查看更多>>摘要：? 2022 Elsevier B.V.Due to its excellent electrochemical properties, MoO3 is considered to be a promising electrode material in the field of energy storage, but it still suffers low electronic conductivity and serious aggregation. Herein, the partially expanded graphite paper (EGP) with a three-dimensional porous structure is synthesized by a cathodic electrochemical exfoliation, serving as a conductive substrate for the in-situ growth of MoO3 nanobelts via a simple hydrothermal method. The self-supporting MoO3/EGP composite material directly used as the electrode material of the supercapacitor, shows a high specific capacitance of 7.1 F cm?2 at 1 mA cm?2. In addition, the assembled symmetrical supercapacitor by using MoO3/EGP as electrodes offers an energy density of 0.77 mWh cm?2 at a power density of 2.41 mW cm?2 and the capacitance retention is 84.1% after 5000 cycles at 10 mA cm?2, indicating the excellent cyclic stability. The remarkable electrochemical performance of MoO3/EGP is attributed to the self-supporting porous structure of EGP with high electronic conductivity, which not only effectively prevents the aggregation of MoO3 nanobelts but also promotes the transfer kinetics of ion and electron.
查看更多>>摘要：? 2022 Elsevier B.V.We have deposited silicon and nitrogen doped diamond-like carbon (Si–N–DLC) films via plasma-enhanced chemical vapor deposition using H2 as a dilution gas and investigated the annealing effects on their structure, chemical bonding, and mechanical, optical, and electrical properties. The internal stress decreased with increasing annealing temperature, which increased the critical load. For the Si–N–DLC films annealed at 347–490 °C, sp2 C clustering was almost suppressed, and the amount of bound hydrogen increased. The optical bandgap of the Si–N–DLC films changed little even at 490 °C. Si–N–DLC/p-type Si heterojunctions annealed at 270 °C and 347 °C provided higher rectification ratios than heterojunctions annealed at different temperatures. The improvement in the current-voltage characteristics of these heterojunctions was probably due to the reduction of defects in the Si–N–DLC films by the annealing.
查看更多>>摘要：? 2022 Elsevier B.V.Graphene functionalization offers the opportunity to modify the chemical-physical properties of graphene, therefore broadening the variety of its possible applications. In this work, single- and few-layers graphene as well as highly oriented pyrolytic graphite (HOPG) were functionalized with perfluoropolyether (PFPE) chains via a peroxide decomposition and radical reaction. Samples were prepared using different amounts of PFPE peroxide and the effects of the treatment were studied through Raman spectroscopy, grazing angle Fourier-transform Infrared spectroscopy (GA-FTIR), X-ray Photoelectron Spectroscopy (XPS) and water contact angle measurements. A coherent trend of F[sbnd]C bonds with increasing amount of peroxidic precursor was detected, attacking the sp2 reactive sites of the grains of graphene itself and generating new sp3 hybridizations. The perfluorinated chains were found to give hydrophobic properties to graphenic layers, demonstrating the functionalization route as an easy and universal strategy for the preparation of hydrophobic graphenic substrates.
查看更多>>摘要：? 2022 Elsevier B.V.Diamond has attracted increasing attention because it has high thermal conductive. Here, a freestanding diamond thermal conductive film with a diameter of about 7 in. and an average thickness of 1.54 mm was prepared by DC arc plasma jet CVD with multi-stage magnetic fields. Specifically, the thickness uniformity was ensured by adding the magnetic field during the deposition of the freestanding diamond film. The morphology, structure and thermal conductivity of the diamond film were studied. The results showed that the expansion area of the DC arc plasma approached the surface of the substrate increasing duo to add the bottom magnetic field. Structural characterization revealed that the grain of the diamond film in the arc main were coarse, affected by the shape of DC arc plasma, while in the arc center and edge were fine. The main orientation of polycrystalline structure of the diamond film was the crystalline plane of (220). The Raman peaks of diamond film in different areas moved to a higher wavelength, indicating the existence of compressive stress inside the diamond film. The coarse columnar grain and a few grain boundaries were in the arc main. Therefore, the average value of the thermal conductivity (k⊥) of diamond film measured in the arc main was 1728.9 ± 4.9 W/(m·k). Meanwhile, the thermal conductivity of the arc center and edge area was lower than that of the arc main.
