Preparation method, product and application of a PTFE-modified BiVO4 photoanode

Abstract

The present invention provides a preparation method, product and application of a PTFE-modified BiVO4 photoanode. The above preparation method includes: immersing a BiVO4 electrode in a PTFE dispersion solution and then taking it out, and then calcining to obtain the PTFE-modified BiVO4 photoanode. The preparation method of the present invention introduces PTFE with rich hydrophobic functional groups into the BiVO4 electrode, increases the hydrophobicity of the material, enhances the selectivity of photocatalytic oxidation to H2O2, inhibits the decomposition of H2O2, and increases the accumulation amount of H2O2. The above synergistic effects greatly improve the performance of the BiVO4 electrode in photocatalytic water oxidation to produce H2O2 under visible light, and the prepared PTFE-modified BiVO4 photoanode has excellent stability. In addition, the preparation method has a simple process flow and good experimental repeatability, providing technical support for the preparation of various photocatalytic composite materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic water splitting for H2O2 production materials, and particularly relates to a preparation method, product and application of a PTFE-modified BiVO4 photoanode. Background Art

[0002] Hydrogen peroxide (H2O2), as a green fuel and oxidant, has attracted increasing attention in energy and environmental research. However, the traditional anthraquinone oxidation process for H2O2 production has low economic efficiency and generates a large amount of pollutants during the production process. To achieve sustainable development, using solar energy to produce H2O2 is considered a promising strategy. Therefore, finding effective photocatalytic materials to convert solar energy into chemical energy has become a top priority. In the photocatalytic semiconductor material system, metal oxides such as TiO2, WO3, and BiVO4 have been proven to be able to effectively catalyze water oxidation to produce H2O2 under visible light. Due to their stable chemical properties and suitable conduction bands for photocatalytic water oxidation to produce H2O2, they have been widely studied and have good prospects.

[0003] BiVO4 is a typical n-type semiconductor, and its unique electronic structure, suitable band gap width and energy band position have attracted extensive attention from researchers. At the same time, its preparation process is simple and can be obtained quickly by electrodeposition, so it is widely used in the field of photocatalysis. However, due to the slow and ineffective conduction of photo-generated electrons generated by BiVO4, the separation rate of photo-generated carriers is low, and photo-corrosion is likely to occur during the photocatalytic process, resulting in unsatisfactory photocatalytic stability of BiVO4. At the same time, its slow water oxidation kinetics problem also greatly limits its efficiency in photocatalytic water oxidation. The water oxidation reaction is a multi-electron process, as shown in equations (1) and (2). In addition to the two-electron reaction of H2O2, the four-electron reaction of O2 also occurs simultaneously, and there is a competitive relationship between the two. And the four-electron reaction of O2 is more thermodynamically favorable, which seriously inhibits the selectivity of H2O2. So far, researchers have improved the selectivity of H2O2 by modifying the BiVO4 photoanode (such as doping, constructing composite structures, surface loading of cocatalysts, etc.) in a NaHCO3 solution.

[0004] 2H2O + 4e - / h + →O2 + 2H2 (E o =+1.23V vs RHE) (1)

[0005] 2H2O + 2e - / h + →H2O2 + H2 (E o =+1.77V vs RHE) (2)

[0006] According to the currently reported BiVO4 photocatalyst for water oxidation to produce H2O2, irregular BiVO4 crystals were prepared by the hydrothermal method, and the oxygen vacancies were changed by calcination under different conditions to endow it with good performance for photocatalytic water oxidation to produce H2O2. However, its process is complex, the cost is high, and the commercial value is small. Summary of the Invention

[0007] The object of the present invention is to solve the deficiencies of the existing BiVO4 photocatalytic water oxidation to produce H2O2. The basic idea of the present invention to solve the above problems is as follows: Without changing the thermodynamic parameters, the BiVO4 photoanode is modified by regulating the reaction product rate, a kinetic idea. By reducing the desorption of O2 and inhibiting the four-electron reaction of O2, the reaction is made to proceed in the direction of the two-electron reaction of H2O2, thereby increasing the accumulation amount of H2O2.

