JP2541530B2 - Solid electrolyte device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite electrode for a solid electrolyte.
The devices include, for example, oxygen sensors, oxygen pumps, fuel cells, steam electrolyte cells and electrochemical reactors.

The solid electrolyte device of interest usually consists of an electrolyte membrane held between two electrodes and permeable to oxygen ions. Examples of solid electrolyte materials include zirconium oxide partially or fully stabilized by the addition of calcium oxide, magnesium oxide, yttrium oxide, scandium oxide or one of several rare earth oxides. , Thorium oxide, or cerium oxide with the addition of calcium oxide or yttrium oxide or a suitable oxide of a rare earth oxide. Electrodes for these devices are usually composed of porous membranes of metals such as Pt, Ag, Au, Pd, Ni, and Co, or highly conductive metal oxides. These electrodes participate in charge transfer reactions by donating or accepting electrons between gaseous oxygen molecules or fuel (such as hydrogen, carbon monoxide or methane) and oxygen ions in the solid electrolyte. The electrodes also help catalyze the reaction. For example, Pt, the most commonly used electrode material for solid electrolyte oxygen sensors and oxygen pumps, is used at temperatures above 600-700 ° C for oxygen charge transfer reactions (O ₂ + 4e20 ^2- ) at the electrode / electrolyte interface. Shows high catalytic performance. The physical and chemical properties of the electrodes play an important role in determining the response rate and efficiency of solid electrolyte devices.

The potentiometric sensor or Nernst sensor is completely
Or partially stabilized zirconium oxide and O ₂
/ O ² -Oxygen ion conducting membrane of solid electrolyte (having negligible electronic conductivity) like two electrodes reversible to redox equilibrium. When both electrodes of such a cell are exposed to different oxygen partial pressures, an emf occurs across the cell. Its emf is given by the Nernst equation for air as the reference atmosphere: E (mV) = 0.0496T Log (0.21 / pO ₂ ), where pO ₂ is the unknown oxygen partial pressure and T is the absolute temperature. The emf is measured by making electrical contact with the electrodes.

Australian Patent No. 466,251 describes various geometrically different solid electrolyte oxygen sensors. The most commonly used form is an open-ended or closed-end tube made of solid electrolyte only. Another design uses a disk-shaped or pellet-shaped solid electrolyte enclosed in one end of a metal or ceramic support tube. In all cases, the reference environment, which is typically air, is maintained on one side of the tube (typically inside),
The test environment is exposed on the other side of the tube.

In potentiometric sensors, the ability of the electrodes to carry the current is not critical, but especially at low sensor temperatures (below 600 ° C)
In the above application, an electrode having a high charge transfer rate is particularly required. At 600 to 700 ° C. or higher, a solid electrolyte oxygen sensor having a noble metal electrode is generally used. Below their temperature, they have a low response rate, high impedance, easy to pick up electrical noise, large error, and exceptionally high sensitivity to impurities in flue gas.

Other solid state semiconductor electrochemical devices such as oxygen pumps, fuel cells, steam electrolyzers and electrochemical reactors can consist of fully stabilized or partially stabilized zirconium oxide electrolyte tubes, Electrodes are coated on the outside or inside of the tube. Several such cells can be connected in series, in parallel, or in series and in parallel to achieve the desired customization. For example, in an oxygen pump, several cells can be operated in concert to increase oxygen production. In a fuel cell configuration, the highest theoretical voltage that can be drawn from a single cell is about 1.0-1.5 volts, so several small cells can be connected in series and parallel to increase the total current and voltage. Can be connected to. In all of these devices, the current capacity of the cell and thus the overall efficiency is determined by (i) the electrode / electrolyte interfacial resistance to the charge transfer reaction, and (ii) the electrolyte resistance. The interfacial resistance to charge transfer depends primarily on the electrochemical behavior, physical and chemical properties of the electrode. Due to the high resistance of the electrode and electrolyte at low temperatures, the battery must be operated near 900-1000 ° C. Operating the cells at low temperatures is important to maximize efficiency and extend cell life. Voltage loss in the electrolyte can be reduced by using a thin, mechanically strong electrolyte membrane. Conventional metal-only or metal oxide-only electrodes have high resistance at low temperatures, so the electrode / electrolyte interface Better electrode materials need to be created to reduce the overpotential loss across.

