Hollow Spherical Structure Research Articles

Mixed-metal MOF-derived Co–Mn–O hollow spheres as anodes for lithium storage

A Co–Mn–O/C composite is obtained by incorporating two metal ions from Co(Ac)2 and Mn(Ac)2 into a mixed-metal–organic framework (MOF) followed by high-temperature carbonization in air. The Co–Mn–O/C composite has a unique hollow-sphere structure with the shells constructed with Co–Mn–O grains embedded in an amorphous carbon matrix, which combines the advantage of efficient strain absorption and high conductivity. As a modulator, acetic acid has a large influence on the particle size and surface area of the Co–Mn–O/C hollow spheres that further affect their electrical properties, and an optimum Co:Mn ratio can result in greatly enhanced electrochemical performances. More importantly, the metallic Co nanoparticles in the Co–Mn–O/C composite also have the impact on adjusting the solid electrolyte interphase (SEI) layer, which helps in maintaining high morphological integrity and considerable electrochemical performance. At an optimum Co:Mn ratio, the Co–Mn–O/C electrode produces outstanding performance in both cycle and rate tests. A high-rate capacity of 1088.5 mAh g−1 is observed after 600 cycles at 1000 mA g−1 and a capacity of 775.9 mAh g−1 is reserved even after the current density rise to 8000 mA g−1. The Co–Mn–O/C composite is expected to serve as a low-cost and high-performance anode for lithium-ion batteries.

The water resistance enhanced strategy of Mn based SCR catalyst by construction of TiO2 shell and superhydrophobic coating

The Mn-based catalyst with hollow spherical structure was prepared by hydrothermal method and used for selective catalytic reduction (SCR) of NO with NH3. Mn-based catalysts exhibit excellent de-NOx performance at low-temperature, but narrow operating temperature window and poor water resistance restrict its application. Effectively expanding the operating temperature window and improving the H2O resistance of the Mn-based catalyst are the keys to industrial application. In this article, the H-MnO2 catalyst was prepared by hydrothermal method and modified by kinetic adsorption and vapor deposition methods. The TiO2 layer can effectively limit the excessive redox performance and improve the acidity of the catalyst surface, the NO conversion above 90% at 140–380 °C of H-MnO2@TiO2 catalyst. The phenyltrimethoxysilane was deposited on the surface of the H-MnO2@TiO2 catalyst by vapor deposition method. The NO conversion rate of the H-MnO2@TiO2@HL catalyst exceeds 80% in the temperature range of 180–380 °C. When the H2O was introduced, the NO conversion rate increases from 70% to 85% at 180 °C. The in situ DRIFTs results showed NH3 and NO could be adsorbed and activated on the catalyst surface, and the catalytic reaction follows Langmuir-Hinshelwood (L-H) mechanism. Under the presence of H2O, the NH4+ bonding to Brønsted acid sites were inhibited but the NH3 bonding to Lewis acid site was almost unaffected. In summary, through two-step modification, the operating temperature window and water resistance of Mn-based catalysts are effectively improved. It can be seen that a reasonable structure design can effectively improve the comprehensive performance of the catalyst.

Tunable Multiple Morphological Transformation of Supramolecular Hyperbranched Polymers Based on an A2B6-type POSS Monomer

The growing demands of supramolecular hyperbranched polymers integrating noncovalent interaction and unique topological structure merits had received considerable interests in the fabrication of novel materials for advanced applications. Herein, we prepared A2B6-type POSS-containing supramolecular hyperbranched polymers with multiple morphologies including lamellar-like, branched, hollow, core-shell and porous spherical structures through regulating self-assembling monomer concentrations and solvent polarities. The incorporation of appropriate emulative guest molecules would further trigger morphological transformations (such as vesicles and spherical micelles) by synergistic effects of unique POSS aggregation ability, supramolecular complexations and hydrophilic-hydrophobic interactions. Thus, this facile and universal strategy may enable a modular nanofabrication of supramolecular hyperbranched polymers with diversiform topological structure and sophisticated multifunctionality for their potential applications.

Large Deformation and Energy Absorption Behaviour of Perforated Hollow Sphere Structures under Quasi-Static Compression.

