JP2005259368A - Operation method of fuel cell - Google Patents

Operation method of fuel cell Download PDF

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JP2005259368A
JP2005259368A JP2004065551A JP2004065551A JP2005259368A JP 2005259368 A JP2005259368 A JP 2005259368A JP 2004065551 A JP2004065551 A JP 2004065551A JP 2004065551 A JP2004065551 A JP 2004065551A JP 2005259368 A JP2005259368 A JP 2005259368A
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oxygen electrode
oxygen
voltage
electrode
fuel cell
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Atsushi Nonaka
篤 野中
Hideki Shintaku
英城 新宅
Osamu Yamazaki
修 山▲崎▼
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Osaka Gas Co Ltd
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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

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Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method of a fuel cell which is small in size, low in cost, capable of achieving a long life by well recovering a deterioration of an oxygen electrode. <P>SOLUTION: The operation method of the fuel cell supplies an oxygen-containing gas to oxygen electrodes and a hydrogen-containing gas to fuel electrodes to generate electric power by being provided with a plurality of cells having oxygen electrodes on one faces and fuel electrodes on the other faces of electrolyte layers, respectively, in a state to electrically connect the cells in series with one another. The method applies prescribed high voltages to the oxygen electrodes in a state of stopping the supply of the oxygen-containing gas to the oxygen electrodes while keeping the supply of the hydrogen-containing gas to the fuel electrodes, after that, the high voltages applied to the oxygen electrodes is swept by a low voltages lower than the high voltages applied to the oxygen electrodes. Next, a voltage raising process to sweep the low voltages applied to the oxygen electrodes to the high voltages, is applied, then, an oxygen electrode voltage varying operations to conduct voltage lowering processing to sweep the high voltages to the oxygen electrodes to the low voltages is applied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、燃料電池、特に、電解質層の一方の面に酸素極を備え且つ他方の面に燃料極を備えた複数のセルが、電気的に直列接続される状態で設けられ、酸素含有ガスを前記酸素極に供給し、水素含有ガスを前記燃料極に供給して発電する燃料電池の運転方法に関する。   The present invention relates to a fuel cell, in particular, an oxygen-containing gas provided with a plurality of cells each having an oxygen electrode on one side of an electrolyte layer and a fuel electrode on the other side, electrically connected in series. Is supplied to the oxygen electrode, and a hydrogen-containing gas is supplied to the fuel electrode.

燃料電池は、通常、酸素極に供給される酸素含有ガスとして空気を用いる。空気中には、酸素極を構成する電極材に担持されている電極触媒に吸着されて、燃料電池の性能を劣化させる有機物や二酸化窒素等の不純物が含まれている場合がある。
このため、従来は、燃料電池の劣化の原因となる空気中の不純物を除去するガス処理装置を設けて、当該ガス処理装置により空気中から前記不純物を除去して酸素極に供給することで燃料電池の性能の劣化を防止していた。
しかし、このようなガス処理装置を設ける場合には、燃料電池の価格が上昇し、装置が大型になるという問題があった。
これに対し、燃料極への水素含有ガスの供給を継続しながら、酸素極への酸素含有ガスの供給を停止した状態で、酸素極に電圧を印加して、セルに発電状態と同じ向きの電流を流すことにより、酸素極で水素を発生させる劣化回復処理を行う燃料電池の運転方法がある（例えば、特許文献１参照）。この燃料電池の運転方法では、ガス処理装置を設けないので、低価格化並びに小型化を実現しながら燃料電池の劣化を防止することができる。 A fuel cell normally uses air as an oxygen-containing gas supplied to the oxygen electrode. The air may contain impurities such as organic matter and nitrogen dioxide that are adsorbed by the electrode catalyst supported on the electrode material constituting the oxygen electrode and deteriorate the performance of the fuel cell.
For this reason, conventionally, a gas processing device that removes impurities in the air that cause deterioration of the fuel cell is provided, and the impurities are removed from the air by the gas processing device and supplied to the oxygen electrode. The battery performance was prevented from deteriorating.
However, when such a gas processing apparatus is provided, there is a problem that the price of the fuel cell increases and the apparatus becomes large.
In contrast, while the supply of the hydrogen-containing gas to the fuel electrode is continued, the supply of the oxygen-containing gas to the oxygen electrode is stopped, the voltage is applied to the oxygen electrode, and the cell is in the same direction as the power generation state. There is a method of operating a fuel cell that performs deterioration recovery processing in which hydrogen is generated at an oxygen electrode by passing an electric current (see, for example, Patent Document 1). In this fuel cell operating method, since no gas treatment device is provided, deterioration of the fuel cell can be prevented while realizing a reduction in price and size.

特開２０００−２６０４５４号公報JP 2000-260454 A

しかしながら、特許文献１の方法は、酸素極に電圧を印加することで、ある程度劣化を回復することができるが、燃料電池を更に長寿命化させるために、良好に酸素極の劣化を回復できる技術が求められている。   However, although the method of Patent Document 1 can recover the deterioration to some extent by applying a voltage to the oxygen electrode, it can recover the deterioration of the oxygen electrode satisfactorily in order to further extend the life of the fuel cell. Is required.

