JP5104677B2 - Fuel cell diagnostic apparatus and diagnostic method - Google Patents

Fuel cell diagnostic apparatus and diagnostic method Download PDF

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JP5104677B2
JP5104677B2 JP2008233256A JP2008233256A JP5104677B2 JP 5104677 B2 JP5104677 B2 JP 5104677B2 JP 2008233256 A JP2008233256 A JP 2008233256A JP 2008233256 A JP2008233256 A JP 2008233256A JP 5104677 B2 JP5104677 B2 JP 5104677B2
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fuel cell
electrode assembly
membrane electrode
catalyst layer
electric double
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JP2010067488A (en
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雄一郎 杉山
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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
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Description

本発明は燃料電池の診断装置と診断方法に関し、特に、燃料電池を破壊することなく、当該燃料電池を構成する膜電極接合体における触媒層の経時的な厚さの変化を推定することのできる診断装置および診断方法に関する。   The present invention relates to a diagnostic apparatus and a diagnostic method for a fuel cell, and in particular, can estimate a change in thickness of a catalyst layer over time in a membrane electrode assembly constituting the fuel cell without destroying the fuel cell. The present invention relates to a diagnostic apparatus and a diagnostic method.

燃料電池の一形態として固体高分子型燃料電池が知られている。固体高分子型燃料電池は他の形態の燃料電池と比較して作動温度が低く（−３０℃〜１００℃程度）、低コスト、コンパクト化が可能なことから、自動車の動力源等として期待されている。   A solid polymer fuel cell is known as one form of the fuel cell. Solid polymer fuel cells have lower operating temperatures (about -30 ° C to 100 ° C) compared to other types of fuel cells, are low in cost, and can be made compact. ing.

固体高分子型燃料電池は、燃料電池の発電部である膜電極接合体（ＭＥＡ）を主要な構成要素とし、それをガス流路を備えたセパレータで挟持することにより、単セルと呼ばれる１つの燃料電池を形成している。膜電極接合体は、イオン交換膜である固体電解質樹脂膜の両面に触媒層を積層した構造を持つ。触媒層は、電解質樹脂と触媒担持導電体とを含む触媒混合物で形成され、触媒には主に白金系の金属が用いられ、該触媒を担持する導電体にはカーボン粉末が主に用いられる。   A polymer electrolyte fuel cell has a membrane electrode assembly (MEA), which is a power generation part of a fuel cell, as a main component, and is sandwiched between separators each having a gas flow path. A fuel cell is formed. The membrane electrode assembly has a structure in which a catalyst layer is laminated on both surfaces of a solid electrolyte resin membrane that is an ion exchange membrane. The catalyst layer is formed of a catalyst mixture containing an electrolyte resin and a catalyst-carrying conductor. A platinum-based metal is mainly used for the catalyst, and a carbon powder is mainly used for the conductor carrying the catalyst.

燃料電池の発電部である膜電極接合体は、電気化学的反応による発電反応によって経時的に劣化するのを避けられず、故障を起こすようになる。代表的な故障モードとしては、膜電極接合体を構成する触媒層における白金等である触媒粒子の劣化による発電有効表面積の低下と、触媒層を構成するカーボンの腐食（２Ｈ２Ｏ＋Ｃ→４Ｈ＋＋４ｅ−＋ＣＯ２）により触媒層厚さが次第に薄くなって薄膜化することによる性能低下、の２つが挙げられる。 The membrane electrode assembly, which is a power generation part of a fuel cell, inevitably deteriorates over time due to a power generation reaction due to an electrochemical reaction, and causes a failure. Typical failure modes include a decrease in the effective power generation surface area due to deterioration of catalyst particles such as platinum in the catalyst layer constituting the membrane electrode assembly, and corrosion of the carbon constituting the catalyst layer (2H 2 O + C → 4H + + 4e). - + CO 2) performance degradation due to the catalyst layer thickness is thinned gradually thinned by, two like.

