Publisher: American Chemical Society (ACS)

Issue: 24

License: [{"start"=>{"date-parts"=>[[2023, 11, 28]], "date-time"=>"2023-11-28T00:00:00Z", "timestamp"=>1701129600000}, "content-version"=>"vor", "delay-in-days"=>0, "URL"=>"https://creativecommons.org/licenses/by/4.0/"}]

Publication date(s): 2023/12/15 (print) 2023/11/28 (online)

Pages: 15956-15966

Volume: 13 Issue: 24

Journal: ACS Catalysis

Link: [{"URL"=>"https://pubs.acs.org/doi/pdf/10.1021/acscatal.3c03214", "content-type"=>"application/pdf", "content-version"=>"vor", "intended-application"=>"unspecified"}, {"URL"=>"https://pubs.acs.org/doi/pdf/10.1021/acscatal.3c03214", "content-type"=>"unspecified", "content-version"=>"vor", "intended-application"=>"similarity-checking"}]

URL: http://dx.doi.org/10.1021/acscatal.3c03214

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.