CN108226256A - With CoMoO4Stabilizing zirconia base for sensitive electrode blendes together electric potential type triethylamine sensor and preparation method thereof - Google Patents

Abstract

A stable zirconia-based mixed potential triethylamine sensor with _CoMoO4 as a sensitive electrode and a preparation method thereof belong to the technical field of gas sensors. The sensor is sequentially composed of an _Al2O3 ceramic plate with a Pt heating electrode, a stabilized zirconia _substrate , a Pt reference electrode, and _{a CoMoO4} sensitive electrode material prepared by a hydrothermal method; the reference electrode and the sensitive electrode are separated from each other and Both ends of the upper surface of the stabilized zirconia substrate are symmetrically prepared, and the lower surface of the stabilized zirconia substrate is bonded with an Al ₂ O ₃ ceramic plate with a Pt heating electrode. In the present invention, stable zirconia is used as the ion-conducting layer, CoMoO ₄ composite oxide material with high electrochemical catalytic activity is used as the sensitive electrode, and the microscopic morphology of the sensitive electrode layer is changed by different calcination temperatures (800°C-1100°C). Reach the purpose of improving the sensitivity characteristic of triethylamine.

Description

Stable Zirconia-Based Hybrid Potentiometric Triethylamine Sensing Using CoMoO4 as Sensitive Electrode device and its preparation method

technical field

The invention belongs to the technical field of gas sensors, and in particular relates to a stable zirconia-based mixed potential triethylamine (TEA) sensor with _CoMoO4 as a sensitive electrode and a preparation method thereof, which is mainly used for the rapid detection of volatile organic amines.

Background technique

Triethylamine (TEA) is one of the most important volatile organic amines. It is colorless, transparent, flammable, explosive, highly toxic, and highly irritating. It has been widely used in industrial production processes, including organic solvents, Inhibitors, preservatives, catalysts, synthetic dyes, etc. Meanwhile, TEA may also be produced during the decay of dead fish and marine organisms, and the gas concentration increases significantly with the degree of death. What's more, it can cause a variety of harmful health effects such as: eye irritation, breathing problems, pulmonary edema, and even death. Therefore, it is of great significance to develop real-time, fast, portable and low-cost TEA gas sensors with high sensitivity, high selectivity and high stability.

So far, metal-oxide-semiconductor (MOS) TEA sensors based on SnO ₂ , ZnO, α-Fe ₂ O ₃ , α-MoO ₃ , Zn ₂ SnO ₄ , and NiFe ₂ O ₄ have been used due to their low fabrication cost, good portability, The advantages of good sensing characteristics and high sensitivity have been extensively studied. But most MOS gas sensors lack fast response and selectivity. In contrast, solid-state electrolyte gas sensors have attracted much attention due to their excellent sensing performance for various dangerous, flammable, and explosive gases. Among them, mixed-potential gas sensors based on yttria-stabilized zirconia (YSZ) electrolytes are considered to be the most potential candidate devices due to their better environmental stability and excellent selectivity. So far, a variety of YSZ gas sensors have been developed for the detection of NO ₂ , NH ₃ , SO ₂ , H ₂ S, VOCs and hydrocarbons. However, YSZ-based gas sensors based on the hybrid potential model for realizing rapid detection of TEA have not been reported yet.

The sensitive mechanism of the stable zirconia-based mixed potential gas sensor is: the TEA gas to be measured in the atmosphere diffuses to the three-phase reaction interface through the sensitive electrode layer, and the concentration of the TEA to be measured will gradually increase due to the reaction (1) during the diffusion process. The porosity of the oxide sensitive electrode determines the degree of reduction of the TEA concentration of the gas to be measured. At the three-phase interface of gas/YSZ conductive layer/sensitive electrode, electrochemical reduction reaction and electrochemical oxidation reaction occur simultaneously, reactions (2) and (3) constitute a local battery, when the two reaction rates are equal, the reaction reaches Balanced, a mixed potential is formed on the sensitive electrode, and the potential difference between it and the reference electrode is used as the detection signal of the sensor. The magnitude of the detection signal is determined by the rate of electrochemical reactions (2) and (3), and the reaction rate depends on the electrochemical and chemical catalytic activity of the sensitive electrode material, the microstructure of the electrode material (such as the porosity, particle size, and morphology of the material). Wait). Therefore, it is necessary to develop sensitive electrode materials with high electrochemical catalytic activity for TEA detection to construct high-performance TEA gas sensors.

