We
report the discovery of a rule-breaking two-dimensional aluminum boride
(AlB6–ptAl–array) nanosheet with a planar
tetracoordinate aluminum (ptAl) array in a tetragonal lattice by comprehensive
crystal structure search, first-principles calculations, and molecular
dynamics simulations. It is a brand new 2D material with a unique
motif, high stability, and exotic properties. These anti-van’t
Hoff/Le Bel ptAl-arrays are arranged in a highly ordered way and connected
by two sheets of boron rhomboidal strips above and below the array.
The regular alignment and strong bonding between the constituents
of this material lead to very strong mechanical strength (in-plane
Young’s modulus Y
x
= 379, Y
y
= 437 N/m,
much larger than that of graphene, Y = 340 N/m) and high
thermal stability (the framework survived simulated annealing at 2080
K for 10 ps). Additionally, electronic structure calculations indicate
that it is a rare new material with triple Dirac
cones, Dirac-like fermions, and node-loop features. Remarkably, this
material is predicted to be a 2D phonon-mediated superconductor with T
c = 4.7 K, higher than the boiling point of
liquid helium (4.2 K). Surprisingly, the T
c can be greatly enhanced up to 30 K by applying tensile
strain at 12%. This is much higher than the temperature of
liquid hydrogen (20.3 K). These outstanding properties may pave the
way for potential applications of an AlB6–ptAl–array
in nanoelectronics and nanomechanics. This work opens up a new branch
of two-dimensional aluminum boride materials for exploration. The
present study also opens a field of two-dimensional arrays of anti-van’t
Hoff/Le Bel motifs for study.
The ever-increasing anthropic NO emission from fossil fuel combustion has resulted in a series of severe environmental issues. Ambient electrocatalytic NO reduction has emerged as a promising route for sustainable...
As an environmentally friendly and
sustainable strategy to produce
ammonia, the electrocatalytic nitrogen reduction reaction (eNRR) is
facing the challenge of low conversion rates and high overpotential,
to solve which efficient catalysts are urgently needed. Here, a new
class of two-dimensional metal–organic layers (MOLs) TM3(HAB)2 (TM = 30 transition metals; HAB = hexaaminobenzene)
were evaluated via a three-step high-throughput screening
combined with the spin-polarized density functional theory (DFT) method
to obtain eligible TM3(HAB)2 catalysts embedded
with transition metal atoms from 3d to 5d. Our investigation revealed
that Nb3(HAB)2, Mo3(HAB)2, and Tc3(HAB)2 are eligible NRR candidates,
among which Tc3(HAB)2 possesses the best catalytic
performance with a lowest onset potential of −0.63 V via both distal and alternating pathways and an ultralow
NH3 desorption free energy of 0.22 eV. Furthermore, the
band structures of three catalysts show their nice conductivity. The
corresponding projected density of states (PDOS) illustrate that high
catalytic activity can be ascribed to apparent orbital hybridization
and charge transfer between catalysts and adsorbed N2.
Later, stability and selectivity of all three candidates were computed,
Tc3(HAB)2 and Nb3(HAB)2 catalysts are proved to facilitate dinitrogen reduction and exhibit
good stability and high selectivity, yet NRR on the Mo3(HAB)2 catalyst is inhibited by hydrogen evolution reaction
(HER). Based on the abovementioned studies, we concluded that Tc3(HAB)2 and Nb3(HAB)2 monolayers
are promising catalysts for nitrogen fixation. We expect this work
to fill the gap of exploring more eligible single-atom catalysts (SACs)
anchored with transition metal atoms on MOLs for NRR.
A systematic study on the catalytic performance of dual transition metal atoms (3d, 4d and 5d) embedded three types of N-doped graphene (DV, TV, QV) for electrocatalytic nitrogen reduction reaction...
Since the discovery of graphene, 2D materials have captured the minds of scientists because of their attractive and unique electronic properties. In particular, magnetic 2D materials have become a subject of extensive discussions today. Using density functional theory calculations, it is shown that 2D SiN sheet (built out of nonmetallic main group atoms) is a ferromagnetic semiconducting material with a magnetic moment 1 μB per unit cell and an indirect bandgap of 1.55 eV. Calculated phonon spectrum and conducted ab initio molecular dynamics simulation reveal thermal and dynamical stability of the designed material. It is shown that the ferromagnetic state is stable up to 20 K. Magnetism of silicon mononitride can be described by the presence of an unpaired electron located on silicon atoms. The semiconducting and ferromagnetic properties of SiN monolayer open many opportunities for its potential use in spintronic and nanoelectronic devices.
Electrosynthesis of ammonia under mild conditions has been impeded by the lack of high-performance electrocatalysts. Inspired by the high activity and selectivity of singleatom catalysts (SACs) with maximum atom utilization, we systematically explored a new class of two-dimensional SACs formed by embedding 30 types of transition metals (TMs) in twodimensional (2D) parallel patterning of tetracyanoethylene (TCNE) networks (labeled as p-TM[TCNE], p means parallel) for the nitrogen reduction reaction (NRR) through the combination of high-throughput screening and density functional theory calculations. Three p-TM[TCNE] (TM = Mo, Nb, Ti) catalysts stand out with high catalytic activity and selectivity. The full reaction path search demonstrates that these three catalysts prefer the distal mechanism, among which p-Mo[TCNE] has the lowest limiting potential of −0.36 V. The origin of high activity might be ascribed to the joint effects from exposed active sites in 2D planar structures, high stability and metallic properties of catalysts, and efficient charge transfer between adsorbed N 2 and active sites. Interestingly, the catalytic performance can be correlated well with the magnetic moment of transition metal, which indicates that the magnetic moment could be used as an efficient descriptor for the NRR. This work will shed some light on the rational design of efficient NRR catalysts and stimulate further efforts of both experiment and theory in this field.
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