查看更多>>摘要：Extensive investigations have been made over the past two decades on the two-dimensional molybdenum sulfide (MoS2) since their dominating characteristics for the various applications including electrocatalysis and energy storage. Albeit MoS2 possesses the plentiful active sulfur edges, but their deficient inactive facets lead the poor conductivity and low efficiency. In this work, we attempted to activate more active sites by the insertion of doping transition metals such as nickel (Ni), copper (Cu) and iron (Fe) into MoS2 matrix. A facile chemical precipitation methodology was used to prepare the greatly active Fe, Cu and Ni metal doped MoS2 nanoarrays for hydrogen evolution and supercapacitors. Microscopic studies revealed the tuned morphology composed of nanoarrays structured domains of grains for metals doped MoS2 with the vertically aligned layers and extended layer spacing. The modified morphological properties, enriched surface area and plentiful active edges were apparently established for the metal doped MoS2. Hydrogen evolution results revealed that the improved electrocatalytic activity for Fe doped MoS2 nanoarrays with the low overpotentials, small Tafel slopes and unremitting reactions over 24 h in the acid and alkaline solution. The highly porous structured Cu doped MoS2 nanostructures owned the maximum capacitance of 353 F.g(-1) at 1 A.g(-1) current density with an admirable retaining capacity of similar to 94% after 5000 cycles. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this study we report the use of a hybrid separator coated with mesoporous multi-walled carbon nano tubes (MWCNTs) and ferroelectric BaTiO3 (BTO) as a "conductive scaffold" and polysulfide barrier for high-performance lithium-sulfur batteries. The effectiveness of the hybrid separator was verified by using a high sulfur cathode (70%). The modified separator effectively limited the migration of lithium polysulfides, improved the integrity of the sulfur cathode, and provided a conductive channel for ion and electron transport. As a result, the cell utilizing the separator coated with MWCNT and BTO (AHT-MWCNT-BTO) exhibited excellent electrochemical performance and rate kinetics, delivering a high initial discharge capacity of 1388.6 mAh g(-1) at 0.1 C-rate, corresponding to 83% sulfur utilization in the electrode. Additionally, the cycling performance revealed a 77% capacity retention of the initial value after 100 repeated cycles at 0.5 C-rate. Furthermore, even at a high current density of 2.0 C, the cell with the AHT-MWCNT-BTO-coated separator delivered a discharge capacity of 422.8 mAh g(-1) after 350 cycles, besides significantly increasing the sulfur utilization and effectively improving the electrochemical conversion of trapped polysulfides. These results reveal the exceptional potential of AHT-MWCNT-BTO-coated separators in the development of next generation high-performance lithium-sulfur batteries. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Two kinds of Ag2S-Zn0.5Cd0.5S heterostructural photocatalysts were synthesized via a simple two-step hydrothermal method. The photochemical (PEC) properties of Zn0.5Cd0.5S nanoparticles modified by Ag2S are closely related to the reaction time of Zn0.5Cd0.5S nanoparticles. Compared with the Ag2S-Zn0.5Cd0.5S heterostructure prepared at low temperature, the Ag2S-Ag-Zn-Cd-S composite prepared at high temperature has higher charge transfer/separation efficiency and longer carrier life. The photocatalytic performance of Ag2S-Ag-Zn-Cd-S composites for the degradation of Rhodamine B (RhB) under visible light irradiation (lambda = 420 nm) was significantly improved. The AZCS-180-4 h photocatalyst exhibited the highest degradation efficiency (83.1% within 40 min) with a rate constant of 0.0401 min-1 which exhibited prominent stability and repeatability, and can still maintain high photocatalytic activity after at least four cycles. Meanwhile, the study of photocatalytic mechanism shows that the photo-induced h+ radical is the predominant active species in this photocatalytic system, followed bymiddotOH andmiddotO2- play a secondary role. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Co3O4 has been proven to be a potential catalyst for oxygen evolution reaction (OER) because of its low cost and abundant resources. However, pure Co3O4 has the disadvantages of poor conductivity and low catalytic activity. Here, we successfully synthesized three-dimensional (3D) network Co3O4 composed of nanowires grown on nickel foam (NF). Using a lithium-ion rocking chair transport mechanism, Co3O4 nanowires were transformed into porous amorphous Co3O4, which greatly reduces the resistance in the OER process and enhances active site exposure. Meanwhile, the increase of Co2+ greatly improved the OER performance. However, excessive cycling of lithium-ion batteries can form a thick solid electrolyte interface (SEI) on the surface, which has a negative impact on OER. Specifically, we found that 5-cycle Co3O4 has the best OER performance, showing an initial potential of 1.42 V vs RHE, a reduced overpotential of 311 mV at 50 mA cm-2 and a low Tafel slope of 76 mV decade-1, which is better than commercial RuO2. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：High-performance surface-enhanced Raman scattering (SERS)-active substrate can be fabricated by deposited silver (Ag) nanoparticles on the pyramidal silicon with Ga-doped zinc oxide (ZnO) nanoneedles. Properly manufacturing a ZnO seed layer on pyramidal silicon may be beneficial to grow vertically aligned Ga-doped ZnO nanoneedles to deposit silver nanoparticles uniformly. Suitable silver sputtering duration on the Ga-doped ZnO nanoneedles has been upgraded to produce the most remarkable SERS effect in rhodamine 6G (R6G) molecules. SERS results show that Ag/Ga doped ZnO/pyramidal silicon is better than Ag/pyramidal silicon and Ag/silicon substrates. This phenomenon is attributed to Ag/Ga-doped ZnO/pyramidal silicon geometry, providing more hot spots and surface-active sites to exhibit high SERS enhancement, good reproducibility, and long-term stability. Ag/Ga doped ZnO/pyramidal silicon can also provide excellent SERS active substrates for detecting different types of drugs with low detection limits, such as amoxicillin (10(-10) M) and irinotecan (10(-7) M). (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Coupling a semiconductor with exposed high-activity crystal facets and a suitable co-catalyst to form a heterojunction is considered to be a feasible measure to improve photocatalytic activity. Therefore, the novel BiOBr/(001)-TiO2/Ti3C2Tx (BTT-y) were synthesized by in-situ construction. The BTT-y possess a remarkable Rhodamine B (RhB) degradation performance due to there is a better synergy among the three substances. The improvement of RhB degradation performance is mainly attributed to the perfect matching of BiOBr and (001)-TiO2 band structure positions, which is conductive to the formation of heterojunction and thus could expand visible-light absorption range and inhibit the recombination of photo-generated carriers. Furthermore, Ti3C2Tx in the heterojunction would further separate the photo-generated carriers. This study provided reference insights for improving photocatalytic performance with 2D/2D/2D structure. (C) 2021 Elsevier B.V. All rights reserved.
Abd-Lefdil, MohammedEl Khakani, My AliElhmaidi, Zakaria OuladSaucedo, Edgardo...
9页
查看更多>>摘要：The pulsed laser deposition (PLD) technique was used to deposit CZTS thin films onto SLG/Mo substrates via the KrF-laser ablation of a composite target consisting of Cu2ZnSnS4 pellet onto which Zn strips were purposely affixed. The effect of the substrate temperature (T-sub) of the PLD-CZTS films on their structure and properties was systematically studied over the 25-500 degrees C temperature range. The Zn content of the films was found to increase mainly when T-sub is raised from 300 to 500 degrees C. While both XRD and Raman analyses confirmed that the films consist of the kesterite-single-phase of which crystallinity improves when T-sub is increased (from RT up to 400 degrees C), the near resonant Raman (at 325 nm) revealed the presence of ZnS phase at high T-sub (> 400 degrees C). The optical energy band gap (Eg) of the PLD-CZTS films was consistently found to decrease from 1.9 to 1.4 eV when T-sub is increased from RT to 500 degrees C. Our results pointed out the T-sub = 400 degrees C as the optimal deposition temperature that meets at best the properties required for the PLD-CZTS films for PV application. The post-annealing (in presence of S and Sn vapors at 560 degrees C) of the PLD-CZTS films has improved further their crystallinity and led to the formation of some ZnS secondary phase at their surface. By appropriately integrating these post-annealed films into SLG/Mo/CZTS/CdS/ZnO/ITO photovoltaic devices, we were able to demonstrate their photoconversion ability with a PCE of 3.3 % (V-oc = 512 mV, J(sc) = 12.5 mA/cm(2) and a FF = 51.5 %). The analysis of their EQE spectrum suggests that the effective carrier collection length in the CZTS absorption layer needs to be extended further to achieve higher photoconversion efficiencies. (C) 2021 Elsevier B.V. All rights reserved.
