CN111841654A - D35-TiO2Nanocrystalline thin film and preparation method and application thereof - Google Patents

Abstract

The invention relates to the field of chemical materials and the field of pollutant treatment, and particularly discloses D35-TiO₂A nanocrystalline film, a preparation method and application thereof. The preparation method comprises the following steps: deposition of dense crystalline TiO on precleaned FTO glass substrates by spray pyrolysis₂A hole blocking layer followed by the addition of TiO₂Loading nano particles on the porous TiO nano material repeatedly and sintering the nano particles to obtain the mesoporous TiO₂A nano-crystalline film, and finally adding mesoporous TiO₂And adding the nanocrystalline film into a D35 dye solution for sensitization, washing and drying to obtain the nano-crystalline film. The invention obviously improves the D35-TiO by limiting the core parameters of the key process₂The success rate of the nano-crystal film preparation is improved, and the degradation efficiency of the nano-crystal film on BPA in photoelectrocatalysis degradation is effectively improved.

Description

A kind of D35-TiO2 nanocrystalline film and its preparation method and application

technical field

The invention relates to the field of chemical materials and pollutant treatment, in particular to a dye-sensitized titanium dioxide nano-film material for photocatalytic degradation of pollutants.

Background technique

Contamination with endocrine disruptors (EDCs) has recently attracted widespread public attention. Bisphenol A (BPA) is a typical representative of EDCs and is widely used as a raw material for the manufacture of epoxy resins and polycarbonate plastics. Currently, BPA has been reported to leach from polycarbonate baby bottles, drinking water tanks, and reusable containers, indicating that it has become ubiquitous in aquatic environments.

Titanium dioxide (TiO ₂ ) photocatalytic reaction can effectively remove stubborn compounds, and TiO ₂ is commonly used in wastewater purification due to its high photocatalytic activity, chemical stability, non-toxicity, and low cost. However, _TiO2 has a wide band gap (3.2 eV) and can only absorb ultraviolet light. However, the ultraviolet photon flux only accounts for 3%-5% of the entire solar spectrum, and the use of artificial ultraviolet light consumes a lot of energy and the economic cost is high. In addition, electrons injected into the conduction band (CB) of _TiO2 easily recombine with holes left in its valence band (VB), thereby reducing the photocatalytic efficiency. The above problems limit the practical application of pure _TiO photocatalysis.

In recent years, dye sensitization has been successfully used in solar cells, as well as in water splitting and pollutant decomposition. Sensitizers are a key part in dye sensitization, which affects visible light absorption, photocatalytic performance, and stability. _P25TiO2 was sensitized with eosin Y, rhodamine B and erythrosine to degrade 2,4-dichlorophenol. Although such photocatalysts are capable of degrading organic pollutants, they exhibit low photoconversion efficiency and insufficient stability. Transition metal-based dyes, such as ruthenium Ru(II) or iridium Ir(III) complexes, have received extensive attention due to their wide light absorption range and high stability. However, they are expensive to synthesize, and their ecotoxicity cannot be ignored. Organic dyes, such as porphyrins and phthalocyanines, have high extinction coefficients and chemical stability. Due to their stable and tunable physicochemical properties, many researchers use them for water treatment. In recent years, the D35 organic dye developed by Hagfeldt has exhibited excellent photovoltaic performance in dye-sensitized solar cells (DSC) due to its wide light absorption range, high molar extinction coefficient, and good stability.

In dye-sensitized photocatalysis, most studies have focused on suspension systems to facilitate synthesis. However, there are four typical disadvantages of the suspension reaction system: 1) the rapid recombination of light-induced charge carriers; 2) the severe agglomeration of nanoparticles, which reduces the surface area and inhibits the catalytic activity of the photocatalyst; 3) the process of separation of the nanoparticle photocatalyst from the solution Complex and easy to cause secondary pollution; 4) The problem of material recovery limits its practical application.

Therefore, it is necessary to develop a dye-sensitized photocatalytic material with a simpler preparation method, higher degradation rate of micro-pollutants, better stability, and convenient recycling and reuse.

SUMMARY OF THE INVENTION

In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a D35-TiO ₂ nanocrystalline thin film and its preparation method and application.

