High-entropy alloy nanocages with highly ordered {100} facets and ultrathin features for water splitting in an acidic medium

Abstract

High-entropy alloy (HEA) nanoparticles have been recognized as one kind of efficient electro-catalyst for water splitting. However, their higher catalytic activity is restrained by the difficulty in precisely shaping the HEAs into ordered facets and fully exposed surface structures. Herein, we report a seed-mediated conformal growth and partial etching method for the controlled synthesis of PtIrRuRhPd HEA cubic nanocages (CNCs), which feature the ordered {100} facets and ultrathin shells of five atomic layers. The slow injection of a PtIrRuRh layer on Pd nanocubes and the subsequent capture of dissociative Pd atoms in the etching step are responsible for the formation of nearly equimolar PtIrRuRhPd HEAs. Due to the synergistic effects derived from the multicomponent high-entropy effects, the ordered (100) facets, and the ultrathin feature, the PtIrRuRhPd HEA CNCs exhibit significantly high electro-catalytic activities for hydrogen and oxygen evolution reactions in an acidic medium, with overpotentials of 20 mV and 272 mV at 10 mA cm⁻² (η₁₀), respectively. As electrodes for a water electrolyzer, the PtIrRuRhPd HEA CNCs afford an η₁₀ as low as 196 mV, together with superior long-term durability for 200 000 s.