A cobalt phosphate / electron-rich gold / bismuth vanadate photoanode, a preparation method and application thereof

Abstract

The application provides a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode and a preparation method and application thereof. The preparation of the photoanode comprises the following steps: taking an FTO glass plate as a working electrode, depositing a bismuth vanadate film on the FTO glass plate to obtain BiVO4; soaking the BiVO4 in a gold nanoparticle solution to obtain Au / BiVO4; taking the Au / BiVO4 as a working electrode, taking a mixed solution containing a cobalt salt and a phosphate as an electrolyte solution, depositing cobalt phosphate on the Au / BiVO4 to obtain CoPi / Au / BiVO4; and annealing the CoPi / Au / BiVO4 under a reducing atmosphere to obtain an SMSI-CoPi / Au δ‑ / BiVO4 photoanode. The cobalt phosphate / electron-rich gold / bismuth vanadate photoanode of the application is induced to form electron-rich gold and doped with vanadium source due to strong metal-support interaction, and the photocurrent density of the photoanode is significantly improved under the synergistic effect of gold doping, cobalt phosphate loading and strong metal-support interaction. The photocurrent density of the SMSI-CoPi / Au δ‑ / BiVO4 photoanode reaches 5.2 mA cm ‑2 at a water oxidation potential (1.23 V vs. RHE).

Description

Technical Field

[0001] This application belongs to the field of photoelectrocatalytic materials technology, and more specifically, relates to a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode, its preparation method, and its application. Background Technology

[0002] With social development and continuous economic growth, energy and environmental issues have become significant constraints on social progress. Finding efficient and pollution-free clean energy is a crucial step towards achieving green and low-carbon development. Hydrogen energy, hailed as the "ultimate energy of the 21st century," is a recognized clean energy source. Developing hydrogen energy is considered a vital path for my country's clean energy transformation and achieving "dual carbon" (carbon dioxide, carbon emissions, and carbon sequestration). Utilizing sunlight to produce hydrogen to replace fossil fuels is a goal for researchers. Photoelectrochemical (PEC) technology, with its low production cost and high photoelectric performance, has received widespread attention in recent years for its application in producing pollution-free clean energy.

[0003] Bismuth vanadate (BiVO4), as a semiconductor material, possesses a narrow band gap and a sufficiently deep valence band, resulting in a wide absorption range for sunlight. Its good stability and environmental friendliness have also attracted widespread attention in the field of photoelectrocatalytic hydrogen production. While bismuth vanadate exhibits a sufficiently high theoretical photocurrent density due to its excellent properties, problems such as severe electron-hole recombination and slow surface water oxidation kinetics still exist, leading to extremely low actual photocurrent densities and limiting its hydrogen and oxygen production efficiency.

[0004] Currently, patent CN202011481971.4 has invented a gold (Au) nanoparticle-modified bismuth vanadate (BiVO4) photoanode, which utilizes the plasmon resonance effect on the gold surface to expand the light absorption range and increase the photocurrent density. However, the electron-hole recombination rate at the gold-bismuth vanadate interface and the slow water oxidation reaction rate on the bismuth vanadate surface have not been effectively solved, and the photocurrent density still needs to be improved. Summary of the Invention

[0005] The purpose of this application is to provide a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode, its preparation method, and its application, in order to solve the technical problems of slow water oxidation reaction rate and low photocurrent density on the surface of bismuth vanadate photoanodes in the prior art.

[0006] To achieve the above objectives, a first aspect of this application provides a method for preparing a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode, comprising the following steps:

[0007] BiVO4 was obtained by depositing a bismuth vanadate film on an FTO glass plate as the working electrode.

[0008] The BiVO4 was immersed in a gold nanoparticle solution to obtain Au / BiVO4;

[0009] Using the Au / BiVO4 as the working electrode and a mixed solution containing cobalt salt and phosphate as the electrolyte solution, cobalt phosphate is deposited on it to obtain CoPi / Au / BiVO4;

[0010] The CoPi / Au / BiVO4 was annealed under a reducing atmosphere to obtain SMSI-CoPi / Au δ- / BiVO4 photoanode.

