Ag / agcl modified cobalt oxide nanocomposite and method

Abstract

The application belongs to the technical field of gas sensing material preparation, and discloses an Ag / AgCl modified Co3O4 nano-composite material, a preparation method and application, and comprises the following steps: dissolving inorganic compounds of Ag elements and inorganic compounds of Co elements in deionized water, adding a proper amount of NaCl solution first, then adding N2H4.H2O solution, and obtaining Ag / AgCl loaded alpha-Co(OH)2 nanosheet material by using coprecipitation and in-situ reduction method; and drying and sintering the Ag / AgCl loaded alpha-Co(OH)2 nanosheet material to obtain the Ag / AgCl modified Co3O4 nano-composite material. The application provides a preparation method of a low-temperature high-response gas sensing material, the prepared Ag / AgCl loaded Co3O4 material has higher ethanol gas response performance, can significantly reduce the optimal working temperature of the sensing material, has potential application prospect, and can be used for monitoring alcohol pollutant gases in atmospheric environment, chemical plant environment, home environment and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas sensing material preparation, and particularly relates to an Ag / AgCl modified Co3O4 nanocomposite, a preparation method and application. BACKGROUND

[0002] At present, gas sensing technology plays a very important role in the trend of development in the new era and is widely used in air quality monitoring, medical diagnosis, industrial production control and food safety detection. Semiconductor metal oxide gas sensors have unique advantages such as simplicity, portability, compatibility, and relatively simple configuration and working principle, so they are favored by more and more researchers and are widely used to detect toxic and harmful inorganic compound gases or volatile organic compound gases. According to the difference of the main carriers of semiconductor metal oxides, they can be divided into two categories of n-type and p-type, among which n-type semiconductor metal oxides with electrons as the main carriers are SnO2, ZnO, TiO2, In2O3, Al2O3, WO3, etc., and p-type semiconductors with holes as the main carriers are NiO, CeO2, Mn2O3, Co3O4, CuO, etc. By modifying the metal oxide materials, such as element doping, metal loading, defect engineering, heterojunction, etc., the response performance of the target gas can be significantly improved. Therefore, designing and developing semiconductor metal oxide gas sensing materials with high performance can effectively promote the development of gas sensing industry and has very broad application prospects.

[0003] As the core component of gas sensors, gas molecules interact with sensing materials, causing changes in the physical properties of sensing materials. By collecting the differences in the changes of the electrical signals of sensing materials and establishing the relationship between the changes of the electrical signals of sensing materials and the content of gas molecules, the purpose of analyzing and detecting target gas molecules can be achieved. However, most metal oxide sensing materials need to be operated at a relatively high working temperature to detect target gas molecules, and have the problem of low response value. By modifying metal oxide materials with noble metals, combining the unique electronic and chemical sensitization properties of noble metals, not only can the gas sensing response be significantly improved, but also the gas sensing reaction activation energy can be effectively reduced, thereby reducing the optimal working temperature of the sensing material. Therefore, the research on noble metal and its composite modified oxide gas sensing materials can solve the problems of low response and high optimal working temperature in the gas sensing process, and provide important theoretical guidance and effective experimental basis for the development and design of low-temperature high-response gas sensing materials.

[0004] Through the above analysis, the problems and defects of the prior art are that the existing gas sensing materials need to be operated at a relatively high working temperature to detect target gas molecules, and have the problem of low response value and poor sensing performance. SUMMARY

[0005] In view of the problems existing in the prior art, the application provides an Ag / AgCl modified Co3O4 nanocomposite, a preparation method and application thereof.

[0006] The application is achieved in the following manner: an Ag / AgCl modified Co3O4 nanocomposite is composed of an inorganic compound of Ag element and an inorganic compound of Co element, wherein the amount of Co element is 2.0 mmol.

[0007] The molar ratio of the inorganic compound of Ag element to the inorganic compound of Co element is 0%, 0.3%, 0.6%, 1.2%, 2.4%, preferably 1.2%.

[0008] Further, the inorganic compound of Ag element is AgNO3; and the inorganic compound of Co element is any one of Co(NO3)2·6H2O and Co(Ac)2·4H2O.

[0009] Another object of the application is to provide a method for preparing the Ag / AgCl modified Co3O4 nanocomposite.

