Bismuth titanate and bismuth vanadate compounded high-performance photoelectrode and preparation method thereof

Abstract

The invention discloses a bismuth titanate and bismuth vanadate compounded high-performance photoelectrode and a preparation method thereof, and belongs to the technical field of electrode materials. The bismuth titanate composite bismuth vanadate high-performance photoelectrode comprises the BiVO4 layer, the BiVO4-x layer, the Bi4Ti3O12 layer and the NiCoBi layer, the bismuth titanate layer serves as a hole transport layer, the surface state is passivated, transport of carriers is promoted, recombination of surface charges is reduced, and the performance of the electrode is greatly improved; the NiCoBi layer improves the photo-corrosion defect of the material, the catalytic ability of water decomposition is improved, and the stability is obviously improved; and meanwhile, a heterojunction is formed between the BiVO4 layer and the Bi4Ti3O12 layer, so that the separation efficiency of photon-generated carriers is enhanced, and the high-performance photoelectrode with high stability, high carrier separation efficiency and high surface catalytic oxygen production efficiency is finally obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and in particular relates to a high-performance photoelectrode of bismuth titanate composited with bismuth vanadate and a preparation method thereof. Background Art

[0002] As the global energy crisis and environmental pollution intensify, the efficient use of solar energy has become a core path to achieving a sustainable energy transition. Photoelectrochemical (PEC) water splitting technology, which directly utilizes solar energy to split water into hydrogen and oxygen, combines environmental friendliness with energy storage capabilities and is considered a key technology for addressing energy and environmental challenges. The principle of photoelectrochemistry is to generate electron-hole pairs in semiconductor materials through photoexcitation, then utilize charge separation and transfer to drive redox reactions, thereby converting light energy into chemical energy.

[0003] Among them, bismuth vanadate (BiVO4) is widely considered one of the most promising photoanode materials due to its suitable band gap (~2.4eV), excellent chemical stability, and visible light response characteristics. The conduction band position of BiVO4 is close to 0V vs. NHE, which can effectively promote proton reduction, while the valence band position (~2.5V vs. NHE) has strong oxidation ability, theoretically achieving up to 7.5mA cm -2 However, unmodified BiVO4 suffers from problems such as high photogenerated carrier recombination rate and slow surface oxygen evolution reaction (OER) kinetics, which seriously limit its practical application. Therefore, it is necessary to provide a convenient and efficient method to modify BiVO4 so that it has strong photogenerated carrier transport ability and good surface catalytic oxygen production efficiency. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a high-performance photoelectrode of bismuth titanate composite bismuth vanadate and a preparation method thereof.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] The present invention provides a high-performance photoelectrode of bismuth titanate composite bismuth vanadate, comprising a conductive substrate and a BiVO4 layer, a BiVO 4-x layer, Bi4Ti3O 12 layer and NiCoBi layer; wherein x refers to the number of oxygen atoms reduced on the surface of bismuth vanadate after photochemical etching, 0<x<4.

[0008] Furthermore, the BiVO 4-x The layer is obtained by photochemical etching of BiVO4.4-x The layer is rich in oxygen vacancies;

[0009] And / or, the Bi4Ti3O 12 The layer is composed of two-dimensional Bi4Ti3O 12 Nanosheet composition.

[0010] The present invention provides a method comprising a BiVO4 layer, a BiVO 4-x layer, Bi4Ti3O 12 High-performance photoelectrodes of bismuth titanate composite bismuth vanadate with NiCoBi layers, BiVO 4-x The layer increases the charge separation and regulates the energy band; Bi4Ti3O 12 The layer acts as a hole transport layer, passivating the surface state, promoting the transport of carriers, reducing the recombination of surface charges, and greatly improving the performance of the electrode; the NiCoBi layer improves the photocorrosion defects of the material and greatly improves the surface catalytic oxygen production efficiency; at the same time, the BiVO 4-x layer and Bi4Ti3O 12 A heterojunction is formed between the layers, which enhances the separation efficiency of photogenerated carriers, and ultimately obtains a high-performance photoelectrode with high stability, high carrier separation efficiency and high surface catalytic oxygen production efficiency.

[0011] The second technical solution of the present invention:

[0012] The present invention also provides a method for preparing the high-performance photoelectrode of bismuth titanate composite bismuth vanadate, comprising the following steps:

[0013] S1. Electrochemically depositing BiVO4 (bismuth vanadate) on a conductive substrate to form a BiVO4 layer to obtain a photoelectrode modified with a BiVO4 layer, referred to as a BiVO4 photoelectrode;

[0014] S2. Immerse the BiVO4 photoelectrode in a potassium borate solution containing anhydrous sulfurous acid and etch under light conditions to form BiVO on the surface of the BiVO4 layer. 4-x layer, and obtain BiVO 4-x Photoelectrodes;

[0015] S3. In the BiVO 4-x Bismuth titanate ethanol solution is deposited on the surface of the photoelectrode to form Bi4Ti3O 12 (bismuth titanate) layer, obtaining Bi4Ti3O 12 / BiVO 4-x Composite photoelectrode;

[0016] S4. Add nickel sulfate hexahydrate to potassium borate solution, stir evenly and then add cobalt nitrate hexahydrate, stir and dissolve to obtain a precursor solution; with the Bi4Ti3O 12 / BiVO4-x The composite photoelectrode is used as a working electrode, and the precursor solution is used as an electrolyte solution to perform electrochemical deposition to form a NiCoBi layer, thereby obtaining the high-performance photoelectrode of the bismuth titanate composite bismuth vanadate.

