Cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst, its preparation method and application
By loading cobalt oxide nanoparticles onto sodium bismuth titanate micron-sized blocks, a cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst was prepared. This solved the problem that the application of sodium bismuth titanate-based materials in piezoelectric catalytic hydrogen production had not been reported, improved the carrier separation efficiency, and realized efficient piezoelectric catalytic water splitting for hydrogen production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGDAO UNIV OF SCI & TECH
- Filing Date
- 2023-03-13
- Publication Date
- 2026-05-26
AI Technical Summary
Among existing lead-free piezoelectric material systems, there are no reports on the application of sodium bismuth titanate-based materials in piezoelectric catalytic hydrogen production, and their low carrier separation efficiency limits their piezoelectric catalytic hydrogen production performance.
Cobalt oxide nanoparticles were loaded onto sodium bismuth titanate micron-sized blocks, and a cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst was prepared by photo-oxidation deposition. The Schottky interface between cobalt oxide and sodium bismuth titanate was used to promote charge separation and migration, thereby improving the carrier separation efficiency.
The piezoelectric catalytic hydrogen production performance of sodium bismuth titanate material was significantly improved, achieving a highly efficient piezoelectric catalytic hydrogen production effect.
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Figure CN116426966B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of piezoelectric catalytic hydrogen production technology, specifically to a cobalt oxide nanoparticle-supported bismuth titanate piezoelectric catalyst, its preparation method, and its application. Background Technology
[0002] Hydrogen energy possesses excellent qualities such as good combustion performance, high calorific value, and zero pollution from combustion products, making it a hot topic of research and development worldwide. Utilizing piezoelectric catalytic water splitting to produce hydrogen leverages inexhaustible mechanical energy from nature to drive the decomposition of water molecules, representing a cutting-edge technology in renewable energy hydrogen production. Under mechanical vibration (such as stirring, oscillation, ultrasound, ball milling, etc.), the piezoelectric catalyst deforms, causing a shift in the centers of positive and negative charges within the catalyst, resulting in macroscopic polarization. During this continuous change in polarization, internal charges move directionally, triggering redox reactions on the catalyst surface to decompose water molecules into hydrogen and oxygen. Currently, the development of high-performance piezoelectric catalysts is crucial for the application of piezoelectric catalytic water splitting hydrogen production technology.
[0003] The basis of piezoelectric catalysis is the piezoelectric effect; therefore, researchers tend to select material systems with excellent piezoelectric properties for catalytic research. Lead-containing piezoelectric materials (such as lead zirconate titanate) have outstanding advantages such as large remanent polarization, high piezoelectric coefficient, and electromechanical coupling constant. However, they contain a large amount of lead (more than 60% by mass), which can easily cause environmental hazards during preparation and piezoelectric catalytic applications, greatly limiting their industrial application.
[0004] Currently, lead-free piezoelectric material systems are mainly represented by barium titanate, potassium sodium niobate, and sodium bismuth titanate. Among them, the piezoelectric properties of barium titanate and potassium sodium niobate-based lead-free systems are significantly affected by temperature due to the influence of polymorphic phase transitions near room temperature, which poses certain difficulties for practical applications. In contrast, sodium bismuth titanate-based piezoelectric materials have a Curie temperature as high as 320℃. Due to their large remanent polarization, high piezoelectric coefficient, and excellent stability, they are currently commonly used as piezoelectric ceramics. For example, patent document CN108147813A discloses a high-coefficient sodium bismuth titanate-based lead-free piezoelectric ceramic and its preparation method, which dopes rubidium into the sodium bismuth titanate-based lead-free piezoelectric ceramic to improve its piezoelectric coefficient.
[0005] However, no research papers or patents have been reported on the application of sodium bismuth titanate-based materials in piezoelectric catalytic hydrogen production. Summary of the Invention
[0006] This invention addresses the aforementioned problems in the prior art by providing a cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst, its preparation method, and its application.
