Composite gas-sensitive material based on CuO-SnO2, preparation method of composite gas-sensitive material and gas sensor

Abstract

The invention relates to a composite gas sensitive material based on CuO-SnO2, a preparation method thereof and a gas sensor. The preparation method of the composite gas sensitive material comprises the following steps: mixing a tin source, a copper source and reduced graphene oxide to prepare a precursor dispersion liquid; carrying out heat treatment on the precursor dispersion liquid, carrying out solid-liquid separation, and retaining a solid-phase intermediate; and carrying out calcination treatment on the intermediate. The composite gas-sensitive material not only has good gas adsorption capacity, but also has relatively high hydrogen sulfide gas sensitivity at a relatively low temperature under the action of a ternary heterojunction by doping reduced graphene oxide, copper oxide and tin oxide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a CuO-SnO2-based composite gas-sensitive material, a preparation method thereof and a gas sensor. BACKGROUND

[0002] Hydrogen sulfide is a highly toxic, corrosive and flammable gas, which widely exists in industrial production processes such as petroleum chemical industry, sewage treatment and natural gas exploitation. Hydrogen sulfide is extremely harmful to the human body and can even cause corrosion to equipment. Therefore, it is crucial to detect hydrogen sulfide gas quickly, accurately and sensitively.

[0003] However, the conventional hydrogen sulfide sensor generally has low sensitivity, which is difficult to meet the requirements of hydrogen sulfide detection accuracy and stability in actual applications. SUMMARY

[0004] Therefore, it is necessary to provide a CuO-SnO2-based composite gas-sensitive material with high sensitivity to hydrogen sulfide, a preparation method thereof and a gas sensor.

[0005] In a first aspect, the present application provides a preparation method of a composite gas-sensitive material.

[0006] The preparation method of the composite gas-sensitive material comprises the following steps:

[0007] Mixing a tin source and a copper source to prepare a precursor dispersion liquid;

[0008] Performing heat treatment on the precursor dispersion liquid, solid-liquid separation, and retaining a solid-phase intermediate;

[0009] Performing calcination treatment on the solid-phase intermediate.

[0010] In some embodiments, the heat treatment process comprises:

[0011] Reacting at 150℃-220℃ for 8h-16h.

[0012] In some embodiments, the calcination treatment process comprises:

[0013] Raising the temperature to 350℃-450℃ at a temperature raising rate of 8℃ / min-12℃ / min, and calcining at 350℃-450℃ for 1h-3h.

[0014] In some embodiments, the molar ratio of copper ions to tin ions in the precursor dispersion liquid is 1:(1-3).

[0015] In some embodiments, the tin source comprises one or more of tin tetrachloride and its hydrate; and / or

[0016] The copper source includes one or more of copper chloride and hydrates thereof.

[0017] In some embodiments, the precursor dispersion further includes reduced graphene oxide, and the mass concentration of the reduced graphene oxide in the precursor dispersion is 0.08 g / L to 0.2 g / L.

[0018] In some embodiments, the step of preparing the precursor dispersion includes:

[0019] Mixing the tin source and the copper source with a first solvent to prepare a mixed solution;

[0020] Mixing the reduced graphene oxide, a second solvent, and the mixed solution to prepare the precursor dispersion.

[0021] In a second aspect, the application provides a composite gas-sensitive material.

[0022] A composite gas-sensitive material is prepared by the method described above.

[0023] In a third aspect, the application provides a gas sensor.

[0024] A gas sensor includes a micro-hotplate and a gas response layer on at least a portion of the surface of the micro-hotplate, and the gas response layer contains the composite gas-sensitive material described above.

[0025] In some embodiments, the method of preparing the gas response layer includes:

[0026] Obtaining a dispersion slurry containing the composite gas-sensitive material;

[0027] Coating the dispersion slurry on at least a portion of the surface of the micro-hotplate and heating and aging.

