Semiconductor in-vehicle environment formaldehyde sensing material and preparation method thereof

Abstract

The invention discloses a semiconductor in-vehicle environment HCHO sensing material and a preparation method thereof. The method comprises the following steps: step 1, preparing a precursor solution of an Sn element; 2, preparing a precursor solution of an Sb element; step 3, synthesizing and preparing SnO2 semiconductor HCHO sensing materials doped with different contents of Sb by using a self-built CSHS reaction device; step 4, preparing nano SnO2 semiconductor HCHO sensing material powder doped with different contents of Sb; and step 5, preparing the pole piece for testing the sensing performance of HCHO. The Sb-doped nano SnO2 semiconductor HCHO sensing material prepared by the method is good in structural consistency and excellent in sensing performance, the preparation method is green, energy-saving and efficient, 24-hour continuous preparation can be realized, and the material yield is high.

Description

Technical Field

[0001] The present invention relates to the technical field of metal oxide semiconductor gas sensing materials, and in particular to a Sb-doped nano-tin oxide (SnO2) semiconductor in-vehicle formaldehyde (HCHO) sensing material and a supercritical hydrothermal preparation method and application thereof. Technical Background

[0002] HCHO is a colorless organic compound with a pungent odor. According to the "Guidelines for Passenger Car Interior Air Quality Assessment" GB / T 27630-2011, the HCHO concentration in the car air shall not exceed 0.1 mg / m 3 The World Health Organization believes that when the HCHO concentration is higher than 80ppb (0.1mg / m 3 ), it will cause potential harm to human health. Long-term contact may cause headaches, sore throat, allergic reactions, and in severe cases may even lead to gene mutations and malignant tumors. Some HCHO-sensitive people, such as asthma patients, pregnant women, and children, need to pay special attention. With the rapid development of my country's new energy vehicle industry, the sales volume of domestic new energy vehicles has shown an increasing trend year by year, making people pay more and more attention to the problem of excessive HCHO in the interior environment of new cars. Therefore, it is urgent to develop a sensing material that can be used for real-time monitoring of HCHO in the interior environment of the car.

[0003] Metal oxide semiconductor gas sensors have won wide recognition in many fields such as environmental protection, pollution control and safety monitoring due to their excellent sensing performance, convenient integration characteristics and affordable cost, and have become a powerful assistant in detecting toxic and harmful gases. However, when performing real-time monitoring of HCHO inside the vehicle, these sensors face the challenges of high detection threshold, insufficient selectivity and susceptibility to interference from air humidity. In view of this, the development of HCHO gas sensing materials with low detection threshold, high selectivity and certain moisture resistance has become a research frontier and hot topic in the field of automotive sensor technology. Summary of the invention

[0004] In view of the problems existing in the background technology, the purpose of the present invention is to provide a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material and a supercritical hydrothermal preparation method and application thereof.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A supercritical hydrothermal preparation method of Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material comprises the following steps:

[0007] Step 1: Prepare the precursor solution of Sn element;

[0008] Step 2: preparing a precursor solution of Sb element;

[0009] Step 3: Use the self-built continuous supercritical hydrothermal synthesis (CSHS) reaction device to synthesize SnO2 semiconductor HCHO sensing materials doped with different contents of Sb;

[0010] Step 4: preparing nano SnO2 semiconductor HCHO sensing material powders doped with different contents of Sb;

[0011] Step 5: Prepare the electrode for testing the HCHO sensing performance.

[0012] Furthermore, the method for preparing the precursor solution of the Sn element in step one is as follows: accurately measure the target volume of ultrapure water with a measuring cylinder, place it in a reagent bottle, measure the density of SnCl4, use a pipette to measure the target volume of liquid SnCl4, place it in a reagent bottle, place the reagent bottle on a magnetic stirrer after the solute is dissolved, and stir at a speed of 600r / min for 30min to obtain a precursor solution of the Sn element.

