3 research outputs found
Turning Nonmagnetic Two-Dimensional Molybdenum Disulfides into Room-Temperature Ferromagnets by the Synergistic Effect of Lattice Stretching and Charge Injection
Exploring two-dimensional (2D) room-temperature
magnetic materials
in the field of 2D spintronics remains a formidable challenge. The
vast array of nonmagnetic 2D materials provides abundant resources
for exploration, but the strategy to convert them into intrinsic room-temperature
magnets remains elusive. To address this challenge, we present a general
strategy based on surface halogenation for the transition from nonmagnetism
to intrinsic room-temperature ferromagnetism in 2D MoS2 based on first-principles calculations. The derived 2D halogenated
MoS2 are half-semimetals with a high Curie temperature
(TC) of 430ā589 K and excellent
stability. In-depth mechanistic studies revealed that this marvelous
nonmagnetism-to-ferromagnetism transition originates from the modulation
of the splitting as well as the occupation of the Mo d orbitals by
the synergy of lattice stretching and charge injection induced by
the surface halogenation. This work establishes a promising route
for exploring 2D room-temperature magnetic materials from the abundant
pool of 2D nonmagnetic counterparts
Two-Dimensional Transition Metal Boron Cluster Compounds (MB<sub><i>n</i></sub>enes) with Strain-Independent Room-Temperature Magnetism
Two-dimensional
(2D) metal borides (MBenes) with unique electronic
structures and physicochemical properties hold great promise for various
applications. Given the abundance of boron clusters, we proposed employing
them as structural motifs to design 2D transition metal boron cluster
compounds (MBnenes), an extension of MBenes.
Herein, we have designed three stable MBnenes (M4(B12)2, M = Mn, Fe, Co)
based on B12 clusters and investigated their electronic
and magnetic properties using first-principles calculations. Mn4(B12)2 and Co4(B12)2 are semiconductors, while Fe4(B12)2 exhibits metallic behavior. The unique structure in
MBnenes allows the coexistence of direct
exchange interactions between adjacent metal atoms and indirect exchange
interactions mediated by the clusters, endowing them with a NeĢel
temperature (TN) up to 772 K. Moreover,
both Mn4(B12)2 and Fe4(B12)2 showcase strain-independent room-temperature
magnetism, making them potential candidates for spintronics applications.
The MBnenes family provides a fresh avenue
for the design of 2D materials featuring unique structures and excellent
physicochemical properties
Refining Defect States in W<sub>18</sub>O<sub>49</sub> by Mo Doping: A Strategy for Tuning N<sub>2</sub> Activation towards Solar-Driven Nitrogen Fixation
Photocatalysis
may provide an intriguing approach to nitrogen fixation,
which relies on the transfer of photoexcited electrons to the ultrastable
Nī¼N bond. Upon N<sub>2</sub> chemisorption at active sites
(e.g., surface defects), the N<sub>2</sub> molecules have yet to receive
energetic electrons toward efficient activation and dissociation,
often forming a bottleneck. Herein, we report that the bottleneck
can be well tackled by refining the defect states in photocatalysts
via doping. As a proof of concept, W<sub>18</sub>O<sub>49</sub> ultrathin
nanowires are employed as a model material for subtle Mo doping, in
which the coordinatively unsaturated (CUS) metal atoms with oxygen
defects serve as the sites for N<sub>2</sub> chemisorption and electron
transfer. The doped low-valence Mo species play multiple roles in
facilitating N<sub>2</sub> activation and dissociation by refining
the defect states of W<sub>18</sub>O<sub>49</sub>: (1) polarizing
the chemisorbed N<sub>2</sub> molecules and facilitating the electron
transfer from CUS sites to N<sub>2</sub> adsorbates, which enables
the Nī¼N bond to be more feasible for dissociation through proton
coupling; (2) elevating defect-band center toward the Fermi level,
which preserves the energy of photoexcited electrons for N<sub>2</sub> reduction. As a result, the 1 mol % Mo-doped W<sub>18</sub>O<sub>49</sub> sample achieves an ammonia production rate of 195.5 Ī¼mol
g<sub>cat</sub><sup>ā1</sup> h<sup>ā1</sup>, 7-fold
higher than that of pristine W<sub>18</sub>O<sub>49</sub>. In pure
water, the catalyst demonstrates an apparent quantum efficiency of
0.33% at 400 nm and a solar-to-ammonia efficiency of 0.028% under
simulated AM 1.5 G light irradiation. This work provides fresh insights
into the design of photocatalyst lattice for N<sub>2</sub> fixation
and reaffirms the versatility of subtle electronic structure modulation
in tuning catalytic activity