本発明は上記の問題に鑑みてなされたものであり、その目的は、小型化並びに低価格で、酸素極の劣化を良好に回復して燃料電池の長寿命化を図ることができる燃料電池の運転方法を提供する点にある。   The present invention has been made in view of the above problems, and an object of the present invention is to reduce the size and cost of the fuel cell, and to improve the life of the fuel cell by successfully recovering the deterioration of the oxygen electrode. The point is to provide a driving method.

この目的を達成するための本発明に係る燃料電池の運転方法は、電解質層の一方の面に酸素極を備え且つ他方の面に燃料極を備えた複数のセルが、電気的に直列接続される状態で設けられ、酸素含有ガスを前記酸素極に供給し、水素含有ガスを前記燃料極に供給して発電する燃料電池の運転方法であって、その第一特徴構成は、前記燃料極への水素含有ガスの供給を継続しながら、前記酸素極への酸素含有ガスの供給を停止した状態で、前記酸素極に所定の高電圧を印加した後に、前記酸素極に印加した前記高電圧を前記高電圧よりも低い低電圧に掃引し、次に、前記酸素極に印加した前記低電圧を前記高電圧に掃引する電圧上昇処理を行った後に前記酸素極に印加した前記高電圧を前記低電圧に掃引する電圧低下処理を行う酸素極電圧変動操作を実行する点にある。   In order to achieve this object, the fuel cell operating method according to the present invention is such that a plurality of cells each having an oxygen electrode on one surface of the electrolyte layer and a fuel electrode on the other surface are electrically connected in series. A fuel cell operating method for generating power by supplying an oxygen-containing gas to the oxygen electrode and supplying a hydrogen-containing gas to the fuel electrode, wherein the first characteristic configuration is to the fuel electrode The high voltage applied to the oxygen electrode is applied after a predetermined high voltage is applied to the oxygen electrode while the supply of the oxygen-containing gas to the oxygen electrode is stopped while continuing the supply of the hydrogen-containing gas. The high voltage applied to the oxygen electrode is swept to a low voltage lower than the high voltage, and then the voltage applied to the oxygen electrode after the voltage increasing process is performed to sweep the low voltage applied to the oxygen electrode to the high voltage. Oxygen electrode voltage fluctuation with voltage drop treatment sweeping to voltage Lies in the fact that to run the work.

即ち、本第一特徴構成によれば、電圧上昇処理及び電圧低下処理を行う酸素極電圧変動操作を実行することにより、電圧低下処理により酸素極を劣化させる劣化原因ガスを還元除去するのに加え、酸素極上でＰｔ等の酸化反応を起こさせて、付着している有機物や金属等の不純物を酸化除去することができ、酸素極の劣化を効果的に回復させることができる。
従って、本第一特徴構成により、例えば、ガス処理装置を設けずに小型化並びに低価格化を実現しながら、良好に酸素極の劣化を回復できる燃料電池の運転方法を実現でき、当該燃料電池の運転方法を適切な時期に実行することで、燃料電池の長寿命化を図ることができる。 That is, according to the first characteristic configuration, in addition to reducing and removing the deterioration-causing gas that degrades the oxygen electrode by the voltage reduction process, the oxygen electrode voltage fluctuation operation for performing the voltage increase process and the voltage decrease process is executed. By causing an oxidation reaction of Pt or the like on the oxygen electrode, impurities such as attached organic substances and metals can be oxidized and removed, and deterioration of the oxygen electrode can be effectively recovered.
Therefore, according to the first characteristic configuration, for example, it is possible to realize a fuel cell operation method that can satisfactorily recover the deterioration of the oxygen electrode while realizing miniaturization and cost reduction without providing a gas treatment device. By executing the operation method at an appropriate time, it is possible to extend the life of the fuel cell.

この目的を達成するための本発明に係る燃料電池の運転方法は、電解質層の一方の面に酸素極を備え且つ他方の面に燃料極を備えた複数のセルが、電気的に直列接続される状態で設けられ、酸素含有ガスを前記酸素極に供給し、水素含有ガスを前記燃料極に供給して発電する燃料電池の運転方法であって、その第二特徴構成は、前記燃料極への水素含有ガスの供給を継続しながら、前記酸素極への酸素含有ガスの供給を停止した状態で、前記酸素極に所定の低電圧を印加した後に、前記酸素極に印加した前記低電圧を前記低電圧よりも高い高電圧に掃引し、次に、前記酸素極に印加した前記高電圧を前記低電圧に掃引する電圧低下処理を行った後に前記酸素極に印加した前記低電圧を前記高電圧に掃引する電圧上昇処理を行う酸素極電圧変動操作を実行する点にある。   In order to achieve this object, the fuel cell operating method according to the present invention is such that a plurality of cells each having an oxygen electrode on one surface of the electrolyte layer and a fuel electrode on the other surface are electrically connected in series. In which the oxygen-containing gas is supplied to the oxygen electrode and the hydrogen-containing gas is supplied to the fuel electrode to generate electric power. While the supply of the hydrogen-containing gas is continued, the supply of the oxygen-containing gas to the oxygen electrode is stopped, and after applying a predetermined low voltage to the oxygen electrode, the low voltage applied to the oxygen electrode is reduced. The high voltage applied to the oxygen electrode is swept to a high voltage higher than the low voltage, and then the low voltage applied to the oxygen electrode is applied to the high voltage after performing a voltage reduction process for sweeping the high voltage applied to the oxygen electrode to the low voltage. Oxygen electrode voltage fluctuation with voltage rise processing sweeping to voltage Lies in the fact that to run the work.