[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:
[0008] On one hand, the present invention provides a method for preparing a cobalt oxide nanoparticle-supported bismuth titanate piezoelectric catalyst, characterized in that,
[0009] Take sodium bismuth titanate micron-sized blocks, electron sacrificial agent, cobalt salt, and deionized water, mix them, stir in the dark, and remove dissolved oxygen from the solution;
[0010] A cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst was obtained by photo-oxidation deposition, followed by irradiation with a xenon lamp for a preset time, washing with deionized water, and drying.
[0011] Further, a method to remove dissolved oxygen from the solution is to bubble the material with argon gas.
[0012] Furthermore, the cobalt salt is cobalt nitrate hexahydrate or cobalt chloride hexahydrate, and the electron sacrificial agent is sodium iodate or potassium bromate.
[0013] Furthermore, the illumination time is controlled to be 1-6 hours; or the concentration of cobalt salt is controlled to be 0.1-1 mmol / L.
[0014] Furthermore, the method for preparing the sodium bismuth titanate micron cubes is as follows: titanium source and bismuth source are added to sodium hydroxide solution and subjected to hydrothermal reaction to obtain sodium bismuth titanate micron cubes.
[0015] Among them, the titanium source is preferably titanium dioxide or tetrabutyl titanate, and the bismuth source is preferably bismuth nitrate pentahydrate or bismuth chloride; the molar ratio of titanium source to bismuth source is 2:1.
[0016] Furthermore, the hydrothermal reaction temperature is 140-200℃, and the reaction time is 12-48h; the concentration of the sodium hydroxide solution is 9-16mol / L.
[0017] On the other hand, the present invention provides a cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst, characterized in that it is prepared by the above-described preparation method.
[0018] In another aspect, the present invention provides an application of the above-mentioned cobalt oxide nanoparticle-supported sodium titanate piezoelectric catalyst, characterized in that it is used for piezoelectric catalytic water splitting to produce hydrogen.
[0019] The low carrier separation efficiency in sodium bismuth titanate materials limits their piezoelectric catalytic hydrogen production performance.
[0020] Among numerous metal oxides, cobalt oxide possesses a suitable band structure, a simple preparation method, and excellent hole migration kinetics, and has played an important role in enhancing photocatalytic hydrogen production. However, to date, there have been no reports on cobalt oxide's application in piezoelectric catalytic water splitting for hydrogen production.
[0021] The beneficial effects of this invention are as follows: This invention creatively loads cobalt oxide onto sodium bismuth titanate micron-sized blocks to prepare a cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst. Cobalt oxide nanoparticles, which do not possess piezoelectric catalytic activity, are loaded onto the surface of the sodium bismuth titanate material, thus modifying the surface of the sodium bismuth titanate micron-sized blocks. The Schottky interface between the two promotes charge separation, and a built-in field is formed between the cobalt oxide and the sodium bismuth titanate micron-sized blocks due to charge diffusion, effectively promoting charge migration and separation, and significantly improving the carrier separation efficiency of the sodium bismuth titanate material. This composite material is used for piezoelectric catalytic water splitting to produce hydrogen as a supported cocatalyst, achieving highly efficient piezoelectric catalytic water splitting to produce hydrogen from sodium bismuth titanate micron-sized blocks, greatly enhancing its application prospects in piezoelectric catalytic hydrogen production performance. Attached Figure Description
[0022] Figure 1 These are scanning electron microscope images of the sodium bismuth titanate micron-sized cube of Example 1 of the present invention;
[0023] Figure 2 These are scanning electron microscope images of the sodium bismuth titanate micron-sized cube of Example 2 of the present invention;
[0024] Figure 3 These are scanning electron microscope images of the sodium bismuth titanate micron-sized cube of Example 3 of the present invention;
[0025] Figure 4 This is the XRD pattern of the sodium bismuth titanate micron block of Example 2 of the present invention;
[0026] Figure 5 These are TEM images and elemental analyses of the cobalt oxide nanoparticle-supported sodium titanate piezoelectric catalyst prepared in Example 2 of this invention.
