奈米白金/氧化鎳/多壁奈米碳管混成電觸媒之合成與特性研究

Synthesis and Characterization of Pt/NiO/MWCNTs Hybrid Electrocatalysts

鄭伊伶(I-Ling Cheng)

指導教授 ： 林鴻明

大同大學/工程學院/材料工程學系所/碩士(2010年)

摘要

本研究動機在於合成奈米混成觸媒，以開發燃料電池之陽極材料，並對此材料之結構特性與電化學反應之間做相關性的實驗與討論。期望經由導入多壁奈米碳管作為載體，製作混成鉑與氧化鎳觸媒系統，研究此三相結構所造成的電催化反應。
第一部分以多元醇法合成以碳黑(Vulcan xc-72)、奈米碳管為載體的鉑系混成觸媒，藉由電催化實驗來探討載體效應。實驗結果顯示，整體電流強度以鉑/奈米碳管具有較優異的表現。第二部分以化學沉浸法合成奈米碳管承載氧化鎳之混成材料，藉由電催化效應之實驗結果顯示，此混成材料不具電觸媒特性。
第三、四部分結合化學沉浸法與多元醇法，成功地合成不同比例成份之鉑/氧化鎳/奈米碳管混成材料。經多元醇法還原出之奈米鉑微粒，粒徑約為3-7奈米，均勻分散於約10奈米之氧化鎳及奈米碳管表面。以靜電噴塗法製備電極進行循環伏安量測，比較不同成分比例之鉑/氧化鎳/奈米碳管混成材料和鉑/奈米碳管之電催化反應。實驗結果顯示，鉑/氧化鎳/奈米碳管具有比鉑/奈米碳管高之電流密度，其中以鉑(10wt%)/氧化鎳/奈米碳管具有最高之電流密度。我們推論，氧化鎳可以提供氧，將吸附於鉑表面的一氧化碳予以氧化，此一行為可解決燃料電池陽極觸媒金屬被一氧化碳毒化之問題。同時，使用少量的鉑即可達到高電流密度，成本得以降低。所以，本研究驗證此新型之奈米混成觸媒可能成為高效益低成本之燃料電池陽極觸媒材料。

關鍵字

直接甲醇燃料電池 ； 觸媒 ； 白金 ； 氧化鎳

並列摘要

The motivation of this study is to synthesis a novel nano-hybrid catalysts for anode materials in fuel cell application. The electro-catalytic characteristic of the nano-hybrid catalyst is also studied. Multi-walled carbon nanotubes are used as support to examine the supporting effect for electro-catalysts.
First, Pt/Vulcan-xc72, and Pt/MWCNTs are synthesized by polyol method to study the supporting effect. The result of C-V analysis shows the eletro-catalytic behavior of Pt/MWCNTs is better than that of Pt/Vulcan-xc72. This indicates the good supporting effect of carbon nanotubes.
The nanocomposite Pt/NiO/MWCNTs are prepared by two-step procedure, impregnation method and polyol methods, with different ratio of Pt/(NiO-MWCNTs) and NiO/(Pt-MWCNTs). The structures of catalysts are characterized by FESEM, HRTEM and XRD. The contents of each component in the nanocomposites are determined by TGA. The results indciate the novel Pt/NiO/MWCNTs can be synthesized successfully. The particle sizes of NiO and Pt are about 10nm and 3-5 nm, respectively. The CO poisoning behavior of catalysts during methanol oxidation reactions have been investigated in C-V measurements. The results of C-V analysis show that the addition of NiO will enhance the electro-catalyst performance than that of pure Pt/MWCNTs. The best composition of nano-hybrid catalyst is Pt(10wt%)/(NiO-MWCNTs). The addition of NiO may provide oxygen to oxidize the carbon monoxide which adsorbs on the surface of Pt catalyst. This CO oxidation behavior may solve the problem of CO poison to Pt catalyst. Moreover, the less using amount of Pt has higher oxidation current density that will low the cost of catalysts to be used. The synthesized novel nano-hybrid catalysts in this study can be an excellent candidate for anode materials in fuel cell application.

並列關鍵字

catalyst ； Pt ； NiO ； DMFC

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