Unraveling the Nature of Sites Active toward Hydrogen Peroxide Reduction in Fe‐N‐C Catalysts

Fe‐N‐C catalysts with high O(2) reduction performance are crucial for displacing Pt in low‐temperature fuel cells. However, insufficient understanding of which reaction steps are catalyzed by what sites limits their progress. The nature of sites were investigated that are active toward H(2)O(2) reduction, a key intermediate during indirect O(2) reduction and a source of deactivation in fuel cells. Catalysts comprising different relative contents of FeN(x)C(y) moieties and Fe particles encapsulated in N‐doped carbon layers (0–100 %) show that both types of sites are active, although moderately, toward H(2)O(2) reduction. In contrast, N‐doped carbons free of Fe and Fe particles exposed to the electrolyte are inactive. When catalyzing the ORR, FeN(x)C(y) moieties are more selective than Fe particles encapsulated in N‐doped carbon. These novel insights offer rational approaches for more selective and therefore more durable Fe‐N‐C catalysts.