JPH11271269A - Hydrocarbon gas component detecting method, and detecting sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily, quickly and precisely measure components of a hydrocabon gas in detected gas, irrespective of concentrations of hydrogen, carbon monoxide and oxygen in the detected gas. SOLUTION: Two different electrodes 14, 16 are provided in surfaces, exposed to same detected gas, of oxide ion conductive solid electrolytes 10a-10e, and an oxide containing a specific rare-earth element is made to be contained at least in one of the electrodes 14, 16 to constitute a sensor element. Oxygen partial pressure of a gas detecting space 23 is controlled using an electrochemical oxygen pump cell, and hydrocarbon components in the detected gas are detected with high precision from a potential difference between the different electrodes 14, 16 formed in the solid electrolytes 10a-10e.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the detection of a hydrocarbon gas component in an atmosphere, particularly in a combustion gas discharged from an internal combustion engine. The present invention relates to a method for detecting a hydrocarbon gas component that can be measured with high accuracy, and a sensor for detecting a hydrocarbon gas component that can be used in the method.

[0002]

2. Description of the Related Art In the automobile industry, the concentration of a hydrocarbon gas component contained in an exhaust gas of an internal combustion engine is simply detected with the aim of detecting catalyst deterioration and applying it to engine control. A method that can be used and a sensor that can be used in the method are being developed. As sensors of the type described above, sensors using a thermocouple and a resistance thermometer, and sensors using a zirconia solid electrolyte have been proposed.

A sensor using a thermocouple and a resistance temperature detector applies an oxidation catalyst to the temperature sensor, and changes in temperature due to heat generated when combustible gas is burned on the temperature sensor by the catalytic action of the oxidation catalyst. Is detected as a change in electromotive force or resistance of the temperature measuring element. Although these sensors are very simple, they are susceptible to flammable gases other than hydrocarbons, such as hydrogen and carbon monoxide. There are problems such as being susceptible.

As sensors using a zirconia solid electrolyte, electromotive force type and current type sensors have been proposed. As an electromotive force sensor, for example, a Pt electrode and a Pt electrode containing Bi are provided as an electrode pair on a zirconia solid electrolyte, and a difference in electrode potential resulting from a difference in catalytic activity between the two electrodes is detected as an electromotive force. Sensor (Japanese Unexamined Patent Publication Nos. Hei 8-510561 and Hei 8-51084)
Is mentioned. Although this sensor is highly selective for hydrocarbons, it is susceptible to changes in oxygen concentration and therefore
For hydrocarbon gas components, it is more suitable for equilibrium point detection than quantitative detection.

On the other hand, as a current sensor, for example, two spaces (a front chamber and a rear chamber) each having a zirconia pump cell are provided in parallel to the gas inflow direction, oxygen is exhausted in the front chamber, and oxygen is exhausted in the rear chamber. A sensor for detecting the concentration of flammable gas from the amount of oxygen (pump current) sent to burn the remaining flammable gas (JP-A-8-247995) may be mentioned. This means that although it is possible to quantitatively detect hydrocarbon gas components without being affected by changes in the oxygen concentration in the atmosphere, the output is small, and even higher sensitivity is required to perform quantitative detection in the minute concentration range. is necessary.

As described above, when the conventional sensor is used, various sensors such as those that are susceptible to flammable gases other than hydrocarbon gas components, susceptible to fluctuations in measurement conditions, and have low detection sensitivity. There was a problem.

The present invention has been made in order to solve the problems of the prior art method and sensor, and an object of the present invention is to provide a low concentration hydrocarbon of several hundred ppm or less in a test gas. The method for detecting a hydrocarbon gas component, which can easily and quickly and accurately measure a gas component without being affected by the concentrations of hydrogen, carbon monoxide and oxygen in a test gas, and the method may be used for the method. An object of the present invention is to provide a sensor for detecting a hydrocarbon gas component.

