Composite photoelectrode for photocatalytic preparation of ketones from polyols, preparation method and application

Abstract

This invention relates to the field of photoelectrocatalytic organic synthesis technology, specifically to a composite photoelectrode for photoelectrocatalytic preparation of ketone compounds from polyols, its preparation method, and its application. The method includes: dropping a dimethyl sulfoxide solution of vanadium acetylacetonate onto an FTO conductive glass plated with bismuth iodide, wherein the ratio of the amount of vanadium acetylacetonate to the deposition area of ​​bismuth iodide is 10-15 mmol:1 cm². 2 The bismuth oxy iodide deposition on the FTO conductive glass was carried out until the dimethyl sulfoxide solution of vanadium acetylacetonate completely covered the bismuth oxy iodide deposition, followed by calcination to obtain a BiVO4 photoanode. An ethanol solution of [2-(9H-carbazole-9-yl)ethyl]phosphonic acid was spin-coated onto the BiVO4 photoanode and dried to obtain a 2PACz / BiVO4 photoanode. A second constant-potential electrodeposition was performed, followed by washing to obtain the composite photoelectrode. The calcination conditions included a calcination temperature of 600-800℃, a calcination time of 2-4 h, and a heating rate of 8-12℃ / min. This composite photoelectrode can photocatalyze the conversion of polyols into ketone compounds.

Description

Technical Field

[0001] This invention relates to the field of photoelectrocatalytic organic synthesis technology, specifically to a composite photoelectrode for photoelectrocatalytic preparation of ketone compounds from polyols, its preparation method, and its application. Background Technology

[0002] Selective oxidation of polyols to prepare high-value-added ketones is an important pathway for the utilization of biomass resources. Polyols such as glycerol, glycerol, and pentanediol are widely available, and their selective oxidation products, such as dihydroxyacetone and hydroxy ketones, have significant applications in pharmaceuticals, cosmetics, and food additives.

[0003] Traditional polyol oxidation methods mainly employ chemical oxidation (such as chromic acid, potassium permanganate, etc.) or thermocatalytic oxidation (such as supported noble metal catalysts). These methods suffer from drawbacks such as poor selectivity, harsh reaction conditions, and the use of toxic oxidants or noble metals.

[0004] In recent years, photoelectrocatalytic oxidation technology has attracted widespread attention due to its advantages such as mild reaction conditions, selective oxidation through electrode potential control, and the ability to utilize solar energy. However, existing photoelectrocatalytic systems mainly focus on glycerol oxidation, and research on the catalytic performance and selective oxidation of other polyol substrates (such as methoxy-substituted polyols, butanetriol, pentanetriol, etc. with different carbon chain lengths) remains lacking.

[0005] Bismuth vanadate (BiVO4) is a typical visible-light-responsive photoanode material with suitable band structure and good stability. 2PACz ([2-(9H-carbazole-9-yl)ethyl]phosphonic acid) is a carbazole-based organic molecule that can form a hole transport layer through self-assembly. FeOOH, as a co-catalyst, can reduce the oxygen evolution overpotential and improve catalytic selectivity. However, a method for combining these three components for the selective oxidation of polyols to prepare ketone compounds has not yet been reported.

[0006] In summary, there is an urgent need to provide a composite photoelectrode with excellent selectivity for the selective conversion of polyols into ketone compounds via photoelectrocatalysis. Summary of the Invention

[0007] This invention addresses the technical problem of how to provide a composite photoelectrode with excellent selectivity for the selective conversion of polyols into ketone compounds via photoelectrocatalysis.

[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a composite photoelectrode for photocatalytic preparation of ketone compounds from polyols, comprising the following steps:

[0009] S1. Mix bismuth nitrate pentahydrate, potassium iodide and water, add concentrated nitric acid solution, adjust the pH to 1.5-2.0, then add ethanol solution of p-benzoquinone, stir until clear, and obtain the first electrolyte;

[0010] S2. Using the first electrolyte obtained in step S1 as the electrolyte, perform first constant potential electrodeposition on the FTO conductive glass, wash it, and obtain FTO conductive glass with bismuth iodide deposition.

[0011] S3. Add a dimethyl sulfoxide solution of vanadium acetylacetonate to the FTO conductive glass with bismuth iodide deposition obtained in S2 until the vanadium acetylacetonate solution completely covers the bismuth iodide deposition on the FTO conductive glass. The ratio of vanadium acetylacetonate to the electrodeposition area of ​​bismuth iodide deposition is 10⁻¹⁵ mmol: 1 cm². 2 The BiVO4 photoanode was obtained by calcination at a temperature of 600-800℃ for 2-4 h with a heating rate of 8-12℃ / min.

