SnO2 Composites Research Articles

Fluorine-doped SnO2 nanoparticles anchored on reduced graphene oxide as a high-performance lithium ion battery anode

The composite of fluorine-doped SnO2 anchored on reduced graphene oxide (F-SnO2/rGO) has been synthesized through a hydrothermal method. F-SnO2 particles with average size of 8 nm were uniformly anchored on the surfaces of rGO sheets and the resulting composite had a high loading of F-SnO2 (ca. 90%). Benefiting from the remarkably improved electrical conductivity and Li-ion diffusion in the electrode by F doping and rGO incorporation, the composite material exhibited high reversible capacity, excellent long-term cycling stability and superior rate capability. The electrode delivered a large reversible capacity of 1037 mAh g−1 after 150 cycles at 100 mA g−1 and high rate capacities of 860 and 770 mAh g−1 at 1 and 2 A g−1, respectively. Moreover, the electrode could maintain a high reversible capacities of 733 mAh g−1 even after 250 cycles at 500 mA g−1. The outstanding electrochemical performance of the as-synthesized composite make it a promising anode material for high-energy lithium ion batteries.

Fast facile synthesis of SnO2/Graphene composite assisted by microwave as anode material for lithium-ion batteries

SnO2 is promising as anode material for Lithium ion batteries(LIBs) due to its high specific capacity and low opening potential. However, its poor electronic conductivity as well as serious volume effect significantly restrict its application in LIBs. In this work, a facile hydrothermal method assisted with microwave is performed to realize the composite of SnO2 and graphene within only 30minutes without any chelating agents. It is highly time-efficient with relatively high SnO2 loading of 89.97wt.%. Ultrasmall nano-particles of SnO2 well disperse on the surface of the graphene with average particle size of 3–8nm and larger surface area of 417.45m2g−1. Simultaneously, high charge/discharge capacity of 969.4/978.6mAhg−1 is obtained after 100 cycles at 200mAg−1. Even increasing the current density to 1Ag−1, high reversible charge/discharge capacities of 740.0/747.0mAhg−1 are still remained after 200 cycles. In addition, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are performed to further study the composite material prepared by facile microwave hydrothermal method. It is considered to be a high efficient way to obtain SnO2/graphene composite with excellent electrochemical properties as anode material for applications.

Thermogravimetric investigation of oxygen deficiency in SnO2 reduced at 500 °C or below

The oxygen deficiency of SnO2 was investigated by thermogravimetric analysis (TGA). The powder samples were reduced in 0.5% H2/N2 at 200–500°C and, their weight changes were evaluated by TGA under flowing O2. The results showed that the response of SnO2 against H2/N2 differed from that against H2/air, which is the gas mixture typically used to evaluate SnO2-based gas sensors. The subsequently obtained TGA traces of the powders reduced under H2/N2 showed two stepwise weight gains. The first weight gain began near room temperature and ended at approximately 200°C. The second weight gain was observed between 400 and 600°C, which became prominent when the sample was reduced at 400°C or above. The existence of two types of oxygen sites was deduced from the temperature dependence of the weight changes in the TGA traces and they were related to the positions of oxygen sites in the surface and bulk regions. SnO2 was tolerant to the oxygen deficiency, and the extent of deficiency was dependent on the crystallinity and the grain size. For example, the composition of SnO2 precipitated in SnF2 aqueous solution through a hydrolysis reaction was estimated to be SnO1.94 after the reduction at 400°C in 0.5% H2/N2. Small grains with lower crystallinity tended to accept greater oxygen deficiency under a certain condition.

In Situ Synthesis of Tungsten-Doped SnO2 and Graphene Nanocomposites for High-Performance Anode Materials of Lithium-Ion Batteries.

The composite of tungsten-doped SnO2 and reduced graphene oxide was synthesized through a simple one-pot hydrothermal method. According to the structural characterization of the composite, tungsten ions were doped in the unit cells of tin dioxide rather than simply attaching to the surface. Tungsten-doped SnO2 was in situ grown on the surface of graphene sheet to form a three-dimensional conductive network that enhanced the electron transportation and lithium-ion diffusion effectively. The issues of SnO2 agglomeration and volume expansion could be also avoided because the tungsten-doped SnO2 nanoparticles were homogeneously distributed on a graphene sheet. As a result, the nanocomposite electrodes of tungsten-doped SnO2 and reduced graphene oxide exhibited an excellent long-term cycling performance. The residual capacity was still as high as 1100 mA h g-1 at 0.1 A g-1 after 100 cycles. It still remained at 776 mA h g-1 after 2000 cycles at the current density of 1A g-1.

