CN110530941B - Cu doped Sn3O4Gas sensitive material, formaldehyde gas sensor, preparation method and application thereof - Google Patents
Cu doped Sn3O4Gas sensitive material, formaldehyde gas sensor, preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to the technical field of gas sensors, in particular to Cu-doped Sn3O4The gas sensitive material, the formaldehyde gas sensor, the preparation method and the application thereof. The gas sensitive material includes: sn (tin)3O4Nanosheets and copper ions, said Sn3O4The nanosheets form a three-dimensional flower-like structure after being stacked, and the copper ions exist in Sn3O4Substitution of Sn in the crystal lattice3O4Part of tin ions in the crystal lattice and Sn3O4On-chip and Sn3O4In the lattice space. The Sn with flower-like structure doped with Cu3O4The prepared gas sensor has a large response value, good formaldehyde gas selectivity, fast response and recovery speed at a lower working temperature, can effectively reduce the complexity of experimental operation, and saves the experimental cost.
Description
Technical Field
The invention relates to the technical field of gas sensors, in particular to Cu-doped Sn3O4The gas sensitive material, the formaldehyde gas sensor, the preparation method and the application thereof.
Background
This information disclosed in this background of the invention is only for the purpose of increasing an understanding of the general background of the invention and is not necessarily to be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
With the rise of the era of artificial intelligence and internet of things information, in a chain for acquiring, transmitting and processing information, a sensor plays a very important role in an information technology chain as a frontmost device for acquiring information. In recent years, the rapid development of social economy brings great wealth and endless convenience to people, and brings damage to our living environment which cannot be worn out. The waste gas produced in the industrial production process, the tail gas discharged by motor vehicles, formaldehyde produced in house decoration and other air pollutions can stimulate eyes and skin of people, cause the eyes to be inflamed and skin to be allergic, stimulate the respiratory system of people, cause diseases such as cough, asthma and the like, even cause fatal diseases such as lung cancer, skin cancer and the like, and cause great threat to the health of people. Therefore, in order to monitor various flammable, explosive, toxic and harmful gases in the environment in real time and guarantee the life and property safety of people, the gas sensor plays a vital role in the production and life of people.
Compared with the method for sampling and analyzing gas by utilizing equipment such as hue separation, an ultraviolet-visible spectrophotometer, an infrared absorption instrument and the like, the metal oxide semiconductor gas sensor has the advantages of simple structure, low price, convenience in use and the like. A metal oxide material commonly used in gas sensors is SnO2、In2O3、Fe2O3、Co3O4CuO, etc., the inventors believe that: common methods for preparing metal oxide semiconductors, such as pulsed laser deposition, magnetron sputtering, chemical vapor deposition, etc., generally require complex operating steps and expensive experimental equipment; moreover, the gas sensor made of a single metal oxide material generally has the defects of high working temperature (200-.
Disclosure of Invention
In view of the above problems, the present invention is directed to providing a Cu doped Sn3O4The gas sensitive material, the formaldehyde gas sensor, the preparation method and the application thereof. The invention constructs Cu/Sn by doping metal ions3O4Composite metal oxide semiconductor materialThe metal oxide semiconductor gas sensor can effectively enhance the selectivity of the metal oxide semiconductor gas sensor at a lower working temperature, accelerate the response and recovery speed of the sensor and obviously improve the response of the sensor to test gas.
The first purpose of the invention is to provide Cu doped Sn3O4The gas sensitive material and the preparation method thereof.
The second purpose of the invention is to provide a Cu-doped Sn-based alloy3O4A formaldehyde gas sensor of gas sensitive material and a preparation method thereof.
The third purpose of the invention is to provide the Cu doped Sn3O4The gas sensitive material, the formaldehyde gas sensor and the application of the preparation method.
In order to realize the purpose, the invention discloses the following technical scheme:
firstly, the invention discloses a Cu doped Sn3O4The gas sensitive material of (1), comprising: sn (tin)3O4Nanosheets and copper ions, said Sn3O4The nanosheets form a three-dimensional flower-like structure after being stacked, and the copper ions exist in Sn3O4Substitution of Sn in the crystal lattice3O4Part of tin ions in the crystal lattice and Sn3O4On-chip and Sn3O4In the lattice space.
As a further technical solution, said Sn3O4The thickness of the nano-sheet is between 10 and 25nm, and the diameter is between 1 and 4 mu m.
