Immiscible Metal‐Regulated Surface Segregation Enables Core–Shell Bi–PtMn Catalysts With Benchmark Performance in Direct Methanol Fuel Cells

ABSTRACT Although the Bi–Pt ensemble effect endows Bi–Pt‐based catalysts with remarkable CO tolerance in the methanol oxidation reaction (MOR), the lack of precise atomic‐level control over Bi–Pt surface structures leads to an intrinsic activity–selectivity trade‐off. Herein, we propose a facile immiscible‐metal‐induced surface‐segregation strategy to construct a core–shell Bi–PtMn catalyst that simultaneously achieves outstanding MOR performance and high selectivity toward the CO‐free pathway. Exploiting the immiscibility between Mn and Bi enables precise regulation of surface‐segregated Bi, leading to a well‐defined core–shell structure with an ordered L1 0 ‐PtMn core and a PtBi shell. The catalyst delivers benchmark mass activity of 61.81 A mg Pt −1 , 4.0 and 16.2 times that of Bi‐Pt and Pt/C, respectively. Furthermore, as a practical anodic electrocatalyst for direct methanol fuel cells, the catalyst achieves a peak power density of 294.21 mW cm −2 at an ultralow Pt loading of 0.5 mg Pt cm −2 . Mn lowers the barrier of the rate‐determining step by facilitating C─H bond cleavage, as corroborated by theoretical calculations and kinetic isotope effect (KIE) measurements. This work provides a design principle based on immiscible metal thermodynamics for atomic‐level surface engineering of electrocatalysts.