[0017] The present invention deposits BiVO4 on a conductive substrate to obtain a BiVO4 photoelectrode; then photochemically etches the BiVO4 photoelectrode to obtain a BiVO4 photoelectrode. 4-x Photoelectrode; then Bi4Ti3O 12 Loaded in BiVO 4-x The surface of the photoelectrode; finally, NiCoBi is electrodeposited to obtain a high-performance photoelectrode of bismuth titanate and bismuth vanadate. The operation is simple and safe, the materials are easily available, and large-scale production can be achieved.

[0018] Furthermore, in step S1, the preparation steps of the BiVO4 photoelectrode include:

[0019] a. Potassium iodide is dissolved in water, followed by the addition of bismuth nitrate pentahydrate and lactic acid, and the mixture is stirred uniformly. Concentrated nitric acid is added to adjust the pH to 1.6-1.8 to obtain solution A; p-benzoquinone is dissolved in ethanol to obtain solution B; solution A and solution B are mixed to obtain electrolyte A; a conductive substrate is immersed in electrolyte A and subjected to electrochemical deposition to obtain a conductive substrate having a BiOI thin film deposited thereon. Lactic acid is used as a buffer to more uniformly increase the pH at the electrode / electrolyte interface, thereby allowing BiIO crystals to grow more uniformly throughout the film;

[0020] b. Vanadyl acetylacetonate was dissolved in dimethyl sulfoxide to obtain a solution C; the solution C was dropwise coated on the conductive substrate having the BiOI film deposited thereon obtained in step a, and then annealed at 430 to 480°C, soaked in alkali, rinsed and dried to obtain a BiVO4 photoelectrode.

[0021] Exemplarily, the conductive substrate is conductive glass-doped fluorine tin oxide (FTO).

[0022] Furthermore, in step a, the molar ratio of p-benzoquinone, potassium iodide, bismuth nitrate pentahydrate and lactic acid is 0.046:0.4:0.015:0.03;

[0023] And / or, in step a, when a conductive substrate with a BiOI thin film deposited thereon is obtained, the electrochemical deposition method is a time-current curve method, the working electrode is a conductive substrate, the counter electrode is a platinum mesh, and the reference electrode is an Ag / AgCl electrode, and the specific steps are as follows: Step 1: the initial voltage is -0.35 V, the sampling interval is 0.1 s, the deposition time is 10 to 30 s, the rest time is 0 s, and the sensitivity is 1×10 -3A; Step 2: Initial voltage is -0.1 V, sampling interval is 0.1 s, deposition time is 1000-1200 s, static time is 0 s, sensitivity is 1×10 -3 A;

[0024] And / or, in step b, the ratio of dimethyl sulfoxide to vanadyl acetylacetonate is 2 mL:0.2 mol;

[0025] And / or, in step b, the dripping amount is 45 μL / cm 2 ;

[0026] And / or, in step b, the annealing treatment time is 2 hours.

[0027] Furthermore, in step a, the usage ratio of water, potassium iodide, bismuth nitrate pentahydrate and lactic acid is 25 mL: 0.4 mol: 0.015 mol: 0.03 mol; and / or the usage ratio of anhydrous ethanol and p-benzoquinone is 10 mL: 0.046 mol.

[0028] Furthermore, the concentration of the alkali solution is 1 mol / L. Exemplarily, the alkali solution is a NaOH solution.

[0029] Furthermore, the alkali solution soaking time is 20 to 50 minutes, and the excess V2O5 is removed by alkali solution soaking.

[0030] Furthermore, in step S2, the usage ratio of the potassium borate solution to the anhydrous sodium sulfite solution is 50 mL: 0.2 mol;

[0031] And / or, the concentration of the potassium borate solution is 1 mol / L and the pH value is 9.5;

[0032] And / or, the etching time under the illumination condition is 10 minutes.

[0033] Furthermore, in step S3, the preparation method of the bismuth titanate is: bismuth oxide, titanium dioxide, sodium chloride and potassium chloride are mixed in a molar ratio of 0.2:0.3:4:4, fully ground, calcined at 600-800° C. for 2 h, and then washed and dried to obtain bismuth titanate.

[0034] Furthermore, the preparation steps of the ethanol solution of bismuth titanate are: dissolving bismuth titanate in ethanol, ultrasonicating, and centrifuging to obtain a supernatant which is the ethanol solution of bismuth titanate.

[0035] Exemplarily, the ethanol solution of bismuth titanate is prepared by dissolving 50 mg of bismuth titanate in 50 mL of ethanol, ultrasonicating for 8 hours, and centrifuging at 3000 rpm for 5 minutes. The obtained supernatant is the ethanol solution of bismuth titanate.

[0036] Furthermore, in step S3, in the BiVO 4-x Bismuth titanate ethanol solution is deposited on the surface of the photoelectrode to form Bi4Ti3O 12 The steps of layering are: 4-x The photoelectrode was placed on a drying table, the temperature was set to 60 ° C, and the ethanol solution of bismuth titanate was dripped onto the BiVO 4-x After the surface of the photoelectrode is dry, add it again and repeat the addition 2 to 4 times.

