RESUMO
Galvanic exchange seeds the growth of Pt nanostructures on the Ni foam monolith. Subsequent atomic layer deposition of ultrathin Al2O3 followed by annealing under air affords supported Pt catalysts with ultralow loading (0.020 ppm). In addition to the expected enhancement of the stability of the Pt particles on the surface, the â¼2 nm Al2O3 overcoat appears to also play a crucial role in the overall structural integrity of the NiOx nanoplates that grow on the Ni foam surface as a result of the preparative route. The resulting material is physically robust toward repeated handling and showcases retention of catalytic activity over 10 standard catalyst recycling trials, standing in marked contrast to the uncoated samples. Catalyst activity was tested via the hydrogenation of various functionalized styrenes at low temperatures and low hydrogen pressure in ethanol as a solvent, with a TOF as high as 9.5 × 106 h-1 for unfunctionalized styrene. Notably, the catalysts show excellent tolerance toward F, Cl, and Br substituents and no hydrogenation of the aromatic ring.
RESUMO
The interaction of hydrogen-terminated silicon nanoparticles (H-SiNPs) with Karstedt's catalyst at various temperatures was investigated. The results indicate that at room temperature, the oxidative addition of Pt(0) onto H-SiNPs is irreversible, and the catalyst is not eliminated from the surface of H-SiNPs, enabling a facile synthesis of Pt-loaded SiNPs that can undergo ligand exchange. The nature of the Pt-on-Si ensemble is characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Reaction conditions that enable effective hydrosilylation are discussed. It is found that higher temperatures favor reductive elimination of the catalyst and hydrosilylation of 1-octene onto the surface of the H-SiNPs.