A composite photoelectrode and its preparation method and application

Abstract

The present invention discloses a composite photoelectrode, a preparation method, and an application thereof, belonging to the technical field of photoelectrochemical analysis. Specifically, a BVO photoelectrode is used as a working electrode, a platinum mesh is used as a counter electrode, an Hg / HgO electrode is used as a reference electrode, and a nickel sulfate hexahydrate solution is used as an electrolyte. Photoelectrodeposition is performed on the BVO photoelectrode to obtain a BVO / B:NiOOH photoelectrode. The present invention also discloses a composite photoelectrode prepared by the above preparation method and its application in photoelectrocatalytic water decomposition. In the present invention, B:NiOOH is deposited on the surface of the BVO photoelectrode by photoelectrodeposition, which significantly improves the photocorrosion defects of bismuth vanadate itself and significantly improves its stability. The preparation method provided by the present invention is simple and safe to operate, and the materials are readily available, which can achieve large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectrochemical analysis, and in particular relates to a composite photoelectrode and a preparation method and application thereof. Background Art

[0002] Photoelectrocatalytic water splitting is a technology that uses a photoelectrocatalyst to split water into hydrogen and oxygen. Photoelectrocatalytic technology can achieve efficient conversion of renewable energy, reduce dependence on fossil fuels, and thus reduce carbon dioxide emissions. Producing hydrogen through photoelectrocatalytic water splitting can replace traditional fossil fuels, reducing carbon dioxide emissions at the source. The hydrogen combustion product is water, which does not produce greenhouse gases.

[0003] With the transformation of the global energy structure and the increasing emphasis on environmental protection, the research and development of photoelectrochemical water splitting to produce hydrogen has become a hot topic in current scientific research. As a photoanode material, BiVO4 plays a key role in photoelectrochemical water splitting. BiVO4 is a semiconductor material with a narrow band gap (2.4-2.5 eV) and a deep valence band edge, which can achieve water oxidation under visible light irradiation. This makes BiVO4 an ideal photoanode material for photoelectrochemical water splitting to produce hydrogen. However, the BiVO4 photoanode has poor charge transport properties and a short diffusion length of photogenerated carriers, resulting in severe charge recombination and slow water oxidation kinetics, which limits its performance.

[0004] Therefore, how to modify BiVO4 through a simple and convenient method to improve the transport of photogenerated carriers and the actual water decomposition performance while improving stability is a technical problem that technicians in this field urgently need to solve. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a composite photoelectrode and a preparation method and application thereof.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] A method for preparing a composite photoelectrode comprises the following steps: using a BVO photoelectrode as a working electrode, a platinum mesh as a counter electrode, a Hg / HgO electrode as a reference electrode, and a nickel sulfate hexahydrate solution as an electrolyte; performing photoelectrochemical deposition on the BVO photoelectrode to obtain a BVO / B:NiOOH photoelectrode.

[0008] Beneficial Effects: The electrolyte in the present invention is alkaline. Since the service life of the Ag / AgCl reference electrode is greatly reduced in alkaline environments, the present invention selects Hg / HgO, which is suitable for alkaline environments, as the reference electrode. Compared with most single-layer composite photoanodes, the photocurrent density of the BVO / B:NiOOH photoelectrode provided by the present invention can reach 4.15 mA cm -2 , while the photocurrent density of BVO is 1.86 mA cm -2 The photocurrent density of the composite photoelectrode obtained in the present invention is 2.23 times that of the BVO photoelectrode, and in terms of stability, the BVO / B:NiOOH obtained in the present invention has a certain recovery on the basis of maintaining stability.

[0009] Preferably, the potential of the photodeposition is -0.45 V, the operation time is 5 min, the sampling interval is 0.1 s, the standing time is 2 s, and the sensitivity is 1×10 -5 A, light intensity is 100 mW cm -2 .

[0010] Preferably, the deposition temperature of the photoelectric deposition is 15-30°C, which is room temperature.

[0011] Beneficial effects: During the photoelectric deposition process of the present invention, if the potential is higher than the above-mentioned potential, the reaction is too fast and the deposition amount of B:NiOOH cannot be controlled; if the potential is lower than the above-mentioned potential, the substrate BiVO4 of the material itself is prone to oxidation and reduction; if the time is higher than the above-mentioned time, the deposition amount of B:NiOOH is large, which is incompatible with the conductivity of the material itself; if the time is lower than the above-mentioned time, the deposition amount of B:NiOOH is small, and the material performance cannot be fully stimulated.

[0012] Preferably, the BVO photoelectrode is frontally irradiated during the photoelectric deposition process.

[0013] Preferably, the electrolyte is obtained by dissolving nickel sulfate hexahydrate in potassium borate buffer solution.

