中溫PTFE/Nafion/TEOS膜之燃料電池低相對溼度操作之研究

Research of middle temperature PTFE/Nafion/TEOS membranes operating with low relative humidity

王峻聲(Jiun-Sheng Wang)

指導教授 ： 翁芳柏

元智大學/工程學院/機械工程學系/碩士(2006年)

https://doi.org/10.6838/YZU.2006.00095

摘要

本文研究以加入四乙氧基矽烷(tetraethoxysilane, TEOS)為新材料之自製薄膜PTFE/Nafion/TEOS(PNS膜)為PEMFC的新膜材，並探討其於低溫(60℃~70℃)不同入口相對溼度(25%RH~100%RH)操作之性能與長時間放電電壓穩定性並與一般MEA(Nafion112)比較，而在中溫(80℃~120℃)加入一固定背壓20psi或常壓下，於不同入口相對溼度(25%RH~100%RH)下操作，探討其性能與長時間放電電壓穩定性。
自製膜電極組(MEA)於低溫(60℃~70℃)下不論入口相對溼度如何性能皆優於一般MEA(Nafion112)，且長時間放電操作下電壓穩定性亦較一般MEA(Nafion112)好，在電池阻抗方面自製MEA表現亦穩定且阻抗值較低，這是因為新加入基材TEOS所持有的吸附水分子的性質的緣故。在中溫(80℃~120℃)操作部分，發現必須加入一背壓使電池壓力超過飽和蒸氣壓與氣體溶解度增加才能穩定操作。一般MEA在電池超過80℃的狀況已無法順利操作，而自製MEA的性能雖然隨著入口相對濕度的下降而下降，但其長時間放電電壓穩定性可忍受入口相對溼度降低至46.76%RH的操作尚能穩定。於低溫、中溫操作後再次於低溫操作，發現自製膜經過中低溫不同溼度變化長時間約100小時的操作後性能沒有明顯的差異。

關鍵字

中溫 ； PEMFC ； 複合膜 ； 矽酸鹽 ； TEOS ； 相對濕度

並列摘要

The performance and constant-current discharge stability of PTFE/Nafion/Silicate composite membranes(PNS membrane) prepared by impregnating PTFE/Nafion composite membrane via sol-gel processing with TEOS(tetraethoxysilane) is studied for operation at low temperature (60℃~70℃) and medium temperature(80℃~120℃) with different humidity(25%RH~100%RH), back pressure(0, 20psi) in PEMFC and compared with Nafion112 at the same conditions.When operated at low cell temperature (60℃~70℃) with different cell humidiy, PNS membrane performs better than Nafion112 and discharges at constant current more stable than Nafion112, which is due to that TEOS could hold water in PNS membrane. While operated at middle temperature (80℃~120℃),the results shows that PNS membranes couldn’t operate without back pressure, which let the cell pressure exceed saturation pressure and the solubility of hydrogen and oxygen in the liquid water film increase. The performance and stability of PNS membrane decrease with lower inlet relative humidity while a back pressure 20psi is applied, however the stability remains unless the inlet relative humidity lower than 46.76%RH. On the other hand, Nafion112 can not operate stably at cell temperature higher than 80℃, whether a back pressure is applied or not. After operated at low and middle temperature, repeat the experiment at low temperature with inlet gas 100%RH humidified and the results shows that the performances are similar, which means PNS membrane could operate at low and middle temperature with different inlet relative humidity at least 100 hours.

並列關鍵字

Medium temperature ； PEMFC ； Composite membrane ； Silicate ； relative humidity

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