Perfluoromanganese phthalocyanine composite bismuth vanadate photoelectrode, preparation method thereof and application of photoelectrode in synthesis of formamide from biomass through photoelectrocatalysis

Abstract

The invention provides a perfluoromanganese phthalocyanine composite bismuth vanadate photoelectrode, a preparation method thereof and application of the photoelectrode in synthesis of formamide from photoelectrocatalytic biomass, belongs to the technical field of photoelectrocatalysis, and is used for efficiently promoting photoelectrocatalytic biomass conversion. Firstly, bismuth vanadate grows on a conductive substrate by adopting an electro-deposition method, then perfluoromanganese phthalocyanine is loaded on the bismuth vanadate by adopting a constant-temperature impregnation method, the perfluoromanganese phthalocyanine / bismuth vanadate photoelectrode is obtained, and the prepared composite photoelectrode can be directly applied to value-added conversion of a photoelectrocatalytic biomass raw material to synthesize formamide. And high Faraday efficiency and stability are shown. Metal phthalocyanine is used as a common molecular catalyst, has an M-N4 monatomic site, and can form an M1-O-M2 bond with the bismuth vanadate photo-anode to accelerate charge transfer between interfaces. The perfluoromanganese phthalocyanine molecules can reduce the energy barrier of formaldehyde free radicals formed by C-C bond breakage and formamide generated by C-N coupling in the reaction process, so that more excellent PEC formamide generation performance is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectrocatalysis, and particularly relates to a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode, a preparation method thereof, and an application thereof in the photoelectrocatalytic synthesis of formamide from biomass. Background Art

[0002] Organic nitrogen compounds widely exist in the fields of nature and chemical industrial synthesis, such as amides, amino acids, proteins, etc., and are of great significance to life activities and human health. Among them, formamide plays an important role in drug synthesis, pesticides, paper softeners, etc. Especially with the revival of the synthetic fiber (such as nylon) industry, the demand for formamide has been further driven, promoting market growth. Therefore, it is urgent to develop formamide through technological upgrading and production capacity integration. At present, the main method for preparing formamide HCONH2 is to directly catalyze carbon monoxide CO and ammonia NH3 under high temperature and high pressure, which has disadvantages such as high energy consumption and harsh conditions.

[0003] Biomass raw materials are widely sourced and diverse in types, such as sugars, alcohols, aldehydes, etc., and have advantages such as low cost, wide resources, and environmental friendliness. At present, compared with traditional chemical synthesis, using biomass raw materials as a carbon source to synthesize high-value chemicals through photoelectrocatalytic conversion has advantages such as mild conditions, low energy consumption, and environmental friendliness, and is an important means to replace traditional chemical synthesis methods. However, using biomass raw materials to synthesize formamide requires overcoming difficulties such as the energy barrier of C-C bond cleavage and low product selectivity, so no relevant technologies have been disclosed. The present invention proposes to use a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode to photoelectrocatalytically prepare formamide from biomass raw materials, effectively reducing the energy barriers of C-C bond cleavage to form formaldehyde radicals and C-N coupling to form formamide during the reaction process, accelerating the catalytic reaction rate, improving the formamide product selectivity, efficiently upgrading biomass derivatives to formamide, and increasing the added value of the anodic reaction. Summary of the Invention

[0004] The present invention provides a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode, which can be directly applied to the photoelectrocatalytic synthesis of formamide and exhibits high Faraday efficiency and yield of formamide. As a common molecular catalyst, metal phthalocyanine has an M-N4 single-atom site, which can form an M1-O-M2 bond with the photoanode, accelerating the interfacial charge transfer and improving the anodic reaction efficiency, providing a practical method for realizing the efficient solar biomass conversion coupled hydrogen production technology.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A perfluoromanganese phthalocyanine composite bismuth vanadate photoanode. The perfluoromanganese phthalocyanine composite bismuth vanadate photoanode is prepared by impregnating perfluoromanganese phthalocyanine on the bismuth vanadate photoanode using the impregnation method. The perfluoromanganese phthalocyanine is uniformly distributed on the surface of the photoanode and tightly combined with bismuth vanadate.

