Potential type carbon monoxide sensor taking samarium vanadate as sensitive electrode

Abstract

The invention discloses a preparation method of a samarium vanadate powder material and a potential type carbon monoxide sensor taking samarium vanadate as a sensitive material. The sensor comprises a YSZ substrate, a zinc ferrite sensitive electrode, a reference electrode, an Ag point and an Ag lead, the sensitive material and the reference electrode are stacked and distributed on the surfaces of the two sides of the YSZ substrate, and the sensitive electrode is composed of platinum on the lower layer and samarium vanadate on the upper layer; the sensitive material has good electrocatalytic activity on carbon monoxide, and has high carbon monoxide sensitivity, selectivity and response rate. The sensor can detect the concentration of low-concentration carbon monoxide in real time, and the response of the sensor to detected gas is further improved.

Description

Technical Field

[0001] The present invention relates to the field of gas sensors, and in particular to a potential-type carbon monoxide sensor using samarium vanadate as a sensitive electrode. Background Art

[0002] Carbon monoxide (CO) is an odorless, tasteless, and colorless gas. Compared to oxygen, human blood has an affinity for CO 250-300 times higher, making it extremely toxic to humans and animals. Exposure to high concentrations of CO can cause adverse effects on human health, including chemical asphyxiation and fatal respiratory and cardiovascular effects, and even death in severe cases. In addition, vehicle-mounted power batteries can cause mechanical structural damage to the battery, battery short circuits, and battery overheating after a collision, making fire accidents very likely to occur. Real-time detection of the CO concentration inside the power battery and early warning of thermal runaway of the vehicle-mounted power battery can effectively improve the safety of electric vehicles. This requires the sensor to have high sensitivity and be able to quickly detect the CO concentration.

[0003] At present, most carbon monoxide sensors are resistance sensors based on semiconductor materials, but resistance sensors are easily affected by temperature, humidity, airflow, etc., have poor cross-interference resistance, and high false alarm rate. In comparison, potential sensors have the advantages of good stability at high temperatures, strong corrosion resistance, high sensitivity, and fast response speed, and are suitable for real-time detection of CO concentration. Electrochemical CO sensors are mainly composed of three parts: electrolyte, reference electrode, and sensitive electrode: solid electrolyte plays the role of carrier conduction. Years of commercial applications have confirmed that yttrium-stabilized zirconia (YSZ) is an electrolyte with excellent high-temperature performance; the reference electrode mainly uses materials with low catalytic activity and good thermal stability for the target gas, such as precious metal Pt; as a key functional component, the sensitive electrode should have excellent adsorption, electrochemical identification, and energy conversion functions for the target gas.

[0004] Vanadates have been widely studied in the fields of sensors, photocatalysis and batteries due to their simple preparation methods, low cost and excellent catalytic performance. Samarium vanadate is a functional material of orthovanadate with excellent catalytic performance and is widely used in catalysts, soft magnetic materials, etc. Studies have shown that zinc ferrite with an octahedral structure has good electrochemical properties for carbon monoxide and can be used as a sensitive electrode for carbon monoxide sensors. Summary of the invention

[0005] The present invention provides a potential type carbon monoxide sensor using samarium vanadate as a sensitive electrode. The sensitive material has good electrocatalytic activity to carbon monoxide, can further improve the response of the sensor to the detected gas, and significantly improve the response speed.

[0006] The potential type carbon monoxide sensor of the present invention uses samarium vanadate as a sensitive electrode material, a reference electrode including but not limited to platinum, and a solid electrolyte of YSZ.

[0007] Wherein, YSZ is yttria-stabilized zirconia, which refers to ZrO2 stabilized with 5wt% Y2O3.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing samarium vanadate is carried out according to the following steps:

[0010] In this study, the co-precipitation method was used to prepare SmVO4 material.

[0011] (1) Add 11.3 mL of nitric acid to 61.6 mL of deionized water to prepare a dilute nitric acid solution.

[0012] (2) Use an analytical balance to weigh 1.792 g of Sm(NO3)3·6H2O and add it to the prepared dilute nitric acid solution. Stir magnetically until it is completely dissolved.

[0013] (3) Use an analytical balance to weigh 0.9 g of NH4VO3, add it to the solution in (2) and stir for 1 hour.

[0014] (4) Add ammonia water to adjust the pH of the solution to 5, and the solution becomes reddish brown.

[0015] (5) The solution (4) was transferred to a 100 mL stainless steel reactor lined with Teflon for hydrothermal reaction. The hydrothermal reaction was maintained at 180°C for 10 h.

[0016] (6) Wash the sample by centrifugation three times with alcohol and deionized water alternately to remove impurities.

[0017] (7) Store the precipitate in a drying oven at 60°C for 24 h.

