Coordination structure of Jacobsen catalyst with N-modified graphene and their electrocatalytic properties for reducing oxygen molecules

Abstract

Hybridization of the molecular active species with nanoscale materials can serve as a promising route for creating new catalytic nature. Jacobsen catalysts containing Co-O-2/N-2 structure are well known for converting epoxides to diols. Herein, the Jacobsen catalyst is hybridized with N-doped graphene-based materials. The generation of molecularly dispersed Co-O-2/N-2-N-graphene structure on the surface of graphene-based materials is revealed by X-ray absorption, solid-state nuclear magnetic resonance, and X-ray photoelectron spectroscopic measurements. The resulting hybrid shows excellent catalytic performances for electrochemical oxygen reduction reactions (ORR), such as onset (0.91 V) and half-wave (0.80 V) potentials, current density (5.38 mA/cm(2)), and turnover frequency (0.2 s(-1)). Characterizations and electrochemical measurements with control samples suggest that the Co-O-2/N-2-N-graphene structure is critical for the catalytic properties. Further study with aftercycle-samples highlighted the superior stability of the active species. Theoretical calculation suggests favored ORR reactions of the fifth axial coordination of Co-O-2/N-2 by pyridinic N dopants.