WO2018082585A1

WO2018082585A1 - Synthesis method for composite gas sensitive material of porous zinc oxide nanosheet loaded with a high-dispersion nano precious metal

Info

Publication number: WO2018082585A1
Application number: PCT/CN2017/109017
Authority: WO
Inventors: 占金华; 封振宇; 韩雪; 马妍星
Original assignee: 山东大学
Priority date: 2016-11-02
Filing date: 2017-11-02
Publication date: 2018-05-11
Also published as: CN106541143A

Abstract

Disclosed is a synthesis method for a composite gas sensitive material of a porous zinc oxide nanosheet loaded with a high-dispersion nano precious metal. The method comprises the following steps: (1) basic zinc carbonate is immersed into a water solution of precious metal ions, stirring is conducted in the absence of light, and a reaction solution containing precipitate is obtained; and (2) the precipitate in the reaction solution obtained in step (1) is subjected to centrifugal washing, drying and calcination, and the composite gas sensitive material is obtained. The material can be used for gas sensitive sensing detection of volatile organic pollutants (VOCs and chlorobenzene gases), the gas sensitive response is good, the synthesis method for the material is green and simple and convenient, with good repeatability, and mass production and application to gas sensing detection can be easily achieved.

Description

Method for synthesizing porous zinc oxide nanosheet loaded high dispersion nano precious metal composite gas sensing material

Technical field

The invention relates to a method for synthesizing a porous zinc oxide nanosheet loaded high-dispersion nano precious metal composite gas sensing material, and belongs to the field of preparation of inorganic nano materials.

Background technique

Indoor air quality researchers say that all volatile organic compounds sampled and analyzed indoors are VOCs, and volatile organic compounds (VOCs) are one of the three types of indoor air pollutants. As people's indoor time continues to grow, the relationship between indoor environment and people becomes more important and more important. There are many methods for detecting VOCs, such as gas chromatography, infrared, SPR photodiode detection, weight chemical sensor method, catalytic combustion sensor method, photoionization detector method, etc. However, these methods have some disadvantages: analysis and detection The hysteresis is not conducive to on-line detection; sample pretreatment and detection procedures are more complicated. Gas sensing can just make up for the weakness of the above detection methods, so the research on the synthesis method of gas sensing materials is particularly important.

The conductive gas sensor (gas sensor) detects the change in the concentration of the gas to be measured by detecting the change in the conductivity (resistance) before and after the reaction of the sensor element with the substance to be tested. As a common n-type semiconductor gas sensing material, zinc oxide has obvious gas-sensitive response in the detection of some VOCs and polychlorinated biphenyls, such as ethanol, acetone, chlorobenzene and the like. Various morphological nano-zinc oxide materials, for example, nanorods, nanosheets, multi-structured nanoflowers, nano-hollow structures, and the like, have been prepared by liquid phase synthesis. However, the inherent selectivity of the zinc oxide material itself also causes it to be unresponsive to a portion of the VOCs, for example, the gas-sensitive response to benzene, toluene, xylene, and the like is scarce. Precious metals (gold, platinum, palladium, silver) have excellent heterogeneous catalytic activity of organic gases, and their incorporation can effectively improve the deficiency of zinc oxide materials, increase the types of gases that can be simultaneously detected, and further increase the zinc oxide to various VOCs. Gas sensing performance.

Nano-gold, platinum, and palladium perform well in the field of catalytic oxidation of VOCs, and the catalytic performance of small particles of 2-10 nm tends to be good. Small-sized monodisperse nano-gold, platinum, palladium, and silver are usually carried out by means of small organic molecules having a functional group such as a mercapto group, an amino group or a carboxyl group, or a macromolecular surfactant such as polyvinylpyrrolidone or tritonone as a protective agent. synthesis. Although this method can regulate the morphology and size of nano precious metals, it also covers the active sites of noble metal nanoparticles, thus affecting the surface adsorption and electron conduction of nano precious metals. At the same time, the distribution and content of precious metal nanoparticles also affect the gas sensing properties of the composite.