[0027] Figure 6 This is the XPS spectrum of cobalt element in Example 2 of the present invention;
[0028] Figure 7 This is a graph showing the hydrogen production performance analysis of Example 2 and Comparative Example 1 as piezoelectric catalysts in this invention;
[0029] Figure 8 These are impedance analysis diagrams of Embodiment 2 and Comparative Example 1 of the present invention;
[0030] Figure 9 These are the photoluminescence spectra of Embodiment 2 and Comparative Example 1 of the present invention;
[0031] Figure 10 This is a Mott-shockey diagram of Embodiment 2 and Comparative Example 1 of the present invention. Detailed Implementation
[0032] The principles and features of the present invention are described below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0033] Example 1
[0034] The preparation method of the cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst in this embodiment is as follows:
[0035] 1. Preparation of sodium bismuth titanate micron cubes
[0036] Titanium dioxide and bismuth nitrate pentahydrate in a molar ratio of 2:1 were added to a 9 mol / L sodium hydroxide solution and stirred to obtain a dispersion.
[0037] The dispersion was transferred to a polytetrafluoroethylene liner and placed in a hydrothermal reactor. After sealing, it was placed in a muffle furnace and the heating rate was controlled at 6℃ / min. The temperature was raised to 140℃ and the hydrothermal reaction was carried out for 48 hours.
[0038] After the reactor cooled naturally to room temperature, the obtained sample was washed five times with deionized water and dried at 60°C for 12 hours to obtain sodium bismuth titanate micron cubes.
[0039] 2. Preparation of cobalt oxide nanoparticles-supported sodium bismuth titanate piezoelectric catalyst
[0040] Weigh 0.2 g of sodium bismuth titanate micron cubes and 100 mL of deionized water and add them to the photoreactor. Add sodium iodate and cobalt nitrate hexahydrate, stir in the dark for 30 min, and bubble with argon gas to remove dissolved oxygen from the solution. The concentration of sodium iodate is 2 g / L and the concentration of cobalt nitrate hexahydrate is 1 mmol / L.
[0041] The photoreaction vessel was irradiated with a xenon lamp for 1 hour, washed five times with deionized water, and dried at 50°C to obtain the cobalt oxide nanoparticle-supported bismuth titanate piezoelectric catalyst BNT@CoOx.
[0042] Example 2
[0043] The preparation method of the cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst in this embodiment is as follows:
[0044] 1. Preparation of sodium bismuth titanate micron cubes
[0045] Titanium dioxide and bismuth chloride in a molar ratio of 2:1 were added to a 14 mol / L sodium hydroxide solution and stirred to obtain a dispersion.
[0046] The dispersion was transferred to a polytetrafluoroethylene liner and placed in a hydrothermal reactor. After sealing, it was placed in a muffle furnace and the heating rate was controlled at 6℃ / min. The temperature was raised to 200℃ and the hydrothermal reaction was carried out for 12 hours.
[0047] After the reactor cooled naturally to room temperature, the obtained sample was washed five times with deionized water and dried at 60°C for 12 hours to obtain sodium bismuth titanate micron cubes.
[0048] 2. Preparation of cobalt oxide nanoparticles-supported sodium bismuth titanate piezoelectric catalyst
[0049] Weigh 0.2 g of sodium bismuth titanate micron cubes and 100 mL of deionized water and add them to the photoreactor. Add sodium iodate and cobalt nitrate hexahydrate, stir in the dark for 30 min, and bubble with argon gas to remove dissolved oxygen from the solution. The concentration of sodium iodate is 2 g / L and the concentration of cobalt nitrate hexahydrate is 0.5 mmol / L.
[0050] The photoreaction vessel was irradiated with a xenon lamp for 3 hours, then washed five times with deionized water and dried at 50°C to obtain the cobalt oxide nanoparticle-supported bismuth titanate piezoelectric catalyst BNT@CoOx.
