Iron, Nitrogen Co‐Doped Carbon Spheres as Low Cost, Scalable Electrocatalysts for the Oxygen Reduction Reaction

Atomically dispersed transition metal‐nitrogen‐carbon catalysts are emerging as low‐cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost‐effective and scalable synthesis strategy for these catalysts is still required, as well as a greater understanding of their mechanisms. Herein, iron, nitrogen co‐doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization and high‐temperature post carbonization. It is determined that FeN4 is the main form of iron existing in the obtained Fe@NCS. Two different precursors containing Fe2+ and Fe3+ are compared. Both chemical and structural differences have been observed in catalysts starting from Fe2+ and Fe3+ precursors. Fe2+@NCS‐A (starting with Fe2+ precursor) shows better catalytic activity for the oxygen reduction reaction. This catalyst is studied in an anion exchange membrane fuel cell. The high open‐circuit voltage demonstrates the potential approach for developing high‐performance, low‐cost fuel cell catalysts. Atomic dispersed Fe‐N‐C electrocatalysts for the oxygen reduction reaction are developed from low‐cost precursors and a scalable synthesis process. A combination of advanced characterizations suggests that catalysts starting with Fe2+ precursors show Fe‐N4 moiety, and the central Fe is in the Fe2+ oxidation state. The obtained catalyst has been applied in an alkaline exchange membrane fuel cell and shows attractive performance.