Mechanistic insights into a non-classical diffusion pathway for the formation of hollow intermetallics: A route to multicomponent hollow structures

Abstract

Hollow nanostructures are used for various applications including catalysis, sensing, and drug delivery. Methods based on the Kirkendall effect have been the most successful for obtaining hollow nanostructures of various multicomponent systems. The classical Kirkendall effect relies on the presence of a faster diffusing species in the core; the resultant imbalance in flux results in the formation of hollow structures. Here, an alternate non-Kirkendall mechanism that is operative for the formation of hollow single crystalline particles of intermetallic PtBi is demonstrated. The synthesis method involves sequential reduction of Pt and Bi salts in ethylene glycol under microwave irradiation. Detailed analysis of the reaction at various stages indicates that the formation of the intermetallic PtBi hollow nanoparticles occurs in steps. The mechanistic details are elucidated using control experiments. The use of microwave results in a very rapid synthesis of intermetallics PtBi that exhibits excellent electrocatalytic activity for formic acid oxidation reaction. The method presented can be extended to various multicomponent systems and is independent of the intrinsic diffusivities of the species involved. Hollow intermetallic PtBi is obtained via an unexpected non-classical diffusion pathway in a microwave-assisted synthesis. The mechanistic details of formation of hollow intermetallic due to the curvature effect and the electrocatalytic activity of the product for formic acid oxidation are presented. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.