[0028] The above method for preparing the composite gas-sensitive material includes compounding a tin source and a copper source to form a precursor dispersion, heat-treating the precursor dispersion to generate a solid-phase intermediate, and calcining the solid-phase intermediate to obtain a Cu-SnO2-doped composite gas-sensitive material. In the composite gas-sensitive material, CuO can respond to hydrogen sulfide gas through selective adsorption, and SnO2 colloidal quantum dots can effectively increase the specific surface area of the composite gas-sensitive material, thereby improving the gas adsorption efficiency and ultimately effectively improving the response value of the composite gas-sensitive material at different working temperatures. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0030] Figure 1 The micro-morphology diagram of the reduced graphene oxide in the embodiment 1 of the present application.

[0031] Figure 2 The micro-morphology diagram of the composite gas sensitive material in the embodiment 1 of the present application.

[0032] Figure 3 The XPS spectrogram of the composite gas sensitive material in the embodiment 1, 4, and the comparative example 1 of the present application.

[0033] Figure 4 The Sn 3d spectrogram of the composite gas sensitive material in the embodiment 1, 4, and the comparative example 1 of the present application.

[0034] Figure 5 The O 1s spectrogram of the composite gas sensitive material in the embodiment 1, 4, and the comparative example 1 of the present application.

[0035] Figure 6 The Cu 2p spectrogram of the composite gas sensitive material in the embodiment 1, 4 of the present application.

[0036] Figure 7 The gas sensitive performance test comparison diagram of the composite gas sensitive material in the embodiment 1-3, and the comparative example 1 of the present application.

[0037] Figure 8 The gas sensitive performance test comparison diagram of the composite gas sensitive material in the embodiment 4-6, and the comparative example 1 of the present application.

[0038] Figure 9 The continuous dynamic response recovery transient curve of the composite gas sensitive material in the embodiment 1 of the present application to hydrogen sulfide gas with different concentrations.

[0039] Figure 10 The gas selectivity test schematic diagram of the composite gas sensitive material in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0040] In order to make the above purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail. In the following description, a lot of specific details are set forth in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0041] In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified. In the present application, the meaning of "at least one" is one or more, such as one, two, and more than two. The meaning of "a plurality of" or "several" is at least two, such as two, three, etc.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0043] When a numerical range is disclosed herein, the range is to be construed as having been recited to the full extent of the range, including every value within the range and every sub-range between values within the range. Further, when a range is provided, it is intended to include the endpoints of the range and every value within the range. In addition, it is intended that when a plurality of ranges are provided, the ranges can be combined and the description shall apply to those sub-ranges as well. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass both the stated range and sub-ranges within the stated range.

[0044] Unless otherwise specified, all steps of the present application can be carried out in sequence or randomly. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0045] In the present application, "above" or "below" includes the number itself. For example, 1 below includes 1.

[0046] In the present application, the temperature parameters, unless otherwise specified, allow both constant temperature treatment and fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows fluctuations within the accuracy range controlled by the instrument. Fluctuations within a range of, for example, ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0047] Hydrogen sulfide is a toxic, corrosive and flammable gas, which is widely present in the industrial production processes such as petroleum and chemical industry, sewage treatment and natural gas exploitation. Hydrogen sulfide is extremely harmful to human body and can even cause corrosion to equipment. Therefore, it is of great significance to detect hydrogen sulfide gas quickly, accurately and sensitively.

[0048] In the field of hydrogen sulfide gas detection, the traditional detection materials and the sensors prepared based thereon have many limitations. For example, copper, as a kind of excellent hydrogen sulfide sensor sensitive material, has good selective adsorption effect on hydrogen sulfide, but still has the shortcomings of poor adsorption capacity and low sensitivity. Although the metal oxide semiconductor colloidal quantum dots have the advantages suitable for gas sensitive materials, such as high specific surface area of porous membrane structure and can be deposited on any substrate, there are still problems of low sensitivity and high detection limit when used for hydrogen sulfide detection, which is difficult to meet the requirements of detection accuracy and stability in actual application.

[0049] Based on this, the first aspect of the present application provides a preparation method of a composite gas sensitive material with high sensitivity to hydrogen sulfide.

