Transparent super-hydrophobic photocatalytic antireflection self-cleaning coating

Abstract

The present application belongs to the technical field of surface self-cleaning coating, and specifically discloses a transparent super-hydrophobic photocatalytic antireflection self-cleaning coating, which comprises a super-hydrophobic coating and a plurality of photocatalytic island-shaped regions distributed on the surface of the super-hydrophobic coating, wherein the photocatalytic island-shaped regions are formed by accumulation of photocatalytic nanoparticles, and the components of the super-hydrophobic coating comprise low-surface-energy modified hydrophobic SiO2 nanoparticles, silicate and coupling agent, and the mass ratio of the photocatalytic nanoparticles, the hydrophobic SiO2 nanoparticles, the silicate and the coupling agent is 0.001-0.01:0.05-0.1:1:1-5.The self-cleaning coating is prepared by sol-gel method at room temperature by using photocatalytic nanoparticles, low-surface-energy modified hydrophobic SiO2 nanoparticles, silicate and coupling agent, and a special surface structure is constructed, so that the technical problem that photocatalysis and super-hydrophobicity are difficult to be compatible is overcome.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of surface self-cleaning coating, and particularly relates to a transparent super-hydrophobic photocatalytic anti-reflection self-cleaning coating. BACKGROUND

[0002] With the increasing demand for energy, the application of photovoltaic panels and components in independent mode and grid-connected mode is growing, especially in sunny regions, large photovoltaic power stations are becoming increasingly popular. However, photovoltaic components are placed outdoors for a long time, and are easy to adsorb dust and dust caused by traffic exhaust pollutants in the atmosphere, causing dust to accumulate on the surface of photovoltaic glass, hindering the incidence of sunlight, resulting in a decrease in the transmittance of photovoltaic glass, thereby causing a decrease in photovoltaic efficiency. Therefore, in order to maintain the power generation efficiency, the solar panel needs to be cleaned regularly every few weeks. At present, the cleaning methods mainly include manual, semi-automatic and automatic cleaning. Among them, manual cleaning method, semi-automatic cleaning method mainly include artificial conventional cleaning, mechanical cleaning, high-pressure water gun cleaning. These cleaning methods are time-consuming, expensive, and harmful to the environment, and even can corrode the frame of solar panels and cause damage to the surface of photovoltaic panels.

[0003] Self-cleaning coating has natural self-cleaning ability, low energy consumption, environmental protection and low maintenance. By constructing a self-cleaning coating on the surface of a photovoltaic panel, the cleaning cycle of the surface of the photovoltaic glass can be shortened, the surface cleaning frequency can be reduced, and the power generation efficiency of the photovoltaic component can be maintained. At present, there are three types of self-cleaning coatings: hydrophobic coating, hydrophilic coating and photocatalytic coating. The dust and dirt on the surface of the hydrophobic coating and the hydrophilic coating are carried away by raindrops in different ways; the photocatalytic coating absorbs ultraviolet light in sunlight through the photocatalyst in the coating to generate photo-generated electrons and photo-generated electron holes, which have strong oxidation ability, and the organic pollutants adsorbed on the surface of the coating are oxidized and decomposed. The surface energy of the hydrophilic coating surface can be in a higher state to easily adsorb dust in the environment, while the surface energy of the super-hydrophobic surface is lower, which can significantly reduce the dust deposition rate even without rain. Therefore, the super-hydrophobic coating has a wider range of applications and better self-cleaning performance. By constructing a super-hydrophobic photocatalytic coating, the photocatalytic powder on the surface of the coating can decompose organic pollutants using sunlight, weaken the interfacial bonding force between the organic pollutants and the surface of the photovoltaic glass, and make the organic pollutants easy to be washed away by raindrops, thereby realizing self-cleaning of the surface of the photovoltaic glass.

