JP2006164824A - Separator made of stainless steel for solid polymer fuel cell, and solid polymer fuel cell - Google Patents
Separator made of stainless steel for solid polymer fuel cell, and solid polymer fuel cell Download PDFInfo
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Abstract
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本発明は、低温稼動が可能でメンテナンスも容易な固体高分子型燃料電池に組み込まれるステンレス鋼製セパレータ及び該ステンレス鋼製セパレータを組み込んだ固体高分子型燃料電池に関する。 The present invention relates to a stainless steel separator incorporated in a polymer electrolyte fuel cell that can be operated at a low temperature and is easy to maintain, and a polymer electrolyte fuel cell incorporating the stainless steel separator.
固体高分子型燃料電池は、１００℃以下の低温で動作可能であり、短時間で起動する長所を備えている。各部材が固体からなる簡単な構造のため、メンテナンスが容易で振動や衝撃に曝される用途にも適用できる。しかも、出力密度が高いため小型化に適し、燃料効率が高く騒音が少ない等の長所も備えている。
燃料電池は単セル当りの発電量が極僅かであり、実用に供せられる電力量を取り出すには触媒電極層を固体高分子膜にプレスした膜-電極接合体を一単位とし、セパレータを介して複数の膜-電極接合体をスタックする必要がある。セパレータには、導電性が良好で接触抵抗が低いことが要求されるため従来から黒鉛質のセパレータが使用されてきた。
The polymer electrolyte fuel cell can operate at a low temperature of 100 ° C. or less and has an advantage of starting in a short time. Since each member is a simple structure made of a solid, it is easy to maintain and can be applied to applications where it is exposed to vibration or impact. In addition, the high output density is suitable for downsizing, and has advantages such as high fuel efficiency and low noise.
A fuel cell has very little power generation per unit cell, and in order to extract the amount of power that can be put to practical use, a membrane-electrode assembly in which a catalyst electrode layer is pressed on a solid polymer membrane is used as a unit, and a separator is interposed. It is necessary to stack a plurality of membrane-electrode assemblies. Since the separator is required to have good conductivity and low contact resistance, a graphite separator has been conventionally used.
しかし、黒鉛製セパレータを組み込んだ燃料電池は振動や衝撃に対して脆く亀裂が生じやすい。また、気密性を確保するため十分な厚みのセパレータ形状にするほかなく、コンパクト化の要求に応えられない。しかも、フライス加工等で流路を形成する必要があるため、生産コストが高くなる。そこで、黒鉛に変わるセパレータ素材としてステンレス鋼の適用が検討されている（特許文献１，２）。
ステンレス鋼は、高強度で延性に優れているため薄肉化でき、プレス成形等の安価な加工法で目標のセパレータ形状に加工でき、十分な耐衝撃性，ガス不透過性等の構造的機能が得られる。ステンレス鋼に含まれる成分Ｃｒ，Ｍｏ，Ｆｅ等の酸化物，水酸化物から形成される不動態皮膜で鋼板表面が覆われ、不動態皮膜のバリア効果によって下地鋼が防食されることも、ステンレス鋼製セパレータの利点である。 Stainless steel can be thinned due to its high strength and excellent ductility, and can be processed into the target separator shape by an inexpensive processing method such as press molding, and has sufficient structural functions such as impact resistance and gas impermeability. can get. The steel plate surface is covered with a passive film formed from oxides and hydroxides of the components Cr, Mo, Fe, etc. contained in the stainless steel, and the base steel is protected against corrosion by the barrier effect of the passive film. This is an advantage of the steel separator.
