CN109946358A - A YSZ-based hybrid potential SO2 sensor with MTiO3 as sensitive electrode, preparation method and application thereof - Google Patents

Abstract

A YSZ-based hybrid potential type SO ₂ sensor with MTiO ₃ as a sensitive electrode, a preparation method and its application in the detection of low-concentration SO ₂ in an atmospheric environment belong to the technical field of gas sensors. The sensor is sequentially composed of an Al ₂ O ₃ ceramic plate with a Pt heating electrode, a YSZ substrate, a Pt reference electrode and an MTiO ₃ sensitive electrode; the reference electrode and the sensitive electrode are separately and symmetrically prepared on both ends of the upper surface of the YSZ substrate, YSZ The lower surface of the substrate is bonded with an Al ₂ O ₃ ceramic plate with a Pt heater electrode. In the present invention, YSZ is used as the ion conductive layer, and MTiO ₃ (M is Zn, Co or Ni) composite oxide material is used as the sensitive electrode, and it is found that the device with ZnTiO ₃ as the sensitive electrode shows the highest response. In addition, the device also It showed good sensitivity, low detection limit, good repeatability, selectivity and stability.

Description

A YSZ-based hybrid potential SO2 sensor with MTiO3 as sensitive electrode, preparation method and its application

technical field

The invention belongs to the technical field of gas sensors, in particular to a YSZ-based hybrid potential type SO ₂ sensor with MTiO ₃ as a sensitive electrode, a preparation method and its application in low-concentration SO ₂ detection in atmospheric environment.

Background technique

Sulfur dioxide (SO ₂ ) is a pungent, rotten and irritating gas, which is mainly released during industrial production processes such as the burning of gasoline and coal, and natural processes such as forest fires and volcanic eruptions. Sulfur dioxide is listed as an important harmful pollutant in the atmosphere because when it is emitted into the air, it directly causes the formation of smog and acid rain. These products cause acidification of rivers, soils and lakes, accelerating the corrosion of buildings. In addition, the emission of sulfur dioxide not only causes environmental pollution, but also poses a threat to human health. Regular exposure to airborne SO2 can cause skin and eye infections, chest tightness, increased cardiovascular disease, and other life _- threatening conditions. Numerous studies have shown that even repeated exposure to low concentrations of SO ₂ (below 5 ppm) can cause permanent lung damage. Therefore, with the increasing attention to health risks and environmental challenges, there is an urgent need for us to develop reliable, highly sensitive, and convenient gas sensors to detect low _- concentration SO gas.

At present, in order to realize gas monitoring, solid electrolyte gas sensors with low cost, miniaturization, excellent sensitivity and mechanochemical stability have received more and more attention. Many research teams have developed different _SO sensors using different types of solid electrolytes. Most sensors show good sensitivity to relatively high concentrations of sulfur dioxide gas. However, it is very necessary and meaningful to develop gas sensors for detecting _SO in the low concentration range. In our previous research work, a hybrid solid-state electrochemical gas sensor based on stabilized zirconia (YSZ) and metal oxide sensitive electrodes has been developed to detect low concentrations of H ₂ S and acetone gases. According to the hybrid sensitive mechanism, the sensitive signal of the sensor is generated at the three-phase interface of the sensitive electrode/the gas to be measured/solid electrolyte through the electrochemical reaction. The sensitive performance of the sensor is mainly determined by the electrochemical catalytic activity of the sensitive electrode material to the gas to be measured. Therefore, it is very important to develop and find a sensitive electrode material suitable for the detection of _SO2 .

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a YSZ-based hybrid potential type SO ₂ sensor with MTiO ₃ (M is Zn, Co or Ni) as a sensitive electrode, a preparation method and its practical application in the detection of low concentration SO ₂ in atmospheric environment application. In addition to better sensitivity, the sensor obtained by the invention also has lower detection limit, good selectivity and stability.

