JP2009300224A - Hydrogen gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized inexpensive hydrogen gas sensor capable of properly detecting a hydrogen gas even if an oxygen gas is absent and even not in a heating environment and having good hydrogen gas selectivity. <P>SOLUTION: The hydrogen gas sensor has a detection part formed with a catalyst layer 3 having a catalyst 3a such as platinum which is held by sputtering or the like on at least one side surface of a base material 2 as a solid polymer electrolyte membrane comprising a perfluoro polymer and the like and which has a catalytic function by making contact with a hydrogen gas, and the detection part is joined with air-permeable electrodes 4, thus constituting the sensor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydrogen gas sensor that detects a hydrogen gas concentration in a gas phase or a liquid phase.

  In configuring a hydrogen energy system typified by a fuel cell, the necessity of a hydrogen gas sensor that accurately detects the concentration of hydrogen is extremely high, and various hydrogen gas sensors have been proposed.

As a typical example, in Patent Document 1, a heater coil is embedded in a heat conductive layer, and a surface of the heat conductive layer is covered with a combustion catalyst layer for burning a detection target gas by contact. A sensing element for a catalytic combustion type gas sensor has been proposed in which the conductive layer is made of a fired material mainly composed of tin oxide.
JP 2007-271556 A

  However, the detection element for a contact combustion type gas sensor described in Patent Document 1 embeds a heater coil in a heat conduction layer and covers the surface of the heat conduction layer with a combustion catalyst layer that burns the detection target gas by contact. In this configuration, the change in electrical resistance associated with the reaction between oxygen adsorbed on the surface of the combustion catalyst layer and the target gas is detected, so that the target gas cannot be detected in the absence of oxygen. was there.

  In addition, since it is necessary to provide a heater coil that heats the element temperature of the sensitive part to several hundred degrees in order to cause sufficient adsorption and desorption of oxygen molecules, there is a problem that the power consumption increases for that purpose, and it is necessary to provide a heat-resistant structure. In addition to the hydrogen gas, there is also a problem that it has no gas selectivity in response to flammable gases such as methane gas and carbon monoxide gas.

  In view of the above-mentioned problems, the object of the present invention is to detect hydrogen gas properly even in the absence of oxygen gas or in a heating environment, and to achieve a small size and good hydrogen gas selectivity. The object is to provide an inexpensive hydrogen gas sensor.

  In order to achieve the above object, the hydrogen gas sensor according to the present invention is characterized in that a catalyst layer is formed on at least one side surface of a substrate made of a solid polymer electrolyte as described in claim 1 of the claims. And is provided with a detection unit capable of detecting hydrogen gas in the absence of oxygen gas.

  As a result of intensive research, the inventors of the present application have formed a catalyst layer made of a metal having a catalytic function by contacting hydrogen gas on at least one side surface of a substrate composed of a solid polymer electrolyte. It has been confirmed that a detection unit that exhibits sufficient power generation characteristics when hydrogen gas is supplied toward the catalyst layer in the absence of oxygen gas can be configured.

  At this time, the detection part in which the catalyst layer is formed on at least one side surface of the base material made of the solid polymer electrolyte is joined with a gas-permeable electrode, thereby simultaneously generating power while supplying hydrogen gas to the detection part. This is preferable in that the voltage can be extracted to the outside.

  Preferably, the catalyst layer is supported on the base material by sputtering and is made of a metal or alloy having a catalytic function by contacting with hydrogen gas, or an organometallic or organic substance having catalytic activity. The particle size distribution and supported amount of the catalyst supported on the catalyst support can be suitably controlled.

  As described above, according to the present invention, hydrogen gas can be properly detected even in the absence of oxygen gas or in a heating environment, and it is small and inexpensive with good hydrogen gas selectivity. A hydrogen gas sensor can be provided.

  Hereinafter, a hydrogen gas sensor according to the present invention will be described. As shown in FIG. 1, the hydrogen gas sensor 1 forms a catalyst layer 3 having a catalytic function by contacting hydrogen gas on one side surface of a base material 2 made of a solid polymer electrolyte. It is configured to be joined by an electrode 4 having air permeability.

