An in-situ testing method for researching electronic transmission mechanism of an oxygen vacancy modified SrTiO3@Ag nanotube photocatalyst
By introducing oxygen vacancies and Ag nanoparticles into SrTiO3 nanotubes to form oxygen vacancy-modified SrTiO3@Ag nanotubes, the problems of narrow light absorption range and severe electron recombination of traditional SrTiO3 photocatalysts are solved, and the photocatalytic performance is improved by achieving high efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHENGZHOU UNIV
- Filing Date
- 2025-01-26
- Publication Date
- 2026-05-29
AI Technical Summary
Traditional SrTiO3 photocatalysts suffer from low photocatalytic activity due to their wide band gap, narrow light absorption range, and severe recombination of photogenerated electrons and holes. They are also prone to aggregation and cannot effectively utilize visible light.
SrTiO3 nanotubes were prepared by electrospinning and then heat-treated in an argon-hydrogen mixed atmosphere to introduce oxygen vacancies. Combined with Ag nanoparticle modification, oxygen vacancy-modified SrTiO3@Ag nanotubes were formed. The oxygen vacancies were used to capture photogenerated electrons and transfer them to the Ag nanoparticles to form Schottky junctions to suppress electron recombination.
It significantly improved photocatalytic activity, enhanced photogenerated charge separation efficiency, reduced recombination of photogenerated electrons and holes, and significantly enhanced photocatalytic performance. The photocatalyst activity under visible light was increased by 6.28 times.
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Abstract
Description
[0001] This invention relates to the field of energy materials technology, specifically to a method for preparing SrTiO3@Ag nanotubes with oxygen vacancy modification and the application of in-situ XPS irradiation in mechanism research. Background Technology
[0002] Energy is one of the important factors driving the progress and development of human civilization. Human society's production and daily life...
[0003] Energy utilization, processing, conversion, and innovative development have always been intertwined with this process. However, with global population growth and accelerated industrialization, energy shortages and environmental pollution are two critical issues that urgently need to be addressed. To achieve green, low-carbon, and sustainable development, photocatalysis, which simulates photosynthesis in nature, is a promising new technology for converting solar energy into stable, readily accessible, and high-energy-density chemical energy. Developing low-cost, stable, and efficient photocatalysts to meet the needs of further applications is a key research focus in photocatalysis.
[0004] Among numerous photocatalysts, strontium titanate (SrTiO3), a transition metal oxide with a perovskite structure, stands out for its excellent resistance to photocorrosion and high thermal stability. However, due to its wide band gap, it only responds to high-energy ultraviolet light, resulting in a narrow light absorption range. Furthermore, severe recombination of photogenerated electrons and holes within the material weakens its ability to promote charge separation. Traditional SrTiO3 powder materials suffer from insufficient photocatalytic active sites and are prone to aggregation, leading to limitations and low photocatalytic activity when used alone as a photocatalyst. Therefore, based on photocatalytic principles and current research, constructing heterojunctions and defect engineering are effective strategies to improve photocatalytic activity. One-dimensional semiconductor nanotubes possess excellent morphological and structural characteristics such as high aspect ratio, large specific surface area, and short electron migration distance, which can be used to upgrade SrTiO3 powder materials. To suppress the recombination of photogenerated electron-hole pairs and effectively adjust the electronic structure of SrTiO3 semiconductors to increase carrier concentration, it is essential to directly apply defect engineering strategies to the modification of SrTiO3 nanotubes. Oxygen vacancy defect engineering is expected to effectively improve the photocatalytic activity of wide-bandgap semiconductor SrTiO3, which is limited by narrow light absorption range, low carrier concentration, and rapid photogenerated carrier recombination. At the same time, it can also significantly affect the physicochemical properties of SrTiO3, including intrinsic electronic structure, charge migration, and surface state.
[0005] Furthermore, modifying SrTiO3 by loading highly conductive materials onto its surface is one way to improve its photocatalytic performance.
[0006] An attractive strategy is employed to transfer photogenerated electrons from the conduction band of SrTiO3 to conductors loaded on its surface.
[0007] It suppresses the recombination of photogenerated electrons and holes. Among highly conductive materials, Ag exhibits excellent conductivity and stable properties.
[0008] Its chemical properties make it a suitable co-catalyst material, and it has been widely used to enhance the photocatalytic activity of semiconductors.
[0009] Furthermore, the combination of Ag nanoparticles and SrTiO3 semiconductors can form Schottky junctions at the heterojunction, thereby effectively enhancing the separation of photogenerated electrons and holes.
