Bismuth vanadate photo-anode, preparation method thereof and application of bismuth vanadate photo-anode in photoelectrocatalytic styrene epoxidation reaction
By preparing a bismuth vanadate photoanode and carrying out a two-electron transfer photoelectrocatalytic epoxidation reaction of styrene on it, the high cost problem of the photoanode water oxidation process was solved and the effect of efficiently generating styrene oxide was achieved.
Patent Information
- Application Number
- CN202510837726.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2025-09-23
AI Technical Summary
In the process of water oxidation and oxygen production by photoanode, the coordinated transfer of four electrons and the coupled release of protons are complex, requiring precious metal catalysts, which are costly, and it is difficult to achieve efficient photoelectrocatalytic reactions with existing technologies.
A bismuth vanadate photoanode was used. By drop-coating a vanadyl acetylacetonate solution on a BiOI film and calcining it, a BVO photoanode was formed. Combined with a mixed solution of acetonitrile and water and sodium bromide as the electrolyte, a two-electron transfer photoelectrocatalytic epoxidation reaction of styrene was carried out.
The efficient production of styrene oxide was achieved, with a Faradaic efficiency of 25.72% and a selectivity of 87.15%, which reduced the reaction energy barrier and achieved the dual goals of efficient energy conversion and high-value chemical synthesis.
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Figure CN120683536A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of photoanodes, and in particular relates to a bismuth vanadate photoanode, a preparation method thereof, and an application thereof in a photoelectrocatalytic styrene epoxidation reaction. Background Art
[0002] With the rapid development of the global economy and the continued advancement of industrialization, society's demand for energy continues to grow. As a clean energy carrier, hydrogen produces no carbon dioxide emissions during use and combustion, making it a key element in building a sustainable energy system. The efficient production and large-scale application of hydrogen not only contribute to energy security but also effectively address environmental challenges.
[0003] Artificial photosynthesis aims to convert solar energy directly into hydrogen energy by simulating the energy conversion mechanism of natural photosynthesis, providing innovative solutions and theoretical basis for solving energy and environmental problems. Taking the water splitting reaction as an example, this technology mainly uses the photo / electrocatalytic process to drive the decomposition of water to produce hydrogen and oxygen, which is an important way to achieve efficient collection and storage of solar energy. At present, significant progress has been made in the production of hydrogen by photocathode water splitting. However, the process of photoanode water oxidation and oxygen production still faces many challenges. The core problem is that the reaction involves a complex four-electron cooperative transfer and proton coupling release process. Compared with single-electron or two-electron transfer reactions, the four-electron transfer process requires higher activation energy, and at the same time puts forward more stringent requirements on the active site design, electron transfer efficiency and catalytic stability of the catalyst. It usually needs to rely on precious metal catalysts such as ruthenium and iridium, which significantly increases the reaction cost. Summary of the Invention
[0004] In response to the above situation, the present invention innovatively proposes to use styrene as an organic substrate for photoelectrocatalytic epoxidation reaction, thereby replacing the traditional photoanode water oxidation reaction. Unlike the four-electron transfer mechanism of the water oxidation reaction, the styrene epoxidation reaction only requires a two-electron transfer process, which greatly reduces the kinetic energy barrier of the reaction. More importantly, the olefin photoelectrocatalytic epoxidation reaction can not only produce high-value-added styrene oxide at the photoanode, but can also be coupled with the hydrogen production process of the photocathode, thereby simultaneously achieving the dual goals of efficient energy conversion and high-value chemical synthesis. This strategy provides a new research idea for the development of new artificial photosynthesis systems.
[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a bismuth vanadate photoanode, the preparation method of which comprises the following steps: drop-coating a dimethyl sulfoxide solution of vanadium acetylacetonate on a BiOI film and calcining it, cooling it and soaking it in a sodium hydroxide solution, and washing it to obtain a BVO photoanode.
[0006] The above-mentioned bismuth vanadate photoanode and the preparation method of the BiOI thin film are as follows: potassium iodide and an ethanol solution of p-benzoquinone are added to a nitric acid solution of bismuth nitrate, and stirred to form a dark red solution as an electrodeposition solution, and the cleaned FTO conductive glass is immersed in the electrodeposition solution as the working electrode, an Ag / AgCl electrode is used as the reference electrode, and a Pt wire electrode is used as the counter electrode. Electrodeposition is performed using a three-electrode system to obtain a BiOI thin film.
