TW561258B - Solid-electrolyte type gas sensor and gas sensing device - Google Patents

Abstract

A solid-electrolyte type gas sensor and a gas sensing device using the gas sensor. Co3O4 or Au/Co3O4 is used as sensing material which is coated on an anode on a solid electrolyte substrate. The gas sensor and the gas sensing device work at a relatively lower working temperature as compared to the same type of gas sensor using other sensing materials, and are useful in detecting carbon monoxide and hydrogen.

Description

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V. Description of the invention (1)

Description of the invention: [Field of the invention] sensing element, especially solid state of sensing material The present invention relates to a solid electrolyte gas sensor related to a type of electrolyte gas sensing element using cobalt oxide and selective addition of gold. The present invention also relates to a device including the above-mentioned gas sensing device. [Background of the Invention] In air pollution, the sources of carbon monoxide are emissions from vehicle exhausts and factory flues. There is also a danger of carbon monoxide leaking when coal or gas is used in homes or factories. The air quality standard in China is that the average value of carbon oxide concentration in 8 hours should be less than 9 ppn ^ When the concentration of carbon oxide in 8 hours reaches 35 ppm, human heart muscle metabolism will be impaired, vision, hand dexterity, and learning ability? reduce. When 50 ppm is reached, 'human headache and poor hand coordination function' will cause collapse, dizziness, or even coma or death. Because carbon monoxide gas is colorless, odorless, and non-irritating, it cannot be sensed by the human body, so it cannot be detected unless acute signs of carbon monoxide occur in the presence of large amounts of carbon monoxide. If carbon monoxide alarms can be installed in homes, cars, and houses, the tragedy of carbon monoxide poisoning can be avoided. Therefore, a well-developed carbon monoxide sensor has become a very important subject. Therefore, the present inventor has made efforts to complete the present invention for the study of CO sensing materials. At the same time, it was unexpectedly discovered that the sensing device using the sensing material can sense hydrogen gas.

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The gas sensing elements and sensing devices of the present invention can be applied to prevent dangerous batches, detect toxic gases, environmental protection, home alarms, food quality inspection and physical property inspection. The invention has the following advantages: low detection temperature, high sensitivity, good selectivity, short induction time, and low price. [Prior art] The conventional gas sensors can be roughly divided into four types: infrared type, solid-state semiconductor type, electrochemical type and solid electrolyte type.

At present, the principles of commercially available sensors for measuring carbon monoxide (c0) concentration include non-dispersive infrared light method, electrochemical method, and solid-state semiconductor sensor method: non-dispersive infrared light sensor, simple operation, However, it is not suitable for analyzing small-flow test objects, and the price is high. The electrochemical formula has the advantage of high sensitivity ', but the price is slightly higher, and it has a limit of about 2 years. Solid-state semiconductors are cheap and lightweight, but the signals are less stable. Another type of sensor uses the principle of solid electrolyte (SES) to measure the concentration of gas such as CO. It has the advantages of fast response, stable signal, cheap and light weight. At present, the operating temperature is slightly higher, and there is no commercial solid The electrolyte sensor is an electrolyte, plus the principle of yin and yang. Since the gas concentration of the two electrodes is known, the gas concentration can be determined by exposure. The basic composition is made of solid ion conductor as electrode material. Use of different shades of battery to generate a potential difference, such as a battery

Nernst equation finds another electrode

In 1 993, the principle of solid electrolyte was used to make C0 sense.

561258 V. Description of the invention (3) Research on measuring device. Refer to N · Li, TC Tan, and J · Electrochem. Soc ·, 140, ρ · 1 068 (1 993) by HC Zeng, whose sensing element materials are mainly copper oxide / zinc oxide The measurable C0 concentration range is 0-50 00 ppm, and the operating temperature is 300-450 ° C. In addition, Sn02, Fe2 03, Mo03, and Ιη2 03 can be used to detect the concentration of C0, but there are other gas interference problems (see CN Xu, N. Miura, Υ · Ishida, Κ Matsuda, and Ν Yamazoe Sensor and Actuator B, 65, 163 (2000) and X · Wang, Ν ·

