Method for catalytic degradation of formaldehyde at room temperature

Abstract

The present application relates to a kind of room temperature catalytic formaldehyde high-efficiency degradation method, belong to formaldehyde catalytic degradation technical field.The photocatalyst of the present application is manganese dioxide / cesium tin iodine quantum dot composite catalyst, the solid-liquid ratio mg: μL of manganese dioxide and cesium tin iodine quantum dot solution is 0.5~1:1;Nanometer manganese dioxide catalyst is dispersed in n-hexane solvent by ultrasonic to obtain nanometer manganese dioxide catalyst dispersion liquid;Cesium tin iodine quantum dot is added to nanometer manganese dioxide catalyst dispersion liquid, and is dispersed by ultrasonic, so that cesium tin iodine quantum dot is uniformly loaded on the surface of nanometer manganese dioxide catalyst to obtain manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid;Manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid is uniformly coated on carrier, then the carrier coated with manganese dioxide / cesium tin iodine quantum dot composite catalyst is placed in formaldehyde atmosphere, at room temperature, with light or without light, catalytic formaldehyde is degraded to generate H2O and CO2.The composite catalyst of the present application can improve the degradation efficiency of room temperature formaldehyde.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for catalytically degrading formaldehyde at room temperature, and belongs to the technical field of catalytic degradation of formaldehyde. BACKGROUND

[0002] The source of formaldehyde in indoor air is outdoor and indoor. Chemicals produced by human life are released into the air, which will generate formaldehyde through a series of chemical reactions, and widely exist in outdoor air. Decorative materials and furniture are the indoor source of formaldehyde. Due to its low price, urea-formaldehyde resin is often used as a decorative material adhesive. In the environment with high temperature and high humidity, urea-formaldehyde resin adhesive is easy to release formaldehyde. The release period of formaldehyde in decorative materials is long, and its concentration usually needs to be reduced to 0.1 mg / m 3 Below.

[0003] Formaldehyde is a class I carcinogen, and the maximum allowable concentration of formaldehyde in civil housing is 0.07 and 0.1 mg / m 3 . The end treatment technology for indoor formaldehyde can be divided into adsorption method and catalytic oxidation method. The traditional adsorption method is to use materials with large specific surface area or porous structure to adsorb formaldehyde. This method converts formaldehyde from gas to solid storage, which does not essentially change the nature of formaldehyde, and also has problems such as slow adsorption rate for low concentration formaldehyde, low adsorption capacity, great influence of environmental temperature and humidity, and the need for regular replacement. The catalytic oxidation method can directly decompose formaldehyde into carbon dioxide and water, which is a real sense of formaldehyde purification technology. Therefore, the development of economical and efficient catalytic decomposition materials is the research focus of indoor formaldehyde purification.

[0004] In the research of formaldehyde catalytic decomposition materials, manganese dioxide (MnO2) has good application prospect due to its high low-temperature catalytic activity and low toxicity and low cost. The temperature required for manganese dioxide to catalytically degrade formaldehyde is still high, which is not suitable for application in actual scenes; the degradation at room temperature needs to be loaded on a noble metal base, which is high in cost. Therefore, it is urgent to explore a method for degrading formaldehyde at room temperature and saving cost. SUMMARY

[0005] In view of the problem that formaldehyde is difficult to be catalytically degraded at room temperature in the prior art, the present application provides a method for catalytically degrading formaldehyde at room temperature, that is, a double-semiconductor-phase composite catalyst is formed by compounding a nano-manganese dioxide catalyst and cesium tin iodine quantum dots, which greatly improves the light response of the catalyst, improves the efficiency of formaldehyde degradation at room temperature, and the perovskite material (cesium tin iodine quantum dots) used is a lead-free perovskite, which is non-toxic and harmless and will not harm the human body.

[0006] The application discloses a method for efficiently degrading formaldehyde at room temperature, and a photocatalyst is a manganese dioxide / cesium tin iodine quantum dot composite catalyst.

[0007] The specific steps of the method are as follows:

[0008] (1) dispersing the nanometer manganese dioxide catalyst in a n-hexane solvent to obtain a nanometer manganese dioxide catalyst dispersion liquid;

[0009] (2) adding the cesium tin iodine quantum dots into the nanometer manganese dioxide catalyst dispersion liquid, and ultrasonically dispersing the same to uniformly load the cesium tin iodine quantum dots on the surface of the nanometer manganese dioxide catalyst to obtain a manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid;

[0010] (3) uniformly coating the manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid on a carrier, and then placing the carrier coated with the manganese dioxide / cesium tin iodine quantum dot composite catalyst in a formaldehyde atmosphere, and catalytically degrading the formaldehyde into H2O and CO2 at room temperature under light or without light.

[0011] In the step (1), the particle size of the nanometer manganese dioxide catalyst is 100-500 nm.

