7 research outputs found
Formation of Asymmetric Bowl-Like Mesoporous Particles via Emulsion-Induced Interface Anisotropic Assembly
Mesoporous colloidal particles with tailored asymmetric morphologies
and radially oriented large channels are of great importance for development
of new carriers for nanoencapsulation, high-performance mass transport
nanosystems, and complex assembly structures. However, controllable
anisotropic growth to asymmetric mesoporous particles is very challenging
via the universal surfactant-directed soft-templating method. Herein
we report a simple emulsion-induced interface anisotropic assembly
approach to synthesize bowl-like mesoporous polydopamine particles
with diameter of ∼210 nm, well-controlled radially oriented
mesochannels, and large pore size of ∼11 nm. This interface-driven
approach also creates opportunities for tailoring the assembly and
formation of various asymmetric and symmetric polydopamine particles.
Bowl-like mesoporous carbon particles with radially oriented channels,
high accessible surface area of 619 m<sup>2</sup> g<sup>–1</sup>, and large pore size of ∼8 nm can be fabricated by subsequent
hydrothermal treatment and calcination under nitrogen atmosphere.
Lastly, we demonstrate that the as-derived bowl-like mesoporous carbon
particles manifest enhanced electrocatalytic performance for oxygen
reduction reaction in alkaline electrolyte
Metal–Organic-Frameworks-Derived General Formation of Hollow Structures with High Complexity
Increasing
the complexity of hollow structures, in terms of chemical
composition and shell architecture, is highly desirable for both fundamental
studies and realization of various functionalities. Starting with
metal–organic frameworks (MOFs), we demonstrate a general approach
toward the large-scale and facile synthesis of complex hollow microboxes
via manipulation of the template-engaged reactions between the Prussian
blue (PB) template and different alkaline substances. The reaction
between PB microcubes with NaOH solution leads to the formation of
FeÂ(OH)<sub>3</sub> microboxes with controllable multishelled structure.
In addition, PB microcubes will react with the conjugate bases of
metal oxide based weak acids, generating multicompositional microboxes
(Fe<sub>2</sub>O<sub>3</sub>/SnO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>/GeO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>/Al<sub>2</sub>O<sub>3</sub>, and Fe<sub>2</sub>O<sub>3</sub>/B<sub>2</sub>O<sub>3</sub>), which consist of
uniformly dispersed oxides/hydroxides of iron and another designed
element. Such complex hollow structures and atomically integrated
multiple compositions might bring the usual physiochemical properties.
As an example, we demonstrate that these complex hollow microboxes,
especially the Fe<sub>2</sub>O<sub>3</sub>/SnO<sub>2</sub> composite
microboxes, exhibit remarkable electrochemical performance as anode
materials for lithium ion batteries
Highly Efficient Removal of Organic Dyes from Waste Water Using Hierarchical NiO Spheres with High Surface Area
A facile solvothermal method has been developed for large-scale
preparation of uniform spheres of a nickel–ethylene glycol
complex (Ni-EG complex) with a hierarchical nanostructure. The dispersibility
and hierarchical structure of the Ni-EG particles can be tuned by
varying the concentration of additives added. On the basis of experimental
observations, a plausible mechanism has been proposed to understand
the formation process of the Ni-EG complex spheres. Calcining these
as-prepared Ni-EG complex spheres at 300 °C in air results in
uniform porous NiO spheres with a high specific surface area of 222
m<sup>2</sup> g<sup>–1</sup>. When served as the adsorbent
for Congo red in water, the colloidal suspension of the as-prepared
NiO hierarchical spheres exhibits a high adsorption capacity for the
dye removal, suggesting their potential use in water treatment
Designed Formation of Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> Double-Shelled Nanocages with Enhanced Pseudocapacitive and Electrocatalytic Properties
Hollow
structures with high complexity in shell architecture and
composition have attracted tremendous interest because of their great
importance for both fundamental studies and practical applications.
Herein we report the designed synthesis of novel box-in-box nanocages
(NCs) with different shell compositions, namely, Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> double-shelled nanocages (DSNCs).
