A study on oxygen reduction inhibition at pyridine-terminated self assembled monolayer modified Au(111) electrodes

The electroreduction of oxygen on self-assembled monolayers (SAMs) of various-pyridinedisulfides and pyridinethiols on Au(111) surfaces has been investigated in alkaline solutions. Electrochemical experiments that were carried out in three-electorde cell reveal a, good,correlation between the chain-length of thiol molecules and the oxygen reduction inhibition of the resulting adlayer films. The effect of retarded diffusion of oxygen through the protective film has been investigated by forming additional layer of immobilized cytochrome c (cyt.c) metalloprotein on pyridine moiety during linear sweep voltammetry (LSV) scans. At sufficiently negative cathodic potentials the electrochemical reaction rate has been observed to increase together with the density of defects. Morphological changes at different levels of cathodic polarization were investigated by ex situ scanning tunneling microscopy (STM), indicating oxygen reduction reaction (ORR) induced structural defects at the metallorganic interface. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim