Hierarchical Tin Research Articles

Rapid Synthesis of Hierarchical Tin Disulfide (SnS2) Nanostructures by a Microwave-Assisted Hydrothermal Method for High-Performance Supercapatteries

Rapid Synthesis of Hierarchical Tin Disulfide (SnS₂) Nanostructures by a Microwave-Assisted Hydrothermal Method for High-Performance Supercapatteries

High energy facets and oxygen vacancies guided hierarchical tin dioxide microcubes assembled by cross-stacked nanoslices for ethanol gas-sensing

For metal oxide gas sensors, the upstream theoretical mechanism can provide both quantum guidance for screening favorable materials and important insights in fabricating electronic devices. However, except for widely popular Yamazoe’s ‘receptor-transducer-utility’ model, some specific theoretical models still lack for diverse sensing properties of metal oxide semiconductor currently. Based on a deeper understanding of surface catalytic mechanism, n-type SnO2 was selected as an example to screen a better solution. Herein, hierarchical SnO2 microcubes assembled from cross-stacked nanoslices were synthesized via a self-templated method, and the SnO2 microcubes displayed versatile performances with excellent response to 100 ppm ethanol (Sr = Rair/Rgas = 56.9), relative low optimal working temperature of 170 °C, good repeatability under high R.H. (90%) and ultra-low detection limit even under 0.1 ppm. The performances of SnO2 nanofilms, hierarchical SnO2 nanotubes and commercial SnO2 powder were also studied. The results showed that the increase of exposed higher energy facet of (101) and rich oxygen vacancies on 3D-crossed nanoslices of SnO2 microcubes contribute to outstanding gas sensing performances, which were also confirmed by the DFT calculations. These demonstrate a diverse sensing mechanism and a new insights for state-in-art gas sensing materials of SnO2.

Integration of hierarchical tin Sulfide@Sulfur-Doped carbon porous composites with enhanced performance for triiodide reduction

Constructing composites with positively synergistic effect is deemed as an effective strategy to further improve photovoltaic performance of dye-sensitized solar cells (DSSCs). However, the controllable synthesis of composites with intimate interface is still a big challenge. In this work, the solvothermal synthesis using SnCl2 and SnSO4 as tin source allows to grow the SnS microspheres (cSnS) and irregular SnS (sSnS). Subsequently, the hierarchical tin sulfide@sulfur-doped carbon porous composites (SnS@SC) have been ingenious synthesized by using SnCl2 as tin source through a facile hydrothermal method followed by the pyrolysis of coated glucose containing sulfur species under the nitridation atmosphere. As expected, the as-designed SnS@SC exhibited outstanding catalytic activity for triiodide reduction reaction (IRR) accompanying with a photoelectric conversion efficiency (PCE) of 7.54%, which reaches as high as 98.7% to that of the Pt (7.64%), as well as higher than that of the cSnS (6.21%) and sSnS (5.20%) in parallel. Compared with cSnS and sSnS, the further enhanced performance of SnS@SC can be mainly attributed to the more exposed active sites, the effective permeation of electrolyte, the decreased resistance, intimate interface and synergistic effect between SnS and S-doped carbon. Our discovery provides an extensible pathway to develop the active-site-enriched composites with beneficial structures in the field of the energy conversion.

