An anti-oil photovoltaic panel self-cleaning coating and a preparation method thereof

Abstract

The application discloses an anti-oil stain photovoltaic panel self-cleaning paint and a preparation method thereof. The paint comprises the following components in parts by weight: 17-20 parts of hollow nano titanium dioxide, 5-7 parts of sodium perfluorooctane sulfonate, wherein the hollow nano titanium dioxide is hollow anatase nano titanium dioxide formed by removing the silica core after coating the silica on the outer surface of the hollow nano titanium dioxide, and the hollow nano titanium dioxide contains an oil stain degrading agent. The paint has the dual effects of hydrophilicity and oil repellency and oil stain degradation, greatly improves the cleaning effect, reduces the cleaning cost, and also has excellent stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new materials, and particularly relates to an anti-oil stain photovoltaic panel self-cleaning coating and a preparation method thereof. BACKGROUND

[0002] As a new type of clean energy, photovoltaic power generation has many advantages such as environmental protection, no pollution and no noise compared with traditional power generation, and is a sustainable new energy that has been vigorously developed in China in recent years. Taking January to April 2024 as an example, the cumulative installed capacity of photovoltaic power generation in China has reached an astonishing 67147 million kilowatts, an increase of 52.4% year on year. However, while the photovoltaic industry is developing rapidly, the dust and oil pollution problems on photovoltaic panels have gradually become prominent, which has an undeniable impact on the performance of photovoltaic systems. Although China has made significant progress in the prevention and control of dust pollution on photovoltaic panels, through the application of innovative technologies such as self-cleaning coatings, self-cleaning robots and spraying devices, the negative impact of dust on photovoltaic panels has been effectively reduced, but the prevention and control of oil pollution still faces many technical challenges. Oil stains attached to photovoltaic panels not only significantly reduce light absorption efficiency, leading to a significant decrease in power generation, but also the complex chemical composition in the oil stains can cause corrosion to the photovoltaic panel materials, thereby shortening their service life. More seriously, oil stains have extremely strong adhesion and stability, making it difficult to completely remove them using traditional cleaning methods. Even if high-pressure water guns or chemical cleaning agents are used for cleaning, there may be hidden dangers due to the incomplete removal of oil stains, and even secondary damage to the photovoltaic panel may occur. Therefore, the prevention and control of oil pollution has become a key problem that needs to be solved in the current development of the photovoltaic industry. SUMMARY

[0003] The technical problem to be solved by the present application is to provide an anti-oil stain photovoltaic panel self-cleaning coating. The coating has both hydrophilic and oil-repellent effects and can degrade oil stains, greatly improving the cleaning effect and reducing the cleaning cost, and also showing excellent stability.

[0004] The technical solution adopted by the present application is as follows:

[0005] An anti-oil stain photovoltaic panel self-cleaning coating, characterized in that it comprises the following components: 17-20 parts of hollow nanometer titanium dioxide, 5-7 parts of sodium perfluorooctane sulfonate, the hollow nanometer titanium dioxide is hollow anatase type nanometer titanium dioxide formed by coating the outer surface of silicon dioxide and then removing the silicon dioxide core, and the hollow nanometer titanium dioxide contains an oil stain degrading agent in the inside.

[0006] The perfluorooctane sulfonic acid sodium salt mainly provides non-polar fluorine elements and polar hydrophilic segments on the surface of the coating. The fluorine elements reduce the surface free energy of the coating to some extent, and improve the hydrophobic and oleophobic properties. The strong complexing between fluorine ions and titanium dioxide can improve the high electronegativity of titanium dioxide, improve the charge separation efficiency, significantly promote the hole transfer on the surface of titanium dioxide, and improve the activity of hydroxyl radicals, thereby increasing the photocatalytic degradation efficiency of organic pollutants. The perfluorooctane sulfonic acid sodium salt cannot be too much. If too much is added, the increase of fluorine elements will cause steric hindrance between water and the hydrophilic segments on the surface of titanium dioxide, resulting in a decrease in the hydrophilic property, hindering the release of hydroxyl radicals and oil stain degrading agents through the hydration film to remove organic pollutants in the photocatalytic process, and weakening the oil stain resistance.

