Ordered PdFe Intermetallics Outperform Disordered Alloys and Pd in Acidic Oxygen Reduction Reaction: Unraveling the Role of Atomic Configuration

The oxygen reduction activity of palladium (Pd) can be significantly boosted through alloy formation with transition metals. However, achieving long-term durability in acidic media remains challenging. Herein, ordered PdFe intermetallic (O-PdFe/C) electrocatalysts are synthesized via impregnation-reduction followed by thermal annealing, converting disordered PdFe alloy (D-PdFe/C) into an ordered intermetallic phase. Benefiting from the atomic ordering structure with Pd-Fe covalent bonding and compressive strain, O-PdFe/C delivers outstanding activity relative to D-PdFe/C and Pd/C, as evidenced by a half-wave potential (<i>E</i>_1/2) of 0.854 V vs RHE and mass activity (MA) of 0.17 A mg^-1_Pd in acidic electrolyte. Remarkably, the crystalline substrate of O-PdFe/C maintains exceptional durability with a 131 mV shift after 30000 cycles. The identical location transmission electron microscopy (IL-TEM) characterization reveals that the ordered intermetallic structure suppresses Fe leaching and prevents carbon corrosion, which is the key mechanism for enabling long-term durability. This work demonstrates that atomic ordering represents a promising approach to enhancing the oxygen reduction performance of carbon-supported Pd-based catalysts while effectively mitigating degradation during operation.