Preparation and application of a nanofiber confined Fe single-atom self-cleaning coating material

Abstract

This invention relates to the field of self-cleaning coating materials, and discloses the preparation and application of a nanofiber-confined Fe single-atom self-cleaning coating material. The invention uses wood nanofibers as a carbon-based carrier to obtain nanofiber-confined Fe single-atom materials. The three-dimensional network structure generated during the acidic hydrolysis of methyl orthosilicate enhances the bonding between the nanofiber-confined Fe single-atom materials, nano-silica, and nano-titanium dioxide nanoparticles. After hydrolysis, a diluent is added, and the reaction proceeds to obtain the nanofiber-confined Fe single-atom self-cleaning coating material. This self-cleaning coating material has a simple process, high operability, excellent antistatic properties, superhydrophilicity, and photocatalytic activity. It exhibits excellent anti-fouling potential in self-cleaning coating material applications and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of self-cleaning coating materials, specifically to the preparation and application of a nanofiber-confined Fe single-atom self-cleaning coating material. Background Technology

[0002] With rapid economic development and continuous improvement of infrastructure, the cleaning of various skyscrapers, giant stone sculptures, and large billboards has become a major challenge. Traditional manual cleaning methods are not only time-consuming, labor-intensive, and extremely costly, but also pose significant safety risks to cleaning personnel. Furthermore, these methods are expensive and often incomplete, wasting water resources and potentially damaging the substrate.

[0003] In recent years, there has been considerable research on antifouling coatings for building exteriors. These coatings can reduce the deposition of pollutants on building surfaces and, to some extent, delay pollution. However, this is ultimately only a temporary solution. Self-cleaning coatings have also gained widespread attention in recent years due to their applications in stealth technology, display devices, and sensors. Self-cleaning coatings can remove surface pollutants under the influence of gravity, rainwater, wind, or through photocatalytic degradation, offering advantages such as water conservation, energy saving, and environmental protection. They have broad application prospects in construction, transportation, and new energy fields, but their limited functionality restricts their practical application. Therefore, the development of high-performance self-cleaning coatings has become a research hotspot.

[0004] Currently, the metals in traditional heterogeneous catalysts exist in clusters or oxides, resulting in low metal atom utilization and reduced catalytic performance. Single-atom transition metal heterogeneous catalysts (SACs) are novel heterogeneous catalytic materials formed by uniformly dispersing transition metals in single-atom form on a support. Their advantages, such as high stability, high atom utilization, ease of separation, and reusability, have made them a research frontier in the field of heterogeneous catalysis. Numerous studies have shown that carbon-based supports (such as graphene, carbon nanotubes, and carbon nitride) have large specific surface areas, abundant functional groups, and numerous pores, making them excellent supports for preparing single-atom catalysts. However, these materials are costly to prepare, environmentally toxic, and difficult to scale up. Therefore, it is necessary to develop a low-cost and widely applicable carbon-based support. This invention utilizes wood nanofibers as a carbon-based support to prepare metal single-atom catalytic materials, employing wood nanocellulose as a novel approach that is widely available and low-cost. Meanwhile, this invention prepares graphitized porous nanofiber-confined Fe single-atom self-cleaning materials through high-temperature pyrolysis, applies them to glass coatings, and conducts preliminary research on the photocatalytic degradation efficiency of the nanofiber-confined Fe single-atom coating material on the dye methylene blue, providing a promising technology for the field of self-cleaning coatings. Summary of the Invention

[0005] The technical problem to be solved by this invention is to develop a nanofiber-confined Fe single-atom self-cleaning coating material that is simple to process, highly operable, has excellent antistatic properties, superhydrophilicity and photocatalytic activity, outstanding antifouling potential, and is easy to prepare on a large scale, in order to address the shortcomings of the existing technology.