[0050] Exemplarily, the preparation method of the composite gas sensitive material comprises the following steps:

[0051] Mixing tin source and copper source to prepare a precursor dispersion liquid;

[0052] Heat treating the precursor dispersion liquid, solid-liquid separation, and retaining the solid phase intermediate;

[0053] Calcining the intermediate.

[0054] The above preparation method forms a precursor dispersion liquid by compounding tin source and copper source, generates a solid phase intermediate by heat treating the precursor dispersion liquid, and obtains a Cu-SnO2 doped composite gas sensitive material by calcining the solid phase intermediate. In the above composite gas sensitive material, CuO can respond to hydrogen sulfide gas through selective adsorption, and SnO2 colloidal quantum dots can effectively improve the specific surface area of the composite gas sensitive material, thereby improving the gas adsorption efficiency and effectively improving the response value of the composite gas sensitive material at different working temperatures.

[0055] In some embodiments, the heat treatment process comprises:

[0056] Reacting at 150℃-220℃ for 8h-16h.

[0057] Heat treating the precursor dispersion liquid to form a hydroxide intermediate.

[0058] In some embodiments, the heat treatment is performed in a high-pressure reaction kettle, and a certain pressure is applied to assist the preparation of the hydroxide intermediate.

[0059] In some embodiments, the solid-liquid separation is achieved by centrifugation, and the supernatant is removed and the solid intermediate is retained.

[0060] In some embodiments, the solid intermediate is washed, and the washing solvent includes one or more of anhydrous ethanol and n-hexane.

[0061] In some embodiments, the calcination process includes:

[0062] The temperature is raised to 350-450°C at a temperature raising rate of 8-12°C / min, and the calcination is performed at 350-450°C for 1-3h.

[0063] In some embodiments, the molar ratio of copper ions to tin ions in the precursor dispersion is 1:(1-3). Alternatively, the molar ratio of copper ions to tin ions in the precursor dispersion can be, but is not limited to, 1:1, 2:3, 1:2, 2:5, 1:3, or other values within the range of 1:(1-3).

[0064] In some embodiments, the molar concentration of copper ions in the precursor dispersion is 0.005-0.03 mol / L. Alternatively, the molar concentration of copper ions in the precursor dispersion can be, but is not limited to, 0.005 mol / L, 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, or other values within the range of 0.005-0.03 mol / L.

[0065] In some embodiments, the molar concentration of tin ions in the precursor dispersion is 0.005-0.06 mol / L. Alternatively, the molar concentration of tin ions in the precursor dispersion can be, but is not limited to, 0.005 mol / L, 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, or other values within the range of 0.005-0.06 mol / L.

[0066] In some embodiments, the tin source includes one or more of tin tetrachloride and hydrates thereof.

[0067] In some embodiments, the copper source includes one or more of copper chloride and hydrates thereof.

[0068] In some embodiments, the precursor dispersion further includes reduced graphene oxide.

[0069] In some embodiments, the mass concentration of the reduced graphene oxide in the precursor dispersion is 0.08 g / L to 0.2 g / L. Optionally, the mass concentration of the reduced graphene oxide in the precursor dispersion can be, but is not limited to, 0.08 g / L, 0.09 g / L, 0.1 g / L, 0.11 g / L, 0.12 g / L, 0.13 g / L, 0.14 g / L, 0.15 g / L, 0.17 g / L, 0.2 g / L, or other values within the range of 0.08 g / L to 0.2 g / L.

[0070] The precursor dispersion is prepared by compounding a tin source, a copper source, and reduced graphene oxide (rGO). The precursor dispersion is heat-treated by a hot solvent method to prepare a solid-phase intermediate, and the solid-phase intermediate is further calcined to obtain the rGO / Cu-SnO2 doped composite gas-sensitive material. After the Cu and rGO are doped into SnO2, a ternary heterojunction (p-CuO / n-SnO2 / p-rGO) is formed between p-CuO and p-rGO and n-SnO2, which helps to reduce the activation energy required for the chemical reaction between the composite gas-sensitive material and gas molecules, effectively reduces the gas-sensitive performance of the composite gas-sensitive material at low temperatures, and helps to reduce the working temperature of the composite gas-sensitive material.

