Issue 24, 2016

Hydrothermal synthesis and characterization under dynamic conditions of cobalt oxide nanoparticles supported over magnesium oxide nano-plates

Abstract

A nano-catalyst comprised of oxidized Co NPs supported on MgO nano-plates was synthesized via a hydrothermal co-precipitation strategy and calcination in O2 and subsequently in H2 at 250 °C. Spectro-microscopy characterization was performed by scanning transmission electron microscopy, electron energy loss spectroscopy and scanning X-ray transmission microscopy. Surface measurements under H2 and H2 + CO atmospheres were obtained by ambient pressure X-ray photoelectron spectroscopy and in situ X-ray absorption spectroscopy in the 225–480 °C range. These measurements at the atomic and microscopic levels demonstrated that the oxidized Co nanoparticles uniformly decorated the MgO nano-plates. The surfaces are enriched with Co, and with a mixture of Co(OH)2 and CoO under H2 and H2 + CO atmospheres. Under a H2 atmosphere, the outermost surfaces were composed of (lattice) O2−, CO32− and OH. No inorganic carbonates were observed in the bulk. Chemisorbed CO, likely on the oxidized Co surfaces, was observed at the expense of O2− under 300 mTorr H2 + CO (2 : 1) at 225 °C. Gas phase CO2 was detected under 32 Torr H2 + CO (2 : 1) at 225 °C upon prolonged reaction time, and was attributed to a surface chemical reaction between O2− and chemisorbed CO. Furthermore, sp3 like carbon species were detected on the otherwise carbon free surface in H2 + CO, which remained on the surface under the subsequent reaction conditions. The formation of sp3 like hydrocarbons was ascribed to a surface catalytic reaction between the chemisorbed CO and OH as the apparent hydrogen source.

Graphical abstract: Hydrothermal synthesis and characterization under dynamic conditions of cobalt oxide nanoparticles supported over magnesium oxide nano-plates

Supplementary files

Article information

Article type
Paper
Submitted
15 Jan 2016
Accepted
03 Mar 2016
First published
07 Mar 2016

Dalton Trans., 2016,45, 9932-9941

Hydrothermal synthesis and characterization under dynamic conditions of cobalt oxide nanoparticles supported over magnesium oxide nano-plates

S. Alayoglu, D. J. Rosenberg and M. Ahmed, Dalton Trans., 2016, 45, 9932 DOI: 10.1039/C6DT00204H

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