JPS61223642A - Gaseous hydrogen detecting element and its production - Google Patents

Abstract

PURPOSE:To obtain an excellent H2 detecting element by treating an element dispersed with PtSn on SnO2 into SnO2 particles so as to have respectively specific mol% of a Pt/Sn ratio and Sb/Sn ratio in a specific concn. of gaseous silane atmosphere thereby dispersing an Si oxide on the element surface. CONSTITUTION:The SnO2 particles are added and dispersed to and into an H2PtCl2 soln. of the amt. at which the Pt/Sn ratio attains 1-8mol% and the mixture is subjected to quick freeze dryuing. The SbOCl of the amt. at which the Sb/Sn ratio attains 1-8% is added and mixed to and with the dried matter and thereafter an org. solvent is added thereto to prepare the paste. The paste is coated on an alumina ceramic pipe having an electrode and after the coating is dried, the coating is calcined in the atm. or a gaseous antimony oxide atmosphere. A heater is attached to the calcined element and the element is aged for the prescribed period at 300+ or -50 deg.C and is then treated in the air atmosphere contg. 500-5,000ppm gaseous silane such as SiH2Cl2 to disperse Pt and Sb on SnO2. The gaseous hydrogen detecting element which is dispersed with SiO2 on the surface and has the higher response speed at the lower temp. than heretofore is thus obtd.

Description

[Detailed description of the invention] [Industrial application field 1 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 selectivity sensor is known in which a membrane selectively permeable to hydrogen molecules, such as a combustion-inactive thin film, is formed on a gas-sensitive element. In such sensors, hydrogen gas must pass through a thin film filter, and it takes time for it to be adsorbed by metal oxides.
Response is delayed.

Further, since this sensor detects gas at a relatively high temperature, in an element containing a catalyst such as Pt in a metal oxide, the catalyst deteriorates quickly and loses its function.

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

[Means to solve the problem α 1 Conventionally, various! ! Monoxide in the exhaust gas emitted from the plant @
A mixture of 2 to 10 mol % platinum-containing chloroplatinic acid aqueous solution to 2 tin oxide was freeze-dried, and a mixture of 2 to 8 mol % antimony oxychloride to 2 tin oxide was added to an organic solvent. By applying this paste to an insulator with electrodes and baking it in air, we manufactured a carbon monoxide detection device that can detect carbon monoxide at room temperature without heating the element. There is.

However, when this carbon oxide gas detection element is treated in an atmosphere containing dilute silane gas, Si oxide is dispersed in the element, and the function of Pt as an oxidation catalyst for hydrogen gases other than humans is lost. It has been found that as a result, it becomes difficult for electrons to be exchanged between gases other than hydrogen and the semiconductor surface, and an element capable of selectively detecting hydrogen can be obtained.

Therefore, this invention has a Pt/Sn ratio of 1 to 8 mol%, Sb
/Sn ratio of 1 to 8 mol% of Pt and Sb dispersed on SnO2 is treated in a silane-based gas atmosphere of 500 to 5000 ppm, and Si oxide is dispersed on the element to produce hydrogen. This invention relates to gas detection elements.

Furthermore, this invention provides S n O2 with a Pt/Sn ratio of 1
~8 mol % of HzP tCla solution, e.g. H
2Ptc+6 is added to an aqueous solution dissolved in pure water, SnO2 in the resulting solution is preferably well dispersed by ultrasonication, and then rapidly freeze-dried at a temperature of -40°C or less in a vacuum freeze dryer, for example. Antimony oxychloride (S bo CI
) and mix thoroughly in a mortar or the like, for example, for about 30 minutes, then apply this as a paste in an organic solvent, for example, isopropyl alcohol, to an alumina porcelain tube equipped with an electrode, and dry. 5nOz and HzPt on the surface
A device comprising a layer containing C16 and S bo CI is fired in an air atmosphere or an antimony oxidation gas atmosphere, a heater is attached to the fired device, and the heater is heated to 300°C ±
The device was heated to 50°C and aced for a predetermined period of time, and the resulting element was heated to 300 to 350°C until the concentration of silane gas was 5.
The present invention also relates to a method for manufacturing a hydrogen gas detection element, which comprises dispersing Si oxide on the element by processing in an atmosphere of 00 to 5000 ppm.

[Effect 1 Use pure water to dissolve H2P tC16.

