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Element B in binary metal borides forms various polymetric configurations due to its electron-deficient nature. Here we predict a new pressure-stabilized boron clathrate structure, LaB8, that is recoverable under ambient conditions. Crystal structure searches and first-principles calculations predict a series of thermodynamically stable La–B compounds at high pressures. Besides known LaB4 and LaB6 compounds, trigonal LaB8 is predicted to be thermodynamically stable above 70 GPa. Its B atoms construct face-sharing B26 cages, each surrounding a central La atom. The compound can be recovered to ambient conditions with the B26 cages well preserved. Electron–phonon coupling calculations suggest that it is potentially superconducting with an estimated Tc of 5 K at 70 GPa, which increases to ∼20 K at ambient pressure. The enhanced Tc is attributed to the increased B-derived electronic density of states at the Fermi level and to the softened Eu mode related to vibration of the B26 cages.

The recent discovery of superconductivity near room temperature in highly compressed superhydrides highlights the key role of the hydrogen cage structure in determining the high superconducting critical temperature. Here, we propose a hitherto unknown metastable cage boron allotrope possessing high superconductivity at ambient pressure. Using first-principles calculations with structure searching, we have predicted various dynamically stable structures for MnB12 that can be possibly synthesized at high pressures and high temperatures. Among these structures the tetragonal t-MnB12 contains unique B16 cages, which are linked to each other to form open channels filled with Mn atoms. The removal of Mn atoms leads to the formation of a tetragonal cage boron allotrope t-B, which possesses partial ionicity due to the slight charge transfer between two inequivalent B atoms. t-B is a potential superconductor with an estimated critical temperature of 43 K, the highest value in elemental superconductors at ambient pressure.

In order to produce a photocatalyst with increased visible photocatalytic ability, MIL-125 and melamine were selected as raw materials to prepare Z-scheme g-C3N4/TiO2 heterojunction photocatalyst using a simple calcination method. TEM, HRTEM, XRD, FTIR, EDS, and UV–vis absorption spectra were employed to investigate the prepared specimens. The visible-light catalytic property was examined via the degradation of methylene blue (MB). The recombination and separation activity of electrons and holes (h+/e−) were explored by the transient photocurrent response (TPR) and PL spectra. In contrast with plain TiO2 and g-C3N4, the g-C3N4/TiO2 photocatalyst exhibited increased photocatalytic activities when exposed to visible-light irradiation. With the addition of g-C3N4 at 8 wt%, the Z-scheme g-C3N4/TiO2 heterojunction performed best in the photocatalytic test toward MB dye at a degradation rate of 97.7%. Under visible-light irradiation, the Z-scheme heterojunction between g-C3N4 and TiO2 enables the high-efficient segregation of photogenic electrons and holes (h+/e−), leading to the increased photocatalytic ability. Meanwhile, the large specific surface area of the composite photocatalyst is conducive to the adsorption of the contaminant on the catalyst surface, which has an important effect on the catalytic reaction.

The recent successful findings of H3S and LaH10 compressed above 150 GPa with a record high Tc (above 200 K) have shifted the focus on hydrogen-rich materials for high superconductivity at high pressure. Moreover, some studies also report that transition-metal ternary hydrides could be synthesized at a relatively low pressure (∼10 GPa). Therefore, it is highly desirable to investigate the crystal structures of ternary hydrides compounds at high pressure since they have been long considered as promising superconductors and hydrogen-storage materials with a high Tc, and can be possibly synthesized at low pressure as well. In this work, combining state-of-the-art crystal structure prediction and first-principles calculations, we have performed extensive simulations on the crystal structures of YSHn (n = 1–10) compounds from ambient pressure to 200 GPa. We uncovered three thermodynamically stable compounds with stoichiometries of YSH, YSH2, and YSH5, which became energetically stable at ambient pressure, 143, and 87 GPa, respectively. Remarkably, it is found that YSH contains monoatomic H atoms, while YSH2 and YSH5 contain a mixture of atomlike and molecular hydrogen units. Upon compression, YSH, YSH2, and YSH5 undergo a transition from a semiconductor to a metallic phase at pressures of 168, 143, and 232 GPa, respectively. Unfortunately, electron–phonon coupling calculations reveal that these compounds possess a weak superconductivity with a relatively low Tc (below 1 K), which mainly stem from the low value of density of states occupation at the Fermi level (EF). These results highlight that the crystal structures play a critical role in determining the high-temperature superconductivity.

