Double-Shell Confinement Strategy Enhancing Durability of PtFeTi Intermetallic Catalysts for the Oxygen Reduction Reaction

Abstract

The development of Pt-based catalysts with enhanced activity and stability for the oxygen reduction reaction (ORR) is crucial for fuel cell applications. Pt-M (M = Fe, Co, Ni, Cu, etc.) catalysts exposed to prolonged acidic environments in fuel cells suffer from the leaching of transition metals, leading to accelerated catalyst degradation. Here, we present a double-shell confinement strategy to stabilize ORR catalysts by introducing a Ti-rich layer beneath the Pt skin. This design aims to prevent the leaching of Fe atoms, thus protecting the inner PtFeTi intermetallic structure. The resistance of Ti to acid and corrosion allows it to act as a physical protective layer, inhibiting the leaching of Fe and stabilizing the ordered structure of the internal PtFeTi intermetallic. Density functional theory calculations support that the Ti layer can effectively elevate the vacancy formation energy of Fe, thereby enhancing the structural stability. Mass activity (MA) of the double-shell L1₀-PtFe_0.6Ti_0.4/P–C catalyst is up to 1.04 A mg_Pt^–1. Even after 30,000 potential cycles of accelerated durability test, the MA decreases by only 13.5%. As the fuel cell cathode catalyst, it achieves a peak power density of 1.10 W cm^–2, and the voltage drop at 0.8 A cm^–2 is only 14 mV after 30,000 square-wave potential cycles. These performance metrics surpass the DOE 2025 target and exceed the stability data of many of the representative catalysts. Moreover, this double-shell confinement strategy is also applicable to PtCo-based and PtNi-based catalysts, demonstrating its broad applicability.