SnO2 Hollow Research Articles

Vertically Aligned Hollow TiO2 Shell Protected SnO2 Nanorods By Atomic Layer Deposition for Highly Stable Lithium Storage

Lithium-Ion batteries have shown a significant evolution in the last years regarding energy density and cycling life. Semiconductor nanomaterials such as tin oxide (SnO2) and similar metal-oxide materials such as titanium oxide (TiO2) are gaining significant attention for technologic innovations because of its Li storage stability. Our current study investigates vertically aligned SnO2 nanorods cycling stability for Li-ion batteries and TiO2 integration via atomic layer deposition (ALD) using the stop-valve configuration. 40nm film of ZnO was used as sacrificial layer to create in-tube SnO2 hollow TiO2 shell in vertically oriented nanorods configuration. Stainless steel battery spacer discs were used as substrates for the nanorods growth and coin cell half batteries were fabricated for the anodic Li storage studies. Li foil was used as the counter electrode and the batteries were charged and discharged from 0.1V to 2.5V for 75 cycles. Structural characterization along with the electrochemical study of the material demonstrated a higher capacity retention and improvement in cycling stability due to a better shape preservation during the lithiation process in comparison to the conventional vertical SnO2 nanorods anode configuration. Half battery cycling characterization and structural SEM comparisons and methods are described in detail.

SnO2/polypyrrole hollow spheres with improved cycle stability as lithium-ion battery anodes

SnO2/polypyrrole (SnO2/PPy) hollow spheres were fabricated by a liquid-phase deposition method using colloidal carbon spheres as templates followed by an in-situ chemical-polymerization route. The obtained SnO2/PPy composite particles had a size of 610–730 nm. The thickness of inner shell (SnO2) and outer shell (PPy) for composites was about 35 and 90 nm, respectively. As an anode for lithium ion batteries, the SnO2/PPy composites electrode showed superior rate capability and excellent long-term cycling performance. After a long-term cycling of 600 cycles at different current densities, a capacity of 899 mAh g−1 was achieved at the current density of 100 mA g−1 for SnO2/PPy composites. The excellent electrochemical performance was attributed to the synergistic effect between the PPy coating layer and the hollow SnO2 spheres, which guaranteed vast lithium storage sites, good electronic conductivity, fast lithium ion diffusion, and sufficient void space to buffer the volume expansion.

Zn2SnO4-doped SnO2 hollow spheres for phenylamine gas sensor application

In this paper, Zn2SnO4-doped SnO2 hollow spheres (HSs) were successfully synthesized by a one-step facile hydrothermal strategy without using any surfactants. In order to investigate the morphology, crystalline property and chemical composition of the prepared Zn2SnO4-doped SnO2 HSs, a sequence of techniques inclusive of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were performed. The sensor based on the as-fabricated Zn2SnO4-doped SnO2 HSs exhibited an excellent gas-sensing performance to phenylamine, including good selectivity and good reproducibility as well as reinforced response compared with the pristine SnO2 sample. Such enhanced gas-sensing performances are probably ascribed to the unique porous HS morphology, the strong interfacial interaction between Zn2SnO4 and SnO2 and the existence of heterojunctions. The as-fabricated Zn2SnO4-doped SnO2 HSs may also lead to potential applications in other fields such as lithium-ion batteries, catalysis and dye-sensitized solar cells.

One-pot synthesis of SnO2 hollow microspheres and their formaldehyde sensor application

SnO2 hollow microspheres (HMSs) were successfully synthesized by a one-pot hydrothermal method only using cheap Na2SnO3·3H2O as starting material, without using any templates or surfactants. The characterization results revealed that the SnO2 HMSs, with a diameter range of 450–800nm, composed of numerous small SnO2 nanoparticles, possess a rough and loose surface shell structure. The SnO2 HMSs were employed to fabricate a gas sensor for detecting formaldehyde. The SnO2 HMS sensor exhibited a high response, quick response/recovery characteristic, good reproducibility, and preferable selectivity to ppm level of formaldehyde, suggesting its promising application as a formaldehyde gas sensor. The SnO2 HMSs can be further applied in other fields such as photocatalysts, dye-sensitized solar cells and lithium-ion batteries.

Investigation on structural and magneto-optical properties of electrospun Co-doped SnO2 hollow nanofibers

Pure and Co-doped SnO2 hollow nanofibers were successfully synthesized by electrospinning technique. The structures of as spun and hollow nanofibers were characterized with X-ray diffraction (XRD) and scanning electron microscope (SEM). We observe from the SEM images the formation of well-defined hollow nanofiber network with coarse morphology consisting of fine nanograins. The optical properties of Co doped SnO2 nanofiber was studied with the UV–Vis spectroscopy and photoluminescence. The strong emission band at violet-blue region for all the samples with different intensities confirm the presence of defects related luminescent centres in Co-doped SnO2 nanofibers. The magnetic measurement reveals that Co-doped SnO2 hollow nanofibers show room temperature ferromagnetism at the low field strengths. This may be due to the exchange interaction between the local magnetic moment of Co2+ ions and bound magnetic polarons (BMPs) of SnO2.

