查看更多>>摘要：The development of fine-tuned non-platinum group metals and their derivatives, which are high-performance, economical, and stable electrocatalysts used for the oxygen reduction reaction (ORR), is critical for the large-scale deployment of fuel cells and metal-air batteries. This study presents a novel strategy that uses vitamin B12 (VB) as a bioinspired resource for the ORR; VB was modified using metal and non-metal incorporation to boost the efficiency of the ORR. The chemical structure of VB on a graphene substrate was tailored by synergistically incorporating both iron and sulfur upon pyrolysis, yielding various active sites based on Fe-(N,S)-C and Co-(N,S)-C. The resultant catalysts, termed Fe-SVB/GR, exhibit prominent electrocatalytic performance for the ORR via a favorable 4e(- )reaction pathway. The onset and half-wave potentials of the optimized electrocatalyst were 0.90 and 0.74 V vs. reversible hydrogen electrode, respectively, which are comparable or better than those previously reported for non-platinum group catalysts. The Fe-SVB/GR electrocatalyst developed in this study outperformed a commercial Pt/C catalyst in terms of its durability and methanol tolerance. Therefore, this study introduced a novel strategy to produce bio-derived materials as non-platinum group electrocatalysts used as efficient cathode materials in energy-conversion devices. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Pure and Al-doped ZnO nanoparticles are synthesized by hydrothermal technique. The structural and phase analysis of the prepared powder is attained by X-rays diffraction and concluded that Al doping increases the crystallite size and causes compressive stress formation in the material network. Fourier transforms infrared spectroscopy reveals the formation of the aluminum oxide phase but with a tiny size that XRD cannot detect. The impact of different ratios of Al doping influence on powder morphology is carried out using transmission electron microscopy, and the optical bandgap of all synthesized products with the doping ratio is investigated by UV-visible reflectance. The electronic defects localized in the material band-gap are studied via photoluminescence spectroscopy and inferred that Al doping alters significantly the electronic defects nature present in the band-gap. In this study, the intrinsic oxygen vacancies are removed by replacing Zn when Al atoms are introduced into the material network. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Hydrogenation properties of Mg2-xPrxNi4 (x = 1.0, 1.2 and 1.4) and their structural degradation (amorphization) upon hydrogenation have been investigated using in-situ X-ray diffraction. In Mg1.0Pr1.0Ni4, the crystalline phase was stable up to a temperature of 573 K under 3 MPa of hydrogen pressure and amorphization did not take place. Mg0.6Pr1.4Ni4 was directly transformed to an amorphous hydride, Mg0.6Pr1.4Ni4H~7.2, while Mg0.8Pr1.2Ni4 transformed to amorphous Mg0.8Pr1.2Ni4H~6 through the formation of Mg0.8Pr1.2Ni4H~4 having an orthorhombic structure. While reversible hydrogen absorption and desorption was observed in the first plateau region between Mg0.8Pr1.2Ni4 and Mg0.8Pr1.2Ni4H~4. First principles calculation indicate that the elastic modulus and bulk modulus decreased with increase of the Pr content and hydrogen content in Mg2-xPrxNi4 suggesting that decrease of bulk modulus induce amorphization upon hydrogen absorption. These results clearly indicate that the hydrogenation properties, the stability of crystalline hydride and amorphization behavior strongly depend on the chemical composition of Mg2-xPrxNi4 and their hydrogen content. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Nickel and cobalt phosphates as a kind of low-cost inorganic materials are promising electroactive mate-rials. The structure stability and good dispersibility of micro-spherical materials make them popular in the energy storage field. Therefore, the fabrications of Ni-Co phosphate microspheres with some facile and cost-effective methods have attracted lots of attentions. In this work, we present one-step growth of Ni2Co (PO4)(2 )microspheres using urea as pH regulator. Urea decomposes into NH3 and CO2 during the hydro-thermal reaction process, resulting in the precipitation of Ni-Co phosphates. The as-prepared Ni2Co (PO4)(2) microspheres exhibit uniform and well-dispersed spherical morphology. Compared with traditional Ni2Co (PO4)(2 & nbsp;) particles, Ni2Co (PO4)(2) microspheres exhibit larger electrochemical specific surface area and smaller resistance of electrons/ions