WO2008116417A1

WO2008116417A1 - Gas sensor

Info

Publication number: WO2008116417A1
Application number: PCT/CN2008/070573
Authority: WO
Inventors: Ling Liu; Lei Xie
Original assignee: Rae Systems (Shanghai) Inc.
Priority date: 2007-03-26
Filing date: 2008-03-25
Publication date: 2008-10-02
Also published as: CN101275923B; CN101275923A; WO2008116417A8

Abstract

An oxygen sensor comprises an electrolyte isolation layer (110) with at least one through-hole, a measuring electrode (112) and a counter electrode (114). Said measuring electrode is mounted on one side of said electrolyte isolation layer and said counter electrode (114) is mounted on the other side of said electrolyte isolation layer (110). The size of at least one through-hole meets: Aliquid phase /llisolation layer<6.5×103(Ainlet/linlet),where Aliquid phase is the general section area of said at least through-hole; lisolation layer is the thickness of said through-hole; Ainlet is the section area of said air inlet; linlet is the length of said air inlet. Said through-hole can comprise a hydrophilic liquid absorbing material. Said through-hole deviates from the electric field produced by said measuring electrode (110) and counter electrode (114). Said isolation layer (110) can also be a hydrophilic micro array plate.

Description

Gas sensor technology

The present invention relates to a gas sensor, and more particularly to an electrolytic gas sensor and an electrolytic oxygen sensor. Background technique

The electrochemical oxygen sensor is a sensor that is currently widely used to monitor oxygen. U.S. Patent No. 4,132,616 describes a galvanic cell type oxygen sensor. In operation, oxygen diffuses through a capillary to the measuring electrode, where it combines with water and electrons to produce a reduction reaction that forms hydroxide ions. The hydroxide ions flow through the electrolyte to the counter electrode and react with the lead electrode to form lead oxide, water and electrons. The movement of the hydroxide ions between the measuring electrode and the counter electrode forms a current which is proportional to the percentage concentration of oxygen. Thus, the oxygen concentration can be known by measuring the current.

U.S. Patent Application No. 2005/0034987 describes an electrolytic oxygen sensor whose key component is an electrolyte/electrode assembly, specifically comprising a solid electrolyte, a measuring electrode, a counter electrode and a reference electrode. Wherein the measuring electrode is mounted on one side of the solid electrolyte, and the counter electrode and the reference electrode are mounted on the other side of the solid electrolyte. In operation, oxygen diffuses through a capillary to the measuring electrode, where it combines with hydrogen ions and electrons to produce a reduction reaction that forms water molecules. Water molecules penetrate through the solid electrolyte to the other side. On the other hand, at the counter electrode, water molecules are electrolyzed to form oxygen, hydrogen ions and electrons. In the formed oxygen, hydrogen ions and electrons, oxygen is discharged from an air outlet, hydrogen ions are transferred to the measuring electrode through the solid electrolyte, and electrons are passed from the counter electrode to the measuring electrode through an external circuit. Hydrogen ions that migrate to the measuring electrode and electrons from the counter electrode are used to compensate for the hydrogen ions and electrons consumed by the aforementioned reduction reaction, and form a reduction current. The reduction current is proportional to the percentage concentration of oxygen.

The Chinese invention patent whose patent number is ZL94107055.7 and whose name is "solid polymer electrolyte capillary type oxygen sensor" also describes an electrolytic type oxygen sensor, and also describes a method of fixing the waterproof and gas permeable diffusion electrode by a rolling method. A method of preparation on a solid polymer electrolyte.

In the electrolytic type oxygen sensor, if oxygen generated at the counter electrode and oxygen entering from the outlet hole are reversely diffused to the measuring electrode, the measurement signal becomes large, thereby distorting the measurement result. Therefore, such an electrolytic oxygen sensor must satisfy the following two normal working conditions: First, a plurality of electrodes are connected to each other through the electrolyte, and an ion channel is formed between the measuring electrode and the counter electrode to perform ion transport; Oxygen generated at the electrode and oxygen entering from the vent are diffused back to the measuring electrode to ensure The measurement signal is accurate.

Commercially available electrolytic oxygen sensors, such as electrolytic oxygen sensors manufactured by RAESYSTEMS, mostly use a solid electrolyte Nafion membrane as an electrolyte. Solid Electrolyte The Nafion membrane acts as an ionic conductor to connect the measuring electrode to the counter electrode and prevent reverse diffusion of oxygen. However, the conductivity of Nafion membranes is moisture dependent and very sensitive to humidity. Therefore, such an all-solid electrolytic oxygen sensor is only suitable for use in a humid environment, and is liable to lose water when used in a dry environment, which may result in unstable measurement results. This makes its application very limited. There are also some electrolytic oxygen sensors that immerse the measuring electrode and the electrode in whole or in part in a reservoir containing the acid electrolyte solution, and connect the measuring electrode and the counter electrode with an acid electrolyte solution. Although the sensor is not easy to lose water, in order to ensure that both the measuring electrode and the counter electrode can contact the acid electrolyte solution in various placement modes, a large amount of electrolyte solution must be contained in the liquid storage tank, resulting in a large volume of the sensor. .

In fact, in various electrolytic gas sensors for measuring gas concentration, similar problems as described above are encountered.

Therefore, it is desirable to provide a gas sensor having a novel electrolyte barrier that can serve as both an ion conductor to connect the measuring electrode and the counter electrode, and to prevent the oxidation or reduction reaction from diffusing back to the gas generated at the counter electrode. Measuring electrode.

There is also a need to provide an oxygen sensor having a novel electrolyte barrier that acts as both an ion conductor to connect the measuring electrode to the counter electrode and to prevent reverse diffusion of gas at the counter electrode to the measuring electrode.

There is also a need to provide an oxygen sensor having a novel electrolyte barrier that is both resistant to dryness and small in volume. Summary of the invention

In order to achieve the above object, in accordance with one aspect of the present invention, an oxygen sensor is provided, comprising: an electrolyte barrier comprising at least one through hole filled with an electrolyte; at least one measuring electrode, It is located on one side of the electrolyte compartment, and oxygen which flows in through the pores undergoes a reduction reaction at the measuring electrode to form water molecules;

At least one counter electrode located on the other side of the electrolyte compartment, the water molecules passing through the through hole and oxidized at the counter electrode to form oxygen, hydrogen ions and electrons, and the formed oxygen passes through An outlet is discharged;

Wherein, the size of the at least one through hole satisfies the following conditions: A liquid phase / 1 compartment < 6·5 X 10 (Α inlet / 1 inlet)

Wherein, the A plane is the total cross-sectional area of the at least one through hole, and the 1 spacer is the thickness of the through hole, Α _λ . For the cross-sectional area of the air inlet, 1 is entered. It is the length of the air inlet.