The Cu doped Sn provided by the invention3O4The gas sensitive material of (2) is characterized in that: (1) such Sn having a flower-like structure3O4Compared with the common granular or blocky oxide semiconductor material, the gas sensitive material has the advantages that the specific surface area is obviously improved, and the gas sensitive material has a microporous structure, can provide good adsorption and diffusion paths for gas, and improves the response speed and recovery speed of the sensor. (2) By doping copper ions, Sn is further reduced3O4The structural size of the nano-sheet increases the specific surface area of the material, thereby further improving the response value and the response sum of the gas sensorThe speed is restored. (3) The doped metal copper ions can generate a large number of atomic defects on the material, and the defects are favorable for the adsorption of oxygen molecules in the air, so that the initial resistance of the sensor is increased, and the gas-sensitive response is improved. (4) Part of Cu ions exist in Sn3O4The Cu in the gaps can provide a large number of catalytic active sites, which is beneficial to the formaldehyde gas molecules to carry out chemical reaction on the surface of the sensing film and the related electron transfer on the surface of the film, and improves the sensitivity of the sensor.
Secondly, the invention provides a Cu doped Sn3O4The preparation method of the gas sensitive material comprises the following steps:
(1) dissolving stannous chloride and citrate in water, stirring until the stannous chloride and the citrate are fully dissolved, then adding copper ions, and stirring uniformly to obtain a solution A;
(2) slowly pouring an alkali solution into the solution A, stirring, carrying out hydrothermal reaction on the obtained solution, cooling to room temperature after the hydrothermal reaction is finished, and separating out a solid product, namely the Cu-doped Sn3O4The gas sensitive material of (1).
As a further technical scheme, in the step (1), the adding proportion of the stannous chloride, citrate (such as sodium citrate and the like) and copper ions is 1mmol (2-3) mmol in sequence: (0.1-0.3) mmol, and the dosage of water ensures that the stannous chloride and the citrate can be fully dissolved.
As a further technical scheme, in the step (1), the copper ions are added in the form of inorganic copper salt, such as common copper salt such as copper nitrate, copper chloride, copper sulfate and the like.
As a further technical scheme, in the step (2), the alkali solution includes sodium hydroxide, ammonia water, and the like, and the tin oxides with different valence states and specific shapes can be controllably synthesized by adjusting the PH of the precursor solution.
As a further technical scheme, in the step (2), the addition proportion of the alkali liquor is as follows: stannous chloride: 1 part of alkali liquor: 0.5-1.2, mole ratio.
As a further technical scheme, in the step (2), the hydrothermal reaction conditions are as follows: the reaction is carried out at 160-200 ℃ for 12-15 hours.
As a further technical scheme, the step (2) further comprises the steps of washing and drying the solid product, specifically washing with deionized water and ethanol for multiple times if necessary, and drying at 60-80 ℃ for 12-14 hours after washing is finished to obtain the Cu-doped Sn3O4The gas sensitive material of (1).
Thirdly, the invention discloses a Cu-based doped Sn3O4The formaldehyde gas sensor of gas-sensitive material, this sensor is the indirectly heated formula structure, and it includes: the gas sensor comprises a base, a ceramic tube, a heating wire, an annular metal electrode, a gas-sensitive material and a lead; wherein the gas sensitive material is Cu doped Sn3O4The ceramic tube is provided with a heating wire, and two ends of the heating wire respectively extend to the outside of two ports of the ceramic tube; the two annular metal electrodes are sleeved on the outer surface of the ceramic tube along the circumferential direction of the ceramic tube, and the two annular metal electrodes are arranged at intervals; the gas-sensitive material is arranged on the outer surface of the ceramic tube provided with the annular metal electrode, and the ceramic tube and the annular metal electrode are both wrapped in the gas-sensitive material; the two ends of the heating wire extending to the outside of the ceramic tube are connected with the base; the number of the leads is four, the leads are used for connecting the annular metal electrodes and the base, every two leads correspond to one group of annular metal electrodes, and the two leads are arranged on two sides of one annular metal electrode.
For a further technical scheme, the ceramic tube is made of alumina and the like.
As a further technical scheme, the material of the heating wire is any one of Ni-Cr alloy and Fe-Cr alloy.
As a further technical solution, the material of the metal electrode is a noble metal, such as gold, platinum, palladium, silver, and the like.
As a further technical solution, the material of the wire is a noble metal, such as gold, platinum, palladium, silver, and the like.
As a further technical scheme, the part of the heating wire, which is positioned in the ceramic pipe, is spiral. In order to more quickly provide the temperature required for the sensor function to operate.
