A combinatorial approach to batch fabricating and evaluating fuel cell catalyst surfaces is described. The well-known binary Pt/Ru alloy and two compositional regimes of a novel quaternary Ni/Zr/Pt/Ru system were examined in detail. Catalyst films no thicker than 10 nm were deposited onto an array of 36 gold electrodes 0.5 cm(2) in area that were microfabricated on a 12.5 x 12.5 cm glass substrate. The catalyst films had identical bulk and surface compositions, a result of the atom-level mixing that occurred during the room-temperature cosputtering method used. A multichannel pseudopotentiostat was implemented for electrochemical screening. Compositions with promising and/or contrasting catalytic activities were also studied using X-ray diffraction, X-ray energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. A low-Pt-content Ni31Zr13Pt33Ru23 film was found to exhibit nominally the same activity (at 0.45 V vs a normal hydrogen electrode in 1 M H2SO4, 1 M CH3OH) as the best PtRu alloys studied. This material had a fundamentally different crystal and electronic structure than that observed in the Pt/Ru films and exhibited a significantly higher degree of Pt site utilization. These results were consistent with the existence of a catalytic reaction pathway different than that reported for Pt/Ru. (c) 2005 The Electrochemical Society.