If the amount of Pt/Sn is less than 1 mol % or more than 8 mol %, the hydrogen detection ability will decrease, which is not preferable.

SnO2 in the H2PtCIs solution thus obtained
The yield of the product is improved by rapidly freeze-drying the product after it is well dispersed using ultrasonic waves or the like. ``Elements can be manufactured without rapid drying. In this case, the yield decreases.

Gauge+! In addition to isopropyl, the organic solvent used to make the base is 25% by weight of β-terpineol, 72% by weight of butyl carpitol acetate, 3% by weight of ethyl cellulose, etc. Organic solvents can be used, and in addition to porcelain pipes, pipe mains or root-like insulators that can withstand firing may be used as the base for applying the paste.Drying of the paste can be done naturally for a few minutes or at constant temperature. You can also go with a tank.

Antimony oxidation gas atmosphere is 5bOCI or 5b2
0. Converting to 0.5-7.5+++gC5bzOs moles is 2X10-@~3X10-' mole/Cω3)
Baked at 600-850"C for about 5-30 minutes. If 5bOC1 is used more than 7 or 5B, P
L is coated with Sb, reducing the activity of PL. Firing the device in air or in an atmosphere of antimony oxidation gas is 60
Bake at a temperature of 0 to 850°C for 5 to 60 minutes. 600℃
Firing at a temperature below 5 minutes and for a time below 5 minutes does not result in good doping with antimony. If the firing temperature exceeds 850° C., the activity of Pt becomes low and hydrogen cannot be selectively detected.

Aging of the semiconductor layer is carried out by heating it to 300° C.±50° C. in an air atmosphere for 12 hours or more using a heater attached to the device, and this aging stabilizes the semiconductor layer. Processing of the device in an air atmosphere containing a dichlorosilane (S i 82 Cl This is carried out by heating at 300 to 350°C for 5 to 45 minutes.

The sensitivity of hydrogen detection decreases outside this range of silane gas concentration and processing time. Further, the device is heated to 300±50° C. in air for 12 hours or more to produce a product. Selectivity to hydrogen gas can be further improved by performing the treatment in a silane gas atmosphere and the subsequent heat treatment in air using the same procedure.

In this invention, Si is dispersed on the surface of the element by treating the element with a small amount of silane gas. Furthermore, the element of this invention has an element heating temperature of 250°C to 4°C during hydrogen monitoring.
It responds in 100 to 150 seconds at 00°C, and the operating temperature is in the 300°C range, for example, as is clear from the examples described later.

The present invention will be explained in more detail with reference to Examples below.

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

Examples 1 to 13 H2P tC was added so that SnO2 was in the Pt/Sn molar ratio shown in Table 1, that is, 1 to 8 mol% relative to Sn.
16 is added to a solution dissolved in pure water and dispersed well by ultrasonication, and this dispersed solution is placed in a vacuum freeze dryer and rapidly freeze-dried at -40°C.

Next, this dried sample has an Sb/Sn ratio of 1 to 8 mol%.
Add an amount of antimony oxychloride and mix in a mortar to approx.
Mix well for 0 minutes. Next, isopropyl alcohol is added to the mixture containing antimony oxychloride to form a paste, which is applied to the alumina porcelain tube to which the electrode is attached and allowed to air dry for several minutes. Next, add this element to 700
C. for 15 minutes. Calcination is 2.5 mg of S b
o Sb acid oxidation soot atmosphere created by firing Cl 1st
Table Example 1) Bake in a quartz tube in a gate or air atmosphere (Table 1, Examples 2 to 13). After attaching a heater to the fired element, the heater was energized to heat the element to 300°C, and then aged in air for 12 hours to stabilize the semiconductor layer.
The elements were then heated to 32 days Celsius except for example 1 (comparative example) and treated with 1000 ppL of dichlorosilane (S iH2Cl2).
Four or eight devices were fabricated for each example after a single treatment for 10 to 15 minutes in an air atmosphere containing No. 11. The obtained elements on each side were measured at a temperature of 325°C ± 10°C with a concentration of each test gas of 100 ppm (room temperature), and the electrical resistance (kΩ) and S/N ratio (resistance of the element in clean air) were measured. Table 1 shows the average values of resistance value/resistance value of the element in the test gas. From the comparison of Examples 2 to 5, Example 7, Example 9, and Example 12 in Table 1, the Pt/Sn ratio is 2 to 4 mol%.
is the most preferred, and it appears that as the Pt/Sn ratio approaches 8 mol %, the H2 selectivity tends to decrease. However, this tendency is compensated by increasing Sbl, so that I+ q
With kt-匍+su-shi l-)-, gas selectivity improves. However, both Examples 12 and 13 show that the amounts of Pt and Sb added are at their limits. The elements of Examples 2 to 13 have an
FIG. 1 shows the response characteristics for each sample gas (100 ppm) of one of the elements in the group of six examples 3, which had an extremely good N ratio.