[0004] Currently, self-cleaning coatings are mainly super-hydrophobic coatings or photocatalytic super-hydrophilic coatings. Literature (JI Z, LIU Y, DU F. Rational design of superhydrophobic, transparent hybrid coating with superior durability [J]. Progress in Organic Coatings, 2021, 157) uses phenyl trimethoxy (PTMS), 1H, 1H, 2H, 2H-perfluorodialkyl trimethoxy silane (PFTS), 3-glycidoxy trimethyl (GPTS), trimethoxy (propyl) silane (TTPS) as raw materials to prepare a super-hydrophobic self-cleaning coating by sol-gel method, but the coating has no photocatalytic property and cannot decompose organic pollutants on the surface of the coating. Literature (CN 115625098 A) discloses a preparation method of a self-cleaning super-hydrophobic surface, mixes fluorosilicon resin and organic solvent, then adds hydrophobic nano-silicon dioxide, and sequentially performs magnetic stirring and ultrasonic dispersion treatment to obtain a hydrophobic sol solution, and the self-cleaning super-hydrophobic coating is obtained by spraying and curing at a temperature of 60-90℃, but the coating has no ability to photocatalytically decompose organic pollutants, and although the curing temperature is as low as 60-90℃, it still cannot be cured at room temperature, and the practical application is limited. Literature (BOUTAMART M, BRICHE S, NOUNEH K, et al. Transparent and self-cleaning surfaces based on nanocomposite sol-gel coatings [J]. Chemistry select, 2020, 5(28): 8522-8531) uses titanium isopropyl titanate (TIPT) and tetraethyl orthosilicate (TEOS) as raw materials to prepare a photocatalytic self-cleaning coating by sol-gel method, and the coating is heat-cured at a high temperature of 300-500℃ for 2 hours, and the coating becomes super-hydrophilic (photo-induced super-hydrophilic) under sunlight, but the coating cannot be super-hydrophobic. There are few studies on super-hydrophobic photocatalytic self-cleaning coatings, and the technical problem lies in that the photocatalytic surface has the property of photo-induced super-hydrophilicity, therefore, it is difficult to integrate the two functions of super-hydrophobicity and photocatalysis on the same surface. SUMMARY

[0005] The purpose of the present application is to overcome the defects existing in the prior art, and to provide a transparent super-hydrophobic photocatalytic antireflection self-cleaning coating. By constructing a micro-nano hierarchical structure on the surface of the coating, the reflectivity of the coating is reduced, and the surface of the coating is super-hydrophobic. By mixing photocatalytic nanoparticles, the surface morphology of the coating is controlled, and the photocatalytic nanoparticles are distributed in the form of micron-level clusters on the surface of the coating, so that the super-hydrophobicity and the photocatalytic activity are compatible on the surface of the coating.

[0006] To achieve the above object, one of the technical solutions of the present application is a transparent super-hydrophobic photocatalytic antireflection self-cleaning coating, comprising a super-hydrophobic coating and a plurality of photocatalytic island regions distributed on the surface of the super-hydrophobic coating, the photocatalytic island regions are formed by accumulation of photocatalytic nanoparticles, and the components of the super-hydrophobic coating include low-surface-energy modified hydrophobic SiO2 nanoparticles, silicate and coupling agent, the mass ratio of the photocatalytic nanoparticles, the hydrophobic SiO2 nanoparticles, the silicate and the coupling agent is 0.001-0.01:0.05-0.1:1:1-5.

[0007] In a preferred embodiment of the present application, the photocatalytic nanoparticles are single semiconductor oxides or composite semiconductor oxides, the single semiconductor oxides are one of anatase TiO2, rutile TiO2, oxygen-deficient TiO2 and ZnO, and the composite semiconductor oxides are one of anatase / rutile mixed TiO2, metal-loaded / grafted / doped TiO2, non-metal-doped / grafted TiO2 and TiO2 / ZnO.

[0008] In a preferred embodiment of the present application, the area diameter of the photocatalytic island regions is 3-8 μm, the spacing between the peripherally adjacent photocatalytic island regions is 10-100 μm, and the center distance between the peripherally adjacent photocatalytic island regions is 10-100 μm.

[0009] In a preferred embodiment of the present application, when the photocatalytic island regions are circular, the area diameter is the diameter of the circle, and when the photocatalytic island regions are non-circular, the area diameter is the diameter of the inscribed circle or circumscribed circle containing 90% of the area of the photocatalytic island regions.

[0010] In a preferred embodiment of the present application, the low-surface-energy modified hydrophobic SiO2 nanoparticles include nanometer SiO2 particles modified by silane or fluorosilane or siloxane.

[0011] In a preferred embodiment of the present application, the silicate is one of methyl silicate, ethyl silicate, trimethoxysilane, triethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane and diethyldiethoxysilane, and the coupling agent is one of silane coupling agents KH550, KH560 and KH570.

[0012] In a preferred embodiment of the present application, the surface of the super-hydrophobic coating is a micro-nano hierarchical porous rough structure.