[0013] Furthermore, the method for preparing the precursor solution of the Sb element in step 2 is as follows: accurately measure the target volume of ultrapure water into a reagent bottle using a measuring cylinder, accurately weigh a certain amount of SbCl3 crystals using a balance, place them in the reagent bottle, and add a certain amount of NaOH to the SbCl3 solution to inhibit the hydrolysis of SbCl3; after the solute is dissolved, place the reagent bottle on a magnetic stirrer and stir at a speed of 600r / min for 30min to obtain a precursor solution of the Sb element.

[0014] Furthermore, the CSHS reaction device used in step three is mainly composed of four parts: a liquid phase delivery system, a reaction system, a temperature control system, and a sample collection system.

[0015] Furthermore, the liquid phase delivery system is composed of three identical high-pressure delivery pumps for liquid chromatography and corresponding liquid phase pipelines and adapters.

[0016] Furthermore, the sample collection system is composed of a water cooling device, a filter, and a back pressure valve.

[0017] Furthermore, in step three, the process of preparing SnO2 semiconductor HCHO sensing materials doped with different Sb contents using the CSHS device is as follows: three high-pressure delivery pumps for liquid chromatography respectively pump ultrapure water, Sn element precursor solution, and Sb element precursor solution at room temperature at a certain flow rate and give the three pipelines an initial pressure of more than 22Mpa-25Mpa, relying on the back pressure valve at the end outlet of the system to maintain the internal pressure of the entire system stable; the normal temperature and high pressure Sn and Sb element precursor solutions are merged into a tee for initial mixing, and at the same time, the normal temperature and high pressure ultrapure water flows through the first set of electric heating devices and is heated to 450℃-550℃ to reach supercritical. state, and then the precursor mixed solution of Sn and Sb elements and supercritical water are merged into a four-way mixer for secondary mixing, and then flow into the second set of electric heating device after being fully mixed. The temperature is still maintained at 450℃-550℃, and the precursor mixed solution of Sn and Sb elements is fully contacted with supercritical water for more than 2s to react. After the precursor mixed solution of Sn and Sb elements contacts with supercritical water, it reacts rapidly and crystallizes to form nano-oxides. After the reaction liquid flows out of the second set of electric heating device, it enters the sample collection system for cooling, pressure relief, and filtration, and finally a suspension of nano-SnO2 semiconductor HCHO sensing material doped with different contents of Sb is obtained.

[0018] Furthermore, after the reaction in step 4 is completed, the nano suspension is collected and settled for 12-24 hours. After centrifugation and washing are repeated 6 times, it is frozen for 4 hours using a freeze dryer and freeze-dried for 24 hours. The powder is taken out, ground and placed in a glass container, argon gas is used to exhaust the air in the bottle, and the edge is sealed with sealing tape to obtain nano SnO2 semiconductor HCHO sensing material powders doped with different contents of Sb.

[0019] Furthermore, in step 5, a balance is used to weigh 100 mg of the nano-SnO2 semiconductor HCHO sensing material powder doped with different contents of Sb obtained in step 4, 500 μL of ultrapure water is measured using a pipette, placed in a sample tube, mixed evenly, 2.5 μL of the mixture is drawn using a pipette, and drop-coated on the interdigitated electrode sheet of the gold substrate, dried on a 70°C heating table, and then allowed to stand for 30 minutes to obtain an electrode sheet that can be used to test the HCHO sensing performance.

[0020] Compared with the prior art, the present invention has a series of significant and unique advantages, which are specifically reflected in the following aspects:

[0021] (1) CSHS technology, with its unique process characteristics, has taken an important step in the field of environmental protection. This technology not only reduces the emission of harmful substances in the entire preparation process and realizes green production, but is also particularly suitable for the preparation of multi-component composite metal oxide materials, which provides strong support for the diversified development of materials science. In addition, a major highlight of CSHS technology is that it can achieve continuous and rapid preparation, which means a significant improvement in production efficiency and meets the needs of modern industry for efficient production. More advanced is that the reaction conditions of this technology are highly controllable, which ensures the stability of the preparation process and the reliability of product quality. From an economic point of view, the production cost of CSHS technology is relatively low, which is of immeasurable value for promoting its industrialization process and realizing large-scale production. Therefore, when we apply CSHS technology to the preparation of nano-SnO2 semiconductor HCHO sensor materials, its advantages are more prominent. By finely controlling the type and concentration of the precursor solution and flexibly adjusting the reaction conditions, we can cleverly introduce trace Sb elements during the synthesis process to perform synchronous doping modification on the nano-SnO2 semiconductor HCHO sensor materials. This innovative approach greatly improves the HCHO sensing performance of SnO2 semiconductor materials, giving it broader application prospects in environmental monitoring, in-vehicle air quality control and other fields.