[0010] The purpose of this invention is to provide a reliable and convenient in-situ testing method for studying electron transport pathways, specifically for investigating the electron transport mechanism of oxygen vacancy-modified SrTiO3@Ag nanotube photocatalysts. Therefore, this paper employs an electrospinning process using a sacrificial template method to prepare SrTiO3 hollow nanotubes. Based on this, oxygen vacancies are introduced through heat treatment in an argon-hydrogen mixed atmosphere, with the oxygen vacancy concentration controlled by the heat treatment temperature. After oxygen vacancy modification, the oxygen vacancies can capture activated photogenerated electrons in the SrTiO3 nanotubes and transfer them to Ag nanoparticles anchored nearby for photocatalytic reduction reactions, effectively achieving spatial separation of photogenerated charges. Simultaneously, the presence of the Schottky barrier at the heterojunction interface inhibits the reflow of photogenerated electrons into the SrTiO3 nanotubes, thus preventing the recombination of photogenerated electrons and holes. This invention utilizes defect engineering and the Schottky junction to synergistically enhance photocatalytic performance. Furthermore, the migration direction of photogenerated electrons under 350 nm ultraviolet irradiation was studied using in-situ XPS, providing a scheme for the rational design of photocatalysts with efficient charge carrier dynamics for solar energy conversion. Summary of the Invention
[0011] To achieve the above objectives, the present invention provides the following solution:
[0012] An in-situ testing method for studying the electron transport mechanism of SrTiO3@Ag nanotube photocatalysts modified with oxygen vacancies. The steps are as follows:
[0013] (1) Synthesis of oxygen vacancy modified SrTiO3@Ag nanotubes: Strontium acetate was dissolved in a mixed solution of deionized water, anhydrous ethanol, N,N-dimethylformamide and glacial acetic acid, and polyvinylpyrrolidone was slowly added. After stirring, tetrabutyl titanate was added and stirring was continued until a uniform semi-transparent solution was formed. The solution was electrospun into a pure white polymer film, which was then dried and collected in a crucible for calcination to remove the PVP template, thus obtaining SrTiO3 nanotubes. Then, after high-temperature H2 reduction, the nanotubes were dispersed in AgNO3 solution and stirred continuously. The suspension was then irradiated with ultraviolet light and continuously stirred magnetically. Finally, the product was separated from the liquid, washed with water several times, and dried to obtain oxygen vacancy modified SrTiO3@Ag nanotubes.
[0014] (2) Mechanism study of oxygen vacancy modified SrTiO3@Ag nanotubes: Ultraviolet light irradiation was introduced, and the photogenerated electron transfer behavior was studied by in-situ XPS test. The change of component binding energy before and after irradiation was observed to determine the gain and loss of electrons. The research equipment used was a light source with light guide fiber installed in the original state of the equipment. The light was irradiated onto the sample in the test chamber through the observation window of the equipment.
[0015] In step (1), the stirring time is 8~12 h, the drying temperature is 50~60℃ and the drying time is 10~15 h, the calcination time is 2~5 h and the calcination temperature is 500~700 ℃.
[0016] Furthermore, the calcination process in step (1) involves heating the material in a muffle furnace at a rate of 1-3 °C / min to 500-700 °C and holding it at that temperature for 2-5 h. Strontium acetate is dissolved in 5-6 mL of deionized water per gram, followed by the sequential addition of anhydrous ethanol, dimethylformamide, and glacial acetic acid, followed by stirring and mixing. Polyvinylpyrrolidone is then slowly added to the mixture, followed by prolonged magnetic stirring for 8-12 h. Finally, tetrabutyl titanate is added and stirring continues until a uniform, light yellow, translucent solution is formed.
[0017] Further, in step (1), SrTiO3 nanotubes are uniformly spread in a ceramic boat and placed in a tube furnace. The air in the tube furnace is evacuated using a vacuum pump, and then an argon-hydrogen mixture (H25%, Ar 95%) is continuously supplied at a certain rate. The temperature is increased to 400-800 °C at a rate of 5-10 °C / min and held for 1-3 h. The nanotubes are prepared using a photoreduction method based on oxygen vacancy-modified SrTiO3 nanotubes. Specifically, the sample is dispersed in an AgNO3 solution and continuously stirred to fully adsorb Ag+. Then, the suspension is irradiated with 365 nm ultraviolet light, and magnetic stirring is continuously performed during the irradiation process. Finally, the sample is separated from the liquid and washed multiple times with deionized water and then dried.
[0018] Furthermore, in step (2), 350 nm ultraviolet light irradiation is introduced during the test, and the gain or loss of electrons is determined by observing the change in the binding energy of the components before and after irradiation.
