BiVO4 / CuS / NiFeCoOx photoelectric catalytic material as well as preparation method and application thereof

Abstract

The invention provides a BiVO4 / CuS / NiFeCoOx photoelectrocatalysis material as well as a preparation method and application thereof, and relates to the technical field of photoelectrocatalysis. The preparation method of the photoelectrocatalytic material comprises the following steps: electrically depositing a BiOI film on the surface of a substrate, dropwise adding a vanadyl acetylacetonate solution on the surface of the substrate, and sequentially carrying out high-temperature calcination and alkali liquor soaking to obtain a BiVO4 substrate layer; coating the surface of the substrate layer with a chloroform solution of copper sulfide to obtain a BiVO4 / CuS composite material; and performing first-stage soaking in an iron-nickel-cobalt solution with the pH value of 4.5-5.5, adjusting the pH value of the solution to 6-8, and performing second-stage soaking, thereby finally obtaining the BiVO4 / CuS / NiFeCoOx photoelectric catalytic material. The material has good photoelectrocatalytic activity and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectrocatalysis, and particularly to a BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material, its preparation method and application. Background Art

[0002] Photoelectric materials have shown great potential in air pollution control and energy production, especially in the fields of treating harmful gases in the atmosphere (such as nitrogen monoxide and nitrogen dioxide, etc.) and photoelectrocatalytic water splitting. With the increasing attention to environmental pollution problems, photoelectrocatalytic technology has gradually become an innovative solution. Through solar-driven photoelectrocatalytic reactions, photoelectric materials can not only effectively degrade nitrogen oxides in the atmosphere, but also promote water splitting to generate hydrogen, achieving the dual functions of environmental protection and energy production.

[0003] Among many semiconductor materials, bismuth vanadate (BiVO 4 ) has become a key material in the field of photoelectrocatalysis due to its appropriate bandgap. BiVO 4 can absorb sunlight and generate photogenerated charges, thereby effectively degrading nitrogen monoxide and nitrogen dioxide in the atmosphere and converting these harmful gases into harmless substances. In addition, BiVO 4 performs well in water splitting applications, and photogenerated holes can oxidize water to form oxygen. However, its short carrier diffusion length (about 70 nm) can cause charge recombination, resulting in a low photocurrent density.

[0004] To further improve the photoelectrocatalytic performance of BiVO 4 , researchers have explored optimizing the photocurrent density and charge transfer efficiency by introducing a hole transport layer (HTL). For example, p-type P3HT is introduced as an HTL into the NiCo-LDH / BiVO 4 photoanode, which can increase the photocurrent density to 4.25 mA·cm -2 (1.23 V vs. RHE). In addition, using novel cuprous thiocyanate (CuSCN) as an HTL material can significantly improve the photoelectric conversion efficiency and stability. However, due to the low hole mobility of traditional HTL materials, their performance still has certain limitations. To overcome these problems, researchers have also utilized the photothermal effect to enhance the efficiency of photoelectrocatalytic reactions. The local surface plasmon resonance (LSPR) effect can cause the electrolyte temperature to rise, thereby accelerating the separation and transfer of photogenerated charges. For example, sandwiching a Co 3 O 4 photothermal layer between BiVO 4Between the photoanode film and the FeOOH / NiOOH electrocatalyst, the temperature of the photoanode can be effectively increased, charge transfer can be enhanced, and further the degradation of nitrogen oxides and the water oxidation reaction can be promoted.

[0005] However, how to develop a BiVO 4 photoelectrocatalytic material with both high hole mobility and photothermal effect is an urgent problem to be solved by those skilled in the art. SUMMARY OF THE INVENTION

[0006] The purpose of the present invention is to provide a BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material and its preparation method and application, so as to solve the problem that the existing BiVO 4 photoelectrocatalytic material cannot have both high hole mobility and photothermal effect.

[0007] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a preparation method of a BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material, comprising the following steps:

[0009] 1) Electrodeposit a BiOI film on the surface of a substrate, drop a vanadyl acetylacetonate solution on the surface of the BiOI film, and then perform high-temperature calcination and alkali solution immersion in sequence to obtain a BiVO 4 base layer;

[0010] 2) Coat a chloroform solution of copper sulfide on the surface of the BiVO 4 base layer to obtain a BiVO 4 / CuS composite material;

[0011] 3) Immerse the BiVO 4 / CuS composite material in an iron-nickel-cobalt solution with a pH value of 4.5 to 5.5 for the first-stage immersion, and then adjust the pH value of the solution to 6 to 8 for the second-stage immersion to obtain a BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material.

[0012] Preferably, in step 1), the substrate is a transparent conductive oxide material FTO;

[0013] The electrolyte for electrodeposition is obtained by mixing a potassium iodide solution of bismuth nitrate and a p-benzoquinone solution, wherein the concentration of bismuth nitrate in the potassium iodide solution of bismuth nitrate is 0.03 to 0.05 mol / L, and the concentration of potassium iodide is 0.3 to 0.5 mol / L;

[0014] The pH value of the potassium iodide solution of bismuth nitrate is 1.5 to 2;

[0015] The concentration of the p-benzoquinone solution is 0.18 to 0.28 mol / L;

[0016] The volume ratio of the potassium iodide solution of bismuth nitrate to the p-benzoquinone solution is 3 to 10:1 to 5.

[0017] Preferably, the electrodeposition in step 1) is carried out in a three-electrode system. In the three-electrode system, the substrate is used as the working electrode, the Ag / AgCl electrode is used as the reference electrode, and the Pt electrode is used as the counter electrode;

[0018] The deposition potential of the electrodeposition is -0.05 to -0.15 V vs. AgCl, and the electrodeposition time is 2 to 5 min.

