阅读说明：本技术 一种以锡酸钡为载体负载硫化镉量子点的光催化剂及其制备方法和应用 (Photocatalyst taking barium stannate as carrier and loading cadmium sulfide quantum dots, and preparation method and application thereof ) 是由 戴文新 宋昕杰 江文杰 付贤智 员汝胜 张子重 于 2021-09-13 设计创作，主要内容包括：本发明公开了一种以锡酸钡为载体负载硫化镉量子点的光催化剂及其制备方法和应用。其是通过静电自组装将合成的带负电荷的CdS QDs负载在具有光吸收且带正电荷的BaSnO-(3)钙钛矿半导体载体上而制得所述负载型光催化剂。与BaSnO-(3)相比,CdS QDs/BaSnO-(3)催化剂在可见光条件下光催化去除NO的性能、稳定性及NO-(3)～(-)的选择性都有明显的提高。本发明中通过静电自组装的方法将CdS QDs负载在BaSnO-(3)载体上,其制备方法简单易行,更有利于推广应用。(The invention discloses a photocatalyst taking barium stannate as a carrier to load cadmium sulfide quantum dots, and a preparation method and application thereof. The method is characterized in that synthesized negatively charged CdS QDs are loaded on BaSnO with light absorption and positive charge through electrostatic self-assembly 3 The supported photocatalyst is prepared on a perovskite semiconductor carrier. With BaSnO 3 In contrast, CdS QDs/BaSnO 3 Performance and stability of catalyst for removing NO under visible light photocatalysis and NO 3 ‑ The selectivity of the catalyst is obviously improved. In the invention, CdS QDs are loaded on BaSnO by an electrostatic self-assembly method 3 On the carrier, the preparation method is simple and easy to implement, and is more beneficial to popularization and application.)

1. A photocatalyst taking barium stannate as a carrier to load cadmium sulfide quantum dots is characterized in that: the photocatalyst is BaSnO₃Is a carrier, and CdS QDs is a high-dispersion supported catalyst of an active component.

2. The photocatalyst taking barium stannate as a carrier and loading cadmium sulfide quantum dots as claimed in claim 1, is characterized in that: the photocatalyst contains active ingredient CdS QDs 1.0-5.0 wt%, and BaSnO in balance₃And (3) a carrier.

3. A method for preparing the photocatalyst which takes barium stannate as a carrier and loads cadmium sulfide quantum dots according to any one of claims 1 to 2, and is characterized in that: the method comprises the following steps:

(1) in an oil bath with SnCl₄·5H₂O、Ba(NO₃)₂·6H₂O and H₂O₂The BaSnO is prepared by taking the raw materials as raw materials, quickly mixing and stirring the raw materials, adding ammonia water to adjust the pH, washing, drying and calcining the mixture₃A carrier;

(2) in a water bath with CdCl₂·2.5H₂O and mercaptopropionic acid are taken as raw materials, NaOH is added to adjust the pH after the raw materials are quickly mixed and stirred, and then freshly prepared Na is added₂S·9H₂O and H₂O₂Washing with ethanol, drying, and dissolving in deionized water to obtain CdS QDs water solution;

(3) BaSnO prepared in step (1) by utilizing electrostatic self-assembly method₃And (3) loading the CdS QDs prepared in the step (2) on a carrier to obtain the photocatalyst which takes barium stannate as the carrier and loads cadmium sulfide quantum dots.

4. The production method according to claim 3, characterized in that: SnCl in step (1)₄·5H₂The amount of O is 2.805 g, Ba (NO)₃)₂·6H₂The dosage of O is 2.091 g and H₂O₂The dosage of the compound is 160 mL, and the pH value of the compound is adjusted to 9-10 by ammonia water.

5. The production method according to claim 3, characterized in that: the calcination in the step (1) is specifically calcination in a muffle furnace at 500 ℃ for 4 h.

6. The production method according to claim 3, characterized in that: CdCl in step (2)₂·2.5H₂The amount of O is 0.228g, the amount of MPA is 0.15mL and Na₂S·9H₂The amount of O was 0.240 g and the pH was adjusted to 10-11 with NaOH.

