以DPG人工石墨為質子交換膜燃料電池白金觸媒載體的研究

Abstract

質子交換膜燃料電池是一種乾淨的能源，而其中又以觸媒層及交換膜為發展重點，一般質子交換膜燃料電池使用的觸媒是鉑觸媒及鉑釕觸媒，其中觸媒皆是以碳黑為載體，碳黑是一種比表面積大而傳導性又不差的碳載體，目前研究指出，當燃料電池運作時，碳黑有可能因為腐蝕和氧化，使得吸附於其上的金屬觸媒顆粒產生凝聚，故在觸媒層的研究一般致力於改善顆粒凝聚、二元合金的抗毒化性質及載體的腐蝕性、傳導性。 本實驗主要以自製人工石墨粉來取代部分碳黑載體，因自製人工石墨粉中含有少量奈米碳管，希望可以利用奈米碳管及立體結構石墨，使得金屬觸媒顆粒達到分散效果和電化學效能的改進。使用X-Ray繞射儀及X-Ray光電子能譜儀分析所合成的觸媒顆粒是否為金屬顆粒；利用穿透式電子顯微鏡觀察觸媒顆粒的大小；最後使用電化學循環伏安法求得交換電流大小，以檢測觸媒效能。在碳黑載體中加入30 wt.%的自製人工石墨粉，雖然不能使得觸媒顆粒成長的更小，但是由交換電流的大小可以得知，在Pt/C及Pt-Ru/C兩組觸媒中，交換電流分別提高了9 %及19 %。 經由循環伏安法的結果可以得知，人工石墨粉中的奈米碳管及立體狀石墨有助於改善觸媒的效能。

Proton exchange membrane fuel cell is a clean energy. After hydrogen oxidation and oxygen reduction, the final product is water. The catalysts and membrane play an important role in fuel cell system. The platinum and platinum- ruthenium was the most popular catalyst. And the support was usually carbon black. Carbon black had good conductivity and large specific surface area. The surface of carbon black is oxidized under the cathode environment of a PEFC. Thus, the platinum particles would be agglomerated. In this work, the DPG powders containing few CNTs(carbon nanotubes) and three dimension structure graphite were used as the support of catalyst in proton exchange membrane fuel cell. The CNTs(carbon nanotubes) and three dimension structure graphite might make the catalyst disperse well and the promotion of the electrochemical performance. TEM image of the Pt nanoparticles were obtained by using a JEM-2000FX operating at 200 kV. Exchange current was obtained by cyclic voltammetry method. Exchange current of catalyst supported on mixing powders containing 30 wt.% DPG are higher by 9% and 19%, respectively, than exchange current of catalyst supported on 100wt.% carbon black. The DPG powders containing few fullerenes and CNTs(carbon nanotubes) could be used as the support of catalyst in proton exchange membrane fuel cell.