雙金屬合金觸媒PdxFe1-x其結構對燃料電池陰極氧氣還原反應之電催化活性

Investigation on Electrochemical Activity and Catalyst Structure of PdxFe1-x Nanoparticle as Cathode Catalyst for Oxygen Reduction Reaction

吳禹函(Yu-Han Wu)

指導教授 ： 陳家俊

國立臺灣師範大學/理學院/化學系/碩士(2010年)

摘要

本篇主旨在利用不同方法合成出13nm、7nm及4nm之PdxFe1-x奈米粒子，做為燃料電池陰極觸媒，成本較傳統市售的白金觸媒來的低，並調控Pd及Fe的組成比例，由XRD、TEM、EDS與XAS中的XANES及EXAFS來鑑定奈米粒子之結構及表面組成，並進行電化學分析，利用旋轉電極測量其對氧氣還原反應的催化活性，探討PdxFe1-x的電催化特性與其結構間的關係，發現4nm之PdxFe1-x奈米粒子擁有較佳的催化效果，根據結果顯示，隨著奈米粒子之粒徑趨於變大，則氧氣還原反應的onset potential將向負偏移，而Fe及Pd的表面組成比越趨近於一比一，則mass activity越大，表是吾人利用水相合成出ultra small且表面組成比為一比一的PdxFe1-x/C奈米粒子在燃料電池陰極氧氣還原反應擁有良好的催化特性。

關鍵字

直接甲醇燃料電池 ； 陰極觸媒 ； 氧氣還原反應

並列摘要

The major goal in this research was to develop the electrocatalysts with high activity for oxygen reduction reaction. To date, one of the major challenges to commercialization of fuel cell is to develop cheap and stable fuel cell catalysts for the ORR. To reduce the usage of noble metal, the PdFe catalysts have attracted considerable attention. The reasons are attributed to that Pd is comparatively cheaper than Pt and PdFe demonstrates very high methanol tolerance. These carbon-supported bimetallic electrocatalysts PdxFe1-x were synthesized by three different methods and their particle size were 13nm, 7nm and 4nm respectively. The synthesized catalysts were characterized in terms of structure morphology and catalysts activity by XRD, TEM, EDS and electrochemical measurements. The kinetics of ORR was studied in acid solution by using the rotating disk electrode method. The results showed that the ORR onset potentials of PdxFe1-x showed a shift to more positive potentials with decrease of the particle size. Moreover, the 4 nm PdxFe1-x/C catalysts have best catalytic activity in ORR. Then we found the relationship between catalyst structure and the electrochemical activity of the electrocatalysts, and utilized the XAS technique to study the structure and surface composition. The PdFe catalyst with a surface composition of 50：50 demonstrated high catalytic properties for the ORR and mass activity.

並列關鍵字

DMFC ； cathodic catalyst ； oxygen reduction reaction

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