SnO2-reduced Graphene Oxide Research Articles

Hydrothermal synthesis of an SnO2–rGO nanocomposite using tea extract as a reducing agent for daylight-driven photocatalyst and supercapacitors

In this study, SnO2–reduced graphene oxide (rGO) nanocomposites (NCs) were synthesized via a hydrothermal method using tea extract as a reducing agent.

Mass ratio-dependently tunable enhancement of the optical nonlinearities of SnO2/RGO composites

The composite of graphene and semiconductor nanoparticles has attracted increasing interest in the search for novel nonlinear optical materials. Herein, composites of reduced graphene oxide (RGO) and SnO2 nanoparticles with different mass ratios were synthesized via a facile hydrothermal method. The structural morphology and basic physical properties of the SnO2/RGO composites were characterized using TEM, SEM, XRD, Raman, XPS and UV–Vis spectra, indicating that SnO2 nanoparticles were uniformly anchored on the surface of graphene nanosheets through covalent and partial-ionic bonds. The third-order optical nonlinearities of the composites were studied for the first time by the Z-scan technique using a picosecond laser at 532 nm. It was found that the composites demonstrated saturable absorption and positive nonlinear refraction properties, and both were significantly enhanced compared with pure SnO2 nanoparticles and RGO nanosheets, and the enhancement was tunable with the variation of SnO2:GO mass ratio. The maximum saturable absorption coefficient and the third-order susceptibility of the as-prepared SnO2/RGO composites were obtained to be −2.93×10–11 m W−1 and 2.25 × 10–11 esu, respectively. The maximum saturable absorption modulation depth obtained was 10% with the corresponding saturation light intensity of 0.3 GW cm−2. Moreover, the optimised third-order susceptibility of SnO2/RGO was found much greater than many other materials ever studied. Several involved factors contributing to the nonlinearities were discussed. The results propose that the third-order optical nonlinearities of SnO2/RGO and other similarly structured composites can be potentially tuned to meet certain application requirements of nonlinear optical devices by controlling the mass ratio of semiconductor to graphene.

Cd-doped SnO2-reduced Graphene Oxide Composite Nanofibrous Mats as CO Gas Sensors

Cd-doped SnO2-reduced Graphene Oxide Composite Nanofibrous Mats as CO Gas Sensors

Synergistic Catalysis of SnO2/Reduced Graphene Oxide for VO2+/VO2+ and V2+/V3+ Redox Reactions.

In spite of their low cost, high activity, and diversity, metal oxide catalysts have not been widely applied in vanadium redox reactions due to their poor conductivity and low surface area. Herein, SnO2/reduced graphene oxide (SnO2/rGO) composite was prepared by a sol–gel method followed by high-temperature carbonization. SnO2/rGO shows better electrochemical catalysis for both redox reactions of VO2+/VO2+ and V2+/V3+ couples as compared to SnO2 and graphene oxide. This is attributed to the fact that reduced graphene oxide is employed as carbon support featuring excellent conductivity and a large surface area, which offers fast electron transfer and a large reaction place towards vanadium redox reaction. Moreover, SnO2 has excellent electrochemical activity and wettability, which also boost the electrochemical kinetics of redox reaction. In brief, the electrochemical properties for vanadium redox reactions are boosted in terms of diffusion, charge transfer, and electron transport processes systematically. Next, SnO2/rGO can increase the energy storage performance of cells, including higher discharge electrolyte utilization and lower electrochemical polarization. At 150 mA cm−2, the energy efficiency of a modified cell is 69.8%, which is increased by 5.7% compared with a pristine one. This work provides a promising method to develop composite catalysts of carbon materials and metal oxide for vanadium redox reactions.

Sonochemical preparation and characterization of rGO/SnO2 nanocomposite: Electrochemical and gas sensing performance

The present investigation deals with solution-based sonochemical production of graphene oxide (GO) and reduced graphene oxide-SnO2 (rGO/SnO2) nanocomposite. These rGO/SnO2 nanocomposites were analysed with XRD, TEM, FTIR and UV/visible techniques. While synthesizing rGO/SnO2 nanocomposites, use of the ultrasound generated cavitational events which has evidently improved the uniform deposition of SnO2 on graphene nanosheets. These rGO/SnO2 nanocomposites were explored for their potential electrochemical as well as gas sensing applications. The cyclic voltammetry (CV) studies revealed a good electrochemical performance of rGO/SnO2 nanocomposite with a specific capacitance of 35 F/g. Further, the influence of NO2 gas concentration was investigated on rGO/SnO2 nanocomposite based sensor at various temperatures. The nanocomposite displayed the highest response of 99.9% with a very short response time of 14 s for 100 ppm concentration of NO2 gas at 150 °C. These sonochemically derived rGO/SnO2 nanocomposite based sensor showed excellent performance towards NO2 gas compared to other selected gases under the same conditions.

