JPS5926051A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To increase electromotive force with respect to a change in the concn. of O2 and to improve responsiveness, stability, etc. by using porous carbon or porous metal incorporated therein with a specific amt. of alkali metal vanadate in manufacturing the electrode of a galvanic battery type oxygen sensor on the side in contact with gas to be measured. CONSTITUTION:The positive electrode of an oxygen sensor, i.e., the electrode 3 on the side of gas to be measured, is manufactured by molding by pressure the powder of 3-50% alkali metal vanadate such as LixV2O5(0.02<=X<=1.0), NaYV2O5 (0.15<=Y<=1.0) or the like mixed with carbon powder such as graphite and a water repellent such as ''Teflon'' together with an Ni-screen 2 then heat treating the same and uniting the molding in one body to an electrode material 1. An electrolyte 6 such as alkali metal salt or KOH, phosphoric acid, etc. is put between such porous electrode 3 and a negative electrode (made of Zn, Al, Pt, etc.) 4. The gas to be measured enters the case from the holes 7 thereof. The alkali metal vanadate acts as a catalyst for electrode reaction and the inexpensive sensor having high sensitivity and long term stability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen sensor used for measuring oxygen concentration in the environment at room temperature.

Detecting the oxygen concentration in the atmosphere and connecting it to alarm devices and other interlocking devices to prevent oxygen deficiency in caves and underground passages.
It is becoming more important as the number of underground crops increases. This oxygen#
As an oxygen sensor used for temperature detection (J, a galvanic type Kameike is formed, porous u and one positive pole (θ) are brought into contact with the gas to be measured 1111, or a solid FIT or solute is formed. Then, one y11 pole is brought into contact with the reference oxygen partial pressure (generally, the oxygen partial pressure of air in the atmosphere), and the other FI?, pole is brought into contact with the gas to be measured, and the electromotive force or ■1 current change that occurs. (Well, there is a method that uses an oxide semiconductor whose υytt gas conductivity changes depending on the oxygen partial pressure and determines the yllL air resistance change.Also, there is a method that uses fluorescence quenching due to the oxygen partial pressure. +J% sensors are also being proposed.

In the galvanic type one-cell type, the sensor electrode has a positive electrode (porous T electrode containing platinum, silver, etc. in the box, Zn, Mg, etc. in the negative electrode).
etc. are used. In addition, for solids, solutes, and pond types, Z r O2-Oh 0% Th 02-, Y2
Porous metals such as O3 (conductors are used in combination with porous metals such as platinum and gold).As oxide semiconductors, T'10
KaCoo, MgO-Oo 01M10, etc. are used. Pyrene-silicon membranes are used in sensors that utilize fluorescence quenching.

However, among these metals in the prior art, JIt metals such as platinum, gold, and silver are expensive, and solid YTT metals are expensive.
Solyte does not operate at room temperature. Regarding oxide semiconductor materials, base conductor 717. It has the disadvantage that the change in the conductive YrL ratio with respect to the conductive YrL ratio is small, and it is buried in the fluctuation of the base resistance and does not stop or restore quickly.

However, the fluorescence quenching technology has poor response to oxygen partial pressure and lacks long-term stability, making it far from practical.

■ The present invention was made in view of the current situation, and
The use of an electrode containing an alkali metal vanadate is inexpensive, has a large force and a desired response, and is stable over a long period of time. Our goal is to provide a high performance, highly reliable oxygen sensor.
It is set as one.

To summarize the present invention, the rapid sensor of the present invention includes:
Li X V205s Na yV205 for positive electrode
Porous T1 containing Kasa's alkali metal vanadate
The present invention is characterized by using one electrode, using a base metal, platinum, or an alloy thereof for the negative electrode, and arranging Vll solute between the two electrodes. By containing an alkali metal vanadate 9 salt such as L i x V2O3 or NayV208 in the porous positive electrode that is in contact with gas, oxygen? Change in electromotive force due to change in 7jj↓ degree,
Alternatively, it is possible to obtain an oxygen sensor that has a large degree of coolness in the summer, has a fast response, and is stable for long periods of time.