現在、前記白金等である触媒粒子の劣化程度については、水素の吸着波を電気化学的に観察する手法が知られており、それを用いて、燃料電池を破壊することなく、すなわち非破壊検査で、触媒層の白金（触媒粒子）の劣化程度を推定（測定）することができる。しかし、カーボン腐食による触媒層の薄膜化を非破壊的に測定する手法はなく、燃料電池を分解して膜電極接合体を取り出し、電子顕微鏡等による断面観察により触媒層厚さを測定しており、非破壊でかつ定量的に触媒層の厚さ変化、すなわちカーボン腐食による劣化程度を測定する手段が求められている。   At present, a method of electrochemically observing the adsorption wave of hydrogen is known for the degree of deterioration of the catalyst particles such as platinum, and it is used without destroying the fuel cell, that is, nondestructive inspection. Thus, the degree of deterioration of platinum (catalyst particles) in the catalyst layer can be estimated (measured). However, there is no non-destructive method to measure the thinning of the catalyst layer due to carbon corrosion, the fuel cell is disassembled, the membrane electrode assembly is taken out, and the thickness of the catalyst layer is measured by cross-sectional observation using an electron microscope or the like. Therefore, there is a need for a means for nondestructively and quantitatively measuring the thickness change of the catalyst layer, that is, the degree of deterioration due to carbon corrosion.

非破壊で燃料電池の性能を評価する方法として、特許文献１には、アノード／カソード間に供給ガスの差圧を生じさせたときに差圧時電圧と、同圧の場合の電圧とを比較して、電圧降下要因を計測する手法が記載されている。この方法は、セル毎のガス透過要因を燃料電池を分解することなく知ることができるが、この方法で触媒層の劣化を測定することはできない。   As a non-destructive method for evaluating the performance of a fuel cell, Patent Document 1 compares the voltage at the time of differential pressure when the differential pressure of the supply gas is generated between the anode and cathode and the voltage at the same pressure. Thus, a method for measuring a voltage drop factor is described. Although this method can know the gas permeation factor for each cell without disassembling the fuel cell, the degradation of the catalyst layer cannot be measured by this method.

特許文献２には、燃料電池に通電された一定の電流を瞬間的に遮断した際に該燃料電池の電圧に表れる変化から、その燃料電池の電解質抵抗を非破壊的に測定する燃料電池の診断装置が記載されているが、この診断装置によっても、触媒層の薄膜化による劣化程度を測定することはできない。   Patent Document 2 discloses a fuel cell diagnosis in which an electrolyte resistance of a fuel cell is measured nondestructively from a change that appears in the voltage of the fuel cell when a constant current supplied to the fuel cell is momentarily interrupted. Although an apparatus is described, even this diagnostic apparatus cannot measure the degree of deterioration due to thinning of the catalyst layer.

特許文献３には、膜電極接合体を有するセルを備えた燃料電池における前記セルのサイクリックボルタモグラムを入手し、入手したサイクリックボルタモグラムから測定されるプロトン離脱電気量または酸化被膜生成電気量に基づいて、当該膜電極接合体に在留する水分量を、非破壊的に検出する燃料電池システムが記載されているが、ここにも、当該膜電極接合体を構成する触媒層の薄膜化による劣化程度を測定することについては検討されていない。   Patent Document 3 obtains a cyclic voltammogram of the cell in a fuel cell having a cell having a membrane electrode assembly, and is based on the proton desorption electric quantity or the oxide film generation electric quantity measured from the obtained cyclic voltammogram. In addition, a fuel cell system that non-destructively detects the amount of water remaining in the membrane electrode assembly is described, but here also the degree of deterioration due to thinning of the catalyst layer constituting the membrane electrode assembly It is not considered to measure

特許文献４には、より高い発電効率を持つ燃料電池を得るためのパラメータとして、燃料電池用電極触媒のサイクリックボルタモグラムにおける水素吸着領域におけるピーク電圧値を利用することが記載されているが、ここにも、膜電極接合体を構成する触媒層の薄膜化による劣化程度を測定することについては、特に検討されていない。   Patent Document 4 describes using a peak voltage value in a hydrogen adsorption region in a cyclic voltammogram of a fuel cell electrode catalyst as a parameter for obtaining a fuel cell having higher power generation efficiency. In particular, the measurement of the degree of deterioration due to the thinning of the catalyst layer constituting the membrane electrode assembly is not particularly studied.