[0007] The above-mentioned bismuth vanadate photoanode is electroplated under an external bias voltage of -0.1V vs. Ag / AgCl for 5 minutes.
[0008] The calcination of the bismuth vanadate photoanode is carried out by heating the temperature to 450° C. at a heating rate of 2° C. / min and calcining for 2 hours.
[0009] The above-mentioned bismuth vanadate photoanode, the concentration of the sodium hydroxide solution is 1 mol L -1 .
[0010] The application of the above-mentioned bismuth vanadate photoanode in the photoelectrocatalytic styrene epoxidation reaction.
[0011] In the above application, the BVO photoanode is used as a working electrode, an Ag / AgCl electrode is used as a reference electrode, a Pt wire electrode is used as a counter electrode, and the electrolyte is a mixture of styrene, sodium bromide, acetonitrile and water. The epoxidation reaction of styrene is catalyzed in a three-electrode system.
[0012] In the above application, the voltage is 0.8V vs. Ag / AgCl.
[0013] For the above application, the concentration of sodium bromide in the electrolyte is 10-120 mmol L -1 .
[0014] In the above application, the volume ratio of acetonitrile to water is 1-9:1.
[0015] The present invention uses a mixed solution of acetonitrile and water as the electrolyte, and experimentally determines the optimal volume ratio of the two. Sodium bromide is introduced as a redox medium to form a bismuth vanadate (BVO) photoanode for indirect photoelectrocatalytic styrene epoxidation. Experimental optimization revealed that under a light intensity of 100 mW cm -2 Under simulated sunlight, when the bias voltage is 0.8Vvs.Ag / AgCl, the volume ratio of acetonitrile to water is 3:1, and the concentration of sodium bromide is 40mmol L -1 When is the optimal reaction condition under this system, the Faradaic efficiency of producing styrene oxide can reach 25.72% and the selectivity is as high as 87.15%. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 (a) is the calibration curve of styrene and (b) is the calibration curve of styrene oxide.
[0017] Figure 2 is a scanning electron microscope (SEM) image of the BVO photoanode.
[0018] Figure 3 These are the XRD test results and standard cards of BVO photoanode.
[0019] Figure 4 (a) IT curve of the reaction for one hour under different external bias voltages; (b) comparison of Faraday efficiency and selectivity.
[0020] Figure 5 (a) LSV diagram of the reaction for one hour at different ratios of acetonitrile and water; (b) comparison diagram of Faraday efficiency and selectivity.
[0021] Figure 6 (a) LSV diagram of the reaction for one hour at different sodium bromide concentrations; (b) comparison diagram of Faraday efficiency and selectivity. DETAILED DESCRIPTION
[0022] Example 1 Preparation of Bismuth Vanadate Photoanode
[0023] 0.97g of bismuth nitrate pentahydrate was added to 50mL of dilute nitric acid solution at pH 1.7, covered with plastic wrap, and stirred thoroughly on a mixing table. 3.32g of potassium iodide was then added and stirred until the solution turned reddish-brown. 0.497g of p-benzoquinone was dissolved in 20mL of ethanol solution, stirred evenly, and mixed with the above solution. Stirring was continued until the solution clarified and formed a dark red solution to obtain an electrodeposition solution. About 10mL of the above-prepared electrodeposition solution was taken into a container, and a cleaned FTO conductive glass was immersed in the electrodeposition solution as the working electrode, an Ag / AgCl electrode as the reference electrode, and a Pt wire electrode as the counter electrode. Using a three-electrode system, electrodeposition was performed at an applied bias of -0.1V vs. Ag / AgCl for about 5 minutes. After removal, the electrodeposited layer was rinsed with a little deionized water to produce a BiOI film. 0.106 g of vanadyl acetylacetonate was dissolved in 1.0 mL of dimethyl sulfoxide and ultrasonicated until completely dissolved. 20 μL of the above solution was evenly dropped on the surface of the electrodeposited BiOI using a pipette. The mixture was placed in a muffle furnace and heated to 450 °C at a heating rate of 2 °C / min. The mixture was calcined for 2 h. After cooling, the mixture was taken out and placed in a 1 mol L -1 Soak in a sodium hydroxide solution for about 30 minutes until the surface turns golden yellow to remove V2O5 on the BVO surface. After removal, rinse with deionized water to obtain a BVO photoanode.
