Oxygen Reduction at a Cu-Modified Pt(111) Model Electrocatalyst in Contact with Nafion Polymer

The effect of Nafion on the performance of a model Cu-modified Pt(111) electrocatalyst has been investigated using electrochemical techniques and density functional theory calculations. In this work, we demonstrate that Cu subsurface alloying not only increases the activity of model Pt(111) electrodes toward the oxygen reduction reaction (ORR) but also largely prevents catalyst poisoning by electrolyte components relevant for polymer electrolyte membrane fuel cell applications. Our results indicate that specific adsorption of (bi)sulfates and sulfonates (present in Nafion membranes) on the Cu-modified Pt(111) electrocatalyst is gradually suppressed, which implies that the ORR activity in 0.05 M H 2 SO 4 electrolyte drastically increases, with a change in the corresponding pseudo-half-wave potential of ∼93 mV. Importantly, the Cu-modified Pt(111) electrocatalyst in contact with Nafion polymer shows an activity as high as that in the absence of this polymer in perchloric acid media.