JPH0785874A - Fuel electrode for fuel cell - Google Patents
Fuel electrode for fuel cellInfo
- Publication number
- JPH0785874A JPH0785874A JP5229343A JP22934393A JPH0785874A JP H0785874 A JPH0785874 A JP H0785874A JP 5229343 A JP5229343 A JP 5229343A JP 22934393 A JP22934393 A JP 22934393A JP H0785874 A JPH0785874 A JP H0785874A
- Authority
- JP
- Japan
- Prior art keywords
- platinum
- electrode
- fuel
- catalyst
- fuel gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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Classifications
-
- 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
Landscapes
- Fuel Cell (AREA)
- Inert Electrodes (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は白金系の触媒を用いた燃
料電池の燃料電極に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel electrode for a fuel cell using a platinum catalyst.
【０００２】[0002]
【従来の技術】燃料電池の燃料ガスとして水素を用いる
ことは、経済的に不利であることから、通常、天然ガス
などの炭化水素系の原燃料を、水素分に富んだガスに改
質したものを燃料ガスとして使用している。このような
改質ガスには、水素ガスのほかに二酸化炭素もしくは一
酸化炭素などの不純物が含まれている。2. Description of the Related Art Since it is economically disadvantageous to use hydrogen as a fuel gas for a fuel cell, a hydrocarbon-based raw fuel such as natural gas is usually reformed into a gas rich in hydrogen. It uses things as fuel gas. Such reformed gas contains impurities such as carbon dioxide or carbon monoxide in addition to hydrogen gas.
【０００３】一方、比較的低温で運転される燐酸形燃料
電池や固体高分子形燃料電池では、白金黒やカーボン担
体に、白金または白金合金を担持した白金触媒または白
金合金触媒が電極に使用されている。これらの電極触媒
は、燃料ガス中に一酸化炭素が含有されていると、この
一酸化炭素が吸着して燃料電極における分極が大きくな
り、その結果燃料電池の発生電圧が低下し、特に、燃料
電池の運転温度が低い場合は、発生電圧が極端に低下す
ることが知られている。On the other hand, in a phosphoric acid fuel cell or a polymer electrolyte fuel cell operated at a relatively low temperature, a platinum catalyst or a platinum alloy catalyst in which platinum or a platinum alloy is supported on platinum black or a carbon carrier is used for an electrode. ing. In these electrode catalysts, when carbon monoxide is contained in the fuel gas, the carbon monoxide is adsorbed to increase the polarization in the fuel electrode, resulting in a decrease in the generated voltage of the fuel cell. It is known that the generated voltage drops extremely when the operating temperature of the battery is low.
【０００４】そこで、現状は原燃料を水素分に富んだガ
スに改質する改質装置に、一酸化炭素を除去するか、ま
たはこれを二酸化炭素に酸化するなどの機能を持たせる
ことにより、燃料ガス中の一酸化炭素濃度を、電池の性
能に影響を及ぼさない程度に保つようにしており、ま
た、電池本体では燃料電極に用いる触媒として、一酸化
炭素の被毒を受け難い白金−ルテニウム合金触媒などを
用いることが行なわれている。Therefore, at present, a reformer for reforming a raw fuel into a gas rich in hydrogen has a function of removing carbon monoxide or oxidizing it into carbon dioxide. The concentration of carbon monoxide in the fuel gas is kept to such an extent that it does not affect the performance of the cell, and as a catalyst used in the fuel electrode of the cell body, platinum-ruthenium which is not easily poisoned by carbon monoxide. It is practiced to use an alloy catalyst or the like.
【０００５】[0005]
【発明が解決しようとする課題】一酸化炭素の触媒への
吸着量はその濃度にも比例する。前述のように、改質装
置ににより燃料ガス中の一酸化炭素濃度を低くすること
はできるが、電極上では、燃料ガスの流れに沿って燃料
ガス中の水素が使われていくために、燃料ガスの流れの
下流側は、相対的に一酸化炭素濃度が高くなる。したが
って、燃料ガスの流れの下流側では、一酸化炭素の吸着
量が多くなり、（１）式に示す触媒反応による水素の解
離が妨げられる。The amount of carbon monoxide adsorbed on the catalyst is also proportional to its concentration. As described above, the carbon monoxide concentration in the fuel gas can be lowered by the reformer, but on the electrode, since hydrogen in the fuel gas is used along with the flow of the fuel gas, The carbon monoxide concentration is relatively high on the downstream side of the flow of fuel gas. Therefore, the amount of adsorbed carbon monoxide increases on the downstream side of the flow of the fuel gas, and the dissociation of hydrogen due to the catalytic reaction represented by the equation (1) is prevented.
