JP6331580B2 - Electrode catalyst, catalyst layer precursor, catalyst layer, and fuel cell - Google Patents

Electrode catalyst, catalyst layer precursor, catalyst layer, and fuel cell Download PDF

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JP6331580B2
JP6331580B2 JP2014070535A JP2014070535A JP6331580B2 JP 6331580 B2 JP6331580 B2 JP 6331580B2 JP 2014070535 A JP2014070535 A JP 2014070535A JP 2014070535 A JP2014070535 A JP 2014070535A JP 6331580 B2 JP6331580 B2 JP 6331580B2
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carrier
electrode catalyst
electrode
metal particles
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JP2015191872A (en
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薫 澁谷
薫 澁谷
隆喜 水野
隆喜 水野
中島 昭
昭 中島
灯 林
灯 林
一成 佐々木
一成 佐々木
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Kyushu University NUC
JGC Catalysts and Chemicals Ltd
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Kyushu University NUC
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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Description

本発明は、電極触媒、触媒層前駆体、触媒層、及び当該電極触媒を用いた燃料電池に関する。   The present invention relates to an electrode catalyst, a catalyst layer precursor, a catalyst layer, and a fuel cell using the electrode catalyst.

燃料電池は、酸素と水素をエネルギー源とし、高効率、無公害でCO等の温暖化ガスを発生しない発電システムとして注目されている。実用化が最も進んでいるのは、イオン伝導性を有する高分子膜(イオン交換膜)を電解質として用いる固体高分子形燃料電池(PEFC:Polymer Electrolyte Fuel Cell)である。近年、PEFCは家庭や事業所などの固定設備、あるいは自動車などの移動設備で広く使用され始めている。
PEFC用の電極触媒としては、貴金属粒子を100m/g以上の比表面積をもつ炭素粒子に担持させたものが汎用されている。高い導電性を持つ炭素粒子は燃料電池の電極触媒の担体として優れている。それ故、炭素粒子に、白金や白金とルテニウムもしくは白金と鉄といった貴金属(合金)粒子を担持させた粉末は、高性能なPEFC用電極触媒となる(特許文献1、2参照)。
しかしながら、炭素粒子を担体とする電極触媒は、PEFCの運転条件次第では運転中に炭素の腐食(酸化)を起こしてしまうおそれがある。
そこで、電極触媒の担体を炭素粒子からSnO等の金属酸化物に代えるとともに、担体を連鎖状または房状のストラクチャ構造とした技術が提案されている(特許文献3参照)。
The fuel cell is attracting attention as a power generation system that uses oxygen and hydrogen as energy sources and does not generate greenhouse gases such as CO 2 with high efficiency and no pollution. The most practical application is a polymer electrolyte fuel cell (PEFC) using a polymer membrane having ion conductivity (ion exchange membrane) as an electrolyte. In recent years, PEFCs have begun to be widely used in fixed facilities such as homes and offices or mobile facilities such as automobiles.
As an electrode catalyst for PEFC, a catalyst in which noble metal particles are supported on carbon particles having a specific surface area of 100 m 2 / g or more is widely used. Carbon particles having high conductivity are excellent as a support for an electrode catalyst of a fuel cell. Therefore, a powder in which noble metal (alloy) particles such as platinum, platinum and ruthenium, or platinum and iron are supported on carbon particles becomes a high-performance PEFC electrode catalyst (see Patent Documents 1 and 2).
However, an electrode catalyst using carbon particles as a carrier may cause corrosion (oxidation) of carbon during operation depending on PEFC operation conditions.
Thus, a technique has been proposed in which the electrode catalyst support is changed from carbon particles to a metal oxide such as SnO 2 and the support has a chain or tuft structure (see Patent Document 3).

特開2001−015121号公報JP 2001-015121 A 特開2006−127979号公報JP 2006-127799 A 再表2011/065471号公報No. 2011/066451 gazette

特許文献3に記載された電極触媒は、担体の腐食は生じないものの、PEFC用電極触媒としての活性は必ずしも十分ではない。   Although the electrode catalyst described in Patent Document 3 does not cause corrosion of the support, the activity as an electrode catalyst for PEFC is not always sufficient.

本発明は、活性が高く、燃料電池用として非常に優れる電極触媒、触媒層前駆体、触媒層、及び当該電極触媒を用いた高性能な燃料電池を提供することを目的とする。   An object of the present invention is to provide an electrode catalyst, a catalyst layer precursor, a catalyst layer, and a high-performance fuel cell using the electrode catalyst, which have high activity and are extremely excellent for fuel cells.

