Composite photoelectrode and preparation method and application thereof

Abstract

The invention discloses a composite photoelectrode and a preparation method and application thereof, belongs to the technical field of photoelectrochemical analysis, and particularly relates to a BVO / B: NiOOH photoelectrode obtained by performing photoelectric deposition on a BVO photoelectrode by taking the BVO photoelectrode as a working electrode, a platinum net as a counter electrode, a Hg / HgO electrode as a reference electrode and a nickel sulfate hexahydrate solution as an electrolyte. The invention also discloses the composite photoelectrode prepared by the preparation method and application of the composite photoelectrode in photoelectrocatalytic water decomposition. According to the preparation method, B: NiOOH is deposited on the surface of a BVO photoelectrode through photoelectric deposition, so that the photocorrosion defect of bismuth vanadate is obviously improved, and the stability is obviously improved. The preparation method is simple, convenient and safe to operate, materials are easy to obtain, and large-scale production can be achieved.

Description

Technical Field

[0001] The 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 photoelectrocatalysts to decompose 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. This technology is of great significance in achieving the goals of carbon peak and carbon neutrality. The key to achieving carbon peak and carbon neutrality is to reduce greenhouse gas emissions. By using photoelectrocatalytic water splitting to produce hydrogen, it can replace traditional fossil fuels and reduce carbon dioxide emissions from the source. The product of hydrogen combustion is water, which does not produce greenhouse gases and helps achieve carbon neutrality. In summary, photoelectrocatalytic water splitting is of great significance in achieving the goals of carbon peak and carbon neutrality. By producing clean hydrogen energy, carbon dioxide emissions can be effectively reduced, energy structure transformation and green economic development can be promoted, thereby achieving the goal of sustainable development.

[0003] With the transformation of the global energy structure and the increasing attention to environmental protection, the research and development of photoelectrochemical water splitting technology for hydrogen production has become one of the hot topics 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 realize water oxidation reaction under visible light irradiation. This makes BiVO4 an ideal photoanode material for photoelectrochemical water splitting to produce hydrogen. However, the charge transport characteristics of the BiVO4 photoanode are poor, and the diffusion length of photogenerated carriers is short, 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 transmission 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 object, the present invention provides the following technical solutions:

[0007] A preparation method of 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, and performing photoelectrochemical deposition on the BVO photoelectrode to obtain a BVO / B:NiOOH photoelectrode.

[0008] Beneficial effect: The electrolyte in the present invention is alkaline. Since the service life of the Ag / AgCl reference electrode is greatly reduced in an alkaline environment, the present invention selects Hg / HgO 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 running 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 at 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 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 a 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 with FTO as the working electrode, platinum mesh as the counter electrode, and Ag / AgCl electrode as the reference electrode to obtain a BiOI film, which was evenly dripped with a DMSO solution of vanadium acetylacetonate and then 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 to 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 of 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 make them fully miscible, so as to obtain 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 hours.

[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 conductive glass fluorine-doped tin oxide (FTO) as a substrate, deposits a BiOI film by an electrochemical method, obtains a BVO photoelectrode after calcination, and then deposits B:NiOOH on the surface of the BVO photoelectrode by photoelectric deposition, which promotes the transmission of photogenerated carriers, reduces charge recombination to a certain extent, and greatly improves the performance of water decomposition. The photocurrent density can reach 2.23 times that of BVO. In addition, the present invention deposits B:NiOOH on the surface of the BVO photoelectrode by photoelectric deposition, which significantly improves the photocorrosion defects of bismuth vanadate itself, and the stability is significantly improved. The preparation method provided by the present invention is simple and safe to operate, and the materials are easily available, and large-scale production can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0030] Figure 1 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 is a transmission electron microscope (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 the BVO / B:NiOOH photoelectrode obtained in Example 1;

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

[0035] Figure 6 The linear scanning voltammetry curves of the BVO photoelectrode and the BVO / B:NiOOH photoelectrode obtained in Example 1 in a hole trapping agent solution;

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

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

[0038] Fig. 9The linear scanning voltammetry curves of the BVO / B:NiOOH photoelectrodes obtained in Comparative Example 1 and Example 1 in a hole-scavenging agent-free solution.

