SnO2 Microspheres Research Articles

The crystalline/amorphous stacking structure of SnO2 microspheres for excellent NO photocatalytic performance

Novel crystalline/amorphous stacking structure of SnO2 microsphere provides excellent NO photocatalytic performance by separating the adsorption sites of NO and O2.

The growth behavior of brain-like SnO2 microspheres under a solvothermal reaction with tetrahydrofuran as a solvent and their gas sensitivity.

In this paper, the growth behavior of brain-like SnO2 microspheres synthesized by a tetrahydrofuran (THF) solvothermal method was studied. Unlike water or ethanol as the solvent, THF is a medium polar and aprotic solvent. Compared with other common polar solvents, the THF has no strong irregular effects on the growth process of SnO2. In addition, the viscosity of THF also helps the SnO2 to form a regular microstructure. The growth behavior of the brain-like SnO2 microspheres is controlled by changing the synthesis temperature of the reaction. The SEM and TEM results reveal that the SnO2 forms particles first (125 °C/3 h), and then these nanoparticles connect to each other forming nanowires and microspheres (diameter ≈ 1–2 μm) at 135 °C for 3 h; finally the microspheres further aggregate to form double or multi-sphere structures at 180 °C for 3 h. In this paper, the brain-like SnO2 microspheres obtained at 125 °C for 3 h were selected as sensitive materials to test their gas sensing performance at different operating temperature (50 °C and 350 °C). The H2S was tested at 50 °C which is the lowest operating temperature for the sensor. The combustible gas (H2/CH4/CO) was measured at 350 °C which is the highest temperature for the sensor. They all have extremely high sensitivity, but only H2S has excellent selectivity.

Hydrothermal synthesis of Hydrangea macrophylla-like Ce-doped SnO2 microspheres and their enhanced sensing properties

The hydrangea macrophylla-like SnO2 microspheres doped with different Ce contents (0, 2, 6 and 10 mol%) were synthesized by a facile hydrothermal method. The crystal phase, micro morphology and element composites were investigated by x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) with energy-dispersive spectroscopy (EDS) and x-ray photoelectric spectroscopy (XPS). The results demonstrated the hydrangea macrophylla-like microstructure of the prepared samples and the existence of Ce3+/Ce4+ when doped with Ce element. Furthermore, the synthesized Ce-doped SnO2 samples’ sensing properties were investigated. The SnO2 microspheres doped with 6 mol% showed the largest response to acetone during 0.2–20 ppm at 320 °C as well as good selectivity and reproducibility. As discussed, the Ce doping that generates n-n type heterojunction and the Ce3+/Ce4+ conversion increases the resistance change of Ce-doped SnO2 in reducing atmosphere and enhances the response.

Coca-Cola solvothermal synthesis of mesoporous SnO2 blooming flower-like architecture assembled from single crystal nanorods and its gas sensing properties

The novel synthetic strategy for functional metal oxide nanomaterials by using biomass reaction media has recently attracted great attention. Herein, mesoporous SnO2 blooming flower-like architectures, assembled from single crystal nanorods with a diameter of 50–100 nm, were firstly prepared using Coca-Cola solvothermal route. In contrast, SnO2 microspheres were obtained by hydrothermal reaction. These indicate that the biomasses in Coca-Cola play a regulatory role in the formation of flower-like SnO2 hierarchical structure with uniform mesopore of 12.87 nm. The results of various gases tested show that the sensor based on blooming flower-like SnO2 structure has good performance towards H2S gas at optimum working temperature of 170 °C. The sensitivity to 10 ppm H2S gas is 118.4, being almost three times higher than that of SnO2 microspheres (40.9). The sensor shows good linear relationship ranging 0.05 to 10 ppm with lower detection limit (50 ppb) and good selectivity.

Single crystalline hierarchical SnO2 microsphere and fluoride-mediated hollow structures for photocatalytic activity

The present research study deals with the preparation of tin oxide (SnO2) nanostructures hierarchical hollow microspheres and composed of oriented aligned cone-like SnO2 nanoparticles are prepared by a hydrothermal route using either NH4F as morphology controlling agents. The samples were morphology characterized by FE-SEM with diameter of about 2 μm to 50 nm and XRD showed a homogeneous distribution of quite small grains over scanned area. The FT-IR result shows the stretching vibration of the hierarchical SnO2 solid or hollow microspheres nanoparticles due to its chemical interaction. The optical properties were studied using UV absorption and its opticalband gap value is 3.9 eV. The electrochemical performance of SnO2 tested to determine the oxidation/reduction processes by cyclic and linear sweep voltammetry.

