Carbon Sphere Template Research Articles

Effects of Acid Sites on Thin MCM‐22 Zeolite Catalysts and Their Catalytic Applications for Acetylene Aromatization

AbstractTwo types of thin zeolite MCM‐22 catalysts were prepared by using a carbon sphere template. By applying different calcination methods, a hollow sphere‐type MCM‐22 catalyst (HS‐MCM‐22) and a nanosheet‐type MCM‐22 catalyst (NS‐MCM‐22) were synthesized. Those catalysts were tested and evaluated for acetylene aromatization to see the effects of thin structures. The two types of thin catalysts were found to have higher amounts of acid sites than those of the conventional MCM‐22 catalyst. It was found that the extremely short diffusion length not only enhanced the aromatic yield, but also suppressed the formation of graphitic coke. Notably, the diffusion length of NS‐MCM‐22 was found to be at least 15 times shorter than that of conventional MCM‐22, leading to an 11% and 18% increase in benzene yield, respectively. The thin structure seemed to help the produced aromatics efficiently desorb before they were further converted into carbon precursors and coke. According to the thermogravimetric analysis, the carbon species in the spent thin catalysts were found less graphitic than that of the conventional MCM‐22 catalyst. Because of this, the thin MCM‐22 catalysts were believed to show higher coke removal capability. Especially, the coke removal rate of NS‐MCM‐22 was estimated over 90% despite the severe carbon deposition during the reaction.

Room-temperature ethanol sensors based on amorphous Ta2O5/Pd hybrid microspheres

Ta2O5/Pd hybrid microspheres were readily synthesized via a one-step thermal solution process employing a template composed of glucose carbon spheres, yielding a structure characterized by a rough and porous surface. This morphology offers an expanded contact area and increased sites for ethanol reactions of Ta2O5/Pd hybrid microspheres. At room temperature (25 °C), the Ta2O5/Pd hybrid microspheres exhibited responsiveness to ethanol concentrations ranging from 50 to 700 ppm, displaying a linear response pattern to a narrow concentration gradient of 90–120 ppm. The hybrid exhibited notable sensitivity, manifesting a response value of 5.1–100 ppm ethanol. In addition, they displayed less responsiveness to other VOCs gases, were minimally affected by humidity, and maintained gas-sensitive stability for 30 days, demonstrating excellent selectivity and long-term stability. Based on the fitting curve analysis, the material theoretically demonstrated the ability to detect ethanol at concentrations as low as 101 ppb. Ta2O5/Pd hybrid microspheres modified by glucose carbon sphere templates and noble metal nanoparticles are promising candidates for ethanol room temperature sensing, providing new insights into the development of room temperature sensing.

Porous hollow CaO microsphere synthesized by the template-assisted approach for enhanced CO2 capture

The development of cheap, environmentally friendly adsorbents with high adsorption capacity and good cycle stability is of great significance for reducing excessive CO2 emissions. However, the CaO-based adsorbents with low prices and high theoretical adsorption capacity suffer from serious sintering problems and poor cyclic stability. Herein, we synthesized porous hollow CaO microspheres for enhanced CO2 capture by the template-assisted approach, in which the carbon sphere template with different carbon chain lengths were prepared by hydrothermal method. The interaction between carbon chain lengths, morphologies, and properties of CaO-based adsorbents was systematically investigated. The results show that the porous hollow CaO microsphere prepared with a sucrose carbon template possesses a higher initial CO2 adsorption capacity (15.3 mmol g−1) and better cyclic stability after 20 cycles by reducing the mass transfer length of CO2 and buffering the volume expansion. In addition, the kinetics study reveals that the porous hollow spherical morphology can significantly improve the CO2 adsorption kinetics, especially in the chemical control stage, which provides theoretical guidance for the further understanding of the carbonization process. The systematic study marks the significance of precise tailoring of porous hollow CaO microsphere to achieve the desired performance of CO2 adsorption.

Kinetics-Driven MnO2 Nanoflowers Supported by Interconnected Porous Hollow Carbon Spheres for Zinc-Ion Batteries.