For the development of high-performance spintronic nanodevices, one of the most urgent and challenging tasks is the preparation of two-dimensional materials with room-temperature ferromagnetism and a large magnetic anisotropic energy (MAE). Through first-principles swarm-intelligence structural search calculations, we identify an ideal ferromagnetic Fe3P monolayer, in which Fe atoms show a perfect Kagome lattice, leading to strong in-plane Fe-Fe coupling. The predicted Curie temperature of Fe3P reaches ∼420 K, and its MAE is comparable to those of ferromagnetic materials, such as Fe and Fe2Si. Moreover, the Fe3P monolayer remains as an above room-temperature ferromagnet under biaxial strains as large as 10%. Its lattice can be retained at temperatures of ≤1000 K, exhibiting a high thermodynamic stability. All of these desirable properties make the Fe3P monolayer a promising candidate for applications in spintronic nanodevices.

The search for two-dimensional superconductors has attracted increasing interest because of their potential applications in constructing nanoscale superconducting devices. Through swarm-intelligence based CALYPSO method and the first-principles calculations, we have identified a monolayer structure for yttrium sulfide (t-YS), which is energetically and dynamically stable. The application of biaxial strain turns t-YS to a Bardeen–Cooper–Schrieffer superconductor, which mainly originates from the softening of in-plane modes of Y atoms. The superconducting critical temperature increases monotonously with strain, which reaches 6 K at a maximum strain of 10%. Calculations show that doping at 0.3 holes per unit cell based on a strain of 10% could further enhance the superconductivity to 7.3 K. Simulations have helped to propose a candidate substrate with ∼8.3% lattice mismatch to obtain superconductive t-YS experimentally. The findings will enrich two-dimensional superconductors and stimulate immediate experimental interest.

Pressure is a fundamental tool that can induce structural and electronic transformations, which is helpful to search for exotic materials not accessible at ambient conditions. Here, we have performed an extensive structural study on cubic Mg3As2 in a pressure range of 0–100 GPa by using a combination of structure predictions and first-principle calculations. Interestingly, two novel structures with space groups C2/m and P were uncovered that become energetically most stable at pressures of 12 GPa and 30 GPa, respectively. Phonon dispersions demonstrate that the three phases are dynamically stable in their respective low-enthalpy pressure ranges. The electronic calculations show that Mg3As2 keeps semiconductor properties at pressures up to 100 GPa. The interesting thing is that the direct semi-conducting property of Mg3As2 transforms into indirect semi-conducting when the pressure is above 12 GPa. The current results provide new insights for understanding the behavior of Mg3As2 at high pressures.

Materials possessing both superhard and metallic properties are beneficial for the creation of multifunctional devices under extreme conditions. Here, we report the formation of a new metallic superhard boron nitride at high pressure with stoichiometry B2N3 through first-principles calculations and structure searching. At ambient pressure, B2N3 has layered structures (h-B2N3) consisting of hexagonal B4N4 layers intercalated by triply bonded N2 molecules. With the pressure increasing to ∼10 GPa, h-B2N3 transforms to a three-dimensional tetragonal structure (t-B2N3) with the formation of single N–N bonds. Calculations reveal that t-B2N3 can be recovered under ambient conditions in view of the dynamical, thermal and mechanical stability. Interestingly, t-B2N3 is proposed to be a superhard material with an estimated Vicker's hardness of ∼52 GPa by performing stress–strain calculations. More importantly, electronic calculations show unique two-dimensional metallicity in t-B2N3, which originates from the π orbitals of N–N bonds spreading in the ab plane. In addition, the energy density of ∼2.95 kJ g−1 makes t-B2N3 a potential high-energy density material.