【０００６】 Ｈ2 →２Ｈ2 ＋２ｅ- （１） その結果、下流側では（２）式に示す反応による電極の
カーボンの腐食が起きやすくなる。 Ｃ＋２Ｈ2 Ｏ→ＣＯ2 ＋４Ｈ+ ＋４ｅ- （２） 問題は、以上のようにして電極面の燃料ガスの下流側か
ら電極の腐食が進み、電池の寿命を低下させることであ
る。H 2 → 2H 2 + 2e − (1) As a result, on the downstream side, the carbon of the electrode is likely to be corroded by the reaction represented by the equation (2). C + 2H 2 O → CO 2 + 4H + + 4e − (2) The problem is that the electrode corrosion progresses from the downstream side of the fuel gas on the electrode surface as described above, and the life of the battery is shortened.
【０００７】本発明はこの問題を解決するためになされ
たものであり、その目的は、燃料ガスの下流側で、一酸
化炭素によって腐食されることのない燃料電池の燃料電
極を提供することにある。The present invention has been made to solve this problem, and an object thereof is to provide a fuel electrode for a fuel cell which is not corroded by carbon monoxide on the downstream side of the fuel gas. is there.
【０００８】[0008]
【課題を解決するための手段】上記の課題を解決するた
めに、本発明の燃料電池の燃料電極は、この電極に供給
される燃料ガスの上流側から下流側に至る全域に亘っ
て、触媒に用いる白金微粒子の担持量を、段階的に順次
増加させ、または白金微粒子の粒径が段階的に順次小さ
くなるように形成した触媒層を用いる。もしくは、白金
−ルテニウム合金を担持した触媒を用い、燃料ガスの上
流側から下流側まで、ルテニウムの含有量が段階的に順
次多くなるように触媒層を形成する。In order to solve the above-mentioned problems, the fuel electrode of the fuel cell of the present invention has a catalyst over the entire region from the upstream side to the downstream side of the fuel gas supplied to this electrode. The catalyst layer is formed so that the amount of platinum fine particles used in step 1 is gradually increased stepwise or the particle size of platinum fine particles is gradually decreased stepwise. Alternatively, a catalyst supporting a platinum-ruthenium alloy is used, and a catalyst layer is formed so that the content of ruthenium gradually increases from the upstream side to the downstream side of the fuel gas.
【０００９】[0009]
【作用】燃料電極を上述のように構成することにより、
燃料ガスの流れの下流側で相対的に高くなった一酸化炭
素濃度に対して、燃料ガスの下流側における白金の表面
積が大きいので、白金に水素が吸着しやすくなる。ま
た、触媒に白金−ルテニウム合金を用いるときは、一酸
化炭素がルテニウムに吸着しやすいから、燃料ガスの流
れの下流側で、ルテニウム含有量が多くなる程、白金に
水素が吸着するようになる。[Operation] By configuring the fuel electrode as described above,
Since the surface area of platinum on the downstream side of the fuel gas is large with respect to the relatively high carbon monoxide concentration on the downstream side of the fuel gas flow, hydrogen is easily adsorbed on the platinum. Further, when a platinum-ruthenium alloy is used for the catalyst, carbon monoxide is easily adsorbed on ruthenium. Therefore, hydrogen is adsorbed on platinum as the ruthenium content increases on the downstream side of the fuel gas flow. .
【００１０】いずれの場合も、本発明による燃料電極
は、供給される燃料ガス中の一酸化炭素濃度が高くなる
下流側でも、一酸化炭素に対する耐性が高く、水素の解
離が十分に行なわれるので、カーボンの腐食のような反
応が起こることなく、電池の寿命を延ばすことができ
る。In any case, the fuel electrode according to the present invention has high resistance to carbon monoxide and sufficient hydrogen dissociation even on the downstream side where the concentration of carbon monoxide in the supplied fuel gas increases. The battery life can be extended without causing reactions such as carbon corrosion.
