查看更多>>摘要:? 2022 Elsevier B.V.We report the structural, mechanical and physical properties of the (MoReRu)(1?2x)∕3(PdPt)x and carbon-added (MoReRu)(1?2x)∕3(PdPt)xCy HEAs over wide ranges of x and y values. The former ones are found to crystallize in a hexagonal close-packed (hcp) structure for 0.042 ≤ x ≤ 0.167 and a face-centered cubic (fcc) structure for x = 0.333. For all the hcp compositions, a transformation to the fcc structure is induced by adding a certain range of carbon, whose width is narrowed with increasing x. Both the hcp (MoReRu)(1?2x)∕3(PdPt)x and transformed fcc (MoReRu)(1?2x)∕3(PdPt)xCy HEAs display superconductivity with Tc ranging from 1.75 to 8.17 K and mainly governed by the electron-phonon coupling strength. Furthermore, we show that the trends in Tc and microhardness of these HEAs correlate well the valence electron concentration (VEC), and that the structural transformation is likely due to the combined effects of VEC, lattice distortion and mixing entropy. Our results suggest that the structural transformation due to carbon addition is general for multicomponent alloys with an hcp structure.
查看更多>>摘要:? 2022 Elsevier B.V.The CdIn2S4/In2S3/CaIn2S4 composites were successfully prepared by an extremely simple programmed temperature hydrothermal method, which present a spinyball-like structure with a micro-sphere diameter of about 2.5–3 μm. X-ray diffraction analysis (XRD) results show that CaIn2S4 and CdIn2S4 exist in the form of cubic phase, and In2S3 exists in the form of cubic β-In2S3 in the composites. By discussing the relationship between the change of strain gravity and the change of cell parameters of CaIn2S4 after compounding In2S3 and CaIn2S4, the effects of crystal lattice change, crystal face growth and inhibition on the photocatalytic activity were studied. Meanwhile, through the photoluminescence spectra (PL), electrochemical impedance spectra (EIS), and transient photocurrent response analysis, the recombination of CaIn2S4, In2S3, and CdIn2S4 can accelerate the charge transfer and inhibit the recombination of electron–hole pairs in the CdIn2S4/In2S3/CaIn2S4 composites, so that higher photocatalytic performance can be obtained. Using methyl orange (MO) as the degradation object, the photo-degradation properties of the as-composites were studied and compared, and the results show that spinyball-like In2S3/CaIn2S4 and CdIn2S4/In2S3/CaIn2S4 exhibit high photocatalytic activity for degradation of MO under visible light and simulated sunlight, respectively. Furthermore, with Pt loaded as a co-catalyst, in Na2S aqueous solution, the hydrogen production rate of CdIn2S4/In2S3/CaIn2S4 photocatalysts is 74.9 μmol·g?1 (8 h), which is 8 times that of the commercially available TiO2. Furthermore, based on the results of the trapping experiment of CdIn2S4/In2S3/CaIn2S4, a possible photocatalytic mechanism was proposed, and the effect of multi-path photo-generated electron migration in the photocatalytic process was explained.
查看更多>>摘要:? 2022 Elsevier B.V.High-capacity cathode materials of metal fluorides generally undergo low conductivities and sluggish kinetics derived from a multielectron-transfer conversion reaction mechanism, which severely hinder the cycling stability and rate performance towards their commercialization. Herein, a flexible free-standing FeF3/chitosan pyrolytic carbon/reduced graphene oxide (FeF3/C/RGO) film as an additive-free cathode was designed and prepared by a facile hydrothermal strategy followed by sequential freeze-drying, thermal reduction and fluorination post-treatments. The ultrafine FeF3 nanoparticles (NPs, ~30 nm) are confined within highly ordered RGO film, effectively reducing the Li+ diffusion pathway while the RGO sheets act as a matrix to restrict the complicated interlamination reaction (Fe3+?Fe2+?Fe) between adjacent interlayers with the spacing of ~30 nm. Benefiting from the free-standing structure, the FeF3/C/RGO film can achieve an admirable capacity up to 220 mAh g–1 over 200 cycles at 100 mA g–1, showing great potential for wearable and flexible electronic devices.