特開２００５−２５１４８２号公報JP-A-2005-251482 特開２００５−１６６６０１号公報JP 2005-166601 A 特開２００７−４８４８７号公報JP 2007-48487 A 特開平６−２５１７７３号公報JP-A-6-251773

上記のように、燃料電池で用いられる膜電極接合体における触媒層の劣化度、特にカーボン劣化による触媒層の薄膜化程度を、燃料電池を分解することなく非破壊的に測定する手法は知られていない。実運転される燃料電池において、分解して触媒層の薄膜化程度を測定することは、多くの時間と困難を伴う。   As described above, a technique for measuring the degree of deterioration of a catalyst layer in a membrane electrode assembly used in a fuel cell, particularly the degree of thinning of the catalyst layer due to carbon deterioration, in a nondestructive manner without disassembling the fuel cell is known Not. In a fuel cell that is actually operated, it takes a lot of time and difficulty to measure the degree of thinning of the catalyst layer by decomposition.

本発明は、そのような事情に鑑みてなされたものであり、燃料電池で用いられる膜電極接合体における触媒層の劣化度を非破壊的に測定することのできる燃料電池の診断装置および診断方法を提供することを課題とする。   The present invention has been made in view of such circumstances, and a fuel cell diagnostic apparatus and diagnostic method capable of nondestructively measuring the degree of deterioration of a catalyst layer in a membrane electrode assembly used in a fuel cell. It is an issue to provide.

本発明者らは、多くの実験と研究を行うことにより、劣化を測定しようとする膜電極接合体から得られるサイクリックボルタモグラムにおいて、＋掃引時および−掃引時において電流値がほぼ一定で推移する領域での＋側と−側の電流値の絶対値の和は、当該膜電極接合板の電気二重層容量を示すこと、および、当該電気二重層容量はその膜電極接合体を構成する触媒層のカーボン体積に依存する値であること、従って、サイクリックボルタモグラムから測定される電気二重層容量から、触媒層厚さを推定できること、を知見した。   In the cyclic voltammogram obtained from the membrane electrode assembly to be measured for deterioration by conducting many experiments and researches, the current value changes substantially constant during + sweep and -sweep. The sum of the absolute values of the current values on the + side and − side in the region indicates the electric double layer capacity of the membrane electrode joining plate, and the electric double layer capacity is the catalyst layer constituting the membrane electrode assembly It was found that the catalyst layer thickness can be estimated from the electric double layer capacity measured from the cyclic voltammogram.

本発明は上記の知に基づくものであり、本発明による膜電極接合体を有するセルを備えた燃料電池の診断装置は、診断すべき燃料電池にスイープ波を与えて膜電極接合体のサイクリックボルタモグラムを入手する手段と、入手したサイクリックボルタモグラムから当該膜電極接合体の電気二重層容量を測定する手段と、測定した電気二重層容量から当該膜電極接合体の触媒層の厚さを推定する手段と、を備えることを特徴とする。   The present invention is based on the above knowledge, and a fuel cell diagnostic apparatus having a cell having a membrane electrode assembly according to the present invention provides a cyclic wave of the membrane electrode assembly by applying a sweep wave to the fuel cell to be diagnosed. Means for obtaining a voltammogram, means for measuring the electric double layer capacity of the membrane electrode assembly from the obtained cyclic voltammogram, and estimating the thickness of the catalyst layer of the membrane electrode assembly from the measured electric double layer capacity And means.