[0012] S4. Spin-coat an ethanol solution of [2-(9H-carbazole-9-yl)ethyl]phosphonic acid onto the BiVO4 photoanode obtained in S3, and dry it to obtain a 2PACz / BiVO4 photoanode.

[0013] S5. Using Fe(NO3)3 aqueous solution as the second electrolyte, a second constant potential electrodeposition is performed on the 2PACz / BiVO4 photoanode, followed by washing to obtain the composite photoelectrode.

[0014] The second aspect of the present invention provides a composite photoelectrode for photoelectrocatalytic preparation of ketone compounds from polyols prepared by the above-mentioned preparation method, wherein the composite photoelectrode consists of a BiVO4 layer, a 2PACz layer and a FeOOH layer from bottom to top, the thickness ratio of the BiVO4 layer, the 2PACz layer and the FeOOH layer is 100-500:1:50-400, and the thickness of the FeOOH layer is 100-300 nm.

[0015] A third aspect of the present invention provides an application of the above-mentioned composite photoelectrode, wherein the composite photoelectrode is capable of photoelectrocatalyzing the preparation of ketone compounds from polyols;

[0016] The step of preparing ketone compounds from polyols via photoelectrocatalysis includes:

[0017] Using the composite photoelectrode as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the third electrolyte is a 0.05-0.3 mol / L Na2SO4 aqueous solution containing 20-100 mmol / L of substrate, and the pH of the third electrolyte is 8-12. The product is obtained by applying electricity and irradiating with light.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) High selectivity: The present invention uses FeOOH / 2PACz / BiVO4 composite photoanode, and the carrier separation efficiency is controlled by 2PACz heterojunction. FeOOH co-catalyst selectively adsorbs and activates the secondary hydroxyl groups of polyol molecules. The three-layer structure of a specific thickness combined with specific photoelectrocatalysis achieves high selective conversion of secondary alcohols to ketones. Primary hydroxyl groups are not oxidized or only slightly oxidized, and the selectivity of ketone products can reach more than 80%.

[0020] (2) Wide range of applicable substrates: The method of the present invention is applicable to a variety of polyol substrates, including glycerol, 3-methoxy-1,2-propanediol, 1,2,4-butanetriol, 1,2,5-pentanetriol, etc., and has good catalytic activity for polyols with different carbon chain lengths and substituent structures.

[0021] (3) Mild reaction conditions: This invention is carried out in a weakly alkaline aqueous solution at room temperature, without the need for high temperature and high pressure, and without the use of toxic oxidants or precious metal catalysts, making it environmentally friendly.

[0022] (4) Good catalyst stability: The composite photoanode has good chemical stability under alkaline conditions. The FeOOH co-catalyst can effectively protect the substrate material and the catalyst can be reused.

[0023] (5) Utilizing solar energy: This invention uses visible light responsive materials, which can drive the reaction using sunlight, in line with the requirements of green chemistry and sustainable development. Attached Figure Description

[0024] Figure 1 The X-ray diffraction pattern of the BiVO4 photoanode prepared in Example 1 of this invention.

[0025] Figure 2 Scanning electron microscope image of the FeOOH / 2PACz / BiVO4 composite photoanode prepared in Example 1 of this invention.

[0026] Figure 3 The image shows a comparison of the linear scanning voltammetric curves of the FeOOH / 2PACz / BiVO4 composite photoanode prepared in Example 1 of this invention with those of the control samples, namely FeOOH / BiVO4, 2PACz / BiVO4, and BiVO4.

[0027] Figure 4 This is a comparison chart of the dihydroxyacetone yield and Faraday efficiency of the FeOOH / 2PACz / BiVO4 composite photoanode prepared in Example 1 of this invention.

[0028] Figure 5This is a comparison curve of the stability test of the FeOOH / 2PACz / BiVO4 composite photoanode prepared in Example 1 of the present invention and the control sample, which is BiVO4. Detailed Implementation

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] In the existing technology, [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz) has been used as a composite photoanode material for photoelectrocatalytic water oxidation. However, it has not been applied to the selective oxidation of polyols to prepare high-value-added ketone compounds. Furthermore, the catalytic mechanisms and catalytic environments for photoelectrocatalytic water oxidation and selective oxidation of polyols to prepare ketone compounds are different. Therefore, it is not possible to simply apply composite photoelectrodes suitable for water oxidation to the selective oxidation of polyols to prepare ketone compounds. In addition, the catalyst selectivity for photoelectrocatalytic selective oxidation of polyols to prepare ketone compounds is poor.