In order to realize the purpose of the present invention, the technical scheme of the present invention is as follows:

In the first aspect, the present invention provides a preparation method of D35-TiO ₂ nanocrystalline thin film, the preparation method includes the following steps:

Step 1: Dense crystalline TiO ₂ holes were deposited by spray pyrolysis on a pre-cleaned FTO glass substrate (Pilkingto Corporation, sheet resistance 15 ohm, thickness 2.3 mm, high transmittance) on a hot stage at 550 °C barrier layer;

Step 2: The colloidal TiO ₂ nanoparticles were loaded onto the dense crystalline TiO ₂ hole blocking layer described in step 1 by the doctor blade method, and this operation was cycled three times, and after each cycle, at 100 °C Dry in an oven for 20 minutes (i.e.: blade coating method loading - oven drying - blade coating method loading - oven drying - blade coating method loading - oven drying);

After that, the dried samples were placed in a muffle furnace and sintered at 550 °C for 60 minutes, so that the _TiO2 crystal form was completely transformed into anatase type, and then cooled to 90 °C naturally, and then the samples were immersed in a 35 mM _TiCl4 aqueous solution placed in an oven at 76 °C for 50 minutes to ensure the formation of fine _TiO2 crystals between the _TiO2 nanoparticles so that all particles can be fully connected, then rinse the surface of the sample with deionized water, and repeat the above sintering process again, Naturally cooled to 70 °C to finally obtain a mesoporous _TiO2 nanocrystalline film with a thickness of 16 μm;

Step 3: Immerse the mesoporous TiO ₂ nanocrystal film obtained in step 2 into an acetonitrile solution containing 0.5 mM D35 dye for 10 hours to obtain high D35 coverage on the surface of the TiO ₂ film, and then rinse with absolute ethanol The samples were blown dry with compressed air to obtain D35-TiO ₂ nanocrystalline thin films (ie, D35-sensitized mesoporous TiO ₂ nanocrystalline thin films).

Further, in step 1 of the aforementioned preparation method, the spray precursor solution is an isopropanol solution containing 0.15M butyl titanate and 3M acetylacetone.

When spray pyrolysis was performed, the spray distance was 4 cm from the sample, the single spray time was 15 seconds, the number of spray cycles was 20 times, and the interval between each cycle was 60 seconds to obtain the dense crystalline TiO ₂ space with a thickness of 200 nm. Cavity barrier.

In the specific embodiment of the present invention, as an example, the size of the glass substrate is 5 cm×5 cm, and the size specification of the glass substrate is not limited to this in actual operation.

In the second aspect, the present invention provides a D35-TiO ₂ nanocrystalline thin film. The D35-TiO ₂ nanocrystalline thin film is formed by D35 dye molecules forming a chelating chemical bond with the TiO ₂ surface through a carboxyl group to form a uniform uniformity on the entire TiO ₂ surface. the dye monolayer;

The D35-TiO ₂ nanocrystalline thin film can degrade bisphenol A under the condition that the initial concentration of bisphenol A (BPA) is 15 mg/L and the initial pH is 7 under visible light irradiation, and after 200 minutes, bisphenol A (BPA) can be degraded. The degradation rate of A can exceed 97%.

Further, the aforementioned D35-TiO ₂ nanocrystalline thin film provided by the present invention can be prepared by the aforementioned preparation method of the present invention.

It should be understood that the D35-TiO ₂ nanocrystalline thin film prepared by the aforementioned preparation method of the present invention can be irradiated with visible light under the conditions that the initial concentration of bisphenol A is 15 mg/L and the initial pH is 7. degradation, and the degradation rate of bisphenol A can exceed 97% after 200 minutes. Compared with the existing technology, there is a significant improvement.

In a third aspect, the present invention provides the application of the D35-TiO ₂ nanocrystalline thin film, or the D35-TiO ₂ nanocrystalline thin film prepared by the preparation method of the present invention, in photoelectric catalytic degradation of organic pollutants.

Preferably, the D35-TiO ₂ nanocrystalline thin film of the present invention has an exceptionally excellent degradation effect on bisphenol A under photocatalytic conditions.

Therefore, within the scope of the application, the application can be embodied as a method for photoelectric catalytic _degradation of bisphenol A. The degradation of bisphenol A in the sewage under photocatalytic conditions.

Preferably, when the initial concentration of bisphenol A in the sewage is 0.1-16 mg/L, and the pH value is 4-8, it is more favorable for the D35-TiO ₂ nanocrystalline film provided by the present invention to exert its high-efficiency catalytic effect.

