CN110455889A - Hybrid Potential Acetaldehyde Sensor Based on YSZ and NiTiO3 Sensitive Electrode and Its Preparation Method - Google Patents

Abstract

A hybrid potential type acetaldehyde sensor based on YSZ and _NiTiO sensitive electrodes and a preparation method thereof belong to the technical field of gas sensors. From bottom to top, it consists of an _Al2O3 ceramic plate with a Pt heating electrode, a YSZ substrate, a Pt reference electrode, and a _NiTiO3 sensitive electrode; the Pt reference electrode and the _NiTiO3 sensitive electrode are separately and symmetrically prepared _on the upper surface of the YSZ substrate At _both ends of the YSZ substrate, the lower surface of the YSZ substrate is bonded with an _Al2O3 ceramic plate with a Pt heating electrode. In the present invention, stabilized zirconia (YSZ) is used as the ion-conducting layer, NiTiO ₃ composite oxide material with high electrochemical catalytic activity is used as the sensitive electrode, and the microcosm of the sensitive electrode layer is changed by different calcination temperatures (800°C-1200°C). Morphology, to achieve the purpose of improving the sensitivity of acetaldehyde.

Description

Hybrid Potential Acetaldehyde Sensor Based on YSZ and NiTiO3 Sensitive Electrode and Its Preparation method

technical field

The invention belongs to the technical field of gas sensors, and in particular relates to a hybrid potential type acetaldehyde sensor based on YSZ and _NiTiO3 sensitive electrodes and a preparation method thereof, which is mainly used for rapid detection of volatile aldehydes.

Background technique

Acetaldehyde is one of the most important aldehydes in volatile organic compounds. It is colorless and has a pungent odor. It is burned and emitted indoors (building materials, wood varnishes, etc.) and outdoors (exhaust from automobiles and other vehicles) Acetaldehyde is produced in the process. In addition, acetaldehyde is listed as a first-class carcinogen by the International Agency for Research on Cancer (IARC), which not only plays an important role in environmental pollution, but also threatens human health. According to the regulations of the Occupational Safety and Health Administration (OSHA), the maximum allowable exposure concentration of acetaldehyde is 25ppm, and the working time is 8h. Long-term exposure to acetaldehyde can produce a variety of harmful health effects, such as eye irritation, headaches, DNA damage, changes in the structure of red blood cells, and other problems. Therefore, it is of great significance to develop real-time, fast, portable and low-cost acetaldehyde gas sensors with high sensitivity, high selectivity and high stability.

To date, many research groups have used various methods for the detection of acetaldehyde gas in different applications, such as liquid chromatography, amperometric electrochemical cells, molecular imprinting techniques, and semiconducting metal oxide sensors. Among them, the solid electrolyte gas sensor has the advantages of low cost, fast response, simple structure, good chemical and mechanical stability, etc., and is considered to be the most potential detection technology. Currently, hybrid solid-state electrochemical gas sensors based on stabilized zirconia (YSZ) and metal oxide sensitive electrodes have been developed for the detection of toxic gases such as VOCs. However, the YSZ-based gas sensor based on the hybrid potential type for the rapid detection of acetaldehyde has not been reported. Therefore, it is very important to develop and find a sensitive electrode material suitable for the detection of acetaldehyde.

Contents of the invention

The purpose of the present invention is to provide a kind of mixed potential type acetaldehyde sensor based on YSZ and _NiTiO3 sensitive electrode and its preparation method, to realize the needs of rapid detection of acetaldehyde, and effectively improve the performance of sensor sensitivity, lower detection limit and so on, promote this The practical application of this sensor in the field of volatile aldehyde detection. In addition to fast response speed and high sensitivity, the sensor obtained by the invention also has lower detection limit, good selectivity and stability.

The ultra-fast response acetaldehyde sensor involved in the present invention is a novel hybrid potential type acetaldehyde gas sensor constructed based on stable zirconia (YSZ) solid electrolyte and _NiTiO composite oxide sensitive electrode, YSZ (yttria stabilized zirconia (Yttria stabilized zirconia ( 8 mol% Y ₂ O ₃ —ZrO ₂ )) as ion-conducting layer.

