Patent Application
20220276176
The present disclosure relates to a hydrogen sensor capable of sensing hydrogen based on color change of a metal oxide and a method for manufacturing the same.
Hydrogen gas (H2) is a source of renewable clean energy with a wide range of applications to a chemical field, fuel cell, automobile fuel, and rocket engines. Hydrogen gas as a fuel is in the spotlight as a future energy because it burns completely with a high heat of combustion of 142 kJ/g. However, hydrogen gas is highly volatile, explosive and flammable, and is dangerous when a hydrogen concentration exceeds a critical value.
Hydrogen gas is a flammable gas without color, odor, and taste, and thus cannot be sensed by the human senses. Therefore, in order to safely use hydrogen, a hydrogen sensor is essential. Various types of hydrogen sensors have been reported. Among them, interest in electrical sensors and gasochromic sensors is increasing. However, although the electrical sensor has a high sensing ability, it has a problem in that a malfunction occurs due to electromagnetic noise or use environment thereof is limited.
Hydrogen has recently been developed as an energy source in various industries. In this case, it is necessary to develop a technology to detect hydrogen dissolved in liquid as well as hydrogen in the atmosphere.
One purpose of the present disclosure is to provide a hydrogen sensor capable of simultaneously sensing hydrogen dissolved in liquid as well as gaseous hydrogen in the atmosphere.
Another purpose of the present disclosure is to provide a method for manufacturing the hydrogen sensor.
One aspect of the present disclosure provides a hydrogen sensor comprising: a substrate; a color changeable layer disposed on the substrate and made of an oxide semiconductor material, wherein when the oxide semiconductor material reacts with hydrogen ions or hydrogen atoms, a color thereof changes; a catalyst layer disposed on a surface of the color changeable layer and made of a catalyst material, wherein the catalyst material dissociates hydrogen molecules (H2) into hydrogen atoms (H) or hydrogen ions (H+); and a protective layer disposed to cover a surface of the catalyst layer and an exposed surface of the color changeable layer, and made of a polymer material, wherein the polymer material allows hydrogen molecules to pass therethrough but blocks water molecules.
In one embodiment, the catalyst layer is made of palladium (Pd), platinum (Pt) or an alloy containing at least one thereof.
In one embodiment, the catalyst layer is formed to have a thickness in a range of 4 to 4.5 nm.
In one embodiment, the color changeable layer and the catalyst layer are sealed with the substrate and the protective layer.
In one embodiment, the protective layer is made of PVB (polyvinyl butyral).
In one embodiment, the protective layer is formed to have a thickness in a range of 4.4 to 5.4 μm.
Another aspect of the present disclosure provides a method for manufacturing a hydrogen sensor, the method comprising: depositing tungsten oxide on a substrate to form a color changeable layer; depositing palladium or platinum on the color changeable layer to form a catalyst layer; an performing a cycle 4 to 6 times to form a protective layer covering a surface of the catalyst layer and an exposed surface of the color changeable layer, wherein the cycle is composed of a first step of forming a PVB film on the catalyst layer using a spin coating process of a PVB (polyvinyl butyral) solution and a second step of spin-coating ultrapure water on the PVB film.
In one embodiment of the method, the protective layer is formed to have a thickness in a range of 4.4 to 5.4 μm.
According to the water sensor and the method for manufacturing the same according to the present disclosure, the protective layer made of PVB (polyvinyl butyral) such that hydrogen selectively passe through the protective layer while the protective layer blocks water may seal the color changeable layer and the catalyst layer. Thus, the sensor may sense hydrogen in both the liquid and the atmosphere.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes”, and “including” when used in this specification, specify the presence of the stated features, integers, operations, elements, and/or components, but do not preclude the presence or addition of one or greater other features, integers, operations, elements, components, and/or portions thereof.
Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
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The substrate 110 may act as a support and may not be particularly limited as long as it may support the color changeable layer 120, the catalyst layer 130 and the protective layer 140. For example, the substrate 110 may be made of a material such as polymer, glass, ceramic, or metal.
The color changeable layer 120 may be disposed on the substrate 110 and made of an oxide semiconductor material that reacts with hydrogen ions or hydrogen atoms and thus changes a color thereof. In an embodiment, the color changeable layer 120 may be made of tungsten oxide (WO3). The tungsten oxide changes its color under specific optical and chemical stimuli applied thereto. For example, when hydrogen ions or hydrogen atoms are supplied to the color changeable layer 120, the tungsten oxide reacts with the hydrogen ions or hydrogen atoms to form oxygen vacancies inside the color changeable layer 120, such that the tungsten oxide may absorb light in a near-infrared region, and a color of the tungsten oxide may change from dark gray to dark blue. In one example, when the reacted hydrogen ions or hydrogen atoms are desorbed from the tungsten oxide, a color of the color changeable layer 120 may be converted back to its initial color of the dark gray.