また、本発明による膜電極接合体を有するセルを備えた燃料電池の診断方法は、診断すべき燃料電池にスイープ波を与えて膜電極接合体のサイクリックボルタモグラムを入手し、入手したサイクリックボルタモグラムから当該膜電極接合体の電気二重層容量を測定し、測定した電気二重層容量から当該膜電極接合体の触媒層の厚さを推定することを特徴とする。   The method for diagnosing a fuel cell having a cell having a membrane electrode assembly according to the present invention obtains a cyclic voltammogram of the membrane electrode assembly by applying a sweep wave to the fuel cell to be diagnosed. Then, the electric double layer capacity of the membrane electrode assembly is measured, and the thickness of the catalyst layer of the membrane electrode assembly is estimated from the measured electric double layer capacity.

本発明による装置および方法において、測定した電気二重層容量から当該膜電極接合体の触媒層の厚さを推定する手段および方法は任意であるが、予め当該膜電極接合体の電気二重層容量と触媒層厚さとの関係を示す検量線を求めておき、測定時に測定した電気二重層容量値を前記検量線にプロットして、そこから当該触媒層厚さを読み出すやり方は、実際的である。   In the apparatus and method according to the present invention, means and a method for estimating the thickness of the catalyst layer of the membrane electrode assembly from the measured electric double layer capacity are arbitrary. It is practical to obtain a calibration curve showing the relationship with the catalyst layer thickness, plot the electric double layer capacity value measured at the time of measurement on the calibration curve, and read the catalyst layer thickness therefrom.

本発明による方法において、前記電気二重層容量の値として、当該膜電極接合体の前記サイクリックボルタモグラムにおける＋掃引時での電流値の極小値と−掃引時での電流値の極小値のそれぞれの絶対値の和の値を用いることは有効であり、より正確な触媒層厚さを推測することができる。   In the method according to the present invention, as the value of the electric double layer capacitance, each of a minimum value of a current value at the time of + sweep and a minimum value of a current value at the time of-sweep in the cyclic voltammogram of the membrane electrode assembly. It is effective to use the sum of absolute values, and a more accurate catalyst layer thickness can be estimated.

また、本発明による装置および方法では、当該膜電極接合体のサイクリックボルタモグラムを利用している。前記特許文献２に記載のように、得られるサイクリックボルタモグラムからプロトン離脱電気量または酸化被膜生成電気量（すなわち、電気化学的に有効な白金等の金属触媒の表面積）を測定することができ、この電気量の経時的な変化は白金等の金属触媒の劣化を診断するためのパラメータとして用いることができる。従って、本発明による燃料電池の診断装置および診断方法を用いることにより、触媒層における白金等の金属触媒の有効表面積の低下による劣化とカーボン腐食による触媒層の薄膜化による劣化の双方を、非破壊的にかつ同時に診断することが可能となる。   The apparatus and method according to the present invention uses a cyclic voltammogram of the membrane electrode assembly. As described in Patent Document 2, from the obtained cyclic voltammogram, it is possible to measure the amount of proton desorption electricity or oxide film generation electricity (that is, the surface area of an electrochemically effective metal catalyst such as platinum), This change in the amount of electricity with time can be used as a parameter for diagnosing deterioration of a metal catalyst such as platinum. Therefore, by using the fuel cell diagnostic apparatus and diagnostic method according to the present invention, both degradation due to reduction in the effective surface area of platinum and other metal catalysts in the catalyst layer and degradation due to thinning of the catalyst layer due to carbon corrosion are nondestructive. Diagnosis simultaneously and simultaneously.

本発明によれば、膜電極接合体を構成する触媒層の劣化程度を、燃料電池を破壊することなく測定することができる。カーボン腐食による触媒層の薄膜化による経時的劣化だけでなく、白金等の金属触媒の劣化により有効表面積の経時的低下程度についても、非破壊的に当時に測定することができる。   According to the present invention, the degree of deterioration of the catalyst layer constituting the membrane electrode assembly can be measured without destroying the fuel cell. Not only the deterioration over time due to the thinning of the catalyst layer due to carbon corrosion but also the degree of the effective surface area over time due to the deterioration of the metal catalyst such as platinum can be measured non-destructively at that time.