[0071] In some embodiments, the step of preparing the precursor dispersion comprises:

[0072] The tin source and the copper source are mixed with the first solvent to obtain a mixed solution.

[0073] The reduced graphene oxide, the second solvent, and the mixed solution are mixed to obtain the precursor dispersion.

[0074] In some embodiments, the first solvent comprises oleic acid and oleylamine, and the second solvent comprises ethanol.

[0075] In some embodiments, the tin source and the copper source are ultrasonically dispersed with the first solvent at 50°C to 80°C to form a transparent mixed solution.

[0076] The first solvent comprises oleic acid and oleylamine, which not only can sufficiently dissolve the tin source and the copper source, but also can interact with the surface functional groups of the reduced graphene oxide, so that the reduced graphene oxide can be uniformly dispersed to obtain a uniform precursor dispersion.

[0077] In some embodiments, the volume ratio of the oleic acid to the oleylamine is (4 to 12):1.

[0078] In some embodiments, the step of preparing the reduced graphene oxide comprises:

[0079] A graphene oxide dispersion is obtained;

[0080] Mixing the graphene oxide dispersion liquid and the reducing agent, and reacting at 80-100℃ for 12-36h, and then solid-liquid separation to obtain the reduced graphene oxide.

[0081] In some embodiments, the method for preparing the graphene oxide dispersion liquid comprises:

[0082] The graphene oxide is dispersed in deionized water, and then ultrasonic dispersion is performed to obtain the graphene oxide dispersion liquid.

[0083] In some embodiments, the mass concentration of the graphene oxide in the graphene oxide dispersion liquid is 0.05-0.2g / L.

[0084] In some embodiments, the reducing agent comprises ascorbic acid. Optionally, the mass ratio of ascorbic acid to graphene oxide is (6-15):1.

[0085] In some embodiments, the solid-liquid separation is achieved by centrifugation, and the supernatant is discarded, and the reduced graphene oxide in the solid phase is reserved.

[0086] In some embodiments, the reduced graphene oxide after separation is washed, and the washing solvent comprises one or more of anhydrous ethanol and deionized water.

[0087] In the second aspect of the present application, a composite gas-sensitive material is provided, which is prepared by the above method.

[0088] In the third aspect of the present application, a gas sensor is provided.

[0089] For example, the gas sensor comprises a micro-hotplate and a gas response layer on at least a part of the surface of the micro-hotplate, and the gas response layer comprises the above composite gas-sensitive material.

[0090] In some embodiments, the method for preparing the gas response layer comprises:

[0091] A dispersion slurry containing the composite gas-sensitive material is obtained;

[0092] The dispersion slurry is coated on at least a part of the surface of the micro-hotplate, and then heated and aged.

[0093] In some embodiments, the method for preparing the dispersion slurry comprises:

[0094] The composite gas-sensitive material is ground to obtain a composite gas-sensitive material powder with a particle size of microns;

[0095] The composite gas-sensitive material powder is dispersed in anhydrous ethanol to obtain the dispersion slurry.

[0096] In some embodiments, the mass concentration of the composite gas sensitive material in the dispersion slurry is 20 g / L to 80 g / L. Alternatively, the mass concentration of the composite gas sensitive material in the dispersion slurry can be, but is not limited to, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L or other values within the range of 20 g / L to 80 g / L.

[0097] In some embodiments, the process of heating aging comprises:

[0098] A voltage of 2 V to 3 V is applied to the heating electrode of the micro-hotplate, and the aging is performed for 36 h to 72 h.

[0099] The application will be further described in detail below with reference to specific examples.

[0100] In the following specific examples and comparative examples, the raw materials used, unless otherwise specified, are commercially available products; the instruments used, unless otherwise specified, are commercially available products; and the processes used, unless otherwise specified, are routinely selected by those skilled in the art.

