4 research outputs found
Novel non-covalent interactions involved with the Al<sub>13</sub>M cluster (M = Li, Na, K, Cu, Ag, Au)
<div><p>The complexes of Al<sub>13</sub>M cluster (M = Li, Na, K, Cu, Ag, Au) and Lewis bases NH<sub>3</sub>, H<sub>2</sub>O, C<sub>6</sub>H<sub>6</sub>, and HLi have been predicted and characterised. The results showed that the cluster Al<sub>13</sub>M forms the alkali-bonding or coinage metal-bonding interaction through M with these Lewis bases. These complexes exhibit some similarities and differences in the structures, properties, and nature with conventional molecules. The formation of these interactions has a negligible or small effect on the structures of Al<sub>13</sub>M. This study combines the cluster Al<sub>13</sub>M with non-covalent interactions, which is of great importance in supramolecular chemistry.</p></div
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
Metallic Cobalt Encapsulated in Bamboo-Like and Nitrogen-Rich Carbonitride Nanotubes for Hydrogen Evolution Reaction
Despite being technically possible,
the hydrogen production by means of electrocatalytic water splitting
is still practically unreachable mainly because of the lack of inexpensive
and high active catalysts. Herein, a novel and facile approach by
melamine polymerization, exfoliation and Co<sup>2+</sup>-assisted
thermal annealing is developed to fabricate Co nanoparticles embedded
in bamboo-like and nitrogen-rich carbonitride nanotubes (Co@NCN).
The electronic interaction between the embedded Co nanoparticles and
N-rich carbonitride nanotubes could strongly promote the HER performance.
The optimized Co@NCN-800 exhibits outstanding HER activity with an
onset potential of −89 mV (vs RHE), a large exchange current
density of 62.2 μA cm<sup>–2</sup>, and small Tafel slope
of 82 mV dec<sup>–1</sup>, as well as excellent stability (5000
cycles) in acid media, demonstrating the potential for the replacement
of Pt-based catalysts. Control experiments reveal that the superior
performance should be ascribed to the synergistic effects between
embedded Co nanoparticles and N-rich carbonitride nanotubes, which
originate from the high pyridinic N content, fast charge transfer
rate from Co particles to electrodes via electronic coupling, and
porous and bamboo-like carbonitride nanotubes for more active sites
in HER
In Situ Synthesis of Core–Shell Pt–Cu Frame@Metal–Organic Frameworks as Multifunctional Catalysts for Hydrogenation Reaction
Controllable integration
of metal nanoparticles (NPs) and metal–organic
frameworks (MOFs) is of significant importance in many applications
owing to their unique properties. In situ efficient synthesis of metal
NPs with different structures into MOFs is a great challenge. Herein,
we report the nanostructures of octahedron and flower Pt–Cu
frame@HKUST-1, which is successfully synthesized under a microwave
irradiation method in only 30 min. In this study, Pt–Cu alloys,
serving as the self-template, are synthesized first, followed by the
HKUST-1 shell growing in situ via the consumption of Cu<sup>0</sup>. As multifunctional catalysts, the core–shell structures
exhibit excellent performance for the hydrogenation of 1-hexene. Notably,
octahedron Pt–Cu frame@HKUST-1 displays high turnover number
(TON) and turnover frequency (TOF) of 1004 and 2008 h<sup>–1</sup>, respectively. Thanks to
the protective effect of HKUST-1, the octahedron Pt–Cu frame@HKUST-1
can be recycled for at least four runs without serious loss of activity
and obvious aggregation of Pt–Cu alloys. Furthermore, the size-selective
catalysis is also well-demonstrated by choosing 1-hexene, <i>cis</i>-cyclooctene, and styrene as substrates