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Abstract Recent discovery of ultrathick MoSi2N4(MoN)n monolayers open up an exciting platform to engineer two‐dimensional (2D) material properties via intercalation architecture. In this study, a series of ultrathick MA2N4(M'N) monolayers (M, M' = Mo, W; A = Si, Ge) is computationally investigated under both homolayer and heterolayer intercalation architectures, in which the same and different species of transition metal nitride inner core sublayer are intercalated by outer passivating nitride sublayers, respectively. The MA2N4(M'N) are stable metallic monolayers with excellent mechanical strength. Intriguingly, the metallic states around Fermi level are localized within the inner core sublayer. Carrier conduction mediated by electronic states around the Fermi level is thus spatially insulated from the external environment by the native outer nitride sublayers, suggesting the potential of MA2N4(M'N) in back‐end‐of‐line metal interconnect applications. N and Si (or Ge) vacancy defects at the outer sublayers create ‘punch through’ states around the Fermi level that bridges the carrier conduction in the inner core sublayer and the outer environment, forming an electrical contact akin to the ‘via' structures of metal interconnects. It is further shown that MoSi2N4(MoN) can serve as a quasi‐Ohmic contact to 2D WSe2. These findings reveal the potential of ultrathick MA2N4(MN) monolayers in interconnect and metal contact applications.

Abstract The development of highly efficient sodium‐ion batteries depends critically on the successful exploitation of advanced anode hosts that is capable of overcoming sluggish reaction kinetics while also withstanding severe structural deformation triggered by the large radius of Na+‐insertion. Herein, a hierarchically hybrid material with hetero‐Co3S4/NiS hollow nanosphere packaged into a densified N‐doped carbon matrix (Co3S4/NiS@N‐C) was designed and fabricated utilizing CoNi‐glycerate as the self‐sacrifice template, making the utmost of the synergistic effect of hetero‐Co3S4/NiS with strong electric field and rich reaction active‐sites together with the densified outer‐carbon scaffolds with remarkable electronic conductivity and robust mechanical toughness. As anticipated, as‐fabricated Co3S4/NiS@N‐C anode affords remarkable specific capacity, prolonged cycle lifespan up to 2 400 cycles with an only 0.05% fading each cycle at 20.0 A g−1, and excellent rate feature (354.9 mAh g−1 at 30.0 A g−1), one of the best performances for most existing Co3S4/NiS‐based anodes. Ex situ structural characterizations in tandem with theoretical analysis demonstrate the reversible insertion‐conversion mechanism of initially proceeding with Na+ de‐/intercalation and superior heterogeneous interfacial reaction behavior with strong Na+‐adsorption ability. Further, sodium‐ion full cell and hybrid capacitor based on Co3S4/NiS@N‐C anode exhibit impressive electrochemical characteristics on cycling performance and rate capability, showcasing its outstanding feasibility toward practical use.

Designing novel materials that exhibit superior reversibility and function under ambient conditions can facilitate the development of hydrogen energy applications. Two-dimensional (2D) g-C6N6 monolayers show great potential for use in hydrogen storage owing to their nanoporous structure, ultralight mass, and flexible electronic structure. However, the hydrogen storage potential of these materials is limited by the naturally weak interaction between 2D materials and hydrogen molecules caused by van de Waals forces. To address this issue, we studied the hydrogen storage performance of the complex by decorating active Li ions on a 2D g-C6N6 substrate through first-principles calculations. Our results showed that modifying the Li ions did not cause the original planar structure to deform but rather induced more active sites for hydrogen adsorption by establishing an electrostatic field between the Li ions and the g-C6N6 monolayer. Through this modification, reversible hydrogen storage was achieved under ambient conditions with an average adsorption energy of −0.197 eV/H2 and a high gravimetric capacity of 5.88 wt%. The electronic properties of the material were systematically investigated, and the results suggested that the enhanced capacity of the Li@ g-C6N6 system to store hydrogen resulted from the formation of a polarization field and the induced electrostatic effect. Our research offers a new possibility for achieving reversible hydrogen energy storage at room temperature.

