A lead dioxide crystal material, its preparation method and application

Abstract

The present invention for the first time provides a lead dioxide crystal material, a preparation method and an application thereof. The lead dioxide crystal material has a quasi-single crystal structure of submicron or micron-sized regular rod shapes with high crystallinity, and all exposed surfaces are (110) surfaces and (101) surfaces. When applied as a catalyst, it has higher catalytic activity, reduces the thickness of the anode catalyst layer of a traditional electrolytic water ozone generator, can achieve higher ozone production efficiency with a lower catalyst loading amount, reduces the production cost of the ozone generator, and is suitable for large-scale industrial applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of lead dioxide, and particularly relates to a lead dioxide crystal material, a preparation method thereof, and an application thereof. Background Art

[0002] Ozone is a strong oxidant, and its reduction products are oxygen and water. Therefore, ozone is a clean, safe, and non-polluting oxidant, and has been widely used in processes such as disinfection, medical treatment, water treatment, deodorization, and food processing. At present, there are mainly three common artificial ozone preparation methods, including high-voltage corona method, ultraviolet radiation method, and electrolytic water method. Among them, the biggest advantage of the electrolytic water method is that the prepared ozone concentration is relatively high. However, the electrolytic water ozone production technology has high requirements for the anode electrode material. Platinum (Pt) is an ideal anode catalyst for ozone preparation due to its excellent catalytic performance and high oxygen evolution overpotential. However, its high cost limits its application. Therefore, non-noble metal materials used to replace platinum have been widely studied. Among them, lead dioxide (PbO₂) electrodes have the advantages of high oxygen evolution overpotential, good conductivity, corrosion resistance, low price, and simple preparation process, and have become excellent substitutes for noble metal catalysts such as platinum, and have been widely used in the electrochemical field and are currently difficult to be replaced by other materials. However, the catalytic activity of traditional lead dioxide is still limited. In order to obtain a better catalytic effect, it is necessary to increase the loading amount of lead dioxide, but this will make problems such as coating peeling and lead dissolution pollution more serious. ( M, Pérez JAB, Llanos J, et al. Current Opinion in Electrochemistry, 2021, 27: 100697.)

[0003] In order to overcome the disadvantage of poor catalytic activity of lead dioxide, the prior art performs modification treatment on it, mainly including modifying the substrate, adding an intermediate layer, morphology control, etc. Among them, the morphology of the catalyst directly affects the electrochemical ozone generation (EOP) activity from the perspective of catalytic reaction kinetics. The so-called morphology control mainly refers to changing the crystal shape, crystal size, and crystal structure of lead dioxide.

[0004] Specifically, (1) From the perspective of crystal shape: The common shapes of lead dioxide crystal materials include star-shaped, spherical, cauliflower-shaped, rod-shaped, cubic, etc. Due to the different shapes, the specific surface area of the crystal and the number of reactive sites are also different, thus showing different catalytic reaction activities. For example, the research by Wang et al. shows that rod-shaped, spherical, and star-shaped lead dioxide nanostructures have different surface, structural, and morphological characteristics, thus having different electrocatalytic activities for ozone generation. Among them, rod-shaped lead dioxide has a high proportion of surface oxygen vacancies, which is beneficial to improving the mass transfer and charge transfer processes and enhancing the corresponding electrocatalytic reactions. (Wang X, Wu D, Ge H, et al. Journal of Environmental Chemical Engineering, 2023, 11(4): 110248.)

[0005] (2) From the perspective of crystal size: The sizes of common lead dioxide crystal materials range from nanoscale, sub-micron scale to micron scale from small to large; the high activity of nanoscale catalysts mainly comes from their very high specific surface area. This increase in surface area allows the catalytic reaction sites of the catalyst to be carried out on more catalytic centers, thus improving the catalytic efficiency. At the same time, due to characteristics such as large surface area and prominent quantum effects, nanocatalysts have higher biological and chemical stability, are insensitive to extreme changes, and are more reliable for long-term efficient catalysis. However, due to their high surface energy and the effects of van der Waals forces and electrostatic forces between particles, nanocatalysts are extremely prone to agglomeration and often require appropriate dispersion or anchoring means to ensure their dispersion. In the field of water electrolysis catalysis, lead dioxide as the anode plays a role by stacking on the surface of the proton exchange membrane and forming a relatively compact catalyst layer through steps such as hot pressing. Therefore, the advantages of nanoscale lead dioxide in this field are limited. In contrast, the preparation processes of sub-micron and micron-scale materials are more convenient, the conditions are more relaxed, and the material properties are more stable and less prone to agglomeration. Therefore, controlling the size of the material within a suitable range such as sub-micron or micron scale is what those skilled in the art want to achieve, but the morphology of sub-micron or micron-scale materials is extremely difficult to control. It requires precise coordinated control of various parameters for the uniform growth of crystal seeds to ensure the integrity of the crystal structure and strictly limit the crystal growth time to ensure its appropriate size, which has great technical difficulties.

[0006] (3) From the perspective of crystal structure: lead dioxide is divided into three types: single crystal, polycrystal, and quasi single crystal. A single crystal refers to the atoms or molecules within its crystal structure being arranged periodically in a certain pattern, showing anisotropy; a single crystal has a specific morphology and long-range order. Usually, the size of a single crystal can vary from micrometers to dozens of centimeters, with good crystal morphology and transparency. Different physical properties exist in different directions of the crystal; the crystal has a periodic structure, and when melting, each part requires the same temperature; the crystal grown in an ideal environment should be a convex polygon; the selected area electron diffraction (SAED) pattern of a single crystal appears as a dot pattern, and the lattice fringes with consistent orientation can be observed through a high-resolution transmission electron microscope (HRTEM). Common single crystals usually show regular polyhedron structures such as cubes, cuboids, or flakes due to different exposed surfaces. A polycrystal refers to the aggregation of single crystals with numerous orientations, showing isotropic properties. Polycrystals usually do not have a specific morphology. When the grain size in a polycrystal is small, it is difficult to intuitively present the crystal faces, crystal edges, etc., the sample clarity is poor, and it shows scattered light. The SAED pattern of a polycrystal appears as a ring, and the lattice fringe orientations are observed to be disordered through HRTEM. Common polycrystals generally show irregular spherical, granular, star-shaped, etc. A quasi single crystal is a morphology between polycrystals and single crystals. A quasi single crystal means that the internal atomic arrangement has not reached the high consistency of a single crystal, but generally has already possessed some characteristics of a single crystal and is different from polycrystals, such as a regular and unified crystal shape and exposed crystal faces with consistent orientation. The growth of a single crystal often requires a strict chemical environment and stable and interference-free conditions, and it grows slowly over a period of days to months to ensure the integrity and quality of the crystal. Therefore, the industrialization of single crystals still has obstacles, while the preparation process of quasi single crystals is more relaxed than that of single crystals and is easier to achieve large-scale preparation and application, having the advantages of industrial production.

[0007] Single-crystalline, polycrystalline, and quasi-single-crystalline lead dioxide have significant differences in crystal plane structure characteristics, resulting in obvious differences in catalytic activity when applied as catalysts. Due to the different atomic arrangements or exposed atoms on different crystal planes of the crystal, the physical and chemical properties exhibited will be different. It is manifested that in an electrochemical reaction, the structure and properties of the crystal surface have an important influence on the reaction rate and selectivity, which is called the crystal plane effect. The crystal plane effect is the most significant feature that differentiates single-crystalline and quasi-single-crystalline materials from polycrystalline materials. The crystal plane effect mainly includes two aspects: one is that the crystal plane structure and crystal plane defects have a direct impact on the formation and properties of the electrocatalytic reaction active center; the other is that the crystal plane structure has a significant impact on the adsorption and desorption processes of reactants and products on the surface (Zou C, Ma C, Chen F, et al. Journal of Electroanalytical Chemistry, 2022, 914: 116330). Controlling the morphology and exposed crystal planes of the catalyst through crystal plane engineering has important technical significance and is considered an effective means to regulate electrochemical reactions.

[0008] Currently, the research on the ozone generation mechanism based on the crystal planes of lead dioxide is still in the initial theoretical research stage. Current research believes that the (110) plane and the (101) plane are more conducive to ozone generation. For example, Gibson et al. first proposed an ozone adsorption-desorption generation mechanism based on the (110) crystal plane of β-lead dioxide. The H2O adsorbed on the surface is first oxidized to OH * , and then further oxidized to O * . Two surface O * combine to form O2 * . O2 * further bonds with the adsorbed O * to form O3 *, finally, O3 is generated by desorption (Gibson G, Morgan A, Hu P, et al. Chemical Physics Letters, 2016, 654: 46 - 51). Jiang et al. proposed an ozone generation mechanism based on the lattice oxygen of lead dioxide. They found through in-situ differential electrochemical mass spectrometry with isotope labeling that the oxygen atoms in ozone mainly come from the lattice oxygen of lead dioxide, while the oxygen atoms in oxygen mainly come from the water molecules participating in the reaction, and the lattice oxygen also participates in the generation of oxygen. They further found through DFT calculations that the ozone generation path mediated by lattice oxygen on the (110) and (101) surfaces of lead dioxide is more conducive to ozone generation than the aforementioned adsorption - desorption mechanism (Jiang W, Wang S, Liu J, et al. Journal of Materials Chemistry A, 2021, 9(14): 9010 - 9017). Therefore, based on the above research, it can be seen that to improve the catalytic activity from the perspective of crystal plane effect, the lead dioxide crystal needs to have as many (110) and (101) crystal planes as possible as the exposed surfaces, or even only the (110) and (101) exposed surfaces.

