JP2017096659A - Hydrogen concentration measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen concentration measurement device using solid electrolyte, capable of acquiring hydrogen concentration with high accuracy even when oxygen is contained.SOLUTION: A hydrogen concentration measurement device comprises: a proton conductor solid electrolyte 11 consisting of proton conductive ceramics; a pair of a first electrode 12 and a second electrode 13 holding therebetween the proton conductor solid electrolyte 11; a first hydrogen chamber 14 having a sealed space closer to the first electrode 12, for introducing or encapsulating hydrogen (reference gas) of the known hydrogen concentration; a second hydrogen chamber 16 arranged closer to the second electrode 13, for introducing oxygen and a measurement target gas 15 containing hydrogen; and a voltmeter 19 connected to the first electrode 12 and the second electrode 13, for detecting a potential difference between both electrodes. An oxygen adsorption suppression processing layer is provided on the surface of the second electrode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydrogen concentration measuring device that detects the hydrogen concentration in hydrogen gas containing oxygen.

  Hydrogen gas has a low specific gravity when compared with a combustible gas such as methane gas, and is easily leaked. If leaked, hydrogen gas is highly dangerous. Therefore, conventionally, as a hydrogen concentration measuring device for measuring the concentration of hydrogen gas, for example, there are proposals such as a heat conduction type, a catalytic combustion type, and a solid electrolyte type hydrogen concentration meter.

  As this solid electrolyte type hydrogen concentration meter, a method of measuring the hydrogen concentration using a proton conductor has been proposed (Patent Document 1, etc.). In this hydrogen sensor disclosed in Patent Document 1, a proton conductive solid electrolyte is provided with a pair of a measurement electrode and a reference electrode, and the hydrogen partial pressure of the measurement electrode and the hydrogen gas partial pressure are known and become a standard electrode material. By utilizing the fact that an electromotive force is generated due to a partial pressure difference from the hydrogen partial pressure of the hydrogen-containing gas body, the hydrogen content is obtained by a hydrogen concentration cell.

JP-A-1-291155

  However, since the hydrogen sensor disclosed in Patent Document 1 generally uses a platinum group metal such as platinum as an electrode, it is limited to the detection of the hydrogen concentration in the measurement gas in an oxygen-free state. There is a problem that the concentration of hydrogen contained in the atmosphere in which air or oxygen coexists cannot be directly measured. This is because when oxygen is contained in the gas to be measured, the oxygen reacts with hydrogen on the platinum electrode, and the true hydrogen concentration cannot be obtained with high accuracy.

  Therefore, for example, the advent of a hydrogen concentration measuring device that can accurately determine the hydrogen concentration in a gas containing oxygen is desired.

  In view of the above problems, the present invention provides a hydrogen concentration measuring apparatus that can accurately determine a hydrogen concentration even in an atmosphere in which oxygen, air, or oxygen coexists, for example, when measuring the hydrogen concentration in a gas to be measured. The issue is to provide.

  A first invention of the present invention for solving the above-described problem is a proton conductor solid electrolyte made of ceramics having proton conductivity, and a pair of first electrode and second electrode sandwiching the proton conductor solid electrolyte And a first hydrogen chamber into which hydrogen having a known hydrogen concentration is introduced or sealed, and an atmosphere of a gas to be measured containing oxygen and hydrogen on the second electrode side. A second hydrogen chamber, a voltmeter connected to the first electrode and the second electrode and detecting a potential difference therebetween, and an oxygen adsorption suppression treatment layer on the surface of the second electrode Is in a hydrogen concentration measuring device characterized by

  According to the present invention, the influence of oxygen can be suppressed by forming the oxygen adsorption suppression treatment layer, the hydrogen selectivity can be improved, and for example, the hydrogen concentration in hydrogen gas containing oxygen can be measured with higher accuracy.

  A second invention is the hydrogen concentration measuring apparatus according to the first invention, wherein the oxygen adsorption suppression treatment layer is a layer containing fluorine.

  According to the present invention, when the oxygen adsorption suppression treatment layer is a layer containing fluorine, the influence of oxygen is suppressed by fluorine, the hydrogen selectivity is improved, and for example, the hydrogen concentration in hydrogen gas containing oxygen is further increased. It can measure with high accuracy.

