Preparation of SnO2–graphene from SnS–graphene oxide for enhanced reversible lithium ion storage

SnO₂–graphene nanocomposites (SnO₂–GNS) have been prepared through a simple hydrothermal reaction with SnS–graphene oxide composites as the precursor. The composite material as prepared was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller analysis, and thermogravimetric analysis. The results indicate that SnO₂ nanoparticles possess a good dispersion on the surface of graphene. Electrochemical tests demonstrate the high reversible lithium ion storage properties of SnO₂–GNS. The nanocomposites retained a reversible capacity of 503 mAh?g^?1 after 40 cycles. Moreover, the composite material exhibited higher capacity and better cyclic performance compared to free SnO₂ nanoparticles physically mixed with graphene in the relative weight ratio. The results suggest that the combination of SnO₂ and graphene leads to synergistic performance, which enhances lithium ion storage properties of the overall system.     

Preparation of Co3O4 nanoplate/graphene sheet composites and their synergistic electrochemical performance

Co₃O₄ nanoplate/graphene sheet composites were prepared through a two-step synthetic method. The composite material as prepared was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The platelet-like morphology of Co₃O₄ leads to a layer-by-layer-assembled structure of the composites and a good dispersion of Co₃O₄ nanoplates on the surface of graphene sheets. The electrochemical characteristics indicate that the specific capacitance of the composites is 337.8 F?g^?1 in comparison with the specific capacitance of 204.4 F?g^?1 without graphene sheets. Meanwhile, the composites have an excellent rate capability and cycle performance. The results show that the unique microstructure of the composites enhances the electrochemical capacitive performance of Co₃O₄ nanoplates due to the three-dimensional network of graphene sheets for electron transport increasing electric conductivity of the electrode and providing unobstructed pathways for ionic transport during the electrochemical reaction.     

Tin oxide nano-flower-anchored graphene composites as high-performance anode materials for lithium-ion batteries

The SnO₂ nano-flower/graphene (SnO₂-NF/GN) composites were synthesized by using graphene (GN) and SnO₂ nano-flower (SnO₂-NF). Among them, the SnO₂-NFs were prefabricated by using sodium hydroxide and stannic chloride pentahydrate (SnCl₄·5H₂O) as raw materials. The results of SEM show that the SnO₂-NFs are uniformly dispersed on the surface of GN. Furthermore, compared with the pure SnO₂, the as-prepared SnO₂-NF/GN composites displayed superior cycle performace and high rate capability. The SnO₂-NF/GN composite delivers a specific capacity of 650 mAh g^?1 after 60 cycles and an excellent rate capability of 480 mAh g^?1 at 2000 mA g^?1.     

Facile synthesis of ultrafine SnO<Subscript>2</Subscript> nanoparticles on graphene nanosheets via thermal decomposition of tin-octoate as anode for lithium ion batteries

We demonstrate a facile synthesis of ultrafine SnO₂ nanoparticles within graphene nanosheets (GNSs) via thermal decomposition of tin-octoate, in which tin-octoate is firstly blended with GNSs followed by annealing in air at a low temperature (350 °C) and a short time (1 h). As anode for lithium ion batteries, the SnO₂/GNSs displays superior cycle and rate performance, delivering reversible capacities of 803 and 682 mA h/g at current densities of 200 and 500 mA/g after 120 cycles, respectively, much higher than that of pure SnO₂ and GNSs counterparts (143 and 310 mA h/g at 500 mA/g after 120 cycles, respectively). The enhanced electrochemical performance is attributed to the ultrafine SnO₂ nanoparticle size and introduction of GNSs. GNSs prevent the aggregation of the ultrafine SnO₂ nanoparticles, which alleviate the stress and also provide more electrochemically active sites for lithium insertion and extraction. Moreover, GNSs with large specific surface area (~363 m²/g) act as a good electrical conductor which greatly improves the electrode conductivity and also an excellent buffer matrix to tolerate the severe volume changes originated from the Li-Sn alloying-dealloying. This work provides a straight-forward synthetic approach for the design of novel composite anode materials with superior electrochemical performance.     