以下、本発明を実施の形態に基づき説明する。図１は本発明による燃料電池の診断装置の全体構成図の一例である。   Hereinafter, the present invention will be described based on embodiments. FIG. 1 is an example of an overall configuration diagram of a fuel cell diagnostic apparatus according to the present invention.

図１に示すように、燃料電池の診断装置１は、ポテンショスタット２と、ポテンショスタット２が得た検出結果のデータを解析する解析用コンピュータ３を備える。ポテンショスタット２に対して診断対象の燃料電池４を接続する。   As shown in FIG. 1, the fuel cell diagnosis apparatus 1 includes a potentiostat 2 and an analysis computer 3 that analyzes data of detection results obtained by the potentiostat 2. A fuel cell 4 to be diagnosed is connected to the potentiostat 2.

診断にあたって、ポテンショスタット２は、燃料電池４の各セルに電圧を印加し、各セルから出力される電流値を測定する。測定結果は解析用コンピュータ３に送られ、解析用コンピュータ３は当該セルのサイクリックボルタモグラムを作成する。この例において、ポテンショスタット２は、ＲＨＥに対して０．１Ｖ−１．２Ｖ，５０ｍＶのスイープ波を燃料電池３に入力している。   In the diagnosis, the potentiostat 2 applies a voltage to each cell of the fuel cell 4 and measures a current value output from each cell. The measurement result is sent to the analysis computer 3, and the analysis computer 3 creates a cyclic voltammogram of the cell. In this example, the potentiostat 2 inputs a sweep wave of 0.1 V-1.2 V and 50 mV to the fuel cell 3 with respect to RHE.

図２は、ポテンショスタット２によって入手したサイクリックボルタモグラムの一例を示す。サイクリックボルタモグラムが示すように、セルを流れる電流は、＋掃引時では、電圧の増大とともに徐々に増大し、その後は徐々に減少して極小値を取る。さらに電圧が増大すると再び電流は増大する。−掃引時でも同様であり、電圧の減少とともに、増大した後に減少して極小値を取り、再度の増大する。   FIG. 2 shows an example of a cyclic voltammogram obtained by potentiostat 2. As indicated by the cyclic voltammogram, the current flowing through the cell gradually increases as the voltage increases during the + sweep, and then gradually decreases and takes a minimum value. When the voltage further increases, the current increases again. -It is the same at the time of sweeping. As the voltage decreases, the voltage decreases and then decreases to take a minimum value, and then increases again.

サイクリックボルタモグラムにおいて、電流の漸増また漸減は、膜電極接合体を構成する触媒層における白金触媒の表面にプロトンが吸着するあるいは表面から離脱することで生じているものであり、図２で斜線で示す面積の大小から、白金触媒の有効面積を推測することができる。一方、サイクリックボルタモグラムでの極小値の部分（図で矢印で示す部分）は、白金触媒の表面についているプロトンがすべて放出された状態であり、そこにおける＋掃引時の電流値と−掃引時の絶対値の和を計算することにより、当該膜電極接合体の触媒層が持つ電気二重層容量を入手することができる。膜電極接合体を構成する材料において、白金触媒や電解質成分はコンデンサ成分を有していないので、入手した前記電気二重層容量の値は、純粋に触媒層を構成するカーボンに蓄えられた電気量であり、電気二重層容量の値は触媒層を構成するカーボンの体積の大小、すなわち、触媒層の厚さのみ依存する。   In the cyclic voltammogram, the gradual increase or decrease in current is caused by protons adsorbed on or desorbed from the surface of the platinum catalyst in the catalyst layer constituting the membrane electrode assembly. The effective area of the platinum catalyst can be estimated from the size of the area shown. On the other hand, the portion of the minimum value in the cyclic voltammogram (the portion indicated by the arrow in the figure) is a state in which all protons attached to the surface of the platinum catalyst are released, and the current value at the time of + sweep and the value at the time of − sweep By calculating the sum of absolute values, the electric double layer capacity of the catalyst layer of the membrane electrode assembly can be obtained. In the material constituting the membrane electrode assembly, since the platinum catalyst and the electrolyte component do not have a capacitor component, the obtained value of the electric double layer capacity is the amount of electricity stored purely in the carbon constituting the catalyst layer. The value of the electric double layer capacity depends only on the volume of the carbon constituting the catalyst layer, that is, the thickness of the catalyst layer.

