ChemInform Abstract: Metal-Metal Interactions in Improved Pt-Co-Cr Catalysts Used in Phosphoric Acid Fuel Cells.
✍ Scribed by L. TROEGER; A. FREUND; P. ALBERS; K. SEIBOLD; G. PRESCHER
- Publisher
- John Wiley and Sons
- Year
- 2010
- Weight
- 26 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0931-7597
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✦ Synopsis
Metal-Metal Interactions in Improved Pt-Co-Cr Catalysts Used in Phosphoric Acid Fuel Cells.
-Title studies by XAFS, XPS, and SIMS and characterization of catalyst samples by SEM and XRD show several kinds of interactions between metal atoms and between metal and carbon atoms of the support but no direct Pt-C, Cr-Cr, and Cr-Co interactions. Missing Cr-Cr interactions indicate a highly disordered Pt-Cr alloy partially depleted from Cr, while ab initio XAFS calculations suggest a locally ordered tetragonal PtCo structure. Annealing results in a surface segregation and a preferential oxidation of Cr, but the oxidation of Cr and Co is confined to the surface layers. During thermal treatment the metal oxides are reduced by C from the support which yields especially chromium carbide species. The favorable reduction behavior of Co during cooling promotes the formation of a tetragonal PtCo structure. -