Electrodes (n-type) or hole-conducting (p-type) semiconductor metal oxides combined with a noble metal such as Pt (this electrode is hereinafter referred to as a composite electrode) have only metal or metal oxide only. We have found that it is a much better electrode than the electrode. The use of these electrodes in oxygen sensors reduces the operating temperature to 300 ° C, well below 600 ° C, which can be achieved with conventional metal or metal oxide electrodes.
Also, when those composite electrodes are used in other solid state electrochemical devices, they increase their efficiency and make them available at temperatures below those achievable with conventional metal-only or metal oxide-only electrodes. It can be operated. Further, the composite electrodes have excellent physical properties such as resistance value-particle growth, and adhere well to the surface of the electrolyte, as compared with metal electrodes or metal oxide electrodes.

The reason for the improved electrochemical behavior is due to the components of the composite electrode involved in the dissociation / diffusion / charge transfer reactions and the electrode / electrolyte interface.

Accordingly, one object of the present invention is to provide an ideal (ie, Nernst) under oxidizing excess gas conditions at temperatures well below the temperatures at which conventional noble metal or metal oxide electrodes begin to exhibit non-ideal behavior. The object is to obtain a solid electrolyte oxygen sensor that enables the emf to be generated in the solid electrolyte oxygen sensor. Another object of the present invention is to
The aim is to obtain an electrode that retains the good low temperature behavior of the electrode even after being exposed to temperatures as high as 900 ° C.

In solid electrolyte devices such as oxygen pumps, fuel cell electrochemical reactors and steam electrolyzers, the low electrode / electrolyte interfacial resistance to charge transfer reactions, and thus the ability of the electrodes to carry current and current-potential characteristics, is a potentiometric oxygen sensor Is extremely important unlike.

Yet another object of the present invention is to increase the efficiency of oxygen pumps, fuel cells, electrochemical reactors and steam electrolyzers by operating at low temperatures to reduce energy loss and extend useful life. , To obtain electrode materials for oxygen pumps, fuel cells, electrochemical reactors and steam electrolyzers.

Therefore, according to the invention, a composite electrode for use in a solid electrolyte device comprising a mixture of a noble metal and a semiconductor metal oxide whose conductivity is electronic (n-type) conductivity or hole (p-type) conductivity. The material is obtained.

The noble metal is preferably platinum, silver, gold, iridium, or rhodium, or palladium, or a mixture of any two or more of these metals, or an alloy.

The semiconducting metal oxide may be selected from any suitable oxide having other desirable attributes such as high electronic conductivity, good temperature stability and good chemical compatibility with solid electrolytes. Usually the oxide is selected from one or more transition metals, lanthanides or actinides. In this specification, "transition metal" means atomic number
It is a metal having 21-30, 39-48, and 72-80.

For use in solid electrolyte devices such as oxygen sensors, oxygen pumps, fuel cells, electrochemical reactors or steam electrolyte batteries, the composite electrode material can be provided in the form of a surface layer on top of the solid electrolyte body.

According to one embodiment of the present invention, the surface layer may be composed of a thin porous film of a mixture of noble metal and semiconductor oxide particles.

The present invention also includes a method of manufacturing the composite electrode material of the present invention.

The components of the electrode material can be applied to the surface of the solid electrolyte by suitable known coating methods such as coating, sputtering, ion implantation, spraying or other in situ chemical or electrochemical techniques. Although it is preferred to prepare the semiconductor oxide prior to deposition, the semiconductor metal oxide may be added by adding precursors or by thoroughly mixing the individual components of the oxide material (or the compounds that give rise to them) and sintering the coating. It is preferable to manufacture the product. An oxide material (or its constituent oxides) is added to the noble metal. Any elemental metal or any suitable compound capable of being decomposed into metal with heat can be used.

