41 research outputs found
Relation between the Charge Efficiency of Activated Carbon Fiber and Its Desalination Performance
Four types of activated carbon fibers (ACFs) with different
specific surface areas (SSA) were used as electrode materials for
water desalination using capacitive deionization (CDI). The carbon
fibers were characterized by scanning electron microscopy and N<sub>2</sub> adsorption at 77 K, and the CDI process was investigated
by studying the salt adsorption, charge transfer, and also the charge
efficiency of the electric double layers that are formed within the
micropores inside the carbon electrodes. It is found that the physical
adsorption capacity of NaCl by the ACFs increases with increasing
BrunauerāEmmettāTeller (BET) surface area of the fibers.
However, the two ACF materials with the highest BET surface area have
the lowest electrosorptive capability. Experiments indicate that the
charge efficiency of the double layers is a key property of the ACF-based
electrodes because the ACF material which has the maximum charge efficiency
also shows the highest salt adsorption capacity for CDI
Rechargeable Aluminum-Ion Battery Based on MoS<sub>2</sub> Microsphere Cathode
In recent years,
a rechargeable aluminum-ion battery based on ionic liquid electrolyte
is being extensively explored due to three-electron electrochemical
reactions, rich resources, and safety. Herein, a rechargeable Al-ion
battery composed of MoS<sub>2</sub> microsphere cathode, aluminum
anode, and ionic liquid electrolyte has been fabricated for the first
time. It can be found that Al<sup>3+</sup> intercalates into the MoS<sub>2</sub> during the electrochemical reaction, whereas the storage
mechanisms of the electrode material interface and internal are quite
different. This result is confirmed by ex situ X-ray photoelectron
spectroscopy and X-ray diffraction etching techniques. Meanwhile,
this aluminum-ion battery also shows excellent electrochemical performance,
such as a discharge specific capacity of 253.6 mA h g<sup>ā1</sup> at a current density of 20 mA g<sup>ā1</sup> and a discharge
capacity of 66.7 mA h g<sup>ā1</sup> at a current density of
40 mA g<sup>ā1</sup> after 100 cycles. This will lay a solid
foundation for the commercialization of aluminum-ion batteries
Polymorphous Supercapacitors Constructed from Flexible Three-Dimensional Carbon Network/Polyaniline/MnO<sub>2</sub> Composite Textiles
Polymorphous
supercapacitors were constructed from flexible three-dimensional carbon
network/polyaniline (PANI)/MnO<sub>2</sub> composite textile electrodes.
The flexible textile electrodes were fabricated through a layer-by-layer
construction strategy: PANI, carbon nanotubes (CNTs), and MnO<sub>2</sub> were deposited on activated carbon fiber cloth (ACFC) in
turn through an electropolymerization process, ādipping and
dryingā method, and in situ chemical reaction, respectively.
In the fabricated ACFC/PANI/CNTs/MnO<sub>2</sub> textile electrodes,
the ACFC/CNT hybrid framework serves as a porous and electrically
conductive 3D network for the rapid transmission of electrons and
electrolyte ions, where ACFC, PANI, and MnO<sub>2</sub> are high-performance
supercapacitor electrode materials. In the electrolyte of H<sub>2</sub>SO<sub>4</sub> solution, the textile electrode-based symmetric supercapacitor
delivers superior areal capacitance, energy density, and power density
of 4615 mF cm<sup>ā2</sup> (for single electrode), 157 Ī¼W
h cm<sup>ā2</sup>, and 10372 Ī¼W cm<sup>ā2</sup>, respectively, whereas asymmetric supercapacitor assembled with
the prepared composite textile as the positive electrode and ACFC
as the negative electrode exhibits an improved energy density of 413
Ī¼W h cm<sup>ā2</sup> and a power density of 16120 Ī¼W
cm<sup>ā2</sup>. On the basis of the ACFC/PANI/CNTs/MnO<sub>2</sub> textile electrodes, symmetric and asymmetric solid-state
textile supercapacitors with a PVA/H<sub>2</sub>SO<sub>4</sub> gel
electrolyte were also produced. These solid-state textile supercapacitors
exhibit good electrochemical performance and high flexibility. Furthermore,
flexible solid-state fiber-like supercapacitors were prepared with
fiber bundle electrodes dismantled from the above composite textiles.