The raw materials or reagents involved in the present invention are all common commercially available products, and the operations involved are routine operations in the art unless otherwise specified.

On the basis of common knowledge in the art, the above preferred conditions can be combined with each other to obtain specific embodiments.

The beneficial effects of the present invention are:

The invention provides a preparation method of the D35-TiO ₂ nanocrystalline thin film. By limiting the core parameters of the key process, the preparation success rate of the D35-TiO ₂ nanocrystalline thin film is significantly improved, and its performance in photoelectric catalytic degradation is effectively improved. The degradation efficiency of BPA in .

In the D35- _TiO2 nanocrystalline thin film material, the sensitization of D35 broadens the absorption of visible light by the catalyst, so that the light absorption of the composite material extends to and covers most of the visible spectral region. The D35- _TiO2 nanocrystalline film possesses more efficient photo-generated charge carrier separation efficiency, enabling the D35- _TiO2 nanocrystalline film to significantly enhance the photocatalytic degradation efficiency of visible light-driven BPA. The D35-TiO ₂ nanocrystalline film exhibits high stability in recycling and avoids the problem of photocatalyst-solution separation, which is convenient for recycling and reuse, and provides a new idea for green and sustainable development for degrading organic micro-pollutants in wastewater .

Description of drawings

Figure 1 is an SEM image of the D35- _TiO2 nanocrystalline thin film in Example 1 of the present invention.

FIG. 2 is a high-resolution TEM image of the D35-TiO ₂ nanocrystalline thin film in Example 1 of the present invention.

FIG. 3 is the reaction mechanism of the photodegradation of BPA by the D35-TiO ₂ nanocrystalline thin film according to the present invention.

FIG. 4 is a graph showing the comparison of the performance of D35-TiO ₂ nanocrystalline thin film and ordinary TiO ₂ nanoparticles in visible light catalytic degradation of BPA in Experimental Example 1 of the present invention.

FIG. 5 is a study on the stability of visible light catalytic degradation of BPA by D35-TiO ₂ nanocrystalline thin film in Experimental Example 1 of the present invention.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the examples. It should be understood that the following examples are given for illustrative purposes only, and are not intended to limit the scope of the present invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from the spirit and spirit of the present invention.

The experimental methods used in the following examples are conventional methods unless otherwise specified.

Materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

Example 1

Step 1: Deposition by spray pyrolysis on a pre-cleaned FTO glass (Pilkingto Corporation, sheet resistance 15 ohm, thickness 2.3 mm, high transmittance) substrate (cut to size 5 cm × 5 cm) on a hot stage at 550 °C Dense crystalline TiO ₂ hole blocking layer, the spray precursor solution is an isopropanol solution containing butyl titanate and acetylacetone, wherein the concentration of butyl titanate is 0.15M, and the concentration of acetylacetone is 3M; spray distance The sample is 4 cm high, the single spray time is 15 seconds, the number of spray cycles is 20 times, and the interval between each cycle is 60 seconds, and a dense crystalline TiO ₂ hole blocking layer with a thickness of 200 nm is obtained by controlling the above parameters;

Step 2. Using a doctor blade, colloidal TiO ₂ nanoparticles (DSL 18NR-T model from Dyesol Company, with an average particle size of 20 nm, diluted with terpineol at a mass ratio of 30% to form a colloidal substance) were loaded into the colloidal material by the doctor blade method. On the dense crystalline _TiO2 hole blocking layer, this operation was cycled three times and dried in an oven at 100 °C for 20 min after each cycle, and then the samples were placed in a muffle furnace and sintered at 550 °C for 60 min to make the samples. The _TiO2 crystal type was completely transformed into anatase type, and then cooled to 90 °C naturally, then the sample was immersed in a 35 mM _TiCl4 aqueous solution and placed in a 76 °C oven for 50 minutes to ensure the formation of fine TiO2 between the _TiO2 nanoparticles. ₂ crystals so that all particles can be fully connected, then rinse the surface of the sample with deionized water, repeat the above sintering process again, and naturally cool to 70 °C, and finally obtain a mesoporous _TiO2 nanocrystalline film with a thickness of 16 μm;

Step 3. Immerse the mesoporous TiO ₂ nanocrystalline film obtained in step 2 in an acetonitrile solution of D35 dye with a concentration of 0.5 mM for 10 hours to obtain a high D35 coverage on the surface of the TiO ₂ film, rinse the sample with absolute ethanol and press Air-dried to prepare D35-sensitized mesoporous _TiO2 nanocrystalline thin films.