The electrode material of the present invention makes it possible to manufacture a solid electrochemical cell having a low interfacial impedance between the electrode and the solid electrolyte. Similar devices with conventional electrodes composed of noble metals only, or metal oxides only, exhibit much higher electrode electrolyte interface impedances.

The electrode material of the present invention also allows the fabrication of oxygen sensors whose performance under typical air overburning conditions meets the Nernst equation down to temperatures as low as 300 ° C. The same sensor with conventional electrodes composed of noble metals only or metal oxides only deviates significantly from the Nernst equation below 450 ° C. Therefore, it can be used to measure the oxygen potential of gases (eg, boiler flue gas, internal combustion engine exhaust) in the temperature range of 300 ° C. to 700 ° C. using the electrode-provided sensor of the present invention.
In that temperature range, the conventional electrode is Nernst emf
Requires auxiliary heating to generate. For gases below 300 ° C., the electrodes of the invention can
Although the sensor can be operated with auxiliary heating to the range of 0 ° C to 400 ° C, conventional electrodes are generally heated above 700 ° C. The lower operating temperature reduces the risk that occurs when a heated sensor is placed in the smoke of a combustion device such as a boiler.

The present invention also includes a solid electrolyte incorporating the solid electrode of the present invention.

 In the following description, reference will be made to the accompanying drawings.

FIG. 1 shows a longitudinal section of an oxygen sensor using the electrode of the present invention, and FIG. 2 shows one of the batteries used in a solid electrolyte device such as an oxygen pump, a fuel cell, an electrochemical reactor or a steam electrolyzer. shows the embodiment, the composite electrode Figure 3 is the resistance value of the electrode and the (R ₀₎ [(U _0.38 Sc
_0.62 ) O _{2 + x} and PtO ₂ ] composition plots at three different temperatures, FIG. 4 shows the electrode time constant at 600 ° C. and the composite electrode [(U
_0.38 Sc _0.62 ) composed of O _{2 + x} and PtO ₂ ] composition and plot, FIG. 5 shows electrode resistance (R ₀ ) and composite electrode [composed of (CrNbO ₄ and PtO ₂ Fig. 6 shows a plot of the relationship between the composition and the composition of the composite electrode [(CrNbO ₄ and PtO ₂
Fig. 7 shows a plot of the relationship with the composition of the metal oxide (Fig. 7). Fig. 7 compares the current-voltage characteristics of a metal oxide (CrNbO ₄ ) electrode with a composite electrode consisting of 75 wt% + 25 wt% PtO _2. , FIG. 8 includes comparable results for sensors provided with individual metal oxides or metals that make up the composite electrode,
One composite electrode graphs material shows the performance of the oxygen sensor provided according to the present invention, the 9 to 17 FIG various sensor performance of the semiconductor metal oxide and the metal oxide and Pt (added as PtO ₂₎ FIG. 18 is a graph comparing the sensor performances of the composite electrodes constituting the above, and FIG. 18 is a graph comparing the individual performances of the CrNbO ₄ electrode and the PtO ₂ electrode with the composite electrode composed of two kinds of materials with various ratios.

In Figures 8-18, the solid line represents the theoretical response and the symbols represent the measured response. For clarity, number 8 ~
The ordinate scale in Figure 18 is shown separately for each set of data, as indicated by the scale line on the right side of each figure.