Oxide-derived Tin Nanospheres for Efficient CO2 Electroreduction to Formate

Rational design and engineering of electrocatalysts for electrochemical CO2 reduction (CO2RR) is crucial to effectively, selectively converting CO2 into carbon-neutral chemicals and fuels. In this work, we have developed hierarchical tin oxide nanosphere electrocatalysts to boost the production of formate. Three-dimensional (3D) SnO2 spheres constructed from small crystalline nanoparticles exhibited 71-81% Faradaic efficiencies (FE) and energy efficiency (40-50%) toward formate production at partial current densities of 22-72.4 mA/cmgeo 2 from -0.9 V to -1.3 V vs. the reversible hydrogen electrode (RHE). Such hierarchical sphere-like catalysts outperformed non-hierarchical SnO2 nanoparticles and commercially benchmarking catalysts, achieving a peak 81% FE at superior formate current density of ~50 mA/cmgeo 2 at -1.2 V vs. RHE. The spherical oxide-derived Sn catalysts were highly stable up to 36 hours, preserving long-term partial current density of ~ 45 mA/cmgeo 2 and 68% FE for formate. Such an outstanding performance can be credited to the 3D hierarchical structure, which offers enlarged surface area, larger number of electrochemically active sites, and strongly suppressed H2 evolution. Our results may provide more guidelines for the introduction of hierarchical porosity into CO2RR electrocatalysts for large-scale applications.

Enhanced Gas Sensing of Tin Dioxide Based Sensor for Indoor Formaldehyde Application

Indoor formaldehyde detection is of great important at present. Using efficient solvothermal method, nanosheet-constructed and nanorod-constructed hierarchical tin dioxide (SnO2) microspheres were successfully synthesized in this work and used for the gas sensing material for indoor formaldehyde application. The as-prepared two kinds of SnO2 gas sensing materials were applied to fabricate the gas sensors and formaldehyde gas sensing experiments were carried out. The HCHO gas sensing tests indicate that the gas response of the nanosheet-constructed SnO2 microspheres is about 1.7 times higher than that of the nanorod-constructed SnO2 microspheres. In addition, both of the two SnO2 based gas sensors show almost fast response and recovery time to HCHO gas. For the nanosheet-constructed microspheres, the response value is estimated to be 32.0 at 350 °C to 60 ppm formaldehyde gas, while the response and recovery times are 7 and 5 s, respectively. The simple and efficient preparation method and improved gas sensing properties show that the as-synthesized hierarchical SnO2 microsphere that is constructed by a large amount of nanosheets exhibits significant potential application for the indoor formaldehyde sensing.

Defect evolution of hierarchical SnO2 aggregates for boosting CO2 electrocatalytic reduction

The defect evolution enables the regulation of oxygen vacancies and interfacial chemistry of hierarchical tin oxide aggregates for boosting CO2 electrocatalytic reduction.

Superior lithium-ion storage performance of hierarchical tin disulfide and carbon nanotube-carbon cloth composites

Tin-based composites are promising anode materials for high-performance lithium-ion batteries (LIBs); however, insufficient conductivity, as well as fatal volume expansion during cycling lead to poor electrochemical reversibility and cycling stability. In this work, we demonstrate the lithium-ion storage behaviors of SnS2 anode material deposited on different electrode supports. The SnS2 grown on 3D hierarchical carbon nanotube-carbon cloth composites (SnS2-CNT-CC) shows superior capacity retention and cycle stability, compared to that on planar Mo sheets and carbon cloth. The specific capacity of SnS2 on Mo, CC, and CNT-CC is around 240, 840, and 1250 g−1, respectively. The SnS2-CNT-CC electrode outperforms in the cyclic performance and rate capability compared to other electrode configurations due to the multi-electron pathway and high surface area derived from 3D hierarchical CNT-CC electrode support. Furthermore, a significant decrease in the charge transfer resistance is observed by utilizing 3D hierarchical CNT-CC electrode support. The use of 3D hierarchical structures as electrode support could be the best alternative to enhance the electrochemical performances for the next generation LIBs.

Rational design of ultrathin 2D tin nickel selenide nanosheets for high-performance flexible supercapacitors

A novel strategy is proposed to design and fabrication of hierarchical tin nickel selenide nanosheets with highly exposed active sites for flexible and wearable energy storage systems.