Metal-Organic Frameworks Derived Okra-like SnO2 Encapsulated in Nitrogen-Doped Graphene for Lithium Ion Battery.

A facile process is developed to prepare SnO2-based composites through using metal-organic frameworks (MOFs) as precursors. The nitrogen-doped graphene wrapped okra-like SnO2 composites (SnO2@N-RGO) are successfully synthesized for the first time by using Sn-based metal-organic frameworks (Sn-MOF) as precursors. When utilized as an anode material for lithium-ion batteries, the SnO2@N-RGO composites possess a remarkably superior reversible capacity of 1041 mA h g-1 at a constant current of 200 mA g-1 after 180 charge-discharge processes and excellent rate capability. The excellent performance can be primarily ascribed to the unique structure of 1D okra-like SnO2 in SnO2@N-RGO which are actually composed of a great number of SnO2 primary crystallites and numerous well-defined internal voids, can effectively alleviate the huge volume change of SnO2, and facilitate the transport and storage of lithium ions. Besides, the structural stability acquires further improvement when the okra-like SnO2 are wrapped by N-doped graphene. Similarly, this synthetic strategy can be employed to synthesize other high-capacity metal-oxide-based composites starting from various metal-organic frameworks, exhibiting promising application in novel electrode material field of lithium-ion batteries.

Ultrafine Sn nanocrystals in a hierarchically porous N-doped carbon for lithium ion batteries

We report a simple method of preparing a high performance, Sn-based anode material for lithium ion batteries (LIBs). Adding H2O2 to an aqueous solution containing Sn2+ and aniline results in simultaneous polymerization of aniline and oxidation of Sn2+ to SnO2, leading to a homogeneous composite of polyaniline and SnO2. Hydrogen thermal reduction of the above composite yields N-doped carbon with hierarchical porosity and homogeneously distributed, ultrafine Sn particles. The nanocomposite exhibits excellent performance as an anode material for lithium ion batteries, showing a high reversible specific capacity of 788 mAh·g−1 at a current density of 100 mA·g−1 after 300 cycles and very good stability up to 5,000 mA·g−1. The simple preparation method combined with the good electrochemical performance is highly promising to promote the application of Sn based anode materials.

Supercapacitors based on graphene/pseudocapacitive materials

Composites of graphene and SnO2 were successfully prepared by a single step simultaneous synthesis of SnO2 and reduction of graphene oxide (GO). Three different compositions of precursor solution resulted in different composite materials containing graphene and SnO2. The reaction was realized by microwave-assisted hydrothermal synthesis. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) gave insight into the morphology and composition of the obtained materials. Good capacitive/pseudocapacitive properties of the obtained material suitable for supercapacitor application were registered by cyclic voltammetry, from where specific capacitance values up to 93 F g-1 were determined.

Formation of tin-tin oxide core–shell nanoparticles in the composite SnO2−x/nitrogen-doped carbon nanotubes by pulsed ion beam irradiation

The complex methods of transmission electron microscopy, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy were used to investigate the changes in the morphology, phase composition, and electronic structure of the composite SnO2−x/nitrogen-doped multiwalled carbon nanotubes (SnO2−x/N-MWCNTs) irradiated with the pulsed ion beam of nanosecond duration. The irradiation of the composite SnO2−x/N-MWCNTs leads to the formation of nanoparticles with the core–shell structure on the surface of CNTs with a sharp interfacial boundary. It has been established that the “core” is a metal tin (Sn0) with a typical size of 5–35nm, and the “shell” is a thin amorphous layer (2–6nm) consisting of nonstoichiometric tin oxide with a low oxygen content. The “core–shell” structure SnSnOx is formed due to the process of heating and evaporation of SnO2−x under the effect of the ion beam, followed by vapor deposition on the surface of carbon nanotubes.

