A series of non-precious metal electrocatalysts, namely pyrolyzed carbon-supported cobalt-polypyrrole, Co-PPy-TsOH/C, are synthesized with various cobalt precursors, including cobalt acetate, cobalt nitrate, cobalt oxalate, and cobalt chloride. The catalytic performance towards oxygen reduction reaction (ORR) is comparatively investigated with electrochemical techniques of cyclic voltammogram, rotating disk electrode and rotating ring-disk electrode. The results are analyzed and discussed employing physiochemical techniques of X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, elemental analysis, and extended X-ray absorption fine structure. It shows that the cobalt precursor plays an essential role on the synthesis process as well as microstructure and performance of the Co-PPy-TsOH/C catalysts towards ORR. Among the studied Co-PPy-TsOH/C catalysts, that prepared with cobalt acetate exhibits the best ORR performance. The crystallite/particle size of cobalt and its distribution as well as the graphitization degree of carbon in the catalyst greatly affects the catalytic performance of Co-PPy-TsOH/C towards ORR. Metallic cobalt is the main component in the active site in Co-PPy-TsOH/C for catalyzing ORR, but some other elements such as nitrogen are probably involved, too.
A series of pyrolysed carbon-supported polypyrrole-cobalt, Co-PPy-TsOH/C, have been synthesized as electrocatalysts for oxygen reduction reaction (ORR) with chemically polymerized polypyrrole using different oxidants. The effects of pyrrole polymerizing oxidants on electrocatalytic performance of the final catalysts toward ORR have been comparatively investigated, and the results have been discussed and analyzed with the help of physicochemical characterizations. It's shown that the pyrrole polymerizing oxidants have essential influence on the structure, morphology as well as chemical states of cobalt and nitrogen in the Co-PPy-TsOH/C catalysts, leading to distinct catalytic performance for ORR. In addition, the role of cobalt and nitrogen in catalytic active sites in the catalysts has also been discussed.
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