A method for forming the color changeable layer 120 is not particularly limited. The layer 120 may be formed on the substrate 110 using a known method of forming an oxide thin-film. For example, the color changeable layer 120 may be formed on the substrate 110 using a vapor deposition method such as a sputtering process.
The catalyst layer 130 may be formed on the color changeable layer 120. The catalyst layer 130 may be made of a catalyst material that may dissociate hydrogen molecules (H2) into hydrogen atoms (H) or hydrogen ions (W). For example, the catalyst layer 130 may be made of palladium (Pd), platinum (Pt), or an alloy thereof.
The method of forming the catalyst layer 130 is not particularly limited. For example, the catalyst layer 130 may be formed via vapor deposition using an E-beam evaporator or the like.
In one embodiment, the catalyst layer 130 may be formed to have a thickness of about 4 to 4.5 nm. When the thickness of the catalyst layer 130 is smaller than 4 nm, the hydrogen dissociation reaction may be weakened, resulting in lower reactivity. When it exceeds 4.5 nm, a value of an initial transmittance of the sensor is lowered and thus an amount of change thereof during the hydrogen reaction is small. Thus, it may be difficult to obtain a sufficient signal.
The protective layer 140 may be formed to cover a surface of the catalyst layer 130 and an exposed surface of the color changeable layer 120. For example, the color changeable layer 120 and the catalyst layer 130 may be sealed with the substrate 110 and the protective layer 140.
In an embodiment, the protective layer 140 may be made of a polymer material which hydrogen molecules pass through while blocking water molecules. For example, the protective layer 140 may be made of PVB (polyvinyl butyral).
When the color changeable layer 120 and the catalyst layer 130 are exposed to moisture, the moisture may be adsorbed on the color changeable layer 120 and the catalyst layer 130. The adsorbed moisture may act as a barrier preventing contact of the hydrogen molecules with the metal catalyst of the catalyst layer 130, or may delay a rate of diffusion of the dissociated hydrogen atoms or hydrogen ions into the color changeable layer 120. Further, the tungsten oxide of the color changeable layer 120 may be converted into tungsten hydroxide (HWOx) due to various radical radicals inside the moisture. This may cause a problem in which the performance of the color changeable layer 120 is rapidly deteriorated. The protective layer 140 may allow the hydrogen molecules to pass through but may block water, thereby preventing external moisture from reaching the color changeable layer 120 and the catalyst layer 130. This may prevent the problem caused by the moisture as described above. Further, the protective layer 140 may allow the hydrogen sensor 100 according to an embodiment of the present disclosure to sense hydrogen in water.
In one embodiment, the protective layer 140 may be formed to have a thickness of about 4.4 to 5.4 When the thickness of the protective layer 140 is smaller than 4.4 μm, durability of the hydrogen sensor 100 may decrease, resulting in a problem that a lifetime thereof becomes too short. When it exceeds 5.4 μm, the permeability of the hydrogen molecules through the protective layer is too low. Thus, there may be a problem that the sensing ability of hydrogen of the hydrogen sensor 100 is too low.
In an embodiment, the protective layer 140 may be formed using a solution process. For example, the protective layer 140 may be formed to cover a surface of the catalyst layer 130 and an exposed surface of the color changeable layer 120 using a spin-coating. Specifically, a cycle including a first step of forming a PVB film on the catalyst layer 130 via a spin coating process using a PVB solution containing methanol as a solvent and a second step of spin-coating ultrapure water (D.I water) on the PVB film may be performed a plurality of times to form the protective layer 140 having a preset thickness and waterproof characteristics. In this case, the thickness of the protective layer 140 may be adjusted based on the number of repetitions of the cycle including the first step and the second step.
According to the water sensor according to the present disclosure, the protective layer made of PVB (polyvinyl butyral) such that hydrogen selectively passe through the protective layer while the protective layer blocks water may seal the color changeable layer and the catalyst layer. Thus, the sensor may sense hydrogen in both the liquid and the atmosphere.
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Therefore, it may be identified that the sensor in which the protective layer is made of PVB may have improved durability and color change performance in water. This is because the PVB-based protective film may allow the hydrogen molecules or ions smaller than the water molecules to pass therethrough but may block the water molecules.
Although the disclosure has been described above with reference to the preferred embodiments of the present disclosure, those skilled in the art will understand that various modifications and changes may be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2019-0083060 | Jul 2019 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2020/009078 | 7/10/2020 | WO |
