JP2020161273A - Manufacturing method of electrode material - Google Patents
Manufacturing method of electrode material Download PDFInfo
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- JP2020161273A JP2020161273A JP2019057842A JP2019057842A JP2020161273A JP 2020161273 A JP2020161273 A JP 2020161273A JP 2019057842 A JP2019057842 A JP 2019057842A JP 2019057842 A JP2019057842 A JP 2019057842A JP 2020161273 A JP2020161273 A JP 2020161273A
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- 239000007772 electrode material Substances 0.000 title claims abstract description 107
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 36
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- 229910052799 carbon Inorganic materials 0.000 claims abstract description 63
- 239000000463 material Substances 0.000 claims abstract description 63
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- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 31
- 229910001887 tin oxide Inorganic materials 0.000 claims description 31
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
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- KLFRPGNCEJNEKU-FDGPNNRMSA-L (z)-4-oxopent-2-en-2-olate;platinum(2+) Chemical compound [Pt+2].C\C([O-])=C\C(C)=O.C\C([O-])=C\C(C)=O KLFRPGNCEJNEKU-FDGPNNRMSA-L 0.000 description 3
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- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
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- 229910001111 Fine metal Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
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- 229910052759 nickel Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
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- 229910052763 palladium Inorganic materials 0.000 description 1
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 1
- 238000007540 photo-reduction reaction Methods 0.000 description 1
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- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
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- 239000010409 thin film Substances 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
Description
本発明は、固体高分子方燃料電池用電極に好適な電極材料の製造方法に関する。 The present invention relates to a method for producing an electrode material suitable for an electrode for a polymer electrolyte fuel cell.
電解質に固体高分子膜を使用した固体高分子形燃料電池（ＰＥＦＣ）は、作動温度が８０℃付近と比較的低温であるため、例えば、車載用電源、家庭用等の小規模な固定電源として導入されている。ＰＥＦＣでは、以下の電気化学反応によって電力を取り出すことができる。
アノード反応：２Ｈ2 → ４Ｈ+＋４ｅ- （反応１）
カソード反応：Ｏ2＋４Ｈ+＋４ｅ-→２Ｈ2Ｏ （反応２）
全反応 ：２Ｈ2＋Ｏ2→２Ｈ2Ｏ
A polymer electrolyte fuel cell (PEFC) using a solid polymer membrane as an electrolyte has a relatively low operating temperature of around 80 ° C. Therefore, for example, it can be used as a small-scale fixed power source for automobiles, households, etc. Has been introduced. In PEFC, electric power can be extracted by the following electrochemical reaction.
Anode reaction: 2H 2 → 4H + + 4e - ( Reaction 1)
Cathode reaction: O 2 + 4H + + 4e - → 2H 2 O ( Reaction 2)
Total reaction: 2H 2 + O 2 → 2H 2 O
ＰＥＦＣは、電解質膜と前記電解質膜の両面に積層された電極（アノード及びカソード）とを含む膜電極接合体（ＭＥＡ）と、前記膜電極接合体の両面に積層されたガス拡散層（ＧＤＬ）とからなる発電モジュールを、ガス流路が形成された２つのセパレータで挟んだ構造のセルを基本単位として構成されている。ＰＥＦＣの構成部材は、一般的に、セパレータは金属材料で形成されており、ガス拡散層は多孔質の炭素材料が使用されている。また、電極触媒層（アノード及びカソード）は、担体の表面にＰｔ等の貴金属からなる電極触媒粒子が担持された構造を有し、担体には一般的に炭素材料が使用されている。 PEFCs are a membrane electrode assembly (MEA) including an electrolyte membrane and electrodes (anode and cathode) laminated on both sides of the electrolyte membrane, and a gas diffusion layer (GDL) laminated on both sides of the membrane electrode assembly. The power generation module composed of the above is configured with a cell having a structure sandwiched between two separators having a gas flow path as a basic unit. In the PEFC constituent members, the separator is generally made of a metal material, and the gas diffusion layer is made of a porous carbon material. Further, the electrode catalyst layer (anode and cathode) has a structure in which electrode catalyst particles made of a noble metal such as Pt are supported on the surface of the carrier, and a carbon material is generally used for the carrier.
一方、ＰＥＦＣの膜電極接合体（ＭＥＡ）の電解質膜で使用されるナフィオン（Nafion）は酸性（ｐＨ＝０〜３）であるため、ＰＥＦＣの電極材料は超強酸性条件で使用されることになる。また、通常運転しているときのセル電圧は０．４〜１．０Ｖであるが、起動停止時にはセル電圧が１．５Ｖまで上昇するため、カソードでは、炭素系担体が電気化学的に酸化されてＣＯ2に分解する反応が起こり、炭素系担体が腐食されて触媒活性成分である電極触媒粒子が脱落するという問題があり、アノードにおいても運転初期などに燃料ガスが不足すると、その部分での電圧低下、あるいは濃度分極が生じて局部的に通常と反対の電位となり、炭素系担体の電気化学的酸化分解が起こることがある。 On the other hand, since Nafion used in the electrolyte membrane of the PEFC membrane electrode assembly (MEA) is acidic (pH = 0 to 3), the PEFC electrode material will be used under superacidic conditions. Become. In addition, the cell voltage during normal operation is 0.4 to 1.0 V, but the cell voltage rises to 1.5 V when starting and stopping, so the carbon-based carrier is electrochemically oxidized at the cathode. There is a problem that the carbon-based carrier is corroded and the electrode catalyst particles, which are the catalytically active components, fall off due to the reaction of decomposition into CO 2 , and if the fuel gas is insufficient at the initial stage of operation even at the anode, that part A voltage drop or concentration polarization may occur and the potential may be locally opposite to the normal potential, resulting in electrochemical oxidative decomposition of the carbon-based carrier.
上述した炭素系担体の腐食の問題に対し、特許文献１では、電子伝導性酸化物材料の中でも導電性が高くカソード条件下でも安定な酸化スズ（ＳｎＯ２）を担体として用い、カソード条件下でも安定な酸化スズ粒子上にコロイド法により貴金属微粒子を高分散担持することで、耐久性、電気化学的触媒活性を向上させ、燃料電池自動車寿命に相当する６万回の電位サイクルに耐える電極触媒材料が報告されている。また、特許文献２では、酸化スズ等の電子伝導性酸化物担体を導電補助材に高分散させ、その導電性酸化物担体の上に、白金（Ｐｔ）粒子等を高分散担持することで、電極全体の導電率を向上させ優れた電極性能を得られることが報告されている。 In response to the above-mentioned problem of corrosion of carbon-based carriers, Patent Document 1 uses tin oxide (SnO 2 ) as a carrier, which has high conductivity and is stable even under cathode conditions among electron conductive oxide materials, even under cathode conditions. By highly dispersing and supporting precious metal fine particles on stable tin oxide particles by the colloid method, durability and electrochemical catalytic activity are improved, and an electrode catalyst material that can withstand 60,000 potential cycles equivalent to the life of a fuel cell vehicle. Has been reported. Further, in Patent Document 2, an electron conductive oxide carrier such as tin oxide is highly dispersed in a conductive auxiliary material, and platinum (Pt) particles or the like are highly dispersed and supported on the conductive oxide carrier. It has been reported that the conductivity of the entire electrode can be improved and excellent electrode performance can be obtained.
一方、貴金属を電極触媒とした燃料電池の発電において、電極反応（酸素の還元及び水素の酸化）に実質的に寄与しているのは粒子表面の貴金属触媒のみであり、貴金属を最大限有効利用するには、貴金属触媒粒子を微細化し、少ない貴金属触媒量でより大きい表面積を確保することが求められる。
そこで、本発明者らは、特許文献３において、ＳｎＯ２微粒子を「コア」にして、これに光化学法にて貴金属触媒を「シェル」として析出させた電極材料の製造方法を報告している。この製造方法では、ＳｎＯ２微粒子に光を照射し、貴金属を還元析出させることによって、ＳｎＯ２微粒子の表面に、微粒子状及び／又は薄膜状の貴金属触媒が担持されたコアシェル構造を有する電極材料を製造する。
On the other hand, in the power generation of a fuel cell using a noble metal as an electrode catalyst, only the noble metal catalyst on the particle surface substantially contributes to the electrode reaction (reduction of oxygen and oxidation of hydrogen), and the noble metal is used as effectively as possible. In order to do so, it is required to refine the noble metal catalyst particles and secure a larger surface area with a small amount of the noble metal catalyst.
Therefore, the present inventors have reported in Patent Document 3 a method for producing an electrode material in which SnO 2 fine particles are used as a "core" and a precious metal catalyst is precipitated as a "shell" by a photochemical method. In this production method, an electrode material having a core-shell structure in which a fine particle-like and / or a thin-film noble metal catalyst is supported on the surface of the SnO 2 fine particles is obtained by irradiating the SnO 2 fine particles with light to reduce and precipitate the noble metal. To manufacture.
特許文献３の方法は、燃料電池用電極として有望な電子伝導性酸化物コア、貴金属シェルからなる電極材料を与えるものであるが、コアとなる電子伝導性酸化物は、光還元作用を有する酸化物に制限される。また、光照射を必須とするため、工業的な大量生産には必ずしも適していないという課題があった。 The method of Patent Document 3 provides an electrode material composed of an electron conductive oxide core and a noble metal shell, which are promising as electrodes for a fuel cell. The electron conductive oxide as a core is an oxidation having a photoreducing action. Limited to things. In addition, since light irradiation is essential, there is a problem that it is not always suitable for industrial mass production.
