Preparation method of oxygen vacancy-rich bismuth molybdate / bismuth vanadate composite photo-anode and product and application thereof

Abstract

The invention relates to a preparation method of an oxygen vacancy-rich bismuth molybdate / bismuth vanadate composite photo-anode and a product and application thereof, and belongs to the technical field of photoelectrocatalysis. The invention discloses a preparation method of an oxygen vacancy-rich bismuth molybdate / bismuth vanadate (Bi2Mo2O9 / BiVO4) composite photo-anode, which mainly comprises the following steps: immersing a fluorine ion-doped tin dioxide (FTO) conductive glass substrate into a Bi < 3 + > ion solution and an I <-> ion solution to form a bismuth oxyiodide (BiOI) film, dropwise adding a dimethyl sulfoxide solution of vanadyl acetylacetonate (VO (acac) 2), and putting into a muffle furnace to prepare the BiVO4 photo-anode. And then vertically immersing into a Bi < 3 + > ion solution and a Mo < 6 + > ion solution, and carrying out annealing treatment in an argon atmosphere to prepare the Bi2Mo2O9 / BiVO4 composite photoanode rich in oxygen vacancies. The Bi2Mo2O9 / BiVO4 material rich in oxygen vacancies is a metal oxide composite photo-anode, the photoelectrocatalysis efficiency can be improved, and hydrogen peroxide (H2O2) can be continuously generated in natural seawater through photoelectrocatalytic oxidation of water for a long time.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectrocatalysis, and relates to a preparation method, product and application of a composite photoanode of bismuth molybdate / vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ). Background Art

[0002] Hydrogen peroxide (H 2 O 2 ) is an important chemical raw material and is widely used in fields such as bleaching, disinfection, wastewater treatment and chemical synthesis. In the marine environment, H 2 O 2 can be used to remove organic pollutants, kill harmful microorganisms and improve water quality. Therefore, the development of efficient and environmentally friendly H 2 O 2 production technology has important significance in practical applications.

[0003] Seawater contains a large amount of water molecules and is one of the most abundant water resources on Earth. However, the salts and other impurities in seawater pose great challenges to traditional water treatment and energy production methods. Developing a technology that can efficiently and stably perform photoelectrocatalytic water oxidation to produce H 2 O 2 not only provides a new way for sustainable production of high-value chemicals, but also enables the degradation of pollutants and the recovery of resources in the marine environment.

[0004] The synthesis process of H 2 O 2 currently mainly includes the anthraquinone oxidation method, direct synthesis of hydrogen and oxygen, and electrochemical synthesis routes. In current industrial practices, the anthraquinone process still dominates and is widely used in the large-scale production process of H 2 O 2 . However, this process route has many limitations, mainly including: the cost structure is relatively complex, not only the reaction process is long, but also there are multiple side reactions, resulting in a large amount of harmful by-products; in addition, the high-concentration H 2 O 2 prepared by the anthraquinone method faces significant safety risks during storage and transportation. In addition, the method of directly synthesizing H 2 O 2 from hydrogen and oxygen shows advantages such as a simple reaction mechanism, less by-product generation and high product purity. However, this method relies on expensive hydrogen as a raw material and needs to be carried out under high temperature and high pressure conditions, which poses extremely strict requirements on production equipment and operating conditions, resulting in high overall operating costs.

[0005] Compared with the production of H 2 O 2 by traditional processes, the production of H 2 O 2 by photoelectrocatalysis, usually using water as a raw material, can utilize solar energy as an energy source and convert solar energy into chemical energy stored in H 2 O 2 . This not only enables the effective conversion and storage of energy but also conforms to the global trend of transitioning to clean energy. Moreover, this renewable energy-based approach helps reduce dependence on fossil fuels, lower carbon emissions, and effectively address climate change.