不動態皮膜は耐食性に有効であるものの半導体的な特性を呈し、下地鋼に比較して電気伝導性が劣っている。そのため、通常の不動態皮膜が生成しているステンレス鋼をセパレータに使用すると、電極との接触抵抗が大きく，電池反応で生じた電気エネルギーがジュール熱として消費され，燃料電池の発電効率が低下する。また、ステンレス鋼製セパレータは黒鉛製に比較して耐酸性に劣り、溶出した金属イオンによる固体高分子膜や触媒電極層の汚染に起因する燃料電池の性能低下も懸念される。
優れた耐食性を活用しながらステンレス鋼をセパレータに適用するためには、ステンレス鋼表面の接触抵抗を下げる必要がある。表面接触抵抗を低下させる手段として、貴金属コーティング，ステンレス鋼表面の粗面化等が検討されている。
Although the passive film is effective for corrosion resistance, it exhibits semiconductor-like properties and is inferior in electrical conductivity as compared to the base steel. Therefore, when stainless steel with a normal passive film is used for the separator, the contact resistance with the electrode is large, the electric energy generated by the cell reaction is consumed as Joule heat, and the power generation efficiency of the fuel cell decreases. . Further, stainless steel separators are inferior in acid resistance compared to graphite, and there is a concern that the performance of the fuel cell may be deteriorated due to contamination of the solid polymer membrane or the catalyst electrode layer by the eluted metal ions.
In order to apply stainless steel to the separator while utilizing excellent corrosion resistance, it is necessary to reduce the contact resistance of the stainless steel surface. As means for reducing the surface contact resistance, precious metal coating, roughening of the stainless steel surface, and the like have been studied.
貴金属コーティングは、高価な貴金属を消費することから燃料電池のコストを上昇させる原因であり、燃料電池の普及に経済面からの制約を加える。しかも、貴金属皮膜にピンホールがあると孔食が発生しやすくなるので、製品管理に厳重な注意が必要になる。厚めっきによってピンホールの発生を防止できるが、厚めっきは高価な貴金属の多量消費を意味しコスト低減のネックになる。
粗面化処理で接触抵抗を下げる場合、交番電解による粗面化が理想であるが、高耐食性のステンレス鋼表面を必要な粗面化状態に改質することは困難である。
The noble metal coating is a cause of increasing the cost of the fuel cell because it consumes an expensive noble metal, and imposes economic restrictions on the spread of the fuel cell. In addition, if there is a pinhole in the noble metal film, pitting corrosion is likely to occur, so strict care is required for product management. Thick plating can prevent the occurrence of pinholes, but thick plating means a large consumption of expensive noble metals and becomes a bottleneck in cost reduction.
When reducing the contact resistance by the roughening treatment, roughening by alternating electrolysis is ideal, but it is difficult to improve the surface of the highly corrosion resistant stainless steel to the required roughened state.
本発明は、燃料電池の内部環境下でオーステナイト系ステンレス鋼の接触抵抗の増加傾向が不動態皮膜のＣｒ濃度によって大きく変わるとの新たな知見をベースに、Ｃｒ濃度の高い不動態皮膜をオーステナイト系ステンレス鋼表面に形成することにより、貴金属コーティングや粗面化処理に拠ることなく、優れた耐食性を維持しながら低い表面接触抵抗を呈するステンレス鋼製セパレータを組み込んだ固体高分子型燃料電池を提供することを目的とする。 The present invention is based on the new knowledge that the increasing tendency of the contact resistance of austenitic stainless steel in the internal environment of the fuel cell greatly depends on the Cr concentration of the passive film. Provided is a polymer electrolyte fuel cell that incorporates a stainless steel separator that exhibits low surface contact resistance while maintaining excellent corrosion resistance, without forming on a stainless steel surface, and without relying on precious metal coating or roughening treatment. For the purpose.
本発明の固体高分子型燃料電池用ステンレス鋼製セパレータは、Ｃｒ：１９〜４０質量％を含むオーステナイト系ステンレス鋼を基材とし、基材表面をＣｒ濃度：１９質量％以上の不動態皮膜で覆っている。不動態皮膜は、非酸化性酸を用いた浸漬処理で形成され、温度：７０℃，相対湿度：９８％の湿潤雰囲気に７２時間放置した後でカーボンペーパとの接触抵抗が測定圧力：２０ｋｇｆ／ｃｍ2で５ｍΩ・ｃｍ2以下となるように調質されている。 The stainless steel separator for a polymer electrolyte fuel cell according to the present invention is based on an austenitic stainless steel containing Cr: 19 to 40% by mass, and the surface of the substrate is a passive film having a Cr concentration of 19% by mass or more. Covering. The passive film is formed by a dipping process using a non-oxidizing acid, and after being left in a humid atmosphere at a temperature of 70 ° C. and a relative humidity of 98% for 72 hours, the contact resistance with the carbon paper is measured. has been tempered in such a way that 5mΩ · cm 2 or less in cm 2.
