Spontaneous Emulsification of Organometallic Complexes Applied to the Synthesis of Nanocapsules Active for H2 Release from Ammonia-Borane.

Abstract

Herein, we achieved spontaneous emulsification of organometallic precursors to elaborate subμm metal nanocapsules after interfacial reduction. Depending on the proportion of the three components, water, solvent, and the metal precursor, either thermodynamically stable "surfactant-free microemulsions" (SFME) or metastable Ouzo emulsions are formed. We investigated the catalytic transition metals Au, Pd, and Pt, individually or combined, and stabilized by various ligands. Upon reduction of the precursors, either shells of discrete nanoparticles (NPs) or continuous shells were obtained, for the SFME and Ouzo emulsions, respectively. The Au/Pd mixed emulsions lead to a unique structural morphology, in which the Au-Pd nanoparticles are embedded in a continuous submicronic metal shell. The AuNPs are available to grow larger particles within the NP shell using a seeded growth approach. The water-stable and surfactant-free nanocapsules are appealing as catalysts, and, as such, were evaluated for the hydrolysis of ammonia-borane as a promising catalytic strategy for H₂ release from an H-high-content storage material. This work establishes for the first time a genuine activity of water-compatible gold colloids for this reaction.