In the oxygen sensor of the present invention, the through hole may include a hydrophilic liquid absorbing material, and the ratio of the total cross-sectional area of the at least one through hole to the cross-sectional area of the electrolyte spacer is between 1% and 50%. In the range. Preferably, the ratio of the total cross-sectional area of the at least one through hole to the cross-sectional area of the electrolyte barrier is in the range of 10% to 15%.

Preferably, in the oxygen sensor of the present invention, the position of the through hole is deviated from an electric field formed by the at least one measuring electrode and the at least one counter electrode.

In the oxygen sensor of the present invention, the electrolyte barrier layer may further be a hydrophilic microwell array template, and the ratio of the total cross-sectional area of the microwell array to the cross-sectional area of the electrolyte separator is 0.1%-50. Within the range of %, the porosity of the microwell array template is in the range of 0.1% to 15%.

Preferably, in the oxygen sensor of the present invention, the size of the air outlet hole satisfies the following conditions:

^ Liquid 1 liquid layer / d liquid layer ⁴ > gas 1 air outlet / d air outlet ⁴

Wherein the μ liquid is the viscosity of the electrolyte, 1 the liquid layer is the length of the through hole, the d liquid layer is the diameter of the through hole, μ is the air viscosity, 1 ^ is the length of the air outlet, d ^ is the diameter of the vent.

Preferably, in the oxygen sensor of the present invention, the electrical resistance of the electrolyte in the at least one hole is less than

50Ω.

In the oxygen sensor of the present invention, the electrolyte may be sulfuric acid, and the at least one through hole has a length smaller than 3000 times the total sectional area of the at least one through hole.

The oxygen sensor of the present invention may further comprise a first hydrophilic liquid absorbing material layer disposed between the electrolyte barrier layer and the measuring electrode. A second hydrophilic liquid absorbing material layer may also be included, disposed between the electrolyte barrier layer and the counter electrode. A reference electrode, a third hydrophilic liquid absorbing material layer, an additional electrolyte barrier layer, and a fourth hydrophilic liquid absorbing material layer may also be included, the additional electrolyte barrier layer including at least one through hole, the through hole Filled with the electrolyte, wherein the reference electrode, the third hydrophilic liquid absorbing material layer, the additional electrolyte barrier layer, and the fourth hydrophilic liquid absorbing material layer are sequentially disposed in the Between the third hydrophilic liquid absorbing material layer and the counter electrode.

The oxygen sensor of the present invention may further include a liquid storage tank located on the other side of the electrolyte compartment and containing a moisturizing material that releases moisture. An annular gasket may also be included that is located on at least one of the sides of the electrolyte barrier for preventing oxygen from leaking through the electrolyte barrier. The method may further include: a first oxygen permeable/waterproof membrane located at an end of the vent hole adjacent to the electrolyte compartment, for oxygen Permeable, and for preventing moisture from entering the vent; glass microfiber paper located between the reservoir and the electrolyte barrier to help regulate the humidity of the electrolyte barrier; and second An oxygen permeable/waterproof membrane located at one end of the inlet aperture adjacent the electrolyte barrier, permeable to oxygen and for preventing moisture from entering the inlet aperture.

In the oxygen sensor of the present invention, the electrolyte barrier layer may be a polymer film, the material of the polymer film is selected from the group consisting of polypropylene, polyester, Nafion and GEFC, and the hydrophilic liquid absorbing material is Glass fiber impregnated with electrolyte. In the oxygen sensor of the present invention, the electrolyte spacer structure having at least one through hole can communicate both the measuring electrode and the counter electrode as an ion conductor and prevent the oxygen from diffusing backward to the measuring electrode. At the same time, the oxygen sensor is not only resistant to dryness but also small in size.

According to another aspect of the present invention, a gas sensor is provided, comprising:

An electrolyte barrier comprising at least one through hole filled with an electrolyte; at least one measuring electrode located on one side of the electrolyte compartment, and a gas flowing through an inlet orifice in the measurement a reaction in the reduction reaction and the oxidation reaction at the electrode;

At least one counter electrode located on the other side of the electrolyte barrier, at which another reaction in the reduction reaction and the oxidation reaction occurs,

Wherein the at least one through hole and the air inlet are sized to prevent reverse generation of gas generated at the counter electrode due to oxidation or reduction reaction to the measuring electrode. DRAWINGS

1 is a schematic structural view illustrating an electrolytic type oxygen sensor according to an embodiment of the present invention. Fig. 2 is a schematic structural view showing an electrode/separator/electrode assembly according to another embodiment of the present invention, which is a two-electrode structure and has a single-hole electrolyte spacer.

Fig. 3 is a schematic structural view showing an electrode/separator/electrode assembly according to still another embodiment of the present invention, which is a two-electrode structure and has a porous electrolyte compartment.

Fig. 4 is a schematic structural view showing an electrode/interlayer/electrode assembly according to still another embodiment of the present invention, which is a three-electrode structure and has a porous electrolyte compartment. Detailed ways

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same or corresponding parts will be denoted by the same reference numerals.

I. Oxygen sensor of the invention 1 shows a three-electrode electrolytic oxygen sensor in accordance with an embodiment of the present invention. As shown in FIG. 1, the oxygen sensor 100 includes a barrier layer 110. One side of the spacer 110 is the measuring electrode 112, and the other side is the counter electrode 114 and the reference electrode 116. In the present embodiment, the measuring electrode 112 is a cathode, the counter electrode 114 is an anode, and a negative bias is applied between the measuring electrode and the reference electrode, that is, the potential of the measuring electrode is set lower than the potential of the reference electrode. The housing 120 includes a housing 122 and a housing cover 124 that enclose the barrier layer 110 and the electrodes 112, 114 and 116.

In the sensor 100, the cover 124 and the dustproof film 126 and the restrictor 130 together constitute an inlet assembly. The dust-proof film 126 is located on the cover 124 and may be made of a material such as polypropylene or polyester for preventing dust and other particulate contaminants from entering the sensor 100, protecting the barrier 110 and the measuring electrode 112 from contamination. The cover 124 is located on the restrictor 130 and has an air vent 128 that allows oxygen to pass therethrough. The restrictor 130 has a diffusion capillary 132 that communicates with the air vent 128 on the cover 124.

A key component of sensor 100 is an electrode/interlayer/electrode assembly, which is located in working chamber 140, including said barrier 110 and electrodes 112, 114 and 116. A number of factors, such as the composition and processing of the spacer 110, the process of securing the electrodes 112, 114 and 116 with the spacer 110, and the placement of the electrodes 112, 114 and 116, etc., all affect the performance of the electrode/interlayer/electrode assembly. .

