Preparation method of cotton straw carbon-based gas-sensitive material
By preparing porous cotton straw carbon-based gas-sensitive materials, the problems of high energy consumption and environmental unfriendliness of high-temperature gas sensors were solved, and high-sensitivity detection of toxic and harmful gases at room temperature and resource utilization of waste biomass were achieved.
Patent Information
- Application Number
- CN202410486146.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-22
- Publication Date
- 2025-10-24
AI Technical Summary
Existing gas sensors operate at high temperatures, resulting in high energy consumption and poor stability, and traditional carbon material preparation methods are environmentally unfriendly, which limits their widespread application, especially the unmet demand for high-sensitivity detection of toxic and harmful gases at room temperature.
Using cotton straw as raw material, a porous cotton straw carbon-based gas-sensitive material was prepared through a simple carbonization treatment. Its tubular structure and trace elements were used to increase the gas adsorption sites, achieving high-sensitivity detection of hydrazine, ammonia water, hydrogen peroxide and formaldehyde at room temperature.
It achieves high-sensitivity detection of hydrazine, ammonia, hydrogen peroxide and formaldehyde at room temperature, reduces energy consumption and improves the stability of the sensor, while realizing the resource utilization of waste biomass.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of biomaterial science and the field of gas sensitive sensing materials, and particularly relates to a preparation method of a cotton stalk carbon-based gas sensitive material, which realizes high-sensitivity detection of toxic and harmful gases. BACKGROUND
[0002] The level of toxic gases and volatile organic compounds (VOCs) in indoor air is rising, which may be caused by automobile exhaust, waste burning and unqualified indoor decoration materials. For example, nitrogen oxides (NO x ), ammonia (NH3), formaldehyde (CH2O) and other VOCs, long-term exposure to these toxic and harmful gases will have a risk of cancer.
[0003] In the 1930s, the Brauer P team found that the conductivity of some metal oxides Cu2O changed due to the adsorption of water molecules. This discovery marked the birth of gas sensors and provided a foundation for the development of gas sensing technology. Since then, researchers have gradually conducted more in-depth research on sensing materials and sensitive mechanisms. Currently, a large number of metal oxide (MOS) and composite gas sensing materials have been developed. However, both metal oxide materials and multi-metal composite materials require high detection temperatures, usually greater than 200 ℃, which increases power consumption and affects the stability of the work. Therefore, the development of gas sensing materials with room temperature detection capability has gradually attracted attention. Carbon materials with multiple properties have begun to attract attention. With the application of carbon nanotubes and graphene materials in the field of gas sensing, the research of gas sensors based on carbon nanostructured materials has been opened up. However, the preparation and synthesis method of this type of carbon material needs to go through unsustainable and harsh experimental conditions to a large extent, which is harmful to the environment. Therefore, it is necessary to develop a green, sustainable and cost-effective synthesis method to prepare carbon materials. Gas sensor technology is widely used for real-time detection of pollutants in the air, factory exhaust, explosive gases and human respiratory gases. And it plays a crucial role in environmental monitoring, industrial process control and safety control, and disease diagnosis. Among various types of gas sensors, metal oxides based on semiconductors have attracted extensive research due to their high response, simple operation, high portability and low production cost. Traditional metal oxide-based gas sensors usually operate at high temperatures of 150–500 ℃, because enough thermal energy is needed to overcome the activation energy barrier of the surface redox reaction and increase the free carrier concentration in the metal for gas sensing. However, due to the decrease in sensor stability, the risk of explosive and flammable gases, and the increase in energy consumption, high-temperature operation limits its wide application. On the other hand, room temperature gas sensors are more portable, energy-saving, cost-effective and safe. Moreover, they can be integrated into wireless or flexible devices for next-generation intelligent sensor systems. Therefore, there is an urgent need for efficient and reliable gas sensors that work at room temperature.
[0004] Currently, gas sensing materials prepared from biomass-derived carbon materials have been widely studied due to their wide source, renewable, non-toxic and low cost. Biomass has significant advantages in specific surface area, porosity, element content, etc.
