JPH0678987B2 - Hydrogen sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention utilizes hydrogen or hydrogen-containing compound gas by utilizing the change in light absorption amount caused by reduction of a solid compound by hydrogen atoms dissociated and adsorbed in a catalytic metal. The present invention relates to a hydrogen sensor adapted to detect hydrogen.

(Prior Art) In recent years, hydrogen has been regarded as a promising clean energy, and research and development of a hydrogen sensor for detecting hydrogen itself has been promoted in cooperation with research on an efficient use of hydrogen.

The inventors of the present application have already disclosed, in Japanese Patent Application No. 58-147749, a hydrogen sensor capable of safely detecting hydrogen by utilizing a change in light absorption amount due to reduction of a solid compound by hydrogen atoms dissociated and adsorbed in a catalytic metal. Is proposed. According to this method, a catalytic metal such as palladium Pd that dissociates and adsorbs hydrogen or a hydrogen-containing compound gas and a solid compound such as tungsten trioxide WO ₃ are formed in a stack, and hydrogen atoms from the catalytic metal enter the solid compound. Then, the light absorption amount changes according to the concentration of hydrogen gas due to the reducing action. The hydrogen gas is optically detected based on the change in the light absorption amount.

(Problems to be Solved by the Invention) However, in such a hydrogen sensor,
As shown in the figure, when hydrogen or hydrogen-containing compound gas contained in the atmosphere of the monitoring area is contacted, the light absorption amount of the solid compound changes rapidly due to reduction by hydrogen atoms, and the rise time is relatively short. Despite the time, when the hydrogen gas disappears from the atmosphere, the fall time until the light absorption amount of the fixed compound recovers to the original state is the light absorption amount of the solid compound due to natural diffusion in the catalytic metal. Since a method of waiting for the recovery of is taken, a relatively long time (for example, about 3 to 5 times the rise time) is required, and there is a problem that the time required for the measurement as a whole becomes long. .

(Means for Solving Problems) The present invention has been made in view of the above problems, and includes a catalytic metal that dissociates and adsorbs hydrogen or a hydrogen-containing compound gas, and is reduced by hydrogen atoms in the catalytic metal. The time required for detection of hydrogen is improved by improving the recovery response after the detection operation of the detection sensor of a normal temperature operation type hydrogen sensor that has a detection element that has a laminated structure with a solid compound whose light absorption amount changes. An object of the present invention is to provide a hydrogen sensor capable of shortening

In order to achieve this object, the present invention comprises a laminated structure of a catalyst metal that dissociates and adsorbs hydrogen or a hydrogen-containing compound gas, and a solid compound that is reduced by hydrogen atoms in the catalyst metal, and the catalyst metal front surface is exposed to air in the air. A hydrophilic film for adsorbing water molecules is prepared.

(Examples) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention. First, the structure will be described. 2 is a substrate made of transparent glass or the like. On the surface of the glass substrate 2, solid compound 3, for example, tungsten trioxide (WO ₃ ) is vapor-deposited to a predetermined thickness, and then, As a result, a catalytic metal 4 made of palladium (Pd) is vapor-deposited thinly on the solid compound 3 to the extent that transparency is maintained. As described above, a laminated structure of the catalytic metal 4 that dissociates and adsorbs hydrogen or a hydrogen-containing compound gas and the solid compound 3 that is reduced by hydrogen atoms from the catalytic metal 4 is provided, and the front surface of the catalytic metal 4 further includes water in the air. A hydrophilic film 5 that adsorbs molecules is provided.

Here, the reason why the hydrophilic film 5 is provided on the surface of the catalytic metal 4 is as follows.

As is apparent from another application by the inventors of the present application, based on the results of various experiments, the element 1 is provided by supplying steam or the like to the element 1 having a laminated structure of the solid compound 3 and the catalytic metal 4. Keeping the surface of the element in a high humidity state, the recovery response of the element 1 is improved, and a hydrophilic film 5 for adsorbing water molecules in the air is provided on the front surface of the element 1, that is, the catalytic metal 4. The same function is provided by keeping the surface of the element 1 in a high humidity state without supplying water vapor or the like from the outside.

As the hydrophilic film 5, for example, a silica film (SiO ₂ ) or a film in which an appropriate desiccant is formed thin enough to maintain the density and transparency is used. As the desiccant, for example, phosphorus oxide, calcium chloride, sodium hydroxide or the like is used.

Further, as the solid compound 3, tungsten trioxide (W
Other than O ₃ ), for example, molybdenum trioxide (MoO ₃ ), titanium dioxide (TiO ₂ ), iridium hydroxide (Ir (OH) n), vanadium pentoxide (V ₂ O ₅ ), etc. are used, and a catalyst is also used. As the metal 4, platinum (Pt) or the like is used in addition to palladium (Pd).