The design of two-dimensional superconductors has attracted great research interest owing to their wide application in nanoscale devices. Here, we combine first-principles calculations with structure searching technology to identify a unique stable hexagonal $h\text{\ensuremath{-}}{\mathrm{MnB}}_{3}$ monolayer, exhibiting a slightly higher energy with respect to the reported tetragonal $t\text{\ensuremath{-}}{\mathrm{MnB}}_{3}$. Interestingly, $h\text{\ensuremath{-}}{\mathrm{MnB}}_{3}$ contains two boron kagome layers sandwiched with Mn atoms. It exhibits metallic properties and has a superconducting transition temperature of 24.9 K, which is much higher than 2.9 K in $t\text{\ensuremath{-}}{\mathrm{MnB}}_{3}$. Its superconductivity mainly originates from the coupling between in-plane vibrational phonons of boron kagome layers and electrons of Mn atoms. $h\text{\ensuremath{-}}{\mathrm{MnB}}_{3}$ exhibits a tunable superconductivity, and reaches a maximum of 34 K at 2% tensile strain resulting from the softening in-plane modes of boron kagome layers. The Si (111) surface may be an ideal substrate for the growth of superconductive $h\text{\ensuremath{-}}{\mathrm{MnB}}_{3}$. The unique superconducting mechanism observed here could inspire the searching of more boron kagome based two-dimensional superconductors.

Uranus and Neptune are generally assumed to have helium only in their gaseous atmospheres. Here, we report the possibility of helium being fixed in the upper mantles of these planets in the form of NH3–He compounds. Structure predictions reveal two energetically stable NH3–He compounds with stoichiometries (NH3)2He and NH3He at high pressures. At low temperatures, (NH3)2He is ionic with NH3 molecules partially dissociating into (NH2)− and (NH4)+ ions. Simulations show that (NH3)2He transforms into intermediate phase at 100 GPa and 1000 K with H atoms slightly vibrate around N atoms, and then to a superionic phase at ~2000 K with H and He exhibiting liquid behavior within the fixed N sublattice. Finally, (NH3)2He becomes a fluid phase at temperatures of 3000 K. The stability of (NH3)2He at high pressure and temperature could contribute to update models of the interiors of Uranus and Neptune., Helium is generally considered too inert to be present in giant ice planet mantles. The authors, by first-principles calculations and crystal structure searches, find stable ammonia–helium compounds at the conditions of Uranus and Neptune’s upper mantles, with possible implications in the planet composition models.

PEMFC are considered to be the most promising for automotive energy because of their good working effect, low temperature, high efficiency, and zero pollution. Stainless steel as a PEMFC bipolar plate has unparalleled advantages in strength, cost, and processability, but it is easy to corrode in a PEMFC working environment. In order to improve the corrosion resistance, the surface modification of 316L stainless steel is a feasible solution for PEMFC bipolar plates. In the present study, the plasma-nitrided coating and CrNx coating were prepared by the plasma-enhanced balanced magnetron sputtering technology on the 316L stainless steel surface. The microstructures, phase compositions, and corrosion resistance behavior of the coatings were investigated. The corrosion behavior of the prepared plasma-nitrided coating and CrNx coating was investigated by potentiodynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy (EIS) in both cathodic and anodic environments. The experimental results show that corrosion resistance of the CrNx coating was better than the plasma-nitrided coating. It was indicated that the technology process of nitriding first and then depositing Cr was better than nitriding only.

Searching for experimentally feasible intrinsic quantum anomalous Hall (QAH) insulators is of great significance for dissipationless electronics applications. Here we predict, based on density functional theory (DFT), that four monolayer transition metal tri-bromides (VBr3, FeBr3, NiBr3, and PdBr3) are endowed with intrinsic half-metallicity and possess quantum anomalous Hall insulating phases. DFT+U calculations reveal that the VBr3, NiBr3, and PdBr3 monolayers undergo nontrivial to Mott insulator transitions with increasing on-site Hubbard Coulomb interaction U at 0.5, 2 and 3 eV. The gap opening induced by the spin-orbit coupling drives the systems into the QAH state. The Curie temperatures of the VBr3, NiBr3, and PdBr3 monolayers are ∼190, 100 and 110 K. Additionally, the calculated cleavage energies suggest that the freestanding VBr3, FeBr3, NiBr3, and PdBr3 monolayers can be easily produced by exfoliation using adhesive tape, which may stimulate experimental research interest to achieve QAH phases.