Osmia excavata is an excellent pollinator in nature and plays a vital role in the conservation of agro-ecosystems and food security. Given the important role of the gut bacterial community in host health and regulation of host growth and development, using 16S rRNA gene sequencing data, the present study explored the composition of the gut bacterial community and its diversity at different life stages (eggs, young larvae, old larvae, young pupae, old pupae, and 1-day-old adults in cocoons) of the solitary bee Osmia excavata. The results showed that the core phyla in the gut of O. excavata at different life stages were Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteriota, and the core genera were Sodalis, Tyzzerella, and Ralstonia. The highest intestinal bacterial diversity was found in the Egg period, and the lowest bacterial alpha diversity was found in the 1-day-old Adult period; the bacterial diversity of O. excavata showed a process of decreasing, as it was growing from the Egg period to the 1-day-old Adult period. Our study found that O. excavata undergoes a significant change in the structure of the gut flora when it grows from the young pupae to old pupae stage, a period of growth that coincides with the process of cocooning and isolation from the external environment after food depletion. This suggests that food and environmental factors are key contributors to the structure of the bacterial community in the gut of solitary bees.

The electrochemical nitrogen reduction reaction (NRR) is an attractive pathway for producing ammonia under ambient conditions. The development of efficient catalysts for nitrogen fixation in electrochemical NRRs has become increasingly important, but it remains challenging due to the need to address the issues of activity and selectivity. Herein, using density functional theory (DFT), we explore ten kinds of triple transition metal atoms (M3 = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) anchored on the C2N monolayer (M3-C2N) as NRR electrocatalysts. The negative binding energies of M3 clusters on C2N mean that the triple transition metal clusters can be stably anchored on the N6 cavity of the C2N structure. As the first step of the NRR, the adsorption configurations of N2 show that the N2 on M3-C2N catalysts can be stably adsorbed in a side-on mode, except for Zn3-C2N. Moreover, the extended N-N bond length and electronic structure indicate that the N2 molecule has been fully activated on the M3-C2N surface. The results of limiting potential screen out the four M3-C2N catalysts (Co3-C2N, Cr3-C2N, Fe3-C2N, and Ni3-C2N) that have a superior electrochemical NRR performance, and the corresponding values are −0.61 V, −0.67 V, −0.63 V, and −0.66 V, respectively, which are smaller than those on Ru(0001). In addition, the detailed NRR mechanism studied shows that the alternating and enzymatic mechanisms of association pathways on Co3-C2N, Cr3-C2N, Fe3-C2N, and Ni3-C2N are more energetically favorable. In the end, the catalytic selectivity for NRR on M3-C2N is investigated through the performance of a hydrogen evolution reaction (HER) on them. We find that Co3-C2N, Cr3-C2N, Fe3-C2N, and Ni3-C2N catalysts possess a high catalytic activity for NRR and exhibit a strong capability of suppressing the competitive HER. Our findings provide a new strategy for designing NRR catalysts with high catalytic activity and selectivity.

Hydrogen generation by photocatalytic water-splitting holds great promise for addressing the serious global energy and environmental crises, and has recently received significant attention from researchers. In this work, a method of assembling GeC/MXY (M = Zr, Hf; X, Y = S, Se) heterojunctions (HJs) by combining GeC and MXY monolayers (MLs) to construct direct Z-scheme photocatalytic systems is proposed. Based on first-principles calculations, we found that all the GeC/MXY HJs are stable van der Waals (vdW) HJs with indirect bandgaps. These HJs possess small bandgaps and exhibit strong light-absorption ability across a wide range. Furthermore, the built-in electric field (BIEF) around the heterointerface can accelerate photoinduced carrier separation. More interestingly, the suitable band edges of GeC/MXY HJs ensure sufficient kinetic potential to spontaneously accomplish water redox reactions under light irradiation. Overall, the strong light-harvesting ability, wide light-absorption range, small bandgaps, large heterointerfacial BIEFs, suitable band alignments, and carrier migration paths render GeC/MXY HJs highly efficient photocatalysts for overall water decomposition.

