Dynamic Processes on Gold-Based Catalysts Followed by Environmental Microscopies

Abstract

Abstract:Since the early discovery of the catalytic activity of gold at low temperature, there has been a growing interest in Au and Au-based catalysis for a new class of applications. The complexity of the catalysts currently used ranges from single crystal to 3D structured materials. To improve the efficiency of such catalysts, a better understanding of the catalytic process is required, from both the kinetic and material viewpoints. The understanding of such processes can be achieved using environmental imaging techniques allowing the observation of catalytic processes under reaction conditions, so as to study the systems in conditions as close as possible to industrial conditions. This review focuses on the description of catalytic processes occurring on Au-based catalysts with selected in situ imaging techniques, i.e., PEEM/LEEM, FIM/FEM and E-TEM, allowing a wide range of pressure and material complexity to be covered. These techniques, among others, are applied to unravel the presence of spatiotemporal behaviours, study mass transport and phase separation, determine activation energies of elementary steps, observe the morphological changes of supported nanoparticles, and finally correlate the surface composition with the catalytic reactivity.

Reshaping Dynamics of Gold Nanoparticles under H2 and O2 at Atmospheric Pressure

“…For a better understanding of the reactivity of gold and gold-based nanocatalysts, a number of environmental microscopies have been used to study in situ the structural parameters under reactive gas environments over a wide range of pressure and temperature. , Among these microscopies, environmental gas transmission electron microscopy has emerged as an important tool enabling real-time atomic-scale visualization of structural evolution of nanomaterials under gas environments and temperature. − It has already provided some insights into the reactivity of Au NPs with O 2 and H 2 molecules through atomic-scale and real-time visualization of particle equilibrium shape under these gases. ,, However, environmental gas TEM observations of Au NPs under O 2 and H 2 have until now been limited to low-pressure conditions of little relevance to catalytic reactions. The present work strives to bridge this pressure gap in the study of Au NPs under O 2 and H 2 .…”

Atom Probe Tomography for Catalysis Applications: A Review

“…Pd-Au specimens, with a composition of Pd-38 at.% Au, were studied after NO gas exposure at different temperatures and 60 mbar [52,91,102]. The sample preparation was performed using the electropolishing method from a Pd-38 at.% Au wire, using an aqueous solution of 20% KCN with 3 V DC .…”

Influence of CO addition on the toluene total oxidation over Co based mixed oxide catalysts

“…It is generally admitted that noble metal catalysts are preferred when there are no poisons (such as sulfur compounds, carbon monoxide...) present, and aromatic compounds are involved in the reaction.. However, due to the high cost of the noble metals, many studies have been devoted to the development of suitable catalysts containing only transition metal oxides [4][5][6][7][8][9][10]. Hydrotalcite-like compounds (HT) are presented as precursors of mixed oxides, with an enormous potential for the generation of well dispersed, active and very stable catalyst for several applications [11][12][13].…”