Compositional Evolution of Individual CoNPs on Co/TiO2 during CO and Syngas Treatment Resolved through Soft XAS/X-PEEM.
ACS Catal
; 13(24): 15956-15966, 2023 Dec 15.
Article
de En
| MEDLINE
| ID: mdl-38125980
ABSTRACT
The nanoparticle (NP) redox state is an important parameter in the performance of cobalt-based Fischer-Tropsch synthesis (FTS) catalysts. Here, the compositional evolution of individual CoNPs (6-24 nm) in terms of the oxide vs metallic state was investigated in situ during CO/syngas treatment using spatially resolved X-ray absorption spectroscopy (XAS)/X-ray photoemission electron microscopy (X-PEEM). It was observed that in the presence of CO, smaller CoNPs (i.e., ≤12 nm in size) remained in the metallic state, whereas NPs ≥ 15 nm became partially oxidized, suggesting that the latter were more readily able to dissociate CO. In contrast, in the presence of syngas, the oxide content of NPs ≥ 15 nm reduced, while it increased in quantity in the smaller NPs; this reoxidation that occurs primarily at the surface proved to be temporary, reforming the reduced state during subsequent UHV annealing. O K-edge measurements revealed that a key parameter mitigating the redox behavior of the CoNPs were proximate oxygen vacancies (Ovac). These results demonstrate the differences in the reducibility and the reactivity of Co NP size on a Co/TiO2 catalyst and the effect Ovac have on these properties, therefore yielding a better understanding of the physicochemical properties of this popular choice of FTS catalysts.
Texte intégral:
1
Collection:
01-internacional
Base de données:
MEDLINE
Langue:
En
Journal:
ACS Catal
Année:
2023
Type de document:
Article
Pays de publication:
États-Unis d'Amérique