Structural effects on the activity for the oxygen reduction reaction on n(1Â 1Â 1)-(1Â 0Â 0) series of Pt: correlation with the oxide film formation

► We have studied the activity for the ORR on n(1 1 1)-(1 0 0) series of Pt. ► Step atoms enhance the ORR activity on the surfaces with 5 ≤ n. ► On the surfaces with n < 5, step atoms deactivate the ORR activity. ► The deactivation correlates with the formation of PtO-like species on the step.