The oxygen reduction reaction on a Pt/carbon fuel cell catalyst in the presence of chloride anions

We studied the oxygen reduction reaction on a typical carbon supported Pt f uel cell catalyst in the presence of different anions. Similarly to smooth polycrystalline and single crystal Pt electrodes, the oxygen reduction reac tion (orr) activity decreases in the order ClO4- > HSO4- > Cl-, consistent with the increasing adsorption bond strength of the anions. The orr propert ies of Pt/Vulcan in the presence of adsorbed Cl can be interpreted as a sup erposition of the individual orr properties of the Pt(111)-Cl-ad and Pt(100 )-Cl-ad solid / liquid interface, both with respect to kinetic limitations and to the formation of H2O2. This is in qualitative agreement with the ass umed cubo-octahedral Pt particle shape. Although these results were obtaine d in liquid electrolyte, similar reduced activity and enhanced formation of H2O2 can be expected in a PEMFC, therefore indicating the necessity of chl oride free electrode preparation schemes in order to avoid performance loss es and/or corrosion/degradation effects. (C) 2001 Elsevier Science B.V. All rights reserved.