[0011] Furthermore, the gold nanoparticle solution is prepared by the following method: preparing an aqueous solution of chloroauric acid, adding sodium citrate dihydrate solution to it, and stirring the reaction at 70-90°C for 15-30 min.

[0012] Furthermore, the chloroauric acid aqueous solution is 50 mL of 0.4 mM chloroauric acid, and the sodium citrate dihydrate solution is 5 mL of sodium citrate dihydrate with a mass fraction of 1-2%.

[0013] Furthermore, the soaking time is 5 minutes to 3 hours.

[0014] Furthermore, the mixed solution containing cobalt salt and phosphate contains cobalt nitrate, potassium dihydrogen phosphate, and dipotassium hydrogen phosphate.

[0015] Furthermore, in the mixed solution containing cobalt salt and phosphate, the concentration of cobalt nitrate is 0.001–0.01 mM, the concentration of potassium dihydrogen phosphate is 0.1–0.5 mM, and the concentration of dipotassium hydrogen phosphate is 0.2–1 mM.

[0016] Furthermore, in the preparation process of CoPi / Au / BiVO4, Ag / AgCl is used as the reference electrode, Pt sheet is used as the counter electrode, the electrodeposition potential is 0.4V vs Ag / AgCl, and the time is 1 to 10 minutes.

[0017] Furthermore, the annealing temperature is 200–400℃, and the annealing time is 30–120 min.

[0018] In a second aspect, this application provides a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode, prepared using any of the methods described above.

[0019] A third aspect of this application provides the application of a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode in electrocatalytic water splitting for hydrogen production.

[0020] Compared with the prior art, this application has the following technical effects:

[0021] This application discloses a method for preparing a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode. First, gold nanoparticles are composited onto a bismuth vanadate film, followed by cobalt phosphate composite. Electron-rich gold is then generated in situ through annealing in a reducing atmosphere, forming a cobalt phosphate / electron-rich gold / bismuth vanadate (SMSI-CoPi / Au) photoanode with strong metal-carrier interactions. δ- The bismuth vanadate photoanode, in turn, synergistically improves the electron-hole interface separation efficiency and surface water oxidation kinetics, thereby increasing the photocurrent density of the bismuth vanadate photoanode.

[0022] This application discloses a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode. Due to the strong metal-support interaction, the formation of electron-rich gold and the doping of the vanadium source are induced. Under the synergistic effect of gold doping, cobalt phosphate loading, and strong metal-support interaction, the photocurrent density of the photoanode is significantly improved. At the water oxidation potential (1.23V vs. RHE), the photocurrent density of the SMSI-CoPi / Au... δ- The photocurrent density of the BiVO4 photoanode reaches 5.2 mA / cm². -2 . Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 (a)-(c) are scanning electron microscope images of bismuth vanadate, gold / bismuth vanadate, and cobalt phosphate / gold / bismuth vanadate provided in Example 1 of this application, respectively.

[0025] Figure 2 The SMSI-CoPi / Au provided in Embodiment 1 of this application δ- Photoelectron spectra of Au in / BiVO4 and CoPi / Au / BiVO4;

[0026] Figure 3 The SMSI-CoPi / Au provided in Embodiment 1 of this application δ- / Diagram of electron-rich gold formation and vanadium source doping mechanism in BiVO4;

[0027] Figure 4 BiVO4, Au / BiVO4, CoPi / Au / BiVO4, and SMSI-CoPi / Au provided in Embodiment 1 of this application δ- Comparison of photocurrent densities between / BiVO4 and the CoPi / BiVO4 photoanode provided as a comparative example. Detailed Implementation

[0028] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0029] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0030] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0031] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0032] This application provides a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode and its preparation method, including the following steps:

[0033] (1) Using an FTO glass plate as the working electrode, a bismuth vanadate thin film is deposited on it to obtain BiVO4;

[0034] (2) BiVO4 was immersed in a gold nanoparticle solution to obtain Au / BiVO4;

[0035] (3) Using Au / BiVO4 as the working electrode and a mixed solution containing cobalt salt and phosphate as the electrolyte solution, cobalt phosphate is deposited on it to obtain CoPi / Au / BiVO4;

[0036] (4) Anneal CoPi / Au / BiVO4 in a reducing atmosphere to obtain SMSI-CoPi / Au δ- / BiVO4 photoanode.