[0019] Preferably, the concentration of the vanadyl acetylacetonate solution in step 1) is 0.2 mol / L, and the dropping amount is 50 to 150 μL / cm 2 。

[0020] Preferably, the temperature of the high-temperature calcination in step 1) is 400 to 500 °C, and the high-temperature calcination time is 1 to 3 h;

[0021] The alkali solution in the alkali solution immersion is sodium hydroxide solution, and the concentration is 0.5 to 2 mol / L;

[0022] The temperature of the alkali solution immersion is 20 to 30 °C, and the time is 1 to 60 min.

[0023] Preferably, the concentration of copper sulfide in the chloroform solution of copper sulfide in step 2) is 1 to 10 mg / mL, and the coating amount is 10 to 100 μL / cm 2 。

[0024] Preferably, the molar ratio of each element in the iron-nickel-cobalt solution in step 3) is iron:nickel:cobalt = 1 to 3:5 to 10:1 to 3, and the concentration of iron is 5 to 15 mmol / L;

[0025] The temperature of the first-stage immersion is 20 to 30 °C, and the time is 5 to 30 min.

[0026] Preferably, the temperature of the second-stage immersion in step 3) is 20 to 30 °C, and the time is 15 to 60 min.

[0027] The present invention provides a BiVO 4 / CuS / NiFeCoO x photocatalytic material prepared by the preparation method of the BiVO 4 / CuS / NiFeCoO x photocatalytic material.

[0028] The present invention also provides an application of a BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material in the preparation of hydrogen and oxygen by photoelectrocatalytic water splitting.

[0029] The present invention has at least the following beneficial effects:

[0030] 1. The BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material prepared by the present invention has good photocatalytic activity and stability. In a potassium borate solution with pH = 9.3, under an AM 1.5G xenon lamp light source and a light irradiation of 100 mW / cm 2 under an applied bias voltage of 1.23 V vs. RHE, the photocurrent density is 6.56 mA / cm 2 ; under an applied bias voltage of 1.23 V vs. RHE, after 28 h of reaction, the photocurrent density can be maintained above 95% of the initial value; the photoelectric conversion efficiency (ABPE) under an applied bias voltage of 0.64 V vs. RHE is 2.46%.

[0031] 2. The preparation method of the present invention is an electrodeposition, spin-coating and soaking method to prepare a photoelectrocatalytic material with a layer-by-layer structure, and this method has the advantages of being inexpensive, simple, safe, green and easy to operate.

[0032] 3. In the present invention, CuS with a photothermal effect is used as a hole transport layer, which can enhance the transfer of photo-generated holes from BiVO 4 the light absorption layer to NiFeCoO 4 the cocatalyst; in addition, the photothermal effect generated by CuS can generate additional thermal holes, increase the surface temperature of the photoanode, and accelerate the transfer of carriers, thereby effectively inhibiting the recombination of photo-generated carriers and improving the photoelectrocatalytic performance of the composite photoanode. x 4. The BiVO

[0033] / CuS / NiFeCoO 4 photoelectrocatalytic material of the present invention is combined with a silicon solar cell, and the solar-hydrogen conversion efficiency of the unbiased series device reaches 7.17%. x Description of the Drawings

[0034] Figure 1 For the scanning electron microscope image and transmission electron microscope image of the BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material prepared in Example 1, Figure 1 a in 4 ​ / CuS / NiFeCoO x Scanning electron microscope image of the photocatalytic material, Figure 1 where b in 4 / CuS / NiFeCoO x Transmission electron microscope image of the photocatalytic material;

[0035] Figure 2 For BiVO 4 、BiVO 4 / CuS, BiVO 4 / NiFeCoO x and BiVO 4 / CuS / NiFeCoO x linear sweep curves of the electrodes;

[0036] Figure 3 For BiVO 4 、BiVO 4 / CuS and BiVO 4 / CuS / NiFeCoO x photocurrent conversion efficiency curves;

[0037] Figure 4 The BiVO 4 / CuS / NiFeCoO x photocatalytic material prepared in Example 1 shows the hydrogen and oxygen production at an applied bias of 1.23 V vs. RHE;

[0038] Figure 5 For BiVO 4 and BiVO 4 / CuS / NiFeCoO x photocatalytic material, the curve of current density versus time during water splitting to produce hydrogen;

[0039] Figure 6 Schematic diagram of a bias-free water splitting device driven by a silicon solar cell;

[0040] Figure 7 J-V curve of the silicon solar cell under AM 1.5G simulated solar radiation;

[0041] Figure 8 For BiVO 4 / CuS / NiFeCoO x photocatalytic material - double electrode J-V curves of the platinum cathode and the silicon solar cell (behind and in front of the photoanode). Detailed implementation mode

[0042] The present invention provides a BiVO4 / CuS / NiFeCoO x Preparation method of photo-electrocatalytic material, comprising the following steps:

[0043] 1) Electrodeposit a BiOI film on the surface of a substrate, drop a vanadyl acetylacetonate solution on the surface of the BiOI film, and then perform high-temperature calcination and alkali solution immersion in sequence to obtain a BiVO 4 base layer;

[0044] 2) Coat a chloroform solution of copper sulfide on the surface of the BiVO 4 base layer to obtain a BiVO 4 / CuS composite material;

[0045] 3) Immerse the BiVO 4 / CuS composite material in an iron-nickel-cobalt solution with a pH value of 4.5 to 5.5 for the first-stage immersion, and then adjust the pH value of the solution to 6 to 8 for the second-stage immersion to obtain BiVO 4 / CuS / NiFeCoO x photo-electrocatalytic material.

