SnO2 Nanospheres Research Articles

Kirkendall Effect: Nanofibers Comprising Yolk-Shell Sn@void@SnO/SnO2and Hollow SnO/SnO2and SnO2Nanospheres via the Kirkendall Diffusion Effect and Their Electrochemical Properties (Small 36/2015)

Nanofibers with a unique structure comprising yolk–shell Sn@void@SnO/SnO2 nanospheres are generated by J. S. Cho and Y. C. Kang by applying the nanoscale Kirkendall diffusion process during conventional electrospinning. On page 4673, nanofibers prepared by applying this process exhibit superior electrochemical properties compared to those of porous-structured SnO2 nanofibers prepared by the conventional post-treatment process. The front cover image reveals the highly efficient lithium storage process of nanofibers composed of Sn@void@SnO/SnO2 yolk–shell nanospheres.

Synthesis of polymer/rGO/SnO2 hierarchical structure and its photodegradation of organic pollutants

Tin dioxide (SnO2) behaves excellent properties, but the high recombination rate of photoexcited electron–hole pairs combined with a large band gap restricts its photocatalytic applications. Comparing with pure SnO2 nanospheres, the photocatalytic degradation of rhodamine B (RhB) over polymer/reduced graphene oxide (rGO)/SnO2 composites was enhanced. For the synthesis, graphene oxide (GO) nanosheets were wrapped on the surface of polymer microspheres to form a polymer/GO core–shell structure. Then, SnO2 nanospheres were decorated on polymer/GO microspheres under a hydrothermal condition, meanwhile GO was reduced to rGO. Therefore, polymer/rGO/SnO2 hierarchical structure was obtained. As graphene promote separation of the photoexcited electron–hole pairs and the conduction band potential of SnO2 is more positive than the work function of graphene, electrons can be quickly transferred to the conduction band of SnO2 via graphene leaving over more holes on the surface of catalyst for the de-ethylation of RhB.

Comparative Study of Electrochemical Performance of SnO2 Anodes with Different Nanostructures for Lithium-Ion Batteries.

Powders composed of SnO2 nanostructures including microporous nanospheres, mesoporous nanospheres and nanosheets were synthesized by the direct hydrothermal hydrolyzation of SnCl4, hydrothermal hydrolyzation of SnCl4 using glucose as a soft template and precipitation of SnCl2 ∙ 2H20 using oxalic acid as a precipitant, respectively. The electrochemical performance of the three samples used as the anode of a lithium ion battery was determined using galvanostatic discharge/charge tests and electrochemical impedance spectroscopy. Among of them, the anode composed of microporous SnO2 nanospheres demonstrated outstanding initial discharge and charge capacities of 2480 and 1510 mAh g-1, respectively, with a coulombic efficiency of 60.9% at a current density of 78 mA g-1 (0.1 C). In addition, high initial discharge and charge capacities of 1398 mAh g-1 and 950 mAh g-1, respectively, with a coulombic efficiency of 67.95% were obtained even at a high current density of 550 mA g-1 (0.7 C). Moreover, a reversible capacity of 500 mAh g-1 with a coulombic efficiency of 99.95% was attained even after 50 discharging/charging cycles at 550 mA g-1 (0.7 C). This superior electrochemical performance of the SnO2 anodes can be attributed to the large specific surface area (172.7 m2 g-1), small crystal size (approximately 15 nm) and the interstitial microporous pores (<2 nm) of the particles, which favored lithium-ion diffusion and insertion/desertion at the surface of SnO2 and decreased the polarization and the volume expansion of SnO2. Moreover, the resistance of the cell and Li+ diffusion coefficient were studied by electrochemical impedance spectroscopy.

