In Situ Industrial Bimetallic Catalyst Characterization using Scanning Transmission Electron Microscopy and X-ray Absorption Spectroscopy at One Atmosphere and Elevated Temperature

Eric Prestat(1), Matthew A. Kulsick(2), Paul J. Dietrich(2), Mr. Matthew Smith(1), Mr. Eu-Pin Tien(1), M. Grace Burke(1), Sarah J. Haigh(1), and Nestor J. Zaluzec(1,3), 2017

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We have developed a new experimental platform for in situ scanning transmission electron microscope (STEM) energy dispersive X-ray spectroscopy (EDS) which allows real time, nanoscale, elemental and structural changes to be studied at elevated temperature (up to 1000 °C) and pressure (up to 1 atm). Here we demonstrate the first application of this approach to understand complex structural changes occurring during reduction of a bimetallic catalyst, PdCu supported on TiO2 , synthesized by wet impregnation. We reveal a heterogeneous evolution of nanoparticle size, distribution, and composition with large differences in reduction behavior for the two metals. We show that the data obtained is complementary to in situ STEM electron energy loss spectroscopy (EELS) and when combined with in situ X-ray absorption spectroscopy (XAS) allows correlation of bulk chemical state with nanoscale changes in elemental distribution during reduction, facilitating new understanding of the catalytic behavior for this important class of materials. Keywords: X-ray absorption spectroscopy; electron microscopy; energy dispersive X-ray spectroscopy; nanoparticles; supported catalysts

Impact Statement

Here, the authors studied PdCu on TiO2 under reducing conditions and up to 1000 deg C. As such, the observe differences in structural changes between the different metals and were able to characterize those differences using a multitude of in situ techniques including STEM, EDS, EELS, and XAS. This research both provides an excellent template for future experiments as well as shines light on catalytic behavior for PdCu materials.