Porous SnO2 Research Articles

Trimodally porous SnO2 nanospheres with three-dimensional interconnectivity and size tunability: a one-pot synthetic route and potential application as an extremely sensitive ethanol detector

The rapid and effective transfer of chemical reactants to solid surfaces through porous structures is essential for enhancing the performance of nanomaterials for various energy and environmental applications. In this paper, we report a facile one-pot spray pyrolysis method for preparing highly reactant-accessible and porous SnO2 spheres, which have three-dimensionally interconnected and size-tunable trimodal (microscale, mesoscale and macroscale) pores. For this synthetic method, macroscale polystyrene spheres and mesoscale-diameter, long carbon nanotubes were used as sacrificial templates. The promising potential of the SnO2 spheres with trimodal pores (sizes ≈3, 20 and 100 nm) was demonstrated by the unprecedentedly high response to several p.p.b. levels of ethanol. Such an ultrahigh response to ethanol is explained with respect to the hierarchical porosity and pore-size-dependent gas diffusion mechanism. Spray pyrolysis has been used to prepare tin dioxide nanospheres that contain size-tunable ‘trimodal’ pores. To enhance the performance of porous nanostructures in various energy and environmental applications involving reactions at surfaces and interfaces, it is desirable to gain precise control of multimodal pores in nanostructures. Jong-Heun Lee at Korea University and co-workers have used a simple ‘one-pot’ spray pyrolysis method to produce tin dioxide nanospheres with three levels of pore sizes. Aqueous droplets containing a metal salt, macroscale polystyrene spheres and mesoscale-diameter carbon nanotubes were subjected to pyrolysis, which decomposed the metal salt and polystyrene. Heat treatment then decomposed the carbon nanotubes. The potential of this method was demonstrated by using tin dioxide spheres containing pores with sizes of 3, 20 and 100 nanometres to detect ethanol at levels of several parts per billion. Trimodally porous SnO2 nanospheres with pore sizes of 3, 20 and 100 nm were prepared with facile one-pot spray pyrolysis and their potential for extremely sensitive ethanol detector was demonstrated. The precise control over, as well as the tuning of, multimodal pores in metal oxide nanostructures provides a new and general strategy for enhancing the performance of nanomaterials for various energy and environmental applications.

Porous Double-shelled SnO2 @ C Hollow Spheres as High-Performance Anode Material for Lithium Ion Batteries

The novel porous double-shelled SnO2 @ C hollow spheres possess numerous outstanding properties. Its inner active hollow spheres can effectively improve the tag energy density and its double-shelled carbon wrapping outside of each SnO2-shell can protect the integrity of structure as well as enhance electrical conductivity. This is a significant improvement in the design and synthesis of multi-shell or core-shell functional materials. More valuably, the porous hollow structure can not only facilitate liquid electrolyte fast diffusion into the double-shelled spheres but also buffer large volume changes during lithium ions insertion/extraction. Importantly, due to the prominent dispersibility and high specific surface area, the SnO2 spheres can provide sufficient contact areas between active materials and electrolyte so as to improve its electrochemical performance. As a result, the obtained double-shelled SnO2 nanocomposites exhibit excellent rate capability, enhanced cyclability (911mAhg−1 after 100 circles) and high specific energy density. Undoubtedly, the unique structure can provide a reference to effectively utilize hollow structures.

Novel Carbon-Encapsulated Porous SnO2 Anode for Lithium-Ion Batteries with Much Improved Cyclic Stability.

Porous SnO2 submicrocubes (SMCs) are synthesized by annealing and HNO3 etching of CoSn(OH)6 SMCs. Bare SnO2 SMCs, as well as bare commercial SnO2 nanoparticles (NPs), show very high initial discharge capacity when used as anode material for lithium-ion batteries. However, during the following cycles most of the Li ions previously inserted cannot be extracted, resulting in considerable irreversibility. Porous SnO2 cubes have been proven to possess better electrochemical performance than the dense nanoparticles. After being encapsulated by carbon shell, the obtained yolk-shell SnO2 SMCs@C exhibits significantly enhanced reversibility for lithium-ions storage. The reversibility of the conversion between SnO2 and Sn, which is largely responsible for the enhanced capacity, has been discussed. The porous SnO2 SMCs@C shows much increased capacity and cycling stability, demonstrating that the porous SnO2 core is essential for better lithium-ion storage performance. The strategy introduced in this paper can be used as a versatile way to fabrication of various metal-oxide-based composites.