  A third invention is the hydrogen concentration measuring apparatus according to the first invention, wherein the oxygen adsorption suppression treatment layer is a layer containing silicon.

  According to the present invention, when the oxygen adsorption suppression treatment layer is a layer containing silicon, the influence of oxygen is suppressed, hydrogen selectivity is improved, and for example, the hydrogen concentration in hydrogen gas containing oxygen is more accurately determined. It can be measured.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the second electrode is composed of any one of a single electrode of platinum or palladium and an alloy electrode containing at least one of platinum or palladium. It is in the hydrogen concentration measuring device.

  According to the present invention, even when a single electrode of platinum or palladium, or an alloy electrode containing at least one of platinum or palladium is used as the second electrode, the oxygen adsorption suppression treatment layer allows, for example, hydrogen in hydrogen gas containing oxygen. The concentration can be measured with high accuracy.

  A fifth invention is the hydrogen concentration measuring apparatus according to any one of the first to fourth inventions, further comprising a heater for heating the proton conductor solid electrolyte to a predetermined temperature.

  It is possible to accurately measure the hydrogen concentration in a hydrogen gas containing oxygen, for example, with a heater at a predetermined temperature atmosphere.

  According to the hydrogen concentration measuring apparatus of the present invention, the hydrogen concentration can be obtained with high precision even when the gas to be measured contains, for example, oxygen.

FIG. 1 is a schematic diagram of a hydrogen concentration measuring apparatus according to the first embodiment. FIG. 2 is a schematic diagram for explaining the principle of hydrogen measurement. FIG. 3 is a schematic diagram of an electrode reaction path for detecting hydrogen in a gas containing oxygen. FIG. 4-1 is a measurement result diagram at 300 ° C. after fluorination treatment on the platinum electrode of Test Example 1-1. FIG. 4-2 is a measurement result diagram at 350 ° C. after the fluorination treatment on the platinum electrode of Test Example 1-2. FIG. 4-3 is a measurement result diagram at 400 ° C. after fluorination treatment on the platinum electrode of Test Example 1-3. FIG. 5-1 is a measurement result diagram at 300 ° C. of the platinum electrode untreated in Comparative Example 1-1. FIG. 5-2 is a measurement result diagram of 350 ° C. of the platinum electrode untreated in Comparative Example 1-2. FIG. 5-3 is a measurement result diagram at 400 ° C. of the platinum electrode untreated in Comparative Example 1-3. 6 is a measurement result diagram after the siloxane treatment of Test Example 2. FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment, and when there are two or more embodiments, what comprises combining each embodiment is also included.

<Embodiment 1>
FIG. 1 is a schematic diagram of a hydrogen concentration measuring apparatus according to the first embodiment. As shown in FIG. 1, a hydrogen concentration measuring apparatus 10 according to this embodiment includes a proton conductor solid electrolyte 11 made of ceramics having proton conductivity, and a pair of first electrodes 12 that sandwich the proton conductor solid electrolyte 11. And the second electrode 13 and the first electrode 12 side in a sealed space, a first hydrogen chamber 14 for introducing or enclosing hydrogen (standard gas) having a known hydrogen concentration, and oxygen on the second electrode 13 side. A second hydrogen chamber 16 for introducing a measurement gas 15 containing hydrogen, and a voltmeter 19 connected to the first electrode 12 and the second electrode 13 for detecting the potential difference therebetween are provided. In the present embodiment, the second hydrogen chamber 16 is provided with an introduction part 17 and an exhaust part 18 for introducing and discharging the measurement gas 15. Note that the second hydrogen chamber 16 may be opened and exposed to the atmosphere of the measurement target gas 15. In that case, the second hydrogen chamber 16 becomes, for example, the atmospheric space of the measurement target gas 15.

Here, the proton conductor solid electrolyte 11 generates an electromotive force according to the hydrogen concentration. The proton conductor solid electrolyte 11 is a ceramic having proton conductivity. The ceramics having a proton conductivity, may be, for example, _{CaZr 1-x (M) x} O 3, SrZr 1-x (M) x O 3, BaCe 1-x (M) x O 3 and the like. Here, M = Y, Yb, and Nd, and x = 0.05-0.1 is typical, but the present invention is not limited to these as long as the ceramic has proton conductivity. .

