Atomic Fe-Doped MOF-Derived Carbon Polyhedrons with High Active-Center Density and Ultra-High Performance toward PEM Fuel Cells

A metalorganic gaseous doping approach for constructing nitrogen-doped carbon polyhedron catalysts embedded with single Fe atoms is reported. The resulting catalysts are characterized using scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy; for the optimal sample, calculated densities of Fe-N-x sites and active N sites reach 1.75812 x 10(13) and 1.93693 x 10(14) sites cm(-2), respectively. Its oxygen reduction reaction half-wave potential (0.864 V) is 50 mV higher than that of 20 wt% Pt/C catalyst in an alkaline medium and comparable to the latter (0.78 V vs 0.84 V) in an acidic medium, along with outstanding durability. More importantly, when used as a hydrogen-oxygen polymer electrolyte membrane fuel cell (PEMFC) cathode catalyst with a catalyst loading as low as 1 mg cm(-2) (compared with a conventional loading of 4 mg cm(-2)), it exhibits a current density of 1100 mA cm(-2) at 0.6 V and 637 mA cm(-2) at 0.7 V, with a power density of 775 mW cm(-2), or 0.775 kW g(-1) of catalyst. In a hydrogen-air PEMFC, current density reaches 650 mA cm(-2) at 0.6 V and 350 mA cm(-2) at 0.7 V, and the maximum power density is 463 mW cm(-2), which makes it a promising candidate for cathode catalyst toward high-performance PEMFCs.