According to the present invention, a porous tυ containing an alkali metal such as I+ i x V2O5, Nhy V2O, etc., which is in contact with the gas to be measured, is used as a positive electrode,
The negative electrode is made of aluminum, aluminum, magnesium, platinum, or metallurgy of these metals.
OHlN a O11 etc.
NaC! 1. Neutral m solutes such as KOl, acidic electrolytes such as phosphoric acid f! It is constructed using a solution in which a self-corrosion inhibitor and a precipitating flocculant for the negative electrode are added to the f+ quality as necessary.

The electrode on the gas-to-be-measured side of the oxygen sensor of the present invention is made of a mixed powder of carbon powder, graphite, activated carbon, acetylene black, etc., and a water repellent such as Teflon; ．．・NayVz
O1! It is treated with alkali metal vanadate such as.

According to the test 3.1 of Kifu 11 Meisha et al., the porous 5JI positive bottle in contact with the gas to be measured side (the content ratio of alkali metal vanadate in the bottle is in the range of 3% to 50%, as will be described later). Oxygen reduction■
f, C shows excellent catalytic effect in pseudo reaction. If the content ratio is 3% or less, the catalytic effect on the oxygen reduction reaction will not be sufficiently expressed, while if it is 50% or more, 1. F
IY, the conductivity of the electrode decreases, there is a delay in the supply of yet particles, and the positive electrode reaction does not proceed smoothly.For both C1 and C1, the response of the moe tortoise position to changes in oxygen concentration deteriorates.

The filt of alkali metal vanadate in the present invention
Although the class is not limited to lr, according to the inspection conducted by the present inventors, the chemical formula L i x v2o5(o, o 24x4
1. o ) and the chemical formula N PLyVzOs (0, l
54. , V 41.0 ) can be effectively used.

L i x V2O5 (0,024x41.O) and N
The ratio of L1+ and NIL+ (range of χ, y) in ayV:*05:L+(0,15<;y41) is determined by the ratio of L1+ and NIL+ (range of χ, y) in the tungsten bronze structure or a small amount of mixed phase. In this range, the substance exhibits a catalytic effect of oxygen reduction reaction < nr, polar reaction 9, which fully fulfills the function of oxygen sen-IJ-. For substances that deviate from the addition ratio of Na and Na, they become a mixed phase and are composed of locally different substances, resulting in a lack of uniformity in the internal resistance etc. of the catalytic effect described in Section 2. Due to this, sufficient oxygen sensor function cannot be guaranteed.

Carbon powder, acetylene black, Ketjenblack Fj O, etc., which constitute the porous stop in contact with the gas to be measured (°4 materials) increase the number of reaction points where the positive electrode reaction occurs, and facilitate the inclusion of catalysts. It is an effective constituent material in that it has a large surface area that is effective for positive electrode reactions, and has sufficient conductivity to facilitate the movement of m molecules associated with positive electrode reactions.

Porous metals such as porous Niracle are also effective as porous positive electrode components for the same reason, but when using this material, it is important to avoid oxygen reduction and heterogeneity when the metal is dissolved in y + r, m. In order to prevent chemical reactions, the surface must be protected by means such as carbon spray.

Due to these 44 different porous ', PE jli (when composing the color, the FIX solution is positive (in order to prevent rain from leaking 'C through the J↑I11 hole in the bottle, it is mixed with the OJ fee). Water repellent agents such as applying Teflon powder, Teflon spray, etc. to the surface, or pasting a porous Teflon sheet on one side of the porous positive electrode that is in contact with the gas to be measured. Waterproofing treatment using
Put C.

A porous positive (i@Lt) in contact with the gas to be measured, a mixed powder consisting of the above carbon powder, water repellent, and transition metal complex is molded and pressed together with a metal mesh of nickel, silver, etc., and then heated. It can be produced by firing.

In the present invention, is the alkali metal vanadate listed under 2 broken down? +1115+u porosity in contact with gas side %j jI',
The high performance of the oxygen sensor impregnated with the electrode is due to the fact that these alkali metal vanadates are effective reduction catalysts for oxygen gas. In other words, is it easy to adsorb oxygen gas and the positive electrode? lf, it is easy to supply children to T for smooth polar reaction, and the generated intermediate (acidic 11
When using chlorine, chloride: H20□, alkaline yti
, f 1st position using buttocks P1: no2-) minute 1'+'f
The speed increases.