Effect of the particle size on the electrochemical performance of nano-Li2FeSiO4/C composites

Nano-Li₂FeSiO₄/C composites were prepared from three kinds of nano-SiO₂ (their particle sizes are 15?±?5, 30?±?5, and 50?±?5 nm, respectively) by a traditional solid-state reaction method. The as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elementary analyzer, Brunauer–Emmett–Teller (BET) analysis, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy. XRD results reveal that nano-Li₂FeSiO₄ composites fabricated from nano-SiO₂ (smaller than 30 nm) have less impurity. SEM results indicate that the particle size of nano-Li₂FeSiO₄ composites is nearly accord with the particle size of nano-SiO₂. BET analysis indicates that the specific surface areas of LFS15, LFS30, and LFS50 are 35.10, 35.27, and 26.68 m² g, respectively, and the main pore size distribution of LFS15, LFS30, and LFS50 are 1.5, 5.5, and 10 nm, respectively. Electrochemical measurements indicate that nano-Li₂FeSiO₄ composites prepared from nano-SiO₂ of 30?±?5 nm have the best electrochemical performance among the three samples.     

Facile and surfactant-free synthesis of SnO<Subscript>2</Subscript>-graphene hybrids as high performance anode for lithium-ion batteries

A facile microwave-assisted ethylene glycol method is developed to synthesize the SnO₂ nanoparticles dispersed on or encapsulated in reduced graphene oxide (SnO₂-rGO) hybrids. The morphology, structure, and composition of SnO₂-rGO are investigated by scanning electron microscopy, transmission electron microscope, thermo-gravimetric analyzer, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical performance of SnO₂-rGO as anode materials for lithium-ion batteries was tested by cyclic voltammetry, galvanostatic charge–discharge cycling, and rate capability test. It is found that the SnO₂ nanoparticles with a uniform distribution have p-type doping effect with rGO nanosheets. The as-prepared SnO₂-rGO hybrids exhibit remarkable lithium storage capacity and cycling stability, and the possible mechanism involved is also discussed. Their capacity is 1222 mAhg^?1 in the first cycle and maintains at 700 mAhg^?1 after 100 cycles. This good performance can be mainly attributed to the unique nanostructure, good structure stability, more space for volume expansion of SnO₂, and mass transfer of Li⁺ during cycling.     

Growth of FePO<Subscript>4</Subscript> nanoparticles on graphene oxide sheets for synthesis of LiFePO<Subscript>4</Subscript>/graphene

FePO₄·xH₂O/graphene oxide (FePO₄·xH₂O/GO) composites were prepared by a facile chemical precipitation method. Using the as-prepared FePO₄·xH₂O/GO and LiOH·H₂O as precursors and followed by carbothermal reduction, LiFePO₄/graphene composites were obtained. Scanning electron microscope (SEM) images indicated that the graphene had very good dispersity and uniformly attached to the LiFePO₄ particles. The conductive framework of graphene improved the electrochemical properties of the composites. The composites deliver high initial discharge capacity of 163.4 mAh g^?1 as well as outstanding rate performance.     

Synthesis of Au-functionalized SnO2 nanotubes using TeO2 nanowires as templates and their enhanced gas sensing properties

Au-functionalized SnO₂ nanotubes were prepared for use as gas sensors using TeO₂ nanowires as templates. Transmission electron microscopy revealed tube diameters, tube lengths and tube wall thicknesses ranging from 50 to 200 nm, 5 to 50 μm, and 13 to 18 nm, respectively. The Au-functionalized SnO₂ nanotube sensors showed responses of 179–473 % to 1–5 ppm NO₂ at 300 ^°C. These values are much higher than those obtained using bare SnO₂ nanotubes synthesized in this study and most other SnO₂ one-dimensional nanostructure-based sensors reported in the literature. The NO₂ gas sensing mechanism of the Au-functionalized SnO₂ nanotube sensors is also discussed.     

Preparation of PtSnRh/C-Sb2O5·SnO2 electrocatalysts by an alcohol reduction process for direct ethanol fuel cell