The hybrid potential type acetaldehyde sensor based on YSZ and _NiTiO sensitive electrodes described in the present invention, as shown in Figure 1, consists of an Al ₂ O ₃ ceramic plate with a Pt heating electrode, a YSZ substrate, and a Pt reference electrode from bottom to top. and the sensitive electrode; the reference electrode and the sensitive electrode are separated from each other and symmetrically prepared at both ends of the upper surface of the YSZ substrate, and the lower surface of the YSZ substrate is bonded with an Al ₂ O ₃ ceramic plate with a Pt heating electrode; the sensitive electrode material is NiTiO ₃ , which is prepared by the following method,

Dissolve Ni(NO ₃ ) ₂ ·6H ₂ O in ethanol, stir to dissolve at room temperature; add tetrabutyl titanate to the above solution, continue to stir evenly, then add citric acid and water, and stir at room temperature until a uniform Sol, stand still for 20-30 hours to get gel; the molar ratio of Ni(NO ₃ ) ₂ ·6H ₂ O, tetrabutyl titanate, and citric acid is 1:1:2; Drying under vacuum at 90°C for 12 to 24 hours to obtain the dry gel, and finally sintering the dry gel at 800 to 1200°C for 1 to ₃ hours to obtain the NiTiO sensitive electrode material of the present invention;

A kind of preparation method based on YSZ and _NiTiO sensitive electrode of the present invention mixed potential type acetaldehyde sensor, its steps are as follows:

(1) Making a Pt reference electrode: Use Pt paste on one end of the upper surface of the YSZ substrate to make a 15-20 μm thick Pt reference electrode, and at the same time fold a Pt wire in half and stick it to the middle of the reference electrode as an electrode lead, and then connect the YSZ The substrate is baked at 90-120°C for 1-2 hours, and then the YSZ substrate is sintered at 1000-1100°C for 1-2 hours to remove terpineol in the platinum paste, and finally lower to room temperature;

(2) Make NiTiO ₃ sensitive electrode: adjust NiTiO ₃ sensitive electrode material into slurry with deionized water, the mass concentration is 2-20%; use NiTiO ₃ slurry on the other end of the upper surface of the YSZ substrate symmetrical to the reference electrode Prepare a sensitive electrode with a thickness of 20-30 μm, and also fold a platinum wire in half and stick it on the sensitive electrode as the electrode lead;

(3) Sintering the YSZ substrate prepared in step (2) with the reference electrode and the sensitive electrode at 800-1000°C for 1-3 hours; the heating rate during high-temperature sintering is 1-2°C/min;

(4) Preparation of inorganic binder: Measure 2-4 mL of water glass (Na ₂ SiO ₃ ·9H ₂ O), weigh 0.7-1.0 g of Al ₂ O ₃ powder, mix water glass and Al ₂ O ₃ powder Mix and stir evenly to obtain an inorganic binder;

(5) Use an inorganic adhesive to bond the lower surface of the YSZ substrate and the _Al2O3 ceramic plate with a Pt heating electrode _;

Among them, the Al ₂ O ₃ ceramic plate with Pt heating electrode is obtained by screen printing Pt on the Al ₂ O ₃ ceramic plate, and the Al ₂ O ₃ ceramic plate with Pt heating electrode is used as the heating plate of the sensor;

(6) The device obtained in step (5) is welded and packaged, thereby obtaining the mixed potential type acetaldehyde sensor based on YSZ and _NiTiO sensitive electrodes of the present invention.

In the present invention, stabilized zirconia (YSZ) is used as the ion-conducting layer, NiTiO ₃ composite oxide material with high electrochemical catalytic activity is used as the sensitive electrode, and the microcosm of the sensitive electrode layer is changed by different calcination temperatures (800°C-1200°C). Morphology, to achieve the purpose of improving the sensitivity of acetaldehyde.

Advantages of the present invention:

(1) Using a typical solid electrolyte - stabilized zirconia (YSZ), which has good thermal and chemical stability, it can detect acetaldehyde in complex environments;

(2) The high-performance composite oxide NiTiO ₃ is prepared by a simple sol-gel method as a sensor sensitive electrode, and the preparation method is simple, which is conducive to mass industrial production.

(3) By changing the different calcination temperatures (800°C to 1200°C) of the material, a sensitive electrode layer with a different pore structure is obtained, thereby optimizing the microstructure of the sensitive electrode, which is beneficial for the gas to be measured to quickly reach the three-phase interface to participate in the electrochemical reaction, Thereby improving the response speed and sensitivity of the sensor.

Description of drawings

Figure 1: Schematic diagram of the structure of the YSZ-based hybrid potentiometric acetaldehyde sensor of the present invention.

Names of each part: Pt wire 1, NiTiO ₃ sensitive electrode 2, YSZ substrate 3, Pt reference electrode 4, Pt dots (for sticking electrode leads) 5, inorganic adhesive 6, Al ₂ O ₃ with Pt heating electrode Ceramic plate7.

