Co3O4 nano-array low-temperature carbon monoxide gas sensor and preparation method thereof

Abstract

The invention relates to a Co3O4 nano-array low-temperature carbon monoxide gas sensor and a preparation method thereof, the sensor comprises an alumina ceramic substrate, an Ag-Pd interdigital electrode is arranged on the alumina ceramic substrate, a gas sensitive material is arranged on the surface of the Ag-Pd interdigital electrode, and the gas sensitive material is composed of a Co3O4 nano-array material; the aluminum oxide ceramic substrate and the Ag-Pd interdigital electrode jointly form a sensor chip; before and after the gas sensitive material is in contact with gas to be detected, namely carbon monoxide, the resistance changes, and the related performance of the response value of the sensor is obtained by measuring the change of the resistance between the Ag-Pd interdigital electrodes; the sensor has the advantages of low detection limit and high response, the baseline drift condition can be obviously reduced, the response recovery capability and speed of the gas sensor are improved, and the sensor preparation method is simple and convenient.

Description

Technical Field

[0001] The present invention belongs to the field of gas sensing technology and specifically relates to a Co 3 O 4 Nano-array low-temperature carbon monoxide gas sensor and preparation method thereof. Background Art

[0002] Research on carbon monoxide gas detection is of great significance in the fields of energy collection, environmental monitoring and storage. Resistive carbon monoxide gas sensors that reflect tiny changes in carbon monoxide gas concentrations by changes in resistance have attracted widespread attention due to their simple structure and low cost. Gas sensors based on metal oxide semiconductors (MOS) are currently the most widely used carbon monoxide gas sensors due to their good stability and high sensitivity. However, the high operating temperature of MOS gas sensors (>300°C) will bring about the problem of high sensor energy consumption. Therefore, how to reduce the operating temperature of MOS gas sensors is a current challenge.

[0003] Co 3 O 4 It has good catalytic oxidation properties for CO under low temperature conditions and is an excellent CO gas-sensitive material. Currently, researchers have been working hard to optimize Co 3 O 4 The morphology, structure and size of nanoparticles can be modified to improve their sensing performance. For example, nanowires, nanosheets and other structures can be prepared to increase the specific surface area, thereby improving gas adsorption and reaction activity. For example, Patil et al. used a simple coprecipitation method to prepare Co nanoparticles aggregated from nanoparticles. 3 O 4 Nanorod powder, using thick film coating process to make sensor elements and perform CO gas performance testing (D.Patil, P.Patil, V.Subramanian, P.A.Joy, H.S.Potdar, Highly sensitive and fast responding CO sensor based on Co 3 O 4 nanorods, Talanta 81 (2010) 37–43,). The results showed that the best working temperature of this material for CO was 250 °C and the lowest detection concentration was 5 ppm. Cao et al. synthesized nanosheet Co using a two-step polyol method. 3 O 4 (AM Cao, JS Hu, HP Liang, WG Song, LJ Wan, XL He, XG Gao, SH Xia, J. Phys. Chem. B 110 (2006) 15858–15863.), gas-sensing test results showed that Co 3O 4 The optimal operating temperature for 1000ppm CO is as high as 300℃. 3 O 4 The operating temperature of the CO gas sensor is still relatively high.

[0004] Co 3 O 4 The nanoarray is formed by the self-assembly of highly ordered nanorods. This structure can not only avoid the agglomeration of individual nanorods, but also expose more active sites, thus improving the gas-sensitive response value to CO. 3 O 4 The in-situ growth of the nanoarray on the electrode substrate can not only increase the interfacial bonding strength between the material and the substrate, but also facilitate the gas-solid interface electron transfer reaction and reduce the activation energy required for the reaction, thereby lowering its optimal operating temperature. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a Co 3 O 4 The nanoarray low-temperature carbon monoxide gas sensor and its preparation method can detect carbon monoxide gas at 100°C. Compared with the existing carbon monoxide gas sensors, the operating temperature is reduced by 150-200°C, and the baseline drift can be significantly reduced, and the response recovery ability and speed of the gas sensor can be improved. The sensor preparation method is simple and convenient.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A kind of Co 3 O 4 The nano-array low-temperature carbon monoxide gas sensor comprises an alumina ceramic substrate 1, an Ag-Pd interdigital electrode 2 is arranged on the alumina ceramic substrate 1, a gas sensitive material 3 is arranged on the surface of the Ag-Pd interdigital electrode 2, and the gas sensitive material 3 is composed of Co 3 O 4 The sensor chip is composed of nano-array materials; an alumina ceramic substrate 1 and Ag-Pd interdigital electrodes 2 together constitute a sensor chip; the resistance of the gas sensitive material 3 changes before and after it contacts the gas to be measured, namely carbon monoxide gas, and the relevant performance of the sensor response value is obtained by measuring the change in resistance between the Ag-Pd interdigital electrodes.