即ち、本第二特徴構成によれば、電圧低下処理及び電圧上昇処理を行う酸素極電圧変動操作を実行することにより、酸素極で水素を発生させて劣化原因ガスを還元除去するのに加え、上記第一特徴構成と同様に、酸素極上でＰｔ等の酸化反応を起こさせて、付着している不純物を酸化除去することができ、酸素極の劣化を効果的に回復させることができる。
従って、本第二特徴構成により、小型化並びに低価格化を実現しながら、良好に酸素極の劣化を回復できる燃料電池の運転方法を実現でき、当該燃料電池の運転方法を適切な時期に実行することで、燃料電池の長寿命化を図ることができる。 That is, according to the second characteristic configuration, in addition to generating hydrogen at the oxygen electrode to reduce and remove the deterioration-causing gas by executing the oxygen electrode voltage fluctuation operation for performing the voltage reduction process and the voltage increase process, Similar to the first characteristic configuration, an oxidation reaction of Pt or the like can be caused on the oxygen electrode to oxidize and remove attached impurities, and the deterioration of the oxygen electrode can be effectively recovered.
Therefore, the second characteristic configuration can realize a fuel cell operation method that can satisfactorily recover the deterioration of the oxygen electrode while realizing downsizing and cost reduction, and the fuel cell operation method is executed at an appropriate time. By doing so, the life of the fuel cell can be extended.

本発明に係る燃料電池の運転方法の第三特徴構成は、前記酸素極電圧変動操作を複数回繰返して実行する点にある。
即ち、本第三特徴構成では、酸素極電圧変動操作を複数回繰返して実行するので、酸素極の電極表面全体からより均一に不純物を除去することができ、酸素極の劣化をより効果的に回復させることができる。 A third characteristic configuration of the fuel cell operating method according to the present invention is that the oxygen electrode voltage fluctuation operation is repeated a plurality of times.
That is, in the third characteristic configuration, the oxygen electrode voltage fluctuation operation is repeatedly performed a plurality of times, so that impurities can be more uniformly removed from the entire electrode surface of the oxygen electrode, and the deterioration of the oxygen electrode can be more effectively performed. Can be recovered.

本発明に係る燃料電池の運転方法の第四特徴構成は、前記酸素極電圧変動操作を５回以上１００回以下で繰返して実行する点にある。
即ち、本第四特徴構成によれば、酸素極電圧変動操作の実施回数を５回以上に設定することで、良好に酸素極の劣化を回復させることができ、酸素極電圧変動操作の実施回数を１００回以下とすることで、酸素極電圧変動操作を繰返すことにより、逆に酸素極が劣化して、電気量の減衰率が増大してしまうことを防止することができ、酸素極の劣化をより効果的に回復させることができる。 A fourth characteristic configuration of the fuel cell operation method according to the present invention is that the oxygen electrode voltage fluctuation operation is repeatedly executed at 5 times or more and 100 times or less.
That is, according to the fourth feature configuration, by setting the number of executions of the oxygen electrode voltage fluctuation operation to 5 or more, the deterioration of the oxygen electrode can be recovered well, and the number of times of the oxygen electrode voltage fluctuation operation is performed. By reducing the oxygen electrode voltage fluctuation operation to 100 times or less, it is possible to prevent the oxygen electrode from deteriorating and increasing the attenuation rate of the quantity of electricity. Can be recovered more effectively.

本発明に係る燃料電池の運転方法の第五特徴構成は、前記高電圧が、５００ｍＶ以上９５０ｍＶ以下である点にある。
即ち、本第五特徴構成によれば、高電圧を５００ｍＶ以上に設定することで、酸化還元反応を起こさせて、良好に酸素極の劣化を回復させることができ、高電圧を９５０ｍＶ以下とすることで、過度に高い高電圧を酸素極に印加することにより、逆に、酸素極が劣化して、電気量の減衰率が増大してしまうことを防止することができ、酸素極の劣化をより効果的に回復させることができる。 A fifth characteristic configuration of the method for operating a fuel cell according to the present invention is that the high voltage is 500 mV or more and 950 mV or less.
That is, according to the fifth characteristic configuration, by setting the high voltage to 500 mV or higher, the oxidation-reduction reaction can be caused to satisfactorily recover the deterioration of the oxygen electrode, and the high voltage is set to 950 mV or lower. By applying an excessively high voltage to the oxygen electrode, on the contrary, it is possible to prevent the oxygen electrode from deteriorating and the attenuation rate of the electric quantity from increasing, thereby preventing the oxygen electrode from deteriorating. It can be recovered more effectively.

以下、本発明に係る燃料電池の運転方法（以下、適宜「本発明方法」と略称する）の第一実施形態を図面に基づいて説明する。   Hereinafter, a first embodiment of a fuel cell operation method according to the present invention (hereinafter, abbreviated as “method of the present invention” as appropriate) will be described with reference to the drawings.

図１は、本発明方法を適用する燃料電池の概略を示したものである。この燃料電池は、電解質層１の一方の面に酸素極２を備え且つ他方の面に燃料極３を備えたセル６が設けられ、酸素含有ガスが酸素極２に供給され、水素含有ガスが燃料極３に供給されて発電するように構成してある。   FIG. 1 shows an outline of a fuel cell to which the method of the present invention is applied. In this fuel cell, a cell 6 having an oxygen electrode 2 on one surface of an electrolyte layer 1 and a fuel electrode 3 on the other surface is provided, an oxygen-containing gas is supplied to the oxygen electrode 2, and a hydrogen-containing gas is supplied. The fuel electrode 3 is supplied to generate electricity.

