A method for enhancing urban self-purification based on in-situ modification of building outer wall catalytic coating by poly-energy laser

Abstract

The application provides a kind of urban self-purification enhancement method based on polyenergy laser in-situ modification building outer wall catalytic coating, the urban self-purification enhancement method includes: using polyenergy laser to in-situ scanning on the photocatalytic coating on building outer wall, induce the local high temperature field with temperature greater than 900 DEG C to form on the surface of the photocatalytic coating, make the lattice reconstitution of catalytic material in photocatalytic coating.The urban self-purification enhancement method, by using polyenergy laser in-situ scanning, control the temperature of local high temperature field formed, laser scanning speed and single point irradiation time, in the case of not damaging substrate, the regeneration of aging photocatalytic coating on building outer wall is realized;In addition, the urban self-purification enhancement method also has the advantages of low cost, wide application range and on-site operation, and has broad application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmentally friendly functional material recycling technology, and in particular relates to an urban self-cleaning enhancement method based on in-situ modification of building exterior wall catalytic coatings using focused laser. Background Technology

[0002] With the continuous development of cities, the control of air pollutants (such as nitrogen oxides, volatile organic compounds, and fine particulate matter) has become a widely concerned technical and environmental issue. Photocatalytic coatings, due to their ability to decompose pollutants through photogenerated charge carriers under sunlight, are widely used in air purification applications for urban infrastructure such as building facades and road barriers to achieve air purification. Photocatalysts, represented by titanium dioxide (TiO2), decompose pollutants by forming hydroxyl radicals (…). OH) and superoxide radicals ( O2 - It achieves the oxidative degradation of pollutants, combining energy saving and environmental friendliness.

[0003] However, photocatalytic coatings face a core bottleneck in long-term outdoor applications: on the one hand, the coatings are exposed to complex environmental factors such as ultraviolet radiation, temperature and humidity cycles, and particulate matter deposition for a long time, and their surface active sites are gradually covered by inorganic salts or carbonaceous pollutants; on the other hand, photocatalytic materials such as titanium dioxide may undergo crystal phase transformation, resulting in a decrease in quantum efficiency (for example, the TiO2 crystal phase may transform from the highly active anatase phase to the inert rutile phase, resulting in a decrease in quantum efficiency of more than 50%).

[0004] To improve the performance of photocatalytic coatings in long-term outdoor applications, existing research focuses on developing novel catalytic coatings (such as noble metal doping and the construction of heterojunctions). However, the methods disclosed in the prior art can only improve the lifespan of photocatalytic coatings to a certain extent, but cannot regenerate aged coatings.

[0005] For the regeneration of aged photocatalytic coatings, the main existing methods include: traditional physical cleaning, chemical etching and high-temperature calcination. However, traditional physical cleaning only removes surface deposits and cannot restore the intrinsic activity of the catalyst. Chemical etching is prone to damaging the coating structure. Although high-temperature calcination can decompose pollutants, it requires disassembling the substrate and has extremely high energy consumption (>500℃), making it difficult to operate on-site and lacking engineering applicability.

[0006] CN101579645A discloses an online regeneration method for degraded TiO2 powder photocatalysts after degradation of natural organic matter. This method addresses the problem of complex processes and the need to remove the photocatalyst from the photocatalytic reactor in existing degraded suspended TiO2 photocatalyst regeneration methods. The method described in this paper is as follows: 1. After the photocatalyst becomes degraded during operation of the photocatalytic membrane assembly process, the feed water is stopped, and a portion of the solution in the photocatalytic membrane reactor is discharged using the membrane module; the photocatalyst is TiO2 powder; 2. A regeneration solution is introduced into the photocatalytic membrane reactor to remove adsorbed substances from the catalyst surface; the regeneration solution is an H2O2 solution with a concentration of 0.05 mM; 3. The intensity of the ultraviolet light source is controlled to be 0.1~20 mW / cm². 2 To regenerate by ultraviolet irradiation.

[0007] CN114749173A discloses a method for preparing Ag-TiO2 composite photocatalytic material, comprising the following steps: S1. Femtosecond laser processing is performed on the surface of a titanium metal substrate to form a network micro / nano structure; S2. The titanium metal substrate treated in step S1 is sequentially subjected to NaOH hydrothermal treatment, acid washing, and thermal oxidation treatment to form a nanoflower structure composed of interconnected TiO2 nanosheets on the surface of the titanium metal substrate; S3. The titanium metal substrate treated in step S2 is subjected to AgNO3 reduction treatment to composite Ag nanoparticles on the nanoflower structure, thereby obtaining the Ag-TiO2 composite photocatalytic material.

[0008] It is evident that existing urban self-cleaning enhancement methods (regeneration methods for photocatalytic coatings) all have certain shortcomings, including poor regeneration effect of aged photocatalytic coatings on building exteriors, high cost, narrow applicability, and difficulty in direct on-site operation. Therefore, it is crucial to develop and design a novel urban self-cleaning enhancement method for catalytic coatings on building exteriors. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a method for enhancing the self-cleaning properties of building exterior wall catalytic coatings based on in-situ modification using focused laser. This method employs focused laser for in-situ scanning, controlling the temperature, laser scanning speed, and single-point irradiation time to create a localized high-temperature field, thereby regenerating the aged photocatalytic coating on the building exterior wall without damaging the substrate. Furthermore, this self-cleaning enhancement method also boasts advantages such as low cost, wide applicability, and on-site operation, demonstrating broad application prospects.

[0010] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for enhancing urban self-cleaning based on in-situ modification of a catalytic coating on building exterior walls using focused laser technology, the method comprising: In-situ scanning of the photocatalytic coating on the exterior wall of a building is performed using a focused laser, which induces the formation of a local high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating, thereby causing the lattice reconstruction of the catalytic material in the photocatalytic coating.