【００１１】[0011]
【実施例】以下本発明を実施例に基づき説明する。燃料
電池の電極は、カーボン基材と、カーボンブラックに白
金または白金合金を担持した触媒をＰＴＦＥ（ポレテト
ラフロロエチレン）で結合した触媒層とからなる。本発
明は、白金触媒の白金担持量、白金粒子径、または白金
合金触媒の合金元素であるルテニウム量を、その各々に
ついて段階的に変化させた触媒層を有する燃料電極を構
成したものである。EXAMPLES The present invention will be described below based on examples. The electrode of the fuel cell comprises a carbon base material and a catalyst layer in which a catalyst in which carbon or platinum is supported on carbon black is bonded by PTFE (polytetrafluoroethylene). The present invention constitutes a fuel electrode having a catalyst layer in which the amount of platinum supported on the platinum catalyst, the platinum particle size, or the amount of ruthenium, which is an alloying element of the platinum alloy catalyst, is changed stepwise for each of them.
【００１２】実施例１．白金１０ｗｔ％をカーボンブラ
ックに担持した触媒の所定量を、界面活性剤の入ったイ
オン交換水に、超音波ホモナイザーを用いて均一に分散
させた後、触媒１ｃｍ3 当たり１ｇのＰＴＦＥ（ポレテ
トラフロロエチレン）が混合するようなＰＴＦＥ分散溶
液（濃度６０％，比重１．５）を加え、さらに混合し
て、触媒／ＰＴＦＥ分散溶液を作製し、これを分散液１
とする。 Example 1 A predetermined amount of a catalyst in which 10 wt% of platinum was supported on carbon black was uniformly dispersed in ion-exchanged water containing a surfactant by using an ultrasonic homogenizer, and then 1 g of PTFE (polytetrafluoro) was added per 1 cm 3 of the catalyst. A PTFE dispersion solution (concentration 60%, specific gravity 1.5) such that ethylene) is mixed and further mixed to prepare a catalyst / PTFE dispersion solution.
And
【００１３】次に白金１５ｗｔ％をカーボンブラックに
担持した触媒を用いて、分散液１とと同様の方法で分散
液２を作製する。以下同様にして、それぞれ白金２０ｗ
ｔ％をカーボンブラックに担持した触媒，白金２５ｗｔ
％をカーボンブラックに担持した触媒，および白金３０
ｗｔ％をカーボンブラックに担持した触媒を用いて、分
散液３，分散液４，分散液５を作製する。このとき、分
散液１〜分散液５に使用する触媒は、担持される白金粒
径がほぼ等しいもの（例えば３０Å）とし、使用量も同
体積とする。Next, a dispersion 2 is prepared in the same manner as the dispersion 1, using a catalyst in which 15 wt% of platinum is supported on carbon black. In the same manner, each platinum 20w
Catalyst with t% supported on carbon black, platinum 25 wt
% Supported on carbon black, and platinum 30
Dispersion liquid 3, dispersion liquid 4, and dispersion liquid 5 are prepared using a catalyst in which wt% is supported on carbon black. At this time, the catalysts used in dispersion liquid 1 to dispersion liquid 5 are such that the supported platinum particles have substantially the same particle diameter (for example, 30 Å), and the amount used is also the same.
【００１４】次いで、あらかじめ弗素系樹脂で撥水処理
を施した多孔性カーボン基材表面の一端から他端に向か
って、分散液１，分散液２，分散液３，分散液４，分散
液５の順に、これらが等しい幅を有し、同面積となるよ
うに、ブレード法もしくはスプレー法で塗布する。図１
は分散液１〜分散液５の塗布領域を示し、カーボン基材
の塗布面を上から見た模式図である。図１において、塗
布領域１〜塗布領域５に分散液１〜分散液５を塗布した
ことを表わしている。この状態で全体を乾燥した後、Ｐ
ＴＦＥが溶融する温度で焼成し、カーボン基材上に触媒
層の形成された燃料電極を得ることができる。これを燃
料極１とする。Next, dispersion liquid 1, dispersion liquid 2, dispersion liquid 3, dispersion liquid 4, dispersion liquid 5 from one end to the other end of the surface of the porous carbon substrate which has been subjected to a water repellent treatment with a fluorine resin in advance. In this order, they are applied by the blade method or the spray method so that they have the same width and the same area. Figure 1
Is a schematic view showing a coating area of dispersion liquid 1 to dispersion liquid 5, and is a top view of a coating surface of a carbon base material. In FIG. 1, dispersion liquid 1 to dispersion liquid 5 are applied to coating region 1 to coating region 5. After drying the whole in this state, P
By firing at a temperature at which TFE melts, a fuel electrode having a catalyst layer formed on a carbon substrate can be obtained. This is designated as fuel electrode 1.