Abstract The non‐noble Mn coordinated N, P co‐doping graphene materials were investigated theoretically in this work based on density functional theory calculation. The electronic structure is effectively tuned after the introduction of P heteroatom. The moderate d band center and density of states at Fermi energy of MnN4‐P1‐G indicate that it is of modest adsorption ability for these O‐containing intermediates. The rank of adsorption energies of O‐containing intermediates for MnN4‐P1‐G is OH* > 2OH* > OOH* > O* > O2* > H2O*, whereas the MnN4‐P1‐G favors a four‐electron process instead of two‐electron process. The doping of P on MnN4‐P1‐G can increase the kinetic activity for the rate‐determining step as well as the Ulim for MnN4‐P1‐G significantly increases from 0.38 to 0.45 V compared with MnN4‐G. The spin density and magnetic moments of Mn are effectively tuned by d, p hybridization to lower the adsorption energy of OH intermediates (rate‐determining step [RDS]) so as to improve the catalytic activity. It is concluded that the P‐doped MnN4 catalysts with excellent oxygen reduction reaction activity can be obtained and this study can provide theoretical guidance for the rational design of high‐performance Mn‐based carbon materials catalysts.

Recently, Tl3XSe4 (Abbreviated as TlXSe; X = V, Ta, Nb) crystals have been found to exhibit ultra low lattice thermal conductivities κl (∼0.15 W/mK at 300 K), ultra high figure of merit ZT (3 ∼ 4 at 300 K) and thus show great potentials in the fields of thermoelectric and engineering thermal management. Generally, thermal insulation devices and thermoelectric devices are used in harsh working environment, such high/low temperature, high pressure and so on. In order to further evaluate the industrial application values of TlXSe crystals, in this work, we explored their thermal transport behaviors under high pressures based on first-principles calculations method. The results show that TlXSe materials can maintain structural stability under high pressure up to 8 GPa, and their κl values increase about 2 ∼ 4 times under the high pressure of 0 ∼ 8 GPa. The increases of κl values are mainly due to the co-coupling effects of the increased phonon harmonicity and decreased phonon anharmonicity caused by high pressures. For all that, the κl values of TlXSe compounds are still below 0.5 W/mK at 300 K under the high pressure of 0 ∼ 8 GPa, which are also lower than those of most thermal insulation and thermoelectric materials. This work highlights the future potential applications of TlXSe crystals in thermal management, thermoelectric and many other fields, and thus provides useful information for further experimental and theoretical studies.

The timing of decocooning and nesting during the flowering period are crucial for the reproduction and pollination activities of Osmia excavata. In order to improve the pollination efficiency of O. excavata, it is crucial to find a way to break the cocoon quickly. Our results showed that the decocooning rates at 6, 12, 24, 36, 48, and 72 h after 30 min of water immersion (WI) were 28.67%, 37.33%, 37.33%, 41.33%, 44.33%, and 53.00%, respectively. The decocooning rate fold of 6 h was 14.33 compared with the control group. Transcriptome sequencing resulted in 273 differentially expressed genes (DEGs) being identified between the WI and control groups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that muscle-related functions play important roles in O. excavata decocooning in response to WI. Cluster analysis also showed that DEGs in cardiac muscle contraction and adrenergic signaling in cardiomyocytes were up-regulated in response to WI-promoted decocooning. In conclusion, the rate of decocooning can be improved by WI in a short time. During WI-promoted decocooning, muscle-related pathways play an important role. Therefore, the application of this technology will improve the pollination effect of O. excavata.

Under the background of energy crisis, hydrogen owns the advantage of high combustion and shows considerable environment friendliness; however, to fully utilize this novel resource, the major hurdle lies in its delivery and storage. The development of the in-depth yet systematical methodology for two-dimensional (2D) storage media evaluation still remains to be challenging for computational scientists. In this study, we tried our proposed evaluation protocol on a 2D material, g-C3N5, and its hydrogen storage performance was characterized; and with addition of Li atoms, the changes of its electronical and structural properties were detected. First-principles simulations were conducted to verify its thermodynamics stability; and, its hydrogen adsorption capacity was investigated qualitatively. We found that the charges of the added Li atoms were transferred to the adjacent nitrogen atoms from g-C3N5, with the formation of chemical interactions. Thus, the isolated metallic sites tend to show considerable electropositivity, and can easily polarize the adsorbed hydrogen molecules, and the electrostatic interactions can be enhanced correspondingly. The maximum storage capacity of each primitive cell can be as high as 20 hydrogen molecules with a gravimetric capacity of 8.65 wt%, which surpasses the 5.5 wt% target set by the U.S. Department of Energy. The average adsorption energy is ranged from −0.22 to −0.13 eV. We conclude that the complex 2D material, Li-decorated g-C3N5 (Li@C3N5), can serve as a promising media for hydrogen storage. This methodology provided in this study is fundamental yet instructive for future 2D hydrogen storage materials development.

