Composite material used for catalyzing and degrading nitrogen oxide and preparation method and application thereof

Abstract

The invention discloses a composite material used for catalyzing and degrading nitrogen oxide and its preparation method and application thereof. The invention of the hollow g-C.sub.3N.sub.4 nanospheres/reduced graphene oxide composite-polymer carbonized nanofiber material is prepared as follow: 1) the preparation of silica nanospheres; 2) the preparation of hollow g-C.sub.3N.sub.4 nanospheres; 3) the preparation of graphene oxide; 4) the preparation of surface modified hollow g-C.sub.3N.sub.4 nanoparticles preparation; 5) the preparation of composites; 6) the preparation of composite-polymer carbon nanofiber material. The raw materials used in the process is low cost and easy to get; the operation of the invention is simple and convenient without the use of expensive equipment in the whole process; the composite has high adsorption efficiency of ppb level nitrogen oxide with good repeatability.

Claims

1. A preparation method of a hollow graphitic carbon nitride nanosphere/graphene composite and composite-carbonized polymer nano fiber material, comprising the following steps: (1) preparation of silica nanospheres: adding ethyl silicate into a mixture of ammonia, ethanol and water having a mass ratio of ammonia: ethanol: water: ethyl silicate=1:1520:15:12, the formed mixture standing for 12 hours, adding a mixture of ethyl silicate and octadecyltrimethoxysilane having a mass ratio of ethyl silicate: octadecyltrimethoxysilane=1:1-2 to previously formed the mixture, mixing evenly and standing for 35 hours, a resulted mixture being centrifugated, dried and calcined for 68 hours at 55570 C., and then washed with 1M hydrochloric acid and dried, to obtain the silica nanospheres, (2) preparation of hollow graphitic carbon nitride nanospheres: using the silica nanospheres in the step (1) as a template and mixing with cyanamide in a mass ratio of 1:37 and stirring for 35 hours under vacuum, ultrasonic treating for 23 hours, and then reacting at 6070 C. for 1012 hours and obtaining a solid by centrifugation, the obtained solid being heated to 55570 C. under inert gas atmosphere and calcined for 45 hours producing a powder, then using 4M ammonium acid fluoride to etch the silica nanospheres template in the powder, after centrifuging, washing and drying, obtaining the hollow graphitic carbon nitride nanospheres, (3) preparation of graphene oxide: adding graphite to concentrated sulfuric acid in a ratio of graphite: concentrated sulfuric acid=1g: 2025mL with stirring in an ice water bath, after mixing evenly, adding potassium hypermanganate to the mixture of graphite and concentrated sulfuric acid in a mass ratio of graphite: potassium hypermanganate=1:58, reacting at 3540 C. for 12h pouring the mixture of graphite, concentrated sulfuric acid, and potassium hypermanganate into ice water containing hydrogen peroxide, after centrifugation, washing and drying, obtaining the graphene oxide, (4) preparation of surface modified hollow graphitic carbon nitride nanospheres: adding 3-aminopropyltriethoxysilane to a suspension of the hollow graphitic carbon nitride nanospheres in methylbenzene in a mass ratio of the hollow graphitic carbon nitride nanospheres: 3-aminopropyltriethoxysilane=1g: 35mL, after refluxing for 2024 hours, centrifuging, washing and drying, obtaining the surface modified hollow graphitic carbon nitride nanospheres, (5) preparation of hollow graphitic carbon nitride nanospheres/graphene composite: adding graphene oxide aqueous solution to the surface modified hollow graphitic carbon nitride nanospheres in step (4) dispersed in water with a pH value of 10 in a mass ratio of the surface modified hollow graphitic carbon nitride nanospheres: graphene oxide=1:0.10.3, stirring the mixture of the surface modified hollow graphitic carbon nitride nanospheres and the graphene oxide at room temperature for 12 hours, adding hydrazine hydrate into the mixture in a mass ratio of graphene oxide: hydrazine hydrate=1:12, reacting for 12 hours at 95 C., centrifuging, washing and drying, obtaining the hollow graphitic carbon nitride nanospheres/graphene composite, (6) preparation of composite-carbonized polymer nanofiber material: adding the composite obtained in step (5) to a DMF solution of a polymer with a mass ratio of composite: polymer=1:1520, stirring the mixture of the composite and polymer at room temperature for 58 hours, preparing a nanofiber through electrostatic spinning, the nanofiber being heated to 500520 C. under inert gas atmosphere and calcined for 45 hours, obtaining the composite-carbonized polymer nanofiber material.