[0012] Preferably, the concentration of the nanometer manganese dioxide catalyst dispersion liquid in the step (1) is 5-10 g / L.

[0013] Preferably, the coating amount of the manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid on the carrier in the step (3) is 0.04-0.06 mL / cm 2 .

[0014] Preferably, the carrier in the step (3) is a fiber carrier.

[0015] Under the light condition, the content of the formaldehyde in the formaldehyde atmosphere can be not higher than 4 ppm, the manganese dioxide / cesium tin iodine quantum dot composite catalyst has excellent response to the formaldehyde degradation reaction, can degrade the ultra-low concentration formaldehyde at room temperature, and the degradation efficiency of the low concentration formaldehyde (4 ppm and lower) can reach 50% or more within 1 h at room temperature.

[0016] Preferably, the nanometer manganese dioxide catalyst can be synthesized by using manganese sulfate and concentrated hydrochloric acid as raw materials through a hydrothermal method, and the particle size of the nanometer manganese dioxide catalyst is 100-500 nm.

[0017] Preferably, the cesium tin iodine quantum dots can be synthesized by using tin oxalate and cesium carbonate as precursors and oleic acid and oleylamine as ligands through a hot injection method.

[0018] The principle of the formaldehyde degradation at room temperature of the application (see Figure 2) : the adsorbed oxygen species and hydroxyl groups on the surface of manganese dioxide are partially oxidized by O2 in the gas phase, O2 forms active oxygen species (O 2- / O - ), formaldehyde is adsorbed on the surface of the catalyst to form formate species; O 2- / O - reacts with the formate species to generate H2O and CO2, and the nanometer manganese dioxide catalyst is partially reduced; after the nanometer manganese dioxide catalyst is compounded with cesium tin iodine quantum dots, a manganese dioxide / cesium tin iodine quantum dot composite catalyst is formed, an S-type heterojunction is formed, the light response capability of the composite catalyst is improved, and the light absorption range is also strengthened; when the composite catalyst generates a response under light, the formed double-semiconductor system separates the electron-hole pairs in the reaction, and the photo-generated electrons do not quickly fall back to the valence band from the conduction band of manganese dioxide to recombine with the holes, but recombine with the holes on the valence band of the cesium tin iodine, so that the holes on the manganese dioxide perform oxidation reactions to generate the required superoxide and hydroxyl radicals for degrading formaldehyde, thereby improving the efficiency of degrading formaldehyde.

[0019] The beneficial effects of the present application are:

[0020] (1) The manganese dioxide / cesium tin iodine quantum dot composite catalyst generates a response under light, the formed double-semiconductor system separates the electron-hole pairs in the reaction, the part of the manganese dioxide that is oxidized in the reaction is reduced, so that the catalytic degradation reaction of formaldehyde can continue to proceed, and the efficiency of degrading formaldehyde is improved.

[0021] (2) The nanometer manganese dioxide catalyst and the cesium tin iodine quantum dots are compounded to form a double-semiconductor phase composite catalyst, which greatly improves the light response of the catalyst and improves the efficiency of degrading formaldehyde at room temperature, and under light conditions, the catalyst can catalyze the efficient degradation of ultra-low concentration formaldehyde (4 ppm and lower). BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) image and an energy spectrum diagram of the manganese dioxide / cesium tin iodine quantum dot composite catalyst;

[0023] Figure 2A schematic diagram of the principle of photocatalytic degradation of formaldehyde by the manganese dioxide / cesium tin iodine quantum dot composite catalyst at room temperature;

[0024] Figure 3 A graph of the efficiency of the single-phase nanometer manganese dioxide catalyst in degrading formaldehyde for the comparative example;

[0025] Figure 4 A graph of the efficiency of the manganese dioxide / cesium tin iodine quantum dot composite catalyst in degrading formaldehyde for Example 1. DETAILED DESCRIPTION

[0026] The application will be further described in detail below in conjunction with specific embodiments, but the scope of protection of the application is not limited to the content described.

[0027] The comparative example is a method for degrading formaldehyde by a single-phase nanometer manganese dioxide catalyst at room temperature, and the photocatalyst is a single-phase nanometer manganese dioxide catalyst. The nanometer manganese dioxide catalyst is synthesized by a hydrothermal method using manganese sulfate and concentrated hydrochloric acid as raw materials, and the particle size of the nanometer manganese dioxide catalyst is 100 nm.

[0028] (1) The nanometer manganese dioxide catalyst is ultrasonically dispersed in a n-hexane solvent to obtain a nanometer manganese dioxide catalyst dispersion liquid. The concentration of the nanometer manganese dioxide catalyst dispersion liquid is 5 g / L.