[0037] In step (1) above, the bismuth vanadate film can be prepared by the following method: Prepare 50 mL of a mixed solution with a molar concentration of 0.4 M potassium iodide (KI), 0.018 M bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and 0.03 M lactic acid, and adjust the pH of the solution to 1.2-2.0 by adding concentrated nitric acid (HNO3) dropwise, and stir at 400-500 r / min for 20-30 min; then prepare 20 mL of an ethanol solution with a molar concentration of 0.032 M p-benzoquinone, and stir at 400-500 r / min for 20-30 min. Slowly mix the two solutions and stir vigorously for 20-30 min to obtain an electrolyte containing potassium iodide, bismuth nitrate, lactic acid and p-benzoquinone.

[0038] A three-electrode system was used for constant potential deposition in the aforementioned electrolyte, with an FTO glass plate as the working electrode, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. Using a chronoamperometry method, a thin bismuth oxyiodide (BiOI) seed layer was first formed on the FTO surface by deposition at -0.35V vs Ag / AgCl for 30–90 s. Then, a bismuth oxyiodide layer was obtained by electrodeposition at -0.1V vs Ag / AgCl for 1200–1500 s.

[0039] Prepare 2 mL of a 0.17 M vanadium acetylacetonate dimethyl sulfoxide solution and stir for 10–20 min until homogeneous. Use a pipette to transfer 0.14 mL of this solution dropwise onto the deposited bismuth iodide layer. Then, anneal in a muffle furnace at 420–450 °C for 120–150 min, controlling the heating rate at 2–5 °C / min, and allow to cool naturally. Finally, prepare a 1 M sodium hydroxide (NaOH) solution and immerse the sample in the muffle furnace for 5–10 min to remove excess vanadium pentoxide (V₂O₅) from the surface. Rinse thoroughly with deionized water and dry to obtain bismuth vanadate (BiVO₄).

[0040] In step (2) above, the gold nanoparticle solution is prepared by the following method: A chloroauric acid aqueous solution is prepared, and a sodium citrate dihydrate solution is added to it. The mixture is stirred at 70–90°C for 15–30 min. The chloroauric acid aqueous solution can be 50 mL of 0.4 mM chloroauric acid, and the sodium citrate dihydrate solution can be 5 mL of 1–2% sodium citrate dihydrate. The soaking time is 5 min–3 h. By controlling the soaking time, gold / bismuth vanadate (Au / BiVO4) photoanodes with different film layer thicknesses are obtained. After soaking, the anode is gently rinsed with deionized water and dried in an oven at 60–80°C for 24–36 h.

[0041] In step (3) above, the mixed solution containing cobalt salt and phosphate contains cobalt nitrate, potassium dihydrogen phosphate, and dipotassium hydrogen phosphate. The concentration of cobalt nitrate is 0.001–0.01 mM, the concentration of potassium dihydrogen phosphate is 0.1–0.5 mM, and the concentration of dipotassium hydrogen phosphate is 0.2–1 mM.

[0042] In the preparation of CoPi / Au / BiVO4, a three-electrode system was still used, with Ag / AgCl as the reference electrode and a Pt sheet as the counter electrode. The electrodeposition potential was 0.4V vs Ag / AgCl, and the time was 1–10 min. The thickness of the cobalt phosphate thin film was adjusted by controlling the deposition time.

[0043] In step (4) above, the annealing temperature is 200–400℃, and the annealing time is 30–120 min. The reducing atmosphere is a H2 / Ar mixed gas. Annealing in a reducing atmosphere allows for strong interactions between the metal and the support, inducing electron-rich gold (Au). δ- The formation of cobalt phosphate / electron-rich gold / bismuth vanadate (SMSI-CoPi / Au) and doping with vanadium source yielded a cobalt phosphate / electron-rich gold / bismuth vanadate (SMSI-CoPi / Au) exhibiting strong metal-support interactions. δ- / BiVO4) photoanode.