Sensor 100 may also include first and second oxygen permeable/waterproof membranes 142, glass microfiber paper 144, first and second hydrophilic absorbent material layers 156, and reservoir 150. Wherein, the first oxygen permeable/waterproof membrane 142 is located at one end of the air outlet 154 for preventing moisture from entering the air outlet from the inside of the electrode/separator/electrode assembly; the glass microfiber paper 144 is located at the counter electrode 114 and Between the reservoirs 150, the glass microfiber paper 144 is subjected to sulfuric acid treatment to help balance the amount of electrolyte in the working chamber 140; the second oxygen permeable/waterproof membrane 142 is located between the capillary holes 132 and the working chamber 140 for Water or other substances are prevented from entering the capillary holes 132 from the inside of the working chamber 140, blocking the capillary holes 132. The first and second oxygen permeable/waterproof membranes can be made of Teflon or other suitable materials. The reservoir 150 is located within the housing 122 and includes a hydrophilic liquid absorbing material 152. The hydrophilic liquid absorbing material 152 can release moisture to maintain the barrier layer 110 sufficiently wetted. The hydrophilic liquid absorbing material 152 may be silica gel, polymer or glass fiber paper or the like which has been permeated with sulfuric acid. Preferably, a first hydrophilic liquid absorbing material layer 156 may be disposed between the barrier layer 110 and the measuring electrode 112, and a second hydrophilic liquid absorbing material layer 156 may be disposed between the barrier layer 110 and the counter electrode 114. The first and second hydrophilic liquid absorbing material layers 156 may be glass fiber paper or the like impregnated with an acid electrolyte solution such as sulfuric acid or phosphoric acid. They can effectively ensure that the measuring electrode and the counter electrode are wetted by the acid electrolyte, thus ensuring that the performance of the sensor is independent of its orientation. In addition, an annular gasket 146 may be disposed above the first hydrophilic liquid absorbing material layer 156 and/or below the second hydrophilic liquid absorbing material layer 156 for preventing oxygen in the air entering through the air outlet 154 and electrolysis. Counter The oxygen produced should diffuse into the working chamber 140 through the gas phase from the periphery of the separator.

In operation, oxygen diffuses through the capillary 132 to the measuring electrode 112. At the measuring electrode 112, oxygen traps electrons from the counter electrode 114 and combines with hydrogen ions from the spacer 110 to cause a reduction reaction to form water molecules. The reduction reaction is shown in the following formula (1).

0 ₂ 10 4H ⁺ 10 4e_ → 2H ₂ O ( 1 )

The formed water molecules penetrate into the barrier layer 110.

On the other hand, at the counter electrode 114, water molecules are electrolyzed to generate hydrogen ions and electrons. The electrolysis process is as shown in the following equation (2).

2H ₂ O → 4H ⁺ ten O ₂ ten 4e_ (2)

Since the measuring electrode 112 is provided as a cathode and the counter electrode 114 is provided as an anode, hydrogen ions generated at the counter electrode 114 can diffuse and migrate to the measuring electrode 112 through the spacer 110. The electrons generated at the counter electrode 114 also reach the measuring electrode 112 through an external circuit. In one embodiment, a negative potential of 0.6V is applied between the measuring electrode and the reference electrode by a potentiostatic circuit to provide a negative potential to the measuring electrode 112. At this potential, the measuring electrode undergoes a reduction reaction as shown in the formula (1) while forming a reducing current. Since the reduction current depends on the rate of oxygen consumption, the oxygen concentration at the measurement electrode 112 can be determined by measuring the reduction current.

In addition, oxygen generated at the counter electrode 114 is diffused outside the sensor 100 through the air outlet 154. Since the reaction formulas (1) and (2) are balanced, the reaction in the sensor 100 is to convert the water at the counter electrode to the water at the measuring electrode 112, and convert the oxygen at the measuring electrode 112 to the counter electrode 114. oxygen. Therefore, this oxygen sensor is also referred to as an "oxygen pump". In addition, electrons are released at the counter electrode 114 and captured at the measuring electrode 112. Hydrogen ions migrate from the counter electrode 114 through the spacer 110 to the measuring electrode 112. The barrier layer 110 in turn prevents oxygen from the counter electrode from diffusing into the measuring electrode.

II. Factors affecting the measurement current

As described above, in the electrolytic type oxygen sensor, oxygen diffuses through a capillary to the measuring electrode, and combines with hydrogen ions and electrons there to cause a reduction reaction to form water molecules. Therefore, the rate at which oxygen enters the sensor is limited by a diffusion barrier, such as by capillary pore size. Under this condition, the measuring electrode operates in the so-called limiting current region. U.S. Patent No. 4,132,616 shows a graph of current density versus polarization potential in Figure 1, which is an oxygen electrode polarization curve. The shaded portion of the figure is the limiting current region, and under limiting current conditions, the oxygen concentration at the electrode surface is substantially equal to zero. Therefore, the limiting current is proportional to the flow rate of oxygen, and the flow rate of oxygen is a function of the partial pressure of oxygen in the gas to be measured, thereby determining the oxygen in the air. The concentration of gas. For this reason, in actually measuring the cathode, the oxygen electrode always applies a polarization potential in the diffusion limit region, and the potential is lower than the hydrogen evolution potential, and the limit current value is insensitive to the potential. Under this principle, the limiting current of the working gas sensor will be determined by the diffusion resistance that controls the diffusion of the gas. Diffusion resistance refers to a series of obstacles that the gas reaches the measuring electrode, including the dust-proof membrane, capillary tube, waterproof and permeable electrode film (such as

PTFE) and so on.

The response current of the oxygen sensor generally includes two parts of current: one is the current i which is caused by the diffusion of oxygen from the inlet through the diffusion barrier to the measuring electrode. Second, the current from the side of the counter electrode diffuses to the measuring electrode _3⁄4 «, as shown in equation (1). In order to ensure the authenticity of the measured signal, it is necessary to eliminate the _3⁄4 « as much as possible. The _3⁄4 «may include three parts of current: one is the current caused by the oxygen from one side of the counter electrode reaching the measuring electrode through the gas phase diffusion. The second is the current caused by the oxygen permeation of the oxygen on one side of the counter electrode to the measuring electrode. i «; The third is the current i from the oxygen on one side of the counter electrode that diffuses through the solid to reach the measuring electrode, as shown in equation (2).