[0013] To achieve the above object, another technical solution of the present application is a preparation method of a transparent super-hydrophobic photocatalytic antireflection self-cleaning coating, comprising the following steps:

[0014] (1)Mixing and stirring silicate, silane coupling agent, ethanol, isopropyl alcohol, propylene glycol methyl ether according to the mass ratio of 30-35:30-35:25-35:30-35:70-80 to obtain A sol; mixing and stirring oxalic acid, 0.1 mol / L nitric acid, water according to the mass ratio of 0.5-1.0:120-140:15-25 to obtain B solution; slowly adding B solution into A sol while stirring to obtain C sol;

[0015] (2)Mixing and stirring photocatalytic nanoparticles, low surface energy modified hydrophobic SiO2 nanoparticles, silane coupling agent according to the mass ratio of 0.03-0.15:1.5-2.5:65-75 to obtain D sol;

[0016] (3)Coating C sol obtained in step (1) on the surface of photovoltaic glass substrate, curing at room temperature, then coating D sol obtained in step (2), curing at room temperature to obtain transparent super-hydrophobic photocatalytic antireflection self-cleaning coating.

[0017] B solution is a catalyst for hydrolysis of silicate, and C sol functions as a bonding layer.

[0018] During spraying, C sol and D sol cannot be mixed together and sprayed. C sol is sprayed first, and then D sol is sprayed. The purpose is that C sol functions as a bonding layer, and D sol functions as a functional layer of super-hydrophobicity, photocatalysis and antireflection. After curing at room temperature, part of the cured layer of D sol is embedded into the cured layer of C sol, thereby improving the wear resistance of the functional layer. The method for improving the wear resistance of the functional layer is that the cured layer of D sol is partially pressed into the bonding layer by increasing the air pressure during spraying of D sol, or shortening the distance between the spray gun and the substrate, or pressing mechanically after spraying, etc.

[0019] In a preferred embodiment of the present application, the coating method in step (3) is one of spraying, spin coating and blade coating.

[0020] In a preferred embodiment of the present application, the surface roughness Ra (i.e. the average roughness) of the transparent super-hydrophobic photocatalytic antireflection self-cleaning coating is 10-100 nm.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1. The self-cleaning coating of the present application has the properties of antireflection, super-hydrophobicity and photocatalysis, and also has wear resistance.

[0023] 2. The self-cleaning coating of the present invention can be cured at room temperature and can be sprayed on large-area photovoltaic glass surfaces. Therefore, it can be widely used in photovoltaic, construction, transportation, electronics and other product fields;

[0024] 3. The self-cleaning coating of the present invention is prepared by a sol-gel method and room-temperature curing of photocatalytic nanoparticles, low-surface-energy-modified hydrophobic SiO2 nanoparticles, silicates, coupling agents, etc., to construct a special surface structure, thus overcoming the technical difficulty of the compatibility between photocatalysis and super-hydrophobicity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the transparent super-hydrophobic photocatalytic anti-reflective self-cleaning coating structure of the present invention;

[0026] Figure 2 This is the EDX distribution diagram of the Ti element on the surface of the coating prepared in Example 1;

[0027] Figure 3 This is the EDX distribution diagram of the Ti element on the surface of the coating prepared in Example 2;

[0028] In the figure: 1-photocatalytic island area, 2-superhydrophobic coating, 3-photovoltaic glass substrate. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is described in more detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0030] A transparent super-hydrophobic photocatalytic anti-reflective self-cleaning coating, such as Figure 1 As shown, it includes a super-hydrophobic coating and a plurality of photocatalytic island regions distributed on the surface of the super-hydrophobic coating, wherein the photocatalytic island regions are formed by the accumulation of photocatalytic nanoparticle clusters, and the components of the super-hydrophobic coating include low-surface-energy modified hydrophobic SiO2 nanoparticles, silicate and coupling agent, and the mass ratio of the photocatalytic nanoparticles, hydrophobic SiO2 nanoparticles, silicate and coupling agent is 0.001-0.01:0.05-0.1:1:1-5.

[0031] The photocatalytic nanoparticles are single semiconductor oxides or composite semiconductor oxides, the single semiconductor oxide is one of anatase TiO2, rutile TiO2, oxygen-deficient TiO2 and ZnO, and the composite semiconductor oxide is one of anatase / rutile mixed TiO2, metal-loaded / grafted / doped TiO2, non-metal-doped / grafted TiO2, and TiO2 / ZnO.

[0032] The area diameter of the photocatalytic island region is 3-8 μm, the distance between the periphery of adjacent photocatalytic island regions is 10-100 μm, and the distance between the centers of the periphery of adjacent photocatalytic island regions is 10-100 μm.

[0033] When the photocatalytic island region is circular, the area diameter is the diameter of the circle, and when the photocatalytic island region is non-circular, the area diameter is the diameter of the inscribed circle or circumscribed circle containing 90% of the area of the photocatalytic island region.