[0008]

That is, according to the method for detecting a hydrocarbon gas component of the present invention, a test gas is guided under a predetermined diffusion resistance into a gas detection space defined from the surroundings, and the electrochemical oxygen is detected. Applying a voltage to the pump cell to control the oxygen partial pressure in the detection space, and detecting hydrocarbon gas components in the test gas from the potential difference between two different electrodes formed in the oxide ion conductive solid electrolyte It is characterized by. Further, in the hydrocarbon gas component detection sensor of the present invention, two different electrodes are formed on a surface of the oxide ion conductive solid electrolyte exposed to the same test gas.
t, Pd, Rh, Ag, Ni, Au, or La, C
e, Pr, Nd, Sm, Eu, Gd, Tb, Dy, H
an oxide containing a rare earth element selected from the group consisting of o, Er, Tm, Yb, and Lu; and at least one of the two electrodes is formed of the rare earth element. A sensor element having an oxide containing the same. In the detection sensor of the present invention, a gas detection space partitioned from the surroundings for guiding a test gas under a predetermined diffusion resistance, and an electrochemical oxygen pump cell for controlling the oxygen partial pressure of the detection space are provided. Is particularly preferred.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION For convenience of explanation, the sensor of the present invention will be described first, and then the method of the present invention will be described. <Sensor of the Present Invention> The sensor for detecting a hydrocarbon gas component of the present invention uses a sensor element in which two different electrode portions are provided on the surface of an oxide ion conductive solid electrolyte. The size and shape of the solid electrolyte and the two electrode portions may be appropriately selected. Further, two electrodes are arranged so as to be exposed to the same test gas in order to improve the selectivity to the hydrocarbon gas component. In this case, the two electrodes may be on the same side of the solid electrolyte or on different sides of the solid electrolyte.

Here, in order to particularly easily obtain the selectivity to the hydrocarbon gas of the sensor of the present invention, at least one of the two electrodes is formed so as to have an oxide containing a rare earth element. That is, at least one of the two electrodes may be formed of an oxide containing the rare earth element or a mixture of the oxide and a suitable material (for example, a material such as Pt or Au).

As the oxide containing a rare earth element, rare earth is added to a rare earth oxide, an oxide ion conductive solid electrolyte in which rare earth is dissolved, or an electron conductive oxide such as (La, Sr) MnO ₃ . Are preferred, and among rare earths, La, Ce, Pr, Nd, Sm, Eu, Gd,
Those containing Tb, Dy, Ho, Er, Tm, Yb, and Lu show a great effect. The control of the difference between the catalytic activity and the electrode reaction activity of the two electrodes in the sensor of the present invention can also be performed by producing a mixed electrode using the above materials, using an oxidation catalyst, or providing a temperature gradient between the electrodes. It can be carried out.

The sensor element and the electrode used in the sensor of the present invention may be manufactured by a conventional method in this field, for example, a firing method, a printing method, a sputtering method, a green sheet laminating method, etc. It is appropriately selected according to the sheath shape. As the solid electrolyte of the electrochemical cell, those having oxide ion conductivity can be used. Specifically, a zirconium-based solid electrolyte (ZrO ₂ -M ₂
O ₃ solid solution or ZrO ₂ -MO solid solution, M = Y, Yb,
Gd, Ca, Mg, etc.), ceria-based solid electrolyte (CeO ₂
-M ₂ O ₃ solid solution or CeO ₂ -M solid solution, M = Y, S
m etc.) can be used. From the viewpoints of stability in exhaust gas and oxide ion conductivity, a zirconium-based solid electrolyte is preferable, and ZrO ₂ in which ₃ to 8 mol% of Y ₂ O ₃ is dissolved is most preferable.

In the sensor of the present invention, various measuring devices such as a suitable current source and / or voltage source, ammeter and / or potentiometer are appropriately selected and used. In addition, a device such as a personal computer can be used to control and manage the current source and / or the voltage source or to process a signal from the sensor element.

The sensor element in the sensor of the present invention can be used alone, but can also be used in combination with a sensor element having another function, for example, an oxygen sensor element. In the case where a plurality of sensor elements having different functions can share a component thereof, for example, an oxide ion conductive solid electrolyte, the sensor of the sensor of the present invention is placed on one oxide ion conductive solid electrolyte. A composite sensor may be formed by forming a plurality of sensor elements including the element.

<Method of the Present Invention> In the method of the present invention, by controlling the oxygen concentration in the detection space using an electrochemical pump cell, a very small amount of oxygen can be obtained even under a high oxygen partial pressure or a condition where the oxygen partial pressure fluctuates. Hydrocarbon gas components can be detected with high sensitivity. Here, if the sensor of the present invention is used, the hydrocarbon component can be detected more selectively. As the electrochemical pump cell in the method of the present invention, a pump cell having a conventional metal electrode can be used. However, in order to discharge oxygen from the sensing space without affecting the hydrocarbon gas component, it is necessary to use a hydrocarbon gas. It is preferable that the electrode reaction activity is low with respect to the components and high with respect to oxygen. From such a viewpoint, when the sensor of the present invention is used as a pump cell, the detection accuracy of hydrocarbon gas components is further improved.