Figure 2: XRD patterns of NiTiO ₃ sensitive electrode materials prepared at different sintering temperatures in the present invention (wherein, the abscissa is the angle, and the ordinate is the intensity).

As shown in Figure 2, it is the XRD patterns of NiTiO ₃ sensitive electrode materials at different sintering temperatures. By comparing with the standard spectra, the sintered materials are consistent with the NiTiO ₃ standard card JCPDS (File No. 76-334). It shows that the sensitive electrode material prepared by our invention is NiTiO ₃ material.

Figure 3: SEM images of sensitive electrode materials prepared at different sintering temperatures in the present invention.

As shown in Figure 3, a: 800°C, b: 1000°C, c: SEM images of NiTiO ₃ sensitive electrode materials sintered at 1200°C. It can be seen from the figure that the particle size gradually increases with the increase of sintering temperature. Large, changing the sintering temperature of the sensitive material can change the microscopic morphology of the sensitive electrode, forming a loose and porous structure, and the porosity of the electrode is conducive to the diffusion of gas.

Figure 4: Response curves of sensors using NiTiO ₃ sintered at 800°C, 1000°C and 1200°C as sensitive electrode materials to 50ppm acetaldehyde (where the abscissa is time and the ordinate is potential difference).

As shown in Figure 4, it is the potential difference ΔV (response value of the device is represented by potential difference ΔV) of the device made for embodiment 1,2,3 to 50ppm acetaldehyde, as can be seen from the figure, embodiment 1,2,3 is to 50ppm acetaldehyde The response values of 50ppm acetaldehyde were -16mV, -43mV and -3mV respectively. It can be seen that the YSZ-based hybrid potentiometric acetaldehyde sensor with NiTiO ₃ sintered at 1000 °C as the sensitive electrode material has the highest response value.

Figure 5: The continuous response curve (a) of the sensor using NiTiO ₃ sintered at 1000°C as the sensitive electrode material (where the abscissa is time and the ordinate is potential difference. The working temperature is 575 degrees) and sensitivity curve (b, c ) (wherein, the abscissa is the acetaldehyde concentration, and the ordinate is the potential difference. The working temperature is 575 degrees).

As shown in Figure 5, it is the continuous response curve of the NiTiO _{3 (1000°C)} device. It can be seen from the figure that the response value of the device to 50ppm acetaldehyde is -43mV, and the minimum can detect 200ppb acetaldehyde. This sensor shows Ultrafast response and low detection limit.

Figure 6: Selectivity bar graph of the sensor utilizing _NiTiO3 sintered at 1000 °C as the sensitive electrode material. (Wherein, the abscissa is the potential difference, and the ordinate is the test gas: from top to bottom are ethylene, nitric oxide, ammonia, nitrogen dioxide, carbon monoxide, benzene, toluene, acetic acid, xylene, formaldehyde, ethanol, methanol , n-butyraldehyde);

As shown in Figure 6, it is the selectivity of the NiTiO _{3 (1000°C)} device. It can be seen from the figure that the device shows the greatest sensitivity to acetaldehyde, so it can be seen that the device has good selectivity.

Figure 7: Humidity influence curve of a sensor using NiTiO ₃ sintered at 1000°C as a sensitive electrode material (where the abscissa is the relative humidity, and the ordinate is the potential difference).

As shown in Figure 7, it is the response of NiTiO _{3 (1000°C)} devices to 100ppm acetaldehyde at different humidity. It can be seen from the figure that the response of the device to 100ppm acetaldehyde changes in the humidity range of 20% to 98%. Smaller, indicating that the sensor has good moisture resistance.

Figure 8: Stability curves of sensors utilizing _NiTiO3 sintered at 1000 °C as the sensitive electrode material. (Wherein, the abscissa is time, and the ordinates of the upper and lower graphs are the potential difference and the change in potential difference respectively)

As shown in Figure 8, it is the stability test of the NiTiO _{3 (1000°C)} device within 20 days. It can be seen from the figure that the fluctuation range of the response value of the device within 20 days is small, indicating that the device has good stability. sex.