[0022] (2) The supercritical hydrothermal preparation method of the Sb-doped nano-SnO2 semiconductor HCHO sensing material of the present invention has not only achieved a breakthrough in technology, but also demonstrated excellent performance in practical applications. The Sb-doped nano-SnO2 semiconductor HCHO sensing material prepared by this method has excellent structural consistency, which means that each batch of materials has similar physical and chemical properties, thereby ensuring the stability and reliability of the sensing performance. At the same time, the material has excellent sensing performance, fast response speed to HCHO, high sensitivity, and good selectivity and stability, which makes it have extremely high application value in the field of HCHO detection. More importantly, the preparation method itself is green, energy-saving and efficient. It makes full use of the unique properties of supercritical water, realizes 24-hour uninterrupted continuous preparation, and greatly improves production efficiency. At the same time, due to the precise control of the reaction conditions, the output of the material has also been significantly improved, which is of great significance for meeting market demand and promoting the industrialization process.

[0023] In summary, the present invention not only realizes the green, efficient and controllable preparation process by introducing continuous supercritical hydrothermal synthesis technology and cleverly applying it to the preparation of nano SnO2 semiconductor HCHO sensing materials, but also significantly improves the sensing performance and application value of the materials. This innovative research result has injected new vitality into the development of materials science and sensor technology, and also provided more reliable technical support for fields such as environmental monitoring and in-vehicle air quality control. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 : Schematic diagram of the CSHS device.

[0025] Figure 2 : Response curve of 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material to 80ppb HCHO at 250℃-400℃ in Example 1; Test conditions: HCHO concentration: 80ppb, O2 concentration: 20%, N2 as supplementary gas, total flow rate: 1L / min, reaction temperature 250℃-400℃, humidity: 90% RH.

[0026] Figure 3 : Response and recovery time of 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material to 80ppbHCHO at 350°C in Example 1; Test conditions: HCHO concentration: 80ppb, O2 concentration: 20%, N2 as supplementary gas, total flow rate: 1L / min, reaction temperature 350°C, humidity: 90% RH.

[0027] Figure 4 : Sensing response recovery curve of 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material in Example 1 to 10-100ppb HCHO at 350°C; Test conditions: HCHO concentration: 10-100ppb, O2 concentration: 20%, N2 as supplementary gas, total flow rate: 1L / min, reaction temperature 350°C, humidity: 90% RH.

[0028] Figure 5 : The linear fitting result of the sensor response recovery curve of the 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensor material in Example 1 to 10-100 ppb HCHO at 350°C.

[0029] Figure 6 : The selectivity of the 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material in Example 1 to five gases at 350°C.

[0030] Figure 7: Stability test of the response of the 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material to 80ppbHCHO at 350°C in Example 1; test conditions: HCHO concentration: 80ppb, O2 concentration: 20%, N2 as supplementary gas, total flow rate: 1L / min, reaction temperature 350°C, humidity: 90% RH.

[0031] Figure 8 : XRD patterns of nano-SnO2 semiconductor HCHO sensing materials doped with different contents of Sb in Example 1 and Example 2.

[0032] Note: The Sb-doped nano-SnO2 semiconductor HCHO sensing material prepared in the present invention is an N-type semiconductor. For an N-type semiconductor, the sensitivity S is defined as the ratio of the resistance value (Ra) of the gas sensor element in clean air to the resistance value (Rg) in the target gas, that is, S = Ra / Rg. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. On the contrary, the present invention encompasses any substitutions, modifications, equivalent methods and schemes made on the essence and scope of the present invention as defined by the claims. Further, in order to enable the public to have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. For those skilled in the art, the present invention can be fully understood without the description of these details.