[0007] A preparation method of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode, comprising the following steps:

[0008] (1) Prepare a bismuth vanadate photoanode by electrodeposition.

[0009] (2) Grind and mix manganese acetate and tetrafluorophthalic anhydride in proportion. Calcinate the mixture in a vacuum atmosphere, then centrifuge, wash and dry to obtain perfluoromanganese phthalocyanine powder MnPcF.

[0010] (3) Thoroughly grind the perfluoromanganese phthalocyanine powder and dissolve it in absolute ethanol to obtain solution A. Immerse the conductive surface of the bismuth vanadate photoanode prepared in step (1) downward into solution A, then place it in an oven for impregnation. After a period of time, take it out and anneal in air to obtain a perfluoromanganese phthalocyanine composite bismuth vanadate MnPcF / BVO photoanode.

[0011] Further, the specific process of step (1) is as follows: After cutting the conductive substrate to the required size, ultrasonically clean it in deionized water, ethanol and acetone for 40 - 80 min respectively, and then dry it at 30 - 50 °C for 2 - 12 h. The conductive substrate is fluorine-doped tin oxide conductive glass (FTO) or indium tin oxide thin film (ITO); Dissolve bismuth nitrate pentahydrate and potassium iodide in deionized water to obtain solution B. The concentration of bismuth nitrate pentahydrate in solution B is 0.013 - 0.016 g / mL, and the concentration of potassium iodide is 0.049 - 0.057 g / ml. Then adjust the pH of solution B to 1.5 - 1.8 using concentrated nitric acid; Dissolve p-benzoquinone in absolute ethanol to obtain solution C. The concentration of p-benzoquinone in solution C is 0.01 - 0.02 g / mL; Mix solution B and solution C in a volume ratio of (2 - 4):1 and stir well; Use the conductive substrate as the working electrode, saturated silver / silver chloride Ag / AgCl as the reference electrode, and platinum wire Pt as the counter electrode. Deposit at a constant potential of -0.25 - -0.1 V relative to Ag / AgCl at room temperature for 80 - 190 s to obtain a bismuth iodate precursor electrode; Dissolve vanadyl acetylacetonate in dimethyl sulfoxide to obtain solution D. The concentration of vanadyl acetylacetonate in solution D is 0.033 - 0.058 g / mL; Take 30 - 80 μL of solution D and place it on the bismuth iodate precursor electrode. Anneal it at 300 - 500 °C for 1 - 3 h, then soak it in 0.5 - 1.5 mol / L sodium hydroxide solution for 30 - 60 min, and then rinse with deionized water and dry to obtain a bismuth vanadate BVO photoanode.

[0012] Further, in the step (2), the mass ratio of tetrafluorophthalic anhydride to manganese acetate is (2-5):1; the calcination temperature is 150-300 °C, and the calcination time is 3-8 h.

[0013] Further, in the step (3), the mass concentration of perfluoromanganese phthalocyanine in solution A is 1.0-5.0 mg / mL, the oven temperature is 30-70 °C, the impregnation time is 10-35 h, the annealing temperature is 60-120 °C, and the annealing time is 2-6 h.

[0014] An application of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode, which is applied to the anodic photoelectrocatalytic production of formamide from biomass while coupling cathodic hydrogen production. Specifically, the prepared perfluoromanganese phthalocyanine composite bismuth vanadate MnPcF / BVO photoanode is used as the working electrode, Ag / AgCl is used as the reference electrode, and a Pt wire is used as the counter electrode to form a standard three-electrode system; the reaction electrolyte is an ammonia aqueous solution of 0.05 M sulfuric acid added with biomass raw materials, and under a simulated solar light source (300 W xenon lamp, light intensity of 100 mW / cm 2 ) to carry out a photoelectrocatalytic (PEC) biomass conversion reaction, wherein the biomass raw materials include one or more of sugars, alcohols, and aldehydes, and the concentration of the biomass raw materials in the reaction electrolyte is 0.05-0.5 mol / L, wherein the sugars include glucose and arabinose, the alcohols include methanol, ethylene glycol, glycerol, sorbitol, and erythritol, and the aldehydes include glycolaldehyde and glyceraldehyde.