Synthesis and characterization of visible light-driven Cl-doped SnO2 photocatalysts

Cl-doped SnO2 nanoparticles were synthesized by a rapid annealing treatment from SnO microspheres. SnO2 products were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. SnO2 samples exhibited a desirable visible light photocatalytic property and agglomeration morphology. They comprise many nanocrystals with sizes in the range of 10–60 nm. The Cl-doped SnO2 showed excellent photocatalytic degradation of methyl orange (MO), which can degrade 99.9% MO (20 mg/L) within 60 min under visible light irradiation.

Facile Synthesis of Sn/Reduced Graphene Oxide Composites With Tunable Dielectric Performance Toward Enhanced Microwave Absorption

Electromagnetic (EM) wave absorbing materials are strongly desired for the reason that EM pollution has become a serious problem with the rapid development of modern technology, which brings harm to the environment and human health. Herein, nanocomposites of Sn/reduced graphene oxide (Sn/rGO) as a novel type of EM absorbing materials were synthesized via a facile and efficient strategy. Nanoscale SnO2 microspheres were synthesized by sol-gel method, and the Sn/rGO composites were obtained after hydrothermal process with GO. Samples with different Sn content were fabricated (Sn:rGO = 30:1, 20:1, 10:1, mass ratio), and their EM wave absorption performance were analyzed. By changing the mass ratio of Sn and rGO, dielectric constant of the composites can be adjusted, and better impedance matching can be achieved. The unique capacitive structure and conductive network enable the material to have strong dielectric loss and excellent absorption performance. This research offers a new route for designing and fabricating high-frequency EM wave absorbing materials.

Unraveling the promoted nitrogen dioxide detection performance of N-doped SnO2 microspheres at low temperature

Abstract Nitrogen doping has been proven an efficient strategy to modulate the electronic structure of metal oxides to tune their properties. Herein, we report the synthesis of N-doped SnO2 microspheres through calcining the pristine SnO2 in NH3 atmosphere. Texture characterizations show that N–SnO2 microspheres exhibit 3D-porous architectures with a diameter of ca. 300–500 nm. After NH3 treatment, the SnO2 exhibits the formation of the N-doping and oxygen vacancies on the surface of the material, rich free-electrons and the narrow energy band. It is found that the as-prepared N-doped SnO2 microspheres at 200 °C (N–SnO2-200), show superior selectivity and high response (S = 155 to 5 ppm NO2) compared with its counterparts. DFT calculations and experimental results illustrate that N impurities and oxygen vacancies as N-induced active sites favor the adsorption of NO2 molecules; rich free-electrons increase the amount of adsorbed NO2 molecules; and the narrow energy band promotes the effectively electron transfer during the sensing reaction. Therefore, in this work we unravel the improved NO2 gas-sensing performances of the N-doped SnO2 and provide new guidance for the development of highly efficient metal oxide sensing materials for NO2 detection.

High‐Efficiency Low‐Temperature‐Processed Mesoscopic Perovskite Solar Cells from SnO2 Nanorod Self‐Assembled Microspheres

Mesoporous scaffolds in perovskite solar cells (PSCs) can accelerate the formation of heterogeneous nucleation sites, leading to enhanced quality of perovskite films and uniform perovskite coverage over large areas. Nevertheless, the mesoporous electron transport layers (ETLs) can effectively compensate for the drawback of shorter electron diffusion lengths than their hole counterparts. Therefore, most mesoscopic PSCs usually show superior photovoltaic performance to their planar counterparts. However, mesoporous ETLs, particularly those prepared with metal oxide nanocrystals, often require a high‐temperature sintering process for the removal of residual organics and the improved crystallization of metal oxides. Here, a novel emulsion‐based bottom‐up self‐assembly strategy is used to prepare sizable SnO2 microspheres from oleic acid capped SnO2 nanorods. Combined with an in‐situ ligand‐stripping strategy, the low‐temperature solution‐processed mesoscopic PSCs can achieve efficiency as high as 21.35% with slight hysteresis and good reproducibility. In particular, the emulsion‐based bottom‐up self‐assembly strategy is a general way for preparing microspheres from several kinds of semiconductor nanocrystals, so it will greatly expand the material selection range for preparing efficient mesoscopic PSCs and even inverted mesoscopic devices.