[0006] This invention proposes a method for preparing a self-cleaning coating material with nanofiber-confined Fe single atoms. The method utilizes the three-dimensional network structure generated during the acidic hydrolysis of methyl orthosilicate to enhance the bonding between the nanofiber-confined Fe single-atom material, nano-silica, and nano-titanium dioxide nanoparticles. After hydrolysis, a diluent is added, and the reaction proceeds to obtain the nanofiber-confined Fe single-atom self-cleaning coating material. The specific steps are as follows:

[0007] (1) Softwood fibers were mixed with TEMPO and sodium bromide in pulp and stirred. NaClO solution was added dropwise to initiate the oxidation reaction, and NaOH solution was added during the oxidation process to maintain a constant pH. The oxidized pulp was then thoroughly washed with deionized water until the pH reached neutral and stored under certain conditions. The oxidized pulp was homogenized under certain pressure to obtain wood nanocellulose.

[0008] Preferably, the amount of coniferous wood fiber used is 10g, and the concentrations of TEMPO and sodium bromide are 0.1mmol / g and 1mmol / g, respectively.

[0009] Preferably, the pulp concentration is 1 wt%, and the mixing time is 6 min.

[0010] Preferably, the pH of the added NaClO is 10.0, and the amount of added NaOH is 0.5 mol / L.

[0011] Preferably, the pulp is stored at 4°C.

[0012] Preferably, the oxidized pulp is prepared to a concentration of 1 wt% and homogenized 6 times under a pressure of 100 MPa.

[0013] (2) At room temperature, the wood nanocellulose obtained in step (1) and urea were mixed in an ultrapure aqueous solution and stirred. Fe(NO3)3·9H2O was then added to the mixed solution and stirred. NaCl and KCl were then added and stirred to form a mixed solution. After drying, the solution was pyrolyzed using a one-step pyrolysis method to obtain nanofiber-confined Fe single-atom materials.

[0014] Preferably, the amount of wood-based nanocellulose powder and urea used is 2g and 4g respectively, and the volume of ultrapure water is 500mL.

[0015] Preferably, the amount of Fe(NO3)3·9H2O added is 8 mmol.

[0016] Preferably, the amount of NaCl and KCl added is 2.5g each.

[0017] Preferably, the stirring times for the three stages of the process are 1 hour, 2 hours, and 2 hours respectively.

[0018] Preferably, the pyrolysis temperature is 800℃ and the pyrolysis time is 2h.

[0019] (3) At room temperature, the nanofiber confined Fe single-atom material, nano silica and nano titanium dioxide obtained in step (2) are added to methyl orthosilicate and stirred. Then HCl is added to adjust the pH to obtain a composite hydrolysate.

[0020] Preferably, the amounts of the nanofiber-confined Fe single-atom material, nano-silica, nano-titanium dioxide, and methyl orthosilicate are 1-10 mg, 1-3 g, 1-10 mg, and 1-3 g, respectively.

[0021] Preferably, the pH is adjusted to 2-4.

[0022] Preferably, the reaction time of the process is 3 to 5 hours.

[0023] (4) Diluents ethanol, acetone, propylene glycol and ultrapure water are added sequentially to the composite hydrolysate obtained in step (3) and the reaction conditions are controlled to finally obtain nanofiber confined Fe single-atom self-cleaning coating material.

[0024] Preferably, the amounts of the composite hydrolysate, ethanol, acetone, propylene glycol, and deionized water are 5-15g, 10-15g, 8-15g, 10-25g, and 10-20g, respectively.

[0025] Preferably, the reaction conditions are as follows: the reaction temperature is controlled at 15-25°C, the mechanical stirring time is 5-6 hours, and the mechanical stirring speed is 800-1200 rpm.

[0026] The present invention also provides a method for applying the above-mentioned nanofiber confined Fe single-atom self-cleaning coating material to a glass substrate. The method includes the following steps: placing the glass substrate in ethanol and deionized water for ultrasonic cleaning for 10-20 min in sequence, and drying it in an oven for 5-10 min; after drying, taking the nanofiber confined Fe single-atom self-cleaning coating material obtained in step (4), coating it onto the substrate by wiping, spraying, dipping or other methods, and allowing it to stand and cure for 12-24 h to obtain the nanofiber confined Fe single-atom self-cleaning coating.

