Template-Confined Synthesis of 1 nm High-Entropy-Alloy Nanoparticle Library for Electrocatalysis

High-entropy-alloy (HEA) nanoparticles containing at least five elements are an emerging family of catalysts. Due to the increased complexity of multicomponent atomic mixing, the size reduction of HEA nanoparticles down to around 1 nm is a substantial challenge, which is crucial to enhance the efficiency of atom utilization. Herein, we report a template-confined synthesis strategy for constructing a library of ultrasmall HEA nanoparticles with sizes of approximately 1 nm and compositions containing up to ten elements, including Pt, Pd, Ru, Rh, Fe, Co, Ni, Cu, Mo, and Zn. By leveraging the confinement effect of the mesoporous carbon structure and the autocatalytic reduction of the metal-precursor mixture at a low reaction temperature, we successfully achieve the uniform embedding of a diverse array of ultrasmall multicomponent HEA nanoparticles within the mesoporous framework. Additionally, we demonstrate that the 1 nm PtRuFeCoNi nanoparticles exhibit enhanced mass activity and superior atom utilization in both hydrogen evolution and hydrogen oxidation reactions, surpassing other quinary HEA and commercial Pt/C catalysts. Furthermore, operando X-ray absorption spectroscopy and theoretical calculations suggest a cooperative multielement effect among the five constituent elements, in which Pt- and Ru-containing local environments provide favorable sites for H-intermediate adsorption and contribute to the enhanced catalytic performance.