Preparation method of concrete surface photocatalytic functional coating and construction process of coating

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a preparation method of a photocatalytic functional coating on the surface of concrete and a construction process of the coating. Bismuth oxyhalide nanosheets BiOBr are prepared through a solvothermal method, a solution is transferred into a reaction kettle, silicon dioxide coating is conducted on the BiOBr through a Stber method, a BiOBr-coated SiO core-shell structure is formed, and the photocatalytic functional coating is obtained. The preparation method comprises the following steps: dispersing BiOBr (at) SiO in a mixed solution of ethanol and water to form a photocatalytic suspension, spraying the photocatalytic suspension on the surface of concrete, and curing to obtain the photocatalytic functional coating on the surface of the concrete. Through a core-shell structure, graphene oxide doping and a layered spraying process, the problems of ultraviolet dependence and poor and insufficient binding force of an existing photocatalytic coating are solved, test data shows that the coating is remarkably superior to a traditional technology in the aspects of visible light catalytic efficiency, interface binding strength and scouring resistance, and the coating is suitable for actual engineering scenes such as bridges and tunnels.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a method for preparing a photocatalytic functional coating on a concrete surface and a construction process of the coating. Background Art

[0002] The application in the field of building materials has become an important direction for the development of green building technology. It has the characteristics of decomposing pollutants through photocatalytic reactions and antibacterial and antifungal properties, which significantly improves the comprehensive performance of concrete structures. At present, the mainstream photocatalytic materials on the market are mainly nano-titanium dioxide, such as the ST-K01 TiO2 photocatalyst produced by Toshiba Corporation of Japan, with a specific surface area of ​​45-55m² / g. It generates electron-hole pairs through ultraviolet light excitation to achieve organic degradation. However, this type of material has three major defects: strong dependence on ultraviolet light, accounting for only 3%-5% of the solar spectrum, and low catalytic efficiency under natural light conditions; weak bonding with the concrete matrix, and the shedding rate after rain erosion is as high as 60%; the recombination rate of photogenerated carriers of titanium dioxide exceeds 80%, resulting in low quantum efficiency.

[0003] In the prior art, Chinese patent CN111036234A proposes to use metal injection molding technology to prepare photocatalytic composite coatings, but the process requires 200-400℃ preheating and laser sintering, and the energy consumption exceeds 15kW·h / m², and the construction cost is too high.

[0004] The existing technology generally has the following problems: the insufficient visible light response of photocatalytic materials leads to low utilization rate in actual environment; the poor interface bonding between the coating and the substrate leads to insufficient durability; the complex preparation process leads to high cost and difficulty in industrial application; the photocatalytic active components are easily covered or lost, resulting in poor long-term effectiveness. These problems seriously restrict the application of photocatalytic coatings in actual scenarios such as bridges, tunnels, and building exterior walls. Summary of the invention

[0005] In order to overcome the defects in the prior art, the present invention provides a method for preparing a photocatalytic functional coating on a concrete surface, the method comprising the following steps: Step S1: preparing bismuth oxyhalide nanosheets BiOBr by a solvothermal method, dissolving bismuth nitrate pentahydrate and sodium bromide in a mixed solvent of ethylene glycol and water at a molar ratio of 1:1-1:1.5, wherein the volume ratio of ethylene glycol to water is 3:2-5:2, the reaction temperature is 165-175° C., and the reaction time is 12-13 hours; Step S2: transferring the solution of step S1 to a reaction kettle, reacting at 160-180° C. for 10-14 hours, cooling, centrifuging, washing and drying, the number of centrifugal washing is 5-8 times, and the drying temperature is 60-80° C., to obtain bismuth oxyhalide nanosheets; Step S3: coating BiOBr with silica by Stöber method to form a SiO2 coating layer, dispersing BiOBr in water, adding ethanol and ethyl orthosilicate, and stirring for 12-24 hours to form a BiOBr@SiO2 core-shell structure, wherein the mass ratio of BiOBr to SiO2 is 1:0.2-1:0.5; Step S4: Disperse BiOBr@SiO2 in a mixture of ethanol and water to prepare a photocatalytic suspension with a concentration of 5-15wt%, spray the photocatalytic suspension on the concrete surface, and obtain a photocatalytic functional coating on the concrete surface after curing.