7. The application of the photocatalyst taking barium stannate as a carrier to load cadmium sulfide quantum dots, which is disclosed by claim 1, is characterized in that: the BaSnO₃The photocatalyst of CdS QDs loaded on the carrier is applied to removing low-concentration NO in the atmospheric environment or the room.

8. The application of the photocatalyst taking barium stannate as a carrier to load cadmium sulfide quantum dots, which is disclosed by claim 6, is characterized in that: the BaSnO₃Visible light is introduced into a reaction system for catalyzing and oxidizing NO at room temperature by the photocatalyst of the carrier loaded with CdS QDs.

Technical Field

The invention belongs to the field of environmental protection and air purification reaction, and particularly relates to a photocatalyst taking barium stannate as a carrier and loading cadmium sulfide quantum dots, a preparation method and application thereof.

Background

Since the last 70 s, environmental pollution has been aggravated such as acid rain problem, greenhouse effect, ozone layer hole problem, and water pollution, which are environmental problems that have seriously endangered the normal life and health of human beings. Wherein, in urban air pollution in China, the proportion of automobile exhaust emission is over 70 percent. Since the first automobile was born in 1886, the highly developed logistics technology and transportation technology of automobiles brings convenience and rapidness to human beings, the automobiles become indispensable transportation vehicles for human beings, and the total number of private automobiles in China in 2020 reaches 2.6 hundred million according to incomplete statistics. Although the state has strict standards for the emission of automobile exhaust, certain toxic gases such as carbon monoxide, hydrocarbons, lead and sulfur oxides, especially nitrogen oxide NO, are inevitably present in the automobile exhaust_x. In addition to being derived from automobile exhaust, NO_xAnd combustion of stationary power fuels (e.g., coal, petroleum, etc.) from large-scale plants. NO_xAs one of the main pollutant sources causing air pollution, it has numerous negative effects on the ecological environment, such as acid rain, photochemical smog, ozone layer depletion, greenhouse effect (indirect effect), and the like. Chronic pharyngolaryngitis, chronic bronchitis and the like caused by long-term exposure of human beings to nitric oxides can also cause neurasthenia syndrome and tooth erosion diseases of different degrees. In addition, nitric oxide can also induce lung cell carcinogenesis. The inhaled nitric oxide of human beings has the stimulation effect on respiratory tract and can cause methemoglobinemia.

At present, NO_xThe removal of (95% NO) mainly includes pretreatment of fuel combustion, improvement of combustion mode, and post-treatment of tail gas. The pretreatment method of combustion mainly refers to denitrification treatment of fuel, thereby reducing tail gas NO in the combustion process_xThe amount of the produced nitrogen is limited by the cost and the process, so the existing denitrification process is not well developed and researched. The improvement of the combustion mode mainly adopts an air staged combustion technology, a fuel staged combustion technology, a smoke circulating and re-combusting technology and the like. The automobile exhaust mainly relates to the internal purification technology, such as improving the structure, working mode and control device of the engine, so as to achieve the purposes of improving the combustion efficiency and reducing NO_xThe amount of discharge of (c). The tail gas aftertreatment technology still reduces NO_xThe most effective method is the content, and the two researches, namely catalytic oxidation and catalytic reduction, are most widely applied.

Catalytic oxidation of NO and conventional NO_xThe absorption is quite similar, mainly that NO is directly oxidized to form NO of a hydrophilic phase under the action of a catalyst at lower concentration₃ ^-And NO₂ ^-Adsorbing on the surface of the solid-phase catalyst, and finally transferring to a liquid phase for removal through water washing. It mainly involves the following reactions:

in addition, the photocatalytic oxidation removal of low-concentration NO has good application prospect indoors and outdoors, the low-concentration NO can be directly oxidized only by indoor light or outdoor sunlight, and then nitrate and nitrite adsorbed on the surface of the catalyst are washed away by indoor manual wiping or outdoor rainwater washing, so that the photocatalyst shows good photocatalytic activity again, and the reuse of the catalyst is facilitated.

In recent years, many materials (e.g., TiO)₂Bibbr, etc.) have been used to photocatalyze NO oxidation, but most materials focus only on increasing NO removal, rarelyThere is a research interest in the selectivity of the oxidation products, in particular in the inhibition of the toxic by-product NO₂Is generated. And according to the report, the product NO of NO catalytic oxidation₂Is 5 times as toxic as NO. Obviously, we must control the toxic by-product NO while removing NO catalytically₂The amount of production of (c). In addition, the stability of the catalyst is a measure of whether the catalyst can be used further.