Crystalline silicon is dominating the current solar cell market due to the significant efficiency improvement and cost reduction in last decades. However, its indirect band gap nature leads to inefficient visible-light absorption, which seriously impedes further performance enhancement in silicon-based photovoltaic devices. Thus, it is highly desirable to develop direct band gap silicon materials. Herein, by means of ab initio swarm-intelligence structure-searching method, we predicted a quasi-direct gap semiconducting tri-layer silicene structure consisting of alternating arrays of six-membered Si rings, which can be converted into a direct gap semiconductor of 0.86 eV by applying a low tensile strain (~ 2.5%). Our calculations revealed that the photovoltaic efficiency of the tri-layer silicene reaches 29% at 1.0 µm, which is comparable to that of bulk GaAs with the highest conversion efficiency among thin-film solar cell absorbers.

Controlling magnetism of two-dimensional multiferroics by an external electric field provides special opportunities for both fundamental research and future development of low-cost electronic nanodevices. Here, we report a general scheme for realizing a magnetic phase transition in 2D type-I multiferroic systems through the reversal of ferroelectric polarization. Based on first-principles calculations, we demonstrate that a single-phase 2D multiferroic, namely, ReWCl_{6} monolayer, exhibits two different low-symmetric (C_{2}) phases with opposite in-plane electric polarization and different magnetic order. As a result, an antiferromagnetic-to-ferromagnetic phase transition can be realized by reversing the in-plane electric polarization through the application of an external electric field. These findings not only enrich the 2D multiferroic family, but also uncover a unique and general mechanism to control magnetism by electric field, thus stimulating experimental interest.

Monolayer MoS2 has long been considered as the most promising candidate for wearable photovoltaic devices. However, its photovoltaic efficiency is restricted by its large band gap (2.0 eV). Though the band gap can be reduced by increasing the number of layers, the indirect band gap nature of the resulting multilayer MoS2 is unfavorable. Herein, we report a theoretical discovery of the hitherto unknown symmetry-broken phase (denoted as 1Td) of monolayer MoS2 through a swarm structure search. The 1Td phase has a distorted octahedral coordinated pattern of Mo, and its direct band gap of 1.27 eV approaches the optimal value of 1.34 eV that gives the Shockley–Queisser limit for photovoltaic efficiency. Importantly, the direct band gap nature persists in thin films with multilayers owing to extremely weak vdW forces between adjacent 1Td layers. The theoretical photovoltaic efficiency at 30 nm thickness reaches ∼33.3%, which is the highest conversion efficiency among all the thin-film solar cell absorbers known thus far. Furthermore, several feasible strategies including appropriate electron injection and annealing methods were proposed to synthesize the 1Td phase. Once synthesized, the superior photovoltaic properties of the 1Td phase may lead to the development of an entirely new line of research for transition metal dichalcogenide solar cells.

The corrosion behavior of a high manganese steel in simulated marine splash zone environment was studied by dry-wet cyclic corrosion experiment and electrochemical experiment. Corrosion kinetics, composition, surface morphology, cross-section morphology, element distribution, valence state, polarization curve and electrochemical impedance spectroscopy were analyzed with the aim of characterizing the characteristics of corrosion product films. The results show that in chloride-containing environment, in the initial corrosion products, Mn oxides with porous structure lead to higher corrosion rate. As corrosion extends, the formation of alloy element oxides in corrosion products changes the corrosion properties of rust layers at different stages. Mo oxides form a stable passivation film, which reduces the influence of chloride ion on corrosion. Ni oxides in the inner rust layer facilitate the transformation of goethite, and Cr oxides in the outer rust layer increase the densification of the rust layer. The stability and compactness of Fe3O4, α-FeOOH and FeCr2O4 in the later corrosion products inhibit the corrosion action of manganese iron oxides and slow down the corrosion rate. With the corrosion durations, the corrosion current density of the sample with the corrosion product film first increases and then decreases, and the corrosion potential first moves negative and then shifts in a positive direction subsequently, indicating that the protective effect of the corrosion product film is gradually significant.