I signal = i person □ + i counter electrode (1)

Counter electrode = i gas phase + i liquid phase + i solid phase (2)

Substituting equation (2) into equation (1) yields:

I signal = i inlet + i gas phase + i liquid phase + i solid phase (3)

In addition, the ultimate diffusion current is:

i=nFADC/l (4)

Where n is the number of electrons, F is the Faraday constant, A is the area of mass transport, D is the diffusion coefficient of oxygen (m ² /s), C is the concentration of oxygen, and 1 is the distance traveled by oxygen.

First, the current i caused by oxygen entering through the capillary at the entrance of the sensor is entered. According to equation (4), the i entry is:

i inlet =nFA inlet D oxygen in the gas phase CV1 inlet (5)

Where A _λ . The cross-sectional area of the capillary at the entrance; 1 into. It can be approximated as the length of the capillary at the inlet. For the oxygen reduction reaction, n = 4, F = 96,500 Cmol - in addition, at normal temperature and pressure, the oxygen concentration in the air C = 0.27 kgm ^-3 . Therefore, after substituting equation (5), you can get:

i inlet =4 X 96500 X 0.27A inlet D oxygen in the gas phase / 1 inlet

=10 A inlet D oxygen in the gas phase /1 inlet (6)

Second, for the current i ^, i « and i caused by oxygen from the side of the counter electrode, according to equation (4),

i gas phase = nFA leak D oxygen in the gas phase C/1 compartment = 10 A leaks D oxygen in the gas phase / 1 compartment ( )

Wherein A _β is the area in which oxygen is leaked from the periphery of the electrolyte barrier in a gas phase, 1, which is approximately the thickness of the electrolyte barrier;

i solid phase = nFA solid D oxygen in solid phase C solid phase / 1 compartment

= nFA solid D oxygen in solid phase S solid phase P pressure / 1 compartment

= 3.86 X 10 A solid D oxygen in solid phase S solid phase P pressure /1 compartment (8)

= 3.86X 10 ⁵ A solid P permeability coefficient P pressure / 1 compartment (9)

Where A is the area of the solid electrolyte, the dissolved concentration of oxygen in the solid electrolyte C (kgm - ³ ) = S solid phase P pressure, and the S ø phase is the solubility coefficient of oxygen in the solid electrolyte (kgm - ³ Pa - ^ P pressure is the partial pressure of oxygen (Pa), P«« refers to the permeability coefficient of oxygen in the solid electrolyte; similarly,

1 liquid phase = nFA liquid phase D oxygen in liquid phase S liquid phase P pressure / 1 compartment

= 3.86 X 10 A liquid D oxygen in liquid phase S liquid phase P pressure /1 compartment (10)

Where A « is the cross-sectional area of the liquid electrolyte; s « is the solubility coefficient of oxygen in the liquid electrolyte.

Solid electrolyte compartment

Below, we will first study the case of solid electrolyte compartments. At this time, without considering i « _ffl , equation (3) is simplified as:

I signal = i population + i gas phase + i solid phase (11)

Substituting equations (6), (7), and (9) into equation (11) yields:

I signal = 10 A inlet D oxygen in gas phase / 1 inlet + 10 A leak D oxygen in gas phase / 1 compartment + 3.86 X 10 A solid phase P permeation coefficient P pressure / 1 compartment (12) due to oxygen in such as Nafion The number of permeability P faces in the solid electrolyte compartment is ^10-16 kgm

10_ ⁵ m ² /s; and under normal temperature and pressure, the partial pressure of oxygen P is about 10 ⁴ Pa, so after substituting into equation (12), you can get:

I signal = 10 ⁵ A person. 10-5/1 person. + 10 ⁵ A leak It) - ⁵ / 1 compartment + 3.86X 10 ⁵ A ugly 1. - ¹⁶ 10 ⁴ /1 compartment

= A inlet / 1 inlet + A leak / 1 compartment +3·86 X 10 A solid phase / 1 compartment (13)

The solid electrolyte is Nafion, Nafion-117 a spacer thickness of 4X 10- ⁴ m, 4R sectional area A sensor using Nafion-117 ugly about 8X 10- ⁵ m ² (10 mm diameter), the gas sensor The cross-sectional area of the inlet capillary is A. It is about 8X 10_ ⁹ m ² (0.1 mm in diameter) and the length of the capillary is 1 in. It is about 10_ ³ m. Thus, equation (13) becomes:

I signal = 8 X 10" ⁹ /10 ^-3 +A leak / 1 compartment +3.86 X10" ⁷ X8X10" ⁵ / (4 X 10" ⁴ )

= 8X10-6+A leak / 1 compartment +7.7X10- ⁸ As can be seen from the above equation, the value of the third term is two orders of magnitude smaller than the first two values. Therefore, the third item can be ignored. In addition, since the i ugly is much smaller than the _fff , the oxygen sensor as the interlayer of the solid electrolyte can substantially ensure the truth of the measurement signal as long as it tries to prevent oxygen from diffusing from the periphery of the solid electrolyte barrier to the measuring electrode. In the prior art, an annular gasket is typically placed above and/or below the barrier to prevent oxygen from the counter electrode from diffusing through the gas phase from the periphery of the solid electrolyte barrier to the measuring electrode.

2. Interlayer containing liquid electrolyte

Next, we study the case of a separator having at least one pore and filled with a liquid in the pore, wherein the pore has a diameter d, and the depth of the pore or the thickness of the separator is 1. At this time, i _Bffl can be _ignored , and equation (3) is simplified as: I signal = i inlet + i gas phase + i liquid phase (14)

Substituting equations (6), (7), and (10) into equation (14) yields:

I signal = 10 A inlet D oxygen in gas phase / 1 inlet + 10 A leak D oxygen in gas phase / 1 compartment + 3 · 86 Χ 10 Α liquid phase D oxygen in liquid phase S liquid phase P pressure / 1 compartment (15 )

Oxygen diffusion coefficient D in the aqueous solution «the gas is too similar to 10- ⁹ m ² / s, solubility coefficient S plane is approximately ^{4 X lO-'kgm ^ Pa 1} , and at normal temperature and pressure, oxygen partial pressure P forces It is about 10 ⁴ Pa. Substituting these data into equation (15) yields:

I signal = 10 ⁵ A inlet X 10-5/1 inlet + 10 ⁵ A leak X 10" ⁵ / 1 compartment + 3.86 X 10 ⁵ A fine X 1 (T ⁹ X 4 X 10" ⁷ X 10 ⁴ /1 Compartment

⁼ Α Inlet / 1 Entrance + Α Leak / 1 Compartment + 1.54 X 10 ⁶ Χ Α Liquid / 1 compartment (16)