[0034] The area diameter of a single photocatalytic island region is x≥3 μm. Because the organic pollutants in the air mainly include automobile exhaust and factory exhaust, when the organic pollutants in the air fall on the coating surface, due to the high surface energy of the photocatalytic island region, in order to reduce the surface energy of the system, the organic pollutants in the air automatically preferentially fall on the photocatalytic island region with high surface energy. If the area diameter of the photocatalytic island region is less than 3 μm, the organic pollutants in the air with a particle size of 2.5 μm or less can easily cover the photocatalytic island region, and sunlight is difficult to irradiate the photocatalytic island region, which results in that the organic pollutants are difficult to be decomposed by the photocatalytic island region, and the self-cleaning effect of the coating is poor. Therefore, the area diameter of a single photocatalytic island region needs to satisfy x≥3 μm. The area diameter of a single photocatalytic island region is x≤8 μm. Because if the area diameter of the photocatalytic island region is greater than 8 μm, under the irradiation of sunlight, the photocatalytic island region generates photo-generated electrons and photo-generated electron holes, the photo-generated electron holes have strong oxidizing properties, oxidize the oxygen ions in the TiO2 lattice, and generate oxygen vacancies on the surface of TiO2, thereby causing the photocatalytic island region to be photo-induced super-hydrophilic. When it rains, water droplets with a particle size of 8 μm or more are difficult to cover the island region. At this time, the water droplets falling on the photocatalytic island region are all in the photocatalytic island region, and therefore exhibit photo-induced super-hydrophilic, while the water droplets falling outside the photocatalytic island region are super-hydrophobic, so that the coating surface as a whole cannot be super-hydrophobic, and the self-cleaning effect is not good. Therefore, the area diameter of a single photocatalytic island region needs to satisfy x≤8 μm.

[0035] The photocatalytic island region needs to have a spacing (the distance of the spacing is denoted as z) from the surrounding adjacent photocatalytic island region, if there is no spacing, it will be connected into one piece, under the irradiation of sunlight, the photocatalytic island region is super-hydrophilic, the photocatalytic of the coating cannot be compatible with the super-hydrophobic, and the self-cleaning effect of the coating is poor; the center distance of the adjacent photocatalytic island region is y, y=x+z, wherein x and z satisfy 3≤x≤8 (μm) and 10≤z≤100 (μm), if z≤10 μm, the photocatalytic island region is too dense, the ratio of the super-hydrophobic region to the photocatalytic island region which is super-hydrophilic is small, under the irradiation of sunlight, the photocatalytic island region is super-hydrophilic, the photocatalytic of the coating cannot be compatible with the super-hydrophobic, and the self-cleaning effect of the coating is poor, on the contrary, if z≥100 μm, the photocatalytic island region is too few, the ability of the coating to decompose organic pollutants is poor, during the long-term use, the organic pollutants on the surface of the coating gradually accumulate, which leads to the gradual loss of the super-hydrophobic of the surface, and finally leads to the poor self-cleaning effect, therefore, z needs to satisfy 10≤z≤100 (μm).

[0036] When the shape of the photocatalytic island region is circular, the area diameter x is the diameter of the circle; when the shape of the photocatalytic island region is not circular, the diameter of the inscribed circle or the circumscribed circle can be taken as the area diameter. When the sizes of the two adjacent photocatalytic island regions are different, the area diameters x1 and x2 thereof can be taken respectively, the center distance of the two photocatalytic island regions is y, y=1 / 2(x1)+z+1 / 2(x2), wherein x1, x2 and z satisfy 3≤x1 or x2≤8 (μm) and 10≤z≤100 (μm)

[0037] The low-surface-energy modified hydrophobic SiO2 nanoparticles include silane or fluorosilane or siloxane modified nano-SiO2 particles.

[0038] The surface of the super-hydrophobic coating is a micro-nano hierarchical porous rough structure.

[0039] The silicate is one of n-methyl silicate, n-ethyl silicate, trimethoxysilane, triethoxysilane, dimethyl dimethoxysilane, dimethyl diethoxysilane, diethyl dimethoxysilane and diethyl diethoxysilane, and the coupling agent is one of silane coupling agents KH550, KH560 and KH570.

