Comparison between Dealloyed PtCo3 and PtCu3 Cathode Catalysts for Proton Exchange Membrane Fuel Cells

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• 作者：Zhiqiang Yu ; Junliang Zhang ; Zhongyi Liu ; Joseph M. Ziegelbauer ; Huolin Xin ; Indrajit Dutta ; David A. Muller ; Frederick T. Wagner
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：September 20, 2012
• 年：2012
• 卷：116
• 期：37
• 页码：19877-19885
• 全文大小：459K
• 年卷期：v.116,no.37(September 20, 2012)
• ISSN：1932-7455

文摘

Dealloyed PtCo₃ and PtCu₃ catalysts supported on high surface area carbon (HSC), which were synthesized under different conditions, were tested as cathode electrodes in proton exchange membrane fuel cells. The dealloyed PtCu₃/HSC gave higher initial oxygen reduction reaction (ORR) kinetic activity but much worse durability in a voltage cycling test. Detailed characterization was undertaken to develop insights toward the development of catalysts with both high activity and good durability. In situ X-ray absorption spectroscopy (XAS) analysis showed that dealloyed PtCu₃/HSC exhibited stronger bulk Pt鈥揚t compressive strains and higher bulk d-band vacancies (attributed in part to a greater ligand effect induced by Pt鈥揅u bonding) than dealloyed PtCo₃/HSC, factors which can be expected to correlate with the higher initial activity of dealloyed PtCu₃/HSC. Annular dark field (ADF) imaging and electron energy loss spectroscopy (EELS) mapping demonstrated that a strong majority of metal nanoparticles in both dealloyed PtCu₃/HSC and PtCo₃/HSC have variants of core鈥搒hell structures. However, the most prevalent structure in the dealloyed PtCo₃/HSC gave multiple dark spots in ADF images, approximately half of which were due to Co-rich alloy cores and half of which arose from voids or surface divots. In contrast, the ADF and EELS data for dealloyed PtCu₃/HSC suggested the predominance of Pt shells surrounding single Cu-rich cores. Further work is needed to determine whether the contrast in durability between these catalysts arises from this observed structural difference, from the differences between the corrosion chemistry of Cu and Co, or from other factors not addressed in this initial comparison between two specific catalysts.