本発明者らは、上記の課題を解決することを目的として鋭意検討を行った結果、担体に担持された貴金属粒子のアスペクト比を所定の値以上とすることで、優れた性能を有する電極触媒が製造できることを見いだし、この知見をもとにして本発明を完成するに至った。すなわち、本発明は、以下に示すような電極触媒及びそれを用いた燃料電池を提供するものである。   As a result of intensive studies aimed at solving the above-mentioned problems, the present inventors have made an electrode catalyst having excellent performance by setting the aspect ratio of the noble metal particles supported on the support to a predetermined value or more. The present invention has been completed based on this finding. That is, the present invention provides an electrode catalyst as shown below and a fuel cell using the same.

(1)担体に金属粒子を担持させた電極触媒であって、前記担体がチタン、スズ及びタングステンのうち少なくともいずれか1種の酸化物を含むものであり、前記酸化物の含有量が担体基準で80質量%以上であり、前記担体がスズ、ニオブ、リン、アンチモン及びビスマスのうち少なくともいずれか1種をドーパントとして酸化物換算かつ担体基準で20質量%以下含有し、前記金属粒子のアスペクト比が1.7以上10以下であることを特徴とする電極触媒。
(2)前記金属粒子が貴金属粒子であることを特徴とする上記(1)に記載の電極触媒。(3)前記貴金属粒子を構成する貴金属が白金、パラジウム及びルテニウムのうち少なくともいずれか1種であることを特徴とする上記(2)に記載の電極触媒
(4)前記担体がスズ、リン、アンチモン及びビスマスのうち少なくともいずれか1種をドーパントとして酸化物換算かつ担体基準で20質量%以下含有することを特徴とする上記()に記載の電極触媒。
)前記担体の体積抵抗率が50Ω・cm以下であることを特徴とする上記(1)〜()のいずれか一つに記載の電極触媒。
)前記担体のBET比表面積が40m/g以上であることを特徴とする上記(1)〜()のいずれか一つに記載の電極触媒。
)上述の(1)〜()のいずれか一つに記載の電極触媒を用いたことを特徴とする触媒層前駆体。
)上述の()に記載の触媒層前駆体を用いたことを特徴とする触媒層。
)上記(1)〜()のいずれか一つに記載の電極触媒を用いたことを特徴とする燃料電池。
(1) An electrode catalyst in which metal particles are supported on a support , wherein the support contains at least one oxide of titanium, tin, and tungsten, and the content of the oxide is based on the support 80% by mass or more, and the carrier contains at least one of tin, niobium, phosphorus, antimony and bismuth as a dopant in terms of oxide and 20% by mass or less based on the carrier, and the aspect ratio of the metal particles Is an electrode catalyst characterized by having a value of 1.7 or more and 10 or less .
(2) The electrode catalyst according to (1), wherein the metal particles are noble metal particles. (3) The electrode catalyst according to (2), wherein the noble metal constituting the noble metal particles is at least one of platinum, palladium, and ruthenium .
(4) the carrier is tin, Li down, the electrode according to (1) at least one kind of antimony and bismuth, characterized in that it contains 20 mass% or less in terms of oxide and a carrier reference as a dopant catalyst.
( 5 ) The electrode catalyst according to any one of (1) to ( 4 ) above, wherein the carrier has a volume resistivity of 50 Ω · cm or less.
( 6 ) The electrode catalyst as described in any one of (1) to ( 5 ) above, wherein the support has a BET specific surface area of 40 m 2 / g or more.
( 7 ) A catalyst layer precursor using the electrode catalyst according to any one of (1) to ( 6 ) above.
( 8 ) A catalyst layer characterized by using the catalyst layer precursor described in ( 7 ) above.
( 9 ) A fuel cell using the electrode catalyst according to any one of (1) to ( 6 ) above.

本発明の電極触媒は、活性が高く、燃料電池用として非常に優れている。それ故、本発明の電極触媒を用いた燃料電池は極めて高い性能を発揮することができる。   The electrode catalyst of the present invention has high activity and is very excellent as a fuel cell. Therefore, the fuel cell using the electrode catalyst of the present invention can exhibit extremely high performance.

本発明は、担体に金属粒子を担持させた電極触媒(以下、「本触媒」ともいう。)であって、前記金属粒子のアスペクト比が1.7以上であることを特徴とする。以下、詳細に説明する。   The present invention is an electrode catalyst in which metal particles are supported on a carrier (hereinafter also referred to as “the present catalyst”), and the aspect ratio of the metal particles is 1.7 or more. Details will be described below.

