structure with a crystal length of 200-500 nm and an aspect ratio of 6.5-17:
1.
9. The application of the rod-shaped tungsten trioxide according to claim 8 as a catalyst for photocatalytic, electrocatalytic, or thermocatalytic reactions.