CN111474227A - Potentiometric gas sensor using titanium-doped strontium ferrite as sensitive electrode - Google Patents

Abstract

The invention discloses a potential gas sensor using titanium-doped strontium ferrite as a sensitive electrode, which is perovskite oxide SrFe_1‑xTi_xO_3‑A potentiometric hydrogen sensor as sensitive electrode material, which is characterized by positive response to hydrogen, Volatile Organic Compounds (VOC), carbon monoxide, ammonia gas but not limited to these gases, and is applied to SrFe with positive response_0.5Ti_0.5O_3‑In combination with the conventional electrode material of negative polarity response, the response of the sensor to hydrogen is further enhanced. The sensitive electrode material SrFe in the invention_1‑xTi_xO_3‑The positive response to hydrogen gas is opposite to the conventional negative response including but not limited to L SCF, and the two sensitive electrode materials SrFe are taken as hydrogen gas as an example_0.5Ti_0.5O_3‑Has better electrochemical catalytic activity to hydrogen with L SCF, and contains SrFe_0.5Ti_0.5O_3‑Gas sensors with L SCF as dual sensing electrodes can be further providedThe response to hydrogen is increased.

Description

Potentiometric gas sensor using titanium-doped strontium ferrite as sensitive electrode

technical field

The invention belongs to the field of gas sensors, in particular to a potential type gas sensor using titanium-doped strontium ferrite as a sensitive electrode.

Background technique

In real production and life, a large amount of toxic and harmful gases such as volatile organic compound gas (VOC), carbon monoxide and ammonia gas will be produced, which will cause great harm to human health. As an emerging energy, hydrogen has the advantages of high efficiency, renewable and non-polluting, but because hydrogen is colorless and odorless, it is not easy to detect after leakage, extremely low ignition energy (0.019mJ) and wide explosion limit (4%-75.6 %) also makes hydrogen extremely prone to combustion and explosion, so the monitoring and detection of volatile organic compound gases (VOCs), carbon monoxide, ammonia and hydrogen and other toxic, harmful, flammable and explosive gases is also possible in various places of production and life. appear particularly important.

At present, a more convenient and economical gas monitoring and detection method is a gas sensor, but it has the disadvantages of low sensor response performance and high sensor manufacturing cost. In addition, in the current research results, when the conventional potentiometric gas sensor and the sensitive electrode material are connected to the data acquisition instrument, the response to the gas is generally negative response (H.Zhang, JXYi, X.Jiang, Fast response, highly sensitive and selective mixed-potential H ₂ sensor based on(La,Sr)(Cr,Fe)O _3-δ perovskite sensing electrode,ACSAppl.Mater.Interfaces 9(2017)17218-17225.doi:10.1021/acsami.7b01901.) .

Studies have shown that perovskite oxides with good electrochemical catalytic activity for gases can be used as sensitive electrode materials for gas detection. Pt is often used as a reference electrode in mixed-potential gas sensors for research, but due to the high cost of precious metals, the cost of sensor fabrication is increased. Finding suitable electrode materials to improve the response performance to hydrogen and reduce the cost is an urgent problem to be solved. SrFe _1-x Ti _x O _3-δ has good electrochemical catalytic performance for hydrogen in solid oxide fuels, and can be used as a sensitive electrode for sensors to be studied, while using relatively low-cost perovskite oxides to replace The precious metal platinum can also further reduce the cost of sensor fabrication.

SUMMARY OF THE INVENTION

The present invention aims to provide a potential type gas sensor using titanium-doped strontium ferrite as a sensitive electrode in view of the above-mentioned deficiencies in the prior art. The sensitive electrode material used in the present invention has good electrochemical catalytic activity for including but not limited to hydrogen, volatile organic compounds (VOC), carbon monoxide, ammonia, etc. The present invention preferably has the best detection performance for hydrogen At the same time, the sensitive electrode material used in the present invention can further improve the response of the sensor to the detection gas, and simultaneously replace the traditional Pt reference electrode with perovskite oxide, which can significantly reduce the fabrication cost of the sensor. The following contents are described by taking a potentiometric hydrogen sensor as an example.

One of the potential type hydrogen sensors of the present invention uses perovskite oxide as the sensitive electrode material, and the reference electrode includes but not limited to platinum, and can also be other metals or oxides, including but not limited to GDC, SDC, YSZ or Potentiometric hydrogen sensors constructed by solid electrolytes such as NASICON.

The perovskite oxide is SrFe _1-x Ti _x O _3-δ , 0≤x≤0.9, the present invention preferably has the best performance when x=0.5, wherein, the reason for δ is the existence of oxygen vacancies, part of The element exists in an abnormal valence state and therefore has a non-stoichiometric ratio of oxygen.

Among them, GDC is the abbreviation of Ce _0.8 Gd _0.2 O _1.9-δ , which refers to CeO ₂ doped with 20 mol% Gd ₂ O ₃ .