Further, the control of the oxygen concentration in the detection space performed by the method of the present invention has the effect of improving the stability of the sensor output against changes in the oxygen concentration and improving the detection sensitivity of low-concentration hydrocarbon gas components. . Hereinafter, this effect will be considered in the Nernst electromotive force, which is the simplest example, of the hybrid electromotive force generated in the concentration cell.

The oxygen concentration in the detection space in the method of the present invention
Consideration of Control Effect It is assumed that two electrodes having no catalytic function are provided on a zirconia solid electrolyte, and one of the electrodes is coated with a catalyst capable of completely oxidizing a combustible gas. Here, even if 10% oxygen gas is brought into contact with both electrodes, no electromotive force is generated between both electrodes. However, when a mixed gas of 10% oxygen gas and 100 ppm of flammable gas is brought into contact with both electrodes, combustion of the flammable gas occurs by the catalyst, and the concentration of oxygen gas on the electrode coated with the catalyst is increased. Is reduced and the concentration of oxygen gas in contact with both electrodes becomes different, so that an electromotive force is generated between both electrodes.

The amount of oxygen used for combustible gas combustion is 10
If it is 0 ppm, the oxygen concentration on both electrodes is 10
%, 9.99% (electrode coated with catalyst), and the rate of change of oxygen concentration is only 0.1%. However, when the oxygen concentration is reduced from 10% to 0.1%, the oxygen concentration on both electrodes becomes 0.1% and 0.09%, respectively, and the change rate of the oxygen concentration reaches 10%. Can be obtained. Thus, by controlling the oxygen concentration of the atmosphere to the low concentration side and increasing the rate of change of the oxygen concentration for both electrodes, the generated electromotive force can be increased, and therefore,
The detection sensitivity for low-concentration hydrocarbon gas components is improved. Further, this method has an advantage that the oxygen concentration can be freely set according to a desired detection concentration range and a gas equilibrium point. Further, there is an advantage that the oxygen partial pressure can be detected from the current flowing through the atmosphere control pump cell.

[0019]

The present invention will be described in more detail with reference to the following study examples (including examples and comparative examples). In each examination example, various characteristics of the sensor of the present invention under various conditions were examined using a sensor element having a basic structure. Study Example 1-1: Manufacturing and Structure of Sensor Element FIG. 1 is a schematic structural view of a sensor element (electrochemical cell) used in the present embodiment. The solid electrolyte 1 is preferably zirconia which has oxide ion conductivity and is stabilized with yttria, calcia or the like from the viewpoint of stability. In this example, 6 mol%
Zirconia stabilized with yttria was used. The measurement electrode 2 is formed of Pt, the electrode 6 is formed of Au, and the measurement electrode 5 is formed of one of rare earth oxides of CeO ₂ , Pr ₆ O ₁₁ , Tb ₄ O ₇ , and Sm ₂ O _3. Formed. Also,
For comparison, a sample in which the measurement electrode 5 was formed only of Au was prepared. A conductive mesh 3 is placed on the measurement electrode 2,
The conductive mesh 4 was similarly formed on the electrode 6, and the lead wire was taken out. Here, the electrode 6 mainly plays a role of current collection and has no catalytic activity. The measurement electrode 2, the measurement electrode 5 and the electrode 6 are a plate-shaped solid electrolyte 1
Was formed on the surface by sputtering. The thickness of each of the formed electrodes was about 8000 °. The solid electrolyte (zirconia stabilized with 6 mol% yttria) and P
A sensor having an oxide electrode in which r was dissolved was also manufactured. In producing the electrode, Pr ₆ O ₁₁ and a solid electrolyte were mixed at a predetermined ratio, and the powder was sintered at 1400 ° C. as a target and formed by a sputtering method. Further, a sensor was also manufactured by a method of forming a solid solution layer on the electrolyte surface by applying Pr nitrate to the surface of the electrolyte and heat-treating the solution.