[0101] Example 1

[0102] This example provides a composite gas sensitive material, and the code of the composite gas sensitive material of this example is Cu-SnO2-2.

[0103] The preparation method of the composite gas sensitive material of this comparative example is basically the same as that of Example 1, except that no reduced graphene oxide dispersion liquid is added.

[0104] The preparation method of the composite gas sensitive material of this example is as follows:

[0105] 1.2 mmol of SnCl4·5H2O and 0.6 mmol of CuCl2·2H2O are dispersed in a first solvent, the first solvent contains 20 mL of oleic acid and 2.5 mL of oleylamine, ultrasonic treatment is performed for 10 min at a power of 90 W, and a uniform transparent mixed solution is obtained by continuously stirring at a temperature of 60 ℃ to form a uniform precursor dispersion liquid;

[0106] The precursor dispersion liquid is transferred to a high-pressure reaction kettle with a volume of 50 mL, and the reaction is performed at 180 ℃ for 12 h; after cooling to room temperature, centrifugal treatment is performed at a speed of 400 rpm for 15 min, the supernatant is discarded, the solid-phase intermediate is washed with anhydrous ethanol and n-hexane respectively, and dried at 75 ℃ for 10 h;

[0107] The solid-phase intermediate is placed in a muffle furnace, heated to 400 ℃ at a heating rate of 10 ℃ / min, and calcined at 400 ℃ for 2 h to obtain the composite gas sensitive material.

[0108] Example 2

[0109] The embodiment provides a composite gas-sensitive material, and the code of the composite gas-sensitive material in the embodiment is Cu-SnO2-1.

[0110] The preparation method of the composite gas-sensitive material in the embodiment is basically the same as that in Embodiment 1, and the difference lies in that, when the precursor dispersion liquid is prepared, the total molar ratio of Cu 2+ to Sn 4+ is unchanged, and Cu 2+ :Sn 4+ = 1:4.

[0111] Embodiment 3

[0112] The embodiment provides a composite gas-sensitive material, and the code of the composite gas-sensitive material in the embodiment is Cu-SnO2-3.

[0113] The preparation method of the composite gas-sensitive material in the embodiment is basically the same as that in Embodiment 1, and the difference lies in that, when the precursor dispersion liquid is prepared, the total molar ratio of Cu 2+ to Sn 4+ is unchanged, and Cu 2+ :Sn 4+ = 1:1.

[0114] Embodiment 4

[0115] The embodiment provides a composite gas-sensitive material, and the code of the composite gas-sensitive material in the embodiment is rGO / Cu-SnO2-2.

[0116] The preparation method of the composite gas-sensitive material in the embodiment is as follows:

[0117] 1.2 mmol SnCl4.5H2O and 0.6 mmol CuCl2.2H2O are dispersed in a first solvent, the first solvent contains 20 mL of oleic acid and 2.5 mL of oleylamine, ultrasonic treatment is performed for 10 min under a power of 90 W, and a uniform transparent mixed solution is formed by continuously stirring at a temperature of 60 DEG C; 3.6 mL of a reduced graphene oxide dispersion liquid and 6.4 mL of anhydrous ethanol are sequentially added, and a uniform precursor dispersion liquid is obtained by continuously stirring;

[0118] The precursor dispersion liquid is transferred into a high-pressure reaction kettle with a volume of 50 mL, and reaction is performed at 180 DEG C for 12 h. After cooling to room temperature, centrifugal treatment is performed at a rotating speed of 400 rpm for 15 min, the supernatant is discarded, the solid-phase intermediate is washed by using anhydrous ethanol and n-hexane respectively, and drying is performed at 75 DEG C for 10 h;

[0119] The solid-phase intermediate was placed in a muffle furnace, heated to 400℃ at a heating rate of 10℃ / min, and calcined at 400℃ for 2h to obtain the composite gas-sensitive material.