Detailed ways

Example 1:

The NiTiO ₃ material was prepared by the sol-gel method, and the NiTiO _{3 (1000 °C)} sintered at 1000 °C was used as a sensitive electrode material to make a YSZ-based hybrid potential type acetaldehyde sensor, and the gas-sensing performance of the sensor was tested. The specific process is as follows:

1. Make a Pt reference electrode: use Pt slurry to make a Pt reference electrode with a size of 0.5mm×2mm and a thickness of 15μm on one end of the upper surface of the YSZ substrate with a length and width of 2×2mm and a thickness of 0.2mm, and fold it in half with a Pt wire Then stick the electrode lead wire on the middle position of the reference electrode; then bake the YSZ substrate at 100°C for 1.5 hours, and then sinter the YSZ substrate at 1000°C for 1 hour, so as to eliminate the terpineol in the platinum paste, and finally reduce the to room temperature.

2. Make NiTiO ₃ sensitive electrode: weigh 5mmol of Ni(NO ₃ ) ₂ 6H ₂ O, dissolve in 15mL of ethanol, stir at room temperature until dissolved; add 5mmol of tetrabutyl titanate to the above solution, continue Stir well, add 10mmol citric acid and 15mL water, stir at room temperature until a uniform sol is formed, and let it stand for 24 hours; dry the obtained gel under vacuum at 80°C for 24 hours to obtain a dry gel, and finally dry it at 1000°C Sintered for 3 hours to obtain NiTiO ₃ sensitive electrode material.

Take 5mg of NiTiO ₃ powder and make a slurry with 100 mg of deionized water, and coat the NiTiO ₃ slurry with a sensitive electrode with a size of 0.5mm×2mm and a thickness of 20μm on the other end of the upper surface of the YSZ substrate symmetrical to the reference electrode. Use a platinum wire to fold in half and stick to the sensitive electrode to lead out the electrode lead.

The prepared YSZ substrate with the reference electrode and the sensitive electrode was heated to 800°C at a heating rate of 2°C/min and kept for 2h before cooling down to room temperature.

3. Bonding ceramic plates with heating electrodes. Using an inorganic binder ( _Al2O3 and water glass _{Na2SiO3 9H2O} with a mass volume ratio of _{1 g} : 4 mL) bond the lower surface of the YSZ substrate (the side not coated with the electrodes) with a tape of the same size Al ₂ O ₃ ceramic plates (length and width 2×2mm, thickness 0.2mm) with Pt heating electrodes were bonded.

4. Device welding and packaging. Weld the device on the hexagonal socket, put on the protective cover, and complete the hybrid potential type acetaldehyde sensor.

Example 2:

The NiTiO ₃ material sintered at 800°C is used as the sensitive electrode material to make an acetaldehyde sensor. The manufacturing process is as follows:

The NiTiO ₃ prepared by the aforementioned method was sintered in a muffle furnace at 800° C. to obtain the sensitive electrode material NiTiO _{3 (800° C.)} . The device manufacturing process is the same as that of Example 1.

Example 3:

The NiTiO ₃ material sintered at 1200°C is used as the sensitive electrode material to make an acetaldehyde sensor. The manufacturing process is as follows:

The NiTiO ₃ prepared by the aforementioned method was sintered in a muffle furnace at 1200° C. to obtain the sensitive electrode material NiTiO _{3 (1200° C.)} . The device manufacturing process is the same as that of Example 1.

Connect the sensor to the Rigol signal tester, place the sensor in air, 200ppb acetaldehyde, 500ppb acetaldehyde, 1ppm acetaldehyde, 2ppm acetaldehyde, 5ppm acetaldehyde, 10ppm acetaldehyde, 20ppm acetaldehyde, 50ppm acetaldehyde, 100ppm The voltage signal test is carried out in the atmosphere of acetaldehyde and 200ppm acetaldehyde. The response value of the device is represented by ΔV, and its value is V _{gas to be tested} - V _air .

Table 1: Response data of sensors using NiTiO _{3 (800°C)} , NiTiO _{3 (1000°C)} and NiTiO _{3 (1200°C)} as sensitive electrode materials to 50ppm acetaldehyde

Table 2: Variation data of ΔV with acetaldehyde concentration for sensors using NiTiO _{3 (1000°C)} as sensitive electrode material

Acetaldehyde concentration (ppm) Sensitive electrode and reference electrode potential difference ΔV (mV) 0.2 -4.5 0.5 -7.5 1 -3.5 Sensitivity (mV/decade) -3 1 -3.5 2 -9 5 -12 10 -25 20 -34 50 -43 100 -54.5 200 -62.5 Sensitivity (mV/decade) -26.5