Electronically Coupled SnO2 Quantum Dots and Graphene for Efficient Nitrogen Reduction Reaction

Electrocatalytic N2 reduction reaction (NRR) provides an effective and renewable approach for artificial NH3 production, but still remains a grand challenge because of the low NH3 yield and Faradaic efficiency (FE). Herein, we reported that the SnO2 quantum dots (QDs) supported on reduced graphene oxide (RGO) could efficiently and stably catalyze NRR at ambient conditions. The NRR performance of resulting SnO2/RGO was studied by both experimental techniques and density functional theory calculations. It was found that the ultrasmall SnO2 QDs (2 nm) grown on RGO could provide abundant sites for efficient N2 adsorption. Significantly, the strongly electronically coupled SnO2 QDs and RGO brought about the enhanced conductivity and the decreased work function, which led to a considerably lowered energy barrier of *N2 → *N2H that was the rate-determining step of the NRR process. Meanwhile, the SnO2/RGO exhibited inferior hydrogen evolution reaction activity. As a result, the SnO2/RGO delivered a high NH3 yield of 25.6 μg h-1 mg-1 (5.1 μg cm-2h-1) and an FE of 7.1% in 0.1 M Na2SO4 at -0.5 V (vs RHE), together with the outstanding selectivity and stability, endowing it as a promising electrocatalyst for N2 fixation.

Facile and in-situ spray deposition of SnO2 – reduced graphene oxide heterostructure sensor devices

A facile and economic solution based technique is developed for the deposition of SnO2—Reduced Graphene Oxide (RGO) heterostructure thin films. The single step deposition process leads to uniformly dispersed SnO2 nanocrystallites on well exfoliated RGO sheets as confirmed by x-ray diffraction, Raman spectroscopy and transmission electron microscopy investigations. The response to NO2 gas at room temperature (25 °C) is studied. The interface between n-type SnO2 and p-type RGO flakes forms a hetrostrcuture barrier, which enhances the native sensitivity of pristine RGO towards toxic gases like NO2. The technique allows controlling the density of SnO2 nanoparticles (∼3 nm in size) attached to the RGO flakes and thereby enhancing the response of the heterostructure sensor device. The highest SnO2 loading shows a 14 fold increase in response to 200 ppm of NO2 and a response time as low as 5 s compared to that of ∼200 s for bare RGO films.

Investigation of Microstructure Effect on NO2 Sensors Based on SnO2 Nanoparticles/Reduced Graphene Oxide Hybrids.

The microstructures of metal oxide-modified reduced graphene oxide (RGO) are expected to significantly affect room-temperature (RT) gas sensing properties, where the microstructures are dependent on the synthesis methods. Herein, we demonstrate the effect of microstructures on RT NO2 sensing properties by taking typical SnO2 nanoparticles (NPs) embellished RGO (SnO2 NPs-RGO) hybrids as examples. The samples were synthesized by growing SnO2 NPs on RGO through hydrothermal reduction (SnO2 NPs-RGO-PR), which display the advantages such as high reactivity of the SnO2 surface with NO2, more oxygen vacancies (OV) and chemisorbed oxygen (OC), close contact between SnO2 NPs and RGO, and large surface area, compared to the samples prepared by one-pot hydrothermal synthesis from Sn4+ and GO (SnO2 NPs-RGO-IS), and the assembly of SnO2 NPs on RGO (SnO2 NPs-RGO-SA). As expected, the SnO2 NPs-RGO-PR-based sensor presents high sensitivity towards 5 ppm NO2 (65.5%), but 35.0% for the SnO2 NPs-RGO-IS-based sensor and 32.8% for the SnO2 NPs-RGO-SA-based sensor at RT. Meanwhile, the corresponding response time and recovery time calculated by achieving 90% of the current change of the SnO2 NPs-RGO-PR-based sensor for exposure to NO2 is 12 s and to air is 17 s, respectively, whereas 74/42 s for the SnO2 NPs-RGO-IS-based sensor and 77/90 s for the SnO2 NPs-RGO-SA-based sensor. The results can prove the tailoring sensing behavior of the gas sensor according to different structures of materials.

