Hydrogen sulfide gas sensitive material, preparation method and application thereof

Abstract

The application relates to the technical field of gas sensing, and discloses a hydrogen sulfide gas-sensitive material and a preparation method and application thereof, wherein the method comprises the following steps: (1) mixing a tungsten source, a copper source, a polymer and an organic solvent to obtain a spinning solution; (2) electrostatically spinning the spinning solution to obtain an electrostatic spinning nanofiber membrane; and (3) drying and calcining the electrostatic spinning nanofiber membrane to obtain a hydrogen sulfide gas-sensitive material. The hydrogen sulfide gas-sensitive material is prepared by an electrostatic spinning method, and the hydrogen sulfide gas-sensitive material is a WO3 / CuO nanowire; a sensor prepared based on the hydrogen sulfide material can detect hydrogen sulfide at a low working temperature, and the sensor has good response to hydrogen sulfide gas in the range of 0-100 ppm; in addition, the sensor has good reproducibility, an extremely low detection limit and good sensitivity, and has long-term stability in a hydrogen sulfide atmosphere.

Description

Technical Field

[0001] This invention relates to the field of gas sensing technology, specifically to a hydrogen sulfide gas-sensitive material, its preparation method, and its application. Background Technology

[0002] Hydrogen sulfide (H2S) is a colorless, highly toxic, and flammable gaseous pollutant. Long-term exposure to low concentrations can lead to chronic respiratory diseases, neurological damage, and cardiovascular disease. Inhalation of 500-1000 ppm H2S for 30 minutes can cause loss of consciousness, and even death due to respiratory paralysis or suffocation. Therefore, developing a low-cost, low-detection-limit, and rapid-response H2S sensor is crucial.

[0003] Over the past few decades, metal-semiconductor gas sensors have attracted widespread attention due to their small size, low cost, ease of operation, and good stability. Currently, a significant amount of work focuses on developing hydrogen sulfide sensing materials such as CuO, SnO2, α-Fe2O3, In2O3, WO3, and ZnO. Tungsten oxide (WO3), as a typical n-type broadband semiconductor, is considered a very promising gas sensing material. WO3 nanoparticles, nanofibers, and nanofilms have been reportedly used for detecting H2S gas. However, WO3 materials have limitations, including poor stability and high operating temperature requirements. Solving these problems is a key focus of current scientific research. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of high operating temperature and poor stability of existing WO3 sensing materials when detecting hydrogen sulfide, and to provide a hydrogen sulfide gas-sensitive material, its preparation method and application.

[0005] To achieve the above objectives, the present invention provides a method for preparing a hydrogen sulfide gas-sensitive material, the method comprising the following steps:

[0006] (1) A spinning solution is obtained by mixing a tungsten source, a copper source, a polymer, and an organic solvent;

[0007] (2) Electrospinning the spinning solution to obtain an electrospun nanofiber membrane;

[0008] (3) The electrospun nanofiber membrane is dried and calcined to obtain a hydrogen sulfide gas-sensitive material.

[0009] Preferably, in step (1), the tungsten source is selected from at least one of ammonium metatungstate, tungsten chloride, and tungstic acid;

[0010] Preferably, in step (1), the copper source is selected from at least one of copper chloride, copper acetate, and copper diethylhexanoate;

[0011] Preferably, in step (1), the polymer is selected from at least one of polyvinylpyrrolidone, polyacrylonitrile, and polyvinyl alcohol;

[0012] Preferably, in step (1), the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethyl sulfoxide and dichloromethane.

[0013] Preferably, in step (1), the total weight ratio of the copper source and the tungsten source to the weight of the copper source is 1:0.02 to 0.2;

[0014] Preferably, in step (1), the ratio of the polymer to the organic solvent is 1g: 5-15mL;

[0015] Preferably, in step (1), the ratio of the total weight of the tungsten source and the copper source to the weight of the polymer is 2 to 5:1.

[0016] Preferably, step (1) specifically includes:

[0017] The polymer and organic solvent are first mixed to obtain a polymer solution;

[0018] The tungsten source, copper source, and polymer solution are mixed a second time to obtain a spinning solution.

[0019] Preferably, the conditions for the first mixing include: a temperature of 60–80°C and a time of 2–6 hours;

[0020] Preferably, the conditions for the second mixing include: a temperature of 10–35°C and a time of 10–24 h.

[0021] Preferably, in step (2), the electrospinning process parameters include: a voltage of 15-20 kV, a working distance of 18-22 cm between the needle and the collector, and an injection rate of 0.5-1 mL / h;

[0022] Preferably, in step (2), the ambient temperature for electrospinning is 22-28°C and the humidity is 25-35%.

[0023] Preferably, in step (3), the drying conditions include: a temperature of 80 to 100°C and a time of 0.5 to 3 hours.