[0046] In the present invention, the substrate described in step 1) is a transparent conductive oxide material FTO.

[0047] In the present invention, the substrate described in step 1) also needs to be pretreated before use. The specific operation method is: ultrasonically clean the substrate with a cleaner, acetone, ethanol, and deionized water in sequence for 10 to 15 minutes, and then soak it in ethanol for standby.

[0048] In the present invention, the electrolyte for electrodeposition in step 1) is obtained by mixing a potassium iodide solution of bismuth nitrate with a p-benzoquinone solution. The concentration of bismuth nitrate in the potassium iodide solution of bismuth nitrate is 0.03 to 0.05 mol / L, preferably 0.035 to 0.045 mol / L, and further preferably 0.04 mol / L; the concentration of potassium iodide is 0.3 to 0.5 mol / L, preferably 0.33 to 0.48 mol / L, further preferably 0.35 to 0.45 mol / L, and more preferably 0.4 mol / L.

[0049] In the present invention, the pH value of the potassium iodide solution of bismuth nitrate is 1.5 to 2, preferably 1.7.

[0050] In the present invention, the concentration of the p-benzoquinone solution is 0.18 to 0.28 mol / L, preferably 0.20 to 0.26 mol / L, further preferably 0.22 to 0.25 mol / L, and more preferably 0.23 mol / L.

[0051] In the present invention, the volume ratio of the potassium iodide solution of bismuth nitrate to the p-benzoquinone solution is 3-10:1-5, preferably 4-8:2-4, and more preferably 5:2.

[0052] In the present invention, the electrodeposition in step 1) is preferably carried out in a three-electrode system. In the three-electrode system, the substrate is used as the working electrode, the Ag / AgCl (saturated KCl) electrode is used as the reference electrode, and the Pt electrode is used as the counter electrode.

[0053] In the present invention, the deposition potential of the electrodeposition is -0.05 to -0.15 V vs. AgCl, preferably -0.07 to -0.13 V vs. AgCl, more preferably -0.09 to -0.11 V vs. AgCl, and even more preferably -0.1 V vs. AgCl; the electrodeposition time is 2 to 5 min, preferably 2.5 to 4.5 min, more preferably 3 to 4 min, and even more preferably 3 min.

[0054] In the present invention, the concentration of the vanadyl acetylacetonate solution in step 1) is 0.15 to 0.25 mol / L, preferably 0.18 to 0.23 mol / L, and more preferably 0.2 mol / L; the dropping amount is 50 to 150 μL / cm 2 , preferably 70 to 130 μL / cm 2 , more preferably 90 to 110 μL / cm 2 , and even more preferably 100 μL / cm 2 .

[0055] In the present invention, the temperature of the high-temperature calcination in step 1) is 400 to 500 °C, preferably 440 to 460 °C, and more preferably 450 °C; the high-temperature calcination time is 1 to 3 h, preferably 1.5 to 2.5 h, and more preferably 2 h.

[0056] In the present invention, the alkali solution in the alkali solution immersion in step 1) is a sodium hydroxide solution, and the concentration is 0.5 to 2 mol / L, preferably 0.6 to 1.8 mol / L, more preferably 0.8 to 1.5 mol / L, and even more preferably 1 mol / L.

[0057] In the present invention, the temperature of the alkali solution immersion is 20 to 30 °C, preferably 22 to 28 °C, and more preferably 25 °C; the time is 1 to 60 min, preferably 10 to 50 min, more preferably 20 to 40 min, and even more preferably 30 min.

[0058] In the present invention, the preparation method of copper sulfide in step 2) is as follows: CuCl 2 and S powder are respectively dissolved in oleylamine (OLA), and then CuCl 2The solution is mixed with the S powder solution and transferred to a Teflon-lined stainless steel autoclave at room temperature, and then heat-treated; after the reaction is completed, it is washed five times with a mixed solvent of n-hexane and ethanol to remove OLA on the surface of CuS.

[0059] The temperature of the heat treatment is 80 - 120 °C, preferably 85 - 115 °C, further preferably 90 - 110 °C, and more preferably 95 - 105 °C; the time is 20 - 100 min, preferably 40 - 90 min, further preferably 50 - 80 min, and more preferably 60 min.

[0060] In the present invention, the concentration of copper sulfide in the chloroform solution of copper sulfide in step 2) is 1 - 10 mg / mL, preferably 2 - 8 mg / mL, further preferably 4 - 6 mg / mL, and more preferably 5 mg / mL; the coating amount is 10 - 100 μL / cm 2 , preferably 20 - 80 μL / cm 2 , further preferably 30 - 60 μL / cm 2 , more preferably 50 μL / cm 2 .

[0061] In the present invention, the coating method in step 2) is preferably spin coating, and the spin coating speed is 1000 - 5000 rpm / min, preferably 2000 - 4000 rpm / min, further preferably 2500 - 3500 rpm / min, and more preferably 3000 rpm / min; the time is 10 - 60 s, preferably 15 - 50 s, further preferably 20 - 40 s, and more preferably 30 s.

[0062] In the present invention, after the chloroform solution of copper sulfide in step 2) is coated on the surface of the BiVO 4 substrate layer, it further includes a step of annealing it at 150 - 240 °C, preferably 160 - 220 °C, further preferably 170 - 200 °C, and more preferably 180 °C; the annealing time is 10 - 60 min, preferably 15 - 45 min, further preferably 25 - 35 min, and more preferably 30 min.

