High-selectivity ammonia sensor and preparation method thereof

Abstract

The application relates to an ammonia sensor and a preparation method thereof. The sensor comprises a YSZ solid electrolyte layer, a heating sheet, a reference electrode and a sensitive electrode. The lower surface of the YSZ solid electrolyte layer is attached to the heating sheet, and the upper surface is provided with the reference electrode and the sensitive electrode at intervals. The material of the sensitive electrode is tin ferrite. Compared with the prior art, the application can realize high-selectivity detection of ammonia in mixed gas.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas sensor, in particular to an ammonia sensor and a preparation method thereof. BACKGROUND

[0002] Human exhaled breath contains abundant physiological and disease marker information, among which a variety of components can be used as 'biomarkers' of diseases and metabolic processes. The production of ammonia in exhaled breath is related to nitrogen metabolism in the body, and it has a certain linear relationship with blood urea nitrogen (BUN) in the blood. The kidney function can be diagnosed by detecting the content of ammonia in exhaled breath. In addition, trace amounts of ammonia will be produced in the early stage of protein food spoilage. Real-time monitoring of the change of ammonia content in food can realize the rapid identification of the freshness of the real object.

[0003] The ammonia sensors reported so far have the problem of being easily interfered, especially in the presence of multiple types of organic volatile substances, which are easily infected by ethanol gas. Therefore, it is urgent to develop an ammonia sensor with high selectivity. SUMMARY

[0004] The purpose of the present application is to provide an ammonia sensor and a preparation method thereof, which can effectively solve the problems in the background art.

[0005] The technical scheme to achieve the above-mentioned purpose is: an ammonia sensor, characterized in that it comprises a YSZ solid electrolyte layer (1), a heating sheet (2), a reference electrode (3) and a sensitive electrode (4), the lower surface of the YSZ solid electrolyte layer (1) is attached with the heating sheet (2), and the upper surface is provided with the reference electrode (3) and the sensitive electrode (4) arranged at intervals, and the sensitive electrode (4) adopts a tin ferrite compound.

[0006] Further, the tin ferrite compound comprises manganese dioxide powder and terpineol slurry with a mass ratio of 1:1.5.

[0007] Further, the material of the heating sheet (2) is alumina, and the reference electrode (3) adopts a manganese dioxide compound.

[0008] Further, the manganese dioxide compound comprises tin ferrite and terpineol slurry with a mass ratio of 1:(1-2).

[0009] Further, the YSZ solid electrolyte layer (1) and the heating sheet (2) are both square in shape, and the length and width of the YSZ solid electrolyte layer (1) are equal to those of the heating sheet (2), the reference electrode (3) and the sensitive electrode (4) are both square in shape with the same size, the reference electrode (3) is provided with a reference electrode lead, and the sensitive electrode (4) is provided with a sensitive electrode lead.

[0010] Further, the length of the YSZ solid electrolyte layer (1) and the heating sheet (2) ranges from 1 cm to 2 cm, the width ranges from 1 cm to 2 cm, the thickness of the YSZ solid electrolyte layer (1) ranges from 0.1 cm to 1 cm, and the thickness of the heating sheet (2) ranges from 0.1 mm to 3 mm.

[0011] Further, the length of the reference electrode (3) and the sensitive electrode (4) ranges from 1 mm to 6 mm, the width ranges from 1 mm to 6 mm, and the thickness ranges from 5 um to 20 um.

[0012] The application further provides a preparation method of the ammonia sensor.

[0013] S1: The terpineol slurry containing manganese dioxide is printed on the upper end face of the YSZ solid electrolyte layer (1) by using the screen printing technology, dried, sintered to form the reference electrode (3);

[0014] S2: The terpineol slurry containing tin ferrite is printed on the upper end face of the YSZ solid electrolyte layer (1) by using the screen printing technology, dried to form the sensitive electrode (4);

[0015] S3: Pt paste is point-coated on the surfaces of the reference electrode (3) and the sensitive electrode (4) respectively, then the reference electrode lead and the sensitive electrode lead are respectively led out through the Pt paste, dried, and then placed in a sintering furnace to be sintered at 900 o C for 2 hours to form, and then taken out and cooled to room temperature;

[0016] S4: The heating sheet (2) is placed below the YSZ solid electrolyte layer (1), and the heating sheet (2) and the YSZ solid electrolyte layer (1) are pasted together by using a high-temperature-resistant adhesive, and the sensor preparation is completed.