[0024] Preferably, in step (3), the roasting temperature is 300-600℃ and the time is 2-6h.

[0025] Preferably, the roasting process includes: firstly, a first-stage roasting at 250-350°C, and then a second-stage roasting at 500-550°C;

[0026] Preferably, the conditions for the first stage of roasting also include: a time of 0.5 to 2 hours and a heating rate of 1 to 3 °C / min;

[0027] Preferably, the conditions for the second stage of roasting also include: a time of 2 to 4 hours and a heating rate of 0.5 to 1.5 °C / min.

[0028] A second aspect of the present invention provides a hydrogen sulfide gas-sensitive material prepared by the method described above.

[0029] Preferably, the hydrogen sulfide gas-sensitive material has the morphology of nanowires;

[0030] Preferably, the diameter of the hydrogen sulfide gas-sensitive material is 100–200 nm;

[0031] Preferably, the length of the hydrogen sulfide gas-sensitive material is greater than 1 μm.

[0032] A third aspect of the present invention provides a hydrogen sulfide sensor, the hydrogen sulfide sensor comprising the hydrogen sulfide gas-sensitive material as described above.

[0033] The fourth aspect of the present invention provides the application of the hydrogen sulfide gas-sensitive material or the hydrogen sulfide sensor described above in hydrogen sulfide detection.

[0034] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0035] 1. This invention uses electrospinning technology to dope CuO into WO3 nanowires, and utilizes the interaction between CuO and WO3 to prepare a WO3 / CuO composite material, which is a hydrogen sulfide gas-sensitive material. The unique response mechanism of CuO and H2S can effectively reduce the operating temperature and the minimum detection limit, enabling low-concentration detection. At the same time, by using electrospinning to prepare WO3 / CuO nanowires, the problem of poor stability of nanomaterials can be improved.

[0036] 2. This invention uses CuO as a modifier to improve the sensing performance of WO3 (high operating temperature and long response time). The prepared WO3 / CuO gas-sensitive material has a series of unique physical and chemical properties, such as low detection limit and good stability. CuO can synergistically accelerate the response speed and response intensity of hydrogen sulfide.

[0037] 3. The WO3 / CuO gas-sensitive material prepared by this invention has CuO loaded on the surface and grain gaps of WO3 nanowires. This structure can accelerate the transmission of electrical signals, thereby greatly improving the response and recovery capabilities.

[0038] 4. The WO3 / CuO gas-sensitive material described in this invention has a simple preparation process, is easy to industrialize, and is conducive to the large-scale production and application of sensors.

[0039] 5. A novel heterojunction sensor was prepared based on the WO3 / CuO gas-sensitive material described in this invention for the detection of hydrogen sulfide at low operating temperatures. The sensor exhibits good response to hydrogen sulfide gas in the range of 0–100 ppm. Furthermore, the sensor has good reproducibility, extremely low detection limit, and good sensitivity, and also exhibits long-term stability in a hydrogen sulfide atmosphere.

[0040] 6. The gas sensor based on WO3 / CuO gas-sensitive material provided by this invention can directly address the problem of monitoring and detecting hydrogen sulfide leaks in the atmospheric environment. It can detect leaked hydrogen sulfide in the environment with high sensitivity, high selectivity, and rapid detection, thereby reducing the hazards caused by hydrogen sulfide leaks and ensuring the safety of personnel, environment, and equipment. Attached Figure Description

[0041] Figure 1 This is a scanning electron microscope image of the WO3 / CuO gas-sensitive material prepared in Example 2 of this invention;

[0042] Figure 2 This is a scanning electron microscope mapping image of the WO3 / CuO gas-sensitive material prepared in Example 2 of this invention;

[0043] Figure 3 This is the X-ray diffraction pattern of the WO3 / CuO gas-sensitive material prepared in Example 2 of this invention;

[0044] Figure 4 These are response curves of the gas-sensitive materials prepared in Embodiment 2 and Comparative Examples 1-2 of the present invention to different concentrations of hydrogen sulfide.

[0045] Figure 5 These are the repeatability test results of the WO3 / CuO gas-sensitive material prepared in Example 2 of this invention;

[0046] Figure 6 These are the long-term stability test results of the WO3 / CuO nanowires prepared in Example 2 of this invention;

[0047] Figure 7 These are the long-term stability test results of the WO3 / CuO nanoparticles prepared in Comparative Example 3 of this invention. Detailed Implementation

[0048] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0049] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0050] This invention provides a method for preparing a hydrogen sulfide gas-sensitive material, the method comprising the following steps:

[0051] (1) A spinning solution is obtained by mixing a tungsten source, a copper source, a polymer, and an organic solvent;

[0052] (2) Electrospinning the spinning solution to obtain an electrospun nanofiber membrane;

[0053] (3) The electrospun nanofiber membrane is dried and calcined to obtain WO3 / CuO composite material, namely hydrogen sulfide gas sensitive material.

