KR102758502B1 - A hydrogen gas sensor - Google Patents

Abstract

According to one embodiment of the present invention, a hydrogen detection sensor comprises: a substrate; an insulating layer disposed on an upper portion of the substrate and including a heater and a temperature sensor therein; a hydrogen detection unit formed on an upper surface of the insulating layer and made of an alloy of a catalytic metal and a transition metal, the electrical resistance of which reversibly changes by hydrogen adsorption; and the hydrogen detection unit comprises a first alloy layer and a second alloy layer laminated on an upper portion of the second alloy layer, wherein the transition metal of the first alloy layer and the transition metal of the second alloy layer are mutually different.

Description

Hydrogen detection sensor {A HYDROGEN GAS SENSOR}

The present invention relates to a hydrogen detection sensor, and more particularly, to a hydrogen detection sensor capable of detecting hydrogen by utilizing a change in resistance that occurs when hydrogen dissociates upon penetration and adsorption into a metal.

As interest in eco-friendly energy is increasing, hydrogen is being considered as one of the most promising renewable energy resources as clean energy.

However, hydrogen has the fastest flame speed, so if even a small amount leaks into the air, it can easily explode with a small amount of ignition heat, which is a fatal flaw. Therefore, if hydrogen is to be widely used like fossil fuels, the use of a hydrogen detection sensor that can ensure safety against hydrogen leak accidents is essential.

In particular, as the commercialization of hydrogen fuel cell vehicles accelerates, the importance of developing high-sensitivity hydrogen detection sensors that are inevitably used to prevent hydrogen gas explosion accidents and ensure safety is increasing.

A hydrogen detection sensor can be said to be a transducer element that can detect hydrogen gas and generate an electrical signal of a size proportional to the hydrogen gas concentration.

In particular, groundbreaking sensor technology has been advanced by applying silicon process technologies such as MEMS, and various types of hydrogen detection sensors with many advantages, such as the production of micro-sized ultra-small sensor platforms, high gas sensitivity, fast response speed, and greatly reduced power consumption of sensor elements, are being proposed.

A hydrogen detection sensor that can detect the concentration of hydrogen based on the change in resistance due to hydrogen adsorption and penetration using a double nano palladium thin film is a sensor that has the advantages of excellent selectivity, sensitivity, and response speed for the target gas, and there is an increasing demand for further improvement in the response speed.

In order to reflect the requirements of the above-described hydrogen detection sensor according to one embodiment of the present invention, the following problems are aimed at being solved.

The purpose is to provide a hydrogen detection sensor with an improved hydrogen detection reaction speed compared to conventional sensors.

In addition, a hydrogen detection sensor with improved heater power efficiency is provided.

The problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned can be clearly understood by a person having ordinary knowledge in the relevant technical field from the description below.

According to one embodiment of the present invention, a hydrogen detection sensor comprises: a substrate; an insulating layer disposed on an upper portion of the substrate and including a heater and a temperature sensor therein; a hydrogen detection unit formed on an upper surface of the insulating layer and made of an alloy of a catalytic metal and a transition metal, the electrical resistance of which reversibly changes by hydrogen adsorption; and the hydrogen detection unit comprises a first alloy layer and a second alloy layer laminated on an upper portion of the second alloy layer, wherein the transition metal of the first alloy layer and the transition metal of the second alloy layer are mutually different.

It is preferable that the above catalytic metal contains palladium (Pd).

It is preferable that the transition metal of the first alloy layer includes nickel (Ni), and the transition metal of the second alloy layer includes gold (Au).

It is preferable that the first alloy layer is a line pattern in which a plurality of alloy lines are formed along a preset direction, and the second alloy layer is formed in a laminated manner on top of the plurality of alloy lines.

It is preferable that the thickness of the second alloy layer be formed to be smaller than the thickness of the first alloy layer.

It is preferable that the first alloy layer be formed to have a thickness of 10 nm or more and 60 nm or less, and the second alloy layer be formed to have a thickness of 1 nm or more and 5 nm or less.

It is preferable that the lower part of the above substrate is etched into a preset shape to form an etching area.

It is preferable that the above etching area be formed in the middle portion between one side and the other side of the substrate.

A hydrogen detection sensor according to one embodiment of the present invention can be expected to have the effect of ensuring hydrogen detection stability at high concentrations while simultaneously improving the hydrogen detection response speed by applying a Pd-Ni alloy and a Pd-Au alloy together as a hydrogen detection unit.