酸素極２及び燃料極３は、本実施形態では、Ｐｔ（白金）等の電極触媒を担持したカーボンから成る多孔状の導電材から形成してある。セル６は、電解質層１の一方の面に酸素極２及び集電板４を配置し、他方の面に燃料極３及び集電板４を配置した状態で一体化して構成してある。このセル６の複数を、互いにセパレータ５を介在させて電気的に直列接続される状態で積層し、その両端部に電力取り出し用の集電部７を設けて、セルスタック１０を構成している。セルスタック１０のセル６の積層方向の端部には３個の接続部８を備えた端板９を設けてある。一方の端板９の接続部８には、酸素含有ガスを各セル６に供給する空気供給源１１、水素含有ガスを各セル６に供給する水素含有ガス供給源１２、及び、冷却水を各セル６に供給するための冷却水ポンプ１３が夫々接続されている。水素含有ガス供給源１２と接続部８とを接続する水素含有ガス供給路には、水素含有ガスを加湿する加湿部１４が設けられている。   In this embodiment, the oxygen electrode 2 and the fuel electrode 3 are formed of a porous conductive material made of carbon carrying an electrode catalyst such as Pt (platinum). The cell 6 is integrally configured with the oxygen electrode 2 and the current collector plate 4 disposed on one surface of the electrolyte layer 1 and the fuel electrode 3 and the current collector plate 4 disposed on the other surface. A plurality of cells 6 are laminated in a state where they are electrically connected in series with each other with separators 5 interposed therebetween, and current collecting portions 7 for taking out power are provided at both ends to constitute a cell stack 10. . An end plate 9 having three connection portions 8 is provided at the end of the cell stack 10 in the stacking direction of the cells 6. An air supply source 11 that supplies oxygen-containing gas to each cell 6, a hydrogen-containing gas supply source 12 that supplies hydrogen-containing gas to each cell 6, and cooling water are connected to the connection portion 8 of one end plate 9. Cooling water pumps 13 for supplying the cells 6 are respectively connected. The hydrogen-containing gas supply path that connects the hydrogen-containing gas supply source 12 and the connection portion 8 is provided with a humidifying unit 14 that humidifies the hydrogen-containing gas.

尚、前記水素含有ガス供給路には開閉弁Ｖａ１が設けられており、空気供給源１１と接続部８とを接続する酸素含有ガス供給路には開閉弁Ｖａ２が設けられ、開閉弁Ｖａ１及び開閉弁Ｖａ２の開度を夫々調節して各セル６に水素含有ガス及び酸素含有ガスを供給することで、水素含有ガス中の水素と酸素含有ガス中の酸素との電気化学反応により、通常の発電が行われる。また、冷却水の通流により、各セル６の温度が所定の温度に維持される。   The hydrogen-containing gas supply path is provided with an on-off valve Va1, and the oxygen-containing gas supply path connecting the air supply source 11 and the connection portion 8 is provided with an on-off valve Va2. By adjusting the opening degree of the valve Va2 and supplying each cell 6 with a hydrogen-containing gas and an oxygen-containing gas, a normal power generation is achieved by an electrochemical reaction between hydrogen in the hydrogen-containing gas and oxygen in the oxygen-containing gas. Is done. Further, the temperature of each cell 6 is maintained at a predetermined temperature by the flow of the cooling water.

更に、集電部７には外部電源１５が接続路１６を介して接続されている。この外部電源１５は、例えば、二次電池にて構成することができる。接続路１６には、スイッチ１７が接続されている。   Further, an external power source 15 is connected to the current collector 7 via a connection path 16. The external power source 15 can be constituted by a secondary battery, for example. A switch 17 is connected to the connection path 16.

本発明に係る燃料電池の運転方法について、図２乃至図４に基づいて説明する。図２は、本発明方法の操作手順を示すフローチャートであり、図３は、本発明方法を実施したときの酸素極２（カソード）及び燃料極３（アノード）の概略を示しており、図４は、本発明方法の各ステップを実行したときの電流値（ｍＡ）と、酸素極２の燃料極３に対する電位差（ｍＶ）との関係を示している。ここでは、高電圧Ｖ１は９５０ｍＶに設定し、低電圧Ｖ２は７０ｍＶに設定している。また、セル６の温度は７０℃、アノード、カソードの露点は８０℃に設定しており、アノードには水素を、カソードには窒素を供給している。尚、本発明に係る燃料電池の運転方法は、本実施形態では、ソフトウェア的に構築され、コンピュータ等からなる制御装置（図示せず）により実行されるように構成されている。   A fuel cell operating method according to the present invention will be described with reference to FIGS. FIG. 2 is a flowchart showing an operation procedure of the method of the present invention, and FIG. 3 shows an outline of the oxygen electrode 2 (cathode) and the fuel electrode 3 (anode) when the method of the present invention is carried out. These show the relationship between the current value (mA) when each step of the method of the present invention is executed and the potential difference (mV) of the oxygen electrode 2 with respect to the fuel electrode 3. Here, the high voltage V1 is set to 950 mV, and the low voltage V2 is set to 70 mV. Further, the temperature of the cell 6 is set to 70 ° C., and the dew points of the anode and cathode are set to 80 ° C., and hydrogen is supplied to the anode and nitrogen is supplied to the cathode. In the present embodiment, the fuel cell operating method according to the present invention is constructed by software and configured to be executed by a control device (not shown) including a computer or the like.