Ultra-fine SnO2 nanoparticles doubly embedded in amorphous carbon and reduced graphene oxide (rGO) for superior lithium storage

SnO2 is a well-studied anode material for lithium ion batteries (LIBs). However, it undergoes severe capacity fading because of a large volume change (∼300%) during cycling. Composites of SnO2 with electro-conductive graphene would deliver improved capacity and rate performance. Nevertheless, achieving the theoretical capacity of SnO2 is still elusive, mainly because of disintegration of the active material from graphene and severe aggregation of SnO2, or Sn nanoparticles produced upon cycling. To surmount these limitations, in this work, nanocomposites containing ultra-fine sized SnO2 nanoparticles (UFSN) with reduced graphene oxide and amorphous carbon were synthesized in a single step at low temperature and environmentally benign way, in which ascorbic acid was employed as the carbon source and reducing agent. UFSN could decrease the lithium ion diffusion path length. As a result of effective buffering effect afforded by the mesoporous structure against volume change and improved lithium ion diffusivity, the ternary nanocomposite achieves ultra-high capacity of 1245mAhg−1 after 210 cycles at 100mAg−1 and excellent cycling stability. Since the proposed approach is facile, straightforward, and highly reproducible, it is anticipated that this system would be a potential alternative to the conventional graphite anode for LIBs.

One-pot synthesis of echinus-like Fe-doped SnO2 with enhanced photocatalytic activity under simulated sunlight

Unique echinus-like Fe-doped SnO2 particles constructed from ultrathin nanorods with the 2–4 nm diameter were readily synthesized by one-pot solvothermal method, in which hydrochloric acid was used to control the hydrolysis rates of SnCl4 and FeCl3. The as-prepared sample were characterized by means of transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), and N2 adsorption-desorption analysis, etc. The obtained echinus-like Fe-doped SnO2 composites exhibited enhanced activity for both photodegradation of Rhodamine B (RhB) and photoreduction of Cr(VI) under simulated sunlight irradiation, which could be largely attributed to the Eg decreased by Fe-doping, high specific surface area and porosity of structure.

Flexible carbonized cotton covered by graphene/Co-doped SnO2 as free-standing and binder-free anode material for lithium-ions batteries

A flexible carbonized cotton covered by graphene/Co-doped SnO2 (CGN/SnO2-Co) composite is prepared by in situ and subsequent microwave method, then followed by thermal annealing treatment. The SnO2 nanoparticles with ultra-small size are uniform decorated on the CGN framework, and Co element has been successful doping into SnO2. It is found that doping process does not affect the phase structure of SnO2, but great influence the morphology, the electrical conductivity, and the electrochemical properties on the composites. As a free-standing and binder-free anode for lithium-ions batteries, the discharge capacity of CGN/SnO2-Co have a high value of 549.6mAhg−1 (1996μAcm−2) after 100 cycles at a current density of 100mAg−1, which is much higher than those of cotton covered by graphene/SnO2 (CGN/SnO2) and cotton covered by graphene/Co3O4 (CGN/Co3O4) at the same current. The improved performance of CGN/SnO2-Co can be attributed to the highly stable and conductive CGN framework, ultra-small size of SnO2 nanoparticles, and Co doping effect. It is reasonable to believe that this work has a great potential improve the performance of energy storage devices.

RGO- SnO2 Composites for Supercapacitor Applications

Reduced grapheme oxide (rGO) - SnO2 composites for supercapacitor applications were synthesized and characterized to understand their utility. Graphene Oxide (GO) was prepared through modified Hummer's method and mixed with SnO2 precursor solution prepared through Sol -Gel chemistry to attain rGO- SnO2 composite. The synthesized powder was annealed to get rGO- SnO2 composite. X - ray diffraction and Raman spectroscopic studies show the successful synthesis of GO, SnO2 and rGO-SnO2 composites evidenced by standard signatures. Cyclic Voltammometric studies show interesting results for the composites where the specific capacitance for the composite is 1.62 times higher than that of the pure SnO2.

Ultra-fast and highly-sensitive gas sensing arising from thin SnO2 inner wall supported hierarchical bilayer oxide hollow spheres

Hierarchical SnO2/α-Fe2O3 bilayer hollow spheres with thin inner shell were successfully synthesized by using SnO2 contained carbon spheres as sacrificial templates. The heterojunction formed at the interface as well as the hierarchical structures which provide an effective gas diffusion path resulted in significant enhancement in sensing response to ethanol and acetone as compared to pristine urchin-like α-Fe2O3. Response values of the hollow spheres based sensors towards 100ppm acetone and ethanol could reach to 47.1 and 29.5. Moreover, in contrast to many other types of α-Fe2O3/SnO2 composites reported previously, gas sensors based on the bilayer hollow spheres here exhibited ultra-fast response and recovery speed. The dynamic transients of the sensors demonstrated both their fast response (3–4s) and fast recovery (6–9s) towards acetone in the concentration of 10–100ppm. The unique hierarchical hollow structure with thin inner shell might be responsible for the ultra-fast gas sensing properties. This simple template based strategy is expected to be extended for the fabrication of similar hollow structure semiconductor oxide composites, and this work might provide an effective principle for designing high performance hybrid gas sensing materials.

