Composite photoelectric catalytic material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photoelectrocatalysis, and particularly discloses a composite photoelectrocatalysis material and a preparation method and application thereof. The preparation method comprises the following steps: firstly, carrying out electro-deposition by taking a Bi-containing solution as an electrolyte, coating a precursor solution containing V, and then carrying out annealing treatment to obtain a BiVO4 matrix material; carrying out photo-assisted electro-deposition by taking the BiVO4 base material as a working electrode and taking a solution containing Ni as an electrolyte to obtain NiO / BiVO4; and then coating the NiO / BiVO4 with a solution containing the Ni5P4 nano-particles, so as to obtain the composite photoelectric catalytic material. The composite photoelectric catalytic material obtained by the invention has a built-in electric field, and has high catalytic activity and an excellent catalytic effect; the Ni5P4 greatly improves the yield and the selectivity of H2O2; the preparation method also has the characteristics of simplicity and convenience in operation, less time consumption and low energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectrocatalysis, and particularly to a composite photoelectrocatalytic material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of human society, the demand for fossil fuels has been increasing continuously. However, the overuse of fossil fuels has brought serious environmental pollution problems, especially the large emissions of greenhouse gases, such as carbon dioxide (CO 2 ), ozone (O 3 ), methane (CH 4 ), etc. In order to achieve sustainable development, it is crucial to develop an innovative technology for controlling air pollution and alleviating greenhouse gas emissions, and to find new energy fuels to replace fossil fuels.

[0003] Photoelectrocatalysis (PEC), as an emerging technology, has shown great potential in controlling air pollution and alleviating greenhouse gas emissions. The PEC technology promotes chemical reactions by converting light energy into chemical energy. In the treatment of air pollution, it can effectively degrade harmful gases in the air, such as nitrogen oxides, volatile organic compounds, etc., and convert them into harmless substances. At the same time, the PEC technology can also convert greenhouse gases such as CO 2 into useful chemicals, realizing the reduction of greenhouse gas emissions and the recycling of resources.

[0004] Hydrogen peroxide, commonly known as hydrogen peroxide (H 2 O 2 ), is the cleanest green oxidant. It has the highest active oxygen content (47.1% w / w), and no toxic by-products are generated during the reaction process. Only water (H 2 O) and oxygen (O 2 ) are produced. In addition, the energy density of H 2 O 2 is 3.0 MJL -1 (60 wt% H 2 O 2 ), which is higher than that of compressed hydrogen (35 MPa, 2.8 MJL -1 ). It is a green fuel that can be stored and transported directly and can be used to generate electricity directly. Therefore, H 2 O 2 is considered to be the most promising green energy carrier to replace fossil fuels. Preparing H 2 O 2 by PEC water oxidation is considered to be a green and economical method for synthesizing H 2 O 2 . However, since the water oxidation reaction (WOR) process is controlled by a four-electron reaction with slow kinetics, O 2 is generated instead of high-value-added H2 O 2 Therefore, the proper selection and reasonable design of semiconductor photocatalytic materials are of great significance for the efficient generation of H 2 O 2 as well as the treatment of air pollution and the mitigation of greenhouse gas emissions.

[0005] So far, among various semiconductor photocatalytic materials available for solar-driven H 2 O 2 generation, for example: titanium oxide (TiO 2 ), tungsten oxide (WO 3 ), and zinc oxide (ZnO), etc., bismuth vanadate (BiVO 4 ) stands out as a promising photocatalyst. BiVO 4 with a monoclinic scheelite crystal system has a narrow bandgap of about 2.4 eV, can efficiently absorb sunlight, and has a suitable energy band structure, thus selectively generating H 2 O 2 . In addition, due to the effective mass of the photo-generated carriers of BiVO 4 being much lighter than that of other oxides such as TiO 2 and In 2 O 3 . Therefore, for BiVO 4 , charge extraction is easier. However, the performance of BiVO 4 for solar H 2 O 2 generation is hindered by its inherent drawbacks, such as poor carrier mobility and charge separation efficiency. In addition, due to the easy decomposition of H 2 O 2 , the H 4 yield of bare BiVO 2 O 2 is usually low.

[0006] Therefore, how to provide a composite photoelectrocatalytic material, design the bare BiVO 4 , and at the same time optimize the reaction conditions to improve the efficiency of BiVO 4 -based photocatalytic materials in generating H 2 O 2 under visible light irradiation is a difficult problem to be solved urgently in this field. Summary of the Invention

[0007] In view of this, the present invention provides a composite photoelectrocatalytic material, its preparation method and application to solve the problem of BiVO 4 for solar H 2 O 2Problems such as poor carrier mobility and charge separation efficiency existing at the time of generation, and the problem of low yield.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A preparation method of a composite photoelectrocatalytic material, comprising the following steps:

[0010] 1) Using a solution containing Bi as an electrolyte for electrodeposition, after the electrodeposition is completed, coating a precursor solution containing V, and annealing to obtain BiVO 4 substrate material;

[0011] 2) Using the BiVO 4 substrate material as a working electrode, a solution containing Ni as an electrolyte, and performing photo-assisted electrodeposition to obtain NiO / BiVO 4 ;

[0012] 3) Coating a solution containing Ni 5 P 4 nanoparticles on NiO / BiVO 4 to obtain Ni 5 P 4 / NiO / BiVO 4 composite photoelectrocatalytic material.

[0013] Preferably, the preparation method of the solution containing Bi in step 1) includes: mixing potassium iodide, nitric acid, bismuth nitrate and water to obtain a mixed solution, and then mixing the mixed solution with an ethanol solution of p-benzoquinone to obtain a solution containing Bi

[0014] The preparation method of the precursor solution containing V in step 1) includes: dissolving vanadyl acetylacetonate in an organic solvent.

[0015] Preferably, the molar concentration of bismuth nitrate in the mixed solution is 0.03-0.05 mol / L;

[0016] The molar concentration of potassium iodide in the mixed solution is 0.3-0.5 mol / L;

[0017] The pH value of the mixed solution is 1.5-2;

[0018] The molar concentration of p-benzoquinone in the ethanol solution of p-benzoquinone is 0.18-0.28 mol / L;

[0019] The volume ratio of the mixed solution to the ethanol solution of p-benzoquinone is 3-10:1-5;

[0020] The molar concentration of the precursor solution containing V is 0.18-0.22 mol / L.

[0021] Preferably, the conditions for the electrodeposition in step 1) are: electrodeposition for 180 - 240 s at a voltage of -0.1 V vs. Ag / AgCl;

[0022] The coating amount of the precursor solution containing V is 50 - 200 μL / cm 2 .

[0023] Preferably, the nickel source of the solution containing Ni in step 2) includes nickel sulfate;

[0024] The molar concentration of Ni in the solution containing Ni is 0.02 - 0.03 mol / L;

[0025] The pH value of the solution containing Ni is 6.5 - 7.5.

[0026] Preferably, the conditions for the photo-assisted electrodeposition in step 2) are: at a voltage of 0.6 V vs. SCE, the range of the charge passed during electrodeposition is 0.1 - 0.4 C / cm 2 ; the auxiliary light source is a xenon lamp.

[0027] Preferably, in step 3), the Ni 5 P 4 The mass concentration of Ni 5 P 4 nanoparticles in the solution is 1 - 10 mg / mL;

[0028] The Ni 5 P 4 The particle size of Ni 5 P 4 nanoparticles in the solution is 5 - 10 nm.

[0029] Preferably, the coating amount of the solution containing Ni 5 P 4 nanoparticles in step 3) is 10 - 50 μL / cm 2 .

[0030] Another object of the present invention is to provide a composite photo-electrocatalytic material prepared by the above preparation method.

[0031] Another object of the present invention is to provide an application of the composite photo-electrocatalytic material in the PEC water oxidation for preparing H 2 O 2 .

[0032] From the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The photo-electrocatalytic material in the present invention is a composite structure composed of three different materials, BiVO4 The heterojunction formed by the two materials, BiVO and NiO, leads to the redistribution of charges at the interface, forming a strong built-in electric field at the interface, which is conducive to improving the catalytic activity and promoting the catalytic reaction; and the surface-contact BiVO 4 / NiO heterojunction can significantly shorten the charge transport distance and effectively increase the charge transport channels, thus improving the catalytic effect to a certain extent.

[0034] 2. The preparation method of the present invention is to combine the coating method and the electrodeposition method to fabricate the Ni 5 P 4 / NiO / BiVO 4 photoelectrocatalytic material. Moreover, the time required for electrodeposition and coating is short, improving the preparation efficiency of the Ni 5 P 4 / NiO / BiVO 4 photoelectrocatalytic material. It can be seen that the preparation method in the present invention has the characteristics of simple operation, less time consumption and low energy consumption.

