Zinc-Containing Magnetic Oxides Stabilized by a Polymer: One Phase or Two?

Abstract

Here we developed a new family of Zn-containing magnetic oxides of different structures by thermal decomposition of Zn(acac)2 in the reaction solution of preformed magnetite nanoparticles (NPs) stabilized by polyphenylquinoxaline. Upon an increase of the Zn(acac)2 loading from 0.15 to 0.40 mmol (vs 1 mmol of Fe(acac)3), the Zn content increases, and the Zn-containing magnetic oxide NPs preserve a spinel structure of magnetite and an initial, predominantly multicore NP morphology. X-ray photoelectron spectroscopy (XPS) of these samples revealed that the surface of iron oxide NPs is enriched with Zn, although Zn species were also found deep under the iron oxide NP surface. For all the samples, XPS also demonstrates the atom ratio of Fe(3+)/Fe(2+) = 2:1, perfectly matching Fe3O4, but not ZnFe2O4, where Fe(2+) ions are replaced with Zn(2+). The combination of XPS with other physicochemical methods allowed us to propose that ZnO forms an ultrathin amorphous layer on the surface of iron oxide NPs and also diffuses inside the magnetite crystals. At higher Zn(acac)2 loading, cubic ZnO nanocrystals coexist with magnetite NPs, indicating a homogeneous nucleation of the former. The catalytic testing in syngas conversion to methanol demonstrated outstanding catalytic properties of Zn-containing magnetic oxides, whose activities are dependent on the Zn loading. Repeat experiments carried out with the best catalyst after magnetic separation showed remarkable catalyst stability even after five consecutive catalytic runs.

Efficient Furfuryl Alcohol Synthesis from Furfural over Magnetically Recoverable Catalysts: Does the Catalyst Stabilizing Medium Matter?

“…Appearance of only the strongest reflection was observed for other composite Pd‐containing materials . The XPS data are consistent with those of XRD with the HR Fe 2p XPS spectrum characteristic of solely Fe 3 O 4 , (Figure S6, SI) and the HR Pd 3d XPS spectrum representative of Pd 0 (Figure S7, SI). Thus, although FePd NPs are reported in literature, they were not formed in the reactions conditions described in this paper.…”

“…The magnetic separation of the catalyst is shown in Figure S1 (the Supporting Information, SI). The control experiment carried out without injection of the Pt or Pd precursor shows that particles formed include multicore NPs with a mean size of about 21 nm and a smaller fraction of quasi‐spherical single‐core NPs with diameters in the range of 6–10 nm . The structure of both types of NPs is that of magnetite (Fe 3 O 4 ) as was confirmed by a combination of XRD and XPS .…”

Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature

“…The hydrogenation of nitrobenzene is catalyzed over magnetically recoverable Pt deposited on MWCNTs with high yield of aniline [186]. A new family of Zn-containing magnetic oxides of different structures has been developed for syngas conversion to methanol [187]. A magnetic GO-loaded Cedoped titania (MGO-Ce-TiO2) hybridized composite exhibits good adsorption capacity, high visible-light photoactive and magnetic separability as a novel photocatalyst in the degradation of antibiotic tetracyclines (TC) [188].…”

Metal oxide–zeolite composites in transformation of methanol to hydrocarbons: do iron oxide and nickel oxide matter?

“…Using pyrolysis and gasification both can be successfully transformed to syngas 1, 2 which, in turn, is used in methanol formation. [3][4][5][6] Zeolite ZSM-5 is a well-known catalyst of MTH and MTG transformations. 7 Although this catalyst was used in the MTG process from early 1970s, its deactivation by coke formation dampened its applications.…”