1-2 Electromotive force response to various flammable gases when used as a gas detection cell The various cells prepared in 1-1 were heated to 750 ° C. in an electric furnace, and 0.1% O ₂ —N ₂ Under atmosphere, CH ₄ , C
₃ H _{8, 0~500pp} the H _2, CO various combustible gases
m, and the electromotive force generated between the measurement electrode 2 and the measurement electrode 5 was measured based on the measurement electrode 2. The results are shown in FIGS. Here, FIG. 2 shows the characteristics of the CeO ₂ electrode cell, FIG. 3 shows the characteristics of the Pr ₆ O ₁₁ electrode cell, and FIG.
The characteristics of the ₄ O ₇ electrode cell, the characteristic of FIG. 5 is Sm ₂ O ₃ electrode cell, FIG. 6 shows the characteristics of the Pr solid solution of zirconia electrode cell,
FIG. 7 shows the characteristics of the Au electrode cell. CeO ₂ , Pr ₆ O ₁₁ , Sm ₂ O ₃ , Tb ₄
The characteristics (FIGS. 2 to 5) of the sensor using electrodes made of various rare earth oxides of O ₇ and Au differ depending on the gas type,
Although HC (hydrocarbon) gas such as H ₄ and C ₃ H ₈ showed a large change corresponding to the concentration, the change for H ₂ and CO was extremely small and the selectivity for HC gas was found to be extremely high. Further, in a sensor using an oxide electrode in which Pr is dissolved as a solid solution, CeO is used regardless of the formation method.
_{As with the} electrodes made of various rare earth oxides of Au, Pr ₆ O ₁₁ , Sm ₂ O ₃ , and Tb ₄ O ₇ and Au, characteristics selective to HC gas were exhibited (FIG. 6). On the other hand, A
The sensor using u has sensitivity to each combustible gas (FIG. 7), and H ₂ , CO rather than CH ₄ , C ₃ H _8.
It has been found that the sensitivity to HC gas becomes strong and the selectivity to HC gas cannot be obtained. From this, it was found that the use of the rare earth-containing oxide as the electrode material greatly improved the selectivity to HC. Further, when the characteristics of the above-mentioned sensors were measured while changing the measurement temperature, the output characteristics changed. This indicates that the sensitivity of the electrodes can be controlled by changing the temperature, and that the HC concentration can be detected from the signal between the electrodes having different temperatures.

Study Example 2 2-1: Pump Characteristics in the Presence of O ₂ and HC (C ₃ H ₈ ) A sensor element (electrochemical cell) as shown in FIG.
The pump characteristics of the cell in the presence of O ₂ and HC (C ₃ H ₈ ) were studied. 8, the solid electrolyte 1, the measuring electrode 2, the electrode 6, the conductive meshes 3, 4 are as in Example 1, and the measuring electrode 5 is made of Pt (Comparative Example) or Pr ₆ O ₁₁ (Example). Was. The conductive mesh 3 and the conductive mesh 4 were connected by a lead wire 7 (for example, a Pt lead wire) via an ammeter 8 and a constant voltage power supply 9. In this experiment,
In order to avoid the influence of the catalytic activity of the measurement electrode 2 which is a Pt electrode, two different gas chambers (not shown) are provided above and below in the figure using the solid electrolyte 1 as a partition so that the atmospheres of the two electrodes can be changed independently. The device was used. In this experiment, the same 0.2%
O ₂ -N ₂ was introduced into both gas chambers, a voltage was applied in the direction in which oxygen ions flow from the measurement electrode 5 to the measurement electrode 2, and the current flowing at that time was measured. Further, 300 ppm C ₃ H ₈ was introduced into the gas chamber facing the measurement electrode 5, and the same measurement was performed. FIG. 9 shows a current-voltage characteristic of a cell using Pt as the measurement electrode 5. It can be seen that the characteristics are shifted to the higher potential side by the introduction of C ₃ H ₈ . This is because the measurement electrode 5 (Pt
This is because C ₃ H ₈ burns due to the catalytic activity of the electrode, and a difference in oxygen concentration occurs between the electrode and the counter electrode. P for measuring electrode 5
FIG. 10 shows current-voltage characteristics of a cell using r ₆ O ₁₁ . In this case, the characteristics did not change despite the introduction of C ₃ H ₈ . This indicates that the electrode 5 (Pr ₆ O ₁₁ electrode) has no catalytic activity for HC, and thus has no electrode reaction activity. From this, La, C
e, Pr, Nd, Sm, Eu, Gd, Tb, Dy, H
A sensor element having an electrode formed of an oxide containing a rare earth element selected from o, Er, Tm, Yb, and Lu is effective in applications in which oxygen is pumped without affecting hydrocarbons. It was found to have a pump function.

