JPS60189177A - Operation method of fuel cell - Google Patents

Abstract

PURPOSE:To make possible operation of fuel cell for a long time by performing one or more power generating method which changes active materials to be supplied to positive and negative electrodes of fuel cell to change positive electrode and negative electrode. CONSTITUTION:Since oxidizing agent electrode of fuel cell is kept to high potential in power generation, coagulation of catalyst occurs with the passage of time and output is decreased. Since the potential of fuel electrode is lower compared with that of oxidizing agent electrode, coagulation of catalyst is difficult to occur. The coagulation of electrode catalyst causes decrease in catalyst surface area and results in the output drop of cell. When fuel electrode catalyst which is difficult to coagulate is used as oxidizing electrode, the cell can be operated for a long time without voltage drop. Even if the electrode catalyst which is coagulated by using as oxidizing agent electrode is used as fuel electrode, it can be used as active electrode catalyst because fuel electrode reaction is faster than oxidizing agent electrode reaction.

Description

【発明の詳細な説明】 〔発明の属する分野〕 本発明は、燃料電池の運転方法に関する。[Detailed description of the invention] [Field to which the invention pertains] The present invention relates to a method of operating a fuel cell.

〔従来技術および問題点〕[Prior art and problems]

周知の通シ燃料電池は、対向して配置されたガス拡散電
極の間に、電解質として保持したマトリックスを配し、
ガス拡散電極にそれぞれ空気等をば化剤ガスとし、水素
等を含有するガスを燃料ガスとして通流させて使用する
。燃料電池を長時間運転するためには、電極触媒の活性
を長時間に亘シ保つことが課題である。The well-known conventional fuel cell arranges a matrix held as an electrolyte between gas diffusion electrodes arranged oppositely,
Air or the like is used as a oxidizer gas and gas containing hydrogen or the like is made to flow through the gas diffusion electrodes as a fuel gas. In order to operate a fuel cell for a long time, it is a challenge to maintain the activity of the electrode catalyst for a long time.

例えば従来リン酸を電解質として保持する燃料電池にお
いて、その電極触媒には、炭素微粉末に担持させた白金
が一般に用いられる。この様な構成の電池において酸化
剤極は燃料極に比べ高電位であるために担持された白金
粒子は、その運転時間が長期化するにつれて徐々に凝集
し１１粒子径は増大する。白金粒子径の増大は、白金触
媒の表面積の減少を引きおこし、触媒の活性を著しく劣
化させ、電池出力を低下させる。この酸化剤極の触媒活
性劣化が、燃料電池の長時間に亘る運転を妨げる大きな
原因であシ、従来技術の問題点であった。For example, in conventional fuel cells that hold phosphoric acid as an electrolyte, platinum supported on fine carbon powder is generally used as an electrode catalyst. In a battery having such a configuration, the oxidizer electrode has a higher potential than the fuel electrode, so the supported platinum particles gradually aggregate as the operating time becomes longer, and the particle size increases. An increase in the platinum particle size causes a decrease in the surface area of the platinum catalyst, significantly deteriorating the activity of the catalyst and reducing the battery output. This deterioration of the catalytic activity of the oxidizer electrode is a major cause of hindering long-term operation of the fuel cell, and has been a problem in the prior art.

〔発明の目的〕[Purpose of the invention]

本発明者等は、以上の従来技術の問題に鑑み、燃料電池
の長時間に亘る運転を可能にする運転方法を提供するこ
とを目的としている。In view of the problems of the prior art described above, the present inventors have aimed to provide an operating method that enables a fuel cell to operate for a long period of time.

〔発明の概要〕[Summary of the invention]

本発明は燃料電池の正・負極に供給する活物質を互いに
入れ換え、電池の正・負極を変換する発電方法を一回以
上行なうことを特徴とする。The present invention is characterized in that the power generation method of replacing the active materials supplied to the positive and negative electrodes of the fuel cell with each other and converting the positive and negative electrodes of the battery is performed at least once.

〔発明の効果〕〔Effect of the invention〕

燃料電池の酸化剤極は、起電時において高電位に保たれ
るため、電極触媒の凝集が経時的に起こり電池出力を低
下させるものでちる。一方、燃料極は、酸化剤極に比べ
電位が低く電極触媒の凝集′は起こ、！７にぐい。この
電極触媒の凝集は、触媒表面積の減少を引き起こし、′
１池の出力を低下させるものである。Since the oxidizer electrode of a fuel cell is kept at a high potential during electromotive generation, aggregation of the electrode catalyst occurs over time, reducing the cell output. On the other hand, the potential of the fuel electrode is lower than that of the oxidizer electrode, and agglomeration of the electrode catalyst occurs. 7th day. This agglomeration of the electrocatalyst causes a decrease in the catalyst surface area,
This reduces the output of one pond.

本発明者らは、この凝集が起こシにくい燃料極触媒を酸
化剤極として用いることで、電圧の低下なしに長時間に
亘る運転を可能にするものである。The present inventors have made it possible to operate for a long time without voltage drop by using a fuel electrode catalyst that does not easily cause agglomeration as an oxidizer electrode.

さらに酸化剤極として用い、凝集が起こった電極触媒を
燃料極として用いても、燃料極反応は、酸化剤極反応に
比べ、反応速度が速いため活性な・１ル極触媒として使
用することができる。Furthermore, even if an agglomerated electrode catalyst is used as an oxidizer electrode, the reaction rate at the fuel electrode is faster than that at the oxidizer electrode, so it cannot be used as an active one-lamp electrode catalyst. can.