For rechargeable aqueous zinc-ion batteries (ZIBs), manganese dioxide is one of the most promising candidates as a cathode material because of its cost effectiveness, eco-friendliness, and high specific capacities. However, the ZIBs suffer from poor rate performance and low cycle life due to the weak intrinsic electronic conductivity of manganese dioxide, poor ion diffusion of lump manganese dioxide, and its volumetric expansion during the cycle. Herein, we prepare MnO2@carbon composites (MnO2@IPHCSs) by in situ growing MnO2 nanoflowers on an interconnected porous hollow carbon spheres (IPHCSs) template. IPHCSs, as excellent conductors, significantly improve the conductivity of the manganese dioxide cathode. The hollow porous carbon framework of IPHCSs can offer more ion diffusion paths to internal MnO2@IPHCS carbon composites and acts as a buffer room to cope with the drastic volume contraction and expansion during charge/discharge cycling. The rate performance tests show that MnO2@IPHCSs with high conductivity have a specific capacity of 147 mA h g-1 at 3 C. MnO2@IPHCSs with hollow and nanoflower structures are shown to have excellent ion diffusion performance (ion diffusion coefficient = 10-11 to 10-10 cm2 s-1) in the electrochemical kinetics of the galvanostatic intermittent titration technique. Long cycle performance testing and in situ Raman characterization reveal that MnO2@IPHCSs have high cycling stability (85.5% capacity retention after 800 cycles) and reversibility due to the enhanced structure and increased conductivity. The excellently conductive manganese dioxide supported by IPHCSs has good rate and cycling performance, which can be used to produce superior-performance ZIBs.

V 2 CT X MXene Sphere for Aqueous Ion Storage

Despite the remarkable ion-hosting capability of MXenes, their electrochemical performance is restricted to the ion shuttle barrier stemming from the capacious surface and the sluggish chemical activity of intrinsic transition metal layers. Herein, we construct a vertically aligned array of V 2 CT X flakes utilizing a carbon sphere template (V 2 CT X @CS), with the interlayer galleries outward facing the external electrolyte, to shorten the diffusion length and mitigate the ion shuttle barrier. Moreover, we leverage the high sensitivity of V 2 CT X flakes to the water–oxygen environment, fully activating the masked active sites of transition metal layers in an aqueous environment via continuous electrochemical scanning. Aqueous V 2 CT X @CS/Zn battery delivers a novel capacity enhancement over 42,000 cycles at 10 A g −1 . After activation, the capacity reaches up to 409 mAh g V 2 CT X − 1 at 0.5 A g −1 and remains at 122 mAh g V 2 CT X − 1 at 18 A g −1 . With a 0.95-V voltage plateau, the energy density of 330.4 Wh kg V 2 CT X − 1 surpasses previous records of aqueous MXene electrodes.

High-Performance All-solid-state microsupercapacitors from 3D printing Structure-engineered Graphene-Carbon sphere electrodes

The improvement of the areal energy density of graphene-based microsupercapacitors (MSCs) is reduced by the graphene aggregation issue in electrodes. Solving this issue in MSCs can enhance their electrochemical performance and facilitate their applications in microdevices. Herein, we experimentally realize to prevent graphene aggregation in electrode by engineering its structure via combing both strategies of the addition of spacers of carbon sphere and self-sacrificing template of ethyl cellulose during the 3D printing process. The MSCs based on these electrodes deliver good electrochemical performance with high energy density (4.17 μWh cm−2) and power density (0.22 mW cm−2), promising cycling performance and mechanical flexibility. The method developed here provides a paradigm for preparing high-performance MSCs.

Noble metal modified (002)-oriented ZnO hollow spheres for the degradation of a broad range of pollutants

Zinc oxide hollow spheres were fabricated by applying sucrose-derived carbon spheres as templates that were eliminated through calcination. For this purpose, two synthesis methods were examined and compared, chemical impregnation and solvothermal method. The most suitable ZnO hollow structure was selected for noble metal deposition (Au and Pt at 1 wt%) to further increase the photocatalytic activity. The photocatalytic activity was examined by the decomposition of three different model pollutants (phenol, Na-ibuprofen and diuron) under UV irradiation. The as-synthesized hollow sphere structures and its noble metal composites were further examined by XRD, SEM, IR, DRS, PL. The templates did not modify the structure of ZnO only the morphology and contributed to the preservation of the original structure during calcination. The structural, optical and photocatalytic activity was correlated with both the application of carbon sphere template, and noble metal deposition respective their role in the improvement of the photocatalytic activity.