[0008] Under the hydrophobic strategy, the present invention selects PTFE as the modification material. PTFE is a typical hydrophobic polymer, and its rich hydrophobic functional groups increase the hydrophobicity of the material. By covering the catalyst with the hydrophobic polymer, the generated O2 is difficult to desorb on the surface of the catalyst, forming a solid-gas-liquid three-phase interface on the surface of the catalyst, so that the water oxidation is transferred from the four-electron pathway of O2 to the two-electron pathway of H2O2, thereby adjusting the water oxidation reaction pathway and enhancing the selectivity for H2O2. In addition, PTFE is inexpensive and has high practical value.

[0009] To achieve the above object, the present invention provides a preparation method, product and application of a PTFE-modified BiVO4 photoanode. It solves the problems of low H2O2 accumulation amount and high decomposition rate in the photocatalytic water oxidation of BiVO4 photocatalytic materials to produce H2O2. The preparation process of the PTFE-modified BiVO4 photoanode is simple, has high repeatability, and strong applicability.

[0010] A preparation method of a PTFE-modified BiVO4 photoanode includes:

[0011] Immerse the BiVO4 (bismuth vanadate) electrode in the PTFE (polytetrafluoroethylene) dispersion liquid and then take it out, and then calcine to obtain the PTFE-modified BiVO4 photoanode.

[0012] Preferably, the concentration of the PTFE dispersion liquid is 2-18%. Further preferably, the concentration of the PTFE dispersion liquid is 5-15%. More preferably, it is 9-11%.

[0013] Preferably, the calcination temperature is 300-450 °C, and the heating rate is 2-5 °C / min. Further preferably, the calcination temperature is 330-370 °C, and the heating rate is 2-3 °C / min.

[0014] Preferably, the calcination time is 10 to 40 min, and more preferably 25 to 35 min.

[0015] Preferably, the soaking time of the BiVO4 electrode is 5 to 20 min, and more preferably 8 to 12 min.

[0016] Preferably, the preparation process of the BiVO4 electrode is as follows:

[0017] (1) Using fluorine-doped tin oxide (FTO) as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode, a mixed solution of an aqueous solution containing bismuth nitrate and potassium iodide (KI) and an ethanol solution of p-benzoquinone is used as the electrolyte, and electrodeposition is carried out at a potential of -0.1 ± 0.02 V (vs Ag / AgCl) to obtain a bismuth oxyiodide (BiOI) electrode;

[0018] (2) A dimethyl sulfoxide (DMSO) solution containing vanadyl acetylacetonate is dropped onto the bismuth oxyiodide electrode, and then calcined and washed to obtain the BiVO4 electrode.

[0019] As a further preference, in step (2), the dimethyl sulfoxide solution containing vanadyl acetylacetonate is dropped onto the bismuth oxyiodide electrode so that the solution completely covers the surface of the bismuth oxyiodide electrode. That is, an excessive amount of the dimethyl sulfoxide solution containing vanadyl acetylacetonate is dropped onto the bismuth oxyiodide electrode. Through this technical solution, it is ensured that the entire surface of the bismuth oxyiodide electrode is in full contact with the dimethyl sulfoxide solution containing vanadyl acetylacetonate and reacts completely, ensuring the performance of the final product bismuth vanadate electrode.

[0020] As a further preference, the electrodeposition time is 2 to 10 min, and more preferably 4 to 6 min.

[0021] As a further preference, the calcination temperature is 400 to 500 °C, and the heating rate is 2 to 5 °C / min. More preferably, the calcination temperature is 430 to 470 °C, and the heating rate is 2 to 3 °C / min.

[0022] As a further preference, the calcination time is 1 to 3 h, and more preferably 1.5 to 2.5 h.

[0023] As a further preference, the preparation process of the aqueous solution containing bismuth nitrate and potassium iodide is as follows: First, potassium iodide is added to water and stirred until dissolved, and then bismuth nitrate is added and stirred until evenly mixed, and the pH is adjusted to acidic to obtain the aqueous solution containing bismuth nitrate and potassium iodide.

[0024] Among them, bismuth nitrate is added in the form of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O).

[0025] As a further preference, dilute nitric acid is used to adjust the pH value.

[0026] As a further preferred embodiment, the pH value of the aqueous solution containing bismuth nitrate and potassium iodide is 1.5 to 2. More preferably, it is 1.7.

[0027] As a further preference, in the aqueous solution containing bismuth nitrate and potassium iodide, the concentration of bismuth nitrate is 0.03 to 0.05 mol / L. Even more preferably, it is 0.04 mol / L.