[0019] The beneficial effects of this invention are:
[0020] This invention investigated the migration direction of photogenerated electrons under ultraviolet irradiation using in-situ XPS, confirming that the electron flow from semiconductor SrTiO3 nanotubes to metallic Ag reveals the reason for the enhanced activity of the composite photocatalyst. This invention determines electron gain and loss by observing the changes in the binding energy of components before and after in-situ irradiation testing. In this material system, oxygen vacancies can capture activated photogenerated electrons in SrTiO3 nanotubes and transfer them to Ag nanoparticles anchored nearby for photocatalytic reduction reactions, effectively achieving spatial separation of photogenerated charges. Based on the electron shielding effect, the change in outer electron density caused by electron transport between components is ultimately reflected in the binding energy of the tested elements; an increase in binding energy indicates electron outflow, and vice versa.
[0021] This invention provides an in-situ testing method for studying the electron transport mechanism of SrTiO3@Ag nanotube photocatalysts modified with oxygen vacancies. This method employs in-situ XPS irradiation technology to investigate the migration direction of photogenerated electrons under 350 nm ultraviolet light, taking into account the material's characteristics. Therefore, this invention uses in-situ electrospinning technology to prepare white SrTiO3 nanotubes. The PVP micelle template is removed by calcination; oxygen vacancies are introduced by heat treatment in an argon-hydrogen mixed atmosphere. After oxygen vacancy modification, Ag nanoparticles are deposited on the surface of the SrTiO3 nanotubes via photoreduction. In this material system, oxygen vacancies can capture activated photogenerated electrons in the SrTiO3 nanotubes and transfer them to the Ag nanoparticles anchored nearby for photocatalytic reduction reactions, effectively achieving spatial separation of photogenerated charges. Light absorption is significantly improved, and the utilization rate of visible light is increased, which is beneficial for activating and generating more photogenerated electrons and holes. Meanwhile, the presence of the Schottky barrier at the heterojunction interface also inhibits the reflow of photogenerated electrons into the SrTiO3 nanotubes, thereby preventing the recombination of photogenerated electrons and holes and thus promoting the photocatalytic reaction. The reasons for the enhanced activity of the composite photocatalyst were revealed using in-situ irradiation XPS.
[0022] The in-situ mechanism research method provided by this invention has the following characteristics: (1) Compared with the ordinary XPS test method, the experimental method with added light can better simulate the scenario of photocatalyst in actual use. (2) Traditional mechanism research methods cannot accurately describe the electron transport path under the dual effects of oxygen vacancy modification and Schottky binding, which brings great difficulties to mechanism research, while the XPS test method can reflect the direction of electron transport based on the change of binding energy.
[0023] The photocatalytic performance of the oxygen vacancy-modified SrTiO3@Ag nanotubes prepared in this invention was compared with that of the original SrTiO3 catalyst under the same conditions. The modified sample with the best performance achieved a hydrogen evolution rate of 55.92 µmol / g / h, which is 6.28 times that of the original SrTiO3 nanotubes. It also showed good cycling stability, which is beneficial to the practical application of photocatalysis. Attached Figure Description
[0024] Figure 1 (a) XRD patterns of the oxygen-vacancy-modified SrTiO3@Ag nanotubes and different samples; (b) showing the reduced interplanar spacing and abundant oxygen vacancies in the hydrogenated sample; (c) PL spectra of photocatalysts of different samples; (d) transient photocurrent response;
[0025] Figure 2 (a, b) TEM images of SrTiO3@Ag nanotubes with oxygen vacancy modification obtained in Example 2;
[0026] Figure 3 The photocatalytic hydrogen evolution performance of different samples was tested. (a) Time progress curve of photocatalytic hydrogen evolution; (b) The corresponding average rate of photocatalytic hydrogen evolution.
[0027] Figure 4 Schematic diagram of an in-situ XPS irradiation device;
[0028] Figure 5 The figure shows the in-situ irradiation XPS spectra of SrTiO3@Ag nanotubes with oxygen vacancy modification prepared in Example 2: (a) Sr 3d; (b) Ti 2p; (c) O 1s. Detailed Implementation
[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0030] This invention discloses an in-situ testing method for studying the electron transport mechanism of oxygen vacancy-modified SrTiO3@Ag nanotube photocatalysts. SrTiO3@Ag nanotubes with oxygen vacancy modification were prepared. In this material system, oxygen vacancies can capture activated photogenerated electrons in the SrTiO3 nanotubes and transfer them to Ag nanoparticles anchored nearby for photocatalytic reduction reactions, effectively achieving spatial separation of photogenerated charges. Simultaneously, the presence of the Schottky barrier at the heterojunction interface also inhibits the reflow of photogenerated electrons into the SrTiO3 nanotubes, thereby preventing the recombination of photogenerated electrons and holes. The unmodified SrTiO3 sample has a relatively smooth surface and a diameter between 200 nm and 300 nm. The SrTiO3@OV@Ag sample synthesized after high-temperature hydrogenation and photoreduction treatment still retains a hollow one-dimensional nanotube structure with a diameter of approximately 282 nm and a wall thickness of approximately 41 nm, and its surface shows the presence of many small Ag elemental nanoparticles.