The preparation method of the potential type hydrogen sensor of the present invention comprises the following steps:

Mix the sensitive electrode material and the modified terpineol in a mass ratio of 1:1 and grind for 2h (control particle size ≤10μm); apply the uniformly ground mixed slurry and platinum slurry on the same surface by screen printing. On the electrolyte substrate and keep the two pastes out of contact with each other, the electrode area includes but not limited to 3 mm ² , and sintered at 800-1000 ° C to obtain a sensitive electrode and a platinum electrode respectively; the sensitive electrode and the platinum electrode are connected by a platinum wire (0.05mm in diameter) connection to obtain a positive-polarity response potentiometric hydrogen sensor.

The second potential type hydrogen sensor of the present invention is a dual sensitive electrode potential type hydrogen sensor, which uses SrFe _0.5 Ti _0.5 O _3-δ as the sensitive electrode, including but not limited to LSCF, and can also be other conventional oxides or metal gases. The sensitive material is another sensitive electrode. In the present invention, it is preferred that LSCF be another sensitive electrode, including but not limited to GDC, SDC, YSZ, and NASICON, etc., which are mixed-potential hydrogen sensors constructed with solid electrolytes. The present invention is preferably used when GDC is solid. electrolyte.

Among them, LSCF is the abbreviation of La _0.8 Sr _0.2 Cr _0.5 Fe _0.5 O _3-δ , and is lanthanum chromate doped with 20 mol% Sr and 50 mol% Fe.

The preparation method of the potential type hydrogen sensor of the present invention comprises the following steps:

The sensitive electrode materials SrFe _0.5 Ti _0.5 O _3-δ and LSCF nano-powder were mixed with modified terpineol in a mass ratio of 1:1 and ground for 2 hours (controlling the particle size ≤10 μm); The two slurries are uniformly coated on the same electrolyte substrate respectively and keep the two slurries out of contact with each other, the electrode area includes but not limited to 3mm ² , and is sintered and dense at 1000 ℃; SrFe _0.5 Ti _0.5 O _3-δ The sensitive electrode and the LSCF sensitive electrode are connected by a platinum wire (0.05 mm in diameter) to obtain a double sensitive electrode potential type hydrogen sensor.

The above-mentioned SrFe _0.5 Ti _0.5 O _3-δ , LSCF nano-powder and GDC electrolyte substrate can be self-synthesized or commercially available.

Compared with the prior art, the beneficial effects of the present invention are embodied in:

1. In the potentiometric gas sensor of the present invention, the SrFe _1-x Ti _x O _3-δ perovskite oxide exhibits positive polarity to, including but not limited to, hydrogen, volatile organic compounds (VOC), carbon monoxide, ammonia, etc. response, in contrast to the negative polarity response of conventional materials, and the strontium ferrite oxide SrFe _0.5 Ti _0.5 O _3-δ doped with 50 mol% Ti has the highest response to hydrogen (29.1 mV for 100 ppm hydrogen at 500 °C) ;

2. In the potential type gas sensor of the present invention, SrFe _0.5 Ti _0.5 O _3-δ , including but not limited to LSCF, can also be conventional other oxides or metal gas-sensing materials, including but not limited to hydrogen, Volatile organic compounds (VOC), carbon monoxide, ammonia, etc. showed positive and negative responses, respectively. The voltage response values between the two sensitive electrodes of SrFe _0.5 Ti _0.5 O _3-δ and LSCF were measured as the two respectively. The sum of the voltage response values of the sensitive electrodes can further improve the sensor's response value to gas and expand its application.

3. LSCF or any other conventional oxide or metal gas-sensing material can replace precious metal platinum in this invention, and the production cost is much lower than precious metal platinum, based on this, the production cost of the sensor can be greatly reduced.

Description of drawings

Fig. 1 shows SrFe _0.8 Ti _0.2 O _3-δ /GDC/Pt, SrFe _0.6 Ti _0.4 O _3-δ /GDC/Pt, SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt, SrFe _0.3 Ti _0.7 in Example 1 Schematic diagrams of O _3-δ /GDC/Pt and SrFe _0.1 Ti _0.9 O _3-δ /GDC/Pt sensors.

FIG. 2 is a schematic diagram of the SrFe _0.5 Ti _0.5 O _3-δ /GDC/LSCF sensor in Example 2. FIG.

3 is the XRD pattern of SrFe _1-x Ti _x O _3-δ powder and electrolyte GDC in Example 1. FIG.

4 is a graph showing the dynamic response of SrFe _1-x Ti _x O _3-δ to hydrogen in Example 1.

5 is a dynamic response diagram of the SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt sensor in Example 1 for detecting gases such as hydrogen, ethanol, ammonia, and carbon monoxide.

