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Construction of hierarchical porous NiCo{sub 2}O{sub 4} films composed of nanowalls as cathode materials for high-performance supercapacitor
Graphical abstract: Hydrothermal-synthesized NiCo{sub 2}O{sub 4} mesowall films exhibit porous structure and high capacity as well as good cycling life for supercapacitor application. - Highlights: • Hierarchical porous NiCo{sub 2}O{sub 4} nanowall films are prepared by a hydrothermal method. • NiCo{sub 2}O{sub 4} nanowall films show excellent electrochemical performance. • Hierarchical porous film structure is favorable for fast ion/electron transfer. - Abstract: Hierarchical porous NiCo{sub 2}O{sub 4} films composed of nanowalls on nickel foam are synthesized via a facile hydrothermal method. Besides the mesoporous walls, the NiCo{sub 2}O{sub 4} nanowalls are interconnected with each other to form hierarchical porous structure. These unique porous structured films possess a high specific surface area. The supercapacitor performance of the hierarchical porous NiCo{sub 2}O{sub 4} film is fully characterized. A high capacity of 130 mA h g{sup −1} is achieved at 2 A g{sup −1} with 97% capacity maintained after 2,000 cycles. Importantly, 75.6% of capacity is retained when the current density changes from 3 A g{sup −1} to 36 A g{sup −1}. The superior electrochemical performance is mainly due to the unique hierarchical porous structure with large surface area as well as shorter diffusion length for ion and charge transport.
Construction of CQDs-Bi{sub 20}TiO{sub 32}/PAN electrospun fiber membranes and their photocatalytic activity for isoproturon degradation under visible light
Highlights: • The flexible fiber membranes were prepared by coaxial electrospinning technique. • CQDs-Bi{sub 20}TiO{sub 32} photocatalyst was uniformly fixed on the surfaces of PAN fibers. • The fiber membranes had high photocatalytic activity for degradation of isoproturon. • The composite fiber membranes exhibited good recyclability. - Abstract: The CQDs-Bi{sub 20}TiO{sub 32} photocatalysts exhibited high visible-light responsive photocatalytic activity. To achieve the cyclic utilization of CQDs-Bi{sub 20}TiO{sub 32}, the novel flexible CQDs-Bi{sub 20}TiO{sub 32}/PAN fiber membranes were prepared by a simple coaxial electrospinning technique. It was found that the CQDs-Bi{sub 20}TiO{sub 32} photocatalyst could be firmly and uniformly fixed on the surfaces of electrospun fibers and the composite fiber membranes possessed the hierarchical macro- and mesoporous structure. The loaded CQDs-Bi{sub 20}TiO{sub 32} endowed the composite fiber with an obvious photocatalytic activity for the degradation of the herbicide isoproturon under visible light irradiation. Among these samples, S3 at photocatalyst dosage 15 w/v% had the highest degradation efficiency for isoproturon. Meanwhile, the core-shell structured inorganic-organic hybrid fiber membranes have a significant advantage in the recyclability for photocatalyts. The flexible CQDs-Bi{sub 20}TiO{sub 32}/PAN electrospun fiber membranes would have potential applications in efficient removal of organic contaminants.
Remarkable enhancement of photocatalytic performance via constructing a novel Z-scheme KNbO{sub 3}/Bi{sub 2}O{sub 3} hybrid material
Highlights: • A series of KNbO{sub 3}/Bi{sub 2}O{sub 3} composite materials with different percentage of KNbO{sub 3} have been prepared by simple methods using Bismuth oxide, niobium pentoxide and potassium hydroxide as precursors. • The rate constants of the best photocatalyst (30 wt.% KNbO{sub 3}/Bi{sub 2}O{sub 3}) for the RhB and MO degradation are about 3.7 times and 4.1 times faster than those of pure Bi{sub 2}O{sub 3} and approximately 6.9 times and 7.1 times faster than those of pure KNbO{sub 3}, respectively. • The composite photocatalyst exhibits a good physical and chemical stability during the photocatalytic reaction process. • Results demonstrat that the migration of photogenerated carriers adopts a direct Z-scheme mechanism and ·O{sup 2−}, ·OH, and h{sup +} are the main reactive species in the photocatalytic process. - Abstract: KNbO{sub 3}/Bi{sub 2}O{sub 3} composite materials with different percentage of KNbO{sub 3} have been prepared by simple methods The structural and optical properties of the resulting samples are thoroughly characterized by XRD, UV–vis DRS, SEM, TEM, and N{sub 2}-sorption analysis. The photocatalytic activities of the as-prepared materials for the degradation of rhodamine B (RhB) and methyl orange (MO) are evaluated under UV-light irradiation. The results indicate that the optimal loading amount of KNbO{sub 3} is 30 wt.% (i. e., 30 wt.% KNbO{sub 3}/Bi{sub 2}O{sub 3}), The rate constants of which for the RhB and MO degradation are about 3.7 times and 4.1 times faster than those of pure Bi{sub 2}O{sub 3} and approximately 6.9 times and 7.1 times faster than those of pure KNbO{sub 3}, respectively. Based on a series of characterizations, it can be concluded that the migration of photogenerated carriers adopts a direct Z-scheme mechanism and ·O{sup 2−}, ·OH, and h{sup +} are the main reactive species in the photocatalytic reactions.
