Shell Of Hollow Spheres Research Articles

Ball-in-ball NiS2@CoS2 heterojunction driven by Kirkendall effect for high-performance Mg2+/Li+ hybrid batteries

Mg2+/Li+ hybrid batteries (MLHBs), which support the rapid insertion and removal of Mg2+/Li+ bimetallic ions, are promising energy storage systems. Inspired by the Kirkendall effect, ball-in-ball bimetallic sulfides with heterostructures were prepared as cathode materials for the MLHBs. First, a nickel–cobalt precursor (NiCo-X precursor) with three-dimensional (3D) nanosheets on its surface was prepared using a solvothermal method based on the association reaction between alkoxide molecules. Subsequently, the NiCo-X precursor was vulcanized at high temperature using the potential energy difference as the driving force to successfully prepare NiS2@CoS2 core–shell hollow spheres. When used as the positive electrode material for the MLHBs, the NiS2@CoS2 hollow spheres exhibited excellent Mg2+/Li+ ion storage capacity, high specific capacity, good rate performance, and stable cyclic stability owing to their tough hierarchical structure. At a current density of 500 mA g−1, a specific capacity of 536 mAh g−1 was maintained after 200 cycles. By explaining the transformation mechanism of Mg2+/Li+ in bimetallic sulfides, it was proven that Mg2+ and Li+ worked cooperatively. This study provides a new approach for developing MLHBs with good electrochemical properties.

Tunable fluorescence and magnetic properties of ceria- organic core- shell hollow structures

In this study, mesoscopic ceria- organic core–shell hollow spheres with tunable luminescence and magnetism were demonstrated. The organic layer was grown on the surface of ceria hollow spheres by the reaction of citric acid solution and ethylenediamine via hydrothermal process. With increasing the reaction time from 0 to 6 h, the organic phase varies from discontinuous carbon- rich dots to a nanometrical layer which contains randomly distributed Ce3+- rich clusters. The growth process of the surface organic phase accelerates the formation of defect layers on the surface of ceria hollow spheres, while inhibiting further reduction inside the ceria shell. The synergistic effect formed by the structural changes of the surface organic phase and underlying ceria enables all samples to exhibit ferromagnetic and luminescent properties at room temperature. The ferromagnetic strength closely depends on the continuity and defect content of the Ce3+-rich layer on the surface of the ceria hollow spheres. The enhanced fluorescence, especially the blue and red emissions, is attributed to the defective structure of ceria and the composition of the organic phase.

Fabrication of copper supported porous silica–alumina hollow spheres for catalytic decomposition of nitrous oxide

Copper supported porous silica–alumina hollow sphere catalysts were prepared using surfactant micelles to control the size distribution of interparticle spaces in the hollow sphere shells.

Synthesis of few-layer MoS2@N-doped carbon core–shell hollow spheres using a cationic surfactant as a template for highly stable lithium-ion storage

A cationic surfactant templating route to epitaxial few-layer MoS2@N-doped carbon based on the self-assembledvia S+X−I+ electrostatic interactions is demonstrated, providing new nanostructured MoS2/carbon materials for different surfactant systems.

The enhanced confinement effect of double shell hollow mesoporous spheres assembled with nitrogen-doped copper cobaltate nanoparticles for enhancing lithium–sulfur batteries

The construction of sulfur cathode host which can effectively prevent the diffusion of soluble polysulfides and improve the reaction dynamics is the key to the development of high-performance Li–S batteries. Herein, a nitrogen-doped CuCo2O4 double shell hollow mesoporous sphere structure assembled with ultrafine nanoparticles was reported. As a multifunctional sulfur species carrier, the unique double shell provides multiple confinement spaces, chemisorption and catalytic sites, further impeding the “shuttle effect” of polysulfides. Meanwhile, the higher surface area and abundant porosity reduce the sulfur layer thickness and shorten the charge transfer path respectively, which is conducive to the rapid redox kinetics to polysulfides. Thanks to this enhanced confinement effect, a Li-S cell with the NCuCo2O4@S as the cathode shows excellent cycle stability, high sulfur loading, and rapid charge–discharge capability. This work provides a promising strategy for achieving high performance Li–S batteries by using metal compounds with a unique hollow structure.