Thermal stability enhancement of modified carboxymethyl cellulose films using SnO2 nanoparticles

In this study, in-situ and ex-situ hydrothermal synthesis procedures were applied to synthesize novel CMC/porous SnO2 nanocomposites from rice husk extracted carboxymethyl cellulose (CMC) biopolymer. In addition, the effects of SnO2 nanoparticles on thermal stability of the prepared nanocomposite were specifically studied. Products were investigated in terms of morphology, particle size, chemical structure, crystallinity and thermal stability by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Presence of characteristic bands in the FTIR spectra of samples confirmed the successful formation of CMC and CMC/SnO2 nanocomposites. In addition, FESEM images revealed four different morphologies of porous SnO2 nanoparticles including nanospheres, microcubes, nanoflowers and olive-like nanoparticles with hollow cores which were formed on CMC. These nanoparticles possessed d-spacing values of 3.35ÿ. Thermal stability measurements revealed that introduction of SnO2 nanoparticles in the structure of CMC enhanced stability of CMC to 85%.

Monodispersed SnO2 nanospheres embedded in framework of graphene and porous carbon as anode for lithium ion batteries

Tin peroxide (SnO2) is one of most potential anode materials for lithium ion batteries with high energy density because of its appropriate (de)lithiation potential and high specific capacity. However, the poor cycling property of SnO2 restricts its wide application in lithium ion battery. Herein, a novel monodispersed porous SnO2 nanospheres/graphene/porous carbon composite electrode with excellent performance is constructed. In this electrode, the SnO2 nanospheres with a diameter of ~60nm are embedded in porous carbon, which is filled between the interlayers of graphene sheets. The carbon can protect the SnO2 nanospheres from contacting with the electrolyte. The pores inside both SnO2 nanospheres and carbon can accommodate the huge volume expansion of SnO2 nanoparticles during charge–discharge process. The graphene sheets can greatly improve the strength, stability and flexibility of the electrode. The framework formed by graphene and porous carbon can successfully prevent the aggregation of SnO2 nanospheres and collapse of SnO2 composite electrode. As a result, the composite electrode shows excellent rate performance, which achieves discharge capacities of 816.3, 704.6, 600 and 459.4mAhg−1 at current densities of 0.2, 0.5, 1 and 2Ag−1 and delivers a capacity of 873.2mAhg−1 after 200 cycles at 0.2Ag−1.

In situ synthesis of porous SnO2 nanospheres/graphene composite with enhanced electrochemical performance

A large diameter porous SnO2 nanospheres/graphene composite was synthesized by an in situ hydrothermal method for the first time. TEM images indicate that the porous SnO2 nanospheres are distributed on the graphene nanosheets uniformly.

Synthesis of SnO2 versus Sn crystals within N-doped porous carbon nanofibers via electrospinning towards high-performance lithium ion batteries.

The design of tin-based anode materials (SnO2 or Sn) has become a major concern for lithium ion batteries (LIBs) owing to their different inherent characteristics. Herein, particulate SnO2 or Sn crystals coupled with porous N-doped carbon nanofibers (denoted as SnO2/PCNFs and Sn/PCNFs, respectively) are fabricated via the electrospinning method. The electrochemical behaviors of both SnO2/PCNFs and Sn/PCNFs are systematically investigated as anodes for LIBs. When coupled with porous carbon nanofibers, both SnO2 nanoparticles and Sn micro/nanoparticles display superior cycling and rate performances. SnO2/PCNFs and Sn/PCNFs deliver discharge capacities of 998 and 710 mA h g(-1) after 140 cycles (at 100, 200, 500 and 1000 mA g(-1) each for 10 cycles and then 100 cycles at 100 mA g(-1)), respectively. However, the Sn/PCNF electrodes show better cycling stability at higher current densities, delivering higher discharge capacities of 700 and 550 mA h g(-1) than that of SnO2/PCNFs (685 and 424 mA h g(-1)) after 160 cycles at 200 and 500 mA g(-1), respectively. The different superior electrochemical performance is attributed to the introduction of porous N-doped carbon nanofibers and their self-constructed networks, which, on the one hand, greatly decrease the charge-transfer resistance due to the high conductivity of N-doped carbon fibers; on the other hand, the porous carbon nanofibers with numerous voids and flexible one-dimensional (1D) structures efficiently alleviate the volume changes of SnO2 and Sn during the Li-Sn alloying-dealloying processes. Moreover, the discussion of the electrochemical behaviors of SnO2vs. Sn would provide new insights into the design of tin-based anode materials for practical applications, and the current strategy demonstrates great potential in the rational design of metallic tin-based anode materials.

