Electronic Enhancement Engineering by Atomic Fe-N-4 Sites for Highly-Efficient PEMFCs: Tailored Electric-Thermal Field on Pt Surface

Lowering noble-metal Pt usage and simultaneously enhancing electrocatalytic oxygen reduction reaction (ORR) activity and stability of Pt-based ORR electrocatalysts is the key to realize the large-scale application of fuel cells. Here, an effective strategy is developed to reduce Pt usage through the strong electron interaction between uniform Pt nanoparticles (approximate to 4.0 nm) and abundant atomically dispersed Fe-N-4 sites modified on an ordered mesoporous carbon (OMC) surface for efficiently enhancing ORR performance. Density functional theory (DFT) calculations show that the strong electron interactions between Pt and Fe-N-4 sites decrease the d-band center of Pt in Pt@Fe-N-OMC-2 by 0.21 eV relative to that of as-prepared Pt@OMC, indicating the weakened O-2 adsorption and accelerated desorption of oxygenated species on Pt sites. In situ Raman spectra demonstrate that the introduction of Fe-N-4 moieties promotes the O-OH dissociation process. Finite element method simulations reveal that the electric and thermal field of the embedded Pt nanoparticle surface is enhanced through modifying Fe-N-4 sites on the OMC surface, accelerating the accumulation of ORR-related species (O-2, H+, and H2O), which is conductive to electrocatalyzing the ORR. This innovative approach not only illustrates the synergistic mechanism between Pt and Fe-N-4 sites, but also simultaneously provides new avenues to design advanced electrocatalysts for fuel cells.