[0005] Xinjiang is the largest cotton planting area in China, with the highest yield in the country. In 2022, the world's cotton production was about 25.7 million tons, and Xinjiang's cotton production was about 5.39 million tons, accounting for about one-fifth of the world's total. While cotton production brings huge economic benefits, the byproduct of cotton stalks is also huge. According to the Xinjiang Statistical Yearbook, the amount of cotton production and cotton stalk resources in Xinjiang has been increasing year by year. The amount of cotton stalks increased from about 1.88×107 tons in 2016 to 2.3×107 tons in 2021. In addition, in 2022, the cotton planting area in Xinjiang was 242.6 million mu, an increase of 2.3% over the same period. Cotton production and cotton stalk production. At present, the comprehensive utilization rate of crop straw in Xinjiang has exceeded 90%, but cotton stalks are still mainly used for direct crushing and burning and returning to the field, with a low comprehensive utilization rate, so it is necessary to continuously expand the utilization channels and make cotton stalks from waste to reusable resources. In addition, straw burning, burying and feed utilization, burning will produce a large amount of particulate matter residues, causing a large amount of pollution to the air environment. Now, people pay more and more attention to environmental protection, therefore, it is particularly important to explore new cotton stalk processing methods. Based on the application field of cotton stalks, it has included supercapacitors, pollutant adsorption and other fields. However, few researchers use cotton stalks as raw materials to prepare biomass carbon materials and study their gas sensing performance. Therefore, the invention applies cotton stalks to gas sensors to realize their application in toxic and harmful gas detection. Based on the concept of sustainable development, the invention not only realizes the development of a gas sensitive material with low cost, which can detect hydrazine, ammonia water, hydrogen peroxide and formaldehyde at room temperature, but also realizes the recycling of waste biomass. SUMMARY
[0006] Based on this, the invention uses cotton stalks as raw materials to provide a preparation method of cotton stalk carbon-based gas sensitive material. The preparation method can realize the resourceization and high-value utilization of waste cotton stalks, and use waste cotton stalks in the field of gas sensitive sensing. The gas sensitive material prepared by the invention can realize high sensitivity detection of hydrazine, ammonia water, hydrogen peroxide and formaldehyde at room temperature (25 ℃).
[0007] Preparation of gas sensitive material:
[0008] a. First, wash the collected straw repeatedly with alcohol and deionized water until it is clean;
[0009] b. Cut the clean straw with skin into small pieces about 2 cm long with scissors and other tools, then peel off the skin, and wash the remaining straw again with alcohol and deionized water until it is clean;
[0010] c. Place the clean straw in the sun for 8 hours to fully evaporate the water on the surface of the straw;
[0011] d, the exposed straw is collected and placed in a drying oven at 60℃ for 24 hours, and then the drying oven is turned off and allowed to cool naturally;
[0012] e, the dried straw in step d is taken out and placed in a porcelain boat, then the porcelain boat is placed in a tube furnace, and pyrolysis treatment is carried out after N2 is introduced. After cooling, the obtained sample is washed and dried;
[0013] f, the sample obtained in step e is ground in a corundum mortar for 10 minutes to obtain fine powder, then mixed with a certain proportion of deionized water and continue to grind to obtain a uniform dispersion paste, then uniformly coated on the interdigital electrode sheet, dried at room temperature for 36 hours to prepare a straw-based gas sensor.
[0014] The outstanding feature of the present application is that the abandoned biomass-cotton straw is used as raw material, and after simple carbonization treatment, an excellent gas sensitive material can be obtained. The carbonized cotton straw has a tubular structure, and there are also small pore structures on the tubular structure. This porous structure helps the diffusion of gas molecules and increases the number of adsorbed oxygen molecules, which can provide more adsorption sites for the adsorption of target gas, thereby showing high response to gas. In addition, the carbonized cotton straw contains a variety of trace elements (C, O, K, and Mg, etc.), and the presence of trace elements may reduce the resistance of the gas sensitive material, which will further improve the sensitivity to gas. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 is the X-ray diffraction (XRD) spectrum of the material used in the present application, cotton straw and carbonized cotton straw;
[0016] Figure 2 is the infrared spectrum (FTIR) of the material used in the present application, cotton straw and carbonized cotton straw;
[0017] Figure 3 is the scanning electron microscope (SEM) morphology of the material used in the present application, carbonized cotton straw;
[0018] Figure 4 is the response size curve of the sample prepared by the present application, the sensing material of carbonized cotton straw, to 500 ppm of hydrazine, ammonia water, hydrogen peroxide and formaldehyde vapor at room temperature (25℃). DETAILED DESCRIPTION
[0019] A number of illustrative embodiments of the present application will now be described in detail below. The description makes reference to a number of examples and specific language is used therein for the purpose of clarity. However, no limitation is intended to the application as described or illustrated in this specification, and any variations that would be apparent to one skilled in the art are to be considered within the scope of the present application. The application is not limited to the examples and illustrative embodiments described herein but extend to equivalents and substitutes in the scope of the appended claims.
