SnO2 Shell Research Articles

Effect of shell-dependent variation on the photocatalytic activity of flower-like core-shell SnSe@SnO2

Flower-like core-shell SnSe@SnO2 was prepared by low-temperature in situ oxidation. The relationship between different oxidation times and the formation of core-shell structures of the samples was explored. The results showed that SnSe was obtained by thermal oxidation of SnO2 in close contact with air. The size range of the flower-like core-shell structure SnSe@SnO2 was 15–20 μm. The flower-like structure was self-assembled from nanoplates with a thickness of about 200 nm. This flower-like core-shell structured SnSe@SnO2 has a band gap of about ∼1.4 eV. The electrochemical characterization of the samples was analyzed for charge transfer phenomena at the junctions as well as at the interface between the shell layer and the aqueous solution. The effect of different SnO2 shell layers on the photocatalytic degradation activity of the composites for methylene blue was evaluated. The samples with SnSe oxidized in air for 8 h showed optimal photocatalytic performance and displayed excellent photostability and reusability. In addition, O2− was the main active species for the degradation of the organic dye methylene blue.

Cu2O/SnO2 Heterostructures: Role of the Synthesis Procedure on PEC CO2 Conversion

Addressing the urgent need to mitigate increasing levels of CO2 in the atmosphere and combat global warming, the development of earth-abundant catalysts for selective photo-electrochemical CO2 conversion is a central and pressing challenge. Toward this purpose, two synthetic strategies for obtaining a Cu2O–SnO2 catalyst, namely co-precipitation and core–shell methods, were compared. The morphology and band gap energy of the synthesized materials were strongly different. The photoactivity of the core–shell catalyst was improved by 30% compared to the co-precipitation one, while its selectivity was shifted towards C1 products such as CO and formate. The stability of both catalysts was revealed by an easy and fast EIS analysis, indicating how the effective presence of a SnO2 shell could prevent the modification of the crystalline phase of the catalyst during PEC tests. Finally, directing the selectivity depending on the synthesis method used to produce the final Cu2O–SnO2 catalyst could possibly be implemented in syngas and formate transformation processes, such as hydroformylation or the Fischer–Tropsch process.

Interconnected Sn@SnO2 Nanoparticles as an Anode Material for Lithium-Ion Batteries

Ammonia-borane reduction of tin (II) chloride was utilized to prepare customized and interconnected Sn@SnO2 core–shell nanoparticles. Remarkably, the Sn@SnO2-based electrode delivered a reversible capacity of 722 mAh g–1 at 0.5 C after 200 cycles with a Coulombic efficiency of ∼99%. Also, this electrode exhibited a high rate capability (564 mAh g–1 at 1.0 C), low charge transfer resistance (44.7 Ω), and reasonable electrode polarization (146 mV vs Li/Li+), which led to a high capacity retention (∼94%). Additionally, the kinetics of Li-ion storage of the sample revealed that the capacitance contribution plays a main role at fast C-rates. This new nanoarchitecture is promising for stable lithium-ion storage because of the presence of voids and a SnO2 shell in the interconnected Sn@SnO2 nanoparticles, in which the cavities mitigate its volume expansion upon cycling; meanwhile, the SnO2 layer increases its capacity.

Two-step growth of core-shell TiO2/SnO2 nanorod arrays on FTO and its application in gas sensor

The development of gas sensors based on metal oxide semiconductor (MOS) with highly regular morphology, highly stable structures, and easy preparation is greatly desired but remains a challenge. Herein, we first prepared a highly regular array of TiO2 nanorods on FTO by a modified in situ hydrothermal method. Then a uniform SnO2 layer grew on the nanorods to form a core-shell nanocomposite by an ion-layer adsorption-reaction process. The TiO2/SnO2 sensors show enhanced gas sensing performance compared with the TiO2 sensors, including higher sensitivity to ethanol, lower working temperature, and better long-term stability. And the highest ethanol response can be obtained when the growth cycle of the SnO2 shell was two times. The gas-sensing mechanism of the TiO2/SnO2 nanocomposites was discussed concerning the unique core-shell structure and a heterojunction between TiO2 and SnO2.