かかる状況下、本発明の目的は、光還元反応を利用せずに、電子伝導性酸化物の表面に貴金属触媒を担持させることができる電極材料の製造方法を提供することである。 Under such circumstances, an object of the present invention is to provide a method for producing an electrode material capable of supporting a noble metal catalyst on the surface of an electron conductive oxide without utilizing a photoreduction reaction.
本発明者は、上記課題を解決すべく鋭意研究を重ねた結果、下記の発明が上記目的に合致することを見出し、本発明に至った。 As a result of diligent research to solve the above problems, the present inventor has found that the following invention meets the above object, and has reached the present invention.
すなわち、本発明は、以下の発明に係るものである。
＜１＞ 炭素系導電補助材に担持された電子伝導性酸化物の表面に、微粒子状の貴金属触媒が担持された構造を有する電極材料の製造方法であって、以下の工程（１）〜（３）を含む製造方法。
工程（１）：一次粒子径５ｎｍ以下の電子伝導性酸化物を含むゾルと、炭素系導電補助材とを水系溶媒中で均一になるまで混合した後に、溶媒を留去させて乾燥させる工程
工程（２）：工程（１）で得られた乾燥物を熱処理し、前記電子伝導性酸化物が担持された前記炭素系導電補助材を得る工程
工程（３）：前記電子伝導性酸化物が担持された前記炭素系導電補助材を、貴金属前駆体化合物を含む溶液を均一になるまで混合し、乾燥後、熱処理する工程
＜２＞ 工程（１）において、溶媒を留去させる方法が、凍結乾燥法である＜１＞に記載の電極材料の製造方法。
＜３＞ 前記電子伝導性酸化物が、酸化スズを主体とする電子伝導性酸化物である＜１＞または＜２＞に記載の電極材料の製造方法。
＜４＞ 前記炭素系導電補助材が、高黒鉛化カーボンブラックである＜１＞から＜３＞のいずれかに記載の電極材料の製造方法。
＜５＞ 前記貴金属前駆体化合物が、貴金属アセチルアセトナートである＜１＞から＜４＞のいずれかに記載の電極材料の製造方法。
＜６＞ ＜１＞から＜５＞のいずれかに記載の方法で製造され、前記電子伝導性酸化物の表面に平均粒径４ｎｍ以下の微粒子状となるよう貴金属触媒が担持された電極材料。
That is, the present invention relates to the following invention.
<1> A method for producing an electrode material having a structure in which a fine particle noble metal catalyst is supported on the surface of an electron conductive oxide supported on a carbon-based conductive auxiliary material, wherein the following steps (1) to (1) Manufacturing method including 3).
Step (1): A step of mixing a sol containing an electron conductive oxide having a primary particle diameter of 5 nm or less and a carbon-based conductive auxiliary material in an aqueous solvent until uniform, and then distilling off the solvent and drying. (2): A step of heat-treating the dried product obtained in the step (1) to obtain the carbon-based conductive auxiliary material on which the electron conductive oxide is supported. Step (3): The electron conductive oxide is supported. The carbon-based conductive auxiliary material is mixed with a solution containing a noble metal precursor compound until uniform, dried, and then heat-treated. <2> In step (1), the method of distilling off the solvent is freeze-drying. The method for producing an electrode material according to the method <1>.
<3> The method for producing an electrode material according to <1> or <2>, wherein the electron conductive oxide is an electron conductive oxide mainly composed of tin oxide.
<4> The method for producing an electrode material according to any one of <1> to <3>, wherein the carbon-based conductive auxiliary material is highly graphitized carbon black.
<5> The method for producing an electrode material according to any one of <1> to <4>, wherein the noble metal precursor compound is noble metal acetylacetonate.
<6> An electrode material produced by the method according to any one of <1> to <5>, wherein a noble metal catalyst is supported on the surface of the electron conductive oxide so as to have an average particle size of 4 nm or less.
本発明によれば、炭素系導電補助材に担持された電子伝導性酸化物担体の表面に、貴金属を微粒子状で析出させた電極材料が提供される。 According to the present invention, there is provided an electrode material in which a noble metal is precipitated in the form of fine particles on the surface of an electron conductive oxide carrier supported on a carbon-based conductive auxiliary material.
以下、本発明について例示物等を示して詳細に説明するが、本発明は以下の例示物等に限定されるものではなく、本発明の要旨を逸脱しない範囲において任意に変更して実施できる。なお、本明細書において、「〜」とはその前後の数値又は物理量を含む表現として
用いるものとする。
Hereinafter, the present invention will be described in detail by showing examples and the like, but the present invention is not limited to the following examples and the like, and can be arbitrarily modified and implemented without departing from the gist of the present invention. In addition, in this specification, "~" shall be used as an expression including numerical values or physical quantities before and after it.
本発明は、炭素系導電補助材に担持された電子伝導性酸化物の表面に、微粒子状の貴金属触媒が担持された構造を有する電極材料の製造方法であって、以下の工程（１）〜（３）を含む製造方法（以下、「本発明の電極材料の製造方法」、又は単に「本発明の製造方法」と記載する。）に関する。 The present invention is a method for producing an electrode material having a structure in which a fine particle noble metal catalyst is supported on the surface of an electron conductive oxide supported on a carbon-based conductive auxiliary material, and the following steps (1) to It relates to the manufacturing method including (3) (hereinafter, referred to as "the manufacturing method of the electrode material of this invention", or simply "the manufacturing method of this invention").
工程（１）：一次粒子径５ｎｍ以下の電子伝導性酸化物を含むゾルと、炭素系導電補助材とを水系溶媒中で均一になるまで混合した後に、溶媒を留去させて乾燥させる工程
工程（２）：工程（１）で得られた乾燥物を熱処理し、前記電子伝導性酸化物が担持された前記炭素系導電補助材を得る工程
工程（３）：前記電子伝導性酸化物が担持された前記炭素系導電補助材を、貴金属前駆体化合物を含む溶液を均一になるまで混合し、乾燥後、熱処理する工程
Step (1): A step of mixing a sol containing an electron conductive oxide having a primary particle diameter of 5 nm or less and a carbon-based conductive auxiliary material in an aqueous solvent until uniform, and then distilling off the solvent and drying. (2): A step of heat-treating the dried product obtained in the step (1) to obtain the carbon-based conductive auxiliary material on which the electron conductive oxide is supported. Step (3): The electron conductive oxide is supported. The above-mentioned carbon-based conductive auxiliary material is mixed with a solution containing a noble metal precursor compound until uniform, dried, and then heat-treated.
図１に、本発明の製造方法で製造される電極材料の一例の模式図を示す。
図１に示す電極材料の一例では、炭素系導電補助材に担持された電子伝導性酸化物担体の表面に、１〜数原子層レベルの大きさ（平均粒径４ｎｍ以下）の微粒子状の貴金属触媒が担持されている。
平均粒径４ｎｍ以下の微粒子状の貴金属触媒が電気化学的触媒として機能し、貴金属触媒で被覆された電子伝導性酸化物担体（コア）は、貴金属触媒と炭素系導電補助材との間の電子移動を担う。このような構成を有することにより、貴金属触媒の使用量が少なくとも優れた触媒活性及び導電性を有する電極材料となりうる。
FIG. 1 shows a schematic view of an example of an electrode material manufactured by the manufacturing method of the present invention.
In the example of the electrode material shown in FIG. 1, a noble metal in the form of fine particles having a size of one to several atomic layers (average particle size of 4 nm or less) on the surface of an electron conductive oxide carrier supported on a carbon-based conductive auxiliary material. A catalyst is supported.
A fine particle noble metal catalyst having an average particle size of 4 nm or less functions as an electrochemical catalyst, and an electron conductive oxide carrier (core) coated with the noble metal catalyst has electrons between the noble metal catalyst and a carbon-based conductive auxiliary material. Take charge of movement. By having such a configuration, the amount of the noble metal catalyst used can be at least an electrode material having excellent catalytic activity and conductivity.
本発明の製造方法で製造される電極材料は、固体高分子形燃料電池のカソード用の電極材料や固体高分子形水電解装置のアノード用の電極材料として好適に使用できる。 The electrode material produced by the production method of the present invention can be suitably used as an electrode material for the cathode of a polymer electrolyte fuel cell or an electrode material for an anode of a polymer electrolyte water electrolyzer.
以下、本発明の電極材料の製造方法の各工程についてより詳細に説明する。 Hereinafter, each step of the method for producing the electrode material of the present invention will be described in more detail.
＜工程（１）＞
工程（１）は、一次粒子径５ｎｍ以下の電子伝導性酸化物を含むゾルと、炭素系導電補助材とを水系溶媒中で均一になるまで混合した後に、溶媒を留去させて乾燥させる工程である。
<Process (1)>
In step (1), a sol containing an electron conductive oxide having a primary particle diameter of 5 nm or less and a carbon-based conductive auxiliary material are mixed in an aqueous solvent until uniform, and then the solvent is distilled off and dried. Is.
工程（１）で使用される電子伝導性酸化物を含むゾルは、一次粒子径５ｎｍ以下（好適には３ｎｍ以下）の電子伝導性酸化物の粒子を水系溶媒に高分散したものである。 The sol containing an electron conductive oxide used in the step (1) is a sol in which particles of an electron conductive oxide having a primary particle diameter of 5 nm or less (preferably 3 nm or less) are highly dispersed in an aqueous solvent.
