Observation of heterogeneous catalysts at operating pressure and temperature is important for studying the dynamics of catalyst restructuring, catalyst sintering and the role of morphology on reactivity. Impressive advances in our understanding of catalysts were made possible through the use of Environmental Transmission Electron Microscopy (ETEM). However, the ETEM approach required a differentially pumped TEM and the introduction of gas into the microscope column, limiting the operating pressure to a few Torr. There are many applications, such as automotive exhaust catalysis, where some of the phenomena do not occur at low pressures, and operation at atmospheric pressure is essential. In our studies we have used a Protochips AtmosphereTM closed-cell holder that confines the gas within a very thin (~5 μm) path between a Protochips AduroTM MEMS-based heater device and a thin amorphous SiN window. The catalyst is dispersed onto the Aduro heater, and can be heated to 1000 °C at up to atmospheric pressure, with closed-loop control independent of gas composition and pressure. Using this approach we are studying Pt and Pt-Pd/alumina diesel oxidation catalysts under “realistic” conditions, obtaining atomic-level STEM images in a JEOL 2200FS aberration-corrected STEM/TEM. In this presentation we will describe a study of the role of Pd in enhancing the stability of Pt-Pd diesel oxidation catalysts. This research was supported by NSF GOALI program grant CBET 1438765 and by General Motors Global R&D and at Oak Ridge National Laboratory by the U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office, Propulsion Materials Program.

Atomic-scale observations of heterogeneous catalyst reactions at up to atmospheric pressure

251st National Meeting (2016)

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