24 research outputs found
Interface-Mediated Synthesis of Transition-Metal (Mn, Co, and Ni) Hydroxide Nanoplates
We report a general and efficient
strategy to produce monodisperse
transition-metal (Mn, Co, and Ni) hydroxide nanoplates with tunable
composition through the interface-mediated growth process. It is worth
noting that, using common nitrates as the precursors, the as-obtained
nanoplates were prepared under hydrothermal conditions. Moreover,
the possible formation mechanism of the transition-metal hydroxide
nanoplates has also been investigated. Subsequently, the resulting
transition-metal hydroxides can be eventually transformed into transition-metal
oxide nanoplates and lithium-ion intercalation materials through solid-state
reactions, respectively. Furthermore, the electrochemical properties
of the resulting nanomaterials have also been discussed in detail.
This protocol may be easily extended to fabricate many other metal
hydroxide and oxide nanomaterials
Syntheses of Water-Soluble Octahedral, Truncated Octahedral, and Cubic PtâNi Nanocrystals and Their StructureâActivity Study in Model Hydrogenation Reactions
We developed a facile strategy to synthesize a series
of water-soluble
Pt, Pt<sub><i>x</i></sub>Ni<sub>1â<i>x</i></sub> (0 < <i>x </i>< 1), and Ni nanocrystals. The octahedral,
truncated octahedral, and cubic shapes were uniformly controlled by
varying crystal growth inhibition agents such as benzoic acid, aniline,
and carbon monoxide. The compositions of the Pt<sub><i>x</i></sub>Ni<sub>1â<i>x</i></sub> nanocrystals were effectively
controlled by choice of ratios between the Pt and Ni precursors. In
a preliminary study to probe their structureâactivity dependence,
we found that the shapes, compositions, and capping agents strongly
influence the catalyst performances in three model heterogeneous hydrogenation
reactions
Single-Crystalline Octahedral AuâAg Nanoframes
We report the formation of single-crystalline octahedral
AuâAg
nanoframes by a modified galvanic replacement reaction. Upon sequential
addition of AgNO<sub>3</sub>, CuCl, and HAuCl<sub>4</sub> to octadecylamine
solution, truncated polyhedral silver nanoparticles formed first and
then changed into octahedral AuâAg nanoframes, without requiring
a conventional Ag removal step with additional oxidation etchant.
The nanoframes have 12 sides, and all of the eight {111} faces are
empty. The side grows along the [110] direction, and the diameter
is less than 10 nm. The selective gold deposition on the high-energy
(110) surface, the diffusion, and the selective redeposition of Au
and Ag atoms are the key reasons for the formation of octahedral nanoframes
Energy Upconversion in Lanthanide-Doped Core/Porous-Shell Nanoparticles
Here, we report upconversion nanoparticles
with a core/porous-shell structure in which bulk emission and nanoemission
are simultaneously observed. The activated porous shell can efficiently
tune the bulk emission but has negligible influence on the nanoemission
Sophisticated Construction of Au Islands on PtâNi: An Ideal Trimetallic Nanoframe Catalyst
We have developed a priority-related
chemical etching method to
transfer the starting PtâNi polyhedron to a nanoframe. Utilizing
the lower electronegativity of Ni in comparison to Au atoms, in conjunction
with the galvanic replacement of catalytically active Au to Ni tops,
a unique Au island on a PtâNi trimetallic nanoframe is achieved.
The design strategy is based on the structural priority mechanism
of multimetallic nanocrystals during the synthesis and thus can be
generalized to other analogous metalâbimetallic nanocrystal
combinations (such as Pd and Cu islands on PtâNi nanoframes),
which is expected to pave the way for the future development of efficient
catalysts
Defect-Dominated Shape Recovery of Nanocrystals: A New Strategy for Trimetallic Catalysts
Here we present a
shape recovery phenomenon of PtâNi bimetallic
nanocrystals that is unequivocally attributed to the defect effects.