Miura, Sensor and Actuator B, 66 '74 (200 0) by N. Yamazoe. In 1998, N. Yamazoe et al. Used CdO and Sn02 to be placed on the two pole materials, respectively. The result is highly selective C0, but the operating temperature is about 600 t: If a portable C0 sensor is used, This temperature is too high and consumes a lot of energy. In 2001, the C0 sensor made by platinum (Pt) and platinum-alumina (Pt-Al2 03) as electrodes was not sensitive to CO (only 18 for 100 ppm CO). mV), however, it is hardly affected by hydrogen, water vapor and nitric oxide. The disadvantage is that the detection temperature is as high as 60 ° C. It can be found from the literature that the CO sensor of SES has the disadvantages of high detection temperature, low sensitivity or poor selectivity. Therefore, the object of the present invention is to provide a gas sensing element or device with a lower operating temperature, high sensitivity and selectivity. In order to achieve the above-mentioned object of the present invention, the present inventors have devoted themselves to researching the results, using cobalt oxide and selectively adding gold as a sensing material to make a solid electrolyte sensor, and found that at a lower operating temperature (for example, 1 8 〇1

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300 ° C) can detect carbon monoxide (c0) sensitively, and also found that the solid electrolyte sensor can detect hydrogen (h2), and completed the present invention. "[Summary of the Invention] The object of the present invention is to provide a solid-electrolyte-type gas sensor including: a solid-electrolyte substrate; a cathode placed on the solid-electrolyte substrate; and an anode having a cobalt oxide film on its surface As a sensing material, it is placed on a solid electrolyte substrate. Another object of the present invention is to provide a solid electrolyte gas device, including: a gas sensing element, including a solid electrolyte substrate, Yin on the electrolyte substrate, an anode having a cobalt oxide film on the surface as a sensing material and placed on the solid electrolyte substrate, and a heating element for heating the solid electrolyte substrate; and an electrical connection device, Connect the anode and cathode. [Detailed description of the invention]

Name the sleeve, see 1? To explain the invention in detail. The solid electrolyte gas sensing element of the present invention includes: π β = state electrolyte substrate (40): It is also used as the substrate of the carrier electrode, and the solid electrolyte of the ionized material is used as the electrolyte of the gas sensing element of the present invention. . Examples of materials such as: YSZ (Ytrria

561258 5. Description of the invention (5) '* stabilized Zirconia (zirconia stabilized with yttrium oxide), hafnium oxide (Ce02). Among them, YSZ is preferred. When YSZ is used, the weight ratio of yttrium oxide to hafnium oxide may be in the range of 1: 2 0 to 1: 1, preferably in the range of 1 · 2 0 to 1: 5. It can be formed by calcining at 80 ~ 120.

Cathode (10): It is placed on a solid electrolyte substrate, and can be a general high temperature resistant sintered electrode material, such as gold, platinum, and silver. Anode (20): It is placed on a solid electrolyte base and can be a general high temperature resistant sintered electrode material, such as gold, platinum, and silver. Among them, gold, platinum, and silver are preferred. The anode surface has a sensing material (30). The sensing material is made by mixing cobalt oxide (c0304) with selective addition of gold and an appropriate amount of adhesive and applying it on the anode surface at a temperature of 600 ° C and sintering for 0.5 to 1 hour. . Cobalt oxide is used in powder form. When cobalt oxide and gold are used, the amount of gold is 0.1 to 5% of the total amount of cobalt oxide and gold "preferably 0.5 to 3%. The particle size of gold is preferably 50 nm or less" It is more preferably below 10 nm, and most preferably below 5 ηη. The adhesive may be polyoxyethylene, polyvinyl alcohol or TE0s (tetraethyl orthosilicate) solution often used in the industry. Adhesive The use ratio with the oxide name (or oxidation start and gold) depends on the type of adhesive. Generally, an appropriate amount can be used to make the powder stick together and make the powder form a paste. The TE0s solution can be made of Si (0C2H5) 4, with water and alcohol organic solvents (such as

C2H50H, c3h7oh). Heating element (50): used to heat the solid electrolyte substrate. Heating elements can be used conventionally. The heating temperature is preferably as high as 400 ° F, and more preferably between 170 and 400 ° T, so as to facilitate the operation of the gas sensing element of the present invention. Please refer to FIG. 2, the solid electrolyte gas sensing device of the present invention