Secondly, the invention provides the Cu-based doped Sn3O4The preparation method of the formaldehyde gas sensor of the gas sensitive material comprises the following steps:
s1, doping the Cu with Sn3O4Preparing the gas-sensitive material into uniformly dispersed paste;
s2, uniformly coating the paste in the step S1 on the surface of a ceramic tube with a pair of metal electrodes, naturally airing and drying;
and S3, respectively welding the heating wires and the metal electrodes in the ceramic tube dried in the step S2 on the binding posts of the six-pin base, and then aging to obtain the formaldehyde gas sensor with the indirectly heated structure.
As a further technical solution, in step S1, the preparation method of the paste comprises: doping Cu with Sn3O4Mixing gas-sensitive material powder with deionized water according to a mass-volume ratio (mg/ml) of 185-230:1-1.5, and then grinding and performing ultrasonic treatment to obtain uniformly dispersed paste, wherein the grinding time is 15-30min, and the ultrasonic treatment time is 30-60 min.
As a further technical solution, in step S2, the drying conditions are: drying at 60-80 deg.C for 10-12 h.
As a further technical scheme, in the step S2, the aging time is 22-25 hours.
Finally, the invention discloses the Cu doped Sn3O4Gas sensitive material and preparation method thereof, and Cu-doped Sn-based gas sensitive material3O4The formaldehyde gas sensor of the gas sensitive material and the application in the fields of environmental gas monitoring, industrial gas analysis and the like.
Compared with the prior art, the invention has the following beneficial effects:
(1) the Sn with flower-like structure doped with Cu3O4Is a sensitive material of a formaldehyde gas sensor, the prepared gas sensor has large response value, good formaldehyde gas selectivity, fast response and recovery speed at lower working temperature (160 ℃), can effectively reduce the complexity of experimental operation,and the experiment cost is saved.
(2) The invention reduces flower-shaped Sn by doping copper ions3O4The structural size of the nano-sheet is increased, and Sn is increased3O4The specific surface area of the nano sheet further improves the response value and the response and recovery speed of the gas sensor.
(3) The invention dopes copper ions to lead Sn3O4A large number of atomic defects are generated in the nanosheets, and the defects are favorable for adsorption of oxygen molecules in the air, so that the initial resistance of the sensor is increased, and the gas-sensitive response is improved.
(4) By doping copper ions, part of the copper ions exist in Sn3O4The Cu in the gaps can provide a large number of catalytic active sites, which is beneficial to the formaldehyde gas molecules to carry out chemical reaction on the surface of the sensing film and the related electron transfer on the surface of the film, and improves the sensitivity of the sensor.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 shows Cu-based doping of Sn in example 4 of the present invention3O4The structure of the formaldehyde gas sensor of the gas sensitive material is shown schematically.
FIG. 2 shows Cu-based doping of Sn in example 1 of the present invention3O4A cross-sectional view of a formaldehyde gas sensor of a gas sensitive material.
FIG. 3 shows Sn with different Cu doping amounts in example 1 of the present invention3O4X-ray diffraction (XRD) pattern of the material.
FIG. 4 shows Sn with different Cu doping amounts in example 1 of the present invention3O4Scanning Electron Microscope (SEM) images of the material.
FIG. 5 shows Sn with different Cu doping amounts in example 1 of the present invention3O4Response test of the sensor prepared from the material to 100ppm formaldehyde gas at different working temperatures and response and recovery time at different working temperaturesAnd (5) testing a result graph.
FIG. 6 shows Sn with different Cu doping amounts in example 1 of the present invention3O4The sensor prepared by the material responds to the test result chart of formaldehyde (1-300ppm) with different concentrations at the working temperature of 160 ℃.
FIG. 7 shows Sn with different Cu doping amounts in example 1 of the present invention3O4The selectivity test result of the sensor prepared by the material at the working temperature of 160 ℃ for different gases of 100ppm is shown.
FIG. 8 shows Sn with different Cu doping amounts in example 1 of the present invention3O4The sensor prepared by the material can perform repeatability test on 100ppm formaldehyde gas at the working temperature of 160 ℃ and test a stability test chart within 40 days.
