Directly transforming graphite into iron single atom catalyst for the acidic oxygen reduction reaction

Abstract

Platinum group metal (PGM)-free single atom catalysts (SACs) are highly desired to accelerate the sluggish oxygen reduction reaction (ORR) in acidic media, which has a critical role in renewable energy technologies. Herein, we report the direct transformation of commercial graphite into iron (Fe) single atom anchored graphitic flake via a combination of mechanochemical and thermochemical synthesis. By ball milling graphite with zirconium dioxide balls and capsule in the presence of dry ice, the graphite was mechanochemically functionalized and exfoliated into carboxylated graphitic flake (CGF). Subsequent heat-treatment of CGF with nitrogen containing additives formed nitrogenated graphitic flake (NGF) incorporated with Fe single atoms (Fe1NGF). Importantly, the existing Fe impurity in the pristine graphite was converted into value-added product without adding Fe sources. With an ultralow Fe content (0.4 wt%), the as-prepared Fe1NGF exhibited an acidic ORR performance comparable to Pt/C, including ultrahigh mass activity, surpassing the other reported outstanding Fe-based SACs.