Chemistry Department Colloquium

CHEMISTRY COLLOQUIUM
Friday, August 26th, 2016
11:00am – Hamilton Seminar Room
Chemistry Building, 555


Understanding the fundamental relationships between catalyst activity and structure at the nanoscale will enable the improved design of catalysts. In-situ and operando environmental transmission electron microscopy (ETEM) are powerful techniques for the investigation of structure-reactivity relationships in high surface area catalysts under reaction conditions. With new instruments, atomic resolution imaging and spectroscopy can be carried out in the presence of gas, liquid, light and thermal stimuli. The combination of mass spectrometry and electron energy-loss spectroscopy (EELS) allows catalytic products to be detected and quantified directly in the electron microscope. With aberration corrected TEM, the positions of atomic columns on nanoparticles surfaces can be observed and correlated with changes in conversion. New developments in monochromated EELS allow the electronic and vibrational structure of catalyst surfaces to be probed with focused electron beams. Using the so-called "aloof beam" approach to EELS, radiation damage is minimized potentially allowing electronic surface and defect states to be observed and correlated with catalytic properties.

Examples will be shown which illustrate the information that can be obtained with modern electron imaging and spectroscopy. In situ observations of the structural and chemical changes during activation of reforming catalysts consisting of Ni or NiRu nanoparticles on non-reducible (SiO2) and reducible (CeO2 or doped CeO2) supports will be described. The evolution of the metal and bimetallic structures can be correlated with conversion and selectivity to provide an understanding of nanoscale structure-reactivity relations for partial oxidation and steam reforming. Recent advances in the development of operando methods will be illustrated for CO oxidation on Ru where correlating reactio