Synthesis of SnO2/Sn hybrid hollow spheres as high performance anode materials for lithium ion battery

The hollow SnO2 spheres were synthesized by using carbon spheres as hard templates, and then carbon-coated SnO2/Sn hybrid hollow spheres can be obtained through annealing process after carbon coating. The as-prepared hybrid spheres are well dispersed and coated with a uniform carbon layer. The carbon-coated SnO2/Sn hybrid hollow spheres electrode exhibits high initial Coulombic efficiency (82.3%), high reversible capacity and good cycling stability (the initial charge and discharge capacity of 878.7 and 1061.6 mA h/g was achieved and the discharge capacities maintained 401 mA h/g after 50 cycles at 0.1 C) and good rate performance (1156.8 mA h/g at 0.1 C, 752.2 mA h/g at 0.2 C, 481.4 mA h/g at 0.5 C, 289.5 mA h/g at 1 C, and 120.6 mA h/g at 2 C, and more importantly, when the current density finally backs to 0.1 C, a capacity of 811.6 mA h/g can be restored) for anode materials in lithium ion batteries due to the hierarchical porous structure, carbon coating and the presence of Sn.

Extremely sensitive ethanol sensor using Pt-doped SnO2 hollow nanospheres prepared by Kirkendall diffusion

The pure and 0.3wt% Pt-doped SnO2 hollow nanospheres were prepared by the oxidation of pure and Pt-doped Sn nanoscrystals embedded in carbon matrix and their gas sensing characteristics were investigated. The formation of hollow morphology was attributed to the nanoscale Kirkendall effect due to rapid outward diffusion of Sn ions and relatively slow inward diffusion of oxygen. Pure SnO2 hollow nanospheres showed a high response (resistance ratio) of 93.3 when exposed to 5ppm ethanol. The response to 5ppm ethanol was significantly increased to 1399.9 with doping 0.3wt% Pt. In addition, selectivity to ethanol was also enhanced by Pt doping. Ultrasensitive and selective detection of ethanol in pure and Pt-doped SnO2 nanospheres is explained by the effective electron depletion in hollow structures and catalytic promotion of gas sensing reaction.

Alginate-assisted synthesis of hollow microfibers assembled by SnO2 nanoparticles

A novel alginate-involving method has been developed to prepare hollow SnO2 microfibers, in which a wet spinning process was combined with pyrolysis oxidation to facilitate scalable production. The resulting hollow SnO2 microfibers consisted of numerous SnO2 nanoparticles with pure tetragonal phase within the microfiber walls. Successful synthesis of this 3D hierarchical and interconnected structure depends strongly on the chelation of Sn2+ and alginate into “egg-box” networks and optimized pyrolysis conditions. SnO2 with this novel structure showed comparable electrochemical performance as the anode material for lithium-ion batteries, especially in ultra-long cycling (200mAhg−1 at 200mAg−1 after 2000cycles with a Coulombic efficiency of near 100%). The natural abundance of alginate, and facile scalability of both the conventional wet-spinning and pyrolysis processes hold the promise for massive preparation and practical application of the novel nanostructured SnO2 materials.

3D RGO frameworks wrapped hollow spherical SnO2-Fe2O3 mesoporous nano-shells: fabrication, characterization and lithium storage properties

Three-dimensional (3D) reduced graphene oxide (RGO) frameworks confined hollow spherical SnO2-Fe2O3@RGO nano-shells (3D h-SnO2-Fe2O3@RGO) are successfully obtained by hydrothermal reduction of h-SnO2-Fe2O3@GO in graphene oxide (GO) suspension. As anode materials for lithium-ion batteries (LIBs), the novel 3D h-SnO2-Fe2O3@RGO architectures demonstrate great improvement in cycling performance (∼830mAhg−1 after 100 cycles at 200mAg−1) and rate capability (∼550mAhg−1 at 1000mAg−1for 10 cycles) over that of hollow SnO2 spheres (h-SnO2), h-SnO2-Fe2O3, and 3D RGO frameworks wrapped hollow spherical SnO2@RGO nano-shells (3D h-SnO2@RGO). The 3D porous frameworks and coating graphene nano-shells serve as efficient electron and ion conductive networks as well as buffer for the large volume variation of hollow SnO2-Fe2O3 during cycling. Moreover, the hollow spherical metal oxide mesoporous nano-shells could enlarge the surface area, retard the volume change, prevent aggregation of nanosized active materials and graphene nanosheets.

