WO2014203923A1 - Noble metal catalyst and constant potential electrolyte gas sensor - Google Patents

Noble metal catalyst and constant potential electrolyte gas sensor Download PDF

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WO2014203923A1
WO2014203923A1 PCT/JP2014/066129 JP2014066129W WO2014203923A1 WO 2014203923 A1 WO2014203923 A1 WO 2014203923A1 JP 2014066129 W JP2014066129 W JP 2014066129W WO 2014203923 A1 WO2014203923 A1 WO 2014203923A1
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electrode
gas
noble metal
gold
metal catalyst
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PCT/JP2014/066129
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French (fr)
Japanese (ja)
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皆越知世
前川亨
石橋研二
宮崎洋
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新コスモス電機株式会社
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Priority claimed from JP2013127650A external-priority patent/JP6233562B2/en
Priority claimed from JP2013127648A external-priority patent/JP6326670B2/en
Application filed by 新コスモス電機株式会社 filed Critical 新コスモス電機株式会社
Publication of WO2014203923A1 publication Critical patent/WO2014203923A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/404—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon

Definitions

  • the present invention provides a working electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting a gas, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode.
  • the present invention relates to a noble metal catalyst used in a constant potential electrolytic gas sensor provided facing a housing portion, and the constant potential electrolytic gas sensor.
  • a conventional constant potential electrolytic gas sensor is configured such that an electrode is provided facing an electrolytic solution storage part of an electrolytic cell in which an electrolytic solution is densely stored. For example, an electrode is detected as a gas electrode that detects gas.
  • an electrode is detected as a gas electrode that detects gas.
  • a potentiostat circuit for setting the potential is connected.
  • As the material of the three electrodes a gas-permeable porous PTFE film having water repellency is coated with a noble metal catalyst such as platinum, gold, palladium, etc.
  • an electrolyte an acidic aqueous solution such as sulfuric acid or phosphoric acid is used. Was used.
  • the constant potential electrolytic gas sensor generates a current corresponding to a change in the surrounding environment between the working electrode and the counter electrode by controlling the potential of the working electrode to be constant with respect to a change in the surrounding environment.
  • the gas can be selectively detected depending on the set potential of the potentiostat circuit. Further, by changing the catalyst used for the gas electrode, it is possible to have high selectivity for the target gas.
  • a carbon having a particle diameter of several tens of nanometers supported with gold fine particles of about several hundred nanometers may be used.
  • an immersion support method may be used.
  • the support is immersed in an aqueous solution of a metal salt, the metal component is adsorbed on the support surface, and drying, firing, and reduction are performed.
  • an electrode was produced by applying it to a porous PTFE membrane.
  • constant potential electrolytic gas sensor which is a conventional technique in the present invention, is a general technique, and thus does not show conventional technical documents such as patent documents.
  • the gold-adhered carbon produced by the above-mentioned method has a particle size of gold fine particles larger than that of carbon as a carrier and tends to aggregate in an aqueous solution, so that it is difficult to uniformly disperse the gold fine particles. there were.
  • the gold-adhered carbon produced in such a state that the gold fine particles are not uniform is used as a noble metal catalyst, there are cases where the gas detection performance varies.
  • the firing temperature in the immersion support method may be about 600 ° C., when the carrier is carbon, if the firing temperature is such a high temperature, there is a risk that the carbon as the carrier will burn. there were.
  • an object of the present invention is to provide a noble metal catalyst that hardly causes variations in gas detection performance when used as a noble metal catalyst for each of the electrodes in a potentiostatic gas sensor, and a gas detection performance that hardly varies.
  • An object of the present invention is to provide a potentiostatic gas sensor equipped with a noble metal catalyst capable of keeping the firing temperature low.
  • the first characteristic configuration of the noble metal catalyst according to the present invention for achieving the above object is that gold nanoparticles having an average particle size equal to or smaller than the average particle size of the carbon powder are supported on the carbon powder as a support. is there.
  • the noble metal catalyst of this configuration supports gold nanoparticles having an average particle size equal to or less than the average particle size of the carbon powder, the gold nanoparticles can be supported on the carrier carbon in a dispersed state.
  • the degree of dispersion of the gold nanoparticles can be made substantially uniform. Therefore, if such a gold-supporting carbon is used as a noble metal catalyst in a gas sensor, for example, it is possible to prevent the gas detection performance from varying.
  • attaching gold nanoparticles having an average particle size equal to or less than the average particle size of carbon powder is referred to as “supporting”, and gold nanoparticles having an average particle size larger than the average particle size of carbon powder. It is distinguished from the conventional gold-attached carbon to which is attached.
  • the second characteristic configuration of the noble metal catalyst according to the present invention is that the gold nanoparticles are supported at 5 to 50% by weight of 5 to 50 nm particles.
  • a gold nanoparticle can be carry
  • the content of gold nanoparticles was variously changed from 5 to 50% by weight, and a potentiostatic gas sensor was prepared for each.
  • stable gas sensitivity can be obtained if the added amount of the gold nanoparticles is 5% by weight or more, and the added amount of the gold nanoparticles in the gold-supported carbon is 50% by weight in view of the production cost of the gold-supported carbon. It was recognized that it should be suppressed by
  • the third characteristic configuration of the noble metal catalyst according to the present invention is that the particle size of the carbon powder is in the range of 5 to 300 nm.
  • the particle size of the carbon powder can be set to an arbitrary particle size in the range of 5 to 300 nm, and the particle size of the gold nanoparticle can be set to be equal to or less than the arbitrary particle size.
  • the particle size of carbon black can be adjusted to have such a particle size range.
  • the first characteristic configuration of the constant potential electrolytic gas sensor according to the present invention includes a working electrode that chemically reacts a gas to be detected as a gas electrode that detects gas, a counter electrode with respect to the working electrode, and a reference electrode that controls the potential of the working electrode.
  • the noble metal catalyst according to any one of the first to three characteristic configurations is provided as each electrode. is there.
  • the noble metal catalyst of this configuration can be supported on carbon as a carrier in a state where gold nanoparticles are dispersed, the degree of dispersion of the gold nanoparticles can be made almost uniform. Therefore, if such a gold-supported carbon is used as a noble metal catalyst, it is possible to prevent the gas detection performance from varying in the constant potential electrolytic gas sensor.
  • the second characteristic configuration of the controlled potential electrolysis gas sensor according to the present invention is that the noble metal catalyst includes a carbon powder addition step in which carbon powder is added to a solvent and stirred, and a gold powder in which a colloidal solution in which gold nanoparticles are dispersed is added.
  • a nanoparticle addition step a drying step of drying in a state maintained below the boiling point of the solvent, a firing step of firing carbon powder carrying gold nanoparticles obtained by drying at 250 to 450 ° C., It is in the point produced by performing.
  • gold-supported carbon supported in a state where gold nanoparticles are dispersed can be used as a noble metal catalyst. Since the gold-supporting carbon uses a colloidal solution in the production process, it can be supported on carbon as a carrier in a state in which the gold nanoparticles are dispersed, so the degree of dispersion of the gold nanoparticles is almost uniform. It can be in a state. Therefore, if such a gold-supported carbon is used as a noble metal catalyst, it is possible to prevent the gas detection performance from varying in the constant potential electrolytic gas sensor.
  • the gold-supporting carbon according to the present configuration can suppress the firing temperature to 250 to 450 ° C. during the production process, so there is no possibility that the carbon as the carrier will burn.
  • the third characteristic configuration of the potentiostatic gas sensor according to the present invention is that a surfactant is added in the carbon powder addition step.