[0006] The following is a further optimization of the above technical solution by the present invention: In step S3, the thickness of the SiO2 coating layer is 5-50 nm, and 0.5-2 wt% of graphene oxide is doped in the SiO2 coating layer.

[0007] Further optimization: the volume ratio of ethanol to tetraethyl orthosilicate is 5:1-10:1.

[0008] Further optimization: in step S3, ammonia water is added as a catalyst, and the concentration of the ammonia water is 0.1-0.5 mol / L.

[0009] Further optimization: in step S4, polyethylene glycol is added as a dispersant, and the added amount of the polyethylene glycol is 0.1%-1% of the total mass of the suspension.

[0010] Further optimization: In step S4, the suspension further contains sodium dodecyl sulfate with a mass fraction of 0.05-0.2%.

[0011] Further optimization: In step S4, 0.1-0.5 wt % of epoxy resin is compounded in the photocatalytic suspension sprayed on the concrete surface.

[0012] The present invention also discloses a construction process for a photocatalytic functional coating on a concrete surface, the process comprising the following steps: Step T1: Pretreatment of the concrete surface, including sandblasting to a surface roughness Ra of 10-50 μm, and removal of oil stains and loose particles; Step T2: spraying the photocatalytic suspension in 2-3 layers, with an interval of 10-30 minutes between each layer; Step T3: Use ultraviolet lamp to assist curing, the curing time is 1-3 hours, the curing temperature is 20-35°C, and the ultraviolet wavelength is 365-405nm.

[0013] Further optimization: After step T3, the coating is treated with hydrophobicity by spraying an ethanol solution containing fluorinated silane, and the hydrophobic angle is ≥120°.

[0014] Further optimization: in step T2, the spraying thickness of each layer is 3-8 μm, the spraying pressure is 0.3-0.6 MPa, and the distance between the nozzle and the concrete surface is 30-50 cm.

[0015] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. The present invention uses BiOBr nanosheets as the photocatalytic core. Its narrow bandgap characteristics enable the light absorption range to cover the visible light band, the sunlight utilization rate is increased to more than 45%, and the visible light response capability is significantly improved. Through the optical waveguide effect of the SiO2 coating layer, the incident light forms multiple reflections in the core-shell structure, and the light energy capture efficiency is increased by 30%.

[0016] 2. The present invention dopes graphene oxide and utilizes its π-π conjugation effect to promote the transmission of photogenerated electrons, reducing the carrier recombination rate from 80% of traditional TiO2 to below 35%, and increasing the quantum efficiency to 2.3 times that of traditional coatings. This improvement enables the coating to maintain high catalytic activity under natural light conditions, breaking through the limitation of traditional materials' dependence on ultraviolet light.

[0017] 3. The SiO2 coating layer of the present invention forms a chemical bond with the calcium hydroxide on the surface of the concrete through hydroxyl groups, and has high bonding strength, which is higher than that of the physical adsorption coating, and the interface bonding strength and durability are significantly enhanced. After compounding with epoxy resin, a three-dimensional cross-linked network is formed under ultraviolet assisted curing, and the shedding rate is much better than that of ordinary coatings.

[0018] 4. The addition of sodium dodecyl sulfate in the present invention allows the suspension to penetrate deep into the pore area of ​​the concrete surface, forming a mechanical interlocking effect. In addition, the hydrophobic treatment of fluorinated silane makes the contact angle greater than 120°, which prevents the loss of active components due to rainwater erosion.

[0019] 5. The solvothermal method combined with the Stöber method was used to achieve the low-temperature controllable synthesis of BiOBr@SiO2 core-shell structure, avoiding the high energy consumption problem of the traditional mechanical-thermal coupling process.

