2 research outputs found
Facile Preparation of Well-Dispersed CeO<sub>2</sub>–ZnO Composite Hollow Microspheres with Enhanced Catalytic Activity for CO Oxidation
In
this article, well-dispersed CeO<sub>2</sub>–ZnO composite
hollow microspheres have been fabricated through a simple chemical
reaction followed by annealing treatment. Amorphous zinc–cerium
citrate hollow microspheres were first synthesized by dispersing zinc
citrate hollow microspheres into cerium nitrate solution and then
aging at room temperature for 1 h. By calcining the as-produced zinc–cerium
citrate hollow microspheres at 500 °C for 2 h, CeO<sub>2</sub>–ZnO composite hollow microspheres with homogeneous composition
distribution could be harvested for the first time. The resulting
CeO<sub>2</sub>–ZnO composite hollow microspheres exhibit enhanced
activity for CO oxidation compared with CeO<sub>2</sub> and ZnO, which
is due to well-dispersed small CeO<sub>2</sub> particles on the surface
of ZnO hollow microspheres and strong interaction between CeO<sub>2</sub> and ZnO. Moreover, when Au nanoparticles are deposited on
the surface of the CeO<sub>2</sub>–ZnO composite hollow microspheres,
the full CO conversion temperature of the as-produced 1.0 wt % Au–CeO<sub>2</sub>–ZnO composites reduces from 300 to 60 °C in comparison
with CeO<sub>2</sub>–ZnO composites. The significantly improved
catalytic activity may be ascribed to the strong synergistic interplay
between Au nanoparticles and CeO<sub>2</sub>–ZnO composites
Composition Tunability and (111)-Dominant Facets of Ultrathin Platinum–Gold Alloy Nanowires toward Enhanced Electrocatalysis
The
ability for tuning not only the composition but also the type
of surface facets of alloyed nanomaterials is important for the design
of catalysts with enhanced activity and stability through optimizing
both ensemble and ligand effects. Herein we report the first example
of ultrathin platinum–gold alloy nanowires (PtAu NWs) featuring
composition-tunable and (111) facet-dominant surface characteristics,
and the electrocatalytic enhancement for the oxygen reduction reaction
(ORR). PtAu NWs of different bimetallic compositions synthesized by
a single-phase and surfactant-free method are shown to display an
alloyed, parallel-bundled structure in which the individual nanowires
exhibit Boerdijk–Coxeter helix type morphology predominant
in (111) facets. Results have revealed intriguing catalytic correlation
with the binary composition, exhibiting an activity maximum at a Pt:Au
ratio of ∼3:1. As revealed by high-energy synchrotron X-ray
diffraction and atomic pair distribution function analysis, NWs of
this ratio exhibit a clear shrinkage in interatomic bonding distances.
In comparison with PtAu nanoparticles of a similar composition and
degree of shrinking of atomic-pair distances, the PtAu NWs display
a remarkably higher electrocatalytic activity and stability. The outperformance
of NWs over nanoparticles is attributed to the predominant (111)-type
facets on the surface balancing the contribution of ensemble and ligand
effects, in addition to the composition synergy due to optimal adsorption
energies for molecular and atomic oxygen species on the surface as
supported by DFT computation of models of the catalysts. The findings
open up a new pathway to the design and engineering of alloy nanocatalysts
with enhanced activity and durability