  • the dispersibility of carbon in the solvent can be improved by adding a surfactant.
  • the noble metal catalyst of the present invention is used as a noble metal catalyst for each electrode in a potentiostatic gas sensor.
  • gold nanoparticles having an average particle size equal to or less than the average particle size of the carbon powder are supported on carbon powder as a carrier.
  • the constant potential electrolysis gas sensor X is a gas electrode for detecting a gas.
  • the electrode 13 is provided so as to face the electrolytic solution storage part 31 of the electrolytic bath 30 in which the electrolytic solution 20 is stored.
  • the working electrode 11, the counter electrode 12, and the reference electrode 13 are formed by applying and baking a paste made of a known electrode material on the surface of a porous gas-permeable film 14 having water repellency.
  • the working electrode 11, the counter electrode 12 and the reference electrode 13 are disposed to face each other.
  • the electrolytic cell 30 has an opening 32 that opens laterally to form a gas conduction portion 33.
  • Two gas permeable membranes 14 are provided.
  • One gas permeable membrane 14 is provided with a working electrode 11, and the other gas permeable membrane 14 is provided with a counter electrode 12 and a reference electrode 13.
  • the gas permeable membrane 14 disposed on the working electrode 11 side is attached to the electrolytic cell 30 so as to face the opening 32.
  • the gas to be detected is introduced from the gas conduction part 33 and reacts on the working electrode 11.
  • Each gas permeable membrane 14 and O-ring 15 are fixed by a lid member 16.
  • An electrolytic solution inlet 34 for performing maintenance such as injection of the electrolytic solution 20 is formed on the bottom surface of the electrolytic bath 30.
  • Such a constant potential electrolytic gas sensor X includes a current measuring unit capable of detecting a current based on electrons generated on the working electrode 11 by a reaction of the gas to be detected, and a potential control unit capable of controlling the potential of the working electrode 11. It is used as a gas detection device by connecting to a gas detection circuit (not shown).
  • the constant potential electrolytic gas sensor X of the present invention is used for detection of hydride gas such as silane, phosphine, germane, arsine, diborane.
  • each electrode 10 in the controlled potential electrolytic gas sensor X of the present invention includes a noble metal catalyst, and the noble metal catalyst includes a carbon powder addition step A in which carbon powder is added to a solvent and stirred.
  • the carbon powder is produced by performing a firing step D in which the carbon powder is fired at 250 to 450 ° C.
  • the carbon powder addition step A a predetermined amount of carbon powder is weighed, and water as a solvent is added and sufficiently stirred.
  • a known carbon powder for example, carbon black (particle size of about 5 to 300 nm) can be used, and in particular, acetylene black obtained by thermally decomposing acetylene gas is preferably used, but is not limited thereto. It is not something.
  • This step may be performed by adding a surfactant.
  • a surfactant By adding the surfactant, the dispersibility of carbon in the solvent can be improved.
  • the surfactant any of anionic, cationic, nonionic, and betaine surfactants can be used.
  • a surface treatment such as adding a hydroxyl group to the surface of carbon to increase hydrophilicity may be performed, Alternatively, ultrasonic treatment may be performed as pretreatment.
  • a colloidal solution in which gold nanoparticles are dispersed in the solution obtained in the carbon powder addition step A is added.
  • the colloidal solution in which the gold nanoparticles are dispersed is in a state in which the gold nanoparticles having the above-described particle size are dispersed in the solution.
  • the colloidal gold solution uses an in-solution reduction reaction in which metal ions are reduced to a colloid by adding a citrate solution as a reducing agent to a chloroauric acid solution such as tetrachloroauric acid (III) and heating. However, it is not limited to such a method.
  • the size of colloidal gold particles can be changed by increasing or decreasing the amount of reducing agent added to chloroauric acid.
  • the gold nanoparticles may be particles having a particle size of about 5 to 50 nm, but are not limited to this range. In this case, the particle size distribution is preferably such that the proportion of 5 to 50 nm particles is 90% by weight or more.
  • the solution obtained in the gold nanoparticle addition step B is dried while being maintained at a boiling point or lower of the solvent (water).
  • the temperature set to be equal to or lower than the boiling point of the solvent is not particularly limited, but when the solvent is water, it is preferably about 80 to 100 ° C.
  • a drying method a known method such as reduced-pressure drying, vacuum drying, suction drying, or hot air drying can be applied. Known conditions may be applied as drying conditions in these drying methods.
  • the firing temperature in the present embodiment is a temperature (250 to 450 ° C.) at which the organic substance such as the used surfactant evaporates at a temperature at which carbon oxidation does not proceed under an air atmosphere and atmospheric pressure.
  • the firing time may be set as appropriate until the surfactant, colloid protective agent, and the like are completely eliminated by evaporation, sublimation, and thermal decomposition. Therefore, the firing time can be shortened or extended each time depending on the amount of powder to be fired. However, in consideration of grain growth of gold nanoparticles, a decrease in activity due to sintering, etc., the upper limit of the firing time may be set to about 3 hours, for example. Moreover, you may set so that the baking process D may be complete
  • the controlled potential electrolytic gas sensor X of the present invention can use gold-supported carbon supported in a state where gold nanoparticles are dispersed as a noble metal catalyst. Since the gold-supporting carbon uses a colloidal solution in the production process, it can be supported on carbon as a carrier in a state in which the gold nanoparticles are dispersed, so the degree of dispersion of the gold nanoparticles is almost uniform. It can be in a state. Therefore, if such gold-supported carbon is used as a noble metal catalyst, it is possible to prevent the gas detection performance from varying in the constant potential electrolytic gas sensor X.
  • the gold-supporting carbon according to the present configuration can suppress the firing temperature to 250 to 450 ° C. during the production process, so there is no possibility that the carbon as the carrier will burn.
  • the gold nanoparticles can be dispersed with a particle size of about 5 to 50 nm.
  • the amount of added gold fine particles in the gold-supported carbon prepared by the conventional method is more than 50% by weight, whereas the amount of gold nanoparticles added in the gold-supported carbon prepared by the above method is 5 to 50% by weight.
  • Example 1 A gold-supporting carbon used as a noble metal catalyst in the electrode of the controlled potential electrolysis gas sensor X of the present invention was produced as follows. Each reagent was adjusted so that the content of the gold nanoparticles with respect to the gold-supported carbon was 25% by weight.
  • FIG. 3 shows the particle size distribution (measured by the X-ray small angle scattering method) of the gold nanoparticle powder of Invention Example 1
  • FIG. 4 shows an electron micrograph of the gold-supporting carbon
  • FIG. 5 shows an electron micrograph of a conventional gold-supporting carbon (comparative example) for comparison.
  • the gold nanoparticle powder had a particle size of about 5 to 50 nm.
  • the gold-supported carbon of Invention Example 1 it was recognized that the gold nanoparticles were dispersed and supported on the carbon (FIG. 4).
  • the gold-supporting carbon of the comparative example it was recognized that the gold fine particles were aggregated (FIG. 5).
  • each electrode of the potentiostatic gas sensor X was produced as follows. In the gold-supporting carbon used in each electrode, the content of gold nanoparticles was variously changed from 5 to 50% by weight, and a constant potential electrolytic gas sensor X was produced in each.
  • 0.1 g of gold-supported carbon powder 0.1 mL of surfactant (sodium dodecylbenzenesulfonate), PTFE (polytetrafluoroethylene: Teflon) dispersion (a colloidal solution containing fine particles of PTFE, specific gravity 1.5). 35 mL of each was added and kneaded to prepare an electrode material paste. The obtained electrode material paste was printed on a PTFE sheet, dried, and baked at 280 ° C. for 8 hours to obtain each electrode 10. Each of the obtained electrodes 10 was used as a working electrode 11, a counter electrode 12, and a reference electrode 13, and a potentiostatic gas sensor X was prepared in which the electrolytic solution 20 was a 42% by weight sulfuric acid aqueous solution.
