Hollow Boxes Research Articles

Unraveling the reaction activity of Fe-based compounds toward potassium-ion storage

Iron-based compounds have been extensively applied as anode materials for alkali-ion batteries. Nevertheless, how the intrinsic properties of Fe-based compounds affect their alkali-ion storage behavior still remain blurry, hampering the rational structure design of Fe-based anodes for superior performance. Herein, the reaction activities of various Fe-based compounds (e.g., FeS2, FeSe2, and FeP) toward K/Na/Li-ion storage are studied by rationally encapsulating Fe-compounds into hollow carbon boxes with an identical multi-yolk-shell structure. For potassium storage, FeSe2@C composite manifests the best battery performance with high capacity, superior rate capability, and excellent cycling behavior. FeS2@C exhibits high capacity, but with poor cycling retention and inferior rate capability. FeP@C shows the lowest capacity and poorest rate capability. As disclosed by density functional theory calculation and kinetics analysis, the superior potassium storage behavior of FeSe2@C is due to the high electrical conductivity and proper K+ diffusion ability of FeSe2, as well as its excellent pseudocapacitive behavior. The weak electron conductivity of FeS2 is responsible for its poor rate performance, and the large K+ diffusion barrier of FeP leads to its low reaction activity toward potassium-ion storage. Moreover, FeSe2@C also displays best rate capability among these Fe-based composites for both sodium and lithium storage.

Reduced graphene oxide-wrapped ZnS-SnS2 heterojunction bimetallic hollow cubic boxes as high-magnification and long lifespan supercapacitor anode materials.

Metal sulfides have attracted extensive attention due to their excellent electrochemical performance. However, issues such as poor conductivity and severe volume expansion during charge and discharge processes affect the applications of sulfides as electrode materials. Here, a combination of coprecipitation and high-temperature sulfidation methods are employed to synthesize a ZnS-SnS2 composite with a hollow cubic structure, which is further composited with reduced graphene oxide (RGO) to form ZnS-SnS2 hollow cubic boxes encapsulated in a conductive framework of reduced graphene oxide (RGO) (denoted as ZnS-SnS2@RGO) for electrode materials. The hollow structure effectively alleviates the pulverization of ZnS-SnS2@RGO caused by volume expansion during charge and discharge processes. The heterogeneous structure formed by ZnS and SnS2 effectively reduces the electron transfer resistance of the material. The use of RGO wrapping enhances the conductivity of the ZnS-SnS2 hollow cubic boxes, and RGO's dispersion effect on the ZnS-SnS2 cubes improves particle agglomeration, further mitigating volume expansion of the material. These results indicate the outstanding electrochemical performance of heterostructural ZnS-SnS2 hollow cubic electrodes encapsulated with reduced graphene oxide as a conductive framework. The fabrication process provides a novel approach for addressing volume expansion and poor conductivity issues in other pseudocapacitive materials.

Construction of hollow copper selenide boxes and S-doping for enhanced electromagnetic wave absorption

With the proliferation of the use of wireless communication technologies, lightweight, easily fabricated electromagnetic wave (EMW) absorbers are in great demand for commercial and stealth applications. In this paper, well-defined Cu2O microcubes were successfully converted into S-doped Cu2−xSe micro-cubic boxes at room temperature by a template-directed in situ selenization/sulfidation reaction. The Cu2−xSe boxes were obtained under the combined effect of Kirkendall effect and Ostwald ripening, and the composite products with paraffins exhibited good EMW low-frequency absorption properties at 40 wt%, with RL(min) exceeding − 20 dB from 2.6 mm to 5.0 mm. In addition, the sulfidation process optimized the morphology, composition, interface, defects and conductivity, which further enhanced the EMW absorption performance of the material. The optimized RL(min) of S-doped Cu2−xSe reaches − 44.5 dB at 1.9 mm with an EAB of 4.3 GHz.

