Kinetics of electrochemical O2 reduction on Pt

The experiments show that the kinetics of O2 reduction on Pt (with NAFION as electrolyte) is first order in O2 in a wide range of reaction conditions. Recent DFT calculations indicate that during this reaction the atomic-oxygen coverage may be appreciable. To adjust these two findings, we analyze the reaction kinetics corresponding to the dissociative and associative mechanisms with participation of atomic oxygen. If the reaction steps are described by using the Langmuir equations, the kinetics are predicted to be first order only in the situations when the O coverage is low. With O–O lateral interactions, the model based on the associative mechanism is able to predict the first-order kinetics in a wide range of pressure even if the O coverage is appreciable.