[0035] 3. In the present invention, Ni 5 P 4 is selected as the co-catalyst, and its synthesis raw materials are inexpensive, greatly reducing the cost. In addition, after loading Ni 4 P 5 on NiO / BiVO 4 , the yield and selectivity of generating H 2 O 2 in the PEC water oxidation process are greatly improved.

[0036] 4. The Ni 5 P 4 / NiO / BiVO 4 photoelectrocatalytic material prepared by the present invention not only passivates the interface states at the interface between Ni 5 P 4 and BiVO 4 by inserting a p-NiO layer, reducing the accumulation of holes, but also forms a p-n junction with BiVO 5 P 4 and BiVO 4 . The formed built-in electric field promotes the transfer of holes from BiVO 4 to Ni 4 P 5 , improving the efficiency of generating H 4 O 2 in the PEC water oxidation reaction. 2 in the PEC water oxidation reaction.

[0037] 5. The Ni 5 P 4 / NiO / BiVO 4 The photocatalytic material exhibits excellent H 2 O 2 generation PEC performance. In an electrolyte of 2M KHCO 3 , a photocurrent density of 4.05 mA / cm 2 can be achieved at a potential of 1.78 V vs. RHE, and it exhibits excellent stability.

[0038] 6. Additionally, in order to simulate the practical application of PEC water oxidation to prepare H 2 O 2 , in an electrolyte of 2M KHCO 3 , the Ni 5 P 4 / NiO / BiVO 4 photocatalytic material of the present invention can achieve an H 2 O 2 production rate of 18.78 mol / h / cm2 only at a potential of 1.2 V vs. RHE, showing excellent potential for PEC water oxidation to prepare H 2 O 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0040] Figure 1 SEM images of Ni 5 P 4 / NiO / BiVO 4 , NiO / BiVO 4 and BiVO 4 ; among them, Figure 1 (a) in 4 is the SEM image of BiVO Figure 1 (b) in 4 is the SEM image of NiO / BiVO Figure 1 (c) in 5 is the SEM image of Ni 4 P 4 / NiO / BiVO

[0041] Figure 2 SEM images of Ni 5 P 4 / NiO / BiVO 4TEM images of the photocatalytic material; among them, Figure 2 (a) in it is Ni 5 P 4 / NiO / BiVO 4 transmission electron microscope image at a scale of 100 nm; Figure 2 (b) in it is Ni 5 P 4 / NiO / BiVO 4 high-resolution transmission electron microscope image at a scale of 5 nm;

[0042] Figure 3 is Ni 5 P 4 / NiO / BiVO 4 , NiO / BiVO 4 , Ni 5 P 4 / BiVO 4 and BiVO 4 linear sweep voltammogram;

[0043] Figure 4 is Ni 5 P 4 / NiO / BiVO 4 , NiO / BiVO 4 and BiVO 4 real-time Faraday efficiency diagram of H 2 O 2 generation at different applied potentials. Specific embodiments

[0044] The present invention provides a method for preparing a composite photocatalytic material, comprising the following steps:

[0045] 1) Using a solution containing Bi as the electrolyte for electrodeposition, and after the electrodeposition is completed, coating a precursor solution containing V, and performing annealing treatment to obtain a BiVO 4 substrate material;

[0046] 2) Using the BiVO 4 substrate material as the working electrode and a solution containing Ni as the electrolyte for photo-assisted electrodeposition to obtain NiO / BiVO 4 ;

[0047] 3) Coating a solution containing Ni 5 P 4 nanoparticles on NiO / BiVO 4 to obtain a Ni 5 P 4 / NiO / BiVO 4 composite photocatalytic material.

[0048] In the present invention, the method for preparing the Bi-containing solution in step 1) includes: mixing potassium iodide, nitric acid, bismuth nitrate and water to obtain a mixed solution, and then mixing the mixed solution with an ethanol solution of p-benzoquinone to obtain a Bi-containing solution.

[0049] In the present invention, the molar concentration of bismuth nitrate in the mixed solution is 0.03 - 0.05 mol / L, specifically it can be 0.035 mol / L, 0.04 mol / L, 0.045 mol / L, and further preferably 0.04 mol / L.

[0050] In the present invention, the molar concentration of potassium iodide in the mixed solution is 0.3 - 0.5 mol / L, specifically it can be 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, and further preferably 0.4 mol / L.

[0051] In the present invention, the pH value of the mixed solution is 1.5 - 2, specifically it can be 1.6, 1.7, 1.8, 1.9.