Anti-Arc Erosion Properties of Ag-La2Sn2O7/SnO2 Contacts

La2Sn2O7/SnO2 composite powder was synthesized by chemical co-precipitation, and Ag-La2Sn2O7/SnO2 electrical contact material was prepared by a powder metallurgy method. Anti-arc erosion properties, mass loss and Vickers hardness of the Ag-La2Sn2O7/SnO2 composite were investigated, and its anti-arc erosion mechanism was discussed. Results show that the welding force of Ag-La2Sn2O7/SnO2 composite is much better than that of Ag-SnO2, because the new phase La2Sn2O7 can increase the viscosity of melt pool and improve wettability between silver and tin oxide to some extent. Meanwhile, Flatter arcing area and “beads-like” particles embedded scatteredly in the surface could decentralize arc energy via “pinning effect”, which decreases temperature rise and weakens the damage of surface structure, and better anti-welding property is obtained. Ag-La2Sn2O7/SnO2 composite could be a leading candidate material for electrical contacts in the future.

Copper Ion Beam Irradiation-Induced Effects on Structural, Morphological and Optical Properties of Tin Dioxide Nanowires**Supported by the Department of Physics, the University of AJK, High Tech. Centralized Instrumentation Lab, the University of AJK, Pakistan and the Experimental Physics Division, and the National Center for Physics, Islamabad Pakistan.

The 0.8 MeV copper (Cu) ion beam irradiation-induced effects on structural, morphological and optical properties of tin dioxide nanowires (SnO2 NWs) are investigated. The samples are irradiated at three different doses 5 × 1012 ions/cm2, 1 × 1013 ions/cm2 and 5 × 1013 ions/cm2 at room temperature. The XRD analysis shows that the tetragonal phase of SnO2 NWs remains stable after Cu ion irradiation, but with increasing irradiation dose level the crystal size increases due to ion beam induced coalescence of NWs. The FTIR spectra of pristine SnO2 NWs exhibit the chemical composition of SnO2 while the Cu—O bond is also observed in the FTIR spectra after Cu ion beam irradiation. The presence of Cu impurity in SnO2 is further confirmed by calculating the stopping range of Cu ions by using TRM/SRIM code. Optical properties of SnO2 NWs are studied before and after Cu ion irradiation. Band gap analysis reveals that the band gap of irradiated samples is found to decrease compared with the pristine sample. Therefore, ion beam irradiation is a promising technology for nanoengineering and band gap tailoring.

Sonochemical-driven ultrafast facile synthesis of SnO2 nanoparticles: Growth mechanism structural electrical and hydrogen gas sensing properties

Synthesis of SnO2 nanoparticles have been successfully accomplished moderately at lower temperature by facile, rapid, efficient and mild ultrasonic irradiation method. The as-grown SnO2 nanoparticles are investigated by various characterization techniques in terms of structural, optical, electrical and gas sensing properties. XRD investigation has shown that the SnO2 nanoparticles materials exhibit single rutile crystal phase with high crystallinity. FESEM studies showed uniform and monodisperse morphology of SnO2 nanoparticles. The chemical composition of SnO2 was systematically studied by EDX measurements. Additional confirmation of three Raman shifts (432, 630, 772cm−1) indicated the characteristic properties of the rutile phase of the as-grown SnO2 nanoparticles. The optical properties of SnO2 nanoparticles were examined by DRS, and the electronic band gap of SnO2 nanoparticles were around 3.6eV. Electrical properties of the SnO2 nanoparticles measured at various temperatures have shown the semiconducting properties. Surface area and pore size of synthesized nanoparticles were analyzed from BET. It has been revealed that SnO2 nanoparticles have surface area is 47.8574m2/g and the pore size is 10.5nm. Moreover, hydrogen gas sensor made of SnO2 nanoparticles showed good sensitivity and faster response for the hydrogen gas. This method is template-less and surfactant-free which circumvents rigorous reaction work-up for the former removal, reaction temperature and reaction time compared to hydrothermal synthesis and pertinent to many other oxide materials.

