Template-Free Synthesis of Sb_2S_3 Hollow Microspheres as Anode Materials for Lithium-Ion and Sodium-Ion Batteries

Hierarchical Sb_2S_3 hollow microspheres assembled by nanowires have been successfully synthesized by a simple and practical hydrothermal reaction. The possible formation process of this architecture was investigated by X-ray diffraction, focused-ion beam-scanning electron microscopy dual-beam system, and transmission electron microscopy. When used as the anode material for lithium-ion batteries, Sb_2S_3 hollow microspheres manifest excellent rate property and enhanced lithium-storage capability and can deliver a discharge capacity of 674 m Ah g^(-1) at a current density of 200 m A g^(-1) after 50 cycles. Even at a high currentdensity of 5000 m A g^(-1), a discharge capacity of541 m Ah g^(-1) is achieved. Sb_2S_3 hollow microspheres also display a prominent sodium-storage capacity and maintain a reversible discharge capacity of 384 m Ah g^(-1) at a current density of 200 m A g^(-1) after 50 cycles. The remarkable lithium/sodium-storage property may be attributed to the synergetic effect of its nanometer size and three-dimensional hierarchical architecture, and the outstanding stability property is attributed to the sufficient interior void space,which can buffer the volume expansion.

Silver Hollow Microspheres: Large-scale Synthesis, Characterization and Electromagnetic Shielding Property

A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core–shell particles by a controllable liquid reduced reaction of Ag[（NH3）2]＋ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy （SEM）, transmitted electron microscopy （TEM）, X-ray photoelectron spectra （XPS）, X-ray diffraction （XRD） and energy dispersive X-ray （EDX） etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.

VN nanoparticle-assembled hollow microspheres/N-doped carbon nanofibers:An anode material for superior potassium storage

Thanks to inexpensive and bountiful potassium resources,potassium ion batteries(PIBs)have come into the spotlight as viable alternatives for next-generation battery systems.However,poor electrochemical kinetics due to the large size of the K^(+) is a major challenge for PIB anodes.In this paper,an ingenious design of VN nanoparticleassembled hollow microspheres within N-containing intertwined carbon nanofibers(VN-NPs/N-CNFs)via an electrospinning process is reported.Employed as PIB anodes,VN-NPs/N-CNFs exhibit a superb rate property and prolonged cyclability,surpassing that of other reported metal nitride-based anodes.This is ascribed to:(i)the VN NP-assembled hollow microspheres,which shorten the K^(+) diffusion distance,and mitigate volume expansion;and(ii)the interconnected N-CNFs,which supply numerous active sites for K^(+) adsorption and facilitate rapid electron/ion transport.

Preparation of Amorphous LiZn Ferrites Hollow Microspheres by Self-reactive Quenching Technology

NaCl aqueous solution（15 wt%） was used as the quenching medium to prepare amorphous Lithium-Zinc ferrite hollow microspheres（LiZn FHMs） based on self-reactive quenching technology. Investigations by scanning electro microscope, X-ray diffraction, electron diffraction of transmission electron microscope, and differential scanning calorimetry prove that LiZn FHMs are susceptible to amorphization. It is indicated that NaCl aqueous solution（15 wt%） has ultra-fast quenching speed, and the growth rate of crystals on LiZn FHMs is so large that the formation and growth of the crystal nucleus are significantly restrained. This is the main reason for the formation of amorphous LiZn FHMs.

Effects of Heat Treatment Temperature and Time on Structure and Static Magnetic Property of W-type Ferrite Hollow Microspheres

Hollow spheres of hexagonal ferrite BaCozFelrO27 were fabricated through a spray pyrolysis technique using co-precipitation ferrite powder precursor as materials, followed by calcinations in an air atmosphere. The phase composition, micro-morphology, and static magnetic property of the particles were measured by XRD, SEM, and VSM. The results indicate that the method for preparation of ferrite hollow microspheres （FHM） results in a broad particles size distribution. The density of FHM decreased from 5.31 g/ cm^3 to 2.31 g/cm^3. When the heating rate was 5℃/min, and temperature was 1 200℃ for 4 hours, pure W-type ferrites were formed. With the heat treatment temperature and time increasing, the crystal structure becomes perfect, the saturation magnetization is increased and the coercive force is decreased.