[0063] In the present invention, the molar ratio of each element in the iron-nickel-cobalt solution in step 3) is iron: nickel: cobalt = 1 - 3: 5 - 10: 1 - 3, preferably 1.5 - 2.5: 6 - 9: 1 - 2.5, further preferably 1.8 - 2.3: 7 - 8: 1 - 1.5, and more preferably 2: 7: 1; the concentration of iron is 5 - 15 mmol / L, preferably 7 - 13 mmol / L, further preferably 9 - 11 mmol / L, and more preferably 10 mmol / L.

[0064] In the present invention, the temperature of the first-stage soaking is 20 to 30 °C, preferably 22 to 28 °C, more preferably 25 to 26 °C; the time is 5 to 30 min, preferably 10 to 25 min, more preferably 15 to 20 min, and most preferably 15 min.

[0065] In the present invention, the temperature of the second-stage soaking in step 3) is 20 to 30 °C, preferably 22 to 28 °C, more preferably 25 to 26 °C; the time is 15 to 60 min, preferably 20 to 50 min, more preferably 25 to 40 min, and most preferably 30 min.

[0066] In the present invention, when adjusting the pH value of the solution to 6 to 8 in step 3), it is preferably to adjust the pH value of the solution by using tannic acid solution or sodium hydroxide solution.

[0067] The present invention provides a BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material prepared by the preparation method of the photoelectrocatalytic material. 4 / CuS / NiFeCoO x photoelectrocatalytic material.

[0068] In the present invention, the BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material has a layered structure, including a substrate, a BiVO 4 layer, a hole transport layer CuS with a photothermal effect, and a NiFeCoO x cocatalyst layer.

[0069] The present invention also provides an application of a BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material in the photoelectrocatalytic decomposition of water to produce hydrogen and oxygen. The specific application method is as follows:

[0070] 1. Using the BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material as the working electrode, a Pt sheet as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode to construct a three-electrode system, using a potassium borate solution as the electrolyte, and performing photoelectrocatalytic decomposition of water under light irradiation and an applied bias voltage.

[0071] The concentration of the potassium borate solution is 0.1 to 1.0 mol / L, preferably 0.2 to 0.8 mol / L, more preferably 0.4 to 0.6 mol / L, and most preferably 0.5 mol / L;

[0072] The light source for the light irradiation is an AM 1.5G xenon lamp, and the light irradiance is 10-150 mW / cm 2 , preferably 30-130 mW / cm 2 , more preferably 50-110 mW / cm 2 , even more preferably 80-100 mW / cm 2 ;

[0073] The magnitude of the applied bias voltage is 1.23 V vs. RHE.

[0074] 2. Using BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material as the working anode, a Pt sheet as the cathode, a silicon solar cell is placed behind the photoanode and connected in series with the working anode and cathode to supply energy to the anode and cathode, and a potassium borate solution is used as the electrolyte to carry out photoelectrocatalytic water splitting under light irradiation.

[0075] The concentration of the potassium borate solution is 0.1-1.0 mol / L, preferably 0.2-0.8 mol / L, more preferably 0.4-0.6 mol / L, and even more preferably 0.5 mol / L;

[0076] The light source for the light irradiation is an AM 1.5G xenon lamp, and the light irradiance is 10-150 mW / cm 2 , preferably 30-130 mW / cm 2 , more preferably 50-110 mW / cm 2 , even more preferably 80-100 mW / cm 2 .

[0077] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they cannot be construed as limiting the protection scope of the present invention.

[0078] Example 1

[0079] (1) First, prepare a BiOI nanothin film by electrodeposition using a CHI 660E electrochemical workstation. The specific steps are as follows: Use an FTO conductive glass ultrasonically cleaned successively with detergent, acetone, ethanol, and water as the working electrode, an Ag / AgCl (saturated KCl solution) electrode as the reference electrode, and a Pt electrode as the counter electrode. Add 2 mmol Bi(NO 3 ) 3 ·5H 2O is dissolved in 50 mL of 0.4 mol / L KI solution, and the pH is adjusted to 1.7 with concentrated nitric acid (16 mol / L), and stirred until the solution becomes a clear orange-red solution. Then, 20 mL of 0.23 mol / L ethanol solution of p-benzoquinone is slowly added and stirred for 5 min, and the solution turns blood-red. The above blood-red solution is used as the electrolyte. Electrodeposition is carried out at -0.1 V vs. AgCl constant potential for 3 min to obtain a BiOI nanometer film, and the obtained BiOI nanometer film is rinsed with distilled water.

[0080] Subsequently, BiVO is prepared by calcination 4 Base layer, the specific steps are as follows: 0.10 mL of 0.2 mol / L dimethyl sulfoxide solution of vanadyl acetylacetonate is dropped on the prepared BiOI nanometer film (1 cm 2 ), and the temperature is raised to 450 °C at a heating rate of 2 °C / min in a muffle furnace, and calcined for 2 h. After cooling to room temperature, the electrode sheet is soaked in 1 M NaOH solution for 15 min to remove the excess V 2 O 5 , and rinsed with a large amount of ultrapure water and air-dried to obtain a BiVO 4 Base layer.

