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Catalysts for the oxygen reduction reaction were prepared from the pyrolysis of acetonitrile at 900 °C over iron particles on various supports. The iron phases present in the active materials were characterized by XRD, TEM, and Mössbauer spectroscopy. Typically, the iron particles were encased in carbon after pyrolysis, explaining how they could survive subsequent acid washes. The Fe phases present included metallic gamma iron, cementite, and two oxidized phases. Although the relative abundance of the phases varied with different supports, with treatment time, and after washing, there was no apparent correlation between the presence or abundance of a phase and activity. The phases present are consistent with Fe particles used to catalyze the formation of carbon fibers by catalytic chemical vapor deposition. After being washed with acid, there was no evidence for the presence of nitrogen-stabilized Fe sites on the carbon surface. These results support the hypothesis that Fe catalyzes the formation of ORR-active carbon nanostructures during pyrolysis at 900 °C in a carbon and nitrogen atmosphere and is not part of an active site itself.

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The anaerobic oxidation of ethanol over spinel mixed oxides A 2+ Fe 2 3+ O 4 2− (with A = Co 2+ , Ni 2+ , or Fe 2+ ) was studied by means of in situ diffuse reflectance spectroscopy (DRIFTS) and mass spectrometry (MS). The nature of the surface species formed during the reaction and its related gas products were discussed. Different reaction pathways were proposed depending on the catalyst composition. Acetates appeared to be important surface intermediates in the case of the Ni ferrite which is at the same time the most basic and easily reducible catalyst from the set studied, whereas with Co and Fe ferrites, more direct pathways to oxidation products were evidenced but at higher temperatures.

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