[0011] The urban self-cleaning enhancement method provided by the present invention has the following advantages: (1) The urban self-cleaning enhancement method uses a focused laser to perform in-situ scanning of the photocatalytic coating on the exterior wall of the building. The local high temperature generated by the laser is used to change the crystal phase structure of the catalytic material in the photocatalytic coating, thereby realizing the lattice reconstruction of the catalytic material and improving the separation efficiency and migration rate of photogenerated carriers. This enables the regeneration of the photocatalytic coating after aging. The regenerated photocatalytic coating has better photocatalytic degradation activity for gaseous pollutants (the degradation rate of gaseous pollutants by the regenerated photocatalytic coating is restored to more than 90% of the initial activity), which is conducive to promoting the transformation of urban air quality governance from passive purification (dependent on diffusion dilution) to active degradation (catalytic mineralization of pollutants); (2) The urban self-cleaning enhancement method also has a low cost, which is only 15% to 20% of the cost of new coating construction (materials + labor), reducing the construction and maintenance costs of "self-cleaning cities"; (3) The urban self-cleaning enhancement method can not only be adapted to mainstream photocatalytic coatings, but also realize the regeneration of photocatalytic coatings on planar and curved exterior walls of buildings, which has broad application prospects.

[0012] Preferably, during the in-situ scanning, the laser scanning speed is controlled to be ≥5m / s, and the single-point irradiation time is 0.01ms~1.8ms.

[0013] Preferably, during the in-situ scanning, if the catalytic material is a white semiconductor material with a band gap of not less than 3.2 eV, then the ultraviolet-violet light band with a wavelength of 300 nm to 380 nm or the blue light band with a wavelength of 400 nm to 500 nm is used as the scanning light source.

[0014] Preferably, during the in-situ scanning, if the catalytic material is any one or a combination of at least two of Fe2O3, Fe3O4, Co2O3, MnO2, Mn2O3, Mn3O4, NiO, or CuO, then a green light band with a wavelength of 500nm to 570nm or a red light band with a wavelength of 620nm to 700nm is used as the scanning light source.

[0015] Preferably, the white semiconductor material comprises titanium dioxide and / or zinc oxide.

[0016] Preferably, the in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 1 to 6 times.

[0017] Preferably, during the in-situ scanning, the control pulse interval is greater than the thermal relaxation time.

[0018] Preferably, during the in-situ scanning, the single-pulse energy density is controlled to be less than the ablation threshold.

[0019] Preferably, the thermal relaxation time is >1ms.

[0020] Preferably, the ablation threshold is <5 J / cm. 2 .

[0021] Preferably, during the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter.

[0022] Preferably, the set diameter is 0.9mm to 1.1mm.

[0023] Preferably, the in-situ scanning is performed using an optically self-stabilized focused laser modification device. The method for controlling the diameter of the laser beam spot focused on the surface of the photocatalytic coating to a set diameter is as follows: the laser rangefinder of the optically self-stabilized focused laser modification device monitors the distance between the optically self-stabilized focused laser modification device and the wall in real time. Based on the monitored distance, the input voltage of the piezoelectric ceramic is adjusted by the controller of the optically self-stabilized focused laser modification device. After driving the focusing lens to make axial displacement, the laser source generator is controlled to emit a scanning light source.

[0024] Preferably, in the urban self-cleaning enhancement method, the laser modification equipment is mounted on an unmanned vehicle chassis and pulled by a rigid cable system to move in a two-dimensional plane along the building facade, thereby realizing in-situ scanning of the photocatalytic coating on the building facade.

[0025] Preferably, in the urban self-cleaning enhancement method, the laser modification equipment is mounted on a drone, and the three-dimensional spatial displacement capability of the drone is used to achieve in-situ scanning of the photocatalytic coating on the exterior wall of irregularly shaped buildings.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) The urban self-purification enhancement method described in this invention uses a focused laser to perform in-situ scanning of the photocatalytic coating on the exterior wall of a building. The local high temperature generated by the laser is used to change the crystal phase structure of the catalytic material in the photocatalytic coating, thereby realizing the lattice reconstruction of the catalytic material and improving the separation efficiency and migration rate of photogenerated carriers. This enables the regeneration of the photocatalytic coating after aging. The regenerated photocatalytic coating has better photocatalytic degradation activity for gaseous pollutants (the degradation rate of gaseous pollutants by the regenerated photocatalytic coating is restored to more than 90% of the initial activity), which is conducive to promoting the transformation of urban air quality governance from passive purification (dependent on diffusion and dilution) to active degradation (catalytic mineralization of pollutants). (2) The urban self-cleaning enhancement method described in this invention also has a low cost, which is only 15% to 20% of the cost of new coating construction (materials + labor), thus reducing the construction and maintenance costs of "self-cleaning cities"; (3) The urban self-cleaning enhancement method described in this invention can not only be adapted to mainstream photocatalytic coatings, but also realize the regeneration of photocatalytic coatings on planar and curved building exteriors, and has broad application prospects. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the technical principle of forming a high-energy-density light spot on the surface of a photocatalytic coating.

[0028] Figure 2 This is a schematic diagram of an optically self-stabilized focused laser modification device.

[0029] Figure 3 This is a schematic diagram of a wall-mounted unmanned vehicle equipped with laser modification equipment.

[0030] Figure 4 This is a schematic diagram of a drone equipped with laser modification equipment.

[0031] Figure 5 These are schematic diagrams of the appearance of A-TiO2 / FM, A-TiO2 / FM (1-4) in Example 2, and A-TiO2 / FM (2-1) in Example 3.

[0032] Figure 6 The Raman spectra were obtained by testing A-TiO2 / FM, A-TiO2 / FM (1-4) in Example 2, and A-TiO2 / FM (2-1) in Example 3.

[0033] Figure 7 This is a SEM image of the surface obtained from testing A-TiO2 / FM.

[0034] Figure 8 This is a SEM image of the cross-section obtained from testing A-TiO2 / FM.

[0035] Figure 9 The image shows a SEM image of the surface obtained by testing the A-TiO2 / FM(1-4) provided in Example 2.

[0036] Figure 10 The image shows a SEM image of the cross section obtained by testing the A-TiO2 / FM(1-4) provided in Example 2.

[0037] Figure 11 This is a SEM image of the surface obtained by testing the A-TiO2 / FM(2-1) provided in Example 3.

[0038] Figure 12 The image shows a SEM image of the cross section obtained by testing the A-TiO2 / FM(2-1) provided in Example 3.

[0039] Figure 13 This is a schematic diagram of the testing device used in dynamic formaldehyde degradation activity testing.