(a) Regarding the third item in formula (16) A liquid phase / 1 compartment

If A people. /1 person. Can be more than two orders of magnitude larger than the 1.54 X 10_ ⁶ A fine / 1 compartment, then the effect of i fine can be ignored. At this time, as long as oxygen is prevented from diffusing from the liquid electrolyte compartment through the gas phase to the measuring electrode, the trueness of the measurement signal can be substantially ensured. Therefore, need

(A inlet / 1 inlet) / (1.54 X 10- ⁶ XA fine / 1 compartment) > 100

(A population / 1 entrance) / (A turn / 1 compartment) > 1.54 X 10- ⁴

A fine / 1 compartment < (A population / 1 population) 6.5 X 10 ³ ( 17)

That is, when the A fine / 1 compartment is smaller than Α _λ . /1 _λ . When 6.5 X 10 ³ times, the effect of i fine can be ignored. This is a principle to consider when designing the sensor, that is, the thickness of the spacer and the area of the hole in the spacer are selected according to the size of the inlet capillary. The cross-sectional area of the capillary hole of the sensor gas inlet is A. It is about 8 X 10_ ⁹ m ² (0.1 mm in diameter) and the length of the capillary is 1 person. It is about 10_ ³ m. Then A AD/1 person. = 8 X 10" ⁶ , so that the thin / 1 barrier <0.052. That is, the area of the liquid electrolyte barrier should be less than 0.052 times the thickness of the separator.

Example 1: For a 4R sensor, its cross section is 8 X 10 - ⁵ m ² . When the liquid electrolyte, ie, the cross-sectional area of the barrier occupies 50% of the cross-section of the sensor, A is = 4 X 10_ ⁵ m ² , calculated using the formula (17) A liquid phase / 1 compartment < (A λρ / 1 ΛΡ) 6.5 X 10 ³

4 X 10" ⁵ / 1 compartment < 8 X 10" ⁶ X 6.5 X 10 ³

As long as l > 7.7 X l (T ⁴ m, ie the thickness of the liquid electrolyte is greater than 0.77 mm, the oxygen diffused through the liquid layer to the measuring electrode can be ignored.

Example 2: For a 4R sensor, its cross section is 8 X 10 - ⁵ m ² . When the liquid electrolyte, that is, the pore cross-sectional area of the barrier occupies 1% of the cross section of the sensor, it is calculated by the formula (17). Out

0.01 X 8 X 10" ⁵ / 1 compartment < 8 X 10" ⁶ X 6.5 X 10 ³

As long as l > 1.5 X l (T ⁵ m, ie the thickness of the liquid electrolyte is greater than 15 μm, the oxygen diffused through the liquid layer to the measuring electrode can be ignored.

(b) Regarding the second item in formula (16) A flip / 1 compartment

In addition, it is also necessary to consider the case where oxygen from the side of the counter electrode penetrates the liquid layer in the form of bubbles to reach the measuring electrode. In general, if the resistance of the liquid layer to the gas is greater than the gas pressure on the side of the counter electrode, the gas does not penetrate the liquid layer to reach the measuring electrode, and the accumulation of the gas pressure on the side of the counter electrode is related to the resistance of the outlet hole. If the resistance of the liquid layer to the gas is greater than the resistance of the gas outlet to the gas, then the gas on the side of the counter electrode does not penetrate the liquid layer to reach the measuring electrode.

Next, we will study the conditions that should be satisfied to prevent the oxygen from penetrating the liquid layer in the form of bubbles and reaching the measuring electrode.

The flow in the capillary is approximated as laminar flow [Journal of Fluid Mechanics, 2000, 28(2) 38-39], and the flow resistance of the vent is:

R Outlet = 128 μ Gas 1 Outlet / d Outlet (18)

Among them, the length of the air outlet, which is the diameter of the air outlet, is the air viscosity.

The flow resistance of the liquid electrolyte barrier R «« is:

R liquid channel - 128 μ liquid 1 liquid layer / d liquid layer (19)

Among them, 1 « layer is the length of the liquid layer, d « layer is the diameter of the liquid layer, which is the viscosity of the liquid.

When 1 «« > 1 ^ _3⁄4 , the effect of oxygen penetrating the liquid layer in the form of bubbles can be ignored. Substitute Equations (18) and (19) give:

1 liquid layer / d > gas 1 d air outlet (20)

It is assumed that sulfuric acid is used as the liquid electrolyte. At this time, since the viscosity of the air μ ^=1.8Χ 10 - ⁵ Ρ · s, the viscosity U of the sulfuric acid is about 1.2 X If) - ² Pa · s,

1 liquid layer / d liquid layer ⁴ > 1.5X 10- ^J XI air vent / vent

Example 1: In an extreme case, if the cross-sectional area of the hole, that is, the exposed area of the liquid layer, accounts for 50% of the cross-sectional area of the sensor, that is, the diameter of the hole is 7 mm and the thickness of the liquid layer is 0.77 mm, then

A hole _{^{/ d ^ ¾ 4 <2.1X 10}} 8

Assuming that the venting length is 1 mm, the diameter of the venting hole needs to be greater than 1.5 mm.

Example 2: In the other extreme case, if the cross-sectional area of the hole, that is, the exposed area of the liquid layer, is 1% of the cross-sectional area of the sensor, that is, when the diameter of the hole on the partition is 1 mm, and the thickness of the liquid layer is 15 μm,

1 vent / d vent ⁴ < 10 ¹⁰

At this time, when the length of the air outlet is 1 mm, the diameter of the air outlet needs to be larger than 0.56 mm.

It can be seen that when a liquid electrolyte is used as the electrolyte compartment in the oxygen sensor, it is necessary to consider the influence of the diameter of the pore on the performance of the sensor.

(c) Effect of liquid layer resistance on sensor performance

In addition, when using a liquid electrolyte as the electrolyte barrier, we need to consider whether the liquid layer resistance can meet the sensor performance requirements.

In general, the magnitude of the liquid phase resistance of the sensor affects the potential control accuracy of the sensor's measuring electrode and the response time of the sensor. However, since the operating current of the sensor is generally small, the requirements for the resistance are not critical. For example, when 1 <500, the response current is 0.5 mA, its effect on potential control accuracy is 25 mV. For an oxygen sensor in the ultimate diffusion control zone, this fluctuation in the potential has little effect on the sensor's measured signal.

The liquid phase resistance generally satisfies the following relationship: R = P l / A. For a 6M sulfuric acid solution, its conductivity G = 60 Ω P = l / G. When R < 50Q is required, R/p < 3000, that is, 1/A < 3000. This means that when the thickness of the liquid layer is less than 3,000 times the area of the liquid layer, the liquidus resistance is less than 50 Ω, which has little effect on the measured signal of the sensor.