Large-scale synthesis of hierarchical SnO spheres assisted with poly (N-isopropylacrylamide) for high lithium storage capacity

Hierarchical tin monoxide (SnO) spheres were successfully prepared by using a new facile route, i.e., a one-pot method in an aqueous solution with the assistance of a thermosensitive polymer, poly (N-isopropylacrylamide) (PNIPAM), acting as a surfactant. The synthesized SnO spheres were assembled from irregular SnO nanosheets, which have a thickness of 20 nm and are several nanometers in length, with a rough surface homogeneously decorated by SnO nanoparticles. The formation of this hierarchical structure is achieved through the cooperation of the template-directing growth and self-assembly process. The electrochemical performance of hierarchical SnO was examined as an anode material for lithium-ion batteries. The as-synthesized SnO leads to an excellent electrochemical performance as characterized by the high specific capacity (275 mAh g−1 at 500 mA g−1), cycling stability (400 mAh g−1 after 70 charge-discharge cycles at 200 mA g−1 with 49% capacity retention), and high rate performance (119 mAh g−1 at 1 A g−1). This one-step facial method may provide an attractive alternative approach to the large-scale preparation of high-purity and low-valence transition metal oxides (TMOs) anode materials.

Synthesis and Photo‐Thermal Conversion Properties of Hierarchical Titanium Nitride Nanotube Mesh for Solar Water Evaporation

Hierarchical TiN nanotube mesh (HTNM) is prepared by calcining TiO2 nanotube mesh (TONM) in NH3 flow where the TONM is fabricated by electrochemical anodic oxidation of Ti mesh. Calcining temperature affects not only phase composition but also morphology of the HTNM, which further affects its optical absorption and solar water evaporation conversion efficiency (η). The η can reach to 85.36% under 2.5 kW m−2 simulated solar irradiation because HTNM efficiently utilizes solar light. Moreover, it can be reutilized because of its stabilities of the phase composition and nanostructure during the measurements of solar water evaporation performance.

Ultra-Low Loading of Highly Active Pt and PtSn Catalysts on Hierarchical Tin as Anodes in Direct Methanol Fuel Cells

Pt and PtSn catalysts were synthesized by a single-step electroless process on hierarchical three-dimensional electrodeposited branched metallic Sn structures (BMS). The controlled electrodeposition of Sn on a carbon-paper substrate resulted in a high surface area of BMS, on which the Pt and PtSn alloy catalysts were deposited as thin layers. The PtSn species were reduced on the Sn substrate from Pt-Sn complexes formed in the solution. Several synthetic aspects were studied, such as the acidity of the electroless solution and the electroless process time span. The prepared electrodes were applied as anodes in direct methanol fuel cells. Methanol oxidation on these electrodes exhibited a specific peak power density of 476 mW mg−1 Pt at 0.45 V, 90 mA cm−2 and 70°C, using only 75 μg cm−2 of Pt, which is significantly higher than previously reported platinum-based catalysts.

Hierarchical TiN nanoparticles-assembled nanopillars for flexible supercapacitors with high volumetric capacitance.

Titanium nitride (TiN) is an attractive electrode material in fast charging/discharging supercapacitors because of its excellent conductivity. However, the low capacitance and mechanical brittleness of TiN restricts its further application in flexible supercapacitors with high energy density. Thus, it is still a challenge to rationally design TiN electrodes with both high electrochemical and mechanical properties. Herein, the hierarchical TiN nanoparticles-assembled nanopillars (H-TiN NPs) array as binder free electrodes were obtained by nitriding of hierarchical titanium dioxide (TiO2) nanopillars, which was produced by a simple hydrothermal treatment of anodic TiO2 nanotubes (NTs) array in water. The porous TiN nanoparticles connected to each other to form ordered nanopillar arrays, effectively providing larger specific surface area and more active sites for charge storage. The H-TiN NPs delivered a high volumetric capacitance of 120 F cm-3 at 0.83 A cm-3, which is better than that of TiN NTs arrays (69 F cm-3 at 0.83 A cm-3). After assembling into all-solid-state devices, the H-TiN NPs based supercapacitors exhibited outstanding volumetric capacitance of 5.9 F cm-3 at 0.02 A cm-3 and a high energy density of 0.53 mW h cm-3. Our results reveal a new strategy to optimize the supercapacitive performance of metal nitrides.

