Single-atom Fe–N–C catalysts are the most promising alternative to Pt-group metal catalysts for the cathodic oxygen reduction reaction in fuel cells, but while the chemical environment of their active centres is well understood, their electronic structure remains elusive. Now, using molecular model catalysts, a high-spin trivalent FeN4 site with an axial hydroxyl ligand is identified as the active site in Fe–N–C catalysts.
- Kuang-Min Zhao
- Dao-Xiong Wu
- Shi-Gang Sun