  The first hydrogen chamber 14 forms a sealed space with the surface of the proton conductor solid electrolyte 11. In a space formed by the surfaces of the first hydrogen chamber 14 and the proton conductor solid electrolyte 11, hydrogen serving as a reference for generating an electromotive force by the proton conductor solid electrolyte 11 (hydrogen of a known concentration (standard gas)) An inert gas fluid containing is enclosed. In addition to the enclosure, the reference fluid may be continuously introduced.

  The first electrode 12 is provided on the surface of the proton conductor solid electrolyte 11 on the first hydrogen chamber 14 side. The first electrode 12 preferably has a structure in which the sealed fluid can easily reach the surface of the proton conductor solid electrolyte 11. The second electrode 13 is provided on the opposite surface of the proton conductor solid electrolyte 11. The second electrode 13 preferably has a structure in which the measurement gas 15 introduced from the introduction unit 17 can easily reach the surface of the proton conductor solid electrolyte 11, for example. The voltmeter 19 detects a potential difference between the first electrode 12 and the second electrode 13. The potential difference output from the voltmeter 19 represents the hydrogen concentration of the atmosphere in the second hydrogen chamber 16.

  The heater 21 heats the proton conductor solid electrolyte 11, the first electrode 12, and the second electrode 13. A heater (not shown) may be provided to control the heater 21 so that the proton conductor solid electrolyte 11 maintains a constant temperature.

  Specifically, the lower limit value of the heating temperature by the heater 21 is equal to or higher than a temperature at which a decrease in responsiveness is observed depending on the resistance values of the first electrode 12 and the second electrode 13 (eg, 200 ° C. or higher), Is maintained within a temperature range lower than the temperature at which hydrogen concentration cannot be measured properly due to hydrogen combustion (for example, 500 ° C.), for example, 200 ° C. to 500 ° C. When the temperature is low, the response can be improved by thinning the electrolyte.

  The hydrogen concentration measuring apparatus 10 having such a configuration measures the hydrogen concentration as follows. By heating the heater 21, the proton conductor solid electrolyte 11 is sufficiently heated to generate an electromotive force according to the hydrogen concentration. The proton conductor solid electrolyte 11 generates an electromotive force according to the difference between the hydrogen concentration (partial pressure) in the first hydrogen chamber 14 and the hydrogen concentration (partial pressure) in the atmosphere of the second hydrogen chamber 16. The magnitude of the electromotive force is detected by the voltmeter 19 and is displayed on the display unit or the like as a value indicating the hydrogen concentration of the atmosphere.

  FIG. 2 is a schematic diagram for explaining the principle of hydrogen measurement. The hydrogen concentration (hydrogen gas partial pressure) in the atmosphere can be calculated from the Nernst equation shown in the following equation (1). If the hydrogen concentration in the first hydrogen chamber 14 on one side is known, the concentration of hydrogen to be detected in the second hydrogen chamber 16 can be determined by measuring the electromotive force E due to the difference in hydrogen concentration.

Here, E is an electromotive force (unit: V). R is a gas constant (8.314 J / K · mol). T is an absolute temperature (unit: K). F is the Faraday constant (96485 C / mol). PH ₂ (1) is a hydrogen gas partial pressure (unit: Pa) in the measurement target gas 15 in the second hydrogen chamber 16. PH ₂ (2) is a known hydrogen gas partial pressure (unit: Pa) in the standard gas of the first hydrogen chamber 14.

  Here, when oxygen (or air) is contained in the measurement target gas 15 containing hydrogen, dissociative adsorption of oxygen on the second electrode 13 becomes a problem. This is because water is generated by the reaction between the adsorbed oxygen on the electrode surface on which oxygen is dissociated and adsorbed and the adsorbed hydrogen, and the hydrogen selectivity is lowered.

Next, the problem of hydrogen concentration detection when oxygen is present in the measurement target gas 15 will be described using the schematic diagram of FIG.
FIG. 3 is a schematic diagram of an electrode reaction path for detecting hydrogen in a gas containing oxygen.
As shown in FIG. 3, a second electrode 13 is formed on one surface of the proton conductor solid electrolyte 11. And when measuring the hydrogen concentration in the to-be-measured gas 15 containing hydrogen and oxygen, hydrogen and oxygen exhibit the following reaction behavior. In addition, the numerical value described in FIG. 3 corresponds to the behavior shown below.
(1) First, hydrogen is dissociated and adsorbed on the second electrode 13.
(2) The surface diffusion of the adsorbed hydrogen is performed, and an anodic reaction occurs.
(3) Electrons are exchanged at a three-phase interface comprising a gas phase / electrode phase / electrolyte phase.
(4) Furthermore, oxygen is dissociated and adsorbed onto the second electrode 13.
(5) The cathode selectivity between the adsorbed oxygen and the adsorbed hydrogen causes a decrease in hydrogen selectivity.