One embodiment of a complete sensor constructed of the electrode material of the present invention for use in gas is shown in FIG. One end of the hollow ceramic body 10 is closed by a solid electrolyte disc 11. The electrodes 12 and 13 of the present invention are arranged on the inner surface and the outer surface of the disc 11, respectively. Electrical contact to the electrodes is made by the metal wires 14,15. The wire 14 is pressed against the electrode 12 by a spring load (not shown) exerted by an insulating tube 16. Tube 16 can also be used to carry a reference gas, such as air, to electrode 12. If the tube 16 is a perforated tube, thermocouples (lines 14 and 17) can also be passed through to determine the temperature of the electrolyte disc 11.
In that case the wire 14 forms one leg of the thermocouple.

Instead of the wires 14,15 for making electrical contact to the electrodes 12,13, for example, a layer of platinum, gold, palladium, silver, or an alloy of these metals, or a layer of the electrode material itself is used as the inner surface of the ceramic body. What is attached to the outer surface and extended from the electrodes 12, 13 to the open end of the sensor can be used. The layers could completely cover the surface of the ceramic body,
It may be a continuous strip-shaped layer that covers only a part of the ceramic body 10.

The external electrode 13 is not required for use with molten metal. The electrical contact is made by means of a wire 15 attached to the sensor but not in direct contact with the solid electrolyte disc 11, or as described above, by means of a metal layer on the outer surface or ceramic body, or on the sensor. Another nearby conductor can be used to do the melting metal near the sensor. For long term measurements it is important that the external electrical contacts are not dissolved in or attacked by the molten metal. If a reference gas, such as air, is used, it requires internal electrodes 12 and electrical contact 14.

Alternatively, for use with gases or molten metals, the solid electrolyte may be a closed-end tube or other similar hollow shape and used in place of the disk 11 and ceramic body 10. it can. Another that is particularly suitable when measuring gases is to use a reference environment, for example air, as an external electrode.
The gas or molten metal to be contacted and tested at 13 occupies the interior of the sensor. In the case of gas,
The gas can be delivered to the inner electrode 12 by a tube 16.

One embodiment of a battery for use in a solid state electrochemical device other than an oxygen sensor is shown in FIG. A thin porous layer 21 of the electrode of the present invention is deposited on a hollow porous ceramic substrate 20.
An impermeable electrolyte layer 22 is then formed over this electrode by a suitable combination of ceramic processing techniques.
Then, an external electrode layer 23 of the material of the present invention is formed on the outer surface of the electrolyte layer. An alternative to this structure is the use of a porous substrate support without coating the electrodes of the present invention on the inner and outer surfaces of a pre-sintered electrolyte tube.

The following examples demonstrate the production of composite electrodes of the present invention and the behavior of solid electrolyte devices incorporating those electrodes.

Example 1 Materials were selected from a wide range of semiconductor oxides to demonstrate the superior properties of the composite electrode of the present invention over individual metals or metal oxides. They include: (i) different crystal structures,
(Fluorite, pearlite, orthorhombic, hexagonal, monoclinic, etc.);
(Ii) varying degree of non-stoichiometry (eg V ₂ O ₅ , LaN
iO ₃ and Cr ₂ O ₃ vs. PrO _2-y , TbO _{2 -y} , (Pr _z Gd _1-z ) O _2-x , (N
d _0.9 Sr _0.1 ) CoO _3-x etc.); (iii) Simple transition metal oxides (CoO, NiO, MnO ₂ , ZnO etc.); (iv) Rare earth oxides (Ce)
_{O 2-x, PrO 2-} y, TbO 2-y); (v) Compound between two or three metal oxide _{(CrVO 4, CrNbO 4, LaCrO} 3, PrCoO 3,
(La _0.8 Sr _0.2 ) CrO _3-x , (Nd _0.9 Sr _0.1 ) CoO _3-x, etc. );
Solid solution [(U _z M _1-z ) O _{2 ± x} (M = Sc, Y, Pr, Dy), (Pr
_z Gd _1-z ) O _2-x ]; and (vii) n-type (electron conduction) or p-type (hole conduction) conduction type material.

Simple metal oxides and rare earth oxides were obtained from a chemical manufacturer. Solid solutions and compounds between two or more metal oxides were prepared by one of the following methods.