  • surfactant sodium dodecylbenzenesulfonate
  • PTFE polytetrafluoroethylene: Teflon
  • gas sensitivity was measured for phosphine gas 1 ppm and 0.5 ppm in an environment of 20 ° C. and 50% RH (FIG. 6). Similarly, gas sensitivity measurement was performed for 1 ppm of each gas of silane, phosphine, germane, arsine, and diborane (FIG. 7). The gas sensitivity was defined by the magnitude of the current value flowing from the working electrode 11 to the gas detection circuit 40 in the target gas atmosphere.
  • the potentiostatic gas sensor X in which the amount of added gold nanoparticles in the gold-supported carbon is 5% by weight or more, particularly 20% by weight or more is recognized as a working electrode having a sufficiently high reactivity to gas. It was.
  • the amount of gold nanoparticles added to the gold-supported carbon should be suppressed to 50% by weight, preferably 30% by weight. Therefore, in consideration of gas sensitivity and production cost, the amount of gold nanoparticles added to the gold-supported carbon is preferably about 5 to 50% by weight.
  • the present invention provides a working electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting a gas, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode.
  • the present invention can be used for the noble metal catalyst used in the constant potential electrolytic gas sensor provided facing the housing portion and the constant potential electrolytic gas sensor.

Abstract

A noble metal catalyst causing metal nanoparticles to be supported on carbon particles acting as a carrier, said metal nanoparticles having an average particle diameter of no more than the average particle diameter of the carbon particles. The noble metal catalyst is used for each electrode in a constant potential electrolyte gas sensor (X) comprising: a working electrode (11), as a gas electrode that detects gas, that causes detected gas to chemically react; a counter electrode (12) for the working electrode (11); and a reference electrode (13) controlling the potential of the working electrode. Said electrodes face an electrolyte housing section (31) of an electrolytic cell (30) housing electrolyte (20).

Description

貴金属触媒および定電位電解式ガスセンサNoble metal catalyst and controlled potential electrolysis gas sensor
　本発明は、ガスを検知するガス電極として被検知ガスを電気化学反応させる作用電極、前記作用電極に対する対極、前記作用電極の電位を制御する参照電極を、電解液を収容した電解槽の電解液収容部に臨んで備えた定電位電解式ガスセンサに使用される貴金属触媒、および、当該定電位電解式ガスセンサに関する。 The present invention provides a working electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting a gas, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode. The present invention relates to a noble metal catalyst used in a constant potential electrolytic gas sensor provided facing a housing portion, and the constant potential electrolytic gas sensor.
　従来の定電位電解式ガスセンサは、電極を電解液が密に収容される電解槽の電解液収容部内に臨んで設けて構成してあり、例えば電極としては、ガスを検知するガス電極として被検知ガスを電気化学反応させる作用電極、当該作用電極に対する対極、作用電極の電位を制御する参照電極の３電極を設けてあり、また、これらが接触自在な電解液を収容した電解槽と、各電極の電位を設定するポテンシオスタット回路等を接続してある。前記３電極の材料としては撥水性を有するガス透過性の多孔質ＰＴＦＥ膜に白金や金、パラジウム等の貴金属触媒等を塗布したものが、電解液としては、硫酸やリン酸等の酸性水溶液等が用いられていた。 A conventional constant potential electrolytic gas sensor is configured such that an electrode is provided facing an electrolytic solution storage part of an electrolytic cell in which an electrolytic solution is densely stored. For example, an electrode is detected as a gas electrode that detects gas. There are provided three electrodes, a working electrode for electrochemically reacting gas, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode. A potentiostat circuit for setting the potential is connected. As the material of the three electrodes, a gas-permeable porous PTFE film having water repellency is coated with a noble metal catalyst such as platinum, gold, palladium, etc. As an electrolyte, an acidic aqueous solution such as sulfuric acid or phosphoric acid is used. Was used.
　また、定電位電解式ガスセンサは、周囲の環境変化に対して作用電極の電位を制御して一定に維持することによって、作用電極と対極との間に周囲の環境変化に相当する電流を生じさせる。そして、作用電極の電位が変化せず、またガス種によって酸化還元電位が異なることを利用することにより、ポテンシオスタット回路の設定電位によってはガスの選択的な検知が可能になる。また、ガス電極に用いる触媒を変えることで、目的とするガスに対して高い選択性を持たすことができる。 In addition, the constant potential electrolytic gas sensor generates a current corresponding to a change in the surrounding environment between the working electrode and the counter electrode by controlling the potential of the working electrode to be constant with respect to a change in the surrounding environment. . Further, by utilizing the fact that the potential of the working electrode does not change and the oxidation-reduction potential varies depending on the gas type, the gas can be selectively detected depending on the set potential of the potentiostat circuit. Further, by changing the catalyst used for the gas electrode, it is possible to have high selectivity for the target gas.
　電極に塗布する貴金属触媒としては、例えば粒径が数十ｎｍのカーボンに、数百ｎｍ程度の金微粒子を担持させたものを使用することがあった。このようにカーボンに金微粒子を担持させるには、例えば浸漬担持法を使用することがある。当該浸漬担持法で貴金属粒子を担体に担持させる場合、当該担体を金属塩の水溶液中に浸して、金属成分を担体表面に吸着させ、乾燥・焼成・還元を行う。当該浸漬担持法で金付着カーボンを作製した後、多孔質ＰＴＦＥ膜に塗布して電極を作製していた。 As the noble metal catalyst applied to the electrode, for example, a carbon having a particle diameter of several tens of nanometers supported with gold fine particles of about several hundred nanometers may be used. In order to support the gold fine particles on the carbon as described above, for example, an immersion support method may be used. When the noble metal particles are supported on the support by the immersion support method, the support is immersed in an aqueous solution of a metal salt, the metal component is adsorbed on the support surface, and drying, firing, and reduction are performed. After producing gold-attached carbon by the immersion support method, an electrode was produced by applying it to a porous PTFE membrane.
　尚、本発明における従来技術となる上述した定電位電解式ガスセンサは、一般的な技術であるため、特許文献等の従来技術文献は示さない。 Note that the above-described constant potential electrolytic gas sensor, which is a conventional technique in the present invention, is a general technique, and thus does not show conventional technical documents such as patent documents.
　上述の手法によって作製された金付着カーボンは、金微粒子の粒径が担体であるカーボンの粒径より大きく、水溶液中で凝集し易い傾向にあるため、金微粒子を均一に分散させるのが困難であった。このように金微粒子が不均一な状態で作製された金付着カーボンを貴金属触媒として使用すると、ガス検知性能がバラつくなどの影響を与えることがあった。
　また、浸漬担持法における焼成の温度は６００℃程度とすることがあるが、担体をカーボンとする場合に焼成の温度がこのように高温であると、担体であるカーボンが燃焼してしまう虞があった。 The gold-adhered carbon produced by the above-mentioned method has a particle size of gold fine particles larger than that of carbon as a carrier and tends to aggregate in an aqueous solution, so that it is difficult to uniformly disperse the gold fine particles. there were. When the gold-adhered carbon produced in such a state that the gold fine particles are not uniform is used as a noble metal catalyst, there are cases where the gas detection performance varies.
