Correlative Multiscale 3D Imaging of a Hierarchical Nanoporous Gold Catalyst by Electron, Ion and X‐ray Nanotomography

Abstract

Tomographic imaging of catalysts allows non‐invasive investigation of structural features and chemical properties by combining large fields of view, high spatial resolution, and the ability to probe multiple length scales. Three complementary nanotomography techniques, (i) electron tomography, (ii) focused ion beam—scanning electron microscopy, and (iii) synchrotron ptychographic X‐ray computed tomography, were applied to render the 3D structure of monolithic nanoporous gold doped with ceria, a catalytically active material with hierarchical porosity on the nm and μm scale. The resulting tomograms were used to directly measure volume fraction, surface area and pore size distribution, together with 3D pore network mapping. Each technique is critically assessed in terms of approximate spatial resolution, field of view, sample preparation and data processing requirements. Ptychographic X‐ray computed tomography produced 3D electron density maps with isotropic spatial resolution of 23 nm, the highest so far demonstrated for a catalyst material, and is highlighted as an emerging method with excellent potential in the field of catalysis.

First ptychographic X-ray computed tomography experiment on the NanoMAX beamline

“…Comparison of published PXCT experiments (Dierolf et al, 2010;Guizar-Sicairos et al, 2011Diaz et al, 2012Diaz et al, , 2014Esmaeili et al, 2013;Trtik et al, 2013;Holler et al, 2014Holler et al, , 2017Donnelly et al, 2015;Fløystad et al, 2015;Dam et al, 2015;Fam et al, 2018;Polo et al, 2018;Kahnt et al, 2018;Sala et al, 2019;Becher et al, 2019;Weissenberger et al, 2019; in magenta, cyan and yellow with the present data in red. (Left) The average achieved 2D translational scanning speed (scan dimensions for a single projection divided by the time it took to record one projection) plotted against the imaged volume.…”

3D Analysis of Ordered Porous Polymeric Particles using Complementary Electron Microscopy Methods

“…Polymer composites have been imaged with resolution below 1 μm 35 . The characterization of LiFePO4 nanoplates for batteries with 10 nanometer resolution enabled by soft X-ray and of catalysts with 23 nm space resolution, using synchrotron-based ptychographic X-ray computed tomography have been recently reported 36,37 .…”

Correlative Laboratory Nano‐CT and 360° Electron Tomography of Macropore Structures in Hierarchical Zeolites

“…[ 13 ] Another technique is synchrotron ptychographic X‐ray computed tomography (PXCT) [ 5c,d,14 ] with excellent spatial resolution down to about 20 nm of volumes in the range of (10 µm)³. [ 15 ]…”

“…combined synchrotron PXCT, FIB/SEM tomography, and ET to analyze nanoporous gold catalyst materials. [ 15 ] One recent application, including lab Nano‐CT for correlative studies in combination with FIB/SEM slice and view, was the 3D characterization of the internal structure of a chromatography bead. [ 2a ] Further examples are given by Schurch et al.…”