Lattice Coupling Enables Gradient Strain Tuning Toward Platinum Skin at Intermetallic Nanocatalysts for Boosting Hydrogen Electrocatalysis

Abstract Strain engineering in core–shell nanocatalysts is crucial for optimizing the activity of surficial sites. However, due to the significant difficulty in precise strain control, achieving optimal strain effect and insightful strain‐activity correlations is challenging. In this context, a novel strategy is proposed of precisely tuning the surface strain by leveraging the lattice coupling between Pt shell and the superlattice ordering Pt‐based intermetallic compound core. Two‐atom‐layer Pt‐skinned PtCo‐IMC nanocrystals are synthesized and subjected to heteroatom substitution in IMC core, yielding Pt@Pt 2 CoM (M═Co, Cu, Fe, Cr) nanocatalysts. Gradient strains in ultra‐thin Pt skin are constructed by continuously modulating the lattice parameters of Pt 2 CoM‐IMC cores. Based on this nanocatalyst platform, the influences of gradient strain on both the surface H‐adsorption/desorption and interfacial mass transportation are revealed, which synergistically regulate the hydrogen electrocatalysis kinetics. Pt@Pt 2 CoFe with optimal 5.8% compressive surface strain demonstrates impressive bifunctional hydrogen electrocatalytic activities for hydrogen oxidation (1.33 A/mg Pt ) and evolution (4.58 A/mg Pt ) reactions that are respectively 22.2 and 6.0 times over the strain‐free Pt. Additionally, Pt@Pt 2 CoFe exhibits robust CO tolerance and high stability for long‐term hydrogen electrocatalysis. This work provides a promising route of ingenious surface strain design for developing high‐performance nanocatalysts.