The reference numerals in the drawings denote: 1-base, 2-ceramic tube, 3-heating wire, 4-annular metal electrode, 5-gas sensitive material, 6-lead.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, 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 invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As described in the background, conventional methods for preparing metal oxide semiconductors, such as pulsed laser deposition, magnetron sputtering, chemical vapor deposition, etc., generally require complicated operation steps and expensive experimental equipment; furthermore, the gas sensor of single metal oxide material usually has high working temperature (200-Slow speed and the like. Therefore, the invention provides a Cu-doped Sn3O4The invention is further explained by combining the attached drawings and the specific embodiments.
Example 1
Cu doped Sn3O4The preparation method of the gas-sensitive material comprises the following steps:
(1) adding 5mmol of SnCl2·2H2O and 12.5mmol of Na3C6H5O7·2H2Dissolving O in 12.5mL of deionized water to form a uniform solution, and adding Cu (NO) to the obtained solutions3)2Obtaining Cu (NO)3)2Four mixed solutions with mass concentrations of 0 wt%, 2 wt%, 4 wt% and 6 wt% respectively are magnetically stirred, and the obtained four solutions are labeled as solutions A1, A2, A3 and A4 in sequence;
(2) dissolving 2.5mmol of NaOH in 12.5ml of deionized water, and magnetically stirring to dissolve the NaOH to form a uniform solution, which is marked as solution B;
(3) and (3) slowly adding the solution B in the step (2) into the solutions A1, A2, A3 and A4, and continuing to stir for 2 hours by magnetic force, wherein the obtained solutions are respectively marked as C1, C2, C3 and C4 in sequence.
(4) Respectively transferring the C1, the C2, the C3 and the C4 into a 50mL Teflon-lined high-pressure reaction kettle, heating the kettle at 180 ℃ for 12 hours, naturally cooling the kettle to room temperature, washing the obtained precipitate for 6 times by using deionized water and ethanol, and drying the precipitate at 80 ℃ for 12 hours to obtain Sn with four Cu doping amounts3O4The gas sensitive material of (1);
2. based on Cu doping Sn3O4The preparation method of the formaldehyde gas sensor of the gas sensitive material comprises the following steps:
s1, taking Sn with four Cu doping amounts prepared in the embodiment3O4Respectively mixing 210mg of gas-sensitive material powder with 1.5ml of deionized water, grinding with an agate mortar for 20min, respectively performing ultrasonic treatment for 40min to obtain four kinds of uniformly dispersed Cu-doped Sn3O4Paste of gas sensitive material.
S2, dipping the paste obtained in the step S1 by a line drawing pen, and uniformly coating Al with a pair of gold electrodes2O3Four kinds of ceramic tubes coated with the paste were obtained on the surface of the ceramic tubes.
S3, placing the four ceramic tubes coated with the paste obtained in the step S2 for 12 hours, naturally airing, and then drying at 60 ℃ for 10 hours.
S4, sequentially welding the four ceramic tubes obtained in the step S3 and the resistance heating wires made of Ni-Cr alloy on a base, and then aging the base on an aging table for 24 hours to obtain Sn with four Cu doping amounts3O4The formaldehyde gas sensor prepared from the gas sensitive material is used for testing the performance of the formaldehyde gas sensor.
Example 2
Cu doped Sn3O4The preparation method of the gas-sensitive material comprises the following steps:
(1) adding 5mmol of SnCl2·2H2O and 10mmol of Na3C6H5O7·2H2Dissolving O in 12.0mL of deionized water to form a uniform solution, and adding Cu (NO) to the obtained solutions3)2Obtaining Cu (NO)3)2A mixed solution having a mass concentration of 3 wt% was magnetically stirred, and the resulting solution was designated as solution a;
(2) dissolving 5mmol of NaOH in 12.5ml of deionized water, and magnetically stirring to dissolve the NaOH to form a uniform solution, which is marked as solution B;
(3) slowly adding the solution B in the step (2) into the solution A, and continuing to stir for 2 hours by magnetic force, wherein the obtained solution is marked as C.
(4) Transferring the C into a 50mL Teflon-lined high-pressure reaction kettle, heating at 160 ℃ for 15 hours, naturally cooling to room temperature, washing the obtained precipitate with deionized water and ethanol for 5 times, and drying at 70 ℃ for 14 hours to obtain Cu-doped Sn3O4The gas sensitive material of (1);
2. based on Cu doping Sn3O4Preparation method of formaldehyde gas sensor of gas sensitive materialThe method comprises the following steps:
s1 Cu doped Sn prepared in the embodiment3O4Mixing 185mg of gas-sensitive material powder with 1ml of deionized water, grinding for 15min by using an agate mortar, and then carrying out ultrasonic treatment for 60min to obtain uniformly dispersed Cu-doped Sn3O4Paste of gas sensitive material.
