Electronic Enhancement Engineering by Atomic Fe–N4 Sites for Highly-Efficient PEMFCs: Tailored Electric-Thermal Field on Pt Surface

摘要

Lowering noble-metal Pt usage and simultaneously enhancing electrocatalyticoxygen reduction reaction (ORR) activity and stability of Pt-based ORR electrocatalystsis the key to realize the large-scale application of fuel cells. Here,an effective strategy is developed to reduce Pt usage through the strong electroninteraction between uniform Pt nanoparticles (≈4.0 nm) and abundantatomically dispersed Fe–N4 sites modified on an ordered mesoporous carbon(OMC) surface for efficiently enhancing ORR performance. Density functionaltheory (DFT) calculations show that the strong electron interactions betweenPt and Fe–N_4 sites decrease the d-band center of Pt in Pt@Fe–N–OMC-2 by0.21 eV relative to that of as-prepared Pt@OMC, indicating the weakenedO_2 adsorption and accelerated desorption of oxygenated species on Pt sites.In situ Raman spectra demonstrate that the introduction of Fe–N_4 moietiespromotes the O–OH dissociation process. Finite element method simulationsreveal that the electric and thermal field of the embedded Pt nanoparticlesurface is enhanced through modifying Fe–N_4 sites on the OMC surface,accelerating the accumulation of ORR-related species (O_2, H~+, and H_2O),which is conductive to electrocatalyzing the ORR. This innovative approachnot only illustrates the synergistic mechanism between Pt and Fe–N4 sites,but also simultaneously provides new avenues to design advanced electrocatalystsfor fuel cells.