[0031] This invention discloses the application of oxygen vacancy-modified SrTiO3@Ag nanotubes in high-efficiency photocatalysts, and verifies the improvement of semiconductor photocatalyst performance through multiple modifications. The steps are as follows:
[0032] (1) Preparation of SrTiO3 nanotubes: prepared by electrospinning. Strontium acetate was dissolved in a mixed solution of deionized water, anhydrous ethanol, dimethylformamide (DMF) and glacial acetic acid, and polyvinylpyrrolidone (PVP) was slowly added. After stirring, tetrabutyl titanate (TBOT) was added and stirring continued until a uniform light yellow translucent solution was formed. A suitable needle type was selected, and the appropriate temperature, humidity and other environmental factors were adjusted by a temperature and humidity control system. Appropriate parameters such as rotation speed, injection speed, and step rate were set. The spinning solution was injected into the syringe, and a pure white polymer film was formed by electrospinning using an electrospinning machine. The film was then dried and calcined. White SrTiO3 nanotubes were prepared.
[0033] (2) Synthesis of oxygen vacancy modified SrTiO3 nanotubes: Using the synthesized SrTiO3 sample as raw material, oxygen vacancy modified SrTiO3 nanotubes were synthesized by high temperature H2 reduction method.
[0034] (3) Synthesis of oxygen vacancy-modified SrTiO3@Ag nanotubes: These nanotubes were prepared using a photoreduction method based on oxygen vacancy-modified SrTiO3 nanotubes. Specifically, the sample was dispersed in an AgNO3 solution and continuously stirred to ensure sufficient Ag adsorption. + The suspension was then irradiated with 365 nm ultraviolet light while being continuously stirred magnetically during the irradiation process. Finally, the sample was separated from the liquid, washed multiple times with deionized water, and then dried.
[0035] (4) Mechanism study of oxygen vacancy modified SrTiO3@Ag nanotubes: The photogenerated electron transfer behavior was studied using in-situ irradiation XPS technology.
[0036] In step (2), the concentration of oxygen vacancies introduced is adjusted according to the heating temperature (400 °C, 600 °C, 800 °C). The samples treated at different heating temperatures are named SrTiO3@OV-400, SrTiO3@OV-600, and SrTiO3@OV-800, respectively. In particular, SrTiO3@OV-600 is represented as SrTiO3@OV.
[0037] In step (1), the stirring time is 8-12 h, the drying temperature is 60℃ and the drying time is 10-15 h, the calcination time is 2-5 h and the calcination temperature is 500-700 ℃. In step (3), the stirring time is 9-12 h, the light exposure time is 30-90 min, the drying temperature is 60 ℃ and the drying time is 10-15 h.
[0038] In step (1), strontium acetate is dissolved in 5-6 mL of deionized water per gram, followed by the sequential addition of anhydrous ethanol, dimethylformamide (DMF), and glacial acetic acid, with stirring to mix. Polyvinylpyrrolidone (PVP) is slowly added to the mixture, followed by prolonged magnetic stirring for 8-12 hours. Finally, tetrabutyl titanate (TBOT) is added and stirring continues until a uniform, light yellow, translucent solution is formed.
[0039] In step (1), the ratio of deionized water, anhydrous ethanol, dimethylformamide (DMF), and glacial acetic acid solution is 2:3:3:2. After mixing the above solution evenly, PVP is added and stirring continues.
[0040] In step (2), SrTiO3 nanotubes are evenly spread in a ceramic boat and placed in a tube furnace. The air in the tube furnace is evacuated using a vacuum pump, and then an argon-hydrogen mixture (H25%, Ar 95%) is continuously supplied at a certain rate. The temperature is increased to 400-800 °C at a rate of 5-10 °C / min and held for 1-3 h.
[0041] In step (4), the prepared oxygen vacancy-modified SrTiO3@Ag nanotubes were adhered to the surface of conductive adhesive and sent to an XPS instrument for in-situ irradiation testing. Ultraviolet light with a wavelength of 300 nm was selected as the irradiation source. By observing the changes in the binding energy of the components before and after irradiation, the electron gain and loss situation was determined, and the photogenerated electron transfer behavior after the introduction of oxygen vacancies and Ag nanoparticles was studied.