Therefore, how to improve the reaction activity and stability of the photocatalytic removal of NO and reduce NO₂The conversion rate of (A) has important significance for purifying low-concentration NO in atmospheric environment or indoor.

Disclosure of Invention

The invention provides a method for realizing efficient photocatalytic removal of low-concentration NO at room temperature by visible light irradiation, aims to overcome the defect of photocatalytic removal of NO at room temperature of the photocatalyst, improves the activity and stability of the catalyst at room temperature and the selectivity of the catalyst on nitrate radical, and provides a method for removing NO by BaSnO₃A preparation method and application of a photocatalyst for loading CdS QDs on a carrier. The present invention is directed to an initial BaSnO₃The perovskite semiconductor catalyst has the problems of low activity, selectivity and stability, CdS QDs with visible light response are loaded on the catalyst, and visible light is introduced in the reaction process, so that the performance of catalyzing and removing NO is obviously improved, the selectivity and stability are enhanced, and the preparation method of the catalyst is simple and easy to implement and is favorable for popularization and application.

In order to achieve the purpose, the invention adopts the following technical scheme:

a photocatalyst with barium stannate as carrier and cadmium sulfide quantum dots is prepared from BaSnO₃The high-dispersion load-type low-temperature photocatalyst is a carrier and is formed by taking CdS QDs as main active components; wherein the content of the main active component CdS QDs is 1.0-5.0 wt%, and the balance BaSnO₃And (3) a carrier.

The supported CdS QDs photocatalyst can realize the NO removal efficiency of 87.4% under the conditions of visible light and 25 ℃, and has excellent stability and nitrate radical selectivity.

The barium stannate is used as the carrier for loadingThe preparation method of the photocatalyst of the cadmium sulfide quantum dot adopts SnCl₄·5H₂O and Ba (NO)₃)₂·6H₂O is taken as a raw material to obtain a peroxide precursor by a coprecipitation method, and then the peroxide precursor is washed and calcined to obtain BaSnO₃A carrier; BaSnO obtained by using electrostatic self-assembly method₃Active components CdS QDs are loaded on the carrier. The preparation method comprises the following specific steps:

(1) in an oil bath, to 100 mL H₂O solution and 60 mL H₂O₂2.805 g of SnCl was added to the mixed solution₄·5H₂O and 2.091 g Ba (NO)₃)₂·6H₂O, quickly stirring for 0.5h, then adding ammonia water to adjust the PH to 9-10, washing by centrifugal water, drying in an oven at 80 ℃ for 8 h, and then calcining in a muffle furnace at 500 ℃ for 4 h to prepare white BaSnO₃A carrier;

(2) in a three-necked flask, 20 mL of H was charged₂0.228g CdCl was added to the O solution₂·2.5H₂O and 0.15mL MPA (mercaptopropionic acid) and the pH was adjusted to 10-11 by dropwise addition of NaOH solution. The air in the three-neck flask was then evacuated and replaced with argon (Ar). Under rapid stirring, freshly prepared Na₂S solution (0.24 g Na)₂S+20 mL H₂O) was added to the mixture solution at room temperature. Subsequently, the reaction mixture was heated to 100 ℃ and stirred for a further 0.5 h. After cooling, adding ethanol, centrifuging to separate out the product, and finally dispersing the product in water to form bright yellow CdS QDs aqueous solution.

(3) 1 g of the BaSnO prepared in the step (1) positively charged by ultrasonic treatment₃The carrier was dispersed in 200 mL of deionized water. Then, dropwise adding a certain amount of the CdS quantum dot aqueous solution prepared in the step (2) with negative charge into the dispersion. The mixture was stirred at room temperature for 12 h. Subsequently, the resultant product was collected by centrifugation, washed several times with deionized water, and dried in an oven at 60 ℃.

Wherein the concentration of CdS QDs aqueous solution is 1 mg/mL^-1The concentration of NaOH was 5 mol/L.

The supported CdS QDs catalyst is used at room temperatureThe conversion of low concentration NO is removed. The obtained CdS QDs/BaSnO₃The catalyst can realize the high-efficiency photocatalytic removal of low-concentration NO at room temperature under the irradiation of visible light, and the semiconductor catalyst is expected to be prepared into a smearing type, and the preparation method is simple, convenient and feasible, and is more favorable for popularization and application.