[0052] In the present invention, the molar concentration of p-benzoquinone in the ethanol solution of p-benzoquinone is 0.18 - 0.28 mol / L, specifically it can be 0.19 mol / L, 0.2 mol / L, 0.22 mol / L, 0.23 mol / L, 0.24 mol / L, 0.25 mol / L, 0.26 mol / L, and further preferably 0.23 mol / L.

[0053] In the present invention, the volume ratio of the mixed solution to the ethanol solution of p-benzoquinone is 3 - 10:1 - 5, preferably 4 - 9:2 - 4, further preferably 5 - 8:3, and still further preferably 6 - 7:3.

[0054] The molar ratio of bismuth nitrate in the mixed solution to p-benzoquinone in the ethanol solution of p-benzoquinone is 0.03 - 0.05:0.18 - 0.28, preferably 0.035 - 0.045:0.2 - 0.25, and further preferably 0.04:0.22.

[0055] In the present invention, the molar concentration of the precursor solution containing V is 0.18 - 0.22 mol / L, specifically it can be 0.19 mol / L, 0.2 mol / L, 0.21 mol / L.

[0056] In the present invention, the conditions for electroplating in step 1) are: electroplating at a voltage of -0.1 V vs. Ag / AgCl for 180 - 240 s, and the deposition time can specifically be 185 s, 190 s, 195 s, 200 s, 210 s, 220 s, 230 s.

[0057] In the present invention, the coating amount of the precursor solution containing V is 50 to 200 μL / cm 2 , specifically, it can be 60 μL / cm 2 , 80 μL / cm 2 , 100 μL / cm 2 , 120 μL / cm 2 , 150 μL / cm 2 , 180 μL / cm 2 .

[0058] In the present invention, the annealing treatment in step 1) is a conventional annealing treatment. The temperature of the annealing treatment is preferably 400 to 500 °C, specifically, it can be 420 °C, 450 °C, 480 °C; the time of the annealing treatment is preferably 1.5 to 2.5 h, specifically, it can be 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h.

[0059] In the present invention, in step 1), the electrodeposition uses an FTO substrate, a platinum wire, and an Ag / AgCl electrode as the working electrode, the counter electrode, and the reference electrode respectively; first, a Bi-containing electrode (BiOI electrode) is deposited on the FTO substrate, and then a precursor solution containing V is coated as the V source. After the annealing is completed, BiVO 4 , BiVO 4 matrix material grows on the FTO substrate.

[0060] In the present invention, the nickel source of the solution containing Ni in step 2) includes nickel sulfate.

[0061] In the present invention, the molar concentration of Ni in the solution containing Ni is 0.02 to 0.03 mol / L, specifically, it can be 0.22 mol / L, 0.24 mol / L, 0.25 mol / L, 0.26 mol / L, 0.28 mol / L.

[0062] In the present invention, the pH value of the solution containing Ni is 6.5 to 7.5, specifically, it can be 6.6, 6.8, 7, 7.2, 7.4.

[0063] In the present invention, the conditions for the photo-assisted electrodeposition in step 2) are: at a voltage of 0.6 V vs. SCE, the range of the electric charge passed during the electrodeposition is 0.1 to 0.4 C / cm 2 , specifically, it can be 0.15 C / cm 2 , 0.2 C / cm 2 , 0.25 C / cm 2 , 0.3 C / cm 2 , 0.35 C / cm 2 ; the auxiliary light source is a xenon lamp.

[0064] In the present invention, in step 2), the photo-assisted electrodeposition uses BiVO 4 substrate material, platinum wire and saturated calomel electrode as the working electrode, counter electrode and reference electrode respectively.

[0065] In the present invention, in step 3), the Ni 5 P 4 mass concentration of Ni 5 P 4 nanoparticles in the solution is 1-10 mg / mL, specifically it can be 2 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 8 mg / mL.

[0066] In the present invention, the Ni 5 P 4 particle size of Ni 5 P 4 nanoparticles in the solution is 5-10 nm, specifically it can be 6 nm, 7 nm, 8 nm, 9 nm.

[0067] In the present invention, the coating in step 3) is preferably spin coating, and the rotation speed of spin coating is preferably 1500-4500 rpm, specifically it can be 1800 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm; the time of spin coating is preferably 30 s.

[0068] In the present invention, the coating amount of the solution containing Ni 5 P 4 nanoparticles in step 3) is 10-50 μL / cm 2 , specifically it can be 15 μL / cm 2 , 20 μL / cm 2 , 25 μL / cm 2 , 30 μL / cm 2 , 35 μL / cm 2 , 40 μL / cm 2 , 45 μL / cm 2 .