[0044] The loading of cobalt phosphate (CoPi) in a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode according to an embodiment of this application greatly enhances the surface water oxidation kinetics of the Au / BiVO4 photoanode; and through reducing atmosphere annealing treatment, a strong metal-carrier interaction is formed at the interface between Au and CoPi and BiVO4, and electron-rich gold (Au) is induced in situ. δ- The addition of vanadium doping synergistically improves the efficiency of electron-hole interface separation and surface water oxidation kinetics, thereby increasing the photocurrent density of the bismuth vanadate photoanode.

[0045] The following examples illustrate a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode and its preparation method according to embodiments of this application.

[0046] Example 1

[0047] Example 1 of this application provides a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode and its preparation method, including the following steps:

[0048] (1) Prepare 50 mL of a mixed solution with a molar concentration of 0.4 M potassium iodide, 0.018 M bismuth nitrate pentahydrate, and 0.03 M lactic acid. Adjust the pH of the solution to 1.2–2.0 by adding concentrated nitric acid dropwise, and stir at 450 r / min for 20 min. Then prepare 20 mL of an ethanol solution with a molar concentration of 0.032 M p-benzoquinone, and stir at 450 r / min for 20 min. Slowly mix the two solutions and stir vigorously for 20 min to obtain a mixed solution as the electrolyte.

[0049] (2) A three-electrode system was used for constant potential deposition in the above mixed solution, with an FTO glass plate as the working electrode, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. Using the chronoamperometry method, a thin bismuth oxyiodide seed layer was first formed on the FTO surface by deposition at -0.35V vs Ag / AgCl for 30s, followed by deposition at -0.1V vs Ag / AgCl for 1200s to obtain the bismuth oxyiodide layer.

[0050] Prepare 2 mL of a 0.17 M vanadium acetylacetonate dimethyl sulfoxide solution and stir for 10 min until homogeneous. Use a pipette to transfer 0.14 mL of this solution dropwise onto the deposited bismuth iodide layer. Then, anneal in a muffle furnace at 420 °C for 120 min, controlling the heating rate at 2 °C / min, and allow to cool naturally. Finally, prepare a 1 M sodium hydroxide solution and immerse the sample in the muffle furnace for 5 min to remove excess vanadium pentoxide from the surface. Rinse thoroughly with deionized water and dry to obtain bismuth vanadate (BiVO4). Figure 1 (a).

[0051] (3) Dissolve 1% sodium citrate in 5 ml of deionized water and stir at room temperature for 30 min. Then, measure 50 ml of 0.4 mM chloroauric acid aqueous solution and heat and stir in a 70°C water bath for 10 min. Subsequently, rapidly inject 5 mL of sodium citrate into the chloroauric acid solution and stir vigorously at 70°C for 15 min. Cool to room temperature to obtain a gold nanoparticle solution.

[0052] Bismuth vanadate was immersed in the prepared gold nanoparticle solution in the dark for 30 minutes, gently rinsed with deionized water, and then dried in an oven at 60°C for 24 hours to obtain a gold / bismuth vanadate photoanode (Au / BiVO4). Figure 1 (b)

[0053] (4) Add 0.006 mM cobalt nitrate, 0.4 mM potassium dihydrogen phosphate, and 0.8 mM dipotassium hydrogen phosphate to prepare 50 mL of electrolyte solution, and stir for 10 min until completely mixed. A three-electrode system is still used, with the gold / bismuth vanadate (Au / BiVO4) photoanode as the working electrode, Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and cobalt phosphate as the electrolyte solution. Deposition is carried out at a constant potential of 0.4 V vs. Ag / AgCl for 400 s to obtain the cobalt phosphate / gold / bismuth vanadate (CoPi / Au / BiVO4) photoanode, as shown below. Figure 1 (c)

[0054] (5) The prepared cobalt phosphate / gold / bismuth vanadate photoanode (CoPi / Au / BiVO4) was placed in a tube furnace and annealed at 200°C for 120 min in a reducing atmosphere (H2 / Ar) to obtain cobalt nitrate / electron-rich gold / bismuth vanadate (SMSI-CoPi / Au) with strong metal-support interaction. δ- / BiVO4) photoanode. CoPi / Au / BiVO4, SMSI-CoPi / Au δ- The photoelectron spectrum of Au in BiVO4 is shown below. Figure 2 As shown, SMSI-CoPi / Au δ- The formation of electron-rich gold in BiVO4 and the mechanism of vanadium source doping are as follows: Figure 3 As shown.

