12 research outputs found
Liquid-Phase Templateless Synthesis of Pt-on-Pd<sub>0.85</sub>Bi<sub>0.15</sub> Nanowires and PtPdBi Porous Nanoparticles with Superior Electrocatalytic Activity
This article reports the synthesis of Pt-on-Pd<sub>0.85</sub>Bi<sub>0.15</sub> nanowires (NWs) and PtPdBi porous nanoparticles
(PNPs)
by a facile, one-pot, wet-chemical, and templateless method in the
presence of oleylamine (OAm) and NH<sub>4</sub>Br. The relationship
between the morphology and composition in the PtPdBi trimetallic system
was systematically studied. Interestingly, it is verified that adding
only 5% Bi will produce Pd NWs, which offers a novel approach to synthesize
Pd NWs in the oil phase without any template. On the basis of the
fact of synthesizing Pd<sub>0.85</sub>Bi<sub>0.15</sub> NWs, Pt-on-Pd<sub>0.85</sub>Bi<sub>0.15</sub> NWs with hetero-nanostructures were successfully
synthesized by a one-step method. Furthermore, the number of Pt nanobranches
for Pt-on-Pd<sub>0.85</sub>Bi<sub>0.15</sub> NWs could be easily controlled
via simply changing the synthetic parameters, which could tune the
catalytic properties. PtPdBi PNPs were obtained by the acid pickling
of PtPdBi<sub>2</sub> intermetallic compounds. Most importantly, a
catalytic study indicates that the as-obtained Pt-on-Pd<sub>0.85</sub>Bi<sub>0.15</sub> NWs and PtPdBi PNPs exhibited much higher electrocatalytic
activity and durability for the oxygen reduction reaction (ORR) than
the commercial Pt/C catalyst. We expect that this work will provide
a promising strategy for the development of efficient ORR electrocatalysts
and can also be extended to the preparation of other nanowires or
hetero-nanostructures with desirable functions
Fe<sub>5</sub>C<sub>2</sub> Nanoparticles: A Facile Bromide-Induced Synthesis and as an Active Phase for Fischer–Tropsch Synthesis
Iron carbide nanoparticles have long been considered
to have great
potential in new energy conversion, nanomagnets, and nanomedicines.
However, the conventional relatively harsh synthetic conditions of
iron carbide hindered its wide applications. In this article, we present
a facile wet-chemical route for the synthesis of Hägg iron
carbide (Fe<sub>5</sub>C<sub>2</sub>) nanoparticles, in which bromide
was found to be the key inducing agent for the conversion of FeÂ(CO)<sub>5</sub> to Fe<sub>5</sub>C<sub>2</sub> in the synthetic process.
Furthermore, the as-synthesized Fe<sub>5</sub>C<sub>2</sub> nanoparticles
were applied in the Fischer–Tropsch synthesis (FTS) and exhibited
intrinsic catalytic activity in FTS, demonstrating that Fe<sub>5</sub>C<sub>2</sub> is an active phase for FTS. Compared with a conventional
reduced-hematite catalyst, the Fe<sub>5</sub>C<sub>2</sub> nanoparticles
showed enhanced catalytic performance in terms of CO conversion and
product selectivity
Hybrid of Co<sub>3</sub>Sn<sub>2</sub>@Co Nanoparticles and Nitrogen-Doped Graphene as a Lithium Ion Battery Anode
A facile strategy was designed for the fabrication of hybrid of Co<sub>3</sub>Sn<sub>2</sub>@Co nanoparticles (NPs) and nitrogen-doped graphene (NG) sheets through a hydrothermal synthesis, followed by annealing process. Core–shell architecture of Co<sub>3</sub>Sn<sub>2</sub>@Co pin on NG is designed for the dual encapsulation of Co<sub>3</sub>Sn<sub>2</sub> with adaptable ensembles of Co and NG to address the structural and interfacial stability concerns facing tin-based anodes. In the resulted unique architecture of Co<sub>3</sub>Sn<sub>2</sub>@Co–NG hybrid, the sealed cobalt cover prevents the direct exposer of Sn with electrolyte because of encapsulated structure and keeps the structural and interfacial integrity of Co<sub>3</sub>Sn<sub>2</sub>. However, the elastically strong, flexible and conductive NG overcoat accommodates the volume changes and therefore brings the structural and electrical stabilization of Co<sub>3</sub>Sn<sub>2</sub>@Co NPs. As a result, Co<sub>3</sub>Sn<sub>2</sub>@Co–NG hybrid exhibits extraordinary reversible capacity of 1615 mAh/g at 250 mA/g after 100 cycles with excellent capacity retention of 102%. The hybrid bears superior rate capability with reversible capacity of 793.9 mAh/g at 2500 mA/g and Coulombic efficiency nearly 100%
Sulfur-Doped Carbon for Potassium-Ion Battery Anode: Insight into the Doping and Potassium Storage Mechanism of Sulfur
The sulfur doping strategy has been attracting extensive
interest
in potassium-ion battery carbon anodes for the dual potential of improving
the capacity and kinetics of carbon anodes. Understanding the doping
and potassium storage mechanism of sulfur is crucial to guide the
structural design and optimization of high-performance sulfur-doped
carbon anodes. Herein, presenting a laboratory-synthesized sulfur-doped
hard carbon (SHC) with a sulfur content of 6.4 at. % as an example,
we clarify the sulfur doping mechanism and reveal the role of sulfur
in potassium storage. The high sulfur content of SHC stems from the
selective substitution of sulfur for carbon and the residual trace
of sulfur molecular fragments after sulfurization. As a result, thanks
to the multifaceted roles of doped sulfur in potassium storage, about
twice as much capacity, rate capability, and cycling stability is
achieved for SHC against S-free hard carbon at the same test conditions.