[0028] As a further preference, in the aqueous solution containing bismuth nitrate and potassium iodide, the concentration of potassium iodide is 0.3 to 0.5 mol / L. Even more preferably, it is 0.4 mol / L.

[0029] As a further preference, in the dimethyl sulfoxide solution containing vanadyl acetylacetonate, the concentration of vanadyl acetylacetonate is 0.2 to 0.3 mol / L. Even more preferably, it is 0.22 to 0.24 mol / L.

[0030] As a further preference, in the electrolyte, the volume ratio of the aqueous solution containing bismuth nitrate and potassium iodide (KI) to the ethanol solution of p-benzoquinone is 1:(0.3 to 0.5). Even more preferably, it is 1:0.4.

[0031] As a further preference, in step (2), after calcination, the bismuth vanadate electrode is washed with a sodium hydroxide solution to remove the excess V2O5 on the electrode surface. Even more preferably, the concentration of the sodium hydroxide solution is 0.8 to 1.2 mol / L.

[0032] In step (2), the calcination can be carried out in a muffle furnace.

[0033] As a specific preference, a method for preparing a PTFE-modified BiVO4 photoanode includes the following steps:

[0034] (1) Add KI to water and stir until clear to obtain solution A;

[0035] (2) Take Bi(NO3)3·5H2O and add it to solution A, magnetically stir until an orange suspension is formed, and adjust the pH to 1.7 with dilute nitric acid to obtain solution B;

[0036] (3) Take p-benzoquinone and add it to anhydrous ethanol, and stir until a clear solution is obtained;

[0037] (4) Slowly add the solution obtained in step 3 to solution B and stir to obtain a dark red solution;

[0038] (5) Pour the solution obtained in step 4 into an electrolytic cell, use fluorine-doped tin oxide (FTO) as the working electrode, a Pt electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode, and perform electrodeposition at a potential of -0.1 ± 0.02 V vs Ag / AgCl at room temperature to obtain a BiOI electrode;

[0039] (6) After deposition, rinse the surface of the BiOI electrode with deionized water to remove the excess electrolyte, and air-dry for later use;

[0040] (7) Add vanadyl acetylacetonate to dimethyl sulfoxide (DMSO), and ultrasonically oscillate until completely dissolved;

[0041] (8) Drop the solution in step 7 onto the BiOI electrode, and then calcine and wash the BiOI electrode with an alkaline solution to obtain a BiVO4 electrode;

[0042] (9) Immerse the prepared BiVO4 electrode in a PTFE dispersion, take it out and calcine to obtain a PTFE-modified BiVO4 photoanode.

[0043] The preparation method of the PTFE-modified BiVO4 photoanode of the present invention uses PTFE to modify the BiVO4 electrode, so that PTFE is uniformly distributed on the surface of BiVO4. Utilizing the hydrophobic property of PTFE, the oxygen generated in the process of photoelectrocatalytic water oxidation is adsorbed on the surface of PTFE, inhibiting the generation of O2 and improving the selectivity of H2O2 generation. And the preparation process is simple, with low cost, and is suitable for industrial production.

[0044] The present invention mainly obtains a BiVO4 photoanode by electrodeposition, and uniformly loads the hydrophobic material PTFE onto the BiVO4 photoanode by an impregnation method to obtain a PTFE / BiVO4 photoanode. Introducing PTFE into the semiconductor BiVO4 (BiVO4 electrode), its rich hydrophobic functional groups increase the hydrophobicity of the material. By forming a solid-gas-liquid three-phase interface, the water oxidation is transferred from the four-electron O2 production path to the two-electron H2O2 production path, enhancing the selectivity for H2O2. In addition, the decomposition of H2O2 is inhibited after introducing PTFE, increasing the accumulation amount of H2O2. The above synergistic effects greatly improve the performance of the BiVO4 electrode in photoelectrocatalytic water oxidation to produce H2O2 under visible light, and at the same time, the prepared PTFE-modified BiVO4 photoanode exhibits excellent stability. In addition, the preparation method has a simple process flow and good experimental repeatability, providing technical support for the preparation of various photoelectrocatalytic composite materials.