[0015] The mechanism of the present invention for the photoelectrocatalytic production of formamide from biomass using the MnPcF / BVO photoanode is as follows: in the PEC biomass conversion system, the bulk BVO photoanode absorbs photons and generates photogenerated electron-hole pairs under the condition of simulated solar light illumination. Among them, the photogenerated electrons migrate to the counter electrode Pt wire through the external circuit for hydrogen evolution reaction, while the un-recombined photogenerated holes will transfer to the electrode surface to participate in the C-C bond cleavage to form formaldehyde radicals and C-N coupling to generate formamide. However, the recombination of photogenerated electrons and holes in the BVO photoanode is serious, and most of the photogenerated holes cannot participate in the oxidation reaction, resulting in mediocre Faraday efficiency and selectivity of the bulk BVO photoanode for formamide. In the MnPcF / BVO photoanode provided in the present invention, MnPcF is used as a molecular catalyst and has an M-N4 single-atom site, which can form an M1-O-M2 bond with the BVO photoanode semiconductor to accelerate the interfacial charge transfer. The MnPcF molecule can lower the energy barrier for the C-C bond cleavage to form formaldehyde radicals and C-N coupling to generate formamide during the reaction, thereby obtaining more excellent PEC formamide production performance.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] (1) The preparation method of the present invention is simple. The BVO is grown on a conductive substrate by electrodeposition, and then the MnPcF is loaded on the BVO electrode by impregnation method without physical bonding. In addition, the MnPcF / BVO photoanode provided by the present invention does not use any noble metals, greatly reducing the cost and being suitable for large-scale commercial applications.

[0018] (2) The MnPcF / BVO photoanode prepared by the present invention exhibits high formamide yield and Faraday efficiency in sulfuric acid electrolyte solution, has high photogenerated carrier separation and transport efficiency, and has excellent stability.

[0019] (3) Through the research on the MnPcF / BVO photoanode in the biomass valorization conversion to formamide, the present invention explores the effects of different biomass monomer substrates, different electrolytes and different electrolyte concentrations on the formamide yield, Faraday efficiency and selectivity, further explores its reaction mechanism, and conducts an enlarged reaction in a large-area system, providing a good basis for the further application of photoelectrocatalysis in the field of biomass upgrading and conversion. Description of the Drawings

[0020] Figure 1 XRD patterns of the photoanode materials prepared in Example 1 and Comparative Example 1. In the figure, θ represents the diffraction angle.

[0021] Figure 2 SEM image of the BVO photoanode prepared in Comparative Example 1.

[0022] Figure 3 SEM image of the MnPcF / BVO photoanode prepared in Example 1.

[0023] Figure 4 Faraday efficiency and yield diagrams of the products obtained from the glucose PEC reaction of Example 1. Among them, (a) is the yield diagram and (b) is the Faraday efficiency diagram.

[0024] Figure 5 Faraday efficiency and yield diagrams of the products obtained from the glucose PEC reaction of the BVO photoanode prepared in Comparative Example 1. Among them, (a) is the yield diagram and (b) is the Faraday efficiency diagram.

[0025] Figure 6 Faraday efficiency and yield diagrams of the products obtained from the sorbitol PEC reaction of Example 2. Among them, (a) is the yield diagram and (b) is the Faraday efficiency diagram.

[0026] Figure 7Faraday efficiency diagram and yield diagram of the products obtained from the sorbitol PEC reaction of the BVO photoanode prepared in Comparative Example 2, where (a) is the yield diagram and (b) is the Faraday efficiency diagram.

[0027] Figure 8 Faraday efficiency diagram and yield diagram of the products obtained from the glyceraldehyde PEC reaction of Example 3, where (a) is the yield diagram and (b) is the Faraday efficiency diagram.

[0028] Figure 9 Faraday efficiency diagram and yield diagram of the products obtained from the glyceraldehyde PEC reaction of the BVO photoanode prepared in Comparative Example 3, where (a) is the yield diagram and (b) is the Faraday efficiency diagram.