[0054] In the method provided by the present invention, CuO is doped into WO3 nanowires by electrospinning technology, and WO3 / CuO gas-sensitive materials are prepared by utilizing the interaction between CuO and WO3.

[0055] This invention prepares a hydrogen sulfide gas-sensitive material via electrospinning. The hydrogen sulfide gas-sensitive material is WO3 / CuO nanowires. This gas-sensitive material has a higher specific surface area than single-component WO3 and CuO, which provides more active sites for the adsorption of hydrogen sulfide molecules. It exhibits fast response speed, high repeatability, and high selectivity for hydrogen sulfide, thus improving the sensing performance of the gas-sensitive material. Furthermore, the hydrogen sulfide response performance of this gas-sensitive material is significantly better than that of the original WO3, indicating that the addition of CuO plays a key role in improving the sensing performance of WO3.

[0056] The gas-sensitive material based on WO3 and CuO provided by this invention exhibits good stability, as well as excellent sensitivity and response performance to hydrogen sulfide. This is mainly because the nanofibers obtained by electrospinning form a stable crystalline nanowire framework after high-temperature annealing, which has a high surface area / volume ratio, low weight, and high porosity, resulting in a large specific surface area. As active sites, it can rapidly adsorb and dissociate hydrogen sulfide. Secondly, the gas-sensitive material based on WO3 and CuO forms a pn heterostructure and its oxygen adsorption mechanism, which is beneficial to the improvement of charge migration, transport, and sensing performance.

[0057] The present invention does not limit the specific selection of the tungsten source in step (1), and can be any tungsten source commonly used in the art. In a specific embodiment, the tungsten source is selected from at least one of ammonium metatungstate, tungsten chloride, and tungstic acid, preferably ammonium metatungstate.

[0058] The present invention does not impose any particular limitation on the copper source in step (1). In a specific embodiment, the copper source is selected from at least one of copper chloride, copper acetate, and copper diethylhexanoate, preferably copper chloride.

[0059] In a specific embodiment, in step (1), the polymer is selected from at least one of polyvinylpyrrolidone, polyacrylonitrile and polyvinyl alcohol, preferably polyvinylpyrrolidone (PVP).

[0060] In a specific embodiment, in step (1), the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethyl sulfoxide and dichloromethane, preferably N,N-dimethylformamide (DMF).

[0061] In order to make it easier to mix the various raw materials evenly, in the preferred embodiment, step (1) specifically includes:

[0062] A1. Mix the polymer and organic solvent to obtain a polymer solution;

[0063] A2. Mix the tungsten source, copper source and the polymer solution to obtain a spinning solution.

[0064] To further improve the stability and sensitivity of the hydrogen sulfide gas-sensitive material to hydrogen sulfide gas, in a preferred embodiment, the weight ratio of the total weight of the copper source and the tungsten source to the weight of the copper source is 1:0.02 to 0.2. Specifically, for example, it can be 1:0.02, 1:0.025, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.1, 1:0.15, 1:0.18, or 1:0.2.

[0065] In order to make the conductivity of the spinning solution suitable, in a preferred embodiment, the ratio of the total weight of the tungsten source and the copper source to the weight of the polymer is 2 to 5:1, specifically, for example, 2:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1.

[0066] In some embodiments, the weight fraction of the copper source is 2.5% to 50%, based on the total weight of the tungsten source and the copper source.

[0067] In order to make the viscosity of the spinning solution more suitable, in a preferred embodiment, the ratio of the polymer to the organic solvent is 1g:5 to 15mL, specifically, for example, 1g:5mL, 1g:6mL, 1g:8mL, 1g:9mL, 1g:10mL, 1g:12mL or 1g:15mL.

[0068] To better disperse the polymer, in a preferred embodiment, the conditions for the first mixing include: a temperature of 60–80°C and a time of 2–6 hours.

[0069] In order to better disperse the tungsten source and the copper source, in a preferred embodiment, the conditions for the second mixing include: a temperature of 10 to 35°C and a time of 10 to 24 hours.

[0070] In specific implementation, step (2) includes: loading the spinning solution into a 10ml syringe, attaching a needle with an inner diameter of 0.8mm, placing it on the pusher of the electrospinning instrument, connecting the wire to the needle, wiping the aluminum foil dry with alcohol paper and fixing it on the collector, closing the door of the electrospinning machine, pressing the voltage switch, setting the corresponding parameters, and then obtaining an electrospinned nanofiber membrane on the aluminum foil.

[0071] By controlling the above-mentioned electrospinning process parameters, the length and diameter of the obtained WO3 / CuO can be controlled. In a preferred embodiment, in step (2), the electrospinning process parameters include: a voltage of 15-20 kV, a working distance of 18-22 cm between the needle and the collector, and an injection rate of 0.5-1 mL / h. Under the above process parameters, the obtained WO3 / CuO has a more suitable size and better gas-sensitive performance.