[0045] A PTFE-modified BiVO4 photoanode is prepared by the preparation method described in any one of the above. The PTFE-modified BiVO4 photoanode prepared by the above preparation method has high selectivity for H2O2 generation during photoelectrocatalytic water oxidation, is low in cost, and has high practical value.

[0046] An application of the above PTFE-modified BiVO4 photoanode in the production of H2O2 by photoelectrocatalytic water oxidation.

[0047] Preferably, during the production of H2O2 by photoelectrocatalytic water oxidation, the PTFE-modified BiVO4 photoanode is used as the working electrode, the Pt electrode is used as the electrode, the Ag / AgCl electrode is used as the reference electrode, 1 mol / L NaHCO3 solution is used as the electrolyte, and the illumination source is a 300 W xenon lamp with an AM1.5 filter.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] (1) The preparation method of the present invention utilizes the hydrophobic and gasophilic characteristics of PTFE to prepare a PTFE-modified BiVO4 photoanode, so that the oxygen generated by the reaction is adsorbed on the PTFE surface to form a gas-liquid-solid three-phase interface, inhibiting the four-electron reaction path of O2, thereby promoting the two-electron reaction path of H2O2 and improving the selectivity of H2O2.

[0050] (2) Considering from the aspect of economy, the present invention selects PTFE as the hydrophobic material to modify the BiVO4 electrode, improves the generation rate of the photoelectrocatalytic water oxidation product H2O2, inhibits the decomposition of H2O2, and increases the accumulation amount of H2O2; PTFE is low in price and can also improve the activity of producing H2O2 by photoelectrocatalytic water oxidation, so it has high practical value.

[0051] (3) The PTFE used in the preparation method of the present invention has good stability and heat resistance, prevents the BiVO4 electrode from being oxidized under light illumination conditions, and improves the service life of the BiVO4 electrode.

[0052] (4) The preparation method of the present invention has a simple process flow, good experimental repeatability. The Faraday efficiency of the prepared PTFE-modified BiVO4 photoanode for producing hydrogen peroxide is up to 66%, which is 3.7 times higher than that of single-phase BiVO4, and has good anti-photocorrosion ability and shows good stability. Description of the Drawings

[0053] Figure 1 It is a comparison diagram of the X-ray diffraction patterns of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the single-phase BiVO4 electrode prepared in Comparative Example 1;

[0054] Figure 2 These are the field emission scanning electron microscope images of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the single-phase BiVO4 electrode prepared in Comparative Example 1;

[0055] Figure 3 These are the comparison diagrams of the contact angles of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrodes prepared in Comparative Example 1;

[0056] Figure 4 Ultraviolet-visible absorption spectra of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrodes prepared in Comparative Example 1;

[0057] Figure 5 These are the comparison diagrams of the hydrogen peroxide production performance of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrodes prepared in Comparative Example 1;

[0058] Figure 6 This is the hydrogen peroxide accumulation diagram of the PTFE / BiVO4 electrode prepared in Example 1;

[0059] Figure 7 These are the hydrogen peroxide degradation performance diagrams of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrodes prepared in Comparative Example 1;

[0060] Figure 8 This is the stability diagram of the PTFE / BiVO4 electrode (a) prepared in Example 1 and the BiVO4 electrode (b) prepared in Comparative Example 1. Detailed implementation manners

[0061] Example 1

[0062] Prepare a BiVO4 electrode: Take 3.32 g of KI and add it to 50 mL of deionized water, and stir until a clear solution (Solution A) is obtained. Take 0.970 g of Bi(NO3)3·5H2O and slowly add it to Solution A, and stir magnetically until an orange suspension is obtained. Adjust the pH to 1.7 with dilute nitric acid to obtain a bright red solution (Solution B).

[0063] Take 0.497 g of p-benzoquinone and slowly add it to 20 mL of absolute ethanol, and stir until a clear solution (Solution C) is obtained.

[0064] Mix solution B and solution C and stir vigorously for ten minutes to obtain a dark red solution (electrolyte). Pour the electrolyte into an electrolytic cell, use fluorine-doped tin oxide (FTO) as the working electrode, a Pt electrode as the reference electrode, and an Ag / AgCl electrode as the reference electrode, and perform electro-deposition at -0.1V vs Ag / AgCl potential at room temperature for 5 minutes to obtain a BiOI electrode.