Rectifying resistance switching behaviors of SnO2 microsphere films modulated by top electrodes

Based on the bipolar resistive switching (RS) characteristics of SnO2 films, we have fabricated a new prototypical device with sandwiched structure of Metal/SnO2/fluorine-doped tin oxide (FTO). The SnO2 microspheres film was grown on FTO glass by template-free hydrothermal synthesis, which was evaporated with various commonly used electrodes such as aluminium (Al), silver (Ag), and gold (Au), respectively. Typical self-rectifying resistance switching behaviors were observed for the RS devices with Al and Au electrodes. However, no obvious rectifying resistance switching behavior was observed for the RS device with Ag electrode. Above results were interpreted by considering the different interface barriers between SnO2 and top metal electrodes. Our current studies pave the ways for modulating the self-rectifying resistance switching properties of resistive memory devices by choosing suitable metal electrodes.

Synthesis of hierarchical shell-core SnO2 microspheres and their gas sensing properties

Using SnSO4, d-glucose, urea and water, hierarchical shell-core SnO2 microspheres were successfully synthesized via a simple hydrothermal method. The characterization results showed that the sizes of as-prepared SnO2 microspheres were 0.6–1μm, with shell thicknesses of 40−60 nm. The shell and large core of the SnO2 microspheres were all comprised of the same basic rice-like nanoparticles with diameters of 16−25 nm and lengths of 16−45 nm. Further investigaton showed that the glucose and urea served as structural guiding agents, and urea facilitated the formation of the hierarchical structure. The as-prepared SnO2 nanomaterials were used to fabricate a gas sensor with an electrode blade used for the gas sensitivity tests. The hierarchical shell-core SnO2 microspheres exhibited high sensitivity and selectivity toward ethanol, with a responsivity of 63.8 for 50 ppm ethanol at 250 °C, while the response and recovery time were 7 s and 28 s respectively. Moreover, the responsivity of the materials showed good linearity at ethanol concentrations from 500 ppb to 10 ppm. The simple synthetic method, environmentally-friendly raw materials, and excellent gas sensitivity demonstrate that the as-prepared SnO2 nanomaterial has great potential applications for the sensing of ethanol gas.

Spray-coated monodispersed SnO2 microsphere films as scaffold layers for efficient mesoscopic perovskite solar cells

Mesoporous SnO2 microspheres are a class of promising electron transport materials for mesoscopic perovskite solar cells, but a smooth and dense film as requested by electron transport layer is difficult to realize using the microspheres. Here, a series of monodispersed SnO2 microspheres with high specific surface area and good crystallinity are synthesized via a surfactant-free solvothermal method. These SnO2 microspheres showing small diameters of about 75, 110 and 200 nm with narrow size distribution are achieved by precisely controlling the crystal growth process. They are suitable for constructing the electron transport layers whose thickness is only about hundreds nanometers. Besides, as the microspheres easily slip off from the substrate during the conventional spin coating process, the spray coating method is exploited to prepare high quality electron transport layers. As a result, a power conversion efficiency of 16.85% is yielded by using the 75 nm sized SnO2 microspheres as the electron transport layers. This high power conversion efficiency is attributed to the fast electron transport and inhibited charge recombination. To further improve the charge transfer between the electron transport layer and perovskite layer, graphene quantum dots are added into the SnO2 microspheres, and a best efficiency of 17.08% is obtained.

Facile one-step hydrothermal synthesis of SnO2 microspheres with oxygen vacancies for superior ethanol sensor

This work reports a facile one-step hydrothermal method to synthesize the microsphere SnO2 particles without using any organic agent. The experiment results show that the obtained SnO2 microspheres consisting number of nanocrystalline particles of 2–5 nm in size. Oxygen vacancies are also existing on the surface of the SnO2 microspheres. The as-prepared SnO2 microspheres possess mesoporous structure of remarkably high specific surface area (111.27 m2g-1). The gas sensing properties of the as-prepared SnO2 microspheres for ethanol was investigated. The response and recovery time of SnO2 sensor surprisingly reached to 3 s and 24 s respectively under 100 ppm flow of ethanol at an operating working temperature of 230 °C. The response of sensor for 100 ppm of ethanol is enhanced to 24.9 at 230 °C. The excellent ethanol-sensing performance of the fabricated sensor has been attributed to its small grain size, high specific surface area and number of oxygen vacancies of SnO2. These results indicating that the SnO2 microspheres obtained in this work is a promising and excellent ethanol-sensor material.