[0029] (2) The nanometer manganese dioxide catalyst dispersion liquid is uniformly coated on a carrier (cotton cloth) to ensure that it has a large surface area and can exhibit good catalytic degradation performance. Then, the carrier (cotton cloth) coated with the nanometer manganese dioxide catalyst is placed in a formaldehyde atmosphere, and catalytic degradation of formaldehyde to generate H2O and CO2 is carried out at room temperature under light or without light. The coating amount of the nanometer manganese dioxide catalyst dispersion liquid on the carrier (cotton cloth) is 0.06 mL / cm 2 .

[0030] The efficiency of the single-phase nanometer manganese dioxide catalyst in degrading formaldehyde is shown in Figure 3 At room temperature and normal pressure, the degradation efficiency of the single-phase nanometer manganese dioxide catalyst for formaldehyde is very low, and the light response effect is very poor.

[0031] Example 1: A method for efficiently degrading formaldehyde at room temperature, in which the photocatalyst is a manganese dioxide / cesium tin iodine quantum dot composite catalyst (see Figure 1 ), and the solid-liquid ratio mg: μL of manganese dioxide to cesium tin iodine quantum dot solution is 0.9:1. The nanometer manganese dioxide catalyst is synthesized by a hydrothermal method using manganese sulfate and concentrated hydrochloric acid as raw materials, and the particle size of the nanometer manganese dioxide catalyst is 100 nm. The cesium tin iodine quantum dots are synthesized using tin oxalate and cesium carbonate as precursors and oleic acid and oleylamine as ligands.

[0032] The specific steps of the method are as follows:

[0033] (1) ultrasonic dispersion of the nanometer manganese dioxide catalyst in a n-hexane solvent to obtain a nanometer manganese dioxide catalyst dispersion liquid; wherein the concentration of the nanometer manganese dioxide catalyst dispersion liquid is 5 g / L;

[0034] (2) adding cesium tin iodine quantum dots to the nanometer manganese dioxide catalyst dispersion liquid and ultrasonic dispersion to uniformly load the cesium tin iodine quantum dots on the surface of the nanometer manganese dioxide catalyst to obtain a manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid;

[0035] (3) uniformly coating the manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid on a carrier (gauze) to ensure a large surface area and good catalytic degradation performance, and then placing the carrier (gauze) coated with the manganese dioxide / cesium tin iodine quantum dot composite catalyst in a formaldehyde atmosphere to catalytically degrade the formaldehyde into H2O and CO2 at room temperature with or without light; wherein the coating amount of the manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid on the carrier (gauze) is 0.04 mL / cm2. 2 ;

[0036] The degradation efficiency of the manganese dioxide / cesium tin iodine quantum dot composite catalyst for formaldehyde is shown in Figure 2 Under room temperature and without light, the degradation efficiency of the manganese dioxide / cesium tin iodine quantum dot composite catalyst is significantly improved; under room temperature and with light, the manganese dioxide / cesium tin iodine quantum dot composite catalyst has excellent light response performance and can catalytically degrade ultra-low concentration formaldehyde (4 ppm or lower) at room temperature; the degradation efficiency of the manganese dioxide / cesium tin iodine quantum dot composite catalyst for low concentration formaldehyde (4 ppm or lower) can reach 60% within 1 h at room temperature.

[0037] Example 2: A method for catalytically degrading formaldehyde at room temperature, wherein the photocatalyst is a manganese dioxide / cesium tin iodine quantum dot composite catalyst, the solid-liquid ratio mg: μL of manganese dioxide and cesium tin iodine quantum dot solution is 0.7:1; the nanometer manganese dioxide catalyst is a nanometer manganese dioxide catalyst with a particle size of 300 nm synthesized by a hydrothermal method using manganese sulfate and concentrated hydrochloric acid as raw materials; and the cesium tin iodine quantum dots are synthesized by using tin oxalate and cesium carbonate as precursors and oleic acid and oleylamine as ligands.

[0038] The specific steps of the method are as follows:

[0039] (1) ultrasonic dispersion of the nanometer manganese dioxide catalyst in a n-hexane solvent to obtain a nanometer manganese dioxide catalyst dispersion liquid; wherein the concentration of the nanometer manganese dioxide catalyst dispersion liquid is 5 g / L;

[0040] (2) adding cesium tin iodine quantum dots to the nanometer manganese dioxide catalyst dispersion liquid and ultrasonic dispersion to uniformly load the cesium tin iodine quantum dots on the surface of the nanometer manganese dioxide catalyst to obtain a manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid;

[0041] (3) The manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid is uniformly coated on the carrier (gauze) to ensure that it has a large surface area and can exert a large catalytic degradation performance. Then, the carrier (gauze) coated with the manganese dioxide / cesium tin iodine quantum dot composite catalyst is placed in a formaldehyde atmosphere, and catalyzes the degradation of formaldehyde into H2O and CO2 at room temperature under light or no light conditions. The coating amount of the manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid on the carrier (gauze) is 0.05 mL / cm 2 ;

[0042] Under room temperature and no light conditions, the degradation efficiency of the manganese dioxide / cesium tin iodine quantum dot composite catalyst is significantly improved. Under room temperature and light conditions, the manganese dioxide / cesium tin iodine quantum dot composite catalyst has excellent light response performance and can catalyze the efficient degradation of ultra-low concentration formaldehyde (4 ppm and lower) at room temperature. The degradation efficiency of low concentration formaldehyde (4 ppm and lower) can reach 65% within 1 h at room temperature.