查看更多>>摘要：? 2022 Elsevier B.V.High-performance energy storage devices are in increasing demand for the rapid development of social economy, among which supercapacitors stand out due to their high power density and long cycle life. Here, carbonized cellulose nanofibrils were used to form porous carbon aerogels. And nitrogen from urea was doped in the carbon aerogels to enhance the chemisorption ability and wettability of the surface of carbon materials. Afterwards, manganese oxide/nitrogen-doped carbon aerogels were fabricated through a simple hydrothermal reaction. The composites with a 1:40 mass ratio of carbon aerogels: urea (40-NCMn) showed a maximum specific capacitance of 275.5 F g?1 at 1 A g?1 and an acceptable rate performance of 65.4% when the current density increased 10 times. Using 40-NCMn for positive electrode and activated carbon (AC) for negative electrode, an asymmetric supercapacitor was assembled. It delivered a maximum energy density of 23.3 W h kg?1 and a power density of 600 W kg?1 at 0.5 A g?1. After 3000 cycles at 5 A g?1, it could retain 99.2% of the initial capacitance, implying the manganese oxide/nitrogen-doped carbon aerogel a promising material for supercapacitor electrodes.
查看更多>>摘要：? 2022 Elsevier B.V.Carbon nanotubes have considerable potential for many applications due to their unique physical and chemical properties. In this work, Multiwalled Carbon Nanotubes (MWCNT's) were synthesized by chemical vapor deposition and functionalized with molybdenum disulfide (MoS2) nanoparticles. The obtained nanostructures were characterized by SEM, TEM, Raman, XRD, XPS and TGA. Hybrid nanostructures of MWCNT's/MoS2 with stable MoS2 layer thickness of ~2 nm was obtained. The functionalized nanotubes showed variations in crystal structure, chemical composition, and thermal response with respect to the uncoated ones, so these structures are expected to have potential use in diverse engineering fields.
查看更多>>摘要：? 2021The hierarchically porous hollow?carbon spheres (HPHCSs) are synthesized by activating the hollow?carbon spheres (HCSs) derived from the template-directing method using SiO2 spheres and waste tire pyrolysis oil (WTPO) as templates and carbon precursor, respectively. The developed template-directing coupled with post-activation methodology can not only adjust the pore structure of HPHCSs, but also can not destroy the hollow-sphere-like micromorphology. HPHCSs with a relative-intact hollow sphere microarchitecture and abundant micro-mesoporous structure possess the outstanding hydrophilcity and electrical conductivity. As the capacitive energy-storage electrode, HPHCSs electrode presents excellent rate capability, high capacitance retention and good durability in aqueous and organic electrolytes, exhibiting a good compatibility to different kind of electrolyte ions. Besides, the increased ratio of IR drop of HPHCSs electrode is relatively small among the contrast samples possessing different pore structures with the decrease of the test temperature, exhibiting its exceptional low-temperature performance. The favorable combination of template-directing and post-activation is able to realize the controllability of the pore structure of HPHCSs electrode with high capacitive storage behavior. Furthermore, this work also provides a valuable strategy for the preparation of electrode materials with high capacitive energy-storage ability through the high value-added utilization of WTPO.