6 is a linear relationship diagram of two sensor response values of SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt and SrFe _0.5 Ti _0.5 O _3-δ /GDC/LSCF and the hydrogen concentration of 20-100 ppm in Example 2.

Fig. 7 is the dynamic response of three sensors of SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt, LSCF/GDC/Pt and SrFe _0.5 Ti _0.5 O _3-δ /GDC/LSCF to 100-500ppm hydrogen concentration in Example 2 picture.

Detailed ways

The following two examples are detailed descriptions of the present invention, both taking the detection of hydrogen gas as an example. The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods, specific operating procedures and the results obtained. For a brief description of the results, the following examples are only used to help understand the implementation method and core idea of the present invention, but the protection scope of the present invention is not limited to the following examples.

Example 1:

In this example, strontium ferrite oxides SrFe _0.8 Ti _0.2 O _3-δ , SrFe _0.6 Ti _0.4 O _3-δ , SrFe _0.5 Ti _0.5 O with the doping amounts of Ti are respectively 20, 40, 50, 70, and 90 mol%. _3-δ , SrFe _0.3 Ti _0.7 O _3-δ and SrFe _0.1 Ti _0.9 O _3-δ are the sensitive electrode materials, Pt is the reference electrode, GDC is the solid electrolyte, and the specific preparation method is as follows:

Sensitive electrode materials SrFe _0.8 Ti _0.2 O _3-δ , SrFe _0.6 Ti _0.4 O _3-δ , SrFe _0.5 Ti _0.5 O _3-δ , SrFe _0.3 Ti _0.7 O _3-δ and SrFe _0.1 Ti _0.9 O _3-δ and modification Terpineol was mixed at a mass ratio of 1:1 and ground for 2 hours (the particle size was below 10 μm); the uniformly ground sensitive electrode material and platinum paste were coated on the electrolyte substrate by screen printing, and the electrode area was It is 3mm ² , and sintered at 800-1000℃ to obtain a sensitive electrode and a platinum electrode respectively; the sensitive electrode and the platinum electrode are connected by a platinum wire with a diameter of 0.05mm, that is, SrFe _0.8 Ti _0.2 O _3-δ /GDC is completed /Pt, SrFe _0.6 Ti _0.4 O _3-δ /GDC/Pt, SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt, SrFe _0.3 Ti _0.7 O _3-δ /GDC/Pt and SrFe _0.1 Ti _0.9 O _3-δ The structure of the /GDC/Pt sensor is shown in Figure 1.

Figure 3 shows the sensitive electrode materials SrFe _0.8 Ti _0.2 O _3-δ , SrFe _0.6 Ti _0.4 O _3-δ , SrFe _0.5 Ti _0.5 O _3-δ , SrFe _0.3 Ti _0.7 O _3-δ , SrFe _0.1 Ti _0.9 O _3-δ As well as the XRD pattern of the solid electrolyte GDC, the material has good phase formation and no impurity peaks.

The mixed-potential hydrogen sensor prepared in this example was placed in a tubular muffle furnace, and the sensor was operated at 400-500 ° C, and the response value of the sensor under different hydrogen concentrations was detected by using an Agilent voltage data collector. The material is connected to the positive electrode of the Agilent voltage data collector, and the reference electrode Pt is connected to the negative electrode of the Agilent voltage data collector.

Figure 4 shows sensors SrFe _0.8 Ti _0.2 O _3-δ /GDC/Pt, SrFe _0.6 Ti _0.4 O _3-δ /GDC/Pt, SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt, SrFe _0.3 Ti _0.7 O _3- The dynamic response test of _δ /GDC/Pt and SrFe _0.1 Ti _0.9 O _3-δ /GDC/Pt to 100ppm hydrogen at 500℃, it can be seen from the figure that the SrFe _1-x Ti _x O _3-δ material is in each ratio The following are positive responses to hydrogen, namely V ₁ =E _{SrFe0.8Ti0.2O3-δ} -E _Pt >0, V ₂ =E _{SrFe0.6Ti0.4O3-δ} -E _Pt >0, V ₃ =E _{SrFe0. 5Ti0.5O3-δ} -E _Pt > 0, V ₄ =E _{SrFe0.3Ti0.7O3-δ} -E _Pt >0, V ₅ =E _{SrFe0.1Ti0.9O3-δ} -E _Pt > 0, and the sensor SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt has the best response to hydrogen, which is opposite to the response of the other potential hydrogen sensors (as shown in Figure 6, LSCF/GDC/Pt has a negative response to hydrogen), which is a new type of hydrogen sensor. The response polarity can further expand its application.

Figure 5 is the dynamic response diagram of the SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt sensor for detecting hydrogen, ethanol, ammonia, carbon monoxide and other gases. The detection temperature is 500°C, and the gas concentration is 100ppm. The results show that the sensor has a positive response to gases such as hydrogen, ethanol, ammonia, and carbon monoxide.