The reaction formula is as follows:

2C ₆ H ₁₅ N+39/2O ₂ →12CO ₂ +N ₂ +15H ₂ O (1)

39/2O ₂ +78e ^- → 39O ^2- (2)

2C ₆ H ₁₅ N+39O ^2- → 12CO ₂ +N ₂ +15H ₂ O+78e ^- (3)

Contents of the invention

The purpose of the present invention is to provide a stable zirconia-based mixed potentiometric triethylamine sensor with _CoMoO4 as a sensitive electrode and its preparation method, in order to realize the needs of rapid detection of triethylamine, and effectively improve the sensitivity of the sensor and reduce the lower limit of detection And other properties, promote the practical application of this sensor in the field of volatile organic amine detection. In addition to fast response speed and high sensitivity, the sensor obtained by the invention also has lower detection limit, good selectivity, moisture resistance and stability.

The ultra-fast response triethylamine sensor involved in the present invention is a novel mixed potential triethylamine gas sensor constructed on the basis of a stable zirconia (YSZ) solid electrolyte and a CoMoO ₄ composite oxide sensitive electrode, YSZ (Y ₂ O ₃ ZrO ₂ with a molar doping concentration of 8% was used as the ion-conducting layer.

The stabilized zirconia-based mixed potentiometric triethylamine sensor of the present invention, as shown in Figure 1, consists of an _Al2O3 ceramic plate with a Pt heating electrode, a stabilized zirconia _substrate , a Pt reference electrode and The composition of 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 stabilized zirconia substrate, and the lower surface of the stabilized zirconia substrate is bonded to an Al ₂ O ₃ ceramic plate with a Pt heating electrode; The sensitive electrode material is CoMoO ₄ , which is prepared by the following method:

_CoMoO4 sensitive electrode materials were synthesized by a facile hydrothermal method. Under magnetic stirring, 0.5 mmol Co(NO ₃ ) ₂ ·6H ₂ O and 0.5 mmol Na ₂ MoO ₄ ·2H ₂ O were dissolved in 30-50 mL of a mixed solution of deionized water, ethanol and ethylene glycol; then, The obtained solution is hydrothermally reacted at 160-200°C for 5-8 hours, the reaction product is centrifuged and washed, and the precipitate is collected, and the obtained precipitate is dried under vacuum at 60-90°C; finally, the dried product is separated at 800-1100 Sintering at °C for 1-3 hours to obtain the CoMoO ₄ sensitive electrode material of the present invention; wherein the volume ratio of deionized water, ethanol and ethylene glycol is (1-2):1: (1-2).

The preparation method of triethylamine sensor of the present invention, 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 a CoMoO ₄ sensitive electrode: adjust the CoMoO ₄ sensitive electrode material into a slurry with deionized water, with a mass concentration of 2-20%; use the CoMoO ₄ 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 together as the heating plate of the device;

(6) Welding and packaging the device obtained in step (5), so as to obtain the YSZ-based hybrid potentiometric triethylamine sensor with _CoMoO4 as the sensitive electrode of the present invention.

In the present invention, stable zirconia is used as the ion-conducting layer, CoMoO ₄ composite oxide material with high electrochemical catalytic activity is used as the sensitive electrode, and the microscopic morphology of the sensitive electrode layer is changed by different calcination temperatures (800°C-1100°C). Reach the purpose of improving the sensitivity characteristic of triethylamine.

Advantages of the present invention:

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

(2) The high-performance composite oxide CoMoO ₄ is prepared by a simple hydrothermal synthesis 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 1100°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 triethylamine sensor of the present invention.

Names of each part: Al ₂ O ₃ ceramic plate 1, Pt heating electrode 2, inorganic binder 3, YSZ substrate 4, Pt wire 5, Pt reference electrode 6, CoMoO ₄ sensitive electrode 7.

Figure 2: XRD patterns of CoMoO ₄ sensitive electrode materials prepared by the present invention with different sintering temperatures (wherein, the abscissa is the angle, and the ordinate is the intensity).

As shown in Figure 2, it is the XRD pattern of CoMoO ₄ sensitive electrode materials at different sintering temperatures. By comparing with the standard spectrum, the sintered materials are consistent with the CoMoO ₄ standard card JCPDS (File No.14-587). It shows that the sensitive electrode material prepared by our invention is CoMoO ₄ material.

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

As shown in Figure 3, a: 800 ° C, b: 1000 ° C, c: 1100 ° C sintered SEM images of CoMoO ₄ sensitive electrode materials, it can be seen from the figure that with the increase of sintering temperature, the particle size gradually increases 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: The response curves of sensors using CoMoO ₄ sintered at 800°C, 1000°C and 1100°C as sensitive electrode materials to 100ppm triethylamine (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 device is expressed with potential difference ΔV) of the device made for embodiment 1,2,3 to 100ppm triethylamine, as can be seen from the figure, embodiment 1,2,3 The responses to 100 ppm triethylamine were -48, -102 and -58 mV, respectively. It can be seen that the YSZ-based hybrid potentiometric triethylamine sensor with _CoMoO4 sintered at 1000 °C as the sensitive electrode material has the highest response value.

