Colloidally Prepared Nanoparticles for the Synthesis of Structurally Well‐Defined and Highly Active Heterogeneous Catalysts

Abstract

Colloidally prepared metal nanoparticles are gaining attention for catalytic applications because of the advanced possibilities to tailor particle size and shape, which are often important factors governing activity and selectivity. In the case of bimetallic catalysts, composition is usually difficult to control by traditional techniques, but by colloidal chemistry the relative portions of the metals in the nanoparticles can be exactly predefined. This approach not only offers the advantage of controlling structure and composition but also allows very high particle loadings. Colloidal nanoparticles with well-defined size and shape have a strong tendency to self-organize into well-ordered and close-packed 2D arrangements.[1, 2] Thus, it can be expected that depositing colloidal nanoparticles on powder supports or on monolithic structures will yield catalysts with high particle loadings, which would be of interest for various applications in heterogeneous catalysis.

Ligand Capping of Colloidally Synthesized Nanoparticles—A Way to Tune Metal–Support Interactions in Heterogeneous Gas‐Phase Catalysis

“…In the case of the pristine DDA-capped Pt (Figure 3 b)) exposed to CO and O 2 , the most dominant peak (2068 cm À1 ) indicates that a large part of the Pt surface must be in the metallic state, [26] whereas the shoulder at 2082 cm À1 is characteristic for CO adsorption on Pt d+ as could be expected in the vicinity of oxidized Pt. [28] (Please note that the band at 2197 cm À1 can be assigned to a nitrile species [29] and points to some ligand spillover of the amine from the Pt to the Fe 3 O 4 . The amine is then catalytically dehydrogenated by Fe 3 O 4 to the corresponding nitrile.…”

Revitalizing silver nanocrystals as a redox catalyst by modifying their surface with an isocyanide-based compound

“…Although organic ligands are oen used to stabilize the particles during their colloidal synthesis, it has long been recognized that the organic ligands remaining on the surface could relentlessly "poison" catalytic particles by simply blocking the active sites. [21][22][23][24][25] Here we demonstrate that organic ligands can have a positive impact on the properties of catalytic particles. Specically, we discover that an isocyanide compound can adsorb on the surface of Ag nanocubes to enable the Agcatalyzed redox reaction between isocyanide and nitroaromatic molecules toward the production of an aromatic azo compound under ambient conditions.…”

Ionic liquids in electrocatalysis

“…It has been demonstrated experimentally that such systems may exhibit better selectivity and even higher activities than their uncoated analogs in various hydrogenation reactions [5,[47][48][49][50] . The promotional effect of the IL layer may stem from a twofold manner: (1) ILs may directly interact with the active center as a ligand; (2) ILs would modify the effective concentration of the reactant at the catalytically active sites [50,51] . Especially the importance of the promotional effect as a ligand could be deduced in a unique manner due to the possibility of molecular variation of the IL and possibilities to carry out ultra-high vacuum (UHV)-based characterization due to the extremely low vapor pressure of most ILs [52][53][54] .…”