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Atomic Structures and Mechanical Properties of Magnetron Co-Sputtered Zr-V-N Coatings
No full textZr-V-N coatings with varying Zr and V content were deposited by magnetron sputtering. Transmission electron microscopy (TEM) cross-section images of the coatings show a dense structure with tightly packed V-shaped columns. x-ray diffraction (XRD) and x-ray absorption fine spectroscopy (XAFS) were carried out to characterize the microstructure of the Zr-N-V thin films. The structural models derived from XAFS reveals segregation of metal domains within the Zr-V-N films. The Zr-V-N sample with Zr/V molar ratios around 3.5:1, which has a higher hardness and more stable wear resistance compared with other Zr-V-N coatings, is a promising material for industrial applications
High ionic conductivity and stable phase Na11.5Sn2Sb0.5Ti0.5S12 for all-solid-state sodium batteries
No full textThe quaternary antimony (Sb)-based sulfide sodium solid electrolyte Na11Sn2SbS12 with good moisture stability is attractive for practical application in all-solid-state sodium batteries. However, the Na11Sn2SbS12 exhibits low room temperature ionic conductivity and it is difficult to obtain pure phase due to the limited solubility of Sb in the Na11Sn2SbS12 crystal structure. Herein, titanium (Ti)-doping Na(11+x)Sn(2)Sb(1-x)TixS(12) (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.0) materials are systematically investigated, and the highest room temperature ionic conductivity of 1.01 mS cm(-1) is achieved when x = 0.5 (Na11.5Sn2Sb0.5Ti0.5S12), which is 3 times higher than that of pristine Na11Sn2SbS12. X-ray diffraction and alternating current impedance analyses reveal that the substitution of Sb with Ti can prevent the formation of the NaSbS2 impurity, determining high ionic conductivity. Meanwhile, the Na11.5Sn2Sb0.5Ti0.5S12 demonstrates good air stability with limited H2S gas evolution. Besides, the activation energy, electronic conductivity and electrochemistry stability window for Na11.5Sn2Sb0.5Ti0.5S12 are also evaluated. Moreover, a high reversible capacity and stable cyclic performance of TiS2 based all-solid-state sodium battery using Na11.5Sn2Sb0.5Ti0.5S12 are demonstrated, showing an initial discharge capacity of 177.6 mAh g(-1) at 0.1C with a capacity retention of 83.5% based on the second discharge capacity after 50 cycles at 25 degrees C
Superhydrophilic Sandwich Structure Aerogel Membrane for Emulsion Separation and Heavy Metal Ion Removal
No full textWater pollution has been increasingly becoming a serious environmental and health challenge in recent years. This is compounded by the often coexisting oil pollution and heavy metal pollution. It is of great practical significance to develop materials that can simultaneously deal with these two kinds of water pollution problems. In this study, a simple and green approach is proposed for preparing matrix-free citric acid modified alginate-based aerogel membrane by simple sol spraying, chemical cross-linking, and freeze-drying methods. The aerogel membrane with dense upper and lower surfaces and a loose interlayer possesses the properties of superhydrophilicity and underwater superoleophobic and strong antiadhesion performances, and it can realize the separation of highly viscous miscible oil-water emulsions with a separation efficiency of over 99.5%, even in corrosive and high-salt environments. The membrane has shown strong stability during 3000 min of uninterrupted cross-flow filtration of emulsion, which reflects the good long-term separation performance of the membrane. The prepared membrane can also be used for the removal of various heavy metal ions from water under gravity, with a removal efficiency >99% and an adsorption capacity of about 240 mg/g for Pb2+. The modified membrane which features low cost, a simple and green preparation process, excellent oil-water separation, and heavy metal removal capabilities possesses great application potential in the treatment of polluted water
Deep Bayesian local crystallography
