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Synthesis Of Nitrogen-Doped Carbon-based Single Atom Catalysts And Investigation In Alcohol Oxidation Reactions

Posted on:2023-07-20Degree:MasterType:Thesis
Country:ChinaCandidate:T T FanFull Text:PDF
GTID:2531306773957789Subject:Chemistry
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Supported single-atom catalysts(SACs)have become a hot research topic in the field of heterogeneous catalysis due to their unique electronic structures and maximal atom utilization.Nitrogen-doped carbon materials have a wide range of applications in the field of catalysis due to their unique properties.Since the nitrogen doping process can introduce defective sites and nitrogen species to improve the physicochemical properties,acidity,and wettability of catalysts,they are commonly used as supports for the preparation of SACs.In this thesis,two single-atom catalysts were prepared using(i)in situ self-assembly and pyrolysis strategy;and(ii)ligand-assisted polymerization assembly strategy by loading copper and iron species on nitrogen-doped carbon,respectively,and applied to the catalytic oxidation reaction of alcohols.The main aspects of this thesis are as follows:1.Copper single-atom catalysts(Cu1/N-C)anchored to nitrogen-doped carbon materials were prepared by an in situ self-assembly and pyrolysis strategy.The Zn2+/Cu2+ions and 2-methyl-imidazole ligands were in situ self-assembled to form Cu doped ZIF-8nanocrystals.Following a thermal treatment under H2/Ar atmosphere,the Zn atoms were evaporated and the Cu species were reduced with the carbonization of the organic ligands and F127 to afford Cu1/N-C.The presence of copper atoms was characterized by high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy.This catalyst exhibits extremely high intrinsic catalytic activity(TOF of 7692 h-1)in the oxidation of cinnamyl alcohol to afford cinnamaldehyde,along with exceptional recyclability(at least eight cycles),scalability,and broad substrate scope at 1 atm O2,100?C.DFT calculations reveal that the high activity derives from the low oxidation state and the unique coordination environment of the copper sites in the catalyst.2.The nitrogen-carbon nanosphere supported Fe single-atom catalysts were prepared by a ligand-assisted polymerization assembly strategy.Specially,amino(-NH2)and phenolic hydroxyl groups(-OH)in dopamine hydrochloride chelate with Fe2+,and then followed by a high-temperature heat treatment.This catalyst was characterized by high-resolution transmission electron microscopy,high-angle annular dark-field scanning transmission electron microscopy and X-ray photoelectron spectroscopy.This single-atom catalyst exhibited excellent catalytic activity(TOF of 3271 h-1)for the oxidation of 1-phenylethanol to prepare acetophenone at 1 atm O2,100?C,along with excellent recyclability and scalability.It can efficiently catalyze a series of alcohol derivatives to produce corresponding aldehydes or ketones.The excellent catalytic activity of Fe1/NCS can be attributed to the electronic environment of atomically dispersed Fe sites in the catalyst.
Keywords/Search Tags:heterogeneous catalysis, single atom catalyst, coordination environment, aerobic oxidation of alcohols, catalytic activity
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