[0008] Co 3 O 4 The gas sensitive material 3 composed of nano-array material is prepared by a hydrothermal method.

[0009] The Co 3 O 4The preparation method of the nano-array low-temperature carbon monoxide gas sensor comprises the following steps:

[0010] Step 1: Clean the sensor chip, use ethanol and water to ultrasonically clean the sensor chip with Ag-Pd interdigital electrodes deposited on the surface, and dry it for later use;

[0011] Step 2: Preparation of Nano-Co 3 O 4 Solution, ammonium fluoride, urea and cobalt nitrate hexahydrate are dissolved in water and stirred to prepare nano Co 3 O 4 Solution;

[0012] Step 3: Preparation of Co 3 O 4 The nanoarray was prepared by hydrothermal method. The nanoCo prepared in step 2 3 O 4 The solution was poured into a reactor containing a sensor chip and subjected to a hydrothermal reaction in a drying oven to form Co on the surface of the sensor chip. 3 O 4 Nano-array gas-sensitive materials;

[0013] Step 4: Form Co on the sensor chip and its surface 3 O 4 The gas sensitive material of the nanoarray was placed in a muffle furnace for high temperature annealing to obtain Co 3 O 4 Nanoarray low-temperature carbon monoxide gas sensor.

[0014] Step 2: Mix ammonium fluoride, urea and cobalt nitrate hexahydrate in a ratio of 1:(1.6-2):(2-4) and dissolve in 36-50 ml of water to obtain nano Co 3 O 4 Solution.

[0015] Step 3 The hydrothermal temperature of the reactor is 95-120°C, and the hydrothermal time is 6.5-8h. Finally, Co 3 O 4 Nanoarrays of gas-sensitive materials.

[0016] Step 4: high temperature annealing in a muffle furnace at 180-250°C for 2-3 hours.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Co 3 O 4 The nanoarray is grown in situ on the substrate and has good interfacial bonding with the substrate surface, which is beneficial to the transfer of charges and substances.

[0019] 2. Co of the present invention 3 O 4 Nanoarrays have a larger specific surface area and more adsorption sites, thereby improving the response recovery speed of gas sensors.

[0020] 3. Compared with other carbon monoxide gas sensors, Co 3 O 4 The nanoarray resistive carbon monoxide gas sensor operates at a temperature as low as 100°C, reducing power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of a carbon monoxide gas sensor according to Example 1 of the present invention.

[0022] Figure 2 Example 1Co of the present invention 3 O 4 Scanning electron microscope image of nanoarray gas sensitive material.

[0023] Figure 3 Example 1Co of the present invention 3 O 4 Raman spectroscopy analysis of nanoarray gas sensitive materials.

[0024] Figure 4 Example 1Co of the present invention 3 O 4 XRD analysis of nanoarrays.

[0025] Figure 5 Example 1Co of the present invention 3 O 4 Gas sensing performance test of nanoarray carbon monoxide gas sensor at 75-175℃.

[0026] Figure 6 Example 1Co of the present invention 3 O 4 Gas sensitive response diagram of nanoarray carbon monoxide gas sensor to 50ppm carbon monoxide gas.

[0027] Figure 7 Example 1Co of the present invention 3 O 4 Response recovery time of nanoarray carbon monoxide gas sensor to 50ppm carbon monoxide gas.

[0028] Figure 8 Example 2Co of the present invention 3 O 4 Scanning electron microscope image of nanoarray gas sensitive material.

[0029] Fig. 9 Example 2Co of the present invention3 O 4 Gas sensing performance test of nanoarray carbon monoxide gas sensor at 75-175℃.

[0030] Fig.10 Example 2Co of the present invention 3 O 4 Gas sensitive response diagram of nanoarray carbon monoxide gas sensor to 50ppm carbon monoxide gas.