Overall, this work makes a meaningful exploration of the versatile
applications of textile electrodes to produce polymorphous supercapacitors
Supporting Information from Synthesis and photocatalytic activity of mesoporous g-C<sub>3</sub>N<sub>4</sub>/MoS<sub>2</sub> hybrid catalysts
The key to solving environmental and energy issues through photocatalytic technology requires highly efficient, stable and eco-friendly photocatalysts. Graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) is one of the most promising candidates except for its limited photoactivity. In this work, a facile and scalable one-step method is developed to fabricate an efficient heterostructural g-C<sub>3</sub>N<sub>4</sub> photocatalyst <i>in situ</i> coupled with MoS<sub>2</sub>. The strong coupling effect between the MoS<sub>2</sub> nanosheets and g-C<sub>3</sub>N<sub>4</sub> scaffold, numerous mesopores and enlarged specific surface area helped form an effective heterojunction. As such, the photocatalytic activity of the g-C<sub>3</sub>N<sub>4</sub>/MoS<sub>2</sub> is more than three times higher than that of the pure g-C<sub>3</sub>N<sub>4</sub> in the degradation of RhB under visible light irradiation. Improvement of g-C<sub>3</sub>N<sub>4</sub>/MoS<sub>2</sub> photocatalytic performance is mainly ascribed to the effective suppression of the recombination of charge carriers
Enabling Enhanced Cycling Stability of a LiNi<sub>0.8</sub>Co<sub>0.15</sub>Al<sub>0.05</sub>O<sub>2</sub> Cathode by Constructing a Ti-Rich Surface
Herein, we construct a Ti-rich interface of a LiNi0.8Co0.15Al0.05O2 (NCA) secondary
particle
using titanium nitride (TiN) nanopowders as a dopant to reduce interfacial
reaction. Results show that Ti ions integrate into the layered lattice
during the dissociation of TiāN and was enriched within the
surface layer. The solid TiāO bonding effectively enhances
the interface stability and reduces lattice change toward an improved
cycle stability. As a result, continuous growth of CEI film and dissolution
of transition metal elements were depressed. Both thinner cathodeāelectrolyte
interphases (CEI) and phase transition layers form on the surface
of particles after a long cycle. The Ti-doping NCA cathode (NCATiN)
provides a better capacity retention of 90.9% over 200 cycles
Controllable Edge Exposure of MoS<sub>2</sub> for Efficient Hydrogen Evolution with High Current Density
MoS<sub>2</sub>-based electrocatalysts are promising cost-effective replacements
for Pt-based catalysts for hydrogen evolution by water splitting,
yet achieving high current density at low overpotential remains a
challenge. Herein, a binder-free electrode of MoS<sub>2</sub>/CNF
(carbon nanofiber) is prepared by electrospinning and subsequent thermal
treatment. The growth of MoS<sub>2</sub> nanoplates contained within
or protruding out from the CNF can be controlled by adding urea or
ammonium bicarbonate to the electrospinning precursors, due to the
cross-linking effects of urea and the increased porosity caused by
pyrolysis of ammonium bicarbonate allowing growth through pores in
the CNF. By virtue of the abundant exposed edges in this microstructure
and strong bonding between the catalyst and the conductive carbon
network, the composite material exhibits ultrahigh electrocatalytic
hydrogen evolution activity in acidic solutions, with current densities
of 500 and 1000 mA/cm<sup>2</sup> at overpotentials of 380 and 450
mV, respectively, exceeding the performance of many reported MoS<sub>2</sub>-based catalysts and even commercial Pt/C catalysts. Thus,
MoS<sub>2</sub>/CNF membranes show potential as efficient and flexible
binder-free electrodes for electrocatalytic hydrogen production
Ultrafast-Charging and Long-Life Li-Ion Battery Anodes of TiO<sub>2</sub>āB and Anatase Dual-Phase Nanowires
Ideal
lithium-ion batteries (LIBs) should possess a high power density,
be charged extremely fast (e.g., 100C), and have a long service life.
To achieve them all, all battery components, including anodes, cathodes,
and electrolytes should have excellent structural and functional characteristics.
The present work reports ultrafast-charging and long-life LIB anodes
made from TiO<sub>2</sub>-B/anatase dual-phase nanowires. The dual-phase
nanowires are fabricated with anatase TiO<sub>2</sub> nanoparticles
through a facile and cost-effective hydrothermal process, which can
be easily scaled up for mass production. The anodes exhibit remarkable
electrochemical performance with reversible capacities of ā¼225,
172, and 140 mAh g<sup>ā1</sup> at current rates of 1C, 10C,
and 60C, respectively. They deliver exceptional capacity retention
of not less than 126 and 93 mAh g<sup>ā1</sup> after 1000 cycles
at 60C and 100C, respectively, potentially worthwhile for high-power
applications. These values are among the best when the high-rate capabilities
are compared with the literature data for similar TiO<sub>2</sub>-based
anodes. The Ragone plot confirms both the exceptionally high energy
and power densities of the devices prepared using the dual-phase nanowires.