ゾルに含まれる電子伝導性酸化物としては、燃料電池（特には固体高分子形燃料電池）のアノード条件、カソード条件の少なくともいずれか一方で十分な耐久性と電子伝導性を併せ持つものであればよい。なお、ＰＥＦＣのカソード条件とは、ＰＥＦＣの通常運転時のカソードにおける条件であり、温度が室温〜１５０℃程度、空気等の酸素を含むガスが供給される条件（酸化雰囲気）を意味し、アノード条件とは、ＰＥＦＣの通常運転時のアノードにおける条件であり、温度が室温〜１５０℃程度、水素を含む燃料ガスが供給される条件（還元雰囲気）を意味する。 The electron conductive oxide contained in the sol is one that has sufficient durability and electron conductivity in at least one of the anode condition and the cathode condition of the fuel cell (particularly the polymer electrolyte fuel cell). Good. The cathode condition of PEFC is a condition at the cathode during normal operation of PEFC, and means a condition (oxidizing atmosphere) in which a gas containing oxygen such as air is supplied at a temperature of about room temperature to 150 ° C., and an anode. The condition is a condition at the anode during normal operation of PEFC, and means a condition (reducing atmosphere) in which a fuel gas containing hydrogen is supplied at a temperature of about room temperature to 150 ° C.
電子伝導性酸化物として具体的には、スズ（Ｓｎ）、モリブデン（Ｍｏ）、ニオブ（Ｎｂ）、タンタル（Ｔａ）、チタン（Ｔｉ）及びタングステン（Ｗ）から選択される１種の金属元素の酸化物を主体とする電子伝導性酸化物が挙げられる。ここで、本発明において「主体とする電子伝導性酸化物」とは、（Ａ）母体酸化物のみからなるもの、及び（Ｂ）他元素をドープされた酸化物であって、母体酸化物が８０ｍｏｌ％以上含まれるもの、を意味する。 Specifically, as the electron conductive oxide, one kind of metal element selected from tin (Sn), molybdenum (Mo), niobium (Nb), tantalum (Ta), titanium (Ti) and tungsten (W). Examples thereof include electron-conducting oxides mainly composed of oxides. Here, in the present invention, the "mainly electron-conducting oxide" is (A) an oxide composed of only a matrix oxide and (B) an oxide doped with another element, and the matrix oxide is It means that it is contained in an amount of 80 mol% or more.
ドープされる元素として、具体的には、Ｓｎ，Ｔｉ，Ｓｂ，Ｎｂ，Ｔａ，Ｗ，Ｉｎ，Ｖ，Ｃｒ，Ｍｎ，Ｍｏなどが挙げられる（但し、母体酸化物と異なる元素である。）。ドープされる元素は、母体酸化物より価数が高い元素であり、例えば、母体酸化物が酸化スズの場合で例示すると、上記ドープ種元素のうち、Ｓｎ以外の元素（例えば、Ｎｂ）が選択される。 Specific examples of the element to be doped include Sn, Ti, Sb, Nb, Ta, W, In, V, Cr, Mn, Mo and the like (however, the element is different from the parent oxide). The element to be doped is an element having a higher valence than the matrix oxide. For example, in the case where the matrix oxide is tin oxide, an element other than Sn (for example, Nb) is selected from the above-mentioned doped seed elements. Will be done.
電子伝導性酸化物のなかで好適なものは、酸化スズ又は酸化スズを主体とする電子伝導性酸化物である。元素としてスズ（Ｓｎ）は、ＰＥＦＣカソードや水電解電極のアノード条件として使用される領域において、酸化物であるＳｎＯ2が熱力学的に安定であり、酸化分解が起こらない。また、酸化スズ又は酸化スズを主体とする電子伝導性酸化物は、水系溶媒に高分散できるという利点もある。 Among the electron conductive oxides, suitable ones are tin oxide or an electron conductive oxide mainly composed of tin oxide. As for tin (Sn) as an element, SnO 2 , which is an oxide, is thermodynamically stable in a region used as an anode condition for a PEFC cathode or a water electrolysis electrode, and oxidative decomposition does not occur. Further, the electron conductive oxide mainly composed of tin oxide or tin oxide has an advantage that it can be highly dispersed in an aqueous solvent.
ゾルに含まれる電子伝導性酸化物は、一次粒子径として５ｎｍ以下（好適には３ｎｍ以下）の粒子である。電子伝導性酸化物は、溶媒（分散媒）に一次粒子として分散していることが好ましいが、二次粒子（凝集体）として含有されていてもよい。
二次粒子としての粒径は、本発明の目的を損なわない限りで制限はないが、例えば、５ｎｍ〜５００ｎｍである。
The electron conductive oxide contained in the sol is a particle having a primary particle diameter of 5 nm or less (preferably 3 nm or less). The electron conductive oxide is preferably dispersed as primary particles in a solvent (dispersion medium), but may be contained as secondary particles (aggregates).
The particle size of the secondary particles is not limited as long as the object of the present invention is not impaired, but is, for example, 5 nm to 500 nm.
酸化スズ又は酸化スズを主体とする電子伝導性酸化物の場合では、一次粒子径として５ｎｍ以下、二次粒子径（一次粒子の凝集体）は２０ｎｍ以下であることが好ましい。
一次粒子径５ｎｍ以下、二次粒子径の２０ｎｍ以下である酸化スズ又は酸化スズを主体とする電子伝導性酸化物を高分散に含むゾルは自作してもよいが、市販のゾルを用いれば、ゾルを作製する工程を省略することができる。好適な市販品を例示すると、多木化学株式会社製の「セラメース」シリーズを挙げることができる。
In the case of tin oxide or an electron conductive oxide mainly composed of tin oxide, the primary particle diameter is preferably 5 nm or less, and the secondary particle diameter (aggregate of primary particles) is preferably 20 nm or less.
You may make your own sol containing tin oxide or tin oxide-based electron conductive oxide with a primary particle size of 5 nm or less and a secondary particle size of 20 nm or less in a high dispersion, but if a commercially available sol is used, The step of preparing the sol can be omitted. Examples of suitable commercial products include the "Cerames" series manufactured by Taki Chemical Co., Ltd.
電子伝導性酸化物の一次粒子（結晶子径）はＸ線回折法におけるシェラー式から求めることができる。また、炭素系導電補助材に担持した後の電子伝導性酸化物の平均粒子径（二次粒子径）は、電子顕微鏡像より調べられる電子伝導性酸化物（２０個）の粒子径の平均値により得ることもできる。 The primary particles (crystallite diameter) of the electron conductive oxide can be obtained from the Scheller formula in the X-ray diffraction method. The average particle size (secondary particle size) of the electron-conducting oxide after being supported on the carbon-based conductive auxiliary material is the average particle size of the electron-conducting oxides (20 pieces) examined from the electron microscope image. Can also be obtained by.
電子伝導性酸化物は、結晶であることが好ましい。ゾルに含まれる電子伝導性酸化物が結晶であれば、電子伝導性酸化物を結晶化させるために高温での熱処理を必ずしも行うことなく、結晶性の高い（すなわち、導電率の高い）電子伝導性酸化物担体を炭素系導電補助材に担持することができる。 The electron conductive oxide is preferably crystalline. If the electron-conducting oxide contained in the sol is a crystal, the electron conduction with high crystallinity (that is, high conductivity) does not necessarily have to be heat-treated at a high temperature to crystallize the electron-conducting oxide. The sex oxide carrier can be supported on the carbon-based conductive auxiliary material.
電子伝導性酸化物を含むゾルは、目的とする粒径の電子伝導性酸化物を高分散に含有されるのであれば、従来公知の方法で製造したものを使用可能である。 As the sol containing the electron conductive oxide, a sol produced by a conventionally known method can be used as long as the electron conductive oxide having a target particle size is contained in a high dispersion.
ゾルにおける電子伝導性酸化物の濃度は、高すぎると電子伝導性酸化物が凝集しやすくなるため、電子伝導性酸化物の種類等を考量して、凝集の生じない濃度範囲で適宜決定される。 If the concentration of the electron conductive oxide in the sol is too high, the electron conductive oxide is likely to aggregate. Therefore, the concentration range in which aggregation does not occur is appropriately determined in consideration of the type of the electron conductive oxide and the like. ..
ゾルの溶媒（分散媒）は、水系溶媒が好適に用いられる。なお、本明細書において、「水系溶媒」とは、水または水と相溶可能な有機溶媒との混合溶媒（好適には水を７０体積％以上含む）を意味するものとする。水と相溶可能な有機溶媒としては、例えば、エタノール等の低級アルコールが挙げられる。
また、ゾルの溶媒には、必要に応じてゾル中の電子伝導性酸化物の凝集を抑制する分散剤等の任意の成分を含んでいてもよい。分散剤は、後工程の乾燥、熱処理工程で気化するものが好適である。このような分散剤として、例えば、アンモニアが挙げられる。
As the solvent (dispersion medium) of the sol, an aqueous solvent is preferably used. In the present specification, the "aqueous solvent" means water or a mixed solvent of water and an organic solvent compatible with water (preferably containing 70% by volume or more of water). Examples of the organic solvent compatible with water include lower alcohols such as ethanol.
Further, the solvent of the sol may contain an arbitrary component such as a dispersant that suppresses aggregation of electron conductive oxides in the sol, if necessary. The dispersant is preferably one that is vaporized in the subsequent drying and heat treatment steps. Examples of such a dispersant include ammonia.
本発明の電極材料において、炭素系導電補助材（単に「導電補助材」と記載する場合がある。）は、本発明の電極材料に含まれ、電極を形成した際に電子伝導性を向上させる役割を有し、かつ、電極の骨格としての役割を有する。 In the electrode material of the present invention, the carbon-based conductive auxiliary material (sometimes simply referred to as “conductive auxiliary material”) is included in the electrode material of the present invention and improves electron conductivity when the electrode is formed. It has a role and also has a role as a skeleton of an electrode.