[0042] The technical solution of the present invention will be further described below with reference to specific embodiments:
[0043] Example 1
[0044] The steps for preparing oxygen-vacancy-modified SrTiO3@Ag nanotubes with low-oxygen vacancy modification are as follows:
[0045] (1) Preparation of SrTiO3 nanotubes: prepared by electrospinning. 0.361 g of strontium acetate was dissolved in a mixed solution of 2 mL deionized water, 3 mL anhydrous ethanol, 3 mL dimethylformamide (DMF), and 2 mL glacial acetic acid, and 1.1 g of polyvinylpyrrolidone (PVP) was slowly added, followed by magnetic stirring for 10 h. Finally, 0.6 mL of tetrabutyl titanate (TBOT) was added and stirring continued until a uniform light yellow translucent solution was formed. This solution was poured into a syringe equipped with a 22G metal needle for electrospinning. The jet pump advance speed was set to 0.08 mm / min, and the positive and negative voltages were 15 kV and -5 kV, respectively. The roller receiver was about 20 cm away from the needle and set to 30 revolutions per minute. After spinning, a pure white polymer film forms on the collector, which is then dried in a 60 °C oven. Afterward, it is collected in a crucible and calcined in a muffle furnace at 600 °C in air for 3 h, with a heating rate of 2 °C / min. The white substance prepared according to the above process is SrTiO3 nanotubes.
[0046] (2) Synthesis of oxygen vacancy-modified SrTiO3 nanotubes: Using the synthesized SrTiO3 sample as raw material, oxygen vacancy-modified SrTiO3 nanotubes were synthesized by high-temperature H2 reduction method. During the synthesis process, 300 mg of SrTiO3 nanotubes were evenly spread in a ceramic boat and placed in a tube furnace. The air in the tube furnace was evacuated using a vacuum pump, and then an argon-hydrogen mixture (H2 5%, Ar 95%) was continuously supplied at a certain rate. The temperature was increased to 400℃ at a rate of 5 °C / min and held for 2 h.
[0047] (3) Synthesis of oxygen vacancy modified SrTiO3@Ag nanotubes: These nanotubes were prepared using a photoreduction method based on SrTiO3@OV nanotubes. Specifically, 300 mg of SrTiO3@OV sample was dispersed in 10 mL of AgNO3 solution and stirred continuously for 10 h to fully adsorb Ag. + The suspension was then irradiated with 365 nm ultraviolet light for 1 h, with continuous magnetic stirring during the irradiation process. This facilitated the photocatalytic reduction of Ag around the oxygen vacancies at the active sites of SrTiO3@OV nanotubes. + Ag nanoparticles are formed, and finally the sample is separated from the liquid, washed multiple times with deionized water, and then dried.
[0048] (4) Mechanism study of oxygen vacancy modified SrTiO3@Ag nanotubes: The oxygen vacancy modified SrTiO3@Ag nanotubes prepared in step (3) above were pasted onto the surface of conductive adhesive and then sent to an XPS instrument for in-situ irradiation testing. The X-ray source target of the testing instrument was an aluminum target with a power of 150 W and a radiation energy of 1486 eV. The irradiation source was a wavelength-tunable high-intensity light source, model PLS EM-150, which was introduced into the chamber from the irradiation device installed on the side of the equipment to irradiate the sample. The irradiation source was selected to be ultraviolet light with a wavelength of 300 nm.
[0049] Figure 1 (a) XRD patterns of the oxygen vacancy-modified SrTiO3@Ag nanotubes and different samples; (b) shows that the interplanar spacing of the hydrogenated sample is reduced and it contains abundant oxygen vacancies. It can be seen from the figure that the diffraction peak intensity of SrTiO3@OV is significantly higher than that of SrTiO3, which is due to the increased crystallinity of the material caused by annealing. The diffraction peak intensity of the SrTiO3 cubic phase in SrTiO3@Ag and SrTiO3@OV@Ag is significantly lower than that of SrTiO3 and SrTiO3@OV, respectively, due to the influence of Ag nanoparticle loading. However, no characteristic peaks belonging to Ag were observed, because the loading of Ag nanoparticles is relatively low. This indicates that the introduction of oxygen vacancies and Ag nanoparticles does not destroy the cubic phase structure of SrTiO3. It is worth mentioning that, compared to the untreated sample, the diffraction peak of the (110) crystal plane of the hydrogenated sample is slightly shifted towards a higher diffraction angle. Figure (c) shows the photoluminescence (PL) spectra of different photocatalysts at an excitation wavelength of 300 nm, with the emission peaks of all samples near 390 nm. Unmodified SrTiO3 nanotubes exhibit the strongest emission peak, indicating severe photogenerated electron-hole recombination within them. Introducing oxygen vacancies or loading Ag nanoparticles onto the surface of SrTiO3 nanotubes both reduced the intensity of the PL emission peak. SrTiO3@OV@Ag, however, showed the strongest PL signal quenching, indicating that photogenerated carrier recombination was effectively suppressed, which is beneficial for enhancing photocatalytic activity. In Figure (d), a higher photocurrent indicates a higher separation efficiency of photogenerated electron-hole pairs. It can be observed that SrTiO3@OV@Ag exhibits the highest photocurrent density under simulated solar radiation, far exceeding other photocatalysts. Moreover, its photocurrent is reproducible and maintains the highest photoelectric conversion efficiency during several irradiation or shading cycles. This indicates that SrTiO3@OV@Ag has superior photogenerated electron-hole pair separation and light utilization capabilities compared to other samples. Furthermore, after the light-shielding treatment, the residual photocurrent of SrTiO3@OV@Ag was still higher than that of SrTiO3, indicating that the presence of oxygen vacancies and Ag nanoparticles inhibited the recombination of photogenerated carriers, thereby prolonging the lifetime of photogenerated carriers.