Furthermore, potassium-ion hybrid capacitors assembled based on an
SHC anode demonstrate high energy/power density (139 Wh kg–1/7.3 kW kg–1), along with an extraordinary cycling
stability
A Versatile Route toward the Electromagnetic Functionalization of Metal–Organic Framework-Derived Three-Dimensional Nanoporous Carbon Composites
Designable electromagnetic
parameters accompanied by a low density of metal–organic framework
(MOF)-derived metal/carbon composites are essential prerequisites
for excellent microwave-absorbing materials. However, the conventional
route is confined to slight modification of the physicochemical properties
of metal species and carbon, which also restricts the functionalization
of MOF-derived materials. Here, a facile technique has been improved
by making full use of highly porous structure to uniformly introduce
metallic Co nanoparticles into carbon matrix derived from Cu<sub>3</sub>(btc)<sub>2</sub>. Through changing the starting amount of Co sources,
the composition of the final products can be tuned, offering an effective
route to control electromagnetic properties. Multiple attenuation
mechanisms are employed to realize excellent reflection loss performance,
which can be clarified by modified equivalent circuit mode. Effective
frequency bandwidth (<i>f</i><sub>e</sub>) over the whole
X band can be obtained by optimizing interfacial polarization through
changing interface area and electrical conductivity. Broad <i>f</i><sub>e</sub> covering almost the whole K<sub>u</sub> band
from 12.3 to 18 GHz with a thin thickness of 1.85 mm can be gained
through improving impedance matching and enhancing conduction loss.
The present work not only sheds light on the easy fabrication of high-performance
lightweight microwave-absorbing materials but also paves the way for
extending functionalities of MOF-derived carbon composites
Multifunctional Metal Rattle-Type Nanocarriers for MRI-Guided Photothermal Cancer Therapy
In
the past decade, numerous species of nanomaterials have been
developed for biomedical application, especially cancer therapy. Realizing
visualized therapy is highly promising now because of the potential
of accurate, localized treatment. In this work, we first synthesized
metal nanorattles (MNRs), which utilized porous gold shells to carry
multiple MR imaging contrast agents, superparamagnetic iron oxide
nanoparticles (SPIONs), inside. A fragile wormpore-like silica layer
was manipulated to encapsulate 8 nm oleylamine SPIONs and mediate
the <i>in situ</i> growth of porous gold shell, and it was
finally etched by alkaline solution to obtain the rattle-type nanostructure.
As shown in the results, this nanostructure with unique morphology
could absorb near-infrared light, convert to heat to kill cells, and
inhibit tumor growth. As a carrier for multiple SPIONs, it also revealed
good function for <i>T</i><sub>2</sub>-weighted MR imaging
in tumor site. Moreover, the rest of the inner space of the gold shell
could also introduce potential ability as nanocarriers for other cargos
such as chemotherapeutic drugs, which is still under investigation.
This metal rattle-type nanocarrier may pave the way for novel platforms
for cancer therapy in the future
Efficient and Lightweight Electromagnetic Wave Absorber Derived from Metal Organic Framework-Encapsulated Cobalt Nanoparticles
Porous-carbon-based
nanocomposites are gaining tremendous interest because of good compatibility,
lightweight, and strong electromagnetic wave absorption. However,
it is still a great challenge to design and synthesize porous-carbon-based
composites with strong absorption capability and broad frequency bandwidth.