Example 2:

In this embodiment, SrFe _0.5 Ti _0.5 O _3-δ is a sensitive electrode with positive polarity, LSCF is a sensitive electrode with negative polarity, and GDC is a hydrogen sensor with solid electrolyte. The specific preparation method is as follows:

Sensitive electrode materials SrFe _0.5 Ti _0.5 O _3-δ , LSCF and modified terpineol were mixed at a mass ratio of 1:1 and ground for 2 hours (the particle sizes were all below 10 μm); The sensitive electrode material and the platinum paste are respectively coated on the same electrolyte substrate, the electrode area is 3mm ² , and sintered at 1000℃ to be dense; in SrFe _0.5 Ti _0.5 O _3-δ , the diameter of each connection between the LSCF sensitive electrode and the platinum electrode is 0.05mm platinum wire. That is, the fabrication of the SrFe _0.5 Ti _0.5 O _3-δ /GDC/LSCF sensor is completed, and its structure is shown in FIG. 2 .

6 is a linear relationship diagram of two sensor response values of SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt and SrFe _0.5 Ti _0.5 O _3-δ /GDC/LSCF and the hydrogen concentration of 20-100 ppm in Example 2. According to the fitting, it can be obtained that the response values and concentrations of the two sensors SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt and SrFe _0.5 Ti _0.5 O _3-δ /GDC/LSCF satisfy Y=0.191x+8.8 and Y=0.537 respectively The relation of x+17.6. When the hydrogen concentration is 0.5ppm, the two sensors still have response values of 8.9mV and 17.8mV, and the sensor still has a higher response value under low hydrogen concentration.

Figure 7 shows the dynamic responses of three sensors, SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt, LSCF/GDC/Pt and SrFe _0.5 Ti _0.5 O _3-δ /GDC/LSCF, to different concentrations of hydrogen, as shown in Fig. As shown in the figure, the material SrFe _0.5 Ti _0.5 O _3-δ exhibits a positive response to hydrogen, and LSCF exhibits a negative response to hydrogen. Based on this phenomenon, SrFe _0.5 Ti _0.5 O _3-δ and LSCF are used as dual sensitive electrodes The SrFe _0.5 Ti _0.5 O _3-δ /GDC/LSCF sensor can superimpose the response values of SrFe _0.5 Ti _0.5 O _3-δ /GDC/Pt and LSCF/GDC/Pt to hydrogen, thereby further improving the response value of the sensor to hydrogen , that is, V ₆ =(E _{SrFe0.5Ti0.5O3-δ} -E _Pt )-(E _LSCF -E _Pt )=E _{SrFe0.5Ti0.5O3-δ} -E _LSCF =V ₃ +|V _LSCF/GDC/Pt | > 0, so that the new phenomenon of positive polarity response exhibited by materials such as SrFe _{1- x} Ti _x O _3-δ can be further applied.

It is only an exemplary embodiment of the present invention, and is not intended to limit the performance of the SrFe _1-x Ti _x O _3-δ materials listed in the present invention. Any modifications, equivalents made within the spirit and principle of the present invention Substitutions and improvements, etc., should all be included within the protection scope of the present invention.

Claims (5)

1. a potential type gas sensor with titanium-doped strontium ferrite as a sensitive electrode, is characterized in that: The potential type gas sensor is obtained by constructing a sensitive electrode, a reference electrode and a solid electrolyte, wherein the sensitive electrode is a perovskite oxide SrFe _1-x Ti _x O _3-δ , 0≤x≤0.9; the The reference electrode includes but is not limited to platinum, other metals or metal oxides; the solid electrolyte includes but is not limited to GDC, SDC, YSZ or NASICON and the like. 2. The potentiometric gas sensor according to claim 1, characterized in that: The detection objects of the potentiometric gas sensor include but are not limited to hydrogen, volatile organic compounds, carbon monoxide, and ammonia. 3. A potential type gas sensor, characterized in that: The potential type gas sensor is a dual sensitive electrode potential type gas sensor, which is a mixed potential type gas sensor constructed by dual sensitive electrodes and a solid electrolyte; one of the sensitive electrodes is a perovskite oxide SrFe _1-x Ti _x O _{3 -δ} , 0≤x≤0.9; another sensitive electrode includes but not limited to LSCF, or other metal oxide or metal gas sensitive material; the solid electrolyte includes but not limited to GDC, SDC, YSZ or NASICON. 4. The potential type gas sensor according to claim 3, wherein: The perovskite oxide is SrFe _0.5 Ti _0.5 O _3-δ . 5. The potentiometric gas sensor according to claim 3 or 4, characterized in that: The detection objects of the potentiometric gas sensor include but are not limited to hydrogen gas, volatile organic compounds, carbon monoxide or ammonia gas.

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