[0120] The preparation step of the reduced graphene oxide is:

[0121] The 25mg of graphene oxide was dispersed in 25mL of deionized water, ultrasonically treated at 85W power for 1h to obtain a graphene oxide dispersion; 250mg of ascorbic acid was added to the graphene oxide dispersion, and kept in a constant temperature water bath at 95℃ for 24h. After the reaction was completed, the solution was cooled to room temperature, and high-speed centrifugation was performed at a speed of 15000rpm, the supernatant was discarded, and the precipitate was washed with ethanol and deionized water, respectively, and dried at 75℃ for 10h. The reduced graphene oxide solid powder was dispersed in anhydrous ethanol, ultrasonically treated at 90W power for 1h, and a 1mg / mL reduced graphene oxide dispersion was prepared for standby.

[0122] See Figure 1 , Figure 1 The micro-morphology of the reduced graphene oxide in this example is shown in the figure. As can be seen from the figure, the reduced graphene oxide presents a wrinkled sheet structure.

[0123] See Figure 2 , Figure 2 The micro-morphology of the composite gas-sensitive material in this example is shown in the figure. As can be seen from the figure, the composite gas-sensitive material is composed of many small nanoparticles, and the morphology structure is loose and porous.

[0124] The surface element analysis of the composite gas-sensitive material was performed, and the analysis results are shown in Table 1.

[0125] Table 1 EDS analysis results of the composite gas-sensitive material

[0126]

[0127] As can be seen from Table 1, the composite gas-sensitive material contains Sn, Cu, C, and O four elements, and the doping amount of Cu ions accounts for 1.10%.

[0128] Example 5

[0129] This example provides a composite gas-sensitive material, and the code of the composite gas-sensitive material of this example is rGO / Cu-SnO2-1.

[0130] The preparation method of the composite gas-sensitive material of this example is basically the same as that of Example 4, except that:

[0131] When preparing the precursor dispersion, 1.8mL of reduced graphene oxide dispersion was added.

[0132] Example 6

[0133] This embodiment provides a composite gas-sensitive material, designated as rGO / Cu-SnO2-3.

[0134] The preparation method of the composite gas-sensitive material in this embodiment is basically the same as that in Example 4, except that:

[0135] When preparing the precursor dispersion, 5.4 mL of reduced graphene oxide dispersion was added.

[0136] Comparative Example 1

[0137] This comparative example provides a composite gas-sensitive material, designated as PristineSnO2 CQDs.

[0138] The preparation method of the composite gas-sensitive material in this comparative example is basically the same as that in Example 1, except that no copper source is added.

[0139] Test Example 1

[0140] To determine the surface composition and binding state of the composite gas-sensitive materials, XPS characterization tests were performed on the composite gas-sensitive materials of Examples 1, 4, and Comparative Example 1. All binding energies were corrected with reference to the C 1s peak of the surface amorphous carbon at 284.8 eV on the XPS spectrometer.

[0141] Please see Figure 3 , Figure 3 These are the XPS spectra of the composite gas-sensitive materials of Examples 1, 4, and Comparative Example 1 of this application. Figure 3 As shown: The XPS spectrum of the original SnO2 CQDs in Comparative Example 1 confirms that the synthesized Pristine SnO2 CQDs contain only Sn, O, and C elements, with no other impurity element peaks. In contrast, the rGO / Cu-SnO2-2 synthesized in Example 4 contains peaks for all four elements: Sn, Cu, O, and C, indicating that Cu has been successfully doped into the SnO2 CQDs.

[0142] Please see Figure 4 , Figure 4 These are high-resolution Sn 3d spectra of the composite gas-sensitive materials of Examples 1, 4, and Comparative Example 1 of this application. Figure 4 As shown: the peaks at 495.67 eV and 487.27 eV correspond to Sn, respectively. 4+ Sn 3d 3 / 2 and Sn 3d 5 / 2 The binding energy at the two peaks differs by 8.4 eV, indicating the formation of SnO2. Furthermore, these peaks all exhibit good symmetry, ruling out the presence of metallic tin.