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In addition to the above-mentioned gas sensing element, this is an electrical connection device that connects the anode and the cathode. For example, two anodes (60, 61) are electrically connected to the anode and cathode, and a voltmeter (70) is connected to read the voltage change value. The material of the wire may be a conductive material that does not respond to the detected gas and is resistant to high temperatures, and is preferably a platinum wire. There may also be a current supply (80) connected to the heating element. There may also be a detection chamber (90): for the gas to be measured to detect the gas concentration. And there can be one or more standard gas sources (100): a gas of known concentration is provided as the detection standard, which can be one of known concentrations of carbon oxide or hydrogen in air or nitrogen or inert gas or inert gas. The following examples describe the manufacturing method of the gas sensing element and the gas sensing device of the present invention in detail. However, the scope of the present invention is not limited to the contents of the embodiments. [Example] Preparation Example 1: Preparation of CO3 04 10 g of cobalt carbonate basic salt (2COC03 · 3 (: ο (〇Η) 2 · Η 20) was heated to 400 C in the air for 30 minutes, 8 g of powder co0304 was obtained.

Preparation Example 2: Preparation of Au / Co304 First, 10 g of cobalt carbonate basic salt was heated in the air for 30 minutes to obtain 8 g of CoO04 powder. Then, 500 g of deionized water was taken, and 5 g of the co 3 004 powder was dispersed and suspended therein, and heated to 70 ° C. Take 1 gram of HAuC14 (sold by HAuC14 3H20 ′ Aldrich, containing 10 wt ° / 〇Au) in 20 ml deionized

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Water dilution. The diluted solution of HAuCl4 was dropped into the suspension of the Co. 03. 4 carrier, and the pH of the solution was controlled with NaOH (Uerck, 99% purity) to continuously stir for 3 hours at # = 7 '. The suspension was filtered, washed with deionized f, and the product was dried in an oven. The obtained dried product was reduced in H 2 / (10% H2 / N2, Qialong Co., Ltd. at 200 ° C, and the price was obtained)

Au / C04, wherein the weight of Au is 152% of that of C03, and the average particle size is about 3 nm. i… Preparation Example 3: Preparation of C0304 sensing material Take an appropriate amount of glycerin and drop it into a three-roller to roll and lubricate the surface. Take 5 g of Co.304 powder and pour into three rollers and stir. Then, 0.5 ml of tetraethyl orthosilicate solution (Si (0C2H5) 4 ·· H20: C2H5OH = 65 g: 8 g • 2 7 g) was dropped into the two rollers and stirred for 30 min. A paste-like sensing material was prepared for use when applied to the upper surface of the anode. Preparation Example 4: Preparation of Au / Co3 04 sensing material was performed in the same manner as in Preparation Example 3 above, except that Au / C0304 in Preparation Example 2 was used instead of C03, to obtain a pasty sensing material. Example 1 Manufacturing of a gas sensing element using a sensing material C 〇3 〇4 5 wt% (ratio to Zr02) YSZ (yttrium oxide: oxidation error (weight ratio) = 1: 19, DAICHI KIGENSO KAGAKU KOGYO company (Sold) The powder is pressed into a round sheet with a diameter of about 6 mm and a thickness of about 1 mm. The solid YSZ flakes were heated to 1 400 ° C to enhance their mechanical strength, and a solid electrolyte substrate was prepared. A snake wound platinum mesh for heating is adhered to one side of the reinforced YSZ sheet as a heating element, and the platinum mesh adhesive is removed by calcination, as shown in Fig. 3a. Attach two platinum measuring electrodes on the other side of the circular sheet, and then burn it to remove the stickiness.

