PtAu雙金屬奈米顆粒製作與其在電化學反應的特性研究

Preparation of PtAu Bimetal Nanoparticles for Electrochemical Characteristic Study

郭思汝(Szu-Ju Kuo)

指導教授 ： 林昇佃

共同指導教授 ： 葉君棣(Chuin-T. Yeh)

元智大學/工程學院/化學工程與材料科學學系/碩士(2009年)

摘要

本研究以實驗室先前開發的鉑奈米溶膠觸媒(Pt sols)進行AuCl3(aq)沈積改質，製作Au修飾的Pt顆粒，並探討金的添加對燃料電池陰極白氧氣還原反應的活性與安定性影響。雙金屬觸媒顆粒係以甲醇-citrate系統製作2-3 nm的單顆Pt奈米顆粒，再於室溫下添加不同量的AuCl3經過8小時可製備出4-5 nm的PtAu雙金屬觸媒。TEM分析顯示添加AuCl3後經不同的時間攪拌後，所得PtAuxML顆粒有逐漸變大的趨勢，可推論Au還原在Pt顆粒表面上。藉由XANES分析得知sols溶液的Pt L3-edge white line上升，由Pt還原態偏向氧化態，顯示有PtAu的氧化還原作用，XPS則顯示乾燥後奈米顆粒的Pt金屬價態帶有微小的負電荷，顯示Pt-Au間有電子轉移作用。XRD分析則顯示可能具有的合金結構。電化學實驗結果顯示，隨Au添加攪拌時間增加，所得PtAuxML奈米雙金屬的電化學活性面積及ORR特徵活性有提升的趨勢，但對於ORR反應的觸媒穩定性並無顯著的提升效果，而CO剝除實驗顯示Au添加觸媒可使CO氧化峰提早，可見PtAu奈米雙金屬顆粒可改善燃料電池效能及增加活性。

關鍵字

PtAu sols ； 陰極氧氣還原反應 ； CO剝除

並列摘要

Platinum nanoparticles of 2 - 3 nm were modified by depositing submonolyaer Au. The effect of Au deposition on the activities and stability of Pt nanoparticles were examined for the cathodic oxygen reduction and the CO oxidation reactions.
The deposition using AuCl3 was carried out at 298 K in the methanol-citrate system containing the preformed Pt sol. TEM analysis indicated that the PtAu nanoparticles increased in size with agitation time after addition of AuCl3 and PtAu of 4 – 5 nm size were found after 8 h of agitation. An increase in the white line intensity of Pt L3-edge x-ray absorbance over the PtAu sols suggests that Au deposition may occur via redox reactions. On the other hand, XPS analysis indicated slight increase in Pt electron density in the PtAu collected over carbon support. This suggests charge transfer from Au to Pt. XRD data indicated that PtAu alloy nanoparticles were obtained.
Electrochemical analysis indicated slight increase in per-gram electrochemical active area and per-gram oxygen reduction activity with increase of agitation time after Au addition. However, no significant change in the specific oxygen reduction activity was found. The PtAu showed better CO oxidation activity than the unmodified Pt sols, indicated by the lower onset potential during CO stripping experiments. The results of this study indicated that submonolayer Au deposition can improve the electrochemical activities of Pt catalysts for both the oxygen reduction reaction and the CO oxidation in acidic electrolyte.

並列關鍵字

PtAu sols ； ORR ； CO-stripping

參考文獻

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