No full textThe advent of high-resolution electron and scanning probe microscopy imaging has opened the floodgates for acquiring atomically resolved images of bulk materials, 2D materials, and surfaces. This plethora of data contains an immense volume of information on materials structures, structural distortions, and physical functionalities. Harnessing this knowledge regarding local physical phenomena necessitates the development of the mathematical frameworks for extraction of relevant information. However, the analysis of atomically resolved images is often based on the adaptation of concepts from macroscopic physics, notably translational and point group symmetries and symmetry lowering phenomena. Here, we explore the bottom-up definition of structural units and symmetry in atomically resolved data using a Bayesian framework. We demonstrate the need for a Bayesian definition of symmetry using a simple toy model and demonstrate how this definition can be extended to the experimental data using deep learning networks in a Bayesian setting, namely rotationally invariant variational autoencoders
Novel Platycladus orientalis-shaped Fe-doped ZnO hierarchical nanoflower decorated with Ag nanoparticles for photocatalytic application
No full textThe Ag/Fe-doped ZnO composites were designed by controllable intergration of the three strategies of hierarchical assembly, Fe doping, and Ag loading. The 3D Fe-doped ZnO hierarchical nanoflowers were firstly constructed with Platycladus orientalis-shaped petals via a hydrothermal method, and then Ag na-noparticles were anchored on the surface of Fe-doped ZnO nanoflowers through impregnation/reduction of silver nitrate solution. The samples were characterized by using XRD, SEM, TEM, HRTEM, XPS, Raman spectra, BET, UV-vis DRS, PL, EIS, Mott-Schottky plots, and photocurrent response. The results showed that Fe doping increased BET surface area and oxygen vacancies of ZnO, Ag loading produced the LSP absorption at similar to 530 nm, Fe doping and Ag loading together extended the visible light absorption and facilitated the separation of photogenerated carriers, which favors photocatalytic activity of ZnO. The maximum degradation efficiency of 92.3% for MO was achieved after visible light irradiation for 80 min when the feed atom ratio of Fe to Zn was 1.2% and Ag loading was 4 wt% of Fe-doped ZnO. Four cycle tests had little effect on the morphology and structure of Ag/Fe-doped ZnO, suggesting good cycling stability. The photocatalytic mechanism was elucidated based on the scavenger experiments and energy bands alignment. (C) 2021 Elsevier B.V. All rights reserved
General In Situ Photoactivation Route with IPCE over 80% toward CdS Photoanodes for Photoelectrochemical Applications
No full textCost-effective photoanodes with remarkable electronic properties are highly demanded for practical photoelectrochemical (PEC) water splitting. The ability to manipulate the surface carrier separation and recombination is pivotal for achieving high PEC performance for water splitting. Here, a facile and economical approach is reported for substantially improving the surface charge separation property of CdS photoanodes through in situ photoactivation, which significantly reduces surface charge recombination through the formation of thiosulfate ion which is favorable to the transfer of photogenerated holes and a uniform nanoporous morphology via the dissolving Cd2+ with phosphate ions on the surface of CdS. The resulting CdS electrodes through scalable particle transfer method exhibit nearly tripled photocurrents, with an incident-photon-to-current conversion efficiency (IPCE) at 480 nm exceeding 80% at 0.6 V versus reversible hydrogen electrode (RHE). And the CdS thin films prepared from chemical bath deposition display quadrupled photocurrents after the stir and PEC activation, with an IPCE of 91.7% at 455 nm and 0.6 V versus RHE. With the suppression of photocorrosion in alkaline borate buffer, the activated photoanodes show great stability for solar hydrogen production at the sacrifice of sulfite. This work brings insights into the design of nanoporous metal sulfide semiconductors for solar water splitting
Crystallization kinetics of monatomic antimony
No full textElemental antimony (Sb) has been carried out recently as a phase-change material to overcome composition segregation in a heavily cycled memory cell. Explosive crystal growth of Sb is desirable for fast operation speed in memory; however, poor thermal stability, i.e., fast spontaneous crystallization at room temperature, significantly impedes its applications. In this work, we designed a thermal stability enhanced monatomic Sb in a specific confined structure of [Sb(3 nm)/SiO2(5 nm)](32) and investigated its crystallization kinetics by using the ultrafast differential scanning calorimetry method. It was found that this nanoscale Sb exhibits appealing amorphous thermal stability with a crystallization activation energy of 2.68 eV and the temperature for 10-year data retention more than 361 K. Moreover, strong non-Arrhenius crystallization behavior with a high fragility index of 90 was unrevealed in Sb supercooled liquids, which has the maximum crystal growth rate of 2.17 m s(-1) at 785 K. Thanks to the fast crystal growth rate and attractive thermal stability of this monatomic Sb, it could be one of the most important candidates for high-integrated on-chip memory without any composition segregation.& nbsp;</p