Self-templating construction of hollow microspheres assembled by nanosheets with exposed active planes for sodium ion storage

P2-type layered metal oxides have been considered as one of the promising cathode candidates for high-performance Na-ion batteries(SIBs).However,it is still challenging to balance the contradiction of high energy density and long cycle life due to the structural degradation and sluggish ion diffusion dynamics.Here,the hierarchical P2-Na2/3Ni1/3Mn2/3O2 hollow microspheres assembled by nanosheets are constructed via a self-template approach.The obtained nanosheets with more exposed electrochemical active planes serving as desodiation/sodiation reactors can provide substantial Na+channels,shorten the diffusion pathways,and accommodate the volume changes during charge/discharge process.Benefiting from the facile Na+diffusion paths and optimal architecture modulation,the cathode delivers a high initial Coulombic efficiency of 96.0%with a high energy density of 299.7 Wh·kg^(−1).The highly reversible structural evolutions processes are verified by galvanostatic intermittent titration technique(GITT)and operando electrochemical impedance spectroscopy(EIS)measurement,which would significantly improve the cycle stability(83.3%capacity retention at 1.0 C over 500 loops).Furthermore,the full cell assembled by hard carbon presents a high reversible capacity of 71 mAh·g^(−1)at 0.2 C and promising capacity retention(91.5%after 50 cycles).The designing concept of morphological configuration in this work paves an accessible route for building high-performance electrode materials.

Denatured proteins show new vitality:Green synthesis of germanium oxide hollow microspheres with versatile functions by denaturing proteins around bubbles

The hollow structure has long attracted great attention because of its excellent properties.However,this special structure is usually synthesized through some complex approaches.Herein,we discovered that denatured bovine serum albumin(BSA)can trigger unusual biomineralization for the simple,green and shape-controllable synthesis of germanium oxide(GeOx)hollow microsphere(HMS).At high temperature(60℃),BSA was denatured,and a compact BSA layer was formed around the H2 bubbles.The denatured BSA layer was stable and suitable for anchoring and growing GeOx.By simply changing the BSA concentration and temperature,various morphologies of GeOx could be obtained.Due to the denatured protein skeletons and microenvironment-regulated collapse,GeOx HMS showed great potential for intelligently responsive pesticide delivery in the insect gut,showing superiority over traditional delivery systems,which early release pesticides in the mouth and stomach.Inspired by its large specific surface area,excellent biocompatibility,modifiable functional groups,and high electrocatalytic activity,GeOx HMS was also applied to versatile sensors for H_(2)O_(2) assays at physiological pH and rapid coronavirus COVID-19 detection.This work not only provides some evidence for understanding proteins in depth but also paves a new avenue for the biomineralization-inspired synthesis of hollow structures with versatile functions.

Step-scheme CdS/TiO_(2) nanocomposite hollow microsphere with enhanced photocatalytic CO_(2) reduction activity

Converting solar energy into chemical energy by artificial photosynthesis is promising in addressing the issues of the greenhouse effect and fossil fuel crisis.Herein,a novel photocatalyst,i.e.CdS/TiO_(2) hollow microspheres(HS),were dedicatedly designed to boost overall photocatalytic efficiency.TiO_(2) nanoparticles were in-situ decorated on the inside and outside the shell of Cd S HS,ensuring close contact between TiO_(2) and CdS.The CdS/TiO2 HS with abundant mesopores inside of the shell boost the light absorption via multiscattering effect as well as accessible to reactions in all directions.The heterojunction was scrutinized and the charge transfer across it was revealed by in-situ irradiated X-ray photoelectron spectroscopy(ISI-XPS).Ultimately,the charge transfer in this composite was determined to follow stepscheme mechanism,which not only facilitates the separation of charge carriers but also preserves strong redox ability.Benefited from the intimate linkage between Cd S and TiO_(2) and the favorable step-scheme heterojunction,enhanced photocatalytic CO_(2) reduction activity was accomplished.The CH4 yield rate of CdS/TiO_(2) reaches 27.85μmol g^(–1) h^(–1),which is 145.6 and 3.8 times higher than those of pristine CdS and TiO_(2),respectively.This work presents a novel insight into constructing step-scheme photocatalytic system with desirable performance.

A review of recent progress in preparation of hollow polymer microspheres

The preparation methods of hollow polymer microspheres both at home and abroad are summarized, and their preparation mechanisms and developmental states are presented. These methods include the liquid droplet method, dried-gel droplet method, self-assembly method, microencapsulation method, emulsion polymerization method and the template method. Hollow polystyrene microspheres are the most extensively studied in the research of hollow polymer microspheres. Through comparison of the advantages and disadvantages of different preparation methods, it is concluded that microencapsulation method is most suitable for preparing polystyrene hollow microspheres.