The invention has the following remarkable advantages:

(1) the semiconductor composite has excellent visible light absorption capability, can excite generation of electron-hole pairs under irradiation of visible light, and further promotes generation of hydroxyl free radicals (. OH) and superoxide free radicals (. O)₂ ^-) Thereby promoting the generation of these reactive oxygen species with the reactant molecules NO and O₂The activity of catalyzing NO under the conditions of visible light and room temperature is improved.

(2) The invention uses BaSnO with certain electropositivity₃The perovskite semiconductor is used as a carrier, and CdS quantum dots with electronegativity are loaded on the carrier, so that the electrostatic self-assembly method and the application are simple and easy to implement, and the popularization and the application are facilitated.

Drawings

FIG. 1 shows the 3wt% CdS QDs/BaSnO obtained in example 1₃XRD pattern of (a);

FIG. 2 shows the 3wt% CdS QDs/BaSnO obtained in example 1₃Ultraviolet-diffuse reflectance spectrogram of (1);

FIG. 3 shows the 3wt% CdS QDs/BaSnO obtained in example 1₃A TEM image of (B);

FIG. 4 shows the 3wt% CdS QDs/BaSnO obtained in example 1₃Zeta potential map of (a);

FIG. 5 shows the 3wt% CdS QDs/BaSnO obtained in example 1₃Graph of photocatalytic NO oxidation performance.

Detailed Description

In order to make the aforementioned features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below, but the present invention is not limited thereto.

Example 1

3wt% CdS QDs/ BaSnO₃Preparation of the catalyst

(1) In an oil bath, to 100 mL H₂O solution and 60 mL H₂O₂2.805 g of SnCl was added to the mixed solution₄·5H₂O and 2.091 g Ba (NO)₃)₂·6H₂O, quickly stirring for 0.5h, then adding ammonia water to adjust the PH to 9-10, washing by centrifugal water, drying in an oven at 80 ℃ for 8 h, and then calcining in a muffle furnace at 500 ℃ for 4 h to prepare white BaSnO₃A carrier;

(2) in a three-necked flask, 20 mL of H was charged₂0.228g CdCl was added to the O solution₂·2.5H₂O and 0.15mL MPA, and the pH was adjusted to 10-11 by dropwise addition of a 5M NaOH solution. The air in the three-neck flask was then evacuated and replaced with argon (Ar). Under rapid stirring, freshly prepared Na₂Aqueous S solution (0.24 g Na)₂S+20 mL H₂O) was added to the mixture solution at room temperature. Subsequently, the reaction mixture was heated to 100 ℃ and stirred for a further 0.5 h. After cooling, adding ethanol, centrifuging to separate out product, and dispersing in corresponding deionized water to obtain bright yellow CdS QDs water solution (1 mg. mL)^-1）。

(3) 1 g of BaSnO prepared by ultrasonic treatment₃The carrier was dispersed in 200 mL of deionized water. Then, 30 mL of the CdS quantum dot aqueous solution prepared in step (2) was added dropwise to the dispersion. The mixture was stirred at room temperature for 12 h. Subsequently, the resultant product was collected by centrifugation, washed several times with deionized water, and dried in an oven at 60 ℃.

Example 2

Evaluation of catalyst Performance

The performance evaluation of the catalyst is carried out in a self-designed miniature fixed bed normal pressure continuous reaction device, and the reaction device consists of a gas distribution system, a miniature quartz reaction tube, a humidifying system, a circulating condensing system, a temperature control display and a xenon lamp (420 nm < lambda < 760 nm). Wherein the micro quartz reactor is a square sleeve double-layer structure, the size of an inner tube filled with a catalyst is 20 mm multiplied by 0.5 mm, and circulating water is introduced into the outer layer of the quartz reactor to control the reaction temperature.