[0024] The BVO photoanode was characterized using a Hitachi SU8010 scanning electron microscope. The imaging mode was synchronous imaging of the upper and lower probes of the secondary electron, the landing voltage (HV) was 10.0 kV, the scale was 1.00 μm, and the magnification was 30,000 times (×30.0 k). The obtained SEM images are shown in Figure 2 As can be seen from the image, the prepared BVO photoanode material has a smooth and flat surface, exhibiting a unique worm-like porous microstructure. This unique pore structure significantly increases the material's specific surface area, exposing more active sites and providing a good foundation for subsequent catalytic reactions and other applications.
[0025] According to the data obtained from the XRD test, the experimental results of XRD were analyzed and processed. Figure 3 Characteristic diffraction peaks of BVO appeared at 2θ angles of 19°, 29.5°, and 35°. Comparison of the experimentally obtained XRD pattern with the standard card (PDF#14-0688) revealed that the BVO photoanode sample prepared in this experiment exhibited characteristic peaks at the corresponding angles that were highly consistent with the standard pattern, confirming that the prepared BVO photoanode has a typical monoclinic scheelite crystal structure.
[0026] Example 2 Photoelectrochemical Performance Test of Styrene Epoxidation
[0027] The photoelectrochemical performance of styrene epoxidation was tested at room temperature using a conventional three-electrode system on an electrochemical workstation (CHI660E). The prepared BVO photoanode was used as the working electrode, an Ag / AgCl electrode was used as the reference electrode, and a Pt wire electrode was used as the counter electrode. The light source was a 300 W xenon lamp (PLS-FX300HU, Perfectlight) with an AM1.5G filter. The light intensity at the BVO photoanode working electrode was calibrated to 100 mW cm using an optical power meter. -2 The exposed area of the photoanode is 1×1 cm 2 All PEC tests were performed using FTO backlighting. The electrolyte used was a mixture of acetonitrile and water.
[0028] (1) Linear sweep voltammetry (LSV) test
[0029] Linear sweep voltammetry is a technique used to measure the current response of a photoanode over a range of potentials. During the test, the potential is linearly swept forward or backward from potential V1 to potential V2 as a light source is applied. The data is recorded as the current at various voltages, a phenomenon known as a voltammogram. The test is performed in a mixture of acetonitrile and water over a potential sweep range of -0.4-1.2 V vs. Ag / AgCl at a scan rate of 10 mV / s. Linear sweep voltammetry allows for a quantitative assessment of the efficiency of the photoanode.
[0030] The voltage relative to the reversible hydrogen electrode is calculated using Equation 1:
[0031]
[0032] where E RHE Refers to the switching potential relative to RHE. The value of is 0.1976V at ambient temperature (25℃), E Ag / AgCl is the potential obtained relative to Ag / AgCl.
[0033] (2) Styrene epoxidation reaction time ampere (it) method test
[0034] A 10mM styrene solution, 40mM sodium bromide, and 15ml of a 3:1 volume ratio of acetonitrile and water were added to a single-chamber electrolytic cell. The mixture was stirred on a magnetic stirrer for a period of time to allow for thorough dispersion of the solutes. Using a three-electrode system, the working, reference, and counter electrodes were connected using the same method as described for the LSV test. An IT test was then performed on an electrochemical workstation at 0.8V vs. Ag / AgCl.
[0035] (3) Quantitative analysis and detection of products
[0036] The reaction products were qualitatively and quantitatively analyzed using a high performance liquid chromatography instrument. The conditions of the high performance liquid chromatography instrument were as follows: the chromatographic column was a C18 reverse phase column, the column temperature was 25°C, the mobile phase was acetonitrile: water = 7:3, and the flow rate was 0.5 mL min -1 The detector is a UV detector with a wavelength of 220 nm and an injection volume of 1 μL. First, a standard curve of substrate styrene and product styrene oxide was drawn, as shown in Figure 1 As shown, and then subsequent testing is performed.