In Situ Transformation of LDH into NiCo2S4-NiS2 Nano-heterostructures on Hollow Carbon Boxes to Promote Sulfur Electrochemistry for High-Performance Lithium–Sulfur Batteries

The practical application of lithium–sulfur batteries is hindered by slow redox reaction kinetics and serious lithium polysulfide (LiPS) migration, especially in the scene of high sulfur loading and a lean electrolyte. A strategy has been proposed to catalyze the liquid–solid conversion of lithium polysulfides in “sealed” nanoboxes with the NiCo2S4-NiS2 nano-heterostructures, in which both LiPS migration and retardation reaction kinetics can be handled simultaneously. The design of hollow carbon boxes can alleviate the volume expansion during the cyclic process. Meanwhile, the NiCo2S4-NiS2 nano- heterostructures on hollow carbon boxes can effectively adsorb LiPS and catalyze their quick conversion, which have a synergistic enhancement effect on inhibiting the shuttle effect. Ultimately, this design achieves decent battery performance with a high specific capacity of 1207 mAh g–1 at 0.2C and long-term cyclability with a capacity retention of 60.23% after 450 cycles at 1C as well as a high initial areal capacity of 6.09 mAh cm–2 with a loading of 5 mg cm–2 under an electrolyte/sulfur ratio of 8.0 mL g–1.

Arrangement of reinforcement in variable density timber slab systems for multi-story construction

The arrangement of columns and their spacing in multi-story timber construction is restricted to rectangular grids by the production and shipping sizes of floor assemblies. This is particularly true for hollow box floor systems, for which the punctual supports must be placed at the reinforced edges of the hollow boxes. The arrangement of the columns and their spacing is thereby restricted by the production and shipping sizes of the box ceilings to rectangular grids. To overcome these design limits a new wooden box building system is developed that allows for irregular column layouts through a tailored slab interior design. This development allows for the increased applicability of timber floor systems regardless of site shape or architectural design intent. The slab interior design is dependent on occurring forces and fabrication requirements. Three methods for the internal slab layout are developed and compared: a sequential method, a structurally informed agent-based method, and a geometrically informed agent-based method that uses both a sequential and agent-based approach. The structural performance of each method is compared through the analysis of three reinforcement layouts an architectural testing setup.

Confinement of Prussian Blue Analogs Boxes Inside Conducting Polymer Nanotubes Enables Significantly Enhanced Catalytic Performance for Water Treatment

AbstractTubular nanoreactor with unique void‐confinement effect has captured great attention for catalytic applications but is challenging in controllable fabrication and realizing a synergistically enhanced performance. Herein, a template polymerization‐guided synthetic strategy is presented to confine hollow Prussian blue analog boxes inside conducting polypyrrole nanotubes (H‐CoFe PBA@PPy NTs) as efficient peroxymonosulfate activator toward catalytic oxidation of toxic organic contaminants. This delicately designed H‐CoFe PBA@PPy NTs display a superior kinetic rate constant compared with the pristine CoFe PBA cubes (7.9 fold) and H‐CoFe PBA boxes (22.6 fold). Experimental evidence reveals that the generation of multiple reactive oxygen species in the nanotubes plays a vital role for the significantly enhanced catalytic efficiency for dye degradation. The superior catalytic performance is attributed to the intrinsic bimetallic CoFe PBA to provide abundant active sites, distinct nanotubular structure to concentrate the reactant molecules within a confined space, and excellent electron/mass transport property. This work presents new horizons for the design of high‐efficiency and stable catalysts with space confinement effects to promote future advanced water treatment technology.

Uphill Quenching to Reduce Residual Stress in Aluminium Alloy 7449 Hollow Structures

BackgroundUphill quenching (UHQ) of heat treatable aluminium alloy components is a long established but rarely practiced or investigated method of reducing residual stresses. The efficacy of the technique has not been quantified on thin walled structures before and this investigation will address that deficiency.ObjectiveTo quantify the impact of uphill quenching on thin walled structure with regards to residual stress and warpage, and compare and contrast to both quenching into cold water and a 30% polyalkylene glycol (PAG) solution.MethodsRectilinear hollow boxes were made from the very high strength aerospace aluminium alloy 7449. These were heat treated and aged using a variety of processing methods including uphill quenching from -196 °C to 100 °C using steam. Residual stresses have been characterised using neutron and x-ray diffraction.ResultsCompared to conventional quenching into cold water, both PAG and UHQ are shown to significantly lower the residual stresses. However, while PAG quenching results in a large uniform reduction in both residual stress and warpage, UHQ is much more localised and limited to regions adjacent to direct steam impingement. These regions are also warped. The depth of penetration of the stress relief during UHQ is shown to be 5 mm.ConclusionsWhile uphill quenching is shown to be capable of locally stress relieving an aluminium alloy, it is far less effective compared to PAG quenching.

