KCS

The catalytic properties of organometallic active species depend on the interaction between the metal center and surrounding ligands. Hybridization of the molecular active species with nanoscale materials can serve as a promising route for creating new catalytic nature. Jacobsen catalysts are well known for converting epoxides to diols by epoxide ring-opening reactions. Herein, an organometallic complex containing a Co atom and a tetra-dentate salen ligand, as a representative Jacobsen catalyst, is hybridized with N-doped graphene-based materials. The coordination structure around the Co center 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/cm2), and turnover frequency (0.2 s-1). Characterizations and electrochemical measurements with control samples suggest that the Co-O2/N2-Ngraphene structure is critical for the catalytic properties. Further study with after-cycle-samples highlighted the superior durability and stability of the active species. Theoretical calculation suggests favored ORR reactions of the fifth axial coordination of Co-O2/N2 by pyridinic N dopants.