Sustained CO2-photoreduction activity and high selectivity over Mn, C-codoped ZnO core-triple shell hollow spheres

Solar conversion of CO2 into energy-rich products is one of the sustainable solutions to lessen the global energy shortage and environmental crisis. Pitifully, it is still challenging to attain reliable and affordable CO2 conversion. Herein, we demonstrate a facile one-pot approach to design core-triple shell Mn, C-codoped ZnO hollow spheres as efficient photocatalysts for CO2 reduction. The Mn ions, with switchable valence states, function as “ionized cocatalyst” to promote the CO2 adsorption and light harvesting of the system. Besides, they can capture photogenerated electrons from the conduction band of ZnO and provide the electrons for CO2 reduction. This process is continuous due to the switchable valence states of Mn ions. Benefiting from such unique features, the prepared photocatalysts demonstrated fairly good CO2 conversion performance. This work is endeavoured to shed light on the role of ionized cocatalyst towards sustainable energy production.

Polytriptycene@CdS double shell hollow spheres with enhanced interfacial charge transfer for highly efficient photocatalytic hydrogen evolution

Double shell hollow spheres show highly efficient photocatalytic hydrogen evolution and excellent stability.

Rationally designed yolk–shell Co9S8–Co1−xS hollow spheres for advanced sodium-ion storage

Rationally-designed nitrogen-doped carbon-coated Co9S8–Co1−xS yolk–shell hollow spheres are synthesized to buffer the volume fluctuation and enhance the electrical/ionic conductivity.

Nitrogen-Doped Cobalt Pyrite Yolk-Shell Hollow Spheres for Long-Life Rechargeable Zn-Air Batteries.

Limited by the sluggish four‐electron transfer process, designing high‐performance nonprecious electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is urgently desired for efficient rechargeable Zn–air batteries (ZABs). Herein, the successful synthesis of porous nitrogen‐doped cobalt pyrite yolk–shell nanospheres (N‐CoS2 YSSs) is reported. Benefiting from the abundant porosity of the porous yolk–shell structure and unique electronic properties by nitrogen doping, the as‐prepared N‐CoS2 YSSs possess more exposed active surface, thus giving rise to superior activity for reversible oxygen electrocatalysis and outstanding cycling stability (more than 165 h at 10 mA cm−2) in ZABs, exceeding the commercial Pt/C and RuO2 hybrid catalysts. Moreover, the assembled ZABs, delivering a specific capacity of 640 mAh gZn −1, can be used for practical devices. This work provides a novel tactic to engineer sulfides as high efficiency and promising bifunctional oxygen electrocatalysts for advanced metal–air batteries.

Guided Crystallization of Zeolite Beads Composed of ZSM-12 Nanosponges

The direct route using a bifunctional amphiphilic structuring agent for the synthesis of hierarchical nanozeolites coupled with pseudomorphic transformation was used for the crystallization of hierarchized zeolite beads/hollow spheres composed of ZSM-12 (MTW structural-type) with nanosponge morphology. These beads/hollow spheres have the same average diameter of 20 µm as their counterpart amorphous mesoporous silica beads used as precursor in the starting synthesis mixture. The effects of synthesis parameters, such as stirring and treatment time at 140 °C, on the morphology, structure, and texture of the materials have been investigated using X-ray diffraction (XRD), N2 sorption, scanning electronic microscopy (SEM), and transmission electronic microscopy (TEM) techniques. Static conditions were found necessary to maintain the morphology of the starting amorphous silica beads. An Ostwald ripening phenomenon was observed with the increase in hydrothermal treatment time leading to the dissolution of the interior of some beads to form core shell beads or hollow spheres with larger crystals on the outer surface. These ZSM-12 beads/hollow spheres possess higher porous volume than conventional ZSM-12 zeolite powder and can be used directly for industrial applications.

Synthesis and morphology control of nano CuAl2O4 hollow spheres and their application as an efficient and sustainable catalyst for CO2 fixation

Four morphologies of the nano CuAl2O4 hollow microsphere were generated via different synthesis conditions. The results revealed that the morphology, structure and number of the shells of the CuAl2O4 product were strongly associated with the carbon template source, concentration of metal salts and hydrothermal processing time. By changing carbon template source, the hollow spheres of CuAl2O4 transformed from Yolk shell structure into triple shell hollow spheres. Further investigation also revealed that four types of the sample exhibited a varied catalysis performance for chemical fixation of carbon dioxide to produce cyclic carbonates with the efficiency decreasing from the flower like triple-shelled CuAl2O4 hollow spheres to the Yolk shelled CuAl2O4 hollow spheres. Various epoxides were converted at 85 °C, 0.3 MPa CO2 pressure, a catalyst loading of 0.5 mol% and a reaction time of 10 h in a solventless reaction media with isolated yields up to 98 % of the respective carbonate.