S2, dipping the paste obtained in the step S1 by a line drawing pen, and uniformly coating Al with a pair of gold electrodes2O3And (5) coating the surface of the ceramic tube with the paste to obtain the ceramic tube.
And S3, placing the ceramic tubes coated with the paste obtained in the step S2 for 12h, naturally airing, and drying at 80 ℃ for 12 h.
S4, sequentially welding the ceramic tube obtained in the step S3 and the Ni-Cr alloy resistance heating wire on a base, and then aging on an aging table for 22 hours to obtain Cu-doped Sn3O4A formaldehyde gas sensor prepared from the gas-sensitive material.
Example 3
Cu doped Sn3O4The preparation method of the gas-sensitive material comprises the following steps:
(1) adding 5mmol of SnCl2·2H2O and 15mmol of Na3C6H5O7·2H2Dissolving O in 13.0mL of deionized water to form a uniform solution, and adding Cu (NO) to the obtained solutions3)2Obtaining Cu (NO)3)2A mixed solution having a mass concentration of 5 wt% was magnetically stirred, and the obtained solution was designated as solution a;
(2) dissolving 6mmol of NaOH in 13.0ml of deionized water, and magnetically stirring to dissolve the NaOH to form a uniform solution, which is marked as solution B;
(3) slowly adding the solution B in the step (2) into the solution A, and continuing to stir for 2.5 hours by magnetic force, wherein the obtained solution is marked as C.
(4) Transferring the C into a 50mL Teflon-lined high-pressure reaction kettle, heating at 200 ℃ for 12 hours, naturally cooling to room temperature, and removing deionized water and B from the obtained precipitateCleaning with alcohol for 7 times, and drying at 60 deg.C for 14 hr to obtain Cu-doped Sn3O4The gas sensitive material of (1);
2. based on Cu doping Sn3O4The preparation method of the formaldehyde gas sensor of the gas sensitive material comprises the following steps:
s1 Cu doped Sn prepared in the embodiment3O4230mg of gas sensitive material powder is mixed with 1.5ml of deionized water, ground for 30min by an agate mortar, and then subjected to ultrasonic treatment for 30min to obtain uniformly dispersed Cu-doped Sn3O4Paste of gas sensitive material.
S2, dipping the paste obtained in the step S1 by a line drawing pen, and uniformly coating Al with a pair of gold electrodes2O3And (5) coating the surface of the ceramic tube with the paste to obtain the ceramic tube.
And S3, placing the ceramic tubes coated with the paste obtained in the step S2 for 12h, naturally airing, and drying at 70 ℃ for 12 h.
S4, sequentially welding the ceramic tube obtained in the step S3 and the Ni-Cr alloy resistance heating wire on a base, and then aging the base on an aging table for 25 hours to obtain Cu-doped Sn3O4A formaldehyde gas sensor prepared from the gas-sensitive material.
Example 4
Referring to FIGS. 1 and 2, a Cu-based doped Sn3O4The formaldehyde gas sensor of gas-sensitive material, this sensor is the indirectly heated formula structure, and it includes: the gas sensor comprises a base 1, an alumina ceramic tube 2, a heating wire 3(Ni-Cr alloy), an annular gold electrode 4, a gas-sensitive material 5 and a Pt lead 6; wherein the gas sensitive material 5 is Cu-doped Sn prepared in example 23O4The gas-sensitive material 5, a heater strip 3 is arranged in the alumina ceramic tube 2, and two ends of the heater strip 3 respectively extend to the outside of two ports of the alumina ceramic tube 2; the two annular gold electrodes 4 are sleeved on the outer surface of the ceramic tube along the circumferential direction of the alumina ceramic tube 2, and the two annular gold electrodes 4 are arranged at intervals; the gas-sensitive material 5 is arranged on the outer surface of the alumina ceramic tube 2 provided with the annular gold electrode 4, and the alumina ceramic tube 2 and the annular gold electrode 4 are both coatedWrapped in the bag; the two ends of the heating wire 3 extending to the outside of the alumina ceramic tube 2 are connected with the base 1; the number of the Pt leads is four, and the Pt leads are used for connecting the annular metal electrodes 4 and the base 1, wherein every two leads correspond to one group of annular metal electrodes, and the two leads are arranged on two sides of one annular metal electrode.