Figure 1 is the SEM image of the D35- _TiO2 nanocrystalline thin film. Figure 1a shows the morphologies of the mesoporous _TiO2 nanocrystalline films before the D35 dye sensitization process. Apparently, the film has a mesoporous structure, which is the typical morphology of _TiO2 nanocrystalline thin films. According to the cross-sectional SEM image shown in Fig. 1b, the thickness of the D35- _TiO2 film is around 16 μm.

Figure 2 is a high-resolution TEM image of the D35- _TiO2 nanocrystalline thin film. It can be seen that the morphology and crystal structure of _TiO2 particles in the sensitized samples are similar to those of pure _TiO2 . Therefore, the D35 dye sensitization process only modifies the surface properties of _TiO2 without changing its internal structure. Experimental example 1

This experimental example is used to verify the BPA degradation performance of the D35-TiO ₂ nanocrystalline film prepared in Example 1 in a photocatalytic system.

The reaction mechanism of D35- _TiO2 nanocrystalline films for BPA photodegradation is shown in Fig. 3. Upon photoexcitation, the D35 molecule absorbs visible light, and electrons are excited from the highest occupied molecular orbital (HOMO) of D35 to the lowest vacant orbital (LUMO), and then injected into the conduction band (CB) of _TiO2 to form free electrons (e ^- _CB ) , which enhances the physical separation of photoinduced electrons from holes (h ⁺ _D35 ) in oxidation state D35, so that direct oxidation of part of BPA by h ⁺ _D35 can also occur. Meanwhile, except for a few recombinations between e ^- _CB and h ⁺ _D35 , most of the e ^- _CB was trapped by the dissolved oxygen (O ₂ ) on the surface of TiO ₂ to form superoxide radicals (· O ₂ ^- ), and then oxidatively degrade BPA. In addition, a part of ·O ₂ ^- was subsequently converted into H ₂ O ₂ and further formed hydroxyl radicals (·OH), and the higher oxidation potential of ·OH was more oxidative and contributed to the efficient oxidative degradation of BPA. Free radicals attack oxidized contaminants and produce several intermediates. Finally, the small molecule intermediates are completely mineralized to _CO2 and _H2O . Additionally, when h ⁺ _D35 directly oxidizes BPA or intermediates, the electrons reduce the oxidation state D35 to regenerate the dye, so the photocatalyst can re-enter the next photocatalytic cycle.

100 mL of aqueous BPA solution was added to the reactor, the pH of which was regulated by 0.1 M HCl or NaOH. The initial BPA concentration was 15 mg/L and the pH was 7. Before irradiation, adsorption experiments were performed in the dark for 30 min to achieve sufficient contact between BPA and photocatalyst to establish adsorption equilibrium.

Photocatalytic activity evaluation: The photocatalytic oxidation of BPA was carried out in a two-cell rectangular quartz reactor with a standard three-electrode setup. A 500 W xenon lamp with a filter (420 nm) was placed horizontally outside the reactor as a visible light source, and photons were used as the visible light source. The average light intensity on the surface of the D35-TiO ₂ nanocrystalline thin film in the reaction solution was measured by a densitometer to be 100 mW/cm ² , which is a standard sunlight intensity (AM1.5G). In order to maintain a constant reaction temperature, a cooling water circulation system was applied around the reactor, and the experiments were carried out with slow magnetic stirring. 100 mL of BPA was added to each reactor, the pH of which was regulated by 0.1 M HCl or NaOH. The initial BPA concentration was 15 mg/L and pH 7 unless otherwise stated. Before irradiation, adsorption experiments were performed in the dark for 30 min to achieve sufficient contact between BPA and photocatalyst to establish adsorption equilibrium. Finally, BPA concentration changes were monitored and analyzed by high performance liquid chromatography.

The experimental results show that the degradation of BPA by D35-TiO ₂ nanocrystalline films after 200 minutes under the irradiation of visible light (>400 nm) with a standard sunlight intensity, an initial concentration of BPA of 15 mg/L and an initial pH of 7 Efficiency is as high as 97%.