従って、ある燃料電池について、経時的にサイクリックボルタモグラムを作成し、それから得られる電気二重層容量の変化を追跡することにより、その燃料電池の発電部である膜電極接合体を構成する触媒層の厚さの変化を知ることができる。   Accordingly, a cyclic voltammogram is created over time for a fuel cell, and the change in the electric double layer capacity obtained from the cyclic voltammogram is tracked, whereby the catalyst layer constituting the membrane electrode assembly that is the power generation part of the fuel cell is obtained. You can know the change in thickness.

図３は、同一の燃料電池について、長時間の運転を継続して行いながら、図１に示した装置を用いて入手した複数個のサイクリックボルタモグラムを同一図面上にプロットしたものである。前記したように、運転時間の経過と共に、触媒層の白金触媒の劣化とカーボン腐食による劣化が進行することから、運転初期のサイクリックボルタモグラムが最も外縁をなし、経時的に、次第にほぼ縮小した形となっている。電気二重層容量の値も、運転初期が最も大きく、次第に減少している。   FIG. 3 is a plot of a plurality of cyclic voltammograms obtained using the apparatus shown in FIG. 1 on the same drawing while continuously operating for the same fuel cell. As described above, as the operation time elapses, the deterioration of the platinum catalyst in the catalyst layer and the deterioration due to carbon corrosion progress, so the cyclic voltammogram at the beginning of the operation forms the outermost edge, and gradually shrinks gradually over time. It has become. The value of the electric double layer capacity is also largest at the initial stage of operation and gradually decreases.

従って、ある膜電極接合体を持つ燃料電池について、サイクリックボルタモグラムから得られる電気二重層容量の値と触媒層厚さの関係を示す検量線を予め入手しておき、同じ膜電極接合体を持つ診断対象となる燃料電池についてサイクリックボルタモグラムを入手してそこから電気二重層容量を測定し、その測定値を前記検量線に当てはめることにより、燃料電池を分解することなく、当該膜電極接合体の診断時での触媒層厚さを正確に推測することができる。そして、その値を当初の値と比較することにより、診断時における触媒層のカーボン劣化による薄膜化の進行程度を知ることもできる。   Therefore, for a fuel cell having a certain membrane electrode assembly, a calibration curve indicating the relationship between the electric double layer capacity value obtained from the cyclic voltammogram and the catalyst layer thickness is obtained in advance, and the same membrane electrode assembly is provided. Obtain a cyclic voltammogram for the fuel cell to be diagnosed, measure the electric double layer capacity therefrom, and apply the measured value to the calibration curve, so that the fuel cell can be disassembled without disassembling the membrane electrode assembly. The thickness of the catalyst layer at the time of diagnosis can be accurately estimated. Then, by comparing the value with the initial value, it is possible to know the degree of progress of thinning due to carbon deterioration of the catalyst layer at the time of diagnosis.

