查看更多>>摘要：LiNixCoyAl1?x-yO2 (NCA), as high nickel cathode material, has a high capacity and is one of the most promising cathode materials for lithium-ion batteries. However, the disadvantages such as more residual lithium compounds and serious capacity decay have hindered the industrial application of this material. In order to reduce the residual lithium compound on the surface of the material and restrain the capacity degradation, we designed and prepared a high nickel cathode material by pretreatment washing and subsequent spray drying, which has high cycle life and high discharge specific capacity. Compared to the first discharge specific capacity of 196.6 mAh g?1(0.2 C) for the raw material and 131.4 mAh g?1 after 100 cycles of 1 C, the discharge specific capacity of the modified sample 2V2O5@NCA was increased to 210.4 and 163.8 mAh g?1, respectively. Microstructure observation revealed that V2O5 not only uniformly covers the surface of the secondary particles, but also the presence of electrochemically active LiV3O8, which avoids the direct contact between the active material and electrolyte, thus significantly suppressing the interfacial side reactions between the cathode material and electrolyte and improving the structural stability of the material. Our exploration may pave a way for developing high cycle stability of high nickel cathode materials.
查看更多>>摘要：In order to investigate the effects of the Zn and Sb cosubstitution for Sn on the crystal structure and electrical conductivity of SnP2O7, Sn1?x(Zn2/3Sb1/3)xP2O7 compounds were synthesized in this study. The crystal structure refinement results show the solid solution limit of the Sn1?x(Zn2/3Sb1/3)xP2O7 compounds to be x = 0.15. The electrical conductivity of the compounds was enhanced depending on the level of the composition x. The highest value of 2.2 × 10?2 S cm?1 was obtained for x = 0.15, at 250 °C. It was suggested that the interstitial proton of the Sn1?x(Zn2/3Sb1/3)xP2O7 lattice was introduced by the formation of oxygen vacancies that originated from the cosubstitution of Zn and Sb for Sn. It was confirmed that the introduction of the interstitial proton significantly enhanced the electrical conductivity of the Sn1?x(Zn2/3Sb1/3)xP2O7 compounds. Thus, the Sn1?x(Zn2/3Sb1/3)xP2O7 compounds can be a promising candidate electrolyte with proton conducting at intermediate operating temperatures.
查看更多>>摘要：The Cr3+-modified α-cordierite ceramics Mg2Al4-xCrxSi5O18 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1, named MAS, MASCr0.2, MASCr0.4, MASCr0.6, MASCr0.8, and MASCr1, respectively) have been synthesized via the sol-gel process followed by cold isostatic pressing and sintering. The effects of trivalent chromium ion content in α-cordierite ceramic on microstructure and thermophysical properties were investigated. The MASCr0.2 ceramic exhibits the highest average emissivity value of 0.87 across the whole infrared range of 3–20 μm at 500 °C, especially at the vital infrared wavelength of 3–5 μm, the value can reach 0.92. The emissivity will decrease with the increase of doping amount owing to the growing precipitation of cristobalite and MgAl2O4 spinel phases. The lowest thermal conductivity 2.077 W/m K is discovered in MASCr0.2, a decrease of 23% compared to MAS. The MASCr0.4 ceramic with a close emissivity value compared to MASCr0.2 exhibits the TEC of 7.8 × 10?6 K?1 due to the multiphase structure.
查看更多>>摘要：Herein, the structural, electronic and optical properties of CsPbI3 perovskite with the tetragonal symmetry (β-CsPbI3) and its Br-doped structures are investigated. All calculations are performed by the first-principles method based on Density Functional Theory (DFT). The mixed perovskites CsPb(I1?xBrx)3 are constructed by substituting I- ion with Br- ion in the crystal cell, which the replacement ratios is 1/6, 1/3, 1/2, 2/3, 5/6, and 1. The calculated structural parameters show that crystal volumes of CsPb(I1?xBrx)3 decrease and their structural stabilities are improved with the increasing of Br content. The electronic structures indicate that these crystals are direct-bandgap semiconductors and the bandgap increases by increasing Br content. Partial density of state reveals that electronic properties are mainly associated with [PbI6]4- octahedron. By analyzing optical properties of CsPb(I1?xBrx)3, they are concluded to possess similar properties. Moreover, absorption coefficients heighten (2.0 × 105 - 2.5 × 105 cm?1) with an increasing range of Br content. Therefore, Br doping can adjust the band gap and improve the structural stability, which is expected to be useful for applications in the optoelectronics industry.