[0069] In the present invention, after the photo-assisted electrodeposition in step 2) and the coating of the solution containing Ni 5 P 4 nanoparticles in step 3), annealing treatment is independently further included. The temperature of the annealing treatment is independently preferably 280-320 °C, specifically it can be 290 °C, 300 °C, 310 °C; the time of the annealing treatment is independently preferably 15-45 min, specifically it can be 20 min, 25 min, 30 min, 35 min, 40 min.

[0070] The present invention also provides a composite photo-electrocatalytic material prepared by the above preparation method.

[0071] The present invention also provides an application of the composite photo-electrocatalytic material in the preparation of H 2 O 2 by PEC water oxidation.

[0072] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0073] Example 1

[0074] A preparation method of a Ni 5 P 4 / NiO / BiVO 4 photo-electrocatalytic material, comprising the following steps:

[0075] Step 1: Ultrasonically clean FTO (1 cm × 2 cm) with a cleaner, acetone, ethanol, and deionized water for 10 min respectively to serve as the FTO substrate, and soak it in ethanol for standby;

[0076] Step 2: Dissolve KI (potassium iodide) in 50 mL of deionized water, add HNO 3 (nitric acid) to adjust the pH value of the solution, and then add Bi(NO 3 ) 3 (bismuth nitrate), and stir well for 10 min to form a mixed solution I (the molar concentration of KI is 0.4 mol / L, the molar concentration of Bi(NO 3 ) 3 is 0.04 mol / L, and the pH value is 1.7); subsequently, mix 20 mL of an ethanol solution of p-benzoquinone with a molar concentration of 0.23 mol / L with solution I to form a mixed solution II;

[0077] Step 3: Take the mixed solution II in Step 2 as the electrolyte, and then use the FTO substrate, platinum wire, and Ag / AgCl electrode obtained in Step 1 as the working electrode, counter electrode, and reference electrode respectively, and prepare BiVO 4Substrate material. The conditions for electrodeposition are as follows: electrodeposition is carried out at a voltage of -0.1 V vs. Ag / AgCl for 200 s; after the electrodeposition is completed, the obtained BiIO substrate material is rinsed several times with deionized water and ethanol respectively, and then naturally dried in air; before annealing, 150 μL of a vanadyl acetylacetonate / dimethyl sulfoxide solution with a concentration of 0.2 mol / L is pipetted and evenly coated on the BiIO substrate material, and finally annealed in air at 450 °C for 2 h to obtain BiVO 4 Substrate material;

[0078] Step 4. Dissolve NiSO 4 ·6H 2 O (nickel sulfate) in 70 mL of deionized water to obtain an aqueous nickel sulfate solution with a molar concentration of 0.025 mol / L, and then add 2 mol / L of NaOH (sodium hydroxide) to adjust the pH value of the solution to 7 to form a mixed solution III. Using the mixed solution III as the electrolyte, the BiVO 4 substrate material in step 3 and a platinum wire and a saturated calomel (SCE) electrode are used as the working electrode, counter electrode and reference electrode respectively, and NiO / BiVO 4 is prepared by photo-assisted electrodeposition using a three-electrode system. The conditions for photoelectrodeposition are as follows: under the auxiliary illumination of a xenon lamp, electrodeposition is carried out at a voltage of 0.6 V vs. SCE for a total charge equivalent to passing 0.2 C / cm 2 ; after the photo-assisted electrodeposition is completed, the obtained NiO / BiVO 4 is rinsed several times with deionized water and ethanol respectively, and then naturally dried in air, and finally annealed in an N 2 atmosphere at 300 °C for 30 min;

[0079] Step 5. Take 50 μL of a Ni 5 P 4 solution (the particle size of Ni 5 P 4 is 5 - 10 nm) as the precursor solution, and spin-coat it on the NiO / BiVO 4 in step 4. The spin-coating conditions are: 3000 rpm, 30 s; after spin-coating, anneal in air at 300 °C for 30 min to obtain Ni 5 P 4 / NiO / BiVO 4 composite photocatalytic material.

