Dynamic Self‐Optimization in an Ordered L1 ₀ ‐PtCo Core–Shell Catalyst Decouples Activity and Stability for Acidic Hydrogen Ev

ABSTRACT

The performance of electrocatalysts for acidic hydrogen evolution is limited not only by intrinsic activity, but also by the structural instability under operating conditions. While ordered intermetallic compounds offer superior thermodynamic robustness, their dynamic evolution during catalysis remains poorly understood and rarely exploited. Herein, we introduce a dynamic self‐optimizing core–shell electrocatalyst, L1 ₀ ‐PtCo@Co‐shell, consisting of an ordered  L1 ₀ ‐PtCo intermetallic core encapsulated by an ultrathin Co‐shell. In 0.5 

H ₂ SO ₄ , this catalyst delivers an overpotential of 13 mV at 10 mA cm ⁻² , with mass activity and turnover frequency (TOF) values 15.9 and 4.2 times higher than those of commercial Pt/C, and stable operation for over 450 h. Operando X‐ray absorption fine structure (XAFS) spectroscopy reveals potential‐driven surface reconstruction via inward Co migration to form a highly alloyed PtCo surface. In situ Raman spectroscopy directly captures the co‐adsorption of hydrogen intermediates on adjacent Pt and Co sites, supporting a synergistic Volmer‐Tafel pathway. Density functional theory (DFT) calculations identify the ordered  L1 ₀ core imposes a high Co diffusion barrier, suppressing dissolution while enabling controlled surface reconfiguration. By deliberately harnessing, rather than suppressing, dynamic reconstruction, this work establishes a general design paradigm for designing highly active and durable electrocatalysts for acidic hydrogen evolution.