[0009] It should be clear that the crystal of lead dioxide includes many crystal planes such as (110), (101), (220), (211), (220), (202), (310), (112), (301), (202), etc. However, since the crystal surface structure of the catalyst is determined by its exposed surface, that is, only by means of crystal plane regulation can the exposed crystal planes play the above-mentioned crystal plane effect, which is called the exposed facet / surface (Literature 1: Jiang W, Wang S, Liu J, et al. Journal of Materials Chemistry A, 2021, 9(14): 9010-9017). The detection method of the exposed facet is to characterize the exposed surface of the crystal by high-resolution transmission electron microscopy (HRTEM), and two sets of lattice fringes at a certain angle can be obtained. By measuring the spacing and angle of the lattice fringes and comparing with the lattice parameters of lead dioxide, the crystal direction perpendicular to the exposed facet can be obtained, and thus the crystal plane index of the exposed facet can be determined, that is, the exposed facet is the common perpendicular plane of the crystal planes represented by the two sets of lattice fringes. At the same time, using the selected area electron diffraction (SADE) technology of TEM and the fast Fourier transform (FFT) of the lattice fringes, the diffraction pattern of the current area can be obtained, in which two sets of diffraction vectors at a certain angle can be obtained, corresponding to the two sets of lattice fringes mentioned above respectively. The length of the vector is equal to the reciprocal of the lattice fringe spacing, and the angle between the vectors is equal to the angle between the lattice fringes. By calibrating the diffraction pattern, its zone axis can be determined, and thus the crystal plane index of the current exposed facet can be determined. (Literature 2: Qu J, Wang Y, Mu X, et al.. Advanced Materials, 2022, 34(37): 2203320; Wu X, Ng YH, Wang L, et al.. Journal of Materials Chemistry A, 2017, 5(17): 8117–8124.)

[0010] It should be noted that in the existing technology reports on the regulation of the (101) and (110) crystal planes of lead dioxide, the exposed facets are not (110) and (101) planes or it is impossible to make the exposed facets only (110) and (101). For example, in the research of Wenbin Jiang et al. in Litereture 1, Figure 1 d~j show the lattice fringes of the (110) and (101) crystal planes characterized by HRTEM. However, based on what is shown in this article, Figure 1 the exposed facets should be the common perpendicular planes of the (110) and (101) crystal planes. According to the generally recognized exposed facet characterization method published by Jiangshan Qu et al. in Litereture 2 and comparing with the lead dioxide lattice data, it can be determined that the exposed facets in Litereture 1 are In the research of Xi Wang et al., Figure 1 the lattice fringes of the (101) crystal plane in the local areas of three-shaped lead dioxide are marked, which is not sufficient to prove that the current exposed surface is the (101) crystal plane, and it can be clearly observed that there are fringes with other orientations, indicating that the interior of the crystal is a polycrystalline structure (Wang X, Wu D, Ge H, et al. Journal of Environmental Chemical Engineering, 2023: 110248.).

[0011] Therefore, based on the existing research, when an ideal lead dioxide crystal material is used as a catalyst with high catalytic activity, it must simultaneously possess the following morphological characteristics: (1) regular polyhedron; (2) dimensions with industrial application prospects, such as submicron or micron-scale dimensions; (3) as many crystal planes exposed as possible that are conducive to the generation of ozone. However, it is extremely difficult to control the morphology of lead dioxide crystal materials, and various parameters such as temperature, growth time, ion species and concentration need to be precisely and coordinately controlled to ensure the uniform growth of crystal seeds to guarantee the integrity of the crystal structure. And there is no lead dioxide crystal material with regular submicron or micron-scale rod shape and only (110) and (101) crystal planes exposed in the existing technology. Summary of the Invention

[0012] Aiming at the deficiencies of the existing technology, through a large amount of research and unremitting efforts, the inventor has overcome numerous obstacles in the existing technology. The present invention first provides a lead dioxide crystal material, its preparation method and application. The lead dioxide crystal material has a quasi-single crystal structure of high crystallinity in the shape of submicron or micron-scale regular rods, and all exposed surfaces are (110) and (101) planes. When applied to a catalyst, it has higher catalytic activity, reduces the thickness of the anode catalyst layer of a traditional electrolytic ozone generator, can achieve higher ozone production efficiency with a lower catalyst loading, reduces the production cost of the ozone generator, and is suitable for large-scale industrial applications.

[0013] The present invention adopts the following technical solutions:

[0014] The first object of the present invention is to provide a lead dioxide crystal material. The lead dioxide crystal has a quasi-single crystal structure, and its shape is submicron or micron-scale rod-shaped, and all exposed surfaces of the lead dioxide are (110) and (101) planes.

[0015] The inventors unexpectedly found that it is this unique quasi-single crystal structure that leads to the highly exposed active sites of lead dioxide. The highly active (110) and (101) planes are directly exposed on the crystal surface. At the same time, due to the rich oxygen vacancies on the surfaces of the (110) and (101) planes, during the ozone generation process, the lattice oxygen as an ozone intermediate can be rapidly desorbed and replenished on the material surface, thus exhibiting excellent ozone catalytic activity. Because the lead dioxide has a unique sub-micron or micron rod-like quasi-single crystal structure, it can effectively prevent the catalyst particles in the ozone production system by electrolyzing water from agglomerating excessively and causing performance degradation.

[0016] The Wullf structure of lead dioxide obtained by the crystal modeling software VESTA is as Figure 1 shown.

[0017] The lead dioxide crystal has a quasi-single crystal structure. The detection method is that through a high-resolution transmission electron microscope, lattice fringes with consistent orientations can be observed, and after fast Fourier transform, a spot-like rather than ring-like local diffraction pattern can be obtained, which is beneficial to electron transfer inside the crystal plane.

[0018] Preferably, the proportion of the (110) plane in the total exposed surface is 75% - 95%, and the proportion of the (101) plane in the total exposed surface is 5% - 25%.

[0019] Preferably, the detection method for the exposed surface of the lead dioxide crystal is as follows: along the (110) crystal direction, lattice fringes of the (002) plane and plane can be observed, which are 0.165 - 0.175 nm and 0.320 - 0.350 nm respectively, and the included angle is 90°.

[0020] Preferably, the proportion of the (110) plane in the total exposed surface and the proportion of the (101) plane in the total exposed surface can be calculated according to the following formula:

[0021]

[0022] where a is the length of the longest diagonal of the (110) plane, b is the width in the direction perpendicular to a, θ is the included angle between the hypotenuse of the (110) plane and the horizontal direction, and θ′ is the included angle between the two common sides of the (101) plane and the (110) plane.

[0023] Preferably, the D50 range of the particle size of the lead dioxide crystal is 600 - 1200 nm, and the detection method for the particle size is dynamic light scattering (DLS) technology.

[0024] Preferably, the length of the lead dioxide crystal along the long axis direction is 0.5 - 4 μm, and the length along the short axis direction is 100 - 400 nm.

[0025] Preferably, the quasi-single crystal structure of lead dioxide is a dodecahedron; more preferably, the quasi-single crystal structure of lead dioxide has 4 hexagonal (110) faces and 8 rhombic (101) faces.

[0026] Preferably, the morphology of the quasi-single crystal structure of lead dioxide is entirely β-lead dioxide.

[0027] The second object of the present invention is to provide a method for preparing a lead dioxide crystal material, comprising the following steps:

[0028] (1) Dissolve a lead salt in water, add an inorganic base to form a white suspension; then add PVP to obtain a mixed solution;

[0029] (2) Add a sodium hypochlorite solution to the mixed solution to obtain a yellowish-brown suspension;

[0030] (3) Perform a hydrothermal reaction on the yellowish-brown suspension, cool to room temperature after the reaction ends, collect the precipitate to obtain lead dioxide, and wash and dry it.