That is, when oxygen other than hydrogen is present in the gas 15 to be measured, the surface of the second electrode 13 undergoes a competitive reaction between the anode reaction represented by the following formula (I) and the cathode reaction represented by the following formula (II). It is assumed that the actual electromotive force appears as the mixed potential.
H ₂ ⇔2H ⁺ + 2e ⁻ (Anode reaction) (I)
2H ⁺ + 1 / 2O ₂ + e ⁻ ⇔H ₂ O (cathode reaction) (II)

  Here, as in the conventional case, for example, when a platinum electrode made of only platinum is used for the second electrode 13, the reaction rate is (I) <(II), and the formula (I) It becomes susceptible to the reaction of II). As a result, when the platinum electrode is used for the second electrode 13, as shown in a comparative example described later, the hydrogen concentration is dissociated from the theoretical value, and it is considered difficult to measure the hydrogen concentration with high accuracy. It is done.

  Therefore, in the present embodiment, an oxygen adsorption suppression treatment layer is provided on the surface of the second electrode 13. By forming this oxygen adsorption suppression treatment layer on the surface of the second electrode 13, it is possible to suppress the influence of oxygen contained in the measurement gas 15 and improve the hydrogen selectivity. Thereby, for example, the hydrogen concentration in hydrogen gas containing oxygen can be measured more accurately. Further, an oxygen adsorption suppression treatment layer may be formed not only on the second electrode 13 but also on the proton conductor solid electrolyte 11.

Here, the oxygen adsorption suppression treatment layer is preferably a layer containing fluorine.
By using a fluorine-containing layer as the oxygen adsorption suppression treatment layer, the influence of oxygen is suppressed by fluorine, hydrogen selectivity is improved, and hydrogen concentration in hydrogen gas containing oxygen, for example, can be measured more accurately Can do.

Further, the metal constituting the second electrode 13 is a single electrode of platinum or palladium. Moreover, not only a single electrode but also a platinum alloy electrode or a palladium alloy electrode made of an alloy containing at least one of platinum or palladium and containing other metals may be used.
Examples of the alloy containing at least one of platinum and palladium include platinum / palladium alloys made of platinum and palladium. In addition, as other metals blended with platinum or palladium to form an alloy, for example, metals belonging to Group 8 to Group 10 in the 5th period and 6th period of the periodic table, for example, ruthenium (Ru) , Rhodium (Rh), osmium (Os), iridium (Ir) platinum group metals, and the fifth and sixth periods of the periodic table, such as silver (Ag) and gold (Au) belonging to the eleventh genus Mention may be made of metals. Therefore, the second electrode 13 can be constituted by an alloy of these metals and platinum or palladium. As a metal to mix | blend, it is good also as a 2 component or more.

  The compounding of the other metal component with respect to platinum or palladium should just contain at least another metal component in platinum or palladium.

[Test Example 1]
Next, the advantageous effects of the present invention will be described using Test Example 1.
In the test, SrZr _0.9 Yb _0.1 O ₃ having a thickness of 1 mm was used as the proton conductor solid electrolyte 11. Further, as the second electrode in the second hydrogen chamber 16 of Test Example 1, 100% platinum electrodes (Test Examples 1-1 to 1-3) were used as the platinum single electrode made of only platinum.

In the test, an inert gas (such as nitrogen (N ₂ ) or helium (He)) containing hydrogen (4 Vol%) at normal pressure was sealed in the first hydrogen chamber 14 as a reference gas. In addition, as the measurement target gas 15, a predetermined concentration of hydrogen was contained in air at normal pressure. The predetermined concentration of hydrogen was 0.3 Vol%, 1 Vol%, and 3.5 Vol%.