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] 1. The nanofiber-confined Fe single-atom material of the present invention is prepared by molten salt-assisted high-temperature pyrolysis. The molten salt is a 1:1 NaCl / KCl system. The one-step high-temperature pyrolysis operation is simple and can achieve graphitization of nanofibers, which is conducive to the formation of nitrogen vacancies and single atoms. The polar solvent environment generated by the molten salt causes the metal atomic bonds to break, which is easily anchored by the nitrogen vacancies formed in the nanofibers, thus promoting the formation of single atoms and creating more active sites, which is conducive to the degradation of pollutants and achieves self-cleaning.

[0029] 2. The nanofiber confined Fe single-atom material of the present invention uses wood nanofibers as single-atom carriers, which can provide a new way for the utilization of wood biomass. The self-cleaning material prepared has a wide range of raw material sources, low price, non-toxicity and environmental friendliness.

[0030] 3. The preparation process of the nanofiber confined Fe single-atom self-cleaning coating material of the present invention is simple, easy to operate, and easy to realize industrial production. Attached Figure Description

[0031] Figure 1 This is a digital photograph of a nanofiber-confined Fe single-atom self-cleaning coating material.

[0032] Figure 2 This is a scanning electron microscope (SEM) image of the nanofiber-confined Fe single-atom self-cleaning coating;

[0033] Figure 3 This is a schematic diagram of the water contact angle between blank glass (a) and nanofiber confined Fe single-atom self-cleaning coating (b);

[0034] Figure 4 This is a schematic diagram of the antistatic and dustproof properties of blank glass (a) and nanofiber-confined Fe single-atom self-cleaning coating (b);

[0035] Figure 5 This is a schematic diagram illustrating the photocatalytic effects of a nanofiber-confined Fe single-atom self-cleaning coating and a coating without a nanofiber-confined Fe single-atom self-cleaning coating. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Example 1:

[0038] A method for preparing the nanofiber-confined Fe single-atom self-cleaning coating of the present invention:

[0039] 10g of coniferous wood fiber was weighed and mixed with TEMPO (0.1mmol / g) and sodium bromide (1mmol / g) at a pulp concentration of 1wt% for 6 min. The oxidation reaction was initiated by dropwise addition of NaClO solution at pH 10.0, with 0.5M NaOH solution added during the oxidation process to maintain a constant pH. The oxidized pulp was then thoroughly washed with deionized water until the pH reached neutral and stored at 4℃. The oxidized pulp was prepared to a concentration of 1wt% and homogenized six times under 100MPa pressure to obtain lignocellulose nanoparticles.

[0040] At room temperature, 2g of wood-based nanocellulose powder and 4g of urea were mixed in 500mL of ultrapure water and stirred for 1h. Then, 8mmol of Fe(NO3)3·9H2O was added to the mixed solution and stirred for 2h. Next, NaCl (2.5g) and KCl (2.5g) were added and stirred for 2h to form a homogeneous solution. After drying, the solution was pyrolyzed at 800℃ for 2h using a one-step pyrolysis method to obtain nanofiber-confined Fe single-atom materials.

[0041] 7 mg of the obtained nanofiber confined Fe single-atom material, 2 g of nano-silica and 10 mg of nano-titanium dioxide were added to 2 g of methyl orthosilicate and stirred. The pH was adjusted to 3 with HCl and the reaction was carried out for 3 h to obtain a composite hydrolysate.

[0042] 10g of the obtained composite hydrolysate was added sequentially with 12g of ethanol, 10g of acetone, 16g of propylene glycol, and 15g of ultrapure water. The mixture was mechanically stirred for 5 hours at 25℃ with a stirring speed of 1000rpm to finally obtain a nanofiber confined Fe single-atom self-cleaning coating material.

[0043] Digital photographs of the nanofiber-confined Fe single-atom self-cleaning coating material prepared above are shown below. Figure 1 As shown, the material is stable and transparent.