Nanofibers Comprising Yolk-Shell Sn@void@SnO/SnO2and Hollow SnO/SnO2and SnO2Nanospheres via the Kirkendall Diffusion Effect and Their Electrochemical Properties

Nanofibers with a unique structure comprising Sn@void@SnO/SnO2 yolk-shell nanospheres and hollow SnO/SnO2 and SnO2 nanospheres are prepared by applying the nanoscale Kirkendall diffusion process in conventional electrospinning process. Under a reducing atmosphere, post-treatment of tin 2-ethylhexanoate-polyvinylpyrrolidone electrospun nanofibers produce carbon nanofibers with embedded spherical Sn nanopowders. The Sn nanopowders are linearly aligned along the carbon nanofiber axis without aggregation of the nanopowders. Under an air atmosphere, oxidation of the Sn-C composite nanofibers produce nanofibers comprising Sn@void@SnO/SnO2 yolk-shell nanospheres and hollow SnO/SnO2 and SnO2 nanospheres, depending on the post-treatment temperature. The mean sizes of the hollow nanospheres embedded within tin oxide nanofibers post-treated at 500 °C and 600 °C are 146 and 117 nm, respectively. For the 250th cycle, the discharge capacities of the nanofibers prepared by the nanoscale Kirkendall diffusion process post-treated at 400 °C, 500 °C, and 600 °C at a high current density of 2 A g(-1) are 663, 630, and 567 mA h g(-1), respectively. The corresponding capacity retentions are 77%, 84%, and 78%, as calculated from the second cycle. The nanofibers prepared by applying the nanoscale Kirkendall diffusion process exhibit superior electrochemical properties compared with those of the porous-structured SnO2 nanofibers prepared by the conventional post-treatment process.

(Invited) Electrochemical CO2 Reduction to Formic Acid on Crystalline SnO2 Nanosphere Catalyst

The electrochemical reduction of CO2 is a reaction of much current interest as a possible reaction for energy storage.1 To date, formic acid, carbon monoxide, methanol, and oxalic acid have been prepared by this way. However, the key technological challenge for electrochemical reduction of CO2 is the preparation of the electrode with high catalytic activity, high selectivity and long term stability. Considering these difficulties, developing new material synthesis technology to give innovative new catalysts with optimal performance is the priority. Tin (Sn) and copper (Cu) are considered as promising electrocatalysts to convert carbon dioxide (CO2) to fuels (e.g. formate, methanol or hydrocarbons) because of their low cost, easy availability and reasonable overall Faradaic efficiency towards fuel production.2 However, the deactivation of Sn metal electrodes during CO2 reduction is very fast, and requires at least 0.86 V of overpotential to attain a CO2 reduction partial current density of 4−5 mA cm-2 in an aqueous solution saturated with 1 atm CO2.3 Combined with the advantages of metal tin, we here report a simple one step synthesis of crystalline SnO2 nanosphere with good electrochemical performance of high catalytic activity and high selectivity.

(Invited) Electrochemical CO2 Reduction to Formic Acid on Crystalline SnO2 Nanosphere Catalyst

In this work, the morphology controlled SnO2 nanosphere catalyst has been successfully synthesized and applied to electrochemical CO2 reduction to formic acid in 0.5 M KHCO3. The catalysts were synthesized by a simple hydrothermal method under controlling the different proportions of ethanol to distilled water as mixed solvent. The obtained catalysts were then coated on gas diffusion electrode (SnO2/GDE) as working electrode. It was found that the catalyst prepared from 50% content of ethanol gives the best catalytic activity towards CO2 reduction, where the onset potential was found to be 300 mV more anodic than that of hydrogen evolution. Meanwhile, the SnO2/GDE-50 showed the most stable property for CO2 reduction. The current density and faradaic efficiency increased as the potential increased, reaching a maximum at -1.7 V vs. SHE. At this stage, the maximum faradaic efficiency of 68% with a current density of 6 mA cm-2 was obtained. Moreover, the production rate of format exhibits a maximum value of 518.2 mg L-1 at the cathode potential of -1.9 V vs. SHE.