In addition, by forming an etched area at the lower part of the substrate, it is expected that the power efficiency of the heater can be improved by improving the thermal conductivity generated from the heater.

The effects of the present invention are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below.

FIG. 1 is a drawing schematically illustrating a cross-section of a hydrogen detection sensor according to one embodiment of the present invention.
Figure 2 is a graph comparing the hydrogen response speed for 1% hydrogen concentration in a hydrogen detection sensor according to one embodiment of the present invention and a conventional hydrogen detection sensor under a 23°C environment.
FIG. 3 is a graph comparing the recovery speed after hydrogen gas removal for 1% hydrogen concentration in a hydrogen detection sensor according to an embodiment of the present invention and a conventional hydrogen detection sensor under a 23°C environment.
FIG. 4 is a graph comparing the hydrogen response speed for a 4% hydrogen concentration in a hydrogen detection sensor according to an embodiment of the present invention and a conventional hydrogen detection sensor under a 23°C environment.
FIG. 5 is a graph comparing the recovery speed after hydrogen gas removal for 4% hydrogen concentration in a hydrogen detection sensor according to an embodiment of the present invention and a conventional hydrogen detection sensor under a 23°C environment.
Figure 6 is a plan view of a hydrogen detection sensor for explaining an additional example of forming a first alloy layer.
Figure 7 is a cross-sectional view of section A-A' of Figure 6.
FIG. 8 is a drawing schematically illustrating a cross-section of a hydrogen detection sensor according to another embodiment of the present invention.
FIG. 9 is a diagram illustrating the results of thermal conductivity modeling according to the depth of an etching area in a hydrogen detection sensor according to another embodiment of the present invention.
Figure 10 is a graph of thermal conductivity calculated based on the modeling results of Figure 9.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Regardless of the drawing symbols, identical or similar components will be given the same reference numerals and redundant descriptions thereof will be omitted.

In addition, when describing the present invention, if it is judged that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, it should be noted that the attached drawings are only intended to facilitate easy understanding of the idea of the present invention, and should not be construed as limiting the idea of the present invention by the attached drawings.

Hereinafter, a hydrogen detection sensor according to the present invention will be described with reference to FIGS. 1 to 10.

A hydrogen detection sensor according to one embodiment of the present invention is configured to include a substrate (100), an insulating layer (200), and a hydrogen detection unit (300) as illustrated in FIG. 1.

The substrate (100) is configured to support the insulating layer (200) and hydrogen detection unit (300) to be described later. A substrate of various materials and structures can be used. A substrate made of paper, polymer, glass, metal, ceramic, etc. can be used. In particular, a silicon substrate is preferable, but the material and structure are not particularly limited.

The insulating layer (200) is formed on a substrate (100) and may be configured to include a heater (210) and a temperature sensor (220) therein. In particular, it is preferable to form the insulating layer (200) with a material that undergoes little chemical change even when the heater (210) is heated at a high temperature. The insulating layer (200) may be formed with a silicon nitride film formed through a CVD (Chemical Vapor Deposition) process.

As described above, the insulating layer (200) includes a heater (210) that generates heat by applying power thereto and a temperature sensor (220) for detecting the temperature of the hydrogen detection sensor.

Since the hydrogen detection sensor is affected by external environments such as temperature and humidity, such that the reaction speed increases and the sensitivity decreases as the temperature rises, it is possible to maintain an appropriate temperature of the hydrogen detection sensor according to the purpose of use and environment by controlling the heater (210) in real time based on the temperature detected by the temperature sensor (220).

In addition, in order to insulate between the heater (210), the temperature sensor (220), and the substrate (100), it is preferable to provide an additional insulating layer (120) at the interface between the heater (210), the temperature sensor (220), and the substrate (100).

The hydrogen detection unit (300) is formed on the upper part of the insulating layer (200) and is configured to perform the function of measuring electrical resistance according to hydrogen concentration, and a plurality of hydrogen detection electrodes (not shown) may be arranged at the end of the hydrogen detection unit (300).

These hydrogen-sensing electrodes are configured to be in contact with the hydrogen-sensing unit (300) and can be formed of a conductive material, for example, a metal, and their shape or structure is not particularly limited.

