JPS61223643A - Gaseous hydrogen detecting element and its production - Google Patents

Abstract

PURPOSE:To obtain a gaseous hydrogen detecting element having the higher responsiveness at the lower temp. than heretofore by treating an element dispersed on SnO2 at respectively specific mol% of Pd/Sn, pt/Sn, Sb/Sn ratios in a specific concn. of gaseous silane atmosphere to disperse Si oxide on the element surface. CONSTITUTION:SnO2 particles are dispersed in optional order into an aq. PdCl2 soln. and aq. H2PtCl2 soln. and thereafter the mixture composed of each aq. soln. and SnO2 is subjected to quick freeze drying to obtain the particles dispersed with Pd/Sn=0.1-8mol% and Pt/Sn=0.5-8mol% on SnO2. The dried particles are mixed with SbOCl of the amt. at which the Sb/Sn ratio attains 8-8mol% and thereafter the paste in an org. solvent such as i-C3H7OH is prepd. Such paste is coated on an alumina ceramic pipe provided with an electrode and is dried, then the coating is calcined in the atm. or antimony oxide atmosphere. The calcined element is aged for the prescribed period at 300+ or -50 deg.C. The element after the aging is treated in an air atmosphere contg. the gaseous silane such as SiH2Cl2 at 300-350 deg.C to disperse SiO2 on the element. The H2 detecting element having the high response speed at the low temp. is thus obtd.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a hydrogen gas detection element and a method for manufacturing the same.

[Prior Art] As a hydrogen gas detection element using a metal oxide, a hydrogen-selective sensor is known, in which a hydrogen molecule selectively permeable membrane, such as a combustion-inactive thin film, is formed on a gas-sensitive element. In such a sensor, hydrogen gas must pass through a thin film filter layer, and it takes time for it to be adsorbed on the metal oxide, resulting in a delayed response. Further, since this sensor detects gas at a relatively high temperature, in an element containing a catalyst such as Pd in a metal oxide, the catalyst deteriorates quickly and loses its function.

[Problem to be Solved by the Invention, α1] Therefore, there is a demand for a hydrogen detection element with lower temperature and/or shorter response time.

[Means for Solving the Problems] Conventionally, the gas contained in the stray gas discharged from various devices has been used. a±
In this method, a mixture of stannic oxide and an aqueous solution of chloroplatinic acid containing 2 to 10 mol % of platinum based on the stannic oxide is lyophilized, and 2 to 8 mol % of the stannic oxide is added to the mixture. By adding a mixture containing antimony chloride to an organic solvent to make a paste, applying this paste to an insulator with electrodes, and baking it in air, we have developed a method that can detect carbon monoxide at room temperature without heating the device. Manufactures carbon oxide gas detection equipment).

However, when this -carbon oxide gas detection element is treated in an atmosphere containing dilute silane gas, hydrogen is selectively detected by 30%.
It was found that an element capable of detecting with a high signal-to-noise ratio at a temperature in the 0° C. range can be obtained. However, in the case of this device, the response time to hydrogen is 10
0 to 150 seconds, but it has been found that by also adding palladium chloride to this element, an element with high selectivity for hydrogen gas and whose response time can be shortened to within 50 seconds can be obtained.

Therefore, in this invention, Pd/Sn=0.1 to 8 mol%,
Pt/Sn=0.5-8 mol%, Sb/Sn ratio 0-8
Mol% of Pd or Pt or Pd and Pt and StI
500 to 5000 elements are dispersed on 51102
Processed in a silane-based gas atmosphere of pp.
This invention relates to a hydrogen gas detection element formed by dispersing i-oxide.

Furthermore, this invention creates a palladium chloride (PdCl2) aqueous solution and a chloroplatinic acid (H2P tCL) aqueous solution, which contains 0.1 to 8 mol% of Pd/Sn in stannic oxide.
, the palladium chloride aqueous solution and the chloroplatinic acid aqueous solution in an amount such that Pt/Sn is 0.5 to 8 mol% are added in any order, and the SnO2 in the resulting mixture is preferably dispersed well by ultrasonic waves. After drying, add S bo Cl in an amount such that the Sb/Sn ratio is 0 to 8 mol % and mix thoroughly in a mortar etc. After mixing for about 30 minutes, for example, add this to the dried material with an organic solvent. For example, it is applied as a paste in isopropyl alcohol to an alumina porcelain tube equipped with electrodes and dried, and the surface is coated with SnO2, PdCl2 and H2P tCIs.
or 5n02 and P dCL, H2P tC16 and (
/'5b A device comprising an OCI-containing layer is heated at 600°C to 850°C in an air atmosphere or an antimony oxide gas atmosphere.
℃, a heater is attached to the fired element, heated to 300℃±50℃ with a heater, aged in open air for a specified time, and the obtained element is heated at 300 to 350℃ 5000pp.
The present invention also relates to a method for manufacturing a hydrogen gas detection element, which comprises dispersing S i 02 on the element by processing in an atmosphere of -.