[0037] The reaction electrolyte after the IT test was filtered through an organic PES filter membrane into an injection bottle and then tested on a high-performance liquid chromatograph. The test time was 20 minutes, and each sample was tested three times. According to the peak positions of the styrene and styrene oxide standard substances, the peak areas of styrene and styrene oxide in the chromatogram after each test were recorded. The amount of substance generating styrene oxide and the amount of substance remaining styrene were calculated from the drawn standard curves of styrene and styrene oxide. Finally, the yield of styrene oxide and the selectivity of the substrate were calculated according to Formula 2 and Formula 3, respectively. The Faradaic efficiency was calculated according to Formula 4.
[0038]
[0039] In formula (4), F represents the Faraday constant (96485C mol -1 )
[0040] Example 3
[0041] In order to explore the effect of suitable external bias on the reaction system, the -2 ) of simulated sunlight, the same sodium bromide concentration (40 mmol L -1 ), acetonitrile to water ratio (9:1), styrene concentration 10mmol L -1 It test is carried out for 1h under different external bias conditions, such as Figure 4 Observing the IT curves at six different voltages in the tested range of 0.4-0.9V vs. Ag / AgCl in the figure, it is found that the IT curve is relatively stable in the voltage range of 0.4-0.7V vs. Ag / AgCl. However, the IT curve gradually decreases at voltages of 0.8V and 0.9V, indicating poor stability. This may be due to the aggravation of photocorrosion on the BVO surface under high voltage conditions, indicating that excessively high external bias voltage is not conducive to the stable progress of the reaction.
[0042] The electrolyte after the reaction was tested by high performance liquid chromatography, and the peak area of the electrolyte was brought into the standard curve of styrene oxide and styrene, and then the Faradaic efficiency and selectivity were calculated according to formulas 2, 3, and 4, and the result was Figure 4 b. Comparing the Faradaic efficiency and selectivity at different applied bias voltages, it is clearly evident that at a voltage of 0.8 V vs. Ag / AgCl, sodium bromide-mediated styrene epoxidation achieves the highest Faradaic efficiency and selectivity, with a Faradaic efficiency of 23.05% and a selectivity of 40.46%. Prior to 0.8 V vs. Ag / AgCl, both Faradaic efficiency and selectivity gradually increase with increasing voltage, but the reaction product decreases at a voltage of 0.9 V vs. Ag / AgCl, consistent with the inference from the IT test. Based on this, it can be concluded that a voltage of 0.8 V vs. Ag / AgCl is most suitable for styrene epoxidation using the BVO photoanode, and all subsequent experiments were conducted at this voltage.
[0043] In addition, the effects of different ratios of acetonitrile and water on the reaction results were also tested. -2 ) of simulated sunlight, the same sodium bromide concentration (40 mmol L -1 ) and styrene concentration 10 mmol L -1 Under the conditions of 1:1, 3:1, 6:1, 9:1, 10:0, different volume ratios of acetonitrile and water were selected for LSV curve test, and the results were Figure 5a's LSV curve. It can be seen from the figure that as the proportion of acetonitrile increases, the photocurrent obtained becomes larger. However, when the system is entirely composed of acetonitrile, the LSV curve obtained from the test suddenly decreases. Since sodium bromide is not soluble in acetonitrile, the reaction system is uniform only in a mixed solution of acetonitrile and water, which provides a guarantee for the efficient and stable generation of styrene oxide. Then, under the same external bias voltage (0.8V vs. Ag / AgCl), the effect of the volume ratio of acetonitrile and water in the electrolyte on the epoxidation of styrene by sodium bromide in the BVO system was further explored. After it was tested for 1 hour, the reacted electrolyte was put into a high-performance liquid chromatograph for detection, and the peak area was brought into the standard curve of styrene oxide and styrene, and then the Faraday efficiency and selectivity were calculated according to the above formulas 2, 3, and 4. The results are as follows. Figure 5 As shown in Figure b, it can be seen that when the volume ratio of acetonitrile to water is 3:1, the reaction effect is the best, and the Faradaic efficiency and selectivity of the obtained styrene oxide are the highest, with a Faradaic efficiency of 25.72% and a selectivity of 87.15%.