[0072] More preferably, in step (2), the ambient temperature of the electrospinning is 22-28°C and the humidity is 25-35%.

[0073] In the method described in this invention, in step (3), drying the electrospun nanofiber membrane can remove solvent residues from the spun product and improve the purity of the product. In a preferred embodiment, the heating and drying conditions in step (3) include: a temperature of 80–100°C and a time of 0.5–3 hours.

[0074] In the method described in this invention, in step (3), calcination is used to remove PVP from the electrospun nanofiber membrane and control the transformation of the original material into WO3 / CuO nanowires. In this invention, the calcination temperature can be 300–600°C, and the time can be 2–6 hours.

[0075] In order to better control the phase transformation and grain growth of the material, thereby improving the uniformity and gas-sensitive properties of the material, in a preferred embodiment, the calcination process includes: firstly, calcining at 250-350°C in the first stage, and then heating to 500-550°C in the second stage of calcination.

[0076] More preferably, the conditions for the first stage of roasting also include: a time of 0.5 to 2 hours and a heating rate of 1 to 3 °C / min.

[0077] More preferably, the conditions for the second stage of calcination also include: a time of 2 to 4 hours and a heating rate of 0.5 to 1.5 °C / min.

[0078] The present invention also proposes a hydrogen sulfide gas-sensitive material prepared by the method described above.

[0079] The hydrogen sulfide gas-sensitive material described in this invention is a WO3 / CuO composite material with a nanowire morphology. Studies have shown that one-dimensional WO3 / CuO nanowires exhibit better long-term stability compared to zero-dimensional WO3 / CuO nanoparticles.

[0080] Furthermore, the hydrogen sulfide gas-sensitive material (WO3 / CuO nanowires) has a diameter of 100–200 nm. This structure is beneficial for improving charge migration, transport, and sensing performance, while also providing an ideal diffusion channel for hydrogen sulfide.

[0081] Furthermore, the length of this hydrogen sulfide gas-sensitive material (WO3 / CuO nanowires) is greater than 1 μm.

[0082] The present invention also provides a hydrogen sulfide sensor, which includes the hydrogen sulfide gas-sensitive material as described above.

[0083] The hydrogen sulfide sensor based on WO3 / CuO gas-sensitive material described in this invention has a low optimal operating temperature (150℃). In air, the sensor's response and recovery times to 5ppm H2S are 24s and 78s, respectively, and the response value at 150℃ is 68.43%. In addition, the sensor has good selectivity and long-term stability.

[0084] The gas sensor based on WO3 / CuO gas-sensitive material described in this invention directly addresses the problem of monitoring and detecting hydrogen sulfide leaks in the atmospheric environment. It can detect leaked hydrogen sulfide in the environment with high sensitivity and high selectivity, reducing the hazards caused by hydrogen sulfide leaks and thus ensuring the safety of personnel, environment and equipment.

[0085] This invention does not limit the specific preparation steps of the hydrogen sulfide sensor; any conventional preparation method in the art can be used, as long as it contains the aforementioned hydrogen sulfide gas-sensitive material. In a specific embodiment, the hydrogen sulfide sensor is prepared according to the following steps: mixing and grinding the hydrogen sulfide gas-sensitive material with an organic solvent, and then coating it onto the surface of an electrode to form a sensing film. This invention does not have special requirements for the organic solvent; any commonly used solvent in the art is acceptable, for example, ethanol.

[0086] In a preferred embodiment, the weight ratio of hydrogen sulfide gas-sensitive material to organic solvent is 1:1 to 10; specifically, for example, it can be 1:2, 1:4, 1:5, 1:6, 1:7, 1:8 or 1:10.

[0087] To improve the sensitivity of the hydrogen sulfide sensor, in a preferred embodiment, the thickness of the sensing film is 200–5000 nm, more preferably 200–1000 nm; specifically, the thickness of the sensing film can be 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm.

[0088] The present invention also proposes an application of the hydrogen sulfide gas-sensitive material or hydrogen sulfide sensor described above in hydrogen sulfide detection.

[0089] In a specific implementation, when detecting hydrogen sulfide gas, the aforementioned hydrogen sulfide sensor or hydrogen sulfide gas-sensitive material is brought into contact with a mixed gas containing hydrogen sulfide.

[0090] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available products.

[0091] In the following examples and comparative examples, the room temperature was 23±2℃.

[0092] Example 1

[0093] This embodiment is used to illustrate the hydrogen sulfide gas-sensitive material and its preparation method according to the present invention.