[0040] A preparation method of a transparent super-hydrophobic photocatalytic anti-reflection self-cleaning coating, comprising the following steps:

[0041] (1)Mixing and stirring silicate, silane coupling agent, ethanol, isopropyl alcohol, propylene glycol methyl ether according to the mass ratio of 30-35:30-35:25-35:30-35:70-80 to obtain A sol; mixing and stirring oxalic acid, 0.1 mol / L nitric acid, water according to the mass ratio of 0.5-1.0:120-140:15-25 to obtain B solution; slowly adding B solution into A sol while stirring to obtain C sol;

[0042] (2)Mixing and stirring photocatalytic nanoparticles, low surface energy modified hydrophobic SiO2 nanoparticles, silane coupling agent according to the mass ratio of 0.03-0.15:1.5-2.5:65-75 to obtain D sol;

[0043] (3)Coating C sol obtained in step (1) on the surface of photovoltaic glass substrate, curing at room temperature, then coating D sol obtained in step (2), curing at room temperature to obtain transparent super-hydrophobic photocatalytic anti-reflection self-cleaning coating.

[0044] The coating method in step (3) is one of spraying, spin coating, and blade coating.

[0045] The surface roughness Ra (i.e. roughness average) of the transparent super-hydrophobic photocatalytic anti-reflection self-cleaning coating obtained in step (3) is 10-100 nm.

[0046] The photocatalytic island-like region can be characterized by electron microscopy with energy dispersive spectrometer; the micro-nano hierarchical porous rough structure of the hydrophobic SiO2 nanoparticles on the surface of the coating can be characterized by electron microscopy and atomic force microscopy.

[0047] The coating first needs to meet high transmittance, which does not affect the incidence of sunlight, that is, compared with the transmittance of the glass substrate, the transmittance of the glass surface after the coating of the present application is higher; secondly, it must meet the hydrophobicity and photocatalytic activity to ensure that the coating can not only remove dust particles on the glass surface by water droplets, but also degrade organic stains through the photocatalytic island-like region; further, it must be resistant to gravel impact, that is, the interfacial bonding force between the coating and the glass must be large enough to be wear-resistant, considering that photovoltaic power stations are usually set in desert areas, the evaluation of wear resistance is based on the standard of gravel impact resistance, and finally, for large-scale use on the surface of photovoltaic glass, a coating that can be easily sprayed and cured at room temperature needs to be prepared.

[0048] Example 1

[0049] A transparent super-hydrophobic photocatalytic anti-reflection self-cleaning coating, comprising a super-hydrophobic coating and a plurality of photocatalytic island-like regions distributed on the surface of the super-hydrophobic coating, which are formed by photocatalytic nanoparticle clusters, is prepared by the following method:

[0050] (1) 32 g of tetraethyl orthosilicate, 33 g of silane coupling agent KH560, 30 g of ethanol, 32 g of isopropyl alcohol, and 73 g of propylene glycol methyl ether were stirred at room temperature for 20 min to obtain an A sol. 0.7 g of oxalic acid, 130 g of 0.1 mol / L nitric acid solution, and 20 g of water were stirred at room temperature for 20 min to obtain a B solution. The B solution was slowly added to the A sol while stirring, and the mixture was stirred at room temperature for 2 h to obtain a C sol.

[0051] (2) 2 g of hydrophobic fumed SiO2nanopowder R972, 70 g of silane coupling agent KH560, and 0.032 g of photocatalytic nanopowder P25 (anatase and rutile mixed crystal TiO2nanopowder) were stirred at room temperature for 1 h to obtain a D sol.

[0052] (3) A low-iron sodium calcium silicon photovoltaic glass 300x300 mm having components of SiO255 wt%, Al2O34 wt%, MgO 21 wt%, Na2O 15 wt%, CaO 1 wt%, and K2O 0.2 wt% was used as a substrate. After the glass was cleaned and dried, the C sol was sprayed onto the surface of the glass at room temperature using a spray gun (W-101-101S) with a caliber of 1.0 mm and an air pressure of 0.18-0.24 MPa. After the glass was dried for 15 min, the D sol was sprayed thereon, and the glass was dried for 10 h to obtain a transparent superhydrophobic photocatalytic antireflection self-cleaning coating.