2. The preparation method according to claim 1, wherein: the mass ratio of ammonia, ethanol, water, and ethyl silicate in step (1) is 1:18.7:3.2:1.8; the mass percentage of the ammonia in step (1) is 22%25%; the mass ratio of the ethyl silicate and the mixed liquid of ethyl silicate and octadecyltrimethoxysilane in step (1) is 1:1.5; and the mass ratio of the ethyl silicate and octadecyltrimethoxysilane in the liquid mixture of the ethyl silicate and octadecyltrimethoxysilane in step (1) is 1:0.45.

3. The preparation method according to claim 1, wherein: the mass ratio of said silica nanospheres and cyanamide in step (2) is 1:5.

4. The preparation method according to claim 1, wherein: the ratio of graphite and concentrated sulfuric acid in step (3) is 1g: 23 mL; the mass ratio of graphite and Potassium Permanganate in step (3) is 1:6; and Potassium Permanganate is divided into two batches with the same mass in step (3).

5. The preparation method according to claim 1, wherein: the ratio of said hollow graphitic carbon nitride nanosphere and 3-aminopropyltriethoxysilane in step (4) is 1 g: 3 mL; and the concentration of the hollow graphitic carbon nitride nanosphere in said suspension in step (4) is 1 mg/mL.

6. The preparation method according to claim 1, wherein: the mass ratio of said surface modified hollow graphitic carbon nitride nanospheres and the graphene oxide in step (5) is 1:0.1; the concentration of surface modified hollow graphitic carbon nitride nanospheres in said suspension in step (5) is 1 mg/mL; the concentration of graphene oxide in aqueous solution in step (5) is 0.1 mg/mL; and the mass ratio of said graphene oxide and the hydrazine hydrate in step (5) is 1:1.

7. The preparation method according to claim 1, wherein: the mass ratio of the composite and the polymer in step (6) is 1:20; said polymer in step (6) is selected from any one of PAN, polyvinyl alcohol and polyvinylpyrrolidone; the mass percentage of the polymer in dimethylformamide in step (6) is 10%; and the conditions of said electrostatic spinning in step (6) are as follows: negative voltage-9 kV, positive voltage 18 kV, speed 0.2 mm/min.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1 is the transmission electron microscope (TEM) for the hollow g-C.sub.3N.sub.4 nanospheres (HCNS).

(2) FIG. 2 is the TEM for hollow g-C.sub.3N.sub.4 nanospheres/ reduced graphene oxide composites (HCNS/rGO).

(3) FIG. 3 is the scanning electron microscope (SEM) for the hollow g-C.sub.3N.sub.4 nanospheres/reduction graphene oxide composites (HCNS/rGO).

(4) FIG. 4 is the SEM for the carbonized composite-polymer nanofiber material (CCPF).

(5) FIG. 5 is the TEM for the carbonized composite-polymer carbon nanofiber material (CCPF).

(6) FIG. 6 is a photo for the carbonized composite-polymer nanofiber material (CCPF).

(7) FIG. 7 shows the catalytic effect of the carbonized composite-polymer nanofiber material (CCPF) and several kinds of photocatalyst on NO.

(8) FIG. 8 shows he catalytic cycle of polymer composites (CCPF) on NO.

IMPLEMENTATION EXAMPLES

(9) The examples and figures will be combined below to illustrate the technical scheme of the invention. Unless otherwise stated, the following materials and reagents can be obtained through commercial means.

Example 1

The Preparation of SNS

(10) 22% ammonia (1.55 g), ethanol (29 g) and deionized water (5 g) was mixed, then TEOS (2.8 g) was added to the mixture and keep static for 1 h. The mixture of the above system was added with TEOS and C.sub.18TMOS (a total of 4.22 g, including 2.91 g TEOS and 1.31 g C.sub.18TMOS) and keep static for 3 h. The system was centrifugated (5000 rpm*5 min) to obtain solid followed by drying and been calcined at 550 C. for 6 h. Then the solid was washed by 1M hydrochloric acid and drying to obtain SNS (1.8 g).

Example 2

The Preparation of HCNS

(11) Under vacuum conditions, the template SNS (1 g) in examplel and melamine (5 g) was mixed and stirred for 3 hours and then ultrasonic treatment for 2 hours followed by reacting for 12 hours at 60 C.The above reaction system was centrifugated to obtain white solid. Under Ar atmosphere, the solid is heated to 550 C. at the heating rate of 4.4 C./min for 4 hours. After calcining for 4 hours yellow powder was obtained, and then 4M NH.sub.4HF.sub.2 was used to etch silica nanosphere template. HCNS was obtained after centrifugating, washing 3 times, ethanol washing 1 time and drying at 80 C. in vacuum.

(12) FIG. 1 is the TEM for HCNS, it can be seen that HCNS has a hollow spherical structure.