[0034] Example 1

[0035] A supercritical hydrothermal preparation method of Sb-doped nano SnO2 semiconductor in-vehicle environment HCHO sensing material comprises the following steps:

[0036] Step 1: Prepare 1L of Sn element precursor solution. Use a measuring cylinder to accurately measure 1L of ultrapure water and place it in a reagent bottle. Take 1000μL of liquid SnCl4 and weigh it. Measure the density three times and take the average value as 2.17g / ml. Use a pipette to measure 2417μL of liquid SnCl4 and place it in a reagent bottle. After the solute is dissolved, place the reagent bottle on a magnetic stirrer and stir at 600r / min for 30min to obtain 1L of Sn element precursor solution.

[0037] Step 2: Prepare 1L of precursor solution of Sb element. Use a measuring cylinder to accurately measure 1L of ultrapure water into a reagent bottle, use a balance to accurately weigh 4.6mg of SbCl3 crystals, place them in a reagent bottle, and add a certain amount of NaOH to the SbCl3 solution to inhibit the hydrolysis of SbCl3. After the solute is dissolved, place the reagent bottle on a magnetic stirrer and stir at a speed of 600r / min for 30min to obtain 1L of precursor solution of Sb element. The total concentration of metal ions in the two bottles of precursor solution is controlled to be 0.02mol / L. At this time, the molar percentage of Sb element in the total concentration of metal ions in the two bottles of precursor solution is 0.1%. The molar percentage of Sn element in the total concentration of metal ions in the two bottles of solution is 99.9%.

[0038] Step 3: Use the CSHS reaction device to synthesize and prepare 0.1% Sb-doped SnO2 semiconductor HCHO sensing materials. The CSHS reaction device mainly consists of four parts: liquid phase delivery system, reaction system, temperature control system, and sample collection system. Figure 1 shown.

[0039] Liquid phase delivery system: It consists of three identical high-pressure delivery pumps for liquid chromatography and corresponding liquid phase pipelines and adapters, which are used to deliver deionized water, precursor solution and auxiliary solution respectively.

[0040] Reaction system: It consists of two sets of electric heating devices and corresponding liquid phase pipelines and adapters. The electric heating device (large) is used to heat the room temperature high pressure deionized water to 450℃ to make it reach the supercritical state. The electric heating device (small) is used to keep the straight pipe section at the mixer outlet warm to ensure that the contact time between the mixed solution of the precursor and the additive and the supercritical water reaches more than 2s.

[0041] Temperature control system: Control two sets of electric heating devices to program the temperature and stabilize the temperature above 450℃.

[0042] Sample collection system: It consists of a water cooling device, a filter, and a back pressure valve. The prepared nanomaterials flow out of the system in the form of a suspension after cooling and pressure relief.

[0043] The process of preparing 0.1% Sb-doped SnO2 semiconductor HCHO sensing material using the CSHS device: three high-pressure delivery pumps for liquid chromatography pump ultrapure water, Sn element precursor solution, and Sb element precursor solution at room temperature at 20mL / min, 10mL / min, and 10mL / min respectively, and give the three pipelines an initial pressure of 23Mpa. The back pressure valve at the end outlet of the system is used to maintain the internal pressure of the entire system stable. The precursor solutions of Sn and Sb elements at room temperature and high pressure are introduced into a three-way for primary mixing. At the same time, the ultrapure water at room temperature and high pressure flows through an electric heating device (large) and is heated to 450° C. to reach a supercritical state. Then, the precursor mixed solution of Sn and Sb elements and the supercritical water are introduced into a four-way mixer for secondary mixing. After being fully mixed, they flow into the electric heating device (small). The temperature is still maintained at 450° C., and the precursor mixed solution of Sn and Sb elements is fully contacted with the supercritical water for more than 2 seconds to react. After contacting with the supercritical water, the precursor mixed solution of Sn and Sb elements reacts rapidly and crystallizes to generate nano-oxides. After the reaction liquid flows out of the electric heating device (small), it enters the sample collection system, is cooled, depressurized, and filtered, and finally a suspension of 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material is obtained.