[Function] Since PdCI2 does not dissolve in water, 0.2% l hydrochloric acid is used to prepare the Pdel□ aqueous solution. The concentration of hydrochloric acid may be any concentration that simply dissolves PdC1□.

Chloroplatinic acid dissolves in pure water. Pd/Sn or Pt/
If the amount of Sn is less than 0.1 mol % or less than 0.5 mol %, or if the amount of Pd/Sn or Pt/Sn is more than 8 mol %, hydrogen detection ability will decrease, which is not preferable. The thus obtained PdC1□ and H2P t
After the 5no2 in the CI6 mixture is well dispersed by ultrasonic waves or the like, the product is produced by rapid freeze-drying at -40'C or lower in a vacuum freeze dryer. Organic solvents for making a paste from the mixture of the dried product and antimony oxychloride include isopropylar 1 to 17 B-terpineol 25% by weight, butyl carpitol acetate 72% by weight, ethyl cellulose 3% by weight, etc. In addition to porcelain tubes, a tube or plate-shaped insulator that can withstand firing can be used as the base for all coatings.The paste can be dried naturally for a few minutes, or in a constant temperature oven, etc. You can go there.

Antimony oxidation gas atmosphere is S bo Cl or 5
bzO: + 0.5 to 7.51 ag, converted to 5 bzOz moles, 2X10-'-3XLO-'moles/c++' is baked at 600 to 850'C for about 5 to 30 minutes to create. When 5bOC1 is used in an amount greater than 7.5 ll1g, Pd and pt are coated with sb and Pd
and pt activity decreases. The element is fired in the air or in an atmosphere of antimony oxidation gas at a temperature of 600 to 850° C. for 5 to 60 minutes. Cannot be doped with antimony at temperatures below 600°C and times below 5 minutes, 8
At temperatures exceeding 50°C, the activity of Pd and pt becomes low and hydrogen cannot be selectively detected.

Aging of the element is performed using a heater attached to the element.
Stabilize the 12 semiconductor layer in an air atmosphere by heating to 0±50°C. The device was treated in an air atmosphere containing silane gas using nochlorosilane (Si82C+2) at a concentration of 500 to 5000 ppm, l! In an air atmosphere containing 7s
Or by heating the element to 300-350°C for 5-45 minutes with a heater in monosilane (S i H4) lf . When this silane system is outside the six concentration and treatment time ranges, the sensitivity of hydrogen detection decreases. The device is further heated to 300±50° C. in air for 12 hours or more to produce a product. By repeating the treatment in an air atmosphere containing silane-based γ gas and the subsequent heat treatment in air using the same procedure, selectivity to hydrogen gas can be further improved.

In this invention, Si is dispersed on the surface of the element by treating the element with a small amount of silane gas. Further, as will be clear from the examples described later, the operating temperature is in the 300° C. range, and the response speed is within 50 seconds.6 The present invention will be explained in more detail with reference to examples below.

Hereinafter, unless otherwise specified, the examples will be simply referred to as examples.

Examples 1 to 13 82P tc in PdCl2-0.2% hydrochloric acid solution and pure water in the amounts shown in Table 1 1. Sequentially added aqueous solutions of S n O2 to S n O2, well dispersed S n O2 in this mixture using ultrasonic waves, rapidly freeze-dried this dispersion at -40°C, and then set it in a vacuum freeze dryer. and dry.

Next, an amount of S bo Cl to give the indicated Sb/Sn mol% was mixed with this dried material, and the mixture was mixed in a mortar for about 30 minutes. Isopropyl alcohol was added to this mixture to form a paste, and the electrode was attached. Apply it to the alumina porcelain tube and let it dry naturally. Next, add 2.5 mg of this element to
It was fired at 700'C for 15 minutes in a quartz tube in an antimony oxidation gas atmosphere created by firing S bo Cl.

After attaching a heater to the fired element, the heater was energized to heat the element to 300°C, and then left in the air for 12 hours.
Knee sing for an hour and then heat the device to 325°C except for example 1 (comparative example).
,F,4-. 1 /'t/11'1. ．． ．． ．． 4-The sample was treated once for 10 minutes in an air atmosphere, and then heated in air at 300°C for 12 hours. The obtained device was heated to a temperature of 325°C ± 10°C and the concentration of each test gas was 100%.
Electrical resistance value (kΩ), SN ratio (resistance value of the element in clean air/resistance value of the element when tested inside) and response time (seconds) when measured in air containing ppm (room temperature)
Among the six tables shown in Table 1, Example 1 is a comparative example showing the device without silane treatment, and Examples 2 to 13 are examples. The response time for each example 2 to example 13 was within 30 seconds, and example 2 showed that the amount of Pd and pt added was at the lower limit, and example 1
3I indicates that the amount of Pd, Pt, and Sb added is at the upper limit. The data shown in Table 1 is the average of data from all eight samples made for each side.

