Revealing Correlation of Valence State with Nanoporous Structure in Cobalt Catalyst Nanoparticles by In situ Environmental TEM

Journal Article · Tue May 01 00:00:00 EDT 2012 · ACS Nano

DOI:https://doi.org/10.1021/nn3007652· OSTI ID:1049296

L, Xin H; Diaz, R; Pach, E A; Stach, E A; Salmeron, M; Zheng, H

Simultaneously probing the electronic structure and morphology of materials at the nanometer or atomic scale while a chemical reaction proceeds is significant for understanding the underlying reaction mechanisms and optimizing a materials design. This is especially important in the study of nanoparticle catalysts, yet such experiments have rarely been achieved. Utilizing an environmental transmission electron microscope equipped with a differentially pumped gas cell, we are able to conduct nanoscopic imaging and electron energy loss spectroscopy in situ for cobalt catalysts under reaction conditions. Studies reveal quantitative correlation of the cobalt valence states with the particles' nanoporous structures. The in situ experiments were performed on nanoporous cobalt particles coated with silica, while a 15 mTorr hydrogen environment was maintained at various temperatures (300-600 C). When the nanoporous particles were reduced, the valence state changed from cobalt oxide to metallic cobalt and concurrent structural coarsening was observed. In situ mapping of the valence state and the corresponding nanoporous structures allows quantitative analysis necessary for understanding and improving the mass activity and lifetime of cobalt-based catalysts, for example, for Fischer-Tropsch synthesis that converts carbon monoxide and hydrogen into fuels, and uncovering the catalyst optimization mechanisms.

• Research Organization: Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)
• Sponsoring Organization: USDOE SC OFFICE OF SCIENCE (SC)
• DOE Contract Number: DE-AC02-98CH10886
• OSTI ID: 1049296
• Report Number(s): BNL-96965-2012-JA; R&D Project: NC-001; TRN: US201217%%630
• Journal Information: ACS Nano, Vol. 6, Issue 5; ISSN 1936-0851
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
08 HYDROGEN
36 MATERIALS SCIENCE
CARBON MONOXIDE
CATALYSTS
CHEMICAL REACTIONS
COBALT
COBALT OXIDES
DESIGN
ELECTRON MICROSCOPES
ELECTRONIC STRUCTURE
ELECTRONS
ENERGY-LOSS SPECTROSCOPY
FISCHER-TROPSCH SYNTHESIS
HYDROGEN
LIFETIME
MORPHOLOGY
OPTIMIZATION
REACTION KINETICS
SILICA
VALENCE
catalysis
environmental TEM
electron energy loss spectroscopy
functional nanomaterials