[0037] Furthermore, in step S4, the dosage ratio of the potassium borate solution, nickel sulfate hexahydrate, and cobalt nitrate hexahydrate is 50 mL: 1 mmol: 0.5 mmol, the concentration of the potassium borate solution is 0.5 mol / L, and the pH value is 9.5;

[0038] And / or, the process parameters for forming the NiCoBi layer by electrochemical deposition are: initial voltage of 0 V, sampling interval of 0.1 s, deposition time of 20-30 s, rest time of 2 s, sensitivity of 1×10 -2 A, light intensity is 100 mW·cm -2 .

[0039] The third technical solution of the present invention:

[0040] The present invention also provides the use of a high-performance photoelectrode of bismuth titanate composite bismuth vanadate in the electrolysis of water to produce hydrogen and oxygen.

[0041] Compared with the prior art, the present invention has the following advantages and technical effects:

[0042] 1) The present invention uses a conductive substrate (such as FTO) as a substrate, deposits a BiOI film by an electrochemical method, and obtains a BiVO4 photoelectrode by calcining; and then obtains a BiVO4 photoelectrode by photochemical etching. 4-x photoelectrode; then by 4-x Bi4Ti3O loaded on the photoelectrode 12 Obtain Bi4Ti3O 12 / BiVO 4-x Photoelectrode; Finally, by 12 / BiVO 4-x NiCoBi was loaded on the surface of the photoelectrode by in situ photopolymerization to obtain NiCoBi / Bi4Ti3O 12 / BiVO 4-x Photoelectrodes are easy and safe to operate, and the materials are readily available, allowing for large-scale production.

[0043] 2) The present invention photochemically etches bismuth vanadate to increase charge separation and attach to BiVO 4-xThe bismuth titanate on the surface serves as a hole transport layer, which simultaneously achieves the purpose of improving the performance of the bismuth vanadate photoelectrode and protecting the bismuth vanadate. NiCoBi improves the photocorrosion defects of the material, significantly improving the stability of the material, and ultimately obtaining a high-performance photoelectrode with high carrier separation efficiency and high surface catalytic oxygen production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0045] Figure 1 This is a SEM image of the BiVO4 photoelectrode obtained in step S1 of Example 1;

[0046] Figure 2 NiCoBi / Bi4Ti3O prepared in Example 1 12 / BiVO 4-x SEM image of the composite photoelectrode;

[0047] Figure 3 The BiVO4 photoelectrode obtained in step S1 of Example 1 and the BiVO4 photoelectrode obtained in step S2 are 4-x Composite photoelectrode, Bi4Ti3O obtained in step S3 12 / BiVO 4-x Composite photoelectrode and NiCoBi / Bi4Ti3O in step S4 12 / BiVO 4-x XRD pattern of the composite photoelectrode;

[0048] Figure 4 NiCoBi / Bi4Ti3O prepared in Example 1 12 / BiVO 4-x TEM image of the composite photoelectrode;

[0049] Figure 5 The BiVO4 photoelectrode obtained in step S1 of Example 1 and the NiCoBi / Bi4Ti3O in step S4 12 / BiVO 4-x Photoluminescence spectrum of the composite photoelectrode;

[0050] Figure 6 The BiVO4 photoelectrode obtained in step S1 of Example 1 and the NiCoBi / Bi4Ti3O in step S4 12 / BiVO 4-x Open circuit potential diagram of the composite photoelectrode;

[0051] Figure 7The BiVO4 photoelectrode obtained in step S1 of Example 1 and the BiVO4 photoelectrode obtained in step S2 are prepared in the presence of a hole trap. 4-x Composite photoelectrode, Bi4Ti3O obtained in step S3 12 / BiVO 4-x Composite photoelectrode and NiCoBi / Bi4Ti3O in step S4 12 / BiVO 4-x Linear sweep voltammetry curve of the composite photoelectrode;

[0052] Figure 8 The BiVO4 photoelectrode obtained in step S1 of Example 1 and the BiVO4 photoelectrode obtained in step S2 are obtained without a hole capture agent. 4-x Composite photoelectrode, Bi4Ti3O obtained in step S3 12 / BiVO 4-x Composite photoelectrode and NiCoBi / Bi4Ti3O in step S4 12 / BiVO 4-x Linear sweep voltammogram of the composite photoelectrode. DETAILED DESCRIPTION

[0053] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0054] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0055] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0056] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0057] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0058] The embodiment of the present invention provides a high-performance photoelectrode of bismuth titanate composite bismuth vanadate, comprising a conductive substrate and a BiVO4 layer, a BiVO 4-x layer, Bi4Ti3O 12 layer and NiCoBi layer; wherein x refers to the number of oxygen atoms reduced on the surface of bismuth vanadate after photochemical etching, 0<x<4;

[0059] Among them, BiVO 4-x The layer is obtained by photochemical etching of BiVO4. 4-x The layer is rich in oxygen vacancies; Bi4Ti3O 12 The layer is composed of two-dimensional Bi4Ti3O 12 Nanosheet composition.

[0060] The present invention provides a method comprising a BiVO4 layer, a BiVO 4-x layer, Bi4Ti3O 12 High-performance photoelectrodes of bismuth titanate composite bismuth vanadate with NiCoBi layers, BiVO 4-x The layer increases the charge separation and regulates the energy band; Bi4Ti3O 12 The layer acts as a hole transport layer, passivating the surface state, promoting the transport of carriers, reducing the recombination of surface charges, and greatly improving the performance of the electrode; the NiCoBi layer improves the photocorrosion defects of the material and greatly improves the surface catalytic oxygen production efficiency; at the same time, the BiVO 4-x layer and Bi4Ti3O 12 A heterojunction is formed between the layers, which enhances the separation efficiency of photogenerated carriers, and ultimately obtains a high-performance photoelectrode with high stability, high carrier separation efficiency and high surface catalytic oxygen production efficiency.

