Phase Behavior of Pseudobinary Precious Metal−Carbide Systems

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• 作者：John M. Gregoire ; Michele E. Tague ; Eva H. Smith ; Darren Dale ; Francis J. DiSalvo ; Hctor D. Abrua ; Richard G. Hennig ; R. Bruce van Dover
• 刊名：Journal of Physical Chemistry C
• 出版年：2010
• 出版时间：December 16, 2010
• 年：2010
• 卷：114
• 期：49
• 页码：21664-21671
• 全文大小：457K
• 年卷期：v.114,no.49(December 16, 2010)
• ISSN：1932-7455

文摘

Transition metal carbides exhibit a variety of interesting material properties, including electrochemical stability. When combined with precious metals, Ta and W carbides have shown promise as fuel cell electrode materials; yet, the phase behavior of these precious metal−carbide systems is largely unexplored. We investigated P-M-C phase behavior with P = Pt, Pd, and Ru and M = Ta and W using composition spread thin films. We attained limited control of the deposited carbide phase through variation of the sputter atmosphere and demonstrated decreased corrosion of W−C materials with increasing C content. A high-throughput X-ray diffraction and X-ray fluorescence experiment was employed for thin film characterization, which revealed solubility of Pt, Pd, and Ru in cubic WC. Density functional calculations of the lattice parameter dependence on carbon concentration enabled the determination of carbon concentration from the X-ray data as a function of transition metal stoichiometry. Our measurement of variations in the C stoichiometry and evolution of thin film texture with transition metal composition yielded surprising results. We detail how the combination of the composition spread technique, the high-throughput thin film characterization, and the density functional modeling of ternary carbide alloys provided a deep understanding of the chemical systems.