Ultrasensitive and highly selective detection of methoxy propanol based on Ag-decorated SnO2 hollow nanospheres

Ag-decorated SnO2 hollow spheres with different mass ratios were synthesized through a two-step synthesis route. The morphology of as-prepared materials was characterized via FESEM and TEM microscopes, and the results proved the rough and porous spherical structures. The EDX and XPS patterns verified the elementary composition, especially for Ag/SnO2, the standard peaks of Ag were obviously observed. The N2 isotherm of SnO2 hollow spheres belongs to a type-IV isotherm with a large type H3 hysteresis loop. The pore size distribution covered a range of 35–80nm and the sample showed a high BET surface area of 31.91m2/g. During the systematic examinations of gas sensing performance, 5wt% Ag/SnO2 showed superior properties, including the ultrahigh response of over one hundred to methoxy propanol within a wide concentration range and the excellent selectivity for detecting methoxy propanol among other gases. Moreover, the synthesis mechanism and gas sensing mechanism were discussed, which indicated that both the morphology of SnO2 hollow spheres and the catalytic effect of Ag nanoparticles played important roles on the gas sensing properties, and could be used for the further design of gas sensor utilizing other oxide semiconductors.

Applying Nanoscale Kirkendall Diffusion for Template-Free, Kilogram-Scale Production of SnO2 Hollow Nanospheres via Spray Drying System.

A commercially applicable and simple process for the preparation of aggregation-free metal oxide hollow nanospheres is developed by applying nanoscale Kirkendall diffusion to a large-scale spray drying process. The precursor powders prepared by spray drying are transformed into homogeneous metal oxide hollow nanospheres through a simple post-treatment process. Aggregation-free SnO2 hollow nanospheres are selected as the first target material for lithium ion storage applications. Amorphous carbon microspheres with uniformly dispersed Sn metal nanopowder are prepared in the first step of the post-treatment process under a reducing atmosphere. The post-treatment of the Sn-C composite powder at 500 °C under an air atmosphere produces carbon- and aggregation-free SnO2 hollow nanospheres through nanoscale Kirkendall diffusion. The hollow and filled SnO2 nanopowders exhibit different cycling performances, with their discharge capacities after 300 cycles being 643 and 280 mA h g−1, respectively, at a current density of 2 A g−1. The SnO2 hollow nanospheres with high structural stability exhibit superior cycling and rate performances for lithium ion storage compared to the filled ones.

Facile Synthesis and Acetone Sensing Performance of Hierarchical SnO2 Hollow Microspheres with Controllable Size and Shell Thickness

A facile method to prepare SnO2 hollow microspheres has been developed by using SiO2 microspheres as template and Na2SnO3 as tin resource. The obtained SnO2 hollow microspheres were characterized by X-ray diffraction, scanning electron microscopy, high resolution and transmission electron microscopy, and Brunauer–Emmett–Teller analysis, and their sensing performance was also investigated. It was found that the diameter of SnO2 hollow microspheres can be easily controlled in the range of 200–700 nm, and the shell thickness can be tuned from 7.65 to 30.33 nm. The sensing tests showed that SnO2 hollow microspheres not only have high sensing response and excellent selectivity to acetone, but also exhibit low operating temperature and rapid response and recovery due to the small crystal size and thin shell structure of the hollow microspheres, which facilitate the adsorption, diffusion, and reaction of gases on the surface of SnO2 nanoparticles. Therefore, the SnO2 hollow microsphere is a promising material fo...

Carbon-Coated Hierarchical SnO2 Hollow Spheres for Lithium Ion Batteries.

Hierarchical SnO2 hollow spheres self-assembled from nanosheets were prepared with and without carbon coating. The combination of nanosized architecture, hollow structure, and a conductive carbon layer endows the SnO2 -based anode with improved specific capacity and cycling stability, making it more promising for use in lithium ion batteries.

Enhanced Gas Sensing Properties of SnO2 Hollow Spheres Decorated with CeO2 Nanoparticles Heterostructure Composite Materials.

CeO2 decorated SnO2 hollow spheres were successfully synthesized via a two-step hydrothermal strategy. The morphology and structures of as-obtained CeO2/SnO2 composites were analyzed by various kinds of techniques. The SnO2 hollow spheres with uniform size around 300 nm were self-assembled with SnO2 nanoparticles and were hollow with a diameter of about 100 nm. The CeO2 nanoparticles on the surface of SnO2 hollow spheres could be clearly observed. X-ray photoelectron spectroscopy results confirmed the existence of Ce(3+) and the increased amount of both chemisorbed oxygen and oxygen vacancy after the CeO2 decorated. Compared with pure SnO2 hollow spheres, such composites revealed excellent enhanced sensing properties to ethanol. When the ethanol concentration was 100 ppm, the sensitivity of the CeO2/SnO2 composites was 37, which was 2.65-times higher than that of the primary SnO2 hollow spheres. The sensing mechanism of the enhanced gas sensing properties was also discussed.