The test operating temperatures were 300 ° C., 350 ° C. and 400 ° C., respectively. A 100% platinum electrode was used as the first electrode 12 in the first hydrogen chamber 14.
In addition, the 100% platinum electrode which does not perform a process was used as a comparative example (Comparative Examples 1-1 to 1-3). The measurement results are shown in the figure.

  The surface of the obtained second electrode was subjected to fluorination treatment. This fluorination treatment was adjusted to a concentration of 20 ppm by introducing hydrogen fluoride (HF) into dry air to obtain a fluorination treatment agent. The obtained fluorinating agent was introduced into the second hydrogen chamber 16, and the second electrode 13 and the proton conductor solid electrolyte 11 were fluorinated at 300 ° C. for 32 hours.

  FIGS. 4-1 to 4-3 are test results of 100% platinum electrodes of Test Examples 1-1 to 1-3, and FIG. 4-1 is fluorination of the platinum electrode of Test Example 1-1. FIG. 4-2 is a measurement result diagram of 300 ° C. after the treatment, FIG. 4-2 is a measurement result diagram of 350 ° C. after the fluorination treatment on the platinum electrode of Test Example 1-2, and FIG. It is a measurement result figure of 400 ° C after fluorination processing to the platinum electrode of Example 1-3. Here, the solid line in the figure indicates the theoretical electromotive force derived from the Nernst equation.

  FIGS. 5-1 to 5-3 are test results of 100% platinum electrode untreated in Comparative Examples 1-1 to 1-3, and FIG. 5-1 is an untreated platinum electrode of Comparative Example 1-1. FIG. 5-2 is a measurement result diagram at 300 ° C., FIG. 5-2 is a measurement result diagram at 350 ° C. of the platinum electrode untreated in Comparative Example 1-2, and FIG. It is a measurement result figure of 400 ° C of processing. Here, the solid line in the figure indicates the theoretical electromotive force derived from the Nernst equation.

  Examining the test results, as shown in FIGS. 4-1 to 4-3, when the platinum electrode is subjected to fluorination treatment and used as the second electrode, Comparative Example 1 in FIGS. A tendency closer to the theoretical electromotive force was recognized as compared with the untreated ones shown in 1-3.

  This action / effect is achieved by adsorbing and immobilizing fluorine ions on the electrode surface and / or solid electrolyte surface in the vicinity of the three-phase interface of the gas phase / electrode / solid electrolyte in which the electrode reaction takes place. It is assumed that the surface diffusion is inhibited and the reaction with hydrogen is suppressed.

  This oxygen suppression effect has the same effect when treated with a volatile component when, for example, commercially available fluorine-based rubber is heated at, for example, 100 to 200 ° C., and can be applied as an oxygen adsorption suppression treatment layer. Further, bromine and iodine, which are the same halogen group instead of fluorine, can be applied as a similar oxygen adsorption suppression treatment layer.

<Embodiment 2>
Next, a hydrogen concentration measuring apparatus according to Embodiment 2 of the present invention will be described.
In the present embodiment, the surface of the second electrode 13 contains silicon as an oxygen adsorption suppression treatment layer.
By using a silicon-containing layer as the oxygen adsorption suppression treatment layer, the influence of oxygen is suppressed by silicon, hydrogen selectivity is improved, and for example, the hydrogen concentration in hydrogen gas containing oxygen is measured more accurately. Can do.

Here, it is preferable to use siloxane as a raw material for forming an oxygen adsorption suppression treatment layer containing silicon. Siloxane is a generic name for polymers in which silicon (Si) and oxygen (O) having an organic group such as a methyl group (—CH ₃ ) are alternately bonded (Si—O—Si bond). In particular, it is preferable to use a cyclic siloxane having a cyclic molecular structure skeleton.

  Siloxanes (R-Si-O-Si-R) are low molecular weight compounds such as organic siloxanes in which R is substituted with an alkyl group, and cyclic siloxanes. The latter two are relatively stable compounds. is there.

Among them, the following D3 (trimer), D4 (tetramer), and D5 (pentamer) cyclic siloxanes are preferably used as the electrode treatment agent.
D3: hexamethylcyclotrisiloxane C ₆ H ₁₈ O ₃ Si ₃ , melting point 64 ° C., boiling point 134 ° C. solid D4: octamethyl cyclotetrasiloxane C ₈ H ₂₄ O ₄ Si ₄ , melting point 18 ° C., semi-solid with a boiling point of 175 ° C. D5: Decamethyl cyclopentasiloxane C ₁₀ H ₃₀ O ₅ Si ₅ , liquid with a melting point of −30 ° C. and a boiling point of 210 ° C.