[0014] Preferably, the concentration of nickel sulfate hexahydrate in the electrolyte is 1 mmol / L;

[0015] The concentration of the potassium borate buffer solution is 0.5 mol / L, and the pH value is 9.5.

[0016] Preferably, the method for preparing the BVO photoelectrode comprises the following steps:

[0017] The time-current curve method was selected to carry out electrodeposition using FTO as the working electrode, a platinum mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode to obtain a BiOI thin film. A DMSO solution of vanadium acetylacetonate was evenly dripped on the film, the film was calcined, and then immersed in a NaOH solution to obtain the BVO photoelectrode.

[0018] Preferably, the electroplating electrolyte is obtained by mixing and dissolving a nitric acid solution of potassium iodide and bismuth nitrate pentahydrate with an ethanol solution of p-benzoquinone.

[0019] More preferably, the method for preparing the electrolytic solution for electrodeposition comprises the following steps:

[0020] Take 25 ml of nitric acid solution with a pH of 1.65-1.75, add 0.4 mol / L potassium iodide (KI) and 0.04 mol / L bismuth nitrate pentahydrate (Bi(NO3)3·5H2O), and stir vigorously until the solution is clear and transparent to obtain solution A; take 10 ml of ethanol and place it in another beaker, add 0.23 mol / L p-benzoquinone, and stir vigorously until the precipitate is completely dissolved to obtain solution B; mix the solution A and solution B and stir vigorously to fully dissolve them, thereby obtaining the electrolyte for the electrodeposition.

[0021] Preferably, the initial voltage of the electrodeposition is -0.1 V, the sampling interval is 0.1 s, the deposition time is 180 s, the standing time is 2 s, and the sensitivity is 1×10 -3 A.

[0022] Preferably, the concentration of vanadyl acetylacetonate in the DMSO solution of vanadyl acetylacetonate is 0.2 mol / L.

[0023] Preferably, the calcination is carried out by heating the temperature to 450° C. at a heating rate of 2° C. / min and calcining for 2 h.

[0024] Preferably, the concentration of the NaOH solution is 0.1 mol / L.

[0025] The invention also discloses a composite photoelectrode prepared by a method for preparing the composite photoelectrode.

[0026] The invention also discloses an application of a composite photoelectrode in photoelectrocatalytic water decomposition.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] The preparation method provided by the present invention uses a conductive glass fluorine-doped tin oxide (FTO) substrate and electrochemically deposits a BiOI thin film. After calcination, a BVO photoelectrode is obtained. B:NiOOH is then deposited on the surface of the BVO photoelectrode via photoelectrochemical deposition. This promotes the transport of photogenerated carriers, reduces charge recombination to a certain extent, and significantly improves water splitting performance, with a photocurrent density reaching 2.23 times that of BVO. Furthermore, the photoelectrochemical deposition of B:NiOOH on the BVO photoelectrode significantly improves the photocorrosion defects of the bismuth vanadate itself and significantly enhances its stability. The preparation method provided by the present invention is simple and safe to operate, and the materials are readily available, making it suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0030] Figure 1 This is a scanning electron microscope (SEM) image of the BVO photoelectrode obtained in Example 1;

[0031] Figure 2 This is the SEM image of the BVO / B:NiOOH photoelectrode obtained in Example 1;

[0032] Figure 3 TEM image of the BVO / B:NiOOH photoelectrode obtained in Example 1;

[0033] Figure 4 X-ray diffraction (XRD) patterns of the BVO photoelectrode and BVO / B:NiOOH photoelectrode obtained in Example 1;

[0034] Figure 5 The linear sweep voltammograms of the BVO photoelectrode and the BVO / B:NiOOH photoelectrode obtained in Example 1 in a hole-scavenging agent-free solution;

[0035] Figure 6 The linear sweep voltammograms of the BVO photoelectrode and the BVO / B:NiOOH photoelectrode obtained in Example 1 in a hole-trapping solution are shown;

[0036] Figure 7 The time-current curves of the BVO photoelectrode and BVO / B:NiOOH photoelectrode obtained in Example 1 are shown;

[0037] Figure 8 The photovoltage comparison diagram of the BVO photoelectrode and BVO / B:NiOOH photoelectrode obtained in Example 1;

[0038] Figure 9The linear sweep voltammograms of the BVO / B:NiOOH photoelectrodes obtained in comparative example 1 and example 1 in a hole-scavenging agent-free solution are shown.

[0039] Figure 10 The linear sweep voltammograms of the BVO / B:NiOOH photoelectrodes obtained in comparative example 2 and example 1 in a hole-scavenging agent-free solution are shown. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0043] Unless otherwise specified, the room temperature in the embodiments of the present invention is 15-30°C.