Abstract 2D materials van der Waals heterostructures (vdWHs) provide a revolutionary route toward high‐performance solar energy conversion devices beyond the conventional silicon‐based pn junction solar cells. Despite tremendous research progress accomplished in recent years, the searches of vdWHs with exceptional excitonic solar cell conversion efficiency and optical properties remain an open theoretical and experimental quest. Here, this study shows that the vdWH family composed of MoSi2N4 and WSi2N4 monolayers provides a compelling material platform for developing high‐performance ultrathin excitonic solar cells and photonics devices. Using first‐principle calculations, 51 types of MoSi2N4 and WSi2N4‐based [(Mo,W)Si2N4] vdWHs composed of various metallic, semimetallic, semiconducting, insulating, and topological 2D materials are constructed and classified. Intriguingly, MoSi2N4/(InSe, WSe2) are identified as Type II vdWHs with exceptional excitonic solar cell power conversion efficiency reaching well over 20%, which are competitive to state‐of‐the‐art silicon solar cells. The (Mo,W)Si2N4 vdWH family exhibits strong optical absorption in both the visible and UV regimes. Exceedingly large peak UV absorptions over 40%, approaching the maximum absorption limit of a freestanding 2D material, can be achieved in (Mo,W)Si2N4/α2‐(Mo,W)Ge2P4 vdWHs. The findings unravel the enormous potential of (Mo,W)Si2N4 vdWHs in designing ultimately compact excitonic solar cell device technology.

Using molecular dynamics simulations, we investigate shock-induced sliding of a set of (0 0 1) twist grain boundaries (GBs) in Cu bicrystal, with shock direction parallel to GB and low shock strength. The GB sliding is produced via transverse particle motion in constituent grains and resisted by GB viscosity. Its utmost magnitude su increases first and then decreases with increasing of the angle between [1 0 0] direction in grain and shock direction. Quantitative acoustic wave equation analysis reveals that transverse particle motion exists because of the anisotropic elastic stiffness and particular grain orientation. For GBs of noteworthy sliding, boundary viscosity η is estimated according to the deceleration of volume element in grain, and decreases piecewisely with increasing misorientation angle. su is jointly determined by η and transverse particle velocity dependent on grain orientation.

Since the discovery of the photocatalytic ability of TiO2 electrodes to decompose water [...]

Abstract Metal contacts to two-dimensional (2D) semiconductors are often plagued by the strong Fermi level pinning (FLP) effect which reduces the tunability of the Schottky barrier height (SBH) and degrades the performance of 2D semiconductor devices. Here, we show that MoSi2N4 and WSi2N4 monolayers—an emerging 2D semiconductor family with exceptional physical properties—exhibit strongly suppressed FLP and wide-range tunable SBH. An exceptionally large SBH slope parameter of S ≈ 0.7 is obtained which outperforms the vast majority of other 2D semiconductors. Such intriguing behavior arises from the septuple-layered morphology of MoSi2N4 and WSi2N4 monolayers in which the semiconducting electronic states are protected by the outlying Si–N sublayer. We identify Ti, Sc, and Ni as highly efficient Ohmic contacts to MoSi2N4 and WSi2N4 with zero interface tunneling barrier. Our findings reveal the potential of MoSi2N4 and WSi2N4 as a practical platform for designing high-performance and energy-efficient 2D semiconductor electronic devices.