[0061] The embodiment of the present invention further provides a method for preparing a high-performance photoelectrode of bismuth titanate composite bismuth vanadate, comprising the following steps:

[0062] S1. Electrochemically depositing BiVO4 (bismuth vanadate) on a conductive substrate to form a BiVO4 layer to obtain a photoelectrode modified with a BiVO4 layer, referred to as a BiVO4 photoelectrode;

[0063] S2. Immerse the BiVO4 photoelectrode in a potassium borate solution containing anhydrous sulfurous acid and etch it under light conditions to form BiVO on the surface of the BiVO4 layer. 4-x layer, and obtain BiVO 4-x Photoelectrodes;

[0064] S3. In BiVO 4-x Bismuth titanate ethanol solution is deposited on the surface of the photoelectrode to form Bi4Ti3O 12 (bismuth titanate) layer, obtaining Bi4Ti3O 12 / BiVO 4-x Composite photoelectrode;

[0065] S4. Add nickel sulfate hexahydrate to potassium borate solution, stir evenly, then add cobalt nitrate hexahydrate, stir and dissolve to obtain a precursor solution; Bi4Ti3O 12 / BiVO 4-x The composite photoelectrode is used as a working electrode, and a precursor solution is used as an electrolyte solution to perform electrochemical deposition to form a NiCoBi layer, thereby obtaining a high-performance photoelectrode of bismuth titanate composite bismuth vanadate.

[0066] The present invention deposits BiVO4 on a conductive substrate to obtain a BiVO4 photoelectrode; then photochemically etches the BiVO4 photoelectrode to obtain a BiVO4 photoelectrode. 4-x Photoelectrode; then Bi4Ti3O 12 Loaded in BiVO 4-x The surface of the photoelectrode; finally, NiCoBi is electrodeposited to obtain a high-performance photoelectrode of bismuth titanate and bismuth vanadate. The operation is simple and safe, the materials are easily available, and large-scale production can be achieved.

[0067] In an embodiment of the present invention, the steps of preparing the BiVO4 photoelectrode include:

[0068] a. Potassium iodide is dissolved in water, followed by the addition of bismuth nitrate pentahydrate and lactic acid, and the mixture is stirred uniformly. Concentrated nitric acid is added to adjust the pH to 1.6-1.8 to obtain solution A. p-Benzoquinone is dissolved in ethanol to obtain solution B. Solutions A and B are mixed to obtain electrolyte A. A conductive substrate is immersed in electrolyte A and subjected to electrochemical deposition to obtain a conductive substrate with a BiOI thin film deposited thereon. Lactic acid is used as a buffer to more uniformly increase the pH at the electrode / electrolyte interface, thereby enabling more uniform growth of BiIO crystals throughout the film.

[0069] b. Vanadyl acetylacetonate was dissolved in dimethyl sulfoxide to obtain a solution C; the solution C was dropwise coated on the conductive substrate on which the BiOI film was deposited in step a, and then annealed at 430 to 480°C, soaked in an alkali solution, rinsed and dried to obtain a BiVO4 photoelectrode.

[0070] In an embodiment of the present invention, the conductive substrate is conductive glass-doped fluorine-tin oxide (FTO).

[0071] In an embodiment of the present invention, in step S1, the molar ratio of p-benzoquinone, potassium iodide, bismuth nitrate pentahydrate and lactic acid is 0.046:0.4:0.015:0.03;

[0072] When a conductive substrate with a BiOI thin film deposited thereon is obtained, the electrochemical deposition method is a time-current curve method, the working electrode is a conductive substrate, the counter electrode is a platinum mesh, and the reference electrode is an Ag / AgCl (silver / silver chloride electrode). The specific steps are as follows: Step 1: the initial voltage is -0.35 V, the sampling interval is 0.1 s, the deposition time is 10 to 30 s, the rest time is 0 s, and the sensitivity is 1×10 -3 A; Step 2: Initial voltage is -0.1 V, sampling interval is 0.1 s, deposition time is 1000-1200 s, static time is 0 s, sensitivity is 1×10 -3 A;

[0073] The ratio of dimethyl sulfoxide and vanadyl acetylacetonate was 2 mL: 0.2 mol;

[0074] The dripping volume is 45 μL / cm 2 ;

[0075] The annealing time is 2 h.

[0076] In an embodiment of the present invention, in step S1, the usage ratio of water, potassium iodide, bismuth nitrate pentahydrate and lactic acid is 25 mL: 0.4 mol: 0.015 mol: 0.03 mol; and / or the usage ratio of anhydrous ethanol and p-benzoquinone is 10 mL: 0.046 mol.

[0077] In an embodiment of the present invention, the concentration of the alkali solution is 1 mol / L. Exemplarily, the alkali solution is a NaOH solution.

[0078] In an embodiment of the present invention, the alkali solution soaking time is 20 to 50 minutes, and the excess V2O5 is removed by alkali solution soaking.