[0031] Further, the preparation method specifically includes:

[0032] 1) Dissolve a lead salt in water, add an inorganic base to form a white suspension;

[0033] 2) Pre-dissolve polyvinylpyrrolidone in water to obtain a polyvinylpyrrolidone solution;

[0034] 3) Add the polyvinylpyrrolidone solution described in step 2) to the white suspension described in step 1) to obtain a mixed solution;

[0035] 4) Add a sodium hypochlorite solution to the mixed solution obtained in step 3) to obtain a yellowish-brown suspension, and the molar ratio of the lead salt, polyvinylpyrrolidone, and sodium hypochlorite in the suspension is 1∶1.2 - 3∶1.5 - 2.5;

[0036] 5) Perform a hydrothermal reaction on the yellowish-brown suspension obtained in step 4), the hydrothermal reaction time is 3 - 9 hours, cool to room temperature after the reaction ends, collect the precipitate to obtain lead dioxide; the lead dioxide is washed with a polar solvent of polyvinylpyrrolidone and then dried;

[0037] In the hydrothermal system of the present invention, the ratios of lead salt, polyvinylpyrrolidone and sodium hypochlorite, the hydrothermal reaction time, and the type of oxidant play a crucial regulatory role in the morphology of lead dioxide, which is also a metal oxide crystal. It is necessary to precisely control the synergistic effect of these multiple characteristic parameters to obtain the lead dioxide crystal material with the morphological characteristics described in the present invention. For example, Comparative Examples 3-7 of the present invention demonstrate that changing the type of regulator, the composition ratio, or the type of oxidant cannot obtain the lead dioxide material with the morphology of the present invention; Polyvinylpyrrolidone (PVP) is a non-ionic polymer, and its molecules contain strongly hydrophilic components (pyrrolidone part) and relatively large hydrophobic groups (alkyl groups). By adding a specific ratio of PVP, lead salt, and oxidant in the hydrothermal method, lead dioxide crystals with regular morphology can be obtained, and the hydrothermal reaction time of the present invention can be significantly shortened compared with the prior art, improving production efficiency. PVP chemically adsorbed on the surface of nanocrystals will affect the surface structure and local reaction environment of the nanocrystals, and thus have a positive or negative impact on their catalytic performance. During the growth process of lead dioxide crystals, PVP reduces the growth rate of lead dioxide crystals in these two directions by adsorbing on the (110) plane and the (101) plane, and finally obtains lead dioxide composed only of two exposed surfaces, namely the (110) plane and the (101) plane. Since the morphology of the dioxide crystal is extremely difficult to control, the process of oxidizing divalent lead salt into tetravalent lead and forming lead dioxide is extremely rapid, and a large number of lead dioxide crystal nuclei will be formed in a short time. It is even more difficult to achieve uniform growth of lead dioxide crystals and form a regular and uniform quasi-single crystal structure. The preparation method requires overall fine control, and each parameter cooperates with each other to play a regulatory role in the growth of lead dioxide crystals, so as to prepare the quasi-single crystal lead dioxide crystals with the described morphology. The preparation method of the present invention has an easy-to-control crystal morphology, good stability, and a simple preparation method, and can achieve industrial large-scale production, etc.

[0038] Preferably, in step 1), the lead salt is selected from any one or more of lead acetate, lead nitrate or lead chloride; preferably, in step 1), the inorganic base is selected from any one or more of sodium hydroxide, potassium hydroxide or lithium hydroxide; preferably, in step 1), the pH range of the suspension is 12-14, preferably 14;

[0039] Preferably, in step 1), after adding the inorganic base, the sufficient stirring time is 10-20 minutes;

[0040] Preferably, in step 2), after adding polyvinylpyrrolidone to deionized water, vortex for 1-3 minutes to dissolve it sufficiently;

[0041] Preferably, in step 3), the monomer concentration of polyvinylpyrrolidone solution in the white suspension is 1-12 mmol / L, more preferably 6 mmol / L; the polyvinylpyrrolidone monomer concentration = mass of polyvinylpyrrolidone / relative molecular mass of polyvinylpyrrolidone monomer;

[0042] Preferably, in step 4), the molar ratio of lead salt, polyvinylpyrrolidone and sodium hypochlorite in the suspension is 1:2:2; preferably, the molecular weight of polyvinylpyrrolidone is 5-600 kDa, more preferably 40 kDa; Different monomer concentrations and polymerization degrees of PVP have a key regulating effect on the morphology of lead dioxide, which is also a metal oxide crystal;

[0043] Preferably, in step 4), the available chlorine concentration of the sodium hypochlorite solution is 5 wt%;

[0044] Preferably, in step 5), the temperature of the hydrothermal reaction is 90-150 °C;

[0045] Preferably, in step 5), the time of the hydrothermal reaction is 3-5 h;

[0046] Preferably, in step 5), the polar solvent of polyvinylpyrrolidone is selected from any one or more of deionized water, methanol, ethanol or isopropanol;

[0047] Preferably, in step 5), the number of washing times is 3 times;

[0048] Preferably, in step 5), the drying method is vacuum drying;

[0049] Preferably, in step 5), the drying temperature < 90 °C; more preferably, the drying temperature is 40-80 °C, and the drying time is 24-48 hours.

[0050] The third object of the present invention is to provide the use of a lead dioxide crystal material as described above and a lead dioxide crystal material prepared by the preparation method as described above on a catalyst.

[0051] The fourth object of the present invention is to provide a membrane electrode comprising the catalyst as described above.

[0052] Preferably, the thickness of the catalyst layer on the anode and cathode sides of the membrane electrode is 15-20 μm; preferably, the preparation method of the membrane electrode is: dispersing lead dioxide or platinum carbon in an organic solvent, adding an ionic polymer solution, and continuously ultrasonically dispersing for 60-90 minutes to obtain an anode or cathode catalyst ink; spraying the obtained anode catalyst ink and cathode catalyst ink on both sides of a proton exchange membrane under a carrier gas to obtain a membrane electrode.

[0053] Preferably, the ionomer is Nafion D520, Nafion D521, Nafion D2020 or Nafion D2021; preferably, the proton exchange membrane is Nafion N115, Nafion N117, Nafion N1110, Nafion NR211 or Nafion NR212; preferably, the carrier gas is air, nitrogen or argon, and the pressure is 0.05 - 0.50 Mpa.

[0054] The fifth object of the present invention is to provide a water electrolysis ozone generation system, comprising the lead dioxide crystal material as described above, the lead dioxide crystal material prepared by the preparation method as described above, or comprising the catalyst as described above or comprising the membrane electrode as described above.

[0055] Furthermore, the application steps of the lead dioxide crystal material in the water electrolysis ozone generation system are: assembling the obtained membrane electrode into a water electrolyzer, using deionized water as the electrolyte, loading a DC power supply for electrolysis reaction to obtain ozone products.

[0056] Preferably, the current density of the DC power supply is 500 - 2000 mA / cm 2 , preferably 1500 mA / cm 2 ; preferably, the electrolysis reaction temperature is 20 - 50 °C, more preferably 25 °C.

[0057] The present invention unexpectedly finds that due to having regular highly active crystal planes and a quasi-single crystal structure, compared with amorphous lead dioxide, the lead dioxide obtained in the present invention has higher EOP activity. The water electrolysis ozone generator using this lead dioxide as the anode reduces the thickness of the anode catalyst layer of the traditional water electrolysis ozone generator, can achieve higher ozone production efficiency with a lower catalyst loading, reduces the production cost of the ozone generator, and lays a solid foundation for the large-scale industrial preparation of the above-mentioned lead dioxide with high EOP activity and the corresponding water electrolysis ozone generator devices, breaking through the huge obstacles of the prior art.

[0058] The sixth object of the present invention is to provide the application of any form of lead dioxide as described above in any one or more fields of disinfection, medical treatment, water treatment, deodorization and food treatment.

[0059] Compared with the existing technology, the beneficial effects of the present invention are as follows:

[0060] (1) The present invention first provides a lead dioxide quasi - single - crystal crystal material with a high - crystallinity sub - micron or micron - scale regular rod - like shape, and all exposed surfaces are (110) and (101) surfaces. This solves the problem in the prior art that it is impossible to achieve the exposure of only the (110) and (101) exposed surfaces that are beneficial to ozone generation. Compared with the nanoscale, the sub - micron and micron - scale regular rod - like shapes are easier to achieve large - scale preparation and application, having the advantages of industrial production; the unique quasi - single - crystal structure of the present invention results in a high exposure of active sites of lead dioxide, and the highly active (110) and (101) surfaces are directly exposed on the crystal surface. At the same time, due to the rich oxygen vacancies on the surfaces of the (110) and (101) surfaces, during the process of ozone generation, lattice oxygen as an ozone intermediate can be rapidly desorbed and replenished on the material surface, thus showing excellent ozone catalytic activity; because the lead dioxide has a unique sub - micron or micron - scale rod - like quasi - single - crystal structure, it can effectively avoid the performance decay caused by excessive agglomeration of catalyst particles in the water electrolysis ozone generation system. [[ID=~1]] [[ID=~2]]

[0061] [[ID=~3]](2) The preparation method of the present invention requires the overall fine - tuning of the ratios of lead salt, polyvinylpyrrolidone, and sodium hypochlorite, the hydrothermal reaction time, and the type of oxidant. The above parameters cooperate with each other to regulate the growth of lead dioxide crystals, and then the quasi - single - crystal lead dioxide crystals with the described morphology can be prepared. The hydrothermal reaction time of the preparation method of the present invention can be significantly shortened, improving production efficiency, and the method is simple and easy to implement, with repeatability, and can achieve industrial large - batch production, etc. It turns the preparation of high - performance lead dioxide from theoretical research into reality, and its catalytic performance has been significantly improved compared with the existing level. [[ID=~4]] [[ID=~5]]