オーステナイト系ステンレス鋼は、燃料電池内部のように酸性の湿潤雰囲気下でも優れた耐食性を呈し、フェライト系に比較して加工性に優れているのでプレス加工，切削加工，化学エッチング等で複雑なセパレータ形状にも容易に成形できる。なかでも、量産性に優れたプレス加工が採用可能なことは、作製コストを低減する上で有利である。しかも、Ｃｒ濃度：１９質量％以上の不動態皮膜がステンレス鋼製セパレータ表面にあるため、イオン交換膜や電極に悪影響を及ぼすＮｉ，Ｃｕ等の溶出も抑えられる。 Austenitic stainless steel exhibits excellent corrosion resistance even in an acidic moist atmosphere like the inside of a fuel cell, and is superior in workability compared to ferrite, so it is a complicated separator for pressing, cutting, chemical etching, etc. Easy to shape. Among these, the fact that press work with excellent mass productivity can be adopted is advantageous in reducing the production cost. In addition, since a passive film having a Cr concentration of 19% by mass or more is present on the surface of the stainless steel separator, elution of Ni, Cu and the like that adversely affect the ion exchange membrane and the electrode can be suppressed.
使用可能なオーステナイト系ステンレス鋼としては、Ｃｒ：１９〜４０質量％，Ｎｉ：５〜２６質量％を含み、Ｃ：０.０８質量％以下，Ｓｉ：１.５０質量％以下，Ｍｎ：２.００質量％以下，Ｐ：０.０４５質量％以下，Ｓ：０.０３０質量％以下に規制したSUS 310S等の鋼種がある。
酸浸漬によりＣｒが富化した不動態皮膜を形成させるため１９質量％以上のＣｒ含有量が必要であり、Ｃｒ含有量の増加に伴い接触抵抗が安定し酸性雰囲気下の耐酸性も向上する。しかし、過剰量のＣｒ含有は加工性，熱間加工性を低下させるので、上限を４０質量％とした。接触抵抗の安定性，耐酸性，加工性，熱間加工性を重視する場合、２０〜２６質量％のＣｒ含有量が好ましい。
Usable austenitic stainless steels include Cr: 19-40 mass%, Ni: 5-26 mass%, C: 0.08 mass% or less, Si: 1.50 mass% or less, Mn: 2. There are steel types such as SUS 310S regulated to 00 mass% or less, P: 0.045 mass% or less, and S: 0.030 mass% or less.
In order to form a passivated film enriched with Cr by acid dipping, a Cr content of 19% by mass or more is required. As the Cr content increases, the contact resistance is stabilized and the acid resistance in an acidic atmosphere is improved. However, since an excessive amount of Cr decreases workability and hot workability, the upper limit is set to 40% by mass. When importance is attached to stability of contact resistance, acid resistance, workability, and hot workability, a Cr content of 20 to 26 mass% is preferable.
Ｎｉ含有量は、オーステナイト相の形成及び酸性雰囲気下の耐食性のため、５.０質量％以上が必要である。しかし、過剰量のＮｉ添加は加工性に悪影響を及ぼし、コスト的にも不利であり、更にはセル内に溶出するＮｉイオン量が多くなって触媒の劣化を促進させる。そこで、オーステナイト相の形成に必要な最低限にＮｉ含有量を留めることが好適である。また、必要に応じＭｏ：６質量％以下，Ｃｕ：６質量％以下，Ｔｉ：１.０質量％以下，Ｎｂ：１.０質量％以下，Ａｌ：３.０質量％以下，Ｖ：１.０質量％以下，Ｂ：１.０質量％以下等を含ませても良い。 The Ni content needs to be 5.0% by mass or more for the formation of austenite phase and the corrosion resistance in an acidic atmosphere. However, the addition of an excessive amount of Ni adversely affects workability and is disadvantageous in terms of cost, and further, the amount of Ni ions eluted in the cell increases to promote catalyst deterioration. Therefore, it is preferable to keep the Ni content to the minimum necessary for forming the austenite phase. If necessary, Mo: 6 mass% or less, Cu: 6 mass% or less, Ti: 1.0 mass% or less, Nb: 1.0 mass% or less, Al: 3.0 mass% or less, V: 1. You may include 0 mass% or less, B: 1.0 mass% or less.
