PAN Based Carbon Nanofibers as an Active ORR Catalyst

Polyacrylonitrile (PAN) based carbon nanofibers were prepared by electrospinning and their activity for oxygen reduction reaction (ORR) in acidic media was investigated. Field emission electron microscope (FE-SEM), transition electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) were carried out to investigate the surface morphology, composition, and catalytic activity. Thin carbon nanofibers of a 150 nm diameter were successfully produced by electrospinning using 8 wt% PAN in dimethylformamide, 15 cm pin to plate distance, and applying voltage of 18 kV at different carbonization temperatures of 700, 900, 1000, 1100, and 1200 ^oC. The ORR activity of the prepared carbon nanofibers was evaluated. The PAN based carbon nanofibers showed a considerable ORR activity and this activity was increased by increasing the carbonization temperature. The high ORR onset potentials over 700 mV vs. RHE (milli-volt versus reversible hydrogen electrode) were obtained at temperatures over 1000 ^oC. The activity of PAN based carbon nanofibers increased with increasing carbonization temperature from 700 to 1100 ^oC, this would be related to the increasing in the electrical conductivity at low carbonization temperatures, and the high Pyridine N content at the high carbonization temperatures.