[0040] Figure 14 These are curves showing the catalytic degradation activity of A-TiO2 / FM, A-TiO2 / FM (1-1) in Example 1, A-TiO2 / FM (1-4) in Example 2, and A-TiO2 / FM (2-1) in Example 3 against low concentrations of formaldehyde outdoors under dynamic testing. Figure 15 This is a schematic diagram of the testing apparatus used in static formaldehyde degradation activity testing.

[0041] Figure 16 The curves show the catalytic degradation activity of A-TiO2 / CT and A-TiO2 / CT (1-4) in Example 6 for low concentrations of formaldehyde outdoors under static testing.

[0042] Figure 17 This is a schematic diagram of the testing apparatus used when testing catalytic performance in a natural environment.

[0043] Figure 18 This is a graph showing the catalytic degradation activity curve of A-TiO2 / CT(1-4) against low concentrations of formaldehyde outdoors under static testing in a natural environment, along with real-time monitoring data of natural light intensity. Detailed Implementation

[0044] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0045] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0046] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0048] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0049] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0050] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0051] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0052] In one embodiment, the present invention provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology, the method comprising: In-situ scanning of the photocatalytic coating on the exterior wall of a building is performed using a focused laser, which induces the formation of a local high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating, thereby causing the lattice reconstruction of the catalytic material in the photocatalytic coating.

[0053] The urban self-cleaning enhancement method provided by the present invention has the following advantages: (1) The urban self-cleaning enhancement method uses a focused laser to perform in-situ scanning of the photocatalytic coating on the exterior wall of the building. The local high temperature generated by the laser is used to change the crystal phase structure of the catalytic material in the photocatalytic coating, thereby realizing the lattice reconstruction of the catalytic material and improving the separation efficiency and migration rate of photogenerated carriers. This enables the regeneration of the photocatalytic coating after aging. The regenerated photocatalytic coating has better photocatalytic degradation activity for gaseous pollutants (the degradation rate of gaseous pollutants by the regenerated photocatalytic coating is restored to more than 90% of the initial activity), which is conducive to promoting the transformation of urban air quality governance from passive purification (dependent on diffusion dilution) to active degradation (catalytic mineralization of pollutants); (2) The urban self-cleaning enhancement method also has a low cost, which is only 15% to 20% of the cost of new coating construction (materials + labor), reducing the construction and maintenance costs of "self-cleaning cities"; (3) The urban self-cleaning enhancement method can not only be adapted to mainstream photocatalytic coatings, but also realize the regeneration of photocatalytic coatings on planar and curved exterior walls of buildings, which has broad application prospects.

[0054] In some embodiments, during the in-situ scanning, the laser scanning speed is controlled to be ≥5m / s, and the single-point irradiation time is 0.01ms~1.8ms.

[0055] When performing in-situ scanning as described in this invention, the laser scanning speed is ≥5m / s, for example, it can be 5m / s, 6m / s, 7m / s, 8m / s, 9m / s, 10m / s, 12m / s, 15m / s or 18m / s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] During in-situ scanning as described in this invention, the single-point irradiation time is controlled to be 0.01ms to 1.8ms, for example, it can be 0.01ms, 0.05ms, 0.1ms, 0.2ms, 0.5ms, 0.8ms, 1.0ms, 1.2ms, 1.5ms or 1.8ms, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] In the urban self-cleaning enhancement method provided by this invention, energy is focused through a condensing lens, forming a high-energy-density light spot on the surface of the photocatalytic coating (technical principle as follows). Figure 1 As shown in the figure), by controlling the laser scanning speed to be ≥5m / s and the single-point irradiation time to be 0.01ms~1.9ms, the local temperature gradient was dynamically adjusted, the heat accumulation rate was suppressed (≤106K / s), thereby preventing deep thermal erosion of the photocatalytic coating with a heat-affected depth >50μm and avoiding thermal damage to the substrate.

[0058] In the in-situ scanning described in this invention, for example, a laser head can be driven by an XY-axis precision stepper motor to achieve two-dimensional planar scanning, and the laser scanning speed can be controlled to be ≥5m / s. For example, it can be 5m / s, 6m / s, 7m / s, 8m / s, 9m / s, 10m / s, 12m / s, 15m / s, 18m / s or 20m / s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] During in-situ scanning as described in this invention, a nanosecond / millisecond level pulse controller may be used for pulse regulation to control the single-point irradiation time to be 0.01ms to 1.8ms. For example, it may be 0.01ms, 0.05ms, 0.1ms, 0.5ms, 1ms, 1.5ms, or 1.8ms, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] In some embodiments, during the in-situ scanning, if the catalytic material is a white semiconductor material with a band gap (Eg) of not less than 3.2 eV, then the ultraviolet-violet light band with a wavelength of 300 nm to 380 nm (preferably 355 nm) is used. Photon =3.49eV) or blue light in the wavelength range of 400nm~500nm (preferably blue light with a wavelength of 450nm, E Photon =2.76eV) as the scanning light source.

[0061] The wavelength of the ultraviolet-violet band described in this invention is 300nm~380nm, for example, it can be 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 370nm or 380nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] The wavelength of the blue light band described in this invention is 400nm~500nm, for example, it can be 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, 460nm, 470nm, 480nm, 490nm or 500nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] In some embodiments, during the in-situ scanning, if the catalytic material is any one or a combination of at least two of Fe2O3, Fe3O4, Co2O3, MnO2, Mn2O3, Mn3O4, NiO, or CuO, then a green light band with a wavelength of 500nm to 570nm (preferably green light with a wavelength of 532nm) is used. Photon=2.33eV) or red light in the wavelength range of 620nm~700nm (preferably red light with a wavelength of 635nm, E Photon =1.95eV) as the scanning light source.

[0064] In this invention, the catalytic material is any one or a combination of at least two of Fe2O3, Fe3O4, Co2O3, MnO2, Mn2O3, Mn3O4, NiO, or CuO. Typical but non-limiting combinations include combinations of Fe2O3 and Fe3O4, combinations of Co2O3 and MnO2, combinations of Mn2O3 and Mn3O4, combinations of NiO and CuO, or combinations of Fe2O3, MnO2, and NiO.