オーステナイト系ステンレス鋼は、非酸化性酸を用いた浸漬処理で再不動態化することにより表面接触抵抗が低下する。なかでも、塩酸，硫酸等の非酸化性酸で酸洗したステンレス鋼を固体高分子型燃料電池に組み込むと、表面接触抵抗が低減したセパレータとなる。表面接触抵抗の低減は、Ｃｒが濃化した薄い不動態皮膜がステンレス鋼表面に生じることによるものと推察される。すなわち、Ｃｒ濃度の増加に伴い不動態皮膜が薄膜化するので接触抵抗も低下する。実際、温度：７０℃，相対湿度：９８％の湿潤雰囲気に７２時間放置した後でカーボンペーパとの接触抵抗が測定圧力：２０ｋｇｆ／ｃｍ2で５ｍΩ・ｃｍ2以下となるように浸漬処理条件を制御することによって、燃料電池の内部環境を模擬した長時間の湿潤試験後にも接触抵抗が低位に維持されることが判った。 Austenitic stainless steel has a reduced surface contact resistance by repassivation by immersion treatment using a non-oxidizing acid. In particular, when stainless steel pickled with a non-oxidizing acid such as hydrochloric acid or sulfuric acid is incorporated in a polymer electrolyte fuel cell, a separator with reduced surface contact resistance is obtained. The reduction in surface contact resistance is presumed to be due to the formation of a thin passive film enriched with Cr on the stainless steel surface. That is, as the Cr concentration increases, the passive film becomes thinner, so the contact resistance also decreases. Actually, the immersion treatment conditions were set so that the contact resistance with carbon paper was 5 mΩ · cm 2 or less at a measurement pressure of 20 kgf / cm 2 after being left in a humid atmosphere of temperature: 70 ° C. and relative humidity: 98% for 72 hours. It was found that the contact resistance was maintained at a low level even after a long-time wet test simulating the internal environment of the fuel cell by controlling.
表１のオーステナイト系ステンレス鋼を濃度１０質量％の塩酸に５分浸漬した後、温度：７０℃，相対湿度：９８％の湿潤雰囲気に７２時間放置する湿潤試験に供した。湿潤試験前後に測定圧力：２０ｋｇｆ／ｃｍ2でカーボンペーパに対する接触抵抗を測定し、接触抵抗の変化を調査した。 The austenitic stainless steel shown in Table 1 was immersed in hydrochloric acid having a concentration of 10% by mass for 5 minutes and then subjected to a wet test in which it was left in a humid atmosphere at a temperature of 70 ° C. and a relative humidity of 98% for 72 hours. Before and after the wet test, the contact resistance against carbon paper was measured at a measurement pressure of 20 kgf / cm 2 , and the change in contact resistance was investigated.
湿潤試験前では何れの鋼種も５ｍΩ・ｃｍ2以下の低い接触抵抗を示していた。しかし、湿潤試験後の接触抵抗は、鋼種Ａ-4〜Ａ-8で５ｍΩ・ｃｍ2以下の低位を維持したが、Ｃｒ含有量が不足する鋼種Ａ-1〜Ａ-3では１０ｍΩ・ｃｍ2を超えていた（図１）。別の実験で、湿潤試験前後における接触抵抗の変動傾向は、ステンレス鋼のＣｒ含有量：１９質量％を境に変わることが確認され、Ｃｒ：２０質量％以上のステンレス鋼製セパレータではＮｉ，Ｍｏ含有量に拘わらず低接触抵抗が維持されることが判った。 Before the wet test, all steel types showed a low contact resistance of 5 mΩ · cm 2 or less. However, the contact resistance after humidity test is maintained a 5 m [Omega · cm 2 or less of low in steels A-4~A-8, steels A-1 to A-3 in 10 m [Omega · cm 2 which Cr content is insufficient (Fig. 1). In another experiment, it was confirmed that the fluctuation tendency of the contact resistance before and after the wet test changes at the boundary of the Cr content of stainless steel: 19% by mass, and in the stainless steel separator with Cr: 20% by mass or more, Ni, Mo It was found that low contact resistance was maintained regardless of the content.
