查看更多>>摘要：Microstructural and electrochemical investigations of tri-doped (Gd, Li and Bi) cerium oxide, with theoretical formula Ce_(0.8(1-x-y))Gd_(0.2(1-x-y))Li_xBi_yO_([1.9(1-x.y)+x/~(2+)3y/2]) (x = 0.02 or 0.03 and y = 0.03 or 0.02 and x + y = 0.05) were carried out by XRD, BET, SEM, Raman, and EIS analyses. According to the dilatometer analysis, the synergistic combination of lithium and bismuth promotes the reduction of sintering temperature down to 800-900 °C. A densification > 95% was achieved for the electrolytes sintered at 900 °C. Raman analysis, in agreement with XRD, demonstrated that the lithium and bismuth induced changes due to the growth of the topological disorder and a higher defectiveness provoked by doping. The high dopant concentration (5 moIl%) is well distributed into the lattice and forms a complex network of defects that traps the oxygen vacancies and hence mobile ions promoting the ionic transport. As compared to a single (CGO) or a bi-doped system (BiCGO and LiCGO) an improvement of total conductivity was achieved at lower sintering temperature, with a maximum value for Ce_(0.76)Gd_(0.19)Li_(0.03)Bi_(0.02)O_(1.85) of 2.6810~(-3)-1.66-10~(-1) S cm~(-1) in temperature range of 400-800 °C.
查看更多>>摘要：The combination of active materials and carbon nanotubes (CNTs) provides an effective way to enhance battery capacity and optimize cycle performance. In the present study, the powder electrodeposition technology is employed to synthesize the NiO-Ni/CNTs composite for the first time. This technique contains the following steps. The CNTs are negatively charged by pre-discharge in lithium-ion batteries. Then, the negatived CNTs are uniformly dispersed in the NiCl_2 plating solution by electrostatic repulsion, and the Ni ions are in situ reduced and deposited onto the CNTs. The close combination of CNTs and NiO-Ni improves the overall conductivity and structural stability. As electrode of lithium-ion battery, the reversible capacity is improved due to the coordination of the Ni metal in the mixture of the composite electrode. Besides, the reversible capacity of the composite electrode is 851 mA h g~(-1) at 50 mA g~(-1) after 50 cycles. The "Powder electrodeposition" method in the current work provides a new way for the preparation of other similar powder composite materials. Furthermore, the problem that the traditional electrodeposition process is difficult to apply in the powder materials will be solved.
查看更多>>摘要：The photocatalytic application of CdTe quantum dots (QDs) is restricted by the charge carriers recombination and tendency to aggregate in suspended systems. Novel functionalized CdTe (F-CdTe) QDs and CoNiAl layered double hydroxide (LDH) nanocomposite have been prepared to utilize the unique advantages of CdTe QDs. The nanocomposite is prepared via in situ synthesis of LDH in the presence of as-prepared F-CdTe QDs where the QDs partially intercalated in the interlayer spaces of LDHs. As a result of the effective electronic coupling between F-CdTe QDs and CoNiAl LDH, the light-harvesting ability has been enhanced and the absorption edge expands toward the higher visible light wavelengths. Moreover, the charge carriers recombination in nanocomposite has been considerably suppressed compared to the pristine CoNiAl LDH and F-CdTe QDs. Also, the nanocomposite shows remarkable enhancing in photocatalytic degradation of Acid Red 14 (ARM) and Bisphenol A (BPA) as the sample pollutants. The photogenerated holes and hydroxyl radicals have a determining role in the degradation of ARM. The plausible mechanism is proposed based on the experimental results and theoretical calculations. The prepared nanocomposite represents superior photocatalytic activity after 5 consecutive runs. So, the CdTe QDs can be effectively utilized in photocatalytic applications through the proposed promising approach.