The SO 2 sensor involved in the present invention is a new SO ₂ sensor constructed with YSZ as the solid electrolyte and MTiO ₃ (M is Zn, Co or Ni) composite oxide material with high electrochemical catalytic performance as the sensitive electrode. YSZ (yttrium oxide ₎ Stabilized zirconia (8% mol Y ₂ O ₃ -ZrO ₂ )) was used as the ionically conductive layer.

The YSZ-based hybrid potential type SO ₂ sensor of the present invention, as shown in Figure 1, is composed of an Al ₂ O ₃ ceramic plate with a Pt heating electrode, a YSZ substrate, a Pt reference electrode and a sensitive electrode; The electrodes are separately and symmetrically prepared on both ends of the upper surface of the YSZ substrate, the lower surface of the YSZ substrate and the upper surface of the Al ₂ O ₃ ceramic plate with a Pt heating electrode on the upper surface are bonded together; it is characterized in that: the sensitive electrode material It is MTiO ₃ (M is Zn, Co or Ni), and is prepared by the following method:

Weigh 5-8 mmol M(NO ₃ ) ₂ ·6H ₂ O, dissolve it in 15-20 mL of ethanol, stir and dissolve at room temperature; add tetrabutyl titanate to the above solution, continue to stir evenly, then add citric acid and 15-20 mL of water, stir at room temperature until a uniform sol is formed, and let stand for 20-30 hours; drying the obtained gel under vacuum conditions at 80-90 °C for 12-24 hours to obtain a dry gel, and finally at 700-900 °C Sintering under conditions for 2 to 4 hours to obtain MTiO ₃ (M is Zn, Co or Ni) sensitive electrode material; wherein the molar dosage ratio of M(NO ₃ ) ₂ ·6H ₂ O, tetrabutyl titanate and citric acid is 1 : 1: 1.5 to 3.0.

The preparation steps of the SO ₂ sensor of the present invention are as follows:

(1) Fabrication of Pt reference electrode: use Pt paste at one end of the upper surface of the YSZ substrate to make a Pt reference electrode with a thickness of 15-20 μm, and at the same time fold a Pt wire in half and stick it in the middle of the reference electrode as an electrode lead, then connect the YSZ The substrate is baked at 90-120°C for 1-2 hours, and then the YSZ substrate is sintered at 1000-1200°C for 1-2 hours to remove terpineol in the platinum paste, and finally it is lowered to room temperature;

(2) Making MTiO ₃ (M is Zn, Co or Ni) sensitive electrode: The MTiO ₃ (M is Zn, Co or Ni) sensitive electrode material is adjusted into a slurry with deionized water, and the mass concentration is 2-20%; Use this paste to prepare a sensitive electrode with a thickness of 20-30 μm on the other end of the upper surface of the YSZ substrate symmetrical with the Pt reference electrode, and also fold a platinum wire in half and stick it on the sensitive electrode as an electrode lead;

(3) sintering the YSZ substrate prepared with the reference electrode and the sensitive electrode in the previous step at 800-1000° C. for 1-3 hours; the preferred 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), and 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 the desired inorganic binder;

(5) using inorganic adhesive to bond the lower surface of the YSZ substrate and the upper surface of the Al ₂ O ₃ ceramic plate with the Pt heating electrode on the upper surface;

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 device together;

(6) Welding and encapsulating the bonded device to prepare the YSZ-based hybrid potential sensor with MTiO ₃ (M is Zn, Co or Ni) as the sensitive electrode of the present invention.

In the present invention, YSZ is used as the ion conductive layer, and _{MTiO 3} (M is Zn, Co or Ni) composite oxide material with high electrochemical catalytic activity is used as the sensitive electrode to construct three sensing devices respectively. The response value size of the device can be obtained to obtain a device with higher sensitivity performance.

Advantages of the present invention:

(1) The sensor utilizes a typical solid electrolyte-stabilized zirconia (YSZ), which has good thermal and chemical stability and can detect SO ₂ in harsh environments;

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

(3) By comparing the sensor properties of three new perovskite-type sensitive electrode materials, it is found that the YSZ-based hybrid potential device with ZnTiO ₃ as the sensitive electrode exhibits the highest response to SO ₂ and has a lower detection limit. , good sensitivity, selectivity, repeatability and stability, and has potential application prospects in low-concentration SO ₂ detection.