In addition, although the firing temperature in the immersion support method may be about 600 ° C., when the carrier is carbon, if the firing temperature is such a high temperature, there is a risk that the carbon as the carrier will burn. there were.
　従って、本発明の目的は、定電位電解式ガスセンサにおける前記各電極の貴金属触媒として使用するに際し、ガス検知性能にバラつきが発生しにくい貴金属触媒、および、ガス検知性能にバラつきが発生しにくく、作製時に焼成温度を低く抑えることができる貴金属触媒を備えた定電位電解式ガスセンサを提供することにある。 Accordingly, an object of the present invention is to provide a noble metal catalyst that hardly causes variations in gas detection performance when used as a noble metal catalyst for each of the electrodes in a potentiostatic gas sensor, and a gas detection performance that hardly varies. An object of the present invention is to provide a potentiostatic gas sensor equipped with a noble metal catalyst capable of keeping the firing temperature low.
　上記目的を達成するための本発明に係る貴金属触媒の第一特徴構成は、担体としてのカーボン粉末に、前記カーボン粉末の平均粒径以下の平均粒径を有する金ナノ粒子を担持させた点にある。 The first characteristic configuration of the noble metal catalyst according to the present invention for achieving the above object is that gold nanoparticles having an average particle size equal to or smaller than the average particle size of the carbon powder are supported on the carbon powder as a support. is there.
　本構成の貴金属触媒は、カーボン粉末の平均粒径以下の平均粒径を有する金ナノ粒子を担持させることで、金ナノ粒子を分散させた状態で担体であるカーボンに担持させることができるため、金ナノ粒子の分散の程度を概ね均一な状態とすることができる。そのため、このような金担持カーボンを、例えばガスセンサにおける貴金属触媒として使用すれば、ガス検知性能にバラつきが生じるのを未然に防止することができる。 Since the noble metal catalyst of this configuration supports gold nanoparticles having an average particle size equal to or less than the average particle size of the carbon powder, the gold nanoparticles can be supported on the carrier carbon in a dispersed state. The degree of dispersion of the gold nanoparticles can be made substantially uniform. Therefore, if such a gold-supporting carbon is used as a noble metal catalyst in a gas sensor, for example, it is possible to prevent the gas detection performance from varying.
　尚、本明細書では、カーボン粉末の平均粒径以下の平均粒径を有する金ナノ粒子を付着させることを「担持」と称し、カーボン粉末の平均粒径より大きな平均粒径を有する金ナノ粒子が付着した従来の金付着カーボンと区別している。 In the present specification, attaching gold nanoparticles having an average particle size equal to or less than the average particle size of carbon powder is referred to as “supporting”, and gold nanoparticles having an average particle size larger than the average particle size of carbon powder. It is distinguished from the conventional gold-attached carbon to which is attached.
　本発明に係る貴金属触媒の第二特徴構成は、前記金ナノ粒子は、５～５０ｎｍの粒子が５～５０重量％で担持される点にある。 The second characteristic configuration of the noble metal catalyst according to the present invention is that the gold nanoparticles are supported at 5 to 50% by weight of 5 to 50 nm particles.
　本構成であれば、金ナノ粒子をカーボン粉末に良好に分散させた状態でカーボン粉末に担持させることができる。 If it is this structure, a gold nanoparticle can be carry | supported by carbon powder in the state disperse | distributed favorably to carbon powder.
　また、後述の実施例では、各電極で使用する金担持カーボンにおいて、金ナノ粒子の含有量を５～５０重量％まで種々変更して、それぞれにおいて定電位電解式ガスセンサを作製した。この結果、当該金ナノ粒子の添加量が５重量％以上であれば安定したガス感度が得られ、金担持カーボンの製造コストを鑑みると、金担持カーボンにおける金ナノ粒子の添加量が５０重量％までに抑制するのがよいものと認められた。 In the examples described later, in the gold-supported carbon used in each electrode, the content of gold nanoparticles was variously changed from 5 to 50% by weight, and a potentiostatic gas sensor was prepared for each. As a result, stable gas sensitivity can be obtained if the added amount of the gold nanoparticles is 5% by weight or more, and the added amount of the gold nanoparticles in the gold-supported carbon is 50% by weight in view of the production cost of the gold-supported carbon. It was recognized that it should be suppressed by
　本発明に係る貴金属触媒の第三特徴構成は、前記カーボン粉末の粒径を５～３００ｎｍの範囲にあるものとした点にある。 The third characteristic configuration of the noble metal catalyst according to the present invention is that the particle size of the carbon powder is in the range of 5 to 300 nm.
　本構成では、カーボン粉末の粒径を５～３００ｎｍの範囲にある任意の粒径に設定し、金ナノ粒子の粒径を、当該任意の粒径以下に設定することができる。具体的には、例えばカーボンブラックの粒度を、このような粒径の範囲を有するように調整して使用することができる。 In this configuration, the particle size of the carbon powder can be set to an arbitrary particle size in the range of 5 to 300 nm, and the particle size of the gold nanoparticle can be set to be equal to or less than the arbitrary particle size. Specifically, for example, the particle size of carbon black can be adjusted to have such a particle size range.
　本発明に係る定電位電解式ガスセンサの第一特徴構成は、ガスを検知するガス電極として被検知ガスを化学反応させる作用電極、前記作用電極に対する対極、前記作用電極の電位を制御する参照電極を、電解液を収容した電解槽の電解液収容部に臨んで備えた定電位電解式ガスセンサにおいて、前記各電極として、第一～三特徴構成の何れか一項に記載の貴金属触媒を備える点にある。 The first characteristic configuration of the constant potential electrolytic gas sensor according to the present invention includes a working electrode that chemically reacts a gas to be detected as a gas electrode that detects gas, a counter electrode with respect to the working electrode, and a reference electrode that controls the potential of the working electrode. In the constant potential electrolytic gas sensor provided facing the electrolytic solution storage part of the electrolytic cell containing the electrolytic solution, the noble metal catalyst according to any one of the first to three characteristic configurations is provided as each electrode. is there.
　本構成の貴金属触媒は、金ナノ粒子を分散させた状態で担体であるカーボンに担持させることができるため、金ナノ粒子の分散の程度を概ね均一な状態とすることができる。そのため、このような金担持カーボンを貴金属触媒として使用すれば、定電位電解式ガスセンサにおいて、ガス検知性能にバラつきが生じるのを未然に防止することができる。 Since the noble metal catalyst of this configuration can be supported on carbon as a carrier in a state where gold nanoparticles are dispersed, the degree of dispersion of the gold nanoparticles can be made almost uniform. Therefore, if such a gold-supported carbon is used as a noble metal catalyst, it is possible to prevent the gas detection performance from varying in the constant potential electrolytic gas sensor.
　本発明に係る定電位電解式ガスセンサの第二特徴構成は、前記貴金属触媒は、溶媒にカーボン粉末を添加して撹拌するカーボン粉末添加工程と、金ナノ粒子を分散させたコロイド溶液を添加する金ナノ粒子添加工程と、前記溶媒の沸点以下に維持した状態で乾燥させる乾燥工程と、乾燥して得られた金ナノ粒子を担持させたカーボン粉末を２５０～４５０℃で焼成を行う焼成工程と、を行って作製される点にある。 The second characteristic configuration of the controlled potential electrolysis gas sensor according to the present invention is that the noble metal catalyst includes a carbon powder addition step in which carbon powder is added to a solvent and stirred, and a gold powder in which a colloidal solution in which gold nanoparticles are dispersed is added. A nanoparticle addition step, a drying step of drying in a state maintained below the boiling point of the solvent, a firing step of firing carbon powder carrying gold nanoparticles obtained by drying at 250 to 450 ° C., It is in the point produced by performing.