[0062] [[ID=~6]](3) When the lead dioxide quasi - single - crystal crystal material of the present invention is used to prepare a membrane electrode, the requirement for the thickness of the catalyst layer of the membrane electrode can be reduced, and finally a membrane electrode with high ozone production performance under a low catalyst loading is obtained. In the water electrolysis ozone generation system, the ozone yield of the membrane electrode reaches up to 355 mg / h at a current density of 1500 mA / cm[[ID=~7]] 2 [[ID=~8]]current density. [[ID=~9]] [[ID=~10]]

[0063] [[ID=~11]](4) When the lead dioxide quasi - single - crystal crystal material of the present invention is applied to the water electrolysis ozone generation system, it has higher EOP activity, provides an ideal interface for ozone generation, realizes higher ozone production efficiency, reduces the production cost of ozone generators, and is suitable for large - scale industrial applications. [[ID=~12]] [[ID=~13]]BRIEF DESCRIPTION OF THE DRAWINGS [[ID=~14]] [[ID=~15]]

[0064] [[ID=~16]] Figure 1 [[ID=~17]]It is a Wulff structure model diagram of lead dioxide obtained by VESTA crystal modeling software; [[ID=~18]] [[ID=~19]]

[0065] [[ID=~20]] Figure 2Scanning electron microscope observation image of lead dioxide obtained in Example 1 at 1 μm;

[0066] Figure 3 High-resolution transmission electron microscope observation image of lead dioxide obtained in Example 1 at 2 nm, where the (110) crystal plane stripes with a lattice spacing of 0.333 nm and the (101) crystal plane stripes with a lattice spacing of 0.173 nm can be observed. After Fourier transform, the diffraction spots corresponding to the (110) and (101) crystal planes can be observed, and the angle between the stripes and vectors of the two crystal planes is 90°;

[0067] Figure 4 Standard diffraction spot image of β-lead dioxide in the

[110] crystal direction obtained by the crystal modeling software CrysTBox (CIF#mp-20725);

[0068] Figure 5 Scanning electron microscope cross-section observation image of the membrane electrode obtained in Example 1 at 30 μm; Among them, Figure 5 a in is the scanning electron microscope cross-section observation image of the anode side, Figure 5 b in is the scanning electron microscope cross-section observation image of the cathode side;

[0069] Figure 6 Long-term ozone production performance graph of the membrane electrode obtained in Example 1 applied to a water electrolysis ozone generator.

[0070] Figure 7 Scanning electron microscope observation image of a commercial lead dioxide catalyst purchased from Macklin Reagent at 1 μm;

[0071] Figure 8 Scanning electron microscope observation image of a β-lead dioxide catalyst synthesized by electrochemical deposition at 1 μm;

[0072] Figure 9 X-ray diffraction patterns of lead dioxide obtained in Example 1, lead dioxide synthesized by electrochemical deposition, and commercial lead dioxide from Macklin Reagent at 10° - 80°;

[0073] Figure 10 Scanning electron microscope observation image of lead dioxide obtained in Comparative Example 3 at 1 μm;

[0074] Figure 11 Scanning electron microscope observation image of lead dioxide obtained in Comparative Example 4 at 1 μm;

[0075] Figure 12 Scanning electron microscope observation image of lead dioxide obtained in Comparative Example 5 at 1 μm;

[0076] Figure 13 Scanning electron microscope observation image of the sample obtained in Comparative Example 6 at 10 μm;

[0077] Figure 14 Scanning electron microscope observation image of a conventional hot-pressed membrane electrode at 1 mm. Detailed implementation manners

[0078] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0079] Example 1

[0080] Prepare lead dioxide according to the following steps:

[0081] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water, add 2 g of sodium hydroxide to the obtained solution, stir for 15 minutes to obtain a uniform white suspension, and then add 1.25 g of PVP, and continuously stir for 45 minutes to obtain a uniform light yellow suspension;

[0082] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) during stirring. The suspension gradually turns yellow-brown, and stir for 3 minutes to make it uniformly turbid and dispersed;

[0083] (3) Transfer the suspension obtained in step (2) to a hydrothermal reaction kettle, carry out hydrothermal reaction at 120 °C for 6 hours, cool to room temperature after the reaction, centrifuge to collect the precipitate to obtain the lead dioxide; the obtained lead dioxide is washed 3 times with deionized water and absolute ethanol in sequence, and the filter residue is placed in a vacuum drying oven and dried at 60 °C for 24 hours;

[0084] Furthermore, in this example, the molecular weight of the PVP is 40 kDa;

[0085] Furthermore, the PVP can be pre-dissolved in water before addition to obtain a polyvinylpyrrolidone solution; the PVP pre-dissolved in water has excellent dispersion uniformity, which is more conducive to the formation of the lead dioxide material described in the present invention.

[0086] Through scanning electron microscopy (SEM), it can be observed that the lead dioxide prepared in Example 1 has a regular crystal structure with high crystallinity ( Figure 2 ), which is a dodecahedron structure, and it can be observed that it is the same as the lead dioxide Wulff structure obtained by the crystal modeling software VSETA ( Figure 1)Good correspondence. By measurement, the length of the lead dioxide crystal along the long axis direction is 0.5 - 4 μm, and the length along the short axis direction is 100 - 400 nm. Further, by measuring with the dynamic light scattering technique, the D50 range of the lead dioxide prepared in Example 1 is 600 - 1200 nm.

[0087] Further, by determining the exposed surface of the crystal through a transmission electron microscope, the fringes of the (110) crystal plane and the (002) crystal plane with spacings of 0.333 nm and 0.173 nm respectively can be observed. Through Fourier transform, the diffraction pattern can be observed to be spotty, indicating its quasi-single crystal property. And through calibration, the spots representing the plane and the (002) plane can be obtained ( ) Figure 3 ) The included angle between the vector and the (002) vector is 90°, which is consistent with the standard diffraction spot pattern of β-lead dioxide in the

[110] crystal orientation obtained by the crystal modeling software CrysTBox (CIF#mp - 20725) ( Figure 4 ). Therefore, the

[110] crystal orientation is perpendicular to the diffraction plane, that is, the exposed surface of the prepared lead dioxide crystal is the (110) plane. After determining that the exposed surface is the (110) plane, through SEM characterization of the crystal morphology and Wulff structure, it can be determined that the other exposed surface is the (101) plane. Therefore, the quasi-single crystal structure of the lead dioxide prepared in Example 1 has 4 hexagonal (110) planes and 8 rhombic (101) planes.

[0088] Calculate the proportion of the (110) plane in the total exposed surface and the proportion of the (101) plane in the total exposed surface according to the following formula:

[0089]

[0090] where a is the length of the longest diagonal of the (110) plane, b is the width in the direction perpendicular to a, θ is the included angle between the hypotenuse of the (110) plane and the horizontal direction, and θ′ is the included angle between the two common sides of the (101) plane and the (110) plane.

[0091] Through calculation, the proportion of the (110) plane in the total exposed surface of Example 1 is 75% - 95%, and the proportion of the (101) plane in the total exposed surface is 5% - 25%

[0092] The above shows that the present invention has successfully synthesized a regular quasi-single crystal structure of lead dioxide with exposed surfaces all being (110) planes and (101) planes and in the shape of sub-micron or micron-sized rod-like.

[0093] The application of lead dioxide in a water electrolysis ozone generator is realized according to the following steps:

[0094] 1) After dispersing 250 mg of lead dioxide in 2 mL of isopropanol, 500 mg of Nafion D520 solution (5 wt%) was added, and ultrasonic dispersion was continued for 60 minutes to obtain an anode catalyst ink;

[0095] 2) After dispersing 30 mg of platinum-carbon with a platinum loading of 10% in 2 mL of isopropanol, 60 mg of Nafion D520 solution (5 wt%) was added, and ultrasonic dispersion was continued for 60 minutes to obtain a cathode catalyst ink.

[0096] 3) The anode catalyst ink and cathode catalyst ink obtained in steps 1) and 2) were respectively sprayed on both sides of a Nafion N117 proton exchange membrane under air pressure of 0.2 Mpa to obtain a membrane electrode.

[0097] The cross-sections of the catalyst layers on the anode and cathode sides of the membrane electrode were characterized by SEM as Figure 5 shown. The thickness of the anode side was 17.1 μm, and the thickness of the cathode side was 15.6 μm.

[0098] The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain an ozone product; where the current density was 1500 mA / cm 2 , the reaction temperature was 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolysis reaction, as shown in Table 1, the ozone production rate detected by the ozone detector reached 355 mg / h, and the ozone concentration was 111 mg / L.

[0099] To verify the stability of the prepared lead dioxide, the ozone generator was continuously operated for 240 h, and the ozone production rate was measured by an ozone detector every 24 h ( Figure 6 ). It can be seen from Figure 6 that the membrane electrode made of lead dioxide prepared by this invention has good stability during the operation of the ozone generator. [[ID=??]] [[ID=??]]