[0044] Example 1

[0045] A method for preparing a composite photoelectrode comprises the following steps:

[0046] 1. Preparation of BVO Photoelectrode

[0047] (1-1) FTO pretreatment: Take a 200 × 150 mm piece of FTO and cut it into 20 × 30 mm sections using a glass cutting table. Ultrasonic wash the sections in acetone, ethanol, and ultrapure water for 15 min each. After washing, add ethanol and store until ready for use.

[0048] (1-2) Preparation of the electrolyte: Prepare a nitric acid solution with a pH of 1.7. Take 25 ml of it, add potassium iodide (KI) to 0.4 M, and add bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) to 0.04 M. Stir vigorously until the solution is clear and translucent. Place 10 ml of ethanol in a separate beaker, add 0.23 M p-benzoquinone, and stir vigorously until the precipitate is completely dissolved. Combine the two solutions and stir vigorously to fully dissolve them, to obtain the electrolyte.

[0049] (1-3) The time-current curve method was selected. On a clean FTO, the washed FTO obtained in step (1-1) was used as the working electrode, the platinum mesh was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode. The initial voltage was -0.1 V, the sampling interval was 0.1 s, the deposition time was 180 s, the rest time was 0 s, and the sensitivity was 1×10 -3 A, electrodeposition is performed. After electrodeposition is completed, a thin film is formed on the FTO surface, which is then rinsed and dried to obtain a BiOI thin film.

[0050] (1-4) Using a glass cutting table, cut the BiOI film-coated FTO sheet obtained in step (1-3) into 20 × 10 mm sections. Place the sheet on a high-temperature-resistant corundum sheet, leaving a 3–5 mm gap between the FTO sheets. Add 0.2 M vanadyl acetylacetonate to 5 ml of dimethyl sulfoxide (DMSO). Stir vigorously until no precipitation is apparent. Then, using a pipette, evenly drop 30 μL of the resulting DMSO solution onto the 20 × 10 mm BiOI film. Slowly place the corundum sheet in a muffle furnace and heat at 2°C / min to 450°C. Calcinate for 2 h. After calcination, wait for the muffle furnace to cool to room temperature, slowly remove the corundum sheet, and the surface of the FTO prepared after firing is complete and uniform, and bright yellow. Place the fired FTO in a watch glass and add an appropriate amount of 0.1 M NaOH solution to soak for 20-30 minutes. Rinse the obtained FTO and dry it to obtain a BVO photoelectrode.

[0051] 2. Preparation of BVO / B:NiOOH Photoelectrode

[0052] Prepare a 0.5 M potassium borate buffer solution (pH = 9.5), add 1 mM nickel sulfate hexahydrate (NiSO4·6H2O), and stir until the solution is clear and translucent to obtain the electrolyte. The time-current curve method was selected, with the BVO photoelectrode obtained in step 1 as the working electrode, a platinum mesh as the counter electrode, and a Hg / HgO electrode as the reference electrode. The BVO photoelectrode was irradiated from the front side at a potential of -0.45 V, a deposition temperature of room temperature, a run time of 5 min, a sampling interval of 0.1 s, a rest time of 2 s, and a sensitivity of 1×10 -5 A, light intensity is 100 mW cm -2 , and photoelectrodeposition was performed. After the photoelectrodeposition was completed, the working electrode was rinsed with ultrapure water and dried to obtain a BVO / B:NiOOH photoelectrode.

[0053] Technical effect:

[0054] Performance Characterization

[0055] Figure 1This is the scanning electron microscope (SEM) image of the BVO photoelectrode obtained in step 1. It can be seen that the BVO photoelectrode is a worm-like nanoparticle.

[0056] Figure 2 The SEM image of BVO / B:NiOOH photoelectrode shows that compared with Figure 1 , Figure 2 A large range of fine particle surfaces appeared on the surface of the nanoparticles, and it was preliminarily determined that B:NiOOH had been deposited on BVO.

[0057] Figure 3 This is the transmission electron microscope (TEM) image of the BVO / B:NiOOH photoelectrode. It can be seen that there is a layer of B:NiOOH with a certain thickness on the surface of the bismuth vanadate nanoparticles.

[0058] Figure 4 Figure 2 is the X-ray diffraction (XRD) pattern of the above-mentioned BVO photoelectrode and BVO / B:NiOOH photoelectrode. It can be seen that BVO was successfully prepared, while B:NiOOH is an amorphous layer material without a crystalline structure and thus has no relevant diffraction peaks.

[0059] Figure 5 The linear sweep voltammograms of the BVO photoelectrode and BVO / B:NiOOH photoelectrode in a hole-scavenging agent-free solution show that the photocurrent density of BVO / B:NiOOH can reach 4.15 mAcm at 1.23 V vs. RHE. -2 , while the photocurrent density of BVO is 1.86 mA cm -2 , the photocurrent density of the composite photoelectrode is 2.23 times that of the BVO photoelectrode.