[0044] Step 4: After the reaction is completed, the nano suspension is collected and settled for 12 hours. After centrifugation and washing are repeated 6 times, it is frozen in a freeze dryer for 4 hours and freeze-dried for 24 hours. The powder is taken out, ground and placed in a glass container. Argon is used to exhaust the air in the bottle, and the edge is sealed with sealing tape to obtain 0.1% Sb-doped nano SnO2 semiconductor HCHO sensor material powder.

[0045] Step 5: Use a balance to weigh 100 mg of the 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensor material powder obtained in step 4, use a pipette to measure 500 μL of ultrapure water, put it in a sample tube, mix it evenly, use a pipette to absorb 2.5 μL of the mixture, and drop it on the interdigitated electrode sheet on the gold substrate. Use a 70°C heating table to dry it and let it stand for 30 minutes to obtain an electrode that can be used to test the HCHO sensor performance.

[0046] Example 2

[0047] A supercritical hydrothermal preparation method of Sb-doped nano SnO2 semiconductor in-vehicle environment HCHO sensing material comprises the following steps:

[0048] Step 1: Prepare 1L of Sn element precursor solution. Use a measuring cylinder to accurately measure 1L of ultrapure water and place it in a reagent bottle. Take 1000μL of liquid SnCl4 and weigh it. Measure the density three times and take the average value as 2.17g / ml. Use a pipette to measure 2408μL of liquid SnCl4 and place it in a reagent bottle. After the solute is dissolved, place the reagent bottle on a magnetic stirrer and stir at 600r / min for 30min to obtain 1L of Sn element precursor solution.

[0049] Step 2: Prepare 1L of Sb element precursor solution. Use a measuring cylinder to accurately measure 1L of ultrapure water into a reagent bottle, use a balance to accurately weigh 23mg of SbCl3 crystals, place it in the reagent bottle, and add a certain amount of NaOH to the SbCl3 solution to inhibit the hydrolysis of SbCl3. After the solute is dissolved, place the reagent bottle on a magnetic stirrer and stir at 600r / min for 30min to obtain 1L of Sb element precursor solution. The total concentration of metal ions in the two bottles of precursor solutions is controlled to be 0.02mol / L. At this time, the molar percentage of Sb element in the total metal ion concentration in the two bottles of precursor solutions is 0.5%. The molar percentage of Sn element in the total metal ion concentration in the two bottles of solutions is 99.5%

[0050] Step 3: Use the CSHS reaction device to synthesize and prepare 0.5% Sb-doped SnO2 semiconductor HCHO sensing materials. The CSHS reaction device mainly consists of four parts: liquid phase delivery system, reaction system, temperature control system, and sample collection system. Figure 1 shown.

[0051] Liquid phase delivery system: It consists of three identical high-pressure delivery pumps for liquid chromatography and corresponding liquid phase pipelines and adapters, which are used to deliver deionized water, precursor solution and auxiliary solution respectively.

[0052] Reaction system: It consists of two sets of electric heating devices and corresponding liquid phase pipelines and adapters. The electric heating device (large) is used to heat the room temperature high pressure deionized water to 450℃ to make it reach the supercritical state. The electric heating device (small) is used to keep the straight pipe section at the mixer outlet warm to ensure that the contact time between the mixed solution of the precursor and the additive and the supercritical water reaches more than 2s.

[0053] Temperature control system: Control two sets of electric heating devices to program the temperature and stabilize the temperature above 450℃.

[0054] Sample collection system: It consists of a water cooling device, a filter, and a back pressure valve. The prepared nanomaterials flow out of the system in the form of a suspension after cooling and pressure relief.