In addition, when the amount of Si dispersion for the elements of the group of Example 3 is estimated by calculation, it is about 0.3 times 1%. In addition, when the dispersion state of Pt and Si on the element surface of one of the elements in the group of Example 3 was measured using an electron probe microanalyzer at a magnification of 3000, it was found that S
It was confirmed that Pt was dispersed on nO□, and that Si was dispersed in a manner that almost corresponded to the dispersion state of Pt. Therefore, a large portion of Si is ! It is presumed that it is dispersed on the surface as shown in the model diagram in Figure 2.

Examples 14 to 16 Devices were manufactured in the same manner as Examples 2 to 13, except that the conditions shown in Table 2 were used and the devices were fired in an Sb oxidizing gas atmosphere. 325℃±10'Ci: Electrical resistance value (kΩ) in air containing 100 ppa+ (room temperature) and SN (electrical resistance in clean air/in sample gas) when the element is heated. The average value of the electrical resistance value) ratio is listed in the tJ&2 table. It can be seen that the elements of Examples 14 to 16 all exhibit good selectivity to hydrogen other than alcohols.

It should be noted that Si
The relationship between the content of 82 Cl□ and the S/N ratio for hydrogen and ethyl alcohol is shown in FIG.

Examples 17 to 20 In Examples 17 to 19, elements were manufactured in the same manner as in Examples 2 to 13 except that the amount of dichlorosilane in the silane treatment was changed. Further, in Example 20, an element was manufactured in the same manner as in Examples 17 to 19 except that the silane gas treatment was performed twice. Table 3 shows the average values of the characteristics of the element (element heating temperature during measurement: 325°C±10'C) for each sample gas of 100 ppm (at room temperature). Examples 1 and 17 in the table are comparative examples, and the others are examples. The better selectivity of the device of the invention for hydrogen compared to hydrocarbon gases is demonstrated. A comparison between Example 19 and Example 20 shows that hydrogen selectivity is improved by repeating the silane treatment.

[Brief explanation of the drawing]

FIG. 1 is a response characteristic diagram of one embodiment of the hydrogen gas detection element according to the present invention, FIG. 2 is a model diagram of the dispersion state of Si, and FIG.
The figure is a diagram showing the relationship between the amount of dichlorosilane and the S/N ratio of hydrogen and ethyl alcohol, respectively, when the element is treated with a silane gas. Qianse back tuna A ■Jubikuyashu Dingyeong Lu Jinmu Salmon Time (Park)

Claims (1)

[Claims] 1. Pt/Sn ratio is 1 to 8 mol% on SnO_2, Sb
A hydrogen gas detection element comprising an element in which Pt and Sb having a /Sn ratio of 1 to 8 mol % are dispersed and treated in a silane gas atmosphere of 500 to 5000 ppm to disperse Si oxide on the element. 2. Add SnO_2 to an amount of H_2PtCl_6 solution with a Pt/Sn ratio of 1 to 8 mol%, disperse SnO_2 in the resulting solution well, and then dry.
After adding and mixing SbOCl in an amount such that the Sn ratio is 1 to 8 mol%, this is made into a paste in an organic solvent and applied to an alumina porcelain tube equipped with an electrode, dried, and the surface is coated with SnO.
A device comprising _2 and a layer containing Pt and Sb is fired in an air atmosphere or an antimony oxidation gas atmosphere, a heater is attached to the fired device, and the temperature is heated to 300°C ± 50°C with the heater.
The obtained device was heated to 30°C and aged for a specified time.
Heating to 0~350℃, the concentration of silane gas is 500~
A method for manufacturing a hydrogen gas detection element, which comprises dispersing Si oxide on the element by processing in a 5000 ppm atmosphere. 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.