　本発明の定電位電解式ガスセンサは、金ナノ粒子を分散させた状態で担持する金担持カーボンを貴金属触媒として使用することができる。当該金担持カーボンは、作製の過程でコロイド溶液を使用しているため、金ナノ粒子を分散させた状態で担体であるカーボンに担持させることができるため、金ナノ粒子の分散の程度を概ね均一な状態とすることができる。そのため、このような金担持カーボンを貴金属触媒として使用すれば、定電位電解式ガスセンサにおいて、ガス検知性能にバラつきが生じるのを未然に防止することができる。 In the controlled potential electrolytic gas sensor of the present invention, gold-supported carbon supported in a state where gold nanoparticles are dispersed can be used as a noble metal catalyst. Since the gold-supporting carbon uses a colloidal solution in the production process, it can be supported on carbon as a carrier in a state in which the gold nanoparticles are dispersed, so the degree of dispersion of the gold nanoparticles is almost uniform. It can be in a state. Therefore, if such a gold-supported carbon is used as a noble metal catalyst, it is possible to prevent the gas detection performance from varying in the constant potential electrolytic gas sensor.
　また、本構成による金担持カーボンは、作製の過程で焼成の温度を２５０～４５０℃に抑制することができるため、担体であるカーボンが燃焼する虞はない。 Further, the gold-supporting carbon according to the present configuration can suppress the firing temperature to 250 to 450 ° C. during the production process, so there is no possibility that the carbon as the carrier will burn.
　本発明に係る定電位電解式ガスセンサの第三特徴構成は、前記カーボン粉末添加工程において界面活性剤を添加する点にある。 The third characteristic configuration of the potentiostatic gas sensor according to the present invention is that a surfactant is added in the carbon powder addition step.
　本構成によれば、界面活性剤を添加することで、溶媒に対するカーボンの分散性を向上させることができる。 According to this configuration, the dispersibility of carbon in the solvent can be improved by adding a surfactant.
本発明の定電位電解式ガスセンサを示す断面図である。It is sectional drawing which shows the constant potential electrolytic gas sensor of this invention. 金担持カーボンの作製の概要を示す流れ図である。It is a flowchart which shows the outline | summary of preparation of gold | metal | money carrying | support carbon. 金ナノ粒子の粒度分布を示したグラフである。It is the graph which showed the particle size distribution of the gold nanoparticle. 金担持カーボンの電子顕微鏡の写真図である（本発明例）。It is a photograph figure of the electron microscope of gold | metal | money carrying | support carbon (invention example). 金担持カーボンの電子顕微鏡の写真図である（比較例）。It is a photograph figure of the electron microscope of gold carrying carbon (comparative example). 定電位電解式ガスセンサにおいて、ホスフィンガス１ｐｐｍ，０．５ｐｐｍに対するガス感度測定を行った結果を示したグラフである。It is the graph which showed the result of having performed the gas sensitivity measurement with respect to phosphine gas 1ppm and 0.5ppm in a constant potential electrolytic gas sensor. 定電位電解式ガスセンサにおいて、シラン、ホスフィン、ゲルマン、アルシン、ジボラン１ｐｐｍに対するガス感度測定を行った結果を示したグラフである。It is the graph which showed the result of having performed the gas sensitivity measurement with respect to 1 ppm of silane, a phosphine, a germane, arsine, and diborane in a constant potential electrolytic gas sensor.
　以下、本発明の実施形態を図面に基づいて説明する。
　本発明の貴金属触媒は、定電位電解式ガスセンサにおける各電極の貴金属触媒として使用される。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The noble metal catalyst of the present invention is used as a noble metal catalyst for each electrode in a potentiostatic gas sensor.
　当該貴金属触媒は、担体としてのカーボン粉末に、前記カーボン粉末の平均粒径以下の平均粒径を有する金ナノ粒子を担持させている。 In the noble metal catalyst, gold nanoparticles having an average particle size equal to or less than the average particle size of the carbon powder are supported on carbon powder as a carrier.
　図１に示すように、定電位電解式ガスセンサＸは、ガスを検知するガス電極として被検知ガスを電気化学反応させる作用電極１１、当該作用電極１１に対する対極１２、作用電極の電位を制御する参照電極１３を、電解液２０を収容した電解槽３０の電解液収容部３１に臨んで備えている。 As shown in FIG. 1, the constant potential electrolysis gas sensor X is a gas electrode for detecting a gas. A working electrode 11 for electrochemically reacting a gas to be detected, a counter electrode 12 for the working electrode 11, and a reference for controlling the potential of the working electrode. The electrode 13 is provided so as to face the electrolytic solution storage part 31 of the electrolytic bath 30 in which the electrolytic solution 20 is stored.
　作用電極１１、対極１２及び参照電極１３は、撥水性を有する多孔質のガス透過膜１４の表面に、公知の電極材料より作製したペーストを塗布・焼成して形成してある。作用電極１１と、対極１２及び参照電極１３とは、対向して配置してある。 The working electrode 11, the counter electrode 12, and the reference electrode 13 are formed by applying and baking a paste made of a known electrode material on the surface of a porous gas-permeable film 14 having water repellency. The working electrode 11, the counter electrode 12 and the reference electrode 13 are disposed to face each other.
　電解槽３０は側方に開口する開口部３２を形成してガス導通部３３を形成している。ガス透過膜１４は二枚設けられ、一方のガス透過膜１４には作用電極１１が配設され、他方のガス透過膜１４には対極１２及び参照電極１３が配設される。作用電極１１の側に配設されたガス透過膜１４は、開口部３２に臨むように電解槽３０に取り付けられる。被検知ガスはガス導通部３３より導入され、作用電極１１上で反応する。 The electrolytic cell 30 has an opening 32 that opens laterally to form a gas conduction portion 33. Two gas permeable membranes 14 are provided. One gas permeable membrane 14 is provided with a working electrode 11, and the other gas permeable membrane 14 is provided with a counter electrode 12 and a reference electrode 13. The gas permeable membrane 14 disposed on the working electrode 11 side is attached to the electrolytic cell 30 so as to face the opening 32. The gas to be detected is introduced from the gas conduction part 33 and reacts on the working electrode 11.
　それぞれのガス透過膜１４とＯリング１５とは蓋部材１６によって固定される。電解槽３０の底面には、電解液２０の注入等のメンテナンスを行う電解液注入口３４が形成されている。 Each gas permeable membrane 14 and O-ring 15 are fixed by a lid member 16. An electrolytic solution inlet 34 for performing maintenance such as injection of the electrolytic solution 20 is formed on the bottom surface of the electrolytic bath 30.
　このような定電位電解式ガスセンサＸは、被検知ガスの反応によって作用電極１１上で生じた電子に基づく電流を検知自在な電流測定部と、作用電極１１の電位制御自在な電位制御部とを備えたガス検知回路（図外）に接続して、ガス検知装置として用いられる。本発明の定電位電解式ガスセンサＸは、例えばシラン、ホスフィン、ゲルマン、アルシン、ジボランなどの水素化物ガスの検知に用いられる。 Such a constant potential electrolytic gas sensor X includes a current measuring unit capable of detecting a current based on electrons generated on the working electrode 11 by a reaction of the gas to be detected, and a potential control unit capable of controlling the potential of the working electrode 11. It is used as a gas detection device by connecting to a gas detection circuit (not shown). The constant potential electrolytic gas sensor X of the present invention is used for detection of hydride gas such as silane, phosphine, germane, arsine, diborane.