[0006] In recent years, researchers have been committed to developing efficient photoanode materials. Among numerous metal oxides such as BiVO 4 、WO 3 、TiO 2 , BiVO 4 has been widely studied as one of the most promising photoanode materials due to its high visible light absorption ability and appropriate bandgap. However, the stability of BiVO 4 and the selectivity and efficiency of H 2 O 2 production still need to be improved. Although researchers have effectively improved the photoelectrocatalytic H 4 O 2 production performance of BiVO 2 through means such as element doping, constructing composite photoanodes, and crystal plane engineering. Among them, the strategy of constructing composite photoanodes can not only improve the selectivity and efficiency of photoelectrocatalytic H 2 O 2 production but also improve its stability through passivation. Currently, several materials have been used to construct composite photoanodes with BiVO 4 , such as ZnO, Sb 2 O 3 , SnO 2 . However, there is still much room for improvement in the photoelectrocatalytic performance of these photoanode materials. There is an urgent need to explore other BiVO 4 composite photoanode materials to expand the library of composite photoanode materials and further improve their photoelectrocatalytic H 2 O 2 production performance. In addition, considering the shortage of fresh water resources and the abundance and renewability of natural seawater resources, it is necessary to develop photoanode materials for efficient photoelectrocatalytic H 2 O 2 production in natural seawater electrolytes. Summary of the Invention

[0007] In view of this, one of the objectives of the present invention is to provide bismuth molybdate / vanadate rich in oxygen vacancies (Bi2 Mo 2 O 9 / BiVO 4 ) Preparation method of composite photoanode; The second object of the present invention is to provide bismuth molybdate / bismuth vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode; The third object of the present invention is to provide bismuth molybdate / bismuth vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode (O-Bi 2 Mo 2 O 9 -BiVO 4 ) Application in the photocatalytic preparation of H 2 O 2 ) in.

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

[0009] 1. Preparation method of bismuth molybdate / bismuth vanadate composite photoanode with oxygen vacancies, characterized in that the preparation method includes the following steps:

[0010] (1) Immerse the washed fluorine-doped tin dioxide (FTO) substrate vertically into Bi 3+ solution and I - solution in turn, take it out and continue to immerse it 10-50 times, and then form a bismuth oxyiodide (BiOI) film on the surface of the FTO substrate;

[0011] (2) Uniformly drop a dimethyl sulfoxide solution of vanadyl acetylacetonate (VO(acac) 2 ) on the bismuth oxyiodide (BiOI) film, place it in a muffle furnace and heat it to 300-600 °C, keep it for 1-3 h, and then wash to remove the surface V 2 O 5 to obtain a BiVO 4 film;

[0012] (3) Immerse the BiVO 4 film vertically into Bi 3+ solution and then take it out, continue to immerse it vertically into distilled water and then take it out immediately, and then vertically immerse it into Mo 6+ solution at 40-100 °C, take it out and then vertically immerse it into distilled water and then take it out immediately;

[0013] (4) Repeat step (3) 5 to 30 times and then place it in a tube furnace. Heat it to 300 - 600 °C in an argon atmosphere and anneal for 1 - 3 h to obtain a bismuth molybdate / bismuth vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode.

[0014] Preferably, in step (1), the Bi 3+ solution is a 5 - 25 mM aqueous solution of Bi(NO 3 ) 3 ·5H 2 O, and the I - solution is a 5 - 25 mM aqueous solution of KI;

[0015] In step (2), the concentration of the dimethyl sulfoxide solution of VO(acac) 2 is 100 - 300 mM, and the volume ratio of the dimethyl sulfoxide solution of vanadyl acetylacetonate (VO(acac) 2 ) to the area of the BiVO 4 film must be 20 - 100:1, μL:cm 2 ;

[0016] In step (3), the Bi 3+ solution is a 5 - 25 mM aqueous solution of Bi(NO 3 ) 3 ·5H 2 O solution, the solvent of the Bi 3+ solution is obtained by mixing water and acetic acid in a volume ratio of 15:5 - 19:1, and the Mo 6+ solution is a 2 - 8 mM aqueous solution of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O.

[0017] Preferably, in step (1), the immersion time in the Bi 3+ solution is 5 - 20 s, and the immersion time in the I - solution is 5 - 20 s;

[0018] In step (3), the immersion time in the Bi 3+ solution is 10 - 40 s, and the immersion time in the Mo 6+ solution is 10 - 40 s.

[0019] Preferably, the heating rate of the muffle furnace is 2 - 10 °C / min.