(I) A metal salt that gives the required composition is dissolved in an aqueous medium and then coprecipitated with an aqueous ammonia solution. The coprecipitated powder was dried at high temperature and calcined.

(Ii) The second method is to use metal nitride (only the desired amount).
Dissolve in water and carefully dry the solution. The dried material was then powdered and sintered at high temperature.

(Iii) The transition metal oxide was thoroughly mixed in ethanol, dried and heated to high temperature. It is necessary to grind and calcine the powder many times to complete the reaction.

Completion of the reaction between the metal oxides is done by taking an X-ray diffraction photograph of the calcined powder and comparing the results with the literature data.

 The various metal oxides tested are shown in Table 1.

The subscript "x" indicates a large deviation from the ideal oxygen / metal atomic ratio for the oxide of interest, and "y" indicates a large deviation.

Example 2 First by grinding the powdered oxide with a 25% solution of triethylene glycol until the ethanol has evaporated
Fine pastes in triethylene glycol of the various oxides shown in the table were prepared. This operation was repeated many times until a uniform and consistent paste was obtained.

Example 3 Several kinds of platinum dioxide having different ratios (U _0.38 Sc _0.62 )
O _{2 + x} was prepared by the method described in Example 2. Table 2 shows the composition and name of the composite electrode.

Example 4 By the method described in Example 2, several pastes with different ratios of platinum dioxide and CrNbO ₄ were prepared. Table 3 shows the composition and name of the composite electrode.

Example 5 A fine paste of a composite electrode containing a mixture of 25 weight percent triethylene glycol and 75 weight percent metal oxide was prepared by the method described in Example 2. The composition of the composite electrode is shown in Table 4.

Example 6 Some composite electrodes from Tables 2-4 were heated in air at 600 ° C for 10-15 hours. The X-ray diffraction pattern of the heated electrode shows that platinum dioxide decomposed to platinum without reacting with the metal oxide. In all the tests performed on the composite electrodes to determine the electrode behavior of the composite electrodes, the composite electrodes were preheated at 600 ° C. to decompose platinum dioxide into platinum. In all tests, the composite electrodes consisted of platinum and metal oxide, but for convenience, these composite electrodes were assumed to consist of metal oxide and platinum dioxide. Pt /
The final weight ratio of metal oxide is only slightly different from the weight ratio of PtO ₂ / metal oxide.

Example 7A The composite electrode of Example 3 (Table 2) was treated with 7 mol% Y ₂
O ₃ +93 mol% ZrO ₂ (YSZ7) applied on both flat sides of sintered disc (diameter 9.6-9.7 mm, thickness about 2.5 mm, theoretically about 95% for density electrolyte disc) , Heated in air at 600 ° C. for 15 hours. Then USN / YSZ7 / USN
Complex impedance measurements were performed on (N = 1,2,3,4,5,6 or 7) cells over a temperature range of 450-600 ° C. and a frequency range of 0.5 mHz-1 MHz. Impedance measurements were made on a Solartron 1174 frequency response analyzer. The electrode resistance (which determines the rate of the oxygen exchange reaction at the electrode / electrolyte interface) and the time constant τ ₀ , which determines the response rate of the solid state electrochemical cell to variations such as changes in oxygen partial pressure, are complex Determined by standard analysis of in-plane impedance data.

FIG. 3 shows the relationship between the electrode resistance value R ₀ and the weight percentage of platinum dioxide at various temperatures. The graphs show a minimum at 15-35 wt% PtO ₂ . Simply 15wt% Pt
It is dramatic that the electrode resistance value is reduced by about an order of magnitude only by adding O ₂ . With a PtO ₂ content of 35 wt% or more,
The electrode resistance value is increasing very rapidly.

FIG. 4 shows a graph of the relationship between log τ ₀ and the weight percentage of platinum dioxide at 600 ° C. This graph also shows the minimum value near 40 wt% PtO ₂ .