Hydrothermal synthesis of SnO2 nanocubes and nanospheres and their gas sensing properties

In this work, we reported successful synthesis of SnO2 nanocubes and nanospheres via a facile hydrothermal technique. The as-obtained SnO2 nanostructures have been characterized by X-ray diffraction and field-emission scanning electron microscopy. The formation mechanism of aforementioned SnO2 nanostructures has been proposed in detail, especially SnO2 nanaocubes, which has been systematically investigated by varying the reaction time and the surfactant SDS play a key role in growth process of nanocubes. Furthermore, the gas sensing properties of as-prepared SnO2 nanostructures have been tested towards ethanol. Interestingly, it is noted that gas sensing performance of nanocubes are superior to nanospheres, which certified that the gas sensing properties can be enhanced by controlling the morphologies and the SnO2 nanocubes maybe a promising candidate based materials in the fields of gas sensors.

Morphology-modulation of SnO2 hierarchical architectures by Zn doping for glycol gas sensing and photocatalytic applications.

The morphology of SnO2 nanospheres was transformed into ultrathin nanosheets assembled architectures after Zn doping by one-step hydrothermal route. The as-prepared samples were characterized in detail by various analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption technique. The Zn-doped SnO2 nanostructures proved to be the efficient gas sensing materials for a series of flammable and explosive gases detection, and photocatalysts for the degradation of methyl orange (MO) under UV irradiation. It was observed that both of the undoped and Zn-doped SnO2 after calcination exhibited tremendous gas sensing performance toward glycol. The response (S = Ra/Rg) of Zn-doped SnO2 can reach to 90 when the glycol concentration is 100 ppm, which is about 2 times and 3 times higher than that of undoped SnO2 sensor with and without calcinations, respectively. The result of photocatalytic activities demonstrated that MO dye was almost completely degraded (~92%) by Zn-doped SnO2 in 150 min, which is higher than that of others (MO without photocatalyst was 23%, undoped SnO2 without and with calcination were 55% and 75%, respectively).

Synthesis of tin oxide nanospheres under ambient conditions and their strong adsorption of As(III) from water.

The development of highly efficient As(iii) adsorbents is critical to largely simplify the arsenic treatment process and lower its cost. For the first time, SnO2 nanospheres were demonstrated to possess a highly efficient As(iii) adsorption capability from water in a near neutral pH environment as predicted by the material criterion we recently developed for the selection of highly efficient arsenic adsorbents. These SnO2 nanospheres were synthesized by a simple and cost-effective hydrolysis process with the assistance of ethyl acetate under ambient conditions, which had a good dispersity, a narrow size distribution, a relatively large specific surface area, and a porous structure. A fast As(iii) adsorption was observed in the kinetics study on these SnO2 nanospheres, and their Langmuir adsorption capacity was determined to be ∼112.7 mg g(-1) at pH ∼7. The As(iii) adsorption mechanism on SnO2 nanospheres was examined by both macroscopic and microscopic techniques, which demonstrated that it followed the inner-sphere complex model. These SnO2 nanospheres demonstrated effective As(iii) adsorption even with exceptionally high concentrations of co-existing ions, and a good regeneration capability by washing with NaOH solution.

One-step synthesis of Ni-doped SnO2 nanospheres with enhanced lithium ion storage performance

Ni-doped SnO2 nanospheres were prepared and exhibited excellent cycle performance and capacity retention.

Biopolymer-assisted hydrothermal synthesis of SnO2 porous nanospheres and their photocatalytic properties

Porous SnO2 nanospheres with uniform morphologies and sizes were fabricated via a biopolymer (sodium alginate, SA)-assisted hydrothermal route. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high solution TEM (HRTEM), nitrogen adsorption–desorption, Fourier transform infrared (FT-IR) spectroscopy and UV–vis absorption spectroscopy. The obtained tetragonal SnO2 nanospheres were characteristic of hierarchical mesoporous structures with good crystallinity and high purity. Moreover, it was found that the porous SnO2 nanospheres were composed of numerous tiny nanocrystals as building blocks and the SA played a key role in formation of the porous nanospheres with uniform morphologies and sizes. Additionally, the photocatalytic activity of the obtained porous SnO2 nanospheres under sunlight irradiation was also evaluated by degradation of Rhodamine B (RhB).