High performance H2 sensor based on rGO-wrapped SnO2–Pd porous hollow spheres

Hydrogen (H2) sensors based on metal oxide semiconductors (MOS) are promising for many applications such as a rocket propellant, industrial gas and the safety of storage. However, poor selectivity at low analyte concentrations, and independent response on high humidity limit the practical applications. Herein, we designed rGO-wrapped SnO2–Pd porous hollow spheres composite (SnO2–Pd@rGO) for high performance H2 sensor. The porous hollow structure was from the carbon sphere template. The rGO wrapping was via self-assembly of GO on SnO2-based spheres with subsequent thermal reduction in H2 ambient. This sensor exhibited excellently selective H2 sensing performances at 390 °C, linear response over a broad concentration range (0.1–1000 ppm) with recovery time of only 3 s, a high response of ∼8 to 0.1 ppm H2 in a minute, and acceptable stability under high humidity conditions (e. g. 80%). The calculated detection limit of 16.5 ppb opened up the possibility of trace H2 monitoring. Furthermore, this sensor demonstrated certain response to H2 at the minimum concentration of 50 ppm at 130 °C. These performances mainly benefited from the special hollow porous structure with abundant heterojunctions, the catalysis of the doped-PdOx, the relative hydrophobic surface from rGO, and the deoxygenation after H2 reduction.

Solar photocatalytic degradation of organic pollutants from indoor air using novel direct flame combustion based hollow nanocomposite of Pd/Anatase–Rutile TiO2 mixed phase and evaluation of the biocompatibility

The conventional methods (calcinations) are used to prepare diverse types of nanoparticles, however, to introduce specific properties for their applications, new strategy is required. Therefore, direct air flame combustion is a new technique utilized to synthesize novel nanoparticles instead of calcinations in the oven. In this work, the air flame combustion was used to prepare a new junction of anatase– rutile (A/R) mixed phase TiO2 deposited with palladium nanoparticles (Pd NPs). Herein, an A/R phase junction was obtained by flame combustion of carbon sphere templates. The novel nanocatalyst was characterized using XRD, SEM, TEM, UV–Vis light spectroscopy and SBET method for surface properties. It shows a higher performance during the photocatalytic degradation of formaldehyde gas pollutant under solar irradiation. The enhancement of catalytic activity was found to be 18-fold higher than the commercial TiO2-P25. The results of CO2 generated via the formaldehyde degradation by the novel nanophotocatalyst showed a high photocatalytic efficiency of 60%. Moreover, in the field application, it showed 75% formaldehyde removal when applied in the kitchen indoor air; it reveals also a wide array of antimicrobial activity. Therefore, this system will be more promising in various industrial applications.

A novel synthesis of Ag@ZnO yolk-shell and ZnO hollow sphere nanostructures and comparison of their photocatalytic performances

ZnO hallow spheres and Ag@ZnO yolk-shell nanostructures were synthesized using a hydrothermal method and their dye absorption and photocatalytic performances were investigated. For ZnO hollow spheres preparation, carbon sphere templates were used and ZnO hollow spheres with average size of 200 nm were obtained. Also, Ag@C core-shell spheres with diameters of 350 nm were prepared by a hydrothermal method and were used as template to prepare Ag@ZnO yolk-shell spheres. The samples were characterized using XRD, SEM, TEM, EDX and FT-IR measurements. The results confirmed the formation of yolk-shell nanostructure. The average diameters of ZnO shells and Ag cores, 300 and 55 nm were measured respectively. Then Congo red dye absorption of ZnO hollow spheres and Ag@ZnO yolk-shells were examined. The results showed that the ZnO hollow spheres were a better dye absorbent, but Ag@ZnO yolk-shells had better photocatalytic performance probably due to presence of Ag nanoparticles as a plasmonic material.

A novel Z-scheme CeO2/g-C3N4 heterojunction photocatalyst for degradation of Bisphenol A and hydrogen evolution and insight of the photocatalysis mechanism

CeO2/g-C3N4 heterojunction photocatalyst had been successfully fabricated through a one-step in-situ pyrolysis formation of 3D hollow CeO2 mesoporous nanospheres and 2D g-C3N4 nanosheets together with simultaneous removal of carbon sphere templates after heat treatment. The sample shows high catalytic performances for photocatalytic hydrogen generation and photocatalytic oxidation of Bisphenol A (BPA) under visible light irradiation, and the catalytic degradation route of BPA was suggested by the degradation products determined by GC–MS. The enhancing catalytic activity was attributed to the effective interfacial charge migration and separation. Finally, it was proposed that the CeO2/g-C3N4 heterojunction photocatalyst could follow a more appropriate Z-scheme charge transfer mechanism, which was confirmed by the analysis of experiment and theoretical calculation results.

