In Situ Surface Reconstruction and Carbon Encapsulation for High-Performance Pt-Lean Catalysts beyond Conventional Core-Shell Designs.

Over recent decades, extensive efforts have aimed to enhance fuel cell performance. Pt alloys with 3d transition metals are particularly attractive for boosting oxygen reduction reaction (ORR) activity via strain and electronic effects. However, their structural instability and high Pt usage hinder practical application. Here, we report a highly active and durable catalyst with reduced Pt cost, achieved by integrating a Pt-segregated surface and porous carbon shell. Unlike conventional polymer-coating and carbonization methods, this catalyst is synthesized through a novel 'in situ one-step' process that simultaneously induces Pt segregation and carbon shell formation. This streamlined approach not only simplifies synthesis but also significantly lowers Pt consumption while maintaining superior ORR activity and long-term durability. As a result, the Pt content is reduced to ∼55% of that in commercial catalysts, while preserving high catalytic activity. Under single-cell testing, the catalyst exhibits excellent activity and durability, meeting DOE targets even at a Pt loading of 0.02 mg cm