[0079] In an embodiment of the present invention, in step S2, the ratio of potassium borate solution to anhydrous sodium sulfite solution is 50 mL: 0.2 mol;

[0080] The concentration of potassium borate solution is 1 mol / L and the pH value is 9.5;

[0081] The etching time under light conditions is 10 minutes.

[0082] In an embodiment of the present invention, in step S3, the preparation method of bismuth titanate is: bismuth oxide, titanium dioxide, sodium chloride and potassium chloride are mixed in a molar ratio of 0.2:0.3:4:4, fully ground, calcined at 600-800°C for 2h, and then washed and dried to obtain bismuth titanate.

[0083] In an embodiment of the present invention, the ethanol solution of bismuth titanate is prepared by dissolving bismuth titanate in ethanol, sonicating, and centrifuging to obtain a supernatant, which is the ethanol solution of bismuth titanate. Exemplarily, the ethanol solution of bismuth titanate is prepared by dissolving 50 mg of bismuth titanate in 50 mL of ethanol, sonicating for 8 hours, and centrifuging at 3000 rpm for 5 minutes. The supernatant obtained is the ethanol solution of bismuth titanate.

[0084] In the embodiment of the present invention, in step S3, the BiVO 4-x Bismuth titanate ethanol solution is deposited on the surface of the photoelectrode to form Bi4Ti3O 12 The steps of the layer are: BiVO 4-x The photoelectrode was placed on a drying table, the temperature was set at 60°C, and the ethanol solution of bismuth titanate was dripped onto the BiVO 4-x After the surface of the photoelectrode is dry, add it again and repeat the addition 2 to 4 times.

[0085] In an embodiment of the present invention, in step S4, the ratio of potassium borate solution, nickel sulfate hexahydrate and cobalt nitrate hexahydrate is 50 mL: 1 mmol: 0.5 mmol, the concentration of potassium borate solution is 0.5 mol / L, and the pH value is 9.5;

[0086] The process parameters for electrochemical deposition of NiCoBi layers are as follows: initial voltage 0 V, sampling interval 0.1 s, deposition time 20–30 s, rest time 0 s, and sensitivity 1 × 10 -2 A, light intensity is 100 mW·cm -2 .

[0087] The high-performance photoelectrode of bismuth titanate and bismuth vanadate provided in the embodiment of the present invention can be used for electrolysis of water to produce hydrogen and oxygen.

[0088] The term "tertiary water" refers to a type of experimental water whose conductivity does not exceed 0.50mS / m (i.e. 5.0μS / cm) at 25°C and whose resistivity is not less than 0.2MΩ·cm. It is mainly used for general chemical experiments (such as preparing common reagents, dilution solutions, and buffer solutions), equipment cleaning (such as rinsing spectrophotometer cuvettes and cleaning centrifuge rotors), and environmental cleaning (wiping laboratory tables and fume hoods).

[0089] The term "ultrapure water" refers to water with a resistivity of 18 MΩ·cm (25°C) or close to the limit of 18.3 MΩ·cm (25°C).

[0090] Unless otherwise specified, the room temperature in the present invention is 25±2°C.

[0091] All raw materials used in the examples of the present invention were purchased from commercial sources.

[0092] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0093] The technical solution of the present invention is further illustrated by the following examples.

[0094] Example 1

[0095] This embodiment provides a high-performance photoelectrode of bismuth titanate composite bismuth vanadate, which is composed of FTO and a BiVO4 layer, a BiVO 4-x layer, Bi4Ti3O 12 layer and NiCoBi layer;

[0096] The preparation method of the high-performance photoelectrode of bismuth titanate composite bismuth vanadate comprises the following steps:

[0097] S1. Take a 20cm×15cm piece of FTO conductive glass and cut it into 2cm×3cm specifications using a glass cutting table. Then, ultrasonically wash it with acetone, ethanol and grade tertiary water for 15 minutes each. After washing, put it in an oven to dry to obtain pretreated FTO conductive glass; take 25mL of ultrapure water and place it in a 50mL beaker, add 0.4mol potassium iodide (KI), 0.015mol bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.03mol lactic acid (C3H6O3), stir it thoroughly until the solution is clear and transparent, then add concentrated nitric acid (concentration of 8mol / L) to adjust the pH of the solution to 1.8, and stir it thoroughly until the solution is clear and transparent. Bright, to obtain solution A; take 10mL of anhydrous ethanol (C2H6O) and place it in a 25mL beaker, add 0.046mol of p-benzoquinone, and ultrasonicate for 5min until the precipitate is completely dissolved to obtain solution B; the above-mentioned solution A and solution B are mixed, and vigorously stirred (speed is 500rpm) to fully dissolve them to obtain electrolyte A, and the obtained electrolyte A is used as the electrolyte solution, the above-mentioned pretreated FTO conductive glass is used as the working electrode, the platinum mesh is used as the counter electrode, and the silver / silver chloride electrode is used as the reference electrode. The electrodeposition is carried out by the time-current curve method, and the electrodeposition conditions are: initial voltage -0.35V, sampling interval time 0.1s, deposition time 20s, rest time 0s, sensitivity 1×10 -3 A. After the electrodeposition was completed, the following conditions were adjusted to continue the electrodeposition: initial voltage -0.1 V, sampling interval 0.1 s, deposition time 1020 s, rest time 0 s, sensitivity 1 × 10 -3 A. After the electrodeposition is completed, rinse with ultrapure water and dry to obtain FTO conductive glass with BiOI film deposited on it. Then cut it into 2cm×1cm specifications using a glass cutting table and place it on a corundum sheet with a distance of 2mm between the sheets. Take 2mL of dimethyl sulfoxide (DMSO), add 0.2mol of acetylacetonatovanadium, and stir vigorously (at a speed of 500rpm) until no obvious precipitation is obtained to obtain solution C; use a 100μL pipette to take 45μL of solution C and drop it on the surface of the BiOI film (drop volume 45μL / cm 2 ), then placing the corundum sheet in a muffle furnace, heating it to 450°C at a heating rate of 2°C / min, calcining it for 2 hours, and cooling it to room temperature to obtain fired FTO conductive glass; placing the fired FTO conductive glass in a watch glass, soaking it in 1 mol / L NaOH solution for 20 minutes, rinsing it with grade 3 water, and drying it to obtain a BiVO4 photoelectrode.