[0055] The process of preparing 0.5% Sb-doped SnO2 semiconductor HCHO sensing material using the CSHS device: three high-pressure delivery pumps for liquid chromatography pump ultrapure water, Sn element precursor solution, and Sb element precursor solution at room temperature at 20mL / min, 10mL / min, and 10mL / min respectively, and give the three pipelines an initial pressure of 23Mpa. The back pressure valve at the end outlet of the system is used to maintain the internal pressure of the entire system stable. The precursor solutions of Sn and Sb elements at room temperature and high pressure are introduced into a three-way mixer for primary mixing. At the same time, the ultrapure water at room temperature and high pressure flows through an electric heating device (large) and is heated to 450° C. to reach a supercritical state. Then, the precursor mixed solution of Sn and Sb elements and the supercritical water are introduced into a four-way mixer for secondary mixing. After being fully mixed, they flow into the electric heating device (small). The temperature is still maintained at 450° C., and the precursor mixed solution of Sn and Sb elements is fully contacted with the supercritical water for more than 2 seconds to react. After contacting with the supercritical water, the precursor mixed solution of Sn and Sb elements reacts rapidly and crystallizes to generate nano-oxides. After the reaction liquid flows out of the electric heating device (small), it enters the sample collection system for cooling, pressure relief, and filtration, and finally a suspension of 0.5% Sb-doped nano-SnO2 semiconductor HCHO sensing material is obtained.

[0056] Step 4: After the reaction is completed, the nano suspension is collected and settled for 12 hours. After centrifugation and washing are repeated 6 times, it is frozen in a freeze dryer for 4 hours and freeze-dried for 24 hours. The powder is taken out, ground and placed in a glass container. Argon is used to exhaust the air in the bottle, and the edge is sealed with sealing tape to obtain 0.5% Sb-doped nano SnO2 semiconductor HCHO sensor material powder.

[0057] Step 5: Use a balance to weigh 100 mg of the 0.5% Sb-doped nano-SnO2 semiconductor HCHO sensor material powder obtained in step 4, use a pipette to measure 500 μL of ultrapure water, put it in a sample tube, mix it evenly, use a pipette to absorb 2.5 μL of the mixture, and drop it on the interdigitated electrode sheet on the gold substrate. Use a 70°C heating table to dry it and let it stand for 30 minutes to obtain an electrode that can be used to test the HCHO sensor performance.

[0058] like Figure 2 As shown, the 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material has the best response value for 80 ppb HCHO at 350°C.

[0059] like Figure 3 As shown, the response time of 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material to 80ppb HCHO is 13s and the recovery time is 45s at 350°C and 90%RH, and its HCHO sensing performance is extremely excellent.

[0060] like Figure 4 As shown, the 0.1% Sb-doped nano-SnO2 semiconductor HCHO sensing material in Example 1 exhibits good sensing response to 10-100 ppb HCHO at 350° C. and 90% RH.

[0061] like Figure 5 As shown, the 1% Sb-doped nano-SnO2 semiconductor HCHO sensing material in Example 1 exhibits excellent sensing performance. With the increase of HCHO gas concentration, the sensitivity of the sensing material in Example 1 is significantly improved, and a good linear growth relationship is shown between the sensitivity and the concentration.

[0062] like Figure 6 As shown, the 1% Sb-doped nano-SnO2 semiconductor HCHO sensing material in Example 1 exhibits excellent selectivity.

[0063] like Figure 7 As shown, the 1% Sb-doped nano-SnO2 semiconductor HCHO sensing material in Example 1 exhibits excellent stability. After 7 consecutive tests, its response value to HCHO does not show obvious fluctuation.

[0064] like Figure 8 As shown, there are no impurity peaks of other phases in the XRD spectra of the nano SnO2 semiconductor HCHO sensor materials doped with different contents of Sb in Example 1 and Example 2, which is consistent with the standard card. According to the Scherrer formula, the average particle size of the prepared material is about 4nm.

Claims

1. A supercritical hydrothermal preparation method for Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material, characterized in that: The following steps are involved: Step 1: Prepare the precursor solution of Sn element; Step 2: preparing a precursor solution of Sb element; Step 3: Use the self-built CSHS reaction device to synthesize and prepare SnO2 semiconductor HCHO sensing materials doped with different contents of Sb; Step 4: preparing nano SnO2 semiconductor HCHO sensing material powders doped with different contents of Sb; Step 5: Prepare the electrode for testing the HCHO sensing performance.

2. The supercritical hydrothermal preparation method of a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material according to claim 1, characterized in that: The method for preparing the precursor solution of the Sn element in step one is as follows: accurately measure the target volume of ultrapure water with a measuring cylinder, place it in a reagent bottle, measure the density of SnCl4, use a pipette to measure the target volume of liquid SnCl4, place it in a reagent bottle, place the reagent bottle on a magnetic stirrer after the solute is dissolved, and stir at a speed of 600r / min for 30min to obtain a precursor solution of the Sn element.

