Ethanol and carbon monoxide oxidation in alkaline media is investigated on a series of carbon-supported PtSn nanoparticles synthesized using a polyol reduction method. The PtSn electrocatalysts include two groups where one group is composed of disordered PtSn alloys and the other group composed of PtSn alloys intimately mixed with a SnOx phase. All catalysts were active during cyclic voltammetry experiments but the bi-phase PtSn + SnOx nanoparticles have significantly higher current densities at lower overpotentials compared to the pure alloy PtSn catalysts. During chronoamperommetry measurements all catalysts deactivated with time and only the bi-phase PtSnOx catalysts reached steady-state current densities after 3000 s with all others deactivating continuously. Catalyst bulk and surface structure were correlated with the observed electrochemical performance in alkaline media demonstrating that ethanol electrooxidation in 1 M KOH is more facile when electrocatalysst contain higher total amounts of both Pt and oxides. Alloying of Pt with Sn improves intrinsic, per Pt, catalytic activity and plausibly prevents Pt oxidation. Moreover, oxides decrease deactivation, possibly through improved CO or other intermediate adsorbate oxidation due to enhanced OH surface coverage. (C) 2012 Elsevier Ltd. All rights reserved.