In-situ Surface-Enhanced Raman Spectroscopy Reveals a Mars-van Krevelen-Type Gas Sensing Mechanism in Au@SnO2 Nanoparticle-Based Chemiresistors.

Molecular-level understandings of gas sensing mechanisms of oxide-based chemiresistors are significant for designing high-performance gas sensors; however, the mechanisms are still controversial due to the lack of direct experimental evidence. This work demonstrates efficient in situ surface-enhanced Raman spectroscopy (SERS) tracing of the highly representative SnO2-ethanol gas sensing using Au@SnO2 nanoparticles (NPs), where the Au core and SnO2 shell provide SERS activity and a gas sensing response, respectively. The in situ SERS evidence suggests that the sensing follows a Mars-van Krevelen mechanism rather than the prevailing adsorbed oxygen (AO) model. This mechanism is also observed in sensing other gases based on the Au@SnO2 NPs, showing its universality. This work offers efficient in situ tracing for gas sensing and experimental elucidation of the specific gas sensing mechanism, potentially ending the long-term controversy over the gas sensing mechanisms. Therefore, it is highly significant to this field.

Excellent long-term stable H2S gas sensor based on Nb2O5/SnO2 core-shell heterostructure nanorods

Heterostructured Nb2O5/SnO2 core-shell nanorods are synthesized by a facile hydrothermal strategy and atomic layer deposition (ALD). The SnO2 shell thicknesses varying from 7 to 34 nm exhibit a significant impact on sensing performance. The response enhancement mechanism of the Nb2O5/SnO2 core-shell nanorods is illustrated based on the electron-depletion model. The Nb2O5/SnO2 core-shell nanorods gas sensors were synthesized based on the micro-electromechanical systems (MEMS), which could provide variable operating temperatures for the gas sensors with highly integrated design and low power consumption. The response of the Nb2O5/SnO2 core-shell nanorods gas sensor deposited with 20 nm SnO2 shell towards 20 ppm H2S at 275 °C was 4.0, which showed a 3.8-fold of improvement compared with pristine Nb2O5 nanorods. Furthermore, the well-structured core-shell nanorods gas sensors maintained stable performance after three months, presenting long-term stability and repeatability. The proposed Nb2O5/SnO2 core-shell nanorods gas sensors demonstrate a potential strategy for the practical application in oil and gas drilling platforms and other industrial fields.

Toward high capacity and stable SnO2 hollow nanosphere electrode materials: A case study of Ni-substituted modification

To develop the urgent requirement for high-rate electrodes in next-generation lithium-ion batteries, SnO2-based negative materials have been spotlighted as potential alternatives. However, the intrinsic problems, such as conspicuous volume variation and unremarkable conductivity, make the rate capability behave badly at a high-current density. Here, to solve these issues, this work demonstrate a new and facile strategy for synergistically enhancing their cyclic stability by combining the advantages of Ni doping and the fabrication of hollow nanosphere. Specifically, the incorporation of Ni2+ ions into the tetragonal rutile-type SnO2 shells improves the charge transfer kinetics effectively, leading to an excellent cycling stability. In addition, the growth of surface grains on the hollow nanospheres are restrained after Ni doping, which also reduces the unexpected polarization of negative electrodes. As a result, the as-prepared Ni doped electrode delivers a remarkable reversible capacity of 712 mAh g-1 at 0.1 A g-1 and exhibits outstanding capacity of 340 mAh g-1 at 1.6 A g-1, about 2.58 times higher than that of the pure SnO2 hollow sample.

VO2(M)@SnO2 core–shell nanoparticles: Improved chemical stability and thermochromic property rendered by SnO2 shell

Vanadium dioxide (VO2) has been extensively studied as a thermochromic material for smart windows. However, the poor oxidation stability of VO2 hinders its practical applications. In this paper, to improve the oxidation stability of VO2, the core–shell VO2(M)@SnO2 nanoparticles are synthesized by a solvothermal method. The chemical stability experiments indicate that the SnO2 coating effectively protects VO2 nanoparticles from acid corrosion and oxidation. Moreover, the core–shell structure is proved to enhance the near-infrared modulation ability (ΔTNIR) without impairing the visible light transmittance by both experiments and calculations. The results suggest the promising application of VO2(M)@SnO2 nanoparticles in flexible smart windows and demonstrate that the inorganic optical coating is an effective way in enhancing durability and solar modulation ability of VO2 nanoparticles.