[0020] 2. A bismuth molybdate / bismuth vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode prepared by the above preparation method.

[0021] 3. Application of the above bismuth molybdate / bismuth vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode in the photoelectrocatalytic preparation of H 2 O 2 .

[0022] Preferably, natural seawater is used as the electrolyte in the above application.

[0023] Preferably, the device used in the above application is an H-type electrolytic cell.

[0024] The beneficial effect of the present invention is that the present invention discloses a preparation method of a bismuth molybdate / bismuth vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode. The method mainly immerses the FTO substrate in Bi 3+ solution and I - solution to form a BiOI film, drops a dimethyl sulfoxide solution of VO(acac) 2 , and then places it in a muffle furnace to obtain a BiVO 4 film. Then it is vertically immersed in Bi 3+ solution and Mo 6+ solution, and after annealing treatment, a bismuth molybdate / bismuth vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode is prepared. The bismuth molybdate / bismuth vanadate (Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode prepared by the present invention is a metal oxide composite material, which can improve the photoelectrocatalytic efficiency and can realize the long-term continuous generation of H 2 O 2 by photoelectrocatalytic oxidation of water in natural seawater.

[0025] Other advantages, objects, and features of the present invention will be set forth in part in the following description, and in part will be obvious to those skilled in the art upon examination of the following, or may be learned by practice of the present invention. The objects and other advantages of the present invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out hereinafter. Brief Description of the Drawings

[0026] In order to make the objects, technical solutions, and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, where:

[0027] Figure 1 For BiVO 4 and oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 X-ray diffraction (XRD) comparison diagram of the composite photoanode;

[0028] Figure 2 For BiVO 4 Scanning electron microscopy (SEM) image of the photoanode;

[0029] Figure 3 For the oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 SEM image of the composite photoanode;

[0030] Figure 4 For the oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 Transmission electron microscopy (TEM) image of the composite photoanode;

[0031] Figure 5 For BiVO 4 X-ray photoelectron spectroscopy (XPS) image of the photoanode;

[0032] Figure 6 For the oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 XPS image of the composite photoanode;

[0033] Figure 7 For the oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO4 Electron paramagnetic resonance (EPR) diagram of the composite photoanode;

[0034] Figure 8 H-type electrolytic cell separated by a cation exchange membrane;

[0035] Figure 9 For BiVO 4 And oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 Respectively as the working electrode to generate H 2 O 2 Production and Faraday efficiency comparison diagram in natural seawater containing 2 mol / L potassium bicarbonate;

[0036] Figure 10 For BiVO 4 And oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 Linear sweep voltammetry (LSV) diagram in natural seawater containing 2 mol / L potassium bicarbonate with BiVO

[0037] Figure 11 For BiVO 4 And oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 Respectively as the working electrode to generate H 2 O 2 Time-current diagram;

[0038] Figure 12 For BiVO 4 And oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 Stability test result diagram at 1.54 V vs RHE potential for 2 hours in natural seawater containing 2 mol / L potassium bicarbonate with BiVO

[0039] Figure 13 For BiVO 4 Oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4In natural seawater with a potassium bicarbonate concentration of 2 mol / L, at a potential of 1.54 V vs RHE, the H in the reaction solution was detected using a hydrogen peroxide test paper. 2 O 2 concentration picture. Detailed implementation mode

[0040] The following specific examples illustrate the implementation modes of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following examples only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following examples and the features in the examples can be combined with each other.

[0041] Example 1

[0042] Prepare oxygen vacancy-rich bismuth molybdate / bismuth vanadate (oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode, specifically carried out according to the following steps:

[0043] (1) Immerse the washed fluorine-doped tin dioxide (FTO) conductive glass substrate vertically into a 5 mM Bi(NO 3 ) 3 ·5H 2 O aqueous solution for 10 s, then vertically immerse it into a 5 mM KI aqueous solution for 10 s. After taking it out, continue to repeat the immersion 30 times, and then a bismuth iodide oxide (BiOI) film can be formed on the surface of the FTO substrate;

