(231c) High-Precision Manufacturing of Core-Shell Nanoparticles for Catalysis

Many catalysts consist of nanometer-sized particles dispersed on a high-surface area support. In several cases, these nanoparticles are not just made of a single material, but have a more complex morphology such as a core-shell nature. A high degree of control over the synthesis of such particles could make catalysts substantially more efficient. In the current paper, we will discuss reaction engineering approaches for rational manufacturing of such catalysts. We propose two different ways to make such particles: one in the liquid phase and one in the gas phase using.

Our liquid-phase approach is based on multiphase-flow microfluidic devices. The synthesis of nanoparticles takes place inside aqueous droplets dispersed in oil. Each droplet acts as a batch reactor with a high level of control over reagent flow rates, residence time, mixing and temperature. Moreover, we are able to study kinetics of the reaction in a real time by applying optical fiber ports at different positions of the microchannel.

We use the gas-phase method Atomic Layer Deposition to deposit ultrathin coatings on nanoparticles through a layer-by-layer growth mechanism. The precursors, which are fed into the reactor in subsequent steps, react on the surface of the nanoparticles to deposit a monolayer of the coating. The thickness of the coating is controlled by repeating this cycle a desired number of times. This process is carried out in a fluidized bed reactor, which offers an excellent contact between the solids and reactants and a good scale-up potential.