From the above analysis, when the oxygen sensor uses the liquid electrolyte as the electrolyte separator, the influence of oxygen dissolved in the liquid layer and then diffused to the measuring electrode can be basically ignored. In order to prevent oxygen from the side of the counter electrode from penetrating the liquid layer in the form of bubbles and reaching the measuring electrode, it is necessary to design a liquid electrolyte. The size of the compartment and the venting hole is appropriately selected to satisfy the liquid electrolyte: μ liquid 1 pro/d liquid layer ⁴ > μ gas 1 out gas / d ^ ⁴ . In addition, in order to reduce the influence of the liquid phase resistance of the sensor on the potential control accuracy of the sensor measuring electrode, it is desirable to have a liquid phase resistance of < 50 Ω. In summary, when the oxygen sensor uses a liquid electrolyte as the electrolyte barrier, it is critical to block the diffusion of oxygen to the measuring electrode in the form of a gas phase. As long as the liquid seal is ensured, there is no gas passage, and the air outlet is unobstructed, the effect of oxygen penetrating the liquid layer in the form of bubbles can be eliminated.

III. Electrode/Separator/Electrode Assembly of the Invention

Example 1 : Electrolyte compartment with single pore

Figure 2 illustrates an electrode/interlayer/electrode assembly 240 in accordance with an embodiment of the present invention. The assembly is a two-electrode assembly comprising a spacer 210, a measuring electrode 112 and a counter electrode 114. The measuring electrode 112 is located on one side of the spacer 210, and the counter electrode 114 is located on the other side of the spacer 210. The barrier 210 may be a polymeric film having a hole 214, such as polypropylene, polyester, Nafion, GEFC, etc., and the pores 214 are filled with a hydrophilic absorbent material. Preferably, a first hydrophilic liquid absorbing material layer 156 may be disposed between the barrier layer 210 and the measuring electrode 112, and a second hydrophilic liquid absorbing material layer 156 may be disposed between the barrier layer 210 and the counter electrode 114. The first and second hydrophilic absorbent material layers 156 and the hydrophilic liquid absorbing material in the pores 214 may be glass fibers impregnated with an acid electrolyte solution such as sulfuric acid and phosphoric acid. The first and second hydrophilic absorbent material layers 156 introduce the acid electrolyte solution stored in the hydrophilic liquid absorbing material 152 of the reservoir 150 into the pores 214 by capillary action to connect the pores up and down.

Hole 214 can be anywhere on barrier 210. Preferably, the aperture 214 is offset from the electric field formed by the measuring electrode 112 and the counter electrode 114. The shape of the holes may also be arbitrary, such as a circle, an ellipse, a square, or the like.

In the electrode/interlayer/electrode structure of this embodiment, the spacer 210 having a hole can function to ionize and prevent diffusion of oxygen from the side of the counter electrode. Under the premise of ensuring the smooth passage of the ion channel, the smaller the cross-sectional area of the hole 214, the less likely it is to generate a gas passage in the hole in a dry environment. However, in order to quickly draw the acid electrolyte solution from the reservoir 150 into the hole 214 and wet the measuring electrode and the counter electrode, the larger the area of the hole 214, the better. Considering these two factors comprehensively, combined with the actual needs of ensuring the normal use of the sensor, the cross-sectional area of the hole should preferably be 1% to 50%, preferably in the range of 10 to 15%.

For example, for a 4R sensor, assume that the cross-sectional area of the oxygen inlet capillary is A. Approximately 8 X 10_ ⁹ m ² (0.1 mm diameter), the length of the capillary is 1 in. About 10_ ³ m, the 4R sensor has a cross section of 8 X 10_ ⁵ m ² . A «=4 X 10_ ⁵ m ² when the cross-sectional area of the aperture on the barrier occupies 50% of the cross-section of the sensor. Use the formula (17) A fine / 1 compartment < (人. / 1 person.) 6.5 10 ³ know that as long as 1 compartment > 7.7 X 10_ ⁴ m, that is, the length of the hole of the compartment is greater than 0.77 mm, you can Ignoring the acid electrolysis in the oxygen passage hole 214 on the side of the counter electrode 114 The effect of the solution diffusing to the measuring electrode 112. In addition, it can be known from the formula (20) that if sulfuric acid is used as the electrolyte solution and the length of the vent hole is 1 mm, as long as the diameter of the vent hole is larger than 1.5 mm, the gas on the side of the electrode can be ignored as a bubble. The effect of the acid electrolytic solution in 214 diffusing to the measuring electrode 112.

As another example, for the 4R sensor, it is assumed that the cross-sectional area of the oxygen inlet capillary is A. Approximately 8 X 10_ ⁹ m ² (0.1 mm diameter), the length of the capillary is 1 in. About 10_ ³ m, the 4R sensor has a cross section of 8 X 10_ ⁵ m ² . When the cross-sectional area of the pores on the interlayer occupies 1% of the cross section of the sensor, it can be known from the formula (17) that as long as l > 1.5 X l (T ⁵ _m , that is, the length of the pores of the interlayer is greater than 15 μm, It is possible to ignore the influence of the diffusion of oxygen through the acid electrolytic solution to the measuring electrode. Further, it can be known from the formula (20) that if sulfuric acid is used as the electrolyte solution, the length of the vent hole is 1 mm, as long as the diameter of the vent hole is larger than 0.56 mm It is possible to ignore the influence of the gas on the side of the electrode in the form of bubbles passing through the acid electrolytic solution in the hole 214 to the measuring electrode 112.

If the position of the hole 214 is made to deviate from the electric field formed by the measuring electrode 112 and the counter electrode 114, the actual oxygen passage is increased. Accordingly, the thickness of the barrier 1 can be made smaller.

It has been found that if the acid electrolyte solution is fixed by using a hydrophilic fibrous network absorbent material such as glass fiber, and the solid electrolyte film such as polypropylene, polyethylene, Nafion, and GEFC is not used to fix the acid electrolyte solution, then In a dry environment, the oxygen sensor easily loses moisture. When the acid electrolyte solution infiltrated in the hydrophilic fibrous web layer is reduced, the porous air passage is formed due to the loose hydrophilic fibrous web layer, thereby distorting the measurement signal of the sensor. Example 2: Porous electrolyte compartment

For the above-mentioned single-hole electrolyte separator, the larger the pore area accounts for the cross-sectional area of the sensor, the more difficult it is to fix the acid electrolyte solution in the pore. To this end, the inventors designed a porous electrolyte barrier.

