應用於燃料電池氧氣還原反應之非貴金屬觸媒合成與特性分析

Synthesis and Characterization of Non-noble Metal Catalyst in Oxygen Reduction Reaction of Fuel Cells

杜孟修(Meng-Hsiu Tu)

指導教授 ： 劉如熹

國立臺灣大學/理學院/化學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.02879

摘要

燃料電池之效能主要決定於觸媒催化燃料分解之活性，一般係使用高活性之白金作為觸媒。然白金係貴金屬，其昂貴之價格已成為燃料電池商業化之主要問題。近年來研究學者嘗試將陰極觸媒以非貴金屬觸媒取代白金觸媒，為克服白金價格之其中一種方法。而非貴重金屬觸媒之氧氣還原反應活性低於白金觸媒，故現今研究著重於提升非貴金屬觸媒之活性。一般認為熱處理溫度與碳材對非貴金屬觸媒之結構具相當之影響，並對提升觸媒活性與穩定性具相當助益。此外，氮摻雜於碳材表面亦可催化氧氣還原反應，而氮摻雜產生之結構將受熱處理影響，不同結構之氮具不同催化活性。有鑑於熱處理溫度與碳材影響觸媒活性之機制至今仍未全盤了解，故研究此兩因素將有助於燃料電池之發展。
本研究以含浸法搭配氨氣氣氛變化熱處理溫度，將非貴金屬觸媒擔載於不同維度之碳材。藉由數種分析技術探討最適化合成觸媒之條件，以及零維與二維碳材對觸媒合成機制之影響。兩系列觸媒皆以X光粉末繞射儀分析觸媒之晶體結構；利用同步輻射之X光進行X光吸收光譜鑑定鐵離子之價數；以穿透式電子顯微鏡分析觸媒之形貌與粒徑大小；藉由X光光電子光譜鑑定觸媒之氮結構；以表面積分析儀量測觸媒比表面積；利用循環伏安電位儀於酸性環境進行觸媒氧還原活性量測與甲醇毒化測試。藉由上述方法，確認觸媒之鐵氮相將隨熱處理溫度增加而變化，並以700℃熱處理產生之Fe2N相具最佳活性。而碳材維度將影響觸媒乘載方式，進而可控制觸媒之粒徑與活性。

關鍵字

燃料電池 ； 氧氣還原反應 ； 非貴金屬觸媒 ； 石墨烯

並列摘要

The performance of fuel cell mainly determine by activity of catalyst for fuel decomposition. It’s usually using Pt-based catalyst due to high efficiency. However, Pt is a noble metal; expensive remained a major problem for development fuel cell commercialization. Recent research in cathode catalyst of fuel cell focused on non-noble metal catalyst substitution for Pt-based catalyst, it’s one of solutions to overcome this obstacle. However oxygen reduction reaction (ORR) activity of non-noble metal catalyst is lower than Pt-based catalyst. Thus, improve activity of non-noble metal catalyst become an important issue. Generally, catalytic structure and activity affect by heat treatment which will further influence nitrogen-doped structure in catalyst surface. Different types of nitrogen have different activity for oxygen reduction. Due to the role of heat treatment and carbon support are not fully understood yet, research on these two factors will assist in development fuel cell.
In the present study, synthesis catalyst by impregnation method with various heat temperatures in ammonia condition. Used several analytic techniques to optimize synthesis factors and study formation mechanism with 0 dimension and 2 dimension carbon support. Both catalytic series used X-ray powder diffraction to prove crystal structure. X-ray absorption spectroscopy by using synchrotron radiation was applied for oxidation number of iron. Practical size and morphology studied by transmission electron microscopy. X-ray photoelectron spectroscopy characterized structure of nitrogen in catalyst. Surface area analyzer measured specific surface area. ORR and methanol poison tested by cyclic voltammery. Confirm iron nitride of catalyst change with temperature increase. The best ORR activity is Fe2N phase from 700℃ heat treatment. The carbon support dimension induces diverse loading mode, furthermore control practical size and catalytic activity.

並列關鍵字

Fuel cell ； Oxygen reduction reaction ； Non-noble metal catalyst ； Graphene

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