An electrocatalytic oxygen reduction by copper nanoparticles-modified Au(100)-rich polycrystalline gold electrode in 0.5Â M KOH

► ORR is remarkably electrocatalyzed at nano-Cu/Aur electrode. ► Catalytic activity of nano-Cu/Aur toward ORR is comparable to that of Pt. ► Enrichment of nano-Cu/Aur in Au(100) facet is behind its high catalytic activity.