[0031] The inventors discovered that by adjusting the preparation method during the preparation of the composite photoelectrode, thereby adjusting the thickness and thickness ratio of the composite photoelectrode, a composite photoelectrode can be obtained. Furthermore, by employing a specific photoelectrocatalytic method, the selective oxidation of polyols to prepare ketone compounds can be achieved through photoelectrocatalysis.

[0032] The first aspect of this invention provides a method for preparing a composite photoelectrode for photocatalytic preparation of ketone compounds from polyols, comprising the following steps:

[0033] S1. Mix bismuth nitrate pentahydrate, potassium iodide and water, add concentrated nitric acid solution, adjust the pH to 1.5-2.0, then add ethanol solution of p-benzoquinone, stir until clear, and obtain the first electrolyte;

[0034] S2. Using the first electrolyte obtained in step S1 as the electrolyte, perform first constant potential electrodeposition on the FTO conductive glass, wash it, and obtain FTO conductive glass with bismuth iodide deposition.

[0035] S3. Add a dimethyl sulfoxide solution of vanadium acetylacetonate to the FTO conductive glass with bismuth iodide deposition obtained in S2 until the vanadium acetylacetonate solution completely covers the bismuth iodide deposition on the FTO conductive glass. The ratio of vanadium acetylacetonate to the electrodeposition area of ​​bismuth iodide deposition is 10⁻¹⁵ mmol: 1 cm². 2The BiVO4 photoanode was obtained by calcination at a temperature of 600-800℃ for 2-4 h with a heating rate of 8-12℃ / min.

[0036] S4. Spin-coat an ethanol solution of [2-(9H-carbazole-9-yl)ethyl]phosphonic acid onto the BiVO4 photoanode obtained in S3, and dry it to obtain a 2PACz / BiVO4 photoanode.

[0037] S5. Using Fe(NO3)3 aqueous solution as the second electrolyte, a second constant potential electrodeposition is performed on the 2PACz / BiVO4 photoanode, followed by washing to obtain the composite photoelectrode.

[0038] In this invention, the pH value for water oxidation is generally weakly acidic, while the pH value for alcohol oxidation is generally in the strongly alkaline range of 8-12, with the optimal value being 9. The uppermost FeOOH layer can exist stably under alkaline conditions, and the Fe exposed on its surface... 3+ The site preferentially adsorbs the secondary hydroxyl group of the alcohol molecule, and the alcohol molecule reacts with Fe through the hydroxyl group. 3+ Site coordination forms surface complexes, lowering the oxidation activation energy. Meanwhile, water molecules adsorb weakly on the FeOOH surface, thus inhibiting the competitive reaction.

[0039] The calcination conditions in step S3 can produce a more flat and dense BiVO4 layer, which helps to improve the efficiency of electron transfer and photogenerated hole utilization.

[0040] Synthesis method of 2PACz

[0041] Under nitrogen protection, carbazole (1.86 g, 11.13 mmol) was dissolved in dry dimethyl sulfoxide (DMSO, 20 mL) solvent, and sodium hydride (NaH, 0.49 g, 20.4 mmol) was added. The mixture was stirred at room temperature for 30 minutes. Subsequently, diethyl (2-bromoethyl)phosphonate (C6H) was added to the reaction system. 14 BrO3P (2.64 g, 10.8 mmol) was used, and the mixture was heated to 60 °C and stirred for 20 h. After the reaction was complete, the reaction mixture was slowly poured into 100 mL of water, and then adjusted to acidity with 1 M hydrochloric acid. Subsequently, it was extracted with ethyl acetate (3 × 100 mL). The organic phases were combined, washed with saturated brine, dried with anhydrous magnesium sulfate, filtered to remove the drying agent, and the solvent was evaporated under reduced pressure to obtain a pale yellow liquid product. The product did not require further purification and was used directly in the next reaction.

[0042] The resulting pale yellow liquid product was dissolved in dry dichloromethane (CH2Cl2, 20 mL) solvent, and trimethylsilane bromide (TMSBr, 2.90 mL, 21.5 mmol) was added dropwise under nitrogen protection. The mixture was stirred at room temperature for 6 h. Subsequently, an appropriate amount of methanol (MeOH) was added to quench the reaction, and vigorous stirring was continued for 2 h.