Blending is a promising method to modify the ash-fusion characteristics of coal to meet gasification requirements. To investigate the variation in ash-fusion behavior for high ash-fusion-temperature (AFT) coal through coal blending and its regulating mechanism, the ash-chemistry characteristics of four coals (Nantun, Pengzhuang, Biaodian, and Xiangyuan) were analyzed. Mineral-transformation behaviors in the mixed ashes were investigated by X-ray powder diffractometry using normalized reference intensity ratio software, scanning electron microscopy analyzer equipped with energy-dispersive X-ray spectrometry, and FactSage software. Pengzhuang and Biaodian coals, AFTs meet entrained-flow gasifier requirements when the Xiangyuan mass ratio reaches 20%. The Nantun requires a Xiangyuan mass ratio of XY > 30% because of its high aluminum oxide content. The required Xiangyuan optimal blending mass ratio is 40%–70% for the three high AFT coals to meet gasification requirements in the entrained-flow gasifier. An increased Xiangyuan mass ratio leads to decreasing contents of high melting-point mullite and silica and increasing contents of low melting-point anorthite, hercynite, gehlenite, and hedenbergite. Amorphous matter in three mixed ash types resulted in a decrease in their AFTs. The variation in liquid phase under certain conditions reflects the change in AFT.

Titanium dioxide has been widely used as an efficient transition metal oxide photocatalyst. However, its photocatalytic activity is limited to the ultraviolet spectrum range due to the large bandgap beyond 3 eV. Efforts to reduce the bandgap to achieve a broader spectrum range of light absorption have been successfully attempted via the experimental synthesis of dopant-free metastable surface structures of rutile-type TiO2 (011) 2 × 1. This new surface phase possesses a reduced bandgap of ∼2.1 eV, showing great potential for an excellent photocatalyst covering a wide range of visible light. There is a need to establish the atomistic structure of this metastable surface to understand the physical cause for the bandgap reduction and to improve the future design of photocatalysts. Here, we report computational investigations in an effort to unravel this surface structure via swarm structure-searching simulations. The established structure adopts the anatase (101)-like structure model, where the topmost 2-fol...

Motivated by the high superconducting transition temperature (TC) shown by monolayer FeSe on cubic perovskite SrTiO3(001) and SrTiO3(001)-2×1 reconstructed surfaces, in this study, we explore the atomic and electronic structures of monolayer FeSe on various SrTiO3(001)-2×1 surface reconstructions using the CALYPSO method and first-principles calculations. Our search reveals two new Ti2O2 and Ti2O reconstructed surface structures, besides the Ti2O3 and double TiO2 layer reconstructed surfaces, and the two new Ti2O2 and Ti2O reconstructed surface structures are more stable under Ti-rich conditions than under Ti-poor conditions. The Fermi-surface topology of an FeSe monolayer on Ti2O3- and Ti2O2-type reconstructed STO surfaces is different from that of an FeSe monolayer on a Ti2O-type STO reconstructed surface. The established structure of monolayer FeSe on a Ti2O-type STO(001) reconstructed surface can naturally explain the experimental observation of the electronic band structure on the monolayer FeSe superconductor and obtained electrons counting per Fe atom. Surface states in the mid-gap induced by various STO surface reconstructions will result in band bending. The surface-state-induced band bending is also responsible for the electron transfer from the STO substrate to the FeSe films.

High pressure can drastically alter chemical bonding and produce exotic compounds that defy conventional wisdom. Especially significant are compounds pertaining to oxygen cycles inside Earth, which hold key to understanding major geological events that impact the environment essential to life on Earth. Here we report the discovery of pressure-stabilized divalent ozonide CaO3 crystal that exhibits intriguing bonding and oxidation states with profound geological implications. Our computational study identifies a crystalline phase of CaO3 by reaction of CaO and O2 at high pressure and high temperature conditions; ensuing experiments synthesize this rare compound under compression in a diamond anvil cell with laser heating. High-pressure x-ray diffraction data show that CaO3 crystal forms at 35 GPa and persists down to 20 GPa on decompression. Analysis of charge states reveals a formal oxidation state of −2 for ozone anions in CaO3. These findings unravel the ozonide chemistry at high pressure and offer insights for elucidating prominent seismic anomalies and oxygen cycles in Earth’s interior. We further predict multiple reactions producing CaO3 by geologically abundant mineral precursors at various depths in Earth’s mantle., Calcium and oxygen are abundant elements in the Earth’s mantle, largely present as calcium oxide. Here the authors show, by experiments and computations, that calcium ozonide (CaO3) is stabilized at the high pressures and temperatures characteristic of the lower mantle, with implications for the deep Earth’s chemistry.