[0031] Fig.11 Example 2Co of the present invention 3 O 4 Response recovery time of nanoarray carbon monoxide gas sensor to 50 ppm carbon monoxide gas.

[0032] Fig.12 Example 3Co of the present invention 3 O 4 Scanning electron microscope image of nanoarray gas sensitive material.

[0033] Fig.13 Example 3Co of the present invention 3 O 4 Gas sensing performance test of nanoarray carbon monoxide gas sensor at 75-175℃.

[0034] Fig.14 Example 3Co of the present invention 3 O 4 Gas sensitive response diagram of nanoarray carbon monoxide gas sensor to 50ppm carbon monoxide gas.

[0035] Fig.15 Example 3Co of the present invention 3 O 4 Response recovery time of nanoarray carbon monoxide gas sensor to 50 ppm carbon monoxide gas. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0037] Example 1, reference Figure 1 , a Co 3 O 4 The nano-array low-temperature carbon monoxide gas sensor comprises an alumina ceramic substrate 1, an Ag-Pd interdigital electrode 2 is arranged on the alumina ceramic substrate 1, a gas sensitive material 3 is arranged on the surface of the Ag-Pd interdigital electrode 2, and the gas sensitive material 3 is composed of Co 3 O 4The sensor chip is composed of nano-array materials and prepared by a hydrothermal method; an alumina ceramic substrate 1 and an Ag-Pd interdigital electrode 2 together constitute a sensor chip; the alumina ceramic substrate 1 is 500 μm thick, the interdigital width of the Ag-Pd interdigital electrode 2 is 400 μm, the gap between adjacent interdigital fingers is 200 μm, and the thickness of the Ag-Pd electrode is 100 nm; the resistance of the gas sensitive material 3 changes before and after contacting the gas to be measured, namely carbon monoxide gas, and the relevant performance of the sensor response value is obtained by measuring the change in resistance between the Ag-Pd interdigital electrodes.

[0038] The Co 3 O 4 The preparation method of the nano-array low-temperature carbon monoxide gas sensor comprises the following steps:

[0039] Step 1: Clean the sensor chip, use ethanol and water to ultrasonically clean the sensor chip with Ag-Pd interdigital electrodes deposited on the surface, and dry it for later use;

[0040] Step 2: Prepare nano Co3O4 solution by dissolving 0.296 g ammonium fluoride, 0.474 g urea and 0.592 g cobalt nitrate hexahydrate in 36 ml water and stirring to prepare nano Co 3 O 4 Solution;

[0041] Step 3: Prepare Co3O4 gas sensitive material by hydrothermal method. 3 O 4 The solution was poured into a reactor equipped with a sensor chip and subjected to a hydrothermal reaction in a drying oven at 95°C for 6.5 h to form Co on the surface of the sensor chip. 3 O 4 Nano-array gas-sensitive materials;

[0042] Step 4: Form Co on the sensor chip and its surface 3 O 4 The gas sensitive material of the nanoarray was placed in a muffle furnace at 180°C for 2h to obtain Co 3 O 4 Nanoarray low-temperature carbon monoxide gas sensor.

[0043] The Co prepared in this example 3 O 4 The gas sensitive materials of nano-arrays were tested by scanning electron microscope, such as Figure 2 As shown, the image Co 3 O 4 Countless nano-Co in the overall morphology of the nanoarray 3 O 4 The stacked clusters form a complete array; 3 O4 Nano-array gas sensitive materials were subjected to Raman spectroscopy analysis, and the results were as follows Figure 3 As shown, it can be seen that Co 3 O 4 The nanoarray has five Raman vibration characteristic peaks, indicating that the synthesized material is spinel phase Co 3 O 4 . 3 O 4 The nanoarray gas sensitive materials were analyzed by XRD, such as Figure 4 As shown, the eight diffraction peaks at 19.1, 31.3°, 36.9°, 38.5°, 44.8°, 55.6°, 59.4° and 65.2° correspond to the pure phase sapphire structure Co 3 O 4 The (111), (220), (311), (222), (400), (422), (511) and (440) crystal planes of the synthesized material are Co 3 O 4 .