And (3) performance testing:
(1) FIG. 3 shows that in example 1, Sn with different Cu doping amounts is prepared by a one-step hydrothermal method3O4The X-ray diffraction (XRD) pattern of the material, from which it can be seen: all samples had good crystallinity, and for the sample without Cu doping, the diffraction peak thereof could be compared with that of triclinic Sn3O4Standard card (JCPDS No 16-0737) was well fitted, demonstrating that high purity Sn was synthesized3O4For samples with Cu doping levels of 4 wt% and 6 wt%, a smaller peak corresponding to the (111) plane of Cu (JCPDS Card No.04-0836) was detected.
(2) FIG. 4 shows Sn with different Cu doping amounts in example 13O4Material Scanning Electron Microscope (SEM) images, wherein (a) - (d) show Cu (NO) at the time of preparation, respectively3)2The mass concentrations of the gas sensitive materials are respectively 0 wt%, 2 wt%, 4 wt% and 6 wt%, and can be seen from the figure: all synthesized samples show a flower-shaped structure formed by stacking nano sheets, the diameter of the nano flower is gradually reduced along with the increase of the Cu doping amount, the size of the flower-shaped structure is reduced, the specific surface area of the material can be increased, and the improvement of the sensing response of the sensor material to gas is facilitated.
(3) The sensing performance of the metal oxide semiconductor gas sensor is influenced by the Cu doping content and the working temperature, and Sn prepared in example 1 based on different Cu doping amounts3O4The sensors were placed at 120 deg.C, 140 deg.C, 150 deg.C, 160 deg.C, 170 deg.C, 180 deg.C, 200 deg.C, and 220 deg.C, respectively, and the sensitivity of 100ppm formaldehyde gas was tested, and the test results are shown in FIG. 5. As can be seen from FIG. 5(a), Sn was doped based on 4 wt% Cu3O4The sensor of the material shows the highest response to formaldehyde, so the invention selects 4 wt% as the optimal doping concentration of Cu. At the same time can seeAlthough the response value of the sensor to formaldehyde is larger at a lower working temperature of 120 ℃, the recovery time of the sensor is long at a lower temperature, and the sensor cannot respond to the change of the concentration of the test gas in time. At higher temperatures, the response value of the sensor to formaldehyde is smaller. With reference to fig. 5(b), when the operating temperature is less than 160 ℃, the recovery time of the sensor decreases rapidly with the increase of the temperature, and when the operating temperature is higher than 160 ℃, the recovery time of the sensor decreases slowly with the increase of the temperature, and 160 ℃ is selected as the optimal operating temperature of the sensor in consideration of practical application.
(4) Different Cu doping amount sensors (Cu (NO) prepared for testing example 13)2Mass concentrations of 0 wt% and 4 wt%, respectively, i.e. 0 wt% is a comparative example), and a sensing test was performed on 1-300ppm of formaldehyde at 160 ℃, and the results are shown in fig. 6, which proves that the gas sensor provided by the present invention has a wide detection range on formaldehyde.
(5) Different Cu doping amount sensors (Cu (NO) prepared for testing example 13)20 wt% and 4 wt%, respectively, that is, 0 wt% is a comparative example), and the selectivity of the sensor to formaldehyde gas is tested by placing the sensor in 100ppm of formaldehyde, acetone, ethanol, triethylamine, and xylene, respectively, at a temperature of 160 ℃, and the results are shown in fig. 7.
(6) The sensor prepared in example 1 was tested (Cu (NO)3)2Mass concentration of 4 wt%) and long-term stability, wherein fig. 8(a) is a repeatability test result and fig. 8(b) is a long-term stability test result, the results show that the sensor has excellent repeatability and good long-term stability.