[0065] The wavelength of the green light band described in this invention is 500nm~570nm, for example, it can be 500nm, 510nm, 520nm, 530nm, 540nm, 550nm, 560nm or 570nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] The wavelength of the red light band described in this invention is 620nm~700nm, for example, it can be 620nm, 630nm, 640nm, 650nm, 660nm, 670nm, 680nm, 690nm or 700nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0067] In the urban self-cleaning enhancement method provided by this invention, a wavelength adaptation scheme is designed based on the laser photon energy (E=hc / λ) of the scanning light source and the bandgap of the catalytic material, thereby realizing the regeneration of catalytic materials in different photocatalytic coatings.

[0068] In some embodiments, the white semiconductor material includes titanium dioxide and / or zinc oxide.

[0069] In some implementations, the in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 1 to 6 times, for example, 1, 2, 3, 4, 5 or 6 times.

[0070] In the urban self-cleaning enhancement method provided by the present invention, the controllable regeneration of the photocatalytic coating surface is achieved by stepwise short-pulse irradiation. Combined with the use of a short pulse sequence of 1 to 6 times in the single-point irradiation area, it is more conducive to the lattice reconstruction of the shallow layer (<50μm) of the photocatalytic coating through the cumulative photothermal effect.

[0071] In some implementations, during the in-situ scan, the control pulse interval is greater than the thermal relaxation time.

[0072] In some implementations, during the in-situ scan, the single-pulse energy density is controlled to be less than the ablation threshold.

[0073] In the urban self-cleaning enhancement method provided by the present invention, by controlling the pulse interval to be greater than the thermal relaxation time, heat is ensured to be fully dissipated between pulses; by controlling the single pulse energy density to be less than the ablation threshold, structural thermal decomposition of the deep region (region with a depth > 50 μm) of the photocatalytic coating is avoided.

[0074] In some implementations, the thermal relaxation time (τ) is greater than 1 ms, for example, it can be 1.1 ms, 1.2 ms, 1.5 ms, 2 ms, 3 ms, 4 ms, 5 ms, 6 ms, 7 ms, 8 ms, 9 ms or 10 ms, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0075] In some embodiments, the ablation threshold is <5 J / cm 2 For example, it could be 0.5 J / cm 2 1J / cm 2 1.5J / cm 2 2J / cm 2 2.5J / cm 2 3J / cm 2 3.5J / cm 2 4J / cm 2 4.5J / cm 2 Or 5J / cm 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0076] In some embodiments, during the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter.

[0077] In the urban self-cleaning enhancement method provided by the present invention, by controlling the diameter of the laser beam spot focused on the surface of the photocatalytic coating to a set diameter, the laser beam is continuously focused on the surface of the photocatalytic coating on the building exterior wall, thereby realizing the self-adaptation of the non-flat surface. The urban self-cleaning enhancement method can be used for the regeneration of the photocatalytic coating on the non-flat building exterior wall.

[0078] In some implementations, the set diameter is 0.9mm to 1.1mm, for example, it can be 0.9mm, 0.92mm, 0.94mm, 0.96mm, 0.98mm, 1.0mm, 1.02mm, 1.04mm, 1.06mm, 1.08mm or 1.1mm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0079] In the urban self-cleaning enhancement method provided by this invention, the device for controlling the diameter of the laser beam focused on the surface of the photocatalytic coating to a set diameter can be, for example, such as... Figure 2 The optical self-stabilized focused laser modification device shown includes a controller, a laser rangefinder, a laser source generator, a piezoelectric ceramic, and a focusing lens. The controller is electrically connected to the laser rangefinder, the laser source generator, and the piezoelectric ceramic.

[0080] In some embodiments, the in-situ scanning is performed using an optically self-stabilized focused laser modification device. The method for controlling the diameter of the laser beam spot focused on the surface of the photocatalytic coating to a set diameter is as follows: the laser rangefinder of the optically self-stabilized focused laser modification device monitors the distance between the optically self-stabilized focused laser modification device and the wall in real time (generating a distance data stream). Based on the monitored distance, the input voltage of the piezoelectric ceramic is adjusted by the controller of the optically self-stabilized focused laser modification device. After driving the focusing lens to make axial displacement, the laser source generator is controlled to emit a scanning light source.

[0081] In this invention, the controller is the core processing and command unit of the entire optical self-stabilized focused laser modification equipment. Based on the preset program and the real-time distance data fed back by the laser rangefinder, it synchronously coordinates the light output of the laser source generator and the precise displacement of the piezoelectric ceramic to achieve dynamic control of the laser spot diameter.

[0082] In this invention, the laser rangefinder functions to measure and monitor the instantaneous distance between the optically self-stabilized focused laser modification device and the wall surface in a non-contact, real-time, and precise manner at a set sampling frequency, and continuously feeds the distance data stream back to the controller to provide distance signals for subsequent real-time focus adjustment.

[0083] In this invention, the laser source generator is used to generate and output a laser beam with specific wavelength, energy and pulse parameters according to the instructions of the controller.

[0084] In this invention, the piezoelectric ceramic is used as a precision linear drive mechanism for the focusing lens. Under the drive of the modulation voltage output by the controller, the piezoelectric ceramic will generate axial extension and retraction displacement, which will directly drive the focusing lens to move axially along the optical axis, thereby adjusting the focusing state of the laser beam in real time and ensuring that the laser beam spot diameter is the set diameter.

[0085] In some embodiments, the laser ranging module monitors the distance between the laser modification device and the wall in real time at a sampling frequency of 0.2kHz to 5kHz. For example, the sampling frequency can be 0.2kHz, 0.5kHz, 1kHz, 1.5kHz, 2kHz, 2.5kHz, 3kHz, 3.5kHz, 4kHz, 4.5kHz, or 5kHz, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0086] In some embodiments, the axial displacement is performed within a stroke of ±5 mm. The stroke of the axial displacement can be, for example, ±1 mm, ±1.5 mm, ±2 mm, ±2.5 mm, ±3 mm, ±3.5 mm, ±4 mm, ±4.5 mm, or ±5 mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0087] In some embodiments, the urban self-cleaning enhancement method involves mounting a laser modification device on an unmanned vehicle (e.g., such as...). Figure 3 The wall-mounted unmanned vehicle chassis shown is pulled by a rigid cable system to move in a two-dimensional plane along the building facade, thereby realizing in-situ scanning of the photocatalytic coating on the building facade (thus realizing large-area in-situ modification of the photocatalytic coating on the building facade, with the modified area of ​​the photocatalytic coating on the building facade not less than ≥95% of the total area of ​​the photocatalytic coating).