Facile synthesis of macroporus SnS microspheres as a potential anode material for enhanced sodium ion batteries

Macroporous SnS microspheres with open pores were prepared using a spray pyrolysis process followed by a simple sulfidation process. The macroporous SnO2 microspheres prepared from the precursor solution including tin ions and polystyrene beads transformed into the macroporous and phase-pure SnS microspheres by sulfidation at an optimized temperature of 350°C. The sulfidation process of the SnO2 microspheres without open pores obtained by spray pyrolysis formed SnS–SnO2 and SnS–Sn composite microspheres with filled structures at sulfidation times of 9 and 24h, respectively. The discharge capacities of the macroporous SnS microspheres with open pores and dense SnS–SnO2 and SnS–Sn microspheres for the 50th cycle at a current density of 0.5Ag−1 were 364, 231, and 264mAhg−1, respectively. The macroporous SnS microspheres with open pores showed higher capacities and superior rate capability for sodium ion storage compared to dense SnS–SnO2 and SnS–Sn microspheres.

SnO@amorphous TiO2core-shell composite for advanced lithium storage

Abstract Tin monoxide(SnO) has been considered as a promising candidate for the next-generation lithium storage due to its exceptional specific capacity and unique layered structure. However, the huge volume change of SnO during lithiation/delithiation process tends to cause various mechanical failure problems including the delamination between the current collector and the electrode materials, leading to poor stability of the lithium-ion batteries. Herein we propose to solve the interfacial delamination problem by encapsulating the SnO microspheres in amorphous TiO 2 . The prepared SnO@amorphous TiO 2 core-shell composite is found quite successful in alleviating the interfacial delamination, resulting in higher capacity retention and faster solid-state ion diffusion. Specifically, the SnO@amorphous TiO 2 core-shell composites electrode shows a stable charge capacity of 253.6 mAh g -1 after 200 cycles, which is much higher than that of the pure SnO electrode (141.1 mAh g -1 ). Our work provides a guideline for the design and manufacture of the SnO-based electrodes for LIBs.

Synthesis and enhanced NO2-sensing properties of ZnO-decorated SnO2 microspheres

In this work, ZnO was decorated onto SnO2 microspheres via a facile solvothermal method, and the gas sensing characteristics of the ZnO/SnO2 composites was systematically studied. Results showed that the ZnO/SnO2 composites was highly responsive to NO2, with much lower response to interfering gases such as ethanol and acetone. At the optimum temperature (200 °C), the response of the ZnO/SnO2 composite to 100 ppm NO2 was about 3 times higher than that of pristine SnO2 microspheres. Furthermore, ZnO decoration on SnO2 microspheres led to significant reduction in the response time. The improvement of gas-sensing performance may be ascribed to the formation of more surface adsorption sites on the ZnO/SnO2 composite.

Hydrothermal microwave synthesis of SnO microspheres with excellent photocatalytic activity

SnO samples were prepared from SnCl2 and NH4HCO3 by microwave–hydrothermal method. The effects of temperature on the composition, microstructure, and photocatalytic properties of SnO were studied. Results showed that samples synthesized at 50–90 °C for 10 min were composed of SnO and tiny SnO2 particles. All SnO samples displayed good photocatalytic activities. The sample synthesized at 60 °C was composed of numerous porous microspheres, which were 5–10 µm in size and assembled by SnO nanosheets. In general, the SnO samples possessed excellent visible photocatalytic properties and can degrade 87.5% of methyl orange within 80 min.

