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Herein, via first‐principle calculations and theoretical analysis, a new Dirac semimetal carbon system called C32, which is composed of pentagonal, hexagonal, heptagonal, and octagonal carbon rings is systematically investigated. The stability of C32 is verified by calculating the phonon dispersion, elastic constants, etc., and an appropriate pathway for experimental synthesis is proposed. Besides, it is discovered that the system holds the quadruple rotation and inversion symmetry, resulting in the emergence of eight twisted Dirac cones (D1 and D2) with a highly anisotropic Fermi velocity from 3.83 × 105 to 8.96 × 105 m s−1 along different k directions. To substantiate the semimetallic nature of C32, its nontrivial topological properties are confirmed through the presence of topologically protected edge states, and the nonzero ℤ2 topological invariant. More importantly, by introducing biaxial strain, it is uncovered that Dirac cones can gradually evolve into a nodal line, and the perfect nodal line can be obtained when the biaxial strain is 13.3%. Furthermore, by constructing the tight‐binding model, the appearance of the Dirac cone is perfectly repeated and its evolution into the nodal line under biaxial strain is explained. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) are drawing significant attention due to their intriguing photoelectric properties, and these interesting properties are closely related to the number of layers. Obtaining layer-controlled and high-quality TMD is still a challenge. In this context, we use the salt-assisted chemical vapor deposition to grow multilayered MoSe2 flake and characterize it by Raman spectroscopy, second harmonic generation, and photon luminescence. Spectroscopic analysis is an effective way to characterize the stacking order and optoelectronic properties of two-dimensional materials. Notably, the corresponding mapping reflects the film quality and homogeneity. We found that the grown continuous monolayer, bilayer, and trilayer of MoSe2 sheets with different stacking orders exhibit distinctive features. For bilayer MoSe2, the most stable stacking configurations are the AA' and AB order. And the uniformity of the spectroscopy maps demonstrates the high quality of the stacked MoSe2 sheets. [ABSTRACT FROM AUTHOR]

Spin current generation from charge current in nonmagnetic materials promises an energy-efficient scheme for manipulating magnetization in spintronic devices. In some asymmetric two-dimensional (2D) materials, the Rashba and valley effects coexist owing to strong spin–orbit coupling (SOC), which induces the spin Hall effect due to spin-momentum locking of both effects. Herein, we propose a new Janus structure MoSiAs2Se with both valley physics and the Rashba effect and reveal an effective way to modulate the properties of this structure. The results demonstrated that applying an external electric field is an effective means to modulating the electronic properties of MoSiAs2Se, leading to both type I–II phase transitions and semiconductor–metal phase transitions. Furthermore, the coexistence of the Rashba and valley effects in monolayer MoSiAs2Se contributes to the spin Hall effect (SHE). The magnitude and direction of spin Hall conductivity can also be manipulated with an out-of-plane electric field. Our results enrich the physics and materials of the Rashba and valley systems, opening new opportunities for the applications of 2D Janus materials in spintronic devices. [ABSTRACT FROM AUTHOR]

Cu2O with a cubic structure was prepared by a water bath method, and then a Cu2O/Cu2S core–shell material was obtained by the redox reaction of Cu2O and Na2S with the prepared cubic Cu2O as a template and Na2S·9H2O solution as the reaction solution. At the same time, the effect of sulfidization time on the Cu2O/Cu2S structure and photohydrogen production performance was studied. The structure of the samples was further confirmed and characterized through SEM, HRTEM, XRD and XPS. The photohydrogen production properties of the Cu2O/Cu2S composites with different morphologies were tested. The flower-shaped hollow structure of Cu2O/Cu2S can be obtained by proper sulfidization, and the hydrogen production can reach 1076.95 μmol g−1 after 5 h of illumination. Then, through photocurrent response and impedance spectrum tests and DFT calculations, it is proved that the Cu2O/Cu2S heterostructure can effectively improve the photoresponse ability and carrier transport properties. It was confirmed that the interfacial charge transfer in Cu2O/Cu2S helped increase the photocatalytic hydrogen production performance. [ABSTRACT FROM AUTHOR]