[0065] Remove the BiOI electrode and rinse the surface with deionized water to remove the excess electrolyte, and dry it for later use.

[0066] Take 0.106 g of vanadyl acetylacetonate and add it to 2 mL of dimethyl sulfoxide (DMSO), and ultrasonically vibrate until completely dissolved to obtain a dimethyl sulfoxide solution containing vanadyl acetylacetonate.

[0067] Then take 0.15 mL of this dimethyl sulfoxide solution and drop it onto the BiOI electrode so that the surface of the BiOI electrode is completely covered with the dimethyl sulfoxide solution containing vanadyl acetylacetonate. Put the BiOI electrode into a muffle furnace and bake it at 450 °C for 2 h (heating rate is 2 °C / min). After the temperature drops to room temperature, take it out and wash off the excess V2O5 with 1 mol / L NaOH solution to obtain a BiVO4 electrode.

[0068] Prepare a PTFE / BiVO4 electrode (a PTFE-modified BiVO4 photoanode): Immerse the prepared BiVO4 electrode in a 10% PTFE solution for 10 minutes, then take it out and calcine it in a muffle furnace at 350 °C for 30 minutes (heating rate is 2 °C / min) to obtain a 10% PTFE / BiVO4 electrode.

[0069] Example 2

[0070] Prepare a BiVO4 electrode: Take 3.32 g of KI and add it to 50 mL of deionized water, and stir until a clear solution (solution A) is obtained. Take 0.970 g of Bi(NO3)3·5H2O and slowly add it to solution A, and stir magnetically until an orange suspension is obtained, and adjust the pH to 1.7 with dilute nitric acid to obtain a bright red solution (solution B).

[0071] Take 0.497 g of p-benzoquinone and slowly add it to 20 mL of absolute ethanol, and stir until a clear solution (solution C) is obtained.

[0072] Mix solution B and solution C and stir vigorously for ten minutes to obtain a dark red solution (electrolyte). Pour the electrolyte into an electrolytic cell, use fluorine-doped tin oxide (FTO) as the working electrode, a Pt electrode as the reference electrode, and an Ag / AgCl electrode as the reference electrode, and perform electro-deposition at -0.1V vs Ag / AgCl potential at room temperature for 5 minutes to obtain a BiOI electrode.

[0073] Remove the BiOI electrode and rinse off the excess electrolyte on the surface with deionized water, then air-dry for later use.

[0074] Take 0.106 g of vanadyl acetylacetonate and add it to 2 mL of dimethyl sulfoxide (DMSO). Ultrasonically agitate until completely dissolved to obtain a dimethyl sulfoxide solution containing vanadyl acetylacetonate.

[0075] Then take 0.15 mL of this dimethyl sulfoxide solution and drop it onto the BiOI electrode, so that the surface of the BiOI electrode is completely covered with the dimethyl sulfoxide solution containing vanadyl acetylacetonate. Put the BiOI electrode into a muffle furnace and bake it at 450 °C for 2 h (heating rate is 2 °C / min). After the temperature drops to room temperature, take it out and wash off the excess V2O5 with 1 mol / L NaOH solution to obtain the BiVO4 electrode.

[0076] Prepare the PTFE / BiVO4 electrode (PTFE-modified BiVO4 photoanode): Immerse the prepared BiVO4 electrode in a 5% PTFE solution for 10 min, then take it out and calcine it in a muffle furnace at 350 °C for 30 min (heating rate is 2 °C / min) to obtain the 5% PTFE / BiVO4 electrode.

[0077] Example 3

[0078] Prepare the BiVO4 electrode: Take 3.32 g of KI and add it to 50 mL of deionized water, stir until a clear solution (solution A) is obtained. Take 0.970 g of Bi(NO3)3·5H2O and slowly add it to solution A, magnetically stir until an orange suspension is formed, and adjust the pH to 1.7 with dilute nitric acid to obtain a bright red solution (solution B).

[0079] Take 0.497 g of p-benzoquinone and slowly add it to 20 mL of absolute ethanol, stir until a clear solution (solution C) is obtained.

[0080] Mix solution B and solution C and vigorously stir for ten minutes to obtain a dark red solution (electrolyte). Pour the electrolyte into an electrolytic cell, use fluorine-doped tin oxide (FTO) as the working electrode, a Pt electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode, and perform electro-deposition at -0.1 V vs Ag / AgCl potential at room temperature for 5 min to obtain the BiOI electrode.