[0080] Structure characterization

[0081] The Ni 5 P 4 / NiO / BiVO 4 prepared in Example 1 and NiO / BiVO 4and BiVO 4 SEM tests and analyses were respectively carried out, and the test results are shown in Figure 1 , where Figure 1 in (a) is the SEM image of BiVO 4 ; Figure 1 in (b) is the SEM image of NiO / BiVO 4 ; Figure 1 in (c) is the SEM image of Ni 5 P 4 / NiO / BiVO 4 . It can be seen from Figure 1 that BiVO 4 exhibits a smooth surface worm-like structure. Compared with BiVO 4 , NiO / BiVO 4 shows a coarser worm-like structure with a rough surface, indicating the presence of NiO. Ni 5 P 4 / NiO / BiVO 4 although shows a similar morphology to NiO / BiVO 4 , which can be attributed to the smaller Ni 5 P 4 particles.

[0082] The morphology of the Ni 5 P 4 / NiO / BiVO 4 photoelectrocatalytic material prepared in Example 1 was observed by high-resolution transmission electron microscopy, and the results are shown in Figure 2 . Figure 2 In (a) is the transmission electron microscopy image of Ni 5 P 4 / NiO / BiVO 4 at a scale of 100 nm; Figure 2 In (b) is the high-resolution transmission electron microscopy image of Ni 5 P 4 / NiO / BiVO 4 at a scale of 5 nm. It can be seen from Figure 2 in (b) that the surface of BiVO 4 is covered with a layer of NiO, and Ni 5 P 4 nanoparticles are attached to the surface of NiO. The measured value of the lattice fringe is 0.401 nm, corresponding to the (102) crystal plane of Ni 5 P 4 .

[0083] Performance Test

[0084] The Ni 5 P obtained in Example 1 was respectively4 / NiO / BiVO 4 、NiO / BiVO 4 、BiVO 4 and Ni 5 P 4 / BiVO 4 (The difference between the preparation method and Example 1 is that the NiO light-assisted electrodeposition step is omitted) Linear sweep voltammetry test was carried out under the following test conditions: the electrolyte used was 2MKHCO 3 , the voltage window is 0.3~1.3V(vs.Ag / AgCl), and the scan rate is 10mV s -1 The linear sweep voltammetry curve obtained from the test is shown in Figure 3 As shown, through Figure 3 It can be seen that at a voltage of 1.78 V vs. RHE, Ni 5 P 4 / NiO / BiVO 4 The highest photocurrent density (4.05 mA cm -2 ), and Ni 5 P 4 / BiVO 4 The photocurrent (2.7mAcm -2 ) compared to the previous study, it can be found that the insertion of NiO helps to improve the H 2 O 2 The resulting PEC performance.

[0085] The Ni obtained in Example 1 5 P 4 / NiO / BiVO 4 、NiO / BiVO 4 and BiVO 4 At different applied potentials, H 2 O 2 The real-time Faradaic efficiency generated was tested under the following conditions: the electrolyte used was 2M KHCO 3 , the voltage window is -0.1~1.5V (vs.Ag / AgCl), and the test time is 10min. 2 O 2 The generated real-time Faraday efficiency (FE) graph is as follows: Figure 4 As shown, from Figure 4 It can be seen that at different voltages, Ni 5 P 4 / NiO / BiVO 4 Shows the highest H 2 O 2 The generated Faradaic efficiency (FE) is higher than that of NiO / BiVO 4and BiVO 4 has a greater improvement, indicating that Ni 5 P 4 The loading of the cocatalyst is beneficial to improving the selectivity for H 2 O 2 during the PEC water oxidation process.

[0086] Example 2

[0087] A preparation method of Ni 5 P 4 / NiO / BiVO 4 photoelectrocatalytic material, comprising the following steps:

[0088] Step 1: Ultrasonically clean FTO (1 cm × 2 cm) with a detergent, acetone, ethanol, and deionized water for 15 min respectively to serve as the FTO substrate, and soak it in ethanol for later use;

[0089] Step 2: Dissolve KI (potassium iodide) in 50 mL of deionized water, add HNO 3 (nitric acid) to adjust the pH value of the solution, and then add Bi(NO 3 ) 3 (bismuth nitrate), and stir well for 10 min to form a mixed solution I (the molar concentration of KI is 0.4 mol / L, the molar concentration of Bi(NO 3 ) 3 is 0.04 mol / L, and the pH value is 1.7); Subsequently, mix 20 mL of an ethanol solution of p-benzoquinone with a molar concentration of 0.23 mol / L with solution I to form a mixed solution II;