[0029] Figure 10 Linear sweep voltammogram (LSV) of the photoanode materials prepared in Example 1 and Comparative Example 1. Detailed implementation mode

[0030] In order to further understand the implementation method of the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely. At the same time, the following described examples are only a part of the present invention, not all of it. The following description is only to further illustrate the advantages and features of the present invention, rather than a limitation on the claims of the present invention. Other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0031] Example 1

[0032] (1) Cut the conductive substrate FTO into a cuboid with dimensions of 1 cm × 2 cm × 2 mm, where the size of the conductive surface is 1 cm × 2 cm. Place the cut FTO substrate in deionized water, acetone, and absolute ethanol and ultrasonically clean it for 40 minutes each. Then wash it with deionized water and dry it in an oven at 40 °C for 8 hours to obtain the pretreated FTO.

[0033] Dissolve bismuth nitrate pentahydrate and potassium iodide in deionized water to obtain Solution B. The concentration of bismuth nitrate pentahydrate in Solution B is 0.013 g / mL, and the concentration of potassium iodide is 0.049 g / mL. Subsequently, adjust the pH of Solution B to 1.6 using concentrated nitric acid. Then dissolve p-benzoquinone in absolute ethanol to obtain Solution C. The concentration of p-benzoquinone in Solution C is 0.01 g / mL. Mix Solution B and Solution C in a volume ratio of 2:1 and stir well; use a conductive substrate as the working electrode, a saturated Ag / AgCl as the reference electrode, and a Pt wire as the counter electrode. At room temperature, deposit at a constant potential of -0.2 V relative to Ag / AgCl for 90 s to obtain a bismuth iodate precursor electrode; dissolve vanadyl acetylacetonate in dimethyl sulfoxide to obtain Solution D. The concentration of vanadyl acetylacetonate in Solution D is 0.033 g / mL. Take 40 μL of Solution D and place it on the bismuth iodate precursor electrode. After annealing at 300 °C for 1 h, soak it in 0.5 mol / L sodium hydroxide solution for 30 min, and then rinse with deionized water and dry to obtain a BVO photoanode.

[0034] (2) Mix tetrafluorophthalic anhydride and manganese acetate in a mass ratio of 2.5:1. Calcinate the mixture in a vacuum atmosphere at 150 °C for 8 h, then centrifuge, wash, and dry to obtain MnPcF powder.

[0035] (3) After thoroughly grinding the MnPcF powder, dissolve it in absolute ethanol to obtain Solution A. The mass concentration of MnPcF in Solution A is 2.0 mg / mL. Immerse the conductive surface of the BVO photoanode prepared in step (1) face down in Solution A, then place it in an oven at 50 °C for impregnation for 30 h. After a period of time, take it out and anneal at 60 °C for 5 h to obtain a MnPcF / BVO photoanode.

[0036] Comparative Example 1

[0037] According to the preparation scheme of Example 1, the difference is that only step (1) is carried out to obtain an unmodified BVO photoanode.

[0038] Figure 2 Figure (SEM) of the BVO photoanode prepared in Comparative Example 1. From Figure 2 it can be seen that the synthesized BVO photoanode is in a "worm-like" shape, with regular and uniform morphology. Figure 3 Figure (SEM) of the MnPcF / BVO photoanode prepared in Example 1, Figure 2 Combined with Figure 3 it can be seen that MnPcF is in the form of nanoparticles and is uniformly distributed on the surface of the photoanode, and is tightly combined with BVO. At the same time, the loading of the MnPcF cocatalyst does not affect the morphology and structure of the BVO bulk.

[0039] Figure 1XRD patterns of the photoanode materials prepared in Example 1 and Comparative Example 1. From Figure 1 it can be seen that Example 1 is the same as Comparative Example 1, that is, the diffraction peaks of the two photoanodes both belong to monoclinic BVO (PDF#014-0688) and FTO conductive substrate (PDF#41-1445), and no relevant diffraction peaks of MnPcF are observed, indicating that the loading amount of the MnPcF cocatalyst on the surface of the BVO photoanode is small. Combining with Figure 2 、 Figure 3 , it shows that although no relevant diffraction peaks of MnPcF are observed, the MnPcF cocatalyst has been successfully loaded on the surface of the BVO photoanode and does not affect the morphological structure of the BVO photoanode itself.