[0050] Figure 2The (a, b) TEM images of the oxygen vacancy-modified SrTiO3@Ag nanotubes prepared in Example 2 show that the SrTiO3@OV@Ag sample synthesized after high-temperature hydrogenation and photoreduction treatment still maintains a one-dimensional nanotube structure with hollow features, with a diameter of about 282 nm and a wall thickness of about 41 nm.
[0051] Figure 3 To visually investigate the effects of oxygen vacancies and Ag on the photocatalytic performance of SrTiO3 nanotubes, the photocatalytic hydrogen evolution performance of different samples was tested under simulated solar irradiation, as shown in Figures a and b. SrTiO3 exhibited the lowest photocatalytic hydrogen evolution efficiency, only 8.91 µmol / g / h, due to severe photogenerated carrier recombination. The introduction of oxygen vacancies (SrTiO3@OV) or the loading of Ag nanoparticles (SrTiO3@Ag) significantly improved the photocatalytic hydrogen evolution activity of the original SrTiO3 nanotubes, with average rates reaching 37.59 µmol / g / h and 48.25 µmol / g / h, respectively. The average photocatalytic hydrogen evolution rate of SrTiO3@OV@Ag reached an even higher 55.92 µmol / g / h, 6.28 times that of the unmodified SrTiO3 sample, indicating that the modification strategy of introducing oxygen vacancies and loading Ag can greatly improve the photocatalytic activity of SrTiO3.
[0052] Figure 4 This is a schematic diagram of an in-situ irradiation XPS setup. Oxygen-vacancy-modified SrTiO3@Ag nanotubes are fixed to the sample stage surface using conductive adhesive. X-ray irradiation of the sample excites photoelectrons to escape from the material surface. These photoelectrons then pass through an upper lens group into a hemispherical analyzer, where their kinetic energy is automatically used to create corresponding images on the software. 300 nm ultraviolet light is introduced through an irradiation source.
[0053] Figure 5 The photogenerated electron transfer behavior in the SrTiO3@OV@Ag photocatalytic system was investigated using XPS. Ultraviolet light irradiation was introduced during the testing process, and the changes in the binding energy of the components before and after irradiation were observed to determine the electron gain and loss. The Sr 3d spectrum (Figure a) shows the Sr 3d... 5 / 2 and Sr 3d 3 / 2 The two characteristic signal peaks of the spin orbital changed from 133.03 eV and 134.82 eV before irradiation to 133.06 eV and 134.83 eV after irradiation. Furthermore, in the Ti 2p spectrum (Figure b), these changes are attributed to Ti 2p... 3 / 2 and Ti 2p 1 / 2Before irradiation, the two peaks of the spin orbitals were 458.36 eV and 464.09 eV, respectively, and shifted positively to 458.39 eV and 464.14 eV after irradiation. Furthermore, in the O 1s spectrum (Figure c), the two characteristic signal peaks assigned to lattice oxygen (Ti-O) and surface adsorbed oxygen (-OH) remained fixed at 529.60 eV and 533.51 eV, respectively, indicating that there was no electron flow or the electron flow remained balanced in these two components. Interestingly, the characteristic signal peak of oxygen vacancies underwent a positive shift with the largest offset, changing from 531.50 eV to 531.59 eV, indicating that electrons escaped from oxygen vacancies that were originally electron trapping centers. Considering the relationship between electron cloud density and binding energy, and combining the binding energy changes of Sr 3d, Ti 2p, and O 1s, it can be deduced that photogenerated electrons transferred from SrTiO3 nanotubes to Ag nanoparticles loaded on the surface.