1. Two-electrode assembly

FIG. 3 illustrates an electrode/interlayer/electrode assembly 340 in accordance with another embodiment of the present invention. Similar to the previous embodiment, the assembly is also a two-electrode assembly including a spacer 310, a measuring electrode 112 and a counter electrode 114. The measuring electrode 112 is located on one side of the spacer 310, and the counter electrode 114 is located on the other side of the spacer 310. The barrier layer 310 may be a polymer film having a plurality of holes 314, such as polypropylene, polyester, Nafi ₀ n, GEFC, etc., and the plurality of holes 314 are filled with a hydrophilic liquid absorbing material. Preferably, a first hydrophilic liquid absorbing material layer 156 may be disposed between the barrier layer 310 and the measuring electrode 112, and a second hydrophilic liquid absorbing material layer 156 may be disposed between the barrier layer 310 and the counter electrode 114. The first and second hydrophilic absorbent material layers 156 and the hydrophilic liquid absorbing material of the plurality of pores 314 may be Glass fibers impregnated with an acid electrolyte solution such as sulfuric acid and phosphoric acid. First and second hydrophilic absorbent material layers

156 The acid electrolyte solution stored in the hydrophilic liquid absorbing material 152 of the reservoir 150 is introduced into the plurality of holes 314 by capillary action to connect the holes up and down.

The plurality of apertures 314 can be anywhere on the spacer 310. Preferably, the holes 214 are offset from the electric field formed by the measuring electrode 112 and the counter electrode 114. The shape of the holes may also be arbitrary, such as a circle, an ellipse, a square, or the like.

In the electrode/interlayer/electrode structure of the present embodiment, the spacer 310 having a plurality of holes can function to ionize and prevent diffusion of oxygen from the side of the counter electrode.

An electrolyte barrier having a plurality of pores 314 increases the total pore area compared to an electrolyte barrier having a single orifice. Thus, it is easier to draw the electrolyte solution in the reservoir into the hole 314 by capillary action of the hydrophilic liquid absorbing material, and to infiltrate the measuring electrode and the counter electrode, so that the oxygen sensor quickly enters the working state. On the other hand, with the same total pore area, the larger the number of holes 314, the smaller the cross-sectional area of each hole. Thus, the acid electrolyte in the pores can be better fixed, and in a dry environment, it is not easy to generate a gas passage in the pores. The acid electrolyte solution filled in the well forms an ion channel between the measuring electrode and the counter electrode, and the liquid seal in the hole and the solid portion of the partition separate the upper and lower air chambers, preventing oxygen diffusion on the side of the electrode to the measurement. The electrodes ensure the accuracy of the measured signal. In addition, under the condition of having the same total pore area, the more the number of pores, the lower the requirement for the pores. For example, when the total hole cross-sectional area (ie, the liquid layer exposed area) accounts for 50% of the sensor cross-sectional area of 8 X 10_ ⁵ m ² and the liquid layer thickness is 0.77 mm, if there is only one hole, the diameter of the hole on the interlayer Approximately 7 mm, and assuming that the length of the vent is 1 mm, the diameter of the vent needs to be greater than 1.5 mm. However, if 4 holes are opened in the partition, the diameter of the partition hole is about 3.6 mm, and if the length of the air hole is 1 mm, then

4 1 liquid layer / d liquid layer ⁴ >1.5 X 10- ^J XI air outlet / air outlet

It can be known that the diameter of the vent hole needs to be greater than 0.53 mm. It can be seen that under the condition of having the same total pore area, the more the number of holes, the lower the requirement for the air outlet.

2. Three-electrode assembly

4 shows an electrode/interlayer/electrode assembly 440 in accordance with yet another embodiment of the present invention. The assembly is a three-electrode assembly including a first barrier 410, a second barrier 412, a measurement electrode 112, a counter electrode 114, and a reference electrode 116. The measuring electrode 112 is located on the first side of the first spacer 410, the reference electrode 116 is located between the second side of the first spacer 410 and the first side of the second spacer 412, and the counter electrode 114 is located in the second spacer 412. The second side. The first barrier layer 410 and the second barrier layer 412 may be a polymer film having a plurality of holes 414, such as polypropylene, polyester, Nafion, GEFC, etc., and the plurality of holes 414 are filled with a hydrophilic liquid absorbing material. Preferably, A first hydrophilic liquid absorbing material layer 156 may be disposed between the measuring electrode 112 and the first barrier layer 410, and a second hydrophilic liquid absorbing material layer 156 may be disposed between the first barrier layer 410 and the reference electrode 116. A third hydrophilic liquid absorbing material layer 156 is disposed between the specific electrode 116 and the second barrier layer 412, and a fourth hydrophilic liquid absorbing material layer 156 is disposed between the second barrier layer 412 and the counter electrode 114. The first, second, third and fourth hydrophilic absorbent material layers 156 and the hydrophilic liquid absorbing material of the plurality of pores 314 may be glass fibers impregnated with an acid electrolyte solution such as sulfuric acid and phosphoric acid. The first, second, third and fourth hydrophilic liquid absorbing material layers 156 introduce the acid electrolyte solution stored in the hydrophilic liquid absorbing material 152 of the liquid storage tank 150 into the plurality of holes 414 by capillary action, and the holes are opened up and down. Connected.

The plurality of apertures 414 can be anywhere on the first and second barrier layers. Preferably, the holes 414 are offset from the electric field formed by the measuring electrode 112 and the counter electrode 114. The shape of the holes may also be arbitrary, such as a circle, an ellipse, a square, or the like.

As is well known, the reference electrode 116 acts as a stable potential, which facilitates the measurement of the sensor to be more accurate. In the present embodiment, the reference electrode 116 is disposed in the middle, and a plurality of holes are disposed outside the spacer. This will help to reduce the influence of the detection gas and the interfering gas on the potential of the reference electrode, and ensure that the reference potential does not drift. Example 3: Electrolyte compartment of a microwell array

In this embodiment, the electrolyte barrier layer is a hydrophilic track etched polycarbonate microporous array template, and both sides may be fixed with a hydrophilic fibrous web layer. The hydrophilic fibrous web layer rapidly sucks the acid electrolyte solution into the microporous array of the template by capillary action, and connects the measuring electrode and the counter electrode. In principle, as long as the microwell array template is hydrophilic, chemically resistant (ie stable in concentrated acid), and stable in the sensor operating range of -40 to 65 °C, it can be used.

The thickness of the array template can be in the range of 6 to 11 microns. Different micropore apertures are available for templates of different thicknesses. The micropore diameter may be in the range of 0.015-1 microns depending on the sealing solution.