[0060] Figure 6 Figure 3 is the linear sweep voltammogram of the BVO photoelectrode and BVO / B:NiOOH photoelectrode in a hole scavenger solution. It can be seen that the loading of B:NiOOH in Example 1 has little effect on the performance of the BVO photoelectrode under the hole scavenger, and the overall trends are similar.

[0061] Figure 8 The photovoltage comparison diagram of the above-mentioned BVO photoelectrode and BVO / B:NiOOH photoelectrode shows that after loading B:NiOOH, the surface defect state is alleviated, and the difference between the dark state and the light state is larger, which is 0.138 V for BVO and 0.162 V for BVO / B:NiOOH.

[0062] Application Example 1

[0063] The BVO photoelectrode and BVO / B:NiOOH photoelectrode were used as working electrodes, platinum mesh as counter electrode, Hg / HgO as reference electrode, and 0.5 M potassium borate buffer solution. The actual water splitting test was carried out by selecting the time-current curve method. The results are shown in the figure. Figure 7 shown.

[0064] Figure 7 The time-current curves of the above-mentioned BVO photoelectrode and BVO / B:NiOOH photoelectrode show that the stability of the BVO electrode is significantly improved after loading B:NiOOH. At 0.75 V vs. RHE, the photocurrent density of BVO / B:NiOOH is higher than that of BVO and more stable.

[0065] Comparative Example 1

[0066] A method for preparing a composite photoelectrode, which differs from Example 1 in that, during the preparation of the BVO / B:NiOOH photoelectrode, the deposition time (operation time) is 1 min and 10 min, respectively, and the remaining process steps and parameters are the same as those in Example 1.

[0067] The results are as attached Figure 9 As shown, it can be seen that by testing the composite photoelectrode with a deposition time of 5 min (ie, Example 1), at 1.23 V vs. RHE, the overall trend and photocurrent density are greater than those of the composite photoelectrodes obtained with a deposition time of 1 min and 10 min.

[0068] Comparative Example 2

[0069] A method for preparing a composite photoelectrode is different from Example 1 in that, during the preparation of the BVO / B:NiOOH photoelectrode, the back side of the BVO photoelectrode is irradiated, and the remaining process steps and parameters are the same as those in Example 1.

[0070] The results are as attached Figure 10 As shown, by testing the composite photoelectrode irradiated from the front (ie, Example 1), at 1.23 V vs. RHE, the photocurrent density is greater than that of the composite photoelectrode obtained by back irradiation.

[0071] The above are merely preferred embodiments of the present application, but the scope of protection of the present application 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 this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a composite photoelectrode, characterized in that: BVO / B:NiOOH photoelectrode was obtained by photodeposition on the BVO photoelectrode using BVO as the working electrode, platinum mesh as the counter electrode, Hg / HgO electrode as the reference electrode, and nickel sulfate hexahydrate solution as the electrolyte. The potential of the photodeposition was -0.45 V, the operation time was 5 min, the sampling interval was 0.1 s, the rest time was 2 s, and the sensitivity was 1×10 -5 A, light intensity is 100 mW cm -2 ; The electrolyte is obtained by dissolving nickel sulfate hexahydrate into potassium borate buffer solution; The concentration of the potassium borate buffer solution is 0.5 mol / L, and the pH value is 9.

5.

2. The method for preparing a composite photoelectrode according to claim 1, wherein: The BVO photoelectrode is frontally irradiated during the photodeposition process.

3. The method for preparing a composite photoelectrode according to claim 1, wherein: The concentration of nickel sulfate hexahydrate in the electrolyte is 1 mmol / L.

4. The method for preparing a composite photoelectrode according to claim 1, wherein: The preparation method of the BVO photoelectrode comprises the following steps: The time-current curve method was selected to carry out electrodeposition using FTO as the working electrode, a platinum mesh as the counter electrode, and an Ag / AgCl electrode as the reference electrode to obtain a BiOI thin film. A DMSO solution of vanadium acetylacetonate was evenly dripped on the film, the film was calcined, and then immersed in a NaOH solution to obtain the BVO photoelectrode.

5. The method for preparing a composite photoelectrode according to claim 4, characterized in that: The electrolytic solution for the electrodeposition is obtained by mixing and dissolving a nitric acid solution of potassium iodide and bismuth nitrate pentahydrate with an ethanol solution of p-benzoquinone.

6. The method for preparing a composite photoelectrode according to claim 4, characterized in that: The initial voltage of the electrodeposition was -0.1 V, the sampling interval was 0.1 s, the deposition time was 180 s, the rest time was 2 s, and the sensitivity was 1×10 -3 A.

7. A composite photoelectrode prepared by the method for preparing a composite photoelectrode according to any one of claims 1 to 6.

8. Use of the composite photoelectrode as claimed in claim 7 in photoelectrocatalytic water splitting.

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