　図２に示したように、本発明の定電位電解式ガスセンサＸにおける各電極１０は貴金属触媒を備えており、当該貴金属触媒は、溶媒にカーボン粉末を添加して撹拌するカーボン粉末添加工程Ａと、金ナノ粒子を分散させたコロイド溶液を添加する金ナノ粒子添加工程Ｂと、溶媒の沸点以下に維持した状態で乾燥させる乾燥工程Ｃと、乾燥して得られた金ナノ粒子を担持させたカーボン粉末を２５０～４５０℃で焼成を行う焼成工程Ｄと、を行って作製される。 As shown in FIG. 2, each electrode 10 in the controlled potential electrolytic gas sensor X of the present invention includes a noble metal catalyst, and the noble metal catalyst includes a carbon powder addition step A in which carbon powder is added to a solvent and stirred. A gold nanoparticle addition step B for adding a colloidal solution in which gold nanoparticles are dispersed, a drying step C for drying while maintaining the temperature below the boiling point of the solvent, and a gold nanoparticle obtained by drying. The carbon powder is produced by performing a firing step D in which the carbon powder is fired at 250 to 450 ° C.
　カーボン粉末添加工程Ａでは、カーボン粉末を所定量秤量し、溶媒である水を加え十分攪拌させる。
　カーボン粉末は、公知のカーボン粉末、例えばカーボンブラック（粒径５～３００ｎｍ程度）を使用することができ、特にアセチレンガスを熱分解して得るアセチレンブラックを使用するのがよいが、これに限定されるものではない。 In the carbon powder addition step A, a predetermined amount of carbon powder is weighed, and water as a solvent is added and sufficiently stirred.
As the carbon powder, a known carbon powder, for example, carbon black (particle size of about 5 to 300 nm) can be used, and in particular, acetylene black obtained by thermally decomposing acetylene gas is preferably used, but is not limited thereto. It is not something.
　本工程は界面活性剤を添加して行ってもよい。当該界面活性剤を添加することで、溶媒に対するカーボンの分散性を向上させることができる。界面活性剤は、アニオン系、カチオン系、ノニオン系、ベタイン系界面活性剤のいずれも使用できる。溶媒へのカーボンの分散性を上げるためには、界面活性剤を添加する他、例えば溶媒が水の場合にカーボンの表面に水酸基を付けて親水性を高めるといった表面処理を行ってもよいし、或いは、前処理として超音波処理を行ってもよい。 This step may be performed by adding a surfactant. By adding the surfactant, the dispersibility of carbon in the solvent can be improved. As the surfactant, any of anionic, cationic, nonionic, and betaine surfactants can be used. In order to increase the dispersibility of carbon in the solvent, in addition to adding a surfactant, for example, when the solvent is water, a surface treatment such as adding a hydroxyl group to the surface of carbon to increase hydrophilicity may be performed, Alternatively, ultrasonic treatment may be performed as pretreatment.
　金ナノ粒子添加工程Ｂでは、カーボン粉末添加工程Ａで得られた溶液に金ナノ粒子を分散させたコロイド溶液を添加する。
　金ナノ粒子を分散させたコロイド溶液は、上述した粒度を有する金ナノ粒子が溶液中に分散している状態となっている。当該コロイド溶液には、必要に応じて保護剤などの添加剤を添加してもよい。
　金コロイド溶液は、例えばテトラクロロ金酸（III）などの塩化金酸溶液に還元剤としてクエン酸塩溶液を加えて加熱することにより、金属イオンを還元してコロイドとする溶液内還元反応を利用して作製することができるが、このような手法に限定されるものではない。当該方法においては、塩化金酸に対する還元剤の添加量を増減することにより、金コロイド粒子の大きさを変化させることができる。金ナノ粒子は、約５～５０ｎｍ程度の粒径を有する粒子であればよいが、この範囲に限定されるものではない。この場合、５～５０ｎｍの粒子の割合が９０重量％以上となるような粒度分布とするのがよい。 In the gold nanoparticle addition step B, a colloidal solution in which gold nanoparticles are dispersed in the solution obtained in the carbon powder addition step A is added.
The colloidal solution in which the gold nanoparticles are dispersed is in a state in which the gold nanoparticles having the above-described particle size are dispersed in the solution. You may add additives, such as a protective agent, to the said colloid solution as needed.
The colloidal gold solution uses an in-solution reduction reaction in which metal ions are reduced to a colloid by adding a citrate solution as a reducing agent to a chloroauric acid solution such as tetrachloroauric acid (III) and heating. However, it is not limited to such a method. In this method, the size of colloidal gold particles can be changed by increasing or decreasing the amount of reducing agent added to chloroauric acid. The gold nanoparticles may be particles having a particle size of about 5 to 50 nm, but are not limited to this range. In this case, the particle size distribution is preferably such that the proportion of 5 to 50 nm particles is 90% by weight or more.
　乾燥工程Ｃでは、金ナノ粒子添加工程Ｂで得られた溶液を、溶媒（水）の沸点以下に維持した状態で乾燥させる。溶媒の沸点以下として設定する温度は、特に限定されるものではないが、溶媒が水の場合、８０～１００℃程度とするのがよい。乾燥の手法は、例えば減圧乾燥、真空乾燥、吸引乾燥、熱風乾燥など、公知の手法を適用することができる。これら乾燥の手法における乾燥条件は、公知の条件を適用すればよい。 In the drying step C, the solution obtained in the gold nanoparticle addition step B is dried while being maintained at a boiling point or lower of the solvent (water). The temperature set to be equal to or lower than the boiling point of the solvent is not particularly limited, but when the solvent is water, it is preferably about 80 to 100 ° C. As a drying method, a known method such as reduced-pressure drying, vacuum drying, suction drying, or hot air drying can be applied. Known conditions may be applied as drying conditions in these drying methods.
　焼成工程Ｄでは、乾燥して得られた粉末を２５０～４５０℃で焼成を行う。
　本実施形態における焼成温度は、空気雰囲気、大気圧下でカーボンの酸化が進まない温度で、使用した界面活性剤等の有機物が蒸発する温度（２５０～４５０℃）としてある。
　焼成時間は、界面活性剤、コロイドの保護剤等が蒸発、昇華、熱分解により完全になくなるまでの時間を適宜設定すればよい。そのため、焼成させる粉体の量で、その都度焼成時間の短縮・延長が可能である。しかし、金ナノ粒子の粒成長、焼結による活性の低下などを考慮して、例えば当該焼成時間の上限を３時間程度までと設定してもよい。また、焼成時間を設定せず、所定の温度に達すれば焼成工程Ｄを終了するように設定してもよい。 In the firing step D, the powder obtained by drying is fired at 250 to 450 ° C.
The firing temperature in the present embodiment is a temperature (250 to 450 ° C.) at which the organic substance such as the used surfactant evaporates at a temperature at which carbon oxidation does not proceed under an air atmosphere and atmospheric pressure.
The firing time may be set as appropriate until the surfactant, colloid protective agent, and the like are completely eliminated by evaporation, sublimation, and thermal decomposition. Therefore, the firing time can be shortened or extended each time depending on the amount of powder to be fired. However, in consideration of grain growth of gold nanoparticles, a decrease in activity due to sintering, etc., the upper limit of the firing time may be set to about 3 hours, for example. Moreover, you may set so that the baking process D may be complete | finished if it reaches predetermined temperature, without setting baking time.