Bubbled roller-compacted concrete dam: an idea of a hollow dam

Roller-compacted concrete (RCC) is widely known for its relatively low cost and short construction time. RCC gravity dams require high foundation (rock) bearing capacity. Research studies have been carried out which propose to rationalise the amount of material in the dam by creating inner voids, in the shape of bubbles. As a key requirement, the introduced bubbles should not affect the dam stability and safety. The bubbles will reduce the self-weight of the dam and minimise the required rock-bearing capacity. A system of pipes connecting the bubbles ensures drainage of the bubbles. The proposed dam would save about 12% of the required concrete volume. Different construction methods were studied and the best alternative is the use of precast hollow boxes. This decreases RCC placement in the dam by 32.5%. The objective is to speed the construction process and minimise the risk of the heat of hydration.

Intercalation pseudocapacitance of hollow carbon bubbles with multilayered shells for boosting K-ion storage

A novel carbon skeleton constructed by hollow carbon boxes with a unique multilayered shell and an impressive large interlayer spacing of 0.76 nm, inducing the production of intercalation pseudocapacitance and high performance of K-ion storage.

Construction of frustrated Lewis pairs on TiO2-x derived from perovskite for enhanced photocatalytic CO2 reduction

Exploring high-efficiency photocatalysts to promote CO2 reduction into high value-added products is of great significance. However, the weak adsorption and activation ability for CO2 hampers the efficiency of photocatalytic CO2 reduction. Herein, hierarchical hollow TiO2-x boxes with frustrated Lewis pairs (FLPs) are successfully fabricated by in situ topological transformation of perovskite microcubes. The FLPs on TiO2-x surface are constructed with the OVs (Lewis acid sites) and its proximal surface hydroxyls (Lewis base sites). TiO2-x hollow boxes with FLPs show an excellent CO production rate (65.1 μmol g-1h−1) in pure water without any sacrificial agents or cocatalysts, which is 19.1 times and 36.6 times higher than those of TiO2 without FLPs and commercial TiO2 P25, respectively. This work presents a novel strategy to construct FLPs through in situ topological transformation route and also shows great promise for the future design of high-performance CO2 reduction photocatalysts.

Spout hollow nest boxes provide a drier and less stable microclimate than natural hollows

AbstractArtificial tree hollows (e.g., nest‐boxes) are commonly deployed to mitigate the loss of mature trees within human‐disturbed landscapes. Their effectiveness as a habitat resource, and thus conservation management tool, is strongly influenced by the suitability of internal microclimate conditions. In south‐eastern Australia, spout hollows are a nesting resource used by a diverse community of vertebrate species. We tested the suitability of a novel nest box design (spout boxes) that mimicked the physical characteristics of spout hollows. We monitored the occupancy (n = 193) and internal microclimate (n = 131) of natural hollows and spout boxes within a woodland where natural tree hollows were once abundant. Both natural hollows and spout boxes were occupied and used for breeding by birds and mammals. Natural hollows had consistently higher humidity, and thermal maxima and minima were buffered, when compared with spout boxes. These differences were largely explained by wall thickness. Spout boxes displayed even more extreme temperature variation and lower humidity when not shaded. While more extreme microclimate conditions did not prevent usage, tolerable thresholds for hollow‐dependent species may soon be exceeded under current climate change projections. Managers need to carefully consider nest box design and positioning to ensure the suitability of these supplementary resources for conservation purposes.

Cube-like mixed-phases TiO2 mesocrystalline hollow boxes from in situ topotactic transformation for highly efficient dye-sensitized solar cells

The cube-like TiO2 mesocrystalline hollow boxes (TiO2-MHBs) are fabricated by a topotactic transformation method. TiO2-MHBs consist of one-dimensional nanorod-like rutile TiO2 combined with anatase TiO2. The ordering of TiO2-MHBs is in favor of efficient electron transport. TiO2-MHBs with mesoporous structure show excellent light scattering performance. Dye-sensitized solar cell with TiO2-MHBs light scattering overlayer exhibits an 18.3% increment of cell efficiency (9.51%) compared with the TiO2 nanoparticles film cell (8.04%). The improved photovoltaic performance is attributed to its unique crystallographic property and highly porous structure, which can enhance light scattering capability, quicken electron transport and electrolyte diffusion, and reduce charge recombination.

Construction of Porous Co9S8 Hollow Boxes with Double Open Ends toward High-Performance Half/Full Sodium-Ion Batteries

Herein, uniform Co9S8 hollow boxes (Co9S8-HB) with double open ends have been fabricated by a facile technique involving a solvothermal and subsequent calcination process. On the basis of a time-de...