先ず、本発明方法において、水素含有ガス用開閉弁Ｖａ１を開いて、燃料極３への水素含有ガスの供給を継続しながら、酸素含有ガス用開閉弁Ｖａ２を閉じて、酸素極２への酸素含有ガスの供給を停止させる（ステップ＃１００）。尚、本実施形態では、酸素極２への酸素含有ガスの供給を停止させた後、酸素極２に窒素等の不活性ガスを供給するように構成してある。次に、スイッチ１７を閉じて外部電源１５を調節し、酸素極２に高電圧Ｖ１を印加する（ステップ＃１０１）。その後、酸素極２に印加した高電圧Ｖ１を一定の掃引速度、本実施形態では５０ｍＶ／ｓで、低電圧Ｖ２まで引下げる形態で掃引する（ステップ＃１０２）。このとき、図３（ａ）及び図３（ｂ）に示すように、燃料極３から酸素極２へＨ＋が移動することにより電流が流れ、酸素極２上に水素原子が蓄積され、飽和した水素原子はＨ２となる。このＨ２により酸素極２に存在する劣化原因ガスが還元除去される。 First, in the method of the present invention, the hydrogen-containing gas on-off valve Va1 is opened and the oxygen-containing gas on-off valve Va2 is closed while the supply of the hydrogen-containing gas to the fuel electrode 3 is continued. The supply of the contained gas is stopped (step # 100). In the present embodiment, the supply of the oxygen-containing gas to the oxygen electrode 2 is stopped, and then an inert gas such as nitrogen is supplied to the oxygen electrode 2. Next, the switch 17 is closed and the external power source 15 is adjusted, and the high voltage V1 is applied to the oxygen electrode 2 (step # 101). Thereafter, the high voltage V1 applied to the oxygen electrode 2 is swept in such a manner that the high voltage V1 is lowered to the low voltage V2 at a constant sweep speed, 50 mV / s in this embodiment (step # 102). At this time, as shown in FIGS. 3 (a) and 3 (b), current flows as H + moves from the fuel electrode 3 to the oxygen electrode 2, and hydrogen atoms are accumulated on the oxygen electrode 2 so that saturation occurs. The hydrogen atom thus obtained becomes H 2 . The deterioration cause gas existing in the oxygen electrode 2 is reduced and removed by the H 2 .

次に、ステップ＃１０２において酸素極２への印加電圧が低電圧Ｖ２なった直後に、同じ掃引速度で、酸素極２への印加電圧を低電圧Ｖ２から高電圧Ｖ１へ引上げる形態で掃引する電圧上昇処理を行う（ステップ＃１０３）。この時、図３（ｃ）に示すように、酸素極２から燃料極３へＨ＋が移動することにより電流が流れる。さらに、図３（ｄ）に示すように、酸素極２への印加電圧の値がある値を越えるとＰｔ等の酸化反応による電流が流れる。 Next, immediately after the voltage applied to the oxygen electrode 2 becomes the low voltage V2 in step # 102, the voltage applied to the oxygen electrode 2 is swept in the form of increasing from the low voltage V2 to the high voltage V1 at the same sweep speed. A voltage increase process is performed (step # 103). At this time, current flows as H + moves from the oxygen electrode 2 to the fuel electrode 3 as shown in FIG. Further, as shown in FIG. 3D, when the value of the voltage applied to the oxygen electrode 2 exceeds a certain value, a current due to an oxidation reaction such as Pt flows.

そして、ステップ＃１０３において酸素極２への印加電圧が高電圧Ｖ１になった直後に、同じ掃引速度で、酸素極２への印加電圧を高電圧Ｖ１から低電圧Ｖ２へ引下げる形態で掃引する電圧低下処理を行う（ステップ＃１０４）。このとき、図３（ｅ）に示すように、ステップ＃１０３において酸化したＰｔ等の還元反応による電流が流れ、その後、ステップ＃１０２と同様に、酸素極２上で飽和したＨ＋がＨ２となる反応が起こる。この結果、酸素極２の表面上でのＰｔ等の酸化還元反応により、酸素極２の表面の不純物が除去され、劣化が回復される。 Then, immediately after the applied voltage to the oxygen electrode 2 becomes the high voltage V1 in step # 103, the applied voltage to the oxygen electrode 2 is swept in the form of decreasing from the high voltage V1 to the low voltage V2 at the same sweep speed. A voltage drop process is performed (step # 104). At this time, as shown in FIG. 3E, a current due to a reduction reaction of Pt or the like oxidized in step # 103 flows, and thereafter, H + saturated on the oxygen electrode 2 becomes H 2 , as in step # 102. The following reaction occurs. As a result, the impurities on the surface of the oxygen electrode 2 are removed by the oxidation-reduction reaction of Pt or the like on the surface of the oxygen electrode 2, and the deterioration is recovered.

更に、本実施形態では、上述したステップ＃１０３及びステップ＃１０４からなる酸素極電圧変動操作（ステップ＃１０５）を、複数回繰返して実行する（ステップ＃１０６）。   Further, in the present embodiment, the oxygen electrode voltage fluctuation operation (step # 105) composed of the above-described steps # 103 and # 104 is repeatedly executed a plurality of times (step # 106).

