Efficient Oxygen Reduction Reaction (ORR) Catalysts Based on Single Iron Atoms Dispersed on a Hierarchically Structured Porous Carbon Framework.

Single Fe atoms dispersed on hierarchically structured porous carbon (SA-Fe-HPC) frameworks are prepared by pyrolysis of unsubstituted phthalocyanine/iron phthalocyanine complexes confined within micropores of the porous carbon support. The single-atom Fe catalysts have a well-defined atomic dispersion of Fe atoms coordinated by N ligands on the 3D hierarchically porous carbon support. These SA-Fe-HPC catalysts are comparable to the commercial Pt/C electrode even in acidic electrolytes for oxygen reduction reaction (ORR) in terms of the ORR activity (E =0.81 V), but have better long-term electrochemical stability (7 mV negative shift after 3000 potential cycles) and fuel selectivity. In alkaline media, the SA-Fe-HPC catalysts outperform the commercial Pt/C electrode in ORR activity (E =0.89 V), fuel selectivity, and long-term stability (1 mV negative shift after 3000 potential cycles). Thus, these nSA-Fe-HPCs are promising non-platinum-group metal ORR catalysts for fuel-cell technologies.