Herein, a facile and effective method was developed to synthesize
Co magnetic nanoparticles/metal organic framework (MOF) (Co NPs/ZIF-67)
nanocomposites. Co NPs/porous C composites were subsequently obtained
by annealing Co NPs/ZIF-67 nanocomposites at different temperatures
under an inert atmosphere. The carbonized nanocomposites showed highly
efficient electromagnetic wave absorption capability. Specifically,
the optimal composite (i.e., Co/C-700) possessed a maximum reflection
loss (RL) value of −30.31 dB at 11.03 GHz with an effective
absorption bandwidth (RL ≤ −10 dB) of 4.93 GHz. The
electromagnetic parameters and the absorption performance of the composites
are readily tunable by adjusting the carbonization temperature and
the concentration of Co NPs in the composites. Because of the combination
of good impedance matching, dual-loss mechanism, and the synergistic
effect between Co NPs and porous carbon composites, these Co NPs/MOF-derived
composites are attractive candidates for electromagnetic wave absorbers
Multifunctional Nitrogen-Doped Loofah Sponge Carbon Blocking Layer for High-Performance Rechargeable Lithium Batteries
Low-cost,
long-life, and high-performance lithium batteries not only provide
an economically viable power source to electric vehicles and smart
electricity grids but also address the issues of the energy shortage
and environmental sustainability. Herein, low-cost, hierarchically
porous, and nitrogen-doped loofah sponge carbon (N-LSC) derived from
the loofah sponge has been synthesized via a simple calcining process
and then applied as a multifunctional blocking layer for Li–S,
Li–Se, and Li–I<sub>2</sub> batteries. As a result of
the ultrahigh specific area (2551.06 m<sup>2</sup> g<sup>–1</sup>), high porosity (1.75 cm<sup>3</sup> g<sup>–1</sup>), high
conductivity (1170 S m<sup>–1</sup>), and heteroatoms doping
of N-LSC, the resultant Li–S, Li–Se, and Li–I<sub>2</sub> batteries with the N-LSC-900 membrane deliver outstanding
electrochemical performance stability in all cases, i.e., high reversible
capacities of 623.6 mA h g<sup>–1</sup> at 1675 mA g<sup>–1</sup> after 500 cycles, 350 mA h g<sup>–1</sup> at 1356 mA g<sup>–1</sup> after 1000 cycles, and 150 mA h g<sup>–1</sup> at 10550 mA g<sup>–1</sup> after 5000 cycles, respectively.
The successful application to Li–S, Li–Se, and Li–I<sub>2</sub> batteries suggests that loofa sponge carbon could play a
vital role in modern rechargeable battery industries as a universal,
cost-effective, environmentally friendly, and high-performance blocking
layer
Ultra-large-scale Synthesis of Fe<sub>3</sub>O<sub>4</sub> Nanoparticles and Their Application for Direct Coal Liquefaction
Ultra-large-scale synthesis of iron
oxide nanoparticles (875 g)
has been achieved in a single reaction via a facile solution-based
dehydration process. The obtained nanoparticles capped with hydrophobic
oleic acid ligands are magnetite with the average size of 5 nm. The
synthesized samples exhibit a higher catalytic activity toward the
direct coal liquefaction (DCL) than the commercial Fe<sub>3</sub>O<sub>4</sub> powders. The conversion, oil yield, and liquefaction degree
with the synthesized Fe<sub>3</sub>O<sub>4</sub> nanoparticles are
89.6, 65.1, and 77.3%, respectively. The excellent catalytic performance
of the synthesized Fe<sub>3</sub>O<sub>4</sub> nanoparticles can be
attributed to their extremely small size and high dispersity. This
facile approach to prepare highly active nanocatalyst for the DCL
will be applicable for future industrial processes
Construction of Synergistic Fe<sub>5</sub>C<sub>2</sub>/Co Heterostructured Nanoparticles as an Enhanced Low Temperature Fischer–Tropsch Synthesis Catalyst
Iron
and cobalt catalysts are two major categories for commercial Fischer–Tropsch
synthesis (FTS) catalysts. The two types of catalysts have distinct
merits and shortcomings while they are largely supplementary to each
other. However, until now, there has been a lack of an efficient way
to properly combine those two catalysts into a synergistic one which
possesses the benefits of both catalysts. Herein, the Fe<sub>5</sub>C<sub>2</sub>/Co heterostructured nanoparticles (NPs) were constructed
by a secondary growth strategy, where the Fe/Co molar ratio can be
tuned from 3.3 to 25. Based on the FTS reaction evaluation, we observed
that only with 0.6 wt % Co (Fe/Co = 12) incorporated, the Fe<sub>5</sub>C<sub>2</sub>/Co catalyst exhibits an activity four times higher
than that of pure Fe<sub>5</sub>C<sub>2</sub> catalyst at low temperature.
In this catalyst, Co was responsible for the CO dissociation while
Fe<sub>5</sub>C<sub>2</sub> was responsible for the chain growth at
220 °C. The synergistic effect of both sites may lead to enhanced
performance in FTS reaction. This result provides a perspective for
the construction of Fe–Co bimetallic FTS catalysts