炭素系導電補助材は相互接触性がよく、優れた電子伝導性を有するため、電子伝導性酸化物担体が固定化された炭素系導電補助材を使用して製造された電極材料を用いて、燃料電池用電極や水電解用電極を構成した際に、炭素系導電補助材が互いに接触して低抵抗の導電パスが形成され、電子伝導性に優れた電極となる。すなわち、電子伝導性酸化物に起因する電気化学的酸化への優れた耐久性と、炭素系導電補助材に起因する優れた電子伝導性を併せ持つ電極材料を製造することができる。 Since the carbon-based conductive auxiliary material has good mutual contact and has excellent electron conductivity, an electrode material manufactured using the carbon-based conductive auxiliary material on which the electron conductive oxide carrier is immobilized is used. When an electrode for a fuel cell or an electrode for water electrolysis is formed, carbon-based conductive auxiliary materials come into contact with each other to form a low-resistance conductive path, resulting in an electrode having excellent electronic conductivity. That is, it is possible to produce an electrode material having both excellent durability against electrochemical oxidation caused by an electron conductive oxide and excellent electron conductivity caused by a carbon-based conductive auxiliary material.
また、本発明の電極材料において、電極形成時の骨格としての役割は、炭素系導電補助材が担い、電子伝導性酸化物は炭素系導電補助材に担持される構成であることから、電子伝導性酸化物に由来する電気抵抗を低減できる。このため、電子伝導性酸化物担体が固定化された炭素系導電補助材を用い電極材料を製造することで、電気抵抗が低減された電極材料を得ることができる。 Further, in the electrode material of the present invention, the carbon-based conductive auxiliary material plays a role as a skeleton at the time of electrode formation, and the electron conductive oxide is supported by the carbon-based conductive auxiliary material. The electrical resistance derived from the sex oxide can be reduced. Therefore, by manufacturing the electrode material using the carbon-based conductive auxiliary material on which the electron conductive oxide carrier is immobilized, the electrode material with reduced electrical resistance can be obtained.
本発明の電極材料における炭素系導電補助材は、二次電池や燃料電池に使用される任意の炭素系導電材料を使用することができる。その形状や大きさは、電極の使用目的等を考慮して適宜選択できるが、燃料電池用電極等のガス拡散電極用途では、電極を形成した際の電極内の電気伝導性とガス拡散性が求められる。そのため、電気伝導性とガス拡散性とを両立させるために、炭素系導電補助材が粒子状である場合には、粒径０．０３〜５００μｍ程度であり、繊維状である場合、直径２ｎｍ〜２０μｍ、全長０．０３〜５００μｍ程度であることが好適である。 As the carbon-based conductive auxiliary material in the electrode material of the present invention, any carbon-based conductive material used for a secondary battery or a fuel cell can be used. The shape and size can be appropriately selected in consideration of the purpose of use of the electrode, but in the case of gas diffusion electrode applications such as fuel cell electrodes, the electrical conductivity and gas diffusivity inside the electrode when the electrode is formed are Desired. Therefore, in order to achieve both electrical conductivity and gas diffusivity, when the carbon-based conductive auxiliary material is in the form of particles, the particle size is about 0.03 to 500 μm, and when it is in the form of fibers, the diameter is from 2 nm to. It is preferably about 20 μm and a total length of about 0.03 to 500 μm.
炭素系導電補助材は、特に導電性に優れる結晶性が高い炭素材料を好適に使用することができる。 As the carbon-based conductive auxiliary material, a carbon material having particularly excellent conductivity and high crystallinity can be preferably used.
炭素材料として、カーボンナノチューブや気相成長炭素繊維等の繊維状炭素も使用できるが、特に高黒鉛化カーボンブラックを好適に使用できる。炭素材料が、高結晶性、高純度であると化学的安定性に優れるため好ましい。 As the carbon material, fibrous carbon such as carbon nanotubes and vapor-grown carbon fibers can be used, but highly graphitized carbon black can be particularly preferably used. It is preferable that the carbon material has high crystallinity and high purity because it has excellent chemical stability.
高黒鉛化カーボンブラック（Graphitized Carbon Black, ＧＣＢ）は、カーボンブラックを高温黒鉛化炉で熱処理（例えば、２５００℃以上）して黒鉛化（結晶化）したものである。黒鉛化の程度は、例えば、ラマン分光法で評価することができ、好適にはラマン分光法により求めたＲ値が１．１０以下であるものが好適に使用される。Ｒ値は、黒鉛の結晶化度を示す指標であり、１３６０ｃｍ-1及び１５８０ｃｍ-1のラマンバンドの相対強度比(I1360/I1580)である。 Graphitized carbon black (GCB) is obtained by heat-treating (for example, 2500 ° C. or higher) carbon black in a high-temperature graphitization furnace to graphitize (crystallize) it. The degree of graphitization can be evaluated by, for example, Raman spectroscopy, and preferably, those having an R value of 1.10 or less obtained by Raman spectroscopy are preferably used. R value is an index representing the crystallinity of the graphite, the relative intensity ratio of the Raman band at 1360 cm -1 and 1580cm -1 (I 1360 / I 1580 ).
高黒鉛化カーボンブラックは自作品、市販品のいずれでも使用できる。好適な市販品を例示すると、キャボット社の「ＧＣＢ」シリーズ（品番：ＧＣＢ２００等）や、東海カーボン社製の「トーカブラック」シリーズ（品番：トーカブラック＃３８００等）などが挙げられる。 Highly graphitized carbon black can be used either as a self-made product or as a commercial product. Examples of suitable commercially available products include Cabot's "GCB" series (product number: GCB200, etc.) and Tokai Carbon's "Talker Black" series (product number: Talker Black # 3800, etc.).
本発明で使用される炭素系導電補助材は、１種類でもよいし、または大きさ（粒径、繊維径及び繊維長さ）や結晶性等の異なる２種以上の炭素材料を任意の割合で使用してもよい。 The carbon-based conductive auxiliary material used in the present invention may be one kind, or two or more kinds of carbon materials having different sizes (particle size, fiber diameter and fiber length), crystallinity, etc. may be used in an arbitrary ratio. You may use it.
工程（１）で使用される溶媒（分散媒）は、水系溶媒である。上述の通り、水系溶媒は、水または水と相溶可能な有機溶媒との混合溶媒（好適には水を７０体積％以上含む）を意味する。水と相溶可能な有機溶媒としては、例えば、エタノール等の低級アルコールが挙げられる。 The solvent (dispersion medium) used in the step (1) is an aqueous solvent. As described above, the aqueous solvent means water or a mixed solvent of water and an organic solvent compatible with water (preferably containing 70% by volume or more of water). Examples of the organic solvent compatible with water include lower alcohols such as ethanol.
本発明の電極材料の製造方法では、使用する炭素系導電補助材への電子伝導性酸化物の担持量は、特に限定されず、電子伝導性酸化物担体が固定化された炭素系導電補助材において、電子伝導性酸化物の担持量は粒径や表面積等の電子伝導性酸化物の物性、電子伝導性酸化物の製造方法によっても最適値がかわるため、十分な量の貴金属触媒が析出できる範囲で適宜決定される。
そのため、工程（１）で調製される溶液に含まれる電子伝導性酸化物と炭素系導電補助材の割合（濃度）は、電極材料として目的とする電子伝導性酸化物の担持量になるような仕込み量で適宜決定すればよい。
In the method for producing an electrode material of the present invention, the amount of the electron conductive oxide supported on the carbon-based conductive auxiliary material used is not particularly limited, and the carbon-based conductive auxiliary material on which the electron conductive oxide carrier is immobilized is not particularly limited. In the above, since the optimum value of the amount of the electron conductive oxide supported varies depending on the physical properties of the electron conductive oxide such as particle size and surface area and the method for producing the electron conductive oxide, a sufficient amount of the noble metal catalyst can be precipitated. It is determined appropriately within the range.
Therefore, the ratio (concentration) of the electron conductive oxide and the carbon-based conductive auxiliary material contained in the solution prepared in the step (1) is such that the amount of the electron conductive oxide intended as the electrode material is supported. The amount to be charged may be appropriately determined.
電子伝導性酸化物の担持率は、酸化スズの場合を例示すると、炭素系導電補助材と電子伝導性酸化物の合計を１００重量％としたときに、通常、電子伝導性酸化物が５〜９５重量％であり、好ましくは２０〜９５重量％であり、より好ましくは４５〜９５重量％である。電子伝導性酸化物の担持量が少なすぎると、工程（３）において十分な量の貴金属触媒を析出させることができないおそれがある。電子伝導性酸化物の担持量が多すぎると、凝集して粒径が大きくなりすぎ、電子伝導性酸化物に起因して電極材料の電気抵抗が高くなる場合がある。 For example, in the case of tin oxide, the carrying ratio of the electron conductive oxide is usually 5 to 5 when the total of the carbon-based conductive auxiliary material and the electron conductive oxide is 100% by weight. It is 95% by weight, preferably 20 to 95% by weight, and more preferably 45 to 95% by weight. If the amount of the electron conductive oxide supported is too small, a sufficient amount of the noble metal catalyst may not be precipitated in the step (3). If the amount of the electron conductive oxide carried is too large, it may aggregate and the particle size may become too large, and the electrical resistance of the electrode material may increase due to the electron conductive oxide.
また、本発明の目的を損なわない範囲で、工程（１）で調製される溶液は、電子伝導性酸化物ゾル、炭素系導電補助材以外の成分を含んでいてもよい。
例えば、電子伝導性酸化物及び炭素系導電補助材の分散性を高めるための分散剤は、後工程の乾燥、熱処理工程で気化するものが好適である。
Further, the solution prepared in the step (1) may contain components other than the electron conductive oxide sol and the carbon-based conductive auxiliary material as long as the object of the present invention is not impaired.