[0018] (8) The dried precipitate was placed in a dry pot and then heated to 700 °C in a high-temperature furnace at a rate of 2 °C / min and calcined for 2 h.

[0019] (9) Grind the calcined material in an agate mortar until it becomes a uniform and fine powder. Then stop grinding and transfer it to a dry container and seal it for storage.

[0020] A potential type carbon monoxide sensor is composed of a YSZ substrate, a reference electrode and a sensitive electrode; wherein the reference electrode and the sensitive electrode are distributed on both sides of the YSZ substrate; the sensitive electrode is composed of a lower layer of Pt and an upper layer of samarium vanadate, and the material of the reference electrode is platinum.

[0021] Preparation of Pt reference electrode: screen-print the Pt reference electrode on the front side of the YSZ substrate; sinter the YSZ with the Pt reference electrode at 1200°C for 120 min, and finally cool it naturally to room temperature;

[0022] Preparation of samarium vanadate sensitive electrode: First, use the preparation method of Pt reference electrode to coat Pt on the reverse side of YSZ substrate, and obtain YSZ substrate with Pt on both sides after calcination. Then, mix samarium vanadate powder and organic binder to prepare electrode slurry, and use the electrode slurry to screen print samarium vanadate sensitive electrode on Pt on the reverse side of YSZ substrate, bake at 150℃ for 60min, sinter at 800~1100℃, and finally cool naturally to room temperature;

[0023] Sintering of the sensor: Use a silver wire dipped in a small amount of silver paste to connect the sensitive electrode and the reference electrode respectively, and send them into a drying oven and bake them at 150°C for 120 minutes to make the silver wire and YSZ tightly bonded; thus, a potential-type carbon monoxide sensor based on a tightly connected samarium vanadate sensitive electrode and a YSZ solid electrolyte is obtained.

[0024] Furthermore, a Pt reference electrode is screen-printed on the first surface of the YSZ substrate using Pt paste.

[0025] Furthermore, the content of samarium vanadate powder in the electrode slurry is 70 wt.%, and the content of organic binder is 30 wt.%.

[0026] Furthermore, the organic binder is a mixture of 70 wt.% terpineol, 29 wt.% ethyl cellulose, and 1 wt.% Span 80.

[0027] The above-mentioned organic binder and glaze slurry can be synthesized by oneself or purchased from the market.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. In the potential-type gas sensor of the present invention, samarium vanadate exhibits a positive polarity response to carbon monoxide, has a high response value (the response value of 80 ppm carbon monoxide at 425°C is 40 mV), and has a fast response speed (the response speed of 80 ppm carbon monoxide at 425°C is 12 s);

[0030] 2. The method for preparing samarium vanadate sensitive electrode material has the advantages of high repeatability, high efficiency, low cost and high success rate;

[0031] 3. The solid electrolyte used in the device is YSZ (5% mol doped Y2O3-ZrO2) solid electrolyte material, which has the advantages of high temperature resistance, strong mechanical stability and good ionic conductivity;

[0032] 4. The potential sensor based on YSZ solid electrolyte and samarium vanadate sensitive electrode has high sensitivity and response speed to carbon monoxide gas; BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the potential-type gas sensor based on YSZ solid electrolyte and samarium vanadate sensitive electrode according to the present invention.

[0034] Figure 2 This is the XRD pattern of the samarium vanadate powder in Example 1 (the horizontal axis is the angle, and the vertical axis is the intensity).

[0035] Figure 3 This is the response diagram of samarium vanadate to different concentrations of carbon monoxide in Example 1.

[0036] Figure 4 Schematic diagram of the selectivity of a potential-type sensor made of YSZ substrate and samarium vanadate sensitive electrode material to carbon monoxide and its cross-sensitivity to other gases. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] A potential-type carbon monoxide sensor based on samarium vanadate sensitive electrode and YSZ solid electrolyte, such as Figure 1 As shown, it is composed of a reference electrode 1, an Ag dot 2, an Ag lead 3, an Ag dot 4, an Ag lead 5, a Pt 6 lower layer of a sensitive electrode, a samarium vanadate upper layer of a sensitive electrode 7, and a YSZ substrate 8; the sensitive electrode (6, 7) is composed of a Pt 6 lower layer of a sensitive electrode and a samarium vanadate upper layer of a sensitive electrode 7, and a small portion of the Pt 6 lower layer of the sensitive electrode is not covered by the samarium vanadate upper layer of the sensitive electrode 7, which is used to connect the silver wire; the sensitive electrode (6, 7) and the reference electrode 1 are symmetrically distributed on both sides of the YSZ substrate 8. The Pt lead 3 and the Pt lead 5 are fixed on the sensitive electrode (6, 7) and the reference electrode 1 respectively by using the Ag dot 2 and the Ag dot 4. The samarium vanadate sensitive electrode material is prepared by a coprecipitation method, and is sintered at 800-1100°C to prepare a YSZ-based gas sensor, and the carbon monoxide sensitivity of the sensor is tested. The specific process is as follows:

[0039] Preparation of samarium vanadate powder material: 11.3 mL of nitric acid was added to 61.6 mL of deionized water to prepare a dilute nitric acid solution. Then, 1.792 g of Sm(NO3)3·6H2O was weighed on an analytical balance and added to the prepared dilute nitric acid solution, and magnetic stirring was performed until it was completely dissolved. 0.9 g of NH4VO3 was added to the solution and stirred for 1 hour. The pH of the solution was adjusted to 5 by ammonia water, and the solution was reddish brown at this time. The solution was transferred to a 100 mL stainless steel reactor lined with Teflon for hydrothermal reaction, and the hydrothermal reaction was maintained at 180 ° C for 10 h. After that, it was washed alternately by centrifugation with alcohol and deionized water for 3 times to remove impurities, and the precipitate was stored in a drying oven at 60 ° C for 24 h. Finally, the dried precipitate was placed in a dry pot, and then raised to 700 ° C at a rate of 2 ° C / min in a high-temperature furnace and calcined for 2 h. The calcined material was ground continuously and thoroughly in an agate mortar. When the material to be tested is a uniform and fine powder, the grinding was stopped and the material was transferred to a dry container and sealed for storage.

[0040] (1) Preparation of reference electrode:

[0041] The Pt paste was screen-printed on the front of a YSZ substrate with a side length of 8 mm and a thickness of 0.3 mm. The YSZ substrate printed with the reference electrode was placed in a high-temperature furnace, heated to 1200°C at a rate of 2°C / min and maintained for 120 minutes, and finally cooled naturally to room temperature in the high-temperature furnace. A reference electrode with a side length of 3 mm was obtained.

[0042] (2) Preparation of sensitive electrodes:

[0043] First, Pt was printed on the reverse side of the YSZ substrate near the edge using the method in (1), and then calcined in a high-temperature furnace and cooled naturally.

[0044] Take 7g of samarium vanadate powder and 3g of organic binder (94wt.% pine alcohol, 5wt.% ethyl cellulose, 1wt.% Span 80), mix them evenly and prepare them into sensitive electrode slurry. Screen print the sensitive electrode slurry on the reverse side of the YSZ substrate, covering most of the Pt (its size is 6mm×6mm), and leave a small part of the Pt for connecting the silver wire. Place the YSZ substrate printed with the sensitive electrode in a drying oven and dry it at 150℃ for 120min. Then, the YSZ substrate printed with the reference electrode and the sensitive electrode is heated to 800-1100℃ at a rate of 2℃ / min and sintered, and then naturally cooled to room temperature in a high-temperature furnace to obtain a potential sensor device.

[0045] (3) Preparation of sensor:

[0046] Dip one end of a 0.2 mm diameter Ag wire into a small amount of Ag paste and place it on the Pt surface left on the sensitive electrode side, and dry it at 150°C for 120 min. Similarly, connect the silver wire to the reference electrode surface.

[0047] Figure 1 The schematic diagram of the structure of the potential type gas sensor based on YSZ solid electrolyte and samarium vanadate sensitive electrode of the present invention is shown in FIG. The sensitive electrode and the reference electrode are respectively led out using Ag wire, connected to the two ends of the electrochemical workstation, and the test signal is output on the computer.

[0048] Figure 2 This is the XRD (X-ray diffraction) diagram of samarium vanadate sensitive electrode material prepared by co-precipitation method. It can be clearly seen that the diffraction peak of SmVO4 prepared by this method corresponds well to the standard PDF (86-0994) card, and there are no other impurities and changes in substances, which can be inferred that the prepared powder is pure phase.

[0049] The specific testing process is as follows:

[0050] (1) After the sensor is heated to the operating temperature, the base gas (10% oxygen, 90% nitrogen) is introduced into the quartz tube. When the sensor signal (the potential difference between the sensitive and reference electrodes) reaches stability, the signal value V of the sensor in the base gas is obtained. base .

[0051] (2) The measured gas with different carbon monoxide concentrations (80ppm, 60ppm, 40ppm, 20ppm) is passed into the quartz tube, and the sensor signal value V is obtained when the signal is stable. t CO . (t=80s, 60s, 40s, 20s)

[0052] (3) The base gas (10% oxygen, 90% nitrogen) is reintroduced into the quartz tube. When the sensor signal returns to the base gas (10% oxygen, 90% nitrogen) signal value V base The sensor completes a response and recovery process. The sensor's signal difference between carbon monoxide and base gas is ΔV (ΔV = V t CO -V base ) is the sensor's response value to this concentration of carbon monoxide.

