Advanced Electron Microscopy of Metal–Support Interactions in Supported Metal Catalysts

Abstract

Electron microscopy and its associated techniques have contributed significantly to the characterization of heterogeneous catalysts, especially supported metal catalysts, and can provide nano‐ or atomic‐scale information on the structure, morphology, composition, and electronic state of the area of interest. With the recent advancement in aberration corrections to achieve an image resolution below 0.1 nm and the rapid development of in situ techniques, advanced electron microscopy is poised to probe fundamental questions of heterogeneous catalysis and catalysts. Understanding the nature of metal–support interactions becomes critical if we want to achieve the goal of designing and fabricating nanoarchitectured catalysts with desired performances. To reliably probe the fundamental mechanisms of charge transfer, which is the core of catalysis, between individual nanoscale components and under a realistic gas environment and temperature is still a formidable challenge. This Review discusses the recent contribution of advanced electron microscopy to the study of metal–support interactions, as well as the challenges and opportunities of applying aberration‐corrected electron microscopy techniques to the investigation of atomic‐scale structures of complex heterogeneous catalysts.

Advanced analytical electron microscopy for lithium-ion batteries

“…1,13 Improvements in ultrahigh spatial and energy resolutions have been accompanied by remarkable advances of in situ TEM techniques, which enable the real-time observation of the dynamic structural and chemical evolution in materials under a variety of external stimuli or battery operating conditions. The progress in this field is evident, as demonstrated by the success of in situ mechanical testing or heating while maintaining a high spatial resolution, 14,15 by the imaging of reaction processes in gases and liquids, [16][17][18][19] by the observations of reactions and phase transformations upon external biasing 20,21 and so on. In addition, the newly developed CMOS camera, which enables the direct electron detection and fast image acquisition at over 400 frames per second for 1 × 1 K images, has significantly advanced the capability to observe fast reactions in real time.…”

Supported Noble Metals on Hydrogen‐Treated TiO2 Nanotube Arrays as Highly Ordered Electrodes for Fuel Cells

“…Pt loading on the Pt-air-TNTs electrode was lower than that on Pt-H-TNTs (shown in Table 2); this could be attributed to the anchoring of more Pt atoms because of the increased number of oxygen vacancies and hydroxyl groups that were created during hydrogenation. [27] Prior to Pt electrodeposition, the H-TNTs were pretreated with Pd nanoparticles by using a successive ion adsorption [28] Typically, the TNT sample was initially sensitized in an aqueous solution containing SnCl 2 and HCl for 8 min before the sample was rinsed with deionized water for 30 s to remove excess ions that were weakly bound to the top of TNTs. The sample was then activated by using a solution containing PdCl 2 and HCl for 2 min; finally, the sample was washed with deionized water.…”

“…This indicates that using Pd as an activator could provide more uniform nucleation sites for Pt. [21,27] In contrast to the TNTs that did not contain electrodeosited catalysts, the H-TNT-supported catalysts annealed in H 2 at 450 8C for a further 1 h (Pt-Pd-H-TNTs-1-450-H) exhibited no change in morphology for the Ti sheet. After annealing, the smaller Pt nanoparticles on the Pt-Pd-H-TNTs-1 aggregated together and the mean diameter increased to 6.1 nm, also the surface of the Pt tended to become less rough.…”

Catalysis by gold: New insights into the support effect

“…Generally, metal-support interaction (MSI) plays an important role in affecting the catalytic performances of supported nanocatalysts [22,23], especially for Au-based catalysts that are sensitive to many factors such as the size of GNPs, valence state of gold and synthesis methods [24,25]. The combined effect of the above factors makes the catalytic mechanism of the supported gold systems quite complicated.…”