In addition to the hydrogen detection electrode described above, the hydrogen detection sensor is provided with a temperature sensor electrode and a heater electrode for electrical connection with a heater (210) and a temperature sensor (220), and the temperature sensor electrode and the heater electrode are configured to be electrically connected to the control unit.

In particular, the hydrogen detection unit (300) can be formed of an alloy material of a catalytic metal and a transition metal, the electric resistance of which changes as the amount of hydrogen adsorption increases. The catalytic metal can include palladium (Pd), platinum (Pt), etc., and the transition metal can include nickel (Ni), magnesium (Mg), gold (Au), etc., which can suppress the crystal phase transformation of the catalytic metal.

Meanwhile, pure palladium has a strong ability to adsorb hydrogen, and among the crystal phases of palladium, the alpha (α) phase can reversibly change electrical resistance in proportion to the amount of hydrogen adsorbed, so it is generally used as a hydrogen detection material. However, when the amount of hydrogen adsorbed increases excessively, that is, when exposed to a high concentration of hydrogen of 4% or more, there is a problem that the crystal phase transforms into the beta (β) phase.

The above beta (β) phase palladium has a characteristic in which the electrical resistance converges to a constant value when the amount of hydrogen adsorption increases, so it cannot be used as a hydrogen detection material. In addition, when it transforms from the alpha (α) phase to the beta (β) phase, it undergoes volume expansion, so there is a problem in that cracks or fractures occur internally due to a reversible reaction with hydrogen, which reduces the durability and lifespan of the hydrogen detection unit (300).

Therefore, it is preferable that the hydrogen detection unit (300) be formed of an alloy of palladium, which is a catalytic metal, and nickel or magnesium, which is a transition metal. In this case, when palladium in the alpha (α) phase is alloyed with nickel or magnesium, phase transformation is suppressed, so that even when exposed to a high concentration of hydrogen, transformation from the alpha (α) phase to the beta (β) phase can be prevented. As a result, when the alloy of palladium and nickel is used as a hydrogen detection material, a high concentration of hydrogen can be detected.

Meanwhile, a hydrogen detection unit (300) according to one embodiment of the present invention is composed of a first alloy layer (310) and a second alloy layer (320) laminated on top of the first alloy layer (310).

At this time, it is preferable that the first alloy layer (310) is made of an alloy of palladium (Pd) and nickel (Ni) as described above, and the second alloy layer (320) is made of an alloy of palladium (Pd) and gold (Au).

When a palladium (Pd) and nickel (Ni) alloy is applied to a hydrogen detection unit (300), the stability of high-concentration hydrogen detection is high, but in order to additionally improve the hydrogen detection reaction speed, a second alloy layer (320) made of an alloy of palladium (Pd) and gold (Au) is laminated and formed on top of a first alloy layer (310) made of an alloy of palladium (Pd) and nickel (Ni). Here, the second alloy layer (320) can be formed as a continuous layer, but it may also be formed as a random island type layer.

In order to verify the effect of additional formation of the second alloy layer (320) described above, the resistance change, response time, and recovery time of the hydrogen detection unit (300) were verified when the second alloy layer (320) was applied and not applied in situations where the hydrogen concentration was 1% and 4%, respectively. The results are as shown in <Table 1> below.

H ₂
density Resistance change (Ω) Reaction time (s) Recovery time (s) No.1 No.2 No.3 No.1 No.2 No.3 No.1 No.2 No.3 0.1% 1.3 1.7 0.6 55 25 55 100 60 5 0.3% 2.0 2.5 0.84 26 15.1 7.1 100 50 6 0.5% 2.5 3.1 1.17 18.5 9.4 3.7 85 45 8.6 1% 3.7 4.0 1.62 11 6.5 3.0 68 35 6.2 2% 5.1 5.5 2.29 9.0 4.6 2.1 59 28 4 3% 6.1 6.5 2.96 7.2 3.7 1.8 50 25 3.7 4% 7.0 7.4 3.23 5.6 3.4 1.0 45 20 3.5

In the above Table 1, No. 1 is a hydrogen detection sensor in which only a first alloy layer (310) composed of an alloy of palladium (Pd) and nickel (Ni) is formed at room temperature (22 to 23°C), No. 2 is a hydrogen detection sensor in which a second alloy layer (320) composed of an alloy of palladium (Pd) and gold (Au) is additionally formed on the first alloy layer (310) composed of an alloy of palladium (Pd) and nickel (Ni) at room temperature (22 to 23°C), and No. 3 is a hydrogen detection sensor in which a second alloy layer (320) composed of an alloy of palladium (Pd) and gold (Au) is additionally formed on the first alloy layer (310) composed of an alloy of palladium (Pd) and nickel (Ni) at 80°C.