[0040] Glucose was used as the substrate and an ammonia aqueous solution of 0.05 M sulfuric acid was used as the reaction electrolyte, and the glucose concentration in the reaction electrolyte was 0.15 M; the MnPcF / BVO photoanode prepared in Example 1 and the BVO photoanode prepared in Comparative Example 1 were used as the working electrodes, Ag / AgCl as the reference electrode, and a Pt wire as the counter electrode to form a standard three-electrode system; under a simulated solar light source (300 W xenon lamp, light intensity of 100 mW / cm 2 ), a photoelectrocatalytic (PEC) biomass conversion reaction was carried out. After the reaction for 2 h, the reaction solution was collected and subjected to nuclear magnetic resonance spectroscopy (NMR) testing to analyze the products and calculate the corresponding Faraday efficiency and yield. Figure 4 The Faraday efficiency diagram and yield diagram of the products obtained from the glucose PEC reaction in Example 1. It can be seen that the yield of formamide is 976.6 mmol m -2 h -1 , the Faraday efficiency is 81.0%, and the yield of the by-product formic acid is 180.2 mmol m -2 h -1 , and the Faraday efficiency is 14.9%. Figure 5 The Faraday efficiency diagram and yield diagram of the products obtained from the glucose PEC reaction of the BVO photoanode prepared in Comparative Example 1. It can be seen that the yield of formamide is 418.2 mmol m -2 h -1 , the Faraday efficiency is 47.7%, and the yield of the by-product formic acid is 215.0 mmol m -2 h -1 and the Faraday efficiency is 24.5%. Figure 4 Compared with Figure 5In comparison, the formamide yield of the BiVO4 / MnPcF photoanode was 133.5% higher than that of the BVO photoanode, and the Faraday efficiency was 33.3% higher. This indicates that MnPcF as a cocatalyst effectively reduced the energy barriers for the cleavage of C-C bonds to form formaldehyde radicals and the C-N coupling to form formamide during the reaction, thereby achieving more excellent PEC formamide generation performance. It can be seen that the reaction of photocatalytically converting glucose to formamide using the MnPcF / BVO composite photoanode has great advantages and feasibility.

[0041] Figure 10 Figure 4 shows the linear sweep voltammograms (LSVs) of the photoanode materials prepared in Example 1 and Comparative Example 1. It can be seen that the photocurrent density of the BVO photoanode in Comparative Example 1 was 4.5 mA cm -2 -2 at 1.2 V versus the reversible hydrogen electrode, while the introduction of MnPcF significantly improved the photocatalytic activity of BVO. Among them, the MnPcF / BVO photoanode exhibited the highest photocurrent density (6.4 mA cm -2 ) at 1.2 V versus the reversible hydrogen electrode, demonstrating the excellent PEC catalytic activity of the MnPcF cocatalyst. Combining Figures 1 to 3 this indicates that MnPcF still plays a role in promoting the separation and transport of photo-generated carriers even at a relatively low loading amount.

[0042] Example 2

[0043] (1) The conductive substrate ITO was cut into a cuboid with dimensions of 1 cm × 2 cm × 2 mm, where the size of the conductive surface was 1 cm × 2 cm. The cut ITO substrate was sonicated in deionized water, acetone, and absolute ethanol for 60 min each, then washed with deionized water and dried in an oven at 50 °C for 2 h to obtain the pretreated ITO.

[0044] Dissolve bismuth nitrate pentahydrate and potassium iodide in deionized water to obtain solution B. The concentration of bismuth nitrate pentahydrate in solution B is 0.014 g / mL, and the concentration of potassium iodide is 0.052 g / mL. Subsequently, adjust the pH of solution B to 1.5 using concentrated nitric acid. Then dissolve p-benzoquinone in absolute ethanol to obtain solution C. The concentration of p-benzoquinone in solution C is 0.015 g / mL. Mix solution B and solution C in a volume ratio of 3:1 and stir well; use a conductive substrate as the working electrode, a saturated Ag / AgCl as the reference electrode, and a Pt wire as the counter electrode. At room temperature, deposit at a constant potential of -0.25 V relative to Ag / AgCl for 80 s to obtain a bismuth iodate precursor electrode; dissolve vanadyl acetylacetonate in dimethyl sulfoxide to obtain solution D. The concentration of vanadyl acetylacetonate in solution D is 0.045 g / mL. Take 30 μL of solution D and place it on the bismuth iodate precursor electrode. After annealing at 400 °C for 2 h, soak it in 0.8 mol / L sodium hydroxide solution for 40 min, and then rinse it with deionized water and dry it to obtain a BVO photoelectrode.