〔担体〕
本触媒に用いられる担体(以下、「本担体」ともいう。)としては、金属酸化物を使用することが好ましい。炭素粒子を担体とした場合と異なり、触媒使用時に酸化されることがなく長期間に渡って安定して使用できるからである。
本担体としては、チタン(Ti)、スズ(Sn)、およびタングステン(W)のうち少なくともいずれか1種の酸化物を含むものであることが耐酸性、耐酸化性の観点より好ましい。
また、本担体における前記酸化物の含有量は本担体基準で80質量%以上であることが好ましく、より好ましくは90質量%以上である。
[Carrier]
As the carrier used in the present catalyst (hereinafter also referred to as “the present carrier”), it is preferable to use a metal oxide. This is because, unlike the case where carbon particles are used as a support, the catalyst can be used stably for a long time without being oxidized when the catalyst is used.
The carrier preferably contains at least one oxide of titanium (Ti), tin (Sn), and tungsten (W) from the viewpoint of acid resistance and oxidation resistance.
The content of the oxide in the carrier is preferably 80% by mass or more, more preferably 90% by mass or more based on the carrier.

さらに、本担体は、ドーパントとしてスズ(Sn)、ニオブ(Nb)、リン(P)、アンチモン(Sb)及びビスマス(Bi)のうち少なくともいずれか1種をドーパントとして酸化物換算かつ担体基準で20質量%以下含有することが担体の導電性向上の観点より好ましく、より好ましい含有量は1質量%以上10質量%以下である。
このようなドーパントを用いた例としては、アンチモンドープ酸化スズやニオブドープ酸化チタンなどが好ましく挙げられる。
Furthermore, this carrier has an oxide conversion of 20 (on a carrier basis) with at least one of tin (Sn), niobium (Nb), phosphorus (P), antimony (Sb), and bismuth (Bi) as a dopant. From the viewpoint of improving the conductivity of the carrier, the content is preferably 1% by mass or more and 10% by mass or less.
As an example using such a dopant, antimony-doped tin oxide, niobium-doped titanium oxide, and the like are preferable.

本担体の形状は、白金(Pt)等の各種金属を高分散担持させる観点より、メジアン径として1nm以上500nm以下の粒子状であることが好ましい。また、メジアン径としては、5nm以上100nm以下であることがより好ましく、さらに好ましくは10nm以上40nm以下である。
メジアン径は、後述する担持金属粒子のアスペクト比の測定方法と同様に透過型電子顕微鏡(TEM)による観察にて測定した。
本担体の体積抵抗率(粉体抵抗率)は、50Ω・cm以下であることが好ましく、より好ましくは45Ω・cm以下である。本担体の体積抵抗率が前記した上限値以下であると、燃料電池の電極触媒用担体として、炭素粒子を用いた場合に劣らない効果を発揮できる。体積抵抗率は、交流インピーダンスを測定すれば求められる。
本担体のBET比表面積は、触媒活性の観点より40m/g以上であることが好ましく、43m/g以上であることがより好ましい。BET比表面積は、比表面積計(例えば、マウンテック製M−1220)を用いて測定すれば求められる。
The shape of the carrier is preferably in the form of particles having a median diameter of 1 nm to 500 nm from the viewpoint of highly dispersing and supporting various metals such as platinum (Pt). Further, the median diameter is more preferably 5 nm or more and 100 nm or less, and further preferably 10 nm or more and 40 nm or less.
The median diameter was measured by observation with a transmission electron microscope (TEM) as in the method for measuring the aspect ratio of the supported metal particles described later.
The volume resistivity (powder resistivity) of the carrier is preferably 50 Ω · cm or less, more preferably 45 Ω · cm or less. When the volume resistivity of the support is equal to or less than the above-described upper limit, an effect not inferior when carbon particles are used as a support for an electrode catalyst of a fuel cell can be exhibited. The volume resistivity can be obtained by measuring AC impedance.
The BET specific surface area of the carrier is preferably 40 m 2 / g or more, more preferably 43 m 2 / g or more from the viewpoint of catalytic activity. A BET specific surface area is calculated | required if it measures using a specific surface area meter (for example, M-1220 made from Mountec).