PtSnRh/C-Sb₂O₅·SnO₂ electrocatalysts with different Pt/Sn/Rh atomic ratios (90:05:05, 70:25:05, and 50:45:05) were prepared by an alcohol reduction process using H₂PtCl₆·6H₂O, SnCl₂·2H₂O, RhCl₃·xH₂O as metal sources, ethylene glycol as solvent and reducing agent, and a physical mixture of Vulcan XC72 (85?wt%) and Sb₂O₅·SnO₂ (15?wt%) as support. The electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. The electro-oxidation of ethanol was studied by cyclic voltammetry and chronoamperometry at 25 and 50?°C and in single direct ethanol fuel cell (DEFC) at 100?°C. The diffractograms of PtSnRh/C-Sb₂O₅·SnO₂ electrocatalysts showed the peaks characteristic of Pt face-centered cubic structure and several others peaks associated with ·SnO₂ and Sb₂O₅·SnO₂. Transmission electron micrographs of PtSnRh/C-Sb₂O₅·SnO₂ electrocatalysts showed the metal nanoparticles distributed on the supports with particle sizes of about 2?C3?nm. The electrochemical measurements and the experiments in a single DEFC showed that PtSnRh/C-Sb₂O₅·SnO₂ (90:05:05) and PtSnRh/C-Sb₂O₅·SnO₂ (70:25:05) electrocatalysts exhibited higher performance for ethanol oxidation in comparison with PtSnRh/C electrocatalyst.     

Preparation and electrochemical properties of LiFePO<Subscript>4</Subscript>/graphene composites from tailoring graphene oxides

LiFePO₄/graphene composites have been prepared by using tailoring graphene oxide (GO) nanosheets as precursors. The structure and electrochemical properties of the composites were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman microscopy, and a variety of electrochemical testing techniques. The decrease in graphene size reduces the contact resistance between activated materials, and enhances the lithium-ion transport in LiFePO₄/graphene composites. With low weight fractions of small-size graphene sheets, the composites show better electrochemical performance than those with large size graphene sheets.     

Electric field gradient in nanostructured SnO2 studied by means of PAC spectroscopy using 111Cd or 181Ta as probe nuclei

Electric quadrupole interactions were studied in pure and Mn-doped powder samples and thin films of SnO₂ using perturbed γγ angular correlation spectroscopy (PAC). The powder samples were prepared by Sol gel method and the thin film were prepared on the Si (100) substrate by sputtering technique using Sn in the oxygen atmosphere. The samples were characterized by x-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. The thickness of the film was 100 nm. The average particle size of the SnO₂ powder samples was determined to be smaller than 60 nm. The radioactive ¹¹¹In and ¹⁸¹Hf tracers were introduced in the powder samples during the sol gel chemical process. Radioactive ¹¹¹In was implanted on the SnO₂ thin films using the University of Bonn ion implanter (BONIS). PAC measurements were carried out in a four BaF₂ detector spectrometer in the temperature range of 77–973 K for samples annealed at different temperatures. The PAC results for both nuclear probes show the presence of two electric quadrupole interactions. The major fractions in both cases correspond to the substitutional sites in the rutile phase of SnO₂. The results are compared with previous PAC measurements.     

Encapsulation of SnO2/Sn Nanoparticles into Mesoporous Carbon Nanowires and its Excellent Lithium Storage Properties

A peculiar nanostructure of encapsulation of SnO₂/Sn nanoparticles into mesoporous carbon nanowires (CNWs) has been successfully fabricated by a facile strategy and confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution TEM (HRTEM), X‐ray diffraction (XRD), BET, energy‐dispersive X‐ray (EDX) spectrometer, and X‐ray photoelectron spectroscopy (XPS) characterizations. The 1D mesoporous CNWs effectively accommodate the strain of volume change, prevent the aggregation and pulverization of nanostructured SnO₂/Sn, and facilitate electron and ion transport throughout the electrode. Moreover, the void space surrounding SnO₂/Sn nanoparticles also provides buffer spaces for the volumetric change of SnO₂/Sn during cycling, thus resulting in excellent cycling performance as potential anode materials for lithium‐ion batteries. Even after 499 cycles, a reversible capacity of 949.4 mAh g^?1 is retained at 800 mA g^?1. Its unique architecture should be responsible for the superior electrochemical performance.     

Modification of the structural and optical properties of tin oxide nanoparticles by Co doping and thermal annealing

Enhancement of the UV photoluminescence emission of sol–gel synthesized tin oxide nanoparticles is achieved by a combination of thermal annealing and Co doping. The UV as well as the defect-related visible photoluminescence are correlated to the structural characteristics and surface Sn(OH)₂ content. The nanoparticle structure, size, crystallinity, and Sn(OH)₂ content are monitored by a combination of X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. In the undoped powders, a suitable annealing leads to a significant UV luminescence at around 365 nm. After doping with Co and annealing, the UV emission is further enhanced. The improvement in the UV emission intensity following annealing and Co doping of SnO₂ is demonstrated to be due to a reduction in the hydroxyl content. The defect-related broad visible photoluminescence (～400–650 nm) can be deconvoluted into three bands at around 440 nm (blue), 510 nm (green), and 600 nm (orange). The green emission is related to Sn(OH)₂ determined by Raman spectroscopy. The blue and orange emissions are attributed to oxygen vacancies.     