[0007] Preferably, the particle size of the nanometer titanium dioxide is 55-80 nm.

[0008] Preferably, the oil stain degrading agent is a microbial-based oil stain degrading agent.

[0009] A preparation method of an oil stain-resistant photovoltaic panel self-cleaning coating, characterized in that it comprises the following steps: dispersing 17-20 parts of hollow nanometer titanium dioxide containing an oil stain degrading agent inside into a proper amount of volatile organic solvent, and then adding 5-7 parts of perfluorooctane sulfonic acid sodium salt drop by drop to obtain an oil stain-resistant coating.

[0010] Preferably, the hollow nanometer titanium dioxide is hollow anatase-type nanometer titanium dioxide formed by coating the outer surface of nanometer silicon dioxide and then removing the silicon dioxide core. The preparation method comprises the following steps:

[0011] A1. Mix 25-34 parts of nanometer silicon dioxide with a proper amount of ethanol, grind until no large particle agglomerates are visible, and then disperse into a proper amount of water. Add 3-9 parts of nitric acid, 15-25 parts of tetrabutyl titanate, and then adjust the pH of the system to neutral. React for a period of time to prepare a titanium dioxide sol-gel; the particle size of the nanometer silicon dioxide is 55-80 nm;

[0012] A2. Centrifuge the above-mentioned titanium dioxide sol-gel, wash with ethanol to remove impurities, evaporate the ethanol, heat the obtained nanometer powder in a strong alkali solution to a temperature T for etching to remove the nanometer silicon dioxide, and then calcine at high temperature to obtain hollow nanometer titanium dioxide.

[0013] The particle size of the nanometer silicon dioxide template agent is small, which further reduces the particle size and internal hollow volume of the hollow nanometer titanium dioxide prepared subsequently, and finally leads to a decrease in the roughness of the coating surface, a decrease in the content of the oil stain degrading agent that can be loaded, and a decrease in the oil stain resistance of the coating. If the particle size of the nanometer silicon dioxide template agent is too large, it will increase the particle size and internal hollow volume of the hollow nanometer titanium dioxide prepared subsequently, and finally lead to an increase in the roughness of the coating surface.

[0014] The nitric acid mainly affects the hydrolysis rate of the tetrabutyl titanate and the crystal form of the titanium dioxide. The addition of the nitric acid can slow down the hydrolysis rate of the tetrabutyl titanate, otherwise, the hydrolysis will be too fast, a too thick titanium dioxide layer will be formed on the surface of the silica template, the particle size of the titanium dioxide formed finally will be too large, the roughness of the coating surface will increase, the transmittance in the visible light region will decrease, and the photovoltaic power generation efficiency will be affected. However, too much nitric acid will cause the crystal form of the titanium dioxide generated by the hydrolysis of the tetrabutyl titanate to change from anatase to rutile, and the rutile-type titanium dioxide exhibits photocatalytic inertness and does not have the ability to degrade organic matters, resulting in the decrease of the photocatalytic activity of the coating prepared finally and the decrease of the degradation rate of the organic pollutants.

[0015] Preferably, the hollow nanometer titanium dioxide containing the oil stain degrading agent in the interior is prepared by the following steps:

[0016] B1, placing the hollow nanometer titanium dioxide in a container, controlling the air pressure in the container to be lower than the atmospheric pressure, injecting the oil stain degrading agent into the interior of the container, and making the oil stain degrading agent completely immerse the nanometer titanium dioxide particles;

[0017] B2, slowly releasing the system to the normal air pressure, to obtain the hollow nanometer titanium dioxide containing the oil stain degrading agent in the interior.

[0018] If too much oil stain degrading agent is added and cannot completely enter the interior of the nanometer titanium dioxide particles, the excess oil stain degrading agent can be washed away by ethanol.