In the literature, the photocatalytic properties of zinc oxide are used to deposit precious metals on the surface of single crystal porous zinc oxide. The size and distribution of noble metals can be controlled by controlling the concentration of the system and the reaction time. However, zinc oxide will partially dissolve itself in the light of water, and the morphology will change, and the stability is not good, which makes the process difficult to enlarge.

Chinese patent document CN 103908964 A discloses a noble metal doped zinc oxide nano powder and its preparation and application, The preparation steps are as follows: (1) heating the organic alcohol solvent to 150-190 ° C; (2) adding an aqueous solution of a zinc acetate-precious metal salt mixture, reacting at 150-190 ° C for 5 - 60 min, after the reaction is completed, centrifuging, The obtained solid sample is washed; (3) the sample obtained in the step (2) is dried, and the obtained noble metal-doped zinc oxide nano powder has a particle diameter of 30 to 50 nm. The method for preparing precious metal doped zinc oxide nanopowder is easy to obtain, simple to operate, and suitable for photocatalytic treatment of organic sewage; however, the product prepared by the invention has low specific surface area, requires use of an organic solvent, and has a high treatment temperature.

Chinese patent document CN 102649060A discloses a porous zinc oxide-silver composite nanorod and a preparation method and use thereof. First, the zinc acetate ethanol solution and the oxalic acid dihydrate solution are mixed and placed in a sealed state, and the temperature is maintained at 70 to 90 ° C for at least 5 hours, and then centrifuged, washed and dried, and then the obtained oxalic acid is firstly obtained. The zinc is annealed at 430-470 ° C for at least 2 h, and then added to a silver nitrate glycol solution, stirred under visible light for at least 15 min, and then subjected to centrifugation, washing and drying to obtain a target product. However, the composite nanorods prepared by the invention are composed of zinc oxide particles, and the surface of the porous rod-shaped zinc oxide is loaded with silver particles, which is a deposition between particles, a relatively low specific surface area, and the active sites of the nanoparticles are covered, and is applicable. Visible light photocatalytic degradation in water contaminated with organic matter.

Summary of the invention

In view of the deficiencies of the prior art, the present invention provides a method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material which is simple, green, reproducible and capable of mass production.

The technical solution of the present invention is as follows:

A method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material comprises the following steps:

(1) immersing basic zinc carbonate in an aqueous solution of noble metal ions, and stirring in the dark to obtain a reaction liquid containing a precipitate;

(2) The precipitate in the reaction liquid obtained in the step (1) is washed by centrifugation, dried, and calcined to obtain a composite gas sensitive material.

According to the preferred method of the present invention, the method for preparing basic zinc carbonate in the step (1) comprises the steps of: dissolving zinc acetate and urea in water, reacting at 110-140 ° C for 2-6 h; centrifuging, washing, and drying. Basic zinc carbonate.

Further preferably, the reaction temperature is 120 ° C and the reaction time is 2 h.

Further preferably, the molar ratio of zinc acetate to urea is 1:1-5; preferably, the molar ratio of zinc acetate to urea is 1:2.

Further preferably, the drying conditions are dried at 60 ° C for 12 h.

According to the preferred embodiment of the present invention, the aqueous solution of the noble metal ion in the step (1) is an aqueous solution of chloroauric acid, chloroplatinic acid, palladium chloride or silver nitrate.

According to the preferred embodiment of the present invention, the mass concentration of the noble metal in the aqueous solution of the precious metal ion in the step (1) is 0.1 wt% to 10 wt%; preferably, the mass concentration of the noble metal in the aqueous solution of the noble metal ion in the step (1) is 1 wt. %-5wt%.

According to the preferred method of the present invention, the mass ratio of the basic zinc carbonate to the noble metal in the step (1) is 1:0.05-5.

According to the preferred method of the present invention, the soaking condition in the step (1) is soaked for 12-24 hours at room temperature.

According to the preferred embodiment of the present invention, the drying condition in the step (2) is dried at 60 ° C for 12 h.