High Sensitivity of Porous Cu-Doped SnO<sub>2</sub> Thin Films to Methanol

Porous Cu-doped SnO2 thin films were synthesized by the sol-gel dip-coating method for enhancing methanol sensing performance. The effect of Cu doping concentration on the SnO2 sensibility was investigated. XRD data confirm that the fabricated SnO2 films are polycrystalline with tetragonal rutile crystal structure. AFM and SEM micrographs confirmed the roughness and the porosity of SnO2 surface, respectively. UV-Vis spectrum shows that SnO2 thin films exhibit high transmittance in the visible region ~95%. The band gap (3.80 - 3.92 eV) and the optical thickness (893 - 131 nm) of prepared films were calculated from transmittance data. The sensing results demonstrate that SnO2 films have a high sensitivity and a fast response to methanol. In particular, 3% Cu-SnO2 films have a higher sensitivity (98%), faster response (10-2 s) and shorter recovery time (18 s) than other films.

A novel Ag deposited nanocoordination polymer derived porous SnO2/NiO heteronanostructure for the enhanced photocatalytic reduction of Cr(vi) under visible light

A novel silver deposited SnO2/NiO heteronanostructure is prepared and applied for the photocatalytic reduction of toxic aqueous Cr(vi) under visible light conditions.

Synthesis and characterization of hierarchical porous SnO2 for enhancing ethanol sensing properties

Hierarchical porous SnO2 (HP-SnO2) nanoparticles (NPs) were synthesized via a modified sol-gel method by employing polystyrene (PS) microspheres as a template and SnCl2 as a tin source. The samples presented a three-dimensional random arrangement of macropores with average pore diameter of about 210nm, of which the pores walls were composed of NPs with the size of about 11nm. The N2-sorption analysis showed that the presence of the hierarchical mesoporous structure in the samples. The gas-sensing measurements showed that the response of HP-SnO2 based sensor reached the maximum value at the operating temperature of 240°C, which was 60°C lower than that of SnO2 based sensor. Moreover, the HP-SnO2 exhibited a significant improvement for the response and a short response-recovery time to ethanol vapor. The results indicated that HP-SnO2 NPs were of great potential for application in ethanol sensors.

Au nanoparticle-functionalized 3D SnO2 microstructures for high performance gas sensor

Three-dimensional (3D) nanostructures of metal oxides have been widely used for gas sensor devices. In this work, 3D porous SnO2 microstructures constructed by two-dimensional (2D) nanosheets were prepared via a simple hydrothermal process combined with subsequent annealing. Gold (Au) nanoparticles were successfully immobilized onto the surface of SnO2 nanosheets to serve as a sensitizer by a facile solution reduction process. This novel 3D Au/SnO2 microstructure has been investigated for gas senor and exhibits remarkably enhanced sensing performances to ethanol, e.g. high response, fast recovery time and good stability. The possible sensing mechanism is also discussed in terms of the special effect of Au functionalization.