As confirmed in the above Table 1, in the case of the No. 2 hydrogen detection sensor in which the second alloy layer (320) is additionally formed on the first alloy layer (310), the resistance change is confirmed to increase by 20 to 30% at a hydrogen concentration of 1% or less, and by 6 to 8% at a concentration of 1% or more, compared to the No. 1 hydrogen detection sensor to which only the first alloy layer (310) is applied. Through this, it is understood that when the second alloy layer (320) is applied, the sensitivity (signal change according to concentration change) is similar to or slightly increased compared to when the second alloy layer (320) is not applied.

In addition, in terms of hydrogen response time, the No. 2 hydrogen detection sensor was confirmed to be reduced by 40 to 50% compared to the No. 1 hydrogen detection sensor, and the recovery time was also confirmed to be reduced by 40 to 50% compared to the No. 1 hydrogen detection sensor.

The above-described contents can be confirmed in FIGS. 2 and 3, which compare the resistance change amount, hydrogen reaction speed, and recovery speed of a hydrogen detection sensor according to one embodiment of the present invention to which the first alloy layer (310) and the second alloy layer (320) are applied together and a conventional hydrogen detection sensor to which only the first alloy layer (310) is applied, under an environment of 23°C and a hydrogen concentration of 1%.

In addition, FIGS. 4 and 5 are graphs comparing the resistance change, hydrogen reaction speed, and recovery speed for 4% hydrogen concentration in a hydrogen detection sensor according to an embodiment of the present invention to which the first alloy layer (310) and the second alloy layer (320) are applied together and a conventional hydrogen detection sensor to which only the first alloy layer (310) is applied under a 23°C environment, and as described above, it can be confirmed that the hydrogen reaction speed and recovery speed of the hydrogen detection sensor according to an embodiment of the present invention to which the first alloy layer (310) and the second alloy layer (320) are applied together are reduced compared to the conventional hydrogen detection sensor to which only the first alloy layer (310) is applied even when detecting high concentrations of hydrogen.

Considering the above contents, it can be confirmed that when the second alloy layer (320) is laminated and formed on top of the first alloy layer (310), the sensitivity of the hydrogen detection sensor does not decrease and the response speed is improved by more than twice.

Furthermore, in the case of the No. 3 hydrogen detection sensor in which a second alloy layer (320) is additionally formed on the first alloy layer (310) at a high temperature (80°C) rather than at room temperature, it is confirmed that the resistance change increases by 55 to 65% compared to the hydrogen detection sensor in which the second alloy layer (320) is not additionally formed, and the response time and recovery time are confirmed to decrease by 50 to 60% and 80 to 90%, respectively. Through this, it can be seen that the performance of the hydrogen detection sensor according to an embodiment of the present invention is improved compared to the conventional hydrogen detection sensor not only at room temperature but also at high temperatures.

It is preferable that the thickness of the second alloy layer (320) be formed to be smaller than the thickness of the first alloy layer (310). At this time, the thickness of the first alloy layer (310) is formed to a thickness of 10 nm or more and 60 nm or less, which is the smallest thickness at which a continuous thin film is formed, and the thickness of the second alloy layer (320) is formed to a thickness of 1 nm or more and 5 nm or less.

In addition, the second alloy layer (320) can be formed as a continuous layer, but it is also possible to form it as a random island type layer, and the second alloy layer (320) can be formed through a process of scattering Ni-Au in the form of fine particles on top of the first alloy layer (310).

Meanwhile, a hydrogen detection sensor according to one embodiment of the present invention may be formed of a single-area thin film as illustrated in FIG. 1, but in order to increase reactivity, the first alloy layer (310) may be formed as a line pattern composed of a plurality of alloy lines having a thin line width as illustrated in FIGS. 6 and 7 or as a plurality of nano wire patterns, and the second alloy layer (320) may be formed by laminating the plurality of alloy lines.

At this time, one side and the other side of the alloy line constituting the first alloy layer (310) are configured to be respectively connected to different hydrogen sensing electrodes, and these multiple alloy lines are configured so as not to be mutually short-circuited as much as possible.

