Competitive electronic modulation via iron mediation: Stabilizing PtCo sites in alloy for enhanced fuel cell performance.

Abstract

Low-platinum cathodic electrocatalysts are urgently demanded for proton-exchange membrane fuel cells (PEMFCs) deployment with high intrinsic activity and long-term durability. However, conventional binary PtCo alloys suffer from transition-metal leaching and unfavorable intermediate adsorption. Herein, ternary PtCoFe alloy catalysts featuring competitive electronic modulation are synthesized via an impregnation-reduction route (CE-PtCoFe_0.5). Density functional theory and experimental characterizations reveal strong intraperiod coordination between Fe and Co, where FeCo 3d orbital hybridization far outweighs cross-period PtCo interaction. Preferential electron redistribution in FeCo modulates Co electron density and reduces Co-to-Pt charge transfer, enabling competitive electronic modulation distinct from main charge migration in PtCo. Such modulation upshifts the Pt d-band center to balance intermediate adsorption and elevates Pt/Co vacancy formation energies, suppressing metal dissolution and structural degradation. The optimized CE-PtCoFe_0.5 delivers a high half-wave potential of 0.938 V, an electrochemically active surface area (ECSA) of 122.14 m² g_Pt^-1, and a mass activity of 0.82 A mg_Pt^-1, exceeding binary PtCo and commercial Pt/C. In PEMFCs tests, it achieves a maximum power density of 2.42 W cm^-2 (H₂-O₂) and 1.68 W cm^-2 (H₂-air), showing merely 19.4% peak-power decay after 30, 000 accelerated cycles with negligible particle growth and well-preserved lattice features. This work offers a facile and reliable ternary alloying strategy for the rational design of high-stability low-Pt cathodic catalysts toward PEMFCs applications.