Study Example 3 3-1: Structure and Production of Hydrocarbon Gas Component Measuring Device FIG. 11 shows a typical example of a hydrocarbon gas component measuring device used in the method of the present invention. The device of FIG. 11 is also an example of the sensor of the present invention. The device of the present embodiment is in the form of a plate-like element made by laminating a plurality of ceramic sheets that are baked together. The ceramic sheet is formed of an oxide ion conductive solid electrolyte, and as the material of the oxide ion conductive solid electrolyte, a known material represented by stabilized zirconia can be used. Here, 6
Zirconia stabilized with mol% yttria was used.
Several electrodes are provided on the surface of each solid electrolyte (solid electrolytes 10a to 10e) layer.
13, the measurement electrodes 14 and 16 were made of Pt, and the measurement electrode 15 was made of Pr ₆ O ₁₁ and Au. In the element, a gas detection space 23 (a test gas flows in from the diffusion control passage 11) and an air introduction space 24 are provided. The solid electrolyte 10a mainly acts as an electrochemical pump cell for controlling the oxygen partial pressure in the gas detection space 23, and the solid electrolyte 10a
b mainly functions as an electrochemical cell for detecting gas concentration. Further, the gas detection space 23 and the air introduction space 24 are separated by the solid electrolyte 10b, and the electrodes provided in both spaces (for example, the measurement electrode 14 and the measurement electrode 16,
The electromotive force (V1) generated at the measurement electrodes 15 and 16)
Or from V2), the atmosphere in the detection space can be monitored based on the atmosphere. Further, the voltage applied to the pump cell is controlled based on the electromotive force, so that the oxygen partial pressure in the detection space can be controlled. Each of the above electrodes is provided with a potentiometer 1
8, 19, 20, an ammeter 21 and a variable voltage power supply 22 are connected.

3-2: Effect of oxygen concentration control The measuring element was heated to 750 ° C.
It was left in an O ₂ -N ₂ atmosphere. Here, the measurement electrode 14
The oxygen concentration in the detection space 23 was controlled based on the electromotive force V1 generated between the sensor electrode 16 and the measurement electrode 16 (by the potentiometer 18). The reference voltages used were 15.3 mV, 66.0 mV, and 101.2 mV calculated based on the Nernst electromotive force.
Was used. These values correspond to oxygen concentrations in the sensing space of approximately 10%, 1%, 0.2%. When the oxygen concentration in the detection space is controlled, 0 to 0
500 ppm of C ₃ H ₈ was introduced, and the change of the sensor output V3 (by the potentiometer 20) was measured. The result is shown in FIG. The detection output increases as the control voltage increases (the controlled oxygen concentration decreases), and as a result,
It was found that the detectability of trace gas was improved.

3-3: Detectability of hydrocarbon gas components The measurement element heated to 750 ° C. is left in a 20% O ₂ —N ₂ atmosphere, and the oxygen concentration in the detection space 23 is reduced to about 0.2%.
(Control voltage: 101.2 mV). In this state,
CH ₄ , C ₃ H ₈ , H ₂ , CO various flammable gas is 0 to
Introduced into the test gas in the range of 500 ppm,
The electromotive force generated between the measuring electrode 1 and the measuring electrode 15 is
4 was measured. FIG. 13 shows the results. The sensor output greatly changes with respect to the hydrocarbon gas component, and H ₂ , CO
The change to was very small.

3-4: Characteristics of Pump Cell The oxygen concentration in the detection space 23 is set to about 0.2% (control voltage 10
1.2 mV), and the change in the current flowing through the pump cell when the oxygen concentration in the test gas was changed was measured.
FIG. 14 shows the results. The higher the oxygen concentration, the higher the current. From this, it was found that the oxygen concentration in the test gas can be detected from the change in the current of the pump cell.

