Characterisation of gold catalysts

Abstract

Au-based catalysts have established a new important field of catalysis, revealing specific properties in terms of both high activity and selectivity for many reactions. However, the correlation between the morphology and the activity of the catalyst is not always clear although much effort has been addressed to this task. To some extent the problem relates to the complexity of the characterisation techniques that can be applied to Au catalyst and the broad range of ways in which they can be prepared. Indeed, in many reports only a few characterization techniques have been used to investigate the potential nature of the active sites. The aim of this review is to provide a critical description of the techniques that are most commonly used as well as the more advanced characterization techniques available for this task. The techniques that we discuss are (i) transmission electron microscopy methods, (ii) X-ray spectroscopy techniques, (iii) vibrational spectroscopy techniques and (iv) chemisorption methods. The description is coupled with developing an understanding of a number of preparation methods. In the final section the example of the supported AuPd alloy catalyst is discussed to show how the techniques can gain an understanding of an active oxidation catalyst.

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

“…[11,12,[32][33][34][35][36][37][38][39] Sub-nanometer-sized unsupported gold clusters can accelerate specific reactions with extremely large turnover numbers( TONs) and turnover frequencies (TOFs). [69,70,[79][80][81][82][71][72][73][74][75][76][77][78] In the majority of homogeneous Au catalysts, Au exists in the + 1 oxidation state. [43][44][45] Owing to the localizeds urface plasmon resonance (LSPR)e ffects, [46][47][48] gold nanoparticles (AuNPs) can be used as photocatalysts.…”

Untangling the Role of the Capping Agent in Nanocatalysis: Recent Advances and Perspectives

“…Indeed, because of their high-dispersed state, metal nanoparticles in solution tend to spontaneously agglomerate and coagulate, therefore need to be stabilized [4]. The stabilization of MNPs can be achieved by immobilization on a support or by wrapping them in an organic ligand shell [13][14][15].…”

“…Nanocatalysis combines the advantages of easy separation, handling and reuse, typical of heterogeneous catalysts, and the benefits of homogeneous catalysis, namely high selectivity and efficiency [9]. Nevertheless, understanding the structure-reactivity relationship at atomistic level still represents a major challenge in the ratio design of nanocatalysts [10][11][12][13].…”

Alcohol Synthesis from CO2, H2, and Olefins over Alkali‐Promoted Au Catalysts—A Catalytic and In situ FTIR Spectroscopic Study

“…[24][25][26] Interaction of the CO probe molecule with the Au sites is weak and reversible. [24][25][26] Interaction of the CO probe molecule with the Au sites is weak and reversible.…”

“…[24][25][26] Interaction of the CO probe molecule with the Au sites is weak and reversible. [24,25,[28][29][30] The CO-adsorbate spectra measured at À160 8C for freshly prepared TiO 2 -based catalysts are displayed in Figure 4a.I na ll catalysts ab and around 2125 cm À1 can be seen with as houlder around 2108 cm À1 .T he latter band is assigned to nAu 0 ÀCO, whereas the band around2 125 cm À1 is relatedt o the CO adsorbed on Au d+ + sites. [24,25,[28][29][30] The CO-adsorbate spectra measured at À160 8C for freshly prepared TiO 2 -based catalysts are displayed in Figure 4a.I na ll catalysts ab and around 2125 cm À1 can be seen with as houlder around 2108 cm À1 .T he latter band is assigned to nAu 0 ÀCO, whereas the band around2 125 cm À1 is relatedt o the CO adsorbed on Au d+ + sites.…”