4 research outputs found
Shape-Control of Pt–Ru Nanocrystals: Tuning Surface Structure for Enhanced Electrocatalytic Methanol Oxidation
Despite the fact
that both electrochemical experiments and density
functional theory calculations have testified to the superior electrocatalytic
activity and CO-poisoning tolerance of platinum–ruthenium (PtRu)
alloy nanoparticles toward the methanol oxidation reaction (MOR),
the facet-dependent electrocatalytic properties of PtRu nanoparticles
are scarcely revealed because it is extremely difficult to synthesize
well-defined facets-enclosed PtRu nanocrystals. Herein, we for the
first time report a general synthesis of ultrathin PtRu nanocrystals
with tunable morphologies (nanowires, nanorods, and nanocubes) through
a one-step solvothermal approach and a systematic investigation of
the structure-directing effects of different surfactants and the formation
mechanism by control experiments and time-dependent studies. In addition,
we utilize these {100} and {111} facets-enclosed PtRu nanocrystals
as model catalysts to evaluate the electrocatalytic characteristics
of the MOR on different facets. Remarkably, {111}-terminated PtRu
nanowires exhibit much higher stability and electrocatalytic mass
activity toward MOR, which are 2.28 and 4.32 times higher than those
of {100}-terminated PtRu nanocubes and commercial Pt/C, respectively,
indicating that PtRu {111} facets possess superior methanol oxidation
activity and CO-poisoning resistance relative to {100} facets. Our
present work provides a series of well-defined PtRu nanocrystals with
tunable facets which would be ideal model electrocatalysts for fundamental
research in fuel cell electrocatalysis
High-Index Facets Bounded Platinum–Lead Concave Nanocubes with Enhanced Electrocatalytic Properties
High-index facets bounded platinum-based
alloy nanocrystals usually
exhibit enhanced electrocatalytic activity. However, the high surface
energy, thermodynamic instability, and lattice mismatch make it a
significant challenge to synthesize well-defined bimetallic nanocrystals
with high-index facets. Here we developed a one-step wet-chemical
synthesis of uniform PtPb concave nanocubes (CNCs) enclosed by {520}
high-index facets. The as-prepared PtPb CNCs exhibited high synthetic
yield and highly concave structure with an average size of 14 nm.
Moreover, the synergistic effects and exposed {520} facets endowed
the PtPb CNCs with excellent stability and electrocatalytic mass activity
toward the methanol oxidation reaction (MOR), which was 2.16- and
4.62-times higher than PtPb nanocubes (NCs) and commercial Pt/C catalysts,
respectively. This work provides a new way for rational design and
practical application of efficient catalysts
Easy Synthesis and Imaging Applications of Cross-Linked Green Fluorescent Hollow Carbon Nanoparticles
We propose an ingenious method for synthesizing cross-linked hollow fluorescent carbon nanoparticles (HFCNs) with green emission by simply mixing acetic acid, water, and diphosphorus pentoxide. This is an automatic method without external heat treatment to rapidly produce large quantities of HFCNs, in contrast to other syntheses of fluorescent carbon nanoparticles that required high temperature, complicated operations, or long reaction times. Characterizations of HFCNs through high-resolution transmission electron microscopy, infrared/Raman spectroscopy, and X-ray diffraction indicate that abundant small oxygenous graphite domains existed and endowed the HFCNs with fluorescent properties. After simple post-treatments, the cross-linked HFCNs can be used for cell-imaging applications. Compared with traditional dyes and CdTe quantum dots, HFCNs are the superior fluorescent bioimaging agent according to their low toxicity, stability, and resistance to photobleaching. The HFCNs were also applied to watermark ink and fluorescent powder, showing their promising potentials for further wide usage
A Flexible Metal–Organic Framework: Guest Molecules Controlled Dynamic Gas Adsorption
A flexible metal–organic framework
(MOF) of [Zn<sub>3</sub>(btca)<sub>2</sub>(OH)<sub>2</sub>]·(guest)<sub><i>n</i></sub> (H<sub>2</sub>btca = 1,2,3-benzotriazole-5-carboxylic
acid)
that exhibits guest molecule-controlled dynamic gas adsorption is
reported in which carbon dioxide molecules rather than N<sub>2</sub>, He, and Ar induce a structural transition with a corresponding
appearance of additional steps in the isotherms. Physical insights
into the dynamic adsorption behaviors of flexible compound <b>1</b> were detected by gas adsorption at different temperatures and different
pressures and confirmed by Fourier transform infrared spectroscopy
and molecular simulations. Interestingly, by taking advantage of the
flexible nature inherent to the framework, this MOF material enables
highly selective adsorption of CO<sub>2</sub>/N<sub>2</sub>, CO<sub>2</sub>/Ar, and CO<sub>2</sub>/He of 36.3, 32.6, and 35.9, respectively,
at 298 K. This class of flexible MOFs has potential applications for
controlled release, molecular sensing, noble gas separation, smart
membranes, and nanotechnological devices