Unexpected Link between the Template Purification Solvent and the Structure of Titanium Dioxide Hollow Spheres

Carbon spheres were applied as templates to synthesize titanium dioxide hollow spheres. The templates were purified with either ethanol or acetone, and the effects of this treatment on the properties of the resulting titania were investigated. The photocatalytic activity of the catalysts was measured via the decomposition of phenol model pollutant under visible light irradiation. It was found that the solvent used for the purification of the carbon spheres had a surprisingly large impact on the crystal phase composition, morphology, and photocatalytic activity. Using ethanol resulted in a predominantly rutile phase titanium dioxide with regular morphology and higher photocatalytic activity (r0,phenol = 3.9 × 10−9 M∙s−1) than that containing mainly anatase phase prepared using acetone (r0,phenol = 1.2 × 10−9 M∙s−1), surpassing the photocatalytic activity of all investigated references. Based on infrared spectroscopy measurements, it was found that the carbon sphere templates had different surface properties that could result in the appearance of carbonate species in the titania lattice. The presence or absence of these species was found to be the determining factor in the development of the titania’s properties.

Orientated VSe2 nanoparticles anchored on N-doped hollow carbon sphere for high-stable aqueous energy application

Transition metal dichalcogenides (TMDs) have been considered as the promising energy storage materials due to their unique crystalline structure. In this work, the VSe2 nanoparticles are vertically anchored on N-doping carbon (NC) hollow nanosphere (VSe2@NC) for aqueous energy application. The electrochemical measurements indicate that the VSe2@NC electrode exhibits outstanding electrochemical properties with high specific capacitance and excellent cycling life. Moreover, the asymmetric supercapacitor was assembled by using VSe2@NC cathode and activated carbon anode. It shows high energy density of 85.41 Wh Kg−1 at a power density of 701.99 W Kg−1, and high-stable cycling performance of 90% retention after 2000 cycles. The superior properties are attributed to the particular hollow structure design, which accommodates both the high specific capacity of VSe2 and the desired electrical conductivity of N-doping carbon sphere template.

Facile synthesis of hollow mesoporous MgO nanospheres as ultra-high performance and reusable adsorbent

A facile approach for fabrication of hollow mesoporous MgO nanospheres (HMMN) has been demonstrated. The employed protocol involves the coating of carbon spheres template with MgO nanoparticles, followed by the calcination in presence of air to remove the carbon core at elevated temperature. Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) have been used to characterize the sample. Brunauer-Emmett-Teller (BET) method reveals the specific surface area and the average pore diameter of hollow spheres as 55.1 m2/g and 8.19 nm, respectively. The composite exhibits excellent adsorptive capacity toward Congo red (CR) at room temperature. The adsorption reaches equilibrium within 70 min with the maximum adsorption capacity of 5000 mg/g which is, to the best of our knowledge, the highest reported value. Additionally, the regeneration by calcination shows that adsorbent has high adsorption performance and superb reusability.

Carbon Sphere Template Derived Hollow Nanostructure for Photocatalysis and Gas Sensing.

As a green and preferred technology for energy crisis and environmental issues, continuous research on photocatalysis and gas sensing has come forth at an explosive rate. Thus far, promising synthetic methods have enabled various designs and preparations of semiconductor-based nanostructure which have shown superior activity. This review summarized various synthetic routines toward carbon sphere template derived hollow nanostructures and their successful attempts in synthesize doping, solid solution, heterostructure, and surface modified nanostructures for heterogeneous photocatalysis and gas sensing. Moreover, the challenges and future prospects are briefly discussed. It is eagerly anticipated that this review may broaden the view and in-depth understanding of carbon sphere template derived hollow nanostructures while expected to have further progresses in heterogeneous photocatalysis, gas sensing and other related fields which will make great contributions to their application.

Preparation of CoFe2O4 hollow spheres with carbon sphere templates and their wave absorption performance

In the synthesis of colloidal carbon spheres (CCSs) from glucose by hydrothermal carbonization, agglomeration and cross-linking often occur, affecting their functions as templates. In this study, the effects of various surfactants on the dispersion and particle size of CCS were investigated. The CCS synthesized with dodecyltrimethylammonium bromide was much larger than those of other groups, and the average diameter exceeded 6.4 μm. CCS with complete spherical shape and good dispersion were obtained using sodium polyacrylate, with a diameter of approximately 450 nm CoFe2O4 hollow spheres were prepared by a simple adsorption–calcination method using CCS as the templates, and the effects of different dispersions and particle sizes on the electromagnetic parameters and microwave absorption properties of hollow spheres were studied. The results show that the absorption bandwidth corresponding to reflection loss less than −7 dB widened from 2.64 GHz to 3.44 GHz with improving dispersion of hollow sphere structure. When the size of the hollow sphere increased to the micron level, the thickness required to reach the maximum bandwidth reduced by 0.5 mm. Compared to the unoptimized hollow spheres, the microwave absorption performance of the as-prepared CCCs improved effectively. The effect of surfactants on the dispersion of CCS and the effect of the dispersion and size of CoFe2O4 hollow spheres on their electromagnetic properties are discussed in detail.