湿潤試験後の接触抵抗変動に関する臨界値がステンレス鋼のＣｒ含有量にあることは、次のように推察される。
鋼種Ａ-1，Ａ-5をそれぞれ接触抵抗が最も低下する条件で塩酸溶液に浸漬し、生成した不動態皮膜をTEM観察した。TEM観察では、ビーム径：１ｎｍのX線をUTW型シリコン半導体検出器から不動態皮膜に照射し、不動態皮膜のEDSスペクトルを検出した。得られたEDSスペクトルをピーク分離し、半定量化処理によってＦｅ，Ｃｒ，Ｎｉ，Ｍｏの質量比を算出した。
It is guessed as follows that the critical value regarding the contact resistance fluctuation after the wet test is in the Cr content of stainless steel.
Steel types A-1 and A-5 were each immersed in a hydrochloric acid solution under the condition that the contact resistance was the lowest, and the formed passive film was observed by TEM. In TEM observation, the passive film was irradiated with X-rays having a beam diameter of 1 nm from a UTW type silicon semiconductor detector, and the EDS spectrum of the passive film was detected. The obtained EDS spectrum was subjected to peak separation, and the mass ratio of Fe, Cr, Ni, and Mo was calculated by a semi-quantification process.
図２の算出結果にみられるように、湿潤試験後に接触抵抗が増大した鋼種Ａ-1では、不動態皮膜のＣｒ濃度が鋼中Ｃｒ濃度に対応して低く、高温・高湿度の環境下で下地鋼が容易に酸化されて不動態皮膜が厚膜化し、結果として接触抵抗が上昇した。 As can be seen from the calculation results in FIG. 2, in steel type A-1, whose contact resistance increased after the wet test, the Cr concentration in the passive film was low corresponding to the Cr concentration in the steel, and in a high temperature / high humidity environment. The base steel was easily oxidized and the passive film was thickened, resulting in an increase in contact resistance.
これに対し、湿潤試験後にも接触抵抗の増加が少ない鋼種Ａ-5（図３）では、不動態皮膜のＣｒ濃度が鋼中Ｃｒ濃度に対応して高くなっており、浸漬処理によるＣｒ濃度にも変動がない。この結果は、浸漬処理でステンレス鋼製セパレータの耐食性が低下しないことを意味する。また、鋼中のＮｉに着目すると、浸漬処理によって不動態皮膜のＮｉ量が増加している。不動態皮膜のＮｉ濃度が耐食性に及ぼす影響は定かでないが、Ｎｉ濃度の増加に相応して不動態皮膜のＦｅ量が減少することは確かであることから、湿潤環境下におけるＦｅの酸化抑制が長期にわたって低接触抵抗が維持される原因の一つと考えられる。因みに、湿潤環境下で接触抵抗が増大した鋼種Ａ-1では、不動態皮膜のＦｅ量が増加している。 On the other hand, in steel type A-5 (Fig. 3) in which the increase in contact resistance is small even after the wet test, the Cr concentration of the passive film is high corresponding to the Cr concentration in the steel, There is no change. This result means that the corrosion resistance of the stainless steel separator is not lowered by the immersion treatment. When attention is focused on Ni in the steel, the amount of Ni in the passive film is increased by the immersion treatment. Although the influence of the Ni concentration of the passive film on the corrosion resistance is uncertain, it is certain that the Fe content of the passive film decreases as the Ni concentration increases. This is considered to be one of the reasons why low contact resistance is maintained over a long period of time. Incidentally, in the steel type A-1 having increased contact resistance in a wet environment, the Fe content of the passive film is increased.
