Boosting the ORR performance of modified carbon black via C-O bonds.

Abstract

In the research into oxygen reduction reaction (ORR) catalysts that are applicable to proton exchange membrane fuel cells (PEMFCs), many efforts have been made over a long time period to increase the catalytic activity and reduce the cost. Conductive carbon black is a type of load material widely used in industry. We have developed a cheap carbonization method using Co2+, Zn2+ and 2-methylimidazole (2-MI) on the surface of carbon black. The modified carbon black (MCB) catalyst with high ORR activity has a large diffusion-limited current density (MCB-3 6.18 mA cm-2), a half-wave potential (MCB-3 0.858 V), and no obvious decay after 20 000 cyclic voltammetry cycles. The characterization and controlled experiment results show that the metal content in the MCB is very low, even though it cannot be detected using extended X-ray absorption fine structure spectroscopy (EXAFS), and its ORR activity may be related to the formation of C-O bonds on the surface during the modification process. Subsequent density functional theory calculation results also support this idea. Through the simple modification of carbon black, a catalyst with excellent performance and low price can be obtained. At the same time, the study of the active site of the C-O bond will also provide new ideas for the study of ORR catalysts.