[0043] After the reaction was complete, the solvent was evaporated under reduced pressure, and water (5 mL) was added to redissolve the reaction residue. The solution was then concentrated under reduced pressure. This concentration step was repeated four times to ensure that trimethylsilane bromide and ethoxide were fully converted into the target product. Finally, a grayish-white solid (2-(9H-carbazole-9-yl)ethyl)phosphonic acid was obtained. The crude product was recrystallized with water to give 2PACz (2.91 g, yield 90.94%).

[0044] According to the present invention, in step S1, the molar ratio of bismuth nitrate pentahydrate, potassium iodide, and p-benzoquinone is 1:5-15:4-5;

[0045] The concentration of the ethanol solution of p-benzoquinone is 0.2-0.3 mol / L.

[0046] According to the present invention, in step S3, the concentration of the dimethyl sulfoxide solution of acetylacetone vanadium oxide is 0.1-0.3 mol / L.

[0047] According to the present invention, the conditions for the first constant potential electrodeposition include: using FTO conductive glass as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode; at a voltage of -0.1 V vs. Ag / AgCl; the deposition time for the first constant potential electrodeposition is 3-10 min; and the electroplating area of ​​the FTO conductive glass is 0.5-2 cm². 2 .

[0048] According to the present invention, in step S4, the concentration of the ethanol solution of [2-(9H-carbazole-9-yl)ethyl]phosphonic acid is 0.05-0.2 mol / L;

[0049] The spin coating conditions include: a spin coating speed of 2000-4000 rpm and a spin coating time of 0.5-2 min.

[0050] According to the present invention, in step S5, the concentration of the second electrolyte is 0.01-0.02 mol / L;

[0051] The conditions for the second constant potential electrodeposition include: using a 2PACz / BiVO4 photoanode as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, with a voltage of -1.0 V vs. Ag / AgCl, and a second constant potential electrodeposition time of 10-20 min.

[0052] The second aspect of the present invention provides a composite photoelectrode for photoelectrocatalytic preparation of ketone compounds from polyols prepared by the above-mentioned preparation method, wherein the composite photoelectrode consists of a BiVO4 layer, a 2PACz layer and a FeOOH layer from bottom to top, the thickness ratio of the BiVO4 layer, the 2PACz layer and the FeOOH layer is 100-500:1:50-400, and the thickness of the FeOOH layer is 100-300 nm.

[0053] In this invention, precise control of the thickness and ratio of the three layers can optimize light absorption, suppress carrier recombination, improve hole utilization, and synergistically enhance the activity and selectivity of polyol ketone production.

[0054] According to some preferred embodiments of the present invention, the thickness ratio of the BiVO4 layer, the 2PACz layer and the FeOOH layer is 100-200:1:50-250, and the thickness of the FeOOH layer is 200-300 nm.

[0055] A third aspect of the present invention provides an application of the above-mentioned composite photoelectrode, wherein the composite photoelectrode is capable of photoelectrocatalyzing the preparation of ketone compounds from polyols;

[0056] The step of preparing ketone compounds from polyols via photoelectrocatalysis includes:

[0057] Using the composite photoelectrode as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the third electrolyte is a 0.05-0.3 mol / L Na2SO4 aqueous solution containing 20-100 mmol / L of substrate, and the pH of the third electrolyte is 8-12. The product is obtained by applying electricity and irradiating with light.

[0058] According to the present invention, the conditions for photoelectrocatalysis include: an energizing time of 300-500 min, an applied potential of 1.2 V vs RHE, and a light intensity of 50-200 mW / cm². 2 The illumination time is 300-500 min, the illumination direction is from the BiVO4 layer of the composite photoelectrode to the FeOOH layer, and the temperature is 20-40 ℃.

[0059] In this invention, the composite photoelectrode has a BiVO4 layer at the innermost layer, a 2PACz layer in the middle, and a FeOOH layer at the outermost layer. Irradiation from the FeOOH layer to the BiVO4 layer causes light to pass through the FeOOH layer before entering the inner layer, resulting in some loss of light intensity. Therefore, this invention uses irradiation from the BiVO4 layer to the FeOOH layer of the composite photoelectrode. On the other hand, because an unconventional "back-illumination" method is used, the problem of excessively thick catalyst on the outermost layer affecting light absorption is avoided. The deposition time for preparing the FeOOH layer in this invention exceeds the conventional time used in the field, allowing more FeOOH to be deposited on the surface, resulting in better catalytic performance.

[0060] According to the present invention, the substrate is any one of glycerol, 3-methoxy-1,2-propanediol, 1,2,4-butanetriol, and 1,2,5-pentanetriol.

[0061] Unless otherwise specified, the following examples and comparative examples were conducted under conventional conditions. Unless otherwise specified, the reagents or instruments used were all commercially available products.