Therefore, the value of Tit input to the acid accumulation concentration 11'CX is large, and the response is also quick.

The oxygen sensor according to the present invention can be used without applying a current to the seedlings, so it does not require a constant current source, which simplifies the measurement system. It has a long lifespan. - Since the oxygen sensor of the present invention measures the open circuit pressure to that extent, it can be used in one sip, without having to deal with severe conditions for dead skin cells, and can be used not only in liquid but also in gel and solid forms. It has the great feature that it is also possible to use y+y, l bamboo yt.

Next, the structure of the oxygen sensor according to the present invention will be explained with reference to the drawings. That is, FIG. 1 shows a schematic cross-sectional view showing a specific example of a porous TI positive electrode structure in contact with a gas to be measured 111, in which 1 shows a tunic material layer and 2 shows a nickel mesh. FIG. 2 is a cross-sectional view of the basic structure of an oxygen sensor incorporating this porous positive electrode. 11T of 5 between the poles, solution 5 (arrangement of layers) α and configuration σ.

6 is a container that stores oxygen sensors, 7 is Gj gas J
i7peoplere1''. This If-f, 8'r'F'r
The layers can be tfk-like and colloidal, and can also be formed using the solid 711, I!+'N material of (a).

In addition, when incorporating porous supernatant I ('', TIF, polar layer 1?lf, W(quality j threat 5, nickel mesh wave 1
Rule 51! [To the gas] Turn to 51 so that it will freeze! Null.

As a result, r+'r, 717. l
Properties, gas and ■, polar powder three, tl field 1111 is formed 7; Σ. Note that the nickel mesh 2 has Tl'1. is provided as a support and a current collector for the Giribetsu layer 1.

At this time, in order to extend the life of the electrode, a water repellent agent is added to the outside of the metal mesh that is in contact with the gas to be measured.
4<I: Even if the sheet is crimped or treated with a water repellent by spraying, good.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited by the mouthfeel.

Example 1 5'fyIiσ with different compositions under the conditions shown in Table 1 below
, )/lithium thenadate was prepared. These compounds′
The phase of the snout (composition + 114 structures) was identified by X-ray diffraction.

Table 1 Next, 020 g of carbon powder (passed through 100 meshes), 0.12 g of Teflon powder (passed through 50 meshes), and 008 g of the 4 squares of vanodate shown in Table 1 were frozen and crushed. J is also combined, and the mixture of these four types is 20 m in diameter,
, Nikkei 7L net (50 mesh) is placed inside the disc mold.
Heat for 130 minutes in a dry C'?A at 130''C, then press at a pressure of 400~, and
A porous positive electrode was produced by heat treatment in a 0°C furnace for 30 minutes.

TIT, as a solution 1ji, use engineering N K O+1 as fvi, and as negative zinc, TI"1.Ike type j1 silicon sensor is made 4°1゛6, and N2-0□ mixed gas with different 02 concentration. 1, porosity 1■ positive electrode 71. > m, position (E1
The oxygen partial pressure dependence of the saturated calomel electrode was investigated. The results are shown in Section 31A.

That is, Fig. 3 shows the oxygen partial pressure im at the r Here is a graph showing A is L J, o, 02 VzO
Porous positive electrode containing s,” IJL J, o, 0
8 Vz 05, C is J, l J, 0.2 V2O5
, D is TJ i 0.6 V2o5, E is T, 11.
Fll of porous positive electrode containing OV,,05 (box m
, indicating a change in position.

According to the third PyJ, Fll due to changes in oxygen gas partial pressure
.

As for the change in the polar position, when 0□ causes a partial pressure change from 1% to 100%, and vice versa, when the partial pressure changes from 100% to 1%, the positive electrode containing Li O, 08V2O, +o, 3 s ov ~ -1-0,430V (versus saturated calomel electrode, same below), Li 0.2 V,,
OI, a positive electrode containing 4-0. A17V~O, A6'l
V, regardless of the direction of change in partial pressure.
, 4i IF, the positioning is uJ inverse and ′Ij constant υ, and the tail of the ytt position Kuu, which is Boo against change, is the answer ('zud'
I did it. Sunta, J, 10.02 V2O5, ■)j
-06■205, L 11. When similar 02 partial pressure changes were made for porous positive electrodes containing OV2O, respectively, tFt'tL, -1-0,320V ~ +
0.372V, -1-0308~+0.355V,
A small hysteresis occurred in the range of -1-0,255 V to +0,293 V and showed an 11-position change. However, this hysteresis is a function of the oxygen sensor; there is no problem.
The response of changes in the at position corresponding to changes in partial pressure was also slow. In all the porous positive electrodes in Examples II-+J, there was no temporal change in the m position, and the positive electrodes were stable for a long period of time.

