The spontaneous adsorption of Sb onto nanostructured platinum electrodeposited films with a preferential (100) surface orientation, hereafter denoted Pt-100 pref, was studied by means of electrochemical quartz microbalance (EQCM) and X-ray photoelectron spectroscopy. EQCM results indicated the formation of a Sb monolayer, while XPS analyses confirmed that a fraction of the as-adsorbed Sb adatoms were in a metallic state, while the others were in an oxidized state. After cycling, all of the Sb adatoms were in a metallic state. The electrocatalytic performances towards formic acid oxidation were assessed through cyclic voltammetry and chronoamperometry. On Pt-100 pref, the presence of Sb markedly increased the current on the forward scan up to the potential value (typically 0.20 V) corresponding to a redox reaction occurring on the adatom. After one hour of electrolysis, the current on the Pt-100 pref electrode covered with 75% Sb was ca. 15 mA cm(geometric)(-2) at 0.14 V vs SCE, which is 100 times higher than on the bate Pt-100 pref electrode. The short- and long-term activities of the Pt-100 pref electrode were maintained even when the electrode was disoriented through potential cycling in the Pt oxide formation and reduction region. (C) 2015 Elsevier B.V. All rights reserved.