Electrochemical oxygen reduction activity of intermediate onion-like carbon produced by the thermal transformation of nanodiamond

Onion-like carbon (OLC) is known to form as an intermediate structure when nanodiamond (ND) is heat treated at 1100-1500 degrees C. In this letter, we report on the electrochemical activity of its oxygen reduction reaction (ORR) when prepared at temperatures from 1000 to 2000 degrees C. The ORR activity is found to exhibit excellent correlation with the degree of defects, with OLC prepared at 1400 degrees C found to have the highest activity. This is attributed to the formation of curved graphitic layers containing edges during ND-OLC transformation, which function as active sites for the adsorption and subsequent reduction of oxygen. (C) 2015 Elsevier Ltd. All rights reserved.