Photocatalytic methods are extensively used in the treatment of uranium-containing wastewater. However, the reduction of uranium in natural sunlight remains a central challenge. This work proposed a MoS2 nanoflower-coupled Ti3C2 MXene reduction cocatalyst for bifunctional catalytic systems to remove U(VI) and degrade organic pollutants under natural sunlight. Advanced spectral characterization showed that MoS2/Ti3C2 had excellent photogenerated carrier transfer and light absorption capabilities. The experimental results show that when uranium and organic pollutants coexist, the removal rate of uranium is as high as 99%, and no sacrificial agents or inert gases are involved in this process. Further, theoretical calculations demonstrate that the bond behavior in the MoS2/Ti3C2 composites combines covalent bonds and ionic bonds, and about 0.497 electrons are transferred from Ti3C2 to the MoS2 monolayer. Two possible random adsorption interaction scenarios of [UO2·(H2O)5]2+ on MoS2/Ti3C2 composites are revealed meaningfully. The efficient removal of uranium and organic pollutants under real sunlight confirms the significant potential of the bifunctional photocatalyst for practical applications in radioactive wastewater.

In this paper, we present a productive low-temperature fabrication of Cs-hollandite ceramics by adding Bi2O3 as a sintering aid to achieve high cesium retention. The effects of Bi2O3 addition on the phase composition, crystal structure and aqueous stability of the stoichiometric Ba0.9Cs0.3Cr2.1Ti5.9O16 ceramic waste form were investigated. It was found that adding Bi2O3 can effectively reduce the sintering temperature and promote densification of Cs-containing hollandite products. The Cs-hollandite ceramic with 2 wt% Bi2O3 sintered at 1000 °C showed a single phase with > 98 % cesium retention, which was ∼ 200 °C lower and ∼ 11 % retention rate higher than those of reported Cs-bearing hollandite. Moreover, the leached sample remained stable tetragonal structure, the LRCs was in the order of 10-3 g·m-2·d-1 after 28 days and the leaching indexes > 8, exhibiting good aqueous stability. This route can be considered as a promising solution to prevent cesium loss for incorporating the cesium waste in ceramic hosts.

The decrease in mechanical properties of high-strength steel after welding is an important issue affecting the wide application of high-strength steel. Air-hardening steel is a high-strength steel suitable for lower body structural parts such as subframes. Its application process involves welding, hot forming and other processes. The present work investigates the microstructure and mechanical properties of the air-hardening steel laser welded joint that is air-cooled after hot forming in the two-phase zone (800 °C). The microstructure was characterized by electron backscattered diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that during hot forming, the welded joint transforms from martensite to ferrite and acicular martensite, and the base metal transforms from ferrite to polygonal martensite and ferrite. The difference in martensite morphology between the welded joint and the base metal is attributed to the nucleation positions of austenite. The structural evolution of the welded joint and the base metal is accompanied with the annihilation and reproduction of dislocations, which results in significant changes in hardness. The hardness value dropped from the highest 430 HV to 271 HV in the welded joint, while increased from the lowest 184 HV to 203 HV in the base metal. After hot forming, the tensile strength of the welded sample is reduced by only 36 MPa, and the total elongation is slightly decreased by about 1.5% compared with the unwelded sample. The welded joint and the base metal have similar plastic deformation capabilities, since the acicular martensite in the welded joint displays good plastic deformation ability, and the dislocation density of the welded joint and the base metal is similar. Overall, the microstructure and dislocation density of the air-hardening steel welded joint after hot forming are similar to those of the base metal, which is responsible for the good mechanical properties of air-hardening steel welded joint.

Re-extracting environmentally transportable hexavalent uranium from wastewater produced by spent fuel reprocessing using the photocatalytic technology is a crucial strategy to avoid uranium pollution and recover nuclear fuel strategic resources. Here, we have designed S-scheme 2D/0D C3N5/Fe2O3 heterojunction photocatalysts based on the built-in electric field and the energy band bending theory, and have further revealed the immobilization process of hexavalent uranium conversion into relatively insoluble tetravalent uranium in terms of thermodynamics and kinetics. According to the results, the hexavalent uranium removal and recovery ratios in wastewater are as high as 93.38% and 83.58%, respectively. Besides, C3N5/Fe2O3 heterojunctions also exhibit satisfactory catalytic activity and selectivity even in the presence of excessive impurity cations (including Na+, K+, Ca2+, Mg2+, Sr2+, and Eu3+) or various organics (such as xylene, tributylphosphate, pyridine, tannic acid, citric acid, and oxalic acid). It is believed that this work can provide a potential opportunity for S-scheme heterojunction photocatalysts to re-enrich uranium from spent fuel wastewater.

Garnet is a promising candidate for the long-term immobilization of radionuclides. However, the irradiation stability and occupation mechanism of Ce-doped garnet remains to be further explored. Herein, a single-phase garnet Ca2.5Ce0.5Zr2Fe3O12 was prepared by microwave sintering at 1300 °C for the immobilization of actinide (Ce substitutes), and its phase transition, occupation mechanism, chemical stability and irradiation stability were systematically investigated by the first principle thinking and synchrotron radiation. The results suggested that Ce occupied Ca-site in garnet. The thermal expansion test showed that the thermal expansion stability of Ca2.5Ce0.5Zr2Fe3O12 (7.30 × 10−5 °C−1) was considerably lower than Ca3Zr2Fe3O12. For accelerated irradiation experiments, irradiated by 2 MeV α-particles could lead to an amorphous effect of crystal structure after dose. Furthermore, the leach rate of Ce in Ca2.5Ce0.5Zr2Fe3O12 was approximately 10−5 g m−2 d−1 after irradiation remained. This work provides data support and theoretical basis for the immobilization of actinides in garnet.