[0026]

As is apparent from the above description, according to the method for detecting a hydrocarbon gas component and the detection sensor of the present invention, the method is not affected by hydrogen, carbon monoxide and oxygen gas in the test gas. Further, the concentration of the hydrocarbon gas component in the test gas can be measured simply, quickly and accurately with a small measuring device. As a result, the present invention exerts a great effect on, for example, combustion control of an internal combustion engine such as an automobile and a boiler, and development of a state monitoring / deterioration diagnosis technique for an exhaust gas purification catalyst.
Further, since the sensor of the present invention is composed of a thermally and chemically stable solid electrolyte, it has excellent stability in combustion exhaust gas, and can be used even at a high temperature close to 700 ° C.
It can be directly inserted into a high-temperature exhaust gas atmosphere such as an exhaust pipe, and it is easy to reduce the size and weight.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a sensor element as an example of a hydrocarbon gas component detection sensor of the present invention.

FIG. 2 is a view showing gas detection characteristics when a CeO ₂ electrode is used in the sensor element of FIG. 1 (Example).

FIG. 3 is a diagram showing gas detection characteristics when a Pr ₆ O ₁₁ electrode is used in the sensor element of FIG. 1 (Example).

FIG. 4 is a diagram showing gas detection characteristics when a Tb ₃ O ₇ electrode is used in the sensor element of FIG. 1 (Example).

FIG. 5 is a diagram showing gas detection characteristics when an Sm ₂ O ₃ electrode is used in the sensor element of FIG. 1 (Example).

FIG. 6 is a view showing gas detection characteristics when a Pr solid solution zirconia electrode is used in the sensor element of FIG. 1 (Example).

FIG. 7 is a view showing gas detection characteristics when an Au electrode is used in the sensor element of FIG. 1 (comparative example).

FIG. 8 is a schematic configuration diagram of another example of the hydrocarbon gas component detection sensor of the present invention.

FIG. 9 is a diagram illustrating pump characteristics when a Pt electrode is used in the sensor of FIG. 8 (comparative example).

FIG. 10 is a graph showing pump characteristics when a Pr ₆ O ₁₁ electrode is used in the sensor of FIG. 8 (Example).

FIG. 11 shows an example of a hydrocarbon gas component measuring device used in the method for detecting a hydrocarbon gas component of the present invention (sensor of the present invention).
FIG.

FIG. 12 is a diagram showing an effect of controlling the oxygen concentration of the sensor of FIG. 11;

FIG. 13 is a diagram showing the detection characteristics of hydrocarbon gas of the sensor of FIG. 11;

FIG. 14 is a diagram showing an oxygen concentration-pump current characteristic of the sensor of FIG. 11;

[Explanation of symbols]

1, 10a, 10b, 10c, 10d, 10e: solid electrolyte 2, 5, 14, 15, 16: measuring electrode 3, 4: conductive mesh 6: electrode 7: lead wire 8, 21: ammeter 9: constant voltage Power supply 11: Diffusion control passage 12, 13: Pump electrode 17: Heater 18, 19, 20: Potentiometer 21: Ammeter 22: Variable voltage power supply 23: Detection space 24: Atmospheric introduction space

Claims (3)

[Claims] 1. A gas to be detected is guided under a predetermined diffusion resistance into a gas detection space partitioned from the surroundings, and a voltage is applied to an electrochemical oxygen pump cell to control the oxygen partial pressure in the detection space. A method for detecting a hydrocarbon gas component, comprising detecting a hydrocarbon gas component in a test gas from a potential difference between two different electrodes formed on a solid ion-conductive solid electrolyte. 2. Two different electrodes are formed on a surface of an oxide ion conductive solid electrolyte exposed to the same test gas, and said electrodes are made of Pt, Pd, Rh, Ag, Ni, Au, or La. , C
e, Pr, Nd, Sm, Eu, Gd, Tb, Dy, H
an oxide containing a rare earth element selected from o, Er, Tm, Yb, and Lu; and at least one of the two electrodes is formed of the rare earth element. A sensor for detecting a hydrocarbon gas component, comprising a sensor element having an oxide containing the same. 3. The sensor for detecting a hydrocarbon gas component according to claim 2, wherein a gas detection space defined from the periphery for guiding a test gas under a predetermined diffusion resistance, and an oxygen partial pressure of the detection space. A sensor for detecting a hydrocarbon gas component, the sensor comprising: an electrochemical oxygen pump cell for controlling the pressure of the hydrocarbon gas.