Breaking the Bottleneck: Pt–Ni Nanoalloys as Next-Generation Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells

The oxygen reduction reaction (ORR) remains a pivotal kinetic bottleneck in proton exchange membrane fuel cells (PEMFCs), limiting their overall efficiency and commercial viability. Despite the high catalytic performance of platinum (Pt)-based electrocatalysts, their widespread use is hindered by high cost, limited durability, and relatively low mass activity. To address these challenges, engineered Pt–nickel (Ni) alloy nanostructures have emerged as promising alternatives, offering tunable electronic structures, enhanced stability, and reduced Pt utilization. This review systematically examines the role of Pt–Ni alloy nanostructures in catalyzing the ORR and improving PEMFC performance, emphasizing recent advances in synthetic strategies, structural engineering, and electrochemical behavior. Various architectures—including engineered alloys, core–shell configurations, and hollow or porous nanostructures—are discussed in the context of strain effects, d-band modulation, and synergistic electronic interactions. Additionally, key design strategies such as alloy structural optimization, precise compositional control, and morphology engineering are explored to enhance catalytic activity and long-term durability. Comparative electrochemical analyses demonstrate that well-engineered Pt–Ni nanoalloys can, in some cases, outperform commercial Pt/C catalysts in both mass activity and durability. This review elucidates fundamental structure–performance relationships and presents future perspectives for the rational design of Pt–Ni alloy nanocatalysts aimed at advancing sustainable energy conversion technologies.