Example 7B The composite electrode described in Example 6 (Table 3) was applied to a 10 mol% yttrium oxide + 90 mol% zirconium oxide electrolyte disc and impedance measurements were made as in Example 7A. FIG. 5 shows a graph of the electrode resistance value,
FIG. 6 is a graph showing the relationship between the weight percentage of platinum dioxide and the time constant for CNX / YSZ7 / CNX (X = 1,2,3,4,5 or 6) cells at 600 ° C. The graphs show that the electrode resistance and the time constant are minimum values near 25 wt%.

Example 7C The composite electrode described in Example 6 (Table 3) was coated with 10 mol% yttrium oxide + 90 mol% zirconium oxide on an electrolyte disc and impedance measurements were performed as in Example 7A. Fig. 5 shows a graph of electrode resistance, and Fig. 6 shows CNX / YSZ7 / CNX (X = 1,2,3,600 at 600 ℃.
4,5 or 6) is a graph showing the relationship between the weight percentage of platinum dioxide and the time constant for a battery. The graphs show that the electrode resistance and the time constant are minimum values near 25 wt%.

Constant and electrode resistance value when the composite electrode containing a PtO ₂ in 25～40Wt% is at least one order of magnitude smaller than the constant and the resistance value when any of the components of the composite electrode. The results clearly show that the oxygen exchange reaction at the composite electrode / electrolyte interface is much faster than the oxygen exchange reaction at the metal / electrolyte interface or the metal oxide / electrolyte interface. The results also indicate that both components of the composite electrode are involved in the kinetics of oxygen transfer.

Those phenomena observed for the materials of the present invention are unique and have not previously been observed or reported.

Example 8 To determine the current-voltage characteristics, two cells were used, one was a metal oxide only (CrNbO ₄ ), and the second was 75 wt% CrNbO ₄
An electrode consisting of +25 wt% PtO ₂ is provided, but 10 mol%
It was prepared by applying the respective electrodes to both flat sides of a sintered disc of yttrium oxide + 90 mol% zirconium oxide electrolyte. Temperature of each cell in air
The temperature was raised to 700 ° C., and the cell was allowed to stand for several hours until it was in equilibrium with the surroundings before measurement was performed on the cell. Constant current cutoff technology (galvanostatic)
Current interruption technique) 500-700 ℃
Was recorded over several temperatures. in this way,
A constant current was passed through the working electrode-electrolyte-counter electrode until a steady voltage was reached. Then a fast electronic switch (switching time (0.1 microseconds) interrupted the current, and a transient recorder recorded the voltage as a function of time (10 microseconds after the current was interrupted). The voltage drop in the solid electrolyte (ohmic drop) and the voltage drop between both electrode / electrolyte interfaces (overpotential) are given by the analysis of. The current density (current is normalized to 1 cm ² of electrode / electrolyte contact area) relationship is compared with the corresponding metal oxide only electrode, and the results show the overpotential at the composite electrode / electrolyte interface. Electrode with loss only corresponding metal oxide /
It clearly shows that it is much less than the overpotential loss at the electrolyte interface. These experiments show that composite electrodes have distinctly superior properties to metal oxide only electrodes in applications where the electrode's ability to carry current is important.

Example 9 An oxygen sensor of the kind shown in FIG. 1 was manufactured using the electrodes shown in Tables 1-4. The electrolyte disk used in each case consisted of a sintered mixture of 50 wt% alumina and 50 wt% zirconium oxide-scandium oxide containing 4.7 mol% scandium oxide.
A sensor body was manufactured by eutectic welding a solid electrolyte disc to an alumina tube at high temperature. A complete sensor was fabricated by applying the electrode under test (Pt, metal oxide, or a composite of PtO ₂ and metal oxide) to both flat sides of a welded electrolyte disc. 60 sensor assembly
It gradually heats at 0 ° C to burn triethylene glycol and decompose PtO ₂ into Pt in the case of a composite electrode.

