The development of non-noble metal catalysts is of great interest due to their significant potential application in both fuel cell systems and metal-air batteries, particularly when considering long term commercial deployment. In this regard, novel Co-N-S/C non-noble metal catalysts supported on carbon, are synthesized in this study using a solvent-milling method followed by heat-treatment at elevated temperatures. Pyridine is used as the nitrogen-rich ligand for Co-N-x precursor complex formation. The morphology and composition of the catalyst are characterized by X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM) as well as X-ray photoelectron spectroscopy (XPS). Several catalysts containing different amounts of Co are also synthesized. The optimal Co content is found to be in the range of 10-15 wt% nominal, in terms of catalytic oxygen reduction reaction (ORR) activity. This catalyst shows high electroactivity for the ORR with a high stability in alkaline media. Using rotating disk electrode measurements, and Koutechy-Levich analysis, the overall electron transfer number in the catalyzed ORR is found to be 3.8-4.0, suggesting the catalyzed ORR is a four-electron transfer process from O-2 to H2O. (C) 2012 Elsevier B.V. All rights reserved.