Copper–Carbon: An Efficient Catalyst for Oxygen Reduction

A simple and efficient method was developed to prepare a copper–carbon (Cu–C) catalyst with high oxygen reduction reaction (ORR) activity via direct pyrolysis of a mixture of metal salts (Cu(NO3)2·3H2O and Zn(CH3COO)2) and 1,3,5-benzenetricarbocylic acid at 1010 °C under a N2 stream. It is found that the Cu–C catalyst exhibits superior catalytic activity toward ORR with a half-wave potential of 0.81 V and a four-electron transfer pathway in 0.1 M KOH electrolyte. Generally, it is known that N plays an important role for the high ORR catalytic activities of nonprecious metal-doped carbon materials. Herein, we demonstrate that N is not required for the superior catalytic activity of Cu–C materials. Both the Cu particles and the embedded Cu atoms in the carbon substrate are suggested to provide the ORR active sites. In addition, despite the fact that the Zn is removed during the pyrolysis, the adding of Zn salt in the precursor is important for the enhanced catalytic activity. The evaporation of Zn during the pyrolysis results in the large surface area of the catalyst, which is beneficial to the mass transfer during the catalytic process. Moreover, a large number of carbon defects can be created via the removal of Zn atoms that facilitated the ORR.