Mechanical properties of Q370qE carbon steel can be improved by cladding it with 316L stainless steel. After rolling these materials together, microstructure, hardness, shear strength, and corrosion properties of the cladded metals were evaluated. Hardness and shear tests were performed according to appropriate standards to evaluate the bonds. The results show that the remarkable diffusion of Ni and Cr formed a hard transition zone. The width of this diffusion zone increases with increasing temperature. The shear strength of the clad interface reached a minimum of 385 MPa. In addition, the surfaces of samples were examined by neutral salt spray (NSS) tests and potentiodynamic polarization tests to examine corrosion behavior. The 316L side primarily exhibited pitting corrosion, while the Q370qE side was dominated by uniform corrosion.

Titanium dioxide has been widely used in modern industrial applications, especially as an effective photocatalyst. Recently, freestanding TiO2 films with a markedly reduced bandgap of ∼1.8 eV have been synthesized, indicating that the dimension has a considerable influence on the bulk band gap (>∼3 eV) and enhances the adsorption range of visible light. Titanium oxide compounds have various stoichiometries and versatile properties. Therefore, it is very necessary to explore the electronic properties and functionalities of other titanium oxide films with different stoichiometries. Here, we combined structure searches with first-principle calculations to explore candidate Ti–O films with different stoichiometries. In addition to the experimentally synthesized TiO2 film, the structure searches identified three new energetically and dynamically stable Ti–O films with stoichiometries of Ti3O5, Ti3O2, and Ti2O. Calculations show that the Ti–O films undergo several interesting electronic transformations as the Ti fraction increases, namely, from a wide-gap semiconductor (TiO2, 3.2 eV) to a narrow-gap semiconductor (Ti3O5, 1.80 eV) and then to metals (Ti3O2 and Ti2O) due to the abundance of unpaired Ti_d electrons. In addition to the electronic transformations, we observed nonmagnetic (TiO2) to ferromagnetic (Ti3O5, Ti3O2, and Ti2O) transformations. Notably, the Ti3O5 film possesses both narrow-gap semiconductive and ferromagnetic properties, with a large magnetic moment of 2.0 µB per unit cell; therefore, this film has high potential for use in applications such as spintronic devices. The results highlight metal fraction-induced electronic and magnetic transformations in transition metal oxide films and provide an alternative route for the design of new, functional thin-film materials.Titanium dioxide has been widely used in modern industrial applications, especially as an effective photocatalyst. Recently, freestanding TiO2 films with a markedly reduced bandgap of ∼1.8 eV have been synthesized, indicating that the dimension has a considerable influence on the bulk band gap (>∼3 eV) and enhances the adsorption range of visible light. Titanium oxide compounds have various stoichiometries and versatile properties. Therefore, it is very necessary to explore the electronic properties and functionalities of other titanium oxide films with different stoichiometries. Here, we combined structure searches with first-principle calculations to explore candidate Ti–O films with different stoichiometries. In addition to the experimentally synthesized TiO2 film, the structure searches identified three new energetically and dynamically stable Ti–O films with stoichiometries of Ti3O5, Ti3O2, and Ti2O. Calculations show that the Ti–O films undergo several interesting electronic transformations as the T...