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gum. Use a wiring machine to connect the platinum wire to the heating platinum grid and the measuring electrode. A screen printing machine sold by C.W. Price company was used to print a layer of Coa04 sensing material layer obtained in Preparation Example 3 on the surface of the anode, and the organic solvent was removed by heating at 400 ° C, as shown in FIG. 3b ( (The anode is below / not shown * in the figure). Finally, the sensing element is connected to the measurement base to complete. D. Example 2 Manufacture of gas sensing element using sensing material Au / C0304. The gas sensing element was manufactured in the same steps as in Example 1, but Au / Co3 04 obtained in Preparation Example 4 was used instead of c03. 〇4. Example 3 Manufacturing of Gas Sensing Device The gas sensing element obtained in Example 1 was placed in a test chamber. Connect the power supply by connecting wires from the heating το piece. The lead is connected to the voltmeter through the two electrodes. The test chamber was connected to the carbon monoxide and air cylinders by a tube, and the carbon monoxide and air were mixed before entering the test chamber as the carbon dioxide concentration standard. And completed one of the carbon oxide gas sensing devices of the present invention. In addition, carbon monoxide is replaced with hydrogen to manufacture a hydrogen sensing device. In addition, oxane was used instead of nitric oxide for comparison. Manufacture of the gas sensing device in Example 4 The gas sensing device was manufactured in the same steps as in Example 3, but the gas sensing element using the sensing material Au / C0304 in Example 2 was used instead of the gas in Example 1. Sensing element. The following describes the results of detecting a sample using the gas sensing device of the present invention of the above embodiment. Gas flow sensing was performed with 100: 11, 1), (), (112), (112), and (: 114) at a flow rate of 100 «11/1 ^ 11, respectively. Using c 〇3 〇4 as the sensing material, At various temperatures

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V. Description of the invention (9) The measured voltage signal vs. temperature is defined as the difference between the air and the electromotive force passed in, as shown in the following formula S = EGas-EAir. The sensitivity of SES is measured separately when a concentration of test gas is shown.

Gas · The emf measured in a certain concentration of test gas EAir: The emf measured in the air is not sensitive to the detection of CH4 gas, but for c0, the signal can be obtained under U5 / C, For hydrogen, at about 19 °. The signal can be obtained below 〇. Using Au / C0304 as the sensing material, the voltage signals measured at various temperatures were plotted against the temperature to obtain Figure 5. It shows that the detection of Cl gas is not sensitive, but for C0 and hydrogen, the information can be obtained at about 3 0 π

Au / C0304 was also used as the sensing material, and the voltage signals generated at different concentrations of carbon monoxide were plotted at 25 0 and 270 ° C, respectively, to obtain the sixth figure. Shown at 2 50 X: and 270 ° C, the gas sensing device of the present invention can accurately and sensitively measure the carbon monoxide concentration. Comparative Example 1 A sensing element (Cu0, Ti〇2, Sn〇2) made from a sensing material used in the prior art and a sensing material (c03 & Au / c) used in the present invention (0030) The results are shown in Table 1. For each of these materials, a graph of voltage versus various temperatures was obtained by using CO of 1000 ppm of CO as a gas to be measured, to obtain a graph of FIG. 7. It is shown that the present invention has superior sensitivity and lower induction time at lower operating temperatures than the prior art.

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561258 V. Description of the invention (ίο) Table 1 Metal halide Ts T〇 ST〇 t90 CuO 390 470 22 300 Ti02 230 370 21 300

Sn02 200 260 8 70 CO3O4 170 320 60 60 AU / CO3O4 130 300 121 20

Ts: initial working temperature, unit: ° C

τ〇: Optimum working temperature, niches: ° C

St. : Sensitivity at TO, unit: mV tg) 0: Sensing time connected to 90% of detection sensitivity, unit: second Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention, any Those skilled in the art can make some modifications and retouching without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the attached patent application.

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[Brief description of the drawings] FIG. 1 shows a schematic side view of the structure of a gas sensing element according to an embodiment of the present invention. Fig. 2 is a diagram showing a gas sensing device according to an embodiment of the present invention. Figure 3a is a side view and a diagram of the structure of the heating Gu net in the S E S (Y S Z) sensing element. Figure 3b is a schematic diagram of the structure of the measuring electrode in the S E S (Y S Z) sensing element. Figure 4 is the result of sensing the different temperatures (hydrogen, carbon monoxide, and methane) of 1000 ppm of different materials by Co.304. The signal and the sensing temperature are plotted. Picture 5 is Au / Co304 material pair! 0 00 ppm sensing results of different gases (hydrogen, carbon monoxide, and methyl alcohol), plot the signal and the sensing temperature. Figure 6 is a plot of Au / Co304 material sensitivity (signal s) with CO concentration at different sensing temperatures (270 and 250 ° C). Fig. 7 shows the test results of 1000 ppin CO of different sensing material layers, and plots the signal and the sensing temperature respectively. [Description of Symbols] 10: cathode 20: anode 30: sensing material 40: solid electrolyte substrate 50: heating element

