查看更多>>摘要：The corrosion behavior and surface characterization of an equiatomic CoCrFeMoNi high-entropy alloy (HEA) under various pH conditions were investigated by Mott–Schottky measurements, EIS, polarization, and XPS. The results showed that the passive films formed on the HEA displayed the n–p heterojunction electronic structure due to the generation of different semiconducting constituents. As the pH increased, the donor density decreased, which was attributed to the acceleration in the annihilation rate of the oxygen vacancies. Cr and Mo species were stable and were found enriched in the passive films, while substances of Co, Fe and Ni were depleted, independent of pH. Co and Ni mainly existed in the films in their metallic forms, both of which contributed less to the passive film formation. The stability of Fe was markedly enhanced with the pH increasing, resulting in the main components of the passive films changing from Cr and Mo to Cr, Fe and Mo.
查看更多>>摘要：Cu3SbS4 is an effective, low cost and non-toxic thermoelectric compound for intermediate temperature applications. However, its tetragonal structure needs to be tuned for efficient phonon scattering to reduce thermal conductivity and enhance zT. In this present article, the semiconductive carbon black nano-inclusions effect on Cu3SbS4 thermoelectric performance is studied. The thermoelectric properties of the fabricated samples are investigated in the temperature range of 300–623 K. Addition of amorphous carbon nano-inclusions in Cu3SbS4 causes a reduction in the thermal conductivity by phonon scattering and improvement in the Seebeck coefficient by carrier energy filtering mechanisms. The maximum figure of merit of 0.51 is obtained for 3 mol.% carbon nano-inclusion sample at 623 K. Additionally, enhancement of thermal stability and mechanical stability (hardness) with increased carbon nano-inclusion concentration is observed. It is found that grain boundary hardening and dispersion strengthening are the reasons for the enhancement. Moreover, our detailed studies demonstrate that the addition of carbon nano-inclusions in Cu3SbS4 can produce efficient, non-toxic, and inexpensive state-of-the-art thermoelectric devices.
查看更多>>摘要：In this study, LixP2SyI – type crystalline lithium superionic conductors have been synthesized from nLi2S-LiI (n = 1, 2, 3, and 4) solid solutions and P2S5 using the high energy ball milling process. First, different concentrations of Li2S were mixed and ball-milled with LiI at different molar ratios to obtain various Li2S-LiI solid solutions (nLi2S-LiI). Then, P2S5 was added to the prepared nLi2S-LiI solid solutions to get crystalline solid electrolytes. The crystalline nature and the composition of the prepared nLi2S-LiI solid solutions, and P2S5 added nLi2S-LiI (LixP2SyI) crystalline solids were examined using the powder X-ray diffraction technique. The evolution of the crystalline structural units was captured by laser Raman spectroscopy analysis. The surface morphology changes with varying Li2S concentrations as well as the addition of P2S5 were studied using field emission scanning electron microscopy. Electrochemical impedance spectroscopy analysis revealed that the prepared Li5S2I (3.1 ×10?5 S cm?1) and Li7P2S8I (1.07 ×10?3 S cm?1) solid electrolytes exhibited higher ionic conductivities than the other nLi2S-LiI solid solutions and LixP2SyI crystalline solids, respectively. The result of cyclic voltammetry analysis and DC polarization analysis proved that the prepared nLi2S-LiI solid solutions and LixP2SyI crystalline solids are stable against lithium metal. All-solid-state lithium batteries fabricated using nLi2S-LiI solid solutions and LixP2SyI crystalline solid electrolytes showed comparable electrochemical performances. In the present study, we demonstrated nLi2S-LiI solid solutions and LixP2SyI crystalline solids which could potentially be used as solid electrolytes for the fabrication of ASSBs with good performance.
查看更多>>摘要：In this paper, flexible MXene/graphene composite electrodes were successfully fabricated by inkjet printing process using printable graphene-modified MXene-based ink. The results show that the interlayer spacing in the printed MXene-based composite films is increased through the insertion of graphene nanosheets, which effectively reduces the self-stacking effect of MXene. The printed MXene/1 wt% graphene composite electrodes exhibit excellent stability with 89% resistance retention at a 180° bending angle, high volumetric capacitance of 183.5 F cm?3 at a scanning speed of 5 mV s?1, and long cycle life with 75% capacitance retention after 3000 charge-discharge cycles. Moreover, a flexible supercapacitor based on those electrodes demonstrates a competitive energy density of 0.53 μWh cm?2 at a power density of 10 μW cm?2, which provides prospects for the design of next generation flexible and wearable energy storage devices.
查看更多>>摘要：Silicon-based anode materials with significantly improved lithium storage would play an important role in the next generation high-performance lithium-ion batteries (LIBs). Herein, a simple photo/electrochemical deposition strategy is applied to synthesize a new type of porous Si@Sn composite, using the low-cost SiAl alloy microspheres as precursor. In the dark, the galvanic replacement reaction between Si and Sn2+ induces the in-situ deposition of Sn onto the porous Si microspheres. Under light illumination, both the photogenerated electrons and the electrons from the dissolution of Si lead to the reduction from Sn2+ to Sn. The porous Si@Sn microsphere composite synthesized under the conditions of light irradiation and the optimized pH (8.0) shows excellent lithium storage performance, with a reversible capacity of 1184.4 mAh g?1 after 500 cycles at 1 A g?1 and the first coulombic efficiency of 85.19%. This may be ascribed to the integral 3D porous Si microsphere structure with the embedding of more Sn nanoparticles. This work provides an easy and efficient strategy to design and synthesize the high-performance Si-based anode materials for LIBs.
