Bio-inspired iron/sulfur/graphene nanocomposite and its use in the catalysis of the oxygen reduction reaction at room temperature in alkaline media on a glassy carbon electrode

This work demonstrates the performance of a bio-inspired iron/sulfur/graphene nanocomposite as a non-platinum electrocatalyst for the oxygen reduction reaction (ORR) in an alkaline medium. The catalyst shows the most positive ORR onset potential (1.1V vs. RHE) according to its unique structure in the alkaline medium (KOH solution, pH=13) at low temperature (T =298K). The catalyst is evaluated by the rotating-disk electrode (RDE) method under various rotating speeds (0-2,000rpm) in the potential range -0.02-1.18V vs. a rechargeable hydrogen electrode (RHE). The number of transferred electrons, as one of the most important parameters, is almost constant over a wide range of potentials (0.1-0.8 V), which indicates a more efficient four-electron pathway from O-2 to H2O on the FePc-S-Gr surface. The mean size of catalyst centers are in the nanoscale (<10 nm). The estimated Tafel slope in the appropriate range is about -110mV per decade at low current density, and E-1/2 of FePc-S-Gr displays a negative shift of only 7.1 mV after 10,000cycles.