A novel rose flower-like SnO hierarchical structure synthesized by a hydrothermal method in an ethanol/water system

Abstract Rose flower-like SnO hierarchical 3D architectures consisting of well-ordered microsheets were synthesized by a template-free and surfactant-free hydrothermal method based on the reaction between SnCl2 and NaOH in ethanol/water. The ethanol amount is a crucial factor in controlling the size and morphology of the microsheets. Ethanol can accelerate the delamination of the SnO blocks to the microsheets, and the microsheets changed from a quasi square to an octodecahedral shape with the increase of the ethanol ratio. When the volume ratio of ethanol/water is 2:1, the microstructure of SnO presents a rose flower-like hierarchical architecture with a diameter of about 40 μm, which is regularly composed of numerous well-ordered thin microsheets with octodecahedral shape, and the microsheets were formed by countless nanoparticles. A possible growth mechanism of the architectures was proposed. Moreover, SnO2 nanospheres were synthesized by a similar experiment only without NaOH, which showed that NaOH was crucial to the formation of SnOx.

Synthesis and optoelectrical properties of SnO2 nanospheres derived by microwave-assisted hydrothermal method

SnO2 nanospheres have been synthesized by microwave-assisted hydrothermal method from the starting materials of citric acid and tin metallic particles. From the results of SEM and TEM images, it can be found that the SnO2 nanospheres are uniform with diameter of ~100 nm and aggregated by SnO2 nanocrystals with size of 8–10 nm. The photoluminescence spectrum of the nanospheres shows a peak at ~330 nm and a cutoff wavelength of around 400 nm. The pronounced photocurrent was recoded from the as-prepared SnO2 nanospheres assembled on a Mo thin sheet under the UV illumination, which is suggested for the potential application of UV photodetector.

Ink‐jet Printing of Hollow SnO2 Nanospheres for Gas Sensing Applications

Hollow tin‐oxide (SnO2) nanospheres were synthesized by coating, carbon nanospheres (CNs) as hard templates, with a tin(IV) sol obtained by partial hydrolysis of [Sn(OBut)4] under ambient conditions. Formation of crystalline SnO2 spheres upon calcination was confirmed by powder X‐ray diffraction data, whereas the hollow interiors of SnO2 particles were verified by scanning and transmission electron microscopy of both intact and broken spheres. The shell of SnO2 nanospheres sintered at 700°C consisted of a single layer of nanocrystallites (~6 nm) self‐assembled in a ball‐like superlattice. Tin‐oxide hollow spheres showed an average diameter of 150 nm and could be homogeneously dispersed in water/ethylene glycol (50:50 vol%) mixture to form stable inorganic inks viable for their use in commercial ink‐jet printers demonstrated by printing porous ceramic structures on an interdigitated sensor chip. The integration of large surface and nanoscopic voids in the final structures imparted higher sensitivity to the as‐printed sensors toward both oxidizing (nitrogen dioxide) and reducing gases (methane and ethanol), which validates the enormous potential of printable inorganics in functional applications.

Template-free synthesis of uniform mesoporous SnO2 nanospheres for efficient phosphopeptide enrichment.

A one-step and template-free method to prepare uniform SnO2 nanospheres with a mesoporous structure was developed for the applications in phosphopeptide enrichment. The as-synthesized mesoporous SnO2 nanospheres have a large surface area and highly active surfaces for the effective binding of phosphopeptides. Compared with the non-porous SnO2 and commercial TiO2, mesoporous SnO2 nanospheres represent superior performance in the specific trapping of phosphopeptides from both standard protein and complex nonfat milk digests for mass spectrometry-based phosphoproteomic analysis. The feasible synthetic approach and the excellent enrichment performance make the mesoporous SnO2 nanospheres promising in further phosphoproteomic research.

