(653a) Preparation of Uniform Nanostructures for Heterogeneous Catalysis By Fast Annealing of Monodisperse Metal Nanocrystals

Fundamental understanding of catalyst operation is key for the preparation of improved heterogeneous systems for several catalytic applications. In metal-supported systems, controlling the size, shape and composition of metal nanocrystals is pivotal for drawing structure-activity relationships that can help prepare systems with improved reaction rates, selectivity and stability. To this aim, nanotechnology tools and colloidal synthesis provide a wide variety of synthetic techniques for the preparation of tailored materials with desirable characteristics for catalysis. One of the main issues, however, are the changes to the nanostructures associated with calcination treatments to remove organic ligands and stabilize the overall structure or with the reaction conditions. Finding appropriate ways to activate the materials for catalytic reactions without altering the desired properties of the structures after their synthesis is therefore highly challenging but pivotal to fully exploit the potential of colloidal synthesis for the preparation of heterogeneous catalysts.

In this contribution, we show that uniform nanostructures can be prepared by starting from highly monodisperse metal nanocrystals and by dispersing them onto high-surface area supports. Key to preserving the uniformity of the metal particles is an activation procedure consisting of a fast annealing step that maintains the initial uniform structures in terms of size, shape and composition. Additionally, the activation step allows for an improved thermal stability of the systems by the creation of kinetically stabilized structures that are usually not obtained by conventional calcination treatments. We show how the stabilization of highly uniform metal nanocrystals for catalysis is helpful in understanding structure-activity relationships in heterogeneous systems.