Thermal synthesis of Ga2O3/SnO2 core–shell nanowires and their structural characterization

Ga2O3 core–SnO2 shell nanowires were synthesized by thermal evaporation of the metallic sources (Ga, Sn) in a horizontal quartz tube furnace at atmospheric pressure and in an oxidizing atmosphere. Au thin layers and 200 ppm Au colloid were applied as growth catalyst of Ga2O3 nanowires in vapor–liquid–solid method. Then the SnO2 shells were grown on the Ga2O3 nanowires cores. The configuration with highly sensitive shell and a relatively low conductivity core should enhance the efficiency of sensors based on these materials. Such narrowing of conductive area where a depletion of the charge carriers may occur, should increase the sensitivity, response and recovery time. The structural and material composition characterization of nanowires was performed by X-ray diffraction, energy-dispersive X-ray and Raman spectroscopy. The lattice parameters and strain of SnO2 shell were calculated. Using the catalyst in the form of a 200 ppm Au colloid compared to Au thin film, Ga2O3/SnO2 nanowires more similar to the core–shell structures were obtained.

SnO2 shells-induced rich Co2+ sites and oxygen vacancies in FexCo3-xO4 nanocubes: Enhanced peroxymonosulfate activation performance for water remediation

Cobalt-based heterogeneous composites, as promising peroxymonosulfate (PMS) activators for water remediation, usually suffer from the less reactive sites and metal leakage unfavorable for environmental application. Herein, the well-designed FexCo3-xO4@SnO2 nanocubes are successfully constructed by calcinating Fe-Co prussian blue analogue coated with Sn(OH)Cl. The formation of SnO2 shells preserves the nanocubic microstructure of FexCo3-xO4 to enlarge the specific surface area and induces the generation of rich Co2+ and oxygen vacancy sites on the FexCo3-xO4 surface. The synergy of Co2+ sites and oxygen vacancies contributes to the efficient adsorption and activation of PMS molecules, resulting in the generation of sulfate and hydroxyl radicals as the dominant reactive species for bisphenol A removal. Through adjusting the thickness of SnO2 shells, the optimal composite, FexCo3-xO4@SnO2-2 exhibits the excellent catalytic performance for PMS-involved reaction as compared to the conventional iron/cobalt-based oxides. Moreover, SnO2 shells can effectively inhibit the metal ions leaching during catalytic reaction, which is of great significance for reducing the secondary pollution to water bodies. This study develops a new strategy to regulate the oxygen vacancy sites and inhibit the metal leaching of cobalt ferrites, offering a step forward in the design of high efficient and stable heterogeneous catalysts for water remediation.

Coating conductive polypyrrole layers on multiple shells of hierarchical SnO2 spheres and their enhanced cycling stability as lithium-ion battery anode

SnO2 has been considered as an attractive anode material for lithium-ion batteries. However, its poor cycling life due to dramatic volume change during cycling processes hinders its commercial application. Herein, a facile approach has been proposed to coat conductive polypyrrole layers on every shell of hierarchical SnO2 spheres with a hollow multishelled structure (SnO2@Ppy HoMS). The Ppy layers as a framework on every SnO2 shell can both improve the conductivity and maintain the structural integrity during charging-discharging processes. The composite with multishelled SnO2 as active material can enhance the energy density of the battery, and the voids between shells accommodate the volume expansion. Thanks to these merits, the SnO2@Ppy HoMS anode delivers excellent electrochemical performance, achieving impressive cycling stability of 782 mAh g−1 after 650 cycles at a current density of 0.25C and an ultra-rapid and stable charge–discharge performance of 580 mAh g−1 at 4C for 5000th cycles.

Tailoring the Void Space Using Nanoreactors on Carbon Fibers to Confine SnS2 Nanosheets for Ultrastable Lithium/Sodium-Ion Batteries.