[0044] Example 2:

[0045] A method for preparing the nanofiber-confined Fe single-atom self-cleaning coating of the present invention:

[0046] The glass substrate was ultrasonically cleaned in ethanol and deionized water for 10 minutes and dried in an oven for 7 minutes. After drying, the nanofiber confined Fe single-atom self-cleaning coating material prepared in Example 1 was applied to the substrate by wiping and allowed to cure for 12 hours to obtain the nanofiber confined Fe single-atom self-cleaning coating.

[0047] The nanofiber-confined Fe single-atom self-cleaning coating prepared above is transparent in appearance. When placed under a scanning electron microscope, its structure is as follows: Figure 2As shown, the coating surface is dense and compact. This indicates that the nanofiber-confined Fe single-atom self-cleaning coating prepared by this invention has good adhesion and forms a stable rough surface on the glass substrate.

[0048] Example 3:

[0049] The glass substrate was ultrasonically cleaned in ethanol and deionized water for 10 minutes and dried in an oven for 7 minutes. After drying, the nanofiber confined Fe single-atom self-cleaning coating material prepared in Example 1 was applied to the substrate by dip coating and allowed to stand for curing for 12 hours to obtain the nanofiber confined Fe single-atom self-cleaning coating.

[0050] The water contact angles of blank glass and the nanofiber-confined Fe single-atom self-cleaning coating prepared above were measured using a water contact angle tester. Figure 3 As shown in (a), the contact angle of the blank glass is 38.637°, indicating that it does not possess superhydrophilic properties; Figure 3 As shown in (b), the contact angle of the nanofiber-confined Fe single-atom self-cleaning coating is 3.057°, exhibiting superhydrophilicity. This demonstrates that the nanofiber-confined Fe single-atom self-cleaning coating prepared in this invention can cover the glass surface, giving it superhydrophilicity.

[0051] Example 4:

[0052] The glass substrate was ultrasonically cleaned in ethanol and deionized water for 10 minutes and dried in an oven for 7 minutes. After drying, the nanofiber confined Fe single-atom self-cleaning coating material prepared in Example 1 was applied to the substrate by dip coating and allowed to stand for curing for 12 hours to obtain the nanofiber confined Fe single-atom self-cleaning coating.

[0053] The surface resistance values ​​of the blank glass and the nanofiber-confined Fe single-atom self-cleaning coating prepared above were measured using a surface resistance meter. The surface resistance values ​​were 10 Ω·cm and 10 Ω·cm, respectively. 11 Ω, 10 7 Ω. The resistance to dust adhesion of blank glass and the aforementioned nanofiber-confined Fe single-atom self-cleaning coating was tested using simulated dust, as shown in the results. Figure 4 As shown in (a), the blank glass is covered with dust, while... Figure 4 As shown in (b), the nanofiber-confined Fe single-atom self-cleaning coating exhibits less dust adhesion. This indicates that the nanofiber-confined Fe single-atom self-cleaning coating prepared in this invention not only reduces the surface resistivity of the glass and improves its antistatic properties, but also enhances its resistance to dust adhesion, reducing the impact of dust on the glass surface.

[0054] Example 5:

[0055] The nanofiber-confined Fe single-atom self-cleaning coating was prepared using the same method as in Example 1.

[0056] 2g of nano-silica and 10mg of nano-titanium dioxide were added to 2g of methyl orthosilicate and stirred. The pH was adjusted to 3 with HCl and the reaction was carried out for 3 hours to obtain a composite hydrolysate without nanofiber-confined Fe single-atom materials.

[0057] 10g of the obtained composite hydrolysate was added sequentially with 12g of ethanol, 10g of acetone, 16g of propylene glycol, and 15g of ultrapure water. The mixture was mechanically stirred for 5 hours at 25°C with a stirring speed of 1000 rpm to obtain a self-cleaning coating material without nanofiber confined Fe single atom.

[0058] The glass substrate was ultrasonically cleaned in ethanol and deionized water for 10 minutes and dried in an oven for 7 minutes. After drying, the nanofiber-confined Fe single-atom self-cleaning coating material and the non-nanofiber-confined Fe single-atom self-cleaning coating material were applied to the substrate by wiping and allowed to cure for 12 hours to obtain their respective self-cleaning coatings.

