N-Doped 3D Carbon Aerogel with Trace Fe as an Efficient Catalyst for the Oxygen Reduction Reaction

The development of highly efficient, stable, and low-cost oxygen reduction reaction (ORR) electrocatalysts is urgently required. Herein, a three-dimensional (3D) N-doped carbon aerogel with trace Fe (ca. 0.60wt%) was synthesized by using carbon aerogel as the main raw material with facile KOH activation and a solid-state pyrolysis technique. The pyrolysis temperature and trace amount of Fe play crucial roles in the ORR activity. The optimal product (Fe-N-CA-800) displayed onset and half-potentials of 0.918 and 0.798V in alkaline solution and 0.801 and 0.592V in acidic media, respectively. Besides, the methanol crossover effect and long-term stability for Fe-N-CA-800 were better than those of Pt/C. Furthermore, the Fe-N-x sites were proven to be the main ORR catalytic sites by using SCN-. The robust 3D structure with hierarchical pores, unique chemical composition, and uniform Fe-N-x active sites contributed to the superior ORR performance. The low-cost and efficient Fe-N-CA-800 catalyst presents potential in fuel cells and metal-air batteries.