[0020] 6. The photocatalytic suspension spraying process is implemented in 2-3 layers to form a uniformly covered coating. Compared with the high-temperature sintering process of Japan Toshiba ST-K01 TiO2 coating, this method reduces energy consumption by more than 70%, and the curing temperature is controlled at 20-35°C, significantly reducing construction costs.

[0021] 7. The synergistic effect of the ammonia catalyst system and the polyethylene glycol dispersant ensures the stability of the suspension for more than 72 hours, meeting the needs of industrial continuous spraying.

[0022] 8. The physical isolation of BiOBr by the SiO2 coating layer prevents chemical corrosion between the active components and cement hydration products. Compared with the hybrid material of Ningbo Institute of Materials, the coating of the present invention is significantly better in environmental adaptability and long-term effectiveness.

[0023] 9. The coating of the present invention is compounded with epoxy resin by doping graphene oxide, and the coating has both electrical conductivity and antistatic properties, and the surface resistivity is reduced, and can be applied to bridges and tunnels that require lightning protection.

[0024] The present invention is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The scanning electron microscope spectrum (a) of BiOBr and the transmission electron microscope spectrum (b) of BiOBr@SiO2 in Example 1 of the present invention; Figure 2 This is the XPS spectrum of the product after the reaction of BiOBr@SiO2 and cement hydration product Ca(OH)2 in Example 1 of the present invention; Figure 3 The cross-sectional scanning electron microscope image (a) and EDX images (b, c, d) of the photocatalytic functional coating on the concrete surface in Example 1 of the present invention; Figure 4 The surface scanning electron microscope image (a) and EDX images (b, c, d, e) of the photocatalytic functional coating on the concrete surface in Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0026] In the present invention, the sources of various raw materials are briefly described as follows: Bismuth nitrate pentahydrate: purchased from Sigma-Aldrich, USA, CAS No. 10035-06-0, purity ≥ 99.9%; Sodium bromide: Sinopharm Chemical Reagent Co., Ltd., analytical grade, CAS No. 7647-15-6; Ethylene glycol: Sinopharm Chemical Reagent Co., Ltd., purity ≥ 99.5%, industrial grade; Tetraethyl orthosilicate (TEOS): Alfa Aesar, USA, CAS No. 78-10-4, purity ≥ 98%; Graphene oxide: Changzhou Sixth Element Materials Technology Co., Ltd., model SE2430, sheet thickness 1-5nm; Polyethylene glycol (PEG-400): Dow Chemical Company, USA, molecular weight 380-420, viscosity 70-100mPa·s; Sodium dodecyl sulfate (SDS): Sinopharm Chemical Reagent Co., Ltd., biological reagent grade, CAS No. 151-21-3; Epoxy resin (E-44): Nan Ya Plastics Industry Co., Ltd., epoxy value 0. 41-0.47eq / 100g; Ammonia: Sinopharm Chemical Reagent Co., Ltd., concentration 25%-28%, analytical grade; Fluorosilane (hydrophobic agent): Shin-Etsu Chemical Co., Ltd., model KF-115, CAS No. 101947-16-4; UV lamp: Foshan Lighting Appliance Co., Ltd., model FS-ZW30D, wavelength 365-405nm, power 30W; Hydroxypropyl methylcellulose (HPMC): Dow Chemical Chemical Company, model K4M, viscosity 4000-6000mPa·s; Sodium hyaluronate: Shiseido Co., Ltd., Japan, molecular weight 800,000-1.5 million Da, CAS No. 9067-32-7; Carboxymethyl chitosan: Zhejiang Jinke Pharmaceutical Co., Ltd., deacetylation degree ≥85%, viscosity 50-200mPa·s; Polyglycerol-10 laurate: Hubei Zhenbo Chemical Co., Ltd., CAS No. 34406-66-1, purity ≥99%.

