Coupling High‐Entropy Core with Rh Shell for Efficient pH‐Universal Hydrogen Evolution

Abstract Constructing high‐entropy alloys (HEAs) with core–shell (CS) nanostructure is efficient for enhancing catalytic activity. However, it is extremely challenging to incorporate the CS structure with HEAs. Herein, PtCoNiMoRh@Rh CS nanoparticles (PtCoNiMoRh@Rh) with ∼5.7 nm for pH‐universal hydrogen evolution reaction (HER) are reported for the first time. The PtCoNiMoRh@Rh just require 9.1, 24.9, and 17.1 mV to achieve −10 mA cm ⁻² in acid, neutral, and alkaline electrolyte, and the corresponding mass activity are 5.8, 2.79, and 91.8 times higher than that of Rh/C. Comparing to PtCoNiMoRh nanoparticles, the PtCoNiMoRh@Rh exhibit excellent HER activity attributed to the decrease of Rh 4d especially 4d _5/2 unoccupied state induced by the multi‐active sites in HEA, as well as the synergistic effect in Rh shell and HEA core. Theorical calculation exhibits that Rh‐d _yz , d _x2 , and d _xz orbitals experience a negative shift with shell thickness increasing. The HEAs with CS structure would facilitate the rational design of high‐performance HEAs catalysts.