Table 1 lists the response values of sensors using NiTiO _{3 (800°C)} , NiTiO _{3 (1000°C)} and NiTiO _{3 (1200°C)} as sensitive electrode materials to 50ppm acetaldehyde. It can be seen from the table that all three devices have good response characteristics to acetaldehyde, and the device using NiTiO _{3 (1000°C)} as the sensitive electrode material has the highest response value, which is -43mV. In addition, it can be seen from Table 2 that the detection limit of NiTiO _{3 (1000°C)} device to acetaldehyde reaches 200ppb. The sensitivity to 0.2-1ppm and 1-200ppm acetaldehyde is -3mV/decade and -26.5mV/decade. It can be seen that the currently constructed hybrid potentiometric sensor shows good sensitivity to acetaldehyde, and has a good potential application prospect in the field of atmospheric environment detection.

Claims (4)

1. one kind is based on YSZ and NiTiO₃Sensitive electrode blendes together electric potential type acetaldehyde sensor, from bottom to up successively by adding with Pt The Al of thermode₂O₃Ceramic wafer, YSZ substrate, Pt reference electrode and sensitive electrode composition；Reference electrode and sensitive electrode divide each other It stands and symmetrically prepares in the both ends of YSZ upper surface of base plate, YSZ base lower surface and the Al with Pt heating electrode₂O₃Ceramic wafer It is bonded together；Sensitive electrode material is NiTiO₃, which is prepared by the following method,

By Ni (NO₃)₂·6H₂O is dissolved in ethyl alcohol, at room temperature stirring and dissolving；Butyl titanate is added in above-mentioned solution, Continue to stir evenly, add citric acid and water, is stirred at room temperature to uniform colloidal sol is formed, stand 20~30 hours and coagulated Glue；Ni(NO₃)₂·6H₂O, butyl titanate, citric acid dosage molar ratio be 1:1:2；By obtained gel at 80~90 DEG C It is dried 12~24 hours under vacuum condition and obtains xerogel, xerogel is finally sintered to 1~3h at 800~1200 DEG C, thus Obtain NiTiO₃Sensitive electrode material.

2. described in claim 1 a kind of based on YSZ and NiTiO₃The preparation side for blending together electric potential type acetaldehyde sensor of sensitive electrode Method, its step are as follows:

(1) Pt reference electrode is made: in one end of YSZ upper surface of base plate using the Pt of Pt slurry 15~20 μ m-thicks of production with reference to electricity Pole, while will be sticked to after a Pt doublings on reference electrode middle position as contact conductor, then by YSZ substrate 90~ It is toasted 1~2 hour under the conditions of 120 DEG C, then YSZ substrate is sintered 1~2 hour at 1000~1100 DEG C, excluded in platinum slurry Terpinol is finally down to room temperature；

(2) NiTiO is made₃Sensitive electrode: by NiTiO₃Sensitive electrode material is slurred material with deionized water, and mass concentration is 2~ 20%；Use NiTiO₃Slurry is in the sensitivity for preparing 20~30 μ m-thicks with the other end of the symmetrical YSZ upper surface of base plate of reference electrode Electrode will be equally sticked on sensitive electrode as contact conductor after a platinum filament doubling；

(3) the YSZ substrate that step (2) is prepared with reference electrode and sensitive electrode is sintered 1~3 under the conditions of 800~1000 DEG C Hour；

(4) it prepares inorganic bond: measuring 2~4mL of waterglass, and weigh Al₂O₃0.7~1.0g of powder, by waterglass and Al₂O₃ Powder is mixed and stirred for uniformly, inorganic bond being made；

(5) Al of electrode is heated using inorganic bond by YSZ base lower surface and with Pt₂O₃Ceramic wafer is bonded together；

(6) step (5) is obtained device to be welded, encapsulate, to obtain based on YSZ and NiTiO₃Sensitive electrode blendes together electricity Bit-type acetaldehyde sensor.

3. as claimed in claim 2 a kind of based on YSZ and NiTiO₃The preparation for blending together electric potential type acetaldehyde sensor of sensitive electrode Method, it is characterised in that: heating rate when step (3) high temperature is sintered is 1~2 DEG C/min.

4. as claimed in claim 2 a kind of based on YSZ and NiTiO₃The preparation for blending together electric potential type acetaldehyde sensor of sensitive electrode Method, it is characterised in that: the Al with Pt heating electrode in step (5)₂O₃Ceramic wafer is in Al₂O₃Pass through silk screen on ceramic wafer Printing Pt is obtained, the Al with Pt heating electrode₂O₃Ceramic wafer is used as the heating plate of sensor.