また、酸化剤極として用いた電極に燃料極活物質を供給
することによシ、触媒表面に吸着していた被毒物質を還
元し、活性な触媒面積を拡げる効〔発明の実施例〕 以下本発明の詳細な説明する。In addition, by supplying a fuel electrode active material to the electrode used as an oxidizer electrode, poisonous substances adsorbed on the catalyst surface can be reduced and the active catalyst area can be expanded. [Embodiments of the invention] The following The present invention will be described in detail.

実施例１ 第１図に示すように、電解質層５の両面に片面に電極触
媒１．３を保持した多孔質カーボ／ベーパー２，４の電
極を配し、更にこれら電極の他の面側に活物質供給路の
溝７．８を有する双極性隔離板６を配し、これを積層し
てリン酸電解質燃料電池を構成し各電極面に燃料ガス、
酸化剤ガスの活物質を供給して以下の条件（放１に電流
２２０　ｍＡ／ｃＩｒＬ”、　２０５°Ｃ２常圧）で連
続運転を行なったところ、８０００時間程度で電池出力
は低下した。この電池に使用した白金電極触媒を運転後
、Ｘ−ｒａｙ回折を行なったところ、酸化剤極において
、白金粒子径は、ｌｌ０Ａでらシ運転前（６０Ａ）よシ
増大がみられた。また燃料極では６０Ａであり運転前と
変化はみられながった。次に８０００時間経過時点まで
は、酸化剤極として使用していた電極に、燃料極活物質
を供給し、また燃料極として使用してい九″−極に酸化
剤極活物質を供給して運転すると、単位電池の電池電圧
を縦軸に、運転時間を横軸にとった第２図に示すように
初期運転状態とほぼ同様の状況で運転可能となシ運転時
間が倍増する結果を得た。Example 1 As shown in FIG. 1, porous carbon/vapor electrodes 2 and 4 holding an electrode catalyst 1.3 on one side were arranged on both sides of an electrolyte layer 5, and further on the other side of these electrodes. A bipolar separator 6 having active material supply channel grooves 7 and 8 is arranged, and these are stacked to form a phosphoric acid electrolyte fuel cell, with fuel gas,
When an oxidant gas active material was supplied and continuous operation was performed under the following conditions (current 220 mA/cIrL", 205°C2 normal pressure), the battery output decreased after about 8000 hours.This battery After operating the platinum electrode catalyst used in 60A, and no change was observed from before operation.Next, until 8000 hours had elapsed, the fuel electrode active material was supplied to the electrode that had been used as an oxidizer electrode, and the electrode was being used as a fuel electrode. When operating with the oxidizer electrode active material supplied to the 9"-electrode, the situation is almost the same as the initial operating state, as shown in Figure 2, where the vertical axis is the battery voltage of the unit cell and the horizontal axis is the operating time. The result was that the operating time was doubled.

実施例２ 前記と同様の電池構成、試験条件で電池を運転し、酸化
剤極と燃料極に供給する活物質を互いに変換して運転す
る方法を３回〈り返し行なったところ第３図に示すよう
な結果を得た。この結果は反応活物質の変換なしに運転
した電池より運転時間は倍増している。Example 2 The battery was operated with the same battery configuration and test conditions as described above, and the method of converting the active materials supplied to the oxidizer electrode and the fuel electrode to each other was repeated three times. We obtained the results shown below. This result doubles the operating time compared to a battery operated without conversion of the reactive active material.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は燃料電池の概略構成を示す図、第２図、第３図
は本発明に係る電池の単電池電圧−運転時間の関係を示
す特性図である。 １．３・・・電極触媒 ２．４・・・多孔質カーボンペーパー ５・・・電解質層（マトリックス層） ６・・・双極性隔離板 ７．８・・・溝（活物質供給路゛） 代理人　弁理士　則　近　憲　佑　（はが１名）第　１
　図 ７ 第　２　図 運転＠ｗＳ（ｈｒｓ　） 第　３　図 ４０（３００ｉシｙｏｏｎ 玉転時門（ｌｙｒｓ）FIG. 1 is a diagram showing a schematic configuration of a fuel cell, and FIGS. 2 and 3 are characteristic diagrams showing the relationship between unit cell voltage and operating time of the battery according to the present invention. 1.3... Electrode catalyst 2.4... Porous carbon paper 5... Electrolyte layer (matrix layer) 6... Bipolar separator 7.8... Groove (active material supply channel) Agent: Patent Attorney Kensuke Chika (1 person) No. 1
Fig. 7 Fig. 2 Driving @wS (hrs) Fig. 3 Fig. 40 (300i shyoon ball turn time gate (lyrs)

Claims (1)

【特許請求の範囲】[Claims] 空気等の酸化剤ガスを活物質とする正極、水素等の燃料
ガスを活物質とする負極および正・負極に挾持された電
解質層からなる燃料電池において、発電休止後の任意の
時に、正・負極に供給する活物質を互いに入れ換え、前
ｄピ燃料電池の正・負極を変換して再び発電することを
１回以上行なうことを特徴とする燃料電池の運転方法。In a fuel cell consisting of a positive electrode using an oxidizing gas such as air as an active material, a negative electrode using a fuel gas such as hydrogen as an active material, and an electrolyte layer sandwiched between the positive and negative electrodes, the positive 1. A method of operating a fuel cell, comprising the steps of exchanging the active materials supplied to the negative electrode, converting the positive and negative electrodes of the previous fuel cell, and generating power again at least once.