The light absorption amount of the element 1 shown in FIG. 1 changes as follows.

Upon contact with hydrogen gas (H ₂ ), the catalytic metal 4 dissociates and adsorbs hydrogen (H ₂ ) to generate hydrogen atoms in the catalytic metal 4, and the hydrogen atoms are injected into the solid compound 3. Solid compound 3 which received hydrogen atom injection by catalytic metal 4
Is reduced to HxWO ₃ , the color center density changes and the amount of light absorption changes. The change in the light absorption amount of the solid compound 3 becomes stronger as the hydrogen gas concentration increases. Of course, when the hydrogen gas is removed from the vicinity of the element 1, the protons (H ⁺ ) injected into the solid compound 3 escape again and the solid compound 3 reduces the light absorption amount and returns to the original transparent state.

Such a light absorption phenomenon of the element 1 is caused by, for example, ammonia gas (NH ₃ ) and hydrogen sulfide gas (H ₂ ) in addition to hydrogen gas (H ₂ ).
_The same applies to hydrogen-containing compound gases such as ₂ S) and silane gas (SiH ₄ ).

FIG. 2 is an explanatory view showing an embodiment of a hydrogen gas detection device using the element 1 of FIG.

In FIG. 2, the element 1 is arranged in a cell 8, and the cell 8 is provided with an inlet 14 for introducing a sample gas and an outlet 15 for discharging the sample gas, and a pair of windows 16 and a pair of windows 16 are provided at opposite positions with the element 1 interposed therebetween. 17 are provided. This pair of windows
Outside the 16 and 17, the light source 7 is arranged on the side of the window 16 and the light receiving element 9 is arranged on the side of the window 17 so that the light from the light source 7 is reflected by the window 16, the element 1,
The light is incident on the light receiving element 9 through the window 17 and the window 17. A power source 6 is connected to the light source 7, and the light source 7 continuously emits light.
Alternatively, pulsed light is emitted. Light receiving element 9 is a detection circuit
It is connected to 10, and electrically detects the light reception output corresponding to the change in the amount of transmitted light obtained by the light receiving element 9, and detects the hydrogen gas contained in the sample gas.

Next, the operation will be described with reference to FIG. When a sample gas such as hydrogen gas or a hydrogen-containing compound gas is introduced into the cell 8 through the inlet 14, the amount of light absorption of the solid compound 3 increases and the concentration of hydrogen gas contained in the sample gas increases. The light absorption amount of the solid compound 3 changes. As shown in FIG. 3, the change in the amount of light absorption changes rapidly from the start of measurement, that is, after the introduction of hydrogen gas, the amount of light absorption of the solid compound 3 changes rapidly, and the rise time changes in a relatively short time. I'm going
Eventually, the maximum light absorption amount ODmax is reached.

Next, when the adjusting valve 12 is closed to shut off the introduction of the sample gas, that is, hydrogen gas, and the element 1 is kept in the air atmosphere, as shown in FIG. 3, it is kept in the state of the maximum light absorption amount ODmax until then. Hydrogen atoms escape from the solid compound 3 and the amount of light absorption decreases as the number of hydrogen atoms decreases, and the original transparent state is gradually restored. As is clear from FIG. 3 which compares this recovery speed with FIG. 4 of the conventional example, the fall time is shortened to approximately half that of the conventional case.

(Effects of the Invention) As described above, according to the present invention, a laminated structure of a catalyst metal that dissociates and adsorbs hydrogen or a hydrogen-containing compound gas and a solid compound that is reduced by hydrogen atoms in the catalyst metal is provided, By providing a hydrophilic film that adsorbs water molecules in the air on the metal front surface, the recovery response of the element itself composed of a laminated structure of catalytic metal and solid compound can be improved, and the detection required for hydrogen detection The effect that the required time can be greatly shortened is obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention, FIG. 2 is an explanatory view showing an example of a device configuration using the embodiment of FIG. 1,
FIG. 3 is a graph showing the characteristics of the present invention, and FIG. 4 is a graph showing the characteristics of the conventional example. 1: Element 2: Substrate 3: Solid compound 4: Catalytic metal 5: Hydrophilic film 6: Power supply 7: Light source 8: Cell 9: Light receiving element 10: Detection circuit 11: Sample gas 12: Control valve 14: Inlet 15: Outlet 16,17: Window

Claims (1)

[Claims] 1. A laminated structure comprising a catalytic metal that dissociates and adsorbs hydrogen or a hydrogen-containing compound gas and a solid compound that is reduced by hydrogen atoms in the catalytic metal, and water molecules in the air are provided on the front surface of the catalytic metal. A hydrogen sensor having a hydrophilic film for adsorption.