Molecular-level design of Fe-N-C catalysts derived from Fe-dual pyridine coordination complexes for highly efficient oxygen reduction

Abstract

Iron-nitrogen-carbon (Fe-N-C) materials as the most promising non-precious metal catalysts for oxygen reduction reaction (ORR) to replace Pt-based catalysts are in high demand for large scale application of fuel cells. However, their activity and durability are still critical issues. Development of Fe/N/C-containing precursors is a straightforward strategy for obtaining advanced Fe-N-C ORR catalysts to address these issues. Herein, we report an advanced Fe-N-C catalyst with a hybrid structure of single Fe atom sites (Fe-Nx moieties) and exposed Fe carbides/nitrides nanodots with diameters <2 nm embedded onto highly graphitic N-doped carbon matrix. The catalyst is synthesized by pyrolysis of a new kind of Fe-dual pyridine coordinated complex as the precursor. This facile chemical route results in a non-conventional Fe-N-C catalyst with encapsulated Fe-metallic phase nanoparticles or Fe-Nx moieties. The catalyst exhibits excellent ORR activity and remarkable durability in both acidic and alkaline media. Its onset and half-wave potentials are 1.08 V and 0.88 V vs. (RHE) in 0.1 M KOH, respectively, and 0.95 V and 0.81 V vs. RHE, respectively, in 0.5 M H2SO4. Furthermore, a single proton exchange membrane (PEM) fuel cell fabricated by our catalyst generates the output power of 0.65 W cm−2, which indicates great potential of our hybrid structured Fe-N-C catalyst for the practical application in fuel cells.