Novel inkjet droplet method generating monodisperse hollow metal oxide micro-spheres

A novel method to synthesize monodisperse hollow TiO2, SnO2 and ZnO microspheres was developed. Water droplets generated from an inkjet nozzle contain clusters of polystyrene latex (PSL) particles covered with metal oxide nanoparticles were continuously dried up forming PSL clusters decorated with metal oxide nanoparticles. By heating the clusters up to 400°C, the PSL particles are evaporated forming hollow spheres. Monodisperse hollow TiO2, SnO2 and ZnO spheres in the size range of 5.1–8.6μm were consequently generated with a narrow particle size distribution. And the hollow TiO2, SnO2 and ZnO spheres have 41.0nm, 30.0nm, and 85.3nm sized pores, respectively. The method enables us to have simpler and faster process to generate hollow TiO2, SnO2 and ZnO spheres and to control the diameter of hollow spheres easily by adjusting waveform applied to a nozzle compared to other processes. A potential applicability to photoelectrochemical cells was demonstrated for the prepared hollow TiO2 grown a Si substrate.

The effects of carbon distribution and thickness on the lithium storage properties of carbon-coated SnO2 hollow nanofibers

To alleviate the enormous volume change problem of tin-based anodes for lithium ion batteries (LIBs), carbon-coated tin dioxide (SnO2) hollow nanofibers were prepared by means of single-spinneret electrospinning followed by calcination and hydrothermal treatment. By varying the concentration of glucose and the reaction time during the hydrothermal coating process, the final product with different carbon distribution and thickness could be obtained. Galvanostatic charge/discharge was carried out to evaluate them as potential anode materials for LIBs. It was shown that the main effect of carbon distribution was to control the capacity retention rate, and the carbon thickness played the important role in lithium insertion/extraction properties. The optimum composite nanofibers could be prepared with glucose concentration of 10 mg/ml and hydrothermal time of 20 h, the carbon content and the specific surface area of which were 26.15% and 29.4 m2/g, respectively. And this anode with both the carbon core and deposited thin carbon skin was able to deliver a high reversible capacity of 704.6 mAhg−1 and the capacity retention could retain 68.2% after 80 cycles.

All-in-One Beaker Method for Large-Scale Production of Metal Oxide Hollow Nanospheres Using Nanoscale Kirkendall Diffusion.

A simple and easily scalable process for the formation of metal oxide hollow nanospheres using nanoscale Kirkendall diffusion called the "all-in-one beaker method" is introduced. The Fe2O3, SnO2, NiO, and Co3O4 hollow nanospheres are successfully prepared by the all-in-one beaker method. The detailed formation mechanism of aggregate-free hematite hollow nanospheres is studied. Dimethylformamide solution containing Fe acetate, polyacrylonitrile (PAN), and polystyrene (PS) transforms into aggregate-free Fe2O3 hollow nanospheres. The porous structure formed by the combustion of PS provides a good pathway for the reducing gas. The carbon matrix formed from PAN acts as a barrier, which can prevent the aggregation of metallic Fe nanopowders by surrounding each particle. The Fe-C bulk material formed as an intermediate product transforms into aggregate-free Fe2O3 hollow nanospheres by the nanoscale Kirkendall diffusion process. The mean size and shell thickness of the hollow Fe2O3 nanospheres measured from the TEM images are 52 and 9 nm, respectively. The discharge capacities of the Fe2O3 nanopowders with hollow and dense structures and the bulk material for the 200th cycle at a current density of 0.5 A g(-1) are 1012, 498, and 637 mA h g(-1), respectively, and their capacity retentions calculated compared to those in the second cycles are 92, 45, and 59%, respectively. Additionally, Fe2O3 hollow nanospheres cycled at 1 A g(-1) after 1000 cycles showed a high discharge capacity of 871 mA h g(-1) (capacity retention was 80% from the second cycle). The Fe2O3, SnO2, NiO, and Co3O4 hollow nanospheres show excellent cycling performances for lithium-ion storage because they have a high contact area with the liquid electrolyte and space for accommodating a huge volume change during cycling.

Engineering of multi-shelled SnO2 hollow microspheres for highly stable lithium-ion batteries

Triple-shelled SnO2 hollow microspheres not only maintain a hierarchical structure during lithium insertion and extraction processes, but also improve the capacity of lithium-ion batteries.

The enhanced CO gas sensing performance of Pd/SnO2 hollow sphere sensors under hydrothermal conditions

Pd-doped SnO2 hollow spheres were synthesized via a facile one-step hydrothermal route.

Facile synthesis and application of multi-shelled SnO2 hollow spheres in lithium ion battery

A simple template-free hydrothermal method has been developed to prepare multi-shelled SnO2 hollow spheres with controlled interior texture.