We present the design, fabrication, and utilization of a high-throughput combinatorial electrochemical screening platform consisting of 16 individually addressable, three-electrode chambers for rapid evaluation of supported high-surface-are nanoparticle electrocatalysts. Repeatable hydrogen adsorption/desorption surface area measurements along with oxygen evolution kinetics for carbon supported pure platinum catalysts (Pt/C) illustrate practical reproducibility (+/-10%) across the 16 glassy carbon working electrodes. Automated liquid-precursor impregnation using robotic liquid dispensing is shown to produce catalysts in precisely controllable atomic ratios as confirmed via energy dispersive spectroscopy. The combinatorial array demonstrates the ability to produce reliable trends in electrocatalytic activity data for the oxygen evolution reaction (OER) on both binary Pt-M catalysts (with M=Ir, Re, Ru, Pd), as well as tertiary Pt-Ru-M catalysts (with M=Ir, Pd)), when compared to a more rigorous kinetic analysis on a rotating disk electrode. It was shown that Ru-rich materials are better suited for use as OER catalysts relative to Pt-, Ir-, Pd-, and Re-rich materials. The OER catalyst materials discovered are expected to significantly lower the necessary input power of electrochemical water splitting devices in acidic environments (proton exchange membrane fuel cell electrolyzers). (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3049820] All rights reserved.