[0053] The transmission spectrum of the sample in the wavelength range of 250-2000 nm was measured by a UV-Vis-NIR spectrophotometer (Lambda 750, PerkinElmer) with a step of 1 nm. The surface and cross-sectional morphology of the sample were observed by a scanning electron microscope (SEM, SU-70, Hitachi) with an accelerating voltage of 5 kV, and the energy dispersive X-ray spectroscopy (EDX; Oxford INCA; 20 kV) was used in combination to characterize the element distribution on the surface, especially the Ti element distribution. The water contact angle (WCA) of the sample surface was tested by a general contact angle measuring instrument to characterize the hydrophobic performance. The nanometer morphology of the sample surface was detected by an atomic force microscope (AFM, Dimension Icon, Bruker), and the surface roughness was calculated. The abrasion resistance of the coating surface was tested by a harsh sand abrasion experiment to simulate the daily outdoor sand dust impact on the surface of photovoltaic glass. The sample was placed at an angle of about 40°, and a funnel was fixed about 15 cm away from the lower end of the funnel. The funnel was filled with sand, and each 100 g of sand was one impact cycle. The sand impact experiment was carried out for 5 cycles. The photocatalytic activity of the coating was characterized by the method of photocatalytic degradation of methylene blue (MB). The glass sample was placed in a 5 mg / L MB solution, and the absorbance of the solution at 665 nm was measured after irradiation under a UV lamp (UV intensity at 365 nm was 0.5 mW / cm 2 ) for 20 min, 60 min and 100 min, respectively. The MB solution degradation rate change graph after 100 min irradiation of the coating and the MB solution degradation kinetics curve were drawn, and the rate constant of MB degradation was calculated to evaluate the photocatalytic activity. The photocatalytic island structure characteristics of the self-cleaning coating and the performance results of the self-cleaning coating of the present embodiment are shown in Table 1.

[0054] The transmittance of the glass substrate was 90.6%, and the transmittance of the self-cleaning coating obtained by Example 1 was 91.8%. After the coating was added on the surface of the glass substrate, the transmittance increased by 1.2% compared with the glass substrate. This result was due to the micro-nano hierarchical porous structure of the coating, and the roughness Ra was 42 nm. When the Ra value was higher than 100 nm, the surface was too rough, which would easily cause light scattering and reduce the transmittance. On the contrary, when the Ra value was less than 10 nm, the micro-nano hierarchical porous structure on the surface was not obvious, and the transmittance would not increase but decrease.

[0055] The coating surface was observed by SEM to be a micro-nano hierarchical porous structure. The average roughness Ra measured by AFM was 42 nm, which was in the range of 10 nm≤Ra≤100 nm and corresponded to the structure observed by SEM. Figure 2is the EDX distribution map of Ti element on the surface of the coating, Figure 2 The right graph in FIG. 1 is an enlarged area of the left graph; it can be seen that, Figure 2 The island-shaped region in FIG. 1 is formed by the accumulation of Ti element clusters, Figure 2 The yellow small bright spots dispersed in FIG. 1 are the background of the EDX test; it can be seen that the photocatalytic island-shaped region of the photocatalytic nanoparticle coating has an area diameter x = 4 μm, and the adjacent photocatalytic island-shaped regions have a spacing z = 72 μm, x and z meet the requirements of 3 ≤ x ≤ 8 (μm) and 10 ≤ z ≤ 100 (μm), the center distance of the adjacent photocatalytic island-shaped regions is y, y = x + z = 78 μm, therefore, the water contact angle of the coating reaches 153°, achieving superhydrophobicity, and the rate constant of the photocatalytic decomposition of methylene blue MB reaches 0.0055 min -1 , and has the ability of photocatalytic decomposition of organic pollutants.

[0056] The coating has a water contact angle of 152° after being irradiated with ultraviolet light 365 nm, 1 mW / cm 2 for 24 h, which changes very little compared with the initial 153°, and the coating surface still presents superhydrophobicity. Due to the structural characteristics of the photocatalytic island-shaped region area diameter x and the adjacent photocatalytic island-shaped region spacing z, x and z meet the requirements of 3 ≤ x ≤ 8 (μm) and 10 ≤ z ≤ 100 (μm), even if the coating is irradiated with ultraviolet light, the photocatalytic island-shaped region will not cause the coating surface to lose superhydrophobicity due to photo-induced superhydrophilicity.

[0057] After the coating is subjected to 5 times of sand impact test, each time with 100 g of sand, the water contact angle of the coating still reaches 136°, presenting excellent wear resistance.

[0058] In summary, the self-cleaning coating obtained in Example 1 has the structural characteristics of photocatalytic island-shaped region area diameter x and the adjacent photocatalytic island-shaped region spacing z, which meet the requirements of 3 ≤ x ≤ 8 (μm) and 10 ≤ z ≤ 100 (μm) respectively, and the surface roughness (roughness average Ra) is in the range of 10 nm ≤ Ra ≤ 100 nm, therefore, the coating has the properties of transmittance and superhydrophobicity and photocatalytic performance, and also has wear resistance.

[0059] Example 2

[0060] A kind of transparent super-hydrophobic photocatalytic antireflection self-cleaning coating, including super-hydrophobic coating and multiple photocatalytic island regions formed by photocatalytic nanoparticles cluster accumulation on the surface of super-hydrophobic coating, the preparation method is same with example 1, and the difference from example 1 is that the weight of photocatalytic nano powder P25 (anatase and rutile mixed crystal type TiO2 nano powder) is changed from 0.032g to 0.15g, and the others are same with example 1.The photocatalytic island region structure characteristics and coating performance of the self-cleaning coating obtained in this embodiment are shown in Table 1.