The smaller the capillary pores of the microwell array template, the more pronounced the capillary action and the stronger the ability to retain the aqueous solution, thereby making it easier to ensure the liquid seal. In the case where the microwell array template is completely wetted, the smaller the porosity of the array template, the better the effect of isolating the gas. Preferably, the porosity is no more than 15%. However, in order to ensure ion conduction, the porosity is preferably not less than 0.1%.

In the present embodiment, since the microporous array spacer is used to fix the electrolyte, the design of the air outlet is required to be wider. For arrays having a thickness in the range of 6 to 11 μm and a pore diameter in the range of 0.015-1 μm Column template, porosity <15%, if sulfuric acid is used as the electrolyte solution, and the length of the vent is designed as

1 mm, then the diameter of the vent hole is larger than 0.3 mm to block the oxygen on the side of the counter electrode from penetrating through the liquid layer. This is very beneficial for making small sensors.

In addition, for the hydrophilic microporous array spacer, since the pore size is small and the liquid absorbing ability is strong, the ratio of the total pore area to the cross-sectional area of the sensor can be broadened to 0.1% to 50%, so that more suitable materials can be selected. IV. Gas sensor of the present invention

The above theoretical derivation for the oxygen sensor and the structure of each embodiment can be extended to other electrolytic type gas sensors. For example, the size of the through hole and the inlet hole may be selected according to different gases to be tested, thereby preventing gas generated at the counter electrode from being reversely diffused to the measuring electrode due to oxidation or reduction reaction. It is also possible to select the size of the pores according to different electrolyte solutions, thereby preventing the gas generated at the electrodes from penetrating the liquid layer in the form of bubbles.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto. Various changes and modifications can be made by those skilled in the art based on the above description. Various changes and modifications may be made without departing from the spirit and scope of the invention. The scope of the invention is defined by the appended claims.

Claims

Rights request

1. An oxygen sensor comprising:

An electrolyte barrier layer (110) comprising at least one through hole (214, 314, 414) filled with an electrolyte;

At least one measuring electrode (112) located on one side of the electrolyte compartment, and a hydrogen gas flowing through an inlet hole undergoes a reduction reaction at the measuring electrode to form a water molecule;

At least one counter electrode (114) located on the other side of the electrolyte compartment, the water molecules passing through the through hole and oxidized at the counter electrode to form oxygen, hydrogen ions and electrons Oxygen is discharged through an air outlet;

Wherein, the size of the at least one through hole satisfies the following conditions:

A liquid phase / 1 compartment < 6.5 X 10 (A inlet / 1 inlet)

2 . The oxygen sensor according to claim 1 , wherein the through hole comprises a hydrophilic liquid absorbing material, a total cross-sectional area of the at least one through hole and a cross-sectional area of the electrolyte separator The ratio is in the range of 1% - 50%.

The oxygen sensor according to claim 2, wherein a ratio of a total cross-sectional area of the at least one through hole to a cross-sectional area of the electrolyte separator is in a range of 10% to 15%.

The oxygen sensor according to claim 2 or 3, wherein the position of the through hole is offset from an electric field formed by the at least one measuring electrode and the at least one counter electrode.

The oxygen sensor according to claim 1, wherein the electrolyte barrier layer is a hydrophilic microwell array template, and a total cross-sectional area of the microwell array and a cross-sectional area of the electrolyte separator The porosity of the microwell array template is in the range of 0.1% to 15%, in the range of 0.1% to 50%.

The oxygen sensor according to claim 4 or 5, wherein the size of the air outlet hole satisfies the following conditions: ^ Liquid 1 liquid layer / d liquid layer > μ gas 1 air outlet / d air outlet

The oxygen sensor according to claim 6, wherein the electrolytic solution in the at least one hole has a resistance of less than 50 Ω.

The oxygen sensor according to claim 7, wherein the electrolyte is sulfuric acid, and the length of the at least one through hole is less than 3000 times the total sectional area of the at least one through hole.

The oxygen sensor according to claim 4 or 5, further comprising a first hydrophilic liquid absorbing material layer (156) disposed between the electrolyte barrier layer and the measuring electrode.

10. The oxygen sensor of claim 9 further comprising a second hydrophilic absorbent material layer (156) disposed between said electrolyte barrier and said counter electrode.

11. The oxygen sensor of claim 10, further comprising a reference electrode (116), a third hydrophilic liquid absorbing material layer (156), an additional electrolyte barrier layer (412), and a fourth Hydrophilic absorbent material layer

( 156), the additional electrolyte compartment includes at least one through hole (414), the through hole is filled with the electrolyte, wherein the reference electrode, the third hydrophilic liquid absorbing material layer, The additional electrolyte barrier layer and the fourth hydrophilic liquid absorbing material layer (156) are sequentially disposed between the third hydrophilic liquid absorbing material layer and the counter electrode.

The oxygen sensor according to claim 4 or 5, further comprising:

a reservoir (150), the reservoir being located on the other side of the electrolyte barrier and comprising a moisture releasing material (152).

13. The oxygen sensor of claim 12, further comprising an annular gasket (146) located on at least one of the sides of the electrolyte barrier for preventing oxygen from leaking through the electrolyte barrier .

14. The oxygen sensor according to claim 13, further comprising: a first oxygen permeable/waterproof membrane (142) located at an end of the vent hole adjacent to the electrolyte compartment, permeable to oxygen And for preventing moisture from entering the vent;

a glass microfiber paper (144) positioned between the reservoir and the electrolyte barrier to help regulate the humidity of the electrolyte barrier;

A second oxygen permeable/waterproof membrane (142) is located at one end of the inlet aperture adjacent the electrolyte barrier, is permeable to oxygen, and serves to prevent moisture from entering the inlet aperture.

The oxygen sensor according to claim 1, wherein the electrolyte compartment is a polymer film, and the material of the polymer film is selected from the group consisting of polypropylene, polyester, Nafion and GEFC, the hydrophilic The liquid absorbing material is a glass fiber impregnated with the electrolyte.

16. A gas sensor comprising:

An electrolyte separator (110) comprising at least one through hole (214, 314, 414) filled with an electrolyte;

At least one measuring electrode (112) located on one side of the electrolyte compartment, and a reaction in the reduction reaction and the oxidation reaction occurs at a gas passing through the inlet hole at the measuring electrode;

At least one counter electrode (114) located on the other side of the electrolyte barrier, another reaction in the reduction reaction and the oxidation reaction occurring at the counter electrode,

Wherein the at least one through hole and the air inlet are sized to prevent reverse generation of gas generated at the counter electrode due to oxidation or reduction reaction to the measuring electrode.