[0044] (2) Uniformly drop a dimethyl sulfoxide solution of VO(acac) 2 (concentration of 100 mM) onto the BiOI film prepared in the above step (1). The volume ratio of the dimethyl sulfoxide solution of VO(acac) 2 to the area of the BiOI film is 50:1, μL:cm 2 . Place it in a muffle furnace and heat it to 450 °C at a rate of 5 °C / min. After maintaining for 2 hours, wash it with a 1 mol / L NaOH solution to remove the excess V 2 O 5 on the surface, and then a BiVO 4 film can be obtained;

[0045] (3) Immerse the BiVO 4 film prepared in the above step (2) vertically into a 25 mM Bi(NO3 ) 3 · 5 H 2 O solution (the volume ratio of water to acetic acid in the solvent used is 10:1), take it out after 20 s, continue to vertically immerse it in distilled water and then take it out immediately, and then vertically immerse it in 3.57 mM of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O aqueous solution for 20 s, take it out in the same way and then vertically immerse it in distilled water and take it out immediately;

[0046] (4) Repeat the immersion method in step (3) 10 times and then place it in a tube furnace. Heat it to 500 °C at a rate of 5 °C / min in an argon atmosphere and anneal for 2 hours to obtain oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 Composite photoanode.

[0047] Example 2

[0048] Prepare oxygen vacancy-rich bismuth molybdate / bismuth vanadate (oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode, specifically according to the following steps:

[0049] (1) Vertically immerse the cleaned FTO substrate in 15 mM Bi(NO 3 ) 3 ·5H 2 O aqueous solution for 10 s, then vertically immerse it in 15 mM KI aqueous solution for 10 s. After taking it out, continue to repeat the immersion 10 times to form a BiOI film on the surface of the FTO substrate;

[0050] (2) Uniformly drop the dimethyl sulfoxide solution of VO(acac) 2 (concentration 200 mM) onto the BiOI film prepared in step (1) above. The volume ratio of the dimethyl sulfoxide solution of VO(acac) 2 to the area of the BiOI film is 20:1, μL:cm 2 . Place it in a muffle furnace, heat it to 300 °C at a rate of 5 °C / min, keep it for 3 hours, and then wash it with 1 mol / L NaOH solution to remove the excess V 2 O 5 on the surface to obtain a BiVO 4 film;

[0051] (3) Immerse the BiVO prepared in the above step (2) 4 thin film vertically into 5 mM Bi(NO 3 ) 3 · 5 H 2 O solution (the volume ratio of water to acetic acid in the solvent used is 3:1) for 20 s, then take it out, continue to immerse it vertically into distilled water and then take it out immediately, and then vertically immerse it into 2 mM (NH 4 ) 6 Mo 7 O 24 ·4H 2 O aqueous solution for 20 s, and also take it out and then vertically immerse it into distilled water and then take it out immediately;

[0052] (4) Repeat the immersion method in step (3) 5 times, then place it in a tubular furnace, heat it to 300 °C at a rate of 10 °C / min in an argon atmosphere, and anneal for 3 hours to obtain an oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 composite photoanode.

[0053] Example 3

[0054] Preparation of oxygen vacancy-rich bismuth molybdate / bismuth vanadate (oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 ) composite photoanode, which is specifically carried out according to the following steps:

[0055] (1) Vertically immerse the cleaned FTO substrate into 25 mM Bi(NO 3 ) 3 ·5H 2 O aqueous solution for 10 s, then vertically immerse it into 25 mM KI aqueous solution for 10 s. After taking it out, continue to repeat the immersion 50 times to form a BiOI thin film on the surface of the FTO substrate;

[0056] (2) Uniformly drop the dimethyl sulfoxide solution of VO(acac) 2 (concentration: 300 mM) onto the BiOI thin film prepared in the above step (1). The volume ratio of the dimethyl sulfoxide solution of VO(acac) 2 to the area of the BiOI thin film is 100:1, μL:cm 2 . Place it in a muffle furnace, heat it to 600 °C at a rate of 5 °C / min, keep it for 1 hour, and then wash it with 1 mol / L NaOH solution to remove the excess V 2 O 5 on the surface to obtain BiVO 4Thin film;

