Porous Hollow Microspheres Research Articles

Large-scale fabrication of porous YBO3 hollow microspheres with tunable photoluminescence.

Hollow lanthanide-doped compounds are some of the most popular materials for high-performance luminescent devices. However, it is challenging to find an approach that can fabricate large-scale and well-crystallized lanthanide-doped hollow structures and that is facile, efficient and of low cost. In this study, YBO3: Eu3+/Tb3+ hollow microspheres were fabricated by using a novel multi-step transformation synthetic route for the first time with polystyrene spheres as the template, followed by the combination of a facile homogeneous precipitation method, an ion-exchange process and a calcination process. The results show that the as-obtained YBO3: Eu3+/Tb3+ hollow spheres have a uniform morphology with an average diameter of 1.65 µm and shell thickness of about 160 nm. When used as luminescent materials, the emission colours of YBO3: Eu3+/Tb3+ samples can be tuned from red, through orange, yellow and green-yellow, to green by simply adjusting the relative doping concentrations of the activator ions under the excitation of ultraviolet light, which might have potential applications in fields such as light display systems and optoelectronic devices.

Synthesis of hollow porous carbon microspheres and their application to room-temperature Na-S batteries

A novel electrode material of room-temperature Na-S batteries was designed by hollow porous carbon microspheres (HPCM) derived from metal-organic frameworks (MOFs), which were used as a matrix to form HPCM/S composite by melt-infiltrating method. The electrochemical performance show that the HPCM/S composite as cathode delivered a reversible capacity over 617 mA h g−1 at 0.7C, maintaining over 311 mA h g−1 capacities after 60 cycles. The good electrochemical properties can be attributed to the hollow and porous structure of HPCM, which can host sulfur efficiently and alleviate the volume expansion caused by polysulfide.

NO2 sensing properties of SmFeO3 porous hollow microspheres

Porous hollow microspheres of SmFeO3 were prepared from a simple process involving a metal organic framework (MOF) compound as the templating precursor. With a diameter of about 2 μm, these hollow-centered microspheres are formed by nanoporous thin walls of SmFeO3. Chemoresistive gas sensors based on these microspheres exhibits excellent sensing performance on NO2 at 200 °C, including high sensitivity (response of 10.2 under 200 ppb) with detection limit as low as 50 ppb, high selectivity, and reasonably short time for response and recovery (369 s/478 s). The superior sensing response over other SmFeO3-based NO2 sensors can be ascribed to the electron-accepting reactions during NO2 adsorption, which is facilitated by the special morphological features of the microsphere.

Oxygen and Nitrogen Co‐enriched Sustainable Porous Carbon Hollow Microspheres from Sodium Lignosulfonate for Supercapacitors with High Volumetric Energy Densities

AbstractOxygen and nitrogen co‐enriched hierarchical porous carbon hollow microspheres are synthesized by using biomass‐derivative sodium lignosulfonate as a feedstock through a facile and scalable process. This four‐step synthesis process involves spray drying, thermal stabilization, carbonization, and post nitric acid modification. The as‐obtained carbon exhibits a moderate but efficient porosity (specific surface area of 991 m2 g−1, total pore volume of 0.75 cm3 g−1), small particle size of 0.2–5 μm, high electrode density of 0.45 g cm−3, and abundant surface oxygen/nitrogen species (13.12 at.%/0.97 at.%). Its electrochemical performance is evaluated by assembling into supercapacitors in 7 M KOH electrolyte. The three‐electrode cell presents a high gravimetric capacitance of 284 F g−1 at 0.1 A g−1 and good rate capability of 43.6 % at 20 A g−1. While the two‐electrode cell gives an impressive volumetric capacitance of 21.2 F cm−3 at 0.1 A g−1, marvelous volumetric energy density of 2.9 Wh L−1 at 11.3 W L−1, and remarkable cycling stability of 93.4 % capacitance retention after 10000 cycles, which is superior or comparable to that of commercial activated carbon.