Double-Sided Carbon Covered Hierarchical Tin Oxide Anode for High Capacity Lithium-Ion Batteries

The development of high–capacity anode materials for lithium ion batteries (LIBs) is a key step toward achieving large–scale energy storage applications for portable electronic devices, electrical vehicles, and hybrid electrical vehicles.1 Since its first discovery, the current commercial LIBs have been using graphite as anode material. Although this carbon–based anode is cheap, abundant and reliable, however it provides a limited theoretical capacity of 372 mAh/g, hence hampering the establishment of high–energy density LIBs to meet huge technological demands in the near future.2 To replace the incumbent anode, intensive research has been devoted on the alloy–based materials such as silicon, germanium, tin, and tin oxide (SnO2). Among these candidates, SnO2 is a promising anode material attributing to its low cost, nontoxicity, low operating potential (0.25 V vs. Li/Li+), high theoretical capacity (782 and 1493 mAh/g for alloying/de–alloying and both alloying/de–alloying and conversion reaction, respectively), and easy synthesis in regard to nanostructures.3 It was widely studied that employing the pristine SnO2 anode for LIBs may face a significant barrier because of a severe volume change during the electrochemical cycle, causing pulverization and cracks and eventually the loss of electrical conduction paths. In the meantime, the new–fresh cracks that are exposed to the electrolyte may form a continuous solid electrolyte interphase (SEI)–filming process resulting in a thickened SEI layer on the surface of SnO2 anode. Consequently, the cell cannot avoid a rapid capacity fading.4 To overcome these problems, we synthesized the rational anode material consisting of hierarchical structure and thin double carbon layers. The hierarchical structures of SnO2 anode are aimed at increasing the active surface area, allowing more Li ions can be stored in the spaces, thus promoting a faster Li ion diffusivity. In addition, thin double carbon layers are aimed at alleviating the volume change during charge-discharge reaction, leading to mechanically keep the structure of electrode stable and enhance the ionic conductivity at the interfaces. As the results, our C@SnO2@C anode demonstrated a significant electrochemical performance such as long cycle life and high reversible capacity, hence postulating a solution for commercialization of Sn-based anode for LIBs in the market. [References] Chen, Y. M.; Lu, Z. G.; Zhou, L. M.; Mai, Y. W.; Huang, H. T. Triple–coaxial electrospun amorphous carbon nanotubes with hollow graphitic carbon nanospheres for high– performance Li ion batteries. Energy Environ. Sci. 2012, 5, 7898–7902. Ko, Y. N.; Park, S. B.; Kang, Y. C. Design and fabrication of new nanostructured SnO2–carbon composite microspheres for fast and stable lithium storage performance. Small 2014, 10, 3240–3245. Thomas, R.; Rao, G. M. SnO2 nanowire anchored graphene nanosheet matrix for the superior performance of Li–ion thin film battery anode. J Mater Chem A 2015, 3, 274–280. Zhu, C. R.; Xia, X. H.; Liu, J. L.; Fan, Z. X.; Chao, D. L.; Zhang, H. et al. TiO2 nanotube@SnO2 nanoflake core–branch arrays for lithium–ion battery anode. Nano Energy 2014, 4, 105–112.