Hierarchical SnO2 Nanospheres: Bio-inspired Mineralization, Vulcanization, Oxidation Techniques and the Application for NO Sensors

Controllable synthesis and surface engineering of nanomaterials are of strategic importance for tailoring their properties. Here, we demonstrate that the synthesis and surface adjustment of highly stable hierarchical of SnO2 nanospheres can be realized by biomineralization, vulcanization and oxidation techniques. Furthermore, we reveal that the highly stable hierarchical SnO2 nanospheres ensure a remarkable sensitivity towards NO gas with fast response and recovery due to their high crystallinity and special structure. Such technique acquiring highly stable hierarchical SnO2 nanospheres offers promising potential for future practical applications in monitoring the emission from waste incinerators and combustion process of fossil fuels.

Fabrication and characterization of SnO2 nanospheres for hydrogen detection

This article demonstrates a novel chemical vapor deposition strategy of tin oxide (SnO2) by vapor phase material reaction at room temperature and presents the applications to hydrogen detection using this material. Tin chloride anhydrate was used as the precursor, and it reacted with NH3 to form Sn(OH)4 nanospheres. The samples with Sn(OH)4 nanospheres were subject to drying up at 80 °C, and then they transformed to polycrystalline SnO2 nanospheres. The X-ray diffraction measurement was carried out to investigate the structural properties of the SnO2 films annealed at various temperatures. The morphology of the samples was investigated by field-emission scanning electron microscopy. Micropellistor was fabricated based on the SnO2 catalyst for hydrogen detection. Compared with the traditional method to make SnO2 sensing material (hydrolysis of SnCl4·5H2O in basic solutions), the SnO2 nanospheres prepared by this method have a higher relative sensitivity and a good linearity for the concentration of H2 ranging from 0% v/v to 4% v/v. A short response time about 6 s was achieved.

Formation of Sn@C Yolk–Shell Nanospheres and Core–Sheath Nanowires for Highly Reversible Lithium Storage

As one promising anode material with high theoretical capacity, metallic tin has attracted much research interest in the field of lithium‐ion batteries. Here, two types of tin/carbon (Sn@C) core–shell nanostructures with inner buffering voids are fabricated from SnO2 hollow nanospheres via a facile chemical vapor deposition (CVD) method. The crystallinity and surface topography of SnO2 hollow nanospheres are found to affect the morphology of resultant Sn@C materials. Sn@C yolk–shell nanospheres and core–sheath nanowires are obtained from the as‐prepared SnO2 and high‐temperature annealed SnO2 nanospheres, respectively. The unique Sn@C nanostructures can mitigate the agglomeration/pulverization of Sn nanoparticles and electrical disconnection from the current collector caused by the large volume change during the lithium alloying/dealloying process. Both Sn@C yolk–shell and core–sheath nanostructures show stable cycling performance up to 500 cycles with specific capacities of ca. 430 and 520 mA h g−1, respectively.

Solvothermal Synthesis of Hollow Urchin-Like SnO2 Nanospheres with Superior Lithium Storage Behavior

Hollow urchin-like SnO2 nanospheres with ultrathin nanorods have been successfully synthesized via a simple complex solvothermal route. The formation mechanism of the as-synthesized SnO2 nanospheres was simply explained. When tested as anode, the as-obtained hollow urchin-like SnO2 nanospheres exhibit excellent rate and cycling performances. It was expected that the as-synthesized SnO2 nanospheres could be applied as anode materials for future lithium-ion batteries.

SnO2 nano-spheres/graphene hybrid for high-performance lithium ion battery anodes

SnO2 nano-spheres/graphene composite was fabricated via a simple one-step hydrothermal method with graphene oxide and SnCl4·5H2O as the precursors. The composite was characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and surface area measurement. It is shown that fine SnO2 nano-spheres with an average size of 50–100 nm could be homogeneously deposited on graphene nano-sheets layer by layer. The structural feature enabled SnO2 nano-spheres/graphene hybird as an excellent anode material in lithium ion battery. The composite possesses 1306 mA h g−1 of initial discharge capacity and good capacity retention of 594 mA h g−1 up to the 50th cycle at a current density of 100 mA g−1. These results indicate that the composite is a promising anode material in high-performance lithium ion batteries.