[0044] Based on the above experiments, the effect of sodium bromide concentration on the photoelectrocatalytic styrene epoxidation reaction of BVO photoanode was further determined. -2 ) with simulated sunlight, the same volume ratio of acetonitrile to water (3:1) and a styrene concentration of 10 mmol L -1 Under the condition of different concentrations of sodium bromide (10, 20, 40, 80, 120 mmol L -1 ) to conduct LSV curve test, and the results are as follows Figure 6 LSV curve of a. It can be seen from the figure that as the concentration of sodium bromide increases, the photocurrent obtained by the test increases, proving that the higher the sodium bromide concentration, the higher the electrolyte content in the solution, and thus the faster the redox reaction of bromide ions. Then, the IT test was carried out for 1 hour, and the electrolyte after the reaction was put into the high-performance liquid chromatography for detection. The peak area was brought into the standard curve of styrene oxide and styrene, and then the Faradaic efficiency and selectivity were calculated according to the above formulas 2, 3, and 4. The results are as follows Figure 6 As shown in b. However, it can be seen from the Faraday efficiency and selectivity diagram that the sodium bromide concentration is 40 mmol L -1 When , the reaction effect is best, and the Faradaic efficiency and selectivity of the obtained styrene oxide are the highest, with a Faradaic efficiency of 25.72% and a selectivity of 87.15%. This shows that the higher the concentration of sodium bromide is, the better. Only when an appropriate amount of sodium bromide is used to mediate the reaction can the best effect.
[0045] The present invention successfully prepared a BVO photoanode and designed a bromide-mediated photoelectrocatalytic styrene epoxidation reaction system on the BVO photoanode. Through detailed comparative experiments, the effects of three key parameters on the styrene epoxidation reaction, namely the applied bias voltage, the volume ratio of acetonitrile to water in the electrolyte, and the sodium bromide concentration, were studied in depth. The results showed that at 100mWcm -2 Under the irradiation of simulated sunlight with a light intensity of 0.8V vs. Ag / AgCl, the volume ratio of acetonitrile to water in the electrolyte was 3:1, and the concentration of sodium bromide was 40mmol L -1 When the electrolysis reaction lasted for one hour, the photoelectrocatalytic system showed optimal performance, with the Faradaic efficiency of generating styrene oxide reaching 25.72% and the reaction selectivity reaching 87.15%.
[0046] The present invention provides a more energy-saving, environmentally friendly and green production route for styrene epoxidation.
Claims
1. A bismuth vanadate photoanode, characterized in that The preparation method comprises the following steps: dropping a dimethyl sulfoxide solution of vanadium acetylacetonate on a BiOI film for calcination, cooling the film and then soaking the film in a sodium hydroxide solution, and washing the film to obtain a BVO photoanode.
2. The bismuth vanadate photoanode according to claim 1, wherein The preparation method of BiOI film is as follows: potassium iodide and ethanol solution of p-benzoquinone are added to nitric acid solution of bismuth nitrate, and stirred to form a dark red solution as electrodeposition solution, and cleaned FTO conductive glass is immersed in the electrodeposition solution as the working electrode, Ag / AgCl electrode is used as the reference electrode, and Pt wire electrode is used as the counter electrode. Electrodeposition is carried out using a three-electrode system to obtain BiOI film.
3. A bismuth vanadate photoanode according to claim 2, characterized in that The electroplating is carried out under an external bias voltage of -0.1 V vs. Ag / AgCl for 5 minutes.
4. The bismuth vanadate photoanode according to claim 1, wherein The calcination is carried out by heating the temperature to 450° C. at a heating rate of 2° C. / min and calcining for 2 hours.
5. The bismuth vanadate photoanode according to claim 1, characterized in that The concentration of the sodium hydroxide solution is 1 mol L -1 .
6. Use of the bismuth vanadate photoanode according to claim 1 in the photoelectrocatalytic styrene epoxidation reaction.
7. The use according to claim 6, characterized in that The method is as follows: using the BVO photoanode described in claim 1 as a working electrode, using an Ag / AgCl electrode as a reference electrode, a Pt wire electrode as a counter electrode, and an electrolyte of a mixture of styrene, sodium bromide, acetonitrile and water to catalyze the epoxidation reaction of styrene in a three-electrode system.
8. The use according to claim 7, characterized in that The voltage is 0.8V vs.Ag / AgCl.
9. The use according to claim 7, characterized in that The concentration of sodium bromide in the electrolyte is 10-120 mmol L -1 .
10. The use according to claim 7, characterized in that The volume ratio of acetonitrile to water is 1-9:1.