Enhanced gas sensing properties of hierarchical SnO2 nanoflower assembled from nanorods via a one-pot template-free hydrothermal method

Well-defined three-dimensional (3D) hierarchical tin dioxide (SnO2) nanoflowers with the size of about 200nm were successfully synthesized by a simple template-free hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption analyses were used to characterize the structure and morphology of the products. The as-synthesized full crystalline and large specific surface area SnO2 nanoflowers were assembled by one-dimensional (1D) SnO2 nanorods with sharp tips. A possible self-assembly mechanism for the formation the SnO2 nanoflowers was speculated. Moreover, gas sensing investigation showed the sensor based on SnO2 nanoflowers to exhibit high response and fast response-recovery ability to detect acetone and ethanol at an operating temperature lower than 200°C. The enhancement of gas sensing properties was attributed to their 3D hierarchical nanostructure, large specific surface area, and small size of the secondary SnO2 nanorods.

Novel hierarchical SnO2 microsphere catalyst coated on gas diffusion electrode for enhancing energy efficiency of CO2 reduction to formate fuel

The conversion of carbon dioxide to value-added fuel using electrical energy generated intermittently from renewable energy sources is very promising in terms of energy usage reconciliation. The process converts greenhouse carbon dioxide gas to produce diverse attractive chemicals and fuels like methanol, formate, and other hydrocarbons. In this paper, the electroreduction of CO2 to formate in aqueous solution is performed by using novel hierarchical tin oxide microsphere (HMS-SnO2) particles deposited over gas diffusion layer electrode (HMS-SnO2/GDE). The experiment is carried out in a divided H-type two-compartment cell with a Nafion® membrane as the diaphragm separating the cathodic and anodic compartments. The HMS-SnO2 catalysts are synthesized by a facile hydrothermal self-assembled process using different ratios of ethanol to distilled water in the synthetic solution. Due to the outstanding catalytic activity and selectivity toward CO2 electroreduction, SnO2-86/GDE exhibits a high Faradaic efficiency of 62% toward formate formation at −1.7V vs. SHE (Standard Hydrogen Electrode). The electrode durability is also observed with a stable current density over 12h of continuous electrolysis operation. The superior performance is credited to the morphology- and size-controlled hierarchical structure, which may provide more active sites to accelerate the slow kinetics of CO2 reduction, leading to the improved energy efficiency. During electrolysis process, KHCO3 electrolyte is found to have some contribution to formate formation on the micro-structured tin oxide catalysts coated GDE electrode.

Fabrication of hierarchical Sn-doped ZnO nanorod arrays through sonicated sol−gel immersion for room temperature, resistive-type humidity sensor applications

Hierarchical tin (Sn)-doped zinc-oxide (ZnO) nanorod arrays (SZO) were deposited onto Al-doped ZnO-coated glass substrate by using a sonicated sol–gel immersion method for resistive-type humidity sensor applications. X-ray diffraction patterns revealed that the deposited SZO arrays exhibit a wurtzite structure. SZO possessed smaller average diameter, crystallite size, and thickness than the undoped sample did. The SZO film also exhibited compressive strain and tensile stress values of −0.033% and 77MPa, respectively. Our result showed the sensitivity of the SZO based-sensor improved compared with that of the undoped ZnO, with values of 3.41 and 1.41 at 40% to 70% RH and 70% to 90% RH, respectively. The response and recovery times of the SZO based humidity sensor improved to 230 and 30s, respectively. All these results indicated that SZO had high potential for humidity-sensor applications.

A facile synthesis of hierarchical Sn3O4 nanostructures in an acidic aqueous solution and their strong visible-light-driven photocatalytic activity

Hierarchical tin(III) oxide, Sn3O4, nanospheres were synthesized via hydrothermal reaction under strongly acidic ambient conditions. The morphology of Sn3O4 varied with decreasing pH. The prickly Sn3O4 nanospheres changed into Sn3O4 nanospheres covered with single-crystalline nanoplates having a high BET surface area of ca. 55.05 m2·g–1 and a band gap of ca. 2.25 eV. Small amounts (0.05 g) of the hierarchical Sn3O4 nanostructures completely decomposed a 30% methyl orange (MO) solution in 100 mL deionized water within 15 min under one sun condition (UV + visible light). The Sn3O4 photocatalyst exhibited a fast decomposition rate of 1.73 × 10−1 min−1, which is a 90.86% enhancement relative to that of the commercially available P25 photocatalyst. The high photocatalytic activity of the hierarchical Sn3O4 nanostructures is attributed to its ability to absorb visible light and its high surface-to-volume ratio.