[0094] (1) Dissolve 1g of PVP particles in 8ml of DMF and stir at 60℃ for 2h to obtain a polymer solution; mix ammonium metatungstate and copper(II) dihydrate to obtain a mixture; at room temperature, slowly add 3g of the mixture to the polymer solution and stir for 12h to obtain a spinning solution, wherein the weight percentage of copper(II) dihydrate in the mixture is 2.5%;

[0095] (2) The spinning solution obtained in step (1) was loaded into a 10ml syringe with an inner diameter of 0.8mm and fixed on an electrospinning machine. The electrospinning machine was equipped with a voltage of 17kV. The working distance between the needle and the collector was 20cm. The injection rate was 0.8mL / h. Electrospinning was carried out at 25℃ and 30% humidity for 5h to obtain an electrospinned nanofiber membrane.

[0096] (3) Collect the electrospun nanofiber membrane obtained in step (2), dry it at 80°C for 3 hours, and then put it into a tube muffle furnace. Heat it to 300°C for 1 hour, and continue to heat it to 500°C for 3 hours. The heating rate between room temperature and 300°C is 2°C / min, and the heating rate between 300°C and 500°C is 1°C / min. The obtained WO3 / CuO nanowire material is a hydrogen sulfide gas-sensitive material.

[0097] Example 2

[0098] This embodiment is used to illustrate the hydrogen sulfide gas-sensitive material and its preparation method according to the present invention.

[0099] (1) Dissolve 1g of PVP particles in 8ml of DMF and stir at 60℃ for 2h to obtain a polymer solution; at room temperature, mix ammonium metatungstate and copper(II) dihydrate to obtain a mixture, take 3g of the mixture and slowly add it to the polymer solution and stir for 12h to obtain a spinning solution, wherein the weight percentage of copper(II) dihydrate in the mixture is 5%;

[0100] (2) The spinning solution obtained in step (1) was loaded into a 10ml syringe with an inner diameter of 0.8mm; and fixed on an electrospinning machine with a voltage of 17kV applied; the working distance between the needle and the collector was 20cm; the injection rate was 0.8mL / h; and electrospinning was carried out at 25℃ and 30% humidity for 5h to obtain an electrospinned nanofiber membrane.

[0101] (3) Collect the electrospun nanofiber membrane obtained in step (2), dry it at 90°C for 2 hours, and then put it into a tube muffle furnace. Calcinate it at 300°C for 1 hour, and then continue to calcine it at 500°C for 3 hours. The heating rate between room temperature and 300°C is 2°C / min, and the heating rate between 300°C and 500°C is 1°C / min. WO3 / CuO nanowire material, i.e., hydrogen sulfide gas-sensitive material, is obtained.

[0102] Example 3

[0103] The method described in Example 1 is implemented, except that in step (1), the weight percentage of copper(II) dihydrate in the mixture is 10%.

[0104] Example 4

[0105] The method described in Example 1 is implemented, except that in step (1), the weight percentage of copper(II) dihydrate in the mixture is 15%.

[0106] Example 5

[0107] The method described in Example 2 is implemented, except that in step (2), a voltage of 15kV is applied to the electrospinning machine during electrospinning.

[0108] Specifically, step (2): the spinning solution obtained in step (1) is loaded into a 10ml syringe with an inner diameter of 0.8mm; and fixed on an electrospinning machine with a voltage of 15kV applied; the working distance between the needle and the collector is 20cm; the injection rate is 0.8mL / h; electrospinning is carried out at 25℃ and 30% humidity for 5h to obtain an electrospinned nanofiber membrane.

[0109] Example 6

[0110] The method described in Example 2 is implemented, except that in step (2), the working distance between the electrospinning machine needle and the collector is 22cm during electrospinning.

[0111] Specifically, step (2): the spinning solution obtained in step (1) is loaded into a 10ml syringe with an inner diameter of 0.8mm; and fixed on an electrospinning machine with a voltage of 17kV applied; the working distance between the needle and the collector is 22cm; the injection rate is 0.8mL / h; electrospinning is carried out at 25℃ and 30% humidity for 5h to obtain an electrospinned nanofiber membrane.

[0112] Example 7

[0113] The method described in Example 2 was implemented, except that the operating humidity of the electrospinning machine was 25%.

[0114] Specifically, step (2): the spinning solution obtained in step (1) is loaded into a 10ml syringe with an inner diameter of 0.8mm; and fixed on an electrospinning machine with a voltage of 17kV applied; the working distance between the needle and the collector is 22cm; the injection rate is 0.8mL / h; electrospinning is carried out at 25℃ and 25% humidity for 5h to obtain an electrospinned nanofiber membrane.

[0115] Example 8

[0116] The method described in Example 2 is implemented, except that in step (3), after the electrospun nanofiber membrane is heated and dried, the first stage of calcination temperature is 350°C.