[0081] (2) 0.5 mmol of CuCl 2 and 0.5 mmol of sulfur powder are respectively dissolved in 10 mL and 5.0 mL of oleylamine (OLA) to obtain two precursor solutions. Then the two precursor solutions are mixed and transferred to a Teflon-lined stainless steel autoclave (20 mL) at room temperature, and then heated at 120 °C for 60 min. After the reaction, it is washed five times with a mixed solvent of n-hexane and ethanol to remove the OLA on the surface of CuS, and finally dissolved in chloroform. The CuS solution (5 mg / mL) is spin-coated twice on the BiVO 4 Base layer, the rotation speed of each spin coating is 3000 rpm / min, the time is 30 s, and the total coating amount is 50 μL / cm 2 , and then annealed at 180 °C for 30 min to obtain a BiVO 4 / CuS composite material.

[0082] (3) 2 mL of 10 mM FeCl 3 ·6H 2 O solution, 7 mL of 10 mM NiCl 2 ·6H 2 O solution and 1 mL of 10 mM CoCl 2 ·6H 2 O solution are uniformly mixed in a container. The BiVO 4The BiVO 2 / CuS composite material was immersed in a container for 15 min, then 10 mL of 9 mg / L tannic acid solution and 75 μL of 2 M NaOH solution were added successively to adjust the pH value of the system to 6.8. After continuing to soak for 30 min, the material was taken out, washed with deionized water and dried with N 2 gas flow to obtain BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material.

[0083] Example 2

[0084] (1) First, a BiOI nanometer film was prepared by electrodeposition using a CHI 660E electrochemical workstation. The specific steps were as follows: The FTO conductive glass ultrasonically cleaned successively with detergent, acetone, ethanol, and water was used as the working electrode, the Ag / AgCl (saturated KCl solution) electrode was used as the reference electrode, and the Pt electrode was used as the counter electrode. 2 mmol of Bi(NO 3 ) 3 ·5H 2 O was dissolved in 50 mL of 0.4 mol / L KI solution, and its pH was adjusted to 1.7 with concentrated nitric acid (16 mol / L), and it was stirred until the solution was a clear orange-red solution. Then 20 mL of 0.23 mol / L ethanol solution of p-benzoquinone was slowly added and stirred for 5 min, and the solution turned blood red. The above blood-red solution was used as the electrolyte. Electrodeposition was carried out at a constant potential of -0.1 V vs. AgCl for 3 min to obtain the BiOI nanometer film, and the obtained BiOI nanometer film was rinsed with distilled water.

[0085] Subsequently, a BiVO 4 base layer was prepared by calcination. The specific steps were as follows: 0.10 mL of 0.2 mol / L dimethyl sulfoxide solution of vanadyl acetylacetonate was respectively dropped on the prepared BiOI nanometer film (1 cm 2 ), and it was heated in a muffle furnace at a heating rate of 2 °C / min to 450 °C and calcined for 2 h. After cooling to room temperature, the electrode sheet was soaked in 1 M NaOH solution for 15 min to remove the excess V 2 O 5 , and rinsed with a large amount of ultrapure water and air-dried to obtain the BiVO 4 base layer.

[0086] (2) 0.5 mmol of CuCl 20.5 mmol of sulfur powder was respectively dissolved in 10 mL and 5.0 mL of oleylamine (OLA) to obtain two precursor solutions. Then the two precursor solutions were mixed and transferred to a Teflon-lined stainless steel autoclave (20 mL) at room temperature, and then heated at 80 °C for 100 min. After the reaction, it was washed five times with a mixed solvent of n-hexane and ethanol to remove OLA on the surface of CuS, and finally dissolved in chloroform. The CuS solution (5 mg / mL) was spin-coated twice onto the BiVO 4 substrate layer at a rotation speed of 3000 rpm / min for 30 s each time, and the total coating amount was 50 μL / cm 2 , and then annealed at 180 °C for 30 min to obtain BiVO 4 / CuS composite material.

[0087] (3) 2 mL of 10 mM FeCl 3 ·6H 2 O solution, 7 mL of 10 mM NiCl 2 ·6H 2 O solution and 1 mL of 10 mM CoCl 2 ·6H 2 O solution were uniformly mixed in a container. The BiVO 4 / CuS composite material was immersed in the container for 15 min, then 10 mL of 9 mg / L tannic acid solution and 75 μL of 2 M NaOH solution were added in sequence to adjust the pH value of the system to 6. After continuing to soak for 60 min, the material was taken out, washed with deionized water and dried with N 2 gas flow to obtain BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material.

[0088] Example 3

[0089] (1) First, a BiOI nanometer thin film was prepared by electrodeposition using a CHI 660E electrochemical workstation. The specific steps were as follows: The FTO conductive glass ultrasonically cleaned successively with detergent, acetone, ethanol, and water was used as the working electrode, the Ag / AgCl (saturated KCl solution) electrode was used as the reference electrode, and the Pt electrode was used as the counter electrode. 2.5 mmol of Bi(NO 3 ) 3 ·5H 2O was dissolved in 50 mL of 0.5 mol / L KI solution, and its pH was adjusted to 1.5 with concentrated nitric acid (16 mol / L). It was stirred until the solution became a clear orange-red solution. Then, 20 mL of 0.25 mol / L ethanol solution of p-benzoquinone was slowly added and stirred for 5 min. The solution turned blood-red, and the above blood-red solution was used as the electrolyte. Electrodeposition was carried out at -0.15 V vs. AgCl constant potential for 3 min to obtain a BiOI nanometer film, and the obtained BiOI nanometer film was rinsed with distilled water.