According to the preferred method of the present invention, the calcination condition in the step (2) is 350-500 ° C, and calcination is 1-4 h.

Further preferably, the calcination conditions are calcined at 400 ° C for 2 h.

According to the preferred embodiment of the present invention, the precipitate in the reaction liquid in the step (2) is subjected to centrifugal washing, drying, calcination, and further reacted under a hydrogen atmosphere at 150-180 ° C for 1-4 h; preferably, under a hydrogen atmosphere. The reaction was carried out at 160 ° C for 2 h.

When the aqueous solution of the noble metal ion is an aqueous solution of silver nitrate, the precipitate in the reaction liquid in the step (2) is subjected to centrifugal washing, drying, calcination, and further reduction under a hydrogen atmosphere.

The invention utilizes a room temperature liquid phase ion exchange reaction, and the noble metal ions can be uniformly and controlly attached to the surface of the basic zinc carbonate, and the calcination, the basic zinc carbonate is decomposed to generate a gas such as carbon dioxide to form a porous structure of zinc oxide; At the same time, the noble metal of the zinc oxide nanosheet can be reduced into nanoparticles (the elemental nano gold, platinum, palladium can be stably existed; the elemental nano silver is easily partially oxidized, and can be reduced by hydrogen atmosphere).

Beneficial effect

1. In the porous zinc oxide nanosheet-loaded high-dispersion nano-precious metal composite gas sensing material prepared by the invention, since the liquid phase ion exchange reaction is uniformly performed on the surface of the basic zinc carbonate, the crystal structure of the basic zinc carbonate is relatively in the reaction liquid. Stable, so the noble metal ions are evenly distributed on the surface of the basic zinc carbonate precipitation, so the noble metal nanoparticles are highly dispersed after calcination, the particle size distribution is narrow, and evenly distributed on the surface of the porous zinc oxide nanosheet; by regulating the precious metal ions in the soaking solution The concentration and the time of soaking can control the particle size and loading of the nano precious metal in the prepared material; the surface of the noble metal nanoparticle is covered with no protective agent, the active site is fully exposed, and the particle size is less than 10 nm, which can exist stably for a long time. Excellent sensitivity.

2. In the porous zinc oxide nanosheet-loaded high-dispersion nano-precious metal composite gas sensing material prepared by the invention, the porous zinc oxide nanosheet has uniform pore distribution, large specific surface area, and surface exposed non-polar crystal plane, which is favorable for noble metal nanoparticles. Disperse stable load.

The composite gas sensing material prepared by the method has better sensitivity to gas sensing of VOCs and chlorobenzene gases than pure nano zinc oxide materials, and achieves a highly sensitive response to various gases.

4. The preparation method is green, simple and reproducible, and is a process that can be manufactured and applied on a scale.

DRAWINGS

1 is a transmission electron micrograph of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in Example 1.

2 is a transmission electron micrograph of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in Example 2.

3 is a transmission electron micrograph of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in Example 3.

4 is a transmission electron micrograph of a porous zinc oxide nanosheet-loaded highly dispersed nanopalladium composite gas sensing material prepared in Example 4.

5 is a transmission electron microscope photograph of a porous zinc oxide nanosheet-loaded highly dispersed nanopalladium composite gas sensing material prepared in Example 5. sheet.

6 is a transmission electron micrograph of a porous zinc oxide nanosheet-loaded highly dispersed nanopalladium composite gas sensing material prepared in Example 6.

7 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in Example 1.

8 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in Example 2.

9 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in Example 3.

10 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nanopalladium composite gas sensing material prepared in Example 4.

11 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nanopalladium composite gas sensing material prepared in Example 5.

12 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nanopalladium composite gas sensing material prepared in Example 6.

detailed description

The present invention will be further described below in conjunction with specific embodiments, but is not limited thereto.