[0061] The EDX distribution diagram of Ti element on the surface of the self-cleaning coating obtained in example 2 is shown in Figure 2. Figure 3 As shown in Figure 2, Figure 3 the island region formed by Ti element cluster accumulation in Figure 2, Figure 3 the yellow small bright spots dispersed in Figure 2 are the background of EDX test; it can be seen that the area diameter x of photocatalytic island region of photocatalytic nanoparticle coating is 8 μm, the spacing z of adjacent photocatalytic island region is 10 μm, the center distance of adjacent photocatalytic island region is y, y=x+z=18 μm, the structure characteristics are that the area diameter x of photocatalytic island region and the spacing z of adjacent photocatalytic island region meet the requirements of 3≤x≤8(μm) and 10≤z≤100(μm), and the surface roughness (average roughness Ra) is in the range of 10nm≤Ra≤100nm, therefore, the coating has antireflection and super-hydrophobic and photocatalytic compatible properties, and also has super-hydrophobic and photocatalytic properties; the coating also has wear resistance.

[0062] Comparative example 1

[0063] A kind of transparent super-hydrophobic photocatalytic antireflection self-cleaning coating, the preparation method is same with example 1, and the difference from example 1 is that the weight of photocatalytic nano powder P25 (anatase and rutile mixed crystal type TiO2 nano powder) is changed from 0.032g to 0.0g, that is, no photocatalytic nanoparticles are added in the coating preparation process, and the others are same with example 1.The photocatalytic island region structure characteristics and coating performance of the self-cleaning coating obtained are shown in Table 1.

[0064] The coating obtained in comparative example 1 has no photocatalytic island region, does not meet the requirements of 3≤x≤8(μm) and 10≤z≤100(μm) for the area diameter x of photocatalytic island region and the spacing z of adjacent photocatalytic island region, although the surface roughness (average roughness Ra) is in the range of 10nm≤Ra≤100nm, therefore, the coating has antireflection and super-hydrophobic properties, but has no photocatalytic properties, has certain super-hydrophobic properties, the water contact angle is much lower than that of example 1 and example 2, and cannot have super-hydrophobic and photocatalytic properties at the same time.

[0065] Comparative example 2

[0066] A transparent super-hydrophobic photocatalytic antireflection self-cleaning coating was prepared according to the method of Example 1, except that the weight of the photocatalytic nano-powder P25 (anatase-rutile mixed crystal Ti02 nano-powder) was changed from 0.032 g to 1.5 g, and the other conditions were the same as in Example 1.

[0067] The surface photocatalytic island region structure characteristics and coating performance of the self-cleaning coating obtained in Comparative Example 2 are shown in Table 1 below.

[0068] The coating obtained in Comparative Example 2 has photocatalytic island regions, but the area of the photocatalytic island regions is large, and the spacing between adjacent photocatalytic island regions is 5 μm, which is very narrow. Due to the photo-induced super-hydrophilic reaction of the photocatalytic island regions, the water contact angle is 118°, and the coating does not have super-hydrophobicity. Moreover, the transmittance of the coating is lower than that of the substrate. The structure of the coating does not satisfy the requirement that the diameter x of the photocatalytic island region and the spacing z between adjacent photocatalytic island regions satisfy 3 ≤ x ≤ 8 (μm) and 10 ≤ z ≤ 100 (μm), although the surface roughness (the average roughness Ra) is in the range of 10 nm ≤ Ra ≤ 100 nm. Therefore, the coating obtained in Comparative Example 2 does not have both super-hydrophobicity and photocatalytic performance.

[0069] Comparative Example 3

[0070] The weight of the photocatalytic nano-powder P25 (anatase-rutile mixed crystal Ti02 nano-powder) was changed from 0.032 g in Example 1 to 3.0 g, and the weight of the hydrophobic fumed Si02 nano-powder R972 was changed from 2 g in Example 1 to 0 g, i.e., no hydrophobic Si02 nano-particles were added during the preparation of the coating. The other conditions were the same as in Example 1.

[0071] The surface photocatalytic island region structure characteristics and coating performance of the self-cleaning coating obtained in Comparative Example 3 are shown in Table 1 below.