In recent years, two-dimensional (2D) materials have attracted significant attention due to their distinctive properties, including exceptional mechanical flexibility and tunable electronic properties. Via the first-principles calculation, we investigate the effect of strain on the electronic properties of monolayer SnP2S6 and GeP2S6. We find that monolayer SnP2S6 is an indirect bandgap semiconductor, while monolayer GeP2S6 is a direct bandgap semiconductor. Notably, under uniform biaxial strains, SnP2S6 undergoes an indirect-to-direct bandgap transition at 4.0% biaxial compressive strains, while GeP2S6 exhibits a direct-to-indirect transition at 2.0% biaxial tensile strain. The changes in the conduction band edge can be attributed to the high-symmetry point Γ being more sensitive to strain than K. Thus, the relocation of the conduction band and valence band edges in monolayer SnP2S6 and GeP2S6 induces a direct-to-indirect and indirect-to-direct bandgap transition, respectively. Consequently, the strain is an effective band engineering scheme which is crucial for the design and development of next-generation nanoelectronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Developing highly efficient and durable electrocatalysts toward oxygen evolution reaction (OER) is an urgent demand to produce clean hydrogen energy. In this study, a series of medium‐entropy metal sulfides (MEMS) of (NiFeCoX)3S4 (where X = Mn, Cr, Zn) are synthesized by a facile one‐pot solvothermal strategy using molecular precursors. Benefiting from the multiple‐metal synergistic effect and the low crystallinity, these MEMS show significantly enhanced electrocatalytic OER activity compared with the binary‐metal (NiFe)3S4 and ternary‐metal (NiFeCo)3S4 counterparts. Especially, (NiFeCoMn)3S4 delivers a low overpotential of 289 mV at 10 mA cm−2, a decent Tafel slope of 75.6 mV dec−1 and robust catalytic stability in alkaline medium, outperforming the costly IrO2 benchmark electrocatalyst and the majority of the reported metal sulfide‐based electrocatalysts until now. These MEMS with facile synthesis and excellent electrocatalytic performance bring a great opportunity to design desirable electrocatalysts for practical application. [ABSTRACT FROM AUTHOR]

Lithium-ion capacitors (LICs) are emerging as one of the most advanced hybrid energy storage devices. The key challenge in constructing a high-performance LIC is to couple an appropriate capacitive cathode with an intercalation anode, wherein they can match well in internal kinetics and capacity simultaneously. Here, we present a strategy for constructing an advanced LIC using a 3D N-doped hollow carbon microsphere (NHCM-12) anode combined with a hierarchical porous carbon (NHCM-A) cathode, which have both been prepared by the same polyimide precursor without any additional catalyst and template for the first time. Quantitative kinetics analysis and density functional theory (DFT) calculations are performed to demonstrate the surface-dominated Li-storage mechanism, revealing that pyrrolic-N and pyridinic-N are beneficial for stronger Li adsorption compared to quaternary-N. As expected, the fully assembled LIC (NHCM-12//NHCM-A) delivers a maximum energy density of 162 W h kg−1 and exhibits an outstanding lifespan over 5000 cycles with 86.2% capacity retention. Accordingly, our simultaneous manipulation of hierarchical N-doped porous carbon as both anode and cathode materials for energy storage using the same precursor may open an avenue for fabricating other ideal electrode structures. [ABSTRACT FROM AUTHOR]

Lithium sulfur batteries, one of the most promising energy storage methodologies for emerging electric vehicles, suffer from poor long-term cycling stability due to the shuttle effect caused by the dissolution of high order polysulfides. To enhance the cycling stability of sulfur cathode for high-energy lithium sulfur batteries, it is very critical to mitigating the dissolution of polysulfides. In this work, a caterpillar-like and reconfigurable graphene was designed to serve as the sulfur host. The caterpillar-like graphene highly expanded in solution and tightly restacked in dry condition due to the van der Waals force. Elemental sulfur was trapped and confined inside the restacked graphene layers. High mass loading of 63.8% sulfur in graphene was achieved after the caterpillar-like graphene was dried at 155 °C. The graphene-sulfur electrode has a good rate performance of 708 mAh g −1 at 167.5 mA g −1 , 582 mAh g −1 at 335 mA g −1 , 470 mAh g −1 at 837.5 mA g −1 , 400 mAh g −1 at 1675 mA g −1 and a stable cycling performance with small capacity decay of 0.16% per cycle over 200 cycles at 1675 mA g −1 . Moreover, the underlying mechanism of the restacking effect of caterpillar-like graphene on immobilizing the soluble lithium polysulfides was studied by density functional theory (DFT), which clearly explained how the graphene immobilized the soluble lithium polysulfides by the restacking effect. [ABSTRACT FROM AUTHOR]

The structural, electronic and magnetic properties of monolayer 2 doped with single atom, 3 and 6 clusters ( = , and ) are investigated using first principles approach. Monolayer 2 doped with single atom displays a spin gapless semiconducting character. 2 embedded with 3 and 6 presents rich electronic and magnetic properties. For example, monolayer 2 incorporated with 3 exhibits a half-metallic nature. The substitutions of impurities introduce magnetism except 3. The calculation results demonstrate that monolayer 2 is a promising material for spintronic device when doped with m. [ABSTRACT FROM AUTHOR]