[0051] Example 3
[0052] The preparation method of the cobalt oxide nanoparticle-supported sodium bismuth titanate piezoelectric catalyst in this embodiment is as follows:
[0053] 1. Preparation of sodium bismuth titanate micron cubes
[0054] Tetrabutyl titanate and bismuth chloride in a molar ratio of 2:1 were added to a 16 mol / L sodium hydroxide solution and stirred to obtain a dispersion.
[0055] The dispersion was transferred to a polytetrafluoroethylene liner and placed in a hydrothermal reactor. After sealing, it was placed in a muffle furnace and the heating rate was controlled at 6℃ / min. The temperature was raised to 200℃ and the hydrothermal reaction was carried out for 12 hours.
[0056] After the reactor cooled naturally to room temperature, the obtained sample was washed five times with deionized water and dried at 60°C for 12 hours to obtain sodium bismuth titanate micron cubes.
[0057] 2. Preparation of cobalt oxide nanoparticles-supported sodium bismuth titanate piezoelectric catalyst
[0058] Weigh 0.2 g of sodium bismuth titanate micron cubes and 100 mL of deionized water and add them to the photoreactor. Add potassium bromate and cobalt chloride hexahydrate, stir in the dark for 30 min, and bubble with argon gas to remove dissolved oxygen from the solution. The concentration of potassium bromate is 2 g / L and the concentration of cobalt chloride hexahydrate is 0.1 mmol / L.
[0059] The photoreaction vessel was irradiated with a xenon lamp for 6 hours. After washing five times with deionized water, it was dried at 50°C to obtain the cobalt oxide nanoparticle-supported bismuth titanate piezoelectric catalyst BNT@CoOx.
[0060] Comparative Example 1
[0061] This comparative example uses sodium bismuth titanate micron cubes, prepared using the same method as step 1 in Example 2:
[0062] Titanium dioxide and bismuth chloride in a molar ratio of 2:1 were added to a 14 mol / L sodium hydroxide solution and stirred to obtain a dispersion.
[0063] The dispersion was transferred to a polytetrafluoroethylene liner and placed in a hydrothermal reactor. After sealing, it was placed in a muffle furnace and the heating rate was controlled at 6℃ / min. The temperature was raised to 200℃ and the hydrothermal reaction was carried out for 12 hours.
[0064] After the reactor cooled naturally to room temperature, the obtained sample was washed five times with deionized water and dried at 60°C for 12 hours to obtain sodium bismuth titanate micron-sized cubes (BNT).
[0065] Comparative Example 2
[0066] This comparative example uses cobalt oxide nanoparticles without loaded sodium bismuth titanate microcubes. The preparation method is the same as step 2 of Example 2, but sodium bismuth titanate microcubes were not used.
[0067] Weigh 100 mL of deionized water and add it to the photoreactor. Add sodium iodate and cobalt nitrate hexahydrate, stir in the dark for 30 min, and bubble with argon gas to remove dissolved oxygen from the solution. The concentration of sodium iodate is 2 g / L and the concentration of cobalt nitrate hexahydrate is 0.2 g / L.
[0068] The photoreaction vessel was irradiated with a xenon lamp for 3 hours. After washing with deionized water 5 times, the vessel was dried at 50°C to obtain cobalt oxide nanoparticles (CoOx).
[0069] Comparative Example 3
[0070] The preparation method of the cobalt oxide nanoparticle-supported sodium titanate piezoelectric catalyst in this comparative example is basically the same as that in Example 2, except that the illumination time is 0.5 h.
[0071] Comparative Example 4
[0072] The preparation method of the cobalt oxide nanoparticle-supported sodium titanate piezoelectric catalyst in this comparative example is basically the same as that in Example 2, except that the illumination time is 7 hours.
[0073] Comparative Example 5
[0074] The preparation method of the cobalt oxide nanoparticle-supported sodium titanate piezoelectric catalyst in this comparative example is basically the same as that in Example 2, except that the concentration of cobalt nitrate hexahydrate is 0.05 mmol / L.