さらに、前記のように入手したサイクリックボルタモグラムから触媒層の白金触媒の劣化程度も知ることができるので、本発明による診断装置を用いることによって、燃料電池を分解することなく非破壊的に、触媒層を構成する白金触媒の劣化度とカーボン劣化による薄膜化度を同時に知ることができる。   Furthermore, since the degree of deterioration of the platinum catalyst in the catalyst layer can be known from the cyclic voltammogram obtained as described above, the catalyst can be used nondestructively without disassembling the fuel cell by using the diagnostic device according to the present invention. The degree of deterioration of the platinum catalyst constituting the layer and the degree of thinning due to carbon deterioration can be known simultaneously.

図４は、本発明者が実際に行った実験結果を示す。図において、横軸は電気二重層容量維持率であり、縦軸は触媒層厚さである。ここで、電気二重層容量維持率とは、実験開始時に入手したサイクリックボルタモグラムから測定した電気二重層容量を１としたときの、所定時間経過後に入手したサイクリックボルタモグラムから測定した電気二重層容量の前記１に対する割合を示している。同じ燃料電池について、運転開始時と、運転を継続したときの、触媒層厚さの実測値とそのときのサイクリックボルタモグラムから測定した電気二重層容量を４点について測定し、検量線Ａを得た。   FIG. 4 shows the experimental results actually performed by the present inventors. In the figure, the horizontal axis represents the electric double layer capacity retention rate, and the vertical axis represents the catalyst layer thickness. Here, the electric double layer capacity retention rate is the electric double layer capacity measured from the cyclic voltammogram obtained after elapse of a predetermined time when the electric double layer capacity measured from the cyclic voltammogram obtained at the start of the experiment is 1. The ratio with respect to 1 is shown. For the same fuel cell, measure the double layer capacity measured from the measured value of the catalyst layer thickness and the cyclic voltammogram at the time of starting and continuing the operation, and obtain a calibration curve A It was.

診断対象の燃料電池として、同じ形態である４個の燃料電池を用意し、それぞれについて、５０時間、１００時間、１５０時間、２００時間の運転をした後、図１に示す診断装置を用いて、それぞれのサイクリックボルタモグラムを入手し、そこから電気二重層容量を測定して、電気二重層容量維持率を計算した。   As fuel cells to be diagnosed, four fuel cells having the same form are prepared, and after operating for 50 hours, 100 hours, 150 hours, and 200 hours for each, using the diagnostic device shown in FIG. Each cyclic voltammogram was obtained, the electric double layer capacity was measured therefrom, and the electric double layer capacity retention rate was calculated.

得られた電気二重層容量維持率を利用して、図４の前記検量線Ａからそれぞれの燃料電池の膜電極接合体の持つ触媒層の厚さを推測した。その後、燃料電池を分解して、触媒層の厚さを実測したところ、一致率は９５％と極めて高く、本発明による燃料電池の診断装置および診断方法は充分に実用に耐えることが立証された。   Using the obtained electric double layer capacity retention rate, the thickness of the catalyst layer of the membrane electrode assembly of each fuel cell was estimated from the calibration curve A of FIG. After that, when the fuel cell was disassembled and the thickness of the catalyst layer was measured, the coincidence rate was as high as 95%, and it was proved that the fuel cell diagnostic device and diagnostic method according to the present invention sufficiently withstand practical use. .

本発明による燃料電池の診断装置を示す構成図。The block diagram which shows the diagnostic apparatus of the fuel cell by this invention. ポテンショスタットによって入手したサイクリックボルタモグラムの一例を示す図。The figure which shows an example of the cyclic voltammogram obtained by the potentiostat. 同一の燃料電池について、長時間の運転を継続して行いながら入手した複数個のサイクリックボルタモグラムを同一図面上にプロットした図。The figure which plotted on the same drawing several cyclic voltammograms obtained for the same fuel cell while continuing long-time driving | running. 実験例で用いた電気二重層容量維持率と触媒層厚さおよび検量線を示すグラフ。The graph which shows the electric double layer capacity maintenance factor used by the experiment example, the catalyst layer thickness, and a calibration curve.