Volume of precursor solution effect on the properties of SnO<Subscript>2</Subscript> thin films prepared by nebulized spray pyrolysis technique

Undoped SnO₂ thin films have been deposited on amorphous glass substrates with different precursor solution volume (10, 15, 20 and 25 ml) using simple and cost-effective nebulized spray pyrolysis technique. The influence of precursor solution on structural, optical, photoluminescence and electrical properties had been studied. The X-ray diffraction spectra prove the polycrystalline nature of SnO₂ with tetragonal structure. All the films show a preferred growth orientation along (110) diffraction plane. The average transmittance of SnO₂ thin films varied between 82 and 75% in the visible as well as IR region. The band gap energy decreases from 3.74 to 3.64 eV corresponding to direct transitions with the precursor solution volume had increased from 10 to 20 ml and then increased as 3.72 eV for 25 ml. SEM pictures demonstrated polyhedrons like grains. EDX confirmed the existence of Sn and O elements in all the prepared SnO₂ thin films. Photoluminescence spectra at room temperature revealed that the four emission bands in all the samples such as sharp dominant peak at 361 nm with shoulder peak at 377 nm (UV region), a broad and low intensity peak at 492 nm (blue region) and 519 nm (green region). The electrical parameters were examined by Hall effect measurements, which demonstrated that the film prepared at 20 ml precursor solution volume possess minimum resistivity 2.76?×?10^?3 Ω-cm with activation energy 0.10 eV and maximum figure of merit 1.54?×?10^?2 (Ω/sq)^?1.     

Electrochemical characterization of ionic liquid based gel polymer electrolyte for lithium battery application

High molecular weight polymer poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP), ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIMFSI), and salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based free-standing and conducting ionic liquid-based gel polymer electrolytes (ILGPE) have been prepared by solution cast method. Thermal, electrical, and electrochemical properties of 80 wt% IL containing gel polymer electrolyte (GPE) are investigated by thermogravimetric (TGA), impedance spectroscopy, linear sweep voltammetry (LSV), and cyclic voltammetry (CV). The 80 wt% IL containing GPE shows good thermal stability (~?200 °C), ionic conductivity (6.42?×?10^?4 S cm^?1), lithium ion conductivity (1.40?×?10^?4 S cm^?1 at 30 °C), and wide electrochemical stability window (~?4.10 V versus Li/Li⁺ at 30 °C). Furthermore, the surface of LiFePO₄ cathode material was modified by graphene oxide, with smooth and uniform coating layer, as confirmed by scanning electron microscopy (SEM), and with element content, as confirmed by energy dispersive X-ray (EDX) spectrum. The graphene oxide-coated LiFePO₄ cathode shows improved electrochemical performance with a good charge-discharge capacity and cyclic stability up to 50 cycles at 1C rate, as compared with the without coated LiFePO₄. At 30 °C, the discharge capacity reaches a maximum value of 104.50 and 95.0 mAh g^?1 for graphene oxide-coated LiFePO₄ and without coated LiFePO₄ at 1C rate respectively. These results indicated improved electrochemical performance of pristine LiFePO₄ cathode after coating with graphene oxide.     

Electrochemical performance of SnO2 hexagonal nanoplates

This study reports the electrochemical performance of SnO₂ hexagonal nanoplates (SnO₂-NPs) coated on copper substrate by electrodeposition method in different aqueous electrolytes. The influence of deposition voltage on the morphology of the nanoplates was investigated by scanning electron microscopy. The synthesized SnO₂ was characterized using SEM, X-ray diffraction, Raman, FTIR and UV–visible absorption spectrum. The results clearly have shown that with the increase in deposition voltage at constant deposition time, the thickness of the plate decreased. The obtained nanoplates were of several hundred nanometers in planar dimension and about 50-300 nm in thickness. The electrochemical reaction of SnO₂-NPs with lithium ions were investigated by cyclic voltammetry in LiOH·H₂O, Li₂CO₃, LiNO₃ and Li₂SO₄ aqueous solution. The SnO₂ hexagonal nanoplates deposited on copper substrate can be an ideal anode material for aqueous rechargeable lithium-ion battery.     