Microwave-assisted hydrothermal synthesis of SnO2/reduced graphene-oxide nanocomposite as anode material for high performance lithium-ion batteries

Surfactant and organic solvents free SnO2 nanospheres and SnO2/reduced graphene oxide (SnO2/rGO) nanocomposite were prepared by microwave assisted hydrothermal method. X-ray diffraction (XRD) and Raman spectroscopy results confirm the formation of pure nanocrystalline rutile phase of SnO2 and nanostructured rutile phase of SnO2 over the amorphous structured rGO. FE-SEM, EDX and HR-TEM results showed the formation of spherical shape SnO2 nanoparticles and the formation of spherical shape SnO2 nanoparticles over the crumpled nanosheets like morphology of rGO. The electrochemical measurements of lithium-ion batteries fabricated using pure spherical shape SnO2 nanoparticles and crumpled nanosheets like morphology of SnO2/rGO nanocomposite as an anode material showed the good initial discharge–charge capacity of 2128 and 1718 mA h g−1 respectively. The capacity retention after 50 cycles is found to be 349 mAh g−1 at a current density of 500 mA g−1 for the lithium-ion battery fabricated using pure spherical shape SnO2 nanoparticles and the capacity retention after 300 cycles is found to be 318 mAh g−1 at a current density of 500 mA g−1 for the lithium-ion battery fabricated using SnO2/rGO nanocomposite, which is much better than the reported values. The observed better electrochemical performance of the lithium-ion battery is attributed to the formation of spherical shape SnO2 nanoparticles over the crumpled nanosheets like morphology of highly porous graphene and also increased electronic conductivity of SnO2/rGO nanocomposite. Hence, the crumpled nanosheets like morphology of highly porous of SnO2/rGO nanocomposite prepared by microwave hydrothermal method can be a high-performance anode material for a lithium-ion battery application.

Polyaniline coated graphene hybridized SnO2 nanocomposite: Low temperature solution synthesis, structural property and room temperature ammonia gas sensing

An inorganic-organic hybrid of SnO2-reduced graphene oxide (rGO)-polyaniline (SGP) nanocomposite has been successfully synthesized from surfactant-free precursor by a low temperature solution process. The SGP nanocomposite is found to form from in situ synthesized SnO2-rGO (SG) and polyaniline (PANI), generated via polymerization of aniline monomer at 5–10 °C. The structural properties of SGP have been analyzed by X-ray diffraction, transmission electron and atomic force microscopes. The chemical interaction existed in the nanocomposite has been examined by X-ray photoelectron, Fourier transform infrared and Raman spectroscopies. Compare to pristine SnO2 and SG, the SGP sample shows an enhanced ammonia gas sensing at room temperature. At an optimum content of PANI, high sensitivity, fast response and good selectivity of the gas sensing are observed in the nanocomposite. This enhanced sensing performance can be attributed to well-defined p-n hetero junction formation in the hybridized polyaniline and rGO with nano SnO2 in SGP as confirmed from structural characterization of the sample. It is also seen that the presence of PANI layers in SGP, enhances the chemical stability as reflected from the observation of negligible decrease in the sensing performance of sample up to 30 days period. This facile process can create an avenue for development of various metal oxide semiconductor-graphene-polyaniline nanocomposites for improving room temperature stable ammonia gas sensor.

Photochemical fabrication of SnO2 dense layers on reduced graphene oxide sheets for application in photocatalytic degradation of p-Nitrophenol

A room-temperature photochemical method was introduced to fabricate SnO2-reduced graphene oxide (SnO2-rGO) composite with a new type of structure. SnO2 dense layers were directly grown on the two sides of an rGO sheet through ultraviolet light (UV) irradiation of a mixed precursor solution of SnSO4, H2SO4, and graphene oxide for 6h. The composite possessed a novel flat flake-like structure consisting of two SnO2 dense layers and an rGO sheet sandwiched in between. In contrast to most graphene-based composites, the fabricated composite was non-flexible, wrinkle-free and rGO surfaces were completely covered. The composite could be used in photocatalysis and exhibited remarkably enhanced activity in degradation of p-nitrophenol under low intensity of UV light or sunlight. The activity was more than 12 times that of pure SnO2 and considerably higher than that of other SnO2-rGO composites. The dense layer immobilized the flat structure, promoted the photocatalytic activity, and maintained the long-term stability of the composite. After preservation of more than 12 months in ambient condition, the composite showed a nearly constant activity. This photochemical method can be used to fabricate graphene-based composites with regular structure, high performance, and long-term stability.

