FeNC shell-stabilized L10-PtFe intermetallic nanoparticles for high-performance oxygen reduction

In the pursuit of high-performance proton exchange membrane fuel cells (PEMFCs), obtaining durable Pt-based intermetallic catalysts with small particle sizes for oxygen reduction reaction (ORR) stands as a crucial yet challenging topic. Herein, we propose an idea of catalyst design utilizing Fe-phenanthroline (Phen) complex as precursor to integrate metal-nitrogen-carbon (M-N-C) with the strong anchoring effect into carbon shells, synthesizing highly ordered and small-sized (3.59 nm) PtFe intermetallic catalyst coated with iron-nitrogen-carbon (FeNC) shells (L1 0 -PtFe@FeNC). The strong Fe-Phen interaction ensures the uniform dispersion of Fe species on Pt seeds so as to form protective shells suppressing the agglomeration and dissolution of PtFe nanoparticles (NPs) under the high-temperature annealing or harsh operational conditions. It exhibits excellent mass activity (MA) that is about five-fold increase compared to the commercial Pt/C, as well as the significantly improved MA retention after 30,000 potential cycles (68.2% vs. 45.3%). Nitrogen-doped carbon (NC) shells and pure carbon (C) shells are used as comparison to demonstrate the advantages of FeNC shells. Durability test results show that NC and C shells obviously degrade after potential cycles, while well-preserved FeNC shells guarantee catalyst stability. Theoretical calculations reveal that the strong binding between FeNC shells and the Pt surface enhances the stability of both the nanoparticles and the FeNC shells.