【００１５】ここで比較のために、分散液１と同じ溶液
をその５倍量作製し、弗素系樹脂で撥水処理を施した多
孔性カーボン基材に、ブレード法もしくはスプレー法で
塗布し乾燥した後、ＰＴＦＥが溶融する温度で焼成し、
燃料極２を作製したが、これは従来使用されている燃料
電極に相当するものである。次に、これら燃料極１、燃
料極２を用いて電池を作製した。このとき分散液１を塗
布した側、即ち図１の塗布領域１の方が燃料ガスの上流
側となり、分散液５を塗布した側、即ち図１の塗布領域
５の方が燃料ガスの下流側となるように、電池を構成す
る。For comparison, the same solution as Dispersion 1 was prepared in an amount 5 times that amount, and was applied by a blade method or a spray method to a porous carbon substrate that had been subjected to a water repellent treatment with a fluororesin and dried. After that, fire at a temperature at which PTFE melts,
A fuel electrode 2 was produced, which corresponds to a conventionally used fuel electrode. Next, a battery was produced using these fuel electrode 1 and fuel electrode 2. At this time, the side on which the dispersion liquid 1 is applied, that is, the application region 1 in FIG. 1 is the upstream side of the fuel gas, and the side on which the dispersion liquid 5 is applied, that is, the application region 5 in FIG. 1 is the downstream side of the fuel gas. The battery is configured so that
【００１６】図２は、これら電池の出力特性の経時変化
を示す線図である。図２中の曲線（イ）が燃料極１、即
ち本発明における燃料ガスの下流側に白金担持割合の高
い触媒を用いた燃料電極を有する電池の特性変化を示
し、点線で示した曲線（ロ）が燃料極２、即ち比較のた
めの従来相当の燃料電極を有する電池の特性変化を表わ
している。図２から、燃料ガスの下流側に白金担持割合
の高い触媒を用いた本発明の燃料電極を有する電池の方
が、特性の劣化が少なく、長期間安定性を持続している
ことがわかる。FIG. 2 is a diagram showing the changes over time in the output characteristics of these batteries. The curve (a) in FIG. 2 shows the characteristic change of the fuel electrode 1, that is, the characteristic change of the cell having the fuel electrode using the catalyst having a high platinum loading ratio on the downstream side of the fuel gas in the present invention. ) Represents the change in the characteristics of the fuel electrode 2, that is, the cell having the conventional fuel electrode for comparison. From FIG. 2, it can be seen that the battery having the fuel electrode of the present invention using the catalyst having a high platinum loading ratio on the downstream side of the fuel gas is less deteriorated in characteristics and is stable for a long time.
【００１７】また、運転後の電池を分解して電極の状態
を調べた結果、燃料極２には腐食が見られたのに対し、
本発明の燃料電極は殆ど腐食が認められない。実施例２ ．粒径が９０Åの白金粒子をカーボンブラック
に担持した触媒を用い、実施例１．と同様の方法で分散
液６を作製する。同様にして、粒径が７０Åの白金粒子
をカーボンブラックに担持した触媒，粒径が５０Åの白
金粒子をカーボンブラックに担持した触媒，粒径が３０
Åの白金粒子をカーボンブラックに担持した触媒，粒径
が１０Åの白金粒子をカーボンブラックに担持した触媒
を用いて、それぞれ分散液７，分散液８，分散液９，分
散液１０を作製する。このとき、分散液６〜分散液１０
に用いる触媒は、白金の担持量がほぼ等しいもの（例え
ば２０％）とし、使用量は同体積とする。Further, as a result of disassembling the battery after operation and examining the state of the electrodes, corrosion was observed in the fuel electrode 2, whereas
Almost no corrosion is observed in the fuel electrode of the present invention. Example 2 . Example 1 using a catalyst in which platinum particles having a particle size of 90Å are supported on carbon black. Dispersion liquid 6 is prepared in the same manner as in. Similarly, a catalyst in which platinum particles with a particle size of 70Å are supported on carbon black, a catalyst in which platinum particles with a particle size of 50Å are supported on carbon black, and a particle size is 30
Dispersion liquid 7, dispersion liquid 8, dispersion liquid 9, and dispersion liquid 10 are prepared using a catalyst having Å platinum particles supported on carbon black and a catalyst having platinum particles having a particle size of 10 Å supported on carbon black. At this time, dispersion liquid 6 to dispersion liquid 10
The catalyst used in (1) has a substantially equal amount of platinum supported (for example, 20%), and the amount used is the same.