Hollow sphere structures with perforations (PHSSs) in three different arrangements (simple cubic (SC), body-centred cubic (BCC), and face-centred cubic (FCC)) were fabricated through three-dimensional (3D) printing, and the mechanical behaviours of these PHSSs under quasi-static compression were investigated experimentally and numerically. The results indicated that under uniaxial compression, the PHSSs mainly undergo three stages, i.e., a linear elastic stage, a large deformation or plateau stage, and a densification stage. During the stage of large deformation, the SC and BCC PHSSs experience a preliminary compaction sub-stage after layer-by-layer buckling, while for the FCC PHSS, layer-by-layer collapse and compaction are the dominant deformation behaviours. A numerical simulation was employed to study the mechanical properties of PHSSs with different geometric parameters under quasi-static compression and to explore the effect of the wall thickness, hole diameter, and sphere arrangement on the first peak stress, plateau stress, and specific energy absorption (SEA) of the PHSSs. The results reveal that the geometric parameters have a significant impact on the large deformation behaviour and energy absorption capacity of PHSSs. The presented PHSS is also proven to be much lighter than traditional metallic hollow sphere structure (MHSS) and has higher specific strength and SEA.

Design BH3 domain fusion protein as targeting pro-apoptotic self-assembling nanoparticles

Cancer is a serious global health issue, and apoptosis is a logical and practical cancer therapeutic strategy. Apoptosis responses to internal and external signals. Both BH3 domain in the pro-apoptotic proteins and truncated BH3 domain can stimulate cell apoptosis. However, the faults of peptides in systemic administration restrict the applications of truncated BH3 domain. Ferritin, as an attractive nanoparticle with the capacity of self-assemble to unique hollow spherical structure, could display truncated BH3 domain an N-terminal. Thus, in this study, we designed a pro-apoptosis self-assembling protein nanoparticle by BH3 domain fusion at N-terminal of ferritin. We evaluated the size, cytotoxicity and pro-apoptosis effect of these nanoparticles. The results showed that RGD-BH3-HFn, BH3-HFn and HFn had uniformly spherical structure with sizes at 26.08 ± 0.11 nm, 22.07 ± 0.67 nm, and 16.81 ± 0.88 nm, respectively; RGD-BH3-HFn has stronger cytotoxicity against tumor cells than BH3-HFn and HFn. The total apoptosis ratios (including necrosis) of C6 cells induced by RGD-BH3-HFn, BH3-HFn, and HFn proteins were 15.24%, 10.13% and 2.14%, respectively; those of bEnd.3 cells were 15.47%, 7.33% and 1.70%, respectively; while the total apoptosis rate (including necrosis) of MCF-7 cells were 3.24%, 4.9% and − 1.68%, respectively. The results suggested self-assembling RGD-BH3-HFn could target to C6 cells and bEnd.3 cells, and enhance tumor cells apoptosis, its apoptosis effect against C6 cells was 7.11-fold that of HFn, and apoptosis effect against bEnd.3 cells was 9.08-fold that of HFn. These results indicated BH3 domain can be designed as targeting pro-apoptotic nanoparticles.

Exploration of amorphous hollow FeOOH@C nanosphere on energy storage for sodium ion batteries

Sodium ion batteries (SIBs) have enjoyed a high profile in recent years and gradually been commercialized to supplement the lithium-ion batteries system. However, the large volume expansion of anode materials within discharging and low electrical conductivity hinder the application of SIBs. In this work, a FeOOH@C composite was synthesized with the use of hydrothermal method and pyrolyzing of polydopamine. The amorphous FeOOH exhibits a hollow spherical structure to offer free space for buffering the volumetric variation. Furthermore, the outer carbon served as a protective shell could maintain the sphere integrity and enhance the electrical conductivity. Hence, benefiting from the achieved synergy of the hollow architecture, amorphous structure and carbon shell, the composite presented a long cycle life (316 mA h g−1 after 500 cycles at a current density of 100 mA g−1 and 234.5 mA h g−1 after 400 cycles at 2 A g−1) and high-rate performance (180 mA h g−1 at 5 A g−1), revealing a potential to be a promising candidate for electrode material of SIBs.

Highly-configured TiO2 hollow spheres adorned with N-doped carbon dots as a high-performance photocatalyst for solar-induced CO2 reduction to methane

Transforming CO2 into solar fuel using renewable solar energy and a catalyst is an effective approach that simultaneously addresses energy scarcity and climate deterioration. Therefore, it is necessary, albeit challenging, to design a catalyst that works effectively for this purpose. Herein, we have rationally developed a hybrid catalyst composed of highly-configured TiO2 hollow spheres (TOH) and N-doped carbon dots (CD), referred to as CD/TOH, and use this hybrid as a catalyst for photocatalytic CO2 reduction to produce CH4 under simulated sunlight. The electron microscopy results revealed that the CD/TOH hybrid possesses a porous hollow sphere structure uniformly adorned with N-doped carbon dots. Moreover, the CD/TOH hybrid demonstrates many beneficial properties for CO2 photoreduction reactions, including a large surface area, effective light-harvesting capability, high CO2 adsorption, and, most importantly, significantly enhanced separation of photoexcited charges. Consequently, the CD/TOH containing 2 wt% CD achieves an optimum CH4 formation rate of 26.8 μmol h−1 g−1, corresponding to 98% CH4 selectivity against competitive H2 production. Further, the hybrid also demonstrated stable CO2 reduction activity during consecutive test runs. Thus, the insights gained from this study may aid in the development of effective catalysts for CO2 photoreduction.

