質子交換膜燃料電池陰極觸媒合成、鑑定及活性測試

The Synthesis and Characterization Pt/C Cathode Catalysts for PEMFC

廖怡萱(I-Hsuan Liao)

指導教授 ： 林昇佃

元智大學/工程學院/化學工程與材料科學學系/碩士(2005年)

摘要

本研究目的在於建立碳載體改質技術，合成適合用於質子交換膜燃料電池電極觸媒之碳材，使用於載體鉑觸媒合成，配合氧分子還原活性測試及碳材與觸媒性質分析，建立碳材構造與觸媒活性之關係，篩選出合成最適化觸媒之碳材及觸媒合成方法。
目前用於高分子電解質膜燃料電池最有效之電極觸媒為Pt/C載體觸媒，由於碳載體的性質直接影響載體觸媒的催化效率及穩定，本研究以探討商業碳載體改質處理為切入點，探討影響碳載體特性的關鍵改質參數。藉碳載體改質來提升觸媒的活性、鉑金屬的使用率及降低生產成本。本研究使用目前最常用於燃料電極觸媒合成之Cabot 公司Vulcan XC-72為基材，使用雙氧水為氧化劑，對碳黑表面進行改質反應，增加碳黑表面之含氧官能基，藉以調整碳黑的親疏水性及提升碳黑與觸媒前驅體在觸媒合成過程時之作用力。亦同時使用膠體化方法合成膠體化鉑溶液，探討合成條件對鉑粒徑及穩定性之影響，作為後續研究使用膠體化方法合成載體觸媒前驅體溶液合成之參考。

關鍵字

質子交換膜燃料電池 ； 觸媒 ； 碳黑 ； 陰極

並列摘要

Support plays a vital role in the performance of a catalyst. This issue is more profound in proton exchange membrane fuel cell (PEMFC) applications in which electrocatalysts with very high loading of expensive precious metals are used. Platinum supported on carbon is currently the state-of-the-art cathode catalyst for PEMFC. Carbon black is the choice of catalyst support despite its physical and chemical properties are still not adequate for the demand of PEMFC electrocatalyst. Surface oxidation was employed in this study to enhance the amount of oxygen functional groups on the surface. Commercial carbon black (Cabot XC-72) was used as the carbon and hydrogen peroxide (H2O2) was used as the oxidizing agent in this study. Pt/C catalysts were prepared using carbons with variable amount of oxygen functional groups prepared. Relationship between surface functionality of carbon support and catalyst activity in the oxygen reduction reaction (ORR) was developed.
XPS, TPD and DRIFT results revealed that H2O2 treatment of XC-72 resulted in the formation of oxygen containing functional groups on the surface. The amount of oxygen functional group on carbon surface depends on the concentration of H2O2 employed; the temperature and time of treatment also affect the amount of oxygen on the carbon support. Furthermore, weak acidic surface sites are formed predominantly when H2O2 was used as the oxidizing agent. More active catalysts for the ORR are formed in using carbons with larger amount of weak acid sites, in conjunction with impregnation preparation method. Catalysts with Pt particle size (TEM) of Pt ranged from 1.9~5.8 nm were prepared depending on the type of carbon, preparation method and precursor used. Catalysts with Pt particle sizes around 3.0~3.5 nm showed the best activity towards ORR activity test.

並列關鍵字

PEMFC ； catalyst ； carbon black ； cathode

參考文獻

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