Preparation and photoluminescence enhancement of Li^+ and Eu^(3+) co-doped YPO_4 hollow microspheres

Li＋ and Eu3＋ co-doped YPO4 hollow microspheres were successfully synthesized by a sacrificial template method using polystyrene （PS） as template. Techniques of X-ray diffraction （XRD）, scanning electron microscopy （SEM）, as well as transmission electron microscopy （TEM） were employed to characterize the as-synthesized sample. Furthermore, the photoluminescence （PL） characterization of the Li＋ and Eu3＋ co-doped YPO4 microsphere was carried out and the effects of the doping concentration of Li＋ and Eu3＋ active center concentration as well as calcination temperature on the PL properties were studied in detail. The results showed that the incorporation of Li＋ ions into the YPOa：Eu3＋ lattice could induce a remarkable improvement of the PL intensity. The highest emission intensity was observed with the compound of 5%Li＋ and 5%Eu3＋ co-doped YPO4, whose brightness was increased by a factor of more than 2.2 in comparison with that of the YPO4：5%Eu3＋.

MnS hollow microspheres combined with carbon nanotubes for enhanced performance sodium-ion battery anode

MnS as anode material for sodium-ion batteries(SIBs)has recently attracted great attention because of the high theoretical capacity,great natural abundance,and low cost.However,it suffers from inferior electrical conductivity and large volume expansion during the charge/discharge process,leading to tremendous damage of electrodes and subsequently fast capacity fading.To mitigate these issues,herein,a three-dimensional(3D)interlaced carbon nanotubes(CNTs)threaded into or between MnS hollow microspheres(hollow MnS/CNTs composite)has been designed and synthesized as an enhanced anode material.It can effectively improve the electrical conductivity,buffer the volume change,and maintain the integrity of the electrode during the charging and discharging process based on the synergistic interaction and the integrative structure.Therefore,when evaluated as anode for SIBs,the hollow MnS/CNTs electrode displays enhanced reve rsible capacity(275 mAh/g at 100 mA/g after 100 cycles),which is much better than that of pure MnS electrode(25 mAh/g at 100 mA/g after 100 cycles)prepared without the addition of CNTs.Even increasing the current density to 500 mA/g,the hollow MnS/CNTs electrode still delivers a five times higher reversible capacity than that of the pure MnS electrode.The rate performance of the hollow MnS/CNTs electrode is also superior to that of pure MnS electrode at various current densities from 50 mA/g to 1000 mA/g.

Multi-shelled TiO2/Fe2TiO5 heterostructured hollow microspheres for enhanced solar water oxidation

There remains a pressing challenge in the fabrication of superior photocatalysts for light-driven water oxidation.Here,we designed and fabricated heterostructured TiO2/Fe2TiO5 hollow microspheres with single-,double-,closed-double-,triple-,and core-shell structures and different Fe/Ti molar ratios using a facile sequential templating approach.The closed-double-shelled TiO2/Fe2TiO5 hollow microspheres with 35% Fe exhibited the highest oxygen evolution reaction rate up to 375 μmol＆#183;g-1＆#183;h-1 and good stability for 5 h.The high performance can be attributed to the closed-double shell,which had more reactive sites and greater light-harvesting ability,self-supported thin shells with short charge-transfer paths,and a favorable staggered band alignment between the TiO2 and Fe2TiOs.

Novel hollow microsphere with porous carbon shell embedded with Cu/Co bimetal nanoparticles:Facile large-scale preparation and catalytic hydrogenation performance

Non-noble bimetals have attracted extensive attention for their natural aboundance and low cost,but it remains a big challenge to design and synthesize novel supported non-noble bimetal nanocatalyst in a controllable and high-efficient manner.Herein,a novel hollow spherical supported non-noble bimetal nanocatalyst with porous carbon shell as the continuous matrix and Cu/Co bimetal nanoparticles as the dispersion phase is successfully fabricated by a convenient strategy involving spray drying and subsequent heat treatment.The morphology and microstructure depend catalyst activity of the hollow spherical supported catalyst has been studied systematically.It is found that the heating temperature plays a critical role in determining the microstructure and catalytic performance of the products.With an optimal heating temperature of 600°C,the corresponding product exhibits the highest normalized reaction rate constant(k_(n))of 25.4 s^(-1)g^(-1)for catalytic reduction of 4-notrophenol,which can be attributed to the suitable synergism of the well-defined bimetal structure,combined effect of the two metallic phases and the metal-support interaction.This work provides an additional strategy for the simultaneous formation of both the support and the active loading phase of supported non-noble bimetal nanocatalyst,and may shed some light on the high-efficiency synthesis of other supported heterostructure with various compositions and properties.

