Nitrogen-Doped Ordered Mesoporous Carbon with Different Morphologies for the Oxygen Reduction Reaction: Effect of Iron Species and Synergy of Textural Properties

Nitrogen-doped ordered mesoporous carbons (N-OMCs) with different morphologies are prepared as oxygen reduction reaction (ORR) catalysts through pyrolysis of iron phthalocyanine-infiltrated SBA-15 silica with different mesochannel lengths. Excellent ORR activity with a nearly four-electron transfer process is observed in both alkaline and acidic media. In particular, the difference in half-wave potential for ORR relative to commercial Pt/C catalyst is only 50mV negative in acidic medium, whereas it is 50mV more positive in alkaline medium. Interestingly, it is found that although the use of iron is necessary for the preparation of highly active nitrogen-doped ORR carbon catalysts, its presence is not necessary for N-OMC to be active in the ORR in either alkaline or acidic media. In addition, the ORR activity increases gradually with decreasing mesopore channel length, with maximum activity in N-OMC with short channels, demonstrating the high synergistic influence of structural morphology on ORR in heteroatom-doped carbon.