The performance test of the sensor was conducted at 300 ° C to 600 ° C.
These tests consisted of (i) determination of the cell voltage (E) with air at both electrodes, air at the inner electrode and oxygen-nitrogen mixture (1-100 percent oxygen) at the outer electrode, and (ii) It consisted of the effect of changes in internal air flow rate on the order of one digit on the cell voltage, and (iii) the measurement of sensor resistance by air at both electrodes. Most of the testing was done at 25 ° C temperature intervals between heating and cooling cycles. In order to show that the composite electrode has superior properties to the individual components, first to fourth
All 81 or more electrodes were tested, including all electrodes shown in the table.

Table 5 compares the sensor resistance values at 600 ° C. of the sensor provided with the composite electrode and the sensor provided with the electrode only of the individual metal oxides. Those resistances also include electrolyte resistances (determined by impedance dispersion analysis of some cells). Its electrolyte resistance is 600 ℃
At 0.6 to 1.2K ohms. The resistance value of a sensor provided with a composite electrode is always much lower than the resistance value of a sensor provided with an electrode of semiconductor metal oxide only. Since the resistance of sensors provided with metal oxide only electrodes is much higher, they are extremely sensitive to electrical noise picked up at temperatures below 400-500 ° C. In contrast, sensors equipped with composite electrodes did not exhibit such sensitivity even at temperatures as low as 350 ° C.

Sensors equipped with oxide-only electrodes or platinum electrodes have large zero error (both electrodes have air) and show a large deviation from the Nernst relationship (air on the inner electrode, oxygen-nitrogen mixture on the outer electrode). There is). In contrast, the composite electrode tip operated satisfactorily up to 350 ° C or below. Figures 8-18 compare the results of several sensors provided with the electrodes shown in Tables 1 and 4.

In general, a sensor provided with an oxide-only electrode or a platinum electrode is much more sensitive to changes in the flow rate of the substrate than a sensor provided with a metal oxide + PtO ₂ electrode.

The results clearly show that the composite electrode of the present invention has much lower temperature performance than the metal oxide only electrode or the porous platinum electrode on the solid electrolyte oxygen sensor. In particular, the composite electrode material ensures that the oxygen sensor can operate at temperatures as low as 300 ° C., well below the limits of similar sensors provided with porous platinum or metal oxide electrodes.

Example 10 To compare the response of a metal oxide only electrode and a platinum electrode to a rapid change in oxygen concentration in a gas flow and the response of a metal oxide + PtO ₂ electrode to a rapid change in oxygen concentration in a gas flow. , 10 mol / Y ₂ O ₃ +90 mol% ZrO ₂ sintered disc (diameter about 0.3 mm, thickness 25-3.0 mm) is coated with metal oxide only electrode or platinum electrode on one flat side, The other side was coated with a metal oxide + PtO ₂ electrode. Both electrodes of the cell were simultaneously exposed to a sharp change in oxygen concentration. Given the different response of both electrodes of the cell, a voltage signal is generated. Voltage −
The sign and shape of the time curve give information about the relative response speed of both electrodes. Measure those at 300 ℃ and 500 ℃
Results for several sets of electrodes at temperatures in between showed that the properties of composite electrodes were superior to metal oxide only electrodes or platinum electrodes. In all cases, the composite electrode composed of metal oxide + PtO ₂
It responded much faster compared to metal oxide only electrodes or platinum electrodes.

Those measurements very clearly show that the composite electrode is much faster for the oxygen exchange reaction compared to the metal oxide only electrode or the platinum electrode.