[0019] Preferably, the nanometer silicon dioxide is prepared by the following steps:

[0020] C1, mixing 10-30 parts of water, 35-45 parts of industrial ammonia water and 750-800 parts of ethanol, slowly adding 38-40 parts of tetraethyl silicate, and preparing SiO2 sol-gel after reaction at a temperature of 40-55℃ for a period of time; the industrial ammonia water is an aqueous solution containing ammonia 25%-28%.

[0021] C2, after centrifugation of the SiO2 sol-gel, washing the separated solid product with ethanol, and evaporating to remove the ethanol, to obtain the nanometer silicon dioxide. The ethanol washing removes the water, ammonia and unreacted tetraethyl silicate.

[0022] Preferably, the volatile organic solvent is ethanol.

[0023] Preferably, the temperature T is 82-88℃.

[0024] Preferably, the calcination temperature in step A2 is 450℃.

[0025] The anti-oil stain coating provided by the application has excellent super-hydrophilic / oil-repellent effect, and can form a water film on the surface of a photovoltaic panel in a high humidity climate area through hydration, thereby reducing the adhesion of oil stains and keeping the surface of the photovoltaic panel clean; the anti-oil stain photovoltaic panel self-cleaning coating has excellent oil stain decomposition effect, and the hollow nano TiO2 (anatase crystal form) particles with photocatalytic activity and the biological-based oil stain degrading agent are synergistic, so that the oil stains on the surface can be desorbed and degraded into carbon dioxide, water and other inorganic small molecules in a dry and anhydrous film environment. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of the anti-oil stain photovoltaic panel self-cleaning coating prepared in Example 1 of the application.

[0027] Figure 2 The comparative curve of the transmittance in the visible light region of the photovoltaic panel glass coated with the anti-oil stain photovoltaic panel self-cleaning coating prepared in Example 1 of the application and the untreated photovoltaic panel glass.

[0028] Figure 3 is an image of the degradation performance of the organic pollutants on the surface of the glass coated with the anti-oil stain photovoltaic panel self-cleaning coating characterized by a fluorescence microscope.

[0029] Figure 4 The degradation rate curve in the oil stain resistance performance test of the anti-oil stain photovoltaic panel self-cleaning coating prepared in Example 1 of the application.

[0030] Figure 5 The degradation cycle curve in the oil stain resistance performance test of the anti-oil stain photovoltaic panel self-cleaning coating prepared in Example 1 of the application.

[0031] Figure 6 The comparative curve of the power generation efficiency of the photovoltaic panel coated with the anti-oil stain photovoltaic panel self-cleaning coating prepared in Example 1 of the application and the untreated photovoltaic panel before and after being placed in an outdoor environment for a long time. DETAILED DESCRIPTION

[0032] The specific embodiments of the application will be described in detail below with reference to the specific embodiments. However, the application is not limited to the given embodiments.

[0033] Example 1

[0034] The specific preparation method of the anti-oil stain coating for photovoltaic panels provided by the application is as follows:

[0035] (1) 20 g deionized water, 40 g ammonia water were added into 780 g anhydrous ethanol, after stirring at room temperature for 30 minutes, 39 g tetraethyl silicate was added dropwise, then the temperature was kept at 40℃ and the reaction was continued for 6 hours to prepare SiO2 sol-gel. After centrifugation, the separated solid product was washed with anhydrous ethanol for 3 times, and then dried at 80℃ to obtain 30 g of nano-SiO2 particles as SiO2 template;

[0036] (2) The SiO2 template was wet ground in a agate mortar for 30 minutes, and an appropriate amount of anhydrous ethanol was added during the wet grinding process to keep the volume as constant as possible. After wet grinding, the SiO2 template (containing anhydrous ethanol) was dispersed in 1000 g deionized water, then 6.3 g nitric acid was added, and after fully stirring and mixing at room temperature, 20 g tetrabutyl titanate was added, then ammonia water was added dropwise to adjust the pH of the system to neutral, and then the reaction was continued for 3 hours to prepare a nano-scale core-shell particle sol-gel with a TiO2 (anatase crystal type) shell and a SiO2 core. After centrifugation, the separated solid product was washed with anhydrous ethanol for 3 times, and then dried at 80℃. The obtained nano-powder was etched in 1M sodium hydroxide solution at 85℃ for 6 hours to remove the SiO2 template, and then calcined in a muffle furnace at 450℃ for 2 hours to finally obtain 16 g of hollow nano-TiO2 (anatase crystal type) particles with a particle size of about 80 nanometers;

