DFT Investigation of the Structural, Electronic, and Optical Properties of AsTi (Bi)-Phase ZnO under Pressure for Optoelectronic Applications.

Pressure-induced phases of ZnO have attracted considerable attention owing to their excellent electronic and optical properties. This study provides a vital insight into the electronic structure, optical characteristics, and structural properties of the AsTi (Bi) phase of ZnO under high pressure via the DFT-based first-principles approach. The phase transformation from BN(Bk) to the Bi phase of ZnO is estimated at 16.1 GPa using local density approximation, whereas the properties are explored precisely by the hybrid functional B3LYP. The electronic structure exploration confirms that the Bi phase is an insulator with a wider direct bandgap, which expands by increasing pressure. The dielectric function evidenced that the Bi phase behaves as a dielectric in the visible region and a metallic material at 18 eV. Optical features such as the refractive index and loss function revealed the transparent nature of the Bi phase in the UV range. Moreover, the considered Bi phase is found to possess a high absorption coefficient in the ultraviolet region. This research provides strong theoretical support for the development of Bi-phase ZnO-based optoelectronic and photovoltaic devices.

Influence of Atmospheric Contaminants on the Work Function of Graphite.

Airborne hydrocarbon contamination occurs rapidly on graphitic surfaces and negatively impact many of their material properties, yet much of the molecular details of the contamination remains unknown. We use Kelvin probe force microscopy (KPFM) to study the time evolution of the surface potential of graphite exposed to ambient. After exfoliation in air, the surface potential of graphite is not homogeneous and contains features that are absent in the topography image. In addition, the heterogeneity of the surface potential images increased in the first few days followed by a decrease at longer exposure times. These observations are strong support of slow conformation change, phase separation, and/or dynamic displacement of the adsorbed airborne contaminants.

Multi-layer core-shell metal oxide/nitride/carbon and its high-rate electroreduction of nitrate to ammonia.

The electroreduction of nitrate to ammonia is both an alternative strategy to industrial Haber-Bosch ammonia synthesis and a prospective idea for changing waste (nitrate pollution of groundwater around the world) into valuable chemicals, but still hindered by its in-process strongly competitive hydrogen evolution reaction (HER), low ammonia conversion efficiency, and the absence of stability and sustainability. Considering the unique electronic structure of anti-perovskite structured Fe4N, a tandem disproportionation reaction and nitridation-carbonation route for building a multi-layer core-shell oxide/nitride/C catalyst, such as MoO2/Fe4N/C, is designed and executed, in which abundant Fe-N active sites and rich phase interfaces are in situ formed for both suppressing HER and fast transport of electrons and reaction intermediates. As a result, the sample's NO3RR conversion displays a very high NH3 yield rate of up to 11.10 molNH3 gcat.-1 h-1 (1.67 mmol cm-2 h-1) with a superior 99.3% faradaic efficiency and the highest half-cell energy efficiency of 30%, surpassing that of most previous reports. In addition, it is proved that the NO3RR assisted by the MoO2/Fe4N/C electrocatalyst can be carried out in 0.50-1.00 M KNO3 electrolyte at a pH value of 6-14 for a long time. These results guide the rational design of highly active, selective, and durable electrocatalysts based on anti-perovskite Fe4N for the NO3RR.

Surface oxygen vacancy engineering on TiO2 (101) via ALD technology for simultaneously enhancing charge separation and transfer.

Titanium oxide molecular layers containing extensive SOV content (11.4-16.2%) have been constructed on (101) TiO2 nanotubes through a precisely controlled atomic layer deposition technique, in which the charge separation efficiency and surface charge transfer efficiency are increased to 28.2% and 89.0%, respectively, about 17 and 2 times those of the initial TiO2 nanotubes.

Helium-induced damage in U3Si5 by first-principles studies.

Uranium silicide U3Si5 has been explored as an advanced nuclear fuel component for light water reactor to enhance the accident tolerance. In this paper, in order to understand the fuel performance of U3Si5, the primary point defects, secondary point defects, and the dissolution of He gas were studied by first-principles methods. Compared with U atoms and another type of Si2 atoms, Si1 atoms far from intrinsic Si vacancies are more likely to form point defects, implying that Si vacancies are prone to form separate single vacancies rather than vacancy clusters in the initial stage. From the calculated anti-site defect energies, it can be predicted that non-stoichiometric U-rich phase of U3Si5 are more likely to be formed than Si-rich phase, which are consistent with the chemical analysis of experimentally sintered Si-lean U3Si5 sample. It can be found that a single He atom favors residence in the interstitial site in the U layer directly above/below the intrinsic vacancy. It can also be seen that Vac-U, Vac-Si1, and Vac-Si2 vacancies can energetically accommodate up to 4, 0, and 3 He atoms, respectively. The formation of secondary vacancy defects is strongly dependent on the helium concentration. The current results show that the He-filled vacancy can promote the formation of adjacent secondary vacancy, leading to the formation of gas bubbles. This work may provide theoretical insights into the He irradiation-induced damage in U3Si5 as well as provide valuable clues for improving the design of the UN-U3Si5 composite fuel.