[0020] The terminology used in the description of the application herein is not intended to be limiting and is used solely for description. The use of the singular form "a", "an", and "the" to refer to an item of an embodiment is not intended to exclude the possibility of multiple forms of the item being present unless the context clearly indicates otherwise. Open-ended phrases such as "having", "containing", and the like are intended to include but not limited to the items specifically identified.
[0021] 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. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred materials and methods are described herein.
[0022] The application of a cotton straw carbon-based gas-sensitive material preparation method will be described in detail below. The specific description is as follows:
[0023] The application of a cotton straw carbon-based gas-sensitive material preparation method includes:
[0024] S1, first, the collected straw is repeatedly cleaned with alcohol and deionized water, dried, and cut into pieces;
[0025] S2, the cotton straw short strips obtained in S1 are peeled, repeatedly cleaned with alcohol and deionized water, and then dried after being exposed to the sun;
[0026] S3, the product obtained in S2 is weighed and placed in a porcelain boat, then placed in a high-temperature tube furnace, and 0.2 L / min of nitrogen is introduced, with a heating rate of 5 ℃ / min to 700 ℃, and the temperature is kept constant for 2 h. When the tube furnace cools to room temperature, the product is washed with deionized water and dried. The pyrolyzed product has a rough surface and a short rod structure, which indicates that high temperature does not destroy its macroscopic skeleton structure;
[0027] S4, the sample obtained in S3 is ground in a jade mortar for 10 min to obtain fine powder, then mixed with a certain proportion of deionized water and continue to grind to obtain a uniform dispersion paste, then uniformly coated on the interdigital electrode sheet, and dried at room temperature for 36 h to prepare a straw-based gas sensor.
[0028] In one embodiment of the present application, the cutting length of S1 is 2-3 cm, and the drying condition is 60 ℃ for 8 h.
[0029] In one embodiment of the present application, the exposure time in S2 is 8 h, and the drying condition is 60 ℃ for 24 h.
[0030] For a clearer understanding, the following examples will be described in detail.
[0031] Example 1
[0032] The waste cotton stalks were collected, cleaned repeatedly with alcohol and deionized water, and then dried. The dried stalks with skin were cut into short strips of about 2-3 cm in length with scissors, and the skin was removed. The cleaned cotton stalks were exposed to the sun for 8 h to fully evaporate the water on the surface of the cotton stalks. Then, the exposed cotton stalks were collected and dried in a drying oven at 60 ℃ for 24 h, and the drying oven was closed to naturally cool down. After the sample was dried, it was loaded into a porcelain boat and placed in a tube furnace. After 0.2 L / min of N2 was introduced, the temperature was raised to 300 ℃ at a rate of 5 ℃ / min, and the temperature was kept constant for 3 h. After cooling, the obtained sample was ground thoroughly in a jade mortar for 10 min to obtain fine powder, which was then mixed with a certain proportion of deionized water and ground continuously to obtain a uniformly dispersed paste. The paste was uniformly coated on an interdigital electrode sheet, dried at room temperature for 36 h, and a cotton stalk carbon-based gas sensor (CS-300) was prepared.
[0033] Comparative Example 1
[0034] The same as Example 1, except that the pyrolysis treatment temperature was 400 ℃ (CS-400).
[0035] Comparative Example 2
[0036] The same as Example 1, except that the pyrolysis treatment temperature was 500 ℃ (CS-500).
[0037] Comparative Example 3
[0038] The same as Example 1, except that the pyrolysis treatment temperature was 600 ℃ (CS-600).
[0039] Connect the power supply of the photoelectricity test platform (CGS-MT), under the bias of 4 V, at room temperature (temperature 25 ℃, relative humidity 25%), test the response curves of CS-300, CS-400, CS-500 and CS-600 gas sensors to target gases (hydrazine, ammonia, hydrogen peroxide and formaldehyde). Compared with Example 1 and Comparative Example 2, it is found that as the carbonization temperature increases, the percentage of the response intensity of the gas-sensitive material to the target gas shows a trend of first increasing and then decreasing. Among them, when the carbonization temperature is 400 ℃, the performance is optimal.
