觸媒/奈米碳管複合材料對均一化再生型燃料電池效能影響之研究

Study on Effects of Catalyst/Carbon Nanotubes Composite Electrocatalysts for the Performance of Unitized Regenerative Fuel Cell

張政雄(Cheng-Hsiung Chang)

指導教授 ： 江右君

元智大學/工程學院/機械工程學系/碩士(2008年)

https://doi.org/10.6838/YZU.2008.00216

摘要

均一化再生型燃料電池(URFC)的關鍵技術在於觸媒層，因此除了改良觸媒並增進性能之外，減少觸媒使用量進而減少成本的支出為最大的課題。本研究試著加入奈米碳管與觸媒結合，其原因在於奈米碳管有結構一致和良好的導電性的優點，可以使得觸媒附著或鍵結在奈米碳管表面，達到增加URFC的性能與降低觸媒使用量的目的。
本研究利用含浸法合成Pt與Pt-Ir觸媒，使用化學氣相沉積法進行奈米碳管合成與純化，並進一步製備觸媒/奈米碳管複合材料，使用表面檢測技術進行樣本表面特性分析。接著測試金屬觸媒或奈米碳管複合材料所製成之MEA，對於URFC在燃料電池模式與水電解模式之效能。
利用含浸法合成的Pt觸媒其純度可達99 wt. %，而Pt-Ir觸媒則是約96 wt. %，Pt與Pt-Ir觸媒顆粒大小均約為5-10 nm。合成的Pt與Pt-Ir觸媒的X光繞射分析圖譜，皆有f.c.c結構的Pt或Pt-Ir繞射峰出現。利用CVD法合成的奈米碳管由電子顯微影像發現，其細長且彎曲並有著捲曲糾纏的現象，直徑大約30-80 nm。觸媒/奈米碳管複合材料之電子顯微影像可確認觸媒均勻附著於奈米碳管管壁上。進行URFC的測試後發現，在燃料電池模式，氫氧兩端皆加入商用奈米碳管的性能最佳。在水電解模式中，氫氧兩端皆加入自行合成且純化過的商用奈米碳管可產生最佳效能，甚至優於純金屬觸媒MEA的性能。在產氫能力方面，以氫氧兩端皆加入自製且純化過的奈米碳管即可產生穩定且最大的氫氣產量。

關鍵字

均一化再生型燃料電池 ； 觸媒 ； 奈米碳管 ； 特性分析

並列摘要

The key technology on development of the unitized regenerative fuel cell (URFC) is in catalysts. Therefore, besides the enhancement of catalysts to improve the performance, reduction in the use of catalyst to decrease the cost of system has become the most important issue. This study has attempted to introduce the carbon nanotubes (CNTs) into the catalyst, based on the fact that CNTs have uniform structure and excellent conductivity. This is expected that the catalyst would have good dispersion on CNT surface, thus the high performance of URFC and the decrease in the catalyst use can be achieved.
The impregnation method was employed to prepare the Pt and Pt-Ir catalysts, and the chemical vapor deposition method was used to synthesize the multi-walled carbon nanotubes. And then the catalyst/CNTs composite materials were prepared. All materials were characterized by surface techniques. Next, several sets of membrane electrode assembly (MEA) were made and the performance of URFC on water electrolysis and fuel cell modes were tested.
The results show that the Pt catalyst from impregnation method has a purity of about 99 %, and the purity of Pt-Ir catalyst is approximately 96 %. Both the mean particle sizes of Pt and Pt-Ir catalysts were in the range of 5-10 nm. The XRD patterns indicate Pt (or Pt-Ir) catalyst displays the Pt (or Pt and Ir) fcc structure. The TEM images show that the as-grown CNTs are long and spaghetti-like with a diameter of probably 30-80 nm. The HRTEM images of catalyst/CNT composite also manifest the good dispersion of the catalyst on CNT surface. The test results of URFC show that in fuel cell mode the best capacity occurs as both oxygen and hydrogen electrodes are added the commercial CNTs. In water electrolysis mode, introduction of pCNT onto both electrodes perform the best capacity, which is even superior to that of the MEA composed of noble metals. In view of the hydrogen production, introduction of CNTs only on oxygen electrode can achieve stable and the highest yield.

並列關鍵字

Unitized regenerative fuel cell ； Catalyst ； Carbon nanotubes ； Characterization

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