Construct 3D porous hollow Co3O4 micro-sphere: A potential oxidizer of nano-energetic materials with superior reactivity

High energy density and rapid reactivity are the future trend for nano-energetic materials. Energetic performance of nano-energetic materials depends on the interfacial diffusion and mass transfer during the reacted process. However, the development of desired structure to significantly enhance reactivity still remains challenging. Here we focused on the design and preparation of 3D porous hollow Co3O4 micro-spheres, in which gas-blowing agents (air) and maximize interfacial interactions were introduced to enhance mass transport and reduce the diffusion distance between the oxidizer and fuel (Aluminum). The 3D hierarchical Co3O4/Al based nano-energetic materials show a low-onset decomposition temperature (423 °C), and high heat output (3118 J g−1) resulting from porous and hollow nano-structure of Co3O4 micro-spheres. Furthermore, 3D hierarchical Co3O4/Al arrays were directly fabricated on the silicon substrate, which was fully compatible with silicon-based microelectromechanical systems to achieve functional nanoenergetics-on-a-chip. This approach provides a simple and efficient way to fabricate 3D ordered nano-energetic arrays with superior reactivity and the potential on the application in micro-energetic devices.

Preparation of porous hollow Fe3O4/P(GMA-DVB-St) microspheres and application for lipase immobilization.

Functional porous hollow microspheres with superparamagnetism, Fe3O4/P(GMA-DVB-St) microspheres, were prepared via a dispersion polymerization based on hollow Fe3O4 microspheres. The resulting hollow microspheres were characterized by means of Fourier-transform infrared spectrophotometer (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) gas sorptometry, and vibrating sample magnetometer (VSM). It is verified that the resulting hollow microspheres are porous and have high saturation magnetization. For further application, candida rugosa lipase (CRL) was immobilized onto the hollow microshperes, the loading amount of lipase was 143.88mg CRL/g support and the activity recovery of the obtained immobilized lipase reached 73.25%. Besides, the resulting immobilized CRL (ICRL) were found to have better pH endurance and temperature endurance than the free ones, which showed the optimal catalytic activity with pH of 9.0 and temperature of 60°C. The ICRL displayed excellent reusability as well.

Gas template-assisted spray pyrolysis: A facile strategy to produce porous hollow Co3O4 with tunable porosity for high-performance lithium-ion battery anode materials

Porous hollow Co3O4 microspheres have been synthesized from a mixed cobalt nitrate and urea solution through spray pyrolysis followed by calcination at 600 °C in air. This porous hollow Co3O4 is assembled by nanoparticles and exhibits variable porosity depending on the amount of gas in the system. In pyrolysis process, urea continuously decomposes into gaseous components, which act as a template to control the porous structure. The amount of gas escaping from precursor droplets can directly influence the porosity of the microspheres and the size of the nanoparticles controlled by the ratio of urea to cobalt nitrate. Electrochemical measurements show that the performance of the porous hollow Co3O4 microspheres is related to the porosity and size of the nanoparticles. The sample with optimal porosity delivers a high first charge capacity of 1,417.9 mAh·g−1 at 0.2C (1C = 890 mA·g−1), and superior charge cycle performance of 1,012.7 mAh·g−1 after 100 cycles. In addition, the optimized material displays satisfactory rate performance of 1,012.4 mAh·g−1 at 1C after 50 cycles and 881.3 mAh·g−1 at 2C after 300 cycles. Superior charge/discharge capacity, excellent rate performance and high yield achieved in this study is promising for the development of high-performance Co3O4 anode materials for lithium-ion batteries.

Porous SnO2 hollow microspheres as anodes for high-performance lithium ion battery

SnO2 has been studied as a promising anode material for lithium-ion batteries due to its high theoretical capacity. However, the large volume change (>300%) and severe structural collapse during cycles are serious. To solve these issues, the porous SnO2 dumbbell-shaped hollow microspheres (DSHSs) were synthesized by a sacrificial template method. The porous SnO2 DSHSs deliver a capacity of 695 mAh g−1 when the current density returns from 1600 to 100 mA g−1. After being tested at larger current density of 1.0 A g−1 for 100 cycles, the capacity retain 602 mAh g−1. The superior performance of porous SnO2 DSHSs can be attributed to the porous and hollow microstructure, which provides more lithium storage sites; shorter Li-ion diffusion length and sufficient void space.

