Atomic Structure of Polypyrrole-Modified Carbon-Supported Cobalt Catalyst

Carbon-supported cobalt catalyst (Co-BP) and polypyrrole-modified carbon-supported cobalt catalyst (Co-PPY-BP) are prepared by an impregnation-chemical method and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption fine structure, to investigate their electronic and atomic structures. It is found that a Co ion bonds with two pyrrolic N atoms to form a Co-N-2 bond in the Co-PPY-BP sample. Those two N atoms together with four 0 atoms at 2.04 angstrom constitute a distorted octahedral structure. The Co-N-2 bond, in which the central Co ion has a high valence electron density, is confirmed to be the main active site of Co-PPY-BP toward oxygen reduction reaction in alkaline electrolyte.