Theory Guided Fine‐Tune of Strain Effects in Pt Ternary Alloy via Rare Earth Templating: Achieving High Performance PEMFCs Catalysts

The sluggish kinetics and insufficient durability of platinum‐based catalysts remain crucial barriers limiting proton‐exchange‐membrane fuel cells (PEMFCs) deployment. Here, we report a theory‐guided synthesis combined with rare‐earth templating to realize a previously inaccessible Pt 5 Co‐like phase with tailored atomic‐scale strain. Guided by density functional theory (DFT) calculations, we identified that a Pt 5 Co‐like sublayer can induce a unique mild compressive strain (−1.24%) to the Pt(111) shell and an optimal *OH binding energy shift (Δ E ≈ 0.11 eV ). This shift positions the alloy catalyst near the apex of the oxygen reduction reaction activity volcano. This prediction guided the synthesis of ternary alloy Pt 5 (Ce)Co@Pt multilayer nanoparticles, featuring a Ce‐stabilized core, a Pt 5 Co‐like sublayer, and a Pt‐rich shell. This catalyst demonstrates both exceptionally high activity and durability, achieving a mass activity of 2.6 A∙mg Pt −1 in rotating disk electrode testing. In fuel cell membrane electrode assembly tests, Pt 5 (Ce)Co@Pt achieves a current density of 1.9 A∙cm −2 at 0.7 V under heavy‐duty vehicle conditions. Remarkably, it maintains 1.2 A∙cm −2 after 1 80 000 AST cycles, doubling the U.S. DOE 2025 target. This work demonstrates a rational design strategy that DFT‐guided strain engineering integrates with rare‐earth templating to advance Pt‐based catalysts for fuel cell applications.