Low-temperature cataluminescence sensor for sulfur hexafluoride utilizing coral like Zn-doped SnO2 composite

Gaseous sensor system was developed for the detection of sulfur hexafluoride vapor based on its cataluminescence (CTL) emission by using coral-like Zn-doped SnO2 composite. The test architecture, experiment characteristics and optimal conditions were studied in detail under optimized experiment conditions. Results showed that the gas sensor system covered a linear detection range from 8mg/L to 5600mg/L (R=0.9963, n=7) with a detection limit of 6.2mg/L (S/N=3), which was below the standard permitted concentration. The sensor showed a rapid response of 2s and a recovery time of 30s, respectively. Moreover, pattern recognition method was used to test the recognizable performance of this sensor, which has found that analyte can be distinguished clearly. As sensing materials for a CTL gas sensor, this coral-like Zn-doped SnO2 demonstrates excellent CTL behavior (that is, high sensitivity, superior selectivity to sulfur hexafluoride compared with other eleven kinds of common volatile organic compounds (VOCs) as well as a fast response and recovery). The excellent sensing properties including improved sensitivity, selectivity and stability proved this sensor to be a promising candidate for detecting gas contaminants.

Microwave-Assisted Synthesis of SnO2@polypyrrole Nanotubes and Their Pyrolyzed Composite as Anode for Lithium-Ion Batteries.

Tin dioxide (SnO2) as lithium-ion batteries (LIBs) anode has attracted numerous interests due to its huge Li(+) storage capacity. However, more than 300% volume variation of SnO2 during the charge/discharge process results in dramatic degradation of electrochemical performance and thus poor cyclic stability, which has hindered its application in LIBs. Here, a new strategy is proposed to suppress this volume change via anchoring mesoporous SnO2 on robust polypyrrole nanotubes (PPy NTs) to fabricate nanoarchitectured SnO2 composite. Benefiting from this nanoarchitecture design, the anode presents outstanding rate performance with a reversible specific capacity of about 770 mA h g(-1) at 2000 mA g(-1) and remarkable cyclability accompanied by a high specific capacity of about 790 mA h g(-1) at 200 mA g(-1) after 200 cycles.

SnO2–TiO2 hybrid nanofibers for efficient dye-sensitized solar cells

Pristine SnO2 nanostructures typically result in low open circuit voltage (VOC) <500mV due to the lower Fermi energy (EF) when employed as a photoanode materials in dye sensitized solar cells (DSSCs). On the other hand, the most successful photoanode material, i.e., TiO2 nanoparticle although provides a high VOC⩾800mV result in poor charge collection owing to their inferior electron mobility (μn). Herein, we employ nanofiber–nanoparticle composite of SnO2–TiO2 which showed similar VOC and short circuit current density (JSC) to a reference TiO2 based DSSCs. The nanocomposite developed here involves multi-porous SnO2 nanofibers characterized by a lower EF; however, with higher μn and TiO2 nanoparticles of higher EF and lower μn. The TiO2 particles in the pores of SnO2 nanofibers were developed by TiCl4 treatment, whose concentration is optimized for the saturated JSC and VOC. The best performing DSSCs fabricated using the composite electrodes deliver power conversion efficiency (PCE) of ≈7.9% (VOC≈717mV; JSC≈21mAcm−2), which is significantly higher than pure SnO2 photoanode with PCE≈3.0% (JSC≈14.0mAcm−2 and VOC≈481mV) at similar experimental conditions.

A graphene–SnO2–TiO2 ternary nanocomposite electrode as a high stability lithium-ion anode material

In this work, a solvothermal method combined with a hydrothermal two-step method is developed to synthesize graphene–SnO2–TiO2 ternary nanocomposite, in which the nanometer-sized TiO2 and SnO2 nanoparticles form in situ uniformly anchored on the surface of graphene sheets, as high stability and capacity lithium-ion anode materials. Compared to graphene–TiO2, bulk TiO2 and grapheme–SnO2 composites, the as-prepared nanocomposite delivers a superior rate performance of 499.3 mAhg−1 at 0.2 C and an outstanding stability cycling capability (1073.4 mAhg−1 at 0.2 C after 50 cycles), due to the synergistic effects contributed from individual components, for example, high specific capacity of SnO2, excellent conductivity of 3D graphene networks.