Nitrogen-doped carbon nanofibers on expanded graphite as oxygen reduction electrocatalysts

A single-step chemical vapor deposition method using simple gaseous precursors was employed to grow nitrogen-doped carbon nanofibers from Fe and Ni particles on the surface of expanded graphite (N-CNF/EG). Due to the high electronic conductivity of the expanded graphite the N-CNF/EG could be used as electrocatalysts without the need for harsh purification procedures. Electrochemical testing showed that the N-CNFs grown from Fe exhibited a notable activity for the oxygen reduction in both acidic and alkaline electrolyte, in addition to demonstrating a high durability with a well-preserved catalytic activity after 1600 cycles in O₂-saturated 0.5 M H2SO4. Physicochemical characterization revealed the formation of N-CNFs with a bamboo-like structure, encapsulated Fe particles and high pyridinic nitrogen content. The combination of high ORR-activity, an easily scalable synthesis approach and a highly conductive support material makes N-CNF/EG a promising oxygen reduction catalyst for low temperature fuel cells.