[0045] (2) Mix tetrafluorophthalic anhydride and manganese acetate in a mass ratio of 2:1. Calcinate the mixture in a vacuum atmosphere at 200 °C for 6 h, then centrifuge, wash, and dry to obtain MnPcF particles.

[0046] (3) Thoroughly grind the MnPcF powder and dissolve it in absolute ethanol to obtain solution A. The mass concentration of MnPcF in solution A is 1.0 mg / mL. Immerse the conductive surface of the BVO photoelectrode prepared in step (1) face down in solution A, then place it in an oven at 30 °C and impregnate for 35 h. After a period of time, take it out and anneal at 70 °C for 6 h to obtain a MnPcF / BVO photoelectrode.

[0047] Comparative Example 2

[0048] According to the preparation scheme of Example 2, the difference is that only step (1) is carried out to obtain an unmodified BVO photoelectrode.

[0049] Use sorbitol as the substrate and put it into an ammonia aqueous solution of 0.05 M sulfuric acid as the reaction electrolyte. The concentration of sorbitol in the reaction electrolyte is 0.15 M; use the MnPcF / BVO photoelectrode prepared in Example 2 and the BVO photoelectrode prepared in Comparative Example 2 as the working electrodes, Ag / AgCl as the reference electrode, and a Pt wire as the counter electrode to form a standard three-electrode system; carry out a photoelectrocatalytic (PEC) biomass conversion reaction under a simulated solar light source. After the reaction for 2 h, collect the reaction solution, conduct nuclear magnetic resonance spectroscopy (NMR) testing, analyze the products, and calculate the corresponding Faraday efficiency and yield.

[0050] Figure 6The Faraday efficiency graph and yield graph of the product obtained from the sorbitol PEC reaction in Example 2 show that the yield of formamide is 334.8 mmol m -2 h -1 , the Faraday efficiency is 42.3%, and the yield of the by-product formic acid is 103.9 mmol m -2 h -1 , and the Faraday efficiency is 13.3%. Figure 7 The Faraday efficiency graph and yield graph of the product obtained from the sorbitol PEC reaction of the BVO photoanode prepared in Comparative Example 2 show that the yield of formamide is 179.9 mmol m -2 h -1 , the Faraday efficiency is 24.6%, and the yield of the by-product formic acid is 184.3 mmol m -2 h -1 and the Faraday efficiency is 25.2%. Compared with Figure 6 , the formamide yield of the MnPcF / BVO photoanode is 154.9% higher than that of the BVO photoanode, and the Faraday efficiency is 17.7% higher. It can be seen that although the formamide yield with sorbitol as the substrate is lower than that with glucose as the substrate, a relatively good formamide yield and Faraday efficiency can still be obtained.

[0051] Example 3

[0052] (1) Cut the conductive substrate FTO into a cuboid with dimensions of 1 cm × 2 cm × 2 mm, where the size of the conductive surface is 1 cm × 2 cm. Place the cut FTO substrate in deionized water, acetone, and absolute ethanol and ultrasonicate for 80 min respectively. Then wash it with deionized water and dry it in an oven at 30 °C for 12 h to obtain the pretreated FTO. Dissolve bismuth nitrate pentahydrate and potassium iodide in deionized water to obtain Solution B. The concentration of bismuth nitrate pentahydrate in Solution B is 0.016 g / mL, and the concentration of potassium iodide is 0.057 g / ml. Then adjust the pH of Solution B to 1.8 using concentrated nitric acid. Next, dissolve p-benzoquinone in absolute ethanol to obtain Solution C. The concentration of p-benzoquinone in Solution C is 0.02 g / mL. Mix Solution B and Solution C in a volume ratio of 4:1 and stir well; use the conductive substrate as the working electrode, saturated Ag / AgCl as the reference electrode, and a Pt wire as the counter electrode. At room temperature, deposit at a constant potential of -0.1 V relative to Ag / AgCl for 190 s to obtain the bismuth iodate precursor electrode; dissolve vanadyl acetylacetonate in dimethyl sulfoxide to obtain Solution D. The concentration of vanadyl acetylacetonate in Solution D is 0.058 g / mL. Take 80 μL of Solution D and place it on the bismuth iodate precursor electrode. Anneal it at 500 °C for 3 h and then soak it in 1.5 mol / L sodium hydroxide solution for 60 min. Then rinse it with deionized water and dry it to obtain the BVO photoanode.