查看更多>>摘要：Rare-earth orthoferrites (RFeO3) is emerging as a type of microwave absorbing material (MAM) with development potential because of its excellent structural stability and moderate permittivity and amount of potential energy present. In this study, we employed a simple sol–gel technology to quickly synthesize La1?xCaxFeO3 (x = 0, 0.05, 0.1, 0.15, and 0.2) ferrite MAMs. The FullProf X-ray diffraction refinement demonstrated that all samples formed single-phase LaFeO3 (space group: Pnma). The amount of Ca doping was crucial in determining the particle size, magnetic properties, and electromagnetic parameters of LaFeO3. As a dielectric loss type in MAM, conduction loss is the primary reason and interfacial as well as dipolar polarizations are the secondary reasons for the attenuation of the electromagnetic energy of the samples. The study discovered that an appropriate amount of Ca2+ doping improves LaFeO3 microwave absorption. Therefore, the ideal microwave absorption is achieved in the La1?xCaxFeO3samples when Ca content x = 0.1 and 0.15, where the minimum reflection loss (RLmin) of La0.9Ca0.1FeO3 is ? 39.90 dB at 6.72 GHz and the corresponding matching thickness is 4.0 mm. Although the RLmin of La0.85Ca0.15FeO3 is ? 24.37 dB at 13.44 GHz, the effective absorption bandwidth is 4.56 GHz and the corresponding matching thickness is only 2.0 mm, which almost covers the entire Ku-band. This La1?xCaxFeO3 is expected to be an industrially produced high-performance MAM owing to its excellent microwave absorption performance as well as its simple and rapid synthesis method.
查看更多>>摘要：In this study, CdIn2S4/MoS2 composite structure was prepared by a simple two-step hydrothermal synthesis method, and the CdIn2S4/MoS2 composite structure samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis). Due to the effective loading of MoS2 on the surface of CdIn2S4 particles, the photocatalytic performance of CdIn2S4/MoS2 composite material is significantly improved under visible light irradiation (λ = 420 nm), which indicating the effective inhibit the recombination of photogenerated electron holes. Meanwhile, the visible light response of CdIn2S4 is increased and the life of photoexcitation carrier is prolonged. The CdIn2S4/MoS2 (sample 2CM) composite sample with mole content of 9% has the highest catalytic hydrogen production activity, and its hydrogen production rate is 293 μmol h?1 g?1, which is more than 3 times that of sample C. After 4 cycles of photocatalytic experiments, the photocatalytic activity is still stable, and the XRD diffraction peak does not appear obvious shift, which provides a new way for the design and preparation of efficient and stable photocatalytic materials.
Ulu Okudur F.Mylavarapu S.K.De Sloovere D.Joos B....
12页
查看更多>>摘要：LiNi0.5Mn1.5 O4-δ (LNMO) is a potential candidate for high voltage Co-free cathodes in lithium-ion batteries. In this study, pre-calcination temperature, time, and oven type are showcased as important parameters influencing the particle size and morphology of the LNMO powder synthesized from the aqueous citric acid-acetates-NH3 based method. These parameters determine the amount of organic residues in the precursor powder. A superior initial discharge capacity and capacity retention are obtained by an optimum combination of the particle size and morphology for the Li|LNMO coin cells. Pre-calcination in a forced convection oven at 200 °C for 40 h results in a voluminous and foam-like LNMO precursor powder morphology with the lowest amount of organic residue, leading to a ~ 1–4 μm powder with well-defined facets. Applying 24 h pre-calcination at 170 °C in a natural convection oven results in large LNMO aggregates of ~ 70 μm. Ball-milling of the crystalline LNMO powder is effective to reduce the agglomeration and particle size but deteriorates the electrochemical performance. An initial discharge capacity of 121 mA h g-1 at 0.2 C and a capacity retention of 90% after 400 cycles at 2 C are obtained from the samples prepared by 40 h pre-calcination at 200 °C in a forced-convection oven.