[0027] A method for preparing a photocatalytic functional coating on a concrete surface, the method comprising the following steps: Step S1: preparing bismuth oxyhalide nanosheets BiOBr by a solvothermal method, dissolving bismuth nitrate pentahydrate and sodium bromide in a mixed solvent of ethylene glycol and water at a molar ratio of 1:1-1:1.5, wherein the volume ratio of ethylene glycol to water is 3:2-5:2, the reaction temperature is 165-175° C., and the reaction time is 12-13 hours; Step S2: transferring the solution of step S1 to a reaction kettle, reacting at 160-180° C. for 10-14 hours, cooling, centrifuging, washing and drying, the number of centrifugal washing is 5-8 times, and the drying temperature is 60-80° C., to obtain bismuth oxyhalide nanosheets; Step S3: coating BiOBr with silica by Stöber method, dispersing BiOBr in water, adding ethanol and ethyl orthosilicate, stirring for 12-24 hours to form a BiOBr@SiO2 core-shell structure, wherein the mass ratio of BiOBr to SiO2 is 1:0.2-1:0.5; Step S4: Disperse BiOBr@SiO2 in a mixture of ethanol and water to prepare a photocatalytic suspension with a concentration of 5-15wt%, spray the photocatalytic suspension on the concrete surface, and obtain a photocatalytic functional coating on the concrete surface after curing.

[0028] In step S3, the thickness of the SiO2 coating layer is 5-50 nm, and 0.5-2 wt% of graphene oxide is doped in the SiO2 coating layer.

[0029] The volume ratio of ethanol to tetraethyl orthosilicate is 5:1-10:1.

[0030] In step S3, ammonia water is added as a catalyst, and the concentration of the ammonia water is 0.1-0.5 mol / L.

[0031] In step S4, polyethylene glycol is added as a dispersant, and the amount of polyethylene glycol added is 0.1%-1% of the total mass of the suspension.

[0032] In step S4, the suspension further comprises sodium dodecyl sulfate with a mass fraction of 0.05-0.2%.

[0033] In step S4, 0.1-0.5 wt % of epoxy resin may be compounded into the photocatalytic suspension sprayed on the concrete surface.

[0034] A construction process for a photocatalytic functional coating on a concrete surface, the process comprising the following steps: Step T1: Pretreatment of the concrete surface, including sandblasting to a surface roughness Ra of 10-50 μm, and removal of oil stains and loose particles; Step T2: spraying the photocatalytic suspension in 2-3 layers, with an interval of 10-30 minutes between each layer; Step T3: Use ultraviolet lamp to assist curing, the curing time is 1-3 hours, the curing temperature is 20-35°C, and the ultraviolet wavelength is 365-405nm.

[0035] After step T3, the coating is subjected to hydrophobic treatment by spraying an ethanol solution containing fluorinated silane, with a hydrophobic angle of ≥120°.

[0036] In step T2, the spraying thickness of each layer is 3-8 μm, the spraying pressure is 0.3-0.6 MPa, and the distance between the nozzle and the concrete surface is 30-50 cm.

[0037] The technical solution of the present invention is further illustrated by the following examples and comparative examples, but the protection scope of the present invention is not limited thereto. Example 1

[0038] Bismuth oxyhalide nanosheets BiOBr were prepared by a solvothermal method, the molar ratio of bismuth nitrate pentahydrate to sodium bromide was 1:1.5, the volume ratio of ethylene glycol to water was 5:2, the reaction temperature was 175°C, and the reaction time was 12 hours.

[0039] The solution in step S1 was transferred to a reactor at a temperature of 180°C, a reaction time of 14 hours, centrifugal washing for 5 times, and a drying temperature of 70°C.

[0040] BiOBr was coated with silica by the Stöber method, with a mass ratio of BiOBr to SiO2 of 1:0.5, a volume ratio of ethanol to tetraethyl orthosilicate of 5:1, an ammonia concentration of 0.3 mol / L, 2% doped graphene oxide, and a coating layer thickness of 25 nm.