The sensor prepared by the invention can achieve the excellent technical effects, and the main reason is that: prepared Sn with flower-like structure3O4Compared with the common granular or blocky oxide semiconductor material, the gas sensitive material has the advantages that the specific surface area is obviously improved, the gas sensitive material has a microporous structure, a good adsorption and diffusion path can be provided for gas, the response speed and the recovery speed of the sensor are improved, and the response mechanism of the gas sensor based on the metal oxide material is the resistance change of the sensor in different gases. When the sensor is exposed in air, oxygen molecules adsorbed on the surface of the sensing material can capture free electrons in a conduction band, so that the resistance of the sensor is increased, and when the sensor is exposed in reducing gas, test gas molecules and the adsorbed oxygen can generate chemical reaction to release electrons, so that the resistance of the sensor is reduced, more adsorption sites and good adsorption diffusion channels can improve the response of the sensor, and the response and recovery speed is accelerated. In addition, Sn is further reduced by doping copper ions3O4The specific surface area of the material is increased due to the structural size of the nano-sheets, so that the response value and the response and recovery speed of the gas sensor are further improved. Meanwhile, metal copper ions are doped, so that a large number of atomic defects are generated in the material, the defects are favorable for adsorption of oxygen molecules in the air, the initial resistance of the sensor is increased, and the gas-sensitive response is improved; because at Sn3O4In crystal lattice, Cu2+Will replace Sn3O4Part of Sn in crystal lattice4+The process can be represented by a Kroger-Vink defect symbol as shown in formula (1):
wherein, CuSnRepresents Cu2+Substituted Sn4+The substituent(s) of (a) is defective,
oxygen ions representing the oxygen lattice sites,
representing an oxygen vacancy having two positive charges. The high-concentration oxygen vacancies are beneficial to the surface of the sensing material to adsorb oxygen, and when the sensor is exposed in the air atmosphere, due to the introduction of gaseous oxygen, the oxygen vacancies are reduced and positively charged holes are generated, so that the concentration of electrons in a conduction band is reduced, and the resistance of the sensor is increased, as shown in formula (2). The resistance of the sensor is increased, which is beneficial to improving the sensing performance of the doped sample. In addition, a part of Cu is present in Sn3O4The Cu in the gaps can provide a large number of catalytic active sites, which is beneficial to the chemical reaction of formaldehyde gas molecules on the surface of the sensing film and the related electron transfer on the surface of the film, and improves the sensitivity of the sensor.
In summary, the Cu-doped Sn-based material provided by the invention3O4The formaldehyde gas sensor made of the metal oxide semiconductor material has the advantages of low working temperature, high response, strong selectivity, high response and recovery speed, good repeatability, high stability and the like, and can be used for detecting harmful gas formaldehyde in actual production and life.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (20)
1. Sn doped based on Cu3O4The formaldehyde gas sensor of gas-sensitive material, characterized in that, the sensor is the indirectly heated formula structure, includes: the gas sensor comprises a base, a ceramic tube, a heating wire, an annular metal electrode, a gas-sensitive material and a lead;
wherein the gas sensitive material is Cu doped Sn3O4The gas sensitive material of (1), comprising: sn (tin)3O4Nano-sheetAnd copper ions, said Sn3O4The nanosheets form a three-dimensional flower-like structure after being stacked, and the copper ions exist in Sn3O4Substitution of Sn in the crystal lattice3O4Part of tin ions in the crystal lattice, Sn being present3O4On-chip and Sn3O4In the lattice gaps;
the Cu is doped with Sn3O4The preparation method of the gas-sensitive material comprises the following steps:
(1) dissolving stannous chloride and citrate in water, stirring until the stannous chloride and the citrate are fully dissolved, then adding copper ions, and stirring uniformly to obtain a solution A;
(2) slowly pouring an alkali solution into the solution A, stirring, carrying out hydrothermal reaction on the obtained solution, cooling to room temperature after the hydrothermal reaction is finished, and separating out a solid product, namely the Cu-doped Sn3O4The gas sensitive material of (1);
the ceramic tube is internally provided with a heating wire, and two ends of the heating wire respectively extend to the outside of two ports of the ceramic tube; the two annular metal electrodes are sleeved on the outer surface of the ceramic tube along the circumferential direction of the ceramic tube, and the two annular metal electrodes are arranged at intervals; the gas-sensitive material is arranged on the outer surface of the ceramic tube provided with the annular metal electrode, and the ceramic tube and the annular metal electrode are both wrapped in the gas-sensitive material; the two ends of the heating wire extending to the outside of the ceramic tube are connected with the base; the number of the leads is four, the leads are used for connecting the annular metal electrodes and the base, every two leads correspond to one group of annular metal electrodes, and the two leads are arranged on two sides of one annular metal electrode.
2. The Cu-doped Sn-based alloy of claim 13O4A formaldehyde gas sensor of a gas sensitive material, characterized in that Sn is3O4The thickness of the nano-sheet is between 10 and 25nm, and the diameter is between 1 and 4 mu m.
3. The Cu-doped Sn-based alloy of claim 13O4Formaldehyde gas sensor of gas sensitive material, step (1)The adding proportion of the stannous chloride, the citrate and the copper ions is 1mmol (2-3) mmol in sequence: (0.1-0.3) mmol, and the dosage of water ensures that the stannous chloride and the citrate can be fully dissolved.
4. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that in the step (1), the citrate is sodium citrate.
5. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that in the step (1), the copper ions are added in the form of inorganic copper salt.
6. The Cu-doped Sn-based material of claim 53O4The formaldehyde gas sensor of the gas sensitive material is characterized in that the inorganic copper salt is any one of copper nitrate, copper chloride and copper sulfate.
7. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that in the step (2), the alkali solution comprises any one of sodium hydroxide and ammonia water.
8. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that in the step (2), the addition proportion of the alkali solution is as follows: stannous chloride: lye = 1: 0.5-1.2, mole ratio.
9. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that in the step (2), the hydrothermal reaction conditions are as follows: the reaction is carried out at 160-200 ℃ for 12-15 hours.
10. The base of claim 1Doping Cu with Sn3O4The formaldehyde gas sensor of the gas-sensitive material is characterized in that the step (2) also comprises the steps of washing and drying the solid product, specifically washing with deionized water and ethanol, and drying at 60-80 ℃ for 12-14 hours after washing is finished to obtain the Cu-doped Sn3O4The gas sensitive material of (1).
11. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that the ceramic tube is made of alumina.
12. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that the material of the heating wire is any one of Ni-Cr alloy and Fe-Cr alloy.
13. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that the material of the metal electrode is noble metal, such as any one of gold, platinum, palladium and silver.
14. The Cu-doped Sn-based material of claim 13O4The formaldehyde gas sensor of the gas sensitive material is characterized in that the material of the lead is noble metal, such as any one of gold, platinum, palladium and silver.
15. The Cu-doped Sn-based alloy of any of claims 1 to 143O4The formaldehyde gas sensor of the gas sensitive material is characterized in that the part of the heating wire, which is positioned in the ceramic tube, is spiral.
16. The Cu-doped Sn-based material of claim 13O4The preparation method of the formaldehyde gas sensor of the gas sensitive material is characterized by comprising the following steps:
s1, doping Cu with Sn3O4Preparing the gas-sensitive material into uniformly dispersed paste;
s2, uniformly coating the paste in the step S1 on the surface of a ceramic tube with a pair of metal electrodes, naturally airing and drying;
s3, respectively welding the heating wires and the metal electrodes in the ceramic tube dried in the step S2 on the binding posts of the six-pin base, and then aging to obtain the formaldehyde gas sensor with the indirectly heated structure;
wherein the Cu is doped with Sn3O4A gas sensitive material, comprising: sn (tin)3O4Nanosheets and copper ions, said Sn3O4The nanosheets form a three-dimensional flower-like structure after being stacked, and the copper ions exist in Sn3O4Substitution of Sn in the crystal lattice3O4Part of tin ions in the crystal lattice, Sn being present3O4On-chip and Sn3O4In the lattice gaps;
the Cu is doped with Sn3O4The preparation method of the gas sensitive material comprises the following steps:
(1) dissolving stannous chloride and citrate in water, stirring until the stannous chloride and the citrate are fully dissolved, then adding copper ions, and stirring uniformly to obtain a solution A;
(2) slowly pouring an alkali solution into the solution A, stirring, carrying out hydrothermal reaction on the obtained solution, cooling to room temperature after the hydrothermal reaction is finished, and separating out a solid product, namely the Cu-doped Sn3O4A gas sensitive material.
17. The Cu-doped Sn-based material of claim 163O4A method for preparing a formaldehyde gas sensor of a gas sensitive material, wherein in step S1, the method for preparing the paste comprises: doping Cu with Sn3O4Mixing gas-sensitive material powder and deionized water according to the mass-to-volume ratio of 185-230:1-1.5, wherein the gas-sensitive material powder is mg/ml; and then grinding and ultrasound treatment are carried out to obtain a paste with uniform dispersion, wherein the grinding time is 15-30min, and the ultrasound time is 30-60 min.
18. As claimed in claim 16The Cu-based doped Sn3O4The method for preparing the formaldehyde gas sensor of the gas sensitive material is characterized in that in step S2, the drying conditions are as follows: drying at 60-80 deg.C for 10-12 h.
19. The Cu-doped Sn-based material of claim 163O4The preparation method of the formaldehyde gas sensor of the gas sensitive material is characterized in that in the step S2, the aging time is 22-25 hours.
20. Use of a formaldehyde gas sensor according to any of claims 1 to 15 in the field of environmental gas monitoring, industrial gas analysis.
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