Date of Award
Doctor of Philosophy (PhD)
Mechanical Engineering with a specialization in Chemical Engineering
Palladium catalysts., Nanostructures.
Atomic layer deposition (ALD) has been shown to be effective at controlling metal and metal oxide sites and demonstrated to be a promising tool to apply oxide over-coating layers onto supported metal catalysts with atomically precise thickness control, which allowed optimizing both the stability and activity. The mechanisms for depositing Al2O3, TiO2, palladium and ZnO were investigated with quartz crystal microbalance (QCM) and ellipsometry in order to better understand and improve the process. Presented is a study of ALD from nanometer to single atom size palladium catalysts. There are many uses for of palladium nanoparticles, catalysts, polymer membranes, sensor, plastics and fuel cells as many others. Currently single atom catalysts have been of much interest due to higher activity performance and much investigation due to poor stability. Displayed is a study of palladium single atom catalysts with protective oxide coatings synthesized by ALD to improve the thermal stability. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), scanning transmission electron microscope (STEM) and X-ray absorption spectroscopy (XAS) revealed the presence of palladium single atoms. The catalytic activity of these Pd1 catalysts was evaluated using formic acid and methanol decomposition as probe reactions. The observation of surface nanoparticles supported the further search of alternative mechanisms to stabilize single atoms by ALD. In an additional palladium deposition study, the growth of nanometer size palladium on ZnO-passivated carbon was examined by ALD. X-ray diffraction (XRD), scanning electron microscopy (SEM) and XAS were essential to determine the structure of the catalysts which were tested as cathode material in a rechargeable lithium-oxygen battery. These palladium catalysts synthesized by ALD, showed highly active catalytic effect as regards to electrochemical reactions. The discoveries in this work contribute to a better understanding on various ALD systems in order to stabilize single atoms.
Piernavieja Hermida, Mar, "Design and synthesis of nanostructured palladium catalysts by atomic layer deposition" (2016). Dissertations. 112.