Hydrogen production from seawater and solar energy based on photoelectrochemical cells is extremely attractive due to earth-abundance of seawater and solar radiation. Herein, we report the successful fabrication of novel inorganic-organic 2D/2D WO3/g-C3N4 nanosheet arrays (WO3/g-C3N4 NSAs) grown on a FTO substrate via a facile hydrothermal growth and deposition-annealing process, and their application in natural seawater splitting. The results indicate that the WO3/g-C3N4 NSAs exhibit a photocurrent density of 0.73 mA cm(-2) at 1.23 V versus RHE under AM 1.5G (100 mW cm(-2)) illumination, which is 2-fold higher than that of WO3 NSAs. More importantly, the WO3/g-C3N4 NSA photoanode is quite stable during seawater splitting and the photocurrent density does not substantially decrease after continuous illumination for 3600 s. The remarkably enhanced performance originates primarily from the formation of the WO3/g-C3N4 heterojunction between WO3 and g-C3N4 nanosheets, which accelerates charge transfer and separation, and prolongs the lifetime of electrons as demonstrated by EIS and Mott-Schottky analyses. Finally, a possible mechanism for the improved performance was proposed and discussed.

A family of Zn k O k (k = 12, 16) cluster-assembled solid phases with novel structures and properties has been characterized utilizing a bottom-up approach with density functional calculations. Geometries, stabilities, equation of states, phase transitions, and electronic properties of these ZnO polymorphs have been systematically investigated. First-principles molecular dynamics (FPMD) study of the two selected building blocks, Zn 12 O 12 and Zn 16 O 16 , with hollow cage structure and large HOMO−LUMO gap shows that both of them are thermodynamically stable enough to survive up to at least 500 K. Via the coalescence of building blocks, we find that the Zn 12 O 12 cages are able to form eight stable phases by four types of Zn 12 O 12 −Zn 12 O 12 interactions, and the Zn 16 O 16 cages can bind into three phases by the Zn 16 O 16 −Zn 16 O 16 links of H′, C′, and S′. Among these phases, six ones are reported for the first time. This has greatly extended the family of ZnO nanoporous phases. Notably, some of these phases are even more stable than the synthesized metastable rocksalt ZnO polymorph. The hollow cage structure of the corresponding building block Zn k O k is well preserved in all of them, which leads to their low-density nanoporous and high flexibility features. In addition the electronic integrity (wide-energy gap) of the individual Zn k O k is also retained. Our calculation reveals that they are all semiconductor with a large direct or indirect band gap. The insights obtained in this work are likely to be general in II−VI semiconductor compounds and will be helpful for extending the range of properties and applications of ZnO materials.

To suppress the high loss of nickel (Ni)/poly(vinylidene fluoride) (PVDF) while remaining high dielectric constant (k) near the percolation threshold. In this study, core-shell structured Ni (Ni@NiO) particles were prepared by heat treatment of raw Ni powder under air atmosphere and incorporated into PVDF to prepare Ni@NiO/PVDF dielectric composites. The morphological, dielectric properties and thermal conductivity of the composites are characterized. The results indicate that compared with the raw Ni reinforced PVDF composites, the Ni@NiO particles endow PVDF with a high-k and rather low dissipation factor owing to the presence of NiO shell between Ni core and PVDF which serves as an interlayer between the Ni cores preventing them from contacting with each other. Additionally, the Ni@NiO/PVDF composites still possess a high thermal conductivity. Therefore, the as-prepared Ni@NiO/PVDF composites possess high-k but low loss, high thermal conductivity, making them promising for the industrial application as embedded capacitors.

