Switchable Surfactants for the Preparation of Monodisperse, Supported Nanoparticle Catalysts and the Effects of Calcination

Development of synthesis methods for the preparation of monodisperse, supported nanoparticles remains challenging. Traditional synthetic methods require the use of stabilizing agents such as surfactants or ligands to prevent over growth and aggregation of nanoparticles. The presence of these stabilizers on catalytic surfaces can be detrimental to activity and therefore are typically removed via a high-temperature calcination. Calcination leads to significant and unpredictable growth of the nanoparticles, resulting in a decrease in total surface area and ultimately a decrease in catalytic activity. Here, we demonstrate how switchable surfactants can be used to prepare size controlled, ligand-free supported nanoparticles that are highly active prior to any thermal treatment. It is shown that even a low-temperature calcination of bare nanoparticles significantly changes properties of the active phase beyond those associated with changes in nanoparticle size. Additionally, it is demonstrated that nanoparticle growth during calcination in catalysts prepared via traditional methods is likely a result of weakened van der Waals interactions between the nanoparticle and support due to the presence of the stabilizing ligands.