[0054] Example 2
[0055] The steps for preparing oxygen-vacancy-modified SrTiO3@Ag nanotubes are as follows:
[0056] (1) Preparation of SrTiO3 nanotubes: prepared by electrospinning. 0.361 g of strontium acetate was dissolved in a mixed solution of 2 mL deionized water, 3 mL anhydrous ethanol, 3 mL dimethylformamide (DMF), and 2 mL glacial acetic acid, and 1.1 g of polyvinylpyrrolidone (PVP) was slowly added, followed by magnetic stirring for 10 h. Finally, 0.6 mL of tetrabutyl titanate (TBOT) was added and stirring continued until a uniform light yellow translucent solution was formed. This solution was poured into a syringe equipped with a 22G metal needle for electrospinning. The jet pump was set to a propulsion speed of 0.08 mm / min, with positive and negative voltages of 15 kV and -5 kV, respectively. The roller receiver was positioned approximately 20 cm from the needle and set to 30 revolutions per minute. After spinning, a pure white polymer film forms on the collector, which is then dried in a 60 °C oven. Afterward, it is collected in a crucible and calcined in a muffle furnace at 600 °C in air for 3 h, with a heating rate of 2 °C / min. The white substance prepared according to the above process is SrTiO3 nanotubes.
[0057] (2) Synthesis of oxygen vacancy-modified SrTiO3 nanotubes: Using the synthesized SrTiO3 sample as raw material, oxygen vacancy-modified SrTiO3 nanotubes were synthesized by high-temperature H2 reduction method. During the synthesis process, 300 mg of SrTiO3 nanotubes were evenly spread in a ceramic boat and placed in a tube furnace. The air in the tube furnace was evacuated using a vacuum pump, and then an argon-hydrogen mixture (H2 5%, Ar 95%) was continuously supplied at a certain rate. The temperature was increased to 600 °C at a rate of 5 °C / min and held for 2 h.
[0058] (3) Synthesis of oxygen vacancy modified SrTiO3@Ag nanotubes: These nanotubes were prepared using a photoreduction method based on SrTiO3@OV nanotubes. Specifically, 300 mg of SrTiO3@OV sample was dispersed in 10 mL of AgNO3 solution and stirred continuously for 10 h to fully adsorb Ag. + The suspension was then irradiated with 365 nm ultraviolet light for 1 h, with continuous magnetic stirring during the irradiation process. This facilitated the photocatalytic reduction of Ag around the oxygen vacancies at the active sites of the SrTiO3@OV nanotubes. + Ag nanoparticles are formed, and the sample is finally separated from the liquid, washed multiple times with deionized water, and then dried.
[0059] Example 3
[0060] The steps for preparing oxygen-vacancy-modified SrTiO3@Ag nanotubes are as follows:
[0061] (1) Preparation of SrTiO3 nanotubes: prepared by electrospinning. 0.361 g of strontium acetate was dissolved in a mixed solution of 2 mL deionized water, 3 mL anhydrous ethanol, 3 mL dimethylformamide (DMF), and 2 mL glacial acetic acid, and 1.1 g of polyvinylpyrrolidone (PVP) was slowly added, followed by magnetic stirring for 10 h. Finally, 0.6 mL of tetrabutyl titanate (TBOT) was added and stirring continued until a uniform light yellow translucent solution was formed. This solution was poured into a syringe equipped with a 22G metal needle for electrospinning. The jet pump speed was set to 0.08 mm / min, and the positive and negative voltages were 15 kV and -5 kV, respectively. The roller receiver was about 20 cm away from the needle and set to 30 revolutions per minute. After spinning, a pure white polymer film forms on the collector, which is then dried in a 60 °C oven. Afterward, it is collected in a crucible and calcined in a muffle furnace at 600 °C in air for 3 hours, with a heating rate of 2 °C / min. The white substance prepared according to the above process is SrTiO₂. 3 Nanotubes;
[0062] (2) Synthesis of oxygen vacancy-modified SrTiO3 nanotubes: Using the synthesized SrTiO3 sample as raw material, oxygen vacancy-modified SrTiO3 nanotubes were synthesized by high-temperature H2 reduction method. During the synthesis process, 300 mg of SrTiO3 nanotubes were evenly spread in a ceramic boat and placed in a tube furnace. The air in the tube furnace was evacuated using a vacuum pump, and then an argon-hydrogen mixture (H2 5%, Ar 95%) was continuously supplied at a certain rate. The temperature was increased to 800 °C at a rate of 5 °C / min and held for 2 h.