[0041] BiOBr@SiO2 is dispersed in a mixed solution of ethanol and water to prepare a photocatalytic suspension, and the photocatalytic suspension is sprayed on the concrete surface. After curing, a photocatalytic functional coating on the concrete surface is obtained.

[0042] The concentrations of the components in the prepared photocatalytic suspension are: BiOBr@SiO2 15wt%, polyethylene glycol 0.1wt%, sodium dodecyl sulfate 0.1wt%, epoxy resin 0.1wt%, and the remainder is a mixture of ethanol and water (V / V: 95:5).

[0043] Pretreatment of the concrete surface includes sandblasting and removal of oil stains and loose particles; spraying of photocatalytic suspension, using ultraviolet lamp to assist curing, sandblasting roughness 50μm, spraying pressure 0.45MPa, ultraviolet curing for 1 hour, and hydrophobic angle 122°. Example 2

[0044] In this embodiment, the same points as in Embodiment 1 are not described in detail, and the differences are as follows: Bismuth oxyhalide nanosheets BiOBr were prepared by a solvothermal method, with a molar ratio of bismuth nitrate pentahydrate to sodium bromide of 1:1, a volume ratio of ethylene glycol to water of 3:2, a reaction temperature of 165°C, and a reaction time of 12.5 hours.

[0045] The solution in step S1 was transferred to a reactor at a temperature of 160°C, a reaction time of 10 hours, centrifugal washing for 8 times, and a drying temperature of 60°C.

[0046] The mass ratio of BiOBr to SiO2 is 1:0.2, the volume ratio of ethanol to tetraethyl orthosilicate is 10:1, the concentration of ammonia water is 0.1 mol / L, the doped graphene oxide is 0.5%, and the coating layer thickness is 5 nm.

[0047] The concentrations of the components in the prepared photocatalytic suspension are: BiOBr@SiO2 5wt%, polyethylene glycol 1wt%, sodium dodecyl sulfate 0.05wt%, epoxy resin 0.5wt%, and the remainder is a mixture of ethanol and water (V / V: 95:5).

[0048] The sandblasting roughness is 10 μm, the spraying pressure is 0.3 MPa, the UV curing is 3 hours, and the hydrophobic angle is 120°. Example 3

[0049] In this embodiment, the same points as in Embodiment 1 are not described in detail, and the differences are as follows: Bismuth oxyhalide nanosheets BiOBr were prepared by a solvothermal method, with a molar ratio of bismuth nitrate pentahydrate to sodium bromide of 1:1.25, a volume ratio of ethylene glycol to water of 4:2, a reaction temperature of 170°C, and a reaction time of 13 hours.

[0050] The solution in step S1 was transferred to a reactor at a temperature of 170°C, a reaction time of 12 hours, centrifugal washing for 6 times, and a drying temperature of 70°C.

[0051] The mass ratio of BiOBr to SiO2 is 1:0.35, the volume ratio of ethanol to tetraethyl orthosilicate is 7:1, the concentration of ammonia water is 0.5 mol / L, the doped graphene oxide is 1.2%, and the coating layer thickness is 50 nm.

[0052] The concentrations of the components in the prepared photocatalytic suspension are: BiOBr@SiO2 10wt%, polyethylene glycol 0.5wt%, sodium dodecyl sulfate 0.2wt%, epoxy resin 0.3wt%, and the remainder is a mixture of ethanol and water (V / V: 95:5).

[0053] The sandblasting roughness is 30 μm, the spraying pressure is 0.6 MPa, the UV curing is 2 hours, and the hydrophobic angle is 125°.

[0054] Comparative Example 1 In this comparative example, the same points as Example 1 are not repeated here, and the differences are as follows: the TiO2 coating is not coated with BiOBr.

[0055] Comparative Example 2 In this comparative example, the same points as Example 1 are not repeated here, and the differences are as follows: BiOBr coating without graphene oxide doping.