查看更多>>摘要:? 2022 Elsevier B.V.The development of an efficient and robust photocatalyst is of great importance for the effective treatment of toxic pollutants. In this study, novel Ag3PO4 microspheres were decorated on the nanorod embedded flower-like BiOBr designed for the effective photodegradation of methyl orange (MO) and malachite green (MG) dyes. The synthesized particle was characterized to understand the structural and morphological features using HR-TEM, XRD, SEM, PL, ESR, FT-IR, XPS, EIS and N2 adsorption and desorption. The degradation rate constants for MG (0.0132 min?1) were 3.47 and 3.14 times greater than BiOBr and Ag3PO4. Similarly, the rate constants for MO degradation (0.0151 min?1) are 3.87 and 3.97 times greater than BiOBr and Ag3PO4. The effect of initial MG and MO dye concentration, reaction pH, nanocomposite (NC) concentration was investigated. The NC exhibited excellent visible light photodegradation of 99.8% for MO and 93.4% for MG dyes at 180 min and 200 min respectively. A S-scheme heterojunction were proposed as the possible mechanism for the photodegradation of the dyes. The prepared photocatalyst exhibits excellent structural stability and reusability. The toxicity of the intermediates were predicted by the ecotoxicity analysis using ECOSAR software where the end products were less toxic than parent MG and MO. The degradation pathway were elucidated to predict the possible intermediates and to confirm the complete mineralization of the compound using GC-MS analysis. The proposed study can be implemented for practical application for the degradation of organic pollutants present in the water bodies.
查看更多>>摘要:? 2022 Elsevier B.V.Nickel sulfide (Ni3S2) is a potential anode candidate for sodium-ion batteries due to its abundance, stable structure, and low price. However, its rate and cycling performance require improvement for practical applications. This paper reports the facile synthesis of a unique composite consisting of an interconnected nickel/nickel sulfide nanocomposite (Ni/Ni3S2) by heating a mixture of nickel nanopowder and sulfur. The interconnected nanostructured backbone of the nickel nanoparticles facilitates continuous electron pathways in the composite, while the embedded nanosized nickel sulfide domain reduces the diffusion length and improves reaction kinetics. The Ni/Ni3S2 electrode exhibits excellent rate performance in dimethyl ether (DME) electrolyte, with a current density of 80 A g?1 and capacity of 151 mA h g?1; it also exhibits stable, ultralong cycling performance. Synergism between the unique nanostructure of the composite and the low-viscosity DME electrolyte may be responsible for the extraordinary cycling and rate performance. A full cell with a Na3V2(PO4)3 (NVP) electrode delivers a capacity of 111 mA h g?1 at 100 A g?1; moreover, the Ni/Ni3S2–NVP full cell retains 55% of its capacity after 5000 cycles at 20 A g?1. The developed strategy, which uses a conductive metal-nanoparticle/metal-sulfide nanocomposite, is applicable to other systems and is scalable for practical applications.
查看更多>>摘要:? 2022 Elsevier B.V.Metal sulfides still face significant challenges in terms of large volume expansion and poor conductivity as anodes for lithium ion batteries. For the past few years, many researches have shown that the preparation of the composite of metal sulfide and heteroatom doped graphitized carbon with high conductivity has become an effective method to improve its lithium storage performance. In this work, FeS2 @N/S-C composite was successfully synthesized through homogeneously embedding FeS2 nanoparticles into N and S co-doped biomass-derived graphitized carbon, by using Lonicerae flos as carbon source and bio-template. It is worth noting that the introduction of Fe ions effectively enhances the graphitization degree of the N, S co-doped carbon material derived from Lonicerae flos, thus improves the conductivity and stability of the composite. At the same time, the uniform coating of highly conductive carbon effectively inhibits the growth and agglomeration of FeS2 nanoparticles during the process of charge and discharge. Therefore, the FeS2 @N/S-C electrode exhibits large lithium storage capacity, delivers a high capacity of 1259 mA h g?1 at 0.1 A g?1 after 100 cycles, and excellent long-term cycle performance at 1.0 A g?1 (528 mA h g?1 after 1000 cycles). These results indicate that the as-prepared FeS2 @N/S-C composite is a promising anode.