次に、燃料電池の運転方法の別実施形態について説明する。
上記第一実施形態では、酸素極に所定の高電圧を印加する（ステップ＃１０１、＃１０２）処理を行った後に、電圧上昇処理（ステップ＃１０３）及び電圧低下処理（ステップ＃１０４）を行う酸素極電圧変動操作を実行したが、本実施形態では、酸素極に所定の低電圧を与え、高電圧に掃引する処理を行った後に、電圧低下処理及び電圧上昇処理を行う酸素極電圧変動操作を実行するように構成する。 Next, another embodiment of the fuel cell operation method will be described.
In the first embodiment, after the process of applying a predetermined high voltage to the oxygen electrode (steps # 101 and # 102), the voltage increase process (step # 103) and the voltage decrease process (step # 104) are performed. Although the oxygen electrode voltage fluctuation operation has been executed, in this embodiment, the oxygen electrode voltage fluctuation operation in which a voltage lowering process and a voltage increasing process are performed after applying a predetermined low voltage to the oxygen electrode and performing a process of sweeping to a high voltage. Configure to run

詳細には、第一実施形態のステップ＃１００を実行した後、外部電源１５を調節し、酸素極２に低電圧Ｖ２を印加する。その後、酸素極２に印加した低電圧Ｖ２を一定の掃引速度で高電圧Ｖ１まで引上げる形態で掃引する。次に、酸素極電圧変動操作を実行する。本実施形態の酸素極電圧変動操作は、電圧低下処理（ステップ＃１０４）を行った後に電圧上昇処理（ステップ＃１０３）を行うように構成する。これによって、第一実施形態と同様に、酸素極２の表面上でのＰｔ等の還元反応及び酸化反応により、酸素極２の表面の不純物が除去され、劣化が回復される。尚、この場合においても、酸素極電圧変動操作を、複数回繰返して実行する構成とするのも好ましい実施態様である。   Specifically, after executing Step # 100 of the first embodiment, the external power supply 15 is adjusted, and the low voltage V2 is applied to the oxygen electrode 2. Thereafter, the low voltage V2 applied to the oxygen electrode 2 is swept in such a manner as to be pulled up to the high voltage V1 at a constant sweep speed. Next, an oxygen electrode voltage fluctuation operation is executed. The oxygen electrode voltage fluctuation operation of the present embodiment is configured such that the voltage increase process (step # 103) is performed after the voltage decrease process (step # 104). As a result, as in the first embodiment, impurities on the surface of the oxygen electrode 2 are removed by the reduction reaction and oxidation reaction of Pt and the like on the surface of the oxygen electrode 2, and the deterioration is recovered. In this case, it is also a preferred embodiment that the oxygen electrode voltage fluctuation operation is repeatedly executed a plurality of times.

ここで、図５は、酸素極電圧変動操作の繰返し回数が３０回までの場合の繰返し回数と酸素極２の電気量（クーロン量ｍＣ）との関係を示し、図６は、繰返し回数が非常に多数の場合の繰返し回数と酸素極２の電気量との関係を示しており、酸素極２の電気量が少ない程、酸素極２が劣化し、燃料電池の性能が低下していると言える。セル６の温度は７０℃、アノード、カソードの露点は６０℃から８０℃に設定されている。   Here, FIG. 5 shows the relationship between the number of repetitions of the oxygen electrode voltage fluctuation operation up to 30 times and the amount of electricity of the oxygen electrode 2 (coulomb amount mC), and FIG. The relationship between the number of repetitions in many cases and the amount of electricity of the oxygen electrode 2 is shown. It can be said that the smaller the amount of electricity of the oxygen electrode 2, the more the oxygen electrode 2 deteriorates and the performance of the fuel cell decreases. . The temperature of the cell 6 is set to 70 ° C., and the dew points of the anode and cathode are set to 60 ° C. to 80 ° C.

図５及び図６に示すように、酸素極電圧変動操作の繰返し回数が４回までの場合は、酸素極２の電気量が充分に増加してその劣化が充分に回復しているとは言えず、繰返し回数が１００回を超えると、酸素極電圧変動操作を１回のみ実行する場合よりも酸素極２の電気量が少なくなり、その後さらに大きく減衰する。これは、酸素極電圧変動操作の繰返し回数を過度に多くするとＰｔ等の酸化還元反応が過剰に起きて、酸素極２が劣化することを示している。従って、酸素極電圧変動操作の繰返し回数は５回以上１００回以下に設定する。   As shown in FIG. 5 and FIG. 6, when the number of repetitions of the oxygen electrode voltage fluctuation operation is up to 4, it can be said that the amount of electricity of the oxygen electrode 2 is sufficiently increased and the deterioration is sufficiently recovered. If the number of repetitions exceeds 100, the amount of electricity in the oxygen electrode 2 becomes smaller than that in the case where the oxygen electrode voltage fluctuation operation is executed only once, and then it is further attenuated. This indicates that when the number of repetitions of the oxygen electrode voltage fluctuation operation is excessively increased, an oxidation-reduction reaction such as Pt occurs excessively and the oxygen electrode 2 deteriorates. Therefore, the number of repetitions of the oxygen electrode voltage fluctuation operation is set to 5 or more and 100 or less.