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Claims (1)

561258 1. A solid-electrolyte-type gas sensing element, comprising: a solid-state electrolyte substrate; a cathode 'placed on the solid-state electrolyte substrate; and an oxide film on the surface as a sensing material placed in the solid-state On the electrolyte substrate. 2. The solid-electrolyte-type gas sensing element according to item 1 of the scope of the patent application, wherein the sensing material is a mixture of cobalt oxide powder and an appropriate amount of an adhesive and is coated on the anode surface at 400 to 600 ° C Sintered at temperature. 3 · The solid electrolyte gas sensor as described in item 1 of the scope of patent application The sensing element, wherein the sensing material further comprises not more than 2% by weight of gold based on the total weight of the sensing material. 4. The solid-electrolyte-type gas-sensing element according to item i in the scope of the application for patent, wherein the adhesive is selected from the group consisting of polyoxyethylene, t-ethylene alcohol, or tetraethyl orthoacetate 8 Purpose (TEOS), and mixtures thereof. 5. The solid-electrolyte-type gas sensing element according to item 4 of the scope of the patent application, wherein the adhesive is tetraethyl silicate. 6. The solid-electrolyte-type gas-sensing element according to item 1 of the scope of patent application, wherein the solid-state electrolyte is composed of a metal oxide. 7 · The solid-electrolyte-type gas sensing element according to item 1 of the scope of the patent application, wherein the solid-state electrolyte is composed of a oxidized period (Y2 03) and a zirconia (Zr02) in a weight ratio of 1: 2〇 ~ 1: 1 The mixed mixture is calcined at 800 ~ 1200 ° C. 8. The solid-electrolyte-type gas sensing element described in item 1 of the scope of patent application, which is used to detect carbon monoxide. 0729-8612TW (N); 07910009; patricia.ptd page 16 561258 6. Scope of patent application 9. The solid-electrolyte-type gas sensing device described in item 1 of the scope of patent application, which is used to detect hydrogen. 1 〇. A solid electrolyte type gas sensing device 'includes: a gas sensing element including a solid electrolyte substrate, a cathode placed on the solid electrolyte substrate, and a surface having a cobalt oxide film as a sensor Material, an anode placed on the solid electrolyte substrate, and an electrical connection device that connects the anode and the cathode. 1 1 · The solid electrolyte gas sensing device as described in item 10 of the scope of patent application, further comprising a heating element for heating the solid electrolyte substrate. 12. The solid-electrolyte-type gas sensing device described in item 1 of the patent application scope further includes a power supply for supplying current to the heating element to generate heat. 1, 3 · The solid-electrolyte-type gas sensing device as described in item 10 of the scope of patent application, wherein the sensing material is coated on the anode surface with a mixture of cobalt oxide powder and an appropriate amount of adhesive at 4q0 to 600 It is sintered at a temperature of 0 14. The solid electrolyte gas sensing device described in item 10 of the patent application range, wherein the sensing material further includes gold with a total weight of the sensing material not greater than 2% by weight. ~ Outside 1 5. The solid-state electrolytic sensing device as described in item 丨 0 of the patent application scope, wherein the adhesive is selected from the group consisting of the following groups: /, ene, polyvinyl alcohol, orthosilicate Ethyl ester (TEOS), and its mixed ^ B16. Solid state electrolysis as described in item 15 of the scope of patent application > σ 561258 6. Scope of patent application Body sensing device, wherein the adhesive is a solution of vermiculite tetraethyl acetate (TEOS). 17. The solid-electrolyte-type gas sensing device 'according to item iq of the scope of patent application, wherein the solid-state electrolyte is composed of a metal oxide. 18. The solid-electrolyte-type gas sensing device according to item 1 of the scope of the patent application, wherein the solid-state electrolyte is composed of a mixture of Oxidation (〇3) and Gadolinium Oxide (Zr02) in a weight ratio of 1: 2 ～ 1. Sintered at 800 ~ 1200 ° C. 19 · The solid-electrolyte-type gas sensing device as described in item No. 丨 0 of the scope of patent application, which is used to detect oxidative breakdown. 2〇 The solid-electrolyte-type gas sensing device described in item No. 丨 0 of the scope of patent application, which is used to detect hydrogen fluoride. 0729-8612TWF (N); 07910009; patricia.ptd Page 18