【００１８】次に、実施例１．の場合と同じく、あらか
じめ弗素系樹脂で撥水処理を施した多孔性カーボン基材
表面の一端から他端に向かって、分散液６，分散液７，
分散液８，分散液９，分散液１０の順に、これらが等し
い幅を有し、同面積となるように、ブレード法もしくは
スプレー法で塗布する。カーボン基材への塗布状態は、
図１を参照すれば容易にわかるので図示は省く。そして
乾燥後、ＰＴＦＥが溶融する温度で焼成し、燃料極３を
得ることができる。Next, in the first embodiment. As in the case of, the dispersion liquid 6, the dispersion liquid 7, the dispersion liquid 7,
The dispersion liquid 8, the dispersion liquid 9, and the dispersion liquid 10 are applied in this order by a blade method or a spray method so that they have the same width and the same area. The coating state on the carbon substrate is
The illustration is omitted because it is easily understood by referring to FIG. Then, after drying, the fuel electrode 3 can be obtained by firing at a temperature at which PTFE melts.
【００１９】燃料極３を用いて作製する電池は、燃料極
３の分散液６の塗布領域の方を燃料ガスの上流側とし、
分散液１０の塗布領域の方を燃料ガスの下流側となるよ
うに、電池を構成する。電池の特性は、先に述べた図２
に曲線（ハ）として併記してある。図２からわかるよう
に、燃料ガスの下流側に粒径の小さい白金微粒子を担持
した触媒を用いた本発明の燃料電極を有する電池は、実
施例１．で述べた燃料極１［曲線（イ）］の場合と殆ど
同じであり、従来相当の燃料極２［曲線（ロ）］に比べ
て特性の劣化が少なく、長期間安定性を持続している。In a cell manufactured using the fuel electrode 3, the application area of the dispersion liquid 6 of the fuel electrode 3 is set to the upstream side of the fuel gas,
The cell is configured so that the application area of the dispersion liquid 10 is on the downstream side of the fuel gas. The characteristics of the battery are as shown in FIG.
Is also shown as a curve (C). As can be seen from FIG. 2, the battery having the fuel electrode of the present invention using the catalyst carrying the platinum fine particles having a small particle size on the downstream side of the fuel gas is the battery of Example 1. It is almost the same as the case of the fuel electrode 1 [curve (a)] described above, and the characteristic deterioration is less than that of the conventional equivalent fuel electrode 2 [curve (b)], and the stability is maintained for a long time. .
【００２０】また、実施例１．と同様、運転後の電池を
分解して電極の状態を調べた結果、殆ど腐食が認められ
ない。以上、実施例１．，実施例２．では、電極に供給
される燃料ガス中の一酸化炭素濃度が増すに従って、電
極単位面積当たりの触媒の白金表面積も相対的に増すよ
うに考慮したものである。即ち、一酸化炭素によって白
金に水素が吸着するのが妨げられるるので、白金の表面
積が相対的に大きくなれば、水素が吸着しやすくなるか
らである。In addition, the first embodiment. Similarly to the above, as a result of disassembling the battery after operation and examining the state of the electrodes, almost no corrosion was observed. As described above, Example 1. Example 2. Then, it is considered that the platinum surface area of the catalyst per unit area of the electrode relatively increases as the carbon monoxide concentration in the fuel gas supplied to the electrode increases. In other words, carbon monoxide prevents hydrogen from adsorbing on platinum, so that hydrogen is more likely to adsorb if the surface area of platinum is relatively large.
