Octahedral Co3O4/carbon nanofibers (CNFs) composite-supported Pt catalysts are synthesized using electrospinning, hydrothermal, and reduction methods in sequence, and their structure, chemical bonding states, and electrochemical properties are investigated. To obtain the optimal support, the relative molar ratio of the Co precursor to the solution was adjusted to three different levels: 0.05 M (sample A), 0.1 M (sample B), and 0.2 M Co precursor (sample C). Sample B exhibited the highest electrocatalytic activity of -415.6 mA mg(pt)(-1) and superb electrocatalytic stability compared to commercial Pt/C, Pt/conventional CNFs, sample A, and sample C. This performance improvement can be explained by the combined effects of optimally sized octahedral Co3O4 on the CNF matrix, resulting in the maximum dispersion of Pt catalysts, and the formation of Co(OH)(2) phases, which hinder CO poisoning. (C) 2015 Elsevier B.V. All rights reserved.