[0088] In some embodiments, the traction force of the rigid cable system is ≥50kN, for example, it can be 50kN, 55kN, 60kN, 65kN, 70kN, 75kN, 80kN, 85kN, 90kN, 95kN or 100kN, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0089] In some embodiments, the urban self-cleaning enhancement method involves mounting a laser modification device (powered via an external cable) on a drone (which may be, for example,...). Figure 4 On the drone shown, the three-dimensional spatial displacement capability of the drone (positioning accuracy ±10cm) is used to realize the in-situ scanning of the photocatalytic coating on the irregular building exterior wall (that is, to complete the in-situ modification of the photocatalytic coating on the irregular facade of the high-rise building).

[0090] The urban self-cleaning enhancement method provided by this invention can achieve in-situ regeneration of photocatalytic coatings on the exterior walls of buildings in cities by adapting to various mobile platforms (wall-mounted unmanned vehicles and / or drones), breaking through the engineering limitations of traditional photocatalytic coating regeneration and replacement.

[0091] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0092] A glass fiber membrane (FM, average pore size 0.22 μm) was used to simulate the exterior wall substrate of a high-rise building. 20 mg of anatase TiO2 (A-TiO2, average particle size 50 nm) was dispersed in 10 mL of anhydrous ethanol. After ultrasonic treatment at 40 kHz for 30 min to form a dispersion, the dispersion was deposited onto the FM surface under a vacuum pressure of -0.1 MPa. The surface was then dried at 110 °C for 2 h to form a circular catalytic coating with a diameter of 3 cm, labeled A-TiO2 / FM (appearance as shown). Figure 5 (As shown).

[0093] A glass fiber membrane (FM, with an average pore size of 0.22 μm) was used to simulate the substrate of the exterior wall of a high-rise building. 20 mg of iron oxide (Fe2O3, with an average particle size of 50 nm) was dispersed in 10 mL of anhydrous ethanol. After ultrasonic treatment at 40 kHz for 30 min to form a dispersion, the dispersion was deposited on the surface of FM under a vacuum pressure of -0.1 MPa and then dried at 110 °C for 2 h to form a circular catalytic coating with a diameter of 3 cm, labeled as Fe2O3 / FM.

[0094] A brown, rough-surfaced ceramic plate (CT) was used to simulate the base of the exterior wall of a high-rise building (a square sample of 6cm×6cm). 100mg of anatase titanium dioxide (A-TiO2, average particle size 50nm) was ultrasonically dispersed in 30mL of ethanol to obtain an A-TiO2 slurry. The A-TiO2 slurry was completely coated onto the surface of the ceramic plate (CT) in three batches. After drying at 110℃, a dense catalytic coating was formed, denoted as A-TiO2 / CT.

[0095] Example 1 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology. The method includes: The surface of the A-TiO2 / FM obtained above (i.e. the surface of the A-TiO2 layer) is scanned in situ using a focused laser emitted by a laser source generator. This induces the formation of a local high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating. After the lattice of the catalytic material in the photocatalytic coating is reconstructed, a regenerated catalytic coating is obtained, labeled as A-TiO2 / FM (1-1). During the in-situ scanning, the laser head is driven by a precision stepper motor on the XY axis to control the laser scanning speed to 6m / s, and pulse regulation is performed by a millisecond-level pulse controller to make the single-point irradiation time 1ms. During the in-situ scanning, since the catalytic material is a white semiconductor material (titanium dioxide) with a band gap of 3.2 eV, a blue light laser with a wavelength of 450 nm and a power of 3000 mW is used as the scanning light source. The in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 1. During the in-situ scan, the control pulse interval is greater than the thermal relaxation time, wherein the pulse interval is 1.3 ms and the thermal relaxation time is 1.2 ms; During the in-situ scanning, the single-pulse energy density is controlled to be less than the ablation threshold, wherein the single-pulse energy density is 3 J / cm². 2 The ablation threshold is 4 J / cm. 2 ; During the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter (1.0 mm) by focusing with a condenser lens.

[0096] Example 2 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology. The method includes: The surface of the obtained A-TiO2 / FM (i.e., the surface of the A-TiO2 layer) was scanned in situ using a focused laser emitted from a laser source generator. This induced the formation of a local high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating. After the lattice of the catalytic material in the photocatalytic coating was reconstructed, a regenerated catalytic coating was obtained, labeled A-TiO2 / FM(1-4) (appearance as shown). Figure 5 (as shown) During the in-situ scanning, the laser head is driven by a precision stepper motor on the XY axis to control the laser scanning speed to 6m / s, and pulse regulation is performed by a millisecond-level pulse controller to make the single-point irradiation time 1ms. During the in-situ scanning, since the catalytic material is a white semiconductor material (titanium dioxide) with a band gap of 3.2 eV, a blue light laser with a wavelength of 450 nm and a power of 3000 mW is used as the scanning light source. The in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 4. During the in-situ scan, the control pulse interval is greater than the thermal relaxation time, wherein the pulse interval is 1.3 ms and the thermal relaxation time is 1.2 ms; During the in-situ scanning, the single-pulse energy density is controlled to be less than the ablation threshold, wherein the single-pulse energy density is 3 J / cm². 2 The ablation threshold is 4 J / cm. 2 ; During the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter (1.0 mm) by focusing with a condenser lens.