[0143] See Figure 5 , Figure 5 High resolution O 1s spectra of the composite gas sensitive materials of Example 1, 4, Comparative Example 1. As shown in Figure 5 : The spectra can all be fitted with three Gaussian peaks, and the resulting fitting curves are in good agreement with the original data.

[0144] It can be understood that the three Gaussian peaks correspond to three chemical states of oxygen element respectively: the O 1s peak near 530.5 eV can be attributed to O 2- in the SnO2 lattice, which is called lattice oxygen (O L ). The peak near 531.0 eV is vacancy oxygen (O V ), which is attributed to the oxygen-related vacancies in the SnO2 crystal structure. The peak near 532.1 eV is adsorbed oxygen (O C ), i.e. the oxygen species converted from the oxygen in the air adsorbed by the material.

[0145] Generally, O V can characterize the number of defects and active sites present in the synthesized material, and the increase of its component is conducive to the adsorption of gas and the progress of surface chemical reaction. O C can characterize the number of chemisorbed oxygen on the surface of the gas sensitive material participating in the redox reaction between target gas molecules, and the increase of this component can cause greater resistance change of the surface resistance type sensor, i.e. the improvement of sensitivity.

[0146] See Figure 6 , Figure 6 High resolution Cu 2p spectra of the composite gas sensitive materials of Example 1, 4. As shown in Figure 6 : For rGO / Cu-SnO2-2 of Example 4 and Cu-SnO2-2 of Example 1, the high resolution Cu 2p spectra show four peaks. The two Cu 2p satellite peaks near 962.3 eV and 942.9 eV correspond to CuO phase. The peaks at 952.5 eV and 933.2 eV correspond to the binding energy of Cu 2p 1 / 2 and Cu 2p 3 / 2 respectively, which confirms the presence of Cu 2+ and Cu + ions in the synthesized samples.

[0147] Test Example 2

[0148] The composite gas sensitive materials of Examples 1-6 and Comparative Example 1 were used to prepare gas sensors, and the gas sensitive performance of the gas sensors was tested. The gas diluter was used to output the required concentration of gas, and the gas sensitive performance was tested.

[0149] The preparation method of the gas sensor is as follows:

[0150] The composite gas sensitive material is ground to micron level using a ceramic grinding rod, and the composite gas sensitive material powder is dispersed in anhydrous ethanol to form a dispersion slurry containing 50 mg / ml of the composite gas sensitive material;

[0151] The dispersion slurry is coated on the detection area of the micro-hotplate chip, and is placed in a sealed gas chamber. A voltage of 2.5 V is applied to the heating electrode of the micro-hotplate chip, and the sensor is aged for 48 h to obtain a gas sensor.

[0152] The sensor is exposed to hydrogen sulfide gas with a concentration of 10 ppm at 80-280℃, and the sensor response is as shown in Figure 7 、 8 .

[0153] Please refer to Figure 7 , Figure 7 for the gas sensitive performance test comparison chart of the composite gas sensitive materials of Examples 1-3 and Comparative Example 1. Within the test temperature range, the response of the gas sensor corresponding to Comparative Example 1 to 10 ppm hydrogen sulfide gas gradually increases with increasing temperature, and reaches the highest response value (R a / R g ) 4.4 at 280℃, indicating that its optimal working temperature is at least 280℃, and the applicable scenario is limited. The response values of the gas sensors doped with different Cu change in the same trend, and the response value of the sensor gradually increases when the working temperature increases from 80℃ to 160℃, and reaches the peak value at 160℃.

[0154] Please refer to Figure 8 , Figure 8 for the gas sensitive performance test comparison chart of the composite gas sensitive materials of Examples 4-6 and Comparative Example 1. The doping of rGO causes the working temperature of the gas sensor to be further reduced to 120℃, and the response value of the rGO / Cu-SnO2-2 sensor is the largest, which is attributed to the formation of p-n heterojunction between rGO and Cu-SnO2, which reduces the activation energy required for the chemical reaction between the semiconductor and the gas molecules. The composite gas sensitive material of rGO / Cu-SnO2-2 has a high enough response value at low temperature, and the applicable scenario is the widest.

