High-Density Planar-like Fe2N6 Structure Catalyzes Efficient Oxygen Reduction

Metal-nitrogen-carbon materials have been demonstrated as the most promising non-noble metal catalyst for proton-exchange membrane fuel cells (PEMFCs) but are still limited by the sluggish kinetics and durability ofmetal-nitrogen active sites. Here, we unravel a planar-like Fe2N6 active site as a highly efficient oxygen reduction catalyst for PEMFCs. Our developed planar-like Fe2N6 structure behaves as a distinguished catalytic mechanism for oxygen reduction, which brings synergic advantages of accelerated catalytic kinetics and highly suppressed side reaction, successfully promoting its catalytic activity and stability. As expected, the planar-like Fe2N6 structure with high density exhibits over 700% increase in mass activity than traditional isolated iron-nitrogen sites. Moreover, a PEMFC built with this catalyst also achieves a large peak power density of 845 mW cm(-2), representing a critical breakthrough for practical application of metal-nitrogen-carbon materials in PEMFC systems. Our findings will provide a new avenue toward designing highly active metal-nitrogen sites for heterogeneous catalysis.