Mesostructured Cobalt-Manganese-Oxides as Non-PGM Oxygen Reduction Catalyst in Anion Exchange Membrane Fuel Cells

Abstract

In this study, cobalt-manganese oxides with different compositions ranging from cobalt-rich to manganese-rich compounds were investigated for the applicability as cathode catalyst in AEMFC. The materials were synthesized by a nanocasting procedure using KIT-6-100 as hard template resulting in a mesoporous structure. Powder X-ray diffraction showed spinel structure and additional oxide phases for manganese-rich compounds. Their ORR activity was evaluated by RRDE experiments which could be related to the valence state of manganese as studied by X-ray photoelectron spectroscopy. These results showed that the spinel phase is beneficial for the ORR and the highest activities were achieved for compounds with a manganese valence states around +3.5. Moreover, only a minor decrease in activity after potential cycling proved a good electrochemical stability. Finally, the most active cobalt-manganese oxide with a Co/Mn ratio of 2/1 was applied in the cathodes catalyst layer reaching a peak power density of 145 mW/cm2 which is competitive with studies in literature. These results demonstrate the potential use of this material class as non-PGM catalyst in AEMFC.