Thin Film Platinum Alloys For Use As Catalyst Materials In Fuel Cells C. C. Hays, J. G. Kulleck, B. E. Haines, and S.R. Narayan Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA Measurements of the structural and electrochemical properties of nanostructured thin film alloys in the ternary series Pt-Co-Zr are presented. These alloys have been studied to determine the influence of early transition metal element additions on the catalytic response and chemical stability of platinum-group-metal (PGM) alloys in acid electrolytes. The thin film compositions in the Pt-Co-Zr system were prepared via co-sputtering and the films exhibit a (111) crystallographic orientation. Alloys with Pt-metal contents of less than 50 At. % are stable in 0.1 M perchloric acid electrolytes, and are electrochemically active for the oxygen reduction reaction (ORR). The ORR kinetic currents at 0.9 V are comparable to Pt. The alloys have been cycled over the range 0.0 to 1.2 V NHE, with no degradation of the electrode surface area or decrease in electrochemical performance observed. Our results suggest that Pt-Co-Zr alloys with reduced PGM contents may be competitive with Pt-catalysts. Introduction In state-of-the-art polymer electrolyte fuel cells (PEFCs) using an acid polymer electrolyte, platinum (Pt) and platinum group metal (PGM) alloy catalysts are used as the cathode materials for the reduction of oxygen. Some challenges limiting the widespread application of PEFCs, that utilize PGM catalysts are: 1) slow kinetics for oxygen reduction; 2) insufficient long-term durability manifest by metallurgical effects (e.g., Ostwald particle ripening, and surface area loss due to corrosion); and 3) the high cost of platinum. Motivated by these challenges, we report the results of a study designed to discover new Pt-based, transition metal alloy catalysts that are stable in acid and electrochemically active for the oxygen reduction reaction (ORR). Experimental Thin Film Synthesis Combinatorial film deposition methods, as described in reference 1, were used to simultaneously prepare a wide range of Pt-Co-Zr compositions for evaluation. Figure 1a shows a schematic of the co-sputtering process, while Figure 1b shows the interior of the sputtering system vacuum chamber. All films were co-sputtered from two targets, each made from research grade materials, with minimum purities of 99.99%; Pt 3 Co and Zr (Kurt J. Lesker). A typical co-sputtering procedure consists of evacuating the sputtering chamber to a base chamber pressure of < 1 x 10 -6 Torr, followed by film deposition carried out under an Argon gas pressure of 15 mTorr. ECS Transactions, 25 (1) 619-623 (2009) 10.1149/1.3210613 © The Electrochemical Society 619 Downloaded 02 Jul 2012 to 137.78.7.61. Redistribution subject to ECS license or copyright; see http://www.ecsdl.org/terms_use.jsp