Claims (10)

(57) [Claims] 1. A solid electrolyte device for oxygen ion conduction, wherein the solid electrolyte is gas impermeable and is selected from the group consisting of calcium oxide, magnesium oxide, yttrium oxide, scandium oxide, and rare earth metal oxides. It is selected from the group consisting of zirconium oxide, hafnium oxide, thorium oxide, cerium oxide doped or alloyed with one or more oxides, said solid electrolyte having at least one electrode consisting of the following mixture: (A) Platinum, silver, gold, palladium, iridium or rhodium, and a noble metal selected from the group consisting of mixtures or alloys of two or more of these metals as the minority part, and (b) from atomic number 24 Oxides of transition metals of up to 30; oxides of metals of atomic numbers 49 to 50; Oxides and complex oxides consisting of one or more of these metal oxides, or mixtures of two or more of the above oxides or complex oxides, provided that the complex oxide or oxide mixture containing uranium oxide is The semiconductor metal oxide having electron (n-type) or hole (p-type) conductivity selected from is included in a large number of parts, and the noble metal has a time constant in comparison with a noble metal alone or a semiconductor metal oxide alone. And a solid electrolytic device characterized in that it is present in an amount from 40% to 40% by weight sufficient to reduce the electrode resistance of the electrode. 2. Device according to claim 1, characterized in that the noble metal is present in the electrode in a weight percentage of 15-40%. 3. A device according to claim 1 or 2, characterized in that the semiconductor oxide component is one or more single metal oxides, compounds or other solid solutions. Device to do. 4. The device according to claim 1 or 2, wherein the semiconductor oxide component is a mixture of one or more single metal oxides, compounds or solid solutions. A device characterized by. 5. A device according to any one of claims 1 to 4, wherein the semiconductor oxide component also comprises one or more insulators, ionic conductors or other semiconductor phases. Characterized device. 6. A device according to any one of claims 1 to 5, characterized in that the electrode material is provided in the form of a surface layer on the solid electrolyte body. 7. A device according to any of claims 1 to 5, characterized in that the electrode material is formed as a thin region extending below the surface of the solid electrolyte. 8. A method of manufacturing a solid electrolyte device for oxygen ion conduction, wherein the solid electrolyte is gas impermeable and is selected from the group consisting of calcium oxide, magnesium oxide, yttrium oxide, scandium oxide, and rare earth metal oxides. One or more electrodes selected from the group consisting of zirconium oxide, hafnium oxide, thorium oxide, and cerium oxide doped or alloyed with one or more selected oxides, wherein the solid electrolyte is at least one electrode composed of the following mixture. Having: (a) a minority portion of a noble metal selected from the group consisting of platinum, silver, gold, palladium, iridium or rhodium, and mixtures or alloys of two or more of these metals, and (b) atoms. Oxides of transition metals with numbers 24 to 30, oxides of metals with atomic numbers 49 to 50, atomic numbers 51 to 71 Oxides of lanthanides having, and complex oxides consisting of one or more of these metal oxides, or mixtures of two or more of the above oxides or complex oxides, provided that the complex oxides or oxides containing uranium oxide Excluding a mixture, the semiconductor metal oxide having electron (n-type) or hole (p-type) conductivity selected from is included in a large number of parts, and the noble metal is compared with a noble metal simple substance or a semiconductor metal oxide simple substance. Present in an amount sufficient to reduce the time constant and electrode resistance of the electrode up to 40 percent by weight, the method comprising depositing or forming an electrode on the solid electrolyte. Method for manufacturing solid electrolytic device. 9. The method for producing a solid electrolytic device according to claim 8, wherein the electrode material layer is a porous substrate of an insulator, a porous substrate of an electrolyte, or a porous mixture of an insulator and an electrolyte. Substrate,
Adhering to or forming on at least one of the semiconductor porous substrates, an electrolyte layer and a second composite electrode layer on top of said composite electrode material layer. A method of manufacturing a solid electrolyte device, characterized in that they are respectively attached or formed. 10. The method according to claims 8 and 9, wherein: (a) a semiconductor metal oxide, or a substance or a mixture of substances that produces the oxide by heating, ) A method comprising depositing a layer of a mixture containing a noble metal or a noble metal compound which produces a noble metal by heating, and then heating the layer to form a composite electrode material.