  The substrate 2 is not particularly limited as long as it exhibits proton conductivity. However, perfluorosulfonic acid-based and perfluorocarboxylic acid-based perfluoropolymers having high proton conductivity, poly (styrene- It is preferable to adopt a solid polymer electrolyte membrane made of partially sulfonated styrene-olefin copolymer such as ran-ethylene), sulfonated, etc., such as Nafion (DuPont registered trademark: NAFION), Aciplex (Asahi Kasei Corporation registered trademark: ACIPLEX), etc. Can be suitably used.

  As described above, the catalyst layer 3 is configured such that the catalyst 3a made of a metal having a catalytic function by contacting with hydrogen gas is supported on one side surface of the base material 2 by sputtering. That is, the base material 2 also functions as a carrier for the catalyst 3a.

The sputtering treatment time is preferably less than 90 seconds, and more preferably 60 seconds or less. The DC and RF output values during sputtering are not particularly limited, but are preferably 1.2 W / cm ² or more.

As the catalyst 3a, platinum Pt or a platinum alloy is suitably used. Besides, gold Au, silver Ag, iridium Ir, palladium Pd, ruthenium Ru, osmium Os, cobalt Co, nickel Ni, tungsten W, molybdenum Mo, manganese A metal containing at least one selected from Mn, yttrium Y, vanadium V, niobium Nb, titanium Ti, rare earth metal can be used, and a carbide such as molybdenum carbide Mo ₂ C can be used instead of the metal catalyst. Is also possible. These catalysts may be used alone or in combination, or some or all of them may be used in the form of an alloy.

  Further, the catalyst layer 3 may be configured by supporting a catalyst 3a made of an organic metal or an organic substance having catalytic activity by contacting with hydrogen gas on one side surface of the substrate 2.

  Examples of such organometallic catalysts include N, N'-Bis (salicylidene) ethylene-diamino-metal (= Ni, Fe, V, etc.), N, N'-mono-8-quinoly-σ-phenylenediamino-metal. (= Ni, Fe, V, etc.) can be used, and examples of organic substances include pyrrolopyrrole red pigments and dipyridyl derivatives.

  The electrode 4 only needs to have a configuration in which at least hydrogen gas can be in contact with the detection portion in which the catalyst layer 3 is formed on one side surface of the substrate 2, such as a copper-nickel alloy thin film having a large number of pores, It is also possible to form a metal porous sintered body having a good conductivity.

  Furthermore, the electrode 4 is not limited to being composed of a metal that is a good conductor, but may be composed of carbon paper or carbon cloth having electrical conductivity and air permeability.

  When hydrogen gas flows into the electrode 4a on the catalyst layer 3 side of the hydrogen gas sensor 1 described above, hydrogen is decomposed into hydrogen ions and electrons by the action of the catalyst, and the electrons are supplied to an external circuit connected to the electrode 4a. At this time, the hydrogen gas concentration can be detected by detecting a current value or a voltage value having a correlation with the hydrogen gas concentration by an external circuit.

  The hydrogen gas sensor 1 described above is arranged so that at least the electrode 4a side on which the catalyst layer 3 is formed is aerated with hydrogen gas, and the voltage detection circuit 6 is provided between the electrodes 4a and 4b, thereby being included in the detection target gas. The hydrogen gas concentration can be measured.

  Further, as shown in FIG. 2, a gas diffusion layer 7 made of carbon paper, carbon cloth, or the like may be provided on the surfaces of both electrodes so that the detection target gas is uniformly supplied to the electrodes 4a.

  In the above-described embodiment, the catalyst layer 3 is formed by directly sputtering the catalyst 3a on the base material 2. However, for example, the catalyst layer 3 is formed by applying carbon fiber, carbon nanotube, or the like on one side surface of the base material 2. Alternatively, the catalyst 3a may be supported on the upper surface of the coated layer. When carbon nanotubes are used, the characteristics of the catalyst support are extremely excellent because of the specific surface area.

  Furthermore, in addition to forming the catalyst layer 3 by sputtering, known methods such as vacuum deposition, electron irradiation, CVD, PVD, impregnation, spray coating, spray pyrolysis, kneading, spraying, coating with a roll or iron, It is also possible to form the catalyst layer 3 by employing screen printing, kneading method, photoelectrolysis method, coating method, sol-gel method, dipping method or the like.

  The hydrogen gas sensor according to the present invention only needs to have a detection part in which the catalyst layer 3 is formed on at least one side surface of the substrate 2.

