| 초록 |
The oxygen reduction reaction (ORR), a key reaction for acidic fuel cells, is today most efficiently catalyzed by Pt materials. However, the large scale deployment of acidic fuel cells will be confronted with the grand challenge of developing inexpensive catalysts with high activity and stability. While metal-nitrogen-carbon catalysts are promising, further advances and fundamental insights into the factors governing their catalysis and durability are needed to meet the stringent industrial requirements. To determine whether Fe-N-C materials catalyze the ORR via a direct, consequential or bifunctional mechanism, we have investigated the PRR activity on a set of catalysts, including model catalysts only comprising either FeNxCy moieties or Fe particles. Catalysts comprising different relative contents of FeNxCy moieties and Fe particles encapsulated in N-doped carbon layers (0-100 %) show that both types of sites are active, although moderately, toward H2O2 reduction. In contrast, N-doped carbons free of Fe and Fe particles exposed to the electrolyte are inactive. These novel insights offer rational approaches for more selective and therefore more durable Fe-N-C catalysts. |