Facile, low temperature synthesis of SnO2/reduced graphene oxide nanocomposite as anode material for lithium-ion batteries

We demonstrate a facile, single step, low temperature and energy efficient strategy for the synthesis of SnO2-reduced graphene oxide (RGO) nanocomposite where the crystallization of SnO2 nanoparticles and the reduction of graphene oxide takes place simultaneously by an in situ chemical reduction process. The electrochemical property of the SnO2-RGO composite prepared by using low concentrations of reducing agent shows better Li storage performance, good rate capability (378mAhg−1 at 3200mAg−1) and stable capacitance (522mAhg−1 after 50 cycles). Increasing the reductant concentration lead to crystallization of high concentration of SnO2 nanoparticle aggregation and degrade the Li ion storage property.

Room-temperature methane gas sensing properties based on in situ reduced graphene oxide incorporated with tin dioxide

We report on the relationship between the degree of reduction of graphene oxide (GO) and its room-temperature methane gas-sensing response by comparing four in situ reducing agents of GO: D-glucose, sodium borohydride, L-ascorbic acid and hydrazine hydrate. We found that gas sensing based on D-glucose and L-ascorbic acid had a higher gas response than that based on sodium borohydride and hydrazine hydrate because the residues contained oxygen functional groups. The poorly conductive GO was successfully reduced in situ by L-ascorbic acid to achieve high electrical conductivity and a high methane gas response. The incorporation of tin dioxide (SnO2) into the reduced GO (RGO) further increased the gas response by the p–n junction effect. The heterostructure of L-ascorbic acid-reduced RGO–SnO2 had the highest increase in methane response due to the synergistic effect between dehydroascorbic acid and the SnO2 surface. This was inferred from density functional theory calculations with self-consistently determined Hubbard U potentials (DFT+U). Compared with the current room-temperature methane sensing and fabrication technologies, the sensing technology reported here is cheaper to produce and more environmentally friendly while retaining the best sensitivity and wider sensing range.

SnO2-Reduced Graphene Oxide Nanocomposites via Microwave Route as Anode for Sodium-Ion Battery

SnO2-reduced graphene oxide (SnO2-rGO) nanocomposites are successfully synthesized via a rapid microwave-assisted method (within 150 s). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show the ultrafine SnO2 nanoparticles (~3 nm) are uniformly anchored onto the rGO. The typical SnO2-rGO exhibits a high initial reversible capacity of 260 mAh g−1 at 50 mA g−1, which is higher than that (45 mAh g−1) of the bare SnO2 electrode. The SnO2-rGO electrode also shows high cycling stability (79.6% capacity retention after 100 cycles) and rate capability (150 mAh g−1 at 500 mA g−1). The improved electrochemical performance of the SnO2-rGO is ascribed to extremely tiny SnO2 nanoparticles well distributed on the surface of the rGO and the conductive frameworks provided by rGO, so as to alleviate the aggregation of SnO2 and buffer the volumetric change during charging and discharging.

Graphene-containing materials for use in supercapacitors

Abstract This study demonstrates an asymmetric supercapacitor having SnO2-reduced graphene oxide (RGO) nanocomposite as the cathode and nitrogen-doped graphene (NDG) as the anode. A facile method has been used to synthesize the SnO2-RGO nanocomposite and NDG. Material characteristics were examined using X-ray diffractometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. Electrochemical measurements, including cyclic voltammetry and electrochemical impedance spectroscopy, were performed to evaluate the asymmetric supercapacitor. Optimized asymmetric supercapacitor has been shown to operate under a wide working potential window up to 1.8 V and exhibit a high energy density of 48.7 Wh kg− 1, and excellent electrochemical stability in 2 M H2SO4 aqueous electrolyte.