Synthesis of Ultrathin Functional Boron Nitride Nanosheets and Their Application in Anticorrosion
No full textHexagonal boron nitride (hBN) shows huge promise for metallic corrosion protection due to its excellent impermeability. However, the exfoliation and dispersion of hBN have proven to be very challenging, owing to the strong lip-lip interactions and inherent hydrophobic features. Herein, ultrathin IL-BN nanosheets were synthesized and simultaneously noncovalent functionalized by ionic liquid (IL) through a liquid ball milling strategy to achieve the good compatibility with epoxy (EP), which was characterized by scanning electron microscope (SEM), transmittance electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectronic spectroscopy (XPS), and UV-vis absorbance spectroscopy. Electrochemical measurements confirmed that the addition of 0.5 wt % IL-BN into the EP matrix significantly enhanced the anticorrosion capability of coatings. After 4 weeks of immersion in 3.5 wt % NaCl solution, the IL-BN-EP coating remained with a high coating resistance Rc of 5.6 x 10(9) Tau cm(2), 4 orders of magnitude higher than EP (4.9 x 10(5) Omega cm(2)). SEM and Raman measurements also corroborated that the steel protected by IL-BN-EP was hardly corroded. Moreover, the passivation effect of IL-BN-EP coating was confirmed by potential polarization curve (PPC) tests at the coating defects. The superior anticorrosion performance of IL-BN-EP coating was mainly attributed to the synergistic effect of physical barrier and self-healing property endowed by the well-dispersed IL-BN hybrids
ITO/SnO2 Interface Defect Passivation via Atomic Layer Deposited Al2O3 for High-Efficiency Perovskite Solar Cells
No full textIndium tin oxide (ITO) substrate is widely used as a transparent electrode in perovskite solar cells (PSCs). However, the intrinsic defects, especially on the ITO surface, are one of the most key factors to restrict the power conversion efficiency (PCE) of PSCs. Herein, a facile method to passivate the defects of the ITO/SnO2 interface using an ultrathin aluminum oxide (Al2O3) layer through atomic layer deposition, of which the film thickness is exactly regulated, is first demonstrated. With the optimized film thickness, carrier recombination at the ITO/SnO2 interface is effectively suppressed within the three-cycle Al2O3 layer, which results in an improved charge carrier collection efficiency from the SnO2 electron transporting layer to the ITO electrode. Furthermore, a thinner Al2O3 film (one cycle) does not passivate the interface defect effectively, and a thicker Al2O3 film (five cycles) retards the charge carrier extraction at the ITO/SnO2 interface. The average PCE of the three-cycle Al2O3-based PSC is 19.43%, among which the champion PCE is 20.24%, showing a significant improvement compared with the counterpart with an average PCE of 18.50%
Theoretical Understanding of the Interface Effect in Promoting Electrochemical CO2 Reduction on Cu-Pd Alloys
No full textThe electrochemical conversion of CO2 holds promise to relieve the excess CO2 emission and store renewable energy. Bimetallic copper-based alloys show outstanding activity and selectivity for the electrochemical CO2 reduction reaction (CO2RR). Understanding the catalytic nature of Cu-based alloys may promote the development of high-performance CO2RR electrocatalysts. The interface in the bimetallic system plays a key role in gaining C-2 products in experiments. Here, we performed theoretical simulations to compare the activity of ordered and phase-separated Cu-Pd alloy catalysts for CO2 conversion. The reaction pathways to CO, CH4, C2H4, and C2H5OH are analyzed in detail to uncover the interface effect. Our calculation shows that the ordered Cu-Pd surface is favorable for the formation of C-1 products. The interface between Cu and Pd domains promotes the C-C bond coupling and the subsequent formation of C-2 products. This study provides insights into the catalytic mechanism of the bimetallic system and will be beneficial for designing efficient Cu-based alloy catalysts for the electrochemical CO2RR