[0117] Specifically, in step (3), the electrospun nanofiber membrane obtained in step (2) is collected, dried at 90°C for 2 hours, and then placed in a tube muffle furnace and calcined at 350°C for 1 hour, and then calcined at 500°C for 3 hours. The heating rate between room temperature and 250°C is 2°C / min, and the heating rate between 350°C and 500°C is 1°C / min, to obtain WO3 / CuO nanowire material, i.e. hydrogen sulfide gas-sensitive material.

[0118] Example 9

[0119] The method described in Example 2 is implemented, except that in step (3), after the electrospun nanofiber membrane is heated and dried, the second stage calcination temperature is 550°C.

[0120] Specifically, in step (3), the electrospun nanofiber membrane obtained in step (2) is collected, dried at 90°C for 2 hours, and then placed in a tube muffle furnace and calcined at 350°C for 1 hour, and then calcined at 550°C for 3 hours. The heating rate between room temperature and 250°C is 2°C / min, and the heating rate between 350°C and 550°C is 1°C / min, to obtain WO3 / CuO nanowire material, i.e. hydrogen sulfide gas-sensitive material.

[0121] Example 10

[0122] The method described in Example 2 was implemented, except that in step (3), after the electrospun nanofiber membrane was heated and dried, it was directly heated to 500°C and calcined for 4 hours.

[0123] Specifically, step (3): collect the electrospun nanofiber membrane obtained in step (2), dry it at 90°C for 2 hours, and then place it in a tube muffle furnace and calcine it at 500°C for 4 hours, wherein the heating rate is 2°C / min, to obtain WO3 / CuO nanowire material, namely hydrogen sulfide gas sensitive material.

[0124] Comparative Example 1

[0125] Preparation of WO3 materials (gas-sensitive materials):

[0126] (1) Dissolve 1g of PVP particles in 8ml of DMF and stir at 60℃ for 2h to obtain a polymer solution; at room temperature, slowly add 3g of ammonium metatungstate to the polymer solution and stir for 12h to obtain a spinning solution.

[0127] (2) The spinning solution obtained in step (1) was loaded into a 10ml syringe with an inner diameter of 0.8mm; and fixed on an electrospinning machine with a voltage of 17kV applied. The working distance between the needle and the collector was 20cm; the injection rate was 0.8mL / h; and electrospinning was carried out at 25℃ and 30% humidity for 5h to obtain an electrospun nanofiber membrane.

[0128] (3) Collect the electrospun nanofiber membrane obtained in step (2), dry it at 90°C for 2 hours, and then put it into a tube muffle furnace. Calcinate it at 300°C for 1 hour, and then continue to calcine it at 500°C for 3 hours. The heating rate between room temperature and 300°C is 2°C / min, and the heating rate between 300°C and 500°C is 1°C / min. WO3 nanowire material, i.e., gas-sensitive material, is obtained.

[0129] Comparative Example 2

[0130] Preparation of CuO materials (gas-sensitive materials):

[0131] (1) Dissolve 1g of PVP particles in 8ml of DMF and stir at 60℃ for 2h to obtain a polymer solution; at room temperature, slowly add 3g of copper(II) chloride dihydrate to the polymer solution and stir for 12h to obtain a spinning solution.

[0132] (2) The spinning solution obtained in step (1) was loaded into a 10ml syringe with an inner diameter of 0.8mm; and fixed on an electrospinning machine with a voltage of 17kV applied; the working distance between the needle and the collector was 20cm; the injection rate was 0.8mL / h; and electrospinning was carried out at 25℃ and 30% humidity for 5h to obtain an electrospinned nanofiber membrane.

[0133] (3) Collect the electrospun nanofiber membrane obtained in step (2), dry it at 80°C for 2 hours, and then put it into a tube muffle furnace. Calcinate it at 300°C for 1 hour, and then continue to calcine it at 500°C for 3 hours. The heating rate between room temperature and 300°C is 2°C / min, and the heating rate between 300°C and 500°C is 1°C / min. This yields CuO nanowire material, i.e., gas-sensitive material.

[0134] Comparative Example 3

[0135] Traditional hydrothermal method for preparing WO3 / CuO nanoparticles (gas-sensitive materials):

[0136] (1) WO3 nanocubes with a particle size of 80-200 nm and CuO nanoparticles with a particle size of 100-150 nm were dispersed in ethanol at a mass ratio of 3:1 and subjected to ultrasonic treatment for 30 minutes to obtain a mixed dispersion.

[0137] (2) Stir the mixed dispersion at 50°C for 5 hours to uniformly dope and modify CuO nanoparticles between WO3 nanocubes, and finally obtain WO3 / CuO nanocomposite material, i.e. gas-sensitive material.

[0138] Test Example 1

[0139] (1) The morphology of the WO3 / CuO gas-sensitive material prepared in the examples was characterized by scanning electron microscopy. Figure 1 This is a scanning electron microscope image of the WO3 / CuO gas-sensitive material prepared in Example 2. Figure 2 This is a scanning electron microscope elemental distribution diagram of the WO3 / CuO gas-sensitive material prepared in Example 2.