Example 2 3F sodium vanadate salts having different compositions were prepared in the cases shown in Table 2 below. As a result of XiW diffraction, these substances were all single-phase.

Next, carbon powder (100 mesh 1 addition) 0.20
g, Deflon powder (passed through 50 meshes) o, 12
g and the three types of sodium vanadate and salts o and osy shown in Table 2 above were freeze-pulverized and mixed, and these were placed in a nickel net (
50 mesh), and do the same as in 1 on the skill level side.
A porous 1ij, i positive electrode was produced.

Furthermore, a Kasuriike type oxygen sensor was assembled in the same manner as in Example 1, and Fir, h,
Flu position (II:, versus saturated calomel 71-f, (i
The dependence of acid A4 on partial pressure of (anti) was investigated. The results are shown in Figure 4.

That is, FIG. 4 is a graph showing the oxygen partial pressure dependence of the 1st position of the porous positive electrode of the oxygen sensor in this example, where F is N FLo, 15
Porous gusset I positive containing Vz 05 (L a is Na
0.176 V2O5, H is p+ FL ]-, OV
11i of porous positive electrodes having η of 2o and η, respectively.

(The bottle shows a change of 1111 °C.

According to FIG. 4, electrode F[T] due to changes in oxygen partial pressure.

The change in position is 0□ partial pressure from 1% to 100%, and conversely 100%.
When changing from % to 1%, Na 0.15 V2O, +0.07 V when containing (vs. saturated calomel ■, same below pole) ~ -1-0,111 V %N FLO, l 76
In the case of V2O5-containing treatment → -0,072 to -1-0,10
5V, N a 1. OVz 1,000 in case of O5 sentry.
It was in the range of 108 V to 10,15.5 V. 7J response of electrode m corresponding to partial pressure change was stable for a long period of time, with no temporal change of about d" and about f%.N
a1. Although some hysteresis occurs when OV2O5 is contained, there is no problem with the function of the oxygen sensor.

As is clear from the explanation in Part 2, L j, x
VzOs (Q, Q2iX41.○), N,
y■20. In the oxygen sensor of the present invention, in which a porous positive electrode containing an alkali metal vanadate such as (0,15,<y,plo) is in contact with the constant gas side, the porous positive electrode has a It responds to changes in the potential by adjusting the magnitude of the potential change to a sufficiently large extent, and exhibits long-term stability and excellent characteristics. For this reason,
The oxygen sensor incorporating this porous stop rod can quickly and reliably measure changes in the oxygen concentration in the gas being measured, is stable over a long period of time, is extremely reliable, and has high practical value. Become.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a porous positive electrode in contact with a gas to be measured, FIG. 2 is a cross-sectional view of the basic structure of the oxygen sensor in the present invention, and FIG. 3 is an embodiment of the present invention on the fourth side. This is a 1°h characteristic diagram showing the oxygen partial pressure dependence on the porous layer of 1.2 (Frj of 11μ). 1... m polar interest layer, 2... nickel net making,
3... Porous positive electrode, 4... Negative electrode, 5...
・・H iura 1i layer, 6・・・・Fig. 1
Figure 2

Claims (1)

[Claims] By providing a tonium layer between the metal forming the negative electrode and the positive electrode in contact with the gas to be measured to form a metal-air type nl, the force between the two electrodes can be increased. In the oxygen sensor to be measured, the side that comes into contact with the gas to be measured (1
)T'M& is L1Xv2o, (o, 02-16x≦
Made from porous carbon or porous metal containing 3% to 50% alkali metal vanadate, such as Na y Vt Oa (o, 1 4., 1. O), etc. Oxygen sensor with 11'', Y sign.