〔担持金属〕
本触媒では、触媒活性の観点より本担体に担持させる金属粒子としては、いわゆる貴金属粒子が好ましい。貴金属粒子としては、特に白金(Pt)、パラジウム(Pd)、およびルテニウム(Ru)の少なくともいずれかの粒子であることが好ましい。
本触媒において、本担体に担持させる金属粒子は、アスペクト比が1.7以上であり、好ましいアスペクト比は1.75以上である。本担体に担持させる金属粒子のアスペクト比が1.7以上であると、本触媒を燃料電池用電極触媒として用いた場合の活性が非常に向上する。特に本触媒を、固体高分子形燃料電池(PEFC)用の電極触媒として用いることが好ましい。
なお、アスペクト比があまり大きくなっても、それに見合った効果は得られにくくなるので10以下が好ましく、7以下であることがより好ましい。
アスペクト比は、例えば、担持用の金属粒子を製造する際に制御することができるが詳細は実施例にて説明する。
[Supported metal]
In the present catalyst, so-called noble metal particles are preferred as the metal particles supported on the present carrier from the viewpoint of catalytic activity. The noble metal particles are particularly preferably particles of at least one of platinum (Pt), palladium (Pd), and ruthenium (Ru).
In the present catalyst, the metal particles supported on the present carrier have an aspect ratio of 1.7 or more, and a preferred aspect ratio of 1.75 or more. When the aspect ratio of the metal particles supported on the carrier is 1.7 or more, the activity when the catalyst is used as an electrode catalyst for a fuel cell is greatly improved. In particular, the present catalyst is preferably used as an electrode catalyst for a polymer electrolyte fuel cell (PEFC).
Even if the aspect ratio becomes too large, it is difficult to obtain an effect commensurate with the aspect ratio, so 10 or less is preferable, and 7 or less is more preferable.
The aspect ratio can be controlled, for example, when the metal particles for supporting are manufactured, but details will be described in Examples.

本担体に担持させる金属粒子のメジアン径は触媒活性向上の観点より1nm以上10nm以下であることが好ましく、1nm以上6nm以下であることがより好ましく、1.5nm以上4.5nm以下であることがさらに好ましい。
なお、担持用金属粒子のメジアン径は、後述するアスペクト比の測定方法において、金属粒子の長径を用いて算出した。
The median diameter of the metal particles supported on the carrier is preferably 1 nm or more and 10 nm or less, more preferably 1 nm or more and 6 nm or less, and more preferably 1.5 nm or more and 4.5 nm or less from the viewpoint of improving catalyst activity. Further preferred.
The median diameter of the supporting metal particles was calculated using the major axis of the metal particles in the aspect ratio measurement method described later.

〔本触媒及び燃料電池〕
本触媒は、まず本担体を製造し、続けて所定のアスペクト比を有する金属粒子(特に貴金属粒子)を担持することで容易に製造することができる。具体的な製造方法は、後述する。
本触媒は、極めて活性が高く、燃料電池用として非常に優れている。特に、本触媒を用いたPEFCは極めて高い性能を発揮することができる。なお、具体的には、本触媒を用いて触媒層前駆体(触媒インク)を製造し、さらに触媒層として特定の形状に成形して使用することが好ましい。このような触媒層とは、例えば、触媒層前駆体溶液をカーボンペーパーなどのガス拡散層に吹き付けて燃料電池セルに導入する前の状態としたものをいう。
[This catalyst and fuel cell]
The present catalyst can be easily produced by first producing the present carrier and subsequently supporting metal particles (particularly noble metal particles) having a predetermined aspect ratio. A specific manufacturing method will be described later.
This catalyst is extremely high in activity and very excellent for use in fuel cells. In particular, PEFC using this catalyst can exhibit extremely high performance. Specifically, it is preferable that a catalyst layer precursor (catalyst ink) is produced using the present catalyst, and further formed into a specific shape and used as a catalyst layer. Such a catalyst layer means, for example, a state in which the catalyst layer precursor solution is in a state before being sprayed onto a gas diffusion layer such as carbon paper and introduced into the fuel cell.