符号の説明Explanation of symbols

１…燃料電池の診断装置、２…ポテンショスタット、３…解析用コンピュータ、４…診断対象の燃料電池。 DESCRIPTION OF SYMBOLS 1 ... Fuel cell diagnostic apparatus, 2 ... Potentiostat, 3 ... Computer for analysis, 4 ... Fuel cell of diagnostic object.

Claims (5)

膜電極接合体を有するセルを備えた燃料電池の診断装置であって、
診断すべき燃料電池にスイープ波を与えて膜電極接合体のサイクリックボルタモグラムを入手する手段と、
入手したサイクリックボルタモグラムから当該膜電極接合体の電気二重層容量を測定する手段と、
測定した電気二重層容量から当該膜電極接合体の触媒層の厚さを推定する手段と、
を備えることを特徴とする燃料電池の診断装置。 A fuel cell diagnostic apparatus comprising a cell having a membrane electrode assembly,
Means for applying a sweep wave to the fuel cell to be diagnosed to obtain a cyclic voltammogram of the membrane electrode assembly;
Means for measuring the electric double layer capacity of the membrane electrode assembly from the obtained cyclic voltammogram;
Means for estimating the thickness of the catalyst layer of the membrane electrode assembly from the measured electric double layer capacity;
A fuel cell diagnostic apparatus comprising: 触媒層の厚さを推定する手段は、予め作成した当該膜電極接合体の電気二重層容量と触媒層厚さとの関係を示す検量線から測定した電気二重層容量値での触媒層厚さを読み出す手段であることを特徴とする請求項１に記載の燃料電池の診断装置。   The means for estimating the thickness of the catalyst layer is obtained by calculating the catalyst layer thickness at the electric double layer capacity value measured from a calibration curve indicating the relationship between the electric double layer capacity and the catalyst layer thickness of the membrane electrode assembly prepared in advance. 2. The fuel cell diagnostic apparatus according to claim 1, wherein the diagnostic apparatus is a reading means. 膜電極接合体を有するセルを備えた燃料電池の診断方法であって、
診断すべき燃料電池にスイープ波を与えて膜電極接合体のサイクリックボルタモグラムを入手し、入手したサイクリックボルタモグラムから当該膜電極接合体の電気二重層容量を測定し、測定した電気二重層容量から当該膜電極接合体の触媒層の厚さを推定することを特徴とする燃料電池の診断方法。 A method for diagnosing a fuel cell comprising a cell having a membrane electrode assembly,
Obtain a cyclic voltammogram of the membrane electrode assembly by applying a sweep wave to the fuel cell to be diagnosed, measure the electric double layer capacity of the membrane electrode assembly from the obtained cyclic voltammogram, and use the measured electric double layer capacitance. A method for diagnosing a fuel cell, comprising estimating a thickness of a catalyst layer of the membrane electrode assembly. 触媒層の厚さの推定は、当該膜電極接合体の電気二重層容量と触媒層厚さとの関係を示す検量線を予め作成しておき、該検量線から測定した電気二重層容量値での触媒層厚さを読み出すことにより行うことを特徴とする請求項３に記載の燃料電池の診断方法。   To estimate the thickness of the catalyst layer, a calibration curve indicating the relationship between the electric double layer capacity of the membrane electrode assembly and the catalyst layer thickness is prepared in advance, and the electric double layer capacity value measured from the calibration curve is calculated. 4. The fuel cell diagnosis method according to claim 3, wherein the diagnosis is performed by reading out the catalyst layer thickness. 前記電気二重層容量の値として、当該膜電極接合体の前記サイクリックボルタモグラムにおける＋掃引時での電流値の極小値と−掃引時での電流値の極小値のそれぞれの絶対値の和の値を用いることを特徴とする請求項３または４に記載の燃料電池の診断方法。   The value of the electric double layer capacitance is the sum of the absolute values of the minimum value of the current value at the time of + sweep and the minimum value of the current value at the time of-sweep in the cyclic voltammogram of the membrane electrode assembly. The fuel cell diagnosis method according to claim 3, wherein:
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