Meanwhile, the experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

Example 1

(1) 20 ml of 0.2 mol/L zinc acetate aqueous solution was added to 20 ml of 0.4 mol/L urea aqueous solution, ultrasonically dispersed for 10 min, and then the mixed solution was transferred to a volume of 50 mL of a stainless steel autoclave lined with polytetrafluoroethylene. And allowed to react in an oven at 120 ° C for 5 h. Naturally cooled to room temperature, centrifuged and washed 3 times with deionized water, and dried in an oven at 60 ° C for 12 h to obtain basic zinc carbonate;

(2) immersing 0.2 g of basic zinc carbonate in 20 mL of a 1% by weight aqueous solution of chloroauric acid, and stirring at room temperature for 12 hours to obtain a reaction liquid containing a precipitate;

(3) The precipitate in the reaction liquid obtained in the step (2) is washed by centrifugation, dried in an oven at 60 ° C for 12 h, and finally calcined at 400 ° C for 2 h in a muffle furnace to obtain a composite gas sensitive material.

In the prepared porous zinc oxide nanosheet-loaded high-dispersion nano-gold composite gas sensing material, the nano gold has a particle size of about 2 nm and a loading of about 0.5 wt%.

1 is a transmission electron micrograph of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in the present embodiment. It can be seen from the figure that the nano gold particles are not agglomerated on the surface of the porous zinc oxide, and the distribution is uniform and uniform in size.

7 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nano-gold composite gas sensing material prepared in the present embodiment, and it can be seen from the figure that the diffraction peak of wurtzite zinc oxide (corresponding to the standard card JCPDS No. 36- In addition to 1451), a relatively weak nanogold diffraction peak appears (corresponding to the standard card JCPDS No. 04-0784, which is known as the gold (111) and (200) crystal faces), and there are no other peaks, so the composite material is A composite of zinc oxide and gold, with no other material structure.

Example 2

As described in Example 1, the difference was that an aqueous solution of chloroauric acid having a mass concentration of 3 wt% was used in the step (2).

In the prepared porous zinc oxide nanosheet-loaded high-dispersion nano-gold composite gas sensing material, the nano gold has a particle size of about 5 nm and a loading of about 2 wt%.

2 is a transmission electron micrograph of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in the present embodiment. It can be seen from the figure that the nano gold particles are not agglomerated on the surface of the porous zinc oxide, and the distribution is uniform and uniform in size.

8 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in the present embodiment, and it can be seen from the figure that the diffraction peak of wurtzite zinc oxide is replaced (corresponding to the standard card JCPDS No. 36- In addition to 1451), a nanogold diffraction peak appeared (corresponding to the standard card JCPDS No. 04-0784, which is known as the (111), (200) and (220) crystal faces of gold), and there are no other peaks, so the composite material As a composite of zinc oxide and gold, there is no other material structure.

Example 3

As described in Example 1, the difference was that an aqueous solution of chloroauric acid having a mass concentration of 5 wt% was used in the step (2).

In the prepared porous zinc oxide nanosheet-loaded high-dispersion nano-gold composite gas sensing material, the nano gold has a particle size of about 10 nm and a loading of about 5 wt%.

3 is a transmission electron micrograph of a porous zinc oxide nanosheet-loaded highly dispersed nanogold composite gas sensing material prepared in the present embodiment. It can be seen from the figure that the nano gold particles are not agglomerated on the surface of the porous zinc oxide, and the distribution is uniform and uniform in size.

FIG. 9 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded highly dispersed nano-gold composite gas sensing material prepared in the present embodiment, and the diffraction peak of the wurtzite zinc oxide is not shown in the figure (corresponding to the standard card JCPDS No. 36- In addition to 1451), there is a nano-gold diffraction peak with a certain intensity (corresponding to the standard card JCPDS No. 04-0784, which can be known as the (111), (200) and (220) crystal faces of gold), and there are no other peaks. Therefore, the composite material is a composite material of zinc oxide and gold, and has no other material structure.

