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

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@Pt₂CoM (M═Co, Cu, Fe, Cr) nanocatalysts. Gradient strains in ultra-thin Pt skin are constructed by continuously modulating the lattice parameters of Pt₂CoM-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@Pt₂CoFe 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@Pt₂CoFe 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.