Development of fly ash cenosphere‐based composite for thermal insulation application

AbstractCenosphere‐based composite was developed with addition of clay and other additives, by dry processing route. The performance of cenosphere as high‐temperature insulating material was studied. Cenosphere stands unique among the constituents found in fly ash due to its hollow spherical structure. Cenosphere is utilized in numerous modern applications due to its unique properties such as lightness, high compressive strength, enhanced flow characteristics, less water absorption, chemical inertness, and good thermal resistance. Keeping cenosphere as major component, three different mix recipes for insulating brick were made. The recipes were blended and shaped by pressing, followed by drying and sintering at 1000°C. The prepared samples were analyzed for their physical, mechanical, and thermal properties. The surface and pore distribution are analyzed by scanning electron microscope. Results from the analysis shows that cenosphere can be used as high temperature insulating material.

Constructing built-in electric field in graphitic carbon nitride hollow nanospheres by co-doping and modified in-situ Ni2P for broad spectrum photocatalytic activity

The construction of built-in electric field is generally considered as an effective strategy to enhance photocatalytic performance due to its significant role in charge separation. Herein, a built-in electric field within g-C3N4 hollow nanospheres co-doped with sulfur and oxygen and modified in-situ Ni2P is proposed. Ni2P/SOHC3N4 exhibits significantly enhanced board spectrum photocatalytic properties for hydrogen precipitation (5.21 mmol h−1 g−1) and photocatalytic Cr(VI) reduction without the use of noble metal. It also achieves high photocatalytic sterilization activity and remarkable stability when used to completely inactivate E. coli (107) in 60 min under Vis-NIR light irradiation. The enhanced performance is attributed to the formation of a curved hollow sphere structure, which promotes the electron transfer between the inner and outer layers. In addition, co-doping inhibits the recombination of photogenerated carriers, and the built-in electric field recombined with Ni2P facilitates the electron transfer between the composite interfaces. This design strategy demonstrates an original method of devising multifunctional photocatalysts with enhanced activity and stability.

Fabrication of Cu-hemin metal-organic-frameworks nanoflower supported on three-dimensional reduced graphene oxide for the amperometric detection of H2O2.

A novel electrochemical sensor based on Cu-hemin metal-organic-frameworks nanoflower/three-dimensional reduced graphene oxide (Cu-hemin MOFs/3D-RGO) was constructed to detect H2O2 released from living cells. The nanocomposite was synthesized via a facile co-precipitation method using hemin as the ligand, then decorated with 3D-RGO. The prepared Cu-hemin MOFs showed a 3D hollow spherical flower-like structure with a large specific surface area and mesoporous properties, which could load more biomolecules and greatly enhance the stability by protecting the activity of hemin. In addition, the introduction of 3D-RGO effectively enhanced the conductivity of Cu-hemin MOFs. Thus, the proposed sensor (Cu-hemin MOFs/3D-RGO/GCE) showed excellent electrochemical performances towards H2O2 with a wide linear range (10-24,400μM), high sensitivity (207.34μAmM-1cm-2), low LOD (0.14μM), and rapid response time (less than 3s). Most importantly, we prepared a Cu-hemin MOFs/3D-RGO/ITO electrode with cells growing on it. Compared with detecting H2O2 in cell suspension by GCE-based electrode, adhesion of cells on ITO could shorten the diffusion distance of H2O2 from solution to the surface of the electrode and achieve in situ and a real-time monitor of H2O2 released by living cells. This self-supported sensing electrode showed great potential applications in monitoring the pathological and physiological dynamics of cancer cells.

Communication—Bimetallic-MOFs-Derived ZnO/Bi2O3 Composites as Anode Materials for Advanced Zinc-Based Batteries

In this study, the nano-sized ZnO/Bi2O3 composites were synthesized with the zinc-bismuth bimetallic-MOFs as the precursor for the first time. The metal ions were homogeneously anchored on the self-assembled precursor with a structure of hollow sphere. The results showed that the obtained ZnO presented a typical structure of hexagonal prismatic and an even distribution of element Zn and Bi was realized. Utilized as anode materials of Zn/Ni battery, the composites displays an ultra-high average discharge capacity of 630 mAh g−1 at 1 C and longer cycle life than the unmodified pure ZnO.

