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Atomic structure and valence state of cobalt nanocrystals on carbon under syngas versus hydrogen reduction

DOI: 10.1021/acs.jpcc.2c00482 DOI Help

Authors: Ofentse A. Makgae (Lund University; University of Oxford) , Tumelo N. Phaahlamohlaka (University of the Witwatersrand) , Benzhen Yao (University of Oxford) , Manfred E. Schuster (Johnson Matthey Technology Centre) , Thomas J. A. Slater (Cardiff University; Diamond Light Source) , Peter P. Edwards (University of Oxford) , Neil J. Coville (University of the Witwatersrand) , Emanuela Liberti (University of Oxford; Diamond Light Source) , Angus I. Kirkland (University of Oxford; Diamond Light Source)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: The Journal Of Physical Chemistry C

State: Published (Approved)
Published: April 2022
Diamond Proposal Number(s): 20403

Open Access Open Access

Abstract: The composition of the reducing gas in the activation of Co Fischer-Tropsch synthesis catalysts determines the nature of the catalytically active Co species. This study reports on the effect of H2 versus syngas (H2/CO = 2) on the reducibility of Co3O4 nanoparticles supported on hollow carbon spheres, using ex situ and in situ high-resolution aberration-corrected analytical electron microscopy. High-resolution images revealed twinned fcc Co particles encapsulated in carbon from syngas treatment while H2-treated particles were mostly CoO. Moreover, the electron energy loss of the Co-L3,2 and O-K edge fine structures show improved reducibility in syngas than in H2 at 350 °C. The effect of high temperature on the reducibility of the Co3O4 nanoparticles is also explored. Carbon fiber encapsulation of twinned fcc Co particles observed during the syngas treatment provides sinter resistance at high temperatures. Both ex situ and in situ results indicate that syngas activation is efficient for obtaining highly reduced Co nanoparticles at lower temperatures.

Journal Keywords: Redox reactions; Nanoparticles; Electron energy loss spectroscopy; Catalysts

Subject Areas: Chemistry, Materials

Diamond Offline Facilities: Electron Physical Sciences Imaging Centre (ePSIC)
Instruments: E01-JEM ARM 200CF

Added On: 06/04/2022 15:35


Discipline Tags:

Physical Chemistry Catalysis Chemistry Materials Science Nanoscience/Nanotechnology

Technical Tags:

Microscopy Electron Microscopy (EM) Scanning Transmission Electron Microscopy (STEM)