Herein, we explored a new 2D heterostructure by hybridizing BN and TiB2, especially the photocatalytic activity of composite materials. Based on the key strategy of developing BN hybrid photocatalysts to change the band structure, we studied the influences of TiB2 addition on the structures and photocatalytic performances of Ti3+-B codoped TiO2/BN. The Ti3+ existed in TiBO3 enables excellent photocatalytic performances in hydrogen production and nitrogen fixation compared with pure BN. We also carried out first-principle calculations using the VASP program to explain the excellent photocatalytic hydrogen production performances. Finally, the photocatalytic mechanism of such TiO2/BN hybrid photocatalysts was proposed.

The γ-ray total dose radiation effects on ferroelectric Al-doped HfO2 (HfAlO) thin films with an n-type Si substrate were studied. The I-V, P-V, C-V and fatigue characteristics of the HfAlO-based Metal-Ferroelectric-Insulator-Semiconductor (MFIS) structure were analyzed with the increasing total dose from 0 to 1 Mrad (Si). The remnant polarization (Pr) values, the capacitance (C) values and the switching voltage (Vc) of this MFIS gate structure decreased with the increasing total dose. A TCAD model of Metal/HfAlO/SiO2/Si (MFIS) was proposed to explain the degradation mechanism of ferroelectric properties of the MFIS structure. We find that the new interface defects caused by radiation can reduce the electric field strength with the increasing total dose, which can significantly influence the irradiation properties of the HfAlO/SiO2/n-Si gate structure. These results provide the basis to applications for the HfO2-based devices in radiation working environment.

Abstract Bi3.15Nd0.85Ti2.99Mn0.01O12 (BNTM) thin films with (200)-orientations, (117)-orientations, and mixed-orientations were prepared by sol-gel methods. The influence of orientations on polarization fatigue behaviors of BNTM thin films were systematically investigated at both low and elevated temperatures. It was found that the changed trends of the polarization fatigue of (200)-oriented and (117)-oriented BNTM thin films at elevated temperatures were opposite. The fatigue properties become exacerbated for the (200)-oriented ones and become improved for the (117)-oriented ones, while the reduction of remanent polarization first decreases and then increases for the mixed-oriented ones. It can be assumed that the different roles played by domain walls and interface layer with increasing T in these thin films have caused such differences, which was certified by the lower activation energies (0.12–0.13 eV) of (200)-oriented BNTM thin films compared to those of BNTM thin films (0.17–0.31 eV) with other orientations through the temperature-dependent impedance spectra analysis. With the aid of piezoresponse force microscopy (PFM), the non-neutral tail-to-tail or head-to-head polarization configurations with greater probabilities for (117)-oriented and mixed-oriented thin films were found, while a majority of the neutral head-to-tail polarization configurations can be observed for (200)-oriented ones.

On the catalyst surface, crystal facets with different surface atom arrangements and diverse physicochemical properties lead to distinct catalytic activity. Acquiring a highly reactive facet through surface regulation is an efficient strategy to promote the oxidative decomposition of wastewater organic pollutants via peroxymonosulfate (PMS) activation. However, the mechanism through which crystal facets affect PMS activation is still unclear. In this study, three facet-engineered α-MnO2 with different exposed facets were prepared via a facile hydrothermal route. The prepared 310-MnO2 exhibited superior PMS activation performance to 100-MnO2 and 110-MnO2. Moreover, the 310-MnO2/PMS oxidative system was active over a wide pH range and highly resistant to interfering substances from wastewater. These advantages of the 310-MnO2/PMS system make it highly promising for practical wastewater treatment. Based on quenching experiments, electron paramagnetic resonance (EPR) analysis, solvent exchange, and electrochemical measurements, mediated electron transfer was found to be the dominant nonradical pathway for p-chloroaniline (PCA) degradation. A sulfhydryl group (-SH) masking experiment showed that the highly exposed Mn atoms on the 310-MnO2 surface were sites of PMS activation. In addition, density functional theory (DFT) calculations confirmed that the dominant {310} facet promoted adsorption/activation of PMS, which favored the formation of more metastable complexes on the α-MnO2 surface. The reaction mechanism obtained here clarifies the relationship between PMS activation and crystal facets. This study provides significant insights into the rational design of high-performance catalysts for efficient water remediation.