[0055] Example 2

[0056] Example 2 of this application provides a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode and its preparation method, including the following steps:

[0057] (1) The preparation of electrolyte is the same as in Example 1.

[0058] (2) A three-electrode system was used for constant potential deposition in the above mixed solution, with an FTO glass plate as the working electrode, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. Using the chronoamperometry method, a thin bismuth oxyiodide seed layer was first formed on the FTO surface by deposition at -0.35V vs Ag / AgCl for 60s, followed by deposition at -0.1V vs Ag / AgCl for 1300s to obtain the bismuth oxyiodide layer.

[0059] Prepare 2 mL of a 0.17 M vanadium acetylacetonate dimethyl sulfoxide solution and stir for 10 min until homogeneous. Use a pipette to transfer 0.14 mL of this solution dropwise onto the deposited bismuth iodide layer. Then, anneal in a muffle furnace at 450 °C for 120 min, controlling the heating rate at 5 °C / min, and allow to cool naturally. Finally, prepare a 1 M sodium hydroxide solution and immerse the sample in the muffle furnace for 5 min to remove excess vanadium pentoxide from the surface. Rinse thoroughly with deionized water and dry to obtain bismuth vanadate (BiVO4).

[0060] (3) Dissolve 2% sodium citrate in 5 ml of deionized water and stir at room temperature for 30 min. Then, measure 50 ml of 0.4 mM chloroauric acid aqueous solution and heat and stir in a 90°C water bath for 5 min. Subsequently, rapidly inject 5 mL of sodium citrate into the chloroauric acid solution and stir vigorously at 90°C for 20 min. Cool to room temperature to obtain a gold nanoparticle solution.

[0061] Bismuth vanadate was immersed in the prepared gold nanoparticle solution for 5 minutes in the dark, gently rinsed with deionized water, and then dried in an oven at 60°C for 24 hours to obtain a gold / bismuth vanadate photoanode (Au / BiVO4).

[0062] (4) Add 0.006 mM cobalt nitrate, 0.4 mM potassium dihydrogen phosphate, and 0.8 mM dipotassium hydrogen phosphate to prepare 50 mL of electrolyte solution, and stir for 10 min until completely mixed. A three-electrode system is still used, with the gold / bismuth vanadate (Au / BiVO4) photoanode as the working electrode, Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and cobalt phosphate as the electrolyte solution. Deposition is carried out at a constant potential of 0.4 V vs. Ag / AgCl for 600 s to obtain the cobalt phosphate / gold / bismuth vanadate (CoPi / Au / BiVO4) photoanode.

[0063] (5) The prepared cobalt phosphate / gold / bismuth vanadate photoanode (CoPi / Au / BiVO4) was placed in a tube furnace and annealed at 300℃ for 60 min in a reducing atmosphere (H2 / Ar) to obtain cobalt nitrate / electron-rich gold / bismuth vanadate (SMSI-CoPi / Au) with strong metal-support interaction. δ- / BiVO4) photoanode.

[0064] Example 3

[0065] Example 3 of this application provides a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode and its preparation method, including the following steps:

[0066] (1) The preparation of electrolyte is the same as in Example 1.

[0067] (2) A three-electrode system was used for constant potential deposition in the above mixed solution, with an FTO glass plate as the working electrode, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. Using the chronoamperometry method, a thin bismuth oxyiodide seed layer was first formed on the FTO surface by deposition at -0.35V vs Ag / AgCl for 90s, followed by deposition at -0.1V vs Ag / AgCl for 1500s to obtain the bismuth oxyiodide layer.

[0068] Prepare 2 mL of a 0.17 M vanadium acetylacetonate dimethyl sulfoxide solution and stir for 10 min until homogeneous. Use a pipette to transfer 0.14 mL of this solution dropwise onto the deposited bismuth iodide layer. Then, anneal in a muffle furnace at 420 °C for 150 min, controlling the heating rate at 3 °C / min, and allow to cool naturally. Finally, prepare a 1 M sodium hydroxide solution and immerse the sample in the muffle furnace for 10 min to remove excess vanadium pentoxide from the surface. Rinse thoroughly with deionized water and dry to obtain bismuth vanadate (BiVO4).

