These results imply that the crystallite size of metallic cobalt

in the catalysts prepared from cobalt oxalate and cobalt chloride is obviously larger than that in the other two catalysts, agreeing well with the calculated results from the XRD data. The Co-N structure can be evidently detected in the catalysts synthesized from cobalt acetate, while that in the other catalysts are negligible. Therefore, the EXAFS results suggest that the Co-N bond/structure is not necessary to forming a catalytic active site toward ORR in learn more Co-PPy-TsOH/C catalysts, while the metallic cobalt plays an important role in forming the active site. Smaller Co-Co bond distances/crystallite VX-680 datasheet size is beneficial for enhancing the ORR performance, agreeing well with the results of Yuasa et al. [21]. In their research on Co-PPy/C catalysts, synthesized with electrochemically polymerized PPy, they found

that heat-treatment shortens the distances of Co-Co bond leading to better catalytic performance towards ORR. Figure 9 Fourier-transformed k 3 -weighted EXAFS functions at Co K-edge for Co foil and Co-PPy-TsOH/C catalysts prepared with various cobalt precursors. Conclusions Effects of cobalt precursors on electrochemical performance of Co-PPy-TsOH/C as catalyst towards Selleck PD0332991 ORR have been comparatively studied, and the results have been analyzed with diverse physiochemical techniques. The following conclusions could be drawn from this research: (1) cobalt precursors affect both the catalytic activity of the Co-PPy-TsOH/C catalysts Quisqualic acid and the corresponding ORR mechanism; (2) the electrochemical performance, including both the ORR catalytic activity and the selectivity to four-electron-transfer reaction, of the Co-PPy-TsOH/C catalysts follows the order with respect to the used cobalt precursor that cobalt acetate > cobalt nitrate > cobalt chloride > cobalt oxalate;

(3) the synthesis process, especially the high-temperature pyrolysis, of the catalyst could be interfered by the used cobalt precursors, resulting in different microstructure, morphology, elemental state as well as the ORR performance; (4) lower graphitization degree of carbon and smaller crystallite/particle size of metallic cobalt and the uniform distribution in Co-PPy-TsOH/C catalysts lead to better ORR performance; (5) metallic cobalt is a main component forming the ORR active site in the Co-PPy-TsOH/C catalysts, but some other elements such as nitrogen is probably also involved; and (6) Co-N bond/structure is not necessary to forming a catalytic active site toward ORR in Co-PPy-TsOH/C catalysts, and a small-amount coexistence of CoO in the catalysts does not have an adverse effect on the electrochemical performance.