Incidentally, the response characteristics of one element in the group of Example 6 to each sample gas are shown in FIG.

ノ' Example 14 Processing with S i 82 CI 2 is 1000 for the first time.
Open for 10 minutes with PP, then 1 with 1000pp- for the second time.
The operations were carried out in the same manner as in Examples 2 to 13, except that the total number of bamboos was 0.

Table 2 below shows the performance of the obtained device in comparison with the devices of Examples 1 and 3. In Table 2, the S/N ratio of hydrogen gas is greatly improved in Example 4 compared to Example 3, while the S/N ratio of other gases is decreased, indicating that the hydrogen selectivity has been significantly improved. The element temperature during measurement 6 is 325℃±10
It is ℃.

Example 15 Example 15 shows the production of a device that was operated in the same manner as Examples 2 to 13, except that antimony oxychloride was not added and the treatment was not carried out in an oxidizing atmosphere of antimony oxychloride. The response time of the device of Example 15 is 37 seconds, which is slightly slower than the devices of Examples 2 to 13, but it is still much faster than the case of adding PT alone, and the hydrogen selectivity is also good. The manufacturing conditions and performance of the device of Example 15 are shown in Table 2.

In addition, when the amount of Si dispersion was calculated for the elements of the group of Example 4, it was estimated to be 0.5% by weight.

In addition, the dispersion state of PT, Pd, and Si on the surface of one of the devices in Example 14 was measured using an electron probe microanalyzer.
Measured at 00x magnification. As a result, pt and Pd were dispersed on SnO2 (the dispersion was slight because Pt was a trace amount of 0.5 mol% relative to Sn), and Si was almost in a state of dispersion with Pd and Pt. It was confirmed that they were distributed in a corresponding manner. Therefore, it is presumed that a considerable portion of Si is dispersed on the surfaces of Pd and Pt, as shown in the model diagram of FIG. As a result, it becomes extremely difficult for gases other than hydrogen to transfer electrons to and from the element surface, resulting in a decrease in the S/N ratio.On the other hand, hydrogen adsorption onto the element surface and transfer of electrons occur smoothly, resulting in a S/N ratio. It is thought that the response time will be improved and the response will be faster.

[Brief explanation of drawings]

FIG. 1 is a response characteristic diagram of one embodiment of the hydrogen gas detection element according to the present invention, and FIG. 2 is a model diagram showing the dispersion state of Si. Time (persimmon) Figure 2

Claims (1)

[Claims] 1. Pd/Sn=0.1 to 8 mol%, Pt/Sn=0.
5 to 8 mol%, Sb/Sn = 0 to 8 mol% of Pd and Pt, or an element in which Pd, Pt, and Sb are dispersed on SnO_2 is treated in a silane-based gas atmosphere of 500 to 5000 ppm. A hydrogen gas detection element made by dispersing Si oxide on the element. 2. Make a palladium chloride (PdCl_2) aqueous solution, make a chloroplatinic acid (H_2PtCl_6) aqueous solution, and add 0.1 to 8 mol% of Pd/Sn and 0.5 to 8 mol% of Pt/Sn to stannic oxide. Amounts of the above palladium chloride aqueous solution and chloroplatinic acid aqueous solution are added in an arbitrary order, and after the SnO_2 in the obtained mixture is well dispersed, it is dried, and the dried product has Sb/Sn = 0 to 8 mol%. After adding and mixing a certain amount of antimony oxychloride (SbOCl), it is made into a paste in an organic solvent and applied to an alumina porcelain tube equipped with electrodes, dried, and the surface is coated with SnO_2 and PdCl_2.
and H_2PtCl_6 or SnO_2 and PdCl_2
An element comprising a layer containing H_2PtCl_6 and SbOCl is fired in an air atmosphere or an antimony oxidation gas atmosphere, a heater is attached to the fired element, and the element is heated to 300°C ± 50°C with the heater and aged in air for a predetermined period of time. A method for manufacturing a hydrogen gas detection element, which comprises heating the obtained element to 300 to 350°C and treating it in an atmosphere with a silane gas concentration of 500 to 5000 ppm to disperse Si oxide on the element. . 3. The method for manufacturing a hydrogen gas detection element according to claim 2, wherein the drying after well dispersing SnO_2 is rapid freeze drying.