Study of iron oxide nanoparticle phases in graphene aerogels for oxygen reduction reaction.

Iron oxide nanoparticles have been extensively used for energy production in fuel cells; however, the different phases of iron oxide have not been adequately investigated for their effect on the oxygen reduction reaction (ORR). The low temperature synthesis of four kinds of iron oxide nanoparticles with different phases was incorporated inside 3D reduced graphene oxide (rGO) aerogels and their electrochemical, catalytic and electron transfer properties were determined for ORR. The results showed that, at low potentials (0.20 V), rGO composites containing magnetite, maghemite and goethite catalyse ORR via four-electron transfer kinetics while hematite facilitated two-electron transfer kinetics. At higher potentials (0.70 V), all four catalysts proceeded via a two-electron pathway. [ABSTRACT FROM AUTHOR]