Hydrogenative Depolymerization of Nylons Kumar, Amit; von Wolff, Niklas; Rauch, Michael ...
Journal of the American Chemical Society,
08/2020, Letnik:
142, Številka:
33
Journal Article
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The widespread crisis of plastic pollution demands discovery of new and sustainable approaches to degrade robust plastics such as nylons. Using a green and sustainable approach based on ...hydrogenation, in the presence of a ruthenium pincer catalyst at 150 °C and 70 bar H2, we report here the first example of hydrogenative depolymerization of conventional, widely used nylons and polyamides, in general. Under the same catalytic conditions, we also demonstrate the hydrogenation of a polyurethane to produce diol, diamine, and methanol. Additionally, we demonstrate an example where monomers (and oligomers) obtained from the hydrogenation process can be dehydrogenated back to a poly(oligo)amide of approximately similar molecular weight, thus completing a closed loop cycle for recycling of polyamides. Based on the experimental and density functional theory studies, we propose a catalytic cycle for the process that is facilitated by metal–ligand cooperativity. Overall, this unprecedented transformation, albeit at the proof of concept level, offers a new approach toward a cleaner route to recycling nylons.
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•Pulsed laser deposition of GeTe-Sb2Te3 based heterostructures.•Influence of systematically varied deposition parameters on the microstructure.•Alternation of chemical composition and ...morphology - formation of Ge-Sb-Te layer.•Amorphous GeTe and Ge-Sb-Te, crystalline Sb2Te3 layers independent of parameters.•Sb2Te3 crystallites of different sizes featured by defects, and multiple phases.
Chalcogenide based heterostructures turned out to be a promising approach to further improve outstanding properties of phase change memory materials. For future applications, a deep understanding of the interplay of local structure and properties is crucial. Here, GeTe-Sb2Te3 based heterostructures (HSs) are grown by pulsed laser deposition onto SiO2/Si substrates at room temperature. By combining advanced transmission electron microscopy with X-ray measurement techniques, the influence of systematically varied deposition parameters on the microstructure is analyzed in-depth. Experimental results reveal that the growth rate of GeTe and Sb2Te3 layers depends on laser pulse energy. Nanoscale spectroscopic characterization of the HSs shows interdiffusion of Ge/Sb into Sb2Te3/GeTe layers, respectively. The in-diffusion depends on the layer thickness and deposition parameters. For the lowest laser energy, it leads to the formation of ternary Ge-Sb-Te layer. Whereas GeTe and Ge-Sb-Te are found to be amorphous within the HSs, Sb2Te3 is crystalline in all thin films although some disordered regions are found additionally. Moreover, Sb2Te3 is formed in cubic, vacancy ordered and trigonal structures and contains bilayer as well as twin defects. Overall, this work provides insights into the growth and microstructure of the HSs, which give the reasons for the outstanding performance of Sb2Te3-GeTe HSs.
A noble-metal-free bifunctional electrocatalyst with outstanding activity and stability is of great importance for the development of rechargeable zinc-air batteries (ZABs). Herein, we employed a ...facile strategy to fabricate nitrogen-doped NiCo2O4 nanostructures on carbon paper as a binder-free air cathode for rechargeable ZABs. An optimized process of nitrogen plasma treatment has enhanced the electrical conductivity of the metal oxide and induced abundant active sites into the crystal structures, resulting in enhanced electrocatalytic activities toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Notably, mild plasma treatment leads to efficient N doping while the morphology and specific surface area of the catalyst both remain unchanged. The air cathode with NiCo2O4 doped with nitrogen in 2 min plasma treatment and integrated into a zinc-air battery with liquid electrolyte provided a small charge-discharge voltage gap and distinguished cycling stability superior to the air cathode with noble-metal catalyst counterparts. Furthermore, the solid-state zinc-air battery with this material displays excellent stability with just a small increase of the charge-discharge voltage gap over 20 h of operation. This work illustrates the promising potential of plasma treatment in the fabrication of high-performance catalysts.
•N-doped NiCo2O4 was prepared by hydrothermal method and N2 plasma treatment.•Mild plasma treatment leads to efficient N doping in NiCo2O4.•NiCo2O4 with N2 plasma treatment of 2 min exhibits excellent OER/ORR performances.•N–NiCo2O4-2 min worked as a binder-free air cathode in Zn-air batteries.
Metal–ligand cooperation (MLC) by dearomatization/aromatization provides a unique way for bond activation, which has led to the discovery of various acceptorless dehydrogenative coupling reactions. ...However, most of the studies are based on pincer complexes with a central nitrogen donor. Aiming at exploration of the possibility of MLC by PCP-type pincer complexes, we report herein the synthesis, characterization, structure, and reactivity of pyridine-based PCP-Ru complexes. X-ray structures and DFT calculations indicate a carbenoid character of quaternized pyridine-based PCP-Ru complexes. These complexes undergo dearomatization by direct deprotonation, and the dearomatized complex can react with hydrogen, alcohols, or nitriles to regain aromatization via MLC.
The HelixJet atmospheric plasma‐assisted synthesis can be a new toolbox to realize dedicated nanoparticle architectures such as Janus‐type morphologies. Silicon nanoparticles produced by the ...decomposition of Silane molecules are directed into an in‐flight annealing stage. The applied high‐temperature supplies a metal vapor rich atmosphere containing Manganese, Chromium, Iron, and Tin outgassing from the used steel tube. The metal atoms alloy into the Silicon nanoparticles and form a self‐assembled 'Si/MnxSiy‐alloy' Janus nanosphere architecture. The Janus particles nanochemistry is thoroughly examined in detail by the analytic capabilities of transmission electron microscopy. The combined approach of electron diffraction, EDS, and EELS identifies the Janus particle composition consisting of a pure Si hemisphere interfaced to an alloyed Mn4Si7 hemisphere covered by a thin (MnaFebCrc)Siy surface shell.
A new approach to the formation of designed Si‐based Janus nanospheres is presented using the atmospheric plasma source HelixJet and an in‐flight annealing step releasing secondary elements from the selected steel tubing. Transmission electron microscopy investigation of the Janus nanosphere architectures identified the separation into Si/Mn4Si7 half‐spheres and its coverage by a Cr and Fe‐rich (MnaFebCrc)Siy shell.
Abstract The HelixJet atmospheric plasma‐assisted synthesis can be a new toolbox to realize dedicated nanoparticle architectures such as Janus‐type morphologies. Silicon nanoparticles produced by the ...decomposition of Silane molecules are directed into an in‐flight annealing stage. The applied high‐temperature supplies a metal vapor rich atmosphere containing Manganese, Chromium, Iron, and Tin outgassing from the used steel tube. The metal atoms alloy into the Silicon nanoparticles and form a self‐assembled 'Si/Mn x Si y ‐alloy' Janus nanosphere architecture. The Janus particles nanochemistry is thoroughly examined in detail by the analytic capabilities of transmission electron microscopy. The combined approach of electron diffraction, EDS, and EELS identifies the Janus particle composition consisting of a pure Si hemisphere interfaced to an alloyed Mn 4 Si 7 hemisphere covered by a thin (Mn a Fe b Cr c )Si y surface shell.
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