【００２１】実施例３．白金１０ｗｔ％をカーボンブラ
ックに担持した触媒を用い、実施例１．における分散液
１と同じ分散液１１を作製する。次に、白金１０ｗｔ％
−ルテニウム０．７ｗｔ％合金をカーボンブラックに担
持した触媒を用い、分散液１１と同じ方法で分散液１２
を作製する。以下、同様に、白金１０ｗｔ％−ルテニウ
ム１．３ｗｔ％合金をカーボンブラックに担持した触
媒，白金１０ｗｔ％−ルテニウム２．６ｗｔ％合金をカ
ーボンブラックに担持した触媒，白金１０ｗｔ％−ルテ
ニウム５．２ｗｔ％合金をカーボンブラックに担持した
触媒を用いて、それぞれ分散液１３，分散液１４，分散
液１５を作製する。このとき、分散液１１〜分散液１５
に用いる触媒の白金量を等しくなるようにする。 Example 3 Example 1 using a catalyst in which 10 wt% of platinum is supported on carbon black. The same dispersion liquid 11 as the dispersion liquid 1 in Example 1 is prepared. Next, platinum 10 wt%
Dispersion liquid 12 in the same manner as dispersion liquid 11 using a catalyst in which ruthenium 0.7 wt% alloy is supported on carbon black.
To make. Similarly, platinum 10 wt% -ruthenium 1.3 wt% alloy supported on carbon black, platinum 10 wt% -ruthenium 2.6 wt% alloy supported on carbon black, platinum 10 wt% -ruthenium 5.2 wt% Dispersion liquid 13, dispersion liquid 14, and dispersion liquid 15 are prepared using a catalyst in which an alloy is supported on carbon black. At this time, dispersion 11 to dispersion 15
Make the platinum amounts of the catalysts used in step 1) equal.
【００２２】但し、この場合、白金１０ｗｔ％−ルテニ
ウム合金のルテニウム量が１０ｗｔ％を超えると、電池
の特性が低下するので、ルテニウム量は最大１０ｗｔ％
としなければならない。したがって、ルテニウム量の増
やし方は、上記に限ることなく、１０ｗｔ％までの内
で、例えば２，４，６，８，１０ｗｔ％の５段階とする
など、適当に決めてもよい。In this case, however, if the amount of platinum 10 wt% -the amount of ruthenium in the ruthenium alloy exceeds 10 wt%, the battery characteristics deteriorate, so the maximum amount of ruthenium is 10 wt%.
And have to. Therefore, the method of increasing the amount of ruthenium is not limited to the above, and may be appropriately determined, for example, in 5 steps of 2, 4, 6, 8, 10 wt% within 10 wt%.
【００２３】次いで、実施例１．，実施例２．における
と同様に、あらかじめ弗素系樹脂で撥水処理を施した多
孔性カーボン基材表面の一端から他端に向かって、分散
液１１，分散液１２，分散液１３，分散液１４，分散液
１５の順に、これらが等しい幅を有し、同面積となるよ
うに、ブレード法もしくはスプレー法で塗布する。この
場合も、カーボン基材への塗布状態は、図１を参照すれ
ば容易にわかるので図示は省く。そして乾燥後、ＰＴＦ
Ｅが溶融する温度で焼成し、燃料極４が得られる。Next, the first embodiment . , Example 2 . In the same manner as in, the dispersion liquid 11, the dispersion liquid 12, the dispersion liquid 13, the dispersion liquid 14, the dispersion liquid 15 from one end to the other end of the surface of the porous carbon base material which has been previously subjected to the water repellent treatment with the fluorine-based resin. In this order, they are applied by the blade method or the spray method so that they have the same width and the same area. Also in this case, the coating state on the carbon base material can be easily understood by referring to FIG. And after drying, PTF
The fuel electrode 4 is obtained by firing at a temperature at which E melts.