Phase Separation Effect in Gelation of 3DOM Bioactive Glass

The quaternary phase bioactive glasses (SiO2-CaO-Na2O-P2O5) were synthesized by the sol-gel process. Pluronic P123, using surfactant as structure-directing agents as well as phase separation inducers. The obtained bioactive glasses were characterized regarding morphology by using the scanning electron microscopy (SEM). Polymer colloidal crystals (CCTs) as the template component yielded either three-dimensionally ordered macroporous (3DOM) structure or hollow spheres shaped bioactive glass. The other type of morphology generation is related to the polymerization-induced phase separation (PIPS) in the gelation process. The heterogeneous precursor i.e. silica-rich regions caused the microspheres and solvent-rich areas produced micrometer-scale void space in bicontinuos structure. While the lower pH of starting precursor in 45S4P showed stronger precursor-template interactions than the 53S4P by generating the completely hollow spheres structure.

Synthesis, characterization and electrocatalytic properties of bimetallic sulfides CoS/MnS/N-C for oxygen reduction in alkaline media

Synthesis, characterization and oxygen reduction reaction (ORR) catalytic properties of bimetallic sulfides CoS/MnS/N-C catalyst was discussed. The catalyst was derived from a typical Co based zeolitic imidazolate framework (ZIF-67) and manganese aminoporphyrin. 5,15-Bis(4-aminophenyl)-10,20-bis(4-bromophenyl) porphyrin manganese oxoacetate loaded with ZIF-67 forms a porphyrin loaded ZIF-67. This product was then calcined at 800ˆ∘C and vulcanized with thioacetamide to obtain the bimetallic sulfide product CoS/MnS/N-C. The structure of CoS/MnS/N-C was further characterized by XRD, XPS, FESEM and HRTEM spectra which indicated a novel porous and hollow sphere structure. The electrocatalytic properties of the bimetallic material as well as its parent porphyrin and ZIF-67 were also compared in alkaline condition (0.1 M KOH) with a rotating disk electrode. The prepared catalyst CoS/MnS/N-C exhibits a higher catalytic performance than its precursors (PorMnOAc, ZIF-67 and PorMnOAc loaded ZIF-67) with almost four electron transfers under this condition.

Facile fabrication of hierarchical flowerlike γ-AlOOH hollow spheres decorated with MWCNTs for electromagnetic wave absorption

To explore a type of high-performance microwave absorber with lightweight and thin thickness, the flowerlike γ-AlOOH hollow spheres decorated with multi-walled carbon nanotubes (MWCNTs) were fabricated by a facile hydrothermal method. The microscopic morphology characterization showed the γ-AlOOH microspheres consisted of a hollow inner core and a shell made of numerous flakes. The γ-AlOOH/MWCNTs composites exhibited excellent microwave absorption performance with the reflection loss of − 49.8 dB at 11.1 GHz and effective absorption bandwidth of 4.56 GHz (from 13.44 to 18 GHz) at a thickness of 1.5 mm, which covered almost the entire X band. Furthermore, the unique microstructure of γ-AlOOH exerted a considerable effect on the obtained microwave absorption capacity of the composites, leading to interfacial polarization, multiple reflections, and scattering of electromagnetic wave. Meanwhile, the suitable MWCNTs additive amount played a crucial role in the improvement of impedance matching, conduction loss, and dipole polarization, which benefit the performance of microwave absorption. It is expected that the flowerlike hollow spheres structure in our work can provide a method of designing the novel microwave absorbers.

Design of Trimetallic NiMoFe Hollow Microspheres with Polyoxometalate‐Based Metal‐Organic Frameworks for Enhanced Oxygen Evolution Reaction

AbstractDesign of efficient and inexpensive oxygen evolution reaction (OER) catalysts is the key to realizing the wide application of water electrolysis in industrial production. Herein, we synthesized trimetallic hollow microspheres composed with FeNi nanoparticles and nitrogen‐doped carbon‐based Ni2Mo3N (NiMoFe@NC700) using a “PBA@POMOF” strategy. In order to synthesize the precursor with ideal morphology and structure in the least steps, a polyoxometalate based metal‐organic framework (POMOF) is used as a substrate to grow a Ni−Fe‐based Prussian blue analogue (NiFePBA) on it. Benefiting from the hollow sphere structure formed by stacking flakes, better charge transfer performance and the synergistic effect between Ni2Mo3N and Fe0.64Ni0.36, the final product, NiMoFe@NC700, exhibits low overpotentials of 288 and 360 mV to achieve current densities of 10 and 50 mA cm−2 for OER in 1 M KOH, respectively, which is superior to the benchmark IrO2 catalyst. This work proposes a facile and effective strategy to synthetize carbon‐based polymetallic OER electrocatalysts based on PBA@POMOF.