Description of drawings

Figure 1: Schematic diagram of the structure of the YSZ-based hybrid potential type SO ₂ sensor according to the present invention.

Part Names: Al ₂ O ₃ Ceramic Plate with Pt Heating Electrode 1, Inorganic Binder 2, YSZ Substrate 3, Pt Wire 4, Pt Reference Electrode 5, MTiO ₃ (M:Zn, Co or Ni) Sensitive Electrode 6.

Fig. 2: XRD patterns of three kinds of sensitive electrode materials prepared by the present invention. (where the abscissa is the angle and the ordinate is the intensity).

Figure 2 shows the XRD patterns of the sensitive electrode materials of ZnTiO ₃ , CoTiO ₃ and NiTiO ₃ . By comparing with the standard spectra, the synthesized three sensitive electrode materials are respectively the same as those of the standard card JCPDS (File No. 25-671, 1). -1040, 76-334) are consistent, and it is an orthorhombic composite material. It shows that the sensitive electrode materials prepared by our invention are pure phase ZnTiO ₃ , CoTiO ₃ and NiTiO ₃ materials.

Figure 3: Comparison curves of the response values of sensors constructed with ZnTiO ₃ , CoTiO ₃ and NiTiO ₃ as sensitive electrode materials to 1 ppm SO ₂ at a working temperature of 600°C.

The sensitivity performance test of the device adopts a static test method (the specific process is shown in the embodiment), and the response value of the sensor is represented by ΔV=V _SO2 -V _air . As shown in Figure 3, it is a comparison chart of the response values of the devices prepared in Examples 1, 2, and 3 to 1 ppm SO ₂ . The response values of ₂ are -22.5, -4.5 and -1 mV, respectively. It can be seen that the YSZ _- based hybrid potential SO2 sensor with _ZnTiO3 as the sensitive electrode material has the highest response value.

Figure 4: The sensitivity curve of the sensor using ZnTiO ₃ as the sensitive electrode material to SO ₂ (where the abscissa is the SO ₂ concentration, the ordinate is the potential difference; the operating temperature is 600 degrees).

The sensitivity of the sensor is the slope of the linear relationship between the response value of the sensor in a certain measurement concentration range and the corresponding logarithm of the concentration. As shown in Figure 4, it is a graph of the sensitivity of the sensor to SO ₂ using ZnTiO ₃ as the sensitive electrode material. It can be seen from the figure that the sensitivity of the device to 0.1-2ppm SO ₂ is -23 mV/decade, and the lowest can detect 100ppb SO ₂ , this sensor shows good sensitivity and low detection limit.

Figure 5: Selectivity bar graph of the sensor using ZnTiO ₃ as the sensitive electrode material (where the working temperature is 600 degrees, and the concentration of the gas to be measured is 0.5 ppm).

As shown in Figure 5, it is the selectivity curve of the sensor with ZnTiO ₃ as the sensitive electrode material. It can be seen from the figure that the device shows the greatest sensitivity to SO ₂ , and the response of other interfering gases is low. It can be seen that , the device has good selectivity.

Figure 6: The stability curve of the sensor using ZnTiO ₃ as the sensitive electrode material (where the abscissa is time, and the ordinate is the potential difference and the change in potential difference).

The stability test of the device is to keep the sensor at an operating temperature of 600 degrees, after 20 days of continuous high temperature conditions, test the response value of 1ppm SO ₂ as a standard, and take a point every two days during the test process to record 20 days. The change. As shown in Figure 6, it is the stability test of the device with ZnTiO ₃ as the sensitive electrode material within 20 days. It can be seen from the figure that the fluctuation range of the response value of the device to 1ppm SO ₂ within 20 days is less than 17.8%, indicating that the device has good stability.