以下に、実施例及び比較例により本発明を更に具体的に説明するが、本発明は、これらの実施例により何ら限定されるものではない。
〔実施例1〕
《担体「アンチモンドープ酸化スズ」の調製》
スズ酸カリウム55.71gと吐酒石2.1gを、水144gに溶解して原料液を調製した。360gの水に硝酸アンモニウム0.47g、15質量%濃度のアンモニア水0.6gを溶解して敷水を調製した。50℃に加温されて攪拌下にある敷水に、前記した原料液を硝酸とともに50分かけて添加し、系内のpHを8.2に保持して加水分解を行いゾルを得た。このゾルからコロイド粒子をろ別し、洗浄して複製塩を除去後、粒子を乾燥した。その後、乾燥粒子を空気中350℃で2時間焼成し、さらに空気中550℃で2時間焼成して担体粉末(アンチモンドープ酸化スズの微粉末)を得た。
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
[Example 1]
<< Preparation of carrier "antimony-doped tin oxide">>
A raw material solution was prepared by dissolving 55.71 g of potassium stannate and 2.1 g of tartrate in 144 g of water. The groundwater was prepared by dissolving 0.47 g of ammonium nitrate and 0.6 g of 15% by mass ammonia water in 360 g of water. The above raw material liquid was added to nitric acid heated to 50 ° C. under stirring over 50 minutes together with nitric acid, and hydrolysis was carried out while maintaining the pH in the system at 8.2. The colloidal particles were filtered off from this sol, washed to remove the duplicate salts, and then dried. Thereafter, the dried particles were calcined in air at 350 ° C. for 2 hours, and further calcined in air at 550 ° C. for 2 hours to obtain a carrier powder (antimony-doped tin oxide fine powder).

《白金前駆体溶液の調製》
ヘキサクロロ白金酸20質量%水溶液6.43gに純水93.57gを加えた。そこに炭酸ナトリウム15質量%水溶液を添加してpH9に調整し、30分間攪拌を行った。次に亜硫酸水素ナトリウム30質量%水溶液でpH4に調整し、30分間攪拌を行った。
その後pHに変動が見られなくなるまで、亜硫酸水素ナトリウム30質量%水溶液を添加し、再度30分間攪拌した。最後に炭酸ナトリウム16質量%水溶液15gを添加し、pHを7に調整した。
ろ過、洗浄を行った後、ケーキを純水300mLに懸濁し、陽イオン交換樹脂にてイオン交換を行った。
樹脂を分離し、純水100mLで樹脂の洗浄を行った後、液温80℃にて200mL以下になるまで濃縮して白金前駆体溶液を得た。
<< Preparation of platinum precursor solution >>
93.57 g of pure water was added to 6.43 g of a 20% by mass hexachloroplatinic acid aqueous solution. Sodium carbonate 15 mass% aqueous solution was added there, and it adjusted to pH9, and stirred for 30 minutes. Next, the pH was adjusted to 4 with a 30% by mass aqueous sodium hydrogen sulfite solution, and the mixture was stirred for 30 minutes.
Thereafter, a 30% by mass aqueous solution of sodium hydrogen sulfite was added until the pH was not changed, and the mixture was stirred again for 30 minutes. Finally, 15 g of a 16% by weight aqueous solution of sodium carbonate was added to adjust the pH to 7.
After filtration and washing, the cake was suspended in 300 mL of pure water, and ion exchange was performed with a cation exchange resin.
The resin was separated and washed with 100 mL of pure water, and then concentrated to 200 mL or less at a liquid temperature of 80 ° C. to obtain a platinum precursor solution.

《白金担持触媒の製造、および白金粒子のアスペクト比の調整》
白金前駆体溶液49.02gと純水50.98gを混合し、そこに担体粉末0.8gを添加して10分間攪拌した。その後、30質量%濃度の過酸化水素水4mLを添加し1時間攪拌した。最後に、液温を80℃に調整し、1時間攪拌した。沈殿物を、ろ液の電導度が2.01mS/mに下がるまでろ過洗浄を行った。この洗浄を長く行い、ろ液の電導度を下げるほど、得られる白金粒子のアスペクト比を大きくすることができる。なお、ろ液の電導度はHORIBA製、ポータブル型pH・ORP・電気伝導率メーター D−74により測定した。
洗浄後の沈殿物を80℃で15時間乾燥した後、30℃で水素還元を行い白金担持触媒を得た。
<< Production of platinum-supported catalyst and adjustment of aspect ratio of platinum particles >>
49.02 g of a platinum precursor solution and 50.98 g of pure water were mixed, and 0.8 g of carrier powder was added thereto and stirred for 10 minutes. Thereafter, 4 mL of 30% by mass hydrogen peroxide was added and stirred for 1 hour. Finally, the liquid temperature was adjusted to 80 ° C. and stirred for 1 hour. The precipitate was filtered and washed until the filtrate conductivity dropped to 2.01 mS / m. The longer the washing and the lower the conductivity of the filtrate, the greater the aspect ratio of the resulting platinum particles. The electrical conductivity of the filtrate was measured with a portable pH / ORP / electric conductivity meter D-74 manufactured by HORIBA.
The washed precipitate was dried at 80 ° C. for 15 hours and then subjected to hydrogen reduction at 30 ° C. to obtain a platinum-supported catalyst.