[0062] The M in concentration represents mol / L. For example, 1 M KOH means a 1 mol / L KOH solution.

[0063] Example 1:

[0064] 1. Preparation of BiVO4 photoanode

[0065] S1. The FTO conductive glass (size: 10 mm × 25 mm × 2.2 mm, resistance 8 Ω) is ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each time, three times with each liquid. After cleaning, it is placed in an oven at 50°C. o Dry at C for 30 min. Use transparent tape to control the electroplating area of ​​the dried FTO to 1 cm². 2 ;

[0066] S2. Weigh 0.97 g bismuth nitrate pentahydrate (2 mmol) and 3.32 g potassium iodide (20 mmol) and dissolve them in 50 mL of deionized water. Stir at room temperature for 30 min and slowly add concentrated nitric acid solution to adjust the pH to 1.8. Weigh 0.497 g p-benzoquinone (4.6 mmol) and dissolve it in anhydrous ethanol to prepare a 0.23 mol / L p-benzoquinone solution. Stir vigorously for 10 min. During the stirring process, add the p-benzoquinone solution dropwise to the bismuth nitrate and potassium iodide solution. After the addition is complete, stir for 15 min until the solution is clear and transparent to obtain the first electrolyte.

[0067] S3. Using the cleaned FTO conductive substrate as the working electrode, a platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and the first electrolyte as the electrolyte, a first constant potential electrodeposition was performed at a voltage of -0.1 V vs. Ag / AgCl for 4 min. The deposited glass slide was washed with deionized water to remove residual solution from the surface, and the surface water was removed in air.

[0068] S4. Weigh 0.0795 g of vanadium acetylacetonate and dissolve it in 1.5 mL of dimethyl sulfoxide to obtain a 0.2 M vanadium acetylacetonate solution. Remove the adhesive tape from the surface and add the vanadium acetylacetonate solution dropwise onto bismuth iodide. The ratio of the amount of vanadium acetylacetonate used to the electroplating area of ​​bismuth iodide is 12 mmol: 1 cm. 2 Ensure the solution completely covers bismuth iodide. Place it in a muffle furnace and calcine at 700℃ for 2 h with a heating rate of 2℃ / min to obtain a BiVO4 photoanode.

[0069] 2.2 Preparation of PACz / BiVO4 photoanode

[0070] S1. Weigh 0.055 g of 2PACz solid, dissolve it in 20 mL of anhydrous ethanol to a concentration of 10 mM, and stir for 15 min until completely dissolved.

[0071] S2. Place the prepared BiVO4 photoanode on a spin coater at a speed of 3000 rpm for 1 min. After spin coating, place it on a hot plate to dry for 5 min to remove the ethanol solvent, thus obtaining the 2PACz / BiVO4 photoanode.

[0072] 3. Preparation of FeOOH / 2PACz / BiVO4 composite photoanode

[0073] S1. Weigh 0.00606 g of ferric nitrate nonahydrate (Fe(NO3)3·9H2O) and dissolve it in 10 mL of deionized water. Stir for 10 min until completely dissolved to obtain a 1.5 mmol / L Fe(NO3)3 aqueous solution.

[0074] S2. Using 2PACz / BiVO4 as the working electrode, a platinum sheet as the counter electrode, an Ag / AgCl electrode as the reference electrode, and Fe(NO3)3 aqueous solution as the second electrolyte, a second constant potential electrodeposition was performed at a voltage of -1.0 V vs. Ag / AgCl for 16 min. The electrodeposition was then rinsed with deionized water and air-dried at room temperature to obtain FeOOH / 2PACz / BiVO4 composite photoanode A1.

[0075] The thickness of the BiVO4 layer in the FeOOH / 2PACz / BiVO4 composite photoanode A1 is 120 nm, the thickness of the 2PACz layer is 1 nm, and the thickness of the FeOOH layer is 240 nm.

[0076] The thickness ratio of the BiVO4 layer, the 2PACz layer, and the FeOOH layer is 120:1:240.

[0077] Example 2

[0078] Following the preparation method of Example 1, except that the first constant potential electrodeposition lasted 6 min, the spin coating speed was 3000 rpm for 1 min, and the second constant potential electrodeposition lasted 10 min, to obtain the FeOOH / 2PACz / BiVO4 composite photoanode A2.

[0079] The thickness of the BiVO4 layer in the FeOOH / 2PACz / BiVO4 composite photoanode A2 is 200 nm, the thickness of the 2PACz layer is 1 nm, and the thickness of the FeOOH layer is 210 nm.