[0037] (3) The nano-hollow TiO2 (anatase crystal type) particles were placed in a sealed container, the internal pressure of the container was pumped to about 5 mbar by a vacuum pump, and then a biological oil stain degrading agent (SUKAZME-GRL3X from Weifang Yihao Biological Technology Co., Ltd. or SUKAClean GR / C from Suokehan (Weifang) Biological Engineering Co., Ltd.) was injected into the container using a syringe. After the biological oil stain degrading agent completely covered the hollow nano-TiO2 (anatase crystal type) particles, the system was slowly released to normal pressure. Due to the pressure difference, the biological oil stain degrading agent was absorbed into the shell of the hollow nano-TiO2 (anatase crystal type) particles. After washing with anhydrous ethanol for three times, hollow nano-TiO2 (anatase crystal type) particles containing biological oil stain degrading agent inside were obtained;

[0038] (4) The hollow nano-TiO2 (anatase crystal type) particles containing biological oil stain degrading agent inside were dispersed in anhydrous ethanol, and then 6 g of sodium perfluorooctanesulfonate was added dropwise. After continuing the reaction at room temperature for 2 hours, an anti-oil stain photovoltaic panel self-cleaning coating was prepared;

[0039] The glass substrate for photovoltaic panel is washed with anhydrous ethanol and deionized water alternately for 2 times, then the coating is sprayed on the surface of the photovoltaic glass panel, and the spraying process is kept with the glass panel horizontally placed. After curing at 50℃ for 1 hour, the oil stain-resistant self-cleaning coating on the surface of the photovoltaic glass panel is prepared.

[0040] Example 2

[0041] The difference between the embodiment and the example is that the adding amount of each component: tetrabutyl titanate 15g, tetraethyl silicate 30g, deionized water in step (1) is 10g, the mass of the nanometer silicon dioxide prepared in step (1) is 25g, the nanometer titanium dioxide prepared in step (2) is 12g, the etching temperature in step (2) is 82℃, and the others are the same as in example 1.

[0042] Example 3

[0043] The difference between the embodiment and the example is that the adding amount of each component: tetrabutyl titanate 25g, tetraethyl silicate 40g, deionized water in step (1) is 30g, the mass of the nanometer silicon dioxide prepared in step (1) is 34g, the nanometer titanium dioxide prepared in step (2) is 20g, the etching temperature in step (2) is 88℃, and the others are the same as in example 1.

[0044] Example 4

[0045] The difference between the embodiment and the example is that the adding amount of each component: ammonia in step (1) is 35g, anhydrous ethanol in step (1) is 750g, nitric acid in step (2) is 3g, and the others are the same as in example 1.

[0046] Example 5

[0047] The difference between the embodiment and the example is that the adding amount of each component: ammonia in step (1) is 45g, anhydrous ethanol in step (1) is 800g, nitric acid in step (2) is 9g, and the others are the same as in example 1.

[0048] Example 6

[0049] The difference between the embodiment and the example is that the adding amount of each component: sodium perfluorooctanesulfonate is 5g, tetrabutyl titanate is 15g, and the others are the same as in example 1.

[0050] Example 7

[0051] The difference between the embodiment and the example is that the adding amount of each component: sodium perfluorooctanesulfonate is 7g, tetrabutyl titanate is 25g, and the others are the same as in example 1.

[0052] The coating prepared in the embodiment of the application is tested for performance as follows:

[0053] Visible light transmittance: The transmittance of visible light of the samples (coating-glass vs. pristine glass) was tested using an Agilent Cary 5000 UV-Vis-NIR spectrophotometer. The size of the sample tested was 7.5 cm x 2.5 cm, and a glass slide of the same size was chosen as the control sample during the test. The transmittance of air was set as the baseline for the test. The wavelength range tested was from 300 nm to 1800 nm.