[0057] (3) Immerse the BiVO thin film prepared in step (2) vertically into a 15 mM Bi(NO₃)₃·5H₂O solution for 20 s, then take it out, continue to immerse it vertically into distilled water and take it out immediately, and then immerse it vertically into an 8 mM (NH₄)₆Mo₇O₂₄·4H₂O aqueous solution at 100 °C for 20 s, and also take it out and immerse it vertically into distilled water and take it out immediately after that; 4 Thin film is first vertically immersed in a 15 mM Bi(NO₃)₃·5H₂O solution for 20 s and then taken out, then continuously vertically immersed in distilled water and immediately taken out, and then vertically immersed in an 8 mM (NH₄)₆Mo₇O₂₄·4H₂O aqueous solution at 100 °C for 20 s, and also taken out and vertically immersed in distilled water and immediately taken out after that; 3 ) 3 ·5H 2 O solution for 20 s and then taken out, then continuously vertically immersed in distilled water and immediately taken out, and then vertically immersed in an 8 mM (NH₄)₆Mo₇O₂₄·4H₂O aqueous solution at 100 °C for 20 s, and also taken out and vertically immersed in distilled water and immediately taken out after that; 4 ) 6 Mo 7 O 24 ·4H 2 O aqueous solution for 20 s, and also taken out and vertically immersed in distilled water and immediately taken out after that;

[0058] (4) Repeat the immersion method in step (3) 30 times, then place it in a tubular furnace, heat it to 600 °C at a rate of 2 °C / min in an argon atmosphere, and anneal for 1 hour to obtain an oxygen vacancy-rich Bi₂MoO₆ / BiVO₄ composite photoanode. 2 Mo 2 O 9 / BiVO 4 Composite photoanode.

[0059] Photocatalytic H₂O production 2 O 2 Performance test

[0060] Figure 1 For the XRD phase comparison diagram of the BiVO₄ and oxygen vacancy-rich Bi₂MoO₆ / BiVO₄ composite photoanodes, 4 And oxygen vacancy-rich Bi₂MoO₆ 2 Mo 2 O 9 / BiVO 4 Composite photoanode, Figure 2 For the scanning electron microscope (SEM) image of the BiVO₄ photoanode, 4 SEM image of the BiVO₄ photoanode, Figure 3 For the SEM image of the oxygen vacancy-rich Bi₂MoO₆ / BiVO₄ composite photoanode prepared in Example 1 of the present invention, 2 Mo 2 O 9 / BiVO 4 Composite photoanode, Figure 4 For the transmission electron microscope (TEM) image of the oxygen vacancy-rich Bi₂MoO₆ / BiVO₄ composite photoanode prepared in Example 1 of the present invention, 2 Mo 2 O 9 / BiVO 4 Composite photoanode, Figure 5 For the X-ray photoelectron spectroscopy (XPS) image of the BiVO₄ photoanode, 4 XPS image of the BiVO₄ photoanode, Figure 6 For the oxygen vacancy-rich Bi₂MoO₆ / BiVO₄ composite photoanode prepared in Example 1 of the present invention, 2 Mo 2 O9 / BiVO 4 XPS spectra of the composite photoanode Figure 7 Bi rich in oxygen vacancies prepared in Example 1 of the present invention 2 Mo 2 O 9 / BiVO 4 Electron paramagnetic resonance (EPR) spectra of the composite photoanode. From Figures 1 to 7 it can be seen that the crystal structures of BiVO 4 and Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 photoanodes were analyzed using XRD. The observed diffraction peaks correspond to monoclinic BiVO 4 (JCPDS PDF#14-0688) and Bi 2 Mo 2 O 9 (JCPDS PDF#84-0829). It can be seen therefrom that BiVO 4 is porous and worm-like, and Bi 2 Mo 2 O 9 is small particles evenly attached to the surface of BiVO 4 . The prepared material is aggregated nanoparticles analyzed by TEM images. In the high-resolution TEM image of Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 the lattice fringes of BiVO 4 with lattice spacings of 1.81 and can be identified, corresponding to the (220) and (103) crystal planes of BiVO 4 . The lattice fringes of Bi 2 Mo 2 O 9 are corresponding to its (002) crystal plane. Figure 2 and Figure 3 EDX spectra show that Bi, V, and O elements are evenly distributed on the surface of BiVO 4 , and Bi, Mo, and O elements are evenly distributed on the surface of Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 surface. Through XPS testing, the chemical composition and elemental valence states of substances can be determined. Figure 5 The XPS peaks at the electron binding energies of 159 eV and 164.3 eV in4 Bi 4f electron orbital; the XPS peaks at the electron binding energies of 516.6 eV and 524.2 eV are attributed to BiVO 4 of V 2p electron orbital. Figure 6 Bi annealed in argon atmosphere in 2 Mo 2 O 9 and Bi annealed in air atmosphere 2 Mo 2 O 9 In comparison, a negative shift in the electron binding energy of Bi 4f is observed, which is attributed to the introduction of more oxygen vacancies during calcination in an argon atmosphere. Through EPR testing, Bi annealed in an argon atmosphere 2 Mo 2 O 9 shows a strong EPR signal at g = 2.003, which can be attributed to ionized oxygen vacancies, indicating a relatively high content of oxygen vacancies; while Bi annealed in air atmosphere 2 Mo 2 O 9 shows a weak signal, indicating a relatively low content of oxygen vacancies.