[0010] The inorganic compound of Ag element and the inorganic compound of Co element are dissolved in deionized water, and an appropriate amount of NaCl solution is added, followed by adding N2H4·H2O solution, to obtain Ag / AgCl loaded α-Co(OH)2 nanosheet material by co-precipitation and in-situ reduction; and the Ag / AgCl loaded α-Co(OH)2 nanosheet material is dried and sintered to obtain the Ag / AgCl modified Co3O4 nanocomposite.

[0011] Further, the method for preparing the Ag / AgCl modified Co3O4 nanocomposite comprises the following steps:

[0012] Step one, the inorganic compound of Ag element and the inorganic compound of Co element are dissolved in deionized water, and an appropriate amount of NaCl solution is added, and the mixture is stirred to obtain a uniform mixed solution;

[0013] Step two, under the condition of continuous stirring, N2H4·H2O solution is added to the uniform mixed solution to obtain α-Co(OH)2 and Ag / AgCl loaded α-Co(OH)2 by co-precipitation and in-situ reduction;

[0014] Step three, the obtained alpha-Co(OH)2 and Ag / AgCl loaded alpha-Co(OH)2 are washed with water and ethanol, and the washed alpha-Co(OH)2 and Ag / AgCl loaded alpha-Co(OH)2 are dried by using an oven;

[0015] Step four, the dried alpha-Co(OH)2 and Ag / AgCl loaded alpha-Co(OH)2 are calcined by using a muffle furnace, and then naturally cooled to room temperature to obtain Co3O4 and Ag / AgCl modified Co3O4 nanocomposite.

[0016] Further, the amount of the added deionized water is 20-50 mL; the molar ratio of the N2H4·H2O solution to Co(NO3)2·6H2O is 3:1; and the mass fraction of the N2H4·H2O solution is 80 wt.%.

[0017] Further, the co-precipitation and in-situ reduction time is 1-9 h; the co-precipitation and in-situ reduction temperature is 0℃-80℃; the drying temperature is 60℃-80℃, and the drying time is 3-24 h.

[0018] Further, the muffle furnace has a heating rate of 1℃·min -1 -10℃·min -1 ; the calcination temperature is 300℃-500℃, and the calcination time is 1h-6h.

[0019] Another object of the present application is to provide an application of the Ag / AgCl modified Co3O4 nanocomposite in monitoring alcohol pollutant gas in the atmosphere, a chemical plant, a home or other environments.

[0020] Another object of the present application is to provide an ethanol sensor prepared from the Ag / AgCl modified Co3O4 nanocomposite.

[0021] Another object of the present application is to provide an application of the ethanol sensor in detecting volatile organic compound ethanol gas molecules.

[0022] In combination with the above technical solutions and solved technical problems, the technical solution of the present application has the following advantages and positive effects:

[0023] The present application prepares a nanocomposite sensing material, which can effectively promote and accelerate the gas-solid interface sensing reaction process. The Ag / AgCl modified Co3O4 nanocomposite of the present application improves the ethanol gas response performance. The Ag / AgCl modified Co3O4 nanocomposite of the present application effectively reduces the optimal working temperature of the ethanol gas sensor.

[0024] The application adopts non-toxic harmless components and prepares precursor products under room temperature conditions, reduces energy consumption, and reduces harm to human health and ecological environment. The application provides a preparation method of a low-temperature high-response gas sensing material, and the prepared Ag-loaded Co3O4 material has higher ethanol gas response performance, can significantly reduce the optimal working temperature of the sensing material, has potential application prospect, and can be used for monitoring alcohol pollutant gases in atmosphere, chemical plants, homes and the like.

[0025] The expected income and commercial value of the technical scheme of the application after transformation are: providing important technical guidance and experimental support for developing low-cost, high-sensitivity and low-power ethanol gas sensors.

[0026] Whether the technical scheme of the application overcomes technical bias: it is widely accepted that noble metal modification can be used as an effective strategy to improve gas sensing response, the application aims to suggest using noble metal composite Ag / AgCl as a modification component to improve gas sensing performance, break the understanding that only single noble metal composition can effectively improve gas sensing performance. The application has new understanding of the essence of improving gas sensing response, and will have important guiding role for designing and developing high-response gas sensing materials and developing high-performance sensors. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a preparation method flow chart of the Ag / AgCl modified Co3O4 nanocomposite provided by the embodiment of the application;

[0028] Figure 2 is a scanning electron microscope image of alpha-Co(OH)2 and Ag / AgCl loaded alpha-Co(OH)2 provided by the embodiment of the application;