[0098] S2. Take 50mL of ultrapure water and place it in a 100mL beaker. Add 1mol of boric acid (H3BO3) and 1mol of potassium chloride (KCl), stir thoroughly, add potassium hydroxide (KOH) to adjust the pH of the solution to 9.5, then add 0.2mol of anhydrous sodium sulfite (Na2SO3), stir thoroughly until the solution is clear and transparent, and obtain solution C; immerse the BiVO4 photoelectrode obtained in step S1 in solution C, illuminate the BiVO4 photoelectrode with a xenon lamp (AM1.5G) for 10 minutes, rinse with ultrapure water, and dry to obtain BiVO 4-x Photoelectrode.

[0099] S3. Take 0.02 mol of bismuth oxide (Bi2O3), 0.03 mol of titanium dioxide (TiO2), 0.4 mol of sodium chloride (NaCl) and 0.4 mol of potassium chloride (KCl), mix them, add them into a mortar and grind them thoroughly, then calcine the mixed powder at 740℃ for 2h, wash the resulting product with deionized water 3 times, then wash it with ethanol 3 times, and dry it at 80℃ for 12h to obtain bismuth titanate powder. Take 50 mg of bismuth titanate powder, mix it with 50 mL of ethanol, ultrasonically crush it for 8h, and centrifuge it at 1500 rpm for 5min to obtain mixed solution A; add BiVO 4-x The photoelectrode was placed on the heating plate of the drying table, the temperature was set to 60℃, and 100μl of mixed solution A was transferred with a 100μL pipette and dropped onto the BiVO 4-x The film surface was dried and then added again, and the step was repeated twice to obtain Bi4Ti3O 12 / BiVO 4-x Composite photoelectrode.

[0100] S4. Take 50 mL of 0.5 mol / L potassium borate solution (pH = 9.5), add 1 mmol of nickel sulfate hexahydrate (NiSO4·6H2O), stir until the solution is clear and transparent, then add 0.5 mmol of cobalt nitrate hexahydrate (Co(NO3)2·6H2O), stir until the solution is clear and transparent, to obtain electrolyte B; electrolyte B is used as the electrolyte solution, and the Bi4Ti3O 12 / BiVO 4-x The composite photoelectrode was used as the working electrode, the platinum mesh was used as the counter electrode, and the silver / silver chloride electrode was used as the reference electrode. The electrodeposition was carried out using the time-current curve method. The back irradiation of Bi4Ti3O 12 / BiVO 4-x The electrodeposition process conditions of the composite photoelectrode were as follows: initial potential 0 V, deposition temperature at room temperature, running time 15 s, sampling interval 0.1 s, rest time 2 s, and sensitivity 1 × 10 -2 A, light intensity is 100 mW·cm -2 After the photoelectrodeposition, the working electrode was rinsed with ultrapure water and dried to obtain NiCoBi / Bi4Ti3O 12 / BiVO 4-x The composite photoelectrode is a high-performance photoelectrode of bismuth titanate and bismuth vanadate.

[0101] The SEM image of the BiVO4 photoelectrode obtained in step S1 of this embodiment is as follows: Figure 1 As shown, it can be seen that the microscopic morphology of the BiVO4 photoelectrode is worm-like nanoparticles.

[0102] The NiCoBi / Bi4Ti3O obtained in this example 12 / BiVO 4-x The SEM image of the composite photoelectrode is shown in Figure 2 As shown, it can be seen that compared with BiVO4 photoelectrode, NiCoBi / Bi4Ti3O 12 / BiVO 4-x The composite photoelectrode showed a large range of fine particle surfaces on the surface of the nanoparticles, indicating that NiBi and Na-CuBi2O4 had been deposited on the BiVO4 photoelectrode.

[0103] The BiVO4 photoelectrode obtained in step S1 of this embodiment and the BiVO4 photoelectrode obtained in step S2 4-x Composite photoelectrode, Bi4Ti3O obtained in step S3 12 / BiVO 4-x Composite photoelectrode and NiCoBi / Bi4Ti3O in step S4 12 / BiVO 4-x The XRD pattern of the composite photoelectrode is shown in Figure 3As shown in the figure, it can be seen that the diffraction peaks of the four BiVO4-based samples all correspond to monoclinic BiVO4 (PDF#75-1866), and the narrow and sharp peaks indicate good crystallinity, which preliminarily proves that NiCoBi / Bi4Ti3O 12 / BiVO 4-x Successful preparation of composite photoelectrode.