For example, as the dispersant for enhancing the dispersibility of the electron conductive oxide and the carbon-based conductive auxiliary material, those that are vaporized in the subsequent drying and heat treatment steps are preferable.
均一になるまで混合された電子伝導性酸化物と炭素系導電補助材を含む溶液は、溶媒を留去させて乾燥される。乾燥方法として、溶媒を留去させて乾燥する方法を採用することによって、炭素系導電補助材に高分散に一次粒子径５ｎｍ以下の電子伝導性酸化物を担持させることが可能となる。 The solution containing the electron conductive oxide and the carbon-based conductive auxiliary material mixed until uniform is dried by distilling off the solvent. By adopting a method of distilling off the solvent and drying as a drying method, it is possible to support an electron conductive oxide having a primary particle diameter of 5 nm or less in a highly dispersed carbon-based conductive auxiliary material.
ここで、「溶媒を留去させて乾燥する」とは、減圧することによって溶媒を積極的に蒸発させて乾燥することを意味する。
具体例を挙げると、ロータリーエバポレータ等の減圧装置を使用し、電子伝導性酸化物を含むゾルと炭素系導電補助材を含む溶液を、減圧して乾燥させる方法（本明細書において「蒸発乾固法」と称する場合がある）や、電子伝導性酸化物を含むゾルと炭素系導電補助材を含む溶液を、凍結させた後に、得られた凍結物を真空状態にし、凍結物中の溶媒を昇華させることで乾燥状態にする方法（本明細書において「凍結乾燥法」と称する）が挙げられる。
Here, "drying by distilling off the solvent" means that the solvent is positively evaporated and dried by reducing the pressure.
To give a specific example, a method of depressurizing and drying a solution containing a sol containing an electron conductive oxide and a carbon-based conductive auxiliary material using a decompression device such as a rotary evaporator (in the present specification, "evaporation dryness". After freezing a sol containing an electron conductive oxide and a solution containing a carbon-based conductive auxiliary material, the obtained frozen product is put into a vacuum state, and the solvent in the frozen product is used. Examples thereof include a method of sublimating to a dry state (referred to as “freeze-drying method” in the present specification).
本発明の製造方法においては、凍結乾燥法が、炭素系導電補助材により高分散に電子伝導性酸化物を担持できるので好ましく採用される。
凍結乾燥法では、電子伝導性酸化物を含むゾルと炭素系導電補助材を含む混合溶液を、液体窒素等の冷媒で急速凍結し、凍結状態のまま減圧して分散媒を昇華させて乾燥する。
凍結乾燥において、減圧時の圧力は、２００Ｐａ以下であることが好ましい。
In the production method of the present invention, the freeze-drying method is preferably adopted because the carbon-based conductive auxiliary material can support the electron-conducting oxide in a highly dispersed manner.
In the freeze-drying method, a mixed solution containing a sol containing an electron conductive oxide and a carbon-based conductive auxiliary material is rapidly frozen with a refrigerant such as liquid nitrogen, and the dispersion medium is sublimated and dried by reducing the pressure in the frozen state. ..
In freeze-drying, the pressure at the time of depressurization is preferably 200 Pa or less.
＜工程（２）＞
工程（２）は、工程（１）で得られた乾燥物を熱処理し、前記電子伝導性酸化物が担持された前記炭素系導電補助材を得る工程である。
<Process (2)>
The step (2) is a step of heat-treating the dried product obtained in the step (1) to obtain the carbon-based conductive auxiliary material on which the electron conductive oxide is supported.
工程（１）で得られた乾燥物は、粒子状の電子伝導性酸化物が炭素系導電補助材に分散担持される形態で仮固定されている。そこで、工程（２）により、熱処理を行い炭素系導電補助材への固着力を高める。また、熱処理によって、電子伝導性酸化物の結晶性が高まったり、粒子間の結合性が向上することによって、電子伝導性が向上する傾向にある。 The dried product obtained in the step (1) is temporarily fixed in a form in which particulate electron conductive oxides are dispersed and supported on a carbon-based conductive auxiliary material. Therefore, in step (2), heat treatment is performed to increase the adhesive force to the carbon-based conductive auxiliary material. Further, the heat treatment tends to improve the crystallinity of the electron conductive oxide and the bondability between the particles, thereby improving the electron conductivity.
熱処理方法は、本発明の目的を損なわない限り条件で適宜決定される。すなわち、熱処理条件は、電子伝導性酸化物の還元や、炭素系導電材料の酸化分解が進行しない雰囲気、温度で行われる。熱処理温度や熱処理時間は、電子伝導性酸化物の電子伝導性と、炭素系導電補助材への固着力のバランスを考慮した上で、適宜決定される。電子伝導性酸化物が、酸化スズの場合、熱処理温度が２００〜３００℃であることが好ましい。熱処理時間は、通常、０．５〜３時間程度である。 The heat treatment method is appropriately determined under conditions as long as the object of the present invention is not impaired. That is, the heat treatment conditions are performed in an atmosphere and temperature at which reduction of the electron conductive oxide and oxidative decomposition of the carbon-based conductive material do not proceed. The heat treatment temperature and the heat treatment time are appropriately determined in consideration of the balance between the electron conductivity of the electron conductive oxide and the adhesive force to the carbon-based conductive auxiliary material. When the electron conductive oxide is tin oxide, the heat treatment temperature is preferably 200 to 300 ° C. The heat treatment time is usually about 0.5 to 3 hours.
＜工程（３）＞
工程（３）は、工程（２）で得られた前記電子伝導性酸化物が担持された前記炭素系導電補助材を、貴金属前駆体化合物を含む溶液を均一になるまで混合し、乾燥後、熱処理する工程である。
<Process (3)>
In step (3), the carbon-based conductive auxiliary material on which the electron conductive oxide obtained in step (2) is supported is mixed with a solution containing a noble metal precursor compound until uniform, dried, and then dried. This is the process of heat treatment.
本発明の電極材料において、電極触媒となりうる貴金属としては、例えば、Ｒｕ，Ｉｒ，Ｐｄ，Ｒｈ，Ｏｓ，Ａｕ，Ａｇから選択される貴金属、及びこれらの貴金属を含む合金が挙げられる。
なお、「貴金属を含む合金」とは「上記の貴金属のみからなる合金」と、「上記の貴金属とそれ以外の金属からなる合金で上記の貴金属を１０質量％以上含む合金」を含む。貴金属と合金化される上記「それ以外の金属」は、特に限定されないが、Ｃｏ，Ｎｉ，Ｔｉ，Ｗ，Ｔａ，Ｎｂ，Ｓｎを好適な例として挙げることができ、これらは１種類あるいは２種類以上を使用してもよい。
In the electrode material of the present invention, examples of the noble metal that can serve as an electrode catalyst include a noble metal selected from Ru, Ir, Pd, Rh, Os, Au, and Ag, and an alloy containing these noble metals.
The "alloy containing a noble metal" includes an "alloy composed only of the above noble metal" and an "alloy composed of the above noble metal and other metals and containing 10% by mass or more of the above noble metal". The "other metals" alloyed with the noble metal are not particularly limited, but Co, Ni, Ti, W, Ta, Nb, Sn can be mentioned as suitable examples, and these are one or two types. You may use the above.
なお、これらの貴金属の中でも、Ｐｔ及び／又はＰｔを含む合金は、固体高分子形燃料電池の作動温度である８０℃付近の温度域において、酸素の還元に対する電気化学的触媒活性が高いため、好適に使用される。 Among these precious metals, Pt and / or alloys containing Pt have high electrochemical catalytic activity for oxygen reduction in the temperature range of around 80 ° C., which is the operating temperature of the polymer electrolyte fuel cell. Suitable for use.
本発明の製法方法では、本発明の目的を達成できるのならば、貴金属触媒粒子の前駆体（貴金属前駆体化合物）として任意の化合物を使用でき、白金アンミン錯体等の貴金属元素とアンモニアとの錯体等も使用できるが、好適には貴金属アセチルアセトナートを使用することができる。 In the production method of the present invention, any compound can be used as a precursor (precious metal precursor compound) of the noble metal catalyst particles as long as the object of the present invention can be achieved, and a complex of a noble metal element such as a platinum ammine complex and ammonia. Etc., but preferably the precious metal acetylacetonate can be used.
貴金属前駆体化合物として、貴金属アセチルアセトナートを使用する担持方法（以下、「貴金属アセチルアセトナート」と称す場合がある）であれば、微粒子状の貴金属触媒を、光励起させることなく、電子伝導性酸化物の表面に析出させることができる。 If the carrier method uses noble metal acetylacetonate as the noble metal precursor compound (hereinafter, may be referred to as "noble metal acetylacetonate"), the fine metal catalyst is subjected to electron conductive oxidation without photoexcitation. It can be deposited on the surface of an object.
本発明の電極材料の製造方法では、上記貴金属に対応するアセチルアセトナート化合物を前駆体として使用できる。 In the method for producing an electrode material of the present invention, an acetylacetonate compound corresponding to the noble metal can be used as a precursor.
貴金属前駆体化合物は１種でもよいが、２種以上を用いてもよく、２種以上の貴金属前駆体化合物を使用する場合、金属種は同じであっても異なってもよい。 The noble metal precursor compound may be one kind, two or more kinds may be used, and when two or more kinds of noble metal precursor compounds are used, the metal kind may be the same or different.