[0075] Comparative Example 6
[0076] The preparation method of the cobalt oxide nanoparticle-supported sodium titanate piezoelectric catalyst in this comparative example is basically the same as that in Example 2, except that the concentration of cobalt nitrate hexahydrate is 1.1 mmol / L.
[0077] In addition, the above-described examples and comparative examples were used as catalysts to perform piezoelectric catalytic hydrogen production and the hydrogen production rate was tested according to the following method. The results are shown in Table 1.
[0078] Piezoelectric catalysis for hydrogen production:
[0079] The catalyst was added to an Erlenmeyer flask containing deionized water, with a catalyst content of 0.05 wt.%. Argon gas was used for bubbling under light-protected conditions at a flow rate of 200 sccm, and the solution was stirred for 30 min.
[0080] After sealing, the conical flask was placed in a constant temperature ultrasonic cleaner for ultrasonic treatment. The cleaning was carried out in the dark at a temperature of 25°C, a frequency of 40kHz, and a power of 300W. Every 15 minutes, 1 mL of gas was extracted from the conical flask and injected into a gas chromatograph for analysis to determine the hydrogen content x (%).
[0081] Hydrogen production rate s = (x × V) / (22.4 × m × t) (mol g) -1 h -1 )
[0082] Where V(L) is the gas volume in the conical flask, m(g) is the amount of catalyst used, and t(h) is the ultrasonic treatment time.
[0083] Table 1
[0084] category <![CDATA[Hydrogen production rate s / mmol g -1 h -1 > Example 1 0.48 Example 2 0.49 Example 3 0.46 Comparative Example 1 0.38 Comparative Example 2 0.11 Comparative Example 3 0.39 Comparative Example 4 0.37 Comparative Example 5 0.40 Comparative Example 6 0.36 Blank control (no catalyst added) 0.11
[0085] Through XRD ( Figure 4 Analysis showed that the diffraction peaks of the sample prepared in Example 2 were consistent with the sodium bismuth titanate standard card PDF46-0001. Because the content of the loaded cobalt oxide was very low and mostly non-static, no characteristic peaks appeared in the XRD pattern. TEM elemental mapping... Figure 5 It can be clearly seen that the surface of the sodium bismuth titanate micron-sized cubes is loaded with cobalt oxide nanoparticles. From the XPS spectra ( Figure 6 The presence of cobalt can also be confirmed in the sample. The above characterization confirms that the sample prepared in Example 2 is a micron-sized block of sodium bismuth titanate supported on cobalt oxide nanoparticles.
[0086] In addition, the products prepared in Examples 1 and 3 also exhibit the above-mentioned spectral characteristics, which will not be repeated here.
[0087] like Figure 7As shown, the performance of the cobalt oxide-supported sodium bismuth titanate microcube prepared in Example 2 is significantly better than that of Comparative Example 1 (pure sodium bismuth titanate microcube). From Figure 8 As can be seen, the impedance of the cobalt oxide-supported sodium bismuth titanate micron-sized block is much lower than that of the pure sodium bismuth titanate micron-sized block, indicating that cobalt oxide can promote the migration of electrons within the sodium bismuth titanate at the solid-liquid interface. The charge separation efficiency within the catalyst can be qualitatively compared using photoluminescence spectroscopy, such as... Figure 9 As shown, the emission peak intensity of the cobalt oxide-supported sodium bismuth titanate micron-sized block is significantly lower than that of the pure sodium bismuth titanate micron-sized block, indicating that the cobalt oxide-supported sodium bismuth titanate micron-sized block has a higher charge separation efficiency. Furthermore, the carrier concentration inside the sample was analyzed using the Mott-Shockey equation. Figure 10 It can be seen that the cobalt oxide-supported sodium bismuth titanate micron cubes have a smaller slope, indicating a higher internal carrier concentration. The above analysis shows that cobalt oxide nanoparticles supported on the surface of the sodium bismuth titanate piezoelectric catalyst can promote charge migration at the solid / liquid interface, improve the separation efficiency of internal carriers, and increase the internal carrier concentration, thereby significantly improving the hydrogen production rate of sodium bismuth titanate piezoelectric catalytic water splitting.