【００２４】ここでも、燃料極４を用いた電池を作製す
るが、燃料極４の分散液１１の塗布領域の方を燃料ガス
の上流側とし、分散液１５の塗布領域の方を燃料ガスの
下流側となるように、電池を構成する。図３は、実施例
１．，実施例２．に倣って、燃料極４を用いて作製した
電池の出力特性の経時変化を示す線図であり、曲線
（ニ）で示しているが、同時に図３には、比較のため
に、既に述べた従来の燃料電極に相当する燃料極１を用
いた電池の特性として、曲線（ロ）を再掲してある。In this case as well, a cell using the fuel electrode 4 is prepared. The coating area of the dispersion liquid 11 of the fuel electrode 4 is on the upstream side of the fuel gas, and the coating area of the dispersion liquid 15 is the fuel gas. The battery is configured to be on the downstream side. FIG. 3 shows an example
1 . , Example 2 . 4 is a diagram showing the change over time in the output characteristics of a cell produced using the fuel electrode 4 in accordance with FIG. 4, and is shown by a curve (d). At the same time, FIG. The curve (b) is shown again as the characteristic of the cell using the fuel electrode 1 corresponding to the conventional fuel electrode.
【００２５】図３によれば、燃料ガスの下流側に、ルテ
ニウムを含む割合の多い白金合金触媒を用いた燃料電極
を用いた方が、電池の特性劣化が少なく、長期間安定性
を持続することがわかる。この場合も、運転後の電池を
分解して電極の状態を調べた結果、本発明による燃料電
極には殆ど腐食が認められない。実施例３．でルテニウ
ム量を階段的に増やしたのは、一酸化炭素がルテニウム
に吸着しやすいので、燃料ガスが燃料電極を通る過程
で、ガスの流れの下流側で、ルテニウムが多くなる程、
白金に水素が吸着するようになるからである。According to FIG. 3, when the fuel electrode using the platinum alloy catalyst containing a large proportion of ruthenium is used on the downstream side of the fuel gas, the characteristics of the cell are less deteriorated and the stability is maintained for a long time. I understand. Also in this case, as a result of disassembling the battery after operation and examining the state of the electrode, almost no corrosion is observed in the fuel electrode according to the present invention. Example 3 . The reason why the amount of ruthenium is increased stepwise is that carbon monoxide is easily adsorbed on ruthenium, so that the amount of ruthenium increases on the downstream side of the gas flow in the process of the fuel gas passing through the fuel electrode.
This is because hydrogen will be adsorbed on platinum.
【００２６】以上述べてきたように、本発明の燃料電池
の燃料電極は、白金触媒の白金担持量、白金粒子径、ま
たは白金合金触媒の合金元素であるルテニウム量を、そ
の各々について、例えば等分に５段階に変化させた触媒
層を有する構成として説明したが、この変化のしかた
は、燃料ガスの上流側から下流側にかけて、連続的な勾
配を持たせるのが、最も望ましい状態であるから、等分
な５段階の変化をさらに細分化した燃料電極とすること
も考えられ、このことは実状に応じて決めれるのがよ
い。As described above, in the fuel electrode of the fuel cell of the present invention, the amount of platinum supported on the platinum catalyst, the platinum particle size, or the amount of ruthenium which is an alloying element of the platinum alloy catalyst, for each of them, for example, Although it has been described that the catalyst layer is changed in five stages per minute, the most desirable state of this change is to have a continuous gradient from the upstream side to the downstream side of the fuel gas. It is also conceivable that the fuel electrode is further subdivided into five equally divided changes, and this should be decided according to the actual situation.
【００２７】[0027]
【発明の効果】燃料電池の燃料電極を流れる燃料ガス
は、一酸化炭素を含んでおり、この一酸化炭素濃度が電
極内の上流側より下流側の方が高くなるので、下流側で
は燃料ガスの水素が電極触媒の白金に吸着し難くなるこ
とから、電極の腐食を起こし電池の特性を損なうという
問題に対して、本発明の燃料電極は、電極触媒の白金粒
子の担持量を、燃料ガスの上流側から下流側まで段階的
に順次増やし、または白金粒子の粒子径を燃料ガスの上
流側から下流側まで段階的に順次小さくするなど、燃料
ガスの流れる燃料電極の場所に対応して、上流側から下
流側に向かって、段階的に白金粒子の表面積か大きくな
るようにし、また、電極触媒に白金−ルテニウム合金を
用いる場合は、ルテニウムの含有量を燃料ガスの上流側
から下流側まで段階的に多くすることにより、燃料ガス
の下流側でも水素の解離が十分に行なわれ、電極の腐食
を起こり難くしており、その結果、電池特性の劣化を防
ぎ、電池寿命を延ばすことができる。The fuel gas flowing through the fuel electrode of the fuel cell contains carbon monoxide, and the concentration of this carbon monoxide is higher in the downstream side than in the upstream side of the electrode. Since it becomes difficult for hydrogen to be adsorbed on the platinum of the electrode catalyst, the fuel electrode of the present invention has a problem that the amount of platinum particles carried on the electrode catalyst is changed by the fuel gas. Corresponding to the location of the fuel electrode through which the fuel gas flows, such as increasing stepwise from the upstream side to the downstream side, or gradually decreasing the particle size of the platinum particles from the upstream side to the downstream side of the fuel gas. From the upstream side to the downstream side, the surface area of the platinum particles is gradually increased, and when a platinum-ruthenium alloy is used for the electrode catalyst, the content of ruthenium is changed from the upstream side to the downstream side of the fuel gas. Stage To by many, dissociation of hydrogen is sufficiently performed even in the downstream side of the fuel gas, it has difficult to occur corrosion of electrodes, as a result, prevent the deterioration of the battery characteristics, it is possible to extend the battery life.