Synthesis and enhanced acetone gas-sensing performance of ZnSnO<Subscript>3</Subscript>/SnO<Subscript>2</Subscript> hollow urchin nanostructures

A kind of novel ZnSnO₃/SnO₂ hollow urchin nanostructure was synthesized by a facile, eco-friendly two-step liquid-phase process. The structure, morphology, and composition of samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption techniques. The results revealed that many tiny needle-like SnO₂ nanowires with the average diameter of 5 nm uniformly grew on the surface of the ZnSnO₃ hollow microspheres and the ZnSnO₃/SnO₂ hollow urchin nanostructures with different SnO₂ content also were successfully prepared. In order to comprehend the evolution process of the ZnSnO₃/SnO₂ hollow urchin nanostructures, the possible growth mechanism of samples was illustrated via several experiments in different reaction conditions. Moreover, the gas-sensing performance of as-prepared samples was investigated. The results showed that ZnSnO₃/SnO₂ hollow urchin nanostructures with high response to various concentration levels of acetone enhanced selectivity, satisfying repeatability, and good long-term stability for acetone detection. Specially, the 10 wt% ZnSnO₃/SnO₂ hollow urchin nanostructure exhibited the best gas sensitivity (17.03 for 50 ppm acetone) may be a reliable biomarker for the diabetes patients, which could be ascribed to its large specific surface area, complete pore permeability, and increase of chemisorbed oxygen due to the doping of SnO₂.     

Influence of the liquid environment on the products formed from the laser ablation of tin

Tin targets immersed in ethanol and distilled water were ablated using a UV pulsed laser. The ablated products were investigated with transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy. For ablation in both liquids, the size distribution of the produced particles was bimodal, with particles having diameters of ～10 nm and ～1 μm. Formation mechanisms that caused the bimodal distribution are suggested. Ablation in ethanol resulted in nanoparticles that were found to be single crystals of tin coated with tin hydroxide (Sn(OH)₂) while ablation in water yielded nanoparticles that were polycrystalline tin dioxide (SnO₂) throughout.     

The effect of different concentrations of Na2SnO3 on the electrochemical behaviors of the Mg-8Li electrode

In this research, the effect of the different concentrations of NaSnO₃ as the electrolyte additive in 0.7 mol L^?1 NaCl solution on the electrochemical performances of the magnesium-8lithium (Mg-8Li) electrode are investigated by methods of potentiodynamic polarization, potentiostatic current-time, electrochemical impedance technique, and scanning electron microscopy (SEM). The corrosion resistance of the Mg-8Li electrode is improved when Na₂SnO₃ is added into the electrolyte solution. The potentiostatic current-time curves show that the electrochemical behaviors of the Mg-8Li electrode in the electrolyte solution containing 0.20 mmol L^?1 Na₂SnO₃ is the best. The electrochemical impedance spectroscopy results indicate that the polarization resistance of the Mg-8Li electrode decreases in the following order with the concentrations of Na₂SnO₃: 0.05 mmol L^?1?>?0.00 mmol L^?1?>?0.30 mmol L^?1?>?0.10 mmol L^?1?>?0.20 mmol L^?1. The scanning electron microscopy studies indicate that the electrolyte additive prevents the formation of the dense oxide film on the alloy surface and facilitates the peeling off of the oxidation products.     

Electrochemical performance of CeO<Subscript>2</Subscript> nanoparticle-decorated graphene oxide as an electrode material for supercapacitor

Cerium oxide nanoparticles and cerium oxide nanoparticle-decorated graphene oxide (GO) are synthesized via a facile chemical coprecipitation method in the presence of hexadecyltrimethylammonium bromide (CTAB). Nanostructure studies and electrochemical performances of the as-prepared samples were systematically investigated. The crystalline structure and morphology of the nanocomposites were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), Raman spectrum, and X-ray photoelectron spectroscopy (XPS). Electrochemical properties of the CeO₂ electrode, the GO electrode, and the nanocomposites electrodes were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. The CeO₂ nanoparticle-decorated GO (at the mole ratio of CeO₂/GO = 1:4) electrode exhibited excellent supercapacitive behavior with a high specific capacitance of 382.94 F/g at the current density of 3.0 A/g. These superior electrochemical features demonstrate that the CeO₂ nanoparticle-decorated GO is a promising material for next-generation supercapacitor systems.