In the present study, hydroxyl-terminated polybutadiene (HTPB) liquid rubber was employed to modify epoxy resin using 2,4,6-tri (dimethylaminomethyl) phenol as a catalyst, and methyl hexahydrophthalic anhydride as a curing agent. The reactions between HTPB and epoxy were monitored by Fourier transform infrared (FTIR); the mechanical and dielectric properties of HTPB modified epoxies were evaluated and the morphology was investigated through scanning electronic microscopy (SEM). The FTIR analysis evidenced the occurrence of a chemical reaction between the two components. The mechanical results indicated that the impact strength of HTPB-modified epoxy was superior to that of the pure epoxy. As the HTPB content increased up to 10 phr the best mechanical performances in terms of tensile and flexural properties were achieved when compared to the unmodified epoxy. Higher concentration of HTPB resulted in larger particles and gave lower mechanical strength values. The incorporation of HTPB into epoxy decreased the dielectric constant and dissipation factor over a wide frequency range from 1 to 10 6 Hz, and improved the electrical resistivity. SEM micrographs showed that the modified epoxy exhibited a two-phase morphology where the spherical rubber domains were dispersed in the epoxy matrix.

There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors was fabricated by anchoring carbon dots (CDs) on reduced graphene oxide (rGO). The capacitive properties of electrodes in aqueous electrolytes were systematically studied by galvanostatic charge-discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy. The capacitance of rGO was improved when an appropriate amount of CDs were added to the material. The CD/rGO electrode exhibited a good reversibility, excellent rate capability, fast charge transfer, and high specific capacitance in 1 M H2SO4. Its capacitance was as high as 211.9 F/g at a current density of 0.5 A/g. This capacitance was 74.3% higher than that of a pristine rGO electrode (121.6 F/g), and the capacitance of the CD/rGO electrode retained 92.8% of its original value after 1000 cycles at a CDs-to-rGO ratio of 5:1.

Since most of the existing pristine two-dimensional (2D) materials are either intrinsically nonmagnetic or magnetic with small magnetic moment per unit cell and weak strength of magnetic coupling, introducing transition metal atoms in various nanosheets has been widely used for achieving a desired 2D magnetic material. However, the problem of surface clustering for the doped transition metal atoms is still challenging. Here we demonstrate via first-principles calculations that the recently experimentally characterized endohedral silicon cage V@Si12 clusters can construct two types of single cluster sheets exhibiting hexagonal porous or honeycomb-like framework with regularly and separately distributed V atoms. For the ground state of these two sheets, the preferred magnetic coupling is found to be ferromagnetic due to a free-electron-mediated mechanism. By using external strain, the magnetic moments and strength of magnetic coupling for these two sheets can be deliberately tuned, which would be propitious to their advanced applications. More attractively, our first-principles molecular dynamics simulations show that both the structure and strength of ferromagnetic coupling for the pristine porous sheet are stable enough to survive at room temperature. The insights obtained in this work highlight a new avenue to achieve 2D silicon-based spintronics nanomaterials.

For next‐generation carbon‐based nanoelectronics, it is highly desirable to search for easily obtained 2D carbon allotropes with various appealing properties. Herein, based on first‐principles calculations, a new 2D carbon Dirac semimetal with orthorhombic symmetry is identified, which is composed of a carbon skeleton of para‐xylene and acetylenic linkages, and is thus termed palgraphyne [pæl'græfain]. The calculations of stability reveal not only that palgraphyne is dynamically, thermally (above 1000 K), and mechanically stable, but also that it is energetically more preferable to the recently synthesized β‐graphdiyne and γ‐graphdiyne. Due to the particular atomic‐framework, the calculations of Young's modulus and Poisson's ratio show that palgraphyne is mechanically anisotropic with a sizable ratio between the maximum and minimum value up to 3.29. Remarkably, unlike the case of graphene, the Dirac cones of palgraphyne are distorted. As a result, its electronic transport properties also exhibit anisotropy, with different Fermi velocities along diverse orientations. The highest Fermi velocity reaches up to 8.89 × 105 m s−1 in the kx + ky direction, which is very close to that of prominent graphene (9.0 × 105 m s−1). The findings highlight a distinct 2D anisotropic Dirac semimetal, which has great potential applications in nanodevices.

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