查看更多>>摘要：Catalytic oxidation has been considered as one of the most promising strategies for the removal of indoor HCHO which causes multiple health problems. Alloyed Au-Pt showed potential for catalytic oxidation reactions, but the reports on HCHO oxidation are limited. In addition.understanding on the catalytic mechanism is lacking. In this work, a sodium citrate assistant photodeposition process was developed to fabricate highly dispersed dual Au-Pt alloy with 2-3 nm on the surface of TiO_2. The turnover frequency of Au-Pt/TiO_2 (68.6 h~(-1)) is much higher than that of Pt/TiO_2 (19.9 h~(-1)). This enhancement was also confirmed on different TiO_2 supports and with different Pt loading. Based on the experimental and density functional theory calculations, it was found that the alloyed Au-Pt has more metallic Pt and is beneficial for the adsorption and dissociation of oxygen. Therefore, the rapid conversion of dioxymethylene species to formate species, with reduced reaction barrier, promotes the performance in catalytic oxidation of HCHO.
查看更多>>摘要：The hybrid structure of high conductive carbon materials with large capacitive metal compounds is one of promising strategies for achieving high specific capacity, cycling stability, and ultrafast Li-ion storage capability due to their synergistic effects. This article will demonstrate the novel hybrid structure of a zinc oxysulflde (ZnOS) lamination layer on a sulfur (S)-doped carbon nanofiber (SCNF) matrix via an electro-spinning method with sequential atomic layer deposition (ALD) process and will also present the structural advantages for ultrafast Li-ion batteries (LIBs). As a double-anion material, ZnOS has benefits compared with single ZnO and ZnS during the charge/discharge process, which is accompanied with consecutive conversion and alloying reactions. To verify these factors, structural analysis at the atomic scale and various electrochemical properties were evaluated. The resultant ZnOS/SCNF electrode showed superior electrochemical performance such as high specific capacity (672.8 mAh g~(-1) at 100 mA g~(-1)), good capacity retention (87.8% after 100 cycles), and excellent cycling stability (85.4% after 500 cycles). This is attributed to the facilitated kinetic properties including electron and ion transfer efficiency during the electrochemical reactions, accompanied with the ZnOS/SCNF hybrid structure. In this regards, we believe that the ZnOS/SCNF electrode could be a great reference as a promising research strategy for accomplishing ultrafast LIBs.
查看更多>>摘要：In this work, pre-lithiated VO_2(B) nanobelts are synthesized by a two-step hydrothermal method. After pre-lithiation, the VO_2(B) nanobelts exhibit a uniformly dispersed morphology with a large specific surface area. Compared to pure VO_2(B) nanobelts, the pre-lithiated VO_2(B) nanobelts show much better electrochemical performance in terms of cycling stability and high-rate capability. The lithium-ion diffusivity in the pre-lithiated VO_2(B) nanobelts is enhanced due to enlargement of the crystal lattice after pre-lithiation. The pre-lithiated VO_2(B) nanobelt cathode delivers an initial specific capacity of 264 mA h g~(-1 at 0.1 A g~(-1 with a capacity retention of 81.6% after 100 cycles, which is superior to that obtained for pure VO_2(B) under the same conditions (initial capacity of 221.5 mA h g~(-1 and capacity retention of 63.3%). Moreover, the pre-lithiated VO_2(B) nanobelt electrode exhibits outstanding long-term cycling stability (capacity retention of 87.2% after 800 cycles at 1000 mA g~(-1)). These results indicate that pre-lithiated VO_2(B) nanobelts have great potential to be applied as an advanced cathode material for next-generation lithium-ion batteries.