[0053] (2) Mix tetrafluorophthalic anhydride and manganese acetate in a mass ratio of 5:1. The mixture is calcined in a vacuum atmosphere at 300 °C for 3 h, followed by centrifugation, washing, and drying to obtain MnPcF particles.

[0054] (3) Thoroughly grind the MnPcF powder and dissolve it in absolute ethanol to obtain solution A. The mass concentration of MnPcF in solution A is 5.0 mg / mL. Immerse the conductive surface of the BVO photoanode prepared in step (1) face down into solution A, then place it in an oven at 70 °C for impregnation for 10 h. After a period of time, take it out and anneal it at 120 °C for 2 h to obtain the MnPcF / BVO photoanode.

[0055] Comparative Example 3

[0056] According to the preparation scheme of Example 3, the difference is that only step (1) is carried out to obtain an unmodified BVO photoanode.

[0057] Use glyceraldehyde as the input, and an ammonia aqueous solution of 0.05 M sulfuric acid as the reaction electrolyte. The concentration of glyceraldehyde in the reaction electrolyte is 0.05 M. Respectively use the MnPcF / BVO photoanode prepared in Example 3 and the BVO photoanode prepared in Comparative Example 3 as the working electrode, Ag / AgCl as the reference electrode, and a Pt wire as the counter electrode to form a standard three-electrode system. Carry out a photoelectrocatalytic (PEC) biomass conversion reaction under a simulated solar light source. After the reaction for 2 h, collect the reaction solution and conduct nuclear magnetic resonance spectroscopy (NMR) tests to analyze the products and calculate the corresponding Faraday efficiency and yield.

[0058] Figure 8 It is the Faraday efficiency diagram and yield diagram of the products obtained from the glyceraldehyde PEC reaction in Example 3. It can be seen that the yield of formamide is 754.4 mmol m -2 h -1 , the Faraday efficiency is 80.8%, and the yield of the by-product formic acid is 92.3 mmol m -2 h -1 , and the Faraday efficiency is 15.3%. Figure 9 It is the Faraday efficiency diagram and yield diagram of the products obtained from the glyceraldehyde PEC reaction of the BVO photoanode prepared in Comparative Example 3. It can be seen that the yield of formamide is 358.6 mmol m -2 h -1 , the Faraday efficiency is 47.7%, and the yield of the by-product formic acid is 211.9 mmol m -2 h -1 and the Faraday efficiency is 24.5%. Compared with Figure 8In comparison, the formamide yield of the MnPcF / BVO photoanode was 395.8% higher than that of the BVO photoanode, and the Faradaic efficiency was increased by 32.6%. It can be seen that although the formamide yield with glyceraldehyde as the substrate was lower than that with glucose as the substrate, good formamide yield and Faradaic efficiency could still be obtained.

[0059] The above-described embodiments only represent the implementation modes of the present invention, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A perfluoromanganese phthalocyanine composite bismuth vanadate photoanode, characterized in that, The perfluoromanganese phthalocyanine was loaded on the bismuth vanadate photoanode by the impregnation method, and the perfluoromanganese phthalocyanine was uniformly distributed on the surface of the bismuth vanadate photoanode and tightly combined with the bismuth vanadate.