[0072] The coating obtained in Comparative Example 3 has photocatalytic regions on the surface, and the photocatalytic regions are connected together without any photocatalytic island regions. Due to the photo-induced super-hydrophilic reaction of the photocatalytic regions, the water contact angle is 46°, and the coating has hydrophilicity without hydrophobicity. Moreover, the transmittance of the coating is lower than that of the substrate. The structure of the coating does not satisfy the requirement that the diameter x of the photocatalytic island region and the spacing z between adjacent photocatalytic island regions satisfy 3 ≤ x ≤ 8 (μm) and 10 ≤ z ≤ 100 (μm), although the surface roughness (the average roughness Ra) is in the range of 10 nm ≤ Ra ≤ 100 nm. Therefore, the coating obtained in Comparative Example 3 does not have both super-hydrophobicity and photocatalytic performance.

[0073] Table 1 Photocatalytic island region structure characteristics and coating performance of the self-cleaning coatings obtained in Examples 1-2 and Comparative Examples 1-3

[0074]

[0075]

[0076] Note: The area of the photocatalytic island region is x (μm) in diameter; the distance between the centers of the adjacent photocatalytic island regions on the periphery is y, and the interval between the adjacent photocatalytic island regions on the periphery is z, y = x + z.

[0077] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A transparent super-hydrophobic photocatalytic antireflective self-cleaning coating, characterized in that: It includes a super-hydrophobic coating and a plurality of photocatalytic island regions distributed on the surface of the super-hydrophobic coating, wherein the photocatalytic island regions are formed by stacking clusters of photocatalytic nanoparticles, and the area diameter of the photocatalytic island regions is 3-8 μm, the spacing between adjacent photocatalytic island regions is 10-100 μm, and the center spacing between adjacent photocatalytic island regions is 10-100 μm; when the photocatalytic island regions are circular, their area diameter is the diameter of the circle, and when the photocatalytic island regions are non-circular, their area diameter is the diameter of the inscribed circle or the circumscribed circle containing 90% of the area of ​​the photocatalytic island regions; the transparent super-hydrophobic photocatalytic anti-reflection self-cleaning coating is prepared by the following method: (1) Silicate ester, silane coupling agent, ethanol, isopropyl alcohol, and propylene glycol methyl ether are mixed and stirred in a mass ratio of 30-35:30-35:25-35:30-35:70-80 to obtain sol A; oxalic acid, 0.1 mol / L nitric acid, and water are mixed and stirred in a mass ratio of 0.5-1.0:120-140:15-25 to obtain solution B; while stirring, solution B is slowly added to sol A to obtain sol C; (2) mixing photocatalytic nanoparticles, low surface energy modified hydrophobic SiO2 nanoparticles, and silane coupling agent in a mass ratio of 0.03-0.15:1.5-2.5:65-75 to obtain sol D; (3) The C sol obtained in step (1) is coated on the surface of the photovoltaic glass substrate, and after curing at room temperature, the D sol obtained in step (2) is coated thereon, and after curing at room temperature, a transparent super-hydrophobic photocatalytic anti-reflective self-cleaning coating is obtained.

2. The transparent super-hydrophobic photocatalytic antireflective self-cleaning coating according to claim 1, characterized in that: The photocatalytic nanoparticles are single semiconductor oxides or composite semiconductor oxides, the single semiconductor oxide is one of anatase TiO2, rutile TiO2, oxygen-deficient TiO2 and ZnO, and the composite semiconductor oxide is one of anatase / rutile mixed TiO2, metal-loaded / grafted / doped TiO2, non-metal-doped / grafted TiO2, and TiO2 / ZnO.

3. The transparent super-hydrophobic photocatalytic antireflective self-cleaning coating according to claim 1, characterized in that: The low surface energy modified hydrophobic SiO2 nanoparticles include silane or siloxane modified nano SiO2 particles.

4. The transparent super-hydrophobic photocatalytic antireflective self-cleaning coating according to claim 1, characterized in that: The silicate is one of methyl orthosilicate and ethyl orthosilicate, and the silane coupling agent is one of silane coupling agents KH550, KH560 and KH570.

5. The transparent super-hydrophobic photocatalytic antireflective self-cleaning coating according to claim 1, characterized in that: The surface of the super-hydrophobic coating is a micro-nano hierarchical porous rough structure.

6. The transparent super-hydrophobic photocatalytic antireflective self-cleaning coating according to claim 1, characterized in that: The coating method in step (3) is one of spray coating, spin coating and scraping coating.

7. The transparent super-hydrophobic photocatalytic antireflective self-cleaning coating according to claim 1, characterized in that: The surface roughness Ra of the transparent super-hydrophobic photocatalytic anti-reflective self-cleaning coating obtained in step (3) is 10-100 nm.

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