In this case, the surface area that can come into contact with the first alloy layer (310) and hydrogen is expanded, that is, hydrogen diffuses into the upper and side surfaces of the alloy lines, so that the change in resistance of each alloy line due to hydrogen is large even at a low hydrogen concentration, and furthermore, the diffusion speed of hydrogen is also fast.

In addition, since each alloy line is arranged in parallel and functions as a parallel resistor, the overall resistance of the first alloy layer (310) is calculated as in Equation 1 below. Therefore, even if one or two alloy lines are broken or incorrectly formed during the formation of the first alloy layer (310), it is expected that the change in the overall resistance can be easily read.

<Formula 1>

1/R = 1/R ₁ + 1/R ₂ + 1/R ₃ + 1/R ₄ + … + 1/ _Rn

(Here, R is the total resistance of the first alloy layer, and R ₁ , R ₂ , R ₃ , R ₄ … R _n are the individual resistances of each alloy line.)

Meanwhile, in the case of the heater (210) of the above-described insulating layer (200), it is configured to generate heat by supplying power, and at this time, it is important to minimize the power supply for heat generation of the heater (210).

To this end, a hydrogen detection sensor according to another embodiment of the present invention may be configured to form an etching area (110) by etching a lower portion of a substrate (100) in a preset shape, as shown in FIG. 8.

It is preferable that this etching region (110) be formed in the middle portion between one side and the other side of the substrate (100), and the overall volume of the hydrogen detection sensor is reduced by this etching region (110), which ultimately reduces the heat capacity and thermal conductivity of the hydrogen detection unit (300), and improves the heat efficiency of the heater (210) by attenuating the heat dissipated to the bottom of the element of the hydrogen detection sensor.

In particular, as shown in FIGS. 9 and 10, it is confirmed that the thermal efficiency improves as the depth of the etching area (110) increases, and through this, the overall power efficiency of the hydrogen detection sensor can be maximized.

In addition, the hydrogen detection sensor according to the present invention may further include a control unit that is connected to at least one of the hydrogen detection unit (300), the heater (210), and the temperature sensor (220) to measure and analyze the electrical resistance change of the hydrogen detection unit (300).

This control unit may be formed integrally with the substrate (100) of the hydrogen detection sensor, or may be formed independently, and further, it may be possible to form only a part of the control unit independently.

Above, although the present invention has been described in detail using preferred embodiments, the scope of the present invention is not limited to specific embodiments, and should be interpreted by the appended claims. In addition, those who have acquired common knowledge in this technical field should understand that many modifications and variations are possible without departing from the scope of the present invention.

100: Substrate
110: Etching area
200: Insulation layer
210: Heater
220: Temperature sensor
300: Hydrogen detection unit
310: First alloy layer
320: Second alloy layer

Claims (7)

substrate;
An insulating layer disposed on the upper portion of the substrate and including a heater and a temperature sensor therein; and
A hydrogen sensing part formed on the upper surface of the insulating layer and made of an alloy of a catalytic metal and a transition metal, the electrical resistance of which reversibly changes by hydrogen adsorption;
Including,
The above hydrogen detection unit includes a first alloy layer and a second alloy layer laminated on top of the first alloy layer, wherein the transition metal of the first alloy layer and the transition metal of the second alloy layer are mutually different.
The above catalyst metal includes palladium (Pd).
A hydrogen detection sensor, characterized in that the transition metal of the first alloy layer includes nickel (Ni), and the transition metal of the second alloy layer includes gold (Au).
In claim 1,
The above first alloy layer is a line pattern in which a plurality of alloy lines are formed along a preset direction,
A hydrogen detection sensor, characterized in that the second alloy layer is formed in a laminated manner on top of the plurality of alloy lines.
In claim 1,
The thickness of the second alloy layer is formed to be smaller than the thickness of the first alloy layer,
The thickness of the first alloy layer is formed to be 10 nm or more and 60 nm or less,
A hydrogen detection sensor, characterized in that the second alloy layer has a thickness of 1 nm or more and 5 nm or less.
In claim 1,
A hydrogen detection sensor characterized in that the lower part of the substrate is etched into a preset shape to form an etching area.
In claim 4,
A hydrogen detection sensor, characterized in that the etching region is formed in the middle portion between one side and the other side of the substrate. delete delete

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