Due to its excellent mechanical properties and reinforcement abilities, cellulose has become a promising candidate for developing nanocomposites. However, cellulose agglomeration is an issue that must be solved. In this study, we treated microfibrillated cellulose (MFC) with a mixture of the non-ionic surfactants Span80 and Tween80 (ratio of 1:1) in order to prevent the intermolecular hydrogen bond aggregation of MFC during the process of MFC drying. We used a conical twin-screw extruder to melt compounds for the surfactant-treated MFC and powdered LLDPE. Furthermore, the extruded mixture was hot-pressed into a film, and we also tested the properties of the composite film. We can conclude that there was no agglomeration in the composite film according to microscopic observations and light transmittance test results. Furthermore, the dispersion of the surfactant-treated MFC (STMFC) was uniform until the STMFC filler increased to 10 wt%. The mechanical test results show that when the content of STMFC filler was 10 wt%, the mechanical properties of the composite were optimal. Compared to LLDPE, the STMFC/LLDPE composite film had an increase of 41.03% in tensile strength and an increase of 106.35% in Young’s modulus. Under this system, the DSC results show that the melting point of LLDPE increased from 125 to 131 °C. X-ray diffraction (XRD) results showed that the addition of STMFC did not change the crystallinity of the STMFC/LDPE composites, although the crystallite size increased.

By means of a hybrid density functional, we comprehensively investigate the energetic, electronic, optical properties, and band edge alignments of two-dimensional (2D) CdS/g-C 3 N 4 heterostructures by considering the effect of biaxial strain and pH value, so as to improve the photocatalytic activity. The results reveal that a CdS monolayer weakly contacts with g-C 3 N 4 , forming a type II van der Waals (vdW) heterostructure. The narrow bandgap makes CdS/g-C 3 N 4 suitable for absorbing visible light and the induced built-in electric field between the interface promotes the effective separation of photogenerated carriers. Through applying the biaxial strain, the interface adhesion energy, bandgap, and band edge positions, in contrast with water, redox levels of CdS/g-C 3 N 4 can be obviously adjusted. Especially, the pH of electrolyte also significantly influences the photocatalytic performance of CdS/g-C 3 N 4 . When pH is smaller than 6.5, the band edge alignments of CdS/g-C 3 N 4 are thermodynamically beneficial for oxygen and hydrogen generation. Our findings offer a theoretical basis to develop g-C 3 N 4 -based water-splitting photocatalysts.

In this work, graphene-like ZnO (g-ZnO)-based two-dimensional (2D) heterostructures (ZnO/WS2 and ZnO/WSe2) were designed as water-splitting photocatalysts based on the hybrid density functional. The dependence of photocatalytic properties on the rotation angles and biaxial strains were investigated. The bandgaps of ZnO/WS2 and ZnO/WSe2 are not obviously affected by rotation angles but by strains. The ZnO/WS2 heterostructures with appropriate rotation angles and strains are promising visible water-splitting photocatalysts due to their appropriate bandgap for visible absorption, proper band edge alignment, and effective separation of carriers, while the water oxygen process of the ZnO/WSe2 heterostructures is limited by their band edge positions. The findings pave the way to efficient g-ZnO-based 2D visible water-splitting materials.

In this study, a pulp beating machine was used to premix the pulp fibers with high density polyethylene (HDPE) particles in water. The wet or pre-dried pulp fiber/HDPE mixture was then melt-compounded by a twin screw extruder. For further improving the dispersion of pulp fiber, some mixture was forced to pass through the twin-screw extruder twice. The resulting mixture was compression molded to the composite. The fiber distribution was observed by the aid of an optic and scanning electron microscope. The mechanical and rheological properties and creep resistance of the composites were characterized. Test results demonstrate that when the wet pulp fiber/HDPE mixture was subjected to pre-pressing and oven drying prior to extrusion compounding, the resulting composites exhibited homogeneous fiber distribution, superior flexural property, creep-resistance, and high storage modulus. Particularly, its flexural strength and modulus were 57% and 222% higher, respectively, than that of the neat HDPE, while the composites prepared without pre-dried were 19% and 100% higher, respectively. Drying the wet mixture in advance is more effective than re-passing through the extruder for improving the fiber dispersion and composite performance.