Tomographic Heating Holder forIn SituTEM: Study of Pt/C and PtPd/Al₂O₃Catalysts as a Function of Temperature

Abstract

A tomographic heating holder for transmission electron microscopy that can be used to study supported catalysts at temperatures of up to~1,500°C is described. The specimen is placed in direct thermal contact with a tungsten filament that is oriented perpendicular to the axis of the holder without using a support film, allowing tomographic image acquisition at high specimen tilt angles with minimum optical shadowing. We use the holder to illustrate the evolution of the active phases of Pt nanoparticles on carbon black and PtPd nanoparticles on γ-alumina with temperature. Particle size distributions and changes in active surface area are quantified from tilt series of images acquired after subjecting the specimens to increasing temperatures. The porosity of the alumina support and the sintering mechanisms of the catalysts are shown to depend on distance from the heating filament.

Fine Dispersion of Pt4–5 Subnanoclusters and Pt Single Atoms over Porous Carbon Supports and Their Structural Analyses with X-ray Absorption Spectroscopy

“…However, in comparison with the oxide supports, small and therefore more active nanoparticles tend to agglomerate or sinter on the carbon surface. 11 This is mainly due to the following two reasons. First, inorganic metal complexes are difficult to disperse on hydrophobic carbon surface and their agglomeration results in the formation of large nanoparticles during the reduction process.…”

Structural and Morphological Changes of Co Nanoparticles and Au-10at.%Pd Thin Film Studied by in Situ Heating in a Transmission Electron Microscope

“…An important factor that is characterized during experiments is the temperature measured inside a transmission electron microscope (TEM) (Allard et al, 2009;Asoro et al, 2013;Barwick et al, 2008;Gontard et al, 2014;Ivanov et al, 1995;Kim et al, 2015;Lee et al, 2003;Park et al, 2009;Saka et al, 2008;Takeo et al, 2006;Zhang & Su, 2009). Commercial TEM heating holders are typically based on precision-machined parts that can suffer from slow response time, drift, and instability, particularly at elevated temperatures.…”

“…One method for measuring the actual actual sample temperature is to calibrate the measurement by observing the melting and phase transition points of the samples and comparing the read-out on the heating controller with the known values for the melting and phase transition points of the samples (Saka et al, 2008). Another method relies on the direct contact between catalyst nanoparticles and a tungsten filament with a small thermal mass, instead of using a TEM grid (Gontard et al, 2014). In yet another approach, the sublimation kinetics from the isothermal experiments on silver nanoparticles have been used to measure the actual temperatures of the nanoparticles by considering the localized heating from the electron beam (Asoro et al, 2013).…”

Transmission electron microscopy of thiol-capped Au clusters on C: Structure and electron irradiation effects

“…Although the phase diagrams of nanoparticles and clusters can be predicted theoretically based on thermodynamics, such calculations cannot easily be used to predict nanoparticle shapes that result from kinetic considerations and they usually do not consider the role of the support (Barnard et al, 2009;Kuwauchi et al, 2013;Gontard et al, 2014).…”