《担持白金粒子のアスペクト比の測定方法》
調製した白金担持触媒(白金担持アンチモンドープ酸化スズ触媒:Pt/ATO触媒)について透過型電子顕微鏡による観察を行い、白金の粒子形状を代表する125万倍の像を得た。その像の中で20〜50個の白金粒子の長径と短径をノギスを用いて計測した。長径と短径は垂直である必要はなく、最も長い径を長径、最も短い径を短径とした。各々の粒子について(長径÷短径)でアスペクト比を算出し、全ての粒子のアスペクト比の算術平均をそのサンプルのアスペクト比とした。なお、白金粒子だけでなく他の金属粒子でも同様にしてアスペクト比を測定可能である。
<Method for measuring the aspect ratio of supported platinum particles>
The prepared platinum-supported catalyst (platinum-supported antimony-doped tin oxide catalyst: Pt / ATO catalyst) was observed with a transmission electron microscope, and an image of 1.25 million times representing the particle shape of platinum was obtained. The major axis and minor axis of 20 to 50 platinum particles in the image were measured using calipers. The major axis and the minor axis need not be perpendicular, the longest diameter being the major axis and the shortest diameter being the minor axis. The aspect ratio was calculated for each particle (major axis / minor axis), and the arithmetic average of the aspect ratios of all the particles was taken as the aspect ratio of the sample. The aspect ratio can be measured in the same manner not only with platinum particles but also with other metal particles.

〔実施例2〕
《担体「アンチモンドープ酸化スズ」の調製》
スズ酸カリウム53.4gと吐酒石4.1gを、水144gに溶解して原料液を調製した。それ以外は実施例1と同様に行った。
《白金前駆体溶液の調製》
実施例1と同様に行った。
《白金担持触媒の製造、および白金粒子のアスペクト比の調整》
白金前駆体溶液44.44gと純水35.56gを混合した後、担体粉末0.64gを添加したことと、ろ液の電導度が1.16mS/mになるまでろ過洗浄したこと以外は実施例1と同様に行った。
[Example 2]
<< Preparation of carrier "antimony-doped tin oxide">>
A raw material solution was prepared by dissolving 53.4 g of potassium stannate and 4.1 g of tartarite in 144 g of water. Other than that was carried out in the same manner as in Example 1.
<< Preparation of platinum precursor solution >>
The same operation as in Example 1 was performed.
<< Production of platinum-supported catalyst and adjustment of aspect ratio of platinum particles >>
Implemented except that 44.44 g of platinum precursor solution and 35.56 g of pure water were mixed, then 0.64 g of carrier powder was added, and the filtrate was filtered and washed until the conductivity of the filtrate reached 1.16 mS / m. Performed as in Example 1.

〔比較例1〕
《担体「アンチモンドープ酸化スズ」の調製》および《白金前駆体溶液の調製》は実施例1と同様に行った。
《白金担持触媒の製造、および白金粒子のアスペクト比の調整》
ろ液の電導度が11.40となったところで洗浄を止めたこと以外は実施例1と同様に行った。
[Comparative Example 1]
<< Preparation of carrier "antimony-doped tin oxide" and << Preparation of platinum precursor solution >> were performed in the same manner as in Example 1.
<< Production of platinum-supported catalyst and adjustment of aspect ratio of platinum particles >>
The same procedure as in Example 1 was performed except that the washing was stopped when the electric conductivity of the filtrate reached 11.40.

〔比較例2〕
《担体「アンチモンドープ酸化スズ」の調製》および《白金前駆体溶液の調製》は実施例2と同様に行った。
《白金担持触媒の製造、および白金粒子のアスペクト比の調整》
ろ液の電導度が4.92mS/mとなったところで洗浄を止めたこと以外は実施例2と同様に行った。
[Comparative Example 2]
<< Preparation of carrier "antimony-doped tin oxide" and << Preparation of platinum precursor solution >> were carried out in the same manner as in Example 2.
<< Production of platinum-supported catalyst and adjustment of aspect ratio of platinum particles >>
The same procedure as in Example 2 was performed except that the washing was stopped when the electric conductivity of the filtrate reached 4.92 mS / m.