查看更多>>摘要：? 2022 Elsevier B.V.New magnetically separable BiFeO3/CdS/rGO heterostructures were synthesized by a facile hydrothermal method. The photodegradation processes of two textile dyes, methylene blue (MB) and methyl orange (MO), in the presence of BiFeO3/CdS/rGO heterostructures using visible light irradiation were studied. The effects of three experimental parameters including solution pH, initial dye concentration, and the catalyst dose on the removal of dyes were investigated. The optimized photocatalyst, i.e. BiFeO3/CdS(9)/rGO(4%) composite shows 92% photodegradation of MB and 89% photodegradation of MO after 90 min of visible light illumination, which were found to be about 4.5 times that of pure BiFeO3. The hybridisation of BiFeO3 with CdS can significantly inhibit the recombination of electron-hole pairs in the BiFeO3/CdS/rGO composites and the presence of rGO sheets can reduce electron-hole pairs recombination by acting as electron acceptor and electron transporter. Furthermore, the sheets of rGO can delay aggregation of nanoparticles. No obvious catalytic activity decrement can be seen after five photodegradation processes, that show the high structural stability of BiFeO3/CdS/rGO. In addition, a possible mechanism for the photocatalytic degradation process under visible-light illumination was proposed.
查看更多>>摘要：? 2022 Elsevier B.V.Raman spectroscopy has contributed to many fields of materials science, for example, in studies addressing Diamond-Like Carbon coatings. In the literature, discussions have arisen due to the various interpretations of Raman spectra and some studies have not recommended using it to measure sp2 and sp3 hybridization contents. This article addresses the deconvolution process in Raman spectra, manipulating the Raman shift interval, the presence of Savitzky-Golay smoothing and the appearance of additional bands. X-ray photoelectron spectroscopy was used to quantify the sp2 and sp3 contents, which are discussed below in relation to the ID/IG ratio and the prediction of the amorphization trajectory of graphite. In an attempt to find a relationship between these characterization techniques, a polynomial equation was developed from thirty-three experimental results researched in the literature. The results indicated a coating belonging to the a-C:H class containing 18% of sp3. The relationship between the spectroscopies was complementary and the graphite amorphization trajectory was assertive. The coefficient of determination and the standard deviation proved to be useful parameters for selecting the representative spectrum of the coating. Neglecting or not the appearance of an additional band can provide modifications to the ID/IG ratio at the level of 52%. Representative results of the ID/IG ratio indicated the hypothesis of considering the intensity of the bands only as a function of height. The sp3 content predicted by the equation was maximized to any selected ID/IG value when the G Band was centered at approximately 1559 cm?1. It was observed that the equation can be used qualitatively with less errors in conditions where the deconvolutions present parameters similar to the experimental results whose sp3 content is between 20% and 39.9%.
Soltan A.El-Sherbeny E.F.Abdel-Messih M.F.Ahmed M.A....
10页
查看更多>>摘要：? 2022 Elsevier B.V.Herein, an effective S-scheme heterojunctions were fabricated with ultrasonic aspects for effective decomposition of fluorescein dye and evolution of green hydrogen gas. Mesoporous pristine titania nanoparticles with anatase phase structure and 156 m2/g surface area were synthesized by sol-gel mechanism using pluronic solution as templating agent, however, g-C3N4 sheets generated by thermal treatment of urea at 515 °C. The a-synthesized nanocomposites embedded various compositions of g-C3N4 (1?10) wt% were synthesized by ultrasonic pathway. The properties of the specimens were recorded by HRTEM, XRD, DRS, N2-surface area measurement, PL and XPS. The experimental results reveal the noticeably reduction in sample crystallinity and intensity of PL peak with introduction of 8 wt% g-C3N4 supporting the efficient charge carriers separation. The sonicated heterojunction with 8 wt% g-C3N4 is account for decomposition of 94% of fluorescein anionic dye and production of hydrogen gas with rate 4.9 mmolg?1 h?1 which is eleven fold greater than that of pristine TiO2. The strong redox power of this heterojunction is ascribed to step S-scheme mechanism which promote the charge transportation and enhance the separation efficiency of the charge carriers. This charge migration route is established by trapping scavengers and PL experiments. The photocatalytic property of the optimum sample is still with exceptional reactivity for decomposition of anionic dye pollutant and evolution of hydrogen gas after six consecutive cycles.
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Elsevier