查看更多>>摘要：Antibiotic pollutant as a toxic wastewater is a critical global issue for human and ecosystems. In this work, we introduce a high-performance CuI/FePO4 heterojunction nanocomposite for the elimination of amoxicillin antibiotic under simulated sunlight radiation. The hybrid CuI/FePO4 nanoparticles exhibited an energy gap of 3.03 eV and photodegradation efficiency of 90%, which were better than those of CuI and FePO4 nanostructures. The prominent photocatalytic removal activity of the CuI/FePO4 heterostructures depends on the ultrafine particles, elevated visible-light absorption, and impressive separation and negligible recombination rate of electron-hole pairs due to the generation of p-n heterojunctions. We also presented a photocatalytic degradation pathway utilizing radical quenching analysis, which is based on fundamental function of the ?OH and ?O2? radicals in the photocatalytic elimination of amoxicillin by CuI/FePO4 nanocomposite. These functional properties of the CuI/FePO4 can be beneficial for the development of future photocatalyst materials.
查看更多>>摘要：Designing high capacity, superior rate, satisfactory cycle stability as well as green, low cost, and earth abundant electrode materials is critical for sodium and potassium ion storage. Herein, the first example of synthesizing the heterostructure between WVO4 and V3Se4 embedded in carbon fiber (WVO4/V3Se4/CNFs) as a high capacity and stable anode for sodium (SIBs) and potassium-ion batteries (PIBs) is reported. The composite is skillfully constructing by electrospinning method followed with heat treatment, with the assistance of biomass algae (Chlorella) as adsorbent and reactor. Owing to the unique advantages of hybrid structure and carbon sheaths, the composite architecture demonstrates high reversible capacity, excellent rate properties, and long-term cyclic stability. For sodium storage, the WVO4/V3Se4/CNFs electrode exhibits a high reversible specific capacity of 446 mAh g?1 at 50 mA g?1 after 200 cycles as well as a promising long cycling stability with a high capacity of 137 mAh g?1 at 5 A g?1 even over 25,000 cycles. More importantly, it also delivers high reversible capacity and good rate capability for potassium storage. This work opens up new way for developing satisfied metal oxide anode materials for SIBs and PIBs.
查看更多>>摘要：The development of CeO2-based nanomaterials for catalysis has seen considerable growth in the past decade, resulting of a combination of robust synthesis methods and its facile generation and regeneration of oxygen vacancy defects. Among its applications is the water-gas shift reaction (WGSR), used for purifying H2 from steam-reforming sources, where CeO2 combined with noble metal nanoparticles such as Cu, Au and Pt can present higher catalytical activity when compared to typical Fe-based or Cu/ZnO catalysts. In this work we designed a material for the catalysis of the WGSR seeking to address issues commonly observed for CeO2-Au catalysts: the optimization of the Au nanoparticle (AuNP) size and its maintenance by preventing sintering during catalysis, as well as preventing the formation of undesired side products such as CH4 and CH3OH. Our strategy was to combine a well-known, facile and robust hydrothermal synthesis to obtain CeO2 porous nanorods, and then further expand the native pore structure via a simple acid lixiviation strategy to better accommodate Au nanoparticles. To prevent side product formation, we coated the CeO2 nanorods with ZnO via metalorganic impregnation-decomposition prior to AuNP deposition, based on its reported ability to prevent methanation. While the formation of side products was prevented both with and without ZnO, we observed that ZnO promoted control over the growth of AuNP, resulting in smaller nanoparticles of 1.8 nm when compared to the 2.5 nm obtained without ZnO, and also prevented their sintering during WGSR catalytical tests, granting the material stable catalytic activity even at higher temperatures of 400 and 450 °C.
NSTL
Elsevier