Bimetallic ZIFs derived nitrogen-doped hollow carbon with carbon nanotube bridges as a superior oxygen reduction reaction electrocatalyst

The development of oxygen reduction reaction (ORR) catalysts is critical for energy conversion technologies such as fuel cells. This paper proposes an approach to synthesize a hollow-sphere nitrogen-doped carbon shell loaded with cobalt nanoparticles derived from a polystyrene@bimetallic zeolitic imidazolate framework (PS@BMZIF) core@shell, which exhibits high activity as an ORR catalyst. The ORR activity can be enhanced by performing carbonization in the presence of hydrogen, resulting in the growth of additional carbon nanotubes on the hollow-sphere porous carbon shell (h_CoNC/CNT) derived from the PS@BMZIF. The electrocatalyst obtained exhibits excellent ORR activity with a half-wave potential of 0.894V and long-term stability for 5000 cycles in alkaline media. The h_CoNC/CNT catalyst is applied to the membrane electrode assembly of an anion exchange membrane fuel cell, where it demonstrates a performance of 140mA/cm2 at 0.6V and 133mW/cm2 at the maximum power density and improves mass transfer. The exceptional electrochemical properties of h_CoNC/CNT can be attributed to its desirable hollow-sphere structure with CNTs and the adjustment of efficient active sites of the nitrogen-doped porous material. These findings suggest a potential approach by which to select the structure of the ZIFs and control the pyrolysis condition for ZIF-derived ORR electrocatalysts.

Experimental Study on Thermal Properties of Hollow Sphere Structures

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

Yolk–Shell Structured Nickel Cobalt Sulfide and Carbon Nanotube Composite for High-Performance Hybrid Supercapacitors

Optimizing electrode materials performance and improving the energy density of supercapacitors is a hot research topic. The complex hollow sphere structure material, as a supercapacitor electrode m...

Hollow Molybdate Microspheres as Catalytic Hosts for Enhancing the Electrochemical Performance of Sulfur Cathode under High Sulfur Loading and Lean Electrolyte

AbstractLithium–sulfur battery possesses a high energy density; however, its application is severely blocked by several bottlenecks, including the serious shuttling behavior and sluggish redox kinetics of sulfur cathode, especially under the condition of high sulfur loading and lean electrolyte. Herein, hollow molybdate (CoMoO4, NiMoO4, and MnMoO4) microspheres are introduced as catalytic hosts to address these issues. The molybdates present a high intrinsic electrocatalytic activity for the conversion of soluble lithium polysulfides, and the unique hollow spherical structure could provide abundant sites and spatial confinement for electrocatalysis and inhibiting shuttling, respectively. Meanwhile, it is demonstrated that the unique adsorption of molybdates toward polysulfides exhibits a “volcano‐type” feature with the catalytic performance following the Sabatier principle. The NiMoO4 hollow microspheres with moderate adsorption show the highest electrocatalytic activity, which is favorable for enhancing the electrochemical performance of sulfur cathode. Especially, the S/NiMoO4 composite could achieve a high areal capacity of 7.41 mAh cm−2 (906.2 mAh g−1) under high sulfur loading (8.18 mg cm−2) and low electrolyte/sulfur ratio (E/S, 4 µL mg−1). This work offers a new perspective on searching accurate rules for selecting and designing effective host materials in the lithium–sulfur battery.

Delicate Control on the Shell Structure of Hollow Spheres Enables Tunable Mass Transport in Water Splitting

AbstractIn the study of structure–property relationships for rational materials design, hollow multishell structures (HoMSs) have attracted tremendous attention owing to the optimal balance between mass transfer and surface exposure. Considering the shell structure can significantly affect the properties of HoMSs, in this paper, we provide a novel one‐step strategy to continually regulate the shell structures of HoMSs. Through a simple phosphorization process, we can effectively modify the shell from solid to bubble‐like and even duplicate the shells with a narrow spacing. Benefitting from the structure merits, the fabricated CoP HoMSs with close duplicated shells can promote gas release owing to the unbalanced Laplace pressure, while accelerating liquid transfer for enhanced capillary force. It can provide effective channels for water and gas and thus exhibits a superior electrocatalytic performance in the hydrogen and oxygen evolution reaction.