　上記手法によって、金ナノ粒子を分散させた状態で担持する金担持カーボンを作製することができる。即ち、本発明の定電位電解式ガスセンサＸは、金ナノ粒子を分散させた状態で担持する金担持カーボンを貴金属触媒として使用することができる。当該金担持カーボンは、作製の過程でコロイド溶液を使用しているため、金ナノ粒子を分散させた状態で担体であるカーボンに担持させることができるため、金ナノ粒子の分散の程度を概ね均一な状態とすることができる。そのため、このような金担持カーボンを貴金属触媒として使用すれば、定電位電解式ガスセンサＸにおいて、ガス検知性能にバラつきが生じるのを未然に防止することができる。 By the above method, it is possible to produce gold-carrying carbon that carries gold nanoparticles in a dispersed state. That is, the controlled potential electrolytic gas sensor X of the present invention can use gold-supported carbon supported in a state where gold nanoparticles are dispersed as a noble metal catalyst. Since the gold-supporting carbon uses a colloidal solution in the production process, it can be supported on carbon as a carrier in a state in which the gold nanoparticles are dispersed, so the degree of dispersion of the gold nanoparticles is almost uniform. It can be in a state. Therefore, if such gold-supported carbon is used as a noble metal catalyst, it is possible to prevent the gas detection performance from varying in the constant potential electrolytic gas sensor X.
　また、本構成による金担持カーボンは、作製の過程で焼成の温度を２５０～４５０℃に抑制することができるため、担体であるカーボンが燃焼する虞はない。 Further, the gold-supporting carbon according to the present configuration can suppress the firing temperature to 250 to 450 ° C. during the production process, so there is no possibility that the carbon as the carrier will burn.
　さらに、上記手法で作製した金担持カーボンにおいて、金ナノ粒子は、約５～５０ｎｍ程度の粒径で分散させることが可能となる。その結果、従来の手法により作製した金担持カーボンにおける金微粒子の添加量が５０重量％より多いのに対して、上記手法で作製した金担持カーボンにおける金ナノ粒子の添加量を５～５０重量％程度に減じることができる。従って、本発明の定電位電解式ガスセンサＸは、貴金属触媒における金ナノ粒子の添加量を減じることができるため、センサの製造コストを削減することができる。 Furthermore, in the gold-supported carbon produced by the above method, the gold nanoparticles can be dispersed with a particle size of about 5 to 50 nm. As a result, the amount of added gold fine particles in the gold-supported carbon prepared by the conventional method is more than 50% by weight, whereas the amount of gold nanoparticles added in the gold-supported carbon prepared by the above method is 5 to 50% by weight. Can be reduced to a degree. Therefore, since the controlled potential electrolytic gas sensor X of the present invention can reduce the amount of gold nanoparticles added to the noble metal catalyst, the manufacturing cost of the sensor can be reduced.
〔実施例１〕
　本発明の定電位電解式ガスセンサＸの電極において貴金属触媒として使用する金担持カーボンを以下のようにして作製した。当該金担持カーボンに対する金ナノ粒子の含有量が２５重量％になるように、各試薬を調整した。 [Example 1]
A gold-supporting carbon used as a noble metal catalyst in the electrode of the controlled potential electrolysis gas sensor X of the present invention was produced as follows. Each reagent was adjusted so that the content of the gold nanoparticles with respect to the gold-supported carbon was 25% by weight.
　アセチレンブラック粉末３ｇと、界面活性剤（ドデシルベンゼンスルホン酸ナトリウム）２ｍＬを水６００ｍＬに添加して十分撹拌した（カーボン粉末添加工程Ａ）。
　この撹拌溶液に、金ナノ粒子を分散させたコロイド水溶液（３重量％）を３３．３ｇを添加した（金ナノ粒子添加工程Ｂ）。
　その後、攪拌を続けながら８０℃に保持し、さらに減圧乾燥（１００ｈｐａ、８０℃）させた（乾燥工程Ｃ）。
　乾燥後、取り出した試料粉末を大気圧、空気雰囲気下で４００℃、１時間の焼成を行い（焼成工程Ｄ）、金担持カーボンの粉末を得た（本発明例１）。 3 g of acetylene black powder and 2 mL of a surfactant (sodium dodecylbenzenesulfonate) were added to 600 mL of water and sufficiently stirred (carbon powder addition step A).
To this stirring solution, 33.3 g of a colloidal aqueous solution (3% by weight) in which gold nanoparticles were dispersed was added (gold nanoparticle addition step B).
Then, it kept at 80 degreeC, continuing stirring, and also made it dry under reduced pressure (100 hpa, 80 degreeC) (drying process C).
After drying, the sample powder taken out was calcined at 400 ° C. for 1 hour under atmospheric pressure and air atmosphere (firing step D) to obtain gold-supported carbon powder (Invention Example 1).
　本発明例１の金ナノ粒子の粉末の粒度分布（Ｘ線小角散乱法による測定）を図３に示し、金担持カーボンの電子顕微鏡写真を図４に示した。図５には、比較として従来の金担持カーボン（比較例）の電子顕微鏡写真を示した。 FIG. 3 shows the particle size distribution (measured by the X-ray small angle scattering method) of the gold nanoparticle powder of Invention Example 1, and FIG. 4 shows an electron micrograph of the gold-supporting carbon. FIG. 5 shows an electron micrograph of a conventional gold-supporting carbon (comparative example) for comparison.
　図３より、当該金ナノ粒子の粉末は５～５０ｎｍ程度の粒径を有するものと認められた。また、本発明例１の金担持カーボンでは、金ナノ粒子が分散してカーボンに担持されていると認められた（図４）。一方、比較例の金担持カーボンでは、金微粒子が凝集しているものと認められた（図５）。 From FIG. 3, it was confirmed that the gold nanoparticle powder had a particle size of about 5 to 50 nm. In the gold-supported carbon of Invention Example 1, it was recognized that the gold nanoparticles were dispersed and supported on the carbon (FIG. 4). On the other hand, in the gold-supporting carbon of the comparative example, it was recognized that the gold fine particles were aggregated (FIG. 5).
〔実施例２〕
　定電位電解式ガスセンサＸの各電極を以下のようにして作製した。各電極で使用する金担持カーボンにおいて、金ナノ粒子の含有量を５～５０重量％まで種々変更して、それぞれにおいて定電位電解式ガスセンサＸを作製した。 [Example 2]
Each electrode of the potentiostatic gas sensor X was produced as follows. In the gold-supporting carbon used in each electrode, the content of gold nanoparticles was variously changed from 5 to 50% by weight, and a constant potential electrolytic gas sensor X was produced in each.
　金担持カーボンの粉末０．１ｇ、界面活性剤（ドデシルベンゼンスルホン酸ナトリウム）０．１ｍＬ、ＰＴＦＥ（ポリテトラフルオロエチレン：テフロン）ディスパージョン（ＰＴＦＥの微粒子を含むコロイド溶液、比重１．５）０．３５ｍＬをそれぞれ加え、混錬して電極材料ペーストを調製した。得られた電極材料ペーストをＰＴＦＥシート上に印刷し、乾燥後、２８０℃で８時間焼成することで各電極１０を得た。得られた各電極１０を、それぞれ作用電極１１、対極１２及び参照電極１３とし、電解液２０を４２重量％の硫酸水溶液とした定電位電解式ガスセンサＸを作製した。 0.1 g of gold-supported carbon powder, 0.1 mL of surfactant (sodium dodecylbenzenesulfonate), PTFE (polytetrafluoroethylene: Teflon) dispersion (a colloidal solution containing fine particles of PTFE, specific gravity 1.5). 35 mL of each was added and kneaded to prepare an electrode material paste. The obtained electrode material paste was printed on a PTFE sheet, dried, and baked at 280 ° C. for 8 hours to obtain each electrode 10. Each of the obtained electrodes 10 was used as a working electrode 11, a counter electrode 12, and a reference electrode 13, and a potentiostatic gas sensor X was prepared in which the electrolytic solution 20 was a 42% by weight sulfuric acid aqueous solution.