查看更多>>摘要：In this paper, a bilayer graphene (BLG)/GaAs Schottky junction near-infrared (NIR) photodetector is investigated. The dark current is suppressed by inserting an Al2O3 passivation layer between the BLG and GaAs to prevent electron tunneling. In addition, a layer of Ag nanoparticles (NPs) is spin-coated on the surface of the BLG, which utilizes the plasma effect of the Ag NPs to enhance the local electric field, and promote the excitation and transport of the carriers in the BLG, thereby increasing photocurrent of the device. The combination of interface passivation and plasma effect has greatly improved the performance of BLG/GaAs Schottky junction NIR photodetector. Under the 808 nm incident light, the responsivity of the photodetector is 120 mA/W, which is 20 times higher than the traditional graphene/GaAs photodetector, the detection rate of the device can reach to 3.43 × 1011cm Hz1/2W?1 with the fast response/recovery time of 8.16 μs/98.43 μs. This high-performance BLG/GaAs Schottky junction can be widely used for the photo detection and solar cells fields.
查看更多>>摘要：The type-I MIL-125(Ti)@BiOBr heterojunction was prepared by a foolproof wet chemical strategy. Since the self-doping of Ti3+ was introduced at the sacrifice of MOF, the type-I heterojunction was transformed into the type-II TiO2@BiOBr core-shell hollow heterojunction in situ. The self-doping of Ti3+ and the contact of the heterogeneous interface synergistically promote the photocatalytic activity of TiO2@BiOBr. The optimized Ti@BOB-3(mMIL-125(Ti): mBiOBr = 2:5) has a higher degradation rate (91%) for ciprofloxacin, and the first-order rate constant (0.02225 min?1) is pure 13.09 times of MIL-125(Ti) (0.0017 min?1) and 6.58 times of pure BiOBr (0.00338 min?1). UV-Vis diffuse reflection and photodegradation of antibiotics experiments show that type-II TiO2@BiOBr heterojunction has a broader range of light responses and better photocatalytic performance. The DFT calculation further studied the type-II heterojunction's energy band structure and forbidden band width (1.94 eV). Active species capture experiment and EPR spectrum analysis confirmed that h+ and ?O2- are the main photoactive substances in the photodegradation process. This research is prospected to offer a cornerstone for the in-situ transformation design of different types of heterojunctions.
查看更多>>摘要：Reducing precious metal loading is of paramount importance in electrocatalysis. Here, we propose an efficient strategy to synthesize low-Pt electrocatalysts (3.9 wt%) with hydrogen evolution reaction (HER) performance comparable to that of a state-of-the-art 20% Pt/C electrocatalyst. Graphene quantum dots (GQDs) were used as building blocks for carbon support. Cobalt catalyzed the GQDs assembly into porous carbon nanosheets with plenty of defects and high N doping. Pt was deposited on the support via in-situ electrochemical cycling. The combination of low Pt nanoparticles loading and defective carbon remarkably enhanced the HER activity in both acid (overpotential = 84 mV at 100 mA cm?2, Tafel slope of 45 mV dec?1) and alkaline electrolytes (overpotential = 300 mV at 100 mA?2, Tafel slope of 152 mV dec?1) while showing excellent stability and durability for 45 h.
查看更多>>摘要：An Al-Cu-Li alloy was selected as the model material to get insight into the mechanism of deformation strengthening at cryogenic temperatures. The mechanical properties and microstructure evolution of the alloy fabricated by symmetric rolling and asymmetric rolling (the rolling ratio was 1.3) at different temperatures (25 °C, ? 100 °C, ? 190 °C) were investigated. Smaller grains and denser dislocations were observed in the cryorolled samples, leading to strength enhancement compared to the samples processed at room temperature. The heterogeneous grain structure was made of coarse and fine grains in the samples processed by cryorolling (CR) at ? 100 °C, which resulted in higher strength and better ductility than those processed by CR at ? 190 °C and room temperature rolling. Finally, a new back stress model was employed to calculate the yield strength of the heterogeneous structure, which could explain the highest strength of samples processed by CR at ? 100 °C.
查看更多>>摘要：The surfaces of nanoporous metals are easy to be oxidized under normal ambient condition. This usual attribute permits the exploration of metal-core oxide-shell structure that would be used for supercapacitors (SCs). However, the large-scale application of such electrodes is still limited by the intrinsically low ion diffusion coefficient, poor electronic conductivity and frustrating structural stability. Here we design a defect decorated hierarchical nanoporous CuMn2O4/Cu0.2Ni0.8O/CuxOy @ alloy electrode (HNP-TMO) by dealloying-coarsening-dealloying a sandwich-like NiCuMn/Ni/NiCuMn alloy and followed by self-combusting (2.1 mm s?1). The sandwiched Ni can synergy with unoxidized alloy to provide excellent mechanical stability and electronic conductivity, while the hierarchically porous structure with robust defects can ensure rapid electron/ion transportation. Benefiting from these merits, the HNP-TMO electrode with high mass loading of 7.8 mg cm?2 delivers an ultrahigh area capacity of 6.78 mAh cm?2 at 10 mA cm?2, good rate capability (maintaining 3.33 mAh cm?2 at ultra-high current density of 100 mA cm?2) and outstanding cycling performance with capacity retention of 92.7% after 12000 cycles. Full symmetric supercapacitor also demonstrates high energy and power density of 0.17 mWh cm?2 and 40.15 mW cm?2, respectively, indicating the promise for practical energy storage applications.
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Elsevier