[Test Example 2]
Next, the advantageous effect of the present invention will be described using Test Example 2.
In the test, SrZr _0.9 Yb _0.1 O ₃ having a thickness of 1 mm was used as the proton conductor solid electrolyte 11. Further, as the second electrode in the second hydrogen chamber 16 of Test Example 3, a platinum / gold alloy electrode of platinum / gold alloy (Pt (99 wt%)-Au (1 wt%)) was used.
Siloxane treatment was performed on the surface of the obtained second electrode. This siloxane treatment was adjusted to a concentration of 20 ppm by introducing cyclic siloxane (D4) into dry air to obtain a siloxane treating agent. The obtained siloxane treating agent was introduced into the second hydrogen chamber 16, and the second electrode 13 and the proton conductor solid electrolyte 11 were treated with siloxane at 350 ° C. for 3 hours. It was confirmed by electron probe microanalyzer (EPMA) analysis that the silicon after the siloxane treatment was uniformly attached to the second electrode 13 and the proton conductor solid electrolyte 11.

6 is a measurement result diagram after the siloxane treatment of Test Example 2. FIG. In FIG. 6, ◯ is a measurement result diagram of a 350 ° C. platinum / gold alloy electrode after siloxane treatment, and □ is a measurement result diagram of a 350 ° C. platinum electrode after siloxane treatment. Here, the solid line in the figure indicates the theoretical electromotive force derived from the Nernst equation.
In addition, as an untreated case of a comparative example, in the case of a platinum electrode, it is the measurement result of 350 degreeC of the comparative example 1-2 shown to FIGS. 5-2.
As shown in FIG. 6, a tendency closer to the theoretical electromotive force was recognized as compared with the unprocessed one shown in FIG. Even when a platinum / gold alloy electrode is used, the detection accuracy can be further improved as a hydrogen concentration meter in the atmosphere as in the case of the platinum electrode.

As described above, the siloxane treatment also has the effect of suppressing oxygen, but the effect is significantly better than the fluorination treatment.
Further, it was found that by using siloxane treatment, the theoretical electromotive force can be made asymptotically within the test range, and the hydrogen concentration can be measured with high accuracy.

  As described above, the solid oxide hydrogen concentration meter of the present invention can accurately determine the hydrogen concentration even when oxygen is contained in the gas to be measured. For example, the rocket liquid hydrogen aerospace field, fuel cell, and It can be used in various infrastructure facilities related to hydrogen energy such as hydrogen production, storage and transportation.

DESCRIPTION OF SYMBOLS 10 Hydrogen concentration measuring device 11 Proton conductor solid electrolyte 12 1st electrode 13 2nd electrode 14 1st hydrogen chamber 15 Gas to be measured 16 2nd hydrogen chamber 19 Voltmeter 21 Heater

Claims (5)

A proton conductor solid electrolyte made of ceramics having proton conductivity;
A pair of first and second electrodes sandwiching the proton conductor solid electrolyte;
A first hydrogen chamber in which the first electrode side is a sealed space and hydrogen of a known hydrogen concentration is introduced or sealed;
A second hydrogen chamber on the second electrode side as an atmosphere of a gas to be measured containing oxygen and hydrogen;
A voltmeter connected to the first electrode and the second electrode and detecting a potential difference between the two, and
A hydrogen concentration measuring apparatus comprising an oxygen adsorption suppression treatment layer on a surface of a second electrode. In claim 1,
The hydrogen concentration measuring apparatus, wherein the oxygen adsorption suppression treatment layer is a layer containing fluorine. In claim 1,
The hydrogen concentration measuring device, wherein the oxygen adsorption suppression treatment layer is a layer containing silicon. In any one of Claims 1 thru | or 3,
2. The hydrogen concentration measuring apparatus according to claim 1, wherein the second electrode is formed of any one of a single electrode of platinum or palladium and an alloy electrode containing at least one of platinum or palladium. In any one of Claims 1 thru | or 4,
A hydrogen concentration measuring apparatus comprising a heater for heating the proton conductor solid electrolyte to a predetermined temperature.

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