Y-Doped PtFeNi Medium-Entropy Nano-Alloy with Engineered (111) Facets for Enhanced Oxygen Reduction Reaction

The development of highly efficient and durable Pt-based oxygen reduction reaction (ORR) catalysts is paramount for the widespread adoption of proton exchange membrane fuel cells (PEMFCs). Herein, we present a novel Y-doped PtFeNi medium-entropy alloy catalyst, PtFeNiY₈ (PFNY₈, 8% Y doping), synthesized via a simple one-pot method, achieving preferential exposure of the highly active (111) crystal facet. Systematic experiments and density functional theory calculations demonstrate that Y doping lowers surface energy to promote the formation of the (111) crystal facet, with an optimal doping level of 8% achieving the most stable electronic structure and the most favorable d-band center. The PFNY₈/C catalyst demonstrates outstanding ORR performance, with a half-wave potential (E_1/2) of 0.93 V, mass activity (MA) of 3.00 A mg^-1 _Pt, and excellent durability (after 80,000 ADT cycles, the E_1/2 decreases by only 11 mV, and the MA retention is 73.4%). Furthermore, in PEMFCs, PFNY₈/C demonstrates a peak power density of 1.75 W cm^-2 under H₂/O₂ conditions, outperforming commercial Pt/C. This study offers valuable insights into the role of Y doping in tailoring nanoparticle morphology and facet exposure, presenting a new strategy for designing high-performance Pt-based catalysts for next-generation PEMFCs.