Construction of hybrid Ag2CO3/AgVO3 nanowires with enhanced visible light photocatalytic activity
Highlights: • Hybrid Ag{sub 2}CO{sub 3}/AgVO{sub 3} nanowires were successfully synthesized. • The as-prepared sample displayed highly enhanced photocatalytic activity. • Possible photocatalytic mechanism for RhB degradation was proposed. - Abstract: Visible light driven pollutant degradation by photocatalyst was one of most efficient and economical strategies for environmental application. The focus and challenge was to fabricate efficient artificial photocatalysts. In this work, hybrid Ag{sub 2}CO{sub 3}/AgVO{sub 3} nanowires were first reported to be successfully synthesized by the facile ion-exchange method. The as-prepared Ag{sub 2}CO{sub 3}/AgVO{sub 3} nanowires showed highly improved visible light photocatalytic activity for RhB degradation, and the optimized Ag{sub 2}CO{sub 3}/AgVO{sub 3}-40% photocatalyst exhibited the best photocatalytic activity, which is 3.6 times of pure Ag{sub 2}CO{sub 3} and 13.3 times of pure AgVO{sub 3} catalysts, mainly due to the formation of Ag nanoparticles and Ag{sub 2}CO{sub 3}/AgVO{sub 3} heterojunction for charge separation. The degradation of RhB solution was mainly attributed to direct hole oxidation, which was also confirmed by the active species trapping experiments. Finally, the possible visible light photocatalytic mechanism of Ag/Ag{sub 2}CO{sub 3}/AgVO{sub 3} composites for RhB degradation was proposed.
A construction of Ag-modified raspberry-like AgCl/Ag2WO4 with excellent visible-light photocatalytic property and stability
Highlights: • The Ag-modified raspberry-like AgCl/Ag{sub 2}WO{sub 4} photocatalysts were prepared by a facile solvent-free method. • Ag and AgCl were easily deposited on the Ag{sub 2}WO{sub 4} by one-step solid-sate reaction between Ag{sub 2}WO{sub 4} and HONH{sub 3}Cl. • The morphology of raspberry-like can facilitate the contact of dye molecules and composite photocatalysts. • The photocatalysts exhibit an effective separation of the photoinduced electron-hole pairs. • The photocatalysts show excellent photocatalytic activity and photo-stability under visible light irradiation. - Abstract: A novel multiphase photocatalyst of Ag-modified raspberry-like AgCl/Ag{sub 2}WO{sub 4} composite was successfully fabricated via a facile solvent-free reaction technique, in which the Ag and AgCl were subtlely generated from the one-step reaction between Ag{sub 2}WO{sub 4} particles and HONH{sub 3}Cl as reductant and chlorine source at room temperature. The as-obtained ternary Ag-modified raspberry-like AgCl/Ag{sub 2}WO{sub 4} composites can facilitate the contact of dye molecules and photocatalysts, exhibiting superior photocatalytic property and good recycling ability towards the decomposition of organic dye under the visible-light irradiation. The reductant addition amounts greatly affect the performance of Ag{sub 2}WO{sub 4} photocatalyst. The optimum composite ratio of Ag-modified AgCl/Ag{sub 2}WO{sub 4} samples show significant enhancement of visible-light photocatalytic activities and the degradation rate constant is about 16 times greater than that of pure Ag{sub 2}WO{sub 4}. The highly improved performance of Ag-modified raspberry-like AgCl/Ag{sub 2}WO{sub 4} structure can be ascribed to the surface plasma resonance (SPR) effects of metal Ag and the synergistic effect among composites, accordingly effectively promote the separation of photoinduced electron-hole pairs, widen the absorbance range in the visible light and increase surface area. The h{sup +} and ·OH degraded mechanism for the improved photocatalytic activity of Ag-modified AgCl/Ag{sub 2}WO{sub 4} is proposed based on radical-trapping experiments and ESR spectra records.