Detailed ways

Example 1:

The ZnTiO ₃ material was prepared by the sol-gel method, and the ZnTiO ₃ calcined at 800 °C was used as the sensitive electrode material to make a YSZ-based hybrid potential sensor, and the gas-sensing performance of the sensor to SO ₂ was tested. The specific process is as follows:

1. Making a Pt reference electrode: Use Pt paste to make a layer of 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. After sticking to the middle position of the reference electrode, the electrode lead was drawn out; then the YSZ substrate was baked at 100 °C for 1.5 hours, and then the YSZ substrate was sintered at 1000 °C for 1 hour, so as to eliminate the terpineol in the platinum paste, and finally reduce to room temperature.

2. Making a ZnTiO ₃ sensitive electrode: Weigh 5 mmol of Zn(NO ₃ ) ₂ ·6H ₂ O, dissolve it in 15 mL of ethanol, stir at room temperature until dissolved; add 5 mmol of tetrabutyl titanate to the above solution, continue Stir well, add 10 mmol of citric acid and 15 mL of water, stir at room temperature until a uniform sol is formed, and let stand for 24 hours; the obtained gel is dried under vacuum at 80 °C for 24 hours to obtain a dry gel, and finally at 800 °C After sintering for 3 hours, a ZnTiO ₃ sensitive electrode material was obtained.

Take 5 mg of ZnTiO ₃ powder and mix it with 100 mg of deionized water to make a slurry, and coat the ZnTiO ₃ slurry on the other end of the upper surface of the YSZ substrate symmetrical with the reference electrode. Similarly, a platinum wire is folded in half and stuck to the sensitive electrode to lead out the electrode lead.

The fabricated 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, and then lowered to room temperature.

3. Bond the ceramic plate with the heating electrode. Using an inorganic binder (Al ₂ O ₃ and water glass Na ₂ SiO ₃ ·9H ₂ O, prepared in a mass ratio of 5:1), the lower surface of the YSZ substrate (the side of the uncoated electrode) was mixed with the same size The Al ₂ O ₃ ceramic plate (length and width 2×2mm, thickness 0.2mm) of the Pt heating electrode is bonded;

4. Device welding and packaging. Weld the device on the hexagonal socket and put on the protective cover to complete the hybrid potential type SO ₂ sensor.

Example 2:

The SO ₂ sensor was fabricated by using the CoTiO ₃ material calcined at 800℃ as the sensitive electrode material. The preparation process and device fabrication process of CoTiO ₃ sensitive electrode material are the same as those in Example 1.

Example 3:

The NiTiO ₃ material calcined at 800℃ was used as the sensitive electrode material to fabricate the SO ₂ sensor. The preparation process of the NiTiO ₃ sensitive electrode material and the device fabrication process are the same as those in Example 1.

The sensor was connected to the Rigol signal tester, and the sensor was placed in the atmosphere of air, 100ppb, 200ppb, 500ppb, 1ppm and 2ppm SO ₂ for voltage signal test respectively. The test method of the device adopts the traditional static test method, and the specific process is as follows:

1. Connect the sensor to the Rigol signal tester, and place the device in a test bottle with a volume of 1L filled with air to stabilize, which is the electromotive force value (Vair) of the device in the _air .

2. Quickly transfer the sensor to the test bottle containing SO ₂ gas with the concentration to be measured, until the response signal becomes stable, which is the electromotive force value (V _SO2 ) of the device in SO ₂ .

3. Transfer the device back into the air bottle until stabilization is achieved and the device completes a response recovery process. The electromotive force difference of the device in SO ₂ and air (ΔV=V _SO 2 -V _air ) is the response value of the device to the concentration of SO ₂ . The slope of the linear relationship between the response value of the sensor in a certain measurement concentration range and the corresponding logarithm of the concentration is the sensitivity of the sensor.

Table 1: Comparison of response values of sensors with ZnTiO ₃ , CoTiO ₃ and NiTiO ₃ as sensitive electrode materials to 1 ppm SO ₂ .