[0088] Comparison of data from Comparative Example 1 and the blank control group shows that the sodium bismuth titanate micron cubes themselves have limited effect in piezoelectric catalytic hydrogen production. Comparison of data from Comparative Example 2 and the blank control group shows that cobalt oxide nanoparticles themselves do not have the function of piezoelectric catalytic hydrogen production. However, comparison of data from Example 2 with Comparative Examples 1 and 2 shows that after loading cobalt oxide nanoparticles, which do not have the function of piezoelectric catalytic hydrogen production, onto the sodium bismuth titanate micron cubes, the piezoelectric catalytic hydrogen production efficiency is significantly improved, showing significant progress.
[0089] As can be seen from the data in Table 1 for Example 2 and Comparative Examples 3-6, adjusting the illumination time to be too long or too short, or adjusting the concentration of cobalt salt to be too high or too low, significantly reduces the piezoelectric catalytic hydrogen production rate. This may be because a short illumination time or a low cobalt salt concentration results in insufficient cobalt oxide loading on the sodium bismuth titanate micron cube, making the product closer to the performance of the sodium bismuth titanate micron cube itself; while a long illumination time or a high cobalt salt concentration results in excessive cobalt oxide loading on the sodium bismuth titanate micron cube, causing cobalt oxide to cover the active sites on the surface, leading to a decrease in the piezoelectric catalytic hydrogen production rate.
Claims
1. A method for preparing a cobalt oxide nanoparticle-supported bismuth titanate sodium piezoelectric catalytic hydrogen production catalyst, characterized in that, Take sodium bismuth titanate micron-sized blocks, electron sacrificial agent, cobalt salt, and deionized water, mix them, stir in the dark, and remove dissolved oxygen from the solution; control the concentration of cobalt salt at 0.1-1 mmol / L; The photocatalyst was obtained by irradiating with a xenon lamp for a preset time, controlling the irradiation time to be between 1 and 6 hours, washing with deionized water, and drying. Cobalt oxide nanoparticles supported on sodium bismuth titanate piezoelectric catalyst were then obtained.
2. The method of claim 1, wherein the method is characterized by: Method to remove dissolved oxygen from the solution: bubble the material with argon gas.
3. The method of claim 1, wherein the method is characterized by: The cobalt salt is cobalt nitrate hexahydrate or cobalt chloride hexahydrate, and the electron sacrificial agent is sodium iodate or potassium bromate.
4. The method of claim 1, wherein the method is characterized by: The method for preparing the sodium bismuth titanate micron cube is as follows: titanium source and bismuth source are added to sodium hydroxide solution and subjected to hydrothermal reaction to obtain sodium bismuth titanate micron cube.
5. The method of claim 4, wherein the method is characterized by: The titanium source is titanium dioxide or tetrabutyl titanate, and the bismuth source is bismuth nitrate pentahydrate or bismuth chloride; the molar ratio of titanium source to bismuth source is 2:
1.
6. The preparation method of the cobalt oxide nanoparticle-supported bismuth titanate sodium piezoelectric catalytic hydrogen production catalyst according to claim 4, characterized in that, The hydrothermal reaction temperature is 140-200℃, and the reaction time is 12-48h.
7. The preparation method of the cobalt oxide nanoparticle-supported bismuth titanate sodium piezoelectric catalytic hydrogen production catalyst according to claim 4, characterized in that, The concentration of the sodium hydroxide solution is 9-16 mol / L.
8. A cobalt oxide nanoparticle-supported bismuth titanate sodium piezoelectric catalytic hydrogen production catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.
9. The application of the cobalt oxide nanoparticle-supported sodium titanate piezoelectric catalytic hydrogen production catalyst as described in claim 8, characterized in that, Used for piezoelectric catalytic water production of hydrogen.