[0100] Currently, the lead dioxide used for ozone production by water electrolysis mainly includes commercial lead dioxide reagents synthesized by commercial reagent companies and β-lead dioxide synthesized by electrodeposition method. The former is often a mixture of α-lead dioxide and β-lead dioxide ( Figure 7 ), and the latter is often a large-particle-size block structure ( Figure 8 ). Both of these situations will result in fewer effective electrochemical active sites of lead dioxide, and the ozone production rate will also be limited accordingly. In this method, by adding a certain proportion of polyvinylpyrrolidone in the hydrothermal method, the growth path of lead dioxide crystals was regulated, and regular β-lead dioxide crystals with exposed surfaces of (110) plane and (101) plane were prepared, which have stronger electrochemical ozone production performance than α-lead dioxide and β-lead dioxide with irregular structures. It should be noted that there are some tags like etc. which seem to be some kind of internal identifiers in a specific system and are kept as they are without further translation as per the requirement. Also, there are some tags like [[ID=??]] which might be due to an error in the original input, but they are also kept as they are for translation.

[0101] The X-ray diffraction patterns of the above three kinds of lead dioxide are as Figure 9 shown. It can be seen from the X-ray diffraction patterns that for the lead dioxide prepared by Example 1 of the present method and the electrodeposition method, three obvious strong peaks can be observed at 25.4°, 32° and 49°, corresponding to the (110), (101), (211) crystal planes of β-lead dioxide (PDF#41-1492) respectively. For commercial lead dioxide, two strong peaks different from β-lead dioxide can be observed at 23.3° and 28.6°, corresponding to the (111) and (021) crystal planes of α-lead dioxide (PDF#45-1416) respectively. This indicates that the lead dioxide obtained by the present method and the electrodeposition method is a single β-lead dioxide phase, while commercial lead dioxide is a mixed phase of α-lead dioxide and β-lead dioxide.

[0102] Comparative Example 1

[0103] Commercial lead dioxide (Macklin, >97%) was applied to the water electrolysis ozone generator.

[0104] The preparation process of the membrane electrode of Comparative Example 1 was repeated for Example 1, except that: the catalyst added in Example 1 was replaced with the commercial lead dioxide of Comparative Example 1 with the same mass, and the remaining preparation process of the membrane electrode material was the same as that of Example 1. The preparation parameters and performance are shown in Table 1.

[0105] The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain an ozone product; where the current density was 1500 mA / cm 2 , the reaction temperature was 25 °C. During the electrolytic synthesis of O3, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 h of electrolysis reaction, the ozone yield reached 156 mg / h and the ozone concentration was 79 mg / L as detected by the ozone detector.

[0106] Comparative Example 2

[0107] The β-lead dioxide synthesized by the electrochemical deposition method was applied to the water electrolysis ozone generator:

[0108] The preparation process of the membrane electrode of Comparative Example 2 was repeated for Example 1, except that: the catalyst added in Example 1 was replaced with the β-lead dioxide of Comparative Example 2 with the same mass, and the remaining preparation process of the membrane electrode material was the same as that of Example 1. The preparation parameters and performance are shown in Table 1.

[0109] The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain an ozone product; where the current density was 1500 mA / cm 2, the reaction temperature was 25°C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolytic reaction, the ozone production rate reached 177 mg / h and the ozone concentration was 80 mg / L as detected by the ozone detector.

[0110] Comparative Example 3

[0111] The preparation process and detection method of the lead dioxide and membrane electrode in Comparative Example 3 were referred to Example 1, and the preparation parameters and performance were shown in Table 1. The difference was that no crystal plane regulator PVP was added. Figure 10 Figure 8 is the scanning electron microscope image of the lead dioxide obtained in Comparative Example 3 at 1 μm. It can be observed that the lead dioxide obtained in Comparative Example 3 was in the form of amorphous particles, losing the regular crystal structure of the lead dioxide prepared in Example 1.

[0112] The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolytic reaction to obtain an ozone product; where the current density was 1500 mA / cm 2 , the reaction temperature was 25°C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolytic reaction, the ozone production rate reached 163 mg / h and the ozone concentration was 77 mg / L as detected by the ozone detector.

[0113] Comparative Example 4

[0114] The preparation process and detection method of the lead dioxide and membrane electrode in Comparative Example 4 were referred to Example 1, and the preparation parameters and performance were shown in Table 1. The difference was that the crystal plane regulator was replaced with cetyltrimethylammonium bromide (CTAB). Figure 11 Figure 21 is the scanning electron microscope image of the lead dioxide obtained in Comparative Example 4 at 1 μm. It can be observed that the lead dioxide was in the form of amorphous particles, losing the regular crystal structure of the lead dioxide prepared in Example 1.

[0115] The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolytic reaction to obtain an ozone product; where the current density was 1500 mA / cm 2 , the reaction temperature was 25°C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolytic reaction, the ozone production rate reached 177 mg / h and the ozone concentration was 80 mg / L as detected by the ozone detector.

[0116] Comparative Example 5

[0117] The preparation process and detection method of the lead dioxide and membrane electrode in Comparative Example 5 were referred to Example 1, and the preparation parameters and performance were shown in Table 1. The difference was that the crystal plane regulator was replaced with sodium dodecyl sulfate (SDS).Figure 12 The scanning electron microscope image of the lead dioxide obtained in Comparative Example 5 at 1 μm shows that the lead dioxide is in the form of amorphous particles and has lost the regular crystal structure of the lead dioxide prepared in Example 1.

[0118] The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain ozone products; where the current density was 1500 mA / cm 2 , the reaction temperature was 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 h of electrolysis reaction, the ozone production rate detected by the ozone detector reached 151 mg / h, and the ozone concentration was 74 mg / L.

[0119] Comparative Example 6

[0120] The preparation process and detection method of the lead dioxide and membrane electrode in Comparative Example 6 were referred to Example 1, and the preparation parameters and performance were shown in Table 1. The difference was that the addition amount of PVP with a molecular weight of 40 kDa was 3 g, and the addition amount of NaClO was 10 mL. Figure 13 The scanning electron microscope image of the sample obtained in Comparative Example 6 at 10 μm shows that cubic crystals with a structural size exceeding 10 μm appeared. According to the literature report, it can be judged that it is Pb3O4. The excessively large crystal size led to a significant reduction in its electrochemically active area, thus affecting its EOP performance.

[0121] Comparative Example 7

[0122] The preparation process of the lead dioxide and membrane electrode in Comparative Example 7 was repeated as in Example 1, and the preparation parameters and performance were shown in Table 1. The difference was that the oxidant sodium hypochlorite was replaced with ammonium persulfate ((NH4)2S2O8). The final product obtained from (NH4)2S2O8 was a light yellow jelly-like substance, which indicates that under the experimental conditions of this invention, PVP may react with (NH4)2S2O8, causing crosslinking of PVP and hindering the normal hydrothermal synthesis of lead dioxide.

[0123] Comparative Example 8

[0124] To illustrate the advantages of the lead dioxide prepared by this method in the application of a water electrolysis ozone generator, a commercial ozone water electrolysis generator purchased from a company in Jinhua, Zhejiang was used for comparison. As shown in Table 1, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain ozone products; where the current density was 1500 mA / cm 2 , the reaction temperature was 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 h of electrolysis reaction, the ozone production rate detected by the ozone detector reached 320 mg / h, and the ozone concentration was 104 mg / L.

[0125] The cross-sections of the membrane electrode obtained in Example 1 and the membrane electrode in the commercial ozone water electrolysis generator in Comparative Example 8 were compared by scanning electron microscopy. The thickness of the catalyst layer on the anode side ( Figure 5 a) and the cathode side ( Figure 5 b) of the membrane electrode obtained in Example 1 was 15-20 μm, which was greatly reduced compared to the thickness of the membrane electrode prepared by the hot pressing method purchased from a company in Jinhua, Zhejiang ([[]] Figure 14 ). The thicknesses of the anode and cathode were reduced to 1 / 36 and 1 / 29 of the original, respectively. The catalyst layer of the hot-pressed membrane electrode is usually prepared by rolling, and the usage amounts of the catalyst and the binder are large. In order to improve the adhesion between the catalyst layer and the proton exchange membrane, it is necessary to press the catalyst anode and cathode onto the membrane by controlling the hot pressing temperature and time, which increases the raw material and preparation costs; a thicker catalyst layer will result in a higher ohmic internal resistance, leading to an increase in heat loss and accelerating the decomposition of ozone. In addition, the thickness also affects the water-vapor exchange during the operation of the ozone generator. The application of the lead dioxide catalyst provided by the present invention greatly reduces the usage amount of the catalyst. The thinner catalyst layer enhances the charge transfer inside the membrane electrode during the operation, reduces the heat loss of ozone, and enables the method to achieve an ozone production rate and concentration close to that of a commercial ozone generator at a lower catalyst loading amount than before.