Uniform zeolitic imidazolate framework-67/Ni–Co layered double
hydroxides yolk-shelled structures are first synthesized and then
transformed into Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> DSNCs by thermal annealing in air. Importantly, this strategy
can be easily extended to prepare other complex DSNCs. When evaluated
as electrodes for pseudocapacitors, the Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> DSNCs show a high specific capacitance
of 972 F g<sup>–1</sup> at a current density of 5 A g<sup>–1</sup> and excellent stability with 92.5% capacitance retention after 12 000
cycles, superior to that of Co<sub>3</sub>O<sub>4</sub> NCs with simple
configuration and Co<sub>3</sub>O<sub>4</sub>/Co<sub>3</sub>O<sub>4</sub> DSNCs. Besides, the Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> DSNCs also exhibit much better electrocatalytic
activity for the oxygen evolution reaction than Co<sub>3</sub>O<sub>4</sub> NCs. The greatly improved electrochemical performance of
Co<sub>3</sub>O<sub>4</sub>/NiCo<sub>2</sub>O<sub>4</sub> DSNCs demonstrates
the importance of rational design and synthesis of hollow structures
with higher complexity
One-Pot Synthesis of Cubic PtCu<sub>3</sub> Nanocages with Enhanced Electrocatalytic Activity for the Methanol Oxidation Reaction
Noble metals such as platinum (Pt) are widely used as
catalysts
in fuel cells and other heterogeneous catalytic processes. However,
there is an urgent need to develop substitutes for pure Pt catalysts
to reduce the overall use of precious Pt and at the same time to enhance
poisoning resistance. A promising strategy is to design Pt based bi-
or trimetallic nanostructures because their unique structures and
compositions would enhance their catalytic performance. In this study,
we report the synthesis, characterization, and electrochemical evaluation
of cubic intermetallic PtCu<sub>3</sub> nanocages. The influential
effects of several important experimental parameters on the final
products have been explored through systematic studies on the growth
of PtCu<sub>3</sub> nanocages. Relative to the current commercial
Pt electrocatalyst, these PtCu<sub>3</sub> nanocages possess a more
accessible surface area and a unique hollow structure, which contribute
to improved electrocatalytic activity in the methanol oxidation reaction
Formation of Fe<sub>2</sub>O<sub>3</sub> Microboxes with Hierarchical Shell Structures from Metal–Organic Frameworks and Their Lithium Storage Properties
Fe<sub>2</sub>O<sub>3</sub> microboxes with hierarchically
structured
shells have been synthesized simply by annealing Prussian blue (PB)
microcubes. By utilizing simultaneous oxidative decomposition of PB
microcubes and crystal growth of iron oxide shells, we have demonstrated
a scalable synthesis of anisotropic hollow structures with various
shell architectures. When evaluated as an anode material for lithium
ion batteries, the Fe<sub>2</sub>O<sub>3</sub> microboxes with a well-defined
hollow structure and hierarchical shell manifested high specific capacity
(∼950 mA h g<sup>–1</sup> at 200 mA g<sup>–1</sup>) and excellent cycling performance
Ultrathin and Ultralong Single-Crystal Platinum Nanowire Assemblies with Highly Stable Electrocatalytic Activity
Ultrathin
one-dimensional (1D) nanostructures such as nanowires and nanorods
have drawn considerable attention due to their promising applications
in various fields. Despite the numerous reports on 1D nanostructures
of noble metals, one-pot solution synthesis of Pt 1D nanostructures
still remains a great challenge, probably because of the intrinsic
isotropic crystal growth behavior of Pt. Herein, we demonstrate the
facile solvothermal synthesis of nanowire assemblies composed of ultrathin
(ca. 3 nm) and ultralong (up to 10 μm) Pt nanowires without
involving any template. The oriented attachment mechanism is found
to be partially responsible for the formation of such ultrathin Pt
nanowires. The amine molecules generated during the reaction might
assist the formation of nanowire assemblies. Importantly, the present
system can be extended to synthesize Pt-based alloy nanowire assemblies
such as Pt–Au and Pt–Pd. These Pt nanowires can be easily
cast into a free-standing membrane, which exhibits excellent electrocatalytic
activity and very high stability for formic acid and methanol oxidation
and the oxygen reduction reaction