Figure 5: Continuous response curve (a,b) of the sensor using CoMoO ₄ sintered at 1000°C as a sensitive electrode material (where the abscissa is time and the ordinate is potential difference. The working temperature is 600°C) and sensitivity curve (c ) (wherein, the abscissa is the concentration of TEA, and the ordinate is the potential difference. The working temperature is 600 degrees).

As shown in Figure 5, it is the continuous response curve of the CoMoO _{4 (1000°C)} device. It can be seen from the figure that the response value of the device to 100ppm triethylamine is -102mV, the response time is 1s, and the lowest can detect 100ppb triethylamine. Ethylamine, the sensor exhibited an ultrafast response and a low detection limit.

Figure 6: Selectivity bar graph of the sensor utilizing _CoMoO4 sintered at 1000 °C as the sensitive electrode material. (The abscissa is the potential difference, and the ordinate is the test gas: nitrogen dioxide, carbon monoxide, hydrogen, methane, ammonia, triethylamine, acetone, formaldehyde, benzene, toluene, xylene from top to bottom)

As shown in Figure 6, it is the selectivity of the CoMoO _{4 (1000°C)} device. It can be seen from the figure that the device shows the greatest sensitivity to triethylamine, and the response of other interfering gases is low. It can be seen that, The device has very good selectivity.

Figure 7: Humidity influence curve of a sensor using CoMoO ₄ 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 CoMoO _{4 (1000°C)} devices to 100ppm triethylamine at different humidity. The change in response is less than 6%, indicating that the sensor has good moisture resistance.

Figure 8: Stability curves of the sensor utilizing _CoMoO4 sintered at 1000 °C as the sensitive electrode material. (Wherein, the abscissa is time, and the ordinate is the potential difference value and potential difference change amount respectively)

As shown in Figure 8, it is the stability test of the CoMoO _{4 (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 less than 4.4%, indicating that the secondary device has a good stability.

Detailed ways

Example 1:

The CoMoO ₄ material was prepared by the sol-gel method, and CoMoO _{4 (800 °C)} sintered at 800 °C was used as a sensitive electrode material to fabricate a YSZ-based mixed potential type triethylamine 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. Fabrication of CoMoO ₄ sensitive electrodes: First, CoMoO ₄ materials were prepared by hydrothermal synthesis. Weigh 0.5mmol Co(NO ₃ ) ₂ 6H ₂ O and 0.5mmol Na ₂ MoO ₄ 2H ₂ O and dissolve them in 30mL deionized water, ethanol and ethylene glycol mixed solution (deionized water, ethanol The volume ratio to ethylene glycol is 1: 1: 1). Then, the solution obtained above was transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, and reacted at 180° C. for 6 hours. After centrifugation and washing (deionized water and absolute ethanol), the precipitate was collected and dried in a vacuum oven at 80°C. Finally, the dried product was sintered at 800 °C for 2 h to obtain a CoMoO ₄ sensitive electrode material with a product mass of 0.65 g.

Take 5 mg of CoMoO ₄ powder and make a slurry with 100 mg of deionized water, and coat the CoMoO ₄ slurry on the other end of the upper surface of the YSZ substrate symmetrical to the reference electrode with a layer of sensitive electrode with a size of 0.5 mm × 2 mm and a thickness of 20 μm. 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. The lower surface of the YSZ substrate (the side not coated with electrodes) was bonded to the same _size ribbon using an inorganic binder ( _Al2O3 and water glass _{Na2SiO3 9H2O} , mass volume ratio 1 g: ₄ mL). 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. The device is welded on the hexagonal socket, and the protective cover is put on to complete the mixed potential triethylamine sensor.

Example 2:

The CoMoO ₄ material sintered at 1100°C is used as the sensitive electrode material to make a triethylamine sensor. The manufacturing process is as follows:

The CoMoO ₄ prepared by the aforementioned method was sintered in a muffle furnace at 1100° C. to obtain the sensitive electrode material CoMoO _{4 (1100° C.)} , and the device manufacturing process was the same as in Example 1.

Example 3:

The CoMoO ₄ material sintered at 1000°C is used as the sensitive electrode material to make a triethylamine sensor. The manufacturing process is as follows:

The CoMoO ₄ prepared by the aforementioned method was sintered in a muffle furnace at 1000° C. to obtain the sensitive electrode material CoMoO _{4 (1000° C.)} , and the device fabrication process was the same as in Example 1.