[0126] Example 2

[0127] Prepare lead dioxide according to the following steps, and the detection method refers to Example 1:

[0128] (1) Dissolve 1.5 g of lead nitrate in 30 mL of deionized water. Add 2.8 g of potassium hydroxide to the obtained solution and stir for 20 minutes to obtain a homogeneous white suspension. Subsequently, add 0.25 g of PVP and continuously stir for 60 minutes to obtain a homogeneous light yellow suspension;

[0129] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) during stirring. The suspension gradually turns yellow-brown, and stir for 5 minutes to make it uniformly turbid and dispersed;

[0130] (3) Transfer the suspension obtained in step (2) to a hydrothermal reaction kettle and carry out hydrothermal reaction at a temperature of 120 °C for 6 hours. After the reaction is completed, cool it to room temperature, centrifuge to collect the precipitate to obtain the lead dioxide; the obtained lead dioxide is washed 3 times with deionized water and absolute ethanol in sequence. Place the filter residue in a vacuum drying oven and dry it at 40 °C for 48 hours.

[0131] Furthermore, the PVP in this example has a molecular weight of 40 kDa;

[0132] Further, before adding the PVP, it can be pre-dissolved in water to obtain a polyvinylpyrrolidone solution;

[0133] The preparation process of the membrane electrode material in Example 2 was repeated in Example 1, and the preparation parameters and performance are shown in Table 1. The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain an ozone product; where the current density was 1500 mA / cm 2 , the reaction temperature was 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 h of electrolysis reaction, the ozone yield reached 217 mg / h and the ozone concentration was 93 mg / L as detected by the ozone detector.

[0134] Example 3

[0135] Prepare lead dioxide according to the following steps, and the detection method refers to Example 1:

[0136] (1) Dissolve 2.0 g of lead chloride in 30 mL of deionized water, add 1.2 g of lithium hydroxide to the obtained solution, stir for 10 minutes to obtain a uniform white suspension, and then add 2.0 g of PVP and continuously stir for 30 minutes to obtain a uniform light yellow suspension;

[0137] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) during stirring. The suspension gradually turns yellow-brown, and stir for 1 minute to make it uniformly turbid and dispersed;

[0138] (3) Transfer the suspension obtained in step (2) to a hydrothermal reaction kettle, carry out hydrothermal reaction at 120 °C for 6 hours, cool to room temperature after the reaction, centrifuge to collect the precipitate to obtain the lead dioxide; the obtained lead dioxide was washed 3 times with deionized water and anhydrous ethanol in sequence, and the filter residue was placed in a vacuum drying oven and dried at 60 °C for 36 hours.

[0139] Further, in this example, the molecular weight of the PVP is 40 kDa;

[0140] Further, before adding the PVP, it can be pre-dissolved in water to obtain a polyvinylpyrrolidone solution;

[0141] The preparation process of the membrane electrode material in Example 3 was repeated in Example 1, and the preparation parameters and performance are shown in Table 1. The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain an ozone product; where the current density was 1500 mA / cm 2, the reaction temperature was 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolytic reaction, the ozone production rate reached 223 mg / h and the ozone concentration was 94 mg / L as detected by the ozone detector.

[0142] Example 4

[0143] Prepare lead dioxide according to the following steps, and the detection method refers to Example 1:

[0144] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water. Add 0.2 g of sodium hydroxide to the resulting solution and stir for 15 minutes to obtain a homogeneous white suspension. Then add 1.25 g of PVP and continue stirring for 45 minutes to obtain a homogeneous light yellow suspension.

[0145] (2) Add 25 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) while stirring. The suspension gradually turns yellowish-brown, and stir for 3 minutes to make it uniformly turbid and dispersed.

[0146] (3) Transfer the suspension obtained in step (92) to a hydrothermal reaction kettle and carry out hydrothermal reaction at 150 °C for 3 hours. After the reaction is completed, cool it to room temperature, centrifuge to collect the precipitate to obtain the lead dioxide; wash the obtained lead dioxide with deionized water and absolute ethanol three times in sequence, place the filter residue in a vacuum drying oven, and dry it at 80 °C for 24 hours.

[0147] Furthermore, in this example, the PVP has a molecular weight of 40 kDa;

[0148] Furthermore, the PVP can be pre-dissolved in water before adding to obtain a polyvinylpyrrolidone solution;

[0149] Repeat the preparation process of the membrane electrode material in Example 1. The preparation parameters and performance are shown in Table 1. Assemble the obtained membrane electrode in a water electrolyzer, use deionized water as the electrolyte, load a DC power supply for electrolytic reaction to obtain an ozone product; where the current density is 1500 mA / cm 2 , the reaction temperature was 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolytic reaction, the ozone production rate reached 237 mg / h and the ozone concentration was 89 mg / L as detected by the ozone detector.

[0150] Example 5

[0151] Prepare lead dioxide according to the following steps, and the detection method refers to Example 1:

[0152] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water. Add 0.02 g of sodium hydroxide to the resulting solution and stir for 15 minutes to obtain a homogeneous white suspension. Subsequently, add 1.25 g of PVP and continue stirring for 45 minutes to obtain a homogeneous light yellow suspension.

[0153] (2) Add 15 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) while stirring. The suspension gradually turns yellowish-brown, and stir for 3 minutes to make the turbidity disperse evenly.

[0154] (3) Transfer the suspension obtained in step (2) to a hydrothermal reaction kettle and carry out hydrothermal reaction at 90 °C for 9 hours. After the reaction is completed, cool to room temperature, centrifuge to collect the precipitate to obtain the lead dioxide; wash the obtained lead dioxide with deionized water and absolute ethanol three times in sequence. Place the filter residue in a vacuum drying oven and dry at 60 °C for 36 hours.

[0155] Furthermore, in this embodiment, the molecular weight of the PVP is 40 kDa;

[0156] Furthermore, before adding the PVP, it can be pre-dissolved in water to obtain a polyvinylpyrrolidone solution;

[0157] Repeat Example 1 for the preparation process of the membrane electrode material in Example 5. The preparation parameters and performance are shown in Table 1. Assemble the obtained membrane electrode in a water electrolyzer, use deionized water as the electrolyte, load a DC power supply for electrolysis reaction to obtain an ozone product; where the current density is 1500 mA / cm 2 , the reaction temperature is 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet is detected by an ozone detector. After 24 hours of electrolysis reaction, the ozone yield reaches 229 mg / h and the ozone concentration is 81 mg / L as detected by the ozone detector.

[0158] Example 6

[0159] The application of lead dioxide in a water electrolysis ozone generator is realized according to the following steps:

[0160] 1) Disperse 100 mg of the lead dioxide obtained in Example 1 in 2 mL of ethanol, then add 200 mg of Nafion D521 solution (5 wt%) and continue ultrasonic dispersion for 90 minutes to obtain an anode catalyst ink.

[0161] 2) Disperse 30 mg of platinum-carbon with a platinum loading of 10% in 2 mL of ethanol, then add 60 mg of Nafion D521 solution (5 wt%) and continue ultrasonic dispersion for 90 minutes to obtain a cathode catalyst ink.

[0162] 3) Spray the anodic catalyst ink and cathodic catalyst ink obtained in steps 1) and 2) respectively on both sides of a Nafion N115 proton exchange membrane under nitrogen at a pressure of 0.05 Mpa to obtain a membrane electrode.

[0163] The preparation parameters and performance are shown in Table 1. Assemble the obtained membrane electrode in a water electrolyzer, use deionized water as the electrolyte, apply a DC power supply for electrolysis reaction to obtain an ozone product; where the current density is 1500 mA / cm 2 , the reaction temperature is 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anodic gas outlet is detected by an ozone detector. After 24 hours of electrolysis reaction, the ozone yield reaches 255 mg / h and the ozone concentration is 91 mg / L as detected by the ozone detector.

[0164] Example 7

[0165] The application of lead dioxide in a water electrolysis ozone generator is realized according to the following steps:

[0166] 1) Disperse 100 mg of the lead dioxide obtained in Example 1 in 2 mL of tert-butanol, then add 200 mg of Nafion D521 solution (5 wt%), and continuously perform ultrasonic dispersion for 80 minutes to obtain an anodic catalyst ink.

[0167] 2) Disperse 30 mg of platinum-carbon with a platinum loading of 10% in 2 mL of ethanol, then add 60 mg of Nafion D521 solution (5 wt%), and continuously perform ultrasonic dispersion for 80 minutes to obtain a cathodic catalyst ink.

[0168] 3) Spray the anodic catalyst ink and cathodic catalyst ink obtained in steps 1) and 2) respectively on both sides of a Nafion N1110 proton exchange membrane under argon at a pressure of 0.5 Mpa to obtain a membrane electrode.

[0169] The preparation parameters and performance are shown in Table 1. Assemble the obtained membrane electrode in a water electrolyzer, use deionized water as the electrolyte, apply a DC power supply for electrolysis reaction to obtain an ozone product; where the current density is 1500 mA / cm 2 , the reaction temperature is 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anodic gas outlet is detected by an ozone detector. After 24 hours of electrolysis reaction, the ozone yield reaches 234 mg / h and the ozone concentration is 81 mg / L as detected by the ozone detector.