For the catalytic oxidation of NO, 0.4 g of particles having a size of about 0Filling a catalyst with the particle size of 2-0.3 mm (60-80 meshes) in a quartz reactor, controlling the reaction temperature to be 25 ℃ by using a circulating water bath, controlling the concentration of NO in reaction airflow to be 10 ppm, and filling O in the reaction airflow₂21.0 vol%, the balance being N₂The relative humidity of the reaction gas was controlled to be around 50% (RH = 50%), and the gas flow rate was controlled to be 100 mL/min (GHSV = 30,000 h)^-1) Covering the reactor with aluminum foil for dark reaction, taking NO concentration of 0.5h as equilibrium value, introducing visible light for 0.5h under the same condition, and introducing tail gas via Thermo Scientific Model 42i NO_xAnalyzer online recording NO and NO₂The concentration of (c) is varied. The NO conversion was calculated as follows:

here, [ NO ]]_inAnd [ NO]_outRespectively the NO concentration at the inlet and outlet.

The amount of nitrate and nitrite accumulated during the catalytic oxidation of NO was determined by ion chromatography on the Thermo Fisher Dionex Aquion model. The specific method comprises the following steps: the catalyst sample after continuous reaction is fully immersed in 100 mL of deionized water, washed and filtered to obtain supernatant, and then 5mL of the supernatant is filled into an ion chromatography tube for sample injection analysis. Total NO removal: (n _NO) And NO₂Amount of formation (n _NO2) Calculated using the following formula:

here, ƒ is the gas flow rate in the normal state,Φ _NOis the concentration of the NO at the inlet port,Φ _NOiis the concentration of NO at the gas outlet,Φ _NO2NO at the outlet₂The concentration of (c).

According to this method, raw BaSnO was evaluated separately₃And 3wt% CdS QDs/BaSnO₃The performance of the catalyst for removing NO by photocatalytic oxidation of (1) is shown in the following table:

TABLE 1 BaSnO under visible light₃And 3wt% CdS QDs/BaSnO₃Performance of removing NO by photocatalytic oxidation and product attribution

The results in the above table show that the reaction is comparable to the initial BaSnO₃Catalyst, 3wt% CdS QDs/BaSnO₃Has greatly improved conversion rate of NO and toxic by-product NO₂The amount of produced is greatly reduced, and NO containing the highest valence state N element₃ ^-The selectivity of (A) is also greatly increased. Therefore, the load of CdS QDs can improve the performance and selectivity of the catalyst for photocatalytic oxidation of NO.

FIG. 1 shows BaSnO obtained₃And 3wt% CdS QDs/BaSnO₃XRD pattern of the catalyst. As can be seen from FIG. 1, due to the low loading of CdS QDs, no CdS-related diffraction front appears in the XRD spectrum of the catalyst, which also indicates that the CdS QDs in the catalyst are uniformly dispersed without affecting BaSnO₃The crystal structure of (1).

FIG. 2 shows the BaSnO obtained₃And 3wt% CdS QDs/BaSnO₃Ultraviolet-visible diffuse reflectance spectrum of the catalyst. As can be seen from FIG. 2, the catalyst support BaSnO₃The catalyst has good light absorption only in an ultraviolet region, but after the CdS QDs are loaded, the absorption of the catalyst on visible light is enhanced, which shows that the loaded catalyst can better utilize the visible light and play a role in promoting light.

FIG. 3 shows the resulting 3wt% CdS QDs/BaSnO₃Transmission electron micrograph of catalyst. As can be seen from FIG. 3, the catalyst presents a spherical morphology and the surface is uniformly loaded with a certain amount of CdS QDs, which is helpful for mass transfer of reactants for NO and O₂Has certain promotion effect on the adsorption and activation of the active carbon.

FIG. 4 shows the obtained CdS QDs as load and BaSnO as carrier₃Zeta potential diagram of (2). As can be seen from FIG. 4, the supported CdS QDs are negatively charged and the carriers BaSnO₃The opposite electric property of the positive charge facilitates the electrostatic self-assembly in the solutionStabilized CdS QDs/BaSnO₃A catalyst.

FIG. 5 shows the resulting 3wt% CdS QDs/BaSnO₃NO oxidation activity profile of the catalyst. As can be seen from fig. 5, the catalyst has substantially NO activity under dark conditions, but the conversion of NO is significantly increased under visible light conditions, which represents excellent activity of the catalyst under visible light. While the toxic by-product NO₂The yield of (a) is low and the catalyst still has a good activity after 5 cycles, which also represents the excellent selectivity and stability of the catalyst.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.