Synthesis of Z-scheme multi-shelled ZnO/AgVO3 spheres as photocatalysts for the degradation of ciprofloxacin and reduction of chromium(VI)

Herein, we report the preparation of AgVO3 nanoparticles-decorated multi-shelled ZnO microspheres 0D/3D Z-scheme heterojunction photocatalysts via calcination of carbon sphere template and in situ growth method. The prepared ZnO/AgVO3 composites showed enhanced photocatalytic performance for photodegradation of ciprofloxacin (CIP) and photocatalytic reduction of Cr(VI) compared to the single-phase photocatalysts under the same irradiation conditions. Noticeably, the photocatalytic removal rate of CIP and Cr(VI) reached 90% at 90 min and 45 min, respectively, for the ZnO/AgVO3 composite with an optimal AgVO3 content. The photocatalytic removal rate for CIP and Cr(VI) was, respectively, about 2.43-fold and 4.84-fold as high as that of the pure ZnO. Furthermore, a reasonable degradation pathway for CIP has been proposed based on LC–MS results. The enhanced photocatalytic performance could be attributed to the extended visible-light absorption, promoted separation and transportation efficiency of the photogenerated electron–hole pairs. Significantly, the Z-scheme heterojunction was verified according to radical capture experiments and theoretical calculations based on the density functional theory (DTF) framework. We believe this work will give an innovative view for constructing multi-shelled 0D/3D photocatalytic systems for eliminating environmental pollutants and enhancing environmental remediation.

Performance of natural sensitizers on TiO2 hollow nano sphere based solar cells

Terminalia chebula, Rubia tinctorum and Biancaea sappan are used here as sensitizers on TiO2 hollow-sphere. Anatase-rutile TiO2 hollow-spheres were synthesized using carbon spheres template assisted method. Structural, shape and purity of the prepared TiO2 hollow-spheres are confirmed through XRD, SEM measurements. Absorbance spectra are used to analyze the spectral response of the sensitizers. From the J-V measurements, it is found that Terminalia chebula shows a better performance of open circuit voltage (VOC) ∼ 0.47 V, short circuit current (JSC) ∼ 0.11 mA/cm2 and fill factor 40% compared to all others. The charge transfer resistance and life-time are investigated through Nyquist and Bode plots.

Significantly enhanced photocatalytic performance of mesoporous C@ZnO hollow nanospheres via suppressing charge recombination

Mesoporous C@ZnO hollow nanospheres were prepared by carbon sphere template. The influence of defects and surface state on photocatalytic performance was studied. The photocatalytic activity of C@ZnO nanospheres without treatment is the worst, that of the sample via pickling and annealing is secondary, and the pickling sample is the best. The improved performance can be attributed to the reduction of defects, which suppress the charge recombination. This work helps us better understand the important effects of defects on photocatalytic properties, and provides us with a feasible way to improve the UV photocatalytic activity of ZnO and other metal oxide.

Carbon sphere templated synthesis of LaFeO<sub>3</sub> perovskite and its catalytic performances for RhB oxidation

Carbon sphere was synthesized by hydrothermal method using sucrose as precursor, with particle size and surface properties tuned by hydrothermal time (6–24 h). It was then used as template to prepare LaFeO3 perovskite. X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and N2 physisorption results showed that LaFeO3 with perovskite structure was formed and its crystal system transformed from orthorhombic to cubic with increasing the hydrothermal time of carbon sphere. Compared to the LaFeO3 synthesized without carbon sphere template, the synthesized LaFeO3 perovskite with carbon sphere possessed improved surface area, dispersion and surface chemistry. Room-temperature activity of LaFeO3 for H2O2 decomposition and rodamine B (RhB) oxidation using H2O2 as oxidant was tested, which showed that LaFeO3 is active for RhB oxidation and the best activity is obtained from that prepared with carbon sphere hydrothermally treated for 20 h (denoted as LaFeO3-C20). By comparing the activity of H2O2 decomposition and RhB oxidation, it was inferred that the intermediates of H2O2 decomposition is the active species for RhB oxidation. Long-term stability tests of LaFeO3-C20 for RhB oxidation showed that no activity loss is observable within 6 runs, suggesting that LaFeO3-C20 is highly stable in the reaction.