[0044] The Co prepared in this example was tested using a gas-sensitive test system. 3 O 4 The gas sensing performance of the nano-array low-temperature carbon monoxide gas sensor was tested in the operating temperature range of 75-175°C. Figure 5 As shown, the results show that the optimal working temperature is 100℃, Co 3 O 4 The nano-array low-temperature carbon monoxide gas sensor has a stable sensitivity of about 1.5 when 50ppm carbon monoxide is continuously introduced for 4 cycles, and the baseline is relatively stable with a small drift difference. Figure 6 , 7 As shown, it shows that Co 3 O 4 Nanoarray low-temperature carbon monoxide gas sensor has good repeatability.

[0045] Example 2, a Co 3 O 4 The structure of the nano-array low-temperature carbon monoxide gas sensor is the same as that of Example 1.

[0046] A kind of Co 3 O 4 The preparation method of the nano-array low-temperature carbon monoxide gas sensor comprises the following steps:

[0047] Step 1: Clean the sensor chip, use ethanol and water to ultrasonically clean the sensor chip with Ag-Pd interdigital electrodes deposited on the surface, and dry it for later use;

[0048] Step 2: Prepare nano Co3O4 solution by dissolving 0.296 g ammonium fluoride, 0.592 g urea and 1.184 g cobalt nitrate hexahydrate in 50 ml water and stirring to prepare nano Co 3 O 4 Solution;

[0049] Step 3: Prepare Co3O4 gas sensitive material by hydrothermal method. 3 O 4 The solution was poured into a reactor equipped with a sensor chip and subjected to hydrothermal reaction in a drying oven at 120°C for 8 h to form Co on the surface of the sensor chip. 3 O 4 Nano-array gas-sensitive materials;

[0050] Step 4: Form Co on the sensor chip and its surface 3 O 4 The gas sensitive material of the nanoarray was placed in a muffle furnace at 250°C for 3 h to obtain Co 3 O 4 Nanoarray low-temperature carbon monoxide gas sensor.

[0051] The Co prepared in this example 3 O 4 The gas sensitive materials of nano-arrays were tested by scanning electron microscope, such as Figure 8 As shown, the image Co 3 O 4 Countless nano-Co in the overall morphology of the nanoarray 3 O 4 They are gathered together in piles to form a complete array;

[0052] The Co prepared in this example was tested using a gas-sensitive test system. 3 O 4 The gas sensing performance of the nano-array low-temperature carbon monoxide gas sensor was tested in the operating temperature range of 75-175°C. Fig. 9 As shown, the results show that the optimal working temperature is 100℃, Co 3 O 4 The sensitivity of the nano-array low-temperature carbon monoxide gas sensor to 50ppm carbon monoxide was stabilized at about 1.48 within 4 cycles, and the baseline was relatively stable with a small drift difference. Fig.10 , 11 As shown, it shows that Co 3 O 4 Nanoarray low-temperature carbon monoxide gas sensor has good repeatability.

[0053] Example 3, a Co 3 O 4The structure of the nano-array low-temperature carbon monoxide gas sensor is the same as that of Example 1.

[0054] A kind of Co 3 O 4 The preparation method of the nano-array low-temperature carbon monoxide gas sensor comprises the following steps:

[0055] Step 1: Clean the sensor chip, use ethanol and water to ultrasonically clean the sensor chip with Ag-Pd interdigital electrodes deposited on the surface, and dry it for later use;

[0056] Step 2: Prepare nano Co3O4 solution by dissolving 0.3 g ammonium fluoride, 0.596 g urea and 0.621 g cobalt nitrate hexahydrate in 40 ml water and stirring to prepare nano Co 3 O 4 Solution;

[0057] Step 3: Prepare Co3O4 gas sensitive material by hydrothermal method. 3 O 4 The solution was poured into a reactor equipped with a sensor chip and subjected to a hydrothermal reaction in a drying oven at 115°C for 7.5 h to form Co on the surface of the sensor chip. 3 O 4 Nano-array gas-sensitive materials;

[0058] Step 4: Form Co on the sensor chip and its surface 3 O 4 The gas sensitive material of the nanoarray was placed in a muffle furnace at 200°C for 2.5 hours for high temperature annealing to obtain Co 3 O 4 Nanoarray low-temperature carbon monoxide gas sensor.