[0053] Figure 3 The following is the response characteristic curve of the sensor based on samarium vanadate sensitive electrode to different concentrations of carbon monoxide at an operating temperature of 400-475°C, where the horizontal axis is the carbon monoxide concentration and the vertical axis is the response value. It can be seen that at an operating temperature of 425°C, the sensor shows a large response to the measured gas with different carbon monoxide concentrations, with a maximum response value of 35mV for 80ppm carbon monoxide and a response value of 12mV for 20ppm hydrogen concentration, and the response time is within 12s, indicating that the sensor has the ability to detect low-concentration carbon monoxide in real time.

[0054] Figure 4 The response values ​​of the sensor with samarium vanadate as the sensitive electrode to different gases (CO, CO2, CH4, NH3) with a concentration of 80ppm at different sintering temperatures (800℃, 900℃, 1000℃, 1100℃), where the horizontal axis is the detection gas and the vertical axis is the response value of each gas, the concentration is 80ppm, and the operating temperature is 425℃. At 900℃, the sensor has the highest response value to carbon monoxide, reaching 35mV, while the response values ​​to other gases are all less than carbon monoxide, indicating that the sensor has excellent carbon monoxide selectivity and low cross sensitivity to other gases.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a samarium vanadate powder material, characterized in that ； Follow these steps: In this study, the SmVO4 material was prepared by co-precipitation method. S1: Add 11.3 mL of nitric acid to 61.6 mL of deionized water to prepare a dilute nitric acid solution. S2: Use an analytical balance to weigh 1.792 g of Sm(NO3)3·6H2O and add it to the prepared dilute nitric acid solution. Stir magnetically until it is completely dissolved. S3: Weigh 0.9 g NH4VO3 using an analytical balance, add it to the solution in (2) and stir for 1 hour. S4: Add ammonia water to adjust the pH of the solution to 5, and the solution is reddish brown. S5: The solution (4) was transferred to a 100 mL stainless steel reactor lined with Teflon for hydrothermal reaction, and the hydrothermal reaction was maintained at 180° C. for 10 h. S6: Wash the sample by centrifugation three times with alcohol and deionized water alternately to remove impurities. S7: Store the precipitate in a drying oven at 60°C for 24 h. S8: The dried precipitate was placed in a dry pot, the temperature was raised to 700°C in a high temperature furnace at a rate of 2°C / min, and calcined for 2h. S9: Grind the calcined material in an agate mortar until it becomes a uniform and fine powder. Then stop grinding and transfer it to a dry container and seal it for storage.

2. A potential-type carbon monoxide sensor using samarium vanadate as a sensitive electrode, characterized in that: It consists of a YSZ substrate, a sensitive electrode and a reference electrode. The reference electrode and the sensitive electrode are distributed on both sides of the YSZ substrate; the material of the reference electrode is platinum, and the material of the sensitive electrode is samarium vanadate, and a layer of Pt is printed under the samarium vanadate to improve the signal.

3. A method for manufacturing a potential-type carbon monoxide sensor using samarium vanadate as a sensitive electrode according to claim 2, characterized in that: Take 7g of samarium vanadate powder and 3g of organic binder (94wt.% pine alcohol, 5wt.% ethyl cellulose, 1wt.% Span 80), mix them evenly and prepare sensitive electrode slurry. Screen print the sensitive electrode slurry on the reverse side of the YSZ substrate, covering most of the Pt (its size is 6mm×6mm), and leave a small part of Pt for connecting the silver wire. Place the YSZ substrate printed with the sensitive electrode in a drying oven and dry it at 150℃ for 120min. Then, the YSZ substrate printed with the reference electrode and the sensitive electrode is heated to 800~1100℃ at a rate of 2℃ / min and sintered, and then naturally cooled to room temperature in a high-temperature furnace to obtain a potential sensor device. Dip a small amount of Ag slurry at one end of a 0.2mm diameter Ag wire and place it on the surface of the Pt left on the sensitive electrode side, and dry it at 150℃ for 120min. Similarly, connect the silver wire to the surface of the reference electrode.

4. The YSZ substrate according to claim 2, characterized in that: A 50 μm thick YSZ film was obtained using a tape casting machine, and eight films were stacked into an integral substrate using an isostatic press.

5. The sensitive electrode according to claim 2, characterized in that: Take 7g of zinc ferrite powder and 3g of organic binder, mix them evenly and prepare them into sensitive electrode slurry.

6. The sensitive electrode according to claim 2, characterized in that: The bottom layer is printed with Pt, and the upper layer of samarium vanadate covers most of the Pt, leaving a small portion of Pt for connecting the Ag wire.

7. The organic binder according to claim 5, characterized in that: The invention is composed of 94wt.% of terpineol, 5wt.% of ethyl cellulose and 1wt.% of Span 80.

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