Atomically dispersed iron atoms on nitrogen-doped porous carbon catalyst with high density and accessibility for oxygen reduction

Abstract

• AD-Fe-NPC was successfully developed as oxygen reduction catalysts. • HAADF-STEM images confirmed the atomic dispersion of Fe on AD-Fe-NPC catalysts. • The optimized AD-Fe-NPC structure exhibited superior ORR activity to Pt/C. The development of high-performance, low-cost and high-stability oxygen reduction reaction (ORR) non-platinum catalysts has become one of the main research directions on fuel cells and metal-air batteries. Here, we developed porous carbon catalysts with atomically dispersed nitrogen coordinated iron atoms (Fe-N x ) as the active sites (AD-Fe-NPC) using Fe-doped ZIF-8 and 1,10-phenanthroline as precursors. The additional nitrogen coordinated sites from 1,10-phenanthroline, together with a special structure of ZIF-8 can suppress the agglomeration of Fe atoms, leading to isolated Fe atoms with high density on graphitic carbon during the pyrolysis. As a result, the sample prepared using 50 mg of 1,10-phenanthroline (AD-Fe-NPC-50) exhibited a high activity towards oxygen reduction with a half-wave potential of 0.91 V versus reversible hydrogen electrode in 0.1 M KOH, which is attributed to the high porosity (1011.2 m 2 g −1 ) and density of Fe-N x active sites (1.1 at%). Furthermore, as an air electrode in zinc-air batteries, the AD-Fe-NPC-50 demonstrated a maximum power density of about 201 mA cm −2 and a specific capacity of 782 mA h g Zn −1 at 10 mA cm −2 , which outperformed commercial Pt/C and many state-of-the-art non-precious metal catalysts.