Example 4

(2) 0.5 g of basic zinc carbonate was immersed in 30 mL of a 1 wt% aqueous solution of palladium chloride, and stirred at room temperature for 24 hours in the dark to obtain a reaction liquid containing a precipitate;

In the prepared porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material, the nanopalladium has a particle size of about 2 nm and a loading of about 0.5 wt%.

4 is a transmission electron micrograph of the porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material prepared in the present embodiment. It can be seen from the figure that the nano-palladium particles are not agglomerated on the surface of the porous zinc oxide, and the distribution is uniform and uniform in size.

10 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material prepared in the present embodiment, and the diffraction peak of the wurtzite zinc oxide is not shown in the figure (corresponding to the standard card JCPDS No. 36- In addition to 1451), a relatively weak nanopalladium diffraction peak appeared (corresponding to the standard card JCPDS No. 46-1043, which is known as the (111) and (200) crystal faces of palladium), and there are no other peaks, so the composite material is A composite of zinc oxide and palladium with no other material structure.

Example 5

As described in Example 4, the difference was that a palladium chloride aqueous solution having a mass concentration of 3 wt% was used in the step (2).

In the prepared porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material, the nano-palladium has a particle size of about 5 nm and a loading of about 2 wt%.

FIG. 5 is a transmission electron micrograph of the porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material prepared in the present embodiment. It can be seen from the figure that the nano-palladium particles are not agglomerated on the surface of the porous zinc oxide, and the distribution is uniform and uniform in size.

11 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material prepared in the present embodiment, and it can be seen from the figure that the diffraction peak of wurtzite zinc oxide (corresponding to the standard card JCPDS No. 36- In addition to 1451), a nanopalladium diffraction peak appeared (corresponding to the standard card JCPDS No. 46-1043, which is known as the (111) and (200) crystal faces of palladium), and there are no other peaks, so the composite material is zinc oxide and Palladium composite material, no other material structure.

Example 6

As described in Example 4, the difference was that a palladium chloride aqueous solution having a mass concentration of 5 wt% was used in the step (2).

In the prepared porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material, the nano-palladium has a particle size of about 8 nm and a loading of about 5 wt%.

FIG. 6 is a transmission electron micrograph of the porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material prepared in the present embodiment. It can be seen from the figure that the nano-palladium particles are not agglomerated on the surface of the porous zinc oxide, and the distribution is uniform and uniform in size.

12 is an X-ray diffraction spectrum of a porous zinc oxide nanosheet-loaded high-dispersion nano-palladium composite gas sensing material prepared in the present embodiment, and it can be seen from the figure that the diffraction peak of wurtzite zinc oxide (corresponding to the standard card JCPDS No. 36- In addition to 1451), there is a nanopalladium diffraction peak with a certain intensity (corresponding to the standard card JCPDS No. 46-1043, which is known as the (111) and (200) crystal faces of palladium), and there are no other peaks, so the composite material As a composite of zinc oxide and palladium, there is no other material structure.

Example 7

(2) 0.5 g of basic zinc carbonate was immersed in 30 mL of a 1% by weight aqueous solution of silver nitrate, and stirred at room temperature for 24 hours in the dark to obtain a reaction liquid containing a precipitate;

(3) The precipitate in the reaction liquid obtained in the step (2) is washed by centrifugation, dried in an oven at 60 ° C for 12 h, and then calcined at 400 ° C for 2 h in a muffle furnace; then, the product is placed in a porcelain boat, in a tube type. The composite gas-sensitive material was obtained by reduction in a furnace at 160 ° C for 2 h under a hydrogen atmosphere.

In the prepared porous zinc oxide nanosheet-loaded highly dispersed nanosilver composite gas sensing material, the nano silver has a particle size of about 2 nm and a loading of about 0.5 wt%.

Example 8

As described in Example 1, the difference was that an aqueous solution of chloroplatinic acid having a mass concentration of 1% by weight was used in the step (2).

Example 9

As described in Example 1, the difference was that an aqueous solution of chloroplatinic acid having a mass concentration of 3 wt% was used in the step (2).

