A comparative study of pyrolyzed and doped cobalt-polypyrrole eletrocatalysts for oxygen reduction reaction

The pyrolyzed carbon supported cobalt polypyrrole (Co-PPy/C) catalysts were prepared without or with three selected dopants, namely, sodium dodecylbezene sulfonate (DBSNa), sodium paratoluene sulfonate (TSNa) and sodium bezene sulfonate (BSNa), respectively, through chemical oxidation with ferric chloride as an oxidant. The structure, surface and electrochemical properties of the obtained catalysts were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmitt-Teller (BET) analysis, cyclic voltammetry, rotating disc electrode technique and Raman spectroscopy. The introduction of dopants increased the surface concentrations of nitrogen and cobalt which would provide more active sites for oxygen reduction reaction (ORR), and enhanced the graphitization degree of carbon support which would improve the electron conductivity. The electron numbers of ORR for the non-doped and doped Co-PPy/C were evaluated to be 2.7-3.1, respectively. The pyrolyzed BSNa-doped Co-PPy/C exhibited the best electrocatalytic activity toward ORR due to its higher surface areas, larger amounts of micropores, as well as relatively higher nitrogen and cobalt contents. (C) 2011 Elsevier B.V. All rights reserved.