〔評価方法〕
上記した各実施例および各比較例で得られた触媒粒子に対し、以下のようにして電気化学特性を評価した。
《作用極の調製》
作用極にはAu回転電極(5mm径)を用いた。調製に先立ちAu電極表面は平均径0.5μm、次いで平均径0.03μmのアルミナを用いて研磨した。その後超純水中で超音波洗浄し、自然乾燥した。
次に10mLのサンプル瓶に上述の触媒4.0mg(白金0.8mg相当)をとり、超純水1.786mL、イソプロパノール0.564mL、5質量%ナフィオン溶液(デュポン社製)9.4μLを加え、超音波分散した。その際、溶液の温度が上がるので、瓶を氷水で冷やしながら行い触媒インクを得た。その後、上述のAu回転電極に触媒インク10μLを滴下し、大気下、60℃、15分間の乾燥を行い作用極を得た。
〔Evaluation method〕
The electrochemical characteristics were evaluated as follows for the catalyst particles obtained in each of the above Examples and Comparative Examples.
<Preparation of working electrode>
An Au rotating electrode (5 mm diameter) was used as the working electrode. Prior to the preparation, the surface of the Au electrode was polished with alumina having an average diameter of 0.5 μm and then an average diameter of 0.03 μm. Then, it was ultrasonically cleaned in ultrapure water and naturally dried.
Next, 4.0 mg (equivalent to 0.8 mg of platinum) of the above catalyst is taken into a 10 mL sample bottle, and 1.786 mL of ultrapure water, 0.564 mL of isopropanol, and 9.4 μL of 5 mass% Nafion solution (manufactured by DuPont) are added. And ultrasonic dispersion. At this time, since the temperature of the solution rose, the catalyst ink was obtained by cooling the bottle with ice water. Thereafter, 10 μL of the catalyst ink was dropped onto the Au rotating electrode described above, followed by drying at 60 ° C. for 15 minutes in the air to obtain a working electrode.

《サイクリックボルタンメトリー(CV)測定》
CV測定には三極セルを用い、上述の作用極、対極として白金ワイヤー、参照極にはAg/AgCl電極を用いた。0.1M濃度のHClOを溶媒に用いた。30分間のNパージの後、50mV/sで対可逆水素電極(RHE)0.05V−1.20Vの電位範囲を50回のプレサイクルを行い。その後同条件で3サイクル目の0.05Vから0.4V付近での酸素吸着に起因するピーク面積から白金有効反応面積を求めた。
<Cyclic voltammetry (CV) measurement>
A triode cell was used for CV measurement, a platinum wire as the working electrode and the counter electrode, and an Ag / AgCl electrode as the reference electrode. 0.1 M HClO 4 was used as the solvent. After 30 minutes of N 2 purge, 50 potential cycles of 50V mV / s against a reversible hydrogen electrode (RHE) 0.05V-1.20V were performed. Thereafter, an effective platinum reaction area was determined from the peak area resulting from oxygen adsorption in the vicinity of 0.05 V to 0.4 V in the third cycle under the same conditions.

《酸素還元反応(ORR)測定》
CV測定の後、30分間のOパージを行った。その後0.2Vから1.2V(vs.RHE)、10mV/sの掃引を行いORR活性の測定を行った。その際,回転電極を400、900、1600、2500rpmで回転させ、前もってLSV曲線を得た。
<Oxygen reduction reaction (ORR) measurement>
After CV measurement, O 2 purge for 30 minutes was performed. Then, the ORR activity was measured by sweeping from 0.2 V to 1.2 V (vs. RHE) and 10 mV / s. At that time, the rotating electrode was rotated at 400, 900, 1600, and 2500 rpm, and an LSV curve was obtained in advance.

〔評価結果〕
表1に、上記で得られた各担体の性状を示した。また、表2には、前記した各担体をもとにして製造した触媒の性状および電気化学的性質を示した。
〔Evaluation results〕
Table 1 shows the properties of each carrier obtained above. Table 2 shows the properties and electrochemical properties of the catalysts produced based on the above-mentioned supports.

1)粉体抵抗率(体積抵抗率)
Agilent製、4338B MILLIOHMETERを用いて測定した。
2)結晶子径
XRD(X線回折)測定を行い、Halder−Wagner法により求めた。XRD装置はRIGAKU製、MINIFLEX600を用いた。
3)比表面積
マウンテック製M−1220を用いてBET比表面積を測定した。
1) Powder resistivity (volume resistivity)
Measurements were made using an Agilent 4338B MILLIOHMETER.
2) Crystallite diameter XRD (X-ray diffraction) measurement was performed, and the crystallite diameter was determined by the Halder-Wagner method. As the XRD apparatus, MINIFLEX600 manufactured by RIGAKU was used.
3) Specific surface area The BET specific surface area was measured using M-1220 manufactured by Mountec.