The search for new inorganic electrides has attracted significant attention due to their potential applications in transparent conductors, battery electrodes, electron emitters, as well as catalysts for chemical synthesis. However, only a few inorganic electrides have been successfully synthesized thus far, limiting the variety of electride examples. Here, we show the stabilization of inorganic electrides in the Ti-rich Ti–O system through first-principles calculations in conjunction with swarm-intelligence-based CALYPSO method for structure prediction. Besides the known Ti-rich stoichiometries of Ti2O, Ti3O, and Ti6O, two hitherto unknown Ti4O and Ti5O stoichiometries are predicted to be thermodynamically stable at certain pressure conditions. We found that these Ti-rich Ti–O compounds are primarily zero-dimensional electrides with excess electrons confined in the atom-sized lattice voids or between the cationic layers playing the role as anions. The underlying mechanism behind the stabilization of electrides has been rationalized in terms of the excess electrons provided by Ti atoms and their accommodation of excess electrons by multiple cavities and layered atomic packings. The present results provide a viable direction for searching for practical electrides in the technically important Ti–O system. Computer simulations predict that compounds made of oxygen and titanium atoms form cages that can host electrons in their interstices. A team led by Hanyu Liu and Yanming Ma from Jilin University, China, have investigated the possibility for materials belonging to the family of titanium dioxide, a pigment used in paints and sunscreens, to behave as electrides, materials in which electrons resemble larger negatively charged atoms in the way in which they localize and interact with the surrounding atomic structure. Their calculations show that this occurs if the amount of titanium atoms in the material exceeds that of oxygen atoms by at least a factor of 2, which allows the formation of larger cages in which electrons can be confined. The synthesis of these materials will allow to assess their significance for catalysis or other applications.

Considering that pressure-induced formation of short, strong covalent bonds in light-element compounds can produce superhard materials, we employ structure searching and first-principles calculations to predict a new class of boron nitrides with a stoichiometry of BN2, which are stable relative to alpha-B and alpha-N2 at ambient pressure. At ambient pressure, the most stable phase has a layered structure (h-BN2) containing hexagonal BN layers between which there are intercalated N2 molecules. At 25 GPa, a three-dimensional P42/mmc structure with single N–N bonds becomes the most stable. Dynamical, thermal, and mechanical stability calculations reveal that this structure can be recovered under ambient conditions. Its calculated stress-strain relations demonstrate an intrinsic superhard nature with an estimated Vickers hardness of ∼43 GPa. This structure has a potentially high energy density of ∼4.19 kJ/g.

Nitrogen (N)-doped graphitic carbons with one-dimensional hollow/porous structures were synthesized via a sacrificial template of CdTe@ZIF-8 nanofibers. The N-doped graphitic carbons exhibited better electrocatalytic activity for ORR based on higher diffusion-limited current density and more positive half-wave potential as compared to carbons derived from ZIF-8.

Catalytically active graphene-based hollow TiO2 composites(TiO2/RGO) were successfully synthesized via the solvothermal method. Hollow TiO2 microspheres are uniformly dispersed on RGO. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) were used for the characterization of prepared photocatalysts. The mass of GO was optimized in the photocatalytic removal of rhodamine B (RhB) as a model dye pollutants. The results showed that graphene-based hollow TiO2 composites exhibit a significantly enhanced photocatalytic activity in degradation of RhB under either UV or visible light irradiation. The formation of the graphene-based hollow TiO2 composites and the photocatalytic mechanisms under UV and visible light were also discussed.

In this study, hollow core/shell CeO2@TiO2 photocatalysts were prepared via precipitation-co-hydrothermal method. X-ray diffraction, transmission electron microscopy, UV−Vis diffuse reflectance spectroscopy, thermo-gravimetric–differential thermal analysis, and photoluminescence were used for the characterization of prepared photocatalysts. The synthesis variables were optimized in the photocatalytic removal of rhodamine B (rhB) as a model dye pollutants. The results showed that hollow core/shell CeO2@TiO2 exhibit a significantly enhanced photocatalytic activity in degradation of rhB under either UV or visible light irradiation. The formation of the hollow core/shell CeO2@TiO2 and the photocatalytic mechanisms under UV and visible light were also discussed.