Effect of annealing temperature on structure and photocatalytic efficiency of SnO microspheres synthesized by ultrasonic reaction method

SnO microspheres were synthesized by a simple one-step ultrasonic reaction method. SnO materials were annealed at 150–250 °C to enhance their photocatalytic performance by adjusting their phase composition and lattice distortion. Effects of annealed temperature on the phase composition, microstructure and photocatalytic performance of SnO materials were investigated in detail. The results reveal that the annealing treatment considerably affected phase composition, absorption in the visible light zone, and the photocatalytic activity of the SnO materials. At increased temperature, SnO2 content in the products gradually increased. At 250 °C, SnO materials were transformed to SnO2. Correspondingly, the photocatalytic activity of the samples improved gradually with increasing temperature. The excellent photocatalytic efficiency of 98.3% within 40 min for the SnO microspheres annealed at 225 °C was achieved under the visible-light irradiation. The enhancement of the photocatalytic activity of this sample can be ascribed to lattice distortion of SnO combined with increased SnO2 content.

Monodispersed SnO2 microspheres aggregated by tunable building units as effective photoelectrodes in solar cells

Mesoporous SnO2 microspheres assembled from densely-packed nanocrystalline building units are a class of useful nanomaterials and have extensive optoelectronic applications, but so far it is still a challenge to acquire monodispersed microspheres. Here, monodispersed SnO2 microspheres consisted of aggregated small primary nanocrystallites are synthesized via a surfactant-free solvothermal method. These SnO2 microspheres have high specific surface area, excellent crystallinity and tunable building units. By precisely controlling the nucleation and growth, the obtained microspheres exhibit narrow size distribution, whose diameters are 200 ± 17 and 191 ± 16 nm from pure n-propanol and n-propanol/water mixed solvents, respectively. The sizes of primary nanocrystals slightly increase with the adscititious water. The SnO2 microspheres exhibit large specific surface areas, leading to efficient sensitizer-loading in both dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs). The sub-micron-sized microspheres could also enhance the light-harvesting of the solar cells due to their light-scattering capability. As the primary nanocrystal multiply contacts densely to neighbouring grains, such intergrowth would improve the electron transport through the grain boundaries. Eventually, a power conversion efficiency of 3.83% is yielded for pure SnO2-based DSSCs when the SnO2 microspheres are used as the scattering layers, and an efficiency of 15.41% is obtained when they are used as the electron transport layers in PSCs.

Dopamine-derived N-doped carbon encapsulating hollow Sn4P3 microspheres as anode materials with superior sodium storage performance

Sn4P3 is one of the most promising anode materials for sodium ion batteries (SIBs) owning to the alloying reaction of P and Sn with Na to form Na3P and Na15Sn4, which is beneficial to achieve a high specific capacity, especially for the high volumetric capacity (6650 mAh cm−3). However, the high capacities generate large volume changes, which pulverize the anode material, resulting in poor cycling stability. This restricts its practical applications for SIBs. Here, the dopamine-derived N-doped carbon encapsulating hollow Sn4P3 microspheres (hollow Sn4P3@C) composites are prepared by an in-situ self-polymerization of dopamine on the surface of hollow SnO2 microspheres followed by a carbonization process and a low temperature phosphorization using NaH2PO2 as P source. The results of the structural and morphological characterization can be demonstrated that as-prepared hollow Sn4P3@C composites are constructed by hollow Sn4P3 microspheres with the ultrathin N-doped carbon coating. The as-prepared samples are tested as the anode materials for SIBs. Compared with bared hollow Sn4P3 microspheres, hollow Sn4P3@C composites exhibit better electrochemical sodium storage performance. As a result, hollow Sn4P3@C composites deliver the first discharge and charge specific capacities of 840 and 587 mAh g−1 with a high initial coulombic efficiency of 70% at a current density of 0.2 A g−1. Moreover, hollow Sn4P3@C composites display superior rate capabilities of 555, 438, 339, 239, 157 and 92 mAh g−1 at 0.2 A g−1, 0.5 A g−1, 1 A g−1, 2 A g−1, 5 A g−1 and 10 A g−1, respectively. Meanwhile, hollow Sn4P3@C composites show a high discharge capacity of 372 mAh g−1 at 0.2 A g−1 after long 200 cycles. A detailed electrochemical kinetic analysis indicates that energy storage for Na+ in Sn4P3 is due to a pseudocapacitive mechanism. The good electrochemical sodium storage performance of as-prepared hollow Sn4P3@C composites may be attributed to the introduction of N-doped carbon coating and unique hollow structure. Therefore, our work provides a new structure model for the development of new anode materials for SIBs.