　得られたそれぞれの定電位電解式ガスセンサＸにおいて、２０℃、５０％ＲＨ環境下で、ホスフィンガス１ｐｐｍ，０．５ｐｐｍに対するガス感度測定を行った（図６）。同様に、シラン、ホスフィン、ゲルマン、アルシン、ジボランの各ガス１ｐｐｍに対してのガス感度測定を行った（図７）。
　尚、ガス感度は、対象ガス雰囲気中で、作用電極１１からガス検知回路４０へ流れる電流値の大きさで定義した。 In each of the obtained potentiostatic gas sensors X, gas sensitivity was measured for phosphine gas 1 ppm and 0.5 ppm in an environment of 20 ° C. and 50% RH (FIG. 6). Similarly, gas sensitivity measurement was performed for 1 ppm of each gas of silane, phosphine, germane, arsine, and diborane (FIG. 7).
The gas sensitivity was defined by the magnitude of the current value flowing from the working electrode 11 to the gas detection circuit 40 in the target gas atmosphere.
　この結果、金担持カーボンにおける金ナノ粒子の添加量が５重量％以上、特に２０重量％以上である定電位電解式ガスセンサＸであればガスに対する反応性が十分高い作用電極であることが認められた。また、金担持カーボンの製造コストを鑑みると、金担持カーボンにおける金ナノ粒子の添加量が５０重量％、好ましくは３０重量％までに抑制するのがよい。従って、ガス感度および製造コストを考慮すれば、金担持カーボンにおける金ナノ粒子の添加量は５～５０重量％程度とするのがよい。 As a result, the potentiostatic gas sensor X in which the amount of added gold nanoparticles in the gold-supported carbon is 5% by weight or more, particularly 20% by weight or more is recognized as a working electrode having a sufficiently high reactivity to gas. It was. In view of the production cost of the gold-supported carbon, the amount of gold nanoparticles added to the gold-supported carbon should be suppressed to 50% by weight, preferably 30% by weight. Therefore, in consideration of gas sensitivity and production cost, the amount of gold nanoparticles added to the gold-supported carbon is preferably about 5 to 50% by weight.
本発明は、ガスを検知するガス電極として被検知ガスを電気化学反応させる作用電極、前記作用電極に対する対極、前記作用電極の電位を制御する参照電極を、電解液を収容した電解槽の電解液収容部に臨んで備えた定電位電解式ガスセンサに使用される貴金属触媒、および、当該定電位電解式ガスセンサに利用できる。 The present invention provides a working electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting a gas, a counter electrode for the working electrode, and a reference electrode for controlling the potential of the working electrode. The present invention can be used for the noble metal catalyst used in the constant potential electrolytic gas sensor provided facing the housing portion and the constant potential electrolytic gas sensor.
Ａ　　　　　カーボン粉末添加工程
Ｂ　　　　　金ナノ粒子添加工程
Ｃ　　　　　乾燥工程
Ｄ　　　　　焼成工程
Ｘ　　　　　定電位電解式ガスセンサ
１１　　　　作用電極
１２　　　　対極
１３　　　　参照電極
２０　　　　電解液
３０　　　　電解槽
３１　　　　電解液収容部
  A Carbon powder addition process B Gold nanoparticle addition process C Drying process D Firing process X Constant potential electrolytic gas sensor 11 Working electrode 12 Counter electrode 13 Reference electrode 20 Electrolytic solution 30 Electrolytic tank 31 Electrolytic solution container

Claims (6)

  1. 　担体としてのカーボン粉末に、前記カーボン粉末の平均粒径以下の平均粒径を有する金ナノ粒子を担持させた貴金属触媒。 A noble metal catalyst in which gold nanoparticles having an average particle size equal to or less than the average particle size of the carbon powder are supported on carbon powder as a carrier.
  2. 　前記金ナノ粒子は、５～５０ｎｍの粒子が５～５０重量％で担持される請求項１に記載の貴金属触媒。 The noble metal catalyst according to claim 1, wherein the gold nanoparticles are supported at 5 to 50% by weight of 5 to 50 nm particles.
  3. 　前記カーボン粉末は、粒径が５～３００ｎｍの範囲にある請求項１または２に記載の貴金属触媒。 The noble metal catalyst according to claim 1 or 2, wherein the carbon powder has a particle size in the range of 5 to 300 nm.
  4. 　ガスを検知するガス電極として被検知ガスを化学反応させる作用電極、前記作用電極に対する対極、前記作用電極の電位を制御する参照電極を、電解液を収容した電解槽の電解液収容部に臨んで備えた定電位電解式ガスセンサにおいて、前記各電極として、請求項１～３の何れか一項に記載の貴金属触媒を備える定電位電解式ガスセンサ。 A working electrode that chemically reacts with a gas to be detected as a gas electrode that detects gas, a counter electrode with respect to the working electrode, and a reference electrode that controls the potential of the working electrode, facing an electrolytic solution containing portion of an electrolytic cell containing the electrolytic solution A constant potential electrolytic gas sensor comprising the noble metal catalyst according to any one of claims 1 to 3 as each electrode.
  5. 　前記貴金属触媒は、
    　溶媒にカーボン粉末を添加して撹拌するカーボン粉末添加工程と、
    　金ナノ粒子を分散させたコロイド溶液を添加する金ナノ粒子添加工程と、
    　前記溶媒の沸点以下に維持した状態で乾燥させる乾燥工程と、
    　乾燥して得られた金ナノ粒子を担持させたカーボン粉末を２５０～４５０℃で焼成を行う焼成工程と、を行って作製される請求項４に記載の定電位電解式ガスセンサ。     The noble metal catalyst is
    Adding carbon powder to the solvent and stirring the carbon powder;
    A gold nanoparticle addition step of adding a colloidal solution in which gold nanoparticles are dispersed;
    A drying step of drying in a state maintained below the boiling point of the solvent;
    The constant potential electrolytic gas sensor according to claim 4, which is produced by performing a baking step of baking carbon powder carrying gold nanoparticles obtained by drying at 250 to 450 ° C.
  6. 　前記カーボン粉末添加工程において界面活性剤を添加する請求項５に記載の定電位電解式ガスセンサ。
          The constant potential electrolytic gas sensor according to claim 5, wherein a surfactant is added in the carbon powder addition step.
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JPH08313480A (en) * 1995-05-23 1996-11-29 Gastec:Kk Electrode of constant potential electrolytic gas sensor
JP2004146223A (en) * 2002-10-25 2004-05-20 National Institute Of Advanced Industrial & Technology Negative electrode catalyst for fuel cell
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JPH08313480A (en) * 1995-05-23 1996-11-29 Gastec:Kk Electrode of constant potential electrolytic gas sensor
JP2004146223A (en) * 2002-10-25 2004-05-20 National Institute Of Advanced Industrial & Technology Negative electrode catalyst for fuel cell
JP2012081469A (en) * 2003-02-13 2012-04-26 E I Du Pont De Nemours & Co Electrocatalyst and method for manufacturing

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Publication number Priority date Publication date Assignee Title
WO2019159015A3 (en) * 2018-02-07 2019-10-10 Stratuscent Inc. Sensing elements comprising gold nanoparticle-grafted carbon black
US11788985B2 (en) 2018-02-07 2023-10-17 Stratuscent Inc. Sensing elements comprising gold nanoparticle-grafted carbon black

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