[0170] Example 8

[0171] The application of lead dioxide in a water electrolysis ozone generator is realized according to the following steps:

[0172] 1) After dispersing 100 mg of lead dioxide obtained in Example 1 in 2 mL of dimethyl sulfoxide, 125 mg of Nafion D2020 solution (20 wt%) was added, and ultrasonic dispersion was continued for 90 minutes to obtain an anode catalyst ink;

[0173] 2) After dispersing 30 mg of platinum-carbon with a platinum loading of 10% in 2 mL of dimethyl sulfoxide, 15 mg of Nafion D2020 solution (20 wt%) was added, and ultrasonic dispersion was continued for 90 minutes to obtain a cathode catalyst ink.

[0174] 3) The anode catalyst ink and cathode catalyst ink obtained in steps 1) and 2) were respectively sprayed on both sides of a Nafion NR212 proton exchange membrane under air pressure of 0.2 Mpa to obtain a membrane electrode.

[0175] The preparation parameters and performance are shown in Table 1. The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain an ozone product; where the current density was 1500 mA / cm 2 , the reaction temperature was 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolysis reaction, as shown in Table 1, the ozone production rate reached 245 mg / h and the ozone concentration was 85 mg / L detected by the ozone detector.

[0176] Example 9

[0177] The application of lead dioxide in a water electrolysis ozone generator was realized according to the following steps:

[0178] 1) After dispersing 100 mg of lead dioxide obtained in Example 1 in 2 mL of N-methyl-2-pyrrolidone, 125 mg of Nafion D2021 solution (20 wt%) was added, and ultrasonic dispersion was continued for 90 minutes to obtain an anode catalyst ink;

[0179] 2) After dispersing 30 mg of platinum-carbon with a platinum loading of 10% in 2 mL of N-methyl-2-pyrrolidone, 15 mg of Nafion D2021 solution (20 wt%) was added, and ultrasonic dispersion was continued for 90 minutes to obtain a cathode catalyst ink.

[0180] 3) The anode catalyst ink and cathode catalyst ink obtained in steps 1) and 2) were respectively sprayed on both sides of a Nafion NR212 proton exchange membrane under air pressure of 0.2 Mpa to obtain a membrane electrode.

[0181] The preparation parameters and performance are shown in Table 1. The obtained membrane electrode is assembled in a water electrolyzer, deionized water is used as the electrolyte, and a DC power supply is loaded for electrolysis reaction to obtain ozone products. The current density is 1500 mA / cm 2 , the reaction temperature is 25°C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet is detected by an ozone detector. After 24 hours of electrolysis reaction, the ozone yield reaches 251 mg / h and the ozone concentration is 89 mg / L as detected by the ozone detector.

[0182] Example 10

[0183] Prepare lead dioxide according to the following steps. The detection method refers to Example 1:

[0184] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water, add 2 g of sodium hydroxide to the obtained solution, stir for 15 minutes to obtain a uniform white suspension, and then add 0.31 g of PVP and continue stirring for 45 minutes to obtain a uniform light yellow suspension;

[0185] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) during stirring. The suspension gradually turns yellow-brown, and stir for 3 minutes to make it uniformly turbid and dispersed;

[0186] (3) Transfer the suspension obtained in step (2) to a hydrothermal reaction kettle, carry out hydrothermal reaction at 120°C for 6 hours, cool to room temperature after the reaction, centrifuge to collect the precipitate to obtain the lead dioxide; the obtained lead dioxide is washed 3 times with deionized water and anhydrous ethanol in sequence, and the filter residue is placed in a vacuum drying oven and dried at 60°C for 24 hours;

[0187] Furthermore, in this example, the molecular weight of the PVP is 40 kDa;

[0188] Furthermore, the PVP can be pre-dissolved in water before addition to obtain a polyvinylpyrrolidone solution;

[0189] Repeat Example 1 for the preparation process of the membrane electrode material in Example 10. The preparation parameters and performance are shown in Table 1. The obtained membrane electrode is assembled in a water electrolyzer, deionized water is used as the electrolyte, and a DC power supply is loaded for electrolysis reaction to obtain ozone products. The current density is 1500 mA / cm 2 , the reaction temperature is 25°C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet is detected by an ozone detector. After 24 hours of electrolysis reaction, the ozone yield reaches 238 mg / h and the ozone concentration is 89 mg / L as detected by the ozone detector.

[0190] Example 11

[0191] Prepare lead dioxide according to the following steps. The detection method is referred to Example 1:

[0192] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water. Add 2 g of sodium hydroxide to the resulting solution and stir for 15 minutes to obtain a homogeneous white suspension. Subsequently, add 0.625 g of PVP and continue stirring for 45 minutes to obtain a homogeneous light yellow suspension;

[0193] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) during stirring. The suspension gradually turns yellowish-brown, and stir for 3 minutes to make the turbidity disperse evenly;

[0194] (3) Transfer the suspension obtained in step (2) to a hydrothermal reaction kettle and carry out hydrothermal reaction at 120 °C for 6 hours. After the reaction is completed, cool to room temperature, centrifuge to collect the precipitate to obtain the lead dioxide; the obtained lead dioxide is washed 3 times with deionized water and absolute ethanol in sequence. Place the filter residue in a vacuum drying oven and dry at 60 °C for 24 hours;

[0195] Furthermore, in this example, the molecular weight of the PVP is 40 kDa;

[0196] Furthermore, the PVP can be pre-dissolved in water before addition to obtain a polyvinylpyrrolidone solution;

[0197] Repeat Example 1 for the preparation process of the membrane electrode material in Example 11. The preparation parameters and performance are shown in Table 1. Assemble the obtained membrane electrode in a water electrolyzer, use deionized water as the electrolyte, load a DC power supply for electrolysis reaction to obtain an ozone product; where the current density is 1500 mA / cm 2 , the reaction temperature is 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet is detected by an ozone detector. After 24 hours of electrolysis reaction, the ozone yield reaches 251 mg / h and the ozone concentration is 92 mg / L detected by the ozone detector.

[0198] Example 12

[0199] Prepare lead dioxide according to the following steps. The detection method is referred to Example 1:

[0200] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water. Add 2 g of sodium hydroxide to the resulting solution and stir for 15 minutes to obtain a homogeneous white suspension. Subsequently, add 2.5 g of PVP and continue stirring for 45 minutes to obtain a homogeneous light yellow suspension;

[0201] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) during stirring. The suspension gradually turns yellowish-brown, and stir for 3 minutes to make the turbidity disperse evenly;

[0202] (3) Transfer the suspension obtained in step (2) to a hydrothermal reactor, and carry out hydrothermal reaction at 120 °C for 6 hours. After the reaction is completed, cool it to room temperature, centrifuge to collect the precipitate, and obtain the lead dioxide; the obtained lead dioxide is washed 3 times with deionized water and absolute ethanol in sequence, and the filter residue is placed in a vacuum drying oven and dried at 60 °C for 24 hours;

[0203] Further, in this embodiment, the molecular weight of the PVP is 40 kDa;

[0204] Further, the PVP can be pre-dissolved in water before being added to obtain a polyvinylpyrrolidone solution;

[0205] Repeat Example 1 for the preparation process of the membrane electrode material of Example 12. The preparation parameters and properties are shown in Table 1. Assemble the obtained membrane electrode in a water electrolyzer, use deionized water as the electrolyte, load a DC power supply for electrolysis reaction, and obtain an ozone product; where the current density is 1500 mA / cm 2 , the reaction temperature is 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet is detected by an ozone detector. After 24 hours of electrolysis reaction, the ozone yield reaches 206 mg / h and the ozone concentration is 73 mg / L as detected by the ozone detector.

[0206] Example 13

[0207] Prepare lead dioxide according to the following steps, and the detection method refers to Example 1:

[0208] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water, add 2 g of sodium hydroxide to the obtained solution, stir for 15 minutes to obtain a uniform white suspension, and then add 1.2 g of PVP respectively, and continuously stir for 45 minutes to obtain a uniform light yellow suspension;

[0209] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) during stirring. The suspension gradually turns yellow-brown, and stir for 3 minutes to make it uniformly turbid and dispersed;

[0210] (3) Transfer the suspension obtained in step (2) to a hydrothermal reactor, and carry out hydrothermal reaction at 120 °C for 5 hours. After the reaction is completed, cool it to room temperature, centrifuge to collect the precipitate, and obtain the lead dioxide; the obtained lead dioxide is washed 3 times with deionized water and absolute ethanol in sequence, and the filter residue is placed in a vacuum drying oven and dried at 60 °C for 24 hours;

[0211] Further, in this embodiment, the molecular weight of the PVP is 5 kDa;

[0212] Further, the PVP can be pre-dissolved in water before addition to obtain a polyvinylpyrrolidone solution;

[0213] The preparation process of the membrane electrode material in Example 13 was repeated in Example 1, and the preparation parameters and performance are shown in Table 1. The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain an ozone product; the current density was 1500 mA / cm 2 , the reaction temperature was 25 °C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolysis reaction, the ozone yield reached 255 mg / h and the ozone concentration was 88 mg / L as detected by the ozone detector.

