Atom Probe Tomography for Catalysis Applications: A Review

Abstract

Atom probe tomography is a well-established analytical instrument for imaging the 3D structure and composition of materials with high mass resolution, sub-nanometer spatial resolution and ppm elemental sensitivity. Thanks to recent hardware developments in Atom Probe Tomography (APT), combined with progress on site-specific focused ion beam (FIB)-based sample preparation methods and improved data treatment software, complex materials can now be routinely investigated. From model samples to complex, usable porous structures, there is currently a growing interest in the analysis of catalytic materials. APT is able to probe the end state of atomic-scale processes, providing information needed to improve the synthesis of catalysts and to unravel structure/composition/reactivity relationships. This review focuses on the study of catalytic materials with increasing complexity (tip-sample, unsupported and supported nanoparticles, powders, self-supported catalysts and zeolites), as well as sample preparation methods developed to obtain suitable specimens for APT experiments.

Confining isolated atoms and clusters in crystalline porous materials for catalysis

“…However, more powerful detector and extremely high sample stability is required to obtain reliable information by such analysis 97 . On the other hand, to obtain the chemical composition information in 3D, atom probe tomography (APT), which has been widely used for nanoscale and bulk materials, can be a very useful tool to depict the chemical composition of porous composition materials with atomic resolution 98,99 . For instance, the 3D distributions of Al and Cu in zeolite crystallites and Ni atoms embedded in carbon matrix have been revealed by APT with a spatial resolution below 1 nm [100][101][102] .…”

A review of recent developments for the in situ/operando characterization of nanoporous materials

“…APT is the only tomographic method that allows the 3D chemical analysis of the specimen with atomic-scale resolution and in principle with no limits for light and heavy atoms. [108][109][110][111][112] Through the needle shape of the specimen, several facets with different crystallographic orientations are measured simultaneously and the tip can be considered as a model for a single crystal. [110] The implementation of different advances greatly enhanced the field of application of this technique, such as the local electrode geometry which improved the field effect, and the use of a reflectron enhancing the mass resolution.…”

“…[108][109][110][111][112] Through the needle shape of the specimen, several facets with different crystallographic orientations are measured simultaneously and the tip can be considered as a model for a single crystal. [110] The implementation of different advances greatly enhanced the field of application of this technique, such as the local electrode geometry which improved the field effect, and the use of a reflectron enhancing the mass resolution. The usage of thermal laser impulses for the initiative evaporation allowed the analysis of non-conductive materials.…”

“…[110] The sample preparation via FIB to needle-shaped specimens made it possible to analyze also semiconductors, and even non-conductive materials. [109,110] In particular, for nonconducting zeolites with small crystallite sizes, the needle shaping of the analyte via FIB preparation is crucial since a high electric field is needed to introduce the fundamental emissive behaviour such as field emission, field ionization, and/or field evaporation. [108,110] During the preparation, the possibility of beam damage of sensitive materials (e.g.…”

“…[109,110] In particular, for nonconducting zeolites with small crystallite sizes, the needle shaping of the analyte via FIB preparation is crucial since a high electric field is needed to introduce the fundamental emissive behaviour such as field emission, field ionization, and/or field evaporation. [108,110] During the preparation, the possibility of beam damage of sensitive materials (e.g. zeolites or MOFs) has to be accounted for by minimizing imaging time and the use of protective layers.…”