Poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer was used as a micellar template to fabricate arrays of Pt nanoparticles on mica and glassy carbon (GC) supports. Polymer micellar deposition yields Pt nanoparticles with tunable particle size and surface number density on both mica and GC. After deposition of precursor-loaded micelles onto GC, oxygen plasma etching removes the polymer shell, followed by thermal treatment with H, gas to reduce the Pt. Etching conditions were optimized to maximize removal of the polymer while minimizing damage to the GC. Arrays of Pt nanoparticles with controlled size and surface number density can be prepared on mica (for particle size characterization) and GC to make Pt/GC model catalysts. These model catalysts were characterized by tapping mode atomic force microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry to measure activity for oxidation of carbon monoxide or methanol. Cyclic voltammetry results demonstrate the existence of a correlation between Pt particle size and electrocatalytic properties including onset potential, tolerance of carbonaceous adsorbates, and intrinsic activity (based on active Pt area from CO stripping voltammetry). Results obtained with Pt/GC model catalysts duplicate prior results obtained with Pt/porous carbon catalysts therefore validating the synthesis approach and offering a new, tunable platform to study catalyst structure and other effects such as aging on proton exchange membrane fuel cell (PEMFC) reactions.