Preparation of fcc-2H-fcc Heterophase Pd@Ir Nanostructures for High-performance Electrochemical Hydrogen Evolution

With the development of phase engineering of nanomaterials (PEN), construction of noble metal heterostructures with unconventional crystal phases, including heterophases, has been proposed as an attractive approach towards the rational design of highly efficient catalysts. However, it still remains challenging to realize the controlled preparation of such unconventional-phase noble metal heterostructures and explore their crystal-phase-dependent applications. Here, we synthesize various Pd@Ir core-shell nanostructures with unconventional fcc-2H-fcc heterophase (2H: hexagonal close-packed; fcc: face-centered cubic) through a wet-chemical seeded method. As a result, heterophase Pd66 @Ir34 nanoparticles, Pd45 @Ir55 multi-branched nanodendrites and Pd68 @Ir22 Co10 trimetallic nanoparticles have been obtained via the phase-selective epitaxial growth of fcc-2H-fcc heterophase Ir-based nanostructures on 2H-Pd seeds. Importantly, the heterophase Pd45 @Ir55 nanodendrites exhibit excellent catalytic performance towards electrochemical hydrogen evolution reaction (HER) under acid condition. An overpotential of only 11.0 mV is required to achieve the current density of 10 mA cm-2 on Pd45 @Ir55 nanodendrites, which is lower than those of the conventional fcc-Pd47 @Ir53 counterpart, commercial Ir/C and Pt/C. Our work not only demonstrates an appealing route to synthesize novel heterophase nanomaterials for promising applications in the emerging field of PEN, but also highlights the significant role of crystal phase in determining their catalytic properties. This article is protected by copyright. All rights reserved.