[0080] The thickness ratio of the BiVO4 layer, the 2PACz layer, and the FeOOH layer is 200:1:210.

[0081] Example 3

[0082] Following the preparation method of Example 1, except that the first constant potential electrodeposition lasted for 10 min, the spin coating speed was 2500 rpm for 8 min, and the second constant potential electrodeposition lasted for 18 min, to obtain FeOOH / 2PACz / BiVO4 composite photoanode A3.

[0083] The thickness of the BiVO4 layer in the FeOOH / 2PACz / BiVO4 composite photoanode A3 is 800 nm, the thickness of the 2PACz layer is 5 nm, and the thickness of the FeOOH layer is 300 nm.

[0084] The thickness ratio of the BiVO4 layer, the 2PACz layer, and the FeOOH layer is 160:1:60.

[0085] Example 4

[0086] Following the preparation method of Example 1, except that the first constant potential electrodeposition lasted for 8 min, the spin coating speed was 3000 rpm for 2 min, and the second constant potential electrodeposition lasted for 12 min, to obtain FeOOH / 2PACz / BiVO4 composite photoanode A4.

[0087] The thickness of the BiVO4 layer in the FeOOH / 2PACz / BiVO4 composite photoanode A4 is 400 nm, the thickness of the 2PACz layer is 2 nm, and the thickness of the FeOOH layer is 220 nm.

[0088] The thickness ratio of the BiVO4 layer, the 2PACz layer, and the FeOOH layer is 200:1:110.

[0089] Example 5

[0090] Following the preparation method of Example 1, the difference is that the first constant potential electrodeposition lasted for 9 min, the spin coating speed was 2500 rpm for 5 min, and the second constant potential electrodeposition lasted for 15 min, to obtain the FeOOH / 2PACz / BiVO4 composite photoanode A5.

[0091] The thickness of the BiVO4 layer in the FeOOH / 2PACz / BiVO4 composite photoanode A5 is 600 nm, the thickness of the 2PACz layer is 5 nm, and the thickness of the FeOOH layer is 250 nm.

[0092] The thickness ratio of the BiVO4 layer, the 2PACz layer, and the FeOOH layer is 120:1:50.

[0093] Comparative Example 1

[0094] The preparation method of Example 1 was followed, except that the calcination temperature was 450°C, and the FeOOH / 2PACz / BiVO4 composite photoanode DA1 was obtained.

[0095] Comparative Example 2

[0096] The preparation method of Example 1 was followed, except that the calcination temperature was 900℃, and the FeOOH / 2PACz / BiVO4 composite photoanode DA2 was obtained.

[0097] Comparative Example 3

[0098] Following the preparation method of Example 1, except that the first constant potential electrodeposition lasted for 18 min, the spin coating speed was 3000 rpm for 6 min, and the second constant potential electrodeposition lasted for 21 min, to obtain the FeOOH / 2PACz / BiVO4 composite photoanode DA3.

[0099] The thickness of the BiVO4 layer in the FeOOH / 2PACz / BiVO4 composite photoanode DA3 is 1000 nm, the thickness of the 2PACz layer is 1 nm, and the thickness of the FeOOH layer is 420 nm.

[0100] The thickness ratio of the BiVO4 layer, the 2PACz layer, and the FeOOH layer is 1000:1:420.

[0101] Comparative Example 4

[0102] Following the preparation method of Example 1, except that the first constant potential electrodeposition was performed for 1 min, the spin coating speed was 3000 rpm, the spin coating was performed for 10 min, and the second constant potential electrodeposition was performed for 2 min to obtain the FeOOH / 2PACz / BiVO4 composite photoanode DA4.

[0103] The thickness of the BiVO4 layer in the FeOOH / 2PACz / BiVO4 composite photoanode DA4 is 100 nm, the thickness of the 2PACz layer is 15 nm, and the thickness of the FeOOH layer is 50 nm.

[0104] The thickness ratio of the BiVO4 layer, 2PACz layer, and FeOOH layer is 6.7:1:3.3.

[0105] Test case

[0106] A three-electrode system was adopted, with the prepared FeOOH / 2PACz / BiVO4 / FTO composite photoelectrode as the working electrode (effective area 1 cm²). 2 A platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, and the third electrolyte was a 0.1 mol / L Na₂SO₄ aqueous solution (pH 7) containing 50 mmol / L of substrate. The light source was a 300 W xenon lamp with an AM 1.5G filter, with a light intensity of 100 mW / cm². 2 An applied potential of 1.2 V vs RHE (via formula E) RHE = E Ag / AgCl (+ 0.059×pH + 0.197 V conversion), temperature 30℃.