The electrochemical tests and operando Raman spectra present fast
electrochemical kinetics for both Li<sup>+</sup> and electron transports
in the TiO<sub>2</sub> dual-phase nanowires than in anatase nanoparticles
due to the excellent Li<sup>+</sup> diffusion coefficient and electronic
conductivity of nanowires
Surface Heterostructure Induced by PrPO<sub>4</sub> Modification in Li<sub>1.2</sub>[Mn<sub>0.54</sub>Ni<sub>0.13</sub>Co<sub>0.13</sub>]O<sub>2</sub> Cathode Material for High-Performance Lithium-Ion Batteries with Mitigating Voltage Decay
Lithium-rich layered
oxides (LLOs) have been attractive cathode materials for lithium-ion
batteries because of their high reversible capacity. However, they
suffer from low initial Coulombic efficiency and capacity/voltage
decay upon cycling. Herein, facile surface modification of Li<sub>1.2</sub>Mn<sub>0.54</sub>Ni<sub>0.13</sub>Co<sub>0.13</sub>O<sub>2</sub> cathode material is designed to overcome these defects by
the protective effect of a surface heterostructure composed of an
induced spinel layer and a PrPO<sub>4</sub> modification layer. As
anticipated, a sample modified with 3 wt % PrPO<sub>4</sub> (PrP3)
shows an enhanced initial Coulombic efficiency of 90% compared to
81.8% for the pristine one, more excellent cycling stability with
a capacity retention of 89.3% after 100 cycles compared to only 71.7%
for the pristine one, and less average discharge voltage fading from
0.6353 to 0.2881 V. These results can be attributed to the fact that
the modification nanolayers have moved amounts of oxygen and lithium
from the lattice in the bulk crystal structure, leading to a chemical
activation of the Li<sub>2</sub>MnO<sub>3</sub> component previously
and forming a spinel interphase with a 3D fast Li<sup>+</sup> diffusion
channel and stable structure. Moreover, the elaborate surface heterostructure
on a lithium-rich cathode material can effectively curb the undesired
side reactions with the electrolyte and may also extend to other layered
oxides to improve their cycling stability at high voltage
Pt Submonolayers on Au Nanoparticles: Coverage-Dependent Atomic Structures and Electrocatalytic Stability on Methanol Oxidation
Deposition
of platinum monolayers on Au substrate (denoted as Au@Pt<sub>ML</sub>) has been shown an efficient catalyst design strategy for
the electrocatalysis of alcohol oxidation due to presumed 100% utilization
of Pt atoms and substrate-enhanced catalytic activities. However,
the atomic structure and stability of Pt (sub)Āmonolayers on realistic
nanoparticulate Au surface still remains elusive. Here, we reveal
coverage-dependent atomic structures and electrocatalytic stabilities
of Pt submonolayers (sML) on Au nanoparticles for methanol oxidation
reaction (MOR) by using high-resolution transmission electron microscopy
combined with energy dispersive X-ray spectrum imaging and electrochemical
techniques. At lower Pt coverages, the Pt<sub>sML</sub> more resembled
monatomic-thick layers, whereas higher Pt coverages above 0.5 ML resulted
in 3D subnanometer Pt nanoclusters leading to lower Pt utilization
efficiencies. Moreover, the Au@Pt<sub>sML</sub> catalysts with Pt
coverage below 0.5 ML showed higher structural and electrocatalytic
stability during MOR electrocatalysis. As a result, increasing the
Pt coverage beyond 0.5 ML brought in no obvious gain in the overall
catalytic performance. Our results suggest that the Au@Pt<sub>0.5Ā ML</sub> catalyst appears to be a more reasonable MOR catalyst than previously
reported Au@Pt<sub>1.0Ā ML</sub> catalyst, providing more rational
catalyst design for achieving high Pt utilization efficiency and high
catalytic performance
Fe<sub>3</sub>O<sub>4</sub>āDecorated Porous Graphene Interlayer for High-Performance LithiumāSulfur Batteries
Lithiumāsulfur
(LiāS) batteries are seriously restrained
by the shuttling effect of intermediary products and their further
reduction on the anode surface. Considerable researches have been
devoted to overcoming these issues by introducing carbon-based materials
as the sulfur host or interlayer in the LiāS systems. Herein,
we constructed a multifunctional interlayer on a separator by inserting
Fe<sub>3</sub>O<sub>4</sub> nanoparticles (NPs) in a porous graphene
(PG) film to immobilize polysulfides effectively. The porous structure
of graphene was optimized by controlling the oxidation conditions
for facilitating ion transfer. The polar Fe<sub>3</sub>O<sub>4</sub> NPs were employed to trap sulfur species via strong chemical interaction.
By exploiting the PG-Fe<sub>3</sub>O<sub>4</sub> interlayer with optimal
porous structure and component, the LiāS battery delivered
a superior cycling performance and rate capability. The reversible
discharge capacity could be maintained at 732 mAh g<sup>ā1</sup> after 500 cycles and 356 mAh g<sup>ā1</sup> after total 2000
cycles at 1 C with a final capacity retention of 49%. Moreover, a
capacity of 589 mAh g<sup>ā1</sup> could also be maintained
even at 2 C rate