Modeling Core-Shell Nanocatalysts Preparation using Water in Oil Microemulsions

The development of a new-generation of catalysts with a high catalytic performance requires the ability to manipulate the structure at the nanoscale. Specifically, controlling the metal distribution in bimetallic nanocatalysts is the key to improving their catalytic activity. The long term objective of the present study is implementing the know-how in the preparation of bimetallic nanoparticles in microemulsions. Such a challenge aim can only be reached if the factors affecting the sequence of metals are analyzed. To this end, we developed a computer simulation model on the one-step synthesis of bimetallic nanoparticles in microemulsions. The model predicts the metal distribution in bimetallic nanocatalysts under different experimental conditions. Au/Pt and Au/Ag nanostructures are analyzed and discussed from a mechanistic point of view. Conclusions can be generalized to other bimetallic couples with similar differences in standard reduction potentials. It was proved that both surface and interior compositions can be controlled at nanometer resolution easily by changing the initial reactant concentration inside micelles. Kinetic study shows that the reaction rates of the metal precursors are deeply influenced by the confinement of reactants inside micelles. As a result, the final nanocatalyst shows a more mixed core and a better defined shell as concentration is higher.