【図１】本発明における白金担持量の異なる分散液の基
板への塗布状態を示す模式図FIG. 1 is a schematic diagram showing a coating state of dispersion liquids having different loadings of platinum in the present invention on a substrate.
【図２】本発明の電極を有する電池特性を従来の電池特
性との比較で示した線図FIG. 2 is a diagram showing the battery characteristics having the electrode of the present invention in comparison with the conventional battery characteristics.
【図３】図２とは別の本発明の電極を有する電池特性を
従来の電池特性との比較で示した線図FIG. 3 is a diagram showing a battery characteristic having an electrode of the present invention different from that of FIG. 2 in comparison with a conventional battery characteristic.
なし None
Claims (5)
微粒子を担持した触媒を有する触媒層とからなる燃料電
池の燃料電極であって、この電極に供給される燃料ガス
の上流側から下流側に至る全域に亘って、電極単位面積
当たりの白金微粒子の表面積を段階的に順次増加させた
触媒層を形成することを特徴とする燃料電池の燃料電
極。1. A fuel electrode for a fuel cell, comprising a carbon base material and a catalyst layer having a catalyst in which platinum fine particles are supported on carbon black, the fuel gas being supplied to the electrode from the upstream side to the downstream side. A fuel electrode for a fuel cell, wherein a catalyst layer is formed in which the surface area of platinum fine particles per unit area of the electrode is gradually increased step by step over the entire area.
粒子の表面積の増加はその担持量を段階的に増すことに
より行なうことを特徴とする燃料電池の燃料電極。2. The fuel electrode for a fuel cell according to claim 1, wherein the surface area of the platinum fine particles is increased by gradually increasing the supported amount.
粒子の表面積の増加はその粒径を段階的に小さくするこ
とにより行なうことを特徴とする燃料電池の燃料電極。3. The fuel electrode for a fuel cell according to claim 1, wherein the surface area of the fine platinum particles is increased by gradually reducing the particle size.
合金微粒子を担持した触媒を有する触媒層とからなる燃
料電池の燃料電極であって、この電極に供給される燃料
ガスの上流側から下流側に至る全域に亘って、白金と合
金化する元素の含有量を段階的に順次増加させた触媒層
を形成することを特徴とする燃料電池の燃料電極。4. A fuel electrode for a fuel cell comprising a carbon base material and a catalyst layer having a catalyst in which platinum alloy fine particles are supported on carbon black, the fuel gas being supplied to the electrode from the upstream side to the downstream side. A fuel electrode for a fuel cell, characterized in that a catalyst layer is formed in which the content of elements alloying with platinum is gradually increased stepwise over the entire area up to.
合金化する元素としてルテニウムを用いることを特徴と
する燃料電池の燃料電極。5. The fuel electrode for a fuel cell according to claim 4, wherein ruthenium is used as an element that alloys with platinum.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5229343A JPH0785874A (en) | 1993-09-16 | 1993-09-16 | Fuel electrode for fuel cell |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5229343A JPH0785874A (en) | 1993-09-16 | 1993-09-16 | Fuel electrode for fuel cell |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0785874A true JPH0785874A (en) | 1995-03-31 |
Family
ID=16890679
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5229343A Pending JPH0785874A (en) | 1993-09-16 | 1993-09-16 | Fuel electrode for fuel cell |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0785874A (en) |
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