[0059] The Co prepared in this example 3 O 4 The gas sensitive materials of nano-arrays were tested by scanning electron microscope, such as Fig.12 As shown, the image Co 3 O 4 Countless nano-Co in the overall morphology of the nanoarray 3 O 4 They are gathered together in piles to form a complete array;

[0060] The Co prepared in this example was tested using a gas-sensitive test system. 3 O 4 The gas sensing performance of the nano-array low-temperature carbon monoxide gas sensor was tested in the operating temperature range of 75-175°C. Fig.13 As shown, the results show that the optimal working temperature is 100℃, Co 3 O 4The nano-array low-temperature carbon monoxide gas sensor has a stable sensitivity of about 3.0 when 50ppm carbon monoxide is continuously introduced for 4 cycles, and the baseline is relatively stable with a small drift difference. Fig.14 , 15 As shown, it shows that Co 3 O 4 Nanoarray low-temperature carbon monoxide gas sensor has good repeatability.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A Co3O4 nanoarray low-temperature carbon monoxide gas sensor, comprising an alumina ceramic substrate (1), characterized in that: An Ag-Pd interdigital electrode (2) is provided on an alumina ceramic substrate (1); a gas sensitive material (3) is provided on the surface of the Ag-Pd interdigital electrode (2); the gas sensitive material (3) is composed of a Co3O4 nano-array material; the alumina ceramic substrate (1) and the Ag-Pd interdigital electrode (2) together constitute a sensor chip; the resistance of the gas sensitive material (3) changes before and after contacting a gas to be measured, i.e., carbon monoxide gas; and the relevant performance of the sensor response value is obtained by measuring the change in resistance between the Ag-Pd interdigital electrodes.

2. The Co3O4 nanoarray low-temperature carbon monoxide gas sensor according to claim 1, characterized in that: The gas sensitive material (4) composed of Co3O4 nanoarray material is prepared by a hydrothermal method.

3. A method for preparing a Co3O4 nanoarray low-temperature carbon monoxide gas sensor according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: Clean the sensor chip, use ethanol and water to ultrasonically clean the sensor chip with Ag-Pd interdigital electrodes deposited on the surface, and dry it for later use; Step 2, preparing a nano-Co3O4 solution, dissolving ammonium fluoride, urea and cobalt nitrate hexahydrate in water and stirring to prepare a nano-Co3O4 solution; Step 3, prepare Co3O4 gas sensitive material by hydrothermal method, pour the nano Co3O4 solution prepared in step 2 into a reactor equipped with a sensor chip, and perform hydrothermal reaction in a drying oven to form a gas sensitive material of Co3O4 nano array on the surface of the sensor chip; Step 4: Place the sensor chip and the gas sensitive material with Co3O4 nanoarray formed on its surface into a muffle furnace for high temperature annealing to obtain a Co3O4 nanoarray low-temperature carbon monoxide gas sensor.

4. The preparation method according to claim 3, characterized in that: Step 2: Mix ammonium fluoride, urea and cobalt nitrate hexahydrate in a ratio of 1:(1.6-2):(2-4) and dissolve in 36-50 ml of water to obtain a nano-Co3O4 solution.

5. The preparation method according to claim 3, characterized in that: In step 3, the hydrothermal temperature of the reactor is 95-120° C., and the hydrothermal time is 6.5-8 h. Finally, a gas sensitive material of Co3O4 nanoarray is obtained on the surface of the sensor chip.

6. The preparation method according to claim 3, characterized in that: Step 4: high temperature annealing in a muffle furnace at 180-250°C for 2-3 hours.

7. A method for preparing a Co3O4 nanoarray low-temperature carbon monoxide gas sensor according to any one of claims 3 to 6, characterized in that: The following steps are involved: Step 1: Clean the sensor chip, use ethanol and water to ultrasonically clean the sensor chip with Ag-Pd interdigital electrodes deposited on the surface, and dry it for later use; Step 2, preparing a nano-Co3O4 solution, dissolving 0.296 g of ammonium fluoride, 0.474 g of urea and 0.592 g of cobalt nitrate hexahydrate in 36 ml of water and stirring to prepare a nano-Co3O4 solution; Step 3: Prepare Co3O4 gas sensitive material by hydrothermal method. Pour the nano Co3O4 solution prepared in step 2 into a reactor equipped with a sensor chip, and perform hydrothermal reaction in a drying oven at 95°C for 6.5 hours to form a gas sensitive material of Co3O4 nano array on the surface of the sensor chip. Step 4: Place the sensor chip and the gas sensitive material with Co3O4 nanoarray formed on its surface into a muffle furnace at 180° C. for high temperature annealing for 2 h to obtain a Co3O4 nanoarray low-temperature carbon monoxide gas sensor.

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