Influence of Copper Surface Pretreatment on the Kinetics of Oxygen Reduction Reaction in 0.5 M NaCl Solution: Surface Characterization and Electrochemical Studies

The study of oxygen reduction reaction (ORR) in 0.5 M NaCl on copper revealed that oxygen reduction reaction rates are markedly influenced by the surface condition and increased in the following order: covered with PDTC < pre-reduced < passivated surfaces. On pre-reduced and passivated surfaces, the ORR proceeded via a four electron pathway limited by oxygen diffusion. When the surface is passivated, the ORR is influenced by a combination of the reduction of copper oxide and the normal kinetics of ORR at a pre-reduced surface. The partial reduction of Cu2O oxide enhances the ORR kinetics. A surface covered with PDTC represents the least reactive site towards ORR process. The current densities decreased significantly due to the limitation of O2 access to the surface by the formation of a protective barrier layer. PDTC molecules are bonded on copper surface and form an inhibitive adsorption layer, which plays a major role in slowing down O2 reduction by blocking the active cathodic sites.