Dealloyed PdCu3 thin film electrocatalysts for oxygen reduction reaction

► Dealloyed Pd-Cu thin films show higher ORR activity compared to pure Pd. ► Enhancement of ORR activity is attributed to the strain in the Pd surface layer. ► Dealloying and the ORR activity are dependent on the noble component of alloy. ► The relationship between the structure and ORR activity is better understood.