貴金属前駆体化合物は、例えば、Ｐｔの前駆体としては、白金アセチルアセトナート、白金ヘキサフルオロアセチルアセトナート等を用いることができる。 As the noble metal precursor compound, for example, platinum acetylacetonate, platinum hexafluoroacetylacetonate or the like can be used as the precursor of Pt.
貴金属前駆体化合物の濃度は、本発明の目的を損なわない範囲で、電子伝導性酸化物担体及び犠牲触媒の濃度や貴金属前駆体化合物の金属種等に応じて適宜決定される。貴金属前駆体化合物は、電子伝導性酸化物に対して多すぎると貴金属触媒が凝集して析出しやすくなる一方で、少なすぎると得られる電極材料の触媒活性が不十分なものとなるおそれがある。 The concentration of the noble metal precursor compound is appropriately determined according to the concentration of the electron conductive oxide carrier and the sacrificial catalyst, the metal species of the noble metal precursor compound, and the like, as long as the object of the present invention is not impaired. If the amount of the noble metal precursor compound is too large with respect to the electron conductive oxide, the noble metal catalyst tends to aggregate and precipitate, while if it is too small, the catalytic activity of the obtained electrode material may be insufficient. ..
工程（３）において、貴金属触媒が微粒子状で析出する場合、微粒子の平均粒径は４ｎｍ以下であり、好ましくは平均粒径３ｎｍ以下である。このようにすることで、少ない貴金属の量であっても、大きな表面積を確保できる。 When the noble metal catalyst is precipitated in the form of fine particles in the step (3), the average particle size of the fine particles is 4 nm or less, preferably 3 nm or less. By doing so, a large surface area can be secured even with a small amount of precious metal.
なお、「平均粒径」とは、電子顕微鏡観察より調べられる任意の粒子状の貴金属触媒（５０個）の粒子径を平均した値である。２以上の粒子状の貴金属触媒が連結している場合は、それぞれの粒子について粒子径を求め、他の粒子の粒子径とあわせて平均値を算出する。また、形状が球状以外の場合は、粒子における最大長を示す方向の長さをその粒子径とする。 The "average particle size" is a value obtained by averaging the particle sizes of arbitrary particulate noble metal catalysts (50 pieces) examined by electron microscope observation. When two or more particulate noble metal catalysts are connected, the particle size is obtained for each particle, and the average value is calculated together with the particle size of the other particles. When the shape is other than spherical, the length in the direction indicating the maximum length of the particle is defined as the particle diameter.
工程（３）では、熱処理工程を行うことで、析出した貴金属触媒の活性を高めることができる。熱処理温度や時間は、貴金属触媒粒子が過度に凝集しない温度になるように適宜設定される。 In the step (3), the activity of the precipitated noble metal catalyst can be enhanced by performing a heat treatment step. The heat treatment temperature and time are appropriately set so that the noble metal catalyst particles do not agglomerate excessively.
以上、本発明について述べたが、これらは本発明の例示であり、上記以外の様々な構成を採用することもできる。今回開示された実施形態はすべての点で例示であって制限的なものではない。特に、今回の開示において、明示的に開示されていない事項、例えば、操業条件、各種パラメータ、構成物の寸法、重量、体積などは、当業者が通常実施する範囲を逸脱するものではなく、通常の当業者であれば、容易に想定することが可能な値を採用することができる。 Although the present invention has been described above, these are examples of the present invention, and various configurations other than the above can be adopted. The embodiments disclosed this time are exemplary in all respects and are not restrictive. In particular, matters not explicitly disclosed in this disclosure, such as operating conditions, various parameters, dimensions, weights, volumes of components, etc., do not deviate from the scope normally practiced by those skilled in the art and are usually carried out. Any person skilled in the art can adopt a value that can be easily assumed.
以下に実施例を挙げて本発明をより具体的に説明するが、本発明はこれらに限定される
ものではない。なお、以下の実施例及び図面の説明において、高黒鉛化カーボンブラックを「ＧＣＢ」と表記し、Ｐｔアセチルアセトナートを「Pt（acac)2」と表記し、「酸化スズ粒子を担持した高黒鉛化カーボンブラック」を、電極材料（電極触媒未担持）と記載する場合がある。また、ＰｔとＳｎ酸化物を担持したＧＣＢを「Ｐｔ/ＳｎＯ２/ＧＣＢ」と記載する場合がある。
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the following examples and explanations of the drawings, the highly graphitized carbon black is described as "GCB", Pt acetylacetonate is described as "Pt (acac) 2 ", and "high graphite supporting tin oxide particles" is described. "Carbon black" may be described as an electrode material (without supporting an electrode catalyst). Further, the GCB carrying Pt and Sn oxide may be described as "Pt / SnO 2 / GCB".
１．電極材料の作製
実施例の電極材料として、以下の実施例１、２の電極材料を製造した。作製手順のフローチャートを図２に示す。
1. 1. Preparation of Electrode Material As the electrode material of the example, the following electrode materials of Examples 1 and 2 were manufactured. A flowchart of the manufacturing procedure is shown in FIG.
使用した導電補助材、貴金属前駆体化合物、電子伝導性酸化物は以下の通りである。
＜導電補助材＞
導電補助材として、以下の物性を有する高黒鉛化カーボンブラック（ＧＣＢ）（キャボット社製、ＧＣＢ２００）を使用した。
＜貴金属前駆体化合物＞
貴金属前駆体化合物として、Ｐｔアセチルアセトナート（Ｐｔ（Ｃ5Ｈ7Ｏ2）2、Platinum(II) acetylacetonate，97%,Sigma Aldrich）を使用した。
＜電子伝導性酸化物＞
電子伝導性酸化物として、酸化スズゾル（多木化学製「セラメースＳ−８」；ＳｎＯ2換算酸化スズ含有率：８．２ｗｔ％、一次粒子径：２ｎｍ、二次粒子径：８ｎｍ、ｐＨ：１０、溶媒：水、分散剤：アンモニア）を使用した。
The conductive auxiliary materials, noble metal precursor compounds, and electron conductive oxides used are as follows.
<Conductive auxiliary material>
As the conductive auxiliary material, highly graphitized carbon black (GCB) (manufactured by Cabot Corporation, GCB200) having the following physical properties was used.
<Precious metal precursor compound>
As the noble metal precursor compound, Pt acetylacetonate (Pt (C 5 H7O 2 ) 2 , Platinum (II) acetylacetonate, 97%, Sigma Aldrich) was used.
<Electronic conductive oxide>
As an electron conductive oxide, tin oxide sol (“Ceramece S-8” manufactured by Taki Chemical Co., Ltd .; SnO 2 equivalent tin oxide content: 8.2 wt%, primary particle size: 2 nm, secondary particle size: 8 nm, pH: 10 , Solvent: water, dispersant: ammonia) was used.
＜実施例１＞
工程（１）
実施例１の工程（１）では、蒸発乾固法で酸化スズ粒子を担持したＧＣＢを調製した。
まず、ナスフラスコに入れた純水（１０ｍＬ）中に導電補助材であるＧＣＢと酸化スズゾルであるセラメースを入れて、超音波撹拌機で撹拌した。セラメース（酸化スズゾル）の仕込み量は、電極材料全体に対するＳｎＯ2担持量として３０ｗｔ％となるようにした。次いで、試料が入ったナスフラスコを減圧機能と回転機能が備わったロータリーエバポレータにセットし、超音波をかけながら減圧し溶媒を蒸発させて留去し、粉末を完全に乾燥させ、乾燥物を得た。
<Example 1>
Process (1)
In the step (1) of Example 1, a GCB supporting tin oxide particles was prepared by an evaporation dry method.
First, GCB, which is a conductive auxiliary material, and Cerames, which is tin oxide sol, were put in pure water (10 mL) placed in an eggplant flask, and the mixture was stirred with an ultrasonic stirrer. The amount of ceramics (tin oxide sol) charged was set to 30 wt% as the amount of SnO 2 supported on the entire electrode material. Next, the eggplant flask containing the sample was set in a rotary evaporator equipped with a decompression function and a rotation function, the pressure was reduced while applying ultrasonic waves, the solvent was evaporated and distilled off, and the powder was completely dried to obtain a dried product. It was.
工程（２）
工程（１）で得られた乾燥物を粉砕後、Ｎ2雰囲気下で、昇温速度１℃/分、２５０℃で１時間保持の条件で熱処理を施すことで、酸化スズ粒子が担持されたＧＣＢからなる実施例１の電極材料（電極触媒未担持、ＳｎＯ２/ＧＣＢ）を得た。
Process (2)
After milling step (1) with resulting dried product, under N 2, speed 1 ° C. / minute heating, by heat treatment under conditions of 1 hour hold at 250 ° C., tin oxide particles is carried An electrode material of Example 1 (electrode catalyst not supported, SnO 2 / GCB) made of GCB was obtained.
工程（３）
工程（２）で得られた実施例１の電極材料（電極触媒未担持）に、白金アセチルアセトナート法により、電極触媒粒子であるＰｔ触媒粒子を担持した。Ｐｔ前駆体（Pt（acac)2）の量は、Ｐｔが２０ｗｔ％になるようにした。
ナスフラスコに、酸化スズ粒子を担持したＧＣＢからなる実施例１の電極材料（電極触媒未担持）およびＰｔ前駆体を加え、さらにアセトンを加え溶解させた。次いで、ナスフラスコを氷冷しながら、超音波撹拌装置にて、溶媒が全て揮発するまで撹拌して、乾燥粉末を得た。次いで、得られた乾燥粉末をＮ2雰囲気下で、２１０℃で３時間、２４０℃で３時間還元処理を施すことで、実施例１の電極材料（Ｐｔ/ＳｎＯ２/ＧＣＢ）を得た。
Process (3)
Pt catalyst particles, which are electrode catalyst particles, were supported on the electrode material of Example 1 obtained in step (2) (without supporting the electrode catalyst) by the platinum acetylacetonate method. The amount of Pt precursor (Pt (acac) 2 ) was adjusted so that Pt was 20 wt%.