transfer. The specific capacity of Ni2Co (PO4)(2 & nbsp;) microspheres reaches as high as 153 mAh g(-1 )at a current density of 1 A g(-1), which is 1.59 times higher than that of traditional Ni2Co (PO4)(2) particles. In addition, this facile one-step synthetic method can be applied to fabricate series of Ni-Co phosphates with different Ni/Co atomic ratios. This work provides a facile synthetic method of fabricating Ni-Co phosphate materials, which has potential applications in large-scale manufacture. (C)& nbsp;& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Developing highly efficient strategy for fabrication of bifunctional electrocatalysts for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) is a challenging topic. In this work, we reported the in situ synthesis of N, S co-doped carbon nanorod material (N/S-C) by the facile template-free, one-step pyrolysis approach using N and S co-containing poly(ionic liquid) (PIL) of p[BZ][HSO4](2) as precursor derived from the simple chemically oxidative polymerization of ionic liquid benzidine sulfate ([BZ][HSO4](2)) in the presence of ammonium persulfate as oxidant. The N/S-C catalysts have nanorod morphology with hierarchical porous architectures of abundant micropores and well-defined mesopores featuring high specific surface areas. The ORR performance of N/S-C-800 is extremely satisfactory in alkaline media with the onset and half-potentials of 0.985 V and 0.857 V (vs. RHE), respectively, which are comparable to that of commercial Pt/C (0.990 V and 0.852 V vs. RHE). It also delivers the favorable long-term stability and methanol tolerance, significantly outperforming commercial Pt/C. Moreover, the N/S-C-800 was served as a support for Pt nanoparticles, showing the higher methanol electrooxidation activity (806.74 mA mg(Pt)(-1)) compared with commercial Pt/C (356.32 mA mg(Pt)(-1)). These results show an effective route to design the attractive metal-free carbon-based electrocatalysts for direct methanol fuel cells. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The molybdenum disulfide (MoS2) and ZnO composite system have reported as micro-nano photonic crystals in integrated optics. Based on interface engineering, their tunable nonlinear absorption (NLA) and photoelectric characteristics offer a flexible design strategies for saturation absorber and optical limiters. Nevertheless, the mechanism leading to the tunable NLA behavior has not been clearly elucidated, which were attribute to complex charge transfers and carrier regulation characteristics. In this article, MoS2/ZnO heterostructures with excellent nonlinear properties composed of ZnO nanorods (NRs) wrapped with MoS2 nanosheets were prepared by magnetron sputtering (MS) synthesis of MoS2 on highly stacked ZnO NRs. The MoS2/ZnO heterostructures exhibit an interesting brush-like morphology with abundant heterointerfaces base on optimizing sputtering time and temperature, which was beneficial to provide efficient charge transfer pathways. Due to the uneven distribution of the lowest nucleation free energy, MoS2 nanosheets possess a hybrid mode of parallel (C//) and perpendicular orientations (C) on surface of ZnO NRs, which tends to form the bending and vertical growth of layered MoS2 nanosheets. From electron-photon coupling effect, MoS2 nanosheets, ZnO NRs and MoS2/ZnO heterostructures possess favorable saturation absorption (SA), reverse saturation absorption (RSA) and coexisting absorption behavior, respectively. In addition, a changeover from RSA to SA could be realized in MoS2/ZnO heterostructures by increasing the sputtering time. The NLA coefficient of MoS2/ZnO heterostructures are in the order of 10-10 cm/W, which are about 2 times larger than those of the ZnO NRs. Thus, the MoS2/ZnO heterostructures with excellent NLA properties will be promising candidates in optoelectronic devices.(C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Group 5 metals and their alloys are expected to become a new generation of hydrogen-permeable membranes to replace commercial palladium-based alloys. Recently, we synthesized a new Nb-Hf-Co alloy hydrogen permeation membrane, and the Nb30Hf35Co35 alloy has good mechanical properties and permeability. However, the development of alloys with higher hydrogen permeability is a challenge for these Nb-based membranes. To this end, Nb30Hf35Co35-xFex (0 < x < 35) alloys were developed and their microstructure and hydrogen permeation properties were systematically studied by means of SEM, XRD and TEM, among other techniques. When the Fe content is lower than 10 