2. The preparation method of the perfluoromanganese phthalocyanine composite bismuth vanadate photoanode according to claim 1, characterized in that, It includes the following steps: (1) Prepare the bismuth vanadate photoanode by the electrodeposition method; (2) Grind and mix manganese acetate and tetrafluorophthalic anhydride in proportion, calcine the mixture in a vacuum atmosphere, then centrifuge, wash and dry to obtain perfluoromanganese phthalocyanine powder; (3) Thoroughly grind the perfluoromanganese phthalocyanine powder and dissolve it in absolute ethanol to obtain solution A. Immerse the conductive surface of the bismuth vanadate photoanode prepared in step (1) downward into solution A, then place it in an oven for impregnation. After a period of time, take it out and anneal in air to obtain the perfluoromanganese phthalocyanine composite bismuth vanadate photoanode.

3. The preparation method of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode according to claim 2, characterized in that, The specific process of step (1) is as follows: After cutting the conductive substrate to the required size, ultrasonically treat it in deionized water, ethanol and acetone for 40 - 80 min respectively, and then dry it at 30 - 50 °C for 2 - 12 h; Dissolve bismuth nitrate pentahydrate and potassium iodide in deionized water to obtain solution B, where the concentration of bismuth nitrate pentahydrate in solution B is 0.013 - 0.016 g / mL and the concentration of potassium iodide is 0.049 - 0.057 g / ml; Subsequently, adjust the pH of solution B to 1.5 - 1.8 with concentrated nitric acid; Dissolve p-benzoquinone in absolute ethanol to obtain solution C, where the concentration of p-benzoquinone in solution C is 0.01 - 0.02 g / mL; Mix solution B and solution C in a volume ratio of (2 - 4):1 and stir well; Use the conductive substrate as the working electrode, saturated silver / silver chloride Ag / AgCl as the reference electrode, and platinum wire Pt as the counter electrode. Deposit at a constant potential of -0.25 - -0.1 V relative to Ag / AgCl at room temperature for 80 - 190 s to obtain the bismuth iodate precursor electrode; Dissolve vanadyl acetylacetonate in dimethyl sulfoxide to obtain solution D, where the concentration of vanadyl acetylacetonate in solution D is 0.033 - 0.058 g / mL; Take 30 - 80 μL of solution D and place it on the bismuth iodate precursor electrode. Anneal it at 300 - 500 °C for 1 - 3 h, then soak it in 0.5 - 1.5 mol / L sodium hydroxide solution for 30 - 60 min, and then rinse it with deionized water and dry to obtain the bismuth vanadate BVO photoanode.

4. The preparation method of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode according to claim 3, characterized in that, The conductive substrate is fluorine-doped tin dioxide conductive glass or indium tin oxide thin film.

5. The preparation method of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode according to claim 2, characterized in that, In step (2), the mass ratio of tetrafluorophthalic anhydride to manganese acetate is (2 - 5):1; The calcination temperature is 150 - 300 °C and the calcination time is 3 - 8 h.

6. The preparation method of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode according to claim 2, characterized in that, In step (3), the mass concentration of perfluoromanganese phthalocyanine in solution A is 1.0 - 5.0 mg / mL, the oven temperature is 30 - 70 °C, the impregnation time is 10 - 35 h, the annealing temperature is 60 - 120 °C, and the annealing time is 2 - 6 h.

7. Use of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode as described in claim 1, characterized in that, It is applied to the anodic photoelectrocatalytic production of formamide from biomass while coupling cathodic hydrogen production.

8. Use of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode according to claim 7, characterized in that The process of photocatalytically converting biomass to formamide while coupling hydrogen production at the cathode is as follows: Using the prepared perfluoromanganese phthalocyanine composite bismuth vanadate photoanode as the working electrode, Ag / AgCl as the reference electrode, and a Pt wire as the counter electrode to form a standard three-electrode system; The reaction electrolyte is an aqueous ammonia solution of 0.05 M sulfuric acid added with biomass raw materials, and the photocatalytic biomass conversion reaction is carried out under a simulated solar light source.

9. Use of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode according to claim 7, characterized in that, The concentration of the biomass raw materials in the reaction electrolyte is 0.05 - 0.5 mol / L.

10. Use of a perfluoromanganese phthalocyanine composite bismuth vanadate photoanode according to claim 7, characterized in that, The biomass raw materials include one or more of glucose, arabinose, methanol, ethylene glycol, glycerol, sorbitol, erythritol, glycolaldehyde, and glyceraldehyde.

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