[0061] Similarly, corresponding structural tests were also carried out on the bismuth molybdate / vanadate rich in oxygen vacancies (Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 ) composite photoanodes prepared in Examples 2 and 3, and the results are similar to those of the bismuth molybdate / vanadate rich in oxygen vacancies (Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 ) composite photoanode prepared in Example 1.

[0062] The bismuth molybdate / vanadate rich in oxygen vacancies (Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 composite photoanode prepared in Example 1 above was applied to the specific photocatalytic oxidation of natural seawater to prepare H 2 O 2 , and the specific method is as follows:

[0063] An H-type electrolytic cell separated by a cation exchange membrane was used (such as Figure 8Perform a photoelectrocatalytic reaction as shown. Place a magnetic stir bar in the anodic electrolytic cell, add 35 mL of the prepared electrolyte (natural seawater containing potassium bicarbonate at a concentration of 2 mol / L) to the anodic electrolytic cell, and add 35 mL of the prepared electrolyte (natural seawater containing potassium bicarbonate at a concentration of 2 mol / L) to the cathodic electrolytic cell. Then, place the working electrode and the reference electrode in the anodic electrolytic cell, place the counter electrode in the cathodic cell, and cover the lid of the electrolytic cell. Place the oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 composite photoanode (the reaction area of the electrode is 4 cm 2 ) as the working electrode, a saturated calomel electrode (SCE, Hg / Hg 2 Cl 2 ) as the reference electrode, a platinum sheet as the counter electrode, and the light source is a calibrated solar simulator (PerfectLight, PLS-SXE 300) with an AM 1.5G filter and a light intensity of 100 mW / cm 2 . The photoelectrocatalytic reaction can generate H 2 O 2 .

[0064] Similarly, replace the oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 composite photoanode in the above electrolytic cell with a BiVO 4 photoanode and perform the photoelectrocatalytic reaction under the same conditions.

[0065] Use a CHI760E workstation for photoelectrochemical testing. Turn on the computer connected to the electrochemical workstation, then turn on the electrochemical workstation, open the CHI760E software on the computer, set it according to the test requirements, connect the electrode clips of the electrochemical workstation to the corresponding electrodes, and start the test after connection; after the test, use the potassium permanganate oxidation method combined with ultraviolet-visible spectrophotometry to determine the concentration of H 2 O 2 in the reaction solution. The steps are as follows: Take 1 mL of 3 mol / L sulfuric acid solution and 3 mL of potassium permanganate solution, then take 1 mL of the solution from the reactor, mix these two solutions well, let it stand for 5 minutes, and then measure the absorbance of the solution at 525 nm using ultraviolet-visible spectroscopy, and calculate the concentration of H 2 O 2 through the change in absorbance;