尚、図５に示されているように、酸素極電圧変動操作の繰返し回数がほぼ１０回までは回数の増加に伴って酸素極２の電気量が多くなり、その後、酸素極電圧変動操作の繰返し回数が１０回を超えると、回数の増加に伴って酸素極２の電気量は徐々に減衰する。従って、酸素極電圧変動操作の繰返し回数は、５回以上１０回以下に設定することがより望ましいと言える。   As shown in FIG. 5, the amount of electricity in the oxygen electrode 2 increases with the increase in the number of repetitions of the oxygen electrode voltage fluctuation operation up to about 10, and then the oxygen electrode voltage fluctuation operation is performed. When the number of repetitions exceeds 10, the amount of electricity in the oxygen electrode 2 gradually attenuates as the number increases. Therefore, it can be said that the number of repetitions of the oxygen electrode voltage fluctuation operation is more preferably set to 5 times or more and 10 times or less.

図７は、高電圧Ｖ１の設定値（掃引範囲上限値）と酸素極２における電気量の減衰率との関係について示している。図７に示すように、高電圧Ｖ１を高く設定する程、酸素極２の電気量の減衰率が大きくなる。これは、酸素極電圧変動操作の繰返し回数を多くする場合と同様に、過度に高電圧Ｖ１を高くするとＰｔの酸化還元反応が過剰になり、余計に酸素極２を劣化させることを示している。従って、高電圧Ｖ１は、５００ｍＶ以上９５０ｍＶ以下に設定する。尚、酸素極２の電気量の減衰率を低く抑えるために、例えば、減衰率を−０．１％程度までに抑えることができる６５０ｍＶ以下に高電圧Ｖ１を設定することがより望ましいと言える。
尚、低電圧Ｖ２は、０ｍＶから自然電位に設定する。また、掃引速度に関しては、図示しないが、酸素極２の電気量への影響は特に見られなかった。
従って、図５乃至図７に示されているように、本発明に係る燃料電池の運転方法を実施することで、良好に不純物を除去して燃料電池の発電性能を回復させ、燃料電池の劣化を防止することができるのである。 FIG. 7 shows the relationship between the set value (sweep range upper limit value) of the high voltage V1 and the attenuation rate of the electric quantity at the oxygen electrode 2. As shown in FIG. 7, as the high voltage V1 is set higher, the attenuation rate of the amount of electricity of the oxygen electrode 2 becomes larger. This indicates that, as in the case where the number of repetitions of the oxygen electrode voltage fluctuation operation is increased, if the high voltage V1 is excessively increased, the redox reaction of Pt becomes excessive and the oxygen electrode 2 is excessively deteriorated. . Therefore, the high voltage V1 is set to 500 mV or more and 950 mV or less. In order to keep the attenuation rate of the electric quantity of the oxygen electrode 2 low, for example, it can be said that it is more desirable to set the high voltage V1 to 650 mV or less that can suppress the attenuation rate to about -0.1%.
The low voltage V2 is set from 0 mV to a natural potential. Further, the sweep rate is not shown, but no particular effect on the amount of electricity of the oxygen electrode 2 was observed.
Accordingly, as shown in FIG. 5 to FIG. 7, by implementing the method of operating a fuel cell according to the present invention, it is possible to satisfactorily remove impurities and restore the power generation performance of the fuel cell, thereby deteriorating the fuel cell. Can be prevented.

本発明に係る燃料電池の模式図Schematic diagram of a fuel cell according to the present invention 本発明に係る燃料電池の運転方法を示すフローチャート1 is a flowchart showing a method of operating a fuel cell according to the present invention. 本発明に係る燃料電池の運転方法の各ステップにおける電極の状態図State diagram of electrodes in each step of fuel cell operation method according to the present invention 本発明に係る燃料電池の運転方法の各ステップにおける電流と酸素極の燃料極に対する電位差との関係図FIG. 4 is a relationship diagram between the current and the potential difference between the oxygen electrode and the fuel electrode in each step of the fuel cell operation method according to the present invention. 本発明に係る燃料電池の運転方法における酸素極電圧変動操作の繰返し回数と電気量の関係図FIG. 5 is a diagram showing the relationship between the number of times of oxygen pole voltage fluctuation operation and the amount of electricity in the fuel cell operation method according to the present invention. 本発明に係る燃料電池の運転方法における酸素極電圧変動操作の繰返し回数と電気量の関係図FIG. 5 is a diagram showing the relationship between the number of times of oxygen pole voltage fluctuation operation and the amount of electricity in the fuel cell operation method according to the present invention. 本発明に係る燃料電池の運転方法における酸素極への印加電圧の掃引範囲の上限値と酸素極における電気量の減衰率の関係図FIG. 5 is a graph showing the relationship between the upper limit value of the sweep range of the voltage applied to the oxygen electrode and the attenuation rate of the electric quantity at the oxygen electrode in the fuel cell operation method of the present invention

符号の説明Explanation of symbols

１ 電解質層
２ 酸素極
３ 燃料極
４ 集電板
５ セパレータ
６ セル
７ 集電部
８ 接続部
９ 端板
１０ セルスタック
１１ 空気供給源
１２ 水素含有ガス供給源
１３ 冷却水ポンプ
１４ 加湿部
１５ 外部電源
１６ 接続路
１７ スイッチ DESCRIPTION OF SYMBOLS 1 Electrolyte layer 2 Oxygen electrode 3 Fuel electrode 4 Current collecting plate 5 Separator 6 Cell 7 Current collecting part 8 Connection part 9 End plate 10 Cell stack 11 Air supply source 12 Hydrogen-containing gas supply source 13 Cooling water pump 14 Humidification part 15 External power supply 16 connection path 17 switch