Hierarchical Tin Oxide Nanostructures for Dye‐Sensitized Solar Cell Application

Nanoscale material manipulation is the key to increasing solar light harvesting and photon‐to‐electron conversion efficiency (PCE) for an organic–inorganic photovoltaic system. Many SnO2 1D nanostructures, including nanowires and nanobelts, have been employed because of their potential of enhancing the charge collection properties of DSSCs by eliminating losses caused by grain boundary scattering of carriers in nanoparticle‐based DSSCs. Here, a new approach to growing hierarchical 1D SnO2 nanostructured layer by catalyst‐assisted pulsed laser deposition after introducing NiO into the SnO2 target is reported, and a plausible growth mechanism to describe the observed hierarchical nanostructures is presented. A remarkable improvement in the solar cell performance, including open circuit voltage, short circuit current density, fill factor, and PCE, by simple surface modification of the hierarchical SnO2 nanostructured photoanode is further demonstrated. Surface passivation is achieved on the as‐deposited hierarchical SnO2 nanostructures by dip coating with an MgO passivation layer of appropriately optimized thickness. Such an insulating layer is found to effectively reduce the recombination process caused by the higher electron mobility of SnO2 photoanode nanostructures. Compared with a pristine SnO2 nanobelt photoanode, a tenfold enhancement in their PCE (to 4.14%) has been observed for MgO‐passivated hierarchical SnO2 nanostructures.

Facile synthesis of hierarchical SnS nanostructures and their visible light photocatalytic properties

Hierarchical tin sulfide (SnS) nanoflowers were synthesized by a facile polyol refluxing process using tin (II) chloride and thioacetamide as precursors, ethylene glycol as the solvent, and triethanolamine as the complexing agent. The as-synthesized samples were characterized by XRD, FESEM, TEM and N2 adsorption–desorption analyses. The as-synthesized SnS nanoflowers consist of mesoporous nanoplates composed of nanoparticles with a BET surface area of 30.2m2g−1 and a pore volume of 0.11cm3g−1. The growth mechanisms of the hierarchical nanoflowers were investigated by changing the amount of triethanolamine. The results indicated that the formation and array of chelate complex {[Sn(TEA)n]2+·2Cl−}k clusters control the shape of the SnS product. The photocatalytic properties of the samples were also explored by the photodegradation of RhB under visible light irradiation. The hierarchical nanoflowers show superior absorption ability and visible light photocatalytic activities than the nanoparticles. The facile process and the shape-controlled method presented in this paper can be extended to the synthesis of other layered metal chalcogenides.

Nanowire-based hierarchical tin oxide/zinc stannate hollow microspheres: Enhanced solar energy utilization efficiency for dye-sensitized solar cells and photocatalytic degradation of dyes

Nanowire-based SnO2/Zn2SnO4 hollow microspheres are synthesized using a facile one-pot method for solar energy conversion and environment cleaning. The micrometer-sized hollow spheres possess a hierarchical structure with the shell consisting of nanowires. With the hybrid SnO2/Zn2SnO4 microspheres as photoanodes, the dye-sensitized solar cells (DSSCs) with an overall 4.72% photoconversion efficiency is obtained, nearly 240% improvement over the DSSCs that uses nanorod-based hierarchical SnO2 microspheres. The hybrid microspheres are also determined to be high-performance photocatalyst with a better recyclability for the photodegradation of dyes under simulated sunlight irradiation. These improvements of solar energy utilization are ascribed to the formation of the heterojunctions between SnO2 and Zn2SnO4 to enhance electron transport and charge-separation efficiencies.