Despite
the widespread interest in the examinations of catalytic
and facet-dependent properties of Cu2O crystals, it was
still difficult to grow ultrasmall Cu2O cubes and octahedra
with tunable sizes at a large scale. In this work, CuSO4, NaOH, and sodium ascorbate of varying volumes were added to an
aqueous sodium dodecyl sulfate (SDS) solution to generate Cu2O nanocubes with average edge lengths of 16, 25, 29, 36, 51, 63,
72, and 86 nm in just 10 min. Another series of Cu2O cubes
with wide size tunability in the range of 27–200 nm is accomplished
by simply adjusting the NaOH volume. Similar reaction conditions can
also be used to make a large quantity of Cu2O octahedra
with opposite corner distances of just 34, 41, and 49 nm. Remarkably,
production of these small Cu2O cubes and octahedra is scalable to 500 mL in one reaction. UV–vis
absorption and photoluminescence spectra establish their size and
facet-dependent optical properties, and a modified band diagram of
Cu2O is presented. Recognizing Cu2O nanocrystal
shape evolution is possible by changing the cell potential, we have
proven this concept to yield cubic to truncated octahedral and octahedral
structures by varying the CuSO4 volume. Finally, the tiny
Cu2O cubes and octahedra were pseudomorphically converted
to Cu cubes and octahedra via the introduction of ammonia borane,
so these small copper polyhedra become readily accessible for diverse
catalytic and plasmonic applications.
Alkali
metal–carbon dioxide (Li/Na–CO2) batteries
have generated widespread interest in the past few years
owing to the attractive strategy of utilizing CO2 while
still delivering high specific energy densities. Among these systems,
Na–CO2 batteries are more cost effective than Li–CO2 batteries because the former uses cheaper and abundant Na.
Herein, a Ru/carbon nanotube (CNT) as a cathode material was used
to compare the mechanisms, stabilities, overpotentials, and energy
densities of Li–CO2 and Na–CO2 batteries. The potential of Na–CO2 batteries as
a viable energy storage technology was demonstrated.
Li–CO2 batteries are of great interest among
researchers due to their high energy density and utilization of the
greenhouse gas CO2 to produce energy. However, several
shortcomings have been encountered in the practical applications of
Li–CO2 batteries, among which their poor cyclability
and high charge overpotential necessary to decompose the highly insulating
discharge product (Li2CO3) are the most important.
Herein, the spinel zinc cobalt oxide porous nanorods with carbon nanotubes
(ZnCo2O4@CNTs) composite is employed as a cathode
material in Li–CO2 batteries to improve the latter’s
cycling performance. The ZnCo2O4@CNT cathode-based
Li–CO2 battery exhibited a full discharge capacity
of 4275 mAh g–1 and excellent cycling performance
over 200 cycles with a charge overpotential below 4.3 V when operated
at a current density of 100 mA g–1 and fixed capacity
of 500 mAh g–1. The superior performance of the
ZnCo2O4@CNT cathode composite was attributed
to the synergistic effects of ZnCo2O4 and CNT.
The highly porous ZnCo2O4 nanorod structures
in the ZnCo2O4@CNT catalyst showed enhanced
catalytic activity/stability, which effectively promoted CO2 diffusion during the discharging process and accelerated Li2CO3 decomposition at a low charge overpotential.
Copper nanocubes with average sizes of 82, 95, and 108 nm have been synthesized in an aqueous mixture of cetyltrimethylammonium chloride (CTAC) surfactant, copper acetate, and sodium ascorbate reductant heated at 100 °C for 40 min. Copper nanowires with an average length of 25 μm can also be prepared this way by simply increasing the volume of sodium ascorbate introduced. Small shifts in the plasmonic absorption band positions with tunable particle sizes have been observed. The copper nanocubes were employed to catalyze hydroboration of phenylacetylene and various substituted aryl alkynes with 100 % (E)-product selectivity and 82-95 % product yields. The copper nanocubes are cheap to make and should catalyze a broad scope of organic coupling reactions.
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