[0097] Example 3 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology. The method includes: The surface of the obtained A-TiO2 / FM (i.e., the surface of the A-TiO2 layer) was scanned in situ using a focused laser emitted from a laser source generator. This induced the formation of a localized high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating. After the lattice of the catalytic material in the photocatalytic coating was reconstructed, a regenerated catalytic coating was obtained, labeled A-TiO2 / FM(2-1) (appearance as shown). Figure 5 (as shown) During the in-situ scanning, the laser head is driven by a precision stepper motor on the XY axis to control the laser scanning speed at 6m / s, and pulse regulation is performed by a millisecond-level pulse controller to make the single-point irradiation time 2ms. During the in-situ scanning, since the catalytic material is a white semiconductor material (titanium dioxide) with a band gap of 3.2 eV, a blue light laser with a wavelength of 450 nm and a power of 3000 mW is used as the scanning light source. The in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 1. During the in-situ scan, the control pulse interval is greater than the thermal relaxation time, wherein the pulse interval is 1.3 ms and the thermal relaxation time is 1.2 ms; During the in-situ scanning, the single-pulse energy density is controlled to be less than the ablation threshold, wherein the single-pulse energy density is 3 J / cm². 2 The ablation threshold is 4 J / cm. 2 ; During the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter (1 mm) by focusing with a condenser lens.

[0098] Example 4 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology. The method includes: The surface of the A-TiO2 / FM obtained above (i.e. the surface of the A-TiO2 layer) is scanned in situ using a focused laser emitted by a laser source generator. This induces the formation of a local high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating. After the lattice of the catalytic material in the photocatalytic coating is reconstructed, a regenerated catalytic coating is obtained, labeled as A-TiO2 / FM (2-1). During the in-situ scanning, the laser head is driven by a precision stepper motor on the XY axis to control the laser scanning speed at 5m / s, and pulse regulation is performed in conjunction with a millisecond-level pulse controller to make the single-point irradiation time 1.8ms. During the in-situ scanning, if the catalytic material is a white semiconductor material (zinc oxide) with a band gap of 3.37 eV, then the ultraviolet-violet light band with a wavelength of 350 nm is used as the scanning light source. The in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 1 to 6 times. During the in-situ scan, the control pulse interval is greater than the thermal relaxation time, wherein the pulse interval is 1.2 ms and the thermal relaxation time is 1.1 ms; During the in-situ scanning, the single-pulse energy density is controlled to be less than the ablation threshold, wherein the single-pulse energy density is 2 J / cm². 2 The ablation threshold is 3 J / cm. 2 ; During the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter (1.1 mm) by focusing with a condenser lens.

[0099] Example 5 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology. The method includes: The surface of the Fe2O3 / FM obtained above (i.e. the surface of the Fe2O3 layer) is scanned in situ using a focused laser emitted by a laser source generator. This induces the formation of a local high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating. After the lattice of the catalytic material in the photocatalytic coating is reconstructed, a regenerated catalytic coating is obtained, labeled as Fe2O3(1-1). During the in-situ scanning, the laser head is driven by a precision stepper motor on the XY axis to control the laser scanning speed to 8m / s, and pulse regulation is performed in conjunction with a millisecond-level pulse controller to make the single-point irradiation time 0.01ms. During the in-situ scanning, since the catalytic material is iron oxide (Fe2O3), a red light band with a wavelength of 660nm is used as the scanning light source. The in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 6. During the in-situ scan, the control pulse interval is greater than the thermal relaxation time, wherein the pulse interval is 1.4 ms and the thermal relaxation time is 1.3 ms; During the in-situ scanning, the single-pulse energy density is controlled to be less than the ablation threshold, wherein the single-pulse energy density is 4 J / cm². 2 The ablation threshold is 4.5 J / cm.2 ; During the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter (0.9 mm) by focusing with a condenser lens.

[0100] Example 6 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology. The method includes: The surface of the A-TiO2 / CT obtained above (i.e. the surface of the A-TiO2 layer) is scanned in situ using a focused laser emitted by a laser source generator. This induces the formation of a local high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating. After the lattice of the catalytic material in the photocatalytic coating is reconstructed, a regenerated catalytic coating is obtained, labeled as A-TiO2 / CT (1-4). During the in-situ scanning, the laser head is driven by a precision stepper motor on the XY axis to control the laser scanning speed to 6m / s, and pulse regulation is performed by a millisecond-level pulse controller to make the single-point irradiation time 1ms. During the in-situ scanning, since the catalytic material is a white semiconductor material (titanium dioxide) with a band gap of 3.2 eV, a blue light laser with a wavelength of 450 nm and a power of 3000 mW is used as the scanning light source. The in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 4. During the in-situ scan, the control pulse interval is greater than the thermal relaxation time, wherein the pulse interval is 1.3 ms and the thermal relaxation time is 1.2 ms; During the in-situ scanning, the single-pulse energy density is controlled to be less than the ablation threshold, wherein the single-pulse energy density is 3.5 J / cm². 2 The ablation threshold is 4 J / cm. 2 ; During the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter (1.0 mm) by focusing with a condenser lens.

[0101] Example 7 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings on building exterior walls using focused laser. Except for the use of a 532nm green light band laser (3000mW power) as the scanning light source, the method is the same as in Embodiment 1.

[0102] Example 8 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings on building exterior walls using focused laser. Except for the use of a blue light laser with a wavelength of 450nm (power of 3000mW) as the scanning light source, the method is the same as in Embodiment 5.

[0103] Example 9 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings on building exterior walls using focused laser. Except for the fact that the number of short pulse sequences in the single-point irradiation area is 10, the rest is the same as in Embodiment 1.

[0104] Example 10 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings on building exterior walls using focused laser. Except that the pulse interval (0.5ms) is controlled to be less than the thermal relaxation time (which is 1.2ms), the rest of the method is the same as in Embodiment 1.

[0105] Example 11 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology. In addition to controlling the single-pulse energy density (8 J / cm²) in the aforementioned method, the method also includes... 2 The value is greater than the ablation threshold, which is 4 J / cm. 2 Except for the above, everything else is the same as in Example 1.

[0106] Example 12 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of building exterior wall catalytic coatings using focused laser. Except for the method where the diameter of the laser beam focused on the surface of the photocatalytic coating is controlled to a set diameter (0.6 mm) by using a focusing lens, the rest is the same as in Embodiment 1.

[0107] Example 13 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of building exterior catalytic coatings using focused laser. Except for the method where the diameter of the laser beam focused on the surface of the photocatalytic coating is controlled to a set diameter (1.5 mm) by using a focusing lens, the rest is the same as in Embodiment 1.