A facile post-process method to enhance crystallinity and electrochemical properties of SnO2/rGO composites with three-dimensional hierarchically porous structure

In this work, three SnO2/reduced graphene oxide (SnO2/rGO) composites with a three-dimensional hierarchically porous structure were synthesized via freeze drying and different annealing temperatures in an air atmosphere.

The confinement of SnO2nanocrystals into 3D RGO architectures for improved rate and cyclic performance of LIB anode

In this study, we demonstrate the synthesis of a composite with SnO2 nanoparticles anchored on three-dimensional (3D) reduced graphene oxide (RGO) as an anode for Li ion batteries (LIBs). SnO2 nanoparticles were uniformly deposited on the surface of RGO sheets and the resulting RGO–SnO2 architecture had an interconnected hierarchical structure. This hierarchical RGO–SnO2 architecture exhibited outstanding electrochemical performance with a high reversible capacity of 810 mAh g−1 at 0.1 A g−1 and a high rate capacity of 210 mAh g−1 at 2 A g−1. Moreover, this architecture achieves 99% capacity retention even after 150 cycles at 0.1 A g−1. The improved performance of the RGO–SnO2 architecture is attributed to the uniform dispersion of SnO2 nanoparticles and the 3D macroporous continuity, which afford a highly accessible area, easy ion accessibility, a short ion diffusion length, and rapid mass and charge transport. The composite described here is practically useful in the development of high-energy-density anode materials for LIBs.

SnO2-graphene nanocomposite free-standing film as anode in lithium-ion batteries

SnO2-reduced graphene oxide nanocomposite in the form of a free-standing film was prepared by simple chemical synthesis. The homogeneous and compact formation of the nanocomposite of SnO2 and reduced graphene oxide was confirmed by various analysis methods. When incorporated as anode in lithium-ion batteries, a high capacity (503 mAh g-1) and very stable cycle life were observed. These favorable properties probably arise from the efficient relaxation of high mechanical stress by the reduced graphene-oxide layers during the lithiation-delithiation process within SnO2.

One-pot route to synthesize SnO2-Reduced graphene oxide composites and their enhanced electrochemical performance as anodes in lithium-ion batteries

A simple, one-pot route was developed for the synthesis of SnO2-reduced graphene oxide (RGO) composites. Simultaneous reduction of graphene oxide (GO) and heterogeneous nucleation and growth of SnO2 on the surface of RGO under the supercritical methanol medium resulted in uniform deposition of well-dispersed SnO2 nanoparticles on the RGO sheets. In comparison with the bare SnO2 nanoparticles and bare RGO sheets, the as-synthesized SnO2-RGO composites exhibited enhanced Li-ion storage and high rate performance. The SnO2-RGO composite with a SnO2 loading of 58 wt% delivered a reversible discharge capacity of 776 mAh g−1 after 70 cycles at a current density of 0.1 A g−1 and a rate performance of 147 mAh g−1 at a high current density of 5 A g−1. In addition, after 1000 continuous cycles at 1 A g−1, the composite electrode exhibited a reversible discharge capacity as high as 531 mAh g−1 with excellent capacity retention. The enhanced long-term cyclability and high-rate performance of the SnO2-RGO composite can be attributed to the effective confinement of SnO2 nanoparticles on the RGO sheets, and thus, the interparticle agglomeration and volume change associated with alloying–dealloying of SnO2 during cycling can be prevented and cell integrity can be maintained.

SnO2-reduced graphene oxide nanoribbons as anodes for lithium ion batteries with enhanced cycling stability

A nanocomposite material of SnO2-reduced graphene oxide nanoribbons has been developed. In this composite, the reduced graphene oxide nanoribbons are uniformly coated by nanosized SnO2 that formed a thin layer of SnO2 on the surface. When used as anodes in lithium ion batteries, the composite shows outstanding electrochemical performance with the high reversible discharge capacity of 1,027 mAh/g at 0.1 A/g after 165 cycles and 640 mAh/g at 3.0 A/g after 160 cycles with current rates varying from 0.1 to 3.0 A/g and no capacity decay after 600 cycles compared to the second cycle at a current density of 1.0 A/g. The high reversible capacity, good rate performance and excellent cycling stability of the composite are due to the synergistic combination of electrically conductive reduced graphene oxide nanoribbons and SnO2. The method developed here is practical for the large-scale development of anode materials for lithium ion batteries.