[0054] Emissivity in the infrared light region: The emissivity of the coating-coated photovoltaic panel in the long-wave infrared light region (6-25 microns) was tested using a Thermo Nicolet iS50.

[0055] Contact angle: The contact angle of water droplets / oil droplets (if not specified, the oil used in the test here is gasoline, i.e., a mixture of aliphatic hydrocarbons and naphthenes) on the surface of the coating was measured using a KRüSS DSA25S optical contact angle analysis system. For the measurement of the contact angle in a non-moving state, the water droplets / oil droplets (about 10 μL) were first added to the surface of the sample by a motor-controlled syringe. When the droplet was stable, a side-view image was taken by a camera, and the static contact angle value of the water droplets / oil droplets on the surface of the coating was calculated by fitting using software.

[0056] Rolling / sliding angle: The sliding angle of water droplets / oil droplets on the surface of the coating was measured using a KRüSS DSA25S optical contact angle analysis system. For the measurement of the sliding angle, the inclined sample was used using a motor-controlled rotatable test platform, and the rotation angle of the platform was displayed in real time on the computer connected to the motor. The initial inclination angle of the platform at the start of the test was kept at 0°, and after the water droplets / oil droplets (~10 μL) were added to the surface of the coating by a syringe, the platform was rotated by controlling the motor. When the droplet began to roll on the surface, the rotation was stopped, and the rotation angle displayed on the computer was recorded as the rolling angle. Each sample was measured at three different positions to reduce data errors.

[0057] Oil stain resistance test: We first sprayed the coating on a 1 cm2glass substrate as a test sample, used a fluorescently labeled advanced fatty acid glyceride as an oil stain simulator, and observed the sample before and after oil stain contamination and after light (30 W power ultraviolet light) degradation using an Olympus IX73 fluorescence microscope to characterize the oil stain resistance of the self-cleaning coating of the oil stain-resistant photovoltaic panel. To further quantify the oil stain resistance of the coating, we weighed the sample before and after the addition of the simulated oil stain contaminant and after light degradation, and the specific quantitative indicators are as follows:

[0058]

[0059] In the formula, Vdegradation is the average degradation rate constant, which measures the average degradation rate of organic pollutants by the coating over a period of time; mbefore is the mass of the sample after the addition of simulated oil pollutants; mafter is the mass of the sample after the addition of simulated oil pollutants; mdecline is the mass of the sample after photodegradation; t is the degradation time; and A is the sample area.

[0060]

[0061] In the formula, kdegradation is the degradation rate, which measures the degree of degradation of organic pollutants by the coating; mbefore is the mass of the sample after adding simulated oil pollutants; mafter is the mass of the sample after adding simulated oil pollutants; and mdecline is the mass of the sample after photodegradation.

[0062] In addition, we conducted cyclic tests on the photodegradation process of the coating against oil stains to characterize the durability of the coating's anti-oil stain performance. We used a degradation rate of 95% as the dividing line. A degradation rate greater than 95% was considered effective, and a degradation rate less than 95% was considered ineffective. Therefore, we only recorded how many degradation-cleaning cycles the sample could maintain a degradation rate of 95% as the metric.

[0063] Comparative test of power generation efficiency: The current density-voltage curve was tested using the Titesh PROVA200A solar cell analyzer. The solar source during the test was provided by the Yiguangke SOLARBEAM-06-3A solar simulator, simulating an AM 1.5 solar irradiance of approximately 100mW cm-2.

[0064] The performance tests of the coatings prepared in each embodiment are shown in the table below:

[0065]

[0066]

[0067] like Figure 1 As shown, the self-cleaning coating for an oil-resistant photovoltaic panel prepared in this invention incorporates nanoscale titanium dioxide particles with embedded oil-degrading agents, and the surface is grafted with sodium perfluorooctane sulfonate. The hydrophilic units (such as sodium ions) in the fluorinated sulfonate increase the orientation force component in the van der Waals forces, thereby creating an attraction for polar water molecules in the coating. Meanwhile, the fluorinated groups minimize the dispersion force component in the van der Waals forces, thus creating a repulsive effect on oil molecules in the coating. The anatase TiO2 nanoparticles containing bio-based oil-degrading agents exhibit, on the one hand, extremely high photocatalytic activity, enabling the coating to decompose organic pollutants on the surface under ultraviolet light; on the other hand, under the hydration effect of the hydrophilic layer, the oil-degrading agents become active, reducing the adhesion of surface oil and accelerating the degradation of organic pollutants in a synergistic photocatalytic effect.