[0069] (3) Dissolve 1.5% sodium citrate in 5 ml of deionized water and stir at room temperature for 30 min. Then, measure 50 ml of 0.4 mM chloroauric acid aqueous solution and heat and stir in an 80°C water bath for 10 min. Subsequently, rapidly inject 5 mL of sodium citrate into the chloroauric acid solution and stir vigorously at 80°C for 30 min. Cool to room temperature to obtain a gold nanoparticle solution.

[0070] Bismuth vanadate was immersed in the prepared gold nanoparticle solution in the dark for 3 hours, gently rinsed with deionized water, and then dried in an oven at 60°C for 36 hours to obtain the gold / bismuth vanadate photoanode (Au / BiVO4).

[0071] (4) Add 0.006 mM cobalt nitrate, 0.4 mM potassium dihydrogen phosphate, and 0.8 mM dipotassium hydrogen phosphate to prepare 50 mL of electrolyte solution, and stir for 10 min until completely mixed. A three-electrode system is still used, with the gold / bismuth vanadate (Au / BiVO4) photoanode as the working electrode, Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and cobalt phosphate as the electrolyte solution. Deposition is carried out at a constant potential of 0.4 V vs. Ag / AgCl for 500 s to obtain the cobalt phosphate / gold / bismuth vanadate (CoPi / Au / BiVO4) photoanode.

[0072] (5) The prepared cobalt phosphate / gold / bismuth vanadate photoanode (CoPi / Au / BiVO4) was placed in a tube furnace and annealed at 400℃ for 120 min in a reducing atmosphere (H2 / Ar) to obtain cobalt nitrate / electron-rich gold / bismuth vanadate (SMSI-CoPi / Au) with strong metal-support interaction. δ- / BiVO4) photoanode.

[0073] Comparative Example

[0074] This application provides a CoPi / BiVO4 photoanode and its preparation method as a comparative example, including the following steps:

[0075] (1) Prepare 50 mL of a mixed solution with a molar concentration of 0.4 M potassium iodide, 0.018 M bismuth nitrate pentahydrate, and 0.03 M lactic acid. Adjust the pH of the solution to 1.2–2.0 by adding concentrated nitric acid dropwise, and stir at 450 r / min for 20 min. Then prepare 20 mL of an ethanol solution with a molar concentration of 0.032 M p-benzoquinone, and stir at 450 r / min for 20 min. Slowly mix the two solutions and stir vigorously for 20 min to obtain a mixed solution as the electrolyte.

[0076] (2) A three-electrode system was used for constant potential deposition in the above mixed solution, with an FTO glass plate as the working electrode, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. Using the chronoamperometry method, a thin bismuth oxyiodide seed layer was first formed on the FTO surface by deposition at -0.35V vs Ag / AgCl for 30s, followed by deposition at -0.1V vs Ag / AgCl for 1200s to obtain the bismuth oxyiodide layer.

[0077] Prepare 2 mL of a 0.17 M vanadium acetylacetonate dimethyl sulfoxide solution and stir for 10 min until homogeneous. Use a pipette to transfer 0.14 mL of this solution dropwise onto the deposited bismuth iodide layer. Then, anneal in a muffle furnace at 420 °C for 120 min, controlling the heating rate at 2 °C / min, and allow to cool naturally. Finally, prepare a 1 M sodium hydroxide solution and immerse the sample in the muffle furnace for 5 min to remove excess vanadium pentoxide from the surface. Rinse thoroughly with deionized water and dry to obtain bismuth vanadate (BiVO4).

[0078] (3) Add 0.006 mM cobalt nitrate, 0.4 mM potassium dihydrogen phosphate, and 0.8 mM dipotassium hydrogen phosphate to prepare 50 mL of electrolyte solution, and stir for 10 min until completely mixed. A three-electrode system is still used, with bismuth vanadate (BiVO4) photoanode as the working electrode, Ag / AgCl as the reference electrode, Pt sheet as the counter electrode, and cobalt phosphate as the electrolyte solution. Deposition is carried out at a constant potential of 0.4 V vs. Ag / AgCl for 400 s to obtain cobalt phosphate / bismuth vanadate (CoPi / BiVO4) photoanode.

