Abstract
This work examines the electrocatalytic reduction of molecular oxygen at Pt nanoparticles (nano-Pt) electrodeposited onto polycrystalline gold (poly-Au) electrode in O-2-saturated 0.5 M KOH. Cyclic and hydrodynamic voltammetry techniques were used for the evaluation of the electrocatalytic activity of the nano-Pt modified poly-Au electrodes. The nano-Pt was electrodeposited onto unmodified poly-Au electrode (nano-Pt/Au) and poly-Au electrode modified with a submonolayer (Au-sm) of a thiol compound (typically cysteine) (nano-Pt/Au-sm). In the latter case, Pt nanoparticles were electrodeposited, preferentially, at the bare fraction of the poly-Au electrode free from cysteine [i.e., the Au(111) domains of the poly-Au] while the other facets (i.e., Au(100) and Au(110)) were under the protection of cysteine. The nano-Pt electrodeposited onto the Au-sm is characterized by small average particle size (ca. 10 nm) compared to that electrodeposited onto the unmodified Au electrode (ca. 50-100 nm). The nano-Pt/Au-sm electrode offers a high electrocatalytic activity toward the oxygen reduction reaction (ORR) as compared with the nano-Pt/Au and bare polycrystalline Pt electrodes. A 60 mV positive shift of the onset potential of the ORR was obtained at the nano-Pt/Au-sm electrode as compared to the bare Pt electrode. A proper design of the nano-Pt/Au binary catalyst is the key point which controls the catalytic activity of the proposed electrocatalyst. (c) 2007 The Electrochemical Society.