One-step template-free hydrothermal synthesis of partially Sr-incorporated hierarchical K-CHA zeolite microspheres

Abstract Partially Sr-incorporated hierarchical K-CHA zeolite microsphere of primary truncated bi-pyramidal crystallites was hydrothermally synthesized by one-step template-free hydrothermal process and the formation mechanism was investigated in detail. Its crystallization was accelerated by addition of strontium, and it was formed by three distinct steps: formation and aggregation of amorphous hollow nanospheres, collapse of agglomerated hollow nanospheres to multilayered disc, and rotational intergrowth into thread ball shape microsphere. The hollow nanosphere was formed by thermal expansion of Sr-coated solid silica nanoparticle, and the multilayered disc, by collapse of spherically aggregated hollow nanospheres. The collapse took place to minimize total surface energy by flattening sticky hollow spheres and oriented attachment of crystallites nucleated in the shell of hollow spheres. The multilayered disc grew finally to be thread ball shape microspheres. K-CHA zeolite microspheres displayed hierarchical character and showed excellent 298 K adsorptions for water (316 cm3 g−1), and CO2 (167.0 mg g−1 at 10 bar). The CO2/N2 adsorption selectivity was 10 due to incorporated potassium ions. Evidently, partially Sr-incorporated K-CHA zeolite microsphere was a good adsorbent for solvent dehydration and carbon capture.

Polypyrrole-encapsulated amorphous Bi2S3hollow sphere for long life sodium ion batteries and lithium–sulfur batteries

The well-designed amorphous Bi2S3-polypyrrole core–shell hollow spheres show excellent electrochemical properties in both SIBs and Li–S batteries.

Mesoporous nickel cobalt manganese sulfide yolk–shell hollow spheres for high-performance electrochemical energy storage

Mesoporous Ni–Co–Mn sulfide yolk–shell hollow spheres have been prepared via a self-template route and show excellent electrochemical performance in supercapacitors.

High carbon resistant Ni@Ni phyllosilicate@SiO2 core shell hollow sphere catalysts for low temperature CH4 dry reforming

Abstract Carbon dioxide reforming of methane (DRM) reaction has been widely explored since it is a sustainable process to transform carbon dioxide and methane which are the main greenhouse gases to value added synthesis gas. Herein, Ni@Ni phyllosilicate@SiO2 core shell hollow spheres (Ni@NiPhy@SiO2 HS) with high carbon resistance for DRM at 600 °C (10.4% weight loss after 50 h reaction) have been designed. Additionally, it also showed stable and high conversions (82.5% and 78.4% for carbon dioxide and methane respectively) and carbon resistance (5.5% weight loss) for DRM reaction at 700 °C within the testing time of 600 h. By contrast, for Ni@NiPhy without SiO2 shell, tremendous carbon nanotubes (CNTs) formed for DRM at 600 °C, even though it is interesting to find that there is slight nickel sintering. TPO-MS, H2-TPR, XPS and TEM characterizations showed that the interactions between nickel nanoparticles and NiPhy materials were increased due to the coating of SiO2 shell which also confined nickel and inhibited detaching of nickel from the surface of Ni@NiPhy@SiO2, which eliminates the accumulation of carbon to become CNTs. The synthesis method for core shell HS provides numerous opportunities to design other structured materials such as Ni-M (M = Co, Fe, Mg)@SiO2 HS for the efficient utilization of greenhouse gases through environmentally sustainable processes.

Efficient Charges Separation Using Advanced BiOI-Based Hollow Spheres Decorated with Palladium and Manganese Dioxide Nanoparticles

Multishell hollow structures have attracted tremendous attention due to their outstanding properties for application on photocatalysis. In this work, we demonstrated a straightforward and general method to construct BiOI-based core-double shell hollow spheres for the first time. The core-double shell hollow spheres consist of Pd particles and MnOx loaded onto the inner and outer surfaces of BiOI hollow spheres, respectively (Pd/BiOI/MnOx), and utilized them as an advanced photocatalyst for photocatalytic oxidation of formaldehyde gases and methyl blue. The hollow spheres structure could provide a large specific surface area, exposing a large number of catalytic active sites. Additionally, the Pd particles and MnOx serve the function of separating the reduction and oxidation reactive sites. The unique morphology combined with enhanced light-absorption provided the Pd/BiOI/MnOx core-double shell hollow spheres with high efficiency for the photocatalytic oxidation of formaldehyde gases and methyl blue. In si...

