Critical review: Effects of complex interactions on structure and dynamics of supported metal catalysts

Abstract

This review article takes a new look at the problem of characterization of structural properties and reaction dynamics of supported metal catalysts. Such catalysts exhibit an inherent complexity, particularly due to interactions with the support and the adsorbate molecules, which can be highly sensitive to environmental conditions such as pressure and temperature. Recent reports demonstrate that finite size effects such as negative thermal expansion and large bond length disorder are directly caused by these complex interactions. To uncover the atomistic features underlying the reaction mechanisms and kinetics of metal catalysts, experimental characterization must accommodate the challenging operation conditions of catalytic processes and provide insights into system attributes. The combined application of x-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) for this type of investigations will be examined, and the individual strengths and limitations of these methods will be discussed. Furthermore, spatial and temporal heterogeneities that describe real catalytic systems and can hinder their investigation by either averaging (such as XAS) or local (such as TEM) techniques alone will be addressed by conjoined, multiscale, ab initio density functional theory/molecular dynamics modeling of metal catalysts that can both support and guide experimental studies. When taken together, a new analysis scheme emerges, in which different forms of structure and dynamics can be fully characterized by combining information obtained experimentally by in situ XAS and electron microscopy as well as theoretically via modeling. V

Time‐Resolved, In Situ DRIFTS/EDE/MS Studies on Alumina‐Supported Rhodium Catalysts: Effects of Ceriation and Zirconiation on Rhodium–CO Interactions

“…[40] Moreover, a recent study of γ-Al 2 O 3 -supported Pt particles with an average diameter of 1 nm demonstrated a Pt–Pt bond length contraction at elevated temperatures. [41] The largest rhodium particles were observed for zirconiated rhodium catalysts throughout CO exposure at the temperatures studied. These results suggest that Zr species are in intimate contact with Rh entities to form larger Rh particles under H 2 /He at 323 K, which consequently protects them against oxidative disruption upon exposure to CO/He.…”

Single-Atom Catalysts: From Design to Application

“…Metal-support interactions play a pivotal role in the performance of supported catalysts [148][149][150] by not only enhancing stability, but also by endowing improved catalytic properties such as significantly enhanced catalytic activities and selectivity due to altered electronic structures or synergetic catalytic effects [2,[151][152][153][154]. And in SACs, this effect is more pronounced and is a determining factor in the performance of SACs due to contact between isolated metal atoms and supports [155].…”

Decoding reactive structures in dilute alloy catalysts

“…A useful tool for unlocking this relationship is an operando experiment, in which changes in structural and chemical features are measured simultaneously with the catalytic activity [25][26][27] . However, the small amount of active component in dilute alloys, compounded with low weight loading of the particles, require characterization tools with sufficient surface and chemical sensitivities.…”