In situ construction of conjugated polymer P3HT coupled hierarchical ZnO composite with Z-scheme enhanced visible-light photocatalytic activity
Highlights: • P3HT@H-ZnO photocatalysts were fabricated via a two-step solution method. • The P3HT@H-ZnO composite. exhibited high photodegredation of RhB under visible-light. • Enhanced photocatalytic activity attributed to the closely contacted interface between P3HT and H-ZnO and the matched band gap structure. • The fabricated P3HT@H-ZnO composite follow a Z-scheme mechanism rather than type II heterojunction. - Abstract: Conjugated polymer P3HT coupled with hierarchical ZnO (H-ZnO) photocatalysts were fabricated by a two-step solution method with assembling P3HT nanoparticles on the surface of H-ZnO micro-flowers. Optical properties revealed that the fabricated H-ZnO micro-flowers were rich in defects. The as-prepared P3HT@H-ZnO composite exhibited higher photocatalytic activity than H-ZnO for photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. The enhanced photocatalytic activity was attributed to the strengthened visible light absorption and the closely contacted interface between P3HT and H-ZnO. Based on the reactive species trapping experiments and band gap structure analysis, it can be identified that the effective separation and transfer of the photo-induced electron-hole pairs within the P3HT@H-ZnO composite follow a Z-scheme mechanism rather than type II heterojunction. The present work will provide a new insight to design Z-scheme photocatalysts with enhanced photocatalytic performance via metal-free polymers modification.
Construction of Eu2+ doped H3Sr6(PO4)5·2H2O with novel cruciate multilayer microarchitectures: facile hydrothermal synthesis, growth mechanism, and luminescence properties
Highlights: • H{sub 3}Sr{sub 6}(PO{sub 4}){sub 5}·2H{sub 2}O:Eu{sup 2+} phosphors were synthesized via a simple hydrothermal method. • H{sub 3}Sr{sub 6}(PO{sub 4}){sub 5}·2H{sub 2}O:Eu{sup 2+} showed novel cruciate multilayer microarchitectures. • Phase and morphology were depended on the optimization of the reaction conditions. • H{sub 3}Sr{sub 6}(PO{sub 4}){sub 5}·2H{sub 2}O:Eu{sup 2+} exhibited intense characteristic blue emission of Eu{sup 2+}. - Abstract: A series of monodisperse cruciate multilayer H{sub 3}Sr{sub 6}(PO{sub 4}){sub 5}·2H{sub 2}O:Eu{sup 2+} microarchitectures assembled by crossed nanorods have been successfully synthesized via a facile surfactant-assisted hydrothermal route. XRD and FT-IR confirmed the existence of crystalline water in the phosphor. The FE-SEM images revealed that the phase and morphology of resulting samples were strongly depended on the optimization of the reaction conditions, especially the pH value and the molar ratio of citric acid (CA)/Cations. Furthermore, the possible growth mechanism of H{sub 3}Sr{sub 6}(PO{sub 4}){sub 5}·2H{sub 2}O:Eu{sup 2+} microarchitectures was proposed in detail. Under near-ultraviolet excitation of 365 nm, the as-obtained H{sub 3}Sr{sub 6}(PO{sub 4}){sub 5}·2H{sub 2}O:0.05Eu{sup 2+} sample exhibited intense wide characteristic blue emission of Eu{sup 2+}, which could be decomposed by Gaussian fitting into two peaks corresponding to different Eu{sup 2+} luminous centers. The present results demonstrated that the morphology-tunable H{sub 3}Sr{sub 6}(PO{sub 4}){sub 5}·2H{sub 2}O:Eu{sup 2+} microarchitecture could be used as a potential candidate for future optoelectronic device applications.
Petaloid-shaped ZnO coated carbon felt as a controllable host to construct hierarchical Li composite anode
Prestoring Li metal into the 3D host via thermal infusion strategy has been considered as an effective approach on suppressing Li dendrites growth of Li-metal anode during cycling. However, the fast Li infusing process generally induces uncontrollable and undesirable structures during the formation of composite Li metal anode. It is widely accepted that both physical and chemical interactions between the molten Li and the hosts provide driving forces for Li infusing into the host, but which one plays the dominant role has not been explored clearly. In this work, a 3D carbon felt coated by petaloid zinc oxide (CFZO) is designed as a controllable host for prestoring Li metal via thermal infusion method. It is revealed that the morphology induced physical driving force plays a more important role than the chemical reaction between ZnO and molten Li in the thermal infusion process. The physical driving force originates from the capillarity effect, depending on the roughness of the host according to Wenzel's model. An adjustable Li infusing process can be controlled to fabricate the Li composite electrode with a hierarchical structure (with dense Li-rich layer and porous Li-poor layer). The unique structure of the CFZO-Li not only provides enough spaces for Li deposition, but also disperses local current density to induce a uniform Li deposition behavior, thus Li dendrites can be suppressed effectively. As a result, CFZO-Li anode exhibits promising cycle stability when coupled with both Li-containing (LiNi 0.8 Co 0.15 Al 0.05 O 2 ) and Li-free (sulfur) cathodes.