[0081] Remove the BiOI electrode and rinse off the excess electrolyte on the surface with deionized water, then air-dry for later use.

[0082] Take 0.106 g of vanadyl acetylacetonate and add it to 2 mL of dimethyl sulfoxide (DMSO). Ultrasonically agitate until completely dissolved to obtain a dimethyl sulfoxide solution containing vanadyl acetylacetonate.

[0083] Subsequently, 0.15 mL of this dimethyl sulfoxide solution was dropped onto the BiOI electrode, covering the entire surface of the BiOI electrode with the dimethyl sulfoxide solution containing vanadyl acetylacetonate. The BiOI electrode was placed in a muffle furnace and calcined at 450 °C for 2 h (heating rate: 2 °C / min). After the temperature dropped to room temperature, it was taken out and washed with 1 mol / L NaOH solution to remove the excess V2O5, obtaining the BiVO4 electrode.

[0084] Preparation of the PTFE / BiVO4 electrode (PTFE-modified BiVO4 photoanode): The prepared BiVO4 electrode was immersed in a 15% PTFE solution for 10 min, and then taken out and calcined in a muffle furnace at 350 °C for 30 min (heating rate: 2 °C / min), obtaining the 15% PTFE / BiVO4 electrode.

[0085] Comparative Example 1

[0086] Preparation of the BiVO4 electrode: Take 3.32 g of KI and add it to 50 mL of deionized water, stirring until a clear solution (solution A) is obtained. Take 0.970 g of Bi(NO3)3·5H2O and slowly add it to solution A, magnetically stirring until an orange suspension is formed, and adjusting the pH to 1.7 with dilute nitric acid to obtain a bright red solution (solution B).

[0087] Take 0.497 g of p-benzoquinone and slowly add it to 20 mL of absolute ethanol, stirring until a clear solution (solution C) is obtained.

[0088] Mix solution B and solution C and stir vigorously for ten minutes to obtain a dark red solution (electrolyte). Pour the electrolyte into an electrolytic cell, use fluorine-doped tin oxide (FTO) as the working electrode, a Pt electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode, and perform electro-deposition at -0.1 V vs Ag / AgCl potential at room temperature for 5 min to obtain the BiOI electrode.

[0089] Remove the BiOI electrode, rinse the surface with deionized water to remove the excess electrolyte, and dry it for later use.

[0090] Take 0.106 g of vanadyl acetylacetonate and add it to 2 mL of dimethyl sulfoxide (DMSO), ultrasonically vibrating until completely dissolved to obtain a dimethyl sulfoxide solution containing vanadyl acetylacetonate.

[0091] Subsequently, 0.15 mL of this dimethyl sulfoxide solution was dropped onto the BiOI electrode, covering the entire surface of the BiOI electrode with the dimethyl sulfoxide solution containing vanadyl acetylacetonate. The BiOI electrode was placed in a muffle furnace and calcined at 450 °C for 2 h (heating rate: 2 °C / min). After the temperature dropped to room temperature, it was taken out and washed with 1 mol / L NaOH solution to remove the excess V2O5, obtaining the BiVO4 electrode.

[0092] Product characterization:

[0093] Figure 1 It is a comparison chart of the X-ray diffraction patterns of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the single-phase BiVO4 electrode prepared in Comparative Example 1. It can be seen from the peak positions of the diffraction peaks in Figure 1 that compared with the single-phase BiVO4 electrode, the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 have higher purity and no other impurity phases, oxides, or other impurities.

[0094] Figure 2 It is a field emission scanning electron microscope image of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the single-phase BiVO4 electrode prepared in Comparative Example 1. Among them, a, b, c, and d are the field emission scanning electron microscope images of the BiVO4 electrode, 5% PTFE / BiVO4 electrode, 10% PTFE / BiVO4 electrode, and 15% PTFE / BiVO4 electrode, respectively. It can be seen from a in Figure 2 that BiVO4 is spherical granular; it can be seen from b-d in Figure 2 that in the PTFE / BiVO4 electrodes prepared in Examples 1-3, PTFE is uniformly distributed on the surface of BiVO4 particles. In addition, compared with 10% PTFE / BiVO4, the amount of PTFE on the surface of the 5% PTFE / BiVO4 electrode is less and the hydrophobicity is insufficient, which may be due to the low concentration of the PTFE dispersion, resulting in less PTFE loaded on BiVO4; while the amount of PTFE on the surface of the 15% PTFE / BiVO4 electrode is more and the material is overly hydrophobic, which may be due to the high concentration of the PTFE dispersion, resulting in more PTFE loaded on BiVO4; this is also the reason for the first increase and then decrease in the Faraday efficiency of H2O2.