[0214] Example 14

[0215] Prepare lead dioxide according to the following steps, and the detection method refers to Example 1:

[0216] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water, add 2 g of sodium hydroxide to the obtained solution, stir for 15 minutes to obtain a homogeneous white suspension, then add 1.2 g of PVP and continue stirring for 45 minutes to obtain a homogeneous light yellow suspension;

[0217] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) during stirring. The suspension gradually turns yellow-brown, and stir for 3 minutes to make it uniformly turbid and dispersed;

[0218] (3) Transfer the suspension obtained in step (2) to a hydrothermal reaction kettle, carry out hydrothermal reaction at 120 °C for 4 hours, cool to room temperature after the reaction, centrifuge to collect the precipitate to obtain the lead dioxide; the obtained lead dioxide is washed 3 times with deionized water and anhydrous ethanol in sequence, and the filter residue is placed in a vacuum drying oven and dried at 60 °C for 24 hours;

[0219] Further, the PVP in this example has a molecular weight of 200 kDa;

[0220] Further, the PVP can be pre-dissolved in water before addition to obtain a polyvinylpyrrolidone solution;

[0221] The preparation process of the membrane electrode material in Example 14 was repeated in Example 1, and the preparation parameters and performance are shown in Table 1. The obtained membrane electrode was assembled in a water electrolyzer, deionized water was used as the electrolyte, and a DC power supply was loaded for electrolysis reaction to obtain an ozone product; the current density was 1500 mA / cm 2, the reaction temperature was 25°C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolytic reaction, the ozone production rate reached 209 mg / h and the ozone concentration was 63 mg / L as detected by the ozone detector.

[0222] Example 15

[0223] Prepare lead dioxide according to the following steps. The detection method refers to Example 1:

[0224] (1) Dissolve 2.5 g of lead acetate in 30 mL of deionized water. Add 2 g of sodium hydroxide to the resulting solution and stir for 15 minutes to obtain a homogeneous white suspension. Subsequently, add 1.2 g of PVP with a molecular weight of 600 kDa and continue stirring for 45 minutes to obtain a homogeneous light yellow suspension;

[0225] (2) Add 20 mL of sodium hypochlorite solution with an effective chlorine concentration of 5% to the suspension obtained in step (1) while stirring. The suspension gradually turns yellowish-brown, and stir for 3 minutes to make it turbid and dispersed evenly;

[0226] (3) Transfer the suspension obtained in step (2) to a hydrothermal reaction kettle and carry out hydrothermal reaction at 120°C for 4 hours. After the reaction is completed, cool it to room temperature, centrifuge to collect the precipitate to obtain the lead dioxide; the obtained lead dioxide is washed 3 times with deionized water and anhydrous ethanol in sequence. Place the filter residue in a vacuum drying oven and dry it at 60°C for 24 hours;

[0227] Furthermore, in this example, the molecular weight of the PVP is 600 kDa;

[0228] Furthermore, the PVP can be pre-dissolved in water before addition to obtain a polyvinylpyrrolidone solution;

[0229] Repeat Example 1 for the preparation process of the membrane electrode material in Example 15. The preparation parameters and performance are shown in Table 1. Assemble the obtained membrane electrode into a water electrolyzer, use deionized water as the electrolyte, load a DC power supply to carry out electrolytic reaction to obtain ozone products; where the current density is 1500 mA / cm 2 , the reaction temperature was 25°C. During the electrolytic synthesis of ozone, the ozone concentration at the anode outlet was detected by an ozone detector. After 24 hours of electrolytic reaction, the ozone production rate reached 196 mg / h and the ozone concentration was 61 mg / L as detected by the ozone detector.

[0230] Table 1 Preparation parameters and performance table of examples and comparative examples

[0231]

[0232]

[0233]

[0234] Note: The process parameters actually adopted are allowed to have a deviation of ±2% from the parameters listed in the table.

[0235] The lead dioxide obtained in Examples 2 - 15 of the present invention was characterized by the same method as in Example 1, and the same quasi - single - crystal crystal structure as in Example 1 could be obtained. From the above examples and comparative examples, it can be seen that the preparation method of the present invention requires a holistic and precise regulation of the ratios of lead salt, polyvinylpyrrolidone, and sodium hypochlorite, and the type of oxidant. Each of the above parameters is indispensable and acts as a whole with synergistic effects to regulate the growth of lead dioxide crystals, so as to prepare the quasi - single - crystal lead dioxide crystals with the described morphology. When the lead dioxide material is applied to catalysts and membrane electrodes to test the ozone - generating performance, in this field, it is usually evaluated by two indicators, namely ozone production rate and ozone concentration. Among them, the ozone production rate can be used as a key indicator to measure the energy consumption and current efficiency of water electrolyzers, etc. The ozone production rate = ozone concentration × gas production volume. The higher the ozone production rate, the better the ozone - generating performance of the material. Therefore, this field mainly focuses on the level of the ozone production rate. Since the process of ozone generation by water electrolysis is usually accompanied by changes in gas production volume and ozone concentration, the ozone concentration can be used as an auxiliary indicator to judge the quality of ozone - generating performance. The ozone production rates of the lead dioxide materials prepared in the examples of the present invention are all above 196 mg·h -1 or more, and the highest can reach 355 mg·h -1 , and the ozone production rate of the lead dioxide material of the present invention is significantly improved compared with the comparative examples. The above examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A lead dioxide crystal material, characterized in that: The lead dioxide crystal has a quasi-single crystal structure and is in the shape of a submicron or micron-sized rod. The exposed surfaces of the lead dioxide are all (110) and (101) surfaces. The (110) surface accounts for 75% to 95% of the total exposed surface, and the (101) surface accounts for 5% to 25% of the total exposed surface. The ratio of the (110) face to the total exposed face and the ratio of the (101) face to the total exposed face can be calculated using the following formulas: in, a is the longest diagonal length of the (110) face, b is the width in the direction perpendicular to a, θ is the angle between the hypotenuse of (110) plane and the horizontal direction, is the angle between the two common edges of the (101) face and the (110) face.

2. The lead dioxide crystal material according to claim 1, characterized in that The detection method of the exposed surface of the lead dioxide crystal is as follows: along the (110) crystal direction, the (002) surface and the The lattice fringes on the surface are 0.165~0.175 nm and 0.320~0.350 nm, respectively, with an angle of 90°.

3. The lead dioxide crystal material according to claim 1, characterized in that The particle size D50 of the lead dioxide crystals ranges from 600 to 1200 nm.

4. The lead dioxide crystal material according to claim 1, characterized in that The lead dioxide crystal has a length of 0.5 to 4 μm along the long axis direction and a length of 100 to 400 nm along the short axis direction.

5. The lead dioxide crystal material according to claim 1, characterized in that The quasi-single crystal structure of the lead dioxide is a dodecahedron.

6. The lead dioxide crystal material according to claim 1, characterized in that The quasi-single crystal structure of the lead dioxide has four hexagonal (110) faces and eight rhombus (101) faces.

7. The lead dioxide crystal material according to claim 1, characterized in that The morphology of the quasi-single crystal structure of the lead dioxide is all β-lead dioxide.

8. Use of the lead dioxide crystalline material according to any one of claims 1 to 7 in a catalyst.

9. A membrane electrode, characterized in that The membrane electrode comprises the lead dioxide crystal material according to any one of claims 1 to 7.

10. The membrane electrode according to claim 9, characterized in that The thickness of the catalyst layer on the anode and cathode sides of the membrane electrode is 15 to 20 μm.

11. The membrane electrode according to claim 9, characterized in that The membrane electrode preparation method comprises: dispersing lead dioxide or platinum carbon in an organic solvent, adding an ion polymer solution, and continuously ultrasonically dispersing for 60 to 90 minutes to obtain an anode or cathode catalyst ink; and spraying the obtained anode catalyst ink and cathode catalyst ink respectively on both sides of a proton exchange membrane under a carrier gas to obtain a membrane electrode.

12. The membrane electrode according to claim 11, characterized in that The ionic polymer is Nafion D520, Nafion D521, Nafion D2020 or Nafion D2021.

13. The membrane electrode according to claim 11, characterized in that The proton exchange membrane is Nafion N115, Nafion N117, Nafion N1110, Nafion NR211 or Nafion NR212.

14. The membrane electrode according to claim 11, characterized in that The carrier gas is air, nitrogen or argon, and the pressure is 0.05-0.50 MPa.

15. A water electrolysis ozone generation system, characterized in that: The water electrolysis ozone generation system comprises the lead dioxide crystal material according to any one of claims 1 to 7 or the membrane electrode according to any one of claims 9 to 14.

16. The water electrolysis ozone generating system according to claim 15, characterized in that: The working steps of the water electrolysis ozone generation system are as follows: assembling the membrane electrode in a water electrolyzer, using deionized water as the electrolyte, loading a DC power supply to perform an electrolysis reaction, and obtaining an ozone product.

17. The water electrolysis ozone generating system according to claim 16, characterized in that: The current density of the DC power supply is 500-2000 mA / cm 2 .

18. The water electrolysis ozone generating system according to claim 16, characterized in that: The current density of the DC power supply is 1500 mA / cm 2 .

19. The water electrolysis ozone generating system according to claim 15, characterized in that: The electrolysis reaction temperature is 20-50°C.

20. The water electrolysis ozone generating system according to claim 15, characterized in that: The electrolysis reaction temperature is 25°C.

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