查看更多>>摘要：Dye-sensitized solar cells (DSSCs) with TiO_2 as electron transport layer (ETL) demonstrate great potential in the field of photoelectric devices featuring low cost and high power conversion efficiency (PCE). However, the photovoltaic performance of DSSCs based on TiO_2 ETL is still confined by the undesirable charge recombination occurring in TiO_2 layer (intrinsic defects), dye layer (self-quenching) and at the interface between TiO_2 and electrolyte (back electron transfer). Herein, we firstly adopted a trisiloxane molecule (denoted as TSi) to holistically reduce the abovementioned charge recombination of DSSCs via passivating surface defects of TiO_2, fine-tuning dye molecules arrangement and forming interfacial energy barrier. As a result, the Z907-based DSSCs with TiO_2/TSi ETL deliver a high PCE of 9.43%, increasing over 16% than that of DSSCs without TSi treatment. Meanwhile, the DSSCs based on TiO_2/TSi ETL present stronger endurance to high humidity and better long-term stability versus that of the DSSCs without TSi treatment. Our work provides a simple yet effective strategy to holistically reduce charge recombination of devices for improving the photovoltaic performance and stability of DSSCs.
查看更多>>摘要：A sensing platform based on porous ZnO/Co_3O_4 is introduced for determination of hydrazine in alkaline media. The bimetallic oxides were prepared by calcination of bimetallic zeolitic imidazolate framework (Zn/ CoZIF) as a sacrificial template. Zn/CoZIF and ZnO/Co_3O_4 were characterized via several techniques. The porous ZnO/Co_3O_4 was utilized to modify glassy carbon electrode (ZnO/Co_3O_4/GCE), followed by immobilization of Au nanoparticles (NPs) on its surface to prepare Au/ZnO/Co_3O_4/GCE. The electrode exhibited two linear ranges of 2-1900 μM and 1900-8500 μM with sensitivity of 0.058 and 0.048 μA μM~(-1) for determination of hydrazine in aqueous solution. The sensor showed remarkable lower oxidation potential and limit of detection rather than ZnO/Co_3O_4/GCE. Furthermore, the sensor displayed acceptable selectivity toward oxidation of hydrazine in the presence of some interfering species. The results confirm that Au/ZnO/ Co_3O_4/GCE can be considered as sensitive and reliable sensor toward the oxidation of hydrazine due to the porous structure of ZnO/Co_3O_4, high conductivity of Au NPs, and the synergic effect among the constituents.
查看更多>>摘要：This study is focused on the synthesis condition influence related to structural and spectroscopic properties of the potassium strontium pyrophosphate (K_2SrP_2O_7) co-doped with Eu~(3+) and Eu~(2+) ions. The experimental parameters of the urea assisted combustion synthesis were optimized by temperature and time of calcination as well as reduction atmosphere composition. The obtained materials were structurally characterized using the X-Ray Powder Diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Spectroscopic properties were determined by emission spectra, excitation spectra, luminescence kinetics and luminescence temperature quenching measurements. It was found that increasing concentration of Eu~(3+) ions caused an increase of spectroscopic factors, which correspond to the relative integrated luminescence intensities of ~5D_0-~7F_∫ transitions as well as structural defects. Moreover, the successful Eu~(2+) ion incorporation was proven by optical spectroscopic measurements, which showed the allowed f-d transitions.
查看更多>>摘要：ScAlMgO_4 is a promising material that can be used to fabricate lattice-matched substrates for the epitaxial growth of GaN and InGaN. To improve its crystal quality, we used synchrotron X-ray topography to study the dislocations in a 50.8-mm-diameter ScAUvlgO_4 single crystal grown via the Czochralski method. Dislocation character was analyzed in terms of Burgers vectors by comparing dislocation contrasts recorded using sixg-vectors that represented the m+c, a+c, and c-type crystal planes. The central area of the substrate, which corresponded to the portion grown vertically under the seed crystal, was characterized by millimeter-sized domains bound by mixed-type dislocation arrays with both in-plane and c-axis Burgers vectors. Basal plane dislocations (BPDs) typically formed an arrow-like shape with three branches. Growth striations with alternating high- and low-dislocation-density areas were observed in the diameter-expanding area and high-dislocation-density areas were covered with tangled BPD networks. The mechanisms of dislocation generation, multiplication, and reaction are discussed based on their line directions and dislocation character.