[0095] Figure 3 It is a comparison chart of the contact angles of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrode prepared in Comparative Example 1. Among them, a, b, c, and d are the BiVO4 electrode, 10% PTFE / BiVO4 electrode, 5% PTFE / BiVO4 electrode, and 15% PTFE / BiVO4 electrode, respectively. The contact angles of the four samples are 77.48°, 117.34°, 112.12°, and 122.88°, respectively. It can be seen from Figure 3 that the contact angles of the PTFE / BiVO4 electrodes prepared in Examples 1-3 are significantly larger than those of the BiVO4 electrode prepared in Comparative Example 1, indicating that the introduction of PTFE significantly improves the hydrophobicity of the BiVO4 electrode. And as the concentration of the PTFE dispersion increases, the contact angle of the prepared PTFE / BiVO4 electrode also increases.

[0096] Product performance test:

[0097] The test process of photocatalytic water oxidation to produce hydrogen peroxide is as follows:

[0098] Detect the precipitation of H2O2 by the N,N-diethyl-1,4-phenylenediamine (DPD) method. Dissolve 0.1 g of DPD in 10 ml of a 0.05 mol / L H2SO4 solution to prepare the DPD stock solution. Dissolve 10 mg of peroxidase (POD) in 10 mL of deionized water to make the peroxidase solution, and store it in the refrigerator for later use. Mix 49.85 mL of deionized water, 43.85 mL of 1 mol / L potassium alkaline phosphate, and 6.3 mL of 1 mol / L potassium phosphate to make the potassium phosphate buffer solution.

[0099] Use a 1 mol / L NaHCO3 solution as the electrolyte (the electrolyte is placed in an H-type electrolytic cell, and the anode and cathode are separated by an ion exchange membrane). Use the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrode prepared in Comparative Example 1 as the working electrodes, a Pt electrode as the reference electrode, and an Ag / AgCl electrode as the reference electrode. The illumination source is a 300 W xenon lamp with an AM1.5 filter. All electrodes are illuminated from the back, and a 5-minute reaction is carried out at different potentials. During the irradiation process, collect sample aliquots (1 mL) with a syringe, add 0.4 mL of potassium phosphate buffer solution, 3 ml of water, 0.05 mL of DPD, and 0.05 mL of POD, and shake well for 2 minutes. The resulting solution is analyzed by ultraviolet-visible spectroscopy, and the results are as Figure 4 shown.

[0100] Figure 4 It is the ultraviolet-visible absorption spectra of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrode prepared in Comparative Example 1. As can be seen from Figure 4 it, the band gap of the PTFE / BiVO4 electrodes prepared in Examples 1 to 3 is the same as that of the single-phase BiVO4 electrode prepared in Comparative Example 1, indicating that loading PTFE has no effect on the light absorption range of the BiVO4 photoanode (electrode).

[0101] Figure 5 It is a comparison chart of the hydrogen peroxide production performance of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrode prepared in Comparative Example 1. As can be seen from Figure 5It can be seen that the performance of producing hydrogen peroxide of the PTFE / BiVO4 electrodes prepared in Examples 1-3 is significantly better than that of the BiVO4 electrode prepared in Comparative Example 1. Among the PTFE / BiVO4 electrodes prepared in Examples 1-3, the 10% PTFE / BiVO4 electrode prepared in Example 1 has the best Faraday efficiency, reaching up to 66%, which is 3.7 times higher than that of the single-phase BiVO4 electrode.

[0102] Figure 6 It is the hydrogen peroxide accumulation amount diagram of the 10% PTFE / BiVO4 electrode prepared in Example 1. From Figure 6 it can be seen that when the reaction reaches two hours, the accumulation amount of hydrogen peroxide reaches 3.23 μmol / cm 2 .