Example 10

As described in Example 1, the difference was that an aqueous solution of chloroplatinic acid having a mass concentration of 5 wt% was used in the step (2).

Example 11

As described in Example 7, the difference was that a silver nitrate aqueous solution having a mass concentration of 3 wt% was used in the step (2).

Example 12

As described in Example 7, the difference was that a silver nitrate aqueous solution having a mass concentration of 5 wt% was used in the step (2).

Example 13

(1) 20 ml of 0.2 mol/L zinc acetate aqueous solution was added to 20 ml of 0.2 mol/L urea aqueous solution, ultrasonically dispersed for 10 min, and then the mixed solution was transferred to a volumetric 50 mL stainless steel autoclave lined with polytetrafluoroethylene. And allowed to react in an oven at 110 ° C for 6 h. Naturally cooled to room temperature, centrifuged and washed 3 times with deionized water, and dried in an oven at 60 ° C for 12 h to obtain basic zinc carbonate;

(2) immersing 0.2 g of basic zinc carbonate in 20 mL of a 0.1% by weight aqueous solution of chloroauric acid, and stirring at room temperature for 20 hours in the dark to obtain a reaction liquid containing a precipitate;

(3) The precipitate in the reaction liquid obtained in the step (2) is washed by centrifugation, dried in an oven at 60 ° C for 12 h, and finally calcined at 350 ° C for 4 h in a muffle furnace to obtain a composite gas sensitive material.

Example 14

Method for synthesizing porous zinc oxide nanosheet loaded high dispersion nano precious metal composite gas sensing material, including steps under:

(1) 20 ml of 0.2 mol/L zinc acetate aqueous solution was added to 20 ml of 1 mol/L urea aqueous solution, ultrasonically dispersed for 10 min, and then the mixed solution was transferred to a volumetric 50 mL stainless steel autoclave lined with polytetrafluoroethylene. And allowed to react in an oven at 140 ° C for 3 h. Naturally cooled to room temperature, centrifuged and washed 3 times with deionized water, and dried in an oven at 60 ° C for 12 h to obtain basic zinc carbonate;

(2) immersing 0.2 g of basic zinc carbonate in 20 mL of a 10% by weight aqueous solution of chloroauric acid, and stirring at room temperature for 18 hours in the dark to obtain a reaction liquid containing a precipitate;

(3) The precipitate in the reaction liquid obtained in the step (2) is washed by centrifugation, dried in an oven at 60 ° C for 12 h, and finally calcined at 500 ° C for 1 h in a muffle furnace to obtain a composite gas sensitive material.

Comparative example 1

A porous zinc oxide nanosheet, the preparation steps are as follows:

(2) The basic zinc carbonate obtained in the step (1) is calcined in a muffle furnace at 400 ° C for 2 hours to obtain a porous zinc oxide nanosheet.

Comparative example 2

A method for synthesizing porous zinc oxide nanosheet-loaded nanometer cobalt oxide composite gas sensing material comprises the following steps:

(2) immersing 0.2 g of basic zinc carbonate in 20 mL of a 10% by weight aqueous solution of cobalt acetate, and stirring at room temperature for 24 hours in the dark to obtain a reaction liquid containing a precipitate;

(3) The precipitate in the reaction liquid obtained in the step (2) is washed by centrifugation, dried in an oven at 60 ° C for 12 h, and finally calcined at 400 ° C for 4 h in a muffle furnace to obtain a porous zinc oxide nanosheet-loaded nano-oxide cobalt composite gas. Sensitive material.

Test example 1

The gas sensing materials prepared in Examples 1-14 and Comparative Examples 1 and 2 were tested for gas sensitivity, and the test methods were as follows:

1. The instrument used for testing is the WS-30A gas sensitivity tester produced by Zhengzhou Yusheng Electronic Technology Co., Ltd., and the gas sensor is a side-heating sintered component made according to the traditional method.

2. Add 0.2 g of synthetic gas-sensitive material sample to the mortar, drop a small amount of ethanol until it is ground into a paste, and apply evenly on the periphery of the alumina ceramic tube with gold electrodes at both ends with a fine brush.

