3 research outputs found
Tuning the Physical and Chemical Properties of 2D InSe with Interstitial Boron Doping: A First-Principles Study
InSe monolayer is
a new two-dimensional (2D) material with unique
geometric configuration. Its crystal structure has a large atom interval,
significantly different from those of graphene and MoS<sub>2</sub>, two typical 2D materials. This structural characteristic may facilitate
interstitial doping, which is obviously impossible in graphene and
MoS<sub>2</sub>. In this work, first-principles calculations are employed
to study the effects of interstitial doping of boron atoms on the
electronic and magnetic properties of InSe monolayer. For comparison,
substitutional doping is also studied with In replaced by boron. It
is found that interstitial doping can induce spin-polarized state
and nonzero local magnetic moments. In order to investigate the effects
of doping contents on electronic structures and magnetism, three dopant
concentrations (6.25%, 12.5%, 25%) are taken into account. For interstitial
doping, with increasing the B contents, the local magnetic moments
first emerge and then disappear, corresponding to the nonmonotonic
doping-content dependence. For substitutional doping, no local magnetic
moments are observed with any doping contents. These results show
that B-doping-induced magnetism strongly depends on the doping methods
and doping contents in the InSe monolayer. The reasons leading to
the doping behaviors are discussed in detail. This work opens up an
alternative way for tuning the physical and chemical properties of
2D InSe material, and would be helpful for future InSe-based spintronics
devices
From the Surface Reaction Control to Gas-Diffusion Control: The Synthesis of Hierarchical Porous SnO<sub>2</sub> Microspheres and Their Gas-Sensing Mechanism
A series of hierarchical porous SnO<sub>2</sub> microspheres (SnO<sub>2</sub>-Ms) with same sizes of nanoparticles
were fabricated through
increasing the reaction time of the one-step hydrothermal method.
Especially, these SnO<sub>2</sub>-Ms also have the different specific
surface areas and pores sizes. When they are applied in sintering
type thick film gas sensors, through comparing the gas-sensing property
of the as-prepared SnO<sub>2</sub>-Ms, it can clearly demonstrate
that the surface chemical reaction (SCR) control of the sensing properties
of sensors is gradually replaced by gas diffusion control with the
increasing operation temperature (<i>T</i><sub>o</sub>).
For the first time, this dual control is discovered through contrast
experiments. According to the testing results, the sensing mechanism
of sensors can be explained by many factors, such as the reaction
rate constant of the SCR, the Knudsen diffusion coefficient of the
target gas, the <i>T</i><sub>o</sub>, the specific surface
area, the pore size, and the change of the H<sub>2</sub>O, etc. A
pore canal model and a hollow sphere model are introduced, which can
effectively explain the sensing mechanism of gas sensors. This discovery
can make up for the inadequacy of the surface-control and the diffusion-control
theory, and expound their interrelationship. This discovery also provides
a novel strategy for studying the sensing mechanism of sensors, which
is expected to open up exciting opportunities for improving the sensing
properties of the gas-sensing materials and studying some gas–solid
catalytic phenomena
Homogeneous Ni Single-Atom Sites in the NiZn Intermetallic Nanostructure for Efficient Semihydrogenation of Acetylene
Catalytic
semihydrogenation of acetylene is crucial for ethylene
purification but still faces a grand challenge in circumventing deep
hydrogenation and oligomerization so far, especially for the cost-effective
catalysts. Herein, two Ni-based intermetallic nanocatalysts with different
atomic arrangements were subtly constructed via controlling the reduction
temperature of ZnO-supported NiO particles. The one reduced at 400
°C is L12-type intermetallic Ni3Zn with
separated Ni3 trimers (denoted as Ni/ZnO-R400 or Ni3Zn/ZnO); another reduced at 600 °C is L10-type
intermetallic NiZn with the homogeneous Ni single atoms completely
isolated by Zn atoms (denoted as Ni/ZnO-R600 or NiZn/ZnO). The systematical
evaluations validate NiZn/ZnO as an outstanding noble metal-free catalyst
for acetylene semihydrogenation, showing a significantly enhanced
selectivity toward ethylene relative to Ni3Zn/ZnO (87.5
vs −275.4% at 200 °C) through suppressing not only the
unselective hydrogenation to ethane but also carbon deposition. According
to catalytic evaluations with or without ethylene, microcalorimetry,
and density functional theory calculations, the superior selectivity
of NiZn/ZnO stems from the noncompetitive adsorption between the moderately
σ-bonded acetylene over two neighboring Ni single atoms and
weakly π-bonded ethylene on Ni single-atom sites due to its
unique Ni–Zn–Ni ensemble