[0017] Further, the preparation method of the terpineol slurry containing manganese dioxide in step S1 is as follows: manganese dioxide powder and terpineol slurry are put into a agate mortar in a mass ratio of 1:1.5, mixed and ground uniformly to obtain the terpineol slurry containing manganese dioxide, and the terpineol slurry is prepared by mixing terpineol and ethyl cellulose in a mass ratio of 94:6.

[0018] Further, the preparation method of the terpineol slurry containing tin ferrite in step S2 is as follows: tin ferrite and terpineol slurry are put into a agate mortar in a mass ratio of 1:1.5, mixed and ground uniformly to obtain the terpineol slurry containing tin ferrite, and the terpineol slurry is prepared by mixing terpineol and ethyl cellulose in a mass ratio of 94:6.

[0019] Compared with the prior art, the application has the following advantages:

[0020] 1. This invention provides a portable electrochemical sensor and its preparation method, which can achieve highly selective detection of ammonia in a gas mixture;

[0021] 2. This invention requires only one sensitive electrode and does not require optical coupling or complex algorithms to achieve high selectivity for ammonia gas;

[0022] 3. This invention utilizes stabilized zirconium oxide (YSZ) as an ion-conducting layer and tin ferrite composite oxide material with high electrochemical catalytic activity as a sensitive electrode. A sensitive electrode layer with a specific pore structure is obtained by high-temperature sintering at 900℃, which facilitates the rapid arrival of the gas to be measured at the three-phase interface to participate in the electrochemical reaction, thereby improving the high selectivity and sensitivity of the sensor for ammonia gas.

[0023] 4. The sensor of this invention has a simple structure, is easy to operate, and is inexpensive and portable. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the sensor structure of the present invention;

[0025] Figure 2 This is a morphology image of the sensor's sensitive electrode layer after calcination at 900°C.

[0026] Figure 3 The response signal curves of ammonia gas to the sensor of the present invention at different heating temperatures are shown.

[0027] Figure 4 To use the sensor of this invention at 400 o The response curve of the sensor's sensitive electrode when testing n-hexane, benzene, sulfur dioxide, ethanol, and hydrogen sulfide gases at heating temperature C.

[0028] Figure 5 To test different gases using the sensor of this invention, the response signal of the sensor's sensitive electrode versus the gas concentration relationship curves were obtained when the concentration of each gas varied from 0.8 to 5 ppm.

[0029] Figure 6 To use the sensor of this invention at 400 o The change in the response signal of ammonia at heating temperature C and relative humidity of 0-95%;

[0030] Figure 7 To use the sensor of this invention at 400 o The drift of the response signal to ammonia at heating temperature C over 14 days.

[0031] In the figure: 1 - YSZ solid electrolyte layer, 2 - heating element, 3 - reference electrode, 4 - sensitive electrode. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] like Figure 1 As shown, an ammonia gas sensor includes a YSZ solid electrolyte layer 1, a heating element 2, a reference electrode 3, and a sensitive electrode 4. Both the YSZ solid electrolyte layer 1 and the heating element 2 are square in shape, and their lengths and widths are equal. The lower end face of the YSZ solid electrolyte layer 1 is attached to and fixedly connected to the upper end face of the heating element 2. The heating element 2 is made of alumina. The reference electrode 3 and the sensitive electrode 4 are both square in shape with the same dimensions, and are spaced apart within the YSZ solid electrolyte layer. On the upper surface of layer 1, the lower surface of the reference electrode 3 and the lower surface of the sensitive electrode 4 are respectively attached to and fixedly connected to the upper surface of the YSZ solid electrolyte layer 1. The material of the sensitive electrode 4 is a tin ferrite composite, which includes manganese dioxide powder and terpineol slurry in a mass ratio of 1:1.5. The material of the reference electrode 3 is a manganese dioxide composite, which includes manganese dioxide and terpineol slurry in a mass ratio of 1:1.5. Reference electrode leads are provided on the reference electrode 3, and sensitive electrode leads are provided on the sensitive electrode 4.

[0035] The preparation method of the ammonia sensor specifically includes the following steps:

[0036] (1) Prepare YSZ solid electrolyte layer 1 and heating element 2 of the corresponding size according to the design size requirements;

[0037] (2) Prepare a terpineol slurry by mixing terpineol and ethyl cellulose in a mass ratio of 94:6;

[0038] (3) Mix manganese dioxide powder and terpineol slurry in an agate mortar at a mass ratio of 1:1.5 and grind them evenly to form a terpineol slurry containing manganese dioxide;

[0039] (4) Using screen printing technology, the terpineol paste containing manganese dioxide is printed at the designed position of the reference electrode 3 on the upper end face of the YSZ solid electrolyte layer 1 according to the designed size, so as to obtain the prototype of the reference electrode 3.