Synthesis and NH_(3)/TMA sensing properties of CuFe_(2)O_(4) hollow microspheres at low working temperature

In this work,CuFe_(2)O_(4) hollow microspheres assembled with nanosheets(CuFe_(2)O_(4) HMANs)were synthesized using a solvothermal method followed by an annealing treatment.The effects of annealing temperature on microstructure,chemical composition and gas sensing characteristics of as-prepared samples were investigated.The results showed that annealing treatment played a crucial role in the final products.All samples demonstrated hollow spherical morphology assembled with nanosheets or nanoparticles.The CuFe_(2)O_(4) HMANs annealed at400℃exhibited the best n-type conductometric sensing properties toward low-concentration NH3 at 100℃and49%RH.The sensor response to 10×10^(-6)NH_(3) was 4.0 with a rapid response time of 32 s,and it even showed a response of 1.2 toward 1×10^(-6)NH3 at the same condition,while a response of 3.95 to trimethylamine(TMA).The CuFe_(2)O_(4) HMANs-based NH_(3) sensor also exhibited good selectivity and excellent reproducibility.Therefore,this work provided a novel promised sensing material of low-concentration NH_(3) and TMA for real-time monitoring.

Effects of Shell Composition, Dosage and Alkali Type on the Morphology of Polymer Hollow Microspheres

Polymer hollow microspheres were prepared by performing alkali treatment on the multilayer core/shell polymer latex particles containing carboxyl groups. Effects of the shell composition and dosage as well as alkali type on the morphology of the microspheres were investigated. Results showed that in comparison with acrylonitrile（AN） and methacrylic acid（MAA）, using butyl acrylate（BA） as the shell co-monomer decreased the glass transition temperature（T_g） of shell effectively and was beneficial to the formation of uniform and big hollow structure. Along with the increase of the shell dosage, the alkali-treated microspheres sequentially presented porous and hollow morphology, and the size of microspheres increased, while the hollow diameter increased first and then decreased, and the maximum hollow ratio reached 39.5%. Furthermore, the multilayer core/shell microspheres had better tolerance to NH_3·H_2O than to NaOH. When the molar ratio of alkali to methacrylic acid（MR_（alkali/acid）） for Na OH ranged from 1.15 to 1.30 or MRalkali/acid for NH_3·H_2O ranged from 1.30 to 2.00, the regular polymer hollow microspheres could be obtained.

Rational Fabrication of Size Tunable SnO2 Hollow Microspheres

A designed solution route was developed to fabricate size tunable SnO2 hollow microspheres based on the sol-gel theory. The hydrolysis of SnSO4 released protons to form SnO2 particulates and induced the decrease of pH value. To minimize the high surface energy, the SnO2 particulates tended to assemble into large particles, the size of which was affected by the electrolyte concentration or pH value. Elevating SnSO4 content aroused the decrease of the pH value that directed to the shrinkage of the aggregated particle size of SnO2. Size tunable SnO2 hollow micro- spheres were then rationally fabricated under solvothermal conditions via Ostwald ripening by simply adjusting the SnSO4 concentration. The in situ pH decrease directed to the shrinkage of the particle size from 270 nm to 112 nm. The formation mechanism was confirmed and rationally elucidated by the time dependant morphology evolution. Charge-discharge tests revealed that the reduced particle size aroused an improved lithium ion battery performance.

Formation of CaCO_(3) hollow microspheres in carbonated distiller waste from Solvay soda ash plants

For decades,distiller waste and CO_(2) were not the first choice for production of high valued products.Here,CaCO_(3) hollow microspheres,a high-value product was synthesized from such a reaction system.The synthetic methods,the formation mechanism and operational cost were discussed.When 2.5 L·min^(–1)·L^(–1) CO_(2) was flowed into distiller waste(pH=11.4),spheres with 4–13μm diameters and about 2μm shell thickness were obtained.It is found that there is a transformation of CaCO_(3) particles from solid-cubic nuclei to hollow spheres.Firstly,the Ca(OH)_(2) in the distiller waste stimulated the nucleation of calcite with a non-template effect and further maintained the calcite form and prevented the formation of vaterite.Therefore,in absence of auxiliaries,the formation of hollow structures mainly depended on the growth and aging of CaCO_(3).Studies on the crystal morphology and its changes during the growth process point to the inside–out Ostwald effect in the formation of hollow spheres.Change in chemical properties of the bulk solution caused changes in interfacial tension and interfacial energy,which promoted the morphological transformation of CaCO_(3) particles from cubic calcite to spherical clusters.Finally,the flow process for absorption of CO_(2) by distiller waste was designed and found profitable.