Correction: Helium-induced damage in U3Si5 by first-principles studies.

[This corrects the article DOI: 10.1039/D1RA04031F.].

TBHP/NH4I-Mediated Direct N-H Phosphorylation of Imines and Imidates.

A direct and practical metal-free N-H phosphorylation has been achieved via the TBHP/NH4I-mediated cross-dehydrogenative coupling (CDC) reactions between imines/imidates and P(O)H compounds. This transformation provides an efficient synthetic route to the construction of P-N bonds with good functional group compatibility, leading to the formation of N-phosphorylimines and N-phosphorylimidates in up to 95% yield (33 examples) under mild conditions.

Hetero-nanostructured materials for high-power lithium ion batteries.

The development of high technology electrical devices increased the importance of higher power density or higher capacity at high current density. Especially, rapid charge/discharge issues remain problematic for electric vehicle commercialization. After extensive investigation, researchers introduced hetero-nanostructured materials to the field of lithium ion batteries (LIBs), aiming to enhance the power density or improve the capacity at high current density and life cycle capability. Hetero-nanostructured materials consist of current collectors and directly attached active nanomaterials. Carbon, carbon nanotube (CNT), graphene, Nickel (Ni), Copper (Cu) and Aluminum (Al) were used for current collector, aiming to improve the electron transfer and the cyclability, due to high electrical conductivity and superior buffering effects. Also, Hetero-nanostructure can produce a favorable lithium diffusion condition by creating a lithium diffusion pathway. This article presents an explanation of important factors for high power density or high capacity at high current density. It summarizes the capacity of electrode materials at high current density, including structural descriptions and material types.

Efficient degradation of tetrabromobisphenol A via electrochemical sequential reduction-oxidation: Degradation efficiency, intermediates, and pathway.

Tetrabromobisphenol A (TBBPA), a toxic persistent pollutant, should be effectively removed from the environment. In this study, an electrochemical sequential reduction-oxidation system was proposed by controlling reaction atmosphere with Pd-Fe nanoparticles modified Ni foam (Pd-Fe/Ni) electrode as cathode for TBBPA degradation. To obtain an efficient Pd-Fe/Ni electrode for TBBPA degradation, various factors, like Pd loading, Fe2+ adding amounts, were examined. The Pd-Fe/Ni electrode exhibited higher TBBPA conversion and debromination than the counterparts, due to the synergism of Fe0 and electrochemical reduction. Similar TBBPA conversions and debromination ratios were observed for the cases of sparging N2 only and sparging N2 followed by air, which were higher than those of aeration. Reductive debromination occurred while first bubbling N2, forming tri-BBPA, di-BBPA, mono-BBPA and BPA; and these intermediates were likely to be further oxidized by OH generated from H2O2 together with Pd-Fe/Ni electrode under aeration. Reductive and oxidative intermediates (including aromatic ring-opened product) were identified by HPLC and UPLC-QTOF-MS. Based on the intermediates, the possible TBBPA degradation mechanism and pathway were proposed. This study demonstrates that sequential reduction-oxidation process tuned by N2 and air bubbling was favored for TBBPA degradation, thus, it should be a promising process for HOCs degradation.

[Photoelectrocatalytic degradation of bisphenol A in water by Fe doped-TiO2 nanotube arrays under simulated solar light irradiation].

Seeking an efficient treatment method for bisphenol A ( BPA), a representative endocrine disrupting compound, is important for environmental remediation and human health. Herein, the degradation of BPA by means of photoelectrocatalysis was investigated. Fe doped-TiO2 nanotube arrays ( Fe/TNA ) served as the photoanode, and a xenon lamp simulated the solar light source. First, undoped TiO2 nanotube arrays (TNA) and a series of Fe/TNA were characterized by field emission scanning electron microscopy, X-ray diffraction and UV-Vis diffuse reflectance spectroscopy. The UV-Vis absorption spectra of Fe/TNA showed a red-shift and an enhancement of the absorption in the visible-light region compared to TNA. Then, experimental conditions including Fe doping content, current intensity and aeration rate were varied to demonstrate their effects on the elimination of BPA. It was observed that the degradation of BPA could be fitted to the quasi-first-order equation. Under the following conditions: Fe/TNA prepared by 0.9 mol x L(-1) Fe(NO3)3 solution dip-coating as photoanode, titanium foil as cathode, current intensity of 1.15 mA x cm(-2) and initial BPA concentration of 10 mg x L(-1), 72.3% BPA was decomposed during 4 h reaction, with a rate constant of 5.32 x 10(-3) min(-1). Aeration enhanced the removal rate of BPA to 82.7% and 94.1% with an aerating rate of 1.0 L x min(-1) using titanium foil as cathode and an aerating rate of 0.2 L x min(-1) using carbon cloth as cathode, respectively, and the corresponding rate constants were 7.20 x 10(-3) min(-1) and 11.6 x 10(-3) min(-1), respectively.