Pulverization Control by Confining Fe3O4 Nanoparticles Individually into Macropores of Hollow Carbon Spheres for High-Performance Li-Ion Batteries.

In this article, double carbon shell hollow spheres which provide macropores (mC) for ultrasmall Fe3O4 nanoparticle (10-20 nm) encapsulation individually were first prepared (Fe3O4@mC). The well-constructed Fe3O4@mC electrode materials offer the feasibility to study the volume change, aggregation, and pulverization process of the active Fe3O4 nanoparticles for Li-ion storage in a confined space. Fe3O4@mC exhibits excellent electrochemical performances and delivers a high capacity of 645 mA h g-1 at 2 A g-1 after 1000 cycles. Even at 10 A g-1 or after 1000 cycles at 2 A g-1, the porous carbon structure was well maintained and no obvious aggregation and pulverization of the Fe3O4 nanoparticles was observed, although the volume of the active Fe3O4 particles was expanded to 40-60 nm compared to that of the original particles (10-20 nm). This can be due to the in situ embedment of one Fe3O4 nanoparticle into one macropore individually. The uniform dispersion and confinement of the Fe3O4 nanoparticles in the macropores of the carbon shell could effectively accommodate severe volume variations upon cycling and prevent self-aggregation and spreading out from the carbon shell during the expansion process of the nanoscale Fe3O4 particles, leading to improved capacity retention. Our work confirms the effectiveness for pulverization control by confining Fe3O4 nanoparticles individually into macropores to improve its Li-ion storage properties, providing a novel strategy for the design of new-structured anode materials for Li-ion batteries.

Designing of a spatially separated hetero-junction pseudobrookite (Fe2TiO5-TiO2) yolk-shell hollow spheres as efficient photocatalyst for water oxidation reaction

For the first time, controlled pseudobrookite phase as the yolk and titanium oxide as the shell of hollow spheres were synthesized for the photocatalytic water oxidation. Simple and facile sacrificial hard template strategy was utilized. Firstly, the distribution of TiO2 in the hollow spheres was controlled by loading aqueous solution of 2, 3, and 5mol/L TiCl4 precursor respectively onto carbonaceous template followed by annealing. To prove the Fe3+ ions radial penetration into the hydrophobic core of carbonaceous template, we optimized the ethanol to water ratio. The Fe2TiO5-TiO2 yolk-shell hollow spheres exhibited high oxygen evolution reaction (OER) rate up to 148μmolg−1h−1 under UV–vis light. This was attributed to the better light harvesting due to the geometry of hollow sphere; charge separation by a thin shell-yolk hetero-junction, a void cavity to access reaction solvent to reactive sites and the hetero-junction of Fe-O-Ti in the hollow structure. These findings suggest that our designed Fe2TiO5-TiO2 yolk-shell hollow spheres are beneficial for the photocatalytic water oxidation.

Nano Ag-doped magnetic-Fe3O4@mesoporous TiO2 core–shell hollow spheres: synthesis and enhanced catalytic activity in A3 and KA2 coupling reactions

Nano Ag-doped Fe3O4@mesoporous TiO2 core–shell hollow spheres (h-Fe3O4@m-TiO2/Ag) were efficiently prepared. They were fully characterized by FT-IR, FE-SEM, EDX, ICP, TGA, XRD, and BET methods. In addition, their magnetic properties were determined by means of the VSM method. Also, the ρ shell of the prepared hollow Fe3O4 micro-particles was calculated, being found just slightly lighter than that of solid sphere-like Fe3O4. The catalytic activity of this novel catalyst system was successfully examined as a novel catalyst system in A3 coupling reactions (aldehyde + amine + acetylene). This highly active magnetic catalyst was easily separated using an external magnet and re-used in five consecutive runs in the model reaction without appreciable loss of its catalytic activity.

Type-II hetero-junction dual shell hollow spheres loaded with spatially separated cocatalyst for enhancing visible light hydrogen evolution

The solar water splitting performance of a photocatalyst is limited by the recombination of electron-hole pairs and the slow surface catalytic reactions. To conquer these problems, a new kind of Pt/TiO2/CdS/Co3O4 hollow spheres photocatalyst was proposed and synthesized. Its hydrogen evolution rate is 2000μmolg−1h−1 under 100mWcm−2 visible light irradiation, which is over 540 times higher than that of TiO2/CdS double-shelled hollow spheres under the same conditions. The enhancement can be attributed to the synergistic action between the built-in electric field and spatially separated co-catalysts. This work gives a way to greatly enhance the solar water splitting performance.