次いで、鋼種Ａ-5を使用し浸漬処理が不動態皮膜のＣｒ濃度，接触抵抗に及ぼす影響を調査した。
浸漬処理では、濃度：５質量％，液温：６０℃のオルトケイ酸ソーダ溶液にステンレス鋼を浸漬して１０秒間電解脱脂した後、濃度：１０質量％，液温：５０℃の塩酸溶液に浸漬した。塩酸浸漬後、直ちに水洗し、ドライヤで乾燥させた。なお、接触抵抗に及ぼす不動態皮膜の影響を調査するため，塩酸浸漬時間を種々変更した。
Next, the effect of immersion treatment on Cr concentration and contact resistance of the passive film was investigated using steel type A-5.
In the immersion treatment, stainless steel is immersed in a sodium orthosilicate solution having a concentration of 5% by mass and a liquid temperature of 60 ° C. and electrolytic degreasing for 10 seconds, and then immersed in a hydrochloric acid solution having a concentration of 10% by mass and a liquid temperature of 50 ° C. did. After immersion in hydrochloric acid, it was immediately washed with water and dried with a dryer. In order to investigate the influence of the passive film on the contact resistance, the hydrochloric acid immersion time was variously changed.
浸漬処理後のステンレス鋼から試験片を切り出し、カーボンペーパ（電極）を荷重：２０ｋｇｆ／ｃｍ2で接触させ、ステンレス鋼／カーボンペーパの接触抵抗を測定した。浸漬処理していない未処理ステンレス鋼の接触抵抗は１２０ｍΩ・ｃｍ2であったが、浸漬時間が長くなるに従って接触抵抗が低下し、５分の浸漬処理で約１.９ｍΩ・ｃｍ2となった。しかし、更に長い時間かけて浸漬処理すると却って接触抵抗が増加した。
浸漬処理５分のステンレス鋼を温度：７０℃，相対湿度：９８％の湿潤試験に供した。接触抵抗は１０００時間の湿潤試験後にも５ｍΩ・ｃｍ2以下であり、燃料電池の内部環境でも低い接触抵抗が維持されることが確認できる。
A test piece was cut out from the stainless steel after the immersion treatment, a carbon paper (electrode) was brought into contact with a load of 20 kgf / cm 2 , and the contact resistance of the stainless steel / carbon paper was measured. The contact resistance of the untreated stainless steel not subjected to the immersion treatment was 120 mΩ · cm 2 , but the contact resistance decreased as the immersion time became longer, and was about 1.9 mΩ · cm 2 after the immersion treatment for 5 minutes. . However, the contact resistance increased when the immersion treatment was performed for a longer time.
The stainless steel immersed for 5 minutes was subjected to a wet test at a temperature of 70 ° C. and a relative humidity of 98%. The contact resistance is 5 mΩ · cm 2 or less even after a 1000 hour wet test, and it can be confirmed that a low contact resistance is maintained even in the internal environment of the fuel cell.
板厚：０.２５ｍｍの鋼種Ａ-5（２５Ｃｒ-２０Ｎｉ）をセパレータ形状にプレス成形した後、濃度：１０質量％，温度：５０℃の塩酸に浸漬した。５分浸漬後、水洗し、乾燥させた。
また、片面に白金触媒層を１ｍｇ／ｃｍ2の割合で塗布した厚さ：３６０μｍのカーボンペーパ（TGP-H-120：東レ製）を膜厚：５０μｍのフッ素イオン交換膜（商品名：ナフィオン112）にホットプレスすることにより膜-電極接合体を作製した。膜-電極接合体を中心としてステンレス鋼製セパレータを両側に配置し、燃料電池の単セルを組み上げた。
Plate type: Steel type A-5 (25Cr-20Ni) having a thickness of 0.25 mm was press-formed into a separator shape, and then immersed in hydrochloric acid having a concentration of 10% by mass and a temperature of 50 ° C. After immersion for 5 minutes, it was washed with water and dried.
Also, a platinum catalyst layer coated on one side at a rate of 1 mg / cm 2 Thickness: 360 μm carbon paper (TGP-H-120: manufactured by Toray Industries), film thickness: 50 μm fluorine ion exchange membrane (trade name: Nafion 112) The membrane-electrode assembly was manufactured by hot pressing. A stainless steel separator was placed on both sides centering on the membrane-electrode assembly, and a single cell of the fuel cell was assembled.