[0040] Figure 1 The X-ray diffraction patterns (XRD) of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are shown. The structural composition of the samples is studied by XRD, and it can be seen from the figure that these samples have obvious characteristic peaks at 15.6° and 43.2°, which correspond to the (101) plane of carbon material and 2D carbon material, respectively, indicating that these samples are rich in carbon material.
[0041] The functional groups of the samples are studied by infrared spectrogram, as shown in Figure 2 From the figure we can see that these samples have rich functional groups, which will provide active sites for gas adsorption, thereby having high sensitivity.
[0042] Morphology structure
[0043] The structural morphology of the samples is studied by scanning electron microscope, as shown in Figure 3 From Figure 3 we can observe that the cotton straw has a rich pore structure, and the surface of the structure has small holes of different sizes, which will provide more adsorption sites for gas adsorption, and is expected to have high sensitivity.
[0044] Detection of target atmosphere by gas sensor:
[0045] Connect the power supply of the photoelectricity test platform (CGS-MT), under the bias of 4 V, at room temperature (temperature 25 ℃, relative humidity 25%) test the response intensity percentage of CS-300, CS-400, CS-500 and CS-600 gas sensors to hydrazine, ammonia, hydrogen peroxide and formaldehyde (Fig. Figure 4 ), as Figure 4As shown, the response curves from top to bottom correspond to hydrazine, ammonia, hydrogen peroxide and formaldehyde, respectively, and from left to right are sensors CS-300, CS-400, CS-500 and CS-600, respectively. It can be seen from the response curves that at room temperature, the resistance type sensor of CS-300 has a response of 14000%, 0%, 0% and 0% to 500 ppm of hydrazine, ammonia, hydrogen peroxide and formaldehyde vapor, respectively; the resistance type sensor of CS-400 has a response of 30000%, 300%, 7500% and 1000% to 500 ppm of hydrazine, ammonia, hydrogen peroxide and formaldehyde vapor, respectively; the resistance type sensor of CS-500 has a response of 360%, 24%, 400% and 50% to 500 ppm of hydrazine, ammonia, hydrogen peroxide and formaldehyde vapor, respectively; and the resistance type sensor of CS-600 has a response of 30%, 20%, 6% and 4% to 500 ppm of hydrazine, ammonia, hydrogen peroxide and formaldehyde vapor, respectively.
Claims
1. A method for preparing a cotton stalk carbon-based gas-sensitive material, comprising the following steps: a. first, clean the collected stalks repeatedly with alcohol and deionized water, and then dry them; b. cut the dried stalks with skins into short strips of about 2-3 cm in length with scissors or other tools, remove the skins, and then clean the remaining stalks repeatedly with alcohol and deionized water; c. place the cleaned stalks in the sun for 8 h to fully evaporate the water on the surface of the stalks; d. collect the stalks after sunning, continue to dry them in a drying oven at 60℃ for 24 h, and then cool them naturally in the closed drying oven; e. take out the dried stalks in step d, place them in a porcelain boat, then place the porcelain boat in a tube furnace, and then perform pyrolysis treatment after passing in N2. After cooling, wash and dry the obtained sample; f. grind the sample obtained in step e in a jade mortar for 10 min to obtain fine powder, then mix the powder with a certain proportion of deionized water and continue to grind to obtain a uniformly dispersed paste, then uniformly coat the paste on an interdigital electrode sheet, dry it at room temperature for 36 h, and then prepare a stalk-based gas sensor. The stalks are cotton stalks, and the length of the cut pieces is 2-3 cm.
2. The production method according to claim 1, characterized by, The heating rate during pyrolysis is 5℃ / min, and the nitrogen flow rate is 0.2 L / min.
3. The preparation method according to claim 1, characterized in that The pyrolysis treatment temperature is 300-600℃, and the constant temperature time is 3 h.
4. The method of claim 1, wherein the method further comprises, The drying condition after washing is 50-90℃.
5. The preparation method according to claim 1, characterized in that The method is prepared according to any one of claims 1 to 5.
6. A method for preparing a cotton stalk carbon-based gas sensitive material, characterized in that, 7. The gas sensor prepared based on the cotton stalk carbon-based gas-sensitive material prepared by the method of claim 1 has the use of detecting hydrazine, ammonia water, hydrogen peroxide and formaldehyde.