Constructing synthetic organosulfur additive for high voltage lithium-ion batteries
Despite its high anodic stability, common organosulfur solvents such as ethyl methyl sulfone and sulfolane typically exhibit poor solid-electrolyte interphase (SEI) formation capability. Here, to address this, the fluorinated organic sulfate 4-(trifluoromethyl)-1,3,2-dioxathiolane 2,2-dioxide (TFDTD) was developed as an effective additive for tailoring organosulfur-based electrolytes in lithium-ion batteries. This development was guided by the functionality selection principle and careful evaluation of feasibility in organic synthesis. TFDTD can be readily synthesized through the reaction between trifluoropropylene glycol and sulfuryl chloride. The ring structure of the organic sulfate enables the formation of a stable SEI on the anode, while the fluorination of the sulfate not only enhances its chemical stability and oxidation potential, but also its effectiveness to protect the anode by increasing its reduction potential, rendering it preferentially reduced on the anode surface before the decomposition of other electrolyte components. Introducing TFDTD facilitates the generation of a robust solidelectrolyte interphase on the graphite anode, significantly enhancing cell performance. Moreover, coupling the use of TFDTD with vinylene carbonate provides further protection on the cathode surface, enabling exceptionally stable, high-voltage, long-term cycling of Gr||NMC full cells.
Design, construction, and characterization of a compact DD neutron generator designed for 40Ar/39Ar geochronology
A next-generation, high-flux DD neutron generator has been designed, commissioned, and characterized, and is now operational in a new facility at the University of California Berkeley. The generator, originally designed for 40 Ar/ 39 Ar dating of geological materials, has since served numerous additional applications, including medical isotope production studies, with others planned for the near future. In this work, we present an overview of the High Flux Neutron Generator (HFNG) which includes a variety of simulations, analytical models, and experimental validation of results. Extensive analysis was performed in order to characterize the neutron yield, flux, and energy distribution at specific locations where samples may be loaded for irradiation. A notable design feature of the HFNG is the possibility for sample irradiation internal to the cathode, just 8 mm away from the neutron production site, thus maximizing the neutron flux (n/cm 2 /s). The generator’s maximum neutron flux at this irradiation position is 2.58 x 10 7 n/cm 2 /s ± 5% (approximately 3 x 10 8 n/s total yield) as measured via activation of small natural indium foils. However, future development is aimed at achieving an order of magnitude increase in flux. Additionally, the deuterium ion beam optics were optimized by simulations for various extraction configurations in order to achieve a uniform neutron flux distribution and an acceptable heat load. Finally, experiments were performed in order to benchmark the modeling and characterization of the HFNG.
Design and construction of the CMS Outer Tracker for the phase-2 upgrade
The High-Luminosity LHC (HL-LHC) is expected to deliver an integrated luminosity of 3000–4000 fb −1 over 10 years of operation with the peak instantaneous luminosity reaching about 5–7.5 × 1 0 34 cm −2 s −1 . During Long Shutdown 3, several components of the CMS detector will undergo major improvements, called Phase-2 upgrades, to be able to operate in the challenging environment of the HL-LHC. The current CMS tracker will be replaced. The Phase-2 Outer Tracker (OT) will have increased radiation tolerance, higher granularity, and the capability to handle higher data rates. Moreover, the OT will provide tracking information to the Level-1 trigger for the first time at a hadron collider, allowing trigger rates to be kept at a sustainable level without sacrificing physics potential. For this, the OT will be made of modules with two closely-spaced silicon sensors read out by front-end ASICs that can correlate hits in the two sensors to create short track segments, used in the Level-1 track finder. The modules come in two flavors: strip-strip and pixel-strip, containing different sensor configurations and multiple ASICs. This contribution presents the Phase-2 OT, the finalization of the OT module design, and the quality assurance and control procedures used to ensure that the modules fulfill both the specifications from the assembly steps as well as the proper communication among the ASICs.
Energy group search engine based on surrogate models constructed with the RAVEN/NEWT/PHISICS sequence
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A new procedure for constructing basis vectors of SU(3)⊃SO(3)
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