A facile one pot synthetic route has been developed to obtain octahedral CuIr nanocrystals with Ir-rich {111} facets. Co-decomposition of Cu and Ir precursors in the presence of CTAC (cetyltrimethylammonium chloride) forms CuIr nanocrystals with an Ir-rich {111} facet. A mechanistic study reveals that the surface Cu atoms of the initially formed octahedral-shaped Cu-rich Cu–Ir alloy nanoparticles are replaced by Ir atoms via a galvanic replacement reaction. The formation of the Ir phase is rather slow, leading to the impermeable nature of the Ir shell, which does not allow the dissolution of the Cu phase. The CuIr nanocrystals with an Ir-rich shell show high catalytic activity toward oxygen evolution reaction.

Hollow nanostructures with an inherent high surface area per mass are attractive candidates as economically viable catalysts.Conceptually, a hollow nanostructure can be obtained by forming a desired material phase on a removable template and then by subsequently removing the template core. We recently reported the synthesis of a core-shell type structure with a Cu-rich core and Ir rich shell. However, the Cu phase could not be removed from the core due to the imperviousness of the single crystalline Ir-rich shell. In order to facilitate the Cu phase removal, we introduced the polycrystalline Pd seed into the growth of the CuIr nanocrystal, which resulted in the formation of Pd@CuIr nanocrystals with multiple radial grain boundaries. By placing the Pd@CuIr nanocrystal under oxidizing conditions, we could initiate the outward movement of the Cu phase along the grain boundaries. Herein we report the synthesis of an unusual bilayer hollow nanostructure with a CuIr surface layer and a Pd inner-coating layer, following a facile CuPd alloy phase formation and an outward movement of the Cu phase under oxidizing conditions. We also report the high catalytic performance of the hollow nanostructure in oxygen evolution reaction (OER).Nanostructures with a high surface area per mass such as hollow nanostructures and nanoframes are receiving great attention due to the economical usage of precious metals in catalytic applications, and thus recent research efforts are focused on the preparation of these nanostructures. Alloy nanoparticles also constitute an important catalyst group, 1-5 especially for energy conversion applications. 6-10

A facile one step route has been developed for the synthesis of trimetallic Cu@RhRu core-shell concave nanooctahedra by co-decomposition of Ru, Rh and Cu precursors. A mechanistic study reveals that nanoparticles with a CuRh alloy core and a Ru shell are initially formed and a subsequent migration of Rh to the shell results in the Cu@RhRu core-shell concave nanooctahedron. The shell exhibits atomically mixed Ru and Rh phases with an fcc atomic structure, although the hcp atomic structure is commonly found for the bulk Ru. We also report an unusually high catalytic activity of the Cu@RhRu octahedral nanocrystals toward the oxygen evolution reaction in alkaline solution.

Hierarchical dendritic nanostructures are rare and are usually synthesized by seed mediated epitaxial growth, which requires understanding of the symmetry-directed growth of the epitaxial layer on the facet-controlled nanocrysalline seed. Such a synthetic protocol involves alternation of the reaction conditions, and the one step synthesis of a hierarchical dendritic structure with exact mother to daughter crystal replication is a rarity. Herein we report a convenient one step synthesis of hierarchical dendritic Pt nanostructures with a concave Pt octahedron building unit by adopting reaction conditions in which Pt nanocrystal growth is extremely slow due to the reduction rate slowing the facet-etching process under an oxidizing atmosphere.