[0068] By Figure 2 The contrast curve of the transmittance of the coated photovoltaic panel glass and the untreated photovoltaic panel glass in the solar radiation spectrum region shows that the transmittance of the coated photovoltaic panel glass in the visible light region reaches about 92%, which is higher than that of the untreated glass. This is probably because the nano-scale TiO2 layer acts as an antireflection layer, and the addition of fluorine-containing substances weakens the scattering effect of polar substances on light, to some extent, increasing the transmittance.

[0069] The contact angle of water droplets on the surface of the coated photovoltaic panel glass is about 0°, showing super-hydrophilic properties; the contact angle of oil droplets on the surface is 86.8-94.9°, showing excellent oleophobic properties, and the sliding angle of the oil droplets is 7.6-11°, which is measured in a dry state. However, in a high-humidity environment with a water layer, the contact angle of the oil droplets on the surface is about 72.1°, and the sliding angle is about 1.4°. In the presence of a water layer, the coating is more inclined to be a smooth and oleophobic coating, and the water layer has a very high surface mobility, which can quickly remove the oil droplets incompatible with the surface, which also gives the coating excellent oil stain resistance.

[0070] Figure 3 The image of the organic pollutant degradation performance of the anti-oil stain photovoltaic panel self-cleaning coated glass surface characterized by fluorescence microscopy (since only black and white expression is available, the gray in the figure represents fluorescent green). In this test, we selected a glass substrate with an area of 1 square centimeter, coated the surface with an anti-oil stain photovoltaic panel self-cleaning coating, dropped fluorescently labeled organic pollutants on the surface, and took pictures at the beginning, after 2 hours of irradiation, and after 5 hours of irradiation under 30W ultraviolet light, to observe the degradation of the surface organic pollutants. From the figure, it can be seen that at the beginning of the experiment, the sample surface is a high-saturation fluorescent green, indicating that the surface is covered with fluorescently labeled organic pollutants; when the irradiation time reaches 2 hours, the fluorescent color saturation decreases, indicating that the organic pollutants decrease and the fluorescent label is also degraded; when the irradiation time reaches 5 hours, there is almost no fluorescent color in the visible range, and it becomes completely black, most of the organic pollutants and fluorescent label are decomposed, indicating that the anti-oil stain photovoltaic panel self-cleaning coating has excellent oil stain resistance.

[0071] Figure 4 By calculating the degradation rate of organic matter during the anti-oil stain test, the anti-oil stain performance of the anti-oil stain photovoltaic panel self-cleaning coating is quantified. After 5 hours of ultraviolet irradiation, the degradation rate of the organic pollutants on the surface of the sample reaches 97.5%. Moreover, as Figure 5As shown, in addition to the calculation of the degradation rate in a single degradation process, the average rate of degradation process is also quantified, and the retention of the anti-fouling performance after multiple degradation cycles is also evaluated, which can reflect the durability of the anti-fouling photovoltaic panel self-cleaning coating. The degradation rate of the anti-fouling photovoltaic panel self-cleaning coating for surface contaminants can still be maintained at 0.07616 grams per hour per square centimeter after 50 times of adhesion-degradation-cleaning cycles, and the degradation rate is maintained at 95.2%, even after 60 cycles, the degradation rate can still be maintained at 94.9%.