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

Table 1 lists the response values of sensors using CoMoO _{4 (800°C)} , CoMoO _{4 (1000°C)} and CoMoO _{4 (1100°C)} as sensitive electrode materials to 100ppm triethylamine respectively. It can be seen from the table that all three devices have good response characteristics to triethylamine, and the device using CoMoO _{4 (1000°C)} as the sensitive electrode material has the highest response value, which is -102mV. In addition, it can be seen from Table 2 that the sensitivity of the CoMoO _{4 (1000°C)} device to 5-200ppm triethylamine is -53mV/decade. It can be seen that the currently constructed hybrid potentiometric sensor shows good sensitivity to triethylamine, and has a good potential application prospect in the field of atmospheric environment detection.

Table 1: Response data of sensors using CoMoO _{4 (800°C)} , CoMoO _{4 (1000°C)} and CoMoO _{4 (1100°C)} as sensitive electrode materials to 100ppm triethylamine

Table 2: Variation data of ΔV with the concentration of triethylamine for the sensor using CoMoO _{4 (1000°C)} as the sensitive electrode material

Concentration of triethylamine (ppm) Sensitive electrode and reference electrode potential difference ΔV (mV) 0.1 -3 0.2 -4.5 0.5 -7.5 1 -12.5 2 -19.5 Sensitivity (mV/decade) -14 5 -27 10 -37 20 -68 50 -80 100 -102 200 -106.5 Sensitivity (mV/decade) -53

Claims (6)

1. one kind is with CoMoO₄Stabilizing zirconia base for sensitive electrode blendes together electric potential type triethylamine sensor, from bottom to up successively By the Al for carrying Pt heating electrodes₂O₃Ceramic wafer, stabilizing zirconia substrate, Pt reference electrodes and sensitive electrode composition；Reference electrode It is separate with sensitive electrode and symmetrically prepare in the both ends of stabilizing zirconia upper surface of base plate, stabilizing zirconia substrate following table Face and the Al with Pt heating electrodes₂O₃Ceramic wafer is bonded together；It is characterized in that：Sensitive electrode material is CoMoO₄, by Following method is prepared,

Under magnetic stirring, by 0.5mmol Co (NO₃)₂·6H₂O and 0.5mmol Na₂MoO₄·2H₂O is dissolved in 30~50mL and goes In the mixed solution of ionized water, ethyl alcohol and ethylene glycol；Then, by obtained solution under the conditions of 160~200 DEG C hydro-thermal reaction 5 ~8 hours, reaction product collected precipitation after centrifuging, washing, and gained is deposited under 60~90 DEG C of vacuum condition dry；Finally Desciccate product is sintered to 1~3h at 800~1100 DEG C respectively, so as to obtain CoMoO of the present invention₄Sensitive electrode Material.

2. one kind as described in claim 1 is with CoMoO₄Stabilizing zirconia base for sensitive electrode blendes together electric potential type triethylamine biography Sensor, it is characterised in that：The volume ratio of deionized water, ethyl alcohol and ethylene glycol is (1~2)：1：(1~2).

3. one kind described in claims 1 or 2 is with CoMoO₄Stabilizing zirconia base for sensitive electrode blendes together electric potential type triethylamine biography The preparation method of sensor, its step are as follows：

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

(2) CoMoO is made₄Sensitive electrode：By CoMoO₄Sensitive electrode material is slurred expecting with deionized water, mass concentration for 2~ 20%；Use CoMoO₄Slurry is in the sensitivity that 20~30 μ m-thicks are prepared with the other end of the symmetrical YSZ upper surface of base plate of reference electrode Electrode will be equally sticked on sensitive electrode after a platinum filament doubling as contact conductor；

(3) the YSZ substrates of reference electrode and sensitive electrode are sintered 1~3 under the conditions of 800~1000 DEG C step (2) preparation Hour；

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

(5) step (4) is obtained device to be welded, encapsulate, so as to obtain with CoMoO₄YSZ bases for sensitive electrode blend together electricity Bit-type triethylamine sensor.

4. one kind as claimed in claim 3 is with CoMoO₄Stabilizing zirconia base for sensitive electrode blendes together electric potential type triethylamine biography The preparation method of sensor, it is characterised in that：Heating rate when step (3) high temperature is sintered is 1~2 DEG C/min.

5. one kind as claimed in claim 3 is with CoMoO₄Stabilizing zirconia base for sensitive electrode blendes together electric potential type triethylamine biography The preparation method of sensor, it is characterised in that：It is to measure 2~4mL of waterglass, and weigh Al₂O₃0.7~1.0g of powder, by waterglass With Al₂O₃Powder is mixed and stirred for uniformly, inorganic bond being made.

6. one kind as claimed in claim 3 is with CoMoO₄Stabilizing zirconia base for sensitive electrode blendes together electric potential type triethylamine biography The preparation method of sensor, it is characterised in that：Al with Pt heating electrodes₂O₃Ceramic wafer is in Al₂O₃Pass through silk screen on ceramic wafer Printing Pt is obtained.