[0066] The test process is as follows: Use a 2 mol / L potassium bicarbonate seawater solution as the electrolyte with a pH value of 8.4. Place the oxygen vacancy-rich Bi 2Mo 2 O 9 / BiVO 4 Composite photoanode or BiVO 4 The photoanode was used as the working electrode, and photocatalytic tests were carried out at a potential of 1.54 V vs RHE to detect the production of H 2 O 2 yield and Faraday efficiency diagram. The comparison results are as Figure 9 shown. According to Figure 9 it can be seen that at a potential of 1.54 V vs RHE and after 15 minutes of reaction, using BiVO 4 as the working electrode, the Faraday efficiency can reach 3.72%, and the H 2 O 2 yield is 1.95 ppm; using oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 as the working electrode, the Faraday efficiency can reach 11.20%, and the H 2 O 2 yield is 6.95 ppm. It can be seen that the oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 prepared in this invention has a higher H 2 O 2 production Faraday efficiency and a higher H 2 O 2 yield when used as the working electrode for photocatalytic oxidation of natural seawater.

[0067] Using a 2 mol / L potassium bicarbonate natural seawater solution as the electrolyte with a pH value of 8.4, a stability test was carried out at a potential of 1.54 V vs RHE for 2 hours. Using BiVO 4 as the working electrode, the H 2 O 2 accumulation amount can reach 18.22 ppm; using the oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 composite photoanode as the working electrode, the H 2 O 2 accumulation amount can reach 31.95 ppm.

[0068] Figure 10 For BiVO 4 and oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4LSV diagrams of working electrodes in natural seawater containing 2 mol / L potassium bicarbonate. From Figure 10 It can be seen that the photocurrent density of oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 is significantly higher than that of BiVO 4 . The fact that the photocurrent density of oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 indicates that the photoanode can significantly improve its photoelectric conversion ability.

[0069] Figure 11 Current-time diagrams of H 4 production by BiVO 2 and oxygen vacancy-rich Bi 2 O 9 / BiVO 4 as working electrodes in natural seawater electrolyte containing 2 mol / L potassium bicarbonate. From 2 O 2 It can be seen that the photocurrent density of oxygen vacancy-rich Bi Figure 11 is 103% of the initial value after 900 s of reaction, while that of BiVO 2 Mo 2 O 9 / BiVO 4 is 87% of the initial value, and the photocurrent density of oxygen vacancy-rich Bi 4 Mo 2 O 2 / BiVO 9 is always higher than that of BiVO 4 . This indicates that oxygen vacancy-rich Bi 4 Mo 2 O 2 / BiVO 9 can significantly improve the stability of photocatalytic water oxidation to produce H 4 O 2 in natural seawater electrolyte. 2

[0070] Figure 12 Stability test result diagrams of BiVO 4 and oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 as working electrodes in natural seawater containing 2 mol / L potassium bicarbonate at 1.54 V vs RHE for 2 h. From Figure 12It can be seen that the initial photocurrent density and the photocurrent density at the end of Bi 2 Mo 2 O 9 / BiVO 4 are significantly higher than those of BiVO 4 , and during the 2-hour reaction process, Bi 2 Mo 2 O 9 / BiVO 4 has a higher yield of H 2 O 2 produced by photoelectrocatalytic water oxidation in natural seawater electrolyte than BiVO 4 .

[0071] Figure 13 For BiVO 4 , Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 in natural seawater with a potassium bicarbonate concentration of 2 mol / L, after reacting for 15 minutes at a potential of 1.54 V vs RHE, the picture of detecting the H 2 O 2 concentration in the reaction solution with an H 2 O 2 test paper. It can be seen from Figure 13 that when using BiVO 4 or Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 as the photoanode to participate in the reaction, H 2 O 2 is generated. The darker the color of the H 2 O 2 test paper, the higher the H 2 O 2 concentration. It can be seen that Bi rich in oxygen vacancies 2 Mo 2 O 9 / BiVO 4 can significantly improve the yield of H 2 O 2 produced by photoelectrocatalytic water oxidation in natural seawater electrolyte.

[0072] Similarly, the Bi rich in oxygen vacancies prepared in Example 2 and Example 3 above 2 Mo 2 O 9 / BiVO 4 is used for photoelectrocatalytic oxidation of natural seawater to prepare H 2 O2 , and the result is similar to that of Bi 2 Mo 2 O 9 / BiVO 4 prepared in Example 1.

