The electrochemical reduction of oxygen has been studied on Polyacrylonitrile (PAN) carbon nanofibers (PAN-CNF) with diameters of 100 - 200 nm in alkaline media employing the rotating disk electrode (RDE) method.The PAN-CNF was prepared by electrospinning and subsequent carbonization process at different temperature (600 ℃ - 1000 ℃).It has been found that the electrical conductivity of PAN-CNF increased with the increasing of the carbonized temperature.The RDE results (Fig.a) reveal a high electrocatalytic activity of PAN-CNF carbonized at 1000 ℃ toward oxygen reduction reaction (ORR).From the Koutecky-Levich plot (Fig.b),the ORR proceed a two-electron pathway at low potentials (-0.4 V to -0.6 V) followed by a gradual four-electron pathway at more negative potentials (Inset in Fig.a),indicating its potential application as the electrocatalyst or the support material toward ORR in alkaline media for fuel cell and zinc-air battery.