[0029] Figure 3 is an X-ray diffraction pattern of alpha-Co(OH)2 and Ag / AgCl loaded alpha-Co(OH)2 provided by the embodiment of the application;

[0030] Figure 4 is a scanning electron microscope image of Co4O4 and Ag / AgCl modified Co3O4 provided by the embodiment of the application;

[0031] Figure 5 is an X-ray diffraction pattern of Co3O4 and Ag / AgCl modified Co3O4 provided by the embodiment of the application;

[0032] Figure 6 is a Raman spectrum of Co3O4 and Ag / AgCl modified Co3O4 provided by the embodiment of the application;

[0033] Figure 7is a response-recovery curve diagram of 1.2Ag / AgCl-Co3O4 sensing material provided by the embodiment of the present application to 50ppm ethanol gas at different working temperatures;

[0034] Figure 8 is a response diagram of Co3O4 and Ag / AgCl modified Co3O4 provided by the embodiment of the present application to 50ppm ethanol gas molecules at different working temperatures;

[0035] Figure 9 is a resistance change curve diagram of Co3O4 and Ag / AgCl modified Co3O4 provided by the embodiment of the present application to 50ppm ethanol gas molecules at different working temperatures. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0037] In order to enable those skilled in the art to fully understand how the present application is specifically implemented, this part is an explanatory embodiment for explaining and describing the technical scheme of the claims.

[0038] As shown in Figure 1 The preparation method of the Ag modified Co3O4 nanocomposite provided by the embodiment of the present application comprises the following steps:

[0039] S101, dissolving an inorganic compound of Ag element and an inorganic compound of Co element in deionized water, and adding an appropriate amount of NaCl solution, and stirring to obtain a uniform mixed solution;

[0040] S102, under the condition of continuous stirring, adding N2H4·H2O solution to the uniform mixed solution, and obtaining α-Co(OH)2 and Ag / AgCl loaded α-Co(OH)2 by co-precipitation and in-situ reduction method;

[0041] S103, washing the obtained α-Co(OH)2 and Ag / AgCl loaded α-Co(OH)2 with water and ethanol, and drying the washed α-Co(OH)2 and Ag / AgCl loaded α-Co(OH)2 in an oven;

[0042] S104, calcining the dried α-Co(OH)2 and Ag / AgCl loaded α-Co(OH)2 in a muffle furnace and then naturally cooling to room temperature to obtain Co3O4 and Ag / AgCl modified Co3O4 nanocomposite.

[0043] The inorganic compound of Ag element provided by the embodiment of the present application is selected from AgNO3.

[0044] The inorganic compound of Co element provided by the embodiment of the present application is selected from any one of Co(NO3)2·6H2O and Co(Ac)2·4H2O, preferably Co(NO3)2·6H2O.

[0045] The Co(NO3)2·6H2O provided by the embodiment of the present application is used in an amount of 1.0, 2.0, 3.0, 4.0, 5.0 mmol, preferably 2.0 mmol.

[0046] The NaCl concentration provided by the embodiment of the present application is 10 ppm, 20 ppm, 40 ppm, 60 ppm, preferably 20 ppm.

[0047] The molar ratio of AgNO3 and Co(NO3)2·6H2O provided by the embodiment of the present application is 0%, 0.3%, 0.6%, 1.2%, 2.4%, preferably 1.2%.

[0048] The precipitation and in-situ reduction reaction time provided by the embodiment of the present application is 1h-9h, for example, 1h, 3h, 6h, 9h, preferably 6h.

[0049] The reaction temperature provided by the embodiment of the present application is 0℃-80℃, for example, 0℃, 25℃, 50℃, 80℃, preferably 25℃.

[0050] The drying process provided by the embodiment of the present application is carried out in an oven.

[0051] The drying temperature provided by the embodiment of the present application is 60℃-80℃, for example, 60℃, 65℃, 70℃, 75℃, 80℃, preferably 60℃.

[0052] The drying time provided by the embodiment of the present application is 3h-24h, for example, 3h, 6h, 9h, 12h, 24h, preferably 24h.

[0053] The heating rate provided by the embodiment of the present application is 1℃·min -1 -10℃·min -1 , for example, 1℃·min -1 , 3℃·min -1 , 5℃·min -1 , 7℃·min -1 , 10℃·min -1 , preferably 1℃·min -1 .

[0054] The sintering temperature provided by the embodiment of the present application is 300℃-500℃, for example, 300℃, 350℃, 400℃, 450℃, 500℃, preferably 450℃.