One-Pot Hydrothermal Synthesis of Porous SnO<SUB>2</SUB> Nanostructures for Photocatalytic Degradation of Organic Pollutants

One-Pot Hydrothermal Synthesis of Porous SnO<SUB>2</SUB> Nanostructures for Photocatalytic Degradation of Organic Pollutants

Synthesis of porous SnO2 nanocubes via selective leaching and enhanced gas-sensing properties

Porous micro-/nanostructures are of great interest in many current and emerging areas of technology. In this paper, porous SnO2 nanocubes have been successfully fabricated via a selective leaching strategy using CoSn(OH)6 as precursor. The structure and morphology of as-prepared samples were investigated by several techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric and differential scanning calorimeter analysis (TG⿿DSC), transmission electron microscopy (TEM) and N2 adsorption⿿desorption analyses. On the basis of those characterizations, the mechanism for the formation of porous SnO2 nanocubes has been proposed. Owing to the well-defined and uniform porous structures, porous SnO2 nanocubes possessing more adsorbent amount of analytic gas and accelerate the transmission speed so as to enhance the gas-sensing properties. Gas sensing investigation showed that the sensor based on porous SnO2 nanocubes exhibited high response, short response⿿recovery times and good selectivity to ethanol gas.

Electrical Behavior of SnO2 Polycrystalline Ceramic Pieces Formed by Slip Casting: Effect of Surrounding Atmosphere (Air and CO)

Pieces of porous polycrystalline SnO2 with and without cobalt have been formed by the slip-casting method, using ceramic powders synthesized by the controlled precipitation method. A suitable␣methodology was developed for forming and sintering the pieces to enable controlled modification of their microstructure, principally grain size, porosity, and type of intergranular contacts. Better control of the microstructure was obtained in the samples containing cobalt. In these, predominance of open necks and intergranular contacts was observed, which can represent Schottky barriers. Because of its good structural homogeneity, porosity, and small grain size (of the order of 1 μm), the sample with 2 mol.% Co sintered at 1250°C for 2 h was selected for electrical characterization by complex impedance spectroscopy, varying the operating temperature, concentration and nature of the surrounding gas (air or CO), and bias voltage. The resulting R p and C p curves were very sensitive to variation in these parameters, being most obvious for the C p curves, which showed a phenomenon of low-frequency dispersion when bias voltages other than zero were used, in the presence of O2, and at operating temperature of 280°C. The electrical behavior of the SnO2 with 2 mol.% Co sample sintered at 1250°C was consistent with the nature and microstructural characteristics of the active material and was justified based on the presence of shallow- and deep-type defects, and variations in barrier height and width, caused by adsorption of gas molecules.

Synthesis of Hierarchical Porous Zn-Doped SnO2 Spheres and Their Photocatalytic Properties

The undoped and Zn-doped SnO2 products have been synthesized by a solvothermal method. With the Zn doping concentration changing from 0 to 20 mol%, the SnO2 morphology evolved from aggregated nanoprisms into hierarchical porous spheres. The products were characterized by x-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, selected area electron diffraction, UV-Vis absorption spectra, and photoluminescence spectra analysis. The results showed that Zn doping concentration significantly influenced on the microstructure, size, morphology, and optical property of the SnO2 products. Furthermore, the influence of the doping effect on the photocatalytic performance of the as-prepared SnO2 products was compared. The results revealed that 20 mol% Zn-doped SnO2 with hierarchical porous spheres exhibited excellent efficiency of photocatalytic activity, which could be attributed to their abundant oxygen vacancies, large specific surface area, and porous structure.

Preparation of porous flower-like SnO2 micro/nano structures and their enhanced gas sensing property

Porous flower-like tin oxide (SnO2) structures were obtained using a hydrothermal method combined with a subsequent calcination and acid-washing process. The morphologies and crystal structures of the products were characterized by field emission scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller N2 adsorption-desorption analyses. The process of inducing porosity begins with a flower-like nickel tin sulfur precursor. Thermal decomposition of this flower-like nickel tin sulfur precursor leads to an intimate mixture of porous flower-like NiO/SnO2 hybrids. Porous SnO2 flowers were obtained after removing the cubic phase NiO by an acid-washing process. Furthermore, the gas sensing properties of the as-prepared porous SnO2 flowers to VOCs, such as ethanol, formaldehyde, benzene, toluene, and acetone, were investigated. The porous SnO2 flowers showed a good response and reversibility to some organic vapors, such as ethanol and formaldehyde. The sensing responses to 100 ppm ethanol and formaldehyde were 42.4 and 24.8, respectively. The sensors also exhibited a good response to benzene, toluene, methanol, and 2-propanol. The relationship between the gas-sensing properties and the microstructure of the as-prepared flower-like SnO2 structures was also examined.

