In the present paper anion effects are discussed on different shape-controlled Pt nanoparticles as well as on polycrystalline Pt electrodes of different surface structures In particular the potentials of zero total charge (pztc) were determined by using the CO displacement approach both in sulphuric and perchloric media The CO monolayer oxidative stripping was studied on the different samples CO coverages were independent of the electrolyte provided that the true CO stripping charges corrected for double layer contributions are compared to the charge involved only in the hydrogen adsorption region The classical charge density normalization process is discussed and small changes are proposed Then criteria to evaluate the real surface area of platinum electrodes from charge measurements are proposed in both electrolytes (C) 2010 Elsevier Ltd All rights reserved