3 research outputs found
Controllable Synthesis of Various CaCO<sub>3</sub> Morphologies Based on a CCUS Idea
A novel, green, and economic CaCO<sub>3</sub> synthesis method
using a CO<sub>2</sub>-storage material (CO<sub>2</sub>SM) was developed
based on the strategy of carbon capture, utilization, and storage
(CCUS). In this process, CO<sub>2</sub>SM was used as both a CO<sub>2</sub> source and a crystal modifier to regulate and control the
crystallization of CaCO<sub>3</sub>. 1,4-Butanediol (BDO) and/or 1,2-ethanediamine
(EDA) from CO<sub>2</sub>SM played unexpected roles as a surfactant,
structure-directing agent, and/or pH modulator. The effects of CO<sub>2</sub>SM concentrations, reaction temperatures, and reaction times
were systematically investigated. Pure calcite (bundle-like and dumbbell-like)
and pure vaterite (oblate spheroid and snowball-like) CaCO<sub>3</sub> products were obtained. Moreover, the CO<sub>2</sub>SM was recycled
to prepare same crystal phase CaCO<sub>3</sub> upon the addition of
an appropriate amount of CaÂ(OH)<sub>2</sub> with 120 g·L<sup>–1</sup> CO<sub>2</sub>SM concentration
<i>A</i>‑Site-Doping Enhanced <i>B</i>‑Site Ordering and Correlated Magnetic Property in La<sub>2–<i>x</i></sub>Bi<sub><i>x</i></sub>CoMnO<sub>6</sub>
A series of Bi-doped La<sub>2–<i>x</i></sub>Bi<sub><i>x</i></sub>CoMnO<sub>6</sub> double perovskite
oxides
are synthesized, and the impact of doping on crystal structures and
magnetic properties is investigated comprehensively. X-ray photoelectron
spectroscopy and Raman spectrum analyses reveal that ordering of Co
and Mn ions at <i>B</i>-site is gradually improved with
the rise of Bi concentration. Meanwhile, magnetic disordering is suppressed
greatly by showing larger magnetic moments. Structurally, the Rietveld
refinement shows that the bonds are elongated, while the bond angles
are shrunken after doping, giving rise to lowered Curie temperature.
We also observe a large negative zero-field-cooling magnetization,
which is attributed to the formation of spin antiparallel or canted
ferromagnetic domains and clusters that are separated by the antiphase
boundaries. First-principles calculations confirm the enhanced Co–Mn
ordering upon Bi doping by taking into account both the ordering and
disordering configurations of La<sub>2</sub>CoMnO<sub>6</sub>, LaBiCoMnO<sub>6</sub>, and Bi<sub>2</sub>CoMnO<sub>6</sub>. Moreover, we find a
spin-state transition in the antisite Co ions from high-spin (Co<sup>2+</sup>-t<sub>2g</sub><sup>5</sup>e<sub>g</sub><sup>2</sup>) to
low-spin state (Co<sup>3+</sup>-t<sub>2g</sub><sup>6</sup>e<sub>g</sub><sup>0</sup>), which is consistent with the increased total magnetic
moments by the Bi doping
General Synthesis of MOF Nanotubes via Hydrogen-Bonded Organic Frameworks toward Efficient Hydrogen Evolution Electrocatalysts
The
application scope of metal–organic frameworks
(MOFs)
can be extended by rationally designing the architecture and components
of MOFs, which can be achieved via a metal-containing solid templated
strategy. However, this strategy suffers from low efficiency and provides
only one specific MOF from one template. Herein, we present a versatile
templated strategy in which organic ligands are weaved into hydrogen-bonded
organic frameworks (HOFs) for the controllable and scalable synthesis
of MOF nanotubes. HOF nanowires assembled from benzene-1,3,5-tricarboxylic
acid and melamine via a simple sonochemical approach serve as both
the template and precursor to produce MOF nanotubes with varied metal
compositions. Hybrid nanotubes containing nanometal crystals and N-doped
graphene prepared through a carbonization process show that the optimized
NiRuIr alloy@NG nanotube exhibits excellent electrocatalytic HER activity
and durability in alkaline media, outperforming most reported catalysts.
The strategy proposed here demonstrates a pioneering study of combination
of HOF and MOF, which shows great potential in the design of other
nanosized MOFs with various architectures and compositions for potential
applications