高溫型質子交換膜燃料電池性能活化與老化效應研究

聚苯咪噬的發明，實現了在高溫(120~200oC)下操作質子交換膜燃料電池的需求。在此溫度下電池內部的液態水大致皆蒸發為氣態，因此在低溫型質子交換膜燃料電池內部的積水現象獲得明顯改善。其次隨著操作溫度的上升，觸媒對一氧化碳的忍受能力也隨之上升。當高溫型質子交換膜燃料電池搭配燃料重組器的操作，可減少低溫型質子交換膜燃料電池對重組後燃料成分的嚴苛要求。類似低溫Nafion 膜材之質子交換膜燃料電池的長時間活化現象，PBI 之高溫質子交換膜燃料電池尤須更長時間活化方得穩定且高性能輸出。先前研究中，負載0.2、0.4A/cm2進行長時間放電，所得活化結果各有優劣。因此，在本研究中加入0.3A/cm2進行長時間放電，其最後結果優於0.2、0.4A/cm2。為了解活化成因，研究過程加入交流阻抗分析、循環伏安法等數據做為分析依據，發現活化與觸媒反應燃料的能力增加有關。對PBI質子交換膜燃料電池而言，入口溼度與放電後的生成水是一種負擔，過多的水會造成磷酸的析出，形成PBI membrane離子傳導的老化。因此本研究中加速老化操作分為三項：(1)入口燃料相對濕度控制為5%、10%、20%，測試MEA對濕度的忍受程度，而結果為相對濕度20%會導致MEA破損。(2)活化過程中燃料加濕，研究入口溼度對活化過程之影響，而結果為與乾燥燃料並無差異。(3)兩種燃料入口濕度0%、10%，三種電流負載0.3、0.8、1.6A/cm2進行老化實驗並交叉檢驗其變化。從極化曲線與交流阻抗分析的結果發現，燃料加濕與否影響將導致不同之膜電極阻老化現象。

關鍵字

聚苯咪噬；高溫型質子交換膜燃料電池；活化；老化

並列摘要

It’s the invention of polybenzimidazole (PBI) that makes proton exchange membrane fuel cell (PEMFC) operating at high temperature (120~200℃) possible. For cell temperature higher than 100℃, liquid water flooding that happens for current low temperature PEMFC would be ignored. In addition, tolerance of catalyst for CO would be increased. Therefore, requirement for CO concentration from reformer would be lower comparing to that for low temperature PEMFC. Currently, Nafion-based low temperature PEMFC experiences several hours as pre-treatment for attaining high and stable performance. Similar logic is also applicable for PBI-based high temperature PEMFC with a longer period of time. Previously, pre-treatments with 0.2 and 0.4 A/cm2 were used. In this study, 0.3 A/cm2 was used and we found that this is the optimal choice. Accompanying with AC impedance and cyclic voltammetry, increase of reactivity with catalyst, leading to activation of high temperature PEMFC. For PBI-based PEMFC, inlet fuel humidity and generated water would extract phosphoric acid out of PBI-based membrane and result in decay of its conductivity. In this study, three speeding up tests were used to investigate the decay phenomena via (1) three inlet fuel humidities including 5%, 10 % and 20% were used to learn the limitation of MEA durability and the result of 20% comes out with MEA damage. (2) dry and humidity fuel inlet were utilized to learn their effects on activation and the results come out with same trends. (3) two inlet fuel humidities including 5%, 10 % and three current output including 0.3、0.8、1.6A/cm2 were used alternately to investigate their effects on MEA decay. According to polarization and AC impedance analysis, different fuel humidity would result in distinct MEA decay phenomena.

並列關鍵字

Polybenzimidazole (PBI) ； proton exchange membrane fuel cell (PEMFC) ； activation ； Degradation

參考文獻

[25] 簡偉翔「高溫型質子交換膜燃料電池性能與活化效應探討」元智大學機械工程學系碩士論文(2007)

[2] Q.F.Li, R.H.He, J.O.Jensen, N.J.Bjerrum, The CO poisoning effect in PEMFCs operational at temperatures up to 200°C, J. Electrochem. Soc.150 (2003) A1599-A1605.

[3] K.Lee, A.Ishihara, S.Mitsushima, N.Kamiya, Effect of recast temperature on diffusion and dissolution of oxygen and morphological properties in recast nafion, J. Electrochem. Soc.151 (2004) A639-A645.

[4] G.Liu, H.M.Zhang, J.W.Hu, Y.F.Zhai, D.Y.Xu, Z.-G.Shao, 500 h continuous aging life test on PBI/H3PO4 high-temperature PEMFC, Int.J of Hydrogen Energy 31 (2006) 1855 – 1862

[5] J.O. Jensen, Q. Li, R. He, C. Pan, N.J. Bjerrum, 100–200 ｏC polymer fuel cells for use with NaAlH4, J.Alloys and Compounds 404–406 (2005) 653–656

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高溫型質子交換膜燃料電池性能活化與老化效應研究

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