[0079] BiVO4, Au / BiVO4, CoPi / Au / BiVO4, and SMSI-CoPi / Au prepared in Example 1 of this application δ- The photocurrent density of / BiVO4 and the comparative CoPi / BiVO4 was tested, and the procedure is as follows:

[0080] Weigh 2.473 g of boric acid (H3BO3) and dissolve it in 40 mL of water. Adjust the pH to 9.0–9.5 by adding 2 M potassium hydroxide solution dropwise, stirring continuously for 10–20 min until the solution becomes clear, obtaining a borate (KBi) solution. Use the prepared borate solution as the performance testing buffer. Again, employ a three-electrode system, and test the prepared photoanodes (BiVO4, Au / BiVO4, CoPi / BiVO4, CoPi / Au / BiVO4, and SMSI-CoPi / Au). δ-BiVO4 was used as the working electrode, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. Linear voltammetry (LSV) was employed, with the scan voltage set to 0V–1.23V vs. RHE, the scan rate set to 0.05V / s, and the scan interval set to 0.01s. The light source intensity was set to AM 1.5G. The photocurrent density of the photoanode was measured using back-illuminated FTO glass plates. Different photocurrent densities were obtained by varying the illumination time. The test results are shown below. Figure 4 As shown.

[0081] from Figure 4 It was observed that at the water oxidation potential (1.23V vs. RHE), BiVO4, Au / BiVO4, CoPi / BiVO4, CoPi / Au / BiVO4, and SMSI-CoPi / Au δ- The photocurrent density of the BiVO4 photoanode is 1.7 mA cm⁻¹. -2 2.5mA cm -2 2.9mA cm -2 4.0mA cm -2 5.2mA cm -2 .

[0082] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode, characterized in that, Includes the following steps: BiVO4 was obtained by depositing a bismuth vanadate film on an FTO glass plate as the working electrode. The BiVO4 was immersed in a gold nanoparticle solution to obtain Au / BiVO4; Using Au / BiVO4 as the working electrode, Ag / AgCl as the reference electrode, a Pt sheet as the counter electrode, and a mixed solution containing cobalt salt and phosphate as the electrolyte solution, cobalt phosphate was deposited on it to obtain CoPi / Au / BiVO4; wherein the electrodeposition potential was 0.4 V vs Ag / AgCl, and the time was 1~10 min. The CoPi / Au / BiVO4 was annealed under a reducing atmosphere to obtain SMSI-CoPi / Au δ- / BiVO4 photoanode; the annealing temperature is 200~400 ℃, the annealing time is 30~120 min, and the reducing atmosphere is a mixture of H2 / Ar gas.

2. The method for preparing a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode as described in claim 1, characterized in that, The gold nanoparticle solution was prepared by the following method: preparing an aqueous solution of chloroauric acid, adding sodium citrate dihydrate solution to it, and stirring the mixture at 70-90 °C for 15-30 min.

3. The method for preparing a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode as described in claim 2, characterized in that, The chloroauric acid aqueous solution is 50 mL of 0.4 mM chloroauric acid, and the sodium citrate dihydrate solution is 5 mL of sodium citrate dihydrate with a mass fraction of 1-2%.

4. The method for preparing a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode as described in claim 3, characterized in that, The soaking time is 5 min to 3 h.

5. The method for preparing a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode as described in claim 1, characterized in that, The mixed solution containing cobalt salt and phosphate contains cobalt nitrate, potassium dihydrogen phosphate, and dipotassium hydrogen phosphate.

6. The method for preparing a cobalt phosphate / electron-rich gold / bismuth vanadate photoanode as described in claim 5, characterized in that, In the mixed solution containing cobalt salt and phosphate, the concentration of cobalt nitrate is 0.001~0.01 mM, the concentration of potassium dihydrogen phosphate is 0.1~0.5 mM, and the concentration of dipotassium hydrogen phosphate is 0.2~1 mM.

7. A cobalt phosphate / electron-rich gold / bismuth vanadate photoanode, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The application of the cobalt phosphate / electron-rich gold / bismuth vanadate photoanode as described in claim 7 in electrocatalytic water splitting for hydrogen production.

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