查看更多>>摘要：Six groups of fcc solid/solid diffusion couples, including Ni-Cr-Fe/ low-entropy (pure Ni, and NiCo, NiCr, and NiCoCr) alloys, Ni-Cr-Fe/ medium-entropy (CoCrNi) alloys, and Ni-Cr-Fe/ high-entropy (CoCrFeNi) alloys, were prepared, and their composition profiles were experimentally measured. Concentration-dependent interdiffusion and tracer diffusion coefficients in fcc Ni-Co-Cr-Fe system at 1473 K were retrieved with the aid of High-throughput Determination of Interdiffusion Coefficients (HitDIC) software and their reliability was validated. In most cases, D_(CrCr)~(Ni)> D_(FeFe)~(Ni)> D_(CoCo)~(Ni). The comprehensive comparison between the inter-diffusivities/tracer diffusivities in the NiCo, NiCr, NiCoCr low-entropy, CoCrNi medium-entropy, and CoCrFeNi high-entropy alloys and those reported data available in the literatures indicates that the inter-diffusivities Co, Cr, and Fe in low-entropy alloys are the largest than those in the other two types of alloys. While the tracer diffusivity in Co-Cr-Fe-Ni HEAs may have no sluggish phenomenon when the absolute temperature is used.
查看更多>>摘要：Luminescence thermometry based on the rare earth (RE) doped materials has displayed promising applications in various fields due to its fast response and high spatial resolution. However, the achievement of sensitive and accurate temperature sensing over a wide temperature scope is still a great challenge for this thermal sensing technology. Herein, excited by 980 nm laser, the inverse thermal responses of the near-infrared emissions in Nd~(3+)-Yb~(3+) codoped phosphors, which was attributed to the phonon-assisted energy transfer between RE ions, were employed for ratiometric thermometry within the temperature range of 303-773 K. The modification of thermometric capability for the NIR luminescence was proposed through engineering the aluminate host matrix with SiO_2. The influence of SiO_2 on the luminescence behaviors of Nd~(3+) and Yb~(3+) was systematically investigated through the X-ray diffraction patterns, Fourier-transform infrared spectra, Judd-Ofelt theory calculation, as well as luminescence decay profiles. The results demonstrated that the luminescence and the subsequent thermal sensing properties of Nd~(3+)-Yb~(3+) ion pair were strongly dependent on the host. As the host structure varied from aluminate to aluminosilicate, the spontaneous radiative transition and the energy transfer for RE ions were clearly improved, whereas the multiphonon nonradiative relaxations were weakened. The Nd~(3+)-Yb~(3+) codoped aluminosilicate phosphors synthesised by adding 100 mol% SiO_2 exhibited much high sensitivity (0.7-4.6% K~(-1)) at temperatures ranging from 303 to 773 K, accompanied with a measurement uncertainty of about 0.1 K. This work provides an effective guidance for developing high-performance luminescence-based ratiometric thermometers.
查看更多>>摘要：Si_3N-4 ceramics have shown promising application prospects as the sealing materials for liquid metal batteries (LMBs). However, the joining of Si_3N-4 to the metal shell of LMBs is rather difficult because of the non-wetting property and mismatch of their thermal expansion coefficients (CTEs). Herein, to solve the above issue, W/Si_3N-4 functionally graded materials (FGMs) were designed and fabricated via the spark plasma sintering (SPS) process. The effects of layer numbers and layer components on the phase composition, structure, and thermal stress of the FGMs were systematically investigated using both experimental and simulation methods. W/Si_3N-4 FGMs, with optimal layer numbers, were then utilized for fabricating symmetrical W/Si_3N-4/W FGMs. The thermal stress of the products can be effectively reduced by adjusting the MgO content of the central Si_3N-4 layer. As a result, the optimal product displayed good interface bonding between two adjacent layers and also exhibited high flexural strength (943.9 MPa) and electrical resistivity (2.0 × 10~(12) Ω cm). This route for the fabrication of symmetrical W/Si_3N-4/W FGMs exhibits the advantage of high efficiency, and the products with excellent properties can be used as sealing materials for LMBs.
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Elsevier