Development of Next Generation of Nano-Catalysts Prepared by Novel Methods for Environmental and Energy Application

Supported metal nanoparticles (NPs) catalysts play a critical role in modern chemical industries. Catalytic performance of supported metal NPs, including activity, selectivity, and stability, is influenced by many different factors. These factors include properties of NPs and support materials. In the first part of this project, supported Rh nanocatalysts were produced by a novel doping-segregation method. Different ex-situ and in-situ characterization techniques were utilized to systematically investigate the doping-segregation process in order to gain fundamental knowledge on this phenomenon. This knowledge was employed to produce supported Rh nanocatalysts with outstanding catalytic performance. In the second part of this project, supported Au NPs model catalysts were produced by an innovative helium nanodroplet deposition (HNDD) method. They were systematically investigated by utilizing various characterization techniques. The results indicated that the produced Au NPs were highly stable and catalytically active making them suitable for fundamental study of catalysis.;The techniques utilized for characterization of Rh NPs supported on SrTiO 3 (STO) produced by doping-segregation method included such in-situ techniques as X-ray Diffraction (XRD), X-ray Absorption Fine Structure (XAFS), and Environmental Transmission Electron Microscopy (E-TEM). The results obtained from these techniques indicated that the size of produced Rh NPs can be finely tuned by controlling the segregation temperature. Additional understanding of Rh NPs properties was obtained from in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and a catalytic CO2 hydrogenation reaction. It was implied that the shape of Rh NPs remained consistent across different particle sizes. The outstanding performance of the catalysts was attributed to extremely small size of the Rh NPs and enhanced surface reducibility of STO.;The techniques utilized for studying properties of Au NPs produced by helium nanodroplet include TEM, Temperature-Programed Reaction(TPR), etc. TEM imaging indicated that HNDD method produced NPs with tunable size with narrow distribution. Subsequently, the NPs were deposited on catalytically relevant support materials and characterized by different techniques. More specifically, Au NPs were deposited onto different model TiO2 supports, including TiO2 thin film modified E-TEM chips and TiO2 single crystal. The E-TEM results indicated an outstanding stability of NPs under CO oxidation condition. Moreover, the catalytic activity and good stability of the model catalyst were confirmed by TPR and X-ray photoelectron spectroscopy (XPS) techniques.;In conclusion, in-situ and ex-situ studies of both practical and model nanocatalysts produced by novel synthetic methods developed new knowledge of properties and performance of the new generation of tunable catalytic materials.