[0039] Fig.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. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work 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) Pretreatment of FTO: Take a 200×150 mm FTO and cut it into 20×30 mm pieces using a glass cutting table. Then ultrasonically wash it with acetone, ethanol, and ultrapure water for 15 min respectively. After washing, add ethanol and store it for later use.

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

[0049] (1-3) The time-current curve method was selected. On the 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, 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 standing time was 0 s, and the sensitivity was 1×10 -3 A, perform electrodeposition. After the 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) Cut the FTO with BiOI film obtained in step (1-3) into 20×10 mm in size using a glass cutting table and place it on a high temperature resistant corundum sheet, leaving a distance of 3 to 5 mm between the FTO sheets with BiOI film. Take 5 ml of dimethyl sulfoxide (DMSO), add 0.2 M acetylacetonatovanadium, stir vigorously until there is no obvious precipitation, then use a pipette to take 30 μL of the obtained DMSO solution and evenly drip it on the surface of the BiOI film with a size of 20×10 mm, then slowly place the corundum sheet in a muffle furnace, heat it by 2°C per minute, raise it to 450°C, and calcine it for 2 hours. After calcination, wait for the muffle furnace to cool down to room temperature, slowly take out the corundum sheet, the surface of the FTO produced after firing is complete and uniform, and bright yellow. Place the fired FTO in a watch glass, add an appropriate amount of 0.1M NaOH solution and soak for 20 to 30 minutes, rinse the obtained FTO, dry it, and obtain the BVO photoelectrode.

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

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

[0053] Technical effects:

[0054] Performance Characterization

[0055] Figure 1This is a 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 as a whole.

[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 a 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 : These are the X-ray diffraction (XRD) patterns of the BVO photoelectrode and the BVO / B:NiOOH photoelectrode. It can be seen that BVO is 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 scanning voltammetry curves of the above 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 mA cm 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 The linear scanning voltammetry curves of the above-mentioned BVO photoelectrode and BVO / B:NiOOH photoelectrode in a hole scavenger solution show 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 This is a photovoltage comparison diagram of the above-mentioned BVO photoelectrode and BVO / B:NiOOH photoelectrode. It can be seen 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 0.138V for BVO and 0.162V 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 0.5M potassium borate buffer solution. The actual water decomposition test was carried out by selecting the time-current curve method. The results are shown in 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 0.75V 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 attached Fig. 9 As shown, it can be seen that by testing the composite photoelectrode with a deposition time of 5 minutes (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 minute and 10 minutes.

[0068] Comparative Example 2

[0069] A method for preparing a composite photoelectrode, which differs 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 attached Fig.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 only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a composite photoelectrode, characterized in that: With BVO photoelectrode as working electrode, platinum mesh as counter electrode, Hg / HgO electrode as reference electrode and nickel sulfate hexahydrate solution as electrolyte, photoelectrodeposition was carried out on the BVO photoelectrode to obtain BVO / B:NiOOH photoelectrode.

2. The method for preparing a composite photoelectrode according to claim 1, characterized in that: The potential of the photodeposition was -0.45 V, the running time was 5 min, the sampling interval was 0.1 s, the standing time was 2 s, and the sensitivity was 1×10 -5 A, light intensity is 100 mW cm -2 .

3. The method for preparing a composite photoelectrode according to claim 1, characterized in that: The BVO photoelectrode is frontally irradiated during the photodeposition process.

4. The method for preparing a composite photoelectrode according to claim 1, characterized in that: The electrolyte is obtained by dissolving nickel sulfate hexahydrate into a potassium borate buffer solution.

5. The method for preparing a composite photoelectrode according to claim 4, characterized in that: The concentration of nickel sulfate hexahydrate in the electrolyte is 1 mmol / L; The concentration of the potassium borate buffer solution is 0.5 mol / L, and the pH value is 9.

5.

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

7. The method for preparing a composite photoelectrode according to claim 6, characterized in that: 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.

8. The method for preparing a composite photoelectrode according to claim 6, 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 standing time was 2 s, and the sensitivity was 1×10 -3 A.

9. A composite photoelectrode prepared by the method for preparing a composite photoelectrode as described in any one of claims 1 to 8.

10. Use of the composite photoelectrode as claimed in claim 9 in photoelectrocatalytic water decomposition.

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