[0055] The sintering time provided by the embodiment of the present application is 1h-6h, for example, 1h, 2h, 4h, 6h, preferably 4h.

[0056] Example 1: Preparation of Ag / AgCl modified Co3O4 nanocomposite

[0057] Take 587.9mg Co(NO3)2·6H2O and dissolve in 30mL deionized water, and freshly prepare 5mL of 20mg / mL AgNO3 solution and 5mL of 10mg / mL NaCl solution, then use a pipette to take 60μL of NaCl solution (10mg / mL) and 200μL of AgNO3 solution (20mg / mL) and add them into the above Co(NO3)2·6H2O solution in turn and mix and stir for 10min, and finally take 365.5μL of N2H4·H2O (80wt.%) and add it dropwise into the above mixed solution, and continue to stir at 25℃ for 6h. After the reaction is completed, 1.2Ag / AgCl-α-Co(OH)2 is obtained by centrifugation, water washing, ethanol washing and drying. Finally, take 10mg of Ag / AgCl loaded α-Co(OH)2 and put it into a porcelain boat, and place the porcelain boat in a muffle furnace, and heat it to 1℃·min -1 at a rate of 1℃·min-1 to 450℃ and sinter for 4h, and finally obtain 1.2Ag / AgCl-Co3O4 nanocomposite.

[0058] Example 2: Preparation of modified electrode

[0059] Take 2.0mg of prepared Co3O4 and Ag / AgCl modified Co3O4 respectively and add 200μL of deionized water, and ultrasonic for 1min to obtain a uniform dispersion, then take 1.5μL of the dispersion and drop coat on the surface of a 3×3 gold interdigitated electrode, and place the gold interdigitated electrode in a room temperature condition for drying, and finally obtain a modified electrode loaded with sensing material. Place the modified electrode in a gas sensing test system, and heat it at 300℃ for 2h under an applied bias of 0.2V.

[0060] The embodiment of the present application has achieved some positive effects in the process of research and development or use, and indeed has great advantages compared with the prior art, which will be described below in combination with the data and graphs of the test process.

[0061] 1. Morphology characterization:

[0062] As shown in Figure 2 Fig. 1, the α-Co(OH)2 and Ag / AgCl loaded α-Co(OH)2 prepared by the embodiment of the present application exhibit nanosheet-like structural characteristics, and the introduction of Ag / AgCl does not change the morphology characteristics of the product.

[0063] Figure 3 It can be seen that the X-ray diffraction pattern shows that α-Co(OH)2 is successfully prepared, and with the increase of the amount of AgNO3, the diffraction signal of Ag in the product gradually becomes obvious, indicating that Ag is successfully compounded with α-Co(OH)2.

[0064] Figure 4 It can be seen that Co3O4 and Ag / AgCl modified Co3O4 exhibit nanoparticle morphology characteristics, and the morphology characteristics of the materials before and after sintering have changed significantly.

[0065] Figures 5-6 It can be seen that the sintered product is Co3O4 with a cubic crystal structure, and the Raman spectrum also presents the characteristic Raman scattering signal of Co3O4 material.

[0066] 2. Test the response-recovery curve at different working temperatures

[0067] First, the response of the prepared 1.2Ag / AgCl-Co3O4 sensing electrode material to 50ppm ethanol gas was tested at different working temperatures. As shown in Figure 6 When the resistance value of the sensing material reaches a steady state, a certain amount of ethanol liquid is injected into the gas chamber, and according to the size of the injected ethanol liquid volume and the size of the test chamber volume, the concentration of ethanol gas in the gas chamber can be calculated. As the ethanol liquid rapidly evaporates and fills the entire test chamber, the resistance of the sensing material rises significantly, mainly due to the adsorption of ethanol gas molecules on the surface of the sensing material or the chemical reaction with the adsorbed oxygen species on the surface of the sensing material, causing changes in the surface interface structure of the sensing material, as well as changes in the carrier concentration and mobility of the sensing material, thus leading to changes in the test resistance of the sensing material.