Example 3

The Preparation of GO

(13) The graphite (3 g) is added to concentrated sulfuric acid (69 mL) in the ice water bath under magnetic stirring for 2 h. After mixing evenly, half dose of Potassium Permanganate (9 g) was added to the mixture with the system temperature lower than 20 C. Then the reaction system was heating to 35 C. and stirring for 7 h. The rest of the Potassium Permanganate (9.0 g) was once added to the reaction system and stirring for 12 h. The mixture is poured into the 400 mL ice water, then 3 mL hydrogen peroxide was added to the mixture to get yellow mixture. After centrifugation and followed by washing with 5% hydrochloric acid and deionized water for 3 times and drying in vacuum drying box for 12 h, GO (1.4 g) was obtained.

Example 4

The Preparation of MHCNS

(14) In Ar atmosphere, HCNS (0.5 g) in example 2 was dispersed in toluene (500 mL). KH550 (1.5 mL) was added to the system and refluxing for 24 h. MHCNS (0.53 g) was obtained by centrifugation and washed by ethanol and water 2 times and dried at 80 C. for 12 h.

Examples 5

The Preparation of HCNS/rGO

(15) The surface modified HCNS (100 mg) obtained in example 4 was dispersed in water with ammonia (100 mL) whose pH value is adjusted to 10. Concentration of GO aqueous solution of 0.1 mg/mL (100 mL) was added to the above mixture with stirring at room temperature for 1 h. Then add hydrazine hydrate (10 mg) to the system at 95 C. and react for 1 H to reduce GO to rGO. After centrifugation, washing 3 times and drying at the temperature of 80 C. for 12 h, HCNS/rGO (102 mg) was obtained.

(16) FIG. 2 is the TEM of HCNS/rGO. FIG. 3 is the SEM of HCNS/rGO. Through two figures it can be seen that rGO completely wrapped HCNS, the composite of the two compounds was prepared successfully.

Examples 6

The Preparation of: CCPF

(17) The polyacrylonitrile (2 g) was dissolved in DMF (18 G) with stirring for 3 h to get homogeneous solution. HCNS/rGO (100 mg) was dispersed in the solution with stirring at room temperature for 5 h and then treated by ultrasonic for 2 min. The solution was drawed by 5 mL syringe, The nanofiber was obtained by electrospinning under the condition of the negative pressure 9 kV, pressure 18 kV, speed 0.2 mm/min. In Ar atmosphere, the nanofibers was heating to 500 C. at heating rate of 2 C./min and calcined for 4 h to get final product CCPF.

(18) FIG. 4 is the SEM of CCPF, it can be seen that CCPF is threadiness, with the diameter of about 1 m. FIG. 5 is the TEM of CCPF, it can be seen that there is HCNS on the surface, showed that HCNS was successfully loaded on CCPF. FIG. 6 is the photograph of CCPF, it can be seen that the final product CCPF is a film, which is not the same as the HCNS/rGO powder, and more convenient for application.

Example 7

NO degradation Test Under Visible Light Condition

(19) The prepared CCPF and other catalysts were put in 1.6 L (1020 cm) cylindrical glass container. 100 ppm NO (N2 for gas balance) was diluted to 600 ppb by air. The dilution gas was humidified to 50% by humidifying chamber. The mixed gas was adjusted to the flow of 2.4 L/min. After achieving gas balance in the container, open energy the lamp (20 W). 42i-HL (Thermo Environmental Instruments nitrogen oxides analyzer, Inc.) was used to monitor real-time concentration. The flow gas passing the analyzer is 1 L/min. NO degradation efficiency () was calculated by the equation: (%)=(1C/C.sub.0)100%, C and C.sub.0 represent the concentration of NO in export and entrance, respectively.

(20) FIG. 7 shows the catalytic effect of CCPF and several kinds of photocatalyst for NO, it can be seen from the figure that catalytic efficiency of bulk g-C.sub.3N.sub.4, HCNS, HCNS/rGO and CCPF were 25%, 47%, 64% and 60%. Compared to g-C.sub.3N.sub.4 and HCNS, the catalytic efficiency of HCNS/rGO has improved significantly, implying that through the regulation of micro structure and connection with other material, the catalytic efficiency of g-C.sub.3N.sub.4 can be effectively improved. The catalytic efficiency of CCPF and HCNS/rGO is roughly the same, which proves that it is appropriate to use carbon nanofiber to load HCNS/rGO.

(21) FIG. 8 shows cycle adsorption effect for NO of CCPF. We can see that, after four times of adsorption, CCPF still maintain a high catalytic efficiency, indicating that CCPF has a good practicality.

(22) The above analysis shows that through controlling the microstructure and combining with other materials to form heterojunction, the ability of g-C.sub.3N.sub.4 to NO adsorption and catalysis can be improved. The carbonized nanofiber can load photocatalyst, which is convenient in practical application. The photocatalytic material is capable of absorbing and catalyzing low concentration of NO with the advantage of high catalytic efficiency, recycling and cheap material. Therefore, it has a very good prospect in the future of air purification.