Co@Co3O4@PPD Core@bishell Nanoparticle-Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction

Abstract

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high-performance primary zinc-air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co3O4 core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co3O4@PPD core@bishell structure, obtained via a three-step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co3O4 NPs encapsulated by ultrathin highly graphitized N-doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N-doped graphitic carbon outer shell and ultrathin nanocrystalline Co3O4 inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co3O4@PPD in air-cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm-2. Co@Co3O4 core@shell nanoparticles (NPs) embedded in N-doped graphitic carbon matrix of pyrolyzed polydopamine (PPD), i.e., Co@Co3O4@PPD core@bishell structure are obtained. This material shows high oxygen reduction reaction activity. Consequently, it is used as a cathode catalyst in zinc-air batteries and delivers stable voltage profile over an extended period at a discharge current density of as high as 20 mA cm-2.