[0107] Test Example 1

[0108] The illumination direction was from the BiVO4 layer of the composite photoelectrode to the FeOOH layer, the substrate was glycerol, and the composite photoelectrode was Al.

[0109] Test Example 2

[0110] The method is the same as in Test Example 1, except that the substrate is 3-methoxy-1,2-propanediol.

[0111] Test Example 3

[0112] The method is the same as in Test Example 1, except that the substrate is 1,2,4-butanetriol.

[0113] Test Example 4

[0114] The method is the same as in Test Example 1, except that the substrate is 1,2,5-pentanetriol.

[0115] Test Case 5-Test Case 12

[0116] The method is the same as in Test Example 1, except that the composite photoelectrodes are A2-A5 and DA1-DA4, respectively.

[0117] Test Example 13

[0118] The method is the same as in Test Example 1, except that the direction of illumination is from the FeOOH layer of the composite photoelectrode to the BiVO4 layer.

[0119] Catalytic stability test: Photoelectrocatalysis was performed continuously for 6 hours according to the method in Test Example 1.

[0120] The comparative test case used BiVO4 as the working electrode, with other catalytic conditions remaining unchanged.

[0121] Table 1 shows the catalytic selectivity test results for test examples 1-13.

[0122] Table 1

[0123]

[0124] The results in Table 1 show that the composite photoanode provided by the present invention has good selectivity for the oxidation of four polyols to ketones.

[0125] Following the method in Test Example 1, the applied potential for photoelectrocatalysis was changed to 1.1, 1.3, and 1.4 V vs RHE, and the results are shown in Table 2.

[0126] Table 2

[0127]

[0128] Figure 1 The XRD pattern of the BiVO4 photoanode prepared in Example 1 shows that, except for the FTO substrate diffraction peak, the peaks are at 18.9. o 28.8 o 30.5 o 34.5 o Diffraction peaks appeared at the locations corresponding to the (011), (121), (040), and (200) crystal planes of monoclinic BiVO4 (JCPDS 14-0688), respectively. No impurity peaks were detected, indicating that high-purity monoclinic phase BiVO4 was successfully prepared, laying the foundation for subsequent heterojunction construction.

[0129] Figure 2 The image shows a SEM image of the FeOOH / 2PACz / BiVO4 composite photoanode prepared in Example 1. The bottom layer of BiVO4 has a worm-like morphology. After spin-coating, 2PACz uniformly covers the surface of BiVO4 to form a dense organic layer. After electrodeposition, FeOOH exhibits a nanoflower-like structure. The three-layer structure works synergistically: BiVO4 provides photogenerated carriers, 2PACz promotes hole transport, and FeOOH provides catalytic active sites.

[0130] Figure 3 The LSV curves of the composite photoanode and the control sample are compared. Pure BiVO4 has a low photocurrent density and a peak potential of approximately 0.8 V. The introduction of 2PACz significantly increases the photocurrent density and shifts the peak potential negatively. Further loading with FeOOH results in the highest photocurrent density of FeOOH / 2PACz / BiVO4, with a further negative shift in the peak potential, indicating a synergistic effect between 2PACz and FeOOH: 2PACz optimizes bulk charge separation, while FeOOH accelerates surface reaction kinetics.

[0131] The comparison samples were FeOOH / BiVO4, 2PACz / BiVO4, and BiVO4.

[0132] Figure 4 The yield and Faradaic efficiency of glycerol oxidation to DHA by composite photoanode at different potentials were compared. The Faradaic efficiency of FeOOH / 2PACz / BiVO4 was significantly improved to 42%, which proved that FeOOH plays a key role in selective regulation and preferentially promotes the oxidation of secondary hydroxyl groups to DHA.

[0133] Figure 5 The current-time curves of the composite photoanode and pure BiVO4 under continuous operation at 1.2 V vs. RHE are compared. After 0.5 hours of operation, the current of pure BiVO4 decays to 80%, indicating poor stability. After 6 hours of operation, FeOOH / 2PACz / BiVO4 still maintains about 80% of the initial current, showing a significant improvement in stability. This is because the organic layer of 2PACz prevents direct contact between the electrolyte and BiVO4, inhibiting photocorrosion; and FeOOH consumes surface holes, preventing hole accumulation.