Facile preparation of polymer microspheres and fibers with a hollow core and porous shell for oil adsorption and oil/water separation

Non-solvent assisted electrospinning was proposed for fabricating Polymethylmethacrylate (PMMA) microspheres and fibers with a hollow core and porous shell, which could be used for oil adsorption and oil/water separation. Propanediol was chosen as the non-solvent because of its high surface tension and viscosity as well as large phase separation tendency with polymer, which was beneficial to the formation of both the hollow core and porous shell during the electrospinning. With the increase of the polymer solution concentration, the microsphere gradually evolved to the bead-on-string geometry and finally to a continuous fiber form, indicating the transition from electro-spraying to electrospinning. The hollow core and dense surface pores enhanced the hydrophobicity, oleophilicity, permeability, and specific surface area of the fibers, and hence imparted the fibrous mat a high oil adsorption capacity. When the porous hollow microspheres were electro-sprayed onto the stainless steel mesh followed by the PDMS modification, the modified mesh became super-hydrophobic and super-oleophilic with the contact angle of 153° and sliding angle of 4°. The as-prepared mesh showed rapid oil/water separation with high efficiency and excellent recycling performance. The flux for separation of oil/water mixture could reach as high as 11,000 L m−2 h−1. This facile non-solvent assisted electrospinning method provides a new avenue for preparation of multifunctional porous materials which possess potential applications in large-scale oil/water separation.

Fe-doped γ-Al2O3 porous hollow microspheres for enhanced oxidative desulfurization: facile fabrication and reaction mechanism

Fe-Doped γ-Al2O3 porous hollow microspheres with hierarchical porosity were fabricated as efficient catalysts for H2S selective oxidation.

Microwave Solvothermal Fabrication of Zirconia Hollow Microspheres with Different Morphologies Using Pollen Templates and Their Dye Adsorption Removal

Both porous and scale-like wall zirconia (ZrO2) hollow microspheres were successfully prepared through a facile and mild microwave solvothermal method using the rape pollen as biotemplates. The formation mechanisms were discussed for both ZrO2 hollow microspheres fabricated using pollen biotemplate with different pollen treatments. The porous ZrO2 hollow microspheres had a specific surface area of 40.92 m2·g–1, significantly higher than scale-like wall ZrO2 hollow microspheres (24.79 m2·g–1) and ZrO2 particles (27.99 m2·g–1). The adsorption test results showed that porous ZrO2 hollow microspheres had a higher adsorption capability (96.98 g·mg–1) than scale-like wall ZrO2 hollow microspheres (38.55 g·mg–1) and ZrO2 particles (32.03 g·mg–1) for Congo red. The adsorption followed pseudo-second-order kinetics, and the adsorption process was homogeneous adsorption of monolayer.

Adsorption behavior of three-dimensional magnetic hollow porous Ni-ferrites microsphere for dyes removal

ABSTRACTIn this study, the three-dimensional magnetic hollow porous Ni-ferrites (3D-MHP-NiFe2O4) microsphere has been synthesized. As-prepared 3D-MHP-NiFe2O4 exhibits superior adsorption capacities for brilliant green (BG) (147.93 mg g−1) and acid carmoisine (AC) (44.07 mg g−1). Compared with NiFe2O4 nanoparticles (NiFe2O4-NPs), the enhancement has been ascribed to relatively high specific surface area and unique hollow porous structure, which are favorable for transfer of adsorbates. The Langmuir isotherm model conforms well to the experimental data. The adsorption process obeys the pseudo-second-order kinetic model. The overall rate process has been mainly controlled by intraparticle diffusion. In addition, 3D-MHP-NiFe2O4 exhibits a high stability and good reusability.

Sonochemical synthesis of ZnO hollow microstructure/reduced graphene oxide for enhanced sunlight photocatalytic degradation of organic pollutants

ZnO hollow microspheres and ZnO hollow microspheres/reduced graphene oxide nanocomposites (ZnO-rGO) were synthesized through simple and surfactant free sonochemical method at relatively low temperature. The crystalline structure and morphology of the as-prepared hollow microspheres and their nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, BET surface area analyzer and electron microscopy (SEM, TEM). The photocatalytic performance of the samples was evaluated for the photodegradation of 2,4-dichlorophenoxy acetic acid (2,4-D) under direct sunlight irradiation. The results showed that the synthesized ZnO have porous hollow microspheres structure, which can act as an antenna system transferring the photogenerated electrons within the network structure as compared to the nonporous ZnO nanoparticles. The introduction of graphene oxide is further enhanced the photocatalytic activity evidencing the role of graphene oxide extending the optical absorption to longer wavelength as well as in decreasing the electron-hole pair recombination. The effect of various parameters such as pH and initial concentration of 2,4-D has been also studied. The kinetic parameters have been determined and the underline reaction mechanism has been proposed.