[0103] Take five equal amounts of H2O2 aqueous solution. Four of them are respectively put into the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3 and the BiVO4 electrode prepared in Comparative Example 1, and the remaining one is used as a blank control group; the above five H2O2 aqueous solutions are placed under AM1.5 light illumination conditions for H2O2 degradation experiments. During this period, samples are taken every ten minutes for ultraviolet testing to detect the amount of H2O2 in the solution. Figure 7 It is the comparison diagram of the hydrogen peroxide degradation performance of the PTFE / BiVO4 electrodes prepared in Examples 1, 2, and 3, the BiVO4 electrode prepared in Comparative Example 1, and the blank control group (shown as Photolysis in the figure). From Figure 7 it can be seen that after loading PTFE, the BiVO4 electrode has an obvious inhibitory effect on the degradation of hydrogen peroxide, and the inhibitory effect of the 10% PTFE / BiVO4 electrode prepared in Example 1 is the best.

[0104] Figure 8 It is the stability comparison diagram of the 10% PTFE / BiVO4 electrode prepared in Example 1 ( Figure 8 a) in it) and the BiVO4 electrode prepared in Comparative Example 1 ( Figure 8 b) in it). From Figure 8 it can be seen that after loading PTFE, the stability of the BiVO4 electrode is significantly enhanced, and it still maintains a good photocurrent density after continuous photoelectrocatalytic water oxidation reaction for 5 h, while the photocurrent density of the single-phase BiVO4 electrode drops sharply.

Claims

1. A preparation method of a PTFE-modified BiVO4 photoanode, characterized in that, Comprising: The BiVO4 electrode is immersed in a PTFE dispersion solution and then taken out, and then calcined to obtain the PTFE-modified BiVO4 photoanode; The concentration of the PTFE dispersion solution is 2-18%; The calcination temperature is 300-450 °C, the heating rate is 2-5 °C / min; the calcination time is 10-40 min; The immersion time of the BiVO4 electrode is 5-20 min.

2. The preparation method of the PTFE-modified BiVO4 photoanode according to claim 1, characterized in that, The preparation process of the BiVO4 electrode is as follows: (1) Using fluorine-doped tin oxide as the working electrode, Pt as the counter electrode, Ag / AgCl as the reference electrode, and a mixed solution of an aqueous solution containing bismuth nitrate and potassium iodide and an ethanol solution of p-benzoquinone as the electrolyte, electro-deposition is carried out at a potential of -0.1±0.02 V (vs Ag / AgCl) to obtain a bismuth iodide oxide electrode; (2) A dimethyl sulfoxide solution containing vanadyl acetylacetonate is dropped onto the bismuth iodide oxide electrode, and then calcined and washed to obtain the BiVO4 electrode.

3. The preparation method of the PTFE-modified BiVO4 photoanode according to claim 2, characterized in that, In step (2), the dimethyl sulfoxide solution containing vanadyl acetylacetonate is dropped onto the bismuth iodide oxide electrode so that the solution completely covers the surface of the bismuth iodide oxide electrode.

4. The preparation method of the PTFE-modified BiVO4 photoanode according to claim 2, characterized in that, In step (1), the electro-deposition time is 2-10 min; In the aqueous solution containing bismuth nitrate and potassium iodide, the concentration of bismuth nitrate is 0.03-0.05 mol / L, and the concentration of potassium iodide is 0.3-0.5 mol / L; In the dimethyl sulfoxide solution containing vanadyl acetylacetonate, the concentration of vanadyl acetylacetonate is 0.2-0.3 mol / L; In the electrolyte, the volume ratio of the aqueous solution containing bismuth nitrate and potassium iodide to the ethanol solution of p-benzoquinone is 1:(0.3-0.5).

5. A PTFE-modified BiVO4 photoanode, characterized in that, Prepared by the preparation method according to any one of claims 1-4.

6. An application of the PTFE-modified BiVO4 photoanode according to claim 5 in photocatalytic water oxidation to produce H2O2.

7. The application according to claim 6, characterized in that, In the process of photocatalytic water oxidation to produce H2O2, the PTFE-modified BiVO4 photoanode is used as the working electrode, the Pt electrode is used as the electrode, the Ag / AgCl electrode is used as the reference electrode, and a 1 mol / L NaHCO3 solution is used as the electrolyte, and the illumination source is a 300 W xenon lamp with an AM1.5 filter.

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