[0090] Step 3: Take the mixed solution II in Step 2 as the electrolyte, and then use the FTO substrate, platinum wire, and Ag / AgCl electrode obtained in Step 1 as the working electrode, counter electrode, and reference electrode respectively. Use a three-electrode system to prepare a BiVO 4 substrate material by electrodeposition. The conditions for electrodeposition are: electrodeposit for 240 s at a voltage of -0.1 V vs. Ag / AgCl; after the electrodeposition is completed, rinse the obtained BiIO substrate material with deionized water and ethanol several times, and then naturally dry it in air; before annealing, use a pipette to suck 150 μL of an acetylacetone vanadium / dimethyl sulfoxide solution with a concentration of 0.2 mol / L, uniformly coat it on the BiIO substrate material, and finally anneal it in air at 450 °C for 2 h to obtain a BiVO 4 substrate material;

[0091] Step 4: NiSO 4 ·6H 2O(Nickel sulfate) is dissolved in 70 mL of deionized water to obtain an aqueous nickel sulfate solution with a molar concentration of 0.025 mol / L. Then, 2 mol / L of NaOH (sodium hydroxide) is added to adjust the pH value of the solution to 7, forming a mixed solution Ⅲ. Using the mixed solution Ⅲ as the electrolyte, the BiVO in step 3 4 substrate material and platinum wire, saturated calomel (SCE) electrode are used as the working electrode, counter electrode and reference electrode respectively. The NiO / BiVO is prepared by photo-assisted electrodeposition using a three-electrode system 4 . The conditions for photoelectrodeposition are: under the auxiliary illumination of a xenon lamp, electrodeposition is carried out at a voltage of 0.6 V vs. SCE corresponding to a total charge of 0.4 C / cm 2 ; after the photo-assisted electrodeposition is completed, the obtained NiO / BiVO 4 is rinsed several times with deionized water and ethanol respectively, then naturally dried in air, and finally annealed at 300 °C for 30 min in an N 2 atmosphere;

[0092] Step 5: Take 50 μL of a solution of Ni 5 P 4 (the particle size of Ni 5 P 4 is 5 - 10 nm) as the precursor solution, and spin-coat it on the NiO / BiVO in step 4 4 . The spin-coating conditions are: 4500 rpm, 30 s; after spin-coating, anneal it in an air atmosphere at 300 °C for 30 min to obtain Ni 5 P 4 / NiO / BiVO 4 composite photocatalytic material.

[0093] Example 3

[0094] A preparation method of Ni 5 P 4 / NiO / BiVO 4 photocatalytic material, comprising the following steps:

[0095] Step 1: Ultrasonically clean FTO (1 cm × 2 cm) with a cleaner, acetone, ethanol and deionized water for 10 min respectively. As the FTO substrate, soak it in ethanol for later use;

[0096] Step 2: Dissolve KI (potassium iodide) in 50 mL of deionized water, add HNO 3 (nitric acid) to adjust the pH value of the solution, and then add Bi(NO 3 ) 3 (bismuth nitrate), stir well for 10 min to form a mixed solution Ⅰ (the molar concentration of KI is 0.3 mol / L, Bi(NO3 ) 3 The molar concentration is 0.03 mol / L and the pH value is 2); Subsequently, 20 mL of an ethanol solution of p-benzoquinone with a molar concentration of 0.2 mol / L was mixed with Solution I to form Mixed Solution II;

[0097] Step 3: Take the Mixed Solution II in Step 2 as the electrolyte, and then use the FTO substrate, platinum wire, and Ag / AgCl electrode obtained in Step 1 as the working electrode, counter electrode, and reference electrode respectively. Use a three-electrode system to prepare BiVO 4 substrate material by electrodeposition. The conditions for electrodeposition are: electrodeposit for 180 s at a voltage of -0.1 V vs. Ag / AgCl; After the electrodeposition, the obtained BiIO substrate material was rinsed several times with deionized water and ethanol respectively, and then naturally dried in air; Before annealing, use a pipette to suck 150 μL of a vanadyl acetylacetonate / dimethyl sulfoxide solution with a concentration of 0.2 mol / L, and evenly coat it on the BiIO substrate material. Finally, anneal it in air at 450 °C for 2 h to obtain BiVO 4 substrate material;