Sb2Se3 sensitized heterojunction solar cells

The study deals with the sensitization of the porous SnO2 films deposited on fluorine-doped tin oxide with nanocrystalline Sb2Se3. The sensitization was achieved for three different sensitization times employing chemical solution deposition with antimony chloride and sodium selenosulphate as precursors for Sb3+ and Se2−, respectively. The unsensitized and sensitized photoelectrodes were characterized using X-ray diffractometry, scanning electron microscopy and diffused reflectance spectroscopy. The solar cells fabricated using three different photoelectrodes were characterized for their photovoltaic performance using the photocurrent density versus photovoltage curves. The study revealed that sensitization time significantly influences the photovoltaic parameters namely, short circuit current density (J sc), open circuit voltage (V oc) and fill factor (FF) and hence the photovoltaic efficiency (η).

Synthesis and gas sensing properties of porous hierarchical SnO2 by grapefruit exocarp biotemplate

A biotemplate of grapefruit exocarp was used to synthesis porous hierarchical SnO2 and its gas sensing properties were investigated in this manuscript. Biomorphic SnO2 with lamellar and plicated membranes and porous walls were synthesized by using grapefruit exocarp template combining with ultrasonic shaking and following calcination. The porous hierarchical structure of biomorphic SnO2 was characterized by field emission scanning electron microscope, transmission electron microscopy, nitrogen adsorption–desorption isotherm, etc. The biomorphic SnO2 exhibits small grain size around 10nm, a relatively large BET surface area and mesoporosity. Growth mechanism of biomorphic SnO2 was proposed. The sensing properties of the biomorphic SnO2 to formaldehyde vapor were measured. The optimal operating temperature of the sensor was 200°C and the response value of the sensor to 10ppm formaldehyde was 50. The sensor showed a good selectivity to formaldehyde in methanol, acetone, toluene, benzene and ammonia. The stability and the effect of humidity of the sensor were also tested. The gas sensing mechanism of the biomorphic SnO2 to formaldehyde was analyzed briefly.

Hydrothermal self-assembly of novel porous flower-like SnO2 architecture and its application in ethanol sensor

Different morphologies of tin dioxide (SnO2) architectures were prepared by increasing reaction time (12, 18, 24 and 48h) under a facile hydrothermal process and followed by calcination. The crystal structures and morphologies of the hierarchical architecture were characterized in detail by means of powder X-ray diffraction (XRD), energy dispersive X-ray detector (EDX), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the porous flower-like SnO2 architecture was obtained by 24h hydrotherm treatment. Most importantly, the sensors based on porous flower-like SnO2 architecture exhibited perfect sensing performance toward ethanol with excellent selectivity, high response and fast response-recovery capability compared with other SnO2 nanoflowers for the same ethanol concentration at 300°C. The response value was about 208 and the response-recovery time was around 8 and 7s for 500ppm ethanol, respectively. The enhancement in gas sensing properties was attributed to the unique structures, including the flower-like structure and porous feature, which provided more gas active center and diffusion pathways. The results indicated that porous flower-like SnO2 architecture was a potential candidate for fabricating effective ethanol sensor. Furthermore, the possible growth mechanism and the ethanol sensing mechanism of the architecture were discussed, too.

Growth Mechanism and Electrochemical Properties of Porous Hollow Tin Dioxide Nanospheres

Porous hollow SnO 2 nanospheres were prepared by means of enforced Sn 2+ hydrolysis method under hydrochloric acid medium. These hollow nanospheres with an average diameter of 220nm had a very thin shell thickness of about 40nm and were surrounded by elongated octahedral-like nanoparticles with the apex oriented outside. The experimental conditions, such as HCl content, reaction temperature and time directly dominated the morphology, structure and crystallinity of the obtained samples. A pre-oxidation-nucleation-growth mechanism and inside-out Ostwald-ripening method was proposed on the basis of the previous research and time-dependent experiments. Electrochemical tests showed that the porous hollow SnO 2 nanospheres exhibited improved cycling performance for anode materials of lithium-ion batteries, which retained a high reversible capacity of 540.0mAhg-1, and stable cyclic retention at 120th cycle.