[0090] Subsequently, BiVO was prepared by calcination 4 The base layer, and the specific steps are as follows: 0.15 mL of 0.25 mol / L dimethyl sulfoxide solution of vanadyl acetylacetonate was respectively dropped onto the prepared BiOI nanometer film (1 cm 2 ), and the temperature was raised to 500 °C at a heating rate of 2 °C / min in a muffle furnace and calcined for 1 h. After cooling to room temperature, the electrode sheet was soaked in a NaOH solution with a temperature of 25 °C and a concentration of 1.5 mol / L for 30 min to remove the excess V 2 O 5 , and rinsed with a large amount of ultrapure water and air-dried to obtain a BiVO 4 base layer.

[0091] (2) 0.5 mmol of CuCl 2 and 0.5 mmol of sulfur powder were respectively dissolved in 10 mL and 5.0 mL of oleylamine (OLA) to obtain two precursor solutions. Then, the two precursor solutions were mixed and transferred to a Teflon-lined stainless steel autoclave (20 mL) at room temperature, and then heated at 80 °C for 100 min. After the reaction, it was washed five times with a mixed solvent of n-hexane and ethanol to remove the OLA on the surface of CuS, and finally dissolved in chloroform. The CuS solution (5 mg / mL) was spin-coated twice onto the BiVO 4 base layer, the rotation speed of each spin coating was 3000 rpm / min, the time was 30 s, and the total coating amount was 100 μL / cm 2 , and then annealed at 180 °C for 30 min to obtain a BiVO 4 / CuS composite material.

[0092] (3) 3 mL of 10 mM FeCl 3 ·6H 2 O solution, 8 mL of 10 mM NiCl 2 ·6H 2 O solution and 2 mL of 10 mM CoCl 2 ·6H 2 O solution were uniformly mixed in a container. The BiVO 4The BiVO 2 / CuS composite material was immersed in a container for 15 min, and then 10 mL of 9 mg / L tannic acid solution and 75 μL of 2 M NaOH solution were added successively. The pH value of the system was adjusted to 6.3, and after continued immersion for 60 min, the material was taken out, washed with deionized water, and dried with N 2 gas flow to obtain BiVO 4 x / CuS / NiFeCoO x photoelectrocatalytic material.

[0093] Example 4

[0094] (1) First, a BiOI nanometer film was prepared by electrodeposition using a CHI 660E electrochemical workstation. The specific steps were as follows: The FTO conductive glass ultrasonically cleaned successively with detergent, acetone, ethanol, and water was used as the working electrode, the Ag / AgCl (saturated KCl solution) electrode was used as the reference electrode, and the Pt electrode was used as the counter electrode. 2.3 mmol of Bi(NO 3 ) 3 ·5H 2 O was dissolved in 50 mL of 0.45 mol / L KI solution, and its pH was adjusted to 2 with concentrated nitric acid (16 mol / L), and it was stirred until the solution became a clear orange-red solution. Then, 20 mL of 0.18 mol / L p-benzoquinone ethanol solution was slowly added and stirred for 5 min, and the solution turned blood-red. The above blood-red solution was used as the electrolyte. Electrodeposition was carried out at a constant potential of -0.05 V vs. AgCl for 5 min to obtain the BiOI nanometer film, and the obtained BiOI nanometer film was rinsed with distilled water.

[0095] Subsequently, a BiVO 4 base layer was prepared by calcination. The specific steps were as follows: 0.10 mL of 0.2 mol / L vanadyl acetylacetonate dimethyl sulfoxide solution was respectively dropped on the prepared BiOI nanometer film (1 cm 4 ), and it was heated in a muffle furnace to 450 °C at a heating rate of 2 °C / min and calcined for 2 h. After cooling to room temperature, the electrode sheet was soaked in 3 M NaOH solution for 20 min to remove the excess V 2 ) 2 O 5 , and rinsed with a large amount of ultrapure water and air-dried to obtain the BiVO 4 base layer. 4

[0096] (2) 0.5 mmol of CuCl 20.5 mmol of sulfur powder was dissolved in 10 mL and 5.0 mL of oleylamine (OLA) respectively to obtain two precursor solutions. Then the two precursor solutions were mixed and transferred to a Teflon-lined stainless steel autoclave (20 mL) at room temperature, and then heated at 80 °C for 100 min. After the reaction, it was washed five times with a mixed solvent of n-hexane and ethanol to remove OLA on the surface of CuS, and finally dissolved in chloroform. The CuS solution (5 mg / mL) was spin-coated twice onto the BiVO 4 substrate layer, with a rotation speed of 3000 rpm / min and a time of 30 s for each spin-coating, and the total coating amount was 80 μL / cm 2 , and then annealed at 180 °C for 30 min to obtain BiVO 4 / CuS composite material.

[0097] (3) 1 mL of 10 mM FeCl 3 ·6H 2 O solution, 10 mL of 10 mM NiCl 2 ·6H 2 O solution and 1 mL of 10 mM CoCl 2 ·6H 2 O solution were uniformly mixed in a container. The BiVO 4 / CuS composite material was immersed in the container for 15 min, then 10 mL of 9 mg / L tannic acid solution and 75 μL of 2 M NaOH solution were added in sequence to adjust the pH value of the system to 6.9, and after continuing to soak for 60 min, the material was taken out, washed with deionized water and dried with N 2 air flow to obtain BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material.