[0134] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite photoelectrode for the photoelectrocatalytic preparation of ketone compounds from polyols, characterized in that, Includes the following steps: S1. Mix bismuth nitrate pentahydrate, potassium iodide and water, add concentrated nitric acid solution, adjust the pH to 1.5-2.0, then add ethanol solution of p-benzoquinone, stir until clear, and obtain the first electrolyte; S2. Using the first electrolyte obtained in step S1 as the electrolyte, perform first constant potential electrodeposition on the FTO conductive glass, wash it, and obtain FTO conductive glass with bismuth iodide deposition. S3. Add a dimethyl sulfoxide solution of vanadium acetylacetonate to the FTO conductive glass with bismuth iodide deposition obtained in S2 until the vanadium acetylacetonate solution completely covers the bismuth iodide deposition on the FTO conductive glass. The ratio of vanadium acetylacetonate to the electrodeposition area of ​​bismuth iodide deposition is 10⁻¹⁵ mmol: 1 cm². 2 The BiVO4 photoanode was obtained by calcination at a temperature of 600-800℃ for 2-4 h with a heating rate of 8-12℃ / min. S4. Spin-coat an ethanol solution of [2-(9H-carbazole-9-yl)ethyl]phosphonic acid onto the BiVO4 photoanode obtained in S3, and dry it to obtain a 2PACz / BiVO4 photoanode. S5. Using Fe(NO3)3 aqueous solution as the second electrolyte, a second constant potential electrodeposition is performed on the 2PACz / BiVO4 photoanode, followed by washing to obtain the composite photoelectrode.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of bismuth nitrate pentahydrate, potassium iodide, and p-benzoquinone is 1:5-15:4-5; The concentration of the ethanol solution of p-benzoquinone is 0.2-0.3 mol / L; In step S3, the concentration of the dimethyl sulfoxide solution of acetylacetone vanadium oxide is 0.1-0.3 mol / L.

3. The preparation method according to claim 1, characterized in that, In step S2, the conditions for the first constant potential electrodeposition include: using FTO conductive glass as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode; at a voltage of -0.1V vs. Ag / AgCl; the deposition time for the first constant potential electrodeposition is 3-10 min; and the electroplating area of ​​the FTO conductive glass is 0.5-2 cm². 2 .

4. The preparation method according to claim 1, characterized in that, In step S4, the concentration of the ethanol solution of [2-(9H-carbazole-9-yl)ethyl]phosphonic acid is 0.05-0.2 mol / L; The spin coating conditions include: a spin coating speed of 2000-4000 rpm and a spin coating time of 0.5-2 min.

5. The preparation method according to claim 1, characterized in that, In step S5, the concentration of the second electrolyte is 0.01-0.02 mol / L; The conditions for the second constant potential electrodeposition include: using a 2PACz / BiVO4 photoanode as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, with a voltage of -1.0 V vs. Ag / AgCl, and a second constant potential electrodeposition time of 10-20 min.

6. The composite photoelectrode for the photoelectrocatalytic preparation of ketone compounds from polyols by the preparation method according to any one of claims 1-5, characterized in that, The composite photoelectrode consists of a BiVO4 layer, a 2PACz layer, and a FeOOH layer from bottom to top. The thickness ratio of the BiVO4 layer, the 2PACz layer, and the FeOOH layer is 100-500:1:50-400, and the thickness of the FeOOH layer is 100-300 nm.

7. The composite photoelectrode according to claim 6, characterized in that, The thickness ratio of the BiVO4 layer, 2PACz layer and FeOOH layer is 100-200:1:50-250, and the thickness of the FeOOH layer is 200-300 nm.

8. The application of the composite photoelectrode as described in claim 6 or 7, characterized in that, The composite photoelectrode can photocatalyze the preparation of ketone compounds from polyols; The step of preparing ketone compounds from polyols via photoelectrocatalysis includes: Using the composite photoelectrode as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the third electrolyte is a 0.05-0.3 mol / L Na2SO4 aqueous solution containing 20-100 mmol / L of substrate, and the pH of the third electrolyte is 8-12, photoelectrocatalysis is performed to obtain the product.

9. The application according to claim 8, characterized in that, The conditions for photoelectrocatalysis include: an on-time of 300-500 min, an applied potential of 1.2 V vs RHE, and a light intensity of 50-200 mW / cm². 2 The illumination time is 300-500 min, the illumination direction is from the BiVO4 layer of the composite photoelectrode to the FeOOH layer, and the temperature is 20-40 ℃.

10. The application according to claim 8, characterized in that, The substrate is any one of glycerol, 3-methoxy-1,2-propanediol, 1,2,4-butanetriol, and 1,2,5-pentanetriol.

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