  In the above-described embodiment, the base material formed in a film shape has been described. However, the film thickness is not particularly limited, and can be appropriately set within a range in which an expected effect is achieved. is there. Further, the base material is not limited to a planar body, and may be a solid body. In this case, the electrode forming surface is not limited to the facing surface.

  As a substrate made of a solid polymer electrolyte, a 100 μm thick perfluoro polymer purchased from DuPont, Nafion membrane (NRE-212) is cut into 5 cm square, and the cut Nafion membrane is sandwiched between filter papers. It was pressed with an iron heated to 130 ° C., and water was repeatedly blown until water did not penetrate into the filter paper.

  Thus, platinum (Pt) was supported as a catalyst on one side of a Nafion membrane from which water had been sufficiently removed within a 4 cm square range for a sputtering time of 30 seconds to form a catalyst layer 3 having a thickness of 20 nm. The sputtering conditions for platinum (Pt) were as follows: output 300 W, gas flow rate argon (Ar) 20 cc / min. It is.

  As shown in FIG. 3, the Nafion membrane 2 on which the catalyst layer 3 is formed is extracted in a circular shape having a diameter of 13 mm, and is sandwiched by a metal washer 4 having an outer diameter of 13 mm as an electrode, and the lead wire 5 is drawn out from the metal washer 4 Thus, a hydrogen gas sensor 1 was prototyped.

  As shown in FIG. 4, the prototype hydrogen gas sensor 1 is installed on one end side of a 200 ml cylindrical glass tube 8 and the lead wire 5 is pulled out to the outside. A measuring instrument 6 (MULTIMETER VOAC 7411, Iwasaki Measurement Co., Ltd.) ), Nitrogen gas was allowed to flow into the glass tube 8 from the other end side for 15 minutes to purge the internal air, and the hydrogen gas sensor 1 was placed in a nitrogen atmosphere.

  Next, 1 cc, 2 cc, 5 cc, 20 cc, 20 cc, 30 cc, 40 cc, and 50 cc pure hydrogen were measured with a syringe purged several times with pure hydrogen gas, and injected into the glass tube 8 purged with nitrogen gas. The output change of was measured.

  The output change at this time is shown in FIGS. As a result, it was confirmed that an output appears when hydrogen gas is brought into contact with the hydrogen gas sensor 1 in a nitrogen gas atmosphere, that is, in an environment where oxygen gas is not present (indicated by a solid line in the graph of FIG. 5B).

  A similar experiment was performed on methane gas and carbon monoxide gas as the gas to be detected, but no change in output appeared. From this, it was confirmed that the gas selectivity was also provided.

  Further, when a similar experiment was performed on oxygen gas as a gas to be detected, as shown by the broken line in the graph of FIG. 5 (b), a change in output with a reverse polarity was confirmed, which could be used as an oxygen gas sensor. Was also seen.

Configuration of a hydrogen gas sensor according to the present invention Configuration diagram of a hydrogen gas sensor showing another embodiment Configuration diagram of the prototype hydrogen gas sensor Explanatory drawing of characteristic test of hydrogen gas sensor in the absence of oxygen gas (A) is a data table of a characteristic test of a hydrogen gas sensor in the absence of oxygen gas, and (b) is a graph showing a hydrogen gas concentration voltage characteristic of the hydrogen gas sensor in the absence of oxygen gas.

Explanation of symbols

1: Hydrogen gas sensor 2: Base material made of solid polymer electrolyte 3: Catalyst layer 3a: Catalyst 4: Electrode 4a: Anode electrode 4b: Cathode electrode 5: Lead wire 6: Measuring instrument (voltage detection circuit)
7: Gas diffusion layer 8: Glass tube

Claims (3)

  A hydrogen gas sensor comprising a detection unit capable of detecting hydrogen gas in the absence of oxygen gas, wherein a catalyst layer is formed on at least one side surface of a substrate composed of a solid polymer electrolyte.   The hydrogen gas sensor according to claim 1, wherein the detection unit is joined by an electrode having air permeability.   3. The hydrogen according to claim 1, wherein the catalyst layer is supported on the base material by sputtering and is made of a metal or alloy having a catalytic function by contacting with hydrogen gas, or an organic metal or organic substance having catalytic activity. Gas sensor.

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