High-resolution electron microscopy revealed the overall process of
conversion from concave octahedral Pt<sub>3</sub>Ni to regular octahedral
Pt<sub>3</sub>Ni@Ni upon Ni deposition. Further experiments and theoretical
investigations indicated that the intrinsic defect-dominated growth
mechanism allows the site-selective nucleation of a third metal around
the defects to achieve the sophisticated design of trimetallic Pt<sub>3</sub>Ni@M coreâshell structures (M = Au, Ag, Cu, Rh). Consideration
of geometrical and electronic effects indicated that trimetallic atomic
steps in Pt<sub>3</sub>Ni@M could serve as reactive sites to significantly
improve the catalytic performance, and this was corroborated by several
model reactions. The synthesis strategy based on our work paves the
way for the atomic-level design of trimetallic catalysts
Highly Active and Selective Catalysis of Bimetallic Rh<sub>3</sub>Ni<sub>1</sub> Nanoparticles in the Hydrogenation of Nitroarenes
Because of the requirements of sustainable
development as well
as the desirability of using molecular hydrogen as a chemical reagent,
it is of paramount importance and great challenge to develop highly
active and selective catalysts for the hydrogenation of organic molecules,
including substituted nitroarenes. We approach this question by probing
unsupported bimetallic nanoparticles. A series of novel bimetallic
Rh<sub><i>x</i></sub>Ni<sub><i>y</i></sub> (<i>x</i>, <i>y</i> = 1, 2, 3) nanoparticles were successfully
prepared using our ânoble metal-induced reductionâ strategy.
Unsupported Rh<sub>3</sub>Ni<sub>1</sub> nanoparticles were subsequently
identified to be a highly active and exceedingly selective catalyst
for the hydrogenation of nitroarenes under ambient conditions, underscoring
a remarkable synergistic effect of the two metals. Further experiments
showed that the Rh<sub>3</sub>Ni<sub>1</sub> catalyst could be a highly
efficient, selective, and recyclable catalyst for a range of nitroarene
substrates. This work showcased the value of bimetallic nanoparticles
in catalysts development for sustainable chemistry
Room Temperature Activation of Oxygen by Monodispersed Metal Nanoparticles: Oxidative Dehydrogenative Coupling of Anilines for Azobenzene Syntheses
It is highly challenging but desirable
to develop efficient catalysts
for the activation of oxygen under mild conditions. Here, we report
that various monodispersed metal nanoparticles (Ag, Pt, Co, Cu, Ni,
Pd, and Au) efficiently activated molecular oxygen under mild conditions,
illustrated by the aerobic oxidation of anilines to form either symmetric
or asymmetric aromatic azo compounds. This discovery indicates that
exploiting the catalytic power of nanoparticles could enable sustainable
chemistry suitable for important oxidation reactions
Atomically Dispersed Au-Assisted CâC Coupling on Red Phosphorus for CO<sub>2</sub> Photoreduction to C<sub>2</sub>H<sub>6</sub>
Single-atom catalysts have exhibited great potential
in the photocatalytic
conversion of CO2 to C2 products, but generation
of gaseous multi-carbon hydrocarbon products is still challenging.
Previously, supports of a single atom consist of multiple elements,
making CâC coupling difficult because the coordination environment
of single-atom sites is diversified and difficult to control. Here,
we steer CâC coupling by implanting an Au single atom on the
red phosphorus (Au1/RP), support with uniform structure
composed of a single element, lower electronegativity, and better
ability to absorb CO2. The electron-rich phosphorus atoms
near the Au single atoms can function as active sites for CO2 activation. The Au single atom can effectively reduce the energy
barrier of CâC coupling, boosting the reaction kinetics of
the formation of C2H6. Notably, the C2H6 selectivity and turnover frequency of Au1/RP reach 96% and 7.39 hâ1 without a sacrificial
agent, respectively, which almost represents the best photocatalyst
for C2 chemical synthesis to date. This research will provide
new ideas for the design of high-efficiency photocatalysts for CO2 conversion to C2 products
Ultrathin PtâZn Nanowires: High-Performance Catalysts for Electrooxidation of Methanol and Formic Acid
Herein, we have developed
a Zn<sup>2+</sup> ion induced reduction
strategy (ZIRS) for synthesizing ultrathin PtâZn nanowires
(NWs) with average size of âŒ2.2 nm. The precise selection of
solvent and the addition of ZnCl<sub>2</sub> precursor are of crucial
significance to preparing bimetallic NWs. The NWs exhibited electrocatalytic
performance compared with commercial catalysts, such as electrooxidation
of methanol (MOR) and formic acid (FAOR). Moreover, the prepared PtâZn
NWs can be adopted as a template to prepare Pt-based trimetallic ultrathin
NWs