The electrode material of Example 1 (without supporting the electrode catalyst) and the Pt precursor made of GCB carrying tin oxide particles were added to the eggplant flask, and acetone was further added and dissolved. Next, the eggplant flask was ice-cooled and stirred with an ultrasonic stirrer until all the solvent was volatilized to obtain a dry powder. Next, the obtained dry powder was subjected to a reduction treatment at 210 ° C. for 3 hours and 240 ° C. for 3 hours under an N 2 atmosphere to obtain an electrode material (Pt / SnO 2 / GCB) of Example 1.
＜実施例２＞
工程（１）
実施例２の工程（１）では、凍結乾燥法で酸化スズ粒子を担持したＧＣＢを調製した。
所定の容器に入れた純水（１０ｍＬ）中に導電補助材であるＧＣＢと酸化スズゾルであるセラメースを分散させ、超音波撹拌機で撹拌した。セラメース（酸化スズゾル）の仕込み量は、電極材料全体に対する担持量として３０ｗｔ％となるようにした。
撹拌後の溶液を液体窒素で凍結させて得られた凍結物を、凍結乾燥器（アズワン株式会社、型番：FDU-12AS）を用いて凍結物中の溶媒を昇華させることにより、溶媒を留去して乾燥粉末を得た。凍結乾燥機による昇華の際の条件は、約−５０℃、約１００Ｐａである。
<Example 2>
Process (1)
In the step (1) of Example 2, a GCB supporting tin oxide particles was prepared by a freeze-drying method.
GCB, which is a conductive auxiliary material, and Cerames, which is tin oxide sol, were dispersed in pure water (10 mL) placed in a predetermined container, and the mixture was stirred with an ultrasonic stirrer. The amount of ceramics (tin oxide sol) charged was set to 30 wt% as the amount supported on the entire electrode material.
The solvent was distilled off by submerging the solvent in the frozen product using a freeze dryer (AS ONE Co., Ltd., model number: FDU-12AS) from the frozen product obtained by freezing the stirred solution with liquid nitrogen. To obtain a dry powder. The conditions for sublimation by a freeze dryer are about −50 ° C. and about 100 Pa.
工程（２）
工程（１）で得られた乾燥物を粉砕後、実施例１と同様の条件（Ｎ2雰囲気下で、昇温速度１℃/分、２５０℃で１時間保持）で熱処理を施すことで、酸化スズ粒子が担持されたＧＣＢからなる実施例２の電極材料（電極触媒未担持、ＳｎＯ２/ＧＣＢ）を得た。
Process (2)
After crushing the dried product obtained in step (1), heat treatment is performed under the same conditions as in Example 1 (in an N 2 atmosphere, a heating rate of 1 ° C./min and holding at 250 ° C. for 1 hour). An electrode material of Example 2 (electrode catalyst not supported, SnO 2 / GCB) composed of GCB on which tin oxide particles were supported was obtained.
工程（３）
工程（２）で得られた実施例２の電極材料（電極触媒未担持）に、実施例１と同様の白金アセチルアセトナート法及び熱処理条件で処理し、実施例２の電極材料（Ｐｔ/ＳｎＯ２/ＧＣＢ）を得た。
Process (3)
The electrode material of Example 2 (without supporting the electrode catalyst) obtained in the step (2) was treated with the same platinum acetylacetonate method and heat treatment conditions as in Example 1, and the electrode material of Example 2 (Pt / SnO). 2 / GCB) was obtained.
２．物性評価
２−１．電極材料（電極触媒未担持）の評価
（１）酸化スズ粒子の担持率
熱分析装置（株式会社リガク製、ThermoPlus TG8120）を用いて、実施例１，２の電極材料（電極触媒未担持）を、大気雰囲気下で２００℃まで昇温し、昇温前後の質量差をから酸化スズ粒子の担持率を求めた。
酸化スズ粒子の担持率は、実施例１の電極材料が３０．４ｗｔ％、実施例１の電極材料が３０．４ｗｔ％、２７．２ｗｔ％であった。
2. 2. Physical property evaluation 2-1. Evaluation of electrode material (no electrode catalyst supported) (1) Support rate of tin oxide particles Using a thermal analyzer (ThermoPlus TG8120 manufactured by Rigaku Co., Ltd.), the electrode materials of Examples 1 and 2 (no electrode catalyst supported) were used. The temperature was raised to 200 ° C. in an air atmosphere, and the carrying ratio of tin oxide particles was determined from the mass difference before and after the temperature rise.
The carrying ratio of tin oxide particles was 30.4 wt% for the electrode material of Example 1 and 30.4 wt% and 27.2 wt% for the electrode material of Example 1.
（２）微細構造評価
実施例１，２の電極材料（電極触媒未担持）を、走査型電子顕微鏡（ＦＥ−ＳＥＭ、株式会社日立ハイテクノロジーズ、Ｓ−５２００）で観察した。実施例１の電極材料（電極触媒未担持）のＦＥ−ＳＥＭ像を図３、実施例２の電極材料（電極触媒未担持）のＦＥ−ＳＥＭ像を図４に示す。
図３及び図４の対比から、凍結乾燥法を用いた実施例２の電極材料（電極触媒未担持）の方が、蒸発乾固法を用いた実施例１の電極材料（電極触媒未担持）よりも、ＳｎＯ２粒子がより高分散に担持される傾向があることが認められた。
(2) Evaluation of microstructure The electrode materials (without electrode catalyst) of Examples 1 and 2 were observed with a scanning electron microscope (FE-SEM, Hitachi High-Technologies Corporation, S-5200). The FE-SEM image of the electrode material of Example 1 (without supporting the electrode catalyst) is shown in FIG. 3, and the FE-SEM image of the electrode material of Example 2 (not supporting the electrode catalyst) is shown in FIG.
From the comparison of FIGS. 3 and 4, the electrode material of Example 2 using the freeze-drying method (electrode catalyst not supported) is the electrode material of Example 1 using the evaporation-drying method (electrode catalyst not supported). It was found that the SnO 2 particles tended to be supported in a higher dispersion than the above.
２−２．電極材料（電極触媒あり）
（１）Ｘ線回折法（ＸＲＤ）による評価
実施例１，２の電極材料について、ＸＲＤ測定を行い、Ｐｔ及びＳｎＯ２の結晶性及び粒径（結晶子径）を評価した。図５に実施例１の電極材料、図６に実施例２の電極材料のＸＲＤパターンをそれぞれ示す。
実施例１，２の電極材料のいずれもＰｔのピーク及びＳｎＯ２のピークが認められ、それぞれで結晶性の高い粒子が存在していることが確認された。
2-2. Electrode material (with electrode catalyst)
(1) Evaluation by X-ray Diffraction Method (XRD) The electrode materials of Examples 1 and 2 were subjected to XRD measurement, and the crystallinity and particle size (crystallinity diameter) of Pt and SnO 2 were evaluated. FIG. 5 shows the XRD pattern of the electrode material of Example 1, and FIG. 6 shows the XRD pattern of the electrode material of Example 2.
Pt peaks and SnO 2 peaks were observed in all of the electrode materials of Examples 1 and 2 , and it was confirmed that highly crystalline particles were present in each of them.
また、Scherrer法により求めた、Ｐｔ粒子及びＳｎＯ２粒子の結晶子径を求めた。表１に実施例１の電極材料、表２に実施例１の電極材料のＰｔ粒子及びＳｎＯ２粒子の結晶子径を示す。いずれの条件で調製した電極材料についても、２ｎｍ程度の結晶子径を有するＰｔ微粒子及びＳｎＯ２粒子が形成されていることが明らかになった。 In addition, the crystallite diameters of Pt particles and SnO 2 particles determined by the Scherrer method were determined. Table 1 shows the crystallite diameter of the electrode material of Example 1, and Table 2 shows the crystallite diameters of the Pt particles and SnO 2 particles of the electrode material of Example 1. It was clarified that Pt fine particles and SnO 2 particles having a crystallite diameter of about 2 nm were formed in the electrode material prepared under any of the conditions.
（２）微細構造評価
実施例１の電極材料のＦＥ−ＳＥＭ像を図７、ＳＴＥＭ像を図８に示す。また、実施例２の電極材料のＦＥ−ＳＥＭ像を図９、ＳＴＥＭ像を図１０に示す。
図７、８からわかるようにＳｎＯ２粒子の担持に蒸発乾固法を用いた実施例１の電極材料では、Ｐｔ粒子が凝集している部分が確認され、Ｐｔ粒子の担持状態にばらつきが見られた。一方、図９、１０からわかるようにＳｎＯ２粒子の担持に凍結乾燥法を用いた実施例２の電極材料では、Ｐｔ粒子の凝集が少なく、１〜２ｎｍ程度のＰｔ粒子が高分散に担持されていることがわかった。
(2) Evaluation of microstructure The FE-SEM image of the electrode material of Example 1 is shown in FIG. 7, and the STEM image is shown in FIG. The FE-SEM image of the electrode material of Example 2 is shown in FIG. 9, and the STEM image is shown in FIG.
As can be seen from FIGS. 7 and 8, in the electrode material of Example 1 in which the evaporation-drying method was used to support the SnO 2 particles, a portion where Pt particles were aggregated was confirmed, and the supported state of the Pt particles varied. Was done. On the other hand, as can be seen from FIGS. 9 and 10, in the electrode material of Example 2 in which the freeze-drying method was used to support the SnO 2 particles, the aggregation of Pt particles was small, and Pt particles of about 1 to 2 nm were supported with high dispersion. It turned out that.