[0063] (3) Synthesis of oxygen vacancy modified SrTiO3@Ag nanotubes: These nanotubes were prepared using a photoreduction method based on SrTiO3@OV nanotubes. Specifically, 300 mg of SrTiO3@OV sample was dispersed in 10 mL of AgNO3 solution and stirred continuously for 10 h to fully adsorb Ag. + The suspension was then irradiated with 365 nm ultraviolet light for 1 h, with continuous magnetic stirring during the irradiation process. This facilitated the photocatalytic reduction of Ag around the oxygen vacancies at the active sites of the SrTiO3@OV nanotubes. + Ag nanoparticles are formed, and the sample is finally separated from the liquid, washed multiple times with deionized water, and then dried.
[0064] The above provides a detailed description of the in-situ testing method for studying the electron transport mechanism of SrTiO3@Ag nanotube photocatalysts modified with oxygen vacancies, as provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.
Claims
1. An in-situ testing method for studying the electron transport mechanism of SrTiO3@Ag nanotube photocatalysts modified with oxygen vacancies, characterized in that, The steps are as follows: (1) Synthesis of oxygen vacancy modified SrTiO3@Ag nanotubes: Strontium acetate was dissolved in a mixed solution of deionized water, anhydrous ethanol, N,N-dimethylformamide and glacial acetic acid, and polyvinylpyrrolidone was slowly added. After stirring, tetrabutyl titanate was added and stirring was continued until a uniform semi-transparent solution was formed. A pure white polymer film was formed by electrospinning, dried, collected in a crucible and calcined to remove the PVP template to obtain SrTiO3 nanotubes. After high temperature H2 reduction, the nanotubes were dispersed in AgNO3 solution and stirred continuously. The suspension was then irradiated with ultraviolet light and continuously stirred magnetically. Finally, the product was separated from the liquid and washed with water several times and dried to obtain oxygen vacancy modified SrTiO3@Ag nanotubes. (2) In-situ testing method: SrTiO3@Ag nanotubes were attached to the surface of conductive adhesive and sent to XPS instrument for in-situ irradiation testing. During the pre-vacuuming process, all light sources in the transition chamber and test chamber were turned off to make the sample in a completely dark environment. After the pre-vacuuming was completed, the test was conducted under the same completely dark conditions. The test results were then obtained under dark conditions. 350 nm ultraviolet light was added, and the test results were obtained under illumination conditions.
2. The in-situ testing method for studying the electron transport mechanism of SrTiO3@Ag nanotube photocatalysts with oxygen vacancy modification according to claim 1, characterized in that: In step (1), nanofibers are prepared by electrospinning. The needle type is selected, and the temperature and humidity environmental factors are adjusted by the temperature and humidity control system. The electrospinning parameters are set as follows: polymer solution flow rate is 0.5~2.0 mL / h, roller speed is 80~200 rpm, voltage is 12~25 kV, and the receiving distance between the syringe and the electrospinning receiving roller is 8~20 cm. The environmental parameters are adjusted as follows: ambient temperature is 20~28 ℃, and ambient humidity is 40%~60%. The precursor solution is injected into the syringe with the needle, and a high voltage of 20 kV is applied to the needle. At the same time, a grounded rotating roller is used to receive the fibers.
3. The in-situ testing method for studying the electron transport mechanism of SrTiO3@Ag nanotube photocatalysts with oxygen vacancy modification according to claim 1, characterized in that: In step (1), the temperature is increased to 500-700 °C in a muffle furnace at a rate of 1-3 °C / min and held for 2-5 h. Strontium acetate is dissolved in 5-6 mL of deionized water per gram. Then, anhydrous ethanol, N,N-dimethylformamide and glacial acetic acid are added sequentially and stirred. Polyvinylpyrrolidone is slowly added to the mixed solution and then magnetically stirred for a long time for 8-12 h. Finally, tetrabutyl titanate is added and stirring is continued until a uniform light yellow semi-transparent solution is formed.
4. The in-situ testing method for studying the electron transport mechanism of SrTiO3@Ag nanotube photocatalysts with oxygen vacancy modification according to claim 1, characterized in that: In step (1) high-temperature H2 reduction, SrTiO3 nanotubes are evenly spread in a ceramic boat and placed in a tube furnace. The air in the tube furnace is evacuated using a vacuum pump, and then an argon-hydrogen mixture is continuously supplied at a certain rate. The temperature is raised to 400-800 °C at a rate of 5-10 °C / min and held for 1-3 h.
5. An in-situ testing method for studying the electron transport mechanism of oxygen vacancy-modified SrTiO3@Ag nanotube photocatalysts according to claim 4, characterized in that: In step (1), the volume fraction of H2 in the argon-hydrogen mixture is 5%, and the volume fraction of Ar is 95%.