We present a comparative study (using PBE, PBE0, and HSE functionals) of electronic and atomic structure, magnetism, and phonon dispersion relations of a-Cu2P2O7. Four possible magnetic configurations are considered, FM, AFM-1, AFM-2, and AFM-3. The calculations reveal that a-Cu(2)P2O(7) is mechanically and thermodynamically stable. The elastic moduli indicate a weak resistance of the compound to volume and shear deformations. The electronic structure at the valence band maximum is dominated by O, with a small admixture of Cu-d(x2-y2) states. The conduction band results from the hybridization between Cu and O states which, in the case of AFM-2, produces the largest band gap of 3.966 eV and the smallest magnetic moment of +/- 0.785 m B on Cu. AFM-2 is found to be the lowest-energy structure that may be viewed as consisting of quasi-one-dimensional Cu1 Cu-2 Cu-3 Cu-4 chains along the b axis; the antiferromagnetism is due to two identical Cu O Cu paths with a bond angle of 100.301 ffi. The phonon spectra exhibit four distinct frequency ranges corresponding to different vibrational modes of ions and ionic groups. Thus, a quantitative description of the structural, electronic, and magnetic properties of alpha-Cu(2)P2O(7) is possible using the HSE hybrid functional, which enables computational studies of transition metal pyro compounds.

Developing stable catalysts with higher selectivity and activity within a wide potential range is critical for efficiently converting CO2 to ethanol. Here, the carbon-encapsulated CuNi nanoparticles anchored on nitrogen-doped nanoporous graphene (CuNi@C/N-npG) composite are designedly prepared and display the excellent CO2 reduction performance with the higher ethanol Faradaic effiency (FEethanol ≥ 60%) in a wide potential window (600 mV). The optimal cathodic energy efficiency (47.6%), Faradaic efficiency (84%), and selectivity (96.6%) are also obtained at −0.78 V versus reversible hydrogen electrode (RHE). Combining with the density functional theory (DFT) calculations, it is demonstrated that the stronger metal-support interaction (Ni-N-C) can regulate the surface electronic structure effectively, boosting the electron transfer and stabilizing the active sites (Cu0-Cuδ+) on the surface of CuNi@C/N-npG, finally realizing the controllable transition of reaction intermediates. This work may guide the designs of electrocatalysts with highly catalytic performance for CO2 reduction to C2+ products.

The natural nitrogenase is still the most efficient catalyst on earth to reduce the ambient N2 into ammonia. The central part of the molecular machine is powered by a metallic core, usually a molybdenum atom, whose co-ordination valence state remains an enigma for us to unveil and mimic. Unlike the flexible bio-enzyme, inorganic heterogeneous catalysts are usually rigid in the coordination structure, making their valence states invariable, except some localized defects. In this study, we successfully synthesized a two-dimensional MoS2/Mo2C elec-trocatalyst, which contains a heterostructured interface with efficient charge and magnetism separation, exhibiting a gradual and broad valence state transition from Mo4+ to Mo2+. Density functional theory (DFT) calculations reveal that Mo3+ sites at the interface have a strong N2 adsorption energy of -0.75 eV with the side -on configuration, and an activated hydrogenation of *NH2 species. This bionic electrocatalyst displays a splendid performance in nitrogen reduction reaction with a Faradic efficiency of 42 % at-0.1 V vs RHE.

Electrocatalytic ammonia (NH₃) conversion under ambient atmosphere is crucial to mimic the nature's nitrogen cycle. But currently it is always interrupted by the HER process which is more competitive. Herein, we tactically cultivate a series of incompletely etched Ti₃AlC₂ MAX / Ti₃C₂ MXene based heterostructure catalysts whose composition can be finely tuned through regulation of the LiF percentage in mixed chemical etching agent. Notably, the surface potential difference between MAX and MXene is ~40 mV, indicating that the electron can be readily transferred from MAX to MXene across the interfaces, which is favorable for N2 fixation, yielding an outstanding Faradic efficiency of 36.9%. Furthermore, density functional theory calculations reveal the billiard-like catalysis mechanism, where the intermediates are alternatively adsorbed on MAX or MXene surfaces. Meanwhile, the rate-determining step of *NH → *NH₂ possesses an energy barrier of 0.96 eV on the hetero-interface which follows associative distal mechanism. This work opens a new frontier of heterostructured catalyst for balancing electrical conductivity and catalytic activity in electrocatalysis.

Compared with the Haber Bosch process, the electrochemical nitrogen reduction reaction (NRR) under mild conditions provides an alternative and promising route for ammonia synthesis due to its green and sustainable features. However, the great energy barrier to break the stable NN bond hinders the practical application of NRR. Though Fe is the only common metal element in all biological nitrogenases in nature, there is still a lack of study on developing highly efficient and low-cost Fe-based catalysts for N2fixation. Herein, Co-doped Fe3S4nanoflowers were fabricated as the intended catalyst for NRR. The results indicate that 4% Co-doped Fe3S4nanoflowers achieve a high Faradaic efficiency of 17% and a NH3yield rate of 37.5 μg·h-1·mg-1cat.at-0.55 V versus RHE potential in 0.1 M HCl, which is superior to most Fe-based catalysts. The introduction of Co atoms can not only shift the partial density states of Fe3S4toward the Fermi level but also serve as new active centers to promote N2absorption, lowering the energy barrier of the potential determination step to accelerate the catalytic process. This work paves a pathway of the morphology and doping engineering for Fe-based electrocatalysts to enhance ammonia synthesis.