[0108] Example 14 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings on building exterior walls using focused laser. Except for controlling the laser scanning speed to 3 m / s during in-situ scanning, the rest is the same as in Embodiment 1.

[0109] Example 15 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings on building exterior walls using focused laser. Except for controlling the single-point irradiation time to 0.02ms during in-situ scanning, the rest is the same as in Embodiment 1.

[0110] Example 16 This embodiment provides a method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings on building exterior walls using focused laser. Except for controlling the single-point irradiation time to 15ms during in-situ scanning, the rest is the same as in Embodiment 1.

[0111] pass Figure 5 It can be seen that the appearance of A-TiO2 / FM after regeneration in Example 2 (1-4) and A-TiO2 / FM after regeneration in Example 3 (2-1) did not show significant changes, indicating that the urban self-cleaning enhancement method has little impact on the appearance of the photocatalytic coating.

[0112] A-TiO2 / FM was measured using a Raman spectrometer (532nm laser, 5mW). The obtained Raman spectrum is as follows: Figure 6 As shown, through Figure 6 It can be seen that the A-TiO2 layer in A-TiO2 / FM retains the characteristic peaks of anatase, confirming that no phase transition occurred; scanning electron microscopy was used to test A-TiO2 / FM, and the SEM image of the surface obtained is shown below. Figure 7 The SEM image of the cross-section is as follows: Figure 8 As shown, through Figure 7 and Figure 8 It can be seen that A-TiO2 formed a continuous and dense coating on the FM surface. Cross-sectional observation shows that the coating is tightly bonded to the substrate interface and there is no peeling phenomenon.

[0113] The A-TiO2 / FM(1-4) provided in Example 2 was tested using a Raman spectrometer. The obtained Raman spectra are as follows: Figure 6 As shown, the A-TiO2 / FM(1-4) provided in Example 2 was tested using a scanning electron microscope, and the resulting SEM images of the surface are shown below. Figure 9 As shown, the SEM image of the cross-section is as follows. Figure 10 As shown; through comparison of Raman spectra, it can be seen that the A-TiO2 in the A-TiO2 layer retains its unique anatase structure after laser in-situ modification, but its characteristic peak intensity is significantly reduced, indicating that the surface defect sites of the catalytic material have increased; through comparison of SEM images, it can be seen that the photocatalytic coating is still very dense after laser modification.

[0114] The A-TiO2 / FM(2-1) provided in Example 3 was tested using a Raman spectrometer. The obtained Raman spectrum is as follows: Figure 6 As shown, the A-TiO2 / FM(2-1) provided in Example 3 was tested using a scanning electron microscope, and the resulting SEM image of the surface is shown below. Figure 11 The SEM image of the cross-section is as follows: Figure 12 As shown; by comparing the Raman spectra, it can be seen that the A-TiO2 in the A-TiO2 layer generated a new Raman vibration peak after 2ms in-situ laser modification, proving that the long-pulse laser modification caused the anatase structure in the coating to be partially transformed into a rutile structure; by comparing the SEM images, it can be seen that the dense structure of the photocatalytic coating after long-pulse laser modification was destroyed, and a significant high-temperature melting phenomenon occurred.

[0115] Dynamic formaldehyde degradation activity tests were conducted on the regenerated catalytic coatings obtained in Examples 1-16 and the above-mentioned A-TiO2 / FM. The test method was as follows: Figure 13 The test was conducted using the apparatus shown, with air containing 5 ppm formaldehyde continuously passing through the regenerated catalytic coating. A simulated sunlight lamp was used as the light source for the catalytic reaction, and the light power was controlled at 20 mW / cm². 2 The formaldehyde purification efficiency data obtained after 12 hours are shown in Table 1. The catalytic degradation activity curves of A-TiO2 / FM, A-TiO2 / FM (1-1) in Example 1, A-TiO2 / FM (1-4) in Example 2, and A-TiO2 / FM (2-1) in Example 3 against low-concentration outdoor formaldehyde under dynamic testing are shown in Table 1. Figure 14 As shown.

[0116] The static formaldehyde degradation activity of the regenerated catalytic coatings obtained in Examples 1-16 and A-TiO2 / FM was tested using the following method: Figure 15 The test was conducted using the apparatus shown. The sample to be tested was placed in air containing 5 ppm formaldehyde in a total volume of approximately 20 L. A simulated sunlight lamp was used as the light source for the catalytic reaction, and the light power was controlled at 20 mW / cm². 2 The formaldehyde concentration data obtained after 12 hours are shown in Table 1; among them, the catalytic degradation activity curves of A-TiO2 / CT and A-TiO2 / CT (1-4) in Example 6 for outdoor low-concentration formaldehyde under static testing are shown in Table 1. Figure 16 As shown.

[0117] The catalytic performance of the regenerated catalytic coatings obtained in Examples 4 and 6 above was tested in a natural environment. The test method was as follows: Figure 17The test setup was used, placing the sample in air containing 5 ppm formaldehyde in a volume of approximately 20 L. Natural light was used as the energy source for the catalytic degradation of formaldehyde. Real-time changes in sunlight intensity throughout the day were monitored. At 14:00, the formaldehyde concentration corresponding to the regenerated catalytic coating obtained in Example 4 was 0.5 ppm, and the formaldehyde concentration corresponding to the regenerated catalytic coating obtained in Example 6 was 1.0 ppm. The catalytic degradation activity curves of A-TiO2 / CT(1-4) for low-concentration outdoor formaldehyde under static testing in a natural environment and the real-time monitoring data of natural light intensity are shown below. Figure 18 As shown.