Hollow ceramic microspheres prepared by combining electro-spraying with non-solvent induced phase separation method: A promising feedstock for thermal barrier coatings

Hollow microspheres were prepared by a combination method of electro-spraying and non-solvent induced phase separation, using a slurry of polymer with Y2O3-stabilized ZrO2 powder (YSZ). Subsequent sintering was carried out to obtain porous hollow YSZ microspheres with proper strength aiming to be thermal spraying feedstock. The ESNP particle size and distribution strongly depended on the applied voltage of the electro-spraying process and the jet nozzle diameter. The YSZ microspheres always consisted of a thin spongy shell and highly porous interior structure. The microsphere size decreased from 1000 to 100μm with increasing voltage (10–20kV). The cone-jet mode of electrospray reached steady as the nozzle diameter varied from 0.5 to 0.8mm. Compared with the coatings made from commercial hollow spherical powder, the coatings prepared by ESNP powder had enhanced resistance to sintering and exhibited a longer life than commercial spray powder. It has demonstrated that the ESNP method provides a versatile way to manipulate the microstructure of ceramic microspheres, and could been used to fabricate high performance thermal barrier coatings by plasma spraying.

Tuning Shell Numbers of Transition Metal Oxide Hollow Microspheres toward Durable and Superior Lithium Storage.

Multishelled hollow structured transition metal oxides (TMOs) are highly potential materials for high energy density energy storage due to their high volumetric energy density, reduced aggregation of nanosized subunits, and excellent capacity and durability. However, traditional synthetic methods of TMOs generally require complicated steps and lack compositional/morphological adjustability. Herein, a general and straightforward strategy is developed to synthesize multishelled porous hollow microspheres, which is constituted of nanosize primary TMO particles, using metal acetate polysaccharide microspheres as the precursor. This universal method can be applied to design TMOs' hollow spheres with tunable shell numbers and composition. The hierarchical porous quadruple-shelled hollow microspheres with nanosized Ni-Co-Mn oxide demonstrate an increased number of active sites, boosted rate capability, enhanced volumetric energy density, and showed great tolerance toward volume expansion upon cycling, thus exhibiting excellent Li+ storage capability with high specific capacity (1470 mAh g-1 at 0.2 A g-1 and 1073.6 mAh g-1 at 5.0 A g-1) and excellent cycle retention (1097 mAh g-1 after 250 cycles at 0.2 A g-1) among TMO anode materials for lithium-ion batteries.

Triple-shelled ZnO/ZnFe2O4 heterojunctional hollow microspheres derived from Prussian Blue analogue as high-performance acetone sensors

Semiconductor oxides with hierarchically hollow architecture can provide significant advantages as sensing materials for gas sensing by facilitating the diffusion of target gases and the surface reaction. A cost-efficient and facile strategy is developed to scalably fabricate triple-shelled hollow binary ZnO/ZnFe2O4 (ZZFO) metal oxides microspheres with excellent intimate heterojunctions through a morphology-inherited annealing treatment of single-resource Prussian Blue analogue of Zn3[Fe(CN)6]2·xH2O solid microspheres as self-sacrificial templates. The porous hybrid ZZFO triple-shelled hollow microspheres (TSHMSs) are demonstrated to be composed of crystalline ZnO and ZnFe2O4 nano-domains with well homogeneous dispersion at the nanoscale and large void spaces between adjacent shells. When evaluated as sensors towards acetone vapor, benefiting from the striking synergy and interplay between active bicomponents and the intrinsic structural advantages, the as-fabricated ZZFO TSHMSs sensor exhibited high performances, including excellent sensitivity, good selectivity and high reversibility, rapid response ability at ultralow working temperature (140°C). Of great significance, these prominent findings may pave the way towards optimizational design and efficient fabrication of mixed metal oxides derived from other PBAs or even other MOFs as high-performance gas sensors in the future.

Porous Multishelled Ni2P Hollow Microspheres as an Active Electrocatalyst for Hydrogen and Oxygen Evolution

Tailoring the morphology and microstructure of electrocatalysts is important in improving catalytic performance. Herein, porous multishelled Ni2P hollow microspheres assembled by nanoparticles were prepared through a simple and economical self-templating approach followed by phosphorization. Compared with nanoparticles and hierarchical solid-interior microspheres, the synthesized multishelled, hollow microstructures of Ni2P exhibit significantly higher electrocatalytic activity for the hydrogen evolution reaction in a 1 M KOH electrolyte. Additionally, a NiOOH layer is formed on the surface of Ni2P during anodic polarization, as revealed by electron microscopy, X-ray photoelectron spectroscopy, and in situ Raman analysis. The Ni2P/NiOOH derivative outperforms the benchmark RuO2 in catalyzing the oxygen evolution reaction. Furthermore, pairing the carbon fiber paper-supported multishelled Ni2P as both the anode and cathode results in superior overall alkaline water splitting performance, generating 10 and ...

