An improved fuel cell cathode catalyst composition was pursued by fabricating and screening thin film combinatorial libraries. Results from the Pt-Ru, Pt-Co-Ti, Pt-Co-Cu and Pt-Co-Cr systems are reported. The discrete composition combinatorial libraries were fabricated by plasma sputtering through shadow masks. Each combinatorial library was tested by cyclic voltammetry in a multichannel electrochemical cell. Compositions were ranked based on the onset potential of the oxygen reduction reaction. Several compositions exhibited better onset potentials than pure Pt. The optimum composition from the Pt-Co-Ti system was Pt44Ti12Co44 but showed signs of corrosion after prolonged testing. A wide range of Pt-Co-Cu compositions also outperformed Pt initially, but ultimately failed due to poor corrosion resistance. Among all of the compositions that were screened, the best performance was demonstrated by Pt28Co36Cr36, with an onset potential 107 mV higher than pure Pt and no sign of corrosion. (C) 2007 Elsevier B.V. All rights reserved.