In‐situ Scanning Transmission X‐Ray Microscopy of Catalytic Solids and Related Nanomaterials

Abstract

The present status of in-situ scanning transmission X-ray microscopy (STXM) is reviewed, with an emphasis on the abilities of the STXM technique in comparison with electron microscopy. The experimental aspects and interpretation of X-ray absorption spectroscopy (XAS) are briefly introduced and the experimental boundary conditions that determine the potential applications for in-situ XAS and in-situ STXM studies are discussed. Nanoscale chemical imaging of catalysts under working conditions is outlined using cobalt and iron Fischer-Tropsch catalysts as showcases. In the discussion, we critically compare STXM-XAS and STEM-EELS (scanning transmission electron microscopy-electron energy loss spectroscopy) measurements and indicate some future directions of in-situ nanoscale imaging of catalytic solids and related nanomaterials.

Polyethylene with Reverse Co‐monomer Incorporation: From an Industrial Serendipitous Discovery to Fundamental Understanding

“…[1] Further details on catalyst synthesis can be found in the Supporting Information. Ty pically,a no lefinic co-monomer (i.e., 1-hexene) is added externally to the reaction mixture and has to diffuse through the growing polymer and catalyst material to arrive at the catalytic sites.W eenvisioned that it would be advantageous if the co-monomer was generated on the TEAlmodified active sites within the Ti-scarce catalyst particle close to the active sites that make ah igh molecular weight polymer.T herefore,i nsitu produced olefins (e.g., 1-hexene) would be incorporated into longer polyethylene chains.W e show for the first time that we can relate these macroscale polymer properties to nanoscale chemical imaging of (earlystage polymerisation) Cr/Ti/SiO 2 catalyst particles by making use of scanning transmission X-ray microscopy (STXM) [20][21][22] as an alternative approach to the research of Barzan et al, who studied hydrosilane compounds as co-catalyst. [23] In af irst series of experiments,t he catalyst and its polymerisation behaviour were studied using in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy.T he obtained DRIFT spectra measured as af unction of time-on-stream for the Cr/Ti/SiO 2 catalyst under study are shown in Figure 2a.T he initial spectrum corresponds with ah ighly dehydroxylated catalyst as testified by the sharp silanol and titanol stretching bands located at 3747 cm À1 and 3722 cm À1 ,respectively.During the first 5min, the injection of the TEAl co-catalyst in heptane,for aAl:Cr molar ratio of 2, can be noted by the increase of the methyl and methylene stretching bands of these compounds in the 2800-3000 cm À1 CH stretching region.…”

Characterization of 3D interconnected microstructural network in mixed ionic and electronic conducting ceramic composites

“…[23][24][25] This technique addresses unexplored issues at the mesoscale; how do the phases, interfaces, resulting microstructure and potential changes during operation effect performance? Here we demonstrate the use of this technique to identify and map distinct phases in MIEC ceramic composite membranes.…”

TXM-Wizard: a program for advanced data collection and evaluation in full-field transmission X-ray microscopy

“…In the latter case the final image is built from point-by-point information collected via raster scanning of the sample using a focused X-ray beam (e.g. de Groot et al, 2010). However, when a full-field TXM system is used for XAS, the experiment and data analysis are quite different, mainly because spectra are extracted from the image stack collected, usually resulting in $ 1 Â 10 6 generated spectra (see x6 and Meirer et al, 2011).…”