MOF/TBOT-derived hierarchical C-N/Co/Ti composites with effective elemental separation for enhanced oxygen reduction reaction

C-N/Co/Ti composites derived from ZIF-67@TiO2 precursors have been fabricated by a facile thermal treatment process. The morphology and composition are highly dependent on the available parameters inferring of exact hydrolysis of tetrabutyl titanate and sintering temperature. The obtained hierarchical microstructure is composed of numerous dodecahedron-like hollow boxes decorated with in-situ growth of size-tunable and twisting nanotubes on surfaces. The effective elemental separation of Ti and Co on the upper and lower ends of nanotubes can be realized by regulating the ionic migration and crystalline phase formation process at a high temperature. The as-prepared C-N/Co/Ti composites exhibit the enhanced electrocatalytic activities to oxygen reduction reaction (ORR) via a favorable four-electron pathway and the desired reaction kinetics with the low Tafel slope (67.8 mV dec−1), as well as the excellent methanol tolerance in comparison with the Pt/C electrocatalysts. The superior ORR electrocatalytic performance would be mainly contributed to the combination of the designed multi-phase composition, the enhanced surface adsorption/desorption, the modified surface/interface electron transfer mechanism, and the constructed Co/Ti double-active sites on different locations of microstructure. The present work presents a new insight for the synthesis of C-N-based inorganic composite with outstanding electrocatalytic behavior for ORR process.

Porous SnO2 triple-shelled hollow nanoboxes for high sensitive toluene detection

A unique triple-shelled architecture with nonspherical shape has been successfully synthesized via a controllable multistep approach in case of polycrystalline SnO2 nanoboxes. The morphological characterizations demonstrate that SnO2 triple-shelled hollow boxes (THBs) are hierarchically constructed by numerous SnO2 primary nanoparticles. The formation mechanism of these SnO2 THBs is discussed based on a localized inside-out Ostwald ripening process. When SnO2 THBs are used as sensing material for toluene detection, the improved sensing performance can be attributed to the rational microstructures for fast transfer of gas molecules.

The enhanced ethanol sensing properties of CNT@ZnSnO3 hollow boxes derived from Zn-MOF(ZIF-8)

In this report, a novel hollow boxes shape ZnSnO3 is synthesized via a one-pot surfactant-free method. We synthesize CNT@ZnSnO3 hollow boxes via hydrothermal reaction by using the Zn-MOF(ZIF-8) as the Zn source at the first time. Several characterization techniques are used to investigate the structure, morphology, composition and specific surface area of CNT@ZnSnO3. CNT@ZnSnO3 hollow boxes demonstrated large specific surface area (up to 45.73 m2/g), which is favorable for the strong gas sensor response. The ethanol sensor based on CNT@ZnSnO3 hollow boxes exhibited high response of ethanol up to 166 at 240 °C at the concentration of 100 ppm, which is about 8 times higher than the sensing response of ZnSnO3 nanocubes. Moreover, CNT@ZnSnO3 hollow boxes based ethanol sensor also shows the excellent selectivity and stability. As a novel green gas sensor, CNT@ZnSnO3 hollow boxes show the great potential in the gas sensing field.

Controllable corrosion-assisted fabrication of Au–Ag alloyed hollow nanocrystals for highly efficient and environmentally-stable SERS substrates

Surface enhanced Raman scattering (SERS) substrates with both high activity and long term chemical-stability have been expected in the practical application of the SERS-based detection. In this paper, Au–Ag bimetal nanocrystals are fabricated based on the template-etching reaction in the Ag nanocubes-contained cetylpyridinium chloride (CPC) aqueous solution via adding the HAuCl4 solution. The obtained nanocrystals are Au–Ag alloyed and hollow in structure. Further, it has been found that with the increasing Au/Ag molar ratio, the shape of the alloyed nanocrystals evolve from the truncated nanocubes to the hollow boxes and then nanocages, showing the ever red-shifting surface plasmon resonance from the visible to the infrared region. The formation of the alloyed hollow nanocrystals is attributed to the preferential dissolution of the Ag nanocubes induced by CPC selective adsorption and the three to one galvanic replacement reaction between Ag and Au atoms. Importantly, such Au–Ag alloyed hollow nanocrystals, especially the ones with a low Au/Ag atomic ratio, show both high SERS activity and long term environmental stability compared with pure Ag or Au nanocrystals, and are the ideal candidate for the SERS substrate with practical application value. This work not only demonstrates the nanofabrication route to the alloyed hollow nanocrystals with controllable shapes and tunable optical properties in a large region, but also presents highly active and chemically-stable SERS substrates for the practical SERS-based detection.