[0072] Figure 6 The power generation efficiency of the anti-fouling photovoltaic panel self-cleaning coating coated photovoltaic panel and untreated photovoltaic panel before and after being placed outdoors for one month is tested. As can be seen from the curves in the figure, before the test, the J-V curves of the anti-fouling photovoltaic panel self-cleaning coating coated photovoltaic panel and the untreated photovoltaic panel are roughly the same, and the short-circuit current and open-circuit voltage of the two photovoltaic panels are not much different, indicating that the power generation efficiencies of the two are similar. After being placed outdoors for one month, the untreated photovoltaic panel does not have self-cleaning performance, and various organic and inorganic contaminants adhere to the surface, resulting in a sharp decline in power generation efficiency; while the anti-fouling photovoltaic panel self-cleaning coating coated photovoltaic panel still has a high short-circuit current and open-circuit voltage, indicating that it can maintain the cleanliness of the surface for a long time without manual cleaning and maintain a high power generation efficiency.

[0073] The above has made a detailed description of the present application in combination with specific embodiments. However, the present application is not limited to the above described. Within the knowledge possessed by those skilled in the art, various changes made without departing from the concept of the present application still fall within the protection scope of the present application.

Claims

1. A self-cleaning coating for oil-resistant photovoltaic panels, characterized in that, It comprises the following components by weight: 17-20 parts hollow nano-titanium dioxide and 5-7 parts sodium perfluorooctane sulfonate. The hollow nano-titanium dioxide is formed by coating the outer surface of silica and then removing the silica core, resulting in hollow anatase nano-titanium dioxide. The hollow nano-titanium dioxide contains an oil-degrading agent. The particle size of the nano-titanium dioxide is 55-80 nm. The preparation method includes the following steps: A1. Mix 25-34 parts of nano-silica with an appropriate amount of ethanol, grind until there are no large aggregates visible to the naked eye, disperse in an appropriate amount of water, add 3-9 parts of nitric acid, add 15-25 parts of tetrabutyl titanate, then adjust the pH of the system to neutral, react for a period of time, and prepare titanium dioxide sol gel; the contents of the above components are all parts by weight. A2. After centrifuging the above titanium dioxide sol-gel, washing it with ethanol to remove impurities, evaporating to remove the ethanol, and then etching the obtained nanoparticles in a strong alkaline solution at a temperature T to remove the nano-silica, followed by high-temperature calcination to obtain hollow nano-titanium dioxide.

2. The self-cleaning coating for anti-oil photovoltaic panels according to claim 1, characterized in that: The oil stain degrading agent is a microbial-based oil stain degrading agent.

3. The self-cleaning coating for anti-oil photovoltaic panels according to claim 1, characterized in that, It includes the following steps: Disperse 17-20 parts of hollow nano-titanium dioxide containing an oil stain degrading agent into an appropriate amount of volatile organic solvent, and then add 5-7 parts of sodium perfluorooctane sulfonate dropwise to obtain a coating.

4. The self-cleaning coating for an anti-oil photovoltaic panel according to claim 3, characterized in that, The hollow nano-titanium dioxide containing an oil-degrading agent is prepared through the following steps: B1. Place the hollow nano-titanium dioxide in a container, control the air pressure inside the container to be lower than atmospheric pressure, and inject the oil stain degrading agent into the container so that the oil stain degrading agent completely submerges the nano-titanium dioxide particles. B2. Slowly release the system to normal atmospheric pressure to obtain hollow nano-titanium dioxide containing oil-degrading agents.

5. The self-cleaning coating for an anti-oil photovoltaic panel according to claim 3, characterized in that, The nano-silica is prepared by the following steps: C1. Mix 10-30 parts water, 35-45 parts industrial ammonia, and 750-800 parts ethanol, slowly add 30-40 parts tetraethyl silicate, and react at 40-55°C for a period of time to prepare SiO2 sol-gel; the contents of the above components are all parts by weight. C2. After centrifuging the SiO2 sol-gel, wash the separated solid product with ethanol, and then evaporate the ethanol to obtain nano-silica.

6. The self-cleaning coating for an anti-oil photovoltaic panel according to claim 3, characterized in that: The volatile organic solvent is ethanol.

7. The self-cleaning coating for anti-oil photovoltaic panels according to claim 3, characterized in that: The temperature T is 82-88℃.

8. The self-cleaning coating for anti-oil photovoltaic panels according to claim 1, characterized in that: The calcination temperature in step A2 is 450℃.

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