[0098] Comparative Example 1

[0099] The BiVO 4 substrate layer prepared in step (1) of Example 1 was put into a solution uniformly mixed with 2 mL of 10 mM FeCl 3 ·6H 2 O, 7 mL of 10 mM NiCl 2 ·6H 2 O and 1 mL of 10 mM CoCl 2 ·6H 2 O solution. The BiVO 4 / CuS was immersed in the container for 15 min, then 10 mL of 9 mg / L tannic acid solution and 75 μL of 2 M NaOH solution were added in sequence to adjust the pH value of the system to 6.8, and after continuing to soak for 30 min, the material was taken out, washed with deionized water and dried with N 2 air flow to obtain BiVO4 / NiFeCoO x Composite material.

[0100] The difference between this comparative example and Example 1 is that the use of the CuS hole transport layer is omitted, and only BiVO is sequentially covered on the FTO conductive glass substrate 4 layer and NiFeCoO x layer.

[0101] Comparative Example 2

[0102] On the surface of the BiVO 4 substrate layer prepared in step (1) of Example 1, a CuS solution (5 mg / mL) was spin-coated, and the rotation speed for each spin-coating was 3000 rpm / min, the time was 30 s, and the coating amount was 50 μL / cm 2 , and after two spin-coatings, it was annealed at 180 °C for 30 min to obtain BiVO 4 / CuS composite material.

[0103] The difference between this comparative example and Example 1 is that only the CuS hole transport layer is loaded, and the co-catalyst is not impregnated and loaded. This photo-electrocatalytic material consists of an FTO conductive glass substrate and BiVO sequentially covered on the FTO conductive glass substrate 4 layer and CuS layer.

[0104] Test analysis:

[0105] (I), Structural characterization

[0106] 1. The BiVO 4 / CuS / NiFeCoO x prepared in Example 1 was subjected to SEM and TEM test analyses, and the test results are shown in detail in Figure 1 , where Figure 1 Figure a in 4 / CuS / NiFeCoO x is the SEM image of BiVO Figure 1 Figure b in 4 / CuS / NiFeCoO x is the TEM image of BiVO Figure 1 As can be seen from Figure a in 4 / CuS / NiFeCoO x , BiVO Figure 1 / CuS / NiFeCoO 4 has a worm-like morphology and a relatively rough surface, indicating that it has more active sites. As can be seen from Figure b in x , BiVO 4 / CuS / NiFeCoOx and is evenly coated, which is beneficial to the rapid transfer of photo-generated holes from BiVO 4 to NiFeCoO x .

[0107] (II) Performance Test

[0108] Under the light irradiation of an AM 1.5G xenon light source with 100 mW / cm 2 , the BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material prepared in Example 1, the BiVO 4 substrate layer prepared in step (1) of Example 1, the BiVO 4 / NiFeCoO x composite material prepared in Comparative Example 1, and the BiVO 4 / CuS composite material prepared in Comparative Example 2 (hereinafter referred to as BiVO 4 / CuS / NiFeCoO x , BiVO 4 , BiVO 4 / NiFeCoO x , BiVO 4 / CuS) were tested for linear sweep voltammetry curves and photoelectric conversion efficiency. The tests were all carried out in a three-electrode system with the material to be tested as the working electrode, a Pt sheet as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode. The electrolyte was a 0.5 mol / L boric acid buffer solution with pH = 9.3, and the scan rate was 10 mV / s. The specific test results are as shown in Figure 2 and Figure 3 :

[0109] Figure 2 are the linear sweep voltammetry curves of BiVO 4 , BiVO 4 / CuS, BiVO 4 / NiFeCoO x and BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic materials; it can be seen from Figure 2 that under an applied bias voltage of 1.23 V vs. RHE, the photocurrent densities of BiVO 4 , BiVO 4 / CuS, BiVO 4 / NiFeCoO x and BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic materials are 1.5, 3.8, 4.1 and 6.56 mA / cm2 .

[0110] Figure 3 For BiVO 4 , BiVO 4 / CuS and BiVO 4 / CuS / NiFeCoO x Photocurrent conversion efficiency curves of the photocatalytic materials under different applied bias voltages. It can be seen from Figure 3 that the photocurrent conversion efficiency (ABPE) of BiVO 4 under a bias voltage of 0.88 V vs. RHE is 0.34%, the photocurrent conversion efficiency (ABPE) of BiVO 4 / CuS under a bias voltage of 0.85 V vs. RHE is 0.95%, and the photocurrent conversion efficiency (ABPE) of BiVO 4 / CuS / NiFeCoO x under a bias voltage of 0.64 V vs. RHE is 2.46%.

[0111] In a 0.5 mol / L potassium borate solution with pH = 9.3, under the irradiation of an AM 1.5G xenon light source with a light intensity of 100 mW / cm 2 and under an applied bias voltage of 1.23 V vs. RHE, the hydrogen production and oxygen production amounts of the photocatalytic material BiVO 4 / CuS / NiFeCoO x prepared in Example 1 were tested. The test was carried out in a three-electrode system with the photocathode to be measured as the working electrode, a Pt sheet as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode. The test results are as Figure 4 shown. It can be seen from Figure 4 that under an applied bias voltage of 1.23 V vs. RHE, the hydrogen production and oxygen production rates are 48 and 97 μmol / h, respectively.

[0112] BiVO 4 and BiVO 4 / CuS / NiFeCoO x The stability of the photocatalytic materials for photocatalytic water splitting to produce hydrogen under 1.23 V vs. RHE is as Figure 5 shown. It can be seen from Figure 5 that under an applied bias voltage of 1.23 V vs. RHE, after 3 h of reaction, the photocurrent density of BiVO 4 is only 50% of the initial value, while BiVO 4 / CuS / NiFeCoO x can still remain above 95% of the initial value after 28 h of reaction.

