Binary noble-metal nanocrystals have been actively explored in recent decades. Compared to single-component nanocrystals, a combination of two different metals offers variants in spatial distribution of elemental composition and thus their physicochemical properties could be readily manipulated. Bimetallic nanostructures with a well-defined structure and morphology were often found to exhibit enhanced catalytic performance than their counterparts lacking a well-controlled structure and morphology.Here we describe a facile synthesis of Pd-Ir bimetallic nanostructures in the forms of octapods and nanocages. The success of this synthesis relies on the use of Pd nanocubes as the sacrificing templates and interplay of two different processes: the galvanic replacement between an Ir precursor and the Pd nanocubes and the co-reduction of Pd2+ and Ir3+ by ethylene glycol. The galvanic replacement played a dominant role in the initial stage, through which Pd atoms were dissolved from the side faces whereas Ir atoms were deposited at the corner sites to generate Pd-Ir octapods. As the concentration of Pd2+ in the reaction mixture was increased, co-reduction of Pd2+ and Ir3+ occurred in the late stage of a synthesis. The resultant Pd and Ir atoms were deposited onto the octapods while the Pd atoms in the interiors continued to be etched away due to the galvanic replacement, finally leading to the formation of Pd-Ir nanocages. The octapods and nanocages were then evaluated as catalysts for the selective generation of hydrogen from the decomposition of hydrous hydrazine. The nanocages exhibited better selectivity for hydrogen generation than octapods (66% versus 29%), which can be attributed to their porous surface, hollow interior, as well as a relatively higher Ir/Pd ratio.

Facile synthesis of Pd-Ir bimetallic octapods and nanocages via galvanic replacement and their application for hydrazine decomposition

246th National Meeting (2013)

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