3. After the sample is completely dried on the ceramic tube, solder the four platinum wire lead joints to the component base and heat it. The wire passes through the ceramic tube, and both ends of the heating wire are also welded to the component base to form a gas sensor, and then the component is placed on an aging table and aged at 450 ° C for 5-7 days.

4. After injecting the gas phase analyte into the test chamber, the sensitivity of the gas sensor is reflected by recording the voltage across the load resistor in series with the gas sensor. The sensitivity response value (S) of the gas sensor is defined as S = Ra / Rg, and Ra and Rg are the resistance values of the gas sensor in the air and the gas to be measured, respectively.

The gas sensitivity test results of the gas sensing materials prepared in Examples 1-14 and Comparative Examples 1 and 2 are shown in the following table:

Note: -- indicates that the corresponding data cannot be measured.

Comprehensive analysis, the prepared porous zinc oxide nanosheet-loaded high-dispersion nano-precious metal composite gas sensing material (for example, Examples 1-14) has a significantly better gas sensing detection response value for VOCs and chlorobenzene gases than pure nano zinc oxide. And zinc oxide-loaded nano-cobalt oxide materials (for example, Comparative Examples 1, 2), and achieve a highly sensitive response to a variety of gases, response and recovery time is also faster. Therefore, the method of the present invention has potential development and application value.

Claims

A method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material comprises the following steps:

(1) immersing basic zinc carbonate in an aqueous solution of noble metal ions, and stirring in the dark to obtain a reaction liquid containing a precipitate;

(2) The precipitate in the reaction liquid obtained in the step (1) is washed by centrifugation, dried, and calcined to obtain a composite gas sensitive material.
The method for synthesizing a porous zinc oxide nanosheet-loaded high-dispersion nano precious metal composite gas sensing material according to claim 1, wherein the method for preparing the basic zinc carbonate in the step (1) comprises the following steps: It is dissolved in water with urea and reacted at 110-140 ° C for 2-6 h; it is centrifuged, washed and dried to obtain basic zinc carbonate.
The method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material according to claim 2, wherein the reaction temperature is 120 ° C and the reaction time is 2 h.
The method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material according to claim 2, wherein the molar ratio of zinc acetate to urea is 1:1-5;

Preferably, the molar ratio of zinc acetate to urea is 1:2.
The method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material according to claim 1, wherein the aqueous solution of the noble metal ion in the step (1) is chloroauric acid, chloroplatinic acid or chlorine. An aqueous solution of palladium or silver nitrate.
The method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material according to claim 1, wherein the mass concentration of the noble metal in the aqueous solution of the noble metal ion in the step (1) is 0.1 wt% to 10 wt% %;

Preferably, the mass concentration of the noble metal in the aqueous solution of the noble metal ion in the step (1) is from 1% by weight to 5% by weight.
The method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material according to claim 1, wherein the mass ratio of the basic zinc carbonate to the noble metal in the step (1) is 1:0.05- 5.
The method for synthesizing a porous zinc oxide nanosheet-loaded high-dispersion nano-precious metal composite gas sensing material according to claim 1, wherein the immersion condition in the step (1) is immersion for 12-24 hours at room temperature.
The method for synthesizing a porous zinc oxide nanosheet-loaded high-dispersion nano-precious metal composite gas sensing material according to claim 1, wherein the calcination condition in the step (2) is 350-500 ° C, calcination 1-4 h;

Preferably, the calcination conditions are calcined at 400 ° C for 2 h.
The method for synthesizing a porous zinc oxide nanosheet-loaded highly dispersed nano precious metal composite gas sensing material according to claim 1, wherein the precipitate in the reaction liquid in the step (2) is subjected to centrifugal washing, drying, and calcination, Still reacting at 150-180 ° C for 1-4 h under a hydrogen atmosphere;

Preferably, the reaction is carried out at 160 ° C for 2 h under a hydrogen atmosphere.