1 research outputs found
Intrinsic Mechanism for Carbon Dioxide Methanation over Ru-Based Nanocatalysts
Ruthenium-based
supported catalysts are of great potential
for
CO2 methanation, while the catalytic mechanisms remain
elusive owing to the conjunction of the metal size and support effect,
as well as the possible strong metal/support interactions (SMSI) in
a practical catalyst. Herein, with the deposition of alumina over
the Ru/SiC model nanocatalysts by the method of the atomic layer deposition
(ALD) technique, the corrugated (1011) surface
of Ru nanoparticles can be selectively insulated due to its preference
for alumina deposition, and the intrinsic activity of CO2 conversion was confirmed to depend crucially on the residual planar
(0001) surface. Characterizations including in situ infrared spectroscopy
(IR) combined with density functional theory (DFT) calculation and
the microkinetic modeling revealed that the competitive kinetics of
H2 and CO2 activation on the Ru surface governs
the activity and selectivity of methanation. The terrace sites of
Ru nanocatalysts serve as the genuine active site through the HCOO*
intermediate with the surface occupied by the H* species for further
methanation. The (1011) surface suffers from
a lower capability for hydrogenation due to its preference toward
CO2 adsorption and results in the surface poisoning by
the *C and *CH species, which thus makes it a negligible contribution
toward methanation over Ru nanocatalysts. However, the presence of
the alumina overlayer on the corrugated surface also improves the
stability of the Ru nanocatalyst, to keep its activity even at a high
temperature pretreatment. Our results demonstrate the terrace sites
as the intrinsic active sites for CO2 methanation and also
deepen insights on the catalytic mechanism of CO2 transformation
over Ru-based nanocatalysts