Co-adsorption and sequential adsorption of the co-existence four heavy metal ions and three fluoroquinolones on the functionalized ferromagnetic 3D NiFe2O4 porous hollow microsphere

Functionalized magnetic microsphere NiFe2O4 (MS-NiFe2O4) with a 3D hierarchical porous hollow structure was fabricated using urea as the modifier and soft templates by a simple one-pot solvothermal method. The constructed MS-NiFe2O4 shows excellent dual functions which can not only undergo simultaneous rapid removal of the co-existence metal ions (Cu2+, Cd2+, Cr3+ and Zn2+ ions), but also availably adsorb fluoroquinolone (FQs) (ciprofloxacin (CIP), enrofloxacin (ENR) and norfloxacin (NOR)), and is easily recycled using an external magnetic field. The removal efficiency of eight targets could all reach up to 80% within 60min at pH 5. The independent adsorption of single contaminants, the competitive adsorption of multiple heavy metal ions/organic contaminants, the simultaneous and sequential adsorption of the co-existence of inorganic and organic contaminants onto MS-NiFe2O4 were explored in detail. Competition adsorption occurred between the same type of contaminants. For different types of contaminants, four metal ions did not affect the adsorption of the other three FQs in the sequential and simultaneously adsorption system, and vice versa. The possible adsorption mechanism between targets and MS-NiFe2O4 was revealed.

Cave-embedded porous Mn2O3 hollow microsphere as anode material for lithium ion batteries

The cave-embedded porous Mn2O3 hollow microsphere is synthesized from aqueous manganese chloride by a facile one-step spray pyrolysis. When evaluated as anode materials for LIBs, the as-obtained Mn2O3 microsphere easily allows the electrolyte to penetrate into the hollow interior through the cave, providing more active sites and a shortened Li+ diffusion pathway. As a result, the enhanced charge transfer and lithium ion diffusion kinetics is achieved. Furthermore, the special structure is able to mitigate the stress led by enormous volume variation and maintain the structural integrity during conversion reaction process. Benefiting from the special structural features, the Mn2O3 microspheres with such smart architecture delivers a reversible capacity of ∼1000mAhg−1 at 300mAg−1 after 100th cycle, and maintains a high reversible capacity of 639mAhg−1 at 1600mAg−1, showing better electrochemical performance than the conventional Mn2O3 microspheres.

Multiwalled carbon nanotubes twined α-nickel hydroxide microspheres as high-efficient urea electrooxidation catalysts

Multiwalled carbon nanotube (MWCNT) twined α-Ni(OH)2 microspheres, denoted as α-Ni(OH)2@MWCNT, are synthesized by a facile solvothermal method and are developed as a remarkably active catalyst for urea electrooxidation in alkaline media. Through optimizing the mass ratio between α-Ni(OH)2 and MWCNT, it is found that α-Ni(OH)2@MWCNT catalyst with a weight ratio of 2.5:1 affords the highest current density of 2503 mA cm−2 mg−1 at the potential of 0.58 V versus Hg/HgO and the largest exchange current density of 1.49 × 10−4 mA cm−2 among all the studied catalysts, which are much higher than that of pure α-Ni(OH)2 microspheres and are about one order of magnitude higher than that of reported Ni(OH)2 nanosheets. Additionally, the α-Ni(OH)2@MWCNT catalysts also present superior durability than pure α-Ni(OH)2. The exceptional catalytic performance of α-Ni(OH)2@MWCNT catalysts is attributed to the good electronic transport of MWCNT and favorable mass transport facilitated by α-Ni(OH)2 hollow porous microspheres. These results suggest the feasibility of an easy and low-cost solvothermal method to develop high-efficient catalyst for urea electrooxidation. Bird-nest-like microspheres of α-Ni(OH)2@MWCNT catalyst were synthesized with MWCNT twined α-Ni(OH)2 ultrathin nanosheets by an economical solvothermal method.