[0043] Example 3: A method for catalyzing the efficient degradation of formaldehyde at room temperature, in which the photocatalyst is a manganese dioxide / cesium tin iodine quantum dot composite catalyst, and the solid-liquid ratio mg: μL of manganese dioxide and cesium tin iodine quantum dot solution is 0.5:1. The nanometer manganese dioxide catalyst is synthesized by a hydrothermal method using manganese sulfate and concentrated hydrochloric acid as raw materials, and the particle size of the nanometer manganese dioxide catalyst is 500 nm. The cesium tin iodine quantum dot is synthesized by using tin oxalate and cesium carbonate as precursors and oleic acid and oleylamine as ligands.

[0044] The specific steps of the method are as follows:

[0045] (1) The nanometer manganese dioxide catalyst is ultrasonically dispersed in a n-hexane solvent to obtain a nanometer manganese dioxide catalyst dispersion liquid. The concentration of the nanometer manganese dioxide catalyst dispersion liquid is 5 g / L.

[0046] (2) The cesium tin iodine quantum dot is added to the nanometer manganese dioxide catalyst dispersion liquid, and ultrasonically dispersed to uniformly load the cesium tin iodine quantum dot on the surface of the nanometer manganese dioxide catalyst to obtain a manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid.

[0047] (3) The manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid is uniformly coated on the carrier (gauze) to ensure that it has a large surface area and can exert a large catalytic degradation performance. Then, the carrier (gauze) coated with the manganese dioxide / cesium tin iodine quantum dot composite catalyst is placed in a formaldehyde atmosphere, and catalyzes the degradation of formaldehyde into H2O and CO2 at room temperature under light or no light conditions. The coating amount of the manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion liquid on the carrier (gauze) is 0.06 mL / cm 2 ;

[0048] The degradation efficiency of the manganese dioxide / cesium tin iodine quantum dot composite catalyst is significantly improved under room temperature and no light condition; the manganese dioxide / cesium tin iodide quantum dot composite catalyst has excellent light response performance under room temperature and light condition, and can catalyze the efficient degradation of ultra-low concentration formaldehyde (4 ppm and lower) at room temperature; the degradation efficiency of low concentration formaldehyde (4 ppm and lower) can reach 70% within 1 h at room temperature.

[0049] The specific embodiments of the application are described in detail above, but the application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the application.

Claims

1. A method for the efficient degradation of formaldehyde at room temperature, characterized in that: The photocatalyst is a manganese dioxide / cesium tin iodine quantum dot composite catalyst, and the solid-liquid ratio of manganese dioxide to cesium tin iodine quantum dot solution is 0.5 to 1:1 (mg:μL). The specific steps of this method are as follows: (1) The nano-manganese dioxide catalyst was ultrasonically dispersed in n-hexane solvent to obtain a nano-manganese dioxide catalyst dispersion. (2) Add cesium tin iodine quantum dots to the nano manganese dioxide catalyst dispersion and disperse by ultrasonication so that the cesium tin iodine quantum dots are uniformly loaded on the surface of the nano manganese dioxide catalyst to obtain a manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion. (3) The manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion was uniformly coated on the carrier, and then the carrier coated with the manganese dioxide / cesium tin iodine quantum dot composite catalyst was placed in a formaldehyde atmosphere. At room temperature, the formaldehyde was catalyzed to degrade into H2O and CO2 under light or no light conditions.

2. The method for efficient catalytic degradation of formaldehyde at room temperature according to claim 1, characterized in that: Step (1) The particle size of the nano-manganese dioxide catalyst is 100-500 nm.

3. The method for efficient catalytic degradation of formaldehyde at room temperature according to claim 1, characterized in that: Step (1) The concentration of the nano-manganese dioxide catalyst dispersion is 5-10 g / L.

4. The method for efficient catalytic degradation of formaldehyde at room temperature according to claim 1, characterized in that: In step (3), the coating amount of the manganese dioxide / cesium tin iodine quantum dot composite catalyst dispersion on the support is 0.04–0.06 mL / cm². 2 .

5. The method for efficient catalytic degradation of formaldehyde at room temperature according to claim 1, characterized in that: Step (3) Under light conditions, the formaldehyde content in the formaldehyde atmosphere should not exceed 4 ppm.

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