[0140] Depend on Figure 1 It can be seen that the morphology of the WO3 / CuO gas-sensitive material prepared in Example 2 is nanowires with a diameter of about 100-200 nm.

[0141] Depend on Figure 2 It can be seen that the copper and tungsten elements in the WO3 / CuO gas-sensitive material prepared in Example 2 are evenly distributed.

[0142] Meanwhile, the test results showed that the morphology of the products obtained in the other examples was also nanowires.

[0143] (2) The crystal structure of the products prepared in the examples was analyzed by XRD using an X-ray diffractometer. The results for the product obtained in Example 2 are as follows: Figure 3 As shown.

[0144] Depend on Figure 3 Analysis shows that the product prepared in Example 2 is a composite of monoclinic tungsten oxide and copper oxide, with no other impurity peaks and high purity.

[0145] Meanwhile, test results showed that the products obtained in the other embodiments were also composite materials of tungsten oxide and copper oxide.

[0146] Test Example 2

[0147] The sensing performance of the products (gas-sensitive materials) prepared in the test examples and comparative examples was carried out using the following method: 2 mg of terpineol was placed in a mortar, then 1 mg of the product was added and ground for 3 min. The above material was then coated onto the ceramic tube of the interdigitated gold electrode with a brush, and vacuum dried to form a sensing film, thus obtaining a methane sensor. The thickness of the sensing film and the original resistance of the sensor were measured. The sensor was then placed in a test gas containing different concentrations of hydrogen sulfide, and its resistance change was measured. The test gas was a mixture of air and hydrogen sulfide, and the test temperature was 150 °C. The response intensity of the sensor is S = |Rg - Ra| / Ra*100%, where Rg and Ra represent the resistance of the sensor exposed to the test gas environment and the air environment, respectively.

[0148] (1) Sensitivity test

[0149] The gas-sensitive materials prepared in the examples and comparative examples were tested using the above method. The test results are shown in Table 1 and 2. Figure 4 As shown, Table 1 shows the response intensity at a hydrogen sulfide content of 1 ppm. Figure 4 The graphs show the resistance changes of the sensors prepared in Examples 2, 1, and 2 in different concentrations of hydrogen sulfide.

[0150] Table 1

[0151]

[0152] As can be seen from Table 1, the sensor prepared using the WO3 / CuO nanomaterial described in the embodiments of the present invention has high sensitivity to hydrogen sulfide, fast response speed, and low lower limit of detectable hydrogen sulfide volume concentration. It can respond to hydrogen sulfide with a volume concentration of 1 ppm within 60 s.

[0153] (2) Selective testing

[0154] The sensor prepared by WO3 / CuO in Example 2 was tested for its response to interfering gases. The test gases were a mixture of air and hydrogen sulfide, and a mixture of air and interfering gases, including alcohol, trimethylamine, acetone and ammonia.

[0155] The sensor prepared by WO3 / CuO in Example 2 was placed in a test gas with a hydrogen sulfide content of 1 ppm. The results showed that the response intensity of the hydrogen sulfide sensor was 32.1% after 1 min of contact.

[0156] The sensor prepared by WO3 / CuO in Example 2 was placed in a test gas containing an equal volume concentration of alcohol. The results showed that, at the same volume concentration, the response intensity of alcohol was only 2.1% of that of hydrogen sulfide.

[0157] The sensor prepared by WO3 / CuO in Example 2 was placed in a test gas containing the same volume concentration of trimethylamine. The results showed that, at the same volume concentration, the response intensity of trimethylamine was only 4% of that of hydrogen sulfide.

[0158] The sensor prepared by WO3 / CuO in Example 2 was placed in a test gas containing the same volume concentration of acetone. The results showed that, at the same volume concentration, the response intensity of acetone was only 12.5% ​​of that of hydrogen sulfide.

[0159] The sensor prepared by WO3 / CuO in Example 2 was placed in a test gas containing the same volume concentration of ammonia. The results showed that, at the same volume concentration, the response intensity of ammonia was only 0.7% of that of hydrogen sulfide.

[0160] The above results indicate that the sensor prepared by WO3 / CuO described in this invention is selective for gases, exhibiting high sensitivity and fast response only when the detected gas is hydrogen sulfide.

[0161] (3) Repeatability test

[0162] The sensor made from the WO3 / CuO gas-sensitive material prepared in Example 2 was exposed to test gases containing different concentrations of hydrogen sulfide (1 ppm, 5 ppm, and 10 ppm) at 150°C. The test was performed three times consecutively at each gas concentration. The test results are as follows: Figure 5 As shown.

[0163] Depend on Figure 5 It can be seen that the sensor made of the WO3 / CuO nanowire material provided by this invention has stable response value and baseline resistance.

