We present here a study of methanol (MeOH) decomposition over a series of bimetallic Pt-M catalysts, with M = Au, Pd, Ru, Fe. All samples have the same initial size distribution (similar to 3 nm nanoparticle height), support (ZrO2), and preparation conditions. Therefore, differences in the electronic and catalytic properties of the samples tested are related directly to the addition of the secondary metals (M). We find that the oxidation state as well as the activity of Pt is heavily influenced by the addition of the secondary metal. PtO is found to be highly stable in these systems and increasing concentrations of metallic Pt are associated with the surface segregation of metal M due to its affinity for the oxygen present during air annealing. (C) 2008 Elsevier B.V. All rights reserved.