[0073] In summary, taking Bi 2 Mo 2 O 9 / BiVO 4 prepared by the present invention as the working electrode, compared with BiVO 4 as the working electrode, it has good improvement effects. In a 2 mol / L potassium bicarbonate natural seawater solution, at a potential of 1.54 V vs RHE, the Faraday efficiency of BiVO 4 can reach 3.72% after 15 minutes of reaction, and the H 2 O 2 production is 1.95 ppm; at a potential of 1.54 V vs RHE, the Faraday efficiency of oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 can reach 11.20% after 15 minutes of reaction, and the H 2 O 2 production is 6.95 ppm; at a potential of 1.54 V vs RHE, the material was subjected to a 2-hour stability test using a 2 mol / L potassium bicarbonate natural seawater solution. Oxygen vacancy-rich Bi 2 Mo 2 O 9 / BiVO 4 can continuously produce H 2 O 2 . During the 2-hour test, the H 4 accumulation in BiVO 2 O 2 can reach 18.22 ppm; the H 2 Mo 2 O 9 / BiVO 4 accumulation in H 2 O 2 can reach 31.97 ppm.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing a bismuth molybdate / bismuth vanadate composite photoanode rich in oxygen vacancies, characterized in that: The preparation method comprises the following steps: (1) Immerse the cleaned FTO conductive glass substrate vertically into Bi 3+ Solution and I - The solution is taken out and then repeatedly immersed for 10 to 50 times to form a BiOI film on the surface of the FTO conductive glass substrate; (2) uniformly dropping a dimethyl sulfoxide solution of VO(acac)2 onto the BiOI film, placing the film in a muffle furnace and heating it to 300-600°C, maintaining the temperature for 1-3 hours, and then washing and removing the vanadium pentoxide on the surface to obtain a BiVO4 film; (3) The BiVO4 film is vertically immersed in Bi 3+ After the solution is removed, it is immersed vertically in distilled water and immediately removed, and then immersed vertically in Mo at a temperature of 40 to 100 °C. 6+ solution, take it out and immerse it vertically in distilled water and then take it out immediately; (4) After repeating step (3) 5 to 30 times, the mixture is placed in a tube furnace, heated to 300 to 600° C. in an argon atmosphere, and annealed for 1 to 3 hours to form a bismuth molybdate / bismuth vanadate composite photoanode rich in oxygen vacancies on the surface of the FTO conductive glass.

2. The preparation method according to claim 1, characterized in that: In step (1), the Bi 3+ The solution is a 5-25 mM Bi(NO3)3·5H2O aqueous solution, wherein - The solution is a 5-25 mM KI aqueous solution; In step (2), the concentration of the VO(acac)2 dimethyl sulfoxide solution is 100-300 mM, and the volume ratio of the VO(acac)2 dimethyl sulfoxide solution to the area ratio of the BiVO4 film is 20-100:1, μL:cm 2 ; In step (3), the Bi 3+ The solution is a 5-25 mM Bi(NO3)3·5H2O solution, wherein the Bi 3+ The solvent of the solution is obtained by mixing water and acetic acid in a volume ratio of 15:5 to 19:

1. 6+ The solution is 2-8 mM (NH4)6Mo7O 24 4H2O aqueous solution.

3. The preparation method according to claim 1, characterized in that: In step (1), the immersion of Bi 3+ The time in the solution is 5 to 20 seconds, and the immersion time is 1 - The solution time is 5 to 20 seconds; In step (3), the immersion of Bi 3+ The solution time is 10 to 40 seconds, and the Mo 6+ The solution time is 10 to 40 seconds.

4. The preparation method according to claim 1, characterized in that: The heating rate of the muffle furnace is 2-10°C / min.

5. The oxygen vacancy-rich bismuth molybdate / bismuth vanadate composite photoanode prepared by the preparation method according to claim 1.

6. Use of the oxygen vacancy-rich bismuth molybdate / bismuth vanadate composite photoanode according to claim 5 in the photoelectrocatalytic preparation of hydrogen peroxide.

7. The use according to claim 6, characterized in that: Natural seawater is used as the electrolyte in the application.

8. The use according to claim 6, characterized in that: The device used in the application is an H-type electrolyzer.

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