[0104] The NiCoBi / Bi4Ti3O obtained in this example 12 / BiVO 4-x TEM image of the composite photoelectrode Figure 4 As shown, it can be seen that there is a layer of crystalline material Bi4Ti3O on the surface of bismuth vanadate nanoparticles 12 , indicating that Bi4Ti3O 12 is attached to BiVO 4-x On the layer, a layer of amorphous material NiCoBi can be seen, and it is attached to Bi4Ti3O 12 and BiVO 4-x layer (it should be noted that after photolithography, BiVO 4-x The layer is just a very thin layer on the surface of the BiVO4 layer, which is difficult to show in the TEM image, so the TEM image is BiVO4).

[0105] The BiVO4 photoelectrode obtained in step S1 of this embodiment and the NiCoBi / Bi4Ti3O 12 / BiVO 4-x The steady-state photoluminescence spectra of the composite photoelectrodes when used as photoanodes are shown in Figure 2. Figure 5 As shown in Figure 2, it can be seen that the peak at 730nm is a characteristic peak generated by the emission wavelength and dual frequency, while the emission peak at 510nm is generated by inter-band conversion. 12 / BiVO 4-x The fluorescence peak intensity of the photoanode is greatly reduced, indicating its excellent ability to separate photogenerated electrons and holes.

[0106] The BiVO4 photoelectrode obtained in step S1 of this embodiment and the NiCoBi / Bi4Ti3O 12 / BiVO 4-x The open circuit potential of the composite photoelectrode is shown in Figure 2. Figure 6 As shown in the figure, it can be seen that the photovoltage of unmodified BiVO4 is 0.2V, while that of NiCoBi / Bi4Ti3O 12 / BiVO 4-x The composite photoelectrode has a larger photovoltage of 0.29 V, which means a more favorable driving force for water oxidation.

[0107] In the presence of a hole capture agent (anhydrous sodium sulfite, the same below), the linear sweep voltammetry curves of each photoelectrode were tested (anhydrous sodium sulfite can immediately react with the photogenerated holes of bismuth vanadate, which can more directly reflect the charge separation efficiency of bismuth vanadate). The specific method is as follows: 0.5 mol / L boric acid solution is used as the electrolyte solution, 0.5 mol / L anhydrous sodium sulfite is added, each photoelectrode is used as the working electrode, a platinum mesh is used as the counter electrode, and a silver / silver chloride electrode is used as the reference electrode. The voltage range is -0.6 V to 0.7 V, the sampling interval is 0.1 s, the static time is 0 s, and the sensitivity is 1×10 -3 A, linear sweep voltammetry test. In the presence of hole trapping agent, the BiVO4 photoelectrode obtained in step S1 of this embodiment and the BiVO4 photoelectrode obtained in step S2 are tested. 4-x Composite photoelectrode, Bi4Ti3O obtained in step S3 12 / BiVO 4-x Composite photoelectrode and NiCoBi / Bi4Ti3O in step S4 12 / BiVO 4-x The linear sweep voltammetry curve of the composite photoelectrode is shown in Figure 7 As shown in the figure, it can be seen that under the test conditions with hole capture agent, compared with BiVO4, the BiVO4 after photolithography is 4-x It can improve the current density at low bias, and then load Bi4Ti3O 12 After NiCoBi, in the entire voltage range NiCoBi / Bi4Ti3O 12 / BiVO 4-x The photocurrent density of the composite photoelectrode was significantly increased, reaching 5.8 mA / cm at 1.23 V (vs. RHE). 2 .

[0108] In the absence of hole trapping agents, the linear sweep voltammetry curves of each photoelectrode were tested. The specific method was as follows: 0.5 mol / L boric acid solution was used as the electrolyte solution, each photoelectrode was used as the working electrode, a platinum mesh was used as the counter electrode, and a silver / silver chloride electrode was used as the reference electrode. The voltage range was -0.6 V to 0.7 V, the sampling interval was 0.1 s, the rest time was 0 s, and the sensitivity was 1×10 -3 A, linear sweep voltammetry test. In the absence of hole capture agent, the BiVO4 photoelectrode obtained in step S1 of this embodiment and the BiVO4 photoelectrode obtained in step S2 are 4-x Composite photoelectrode, Bi4Ti3O obtained in step S3 12 / BiVO 4-x Composite photoelectrode and NiCoBi / Bi4Ti3O in step S4 12 / BiVO 4-x The linear sweep voltammetry curve of the composite photoelectrode is shown in Figure 8 As shown in the figure, it can be seen that under the test conditions without hole capture agent, Bi4Ti3O 12 After the final loading of NiCoBi, Bi4Ti3O 12 / BiVO 4-x The photocurrent density of the composite photoelectrode has been significantly improved, NiCoBi / Bi4Ti3O 12 / BiVO 4-x At 1.23 V (vs. RHE), the photocurrent density reached 5.6 mA / cm 2 , and obtain powerful water decomposition ability.

[0109] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-performance photoelectrode of bismuth titanate and bismuth vanadate, characterized in that: It includes a conductive substrate and a BiVO4 layer, a BiVO 4-x layer, Bi4Ti3O 12 layer and NiCoBi layer; wherein x refers to the number of oxygen atoms reduced on the surface of bismuth vanadate after photochemical etching, 0<x<4.

