Abstract
Graphene aerogel-supported manganese ferrite (Mn(x)Fe(3-x)O(4)/GAs) and reduced-graphene oxide/manganese ferrite composite (MnFe(2)O(4)/rGO) were synthesized and studied as cathode catalysts for oxygen reduction reactions in urea/O(2) fuel cells. MnFe(2)O(4)/GAs exhibited a 3D framework with a continuous macroporous structure. Among the investigated Fe/Mn ratios, the more positive oxygen reduction onset potential was observed with Fe/Mn=2/1. The half-wave potential of MnFe(2)O(4)/GAs was considerably more positive than that of MnFe(2)O(4)/rGO and comparable with that of Pt/C, while the stability of MnFe(2)O(4)/GAs significantly higher than that of Pt/C. The best urea/O(2) fuel cell performance was also observed with the MnFe(2)O(4)/GAs. The MnFe(2)O(4)/GAs exhibited an OCV of 0.713 V and a maximum power density of 1.7 mW cm(-2) at 60 °C. Thus, this work shows that 3D structured graphene aerogel-supported MnFe(2)O(4) catalysts can be used as an efficient cathode material for alkaline fuel cells.