(762j) Supported Cobalt Catalysts with Preferentially Exposed Crystal Facets for CO2 Hydrogenation

Supported Cobalt Catalysts with Preferentially
Exposed Crystal Facets for CO₂ Hydrogenation.

Cun Wen, Juan Jimenez, Maryorie Santos, Jason Hattrick-Simpers,
Jochen Lauterbach_,*

University of South
Carolina, Columbia, SC, 29208, USA

*Corresponding author: lauteraj@cec.sc.edu

Global climate change has
been widely acknowledged to be a result of rising CO₂ concentration
in the atmosphere.^1-3 However, curbing CO₂ emission is hindered
by the high thermodynamic stability of CO₂, which leads to low
reactivity in most reactions.⁴ Our recent studies have
demonstrated that by tuning the surface crystal facets of Cobalt catalysts, catalysts
with {110} facets have superior activity toward CO₂ hydrogenation
compared with Co with {111} and {001} facets. More importantly, our previous
studies have shown that the Co catalysts with {110} facets have an unprecedented
self-healing functionality during a hydrogenation reaction.⁵ Similar to other faceted
catalysts reported in literature, the highly active and stable Cobalt catalysts
are not supported and lack the capability to meet industrial requirements for
high heat and mass transfer, facilitated reactor packing, mechanic strength,
and so on. Here, a novel methodology leading to supporting the faceted Co
catalysts without sabotaging the referentially exposed surface crystal facet
will be discussed in this presentation.

In this study, Co catalysts
for CO₂ hydrogenation are based on series of cobalt oxide catalysts
that we have recently published for CO hydrogenation.⁵ The Co nanorods, for
instance, have predominant {110} and {001} facets, while the Co nanoparticles
have {111} and {001} facets. The Co nanorods start to show activity toward CO₂
hydrogenation (130‹C) at 95 ‹C lower than that (225 ‹C) for Co nanoparticles. For
practical applications, the faceted Co catalysts needs to be supported to meet
industrial specifications. As a proof or principle, Al₂O₃
supported Co₃O₄ nanorods are synthesized and tested for
CO₂ hydrogenation. The Al₂O₃ supported Co₃O₄
nanorods have comparable catalytic activity and product selectivity to that of
pure Co₃O₄ nanorods, as shown in Fig. 1. This result
indicates that after supporting the faceted Co₃O₄
nanorods with metal oxide, the superior catalytic performance can be preserved.
More detailed structure characterizations, including XRD, STEM-HAADF, BET, and
ICP, indicate that the preferential crystal facets exposure is preserved after
supported on Al₂O₃.

Figure 1. Comparison between the catalytic performance of a) Co nanorods
and b) Co nanorods@Al₂O₃ in CO₂ hydrogenation.

References

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2. M. Meinshausen,
N. Meinshausen, W. Hare, et al., Nature, 458 (2009) 1158-1162.

3. E. Dlugokencky,
P. Tans, in, NOAA/ESRL.

4. H. Arakawa, M.
Aresta, J.N. Armor, et al., Chem Rev, 101 (2001) 953-996.

5. C. Wen, D.
Dunbar, X. Zhang, et al., Chem Commun, 50 (2014) 4575-4578.