Simultaneous Doping of Nitrogen and Fluorine into Carbon (NFC) as Metal-Free Oxygen Reduction Electrocatalysts

Here, we have simply prepared and optimized nitrogen, fluorine co-doped carbon (NFC) as metal-free oxygen reduction reaction (ORR) electrocatalyst from directly pyrolysing the mixture of carbon black and ammonium fluoride. Electrochemical results reveal that pyrolysis temperature plays an essential role on improving the electrocatalytic performance of NFC for the ORR and it reaches the maximum at 900°C, exhibiting the best ORR electrocatalytic activity in terms of the ORR peak potential, onset potential, and half-wave potential. Furthermore, the number of electrons transferred per oxygen molecular is 3.92, the percentage of four-electron is 96.3% and the percentage of peroxide is 3.74% at the disk potential of −0.4 V. Both XRD and Raman indicate that the higher pyrolysis temperature the greater defective nature of NFC. In special, NFC900 has a high portion of mesopores with the BET surface area of 1057 m2/g, and XPS indicates that N and F have been co-doped into the carbon matrix with F mainly in the ionic C-F bond.