In Site Growth of Crosslinked Nickel–Cobalt Hydroxides@Carbon Nanotubes Composite for a High‐Performance Hybrid Supercapacitor

AbstractMetal–organic frameworks materials have shown great potential in energy storage and conversion research, but their poor electrical conductivity and inferior chemical stability limit their applications. Herein, an in situ‐grown crosslinked nickel–cobalt hydroxides@carbon nanotubes composite with a nanosheet‐covered hollow structure is rationally designed and synthesized successfully from ZIF‐67@carbon nanotubes. Different from other studies, the carbon nanotubes in this composite penetrate the hollow structure, and the active nanosheets also grow on the parts protruding from the hollow boxes via this in situ synthetic route. Compare with pure nickel–cobalt hydroxides, the composite exhibits enhanced electroactivity in terms of the specific capacity and cycling performance. In particular, it delivers a high specific capacity of 916.8 C g−1 at 1 A g−1 and ≈79.0% of its initial value preserves after 4000 cycles. This facile synthetic approach enables the preparation of crosslinked metal–organic framework materials with the potential to meet the demands of energy storage and conversion devices as well as supercapacitors.

Enhanced visible photocatalytic activity of TiO2 hollow boxes modified by methionine for RhB degradation and NO oxidation

Hierarchical TiO2 hollow nanoboxes (TiO2-HNBs) assembled from TiO2 nanosheets (TiO2-NSs) show improved photoreactivity when compared with the building blocks of discrete TiO2-NSs. However, TiO2-HNBs can only be excited by ultraviolet light. In this paper, visible-light-responsive N and S co-doped TiO2-HNBs were prepared by calcining the mixture of cubic TiOF2 and methionine (C5H11NO2S), a N- and S-containing biomacromolecule. The effect of calcination temperature on the structure and performance of the TiO2-HNBs was systematically studied. It was found that methionine can prevent TiOF2-to-anatase TiO2 phase transformation. Both N and S elements are doped into the lattice of TiO2-HNBs when the mixture of TiOF2 and methionine undergoes calcination at 400 °C, which is responsible for the visible-light response. When compared with that of pure 400 °C-calcined TiO2-HNBs (T400), the photoreactivity of 400 °C-calcined methionine-modified TiO2-HNBs (TM400) improves 1.53 times in photocatalytic degradation of rhodamine-B dye under visible irradiation (λ > 420 nm). The enhanced visible photoreactivity of methionine-modified TiO2-HNBs is also confirmed by photocatalytic oxidation of NO. The successful doping of N and S elements into the lattice of TiO2-HNBs, resulting in the improved light-harvesting ability and efficient separation of photo-generated electron-hole pairs, is responsible for the enhanced visible photocatalytic activity of methionine-modified TiO2-HNBs. The photoreactivity of methionine modified TiO2-HNBs remains nearly unchanged even after being recycled five times, indicating its promising use in practical applications.

Thin and Small N-Doped Carbon Boxes Obtained from Microporous Organic Networks and Their Excellent Energy Storage Performance at High Current Densities in Coin Cell Supercapacitors

This work reports the thinnest and smallest hollow N-doped carbon boxes among recently reported hollow N-doped carbon materials. Hollow and N-rich microporous organic networks (H-NMONs) were prepared by the azide–alkyne Huisgen cycloaddition of tetra(4-ethynylphenyl)methane and 1,4-diazidobenzene on the surface of Cu2O nanocubes and the successive acid etching of inner Cu2O. The Cu2O nanocubes played roles of templates and networking catalysts. The networking reaction generated N-rich triazole rings in the MON. Heat treatment of H-NMONs under argon resulted in the formation of hollow N-doped carbon boxes (H-NCBs). The diameter and shell thickness of H-NCBs were 130 and 12 nm, respectively. The H-NCBs showed superior electrochemical performance in H2SO4 electrolyte as energy storage materials for supercapacitors, compared with that in KOH electrolyte. Among the H-NCBs, H-NCB-900 which was obtained by the heat treatment of H-NMON at 900 °C showed the best performance with capacitances of 286 and 251 F/g at current densities of 1 and 10 A/g in two electrode coin cell type supercapacitors and maintained the capacitances of 228 and 206 F/g at higher current densities of 50 and 100 A/g. Moreover, the H-NCB-900 showed excellent cycling stabilities with ∼95% retention of the first capacitance after 10 000 cycles. The excellent electrochemical performance of H-NCBs can be attributed to their efficient N-doping, hollow structure, and thin thickness of shells.