2. The high-performance photoelectrode of bismuth titanate and bismuth vanadate according to claim 1, characterized in that: The BiVO 4-x The layer is obtained by photochemical etching of BiVO4. 4-x The layer is rich in oxygen vacancies; And / or, the Bi4Ti3O 12 The layer is composed of two-dimensional Bi4Ti3O 12 Nanosheet composition.

3. A method for preparing a high-performance photoelectrode of bismuth titanate and bismuth vanadate according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Electrochemically depositing BiVO4 on a conductive substrate to form a BiVO4 layer to obtain a photoelectrode modified with the BiVO4 layer, denoted as a BiVO4 photoelectrode; S2. Immerse the BiVO4 photoelectrode in a potassium borate solution containing anhydrous sulfurous acid and etch under light conditions to form BiVO on the surface of the BiVO4 layer. 4-x layer, and obtain BiVO 4-x Photoelectrodes; S3. In the BiVO 4-x Bismuth titanate ethanol solution is deposited on the surface of the photoelectrode to form Bi4Ti3O 12 layer, and obtain Bi4Ti3O 12 / BiVO 4-x Composite photoelectrode; S4. Add nickel sulfate hexahydrate to potassium borate solution, stir evenly and then add cobalt nitrate hexahydrate, stir and dissolve to obtain a precursor solution; with the Bi4Ti3O 12 / BiVO 4-x The composite photoelectrode is used as a working electrode, and the precursor solution is used as an electrolyte solution to perform electrochemical deposition to form a NiCoBi layer, thereby obtaining the high-performance photoelectrode of the bismuth titanate composite bismuth vanadate.

4. The method for preparing a high-performance photoelectrode of bismuth titanate and bismuth vanadate according to claim 3, characterized in that: In step S1, the preparation steps of the BiVO4 photoelectrode include: a. Potassium iodide is dissolved in water, and then bismuth nitrate pentahydrate and lactic acid are added, stirred evenly, and concentrated nitric acid is added to adjust the pH to 1.6 to 1.8 to obtain solution A; p-benzoquinone is dissolved in ethanol to obtain solution B; the solutions A and B are mixed to obtain electrolyte A; a conductive substrate is immersed in the electrolyte A, and subjected to electrochemical deposition to obtain a conductive substrate having a BiOI thin film deposited thereon; b. Vanadyl acetylacetonate was dissolved in dimethyl sulfoxide to obtain a solution C; the solution C was dropwise coated on the conductive substrate having the BiOI film deposited thereon obtained in step a, and then annealed at 430 to 480°C, soaked in alkali, rinsed and dried to obtain a BiVO4 photoelectrode.

5. The method for preparing a high-performance photoelectrode of bismuth titanate and bismuth vanadate according to claim 4, characterized in that: In step a, the molar ratio of p-benzoquinone, potassium iodide, bismuth nitrate pentahydrate and lactic acid is 0.046:0.4:0.015:0.03; And / or, in step a, when obtaining the conductive substrate on which the BiOI thin film is deposited, the electrochemical deposition method is a time-current curve method; And / or, in step b, the ratio of dimethyl sulfoxide to vanadyl acetylacetonate is 2 mL:0.2 mol; And / or, in step b, the dripping amount is 45 μL / cm 2 ; And / or, in step b, the annealing treatment time is 2 hours.

6. The method for preparing a high-performance photoelectrode of bismuth titanate and bismuth vanadate according to claim 3, characterized in that: In step S2, the usage ratio of the potassium borate solution to the anhydrous sodium sulfite solution is 50 mL: 0.2 mol; And / or, the concentration of the potassium borate solution is 1 mol / L and the pH value is 9.5; And / or, the etching time under the illumination condition is 10 minutes.

7. The method for preparing a high-performance photoelectrode of bismuth titanate and bismuth vanadate according to claim 3, characterized in that: In step S3, the preparation method of the bismuth titanate is: bismuth oxide, titanium dioxide, sodium chloride and potassium chloride are mixed in a molar ratio of 0.2:0.3:4:4, fully ground, calcined at 600-800° C. for 2 hours, and then washed and dried to obtain bismuth titanate.

8. The method for preparing a high-performance photoelectrode of bismuth titanate and bismuth vanadate according to claim 3, characterized in that: In step S3, the BiVO 4-x Bismuth titanate ethanol solution is deposited on the surface of the photoelectrode to form Bi4Ti3O 12 The steps of layering are: 4-x The photoelectrode was placed on a drying table, the temperature was set to 60 ° C, and the ethanol solution of bismuth titanate was dripped onto the BiVO 4-x After the surface of the photoelectrode is dry, add it again and repeat the addition 2 to 4 times.

9. The method for preparing a high-performance photoelectrode of bismuth titanate and bismuth vanadate according to claim 3, characterized in that: In step S4, the ratio of the potassium borate solution, nickel sulfate hexahydrate, and cobalt nitrate hexahydrate is 50 mL: 1 mmol: 0.5 mmol; the concentration of the potassium borate solution is 0.5 mol / L, and the pH value is 9.5; And / or, the process parameters for forming the NiCoBi layer by electrochemical deposition are: initial voltage of 0 V, sampling interval of 0.1 s, deposition time of 20-30 s, rest time of 2 s, sensitivity of 1×10 -2 A, light intensity is 100 mW·cm -2 .

10. Use of the high-performance photoelectrode of bismuth titanate and bismuth vanadate as claimed in any one of claims 1 to 2 in the electrolysis of water to produce hydrogen and oxygen.

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