查看更多>>摘要：The chemical disorder in magnetic shape memory alloys it is an important parameter that impacts on its magneto-mechanical and electronic properties. In this work, Ni_2MnGa thin films were deposited on flexible glass substrates by using DC magnetron sputtering technique. The short-range order/disorder was investigated by means of Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) measurements using at Mn K-edge. Polycrystalline samples of Ni_2MnGa with fixed stoichiometry exhibit 121 structure with low residual stress and similar grain sizes. A phenomenological model taking into account three chemical order parameters associated with main chemical anti-site disorders and reliable lattice tetragonal distortions extracted from X-ray diffraction analyses was used to perform systematic computational simulations. The results reveal the persistence of local tetragonal distortions of the crystal structure with L21 structure under when increasing annealing temperatures that are accompanied by a systematic decrease of the anti-site disorder between Ni and Mn atoms and substitutions between Ni and Ga atoms, with the orderly occupation of the atomic sites of Mn and Ga remaining unstable. This work also shows presents a consistent model to perform quantitative analyses of the chemical anti-site disorders through EXAFS measurements in the on Ni_2MnGa polycrystalline thin films that preserve both the stoichiometry and the L2_1 crystalline structure.
查看更多>>摘要：Flexible multiwall carbon nanotubes (MWCNTs)- 10 wt% tin selenide (SnSe)/poly (3,4- ethylene diox-ythiophene): poly (styrene sulfonate) (PEDOT: PSS)/5 vol% dimethyl sulfoxide (DMSO) (MSPPD) composite films were fabricated by vacuum filtration method, and their thermoelectric properties were investigated. When the electrical conductivity (a) and Seebeck coefficient (S) of these composite films with different contents of MWCNTs were measured at different temperatures, σ had an increasing tendency with the increase of MWCNTs content while S would decrease gradually. MWCNTs would improve carrier concentration (n) and mobility (u) of SnSe/PEDOT: PSS film simultaneously because of MWCNTs with high electrical conductivity and carrier mobility. The maximum power factor PF of 59.35 μWm~(-1)K~(-2) had been obtained for MSPPD10 composite film at 393 K. The MSPPD10 composite film exhibited ex-cellent flexibility, σ decreased only to 86% of its initial stage after bending 1000 cycles using a rod with a radius of 4 mm. A flexible thermoelectric (TE) generator consisting of 5 legs MSPPD10 could generate an open-circuit voltage of 3.73 mV and maximum output power of 14.74 nW when the temperature gradient was 39 K. This research shows that MWCNTs have great potential to enhance the thermoelectric performance of flexible SnSe/PEDOT: PSS composite films for wearable devices.
查看更多>>摘要：In this study, α-Fe_2O_3/rGO was smoothly synthesized by a one-step method and employed to activate persulfate (PS) for the degradation of Bisphenol A (BPA) under sunlight. During the degradation experiment, the degradation rates of BPA for PS, α-Fe_2O_3/8% rGO, and α-Fe_2O_3/8% rGO/PS were 6.6%, 47.6%, and 99.1%, respectively, indicating that the introduction of α-Fe_2O_3/rGO and PS significantly enhanced the photo-catalytic efficiency because that photocatalytic process and PS activation coupling system not only inhibited the recombination of photo-induced carrier pairs, but also reduced the energy consumption of PS activation. Moreover, electron spin resonance spectroscopy (ESR) and trapping experiments were utilized to explore the active species generated during the reaction. The results showed that OH and-So_4~(2-) were the principal oxidative species in this reaction system. These results showed that Fe-loaded rGO has great potential for activating PS to decompose pollutants in water.