Ter-Isahakyan, ArtashesRau, Julia S.Balk, Thomas John
8页
查看更多>>摘要：A thin film combinatorial synthesis approach was utilized to develop a compositional and structural library for the OsRuWCo alloy system. The survey of this alloy space produced 24 unique compositions and their corresponding crystal structures, which represent a phase map where amorphous and single-phase hexagonal close-packed alloys were identified. Based on the identification of a promising candidate film region, a new high entropy alloy based on OsRuWCo, but with non-equiatomic composition, was synthesized in bulk form. The alloy exhibited a single-phase hexagonal close-packed structure in the as-cast state. Three derivatives from this system were also developed by considering the heat of mixing, atomic size, and binary solubility. These new alloys are based on OsRuWCoIr and OsRuWCoFe, both of which exhibit single-phase hexagonal close-packed as-cast structures, as determined by X-ray diffraction and electron microscopy. Additionally, this large compositional space was utilized to evaluate conventional parameters that describe high entropy alloys (Delta S-mix, Delta H-mix, Omega, delta, and VEC), and these were found to elucidate the criteria for solid solution formation in this system. Trends illustrating the evolution from amorphous to crystalline phases are demonstrated and discussed. It is concluded that in this particular case, the dominant factors promoting crystallinity are thermodynamic or electronic, rather than geometric. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Cs3Bi2I9 has been proposed to be an alternate candidate for various optoelectronic applications to meet the stability and toxicity issues associated with the highly performing organic lead halide perovskites. In the present work, we report the in situ formation of cesium bismuth iodide thin films by ultrasonically assisted sequential spray deposition of BiI3 and CsI in ethanol-based precursor solutions. The films formed by varying the layer configurations and relative molarity were investigated to identify the optimum conditions to obtain pure Cs3Bi2I9 films. Further, we probe their structure, morphology, optical and electronic properties in combination with computational studies. X-ray diffraction and Raman spectroscopy confirmed the crystallinity and chemical structure of the spray cast perovskite films. Scanning electron microscopy images present the surface morphology composed of uniformly distributed hexagonal grains of similar to 280 nm in average size. The absorption coefficient of the films was evaluated in the order of similar to 10(6) cm(-1) using UV-Vis-NIR spectral analysis. The calculated direct band gap value of 1.99 eV was in accordance with the theoretical calculations. Furthermore, the optimized Cs3Bi2I9 film was photoconductive. The I-V char-acteristics of FTO/ZnO/Cs3Bi2I9/C-Ag heterojunction revealed a significant rectification behavior with a diode factor of 1.75. FTO/CdS/Cs3Bi2I9/C-Ag heterojunction showed a Voc of 300 mV and Jsc of 0.003 mA cm(-2). Our results imply that the spray deposited Cs3Bi2I9 films have a profound potential for applications in photodetectors and solar cells upon detailed investigations. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Wire arc additive manufacturing (WAAM) has many advantages of high efficiency and low cost to repair blades or blisk made of titanium alloy. In this work, different contents and sizes of ZrO2 particles were added in the single-layer deposition and the multi-layer deposition fabricated by the WAAM technology to investigate the microstructure and mechanical properties of the repaired TC17 titanium alloy. Results show that the content and size of ZrO2 particles have a great influence on the geometry shape and beta grain morphology. Especially, the deposition height (dH) increased and the deposition width (dW) decreased with the increased content of 75 mu m ZrO2 under the direct current arc. The silicides are promoted to form with the addition of ZrO2, and more silicides tend to precipitate between the heat affected bands (HABands). The addition of ZrO2 can extremely increase the ultimate strength and make the plasticity meet the standard requirements. Especially, the ultimate strength of the multi-layer deposition with 0.5 wt% +50 nm ZrO2 was highest, 1116 MPa, which is 100 MPa higher than that of the deposition without ZrO2 addition. Meanwhile, the strength of the multi-layer deposition with the addition of 1 wt%+ 75 mu m ZrO2 have less of an uplifting effect compared with that of 0.5 wt%+ 75 mu m ZrO2. (C) 2021 Elsevier B.V. All rights reserved.
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