Here, we used Pt-based intermetallic nanoparticles (iNPs), individually encapsulated in mesoporous silica shells, as catalysts for the hydrogenation of nitroarenes to functionalized anilines. Different from random alloys, intermetallic compounds (IMCs) present atomically-ordered structures, which is advantageous for catalytic mechanism studies. It is essential to bridge the structure-properties relationship of bimetallic catalysts for the rational design of heterogeneous catalysts. more » The high activity and selectivity of these catalysts result from the creation of oxygen vacancies on the TiO 2 surface by single-site Sn, which leads to efficient, selective activation of the nitro group coupled with a reaction involving hydrogen atoms activated on metal nanoparticles.
Represented as M/Sn-TiO 2 (M = Au, Ru, Pt, Ni), these catalysts decidedly outperform the unpromoted supported metals, even for hydrogenation of nitroarenes substituted with various reducible groups. The promoters are single-site Sn on TiO 2 supports that incorporate metal nanoparticle catalysts. The catalysts are used for the challenging nitroarene hydrogenation and found to have both high activity and selectivity. We extend this class of materials to catalysts that incorporate atomically dispersed metal atoms as promoters. « lessĪtomically dispersed supported metal catalysts are drawing wide attention because of the opportunities they offer for new catalytic properties combined with efficient use of the metals. Taken together, these improvements in functionalization, fabrication, and catalytic activity represent an important advance in the study of these emerging 2D nanostructures. photoluminescence, of the monolayers remained pristine, while the electrocatalytic activity towards the hydrogen evolution reaction is significantly improved. It is proposed that thiol groups at edges and defects sides reduce the AuCl 3 to Au 0 and are in turn oxidized to disulfides. This process may be exploited to enrich the dispersions in laterally large, monolayer nanosheets.
AuCl 3 is preferentially reduced on multi-layer WS 2 and resulting large Au aggregates are easily separated from the colloidal dispersion more » by simple centrifugation. Au nanoparticles (NPs) predominantly nucleate at nanosheet edges with tuneable NP size and density. The work herein illustrates that 2H-semiconducting liquid-exfoliated tungsten disulfide (WS 2) undergoes a spontaneous redox reaction with gold (III) chloride (AuCl 3). Chemical functionalization has evolved into a powerful tool to tailor properties of these 2D TMDs however, functionalization strategies have been largely limited to the metallic 1T-polytype.
Layered transition metal dichalcogenides (TMDs) represent a diverse, emerging source of two-dimensional (2D) nanostructures with broad application in optoelectronics and energy. more » These mechanistic insights reveal how the various defect structures and configurations on 2-D TMD nanostructures facilitate functional group selectivity through distinct mechanisms that depend upon the adsorption geometry, which may have important implications for the design of new and enhanced 2-D catalytic materials across a potentially broad scope of reactions. At lower sulfur vacancy concentrations on the basal planes, parallel adsorption of the nitroarene is favored, and the nitro group is selectively hydrogenated due to a lower kinetic barrier. At tungsten-terminated edges and on regions of the basal planes having high concentrations of sulfur vacancies, vertical adsorption of the nitroarene is favored, thus facilitating hydrogen transfer exclusively to the nitro group due to geometric effects. Microscopic and computational studies reveal the important roles of sulfur vacancy-rich basal planes and tungsten-terminated edges, which are more abundant in nanostructured 2-D materials than in their bulk counterparts, in enabling the functional group selectivity. Free-standing, colloidal 2H-WS 2 nanostructures containing few-layer nanosheets are shown to catalyze the selective hydrogenation of a broad scope of substituted nitroarenes to their corresponding aniline derivatives in the presence of other reducible functional groups. Here, colloidal 2H-WS 2 nanostructures are used as a model 2-D TMD system to understand how high catalytic activity and selectivity can be achieved for useful organic transformations.
Two-dimensional (2-D) TMDs, which contain single- and few-layer nanosheets, are increasingly studied as catalytic materials because of their unique thickness-dependent properties and high surface areas. Transition metal dichalcogenides (TMDs) are well known catalysts as both bulk and nanoscale materials.
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