[0113] Schematic diagram of a bias-free water splitting device driven by a silicon solar cell is as follows Figure 6 shown. The results of the J-V test of the Si solar cell (rated voltage of 1.5 V) are shown in detail in Figure 7 . It can be seen from Figure 7 that the short-circuit current density of the photovoltaic cell is 15.6 mA cm -2 , and the open-circuit voltage is 1.16 V.

[0114] BiVO 4 / CuS / NiFeCoO x The J-V curves of the two-electrode of the photoelectrocatalytic material - platinum cathode and silicon solar cell (behind and in front of the photoanode) are shown in Figure 8 shown, where Si solar cell represents the J-V curve of the Si solar cell under conventional conditions, and Si solar cell (behind BiVO 4 ) represents the J-V curve of the Si solar cell obtained by placing the photoanode above the Si solar cell (the light first irradiates the surface of the photoanode, and the light not absorbed by the photoanode is used to excite the Si solar cell to generate electricity), and BiVO 4 / CuS / NiFeCoO x represents the LSV curve tested in a boric acid buffer solution with an electrolyte of 0.5 mol / L and pH = 9.3. It can be seen from Figure 8 that when the BiVO 4 / CuS / NiFeCoO x photoelectrocatalytic material is combined with the silicon solar cell, the solar-to-hydrogen conversion efficiency of the bias-free series device reaches 7.17%.

[0115] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. BiVO4 / CuS / NiFeCoO x A method for preparing a photoelectrocatalytic material, characterized in that: The following steps are involved: 1) Electrodepositing a BiOI film on the surface of a substrate, dripping a vanadyl acetylacetonate solution on the surface of the BiOI film, and then sequentially calcining at high temperature and soaking in alkaline solution to obtain a BiVO4 base layer; 2) coating a chloroform solution of copper sulfide onto the surface of the BiVO4 substrate to obtain a BiVO4 / CuS composite material; 3) The BiVO4 / CuS composite material is immersed in an iron-nickel-cobalt solution with a pH value of 4.5 to 5.5 for the first stage, and then the solution pH value is adjusted to 6 to 8 for the second stage, to obtain BiVO4 / CuS / NiFeCoO x Photoelectrocatalytic materials.

2. A BiVO4 / CuS / NiFeCoO according to claim 1 x A method for preparing a photoelectrocatalytic material, characterized in that: In step 1), the substrate is a transparent conductive oxide material FTO; The electroplating electrolyte is obtained by mixing a potassium iodide solution of bismuth nitrate and a p-benzoquinone solution, wherein the concentration of bismuth nitrate in the potassium iodide solution is 0.03-0.05 mol / L, and the concentration of potassium iodide is 0.3-0.5 mol / L; The pH value of the potassium iodide solution of bismuth nitrate is 1.5-2; The concentration of the p-benzoquinone solution is 0.18-0.28 mol / L; The volume ratio of the potassium iodide solution of bismuth nitrate to the p-benzoquinone solution is 3-10:1-5.

3. A BiVO4 / CuS / NiFeCoO according to claim 2 x A method for preparing a photoelectrocatalytic material, characterized in that: The electrodeposition in step 1) is carried out in a three-electrode system, wherein the substrate is used as a working electrode, the Ag / AgCl electrode is used as a reference electrode, and the Pt electrode is used as a counter electrode; The deposition potential of the electrodeposition is -0.05 to -0.15 V vs. AgCl, and the electrodeposition time is 2 to 5 minutes.

4. A BiVO4 / CuS / NiFeCoO according to claim 3 x A method for preparing a photoelectrocatalytic material, characterized in that: The concentration of the vanadyl acetylacetonate solution in step 1) is 0.15-0.25 mol / L, and the amount added is 50-150 μL / cm 2 .

5. The method for preparing a BiVO4 / CuS / NiFeCoOx photoelectrocatalytic material according to any one of claims 1 to 4, characterized in that: The high temperature calcination temperature in step 1) is 400-500°C, and the high temperature calcination time is 1-3h; The alkali solution used in the alkali solution soaking is a sodium hydroxide solution with a concentration of 0.5 to 2 mol / L; The alkali solution soaking temperature is 20-30°C and the time is 1-60 minutes.

6. A BiVO4 / CuS / NiFeCoO according to claim 5 x A method for preparing a photoelectrocatalytic material, characterized in that: The concentration of copper sulfide in the chloroform solution of copper sulfide in step 2) is 1-10 mg / mL, and the coating amount is 10-100 μL / cm 2 .

7. A BiVO4 / CuS / NiFeCoO according to claim 6 x A method for preparing a photoelectrocatalytic material, characterized in that: The molar ratio of each element in the iron-nickel-cobalt solution in step 3) is iron:nickel:cobalt=1-3:5-10:1-3, wherein the concentration of iron is 5-15 mmol / L; The soaking temperature in the first stage is 20-30° C. and the soaking time is 5-30 minutes.

8. A BiVO4 / CuS / NiFeCoO according to claim 6 or 7 x A method for preparing a photoelectrocatalytic material, characterized in that: The second stage of soaking in step 3) is performed at a temperature of 20 to 30° C. and for a time of 15 to 60 minutes.

9. A BiVO4 / CuS / NiFeCoO according to any one of claims 1 to 8 x Preparation method of photoelectrocatalytic material BiVO4 / CuS / NiFeCoO prepared x Photoelectrocatalytic materials.

10. The BiVO4 / CuS / NiFeCoO according to claim 9 x Application of photoelectrocatalytic materials in photoelectrocatalytic water decomposition to produce hydrogen and oxygen.

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