3. The supercritical hydrothermal preparation method of a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material according to claim 1, characterized in that: The method for preparing the precursor solution of the Sb element in step 2 is as follows: use a measuring cylinder to accurately measure the target volume of ultrapure water into a reagent bottle, use a balance to accurately weigh a certain amount of SbCl3 crystals, place them in the reagent bottle, and add a certain amount of NaOH to the SbCl3 solution to inhibit the hydrolysis of SbCl3; after the solute is dissolved, place the reagent bottle on a magnetic stirrer and stir at a speed of 600r / min for 30min to obtain a precursor solution of the Sb element.

4. The supercritical hydrothermal preparation method of a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material according to claim 1, characterized in that: The CSHS reaction device used in step three is mainly composed of four parts: liquid phase delivery system, reaction system, temperature control system, and sample collection system.

5. The supercritical hydrothermal preparation method of a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material according to claim 4, characterized in that: The liquid phase delivery system is composed of three identical high-pressure delivery pumps for liquid chromatography and corresponding liquid phase pipelines and adapters.

6. The supercritical hydrothermal preparation method of a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material according to claim 4, characterized in that: The sample collection system is composed of a water cooling device, a filter and a back pressure valve.

7. The supercritical hydrothermal preparation method of a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material according to claim 1, characterized in that: In step 3, the process of preparing SnO2 semiconductor HCHO sensing materials doped with different Sb contents using the CSHS device is as follows: three high-pressure delivery pumps for liquid chromatography respectively pump ultrapure water, Sn element precursor solution, and Sb element precursor solution at a certain flow rate at room temperature and give the three pipelines an initial pressure of more than 22Mpa-25Mpa, relying on the back pressure valve at the end outlet of the system to maintain the internal pressure of the entire system stable; the precursor solutions of Sn and Sb elements at room temperature and high pressure are merged into a tee for initial mixing, and at the same time, the ultrapure water at room temperature and high pressure flows through the first set of electric heating devices and is heated to 450℃-550℃ to reach a supercritical state. Then, the precursor mixed solution of Sn and Sb elements and supercritical water are merged into a four-way mixer for secondary mixing. After being fully mixed, they flow into the second set of electric heating devices. The temperature is still maintained at 450°C-550°C, and the precursor mixed solution of Sn and Sb elements is fully in contact with supercritical water for more than 2s to react. After the precursor mixed solution of Sn and Sb elements contacts with supercritical water, it reacts rapidly and crystallizes to form nano-oxides. After the reaction liquid flows out of the second set of electric heating devices, it enters the sample collection system for cooling, pressure relief, and filtration, and finally a suspension of nano-SnO2 semiconductor HCHO sensing materials doped with different contents of Sb is obtained.

8. The supercritical hydrothermal preparation method of a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material according to claim 1, characterized in that: After the reaction in step 4 is completed, the nano suspension is collected and settled for 12-24 hours. After centrifugation and washing are repeated 6 times, it is frozen for 4 hours using a freeze dryer and freeze-dried for 24 hours. The powder is taken out, ground and placed in a glass container, argon gas is used to exhaust the air in the bottle, and the edge is sealed with sealing tape to obtain nano SnO2 semiconductor HCHO sensing material powders doped with different contents of Sb.

9. The supercritical hydrothermal preparation method of a Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material according to claim 1, characterized in that: In step 5, a balance is used to weigh 100 mg of the Sb-doped nano-SnO2 semiconductor HCHO sensing material powder with different contents obtained in step 4, 500 μL of ultrapure water is measured with a pipette, placed in a sample tube, mixed evenly, 2.5 μL of the mixture is taken with a pipette, and dropped on the interdigitated electrode sheet on the gold substrate, dried on a 70°C heating table, and then allowed to stand for 30 minutes to obtain an electrode sheet that can be used to test the HCHO sensing performance.

10. An Sb-doped nano-tin oxide semiconductor in-vehicle environment HCHO sensing material prepared according to the method according to any one of claims 1 to 9.

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