Herein, a rational design of SnS2 nanosheets confined into bubble-like carbon nanoreactors anchored on N,S doped carbon nanofibers (SnS2 @C/CNF) is proposed to prepare the self-standing electrodes, which provides tunable void space on carbon fibers for the first time by introducing hollow carbon nanoreactors. The SnS2 @C/CNF provides the stable support with greatly enhanced ion and electron transport, alleviates aggregation and volume expansion of SnS2 nanosheets, and promotes the formation of abundant exposed edges and active sites. The volume balance between SnS2 nanosheets and hollow carbon nanoreactors is reached to accommodate the expansion of SnS2 during cycles by controlling the thickness of SnO2 shells, which achieves the best space utilization. The doping of N,S elements enhances the wettability of the carbon nanofiber matrix to electrolyte and Li ions and further improves the electrical conductivity of the whole electrode. Thus, the SnS2 @C/CNF benefits greatly in structural stability and pseudocapacitive capacity for improved lithium/sodium storage performance. As a result of these improvements, the self-standing SnS2 @C/CNF film electrodes exhibit the highly stable capacity of 964.8 and 767.6 mAh g-1 at 0.2 A g-1 , and excellent capacity retention of 87.4% and 82.4% after 1000 cycles at high current density for lithium-ion batteries and sodium-ion batteries, respectively.

Core/Shell Ag/SnO2 Nanowires for Visible Light Photocatalysis

This study presents core/shell Ag/SnO2 nanowires (Ag/SnO2NWs) as a new photocatalyst for the rapid degradation of organic compounds by the light from the visible range. AgNWs after coating with a SnO2 shell change optical properties and, due to red shift of the absorbance maxima of the longitudinal and transverse surface plasmon resonance (SPR), modes can be excited by the light from the visible light region. Rhodamine B and malachite green were respectively selected as a model organic dye and toxic one that are present in the environment to study the photodegradation process with a novel one-dimensional metal/semiconductor Ag/SnO2NWs photocatalyst. The degradation was investigated by studying time-dependent UV/Vis absorption of the dye solution, which showed a fast degradation process due to the presence of Ag/SnO2NWs photocatalyst. The rhodamine B and malachite green degraded after 90 and 40 min, respectively, under irradiation at the wavelength of 450 nm. The efficient photocatalytic process is attributed to two phenomenon surface plasmon resonance effects of AgNWs, which allowed light absorption from the visible range, and charge separations on the Ag core and SnO2 shell interface of the nanowires which prevents recombination of photogenerated electron-hole pairs. The presented properties of Ag/SnO2NWs can be used for designing efficient and fast photodegradation systems to remove organic pollutants under solar light without applying any external sources of irradiation.

TiO2 Hollow Spheres With Flower-Like SnO2 Shell as Anodes for Lithium-Ion Batteries

SnO2 is a promising anode material for lithium-ion batteries due to its high theoretical specific capacity and low operation voltage. However, its poor cycling performance hinders its commercial application. In order to improve the cycling stability of SnO2 electrodes, novel flower-like SnO2/TiO2 hollow spheres were prepared by facile hydrothermal method using carbon spheres as templates. Their flower-like shell and mesoporous structure highlighted a large specific surface area and excellent ion migration performance. Their TiO2 hollow sphere matrix and 2D SnO2 nano-flakes ensured good cycle stability. The electrochemical measurements indicated that novel flower-like SnO2/TiO2 hollow spheres delivered a high specific capacity, low irreversible capacity loss and superior rate performance. After 1,000 cycles at current densities of 200 mA g−1, the capacity of the flower-like SnO2/TiO2 hollow spheres was still maintained at 720 mAh g−1. Their rate capacity reached 486 mAh g−1 when the current densities gradually increase to 2,000 mA g−1.

Core-shell Fe3O4@SnO2 nanochains toward the application of radar-infrared-visible compatible stealth

Multiband-compatible stealth materials play an increasingly crucial role in the field of modern military defence because they can enable the targeted objects to dodge advance detection technologies. In this study, chain-like Fe3O4@poly(ethyleneglycol dimethacrylate-co-methacrylic acid) nanocomposites were constructed as precursors