Highly Stable and Minimally Pt‐Loaded Multiporous Bimetallic Matryoshka Heterostructures for Efficient Hydrogen Evolution Reaction via pH‐Dependent Mechanistic Decoupling

Developing highly efficient and stable electrocatalysts with minimized platinum (Pt) loading is critical for sustainable hydrogen production via water splitting. However, optimizing performance across a wide pH range remains challenging due to distinct reaction mechanisms and stability issues, particularly in corrosive acidic environments. Herein, we report the synthesis of highly uniform and porous Au–Pt Matryoshka heterostructures via a facile galvanic replacement reaction using Au nanorods as templates. This unique architecture maximizes atomic utilization while maintaining a low Pt content in the optimized Pt‐Matryoshka catalysts. Our results indicate distinct pH‐dependent differences in the dominant factors governing the hydrogen evolution reaction activity. In alkaline media (1 M KOH), the activity was dominantly governed by the electrochemically active surface area (ECSA), where the Pt‐100 catalyst exhibited the highest ECSA and a low overpotential of 129 mV at 10 mA cm −2 . Conversely, in acidic media (0.1 M H 2 SO 4 ), the activity was closely associated with charge–transfer kinetics and catalytic properties, rather than being solely governed by surface area effects. The optimized Pt‐150 catalyst achieved an ultra‐low overpotential of 62 mV, comparable to commercial 10% Pt/C, with an exceptionally low Tafel slope of 23 mV dec −1 , indicating a shift to the rapid Volmer–Tafel mechanism. Notably, the Pt‐Matryoshka structure demonstrated excellent durability in highly corrosive acidic conditions, showing a negligible potential degradation of only 0.012 V after 60 h of operation. This improved stability is associated with the synergistic effect of the Au–Pt alloy interface, which suggests limited metal dissolution. This study provides critical insights into the decoupling of pH‐dependent performance factors and presents a robust strategy for designing durable, low‐Pt electrocatalysts for broad‐range pH applications.