Preparation of P2O5-SiO_(2) hollow microspheres in the presence of phosphoric acid

Silica hollow microspheres containing phos-phorous have been prepared by a sol-gel/emulsion method which uses tetraethoxysilane(TEOS)as the precursor for the SiO_(2) and phosphoric acid(H3PO4)as the precursor for P2O5.The hollow structure forms an emulsion system which is composed of an oil phase(kerosene,sorbitan monooleate(Span 80))and an aqueous phase(a viscous sol solution of ethanol,TEOS and H3PO4).Some of the phosphorous remains in thefinal silica shell structure even after calcination at 650°C.The hollow structure of the P2O5-SiO_(2)(silicophosphate)was characterized by X-ray diffraction(XRD),polarized optical microscopy(POM),scanning electron microscopy(SEM),nitrogen adsorption measurement and Fourier transform infrared spectroscopy(FTIR).

Preparation of P(MBA-co-MAA)/Zr(OH)_(4)/P(EGDMA-co-MAA)/TiO_(2)Tetra-layer Hybrid Microspheres and the Corresponding ZrO_(2)/TiO_(2)Double-shelled Hollow Microspheres

Double-shelled zirconia/titania(ZrO_(2)/TiO_(2))hollow microspheres were prepared by the selective removal of the polymer components via the calcination of the corresponding tetra-layer poly(N,N'-methylenebisacryl amide-comethacrylic acid)(P(MBA-co-MAA))/Zr(OH)_(4)/poly(ethyleneglycol dimethacrylate-co-methacrylic acid)(P(EGDMAco-MAA))/TiO_(2)hybrid microspheres.These tetra-layer microspheres were synthesized by the combination of the distillation copolymerization of N,N′-methylenebisacryl amide-co-methacrylic acid(MBA)or ethyleneglycol dimethacrylate(EGDMA)crosslinker and methacrylic acid(MAA)for the preparation of polymer core and thirdlayer as well as the controlled sol-gel hydrolysis of inorganic precursors for the construction of zirconium hydroxide(Zr(OH)_(4))and titania(TiO_(2))layers.The thicknesses of zirconia and titania shell-layers were conveniently controlled via varying the feed of zirconium n-butoxide(Zr(OBu)_(4))and titanium tetrabutoxide(TBOT)during the sol-gel hydrolysis,while the sizes of polymer layers were tuned through a multi-stage distillation precipitation copolymerization.The structure and morphology of the resultant microspheres were characterized by transmission electron microscopy(TEM),X-ray diffractometer(XRD),X-ray photoelectronic spectroscopy(XPS),and thermogrametric analysis(TGA).

SYNTHESIS OF MONODISPERSE HOLLOW POLYMER MICROSPHERES WITH FUNCTIONAL GROUPS BY DISTILLATION PRECIPITATION POLYMERIZATION

Monodisperse hollow polymer microspheres having various functional groups on the shell-layer, such as carboxylic acid, pyridyl and amide, were prepared by two-stage distillation precipitation polymerization in neat acetonitrile in the absence of any stabilizer or additive, during which monodisperse poly（methacrylic acid） （PMAA） afforded from the first-stage polymerization was utilized as the seeds for the second-stage polymerization. The shell layer with different functional groups was formed during the second-stage copolymerization of either divinylbenzene （DVB） or ethyleneglycol dimethacrylate （EGDMA） as crosslinker and the functional comonomers, in which the hydrogen-bonding interaction between the carboxylic acid group of PMAA core and the functional groups of the corresponding comonomers, including carboxylic acid, amide and pyridyl, played an essential role for the formation of monodisperse core-shell functional microspheres. The hollow polymer microspheres were then developed after the subsequent removal of PMAA cores by dissolution in ethanol under basic condition. Transmission electron microscopy （TEM） and scanning electron microscopy （SEM） were used to determine the morphology of the resultant PMAA core, functional core-shell microspheres and the corresponding hollow polymer microspheres with different functional groups. FT-IR spectra confirmed the successful incorporation of the various functional groups on the shell layer of the hollow polymer microspheres.