Strong metal support interaction driven synthesis of ultrasmall high entropy alloy nanoparticles for selective hydrogenation

High-entropy alloys (HEAs) have garnered significant attention due to their nearly infinite number of unprecedented active sites. However, the synthesis of ultrasmall HEA nanoparticles remains challenging due to their inherent thermodynamic instability. In this study, we demonstrate that a strong metal-support interaction (SMSI) can effectively suppress agglomeration through interfacial stabilization. By leveraging a quenching-based approach, we successfully synthesized HEA catalysts with ultralow loading (<0.17 wt%), ultrasmall particle sizes (<3.7 nm), and an SMSI-induced encapsulation layer. The formation of this protective layer enables precise control over the structural and electronic properties of catalyst. To probe the catalytic performance, cinnamaldehyde was employed as a model α,β-unsaturated aldehyde in selective hydrogenation reactions. The results reveal that a lower Pt ratio in HEA-Cu8Pt2 enhances HCAL selectivity, reaching 93.6 %, which is attributed to the modified interfacial electronic environment between TiO₂ and HEA, promoting Pt²⁺ species formation and strong hydrogen spillover. This work provides new insights into the design and regulation of ultrasmall HEA catalysts through SMSI effects.