Joule heating synthesis for single-atomic Fe sites on porous carbon spheres and armchair-type edge defect engineering dominated oxygen reduction reaction performance

Single-atom catalysts (SACs) embedded in heteroatom-doped carbon are the most promising oxygen reduction reaction (ORR) electrocatalysts. However, the expeditious and facile synthesis of high-performance SACs with Fe-N x active sites and identifying the role of edge-type defect at the atomic level in carbon support are essential but remain challenging. Herein, Joule heating is applied to anchor Fe single atoms on newly defect rich porous carbon spheres (Fe-N-DCSs) in milliseconds. Fe-N-DCSs achieves exceptional ORR performance, with a half-wave potential ( E 1/2 ) of 0.90 V and E 1/2 lost of only 20 mV after 30,000 cycles in 0.1 M KOH, and superior Zn-air batteries performances. Density functional theory calculations establish that armchair-type edge defects decorated Fe-N 4 active sites boost the desorption of OH* and diminish the ORR overpotential. This work not only provides a speedy route for the fabrication of SACs but also presents new insights into the excellent ORR activity.