Claims (5)

電解質層の一方の面に酸素極を備え且つ他方の面に燃料極を備えた複数のセルが、電気的に直列接続される状態で設けられ、酸素含有ガスを前記酸素極に供給し、水素含有ガスを前記燃料極に供給して発電する燃料電池の運転方法であって、
前記燃料極への水素含有ガスの供給を継続しながら、前記酸素極への酸素含有ガスの供給を停止した状態で、前記酸素極に所定の高電圧を印加した後に、前記酸素極に印加した前記高電圧を前記高電圧よりも低い低電圧に掃引し、
次に、前記酸素極に印加した前記低電圧を前記高電圧に掃引する電圧上昇処理を行った後に前記酸素極に印加した前記高電圧を前記低電圧に掃引する電圧低下処理を行う酸素極電圧変動操作を実行する燃料電池の運転方法。 A plurality of cells having an oxygen electrode on one surface of the electrolyte layer and a fuel electrode on the other surface are provided in a state of being electrically connected in series, supplying an oxygen-containing gas to the oxygen electrode, A method for operating a fuel cell that generates electricity by supplying a gas containing the fuel electrode,
While the supply of the hydrogen-containing gas to the fuel electrode was continued, the supply of the oxygen-containing gas to the oxygen electrode was stopped, and a predetermined high voltage was applied to the oxygen electrode, and then applied to the oxygen electrode Sweeping the high voltage to a lower voltage lower than the high voltage;
Next, after performing a voltage increase process for sweeping the low voltage applied to the oxygen electrode to the high voltage, an oxygen electrode voltage for performing a voltage decrease process for sweeping the high voltage applied to the oxygen electrode to the low voltage A method of operating a fuel cell that performs a fluctuating operation. 電解質層の一方の面に酸素極を備え且つ他方の面に燃料極を備えた複数のセルが、電気的に直列接続される状態で設けられ、酸素含有ガスを前記酸素極に供給し、水素含有ガスを前記燃料極に供給して発電する燃料電池の運転方法であって、
前記燃料極への水素含有ガスの供給を継続しながら、前記酸素極への酸素含有ガスの供給を停止した状態で、前記酸素極に所定の低電圧を印加した後に、前記酸素極に印加した前記低電圧を前記低電圧よりも高い高電圧に掃引し、
次に、前記酸素極に印加した前記高電圧を前記低電圧に掃引する電圧低下処理を行った後に前記酸素極に印加した前記低電圧を前記高電圧に掃引する電圧上昇処理を行う酸素極電圧変動操作を実行する燃料電池の運転方法。 A plurality of cells having an oxygen electrode on one surface of the electrolyte layer and a fuel electrode on the other surface are provided in a state of being electrically connected in series, supplying an oxygen-containing gas to the oxygen electrode, A method of operating a fuel cell that generates electricity by supplying a gas containing the fuel electrode,
While continuing the supply of the hydrogen-containing gas to the fuel electrode, with the supply of the oxygen-containing gas to the oxygen electrode stopped, a predetermined low voltage was applied to the oxygen electrode, and then applied to the oxygen electrode Sweeping the low voltage to a higher voltage than the low voltage;
Next, after performing a voltage reduction process for sweeping the high voltage applied to the oxygen electrode to the low voltage, an oxygen electrode voltage for performing a voltage increase process for sweeping the low voltage applied to the oxygen electrode to the high voltage A method of operating a fuel cell that performs a fluctuating operation. 前記酸素極電圧変動操作を複数回繰返して実行する請求項１または２に記載の燃料電池の運転方法。   The fuel cell operating method according to claim 1 or 2, wherein the oxygen electrode voltage fluctuation operation is repeated a plurality of times. 前記酸素極電圧変動操作を５回以上１００回以下で繰返して実行する請求項１または２に記載の燃料電池の運転方法。   The method of operating a fuel cell according to claim 1 or 2, wherein the oxygen electrode voltage fluctuation operation is repeatedly executed at 5 times or more and 100 times or less. 前記高電圧が、５００ｍＶ以上９５０ｍＶ以下である請求項１乃至４の何れか一項に記載の燃料電池の運転方法。   The method for operating a fuel cell according to any one of claims 1 to 4, wherein the high voltage is 500 mV or more and 950 mV or less.
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JP2007207671A (en) * 2006-02-03 2007-08-16 Nissan Motor Co Ltd Fuel cell system
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US9065100B2 (en) 2006-02-03 2015-06-23 Nissan Motor Co., Ltd. Fuel cell system with regeneration of electrode activity during start or stop
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JP2013054942A (en) * 2011-09-05 2013-03-21 Honda Motor Co Ltd Method of activating solid polymer fuel cell
RU2516224C2 (en) * 2012-02-02 2014-05-20 Федеральное государственное военное образовательное учреждение высшего профессионального образования "Военный авиационный инженерный университет" (г. Воронеж) Министерства обороны Российской Федерации Method to diagnose fuel element
JP2020140812A (en) * 2019-02-27 2020-09-03 トヨタ自動車株式会社 Fuel cell system and control method of fuel cell system
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