查看更多>>摘要:? 2022 Elsevier B.V.Polyoxometalates (POMs) are known for their unique structural properties and have attracted widespread attention in the field of storage devices, energy conversion materials, catalysis, electronics and molecular sensing. This article focuses on the anchoring of high nuclearity 16-cobalt(II)-containing POM that is, Na30.5K1.5[{Co4(OH)3PO4}4(A-α-GeW9O34)4]?116H2O (Co16-GeW9) using 3-aminopropyl triethoxysilane (APTS) as chemical linker over nickel foam (NiF) and is tested as electrocatalyst for water oxidation studies. The fabricated POM-based electrode (Co16-GeW9@NiF) has been characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. Co16-GeW9 @NiF has been tested for its electrocatalytic water oxidation activity in 1 M KOH (pH 14) and sodium phosphate buffer (pH 7) with NaNO3 as a supporting electrolyte. The catalyst exhibited excellent electrocatalytic oxygen evolution reaction (OER) activity with overpotential of 370 mV at 10 mA/cm2 and a Tafel slope of 84 mV/dec in 1 M KOH, while overpotential of 530 mV at 10 mA/cm2 and a Tafel slope of 153 mV/dec in sodium phosphate buffer. The immobilization of POM over NiF could generate a way for developing efficient electrocatalysts for water oxidation in both neutral and basic pH.
查看更多>>摘要:? 2022 Elsevier B.V.Micro-arc oxidation (MAO) is an environmentally friendly and effective way to generate a dense and homogeneous coating with high corrosion resistance on magnesium alloys. However, the inherent porous structure of MAO coating can lead to the invasion of corrosive media to the substrate and thus reduce its corrosion resistance. Herein, we reported a novel one-step in situ growth of a pore-sealing coating on MAO-coated AZ31B alloy by hydrothermal treatment in Na3PO4 solution. The surface morphology, chemical composition and growth process of the pore-sealing coating were thoroughly studied by FESEM, XRD, FTIR and XPS. The micro-pores and micro-cracks of the MAO coating can be fully covered by the pore-sealing coating with spherical structure, which is mainly composed of Mg(OH)2 and Mg3(PO4)2. The corrosion resistance of the coatings prepared at different hydrothermal time was evaluated by electrochemical test and immersion test. Compared with the bare AZ31B substrate, the current density of the composite coating with hydrothermal treated for 18 h decreased by three orders of magnitude from 8.40 × 10?5 A/cm2 to 1.59 × 10?8 A/cm2, indicating a remarkable enhancement of the corrosion resistance. The MAO/Mg(OH)2/Mg3(PO4)2 composite coating shows high adhesive strength with the substrate, especially the outermost Mg3(PO4)2 layer with the inner Mg(OH)2 layer. In addition, the in situ growth and corrosion protection mechanisms of the pore-sealing composite coating are also proposed.
查看更多>>摘要:? 2022 Elsevier B.V.Preparation of carbonaceous anode with excellent electrochemical performance is important for the utilization of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, carbon powder was synthesized from CaCO3 and CaC2 in CaCl2-NaCl molten salt. The reaction mechanism was discussed in thermodynamics and kinetics. Microstructure of the carbon powder was systemically characterized. Electrochemical performance of the carbon powder was evaluated as anode materials of LIBs and SIBs. The results showed that molten salt can transfer the carbonization process from a solid-solid process to a liquid-solid process. The kinetic barrier of CaO layers on the raw materials was removed in molten salt. The products exhibited better lithium (reversible capacity of ~480 mAhg?1 after 200 cycles and reversible capacity of ~250 mAh·g?1 at 1000 mAg?1) and sodium (reversible capacity of ~290 mAhg?1 after 200 cycles and reversible capacity of ~180 mAh·g?1 at 5000 mA·g?1) storage performance than commercial graphite. This method was easy and efficient to recover more than 70 wt% of carbon in the raw materials within 15 min
查看更多>>摘要:? 2022 Elsevier B.V.Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) has been considered as the most attractive cathode material for lithium-ion batteries (LIBs). However, the fast capacity decay and poor rate performance limit its practical applications. Bulk doping and surface coating have been demonstrated as the most important and effective technologies for enhancing its electrochemical performance; nevertheless, overall performance still remains unsatisfactory. In this study, simple dual-modification strategy was proposed in which samarium (Sm) was both doped into and coated on NCM811 to provide inside and outside synergistic modification. This can comprehensively improve electrochemical performance of NCM811. X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical tests were used to discuss improvement mechanism. Results indicated that parts of Sm successfully enter crystal lattice, which increases interlayer spacing, stabilizes structure, and reduces Li+/Ni2+ mixing. Simultaneously, another part of Sm coated on surfaces in the form of oxide, prevents electrolyte corrosion and inhibits side reactions. With the optimum Sm content (0.5%), obtained NCM811 displayed the highest discharge specific capacity (184.2 mA h g?1 at 1 C), capacity retention (94.19% after 100 cycles at 1 C), and rate performance (152.2 mA h g?1 at 5 C). This study provides efficient approach to improve electrochemical performance of NCM811 as cathode material.