Table ₂ : ΔV of devices with _ZnTiO as sensitive electrode as a function of SO concentration

Table 1 lists the response values of YSZ-based hybrid potential sensors with ZnTiO ₃ , CoTiO ₃ and NiTiO ₃ as sensitive electrodes to 1 ppm SO ₂ respectively. As can be seen from the table, the device with ZnTiO3 as the sensitive electrode exhibited the highest response value of _-22.5mV

Table 2 lists the difference between the electromotive force of the YSZ-based hybrid potential sensor made of ZnTiO ₃ as the sensitive electrode material in the atmosphere of different concentrations of SO ₂ and the electromotive force in the air with the change of SO ₂ concentration. As can be seen from the table, the sensitivity (slope) and detection limit of the device are -23mV/decade and 100ppb, respectively. It can be seen that the device composed _of the new ZnTiO3 sensitive electrode material developed by us shows good sensitivity to SO2, and a YSZ _- based hybrid potential _SO2 sensor with high sensitivity and low detection limit is obtained.

Claims (3)

_1. A YSZ _- based hybrid potential type SO2 sensor with _MTiO3 as a sensitive electrode, which is sequentially composed of an _Al2O3 ceramic plate with a Pt heating electrode, a YSZ substrate, a Pt reference electrode and a sensitive electrode; the reference electrode and the sensitive electrode The electrodes are separated and symmetrically prepared on both ends of the upper surface of the YSZ substrate, and the lower surface of the YSZ substrate is bonded to the Al ₂ O ₃ ceramic plate with a Pt heating electrode; it is characterized in that: the sensitive electrode material is MTiO ₃ , M is Zn, Co or Ni, and the sensitive electrode material is prepared by the following method, Weigh 5mmol of M(NO ₃ ) ₂ ·6H ₂ O, dissolve it in 15mL of ethanol, stir at room temperature until dissolved; add 5mmol of tetrabutyl titanate to the above solution, continue to stir evenly, add 10mmol of citric acid and 15mL of water, stirred at room temperature until a uniform sol was formed, and left it for 24 hours; the obtained gel was dried under vacuum at 80 °C for 24 hours to obtain a dry gel, and finally sintered at 800 °C for 3 hours to obtain MTiO ₃ sensitive Electrode material; wherein the molar dosage ratio of M(NO ₃ ) ₂ ·6H ₂ O, tetrabutyl titanate and citric acid is 1:1:2. _2. a kind of preparation method of YSZ-based hybrid potential type SO sensor with _MTiO as sensitive electrode according to claim 1, the steps are as follows: (1) Making a Pt reference electrode: Use Pt paste at one end of the upper surface of the YSZ substrate to make a Pt reference electrode with a thickness of 15-20 μm, and at the same time fold a Pt wire in half and stick it in 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 1000-1200°C for 1-2 hours to remove terpineol in the platinum paste, and finally it is lowered to room temperature; (2) Making MTiO ₃ sensitive electrode: The MTiO ₃ (M is Zn, Co or Ni) sensitive electrode material is adjusted into a slurry with deionized water, and the mass concentration is 2-20%; A sensitive electrode with a thickness of 20-30 μm is prepared on the other end of the upper surface of the symmetrical YSZ substrate, and a platinum wire is also folded in half and glued to the sensitive electrode as an electrode lead; (3) sintering the YSZ substrate prepared with the reference electrode and the sensitive electrode in the previous step at 800-1000° C. for 1-3 hours; the preferred heating rate during high-temperature sintering is 1-2° C./min; (4) Preparation of inorganic binder: measure 2-4 mL of water glass, weigh 0.7-1.0 g of Al ₂ O ₃ powder, mix water glass and Al ₂ O ₃ powder and stir evenly to obtain the desired inorganic binder. adhesive; (5) using inorganic adhesive to bond the lower surface of the YSZ substrate and the upper surface of the Al ₂ O ₃ ceramic plate with the Pt heating electrode on the upper surface; (6) Welding and encapsulating the bonded device, thereby preparing the YSZ-based hybrid potential sensor with MTiO ₃ as the sensitive electrode according to the present invention. 3. The application of the YSZ-based hybrid potential type SO ₂ sensor with MTiO ₃ as the sensitive electrode of claim 1 in the detection of low-concentration SO ₂ in atmospheric environment.