Role of Surface Steps of Pt Nanoparticles on the Electrochemical Activity for Oxygen Reduction

The design of highly active nanoscale catalysts for the oxygen reduction reaction (ORR) and oxidation of small molecules such as the methanol oxidation reaction (MOR) constitutes the grand scientific and technological challenge in fuel cells. Although increasing surface steps on Pt nanoparticles was shown recently to enhance the activity of electrochemical oxidation of carbon monoxide and methanol electro-oxidation, little is known about the role of surface steps of nanoparticles on ORR activity. Here, we report that the ORR activity of Pt nanoparticles of ∼2 nm is not influenced by surface steps, in contrast to MOR activity. Further, CO annealing experiments and in situ X-ray adsorption measurements clearly compare the role of surface step for ORR and MOR on Pt nanoparticles. The findings provide new insights to design highly active catalysts for proton exchange membrane fuel cells and direct methanol fuel cells.