We have prepared carbon-supported Pt-M (M = Fe, Co, and Ni) alloy nanoparticles with uniform size and composition as cathode catalysts for polymer electrolyte fuel cells. In order to protect the underlying Pt-M alloy from dealloying and maintain high mass activity for the oxygen reduction reaction (ORR), two atomic layers of Ptskin (Pt 2AL ) were formed on the Pt-M nanopartcicles. By means of various types of analysis, including X-ray diffraction (XRD), inductively coupled plasma mass analysis (ICP-MS), thermogravimetry (TG), and transmission electron microscopy (TEM), the formation of monodisperse Pt 2AL -Pt-M/C was confirmed. The kinetically-controlled ORR activities (mass activity, MA k , and area-specific activity, j k ) for the ORR at Nafion ® -coated Pt 2AL -Pt-M/C catalysts in O 2 -saturated 0.1 M HClO 4 solution were evaluated by the use of a multi-channel flow double electrode cell at 65°C. It was found that the initial value of MA k at Pt 2AL -PtNi/C was the highest, i.e., 3.3 times higher than that at a commercial catalyst, carbon-supported Pt (c-Pt/C). In contrast, the Pt 2AL -PtCo/C catalyst exhibited superior durability, so that dealloying was almost entirely suppressed, together with a great mitigation of the particle agglomeration after applying 10 4 cycles of potential steps between 0.6 V and 1.0 V.
Abstract:We have prepared Pt nanoparticles supported on titanium carbide (TiC) (Pt/TiC) as an alternative cathode catalyst with high durability at high potentials for polymer electrolyte fuel cells. The Pt/TiC catalysts with and without heat treatment were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Hemispherical Pt nanocrystals were found to be dispersed uniformly on the TiC support after heat treatment at 600 °C in 1% H2/N2 (Pt/TiC-600 °C). The electrochemical properties (cyclic voltammetry, electrochemically active area (ECA), and oxygen reduction reaction (ORR) activity) of Pt/TiC-600 °C and a commercial Pt/carbon black (c-Pt/CB) were evaluated by the rotating disk electrode (RDE) technique in 0.1 M HClO4 solution at 25 °C. It was found that the kinetically controlled mass activity for the ORR on Pt/TiC-600 °C at 0.85 V (507 A g ). Moreover, the durability of Pt/TiC-600 °C examined by a standard potential step protocol (E = 0.9 V↔1.3 V vs. RHE, holding 30 s at each E) was much higher than that for c-Pt/CB.
OPEN ACCESSCatalysts 2015, 5 967
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