[0068] 3. Test the gas sensing performance comparison and resistance change of different Ag / AgCl modified Co3O4 materials

[0069] It can be seen from Figure 8 that with the increase of Ag modification amount, the response value of the prepared sensing material increases, and the best working temperature moves to a lower temperature. Specifically, the best working temperature and response value of Co3O4 material are 275℃ and 62, respectively, while the best working temperature and response value of 1.2Ag / AgCl-Co3O4 sensing material are 175℃ and 189, respectively, and both the response value and the best working temperature are significantly improved. Among all the Ag / AgCl modified Co3O4 sensing materials, the response value of 1.2Ag / AgCl-Co3O4 sensing material to ethanol gas is the highest. In addition, from Figure 9It can be seen that with the increase of working temperature, the resistance value of the sensing material gradually decreases, and the resistance value of the Ag / AgCl modified Co3O4 sensing material is lower than that of Co3O4. It can be seen that by changing the working temperature, the effective carrier concentration and mobility in the material can be adjusted, and the electronic sensitization of the noble metal can be used to regulate the electrical and physical properties of the sensing material, thereby improving the gas sensing performance of the material.

[0070] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any modification, equivalent replacement and improvement within the technical range disclosed by the present application and within the spirit and principle of the present application shall be covered within the protection scope of the present application.

Claims

1. An Ag / AgCl modified Co3O4 nanocomposite material, characterized in that, The Ag / AgCl modified Co3O4 nanocomposite material is made of inorganic compounds of Ag and Co; wherein the amount of Co is 2.0 mmol and the concentration of NaCl is 20 ppm. The molar ratio of the inorganic compound of Ag to the inorganic compound of Co is 0.3%, 0.6%, 1.2%, and 2.4%. The method for preparing the Ag / AgCl modified Co3O4 nanocomposite material includes: The inorganic compounds of Ag and Co are dissolved in deionized water. First, an appropriate amount of NaCl solution is added, followed by the addition of N₂H₄. Ag / AgCl-supported α-Co(OH)2 nanosheets were obtained by coprecipitation and in-situ reduction in H2O solution; Ag / AgCl-supported α-Co(OH)2 nanosheets were then dried and sintered to obtain Ag / AgCl-modified Co3O4 nanocomposite material. The method for preparing the Ag / AgCl modified Co3O4 nanocomposite material includes the following steps: Step 1: Dissolve the inorganic compounds of Ag and Co in deionized water and stir to obtain a homogeneous mixed solution. Step two: Under continuous stirring, first add an appropriate amount of NaCl solution to the homogeneous mixed solution, and then add N2H4. α-Co(OH)2 supported on Ag / AgCl was obtained from H2O solution by co-precipitation and in-situ reduction. Step 3: Wash the obtained Ag / AgCl-loaded α-Co(OH)2 with water and ethanol, and dry the washed Ag / AgCl-loaded α-Co(OH)2 in an oven; Step four: After calcining the dried Ag / AgCl-loaded α-Co(OH)2 in a muffle furnace, the Ag / AgCl-modified Co3O4 nanocomposite material is obtained by naturally cooling to room temperature.

2. The Ag / AgCl modified Co3O4 nanocomposite material as described in claim 1, characterized in that, The inorganic compound of Ag is AgNO3; the inorganic compound of Co is either Co(NO3)2·6H2O or Co(Ac)2·4H2O.

3. The Ag / AgCl modified Co3O4 nanocomposite material as described in claim 1, characterized in that, The amount of deionized water added is 20-50 mL; the concentration of NaCl is 20 ppm; the N2H4... The molar ratio of H2O solution to Co(NO3)2·6H2O is 3:1; the N2H4 The H2O solution has a mass fraction of 80 wt.%.

4. The Ag / AgCl modified Co3O4 nanocomposite material as described in claim 1, characterized in that, The coprecipitation and in-situ reduction time is 1-9 hours; the coprecipitation and in-situ reduction temperature is 0°C to 80°C; the drying temperature is 60°C to 80°C, and the drying time is 3-24 hours.

5. The Ag / AgCl modified Co3O4 nanocomposite material as described in claim 1, characterized in that, The muffle furnace has a heating rate of 1°C·min. 1 ~10ºC·min 1 The calcination temperature is 300ºC~500ºC, and the calcination time is 1h~6h.

6. The application of the Ag / AgCl modified Co3O4 nanocomposite material as described in any one of claims 1-5 in monitoring alcohol pollutant gases in the environment.

7. An ethanol gas sensor, characterized in that, The ethanol gas sensor is prepared from Ag / AgCl modified Co3O4 nanocomposite material as described in any one of claims 1-5.

8. The application of the ethanol gas sensor as described in claim 7 in the detection of volatile organic compound ethanol gas molecules.

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