[0040] (5) Place the product obtained in step (4) into a drying oven and dry it at 130°C. o Dry at C for 12 hours, then place in a sintering furnace at 1400°C. oC, sintering for 2 hours, cooling to room temperature after shaping, forming a reference electrode 3 on the upper end surface of the YSZ solid electrolyte layer 1;

[0041] (6) Put the tin ferrite and terpineol slurry in a mass ratio of 1:1.5 into an agate mortar, mix and grind uniformly to form a terpineol slurry containing tin ferrite;

[0042] (7) Use screen printing technology to print the terpineol slurry containing tin ferrite on the upper end surface of the YSZ solid electrolyte layer 1 at the design position of the sensitive electrode 4 according to the design size, to obtain a sensitive electrode 4 prototype;

[0043] (8) Put the product obtained after step (7) into a drying oven, set the temperature condition of the drying oven to 130°C, dry for half an hour, take out and cool to room temperature, and form a sensitive electrode 4 on the upper end surface of the YSZ solid electrolyte layer 1;

[0044] (9) Dot Pt paste on the surfaces of the reference electrode 3 and the sensitive electrode 4 respectively, and then lead out the reference electrode lead and the sensitive electrode lead respectively through the Pt paste;

[0045] (10) Put the product obtained after step (9) into a drying oven, dry at 130 o C, dry for 12 hours, then take out and put into a sintering furnace, sinter at 900 o C, sinter for 2 hours, take out and cool to room temperature after shaping;

[0046] (11) Place the heating sheet 2 below the YSZ solid electrolyte layer 1 in the product obtained after step (10), and paste the heating sheet 2 and the YSZ solid electrolyte layer 1 together with a high-temperature resistant adhesive, and the sensor preparation is completed.

[0047] Example 2.

[0048] The difference between Example 2 and Example 1 is that the length of the YSZ solid electrolyte layer 1 and the heating sheet 2 ranges from 1 cm to 2 cm, the width ranges from 1 cm to 2 cm, the thickness of the YSZ solid electrolyte layer 1 ranges from 0.1 cm to 1 cm, and the thickness of the heating sheet 2 ranges from 0.1 mm to 3 mm; the length of the reference electrode 3 and the sensitive electrode 4 ranges from 1 mm to 6 mm, the width ranges from 1 mm to 6 mm, and the thickness ranges from 5 um to 20 um.

[0049] Figure 2 The morphology of the sensor sensitive electrode layer after calcination at 900°C can be seen. The surface of the sensitive layer is porous and loose, which is beneficial to the rapid diffusion of gas.

[0050] After the sensor is prepared, the performance is tested as follows:

[0051] Figure 3 For testing 5ppm ammonia gas by using the electrochemical sensor of the present application, the sensor heating temperature is 400-475 o C, the response curve of the sensitive electrode of the electrochemical sensor of the present application;

[0052] Figure 4 For testing ammonia gas (NH3), n-hexane (C6H 14 ), ethanol (C2H5OH), benzene (C6H6), sulfur dioxide (SO2), hydrogen sulfide (H2S) gas by using the electrochemical sensor of the present application, when the concentration of each kind of gas is 5ppm, the sensor heating temperature is 400 o C, the response curve of the sensitive electrode of the electrochemical sensor of the present application;

[0053] Figure 5 For testing ammonia gas, n-hexane, benzene, sulfur dioxide, ethanol, hydrogen sulfide gas by using the electrochemical sensor of the present application, the sensor heating temperature is 400 o C, the response signal-gas concentration relationship curve of the sensitive electrode of the electrochemical sensor of the present application when the concentration of each kind of gas is 0.8-5ppm;

[0054] Figure 6 For testing 5ppm ammonia gas by using the electrochemical sensor of the present application, the sensor heating temperature is 400 o C, the response signal change amount of the sensitive electrode of the electrochemical sensor of the present application when the relative humidity is 0-95%;

[0055] Figure 7 For testing 5ppm ammonia gas by using the electrochemical sensor of the present application, the sensor heating temperature is 400 o C, the response signal drift amount of the sensitive electrode of the electrochemical sensor of the present application within 14 days;

[0056] Analysis Figure 3 It can be known that the ammonia gas electrochemical sensor exhibits the best response performance to ammonia gas when the heating temperature is 400 o C; analysis Figure 4 It can be known that the selectivity of the ammonia gas electrochemical sensor to ammonia gas is significantly stronger than that to other gases; analysis Figure 5 It can be known that ammonia gas with a concentration of 0.8ppm-5ppm exhibits good selectivity, and the response signal of the sensor after logarithmic transformation and the gas concentration present a linear relationship; analysis Figure 6 It can be known that the sensitive performance of the ammonia gas electrochemical sensor is not affected by humidity. Analysis Figure 7 It can be known that the response signal drift amount of the sensor of the present application within 2 weeks is extremely small (less than 3%), which indicates that the response stability of the sensor to ammonia gas is good;