[0059] The self-cleaning coating substrate prepared above was slowly placed into a beaker containing 50 mL of methylene blue. A dark reaction was carried out for 30 min, followed by a 90 min light reaction. The pollutant removal capabilities of both methods were then recorded and compared. The data are shown below. Figure 5 As shown.

[0060] The photocatalytic degradation ability of the nanofiber-confined Fe single-atom self-cleaning coating of the present invention is higher than that of the coating without nanofiber-confined Fe single-atom self-cleaning coating. This demonstrates the unique advantages of the nanofiber-confined Fe single-atom material of the present invention, which makes full use of solar energy, thereby improving and enhancing the photoelectrochemical performance of the nano-titanium dioxide material, exerting a higher photocatalytic effect, and thus realizing the self-cleaning ability of the material.

[0061] Obviously, the above embodiments are merely examples to clearly illustrate the properties of the coating material, and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A nanofiber-confined Fe single-atom self-cleaning coating material, characterized in that... This material uses wood nanofibers as a carbon-based carrier to obtain nanofiber-confined Fe single-atom materials. The three-dimensional network structure generated during the acidic hydrolysis of methyl orthosilicate enhances the bonding between the nanofiber-confined Fe single-atom materials, nano-silica, and nano-titanium dioxide nanoparticles. After hydrolysis, a diluent is added, and the reaction proceeds to obtain a self-cleaning coating material containing nanofiber-confined Fe single atoms. The preparation method includes the following steps: (1) 10 g of coniferous wood fiber was mixed with 0.1 mmol / g TEMPO and 1 mmol / g sodium bromide at a pulp concentration of 1 wt% and stirred for 6 min. NaClO solution was added dropwise at pH 10.0 to start the oxidation reaction. During the oxidation process, 0.5 mol / L NaOH solution was added to maintain the pH constant. The oxidized pulp was then thoroughly washed with deionized water until the pH reached neutral and stored at 4 ℃. The oxidized pulp was prepared to a concentration of 1 wt% and homogenized 6 times at a pressure of 100 MPa to obtain wood nanocellulose. (2) Then, at room temperature, 2 g of wood nanocellulose powder and 4 g of urea were mixed in 500 mL of ultrapure water and stirred for 1 h. Then, 8 mmol of Fe(NO3)3·9H2O was added to the mixed solution and stirred for 2 h. Then, 2.5 g of NaCl and 2.5 g of KCl were added and stirred for 2 h to form a homogeneous solution. After drying, the solution was pyrolyzed at 800 °C for 2 h using a one-step pyrolysis method to obtain nanofiber confined Fe single-atom material. (3) At room temperature, the nanofiber confined Fe single-atom material, nano silica and nano titanium dioxide obtained in step (2) are added to methyl orthosilicate and stirred. Then HCl is added to adjust the pH. After the reaction, a composite hydrolysate is obtained. (4) Add diluents ethanol, acetone, propylene glycol and ultrapure water to the composite hydrolysate obtained in step (3) in sequence, control the reaction conditions, and finally obtain nanofiber confined Fe single atom self-cleaning coating material.

2. The nanofiber confined Fe single-atom self-cleaning coating material according to claim 1, in step (3), the amounts of nanofiber confined Fe single-atom material, nano silica, nano titanium dioxide and methyl orthosilicate are 1~10 mg, 1~3 g, 1~10 mg and 1~3 g, respectively, the pH is adjusted to 2~4, and the reaction time is 3~5 h.

3. The nanofiber confined Fe single-atom self-cleaning coating material according to claim 1, in step (4), the amounts of composite hydrolysate, ethanol, acetone, propylene glycol and ultrapure water are 5~15 g, 10~15 g, 8~15 g, 10~25 g and 10~20 g, respectively, the reaction temperature is controlled at 15~25 ℃, the mechanical stirring time is 5~6 h, and the mechanical stirring speed is 800~1200 rpm.

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