単セルを７０℃に保ち、アノード側に純水素，カソード側に空気を流し発電させたところ、電流密度０.３Ａ／ｃｍ2，連続２０００時間の放電でセル電圧が０.６２Ｖから０.６１Ｖに低下したが、電圧降下は僅か０.０１Ｖに留まっていた。比較のため塩酸浸漬したSUS316Lステンレス鋼製のセパレータを同様に組み込んだ単セルでは初期のセル電圧が０.６２Ｖと同等であったが、連続放電２０００時間後に０.５Ｖと低下しており、電圧降下が０.１１Ｖと大きな値を示した。
この対比から明らかなように、酸浸漬処理で表面改質したオーステナイト系ステンレス鋼をセパレータに使用するとき、長時間運転後にも電圧降下が少なく、高い発電効率を維持する燃料電池が得られることが判る。
When the single cell was maintained at 70 ° C. and pure hydrogen was supplied to the anode side and air was supplied to the cathode side to generate electricity, the cell voltage changed from 0.62 V to 0.61 V with a current density of 0.3 A / cm 2 and a continuous 2000 hour discharge. However, the voltage drop was only 0.01V. For comparison, in the single cell similarly incorporating a separator made of SUS316L stainless steel immersed in hydrochloric acid, the initial cell voltage was equivalent to 0.62 V, but it decreased to 0.5 V after 2000 hours of continuous discharge. The drop was as large as 0.11V.
As is clear from this comparison, when austenitic stainless steel surface-modified by acid dipping treatment is used for the separator, a fuel cell can be obtained that maintains high power generation efficiency with little voltage drop even after long-time operation. I understand.
以上に説明したように、高Ｃｒ含有オーステナイト系ステンレス鋼を基材とし、非酸化性酸を用いた浸漬処理で表面改質するとき、本来の高耐食性を活かしながら、燃料電池内の酸性湿潤雰囲気に長時間曝されても接触抵抗が低位に維持されるステンレス鋼製セパレータが得られる。ステンレス鋼製であるため複雑なセパレータ形状へも容易に加工でき、安価で長期耐久性に優れ発電効率が高位に安定した固体高分子型燃料電池が構築される。 As described above, when the surface is modified by immersion treatment using a non-oxidizing acid based on a high Cr content austenitic stainless steel, the acidic wet atmosphere in the fuel cell is utilized while utilizing the original high corrosion resistance. A stainless steel separator whose contact resistance is maintained at a low level even when exposed to a long time is obtained. Since it is made of stainless steel, it can be easily processed into a complicated separator shape, and a solid polymer fuel cell is constructed that is inexpensive, has long-term durability, and has a stable power generation efficiency.
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| KR100801429B1 (en) | 2006-10-16 | 2008-02-05 | 현대하이스코 주식회사 | The method for manufacturing a metal seperator of fuel cell |
| KR100844023B1 (en) | 2008-02-19 | 2008-07-04 | 현대하이스코 주식회사 | Stainless separator for fuel cell having metal coating surface and method for the same |
| US9493860B2 (en) | 2012-04-04 | 2016-11-15 | Nippon Steel & Sumitomo Metal Corporation | Chromium-containing austenitic alloy |
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| JP2002270196A (en) * | 2001-03-07 | 2002-09-20 | Matsushita Electric Ind Co Ltd | High molecular electrolyte type fuel cell and operating method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR100801429B1 (en) | 2006-10-16 | 2008-02-05 | 현대하이스코 주식회사 | The method for manufacturing a metal seperator of fuel cell |
| KR100844023B1 (en) | 2008-02-19 | 2008-07-04 | 현대하이스코 주식회사 | Stainless separator for fuel cell having metal coating surface and method for the same |
| US9493860B2 (en) | 2012-04-04 | 2016-11-15 | Nippon Steel & Sumitomo Metal Corporation | Chromium-containing austenitic alloy |
| KR20170003709A (en) * | 2012-04-04 | 2017-01-09 | 신닛테츠스미킨 카부시키카이샤 | Cr-containing austenitic alloy |
| KR101996712B1 (en) * | 2012-04-04 | 2019-07-04 | 닛폰세이테츠 가부시키가이샤 | Cr-containing austenitic alloy |
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