Orbital electron delocalization of axial-coordinated modified FeN and structurally ordered PtFe intermetallic synergistically for efficient oxygen reduction reaction catalysis.

Regulating the chemical environment of materials to optimize their electronic structure, leading to the optimal adsorption energies of intermediates, is of paramount importance to improving the performance of electrocatalysts, yet remains an immense challenge. Herein, we design a harmonious axial-coordination Pt Fe/FeNCCl catalyst that integrates a structurally ordered PtFe intermetallic with an orbital electron-delocalization FeNCCl support for synergistically efficient oxygen reduction catalysis. The obtained PtFe/FeNCCl with a favorable atomic arrangement and surface composition exhibits enhanced oxygen reduction reaction (ORR) intrinsic activity and durability, achieving a mass activity (MA) and specific activity (SA) of 1.637 A mg and 2.270 mA cm, respectively. Detailed X-ray absorption fine spectroscopy (XAFS) further confirms the axial-coupling effect of the FeNCCl substrate by configuring the Fe-N bond to ∼1.92 Å and the Fe-Cl bond to ∼2.06 Å. Additionally, Fourier transforms of the extended X-ray absorption fine structure (FT-EXAFS) demonstrate relatively prominent peaks at ∼1.5 Å, ascribed to the contribution of the Fe-N/Fe-Cl, further indicating the construction of the FeNCCl moiety structure. More importantly, the electron localization function (ELF) and density functional theory (DFT) further determine an orbital electron delocalization effect due to the strong axial traction between the Cl atoms and FeN, resulting in electron redistribution and modification of the coordination surroundings, thus optimizing the adsorption free energy of OH intermediates and effectively accelerating the ORR catalytic kinetic process.