So-Called Metal-Free Oxygen Reduction at Graphene Nanoribbons is in fact Metal Driven

The oxygen reduction reaction (ORR) is of key importance in the field of electrochemical energy production. Remarkable catalytic properties of metal-free graphene nanoribbons towards the ORR were suggested in previous reports. Herein, we show that the electrocatalytic properties of an undoped supposedly metal-free graphene nanoribbon towards the ORR is actually caused by metallic impurities within the graphene nanoribbons.