Oxygen Coordination on Fe–N–C to Boost Oxygen Reduction Catalysis

The coordination environments of iron (Fe) in Fe–N–C catalysts determine their intrinsic activities toward oxygen reduction reactions (ORR). The precise atomic-level regulation of the local coordination environments is thus of critical importance yet quite challenging to achieve. Here, atomically dispersed Fe–N–C catalyst with O–Fe–N2C2 moieties is thoroughly studied for ORR catalysis. Advanced synchrotron X-ray characterizations, along with theoretical modeling, explicitly unraveled the penta-coordinated nature of the Fe center in the catalytic domain and the energetically optimized ORR pathways on the well-tailored O–Fe–N2C2 moieties. The combined structure identification from both experiments and theory provides an opportunity to understand the role of the coordination environments in directing the catalytic activity of single-atom or single-site catalysts; not only the center metal atom but also the whole coordinating atoms participate in the catalytic cycle.