[0164] (4) Stability test

[0165] The sensors fabricated from the WO3 / CuO nanowires prepared in Example 2 and the WO3 / CuO nanoparticles prepared in Comparative Example 3 were subjected to long-term stability tests. The test method involved testing the long-term stability under different concentrations of H2S gas (1 ppm, 4 ppm, and 20 ppm). The test period was 5 days, lasting for 1 month. The test results are as follows: Figure 6 and Figure 7 As shown, Figure 6 The test results are for the sensor fabricated using the WO3 / CuO nanowires obtained in Example 2. Figure 7 The test results are for the sensor prepared from the WO3 / CuO nanoparticles obtained in Comparative Example 3.

[0166] Depend on Figure 6 and Figure 7The results show that, over time, the response of the sensor prepared by the WO3 / CuO nanowires in Example 2 hardly changes, while the sensor prepared by the WO3 / CuO nanoparticles in Comparative Example 3 shows some fluctuations over time. This indicates that the WO3 / CuO nanowires provided by the present invention have better stability than the WO3 / CuO nanoparticles prepared by the traditional hydrothermal method.

[0167] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a hydrogen sulfide gas-sensitive material, characterized in that, The method includes the following steps: (1) A spinning solution is obtained by mixing a tungsten source, a copper source, a polymer, and an organic solvent; (2) Electrospinning the spinning solution to obtain an electrospun nanofiber membrane; (3) The electrospun nanofiber membrane is dried and calcined to obtain a hydrogen sulfide gas-sensitive material.

2. The method according to claim 1, characterized in that, In step (1), the tungsten source is selected from at least one of ammonium metatungstate, tungsten chloride, and tungstic acid; Preferably, in step (1), the copper source is selected from at least one of copper chloride, copper acetate, and copper diethylhexanoate; Preferably, in step (1), the polymer is selected from at least one of polyvinylpyrrolidone, polyacrylonitrile, and polyvinyl alcohol; Preferably, in step (1), the organic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethyl sulfoxide and dichloromethane.

3. The method according to claim 1 or 2, characterized in that, In step (1), the total weight of the copper source and the tungsten source is in the weight ratio of the copper source to the copper source as 1:0.02 to 0.2; Preferably, in step (1), the ratio of the polymer to the organic solvent is 1g: 5-15mL; Preferably, in step (1), the ratio of the total weight of the tungsten source and the copper source to the weight of the polymer is 2 to 5:

1.

4. The method according to any one of claims 1-3, characterized in that, Step (1) specifically includes: The polymer and organic solvent are first mixed to obtain a polymer solution; The tungsten source, copper source, and polymer solution are mixed a second time to obtain a spinning solution.

5. The method according to claim 4, characterized in that, The conditions for the first mixing include: a temperature of 60–80°C and a time of 2–6 hours; Preferably, the conditions for the second mixing include: a temperature of 10–35°C and a time of 10–24 h.

6. The method according to any one of claims 1-5, characterized in that, In step (2), the electrospinning process parameters include: voltage of 15-20 kV, working distance between needle and collector of 18-22 cm, and injection rate of 0.5-1 mL / h; Preferably, in step (2), the ambient temperature for electrospinning is 22-28°C and the humidity is 25-35%.

7. The method according to claim 1 or 6, characterized in that, In step (3), the drying conditions include a temperature of 80 to 100°C and a time of 0.5 to 3 hours.

8. The method according to claim 1 or 7, characterized in that, In step (3), the roasting temperature is 300-600℃ and the time is 2-6h.

9. The method according to claim 1 or 8, characterized in that, The roasting process includes: firstly, roasting at 250-350°C in the first stage, and then heating to 500-550°C in the second stage of roasting; Preferably, the conditions for the first stage of roasting also include: a time of 0.5 to 2 hours and a heating rate of 1 to 3 °C / min; Preferably, the conditions for the second stage of roasting also include: a time of 2 to 4 hours and a heating rate of 0.5 to 1.5 °C / min.

10. A hydrogen sulfide gas-sensitive material prepared by the method according to any one of claims 1-9.

11. The hydrogen sulfide gas-sensitive material according to claim 10, characterized in that, The hydrogen sulfide gas-sensitive material has a morphology of nanowires; Preferably, the diameter of the hydrogen sulfide gas-sensitive material is 100–200 nm; Preferably, the length of the hydrogen sulfide gas-sensitive material is greater than 1 μm.

12. A hydrogen sulfide sensor, characterized in that, The hydrogen sulfide sensor includes the hydrogen sulfide gas-sensitive material as described in claim 10 or 11.

13. The application of the hydrogen sulfide gas-sensitive material according to claim 10 or 11 or the hydrogen sulfide sensor according to claim 12 in hydrogen sulfide detection.

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