[0057] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the application has been described above with the aid of functional building blocks illustrating the principles of operation at a conceptual level. These building blocks have been recognized to be more functional than structural. The actual implementation can always depend on the specific application and design restrictions and, therefore, should not be interpreted as a critical or essential block or function that the application is organized around. The applications can be implemented in hardware, software, firmware, or a combination thereof.

Claims

1. An ammonia gas sensor characterized by comprising: The ammonia gas sensor comprises a YSZ solid electrolyte layer (1), a heating sheet (2), a reference electrode (3) and a sensitive electrode (4), the lower surface of the YSZ solid electrolyte layer (1) is attached with the heating sheet (2), the upper surface is provided with the reference electrode (3) and the sensitive electrode (4) arranged at intervals, and the sensitive electrode (4) is a tin ferrite compound. The tin ferrite compound comprises a tin ferrite and a terpineol slurry with a mass ratio of 1:1.

5. The preparation method of the ammonia gas sensor comprises the following steps: S1: printing the terpineol slurry containing manganese dioxide on the upper end surface of the YSZ solid electrolyte layer (1) by using a screen printing technology, drying and sintering to form the reference electrode (3); S2: printing the terpineol slurry containing tin ferrite on the upper end surface of the YSZ solid electrolyte layer (1) by using a screen printing technology, drying to form the sensitive electrode (4); S3: respectively dotting the Pt slurry on the surfaces of the reference electrode (3) and the sensitive electrode (4), then respectively leading out the reference electrode lead and the sensitive electrode lead through the Pt slurry, drying, and then placing in a sintering furnace to be sintered at 900 DEG C for 2 hours to be formed, and then taking out and cooling to room temperature; S4: placing the heating sheet (2) below the YSZ solid electrolyte layer (1), and sticking the heating sheet (2) and the YSZ solid electrolyte layer (1) together by using a high-temperature resistant adhesive, and then the sensor preparation is completed.

2. The ammonia gas sensor according to claim 1, characterized by The material of the heating sheet (2) is alumina, and the reference electrode (3) is a manganese dioxide compound.

3. The ammonia gas sensor according to claim 2, characterized by The manganese dioxide compound comprises manganese dioxide powder and terpineol slurry with a mass ratio of 1:1.

5.

4. The ammonia gas sensor according to claim 1, characterized by The YSZ solid electrolyte layer (1) and the heating sheet (2) are both square shapes, the length and width of the YSZ solid electrolyte layer (1) are equal to those of the heating sheet (2), the reference electrode (3) and the sensitive electrode (4) are both square shapes with the same size, the reference electrode (3) is provided with a reference electrode lead, and the sensitive electrode (4) is provided with a sensitive electrode lead.

5. The ammonia gas sensor according to claim 4, characterized by The length of the YSZ solid electrolyte layer (1) and the heating sheet (2) ranges from 1 cm to 2 cm, the width ranges from 1 cm to 2 cm, the thickness of the YSZ solid electrolyte layer (1) ranges from 0.1 cm to 1 cm, and the thickness of the heating sheet (2) ranges from 0.1 mm to 3 mm.

6. The ammonia gas sensor according to claim 4, wherein The length of the reference electrode (3) and the sensitive electrode (4) ranges from 1 mm to 6 mm, the width ranges from 1 mm to 6 mm, and the thickness ranges from 5 um to 20 um.

7. The ammonia gas sensor according to claim 1, wherein The preparation method of the terpineol slurry containing manganese dioxide in step S1 is as follows: manganese dioxide powder and terpineol slurry are put into a marquis mortar according to a mass ratio of 1:1.5, mixed and ground uniformly to obtain the terpineol slurry containing manganese dioxide, and the terpineol slurry is prepared by mixing terpineol and ethyl cellulose according to a mass ratio of 94:

6.

8. The ammonia gas sensor according to claim 7, characterized by The preparation method of the terpineol slurry containing tin ferrite in step S2 is as follows: tin ferrite and terpineol slurry are put into an agate mortar in a mass ratio of 1:1.5, mixed and ground uniformly to obtain the terpineol slurry containing tin ferrite, and the terpineol slurry is prepared by mixing terpineol and ethyl cellulose in a mass ratio of 94:6.

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