查看更多>>摘要：The promising candidates for high-performance electrode materials, transition metal species@N-doped mesoporous carbon composites (M/MO/M(OH)_2@NDMCs), were synthesized by carbonization of metal ion-doped polyaniline (PANI) functionalized mesoporous silica SBA-15, followed by etching the mesoporous silica template. The yielded M/MO/M(OH)_2@NDMC can be further converted into sulfide via a simple hy-drothermal sulfidization treatment. The mesoporous structure, large amount of the accessible electro-chemically active nitrogen species, partially graphitic structure, and transition metal compounds of transition metal species@NDMC composites will increase the electronic and ionic conductivity by reducing the internal and ion diffusion resistances resulting in fast diffusion of ions in the electrolyte to the electrode surface. These endowed them good electrochemical performance characteristics for use in supercapacitor electrodes. Correspondingly, NiO/Ni(OH)_2@NDMC, Co/Co(OH)_2@NDMC, and CoS_2@NDMC as the electrodes in 2 M KOH showed specific capacitance of 337, 589, and 1178 F g~(-1) at 2.0 A g~(-1), respectively. Furthermore, the assembled asymmetric supercapacitor device utilizing CoS_2@NDMC as a cathode exhibited a satisfactory energy storage capability (50 Wh kg~(-1) at 750 W kg~(-1)) with an admirable cyclic life (retaining -99% initial capacitance over 6000 repeated cycles). This finding gives these transition metal species@NDMC composites, especially CoS_2@NDMC, prospective applications as high-performance supercapacitor electrode materials, where a fast charge/discharge is required.
查看更多>>摘要：In this study, solvothermal method was adopted to successfully prepare graphene oxide (GO) supported SnO_2 nanocomposites using tin tetrachloride pentahydrate and graphene oxide as raw materials, tetra-methyl ammonium hydroxide (TMAH) as a control agent. The synthetic materials presented the efficient capacity in the photocatalytic degradation and photoelectric conversion. In the photocatalytic degradation of rhodamine B (RB) and methylene blue (MB), sample SnO_2-0.1% GO showed the optimal photocatalytic efficiencies for RB (97.26%) and MB (89.43%) degradation. According to the different degradation performances of RB and MB functional groups, we reasonably explained the electron transfer mechanism at the interface of SnO_2-GO nanomaterials, and verified it in the experiment of photoelectric conversion proceed combined with titanium dioxide nanotube arrays (TiO_2NTs). The enhanced photocurrent density and stability can also be effectively improved due to the effective photoelectron transfer from SnO_2 to GO surface.
查看更多>>摘要：The construction of Fe_2O_3/Fe_2TiO_5 heterostructure has been proven as an effective strategy to improve the photoconversion efficiency of hematite, however its controllable synthesis is still a great challenge. In this study, by performing a comparative investigation on two distinct Ti precursors, a novel, convenient, and low-cost approach for fabricating efficient Fe_2O_3/Fe_2TiO_5 photoanodes is developed. It clearly demonstrates that the adoption of typical TiCl_4 precursor leads to a Fe_2O_3/TiO_2 composite with a lower PEC activity, while a core-shell Fe_2O_3/Fe_2TiO_5 heterostructure is built via using the stable and water-soluble peroxo-titanium complex (PTC) precursor. The as-fabricated photoanode exhibits a comparable photocurrent density of 2.51 mA/cm~2 at 1.23 V vs. RHE to most of Fe_2O_3/Fe_2TiO_5 photoanodes in literatures. Based on various characterizations, the significant enhancement in PEC performance can be attributed to the largely increased donor density and the formation of Fe_2O_3/Fe_2TiO_5 core-shell heterostructure, which effectively facilitate the charge separation and transport in the bulk and surface of photoanode. This work provides a new idea for fabricating high-efficient Fe_2O_3/Fe_2TiO_5 photoanodes.
查看更多>>摘要：Crystal structures, electronic, and magnetic properties of RbCeX_2 (X = S, Se, Te) crystals are investigated using periodic density functional theory (DFT) calculations under hydrostatic pressures up to 10 GPa. The ferromagnetic phase is slightly more stable than the anti-ferromagnetic one for all compounds and pressures. A pressure-induced transition from a magnetic semiconductor (MS) to a spin gapless semiconductor (SGS) is observed only in the case of the X = Te compound. In absence of imposed pressure, the X = Te exhibits a direct a-spin gap of 0.46 eV while its β-gap is 2.30 eV. A pressure of 10 GPa completely suppresses the a-spin gap of RbCeTe_2 and reduces it β-gap to 1.63 eV. This pressure-induced elimination of only one spin gaps is exclusive to the X = Te compound. This property distinguishes the Te compound from its two congeners. The pressure-response characteristics of RbCeTe_2 renders this compound a potential pressure-induced MS → SGS switching material.
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