[0098] Step 4: Dissolve NiSO 4 ·6H 2 O (nickel sulfate) in 70 mL of deionized water to obtain an aqueous nickel sulfate solution with a molar concentration of 0.02 mol / L, and then add 2 mol / L of NaOH (sodium hydroxide) to adjust the pH value of the solution to 6.5 to form Mixed Solution III. Using Mixed Solution III as the electrolyte, the BiVO 4 substrate material in Step 3 and platinum wire, saturated calomel (SCE) electrode are used as the working electrode, counter electrode, and reference electrode respectively. Use a three-electrode system to prepare NiO / BiVO 4 by photo-assisted electrodeposition. The conditions for photoelectrodeposition are: under the auxiliary illumination of a xenon lamp, electrodeposit at a voltage of 0.6 V vs. SCE for a total charge equivalent to 0.3 C / cm 2 ; After the photo-assisted electrodeposition, the obtained NiO / BiVO 4 was rinsed several times with deionized water and ethanol respectively, and then naturally dried in air. Finally, anneal it in an N 2 atmosphere at 300 °C for 30 min;

[0099] Step 5: Take 50 μL of a Ni 5 P 4 solution (the particle size of Ni 5 P 4 is 8 - 10 nm) as the precursor solution, and spin-coat it on the NiO / BiVO 4Above. The spin-coating conditions were: 3000 rpm, 30 s; after spin-coating, annealing was carried out in an air atmosphere at 300 °C for 30 min to obtain Ni 5 P 4 / NiO / BiVO 4 Composite photo-electrocatalytic material.

[0100] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same and similar parts among the embodiments, reference can be made to each other.

[0101] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a composite photoelectrocatalytic material, characterized in that: The steps include: 1) using a solution containing Bi as an electrolyte for electrodeposition, coating a precursor solution containing V after the electrodeposition, and annealing to obtain a BiVO4 matrix material; 2) Using BiVO4 matrix material as working electrode and Ni-containing solution as electrolyte, photo-assisted electrodeposition is performed to obtain NiO / BiVO4; 3) coating a solution containing Ni5P4 nanoparticles on NiO / BiVO4 to obtain a Ni5P4 / NiO / BiVO4 composite photoelectrocatalytic material.

2. The method for preparing a composite photoelectrocatalytic material according to claim 1, characterized in that: The preparation method of the solution containing Bi in step 1) comprises: mixing potassium iodide, nitric acid, bismuth nitrate and water to obtain a mixed solution, and then mixing the mixed solution with an ethanol solution of p-benzoquinone to obtain a solution containing Bi; The preparation method of the precursor solution containing V in step 1) comprises: dissolving vanadium acetylacetonate in an organic solvent to obtain a precursor solution containing V.

3. The method for preparing a composite photoelectrocatalytic material according to claim 2, characterized in that: The molar concentration of bismuth nitrate in the mixed solution is 0.03-0.05 mol / L; The molar concentration of potassium iodide in the mixed solution is 0.3-0.5 mol / L; The pH value of the mixed solution is 1.5 to 2; The molar concentration of p-benzoquinone in the p-benzoquinone ethanol solution is 0.18-0.28 mol / L; The volume ratio of the mixed solution to the ethanol solution of p-benzoquinone is 3-10:1-5; The molar concentration of the precursor solution containing V is 0.18-0.22 mol / L.

4. The method for preparing a composite photoelectrocatalytic material according to any one of claims 1 to 3, characterized in that: The conditions of the electrodeposition in step 1) are: electrodeposition at a voltage of -0.1 V vs. Ag / AgCl for 180 to 240 s; The coating amount of the precursor solution containing V is 50-200 μL / cm 2 .

5. The method for preparing a composite photoelectrocatalytic material according to claim 4, characterized in that: The nickel source of the Ni-containing solution in step 2) comprises nickel sulfate; The molar concentration of Ni in the Ni-containing solution is 0.02-0.03 mol / L; The pH value of the Ni-containing solution is 6.5-7.

5.

6. The method for preparing a composite photoelectrocatalytic material according to claim 5, characterized in that: The conditions of the light-assisted electrodeposition in step 2) are: at a voltage of 0.6 V vs. SCE, the charge amount range of the electrodeposition is 0.1 to 0.4 C / cm 2 ; The auxiliary light source is a xenon lamp.

7. The method for preparing a composite photoelectrocatalytic material according to claim 5 or 6, characterized in that: The mass concentration of Ni5P4 nanoparticles in the solution containing Ni5P4 nanoparticles in step 3) is 1-10 mg / mL; The particle size of the Ni5P4 nanoparticles in the solution containing Ni5P4 nanoparticles is 5-10 nm.

8. The method for preparing a composite photoelectrocatalytic material according to claim 7, characterized in that: The coating amount of the solution containing Ni5P4 nanoparticles in step 3) is 10-50 μL / cm 2 .

9. The composite photoelectrocatalytic material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the composite photoelectrocatalytic material according to claim 9 in preparing H2O2 by PEC water oxidation.

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