In the presence of sulfonated polystyrene (sPS) template, sPS@SnO 2 core shell particles formed via the interaction between the functional group of -SO 3 H on the template surface and ions of Sn 2+ from the precursor of SnSO 4 which were in ethanol-aqueous medium. After high-temperature calcination treatment for removal of sPS, the sPS@SnO 2 changed into SnO 2 hollow spheres. With the further carbonization of the sPS@SnO 2 @glucose composite microspheres, SnO 2 @C composite hollow spheres were fabricated. Using SEM, TEM, and N 2 adsorption - desorption technology, the structure, specific surface area, and the core-shell structure formation mechanism were determined. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) properties of SnO 2 hollow spheres and SnO 2 @C composites were investigated, respectively, in the foam nickel electrode under alkaline condition. The specific capacitance of SnO 2 @C composite hollow spheres could reach 25.8 F g −1 in 1 mol L −1 KOH aqueous solution and showed excellent charge-discharge behavior.

Hollow SnO2 microspheres are prepared from resorcinol–formaldehyde gel and different tin compound precursors, including stannous sulfate (SnSO4), stannous chloride dihydrate (SnCl2·2H2O), and stannic chloride pentahydrate (SnCl4·5H2O) via chemically induced self-assembly in hydrothermal environment. Morphological and structural characterizations of as-prepared hollow SnO2 microspheres are carried out using scanning electron microscopy, X-ray diffraction, and nitrogen adsorption–desorption method. Their electrochemical properties as the supercapacitor electrode materials for application are also investigated using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurement in 1 M H2SO4 electrolyte. There are redox peaks in CV curves and a large number of Faradic plateaus in GCD curves. At different scan rates, all the obtained samples have excellent electrochemical properties. The hollow SnO2 microspheres obtained from SnSO4 and SnCl2·2H2O as precursors show relatively lower specific capacitances of 395 and 347 F g−1, respectively. However, the specific capacitance of SnO2 from SnCl4·5H2O is up to 663 F g−1. The high specific surface area and hollow structure of SnO2 microspheres are due to facilitating the rapid transport of electrolyte ions and improving the electrochemical performance. It is expected that hollow SnO2 microspheres are the promising redox supercapacitor materials.

The fast dose calculator (FDC), a track-repeating algorithm that was initially developed for proton therapy, has been expanded to include carbon. The purpose of this study was to validate FDC as a dose engine for treatment planning of scanning proton and carbon beams at the Shanghai Proton and Heavy Ion Center (SPHIC). For a complete set of clinical reference beams, the absorbed dose calculated with FDC was compared with that measured. A gamma-index analysis found over 94.6% and 100.0% of the measured points for protons had a gamma-index value smaller than unity for the 1%/1 mm and 1.5%/1.5 mm dose/distance agreement criteria, respectively. For carbon, the passing rates were above 80.6% and 92% with and without ripple filter if the criteria was set to 1%/1 mm. The values increased to 90.0%and 96.0% with the criteria 1.5%/1.5 mm. In conclusion, we found that FDC can serve as an accurate dose calculation engine for the SPHIC.

In this study, a method is developed to fabricate sulfonated poly (ether ether ketone)/phosphotungstic acid-polyaniline (SPEEK/HPW-PANI) membranes by in situ polymerization of aniline for the purpose of decreasing the weight loss of HPW in the membranes. The synthesis involves the production of a SPEEK/HPW hybrid membrane followed by different layer of PANI coatings on the membrane surface, and subsequent treatment using drying in vacuum procedures. The scanning electronic microscopy images showed that HPW had good compatibility with SPEEK polymers and energy dispersive X-ray spectroscopy revealed the successfully doping with HPW and polymerization of PANI. The surface of SPEEK/HPW-PANI becomes more compact than that of SPEEK/HPW and pure SPEEK, which may lead to reduce the water uptake and swelling property. The proton conductivity was found for the SPEEK/HPW-PANI-5 composite membrane (91.53 mS/cm at 80°C) higher than that of pure SPEEK membrane (68.72 mS/cm at 80°C). Better thermal stability was determined in both SPEEK/HPW and SPEEK/HPW-PANI membranes than pristine SPEEK membrane. Therefore, PANI is a good potential coating for organic–inorganic hybrid e.g. SPEEK/HPW membrane materials to improve their hydrothermal stable properties and SPEEK/HPW PANI is a material that shows promise as a proton exchange membranes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41033.