Figure 4 is a graph showing the comparison of the performance of D35-TiO ₂ nanocrystalline thin films and ordinary TiO ₂ nanoparticles in visible light catalytic degradation of BPA. It can be seen that the BPA molecule is relatively stable in early water, and its concentration does not change much after only 200 minutes of light, and ordinary TiO ₂ nanoparticles can only remove about 24%. However, the degradation efficiency of BPA by D35-TiO ₂ nanocrystalline film is as high as 97%. .

Figure 5 shows the stable photocatalytic performance of the D35- _TiO2 nanocrystalline film, the BPA degradation efficiency is almost consistent in five consecutive degradation experiments, which indicates that the photocatalytic activity of the D35- _TiO2 film is still maintained after five cycles good. In addition, photocatalysts in the form of thin films are easier to separate and recycle than suspended nanoparticles, which solves the problem of solid-liquid separation between catalysts and aqueous solutions in continuous photocatalytic degradation processes.

Although the present invention has been described in detail above with general description and specific embodiments, some modifications or improvements can be made on the basis of the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention fall within the scope of the claimed protection of the present invention.

Claims (10)

1. a preparation method of D35-TiO ₂ nanocrystalline thin film, is characterized in that, described preparation method comprises the steps: Step 1: On a hot stage at 550 °C, a dense crystalline _TiO2 hole blocking layer was deposited on a pre-cleaned FTO glass substrate by spray pyrolysis; Step 2: The colloidal TiO ₂ nanoparticles were loaded onto the dense crystalline TiO ₂ hole blocking layer described in step 1 by the blade coating method, and the operation was cycled three times and dried in an oven at 100 °C after each cycle 20 minutes; After that, the dried samples were placed in a muffle furnace for sintering at 550 °C for 60 minutes, then cooled to 90 °C naturally, and then the samples were immersed in a 35 mM _TiCl4 aqueous solution and placed in a 76 °C oven for 50 minutes, and then used Rinse the surface of the sample with deionized water, repeat the above sintering process again, and naturally cool to 70 °C; Step 3: Immerse the mesoporous TiO ₂ nanocrystalline film obtained in step 2 in an acetonitrile solution containing 0.5mM D35 dye for 10 hours, then rinse the sample with absolute ethanol and blow dry to obtain D35-TiO ₂ Nanocrystalline films. 2. The preparation method according to claim 1, wherein in step 1, the spray precursor solution is an isopropanol solution containing 0.15M butyl titanate and 3M acetylacetone. 3. preparation method according to claim 1 and 2, is characterized in that, in step 1, spray distance sample 4 centimeters, single spray time is 15 seconds, and spray cycle times is 20 times, and interval 60 times between each cycle. seconds to obtain the dense crystalline TiO ₂ hole blocking layer with a thickness of 200 nm. 4. A D35-TiO ₂ nanocrystalline thin film, characterized in that, the D35-TiO ₂ nanocrystalline thin film is formed by D35 dye molecules through a carboxyl group to form a chelating chemical bond to combine with the TiO ₂ surface, forming a uniform uniform on the entire TiO ₂ surface. Dye monolayer; The D35-TiO ₂ nanocrystalline film can degrade bisphenol A under the conditions of an initial concentration of bisphenol A of 15 mg/L and an initial pH of 7 under the irradiation of visible light, and the degradation of bisphenol A after 200 minutes The rate can exceed 97%. 5 . The D35-TiO ₂ nanocrystalline thin film according to claim 4 , wherein it is prepared by the preparation method according to any one of claims 1 to 3 . 6 . 6. Application of the D35-TiO ₂ nanocrystalline thin film according to claim 4 or 5 in photoelectric catalytic degradation of organic pollutants. 7 . The application according to claim 6 , wherein the organic pollutant is bisphenol A. 8 . 8. A method for photocatalytic degradation of bisphenol A, characterized in that, placing the D35- _TiO nanocrystalline film according to claim 4 or 5 in the sewage containing bisphenol A, under photocatalytic conditions, the bisphenol A Phenol A is degraded. 9 . The method according to claim 8 , wherein the initial concentration of the bisphenol A is 0.1-16 mg/L. 10 . The method according to claim 8 or 9, wherein the pH value of the sewage is 4-8.

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