[0118] Table 1 From Table 1, we can obtain: (1) The appearance of the photocatalytic coatings treated by the urban self-cleaning enhancement methods provided in Examples 1-2 and 4-6 did not change significantly. They still have a dense structure, no peeling phenomenon and no obvious crystal phase change. They also showed excellent photocatalytic performance under both dynamic and static tests. The photocatalytic coatings treated with the urban self-cleaning enhancement methods provided in Examples 1-2 and 4-6 exhibited a formaldehyde purification efficiency of 0.47 mg / (g·h) to 0.62 mg / (g·h) after 12 hours of dynamic testing, a formaldehyde concentration of 2.6 ppm to 3.5 ppm after 12 hours of static testing, and a formaldehyde concentration of 0.5 ppm to 1.0 ppm at 14:00 under static testing in a natural environment. (2) By comparing Example 1 with Example 7 and Example 5 with Example 8, it can be seen that in the urban self-cleaning enhancement method provided by the present invention, a wavelength matching scheme is designed according to the laser photon energy (E=hc / λ) of the scanning light source and the band gap of the catalytic material, thereby realizing the regeneration of catalytic materials in different photocatalytic coatings; (3) By comparing Example 1 and Example 9, it can be seen that in the urban self-cleaning enhancement method provided by the present invention, the controllable regeneration of the photocatalytic coating surface is achieved by step-by-step short pulse irradiation. Combined with the use of 1 to 6 short pulse sequences in the single-point irradiation area, it is more conducive to the lattice reconstruction of the shallow layer (<50μm) of the photocatalytic coating through the cumulative photothermal effect. (4) By comparing Example 1 with Examples 10 and 11, it can be seen that in the urban self-cleaning enhancement method provided by the present invention, by controlling the pulse interval to be greater than the thermal relaxation time, the heat is ensured to be fully dissipated between pulses; by controlling the single pulse energy density to be less than the ablation threshold, the structural thermal decomposition of the deep region (region with a depth > 50 μm) of the photocatalytic coating is avoided. (5) By comparing Example 1 with Examples 12 and 13, it can be seen that in the urban self-cleaning enhancement method provided by the present invention, by controlling the diameter of the laser beam spot focused on the surface of the photocatalytic coating to a set diameter, the laser beam is continuously focused on the surface of the photocatalytic coating on the building exterior wall, thereby realizing the self-adaptation of the non-flat surface. The urban self-cleaning enhancement method can be used for the regeneration of the photocatalytic coating on the non-flat building exterior wall. (6) By comparing Example 1 with Examples 3, 14-16, it can be seen that in the urban self-cleaning enhancement method provided by the present invention, energy is focused by a condensing lens, forming a high-energy-density light spot on the surface of the photocatalytic coating (the technical principle is as follows). Figure 1 As shown in the figure), by controlling the laser scanning speed to be ≥5m / s and the single-point irradiation time to be 0.01ms~1.9ms, the local temperature gradient was dynamically adjusted, the heat accumulation rate was suppressed (≤106K / s), thereby preventing deep thermal erosion of the photocatalytic coating with a heat-affected depth >50μm and avoiding thermal damage to the substrate.

[0119] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for enhancing urban self-cleaning based on in-situ modification of catalytic coatings for building exterior walls using focused laser technology, characterized in that, The urban self-cleaning enhancement method includes: In-situ scanning of the photocatalytic coating on the exterior wall of a building is performed using a focused laser, which induces the formation of a local high-temperature field with a temperature greater than 900°C on the surface of the photocatalytic coating, thereby causing the lattice reconstruction of the catalytic material in the photocatalytic coating.

2. The urban self-cleaning enhancement method according to claim 1, characterized in that, During the in-situ scanning, the laser scanning speed is controlled to be ≥5m / s, and the single-point irradiation time is 0.01ms~1.8ms; And / or, during the in-situ scanning, if the catalytic material is a white semiconductor material with a band gap of not less than 3.2 eV, then the ultraviolet-violet light band with a wavelength of 300 nm to 380 nm or the blue light band with a wavelength of 400 nm to 500 nm is used as the scanning light source; And / or, during the in-situ scanning, if the catalytic material is any one or a combination of at least two of Fe2O3, Fe3O4, Co2O3, MnO2, Mn2O3, Mn3O4, NiO or CuO, then a green light band with a wavelength of 500nm~570nm or a red light band with a wavelength of 620nm~700nm is used as the scanning light source.

3. The urban self-cleaning enhancement method according to claim 2, characterized in that, The white semiconductor material includes titanium dioxide and / or zinc oxide.

4. The urban self-cleaning enhancement method according to claim 1, characterized in that, The in-situ scanning is performed using a step-by-step short-pulse irradiation method, and the number of short-pulse sequences in a single-point irradiation area is 1 to 6 times.

5. The urban self-cleaning enhancement method according to claim 1, characterized in that, During the in-situ scanning, the control pulse interval is greater than the thermal relaxation time; And / or, during the in-situ scan, the single-pulse energy density is controlled to be less than the ablation threshold.

6. The urban self-cleaning enhancement method according to claim 5, characterized in that, The thermal relaxation time is >1ms; And / or, the ablation threshold is <5 J / cm 2 .

7. The urban self-cleaning enhancement method according to claim 1, characterized in that, During the in-situ scanning process, the diameter of the laser beam spot focused on the surface of the photocatalytic coating is controlled to a set diameter.

8. The urban self-cleaning enhancement method according to claim 7, characterized in that, The set diameter is 0.9mm~1.1mm; And / or, the in-situ scanning is performed using an optically self-stabilized focused laser modification device. The method for controlling the diameter of the laser beam spot focused on the surface of the photocatalytic coating to a set diameter is as follows: the laser rangefinder of the optically self-stabilized focused laser modification device monitors the distance between the optically self-stabilized focused laser modification device and the wall in real time. Based on the monitored distance, the input voltage of the piezoelectric ceramic is adjusted by the controller of the optically self-stabilized focused laser modification device. After driving the focusing lens to make axial displacement, the laser source generator is controlled to emit a scanning light source.

9. The urban self-cleaning enhancement method according to claim 1, characterized in that, In the urban self-cleaning enhancement method, a laser modification device is mounted on an unmanned vehicle chassis and pulled by a rigid cable system to move in a two-dimensional plane along the building facade, thereby realizing in-situ scanning of the photocatalytic coating on the building facade.

10. The urban self-cleaning enhancement method according to claim 1, characterized in that, In the urban self-cleaning enhancement method, laser modification equipment is mounted on a drone, and the drone's three-dimensional spatial displacement capability is used to achieve in-situ scanning of photocatalytic coatings on irregularly shaped building exteriors.

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