at%, Nb30Hf35Co35-xFex alloys are composed completely of a eutectic structure. With increasing Fe content, changes in microstructure and constituent phases are observed. In particular, a large amount of new impurity phases (Hf2Fe, Fe2Nb, FeNb and Fe0.7Hf0.3) is formed when the Fe content in the alloys is higher than 20 at%. With these changes, the hydrogen permeability (Phi) of these alloys first increases and then decreases. The Nb30Hf35Co30Fe5 alloy exhibits the largest hydrogen permeability at 673 K, at 3.41 x 10(-8) mol H-2 m(-1) s(-1) Pa-0.5, or 2.2 times that of palladium metal under the same conditions. The increase in the Phi value is mainly due to the increase in hydrogen diffusion coefficient (K) rather than hydrogen solubility (D). The present work demonstrates that Nb-Hf-Co-Fe quaternary alloys are expected to become a more promising hydrogen permeable material compared with traditional ternary alloys. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Electrochemical deposition of rhenium-iron alloy from water-in-salt electrolytes containing a super-high concentration of lithium chloride is investigated. Different techniques, including cyclic voltammetry, chronoamperometry, X-ray fluorescence, scanning electron microscope, X-Ray diffraction, and electrical measurements at cryogenic temperature are used to characterize the alloy electrochemical system and the deposited films. The catalytic effect of iron on rhenium deposition is observed, where the deposition rate of rhenium significantly increases in the presence of iron. Alloying rhenium with iron significantly inhibits the recrystallization of the as-deposited amorphous films. At the same time, it also greatly suppresses the superconductivity of rhenium.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The anchor of functional materials on metal-organic frameworks (MOFs) nanosheets to precisely construct fascinated heterostructures for electrocatalysis is highly promising but challenging owing to the different interfacial thermodynamics and nucleation kinetics. In this work, we design and synthesize ultrafine metal oxides nanoparticles (NPs) homogenously distributed on cobalt-based MOF (Co-MOF) nanosheets for oxygen evolution reaction (OER) by a facile solvothermal reaction and subsequent partially controlled pyrolysis. The ultrafine Co3O4 NPs with a particle size of about 1.5 nm can be obtained from the dispersed elemental Co in Co-MOF and uniformly generated on the surface of the MOF, which is crucial for the for-mation of the unique heterostructure. The well-designed Co-MOF-350 exhibits an efficient electrocatalytic activity with a low overpotential of 239 mV at a current density of 10 mA cm(-2) and a small Tafel slope of 63 mV dec(-1), and an outstanding catalytic stability for OER, much superior to the pure Co-MOF and Co3O4 electrocatalyst. The intriguing OER performance mainly originates from the desirable combination of the abundant active sites, the extended electron transport channel between ultrafine metal oxides and Co-MOF nanosheets. More importantly, the work will help to design novel heteroarchitectured MOFs-based composites as efficient and robust electrocatalysts for practical applications. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In the present work, effect of heat treatment on microstructure and corrosion behaviour of a high Mo containing alpha + beta titanium alloy (Ti-6Al-1 V-4Mo-0.1Si) has been investigated. Heat treatment results in the formation of wide variety of microstructure depending on the heating temperature (below or above the beta transus) and cooling conditions. Martensite was observed after oil quenching (OQ), Widmanstatten alpha (alpha(WS)) + beta after air cooling (AC) and lamellar alpha (alpha(L)) + beta after furnace cooling (FC). The corrosion behaviour of the heat-treated specimens were studied in simulated body fluid (SBF) at 37 & nbsp;C using open circuit potential time (OCP), electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization tests. X-ray photoelectron spectroscopy (XPS) was used to investigate the chemical nature of the corroded surfaces. The study revealed that, in general, OQed samples had increased corrosion resistance than the ACed and FCed samples. XPS confirmed the presence of TiO2 and Al2O3 on the corroded sample. The alloy's improved corrosion resistance was attributed to stable inert TiO2 film. Samples heat treated at 950 & nbsp;C were found to have better corrosion resistance in general.(C) 2022 Elsevier B.V. All rights reserved.
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