３．電気化学的評価（ハーフセル）
３−１．電気化学的表面積（ＥＣＳＡ）の評価
実施例１，２の電極材料について、サイクリックボルタンメトリー（ＣＶ）を行い、ＣＶから求めた水素吸着量から電気化学的表面積（ＥＣＳＡ）を算出した。なお、ＥＣＳＡは、電極材料に含まれるＰｔの有効表面積に相当する。
3. 3. Electrochemical evaluation (half cell)
3-1. Evaluation of Electrochemical Surface Area (ECSA) Cyclic voltammetry (CV) was performed on the electrode materials of Examples 1 and 2, and the electrochemical surface area (ECSA) was calculated from the amount of hydrogen adsorbed obtained from the CV. ECSA corresponds to the effective surface area of Pt contained in the electrode material.
ＣＶの測定条件は以下の通りである。なお、１原子のＰｔに付き １原子のＨが吸着すると仮定すると２１０μＣ/ｃｍ2の電気量となる。
測定：三電極式セル（作用極：電極材料／ＧＣ、対極：Ｐｔ、参照極：Ａｇ／ＡｇＣｌ）
電解液：０．１Ｍ ＨＣｌＯ4（ｐＨ：約１）
測定電位範囲：０．０５〜１．２Ｖ（可逆水素電極基準）
走査速度 ：５０ ｍＶ／ｓ
水素吸着量：０．０５〜０．４Ｖの水素吸着を示すピーク面積から算出
電気化学的表面積（ＥＣＳＡ）：下記式より算出
ＥＣＳＡ＝（水素吸着量）[μＣ] / ２１０[μＣ/ｃｍ2]
The measurement conditions for CV are as follows. Assuming that 1 atom of H is adsorbed per 1 atom of Pt, the amount of electricity is 210 μC / cm 2 .
Measurement: Three-electrode cell (working electrode: electrode material / GC, counter electrode: Pt, reference electrode: Ag / AgCl)
Electrolyte: 0.1M HClO4 (pH: about 1)
Measurement potential range: 0.05 to 1.2 V (based on reversible hydrogen electrode)
Scanning speed: 50 mV / s
Hydrogen adsorption amount: Calculated from the peak area showing hydrogen adsorption of 0.05 to 0.4 V Electrochemical surface area (ECSA): Calculated from the following formula
ECSA = (hydrogen adsorption amount) [μC] / 210 [μC / cm 2 ]
実施例１，２の電極材料のＣＶにおいて水素の吸脱着に由来するピークが観察された（図示せず）。ＣＶから求めた実施例１，２の電極材料の電気化学的表面積（ＥＣＳＡ）の評価結果を図１１に示す。
図１１に示されるように、実施例１の電極材料のＥＣＳＡは６８．４ｍ-2ｇ-1、実施例２の電極材料のＥＣＳＡは８０．８ｍ-2ｇ-1であった。
標準触媒として使用される田中貴金属工業株式会社製Ｐｔ担持カーボン（Ｐｔ/Ｃ、品番：ＴＥＣ１０Ｅ５０Ｅ、Ｐｔ担持率４６ｗｔ％）のＥＣＳＡは８４．２ｍ-2ｇ-1であることから、実施例２の電極材料は標準触媒に匹敵するほどのＥＣＳＡを有していることが確認された。上記の微細構造評価では、実施例２の電極材料におけるＰｔ粒子の粒径は１〜２ｎｍ程度と非常に小さく、高分散担持され、ＥＣＳＡ、すなわち、Ｐｔ有効表面積が増大したことに起因していると判断した。
In the CV of the electrode materials of Examples 1 and 2, peaks derived from the adsorption and desorption of hydrogen were observed (not shown). FIG. 11 shows the evaluation results of the electrochemical surface area (ECSA) of the electrode materials of Examples 1 and 2 obtained from CV.
As shown in FIG. 11, the ECSA of the electrode material of Example 1 was 68.4 m- 2 g -1 , and the ECSA of the electrode material of Example 2 was 80.8 m- 2 g -1 .
Since the ECSA of Pt-supported carbon (Pt / C, product number: TEC10E50E, Pt-supporting ratio 46 wt%) manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., which is used as a standard catalyst, is 84.2 m -2 g -1 , according to Example 2. It was confirmed that the electrode material had ECSA comparable to that of the standard catalyst. In the above microstructure evaluation, the particle size of the Pt particles in the electrode material of Example 2 was very small, about 1 to 2 nm, and it was supported with high dispersion, which was caused by the increase in ECSA, that is, the effective surface area of Pt. I decided.
３−２．ＯＲＲ活性の評価
実施例１，２の電極材料について、ＯＲＲ活性を評価した。
ＯＲＲ活性は、回転ディスク電極法（ＲＤＥ法）でリニアスイープボルタンメトリー（ＬＳＶ）を行い、得られる活性化支配電流（ik）を基に算出するMass activity（単位Ｐｔ質量当たりの活性）を指標とした。
Ｍａｓｓ ａｃｔｉｖｉｔｙ = ｉｋ / 電極上のＰｔ質量
活性化支配電流（ik）は、回転電極測定によって得られた電流−電位曲線について、任意の電位においてi-1とω-1/2でプロットして得られるKoutecky-Levichプロットを作成し、得られた直線を外挿することによって切片から求めた。
具体的な手順として、まず、Ｏ2を５０ｍＬ/分で３０分間バブリングした後、０．２ＶRHEから貴な方向に向けて１０ｍＶ/ｓで１．２０ＶRHEまで電位を走査し、測定を行なった。なお、測定中は常にＯ2を５０ｍＬ/分でパージした。なお、ＶRHEは可逆水素電極（ＲＨＥ）基準の電位である
3-2. Evaluation of ORR activity The ORR activity was evaluated for the electrode materials of Examples 1 and 2.
The ORR activity is indexed by Mass activity (activity per unit Pt mass) calculated based on the activation dominant current (i k ) obtained by performing linear sweep voltammetry (LSV) by the rotating disk electrode method (RDE method). did.
Pt mass on Mass activity = i k / electrode
For the activation dominant current (i k ), create a Koutecky-Levich plot obtained by plotting the current-potential curve obtained by rotating electrode measurement with i -1 and ω -1 / 2 at any potential. Obtained from the section by extrapolating the resulting straight line.
As a specific procedure, first, O 2 was bubbled at 50 mL / min for 30 minutes, and then the potential was scanned from 0.2 V RHE to 1.20 V RHE at 10 mV / s in a noble direction to perform measurement. During the measurement, O 2 was always purged at 50 mL / min. V RHE is a potential based on the reversible hydrogen electrode (RHE).
図１２に、実施例１，２の電極材料のMass activityの評価結果を示す。
図１２の通り、実施例１の電極材料のMass activityは８２．９Ａｇ-1、実施例２の電極材料のMass activityは１５２．５Ａｇ-1であった。このようにＳｎＯ２粒子の担持に凍結乾燥法を用いた実施例２の電極材料のMass activityは、蒸発乾固法を用いた実施例１の電極材料と比較してはるかに大きく、標準触媒（Ｐｔ／Ｃ、Mass activity：１６８Ａｇ-1））に匹敵することが確認された。
FIG. 12 shows the evaluation results of the Mass activity of the electrode materials of Examples 1 and 2.
As shown in FIG. 12, the Mass activity of the electrode material of Example 1 was 82.9 Ag -1 , and the Mass activity of the electrode material of Example 2 was 152.5 Ag -1 . As described above, the mass activity of the electrode material of Example 2 using the freeze-drying method for supporting the SnO 2 particles is much larger than that of the electrode material of Example 1 using the evaporation-drying method, and the standard catalyst ( It was confirmed that it was comparable to Pt / C and Mass activity: 168Ag -1 )).
本発明の電極材料によれば、優れた電子伝導性とガス拡散性、優れた耐久性を有する電極を供することができる。当該電極は、長期運転が必要である固体高分子形燃料電池用の電極に好適である。 According to the electrode material of the present invention, it is possible to provide an electrode having excellent electron conductivity, gas diffusibility, and excellent durability. The electrode is suitable for an electrode for a polymer electrolyte fuel cell that requires long-term operation.
Claims (6)
工程（１）：一次粒子径５ｎｍ以下の電子伝導性酸化物を含むゾルと、炭素系導電補助材とを水系溶媒中で均一になるまで混合した後に、溶媒を留去させて乾燥させる工程
工程（２）：工程（１）で得られた乾燥物を熱処理し、前記電子伝導性酸化物が担持された前記炭素系導電補助材を得る工程
工程（３）：前記電子伝導性酸化物が担持された前記炭素系導電補助材を、貴金属前駆体化合物を含む溶液を均一になるまで混合し、乾燥後、熱処理する工程 A method for producing an electrode material having a structure in which a fine particle noble metal catalyst is supported on the surface of an electron conductive oxide supported on a carbon-based conductive auxiliary material, wherein the following steps (1) to (3) are performed. Manufacturing method including.
Step (1): A step of mixing a sol containing an electron conductive oxide having a primary particle diameter of 5 nm or less and a carbon-based conductive auxiliary material in an aqueous solvent until uniform, and then distilling off the solvent and drying. (2): A step of heat-treating the dried product obtained in the step (1) to obtain the carbon-based conductive auxiliary material on which the electron conductive oxide is supported. Step (3): The electron conductive oxide is supported. The above-mentioned carbon-based conductive auxiliary material is mixed with a solution containing a noble metal precursor compound until uniform, dried, and then heat-treated.
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