[0155] Please refer to Figure 9 , Figure 9 for the continuous dynamic response recovery transient curve of the composite gas sensitive material of Example 4 to hydrogen sulfide gas with different concentrations. As shown in Figure 9As shown, the gas sensor can return to the initial state after the response to hydrogen sulfide gas of different concentrations ends, and the response of the gas sensor sharply rises with the increase of the hydrogen sulfide concentration, indicating that the gas sensor has good linearity to hydrogen sulfide gas.

[0156] Please refer to Figure 10 , Figure 10 The figure is a schematic diagram of the gas selectivity test of the composite gas-sensitive material of embodiment 4. The gas sensor is exposed to 50 ppm HCHO, 50 ppm C7H8 (toluene), 100 ppm H2, 100 ppm C4H 10 ( n-butane), 100 ppm CO and 10 ppm hydrogen sulfide respectively at the optimal working temperature of the gas sensor, and the resistance value change of the sensor is recorded. The following figure is the response result of the sensor to different gases. It can be seen that the gas sensor has excellent selectivity to hydrogen sulfide gas.

[0157] As can be seen from the above test, the gas adsorption capacity of the composite gas-sensitive material of the present application is better. By doping with Cu 2+ and metal oxide SnO2, the selective adsorption of CuO to hydrogen sulfide gas can provide the sensitivity and selectivity of the composite gas-sensitive material. Under the action of the ternary heterojunction (p-CuO / n-SnO2 / p-rGO), the activation energy of the target reaction can be reduced, and thus the hydrogen sulfide detection capability can be excellent at a lower working temperature.

[0158] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.

[0159] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A method for preparing a CuO-SnO2-based composite gas sensitive material, characterized in that, The method comprises the following steps: mixing a tin source and a copper source to prepare a precursor dispersion; heat treating the precursor dispersion, solid-liquid separation, and retaining a solid phase intermediate; calcining the solid phase intermediate.

2. The method of claim 1, wherein the composite gas sensitive material is prepared by mixing the metal oxide and the metal complex. The heat treatment process comprises: reacting at 150-220℃ for 8-16h.

3. The method of claim 1, wherein the composite gas sensitive material is prepared by mixing a gas sensitive material and a polymer. The calcining process comprises: heating at a heating rate of 8-12℃ / min to 350-450℃, and calcining at 350-450℃ for 1-3h.

4. The method of claim 1, wherein the composite gas sensitive material is prepared by mixing a gas sensitive material and a polymer. The molar ratio of copper ions to tin ions in the precursor dispersion is 1:(1-3).

5. The method of claim 1, wherein the composite gas sensitive material is prepared by mixing the metal oxide and the metal complex. The tin source comprises one or more of tin tetrachloride and its hydrates; and / or The copper source comprises one or more of copper chloride and its hydrates.

6. The method of claim 1 to 5, wherein the composite gas sensitive material is prepared by the steps of: The precursor dispersion further comprises reduced graphene oxide; the mass concentration of the reduced graphene oxide in the precursor dispersion is 0.08-0.2g / L.

7. The method of claim 6, wherein the composite gas sensitive material is prepared by mixing the metal oxide and the metal complex in a solution, and drying the solution. The step of preparing the precursor dispersion comprises: mixing the tin source and the copper source with a first solvent to prepare a mixed solution; mixing reduced graphene oxide and a second solvent with the mixed solution to prepare the precursor dispersion.

8. A composite gas sensitive material based on CuO-SnO2, characterized in that, The composite gas sensitive material is prepared by the method of any one of claims 1-7.

9. A gas sensor, characterized by The gas sensor comprises a micro-hotplate and a gas response layer on at least a part of the surface of the micro-hotplate, wherein the gas response layer contains the composite gas sensitive material of claim 8.

10. The gas sensor according to claim 9, characterized by The preparation method of the gas response layer comprises: obtaining a dispersion slurry containing the composite gas sensitive material; coating the dispersion slurry on at least a part of the surface of the micro-hotplate and heating and aging.

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