Temperature Dependence of Oxygen Reduction Reaction Activity at Stabilized Pt Skin-PtCo Alloy/Graphitized Carbon Black Catalysts Prepared by a Modified Nanocapsule Method

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• 作者：Kazuki Okaya ; Hiroshi Yano ; Katsuyoshi Kakinuma ; Masahiro Watanabe ; Hiroyuki Uchida
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2012
• 出版时间：December 26, 2012
• 年：2012
• 卷：4
• 期：12
• 页码：6982-6991
• 全文大小：558K
• 年卷期：v.4,no.12(December 26, 2012)
• ISSN：1944-8252

文摘

We have developed a new catalyst supported on graphitized carbon black (GCB), which exhibits higher resistance to carbon corrosion than a conventional carbon black (CB), in order to favor both high mass activity for the oxygen reduction reaction (ORR) and high durability. To protect the underlying Pt_XCo alloy from corrosion and maintain the modified electronic structure, two monolayers of Pt-skin layer (Pt_2聽ML) were formed on the Pt_XCo core-particles, which were of uniform size and composition. Characterization of the Pt_2聽ML鈥揚tCo(X = 1)/GCB, both by a scanning transmission electron microscope (STEM) with an energy dispersive X-ray (EDX) analyzer and by X-ray diffraction (XRD), indicated the formation of the Pt_2聽ML on the PtCo alloy solid solution nanoparticles. The temperature dependence of the ORR activity of the Pt_2聽ML鈥揚tCo_(2聽nm)/GCB catalyst was evaluated from the hydrodynamic voltammograms in O₂-saturated 0.1 M HClO₄ solution at 30鈥?0 掳C by the channel flow double electrode (CFDE) technique. It was found that the Co dissolution from PtCo particles during the ORR was considerably suppressed by the stabilized Pt-skin structure. The kinetically controlled mass activity (MA_k) for the ORR at the Pt_2聽ML鈥揚tCo_(2聽nm)/GCB at E = 0.85 V vs reversible hydrogen electrode (RHE) was about two times larger than that for a standard commercial c-Pt/CB catalyst at 80鈥?0 掳C. The value of H₂O₂ yield at the Pt_2聽ML鈥揚tCo_(2聽nm)/GCB was found to be very low (0.2%), about one-half of that for c-Pt/CB, and it is thus better able to mitigate the degradation of the polymer electrolyte membrane and gasket material.

Keywords:

polymer electrolyte fuel cell; electrocatalyst; PtCo alloy; Pt-skin; oxygen reduction reaction