実施例1および比較例1で用いた担体は、いずれもドープしたアンチモンの量がSb基準で3.5質量%であり、実施例2および比較例2で用いた担体は、いずれもドープしたアンチモンの量がSb基準で6.7質量%である。
担持白金粒子のアスペクト比が所定の値以上である実施例1の触媒は、同じ担体を用いた比較例1の触媒よりも優れた活性を示している。アンチモンのドープ量を増やした担体を用いた実施例2および比較例2においても同様の効果が得られている。
それ故、担持金属粒子のアスペクト比を所定の値以上とすることで、燃料電池用の電極触媒として優れた活性が得られることが理解できる。
In the carriers used in Example 1 and Comparative Example 1, the amount of doped antimony is 3.5% by mass based on Sb 2 O 4 , and the carriers used in Example 2 and Comparative Example 2 are both The amount of doped antimony is 6.7% by mass based on Sb 2 O 4 .
The catalyst of Example 1 in which the aspect ratio of the supported platinum particles is equal to or higher than a predetermined value shows an activity superior to that of the catalyst of Comparative Example 1 using the same carrier. The same effect is obtained in Example 2 and Comparative Example 2 using a carrier with an increased antimony doping amount.
Therefore, it can be understood that an excellent activity as an electrode catalyst for a fuel cell can be obtained by setting the aspect ratio of the supported metal particles to a predetermined value or more.

Claims (9)

担体に金属粒子を担持させた電極触媒であって、
前記担体がチタン、スズ及びタングステンのうち少なくともいずれか1種の酸化物を含むものであり、
前記酸化物の含有量が担体基準で80質量%以上であり、
前記担体がスズ、ニオブ、リン、アンチモン及びビスマスのうち少なくともいずれか1種をドーパントとして酸化物換算かつ担体基準で20質量%以下含有し、
前記金属粒子のアスペクト比が1.7以上10以下であることを特徴とする電極触媒。
An electrode catalyst having metal particles supported on a carrier,
The carrier contains at least one oxide of titanium, tin and tungsten,
The oxide content is 80% by mass or more based on the carrier;
The carrier contains at least one of tin, niobium, phosphorus, antimony and bismuth as a dopant in terms of oxide and 20% by mass or less based on the carrier,
An electrode catalyst, wherein the metal particles have an aspect ratio of 1.7 or more and 10 or less .
前記金属粒子が貴金属粒子であることを特徴とする請求項1に記載の電極触媒。   The electrode catalyst according to claim 1, wherein the metal particles are noble metal particles. 前記貴金属粒子を構成する貴金属が白金、パラジウム及びルテニウムのうち少なくともいずれか1種であることを特徴とする請求項2に記載の電極触媒。   The electrode catalyst according to claim 2, wherein the noble metal constituting the noble metal particles is at least one of platinum, palladium, and ruthenium. 前記担体がスズ、リン、アンチモン及びビスマスのうち少なくともいずれか1種をドーパントとして酸化物換算かつ担体基準で20質量%以下含有することを特徴とする請求項に記載の電極触媒。 Wherein said carrier tin, Li down, antimony and the electrode catalyst according to claim 1, characterized in that at least one kind containing 20% by weight or less in terms of oxide and a carrier reference as a dopant of bismuth. 前記担体の体積抵抗率が50Ω・cm以下であることを特徴とする請求項1〜請求項のいずれか一項に記載の電極触媒。 The electrode catalyst according to any one of claims 1 to 4 , wherein the volume resistivity of the carrier is 50 Ω · cm or less. 前記担体のBET比表面積が40m/g以上であることを特徴とする請求項1〜請求項のいずれか一項に記載の電極触媒。 The electrode catalyst according to any one of claims 1 to 5 , wherein the support has a BET specific surface area of 40 m 2 / g or more. 請求項1〜請求項のいずれか一項に記載の電極触媒を用いたことを特徴とする触媒層前駆体。 A catalyst layer precursor using the electrode catalyst according to any one of claims 1 to 6 . 請求項に記載の触媒層前駆体を用いたことを特徴とする触媒層。 A catalyst layer comprising the catalyst layer precursor according to claim 7 . 請求項1〜請求項のいずれか一項に記載の電極触媒を用いたことを特徴とする燃料電池。 A fuel cell using the electrode catalyst according to any one of claims 1 to 6 .
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