[0056] Material characterization and performance testing analysis Bismuth oxyhalide (BiOBr), as a new type of photocatalyst, is a type of Bi-based semiconductor. Due to its unique atomic arrangement and electronic configuration, it has high photocatalytic activity under visible light irradiation.

[0057] like Figure 1 As shown, the present invention synthesized a BiOBr@SiO2 core-shell structure.

[0058] like Figure 2 As shown, the bonding between the photocatalytic material and the substrate is improved by nano-SiO2, and a volcanic ash reaction occurs between SiO2 and the hydration product of the substrate.

[0059] like Figure 3 and 4 As shown, the compatibility of the photocatalyst with the cement-based matrix is ​​improved, and the long-term effect of the photocatalysis is increased.

[0060] The coatings prepared in the three embodiments and two comparative examples were subjected to performance tests according to a general method, and the test results are shown in Table 1, wherein the visible light catalytic efficiency is sampled as the NO degradation rate under simulated sunlight (AM1.5G); the interface bonding strength is determined by a pull-out test to determine the adhesion between the coating and the concrete; the scouring shedding rate is the shedding rate after 100 scourings under simulated rainfall (25 mm / h); and the quantum efficiency is the carrier separation efficiency in the photoelectrochemical test.

[0061] Table 1 Performance test results Group Visible light catalytic efficiency (%) Interface bonding strength (MPa) Scouring and shedding rate (%) Quantum efficiency (%) Example 1 45.3 4.8 4.2 38.5 Example 2 37.8 4.1 5.7 32.1 Example 3 41.6 4.5 4.8 35.4 Comparative Example 1 8.0 1.5 62.0 12.0 Comparative Example 2 29.5 2.1 58.0 24.3 As can be seen from Table 1, the BiOBr@SiO2 core-shell structures of Examples 1-3 extend the light absorption range to the visible light band through the narrow band gap characteristics (2.6-2.8 eV) and the optical waveguide effect of the SiO2 coating layer, and the catalytic efficiency is significantly improved to 37.8%-45.3%. In comparison, the efficiency of Comparative Example 1 (traditional TiO2) is only 8% due to its reliance on ultraviolet light, and the efficiency of Comparative Example 2 is reduced to 29.5% due to increased light reflection loss due to the lack of SiO2 coating.

[0062] The chemical bonding (Si-O-Ca) between the SiO2 coating and Ca(OH)2 in concrete makes the bonding strength of Examples 1-3 reach 4.1-4.8 MPa, while that of Comparative Example 1 (physical adsorption) and Comparative Example 2 (without SiO2) drops to 1.5 MPa and 2.1 MPa, respectively. The compounding of epoxy resin further forms a three-dimensional cross-linked network, which enhances the mechanical interlocking between the coating and the substrate.

[0063] Fluorosilane hydrophobic treatment effectively reduces shedding caused by rain erosion. The shedding rates of Examples 1-3 are all lower than 6%, while the shedding rates of Comparative Examples 1 and 2 are as high as 58%-62% due to their loose structures or lack of hydrophobic treatment.

[0064] The π-π conjugation effect of graphene oxide promotes the transfer of photogenerated electrons. The quantum efficiency of Example 1 reaches 38.5%, while that of Comparative Example 2 when undoped is only 24.3%.

[0065] In addition, the SiO2 coating isolates BiOBr from chemical corrosion by cement hydration products, so that the efficiency decay of the coating is less than 8% after 1000 hours of aging.

[0066] The present invention uses BiOBr@SiO2 core-shell structure, graphene oxide doping and layered spraying process to comprehensively solve the problems of UV dependence, poor binding force and insufficient long-term effectiveness of existing photocatalytic coatings. Test data show that the coating is significantly superior to traditional technologies in terms of visible light catalytic efficiency, interface bonding strength and erosion resistance, and is suitable for actual engineering scenarios such as bridges and tunnels.

[0067] For those skilled in the art, according to the teachings of the present invention, without departing from the principles and spirit of the present invention, changes, modifications, substitutions and variations made to the implementation methods are still within the protection scope of the present invention.

Claims

1. A method for preparing a photocatalytic functional coating on a concrete surface, characterized in that: The method comprises the following steps: Step S1: preparing bismuth oxyhalide nanosheets BiOBr by a solvothermal method, dissolving bismuth nitrate pentahydrate and sodium bromide in a mixed solvent of ethylene glycol and water at a molar ratio of 1:1-1:1.5, wherein the volume ratio of ethylene glycol to water is 3:2-5:2, the reaction temperature is 165-175° C., and the reaction time is 12-13 hours; Step S2: transferring the solution of step S1 to a reaction kettle, reacting at 160-180° C. for 10-14 hours, cooling, centrifuging, washing and drying, the number of centrifugal washing is 5-8 times, and the drying temperature is 60-80° C., to obtain bismuth oxyhalide nanosheets; Step S3: coating BiOBr with silica by Stöber method to form a SiO2 coating layer, dispersing BiOBr in water, adding ethanol and ethyl orthosilicate, and stirring for 12-24 hours to form a BiOBr@SiO2 core-shell structure, wherein the mass ratio of BiOBr to SiO2 is 1:0.2-1:0.5; Step S4: Disperse BiOBr@SiO2 in a mixture of ethanol and water to prepare a photocatalytic suspension with a concentration of 5-15wt%, spray the photocatalytic suspension on the concrete surface, and obtain a photocatalytic functional coating on the concrete surface after curing.

2. The method for preparing a photocatalytic functional coating on a concrete surface according to claim 1, characterized in that: In step S3, the thickness of the SiO2 coating layer is 5-50 nm, and 0.5-2 wt% of graphene oxide is doped in the SiO2 coating layer.

3. The method for preparing a photocatalytic functional coating on a concrete surface according to claim 1, characterized in that: The volume ratio of ethanol to tetraethyl orthosilicate is 5:1-10:

1.

4. The method for preparing a photocatalytic functional coating on a concrete surface according to claim 1, characterized in that: In step S3, ammonia water is added as a catalyst, and the concentration of the ammonia water is 0.1-0.5 mol / L.

5. The method for preparing a photocatalytic functional coating on a concrete surface according to claim 1, characterized in that: In step S4, polyethylene glycol is added as a dispersant, and the amount of polyethylene glycol added is 0.1%-1% of the total mass of the suspension.

6. The method for preparing a photocatalytic functional coating on a concrete surface according to claim 1, characterized in that: In step S4, the suspension further comprises sodium dodecyl sulfate with a mass fraction of 0.05-0.2%.

7. The method for preparing a photocatalytic functional coating on a concrete surface according to claim 1, characterized in that: In step S4, 0.1-0.5 wt % of epoxy resin is compounded in the photocatalytic suspension sprayed on the concrete surface.

8. A construction process for a photocatalytic functional coating on a concrete surface prepared by the method according to any one of claims 1 to 7, characterized in that: The process includes the following steps: Step T1: Pretreatment of the concrete surface, including sandblasting to a surface roughness Ra of 10-50 μm, and removal of oil stains and loose particles; Step T2: spraying the photocatalytic suspension in 2-3 layers, with an interval of 10-30 minutes between each layer; Step T3: Use ultraviolet lamp to assist curing, the curing time is 1-3 hours, the curing temperature is 20-35°C, and the ultraviolet wavelength is 365-405nm.

9. The construction process of a photocatalytic functional coating on a concrete surface according to claim 8, characterized in that: After step T3, the coating is subjected to hydrophobic treatment by spraying an ethanol solution containing fluorinated silane, with a hydrophobic angle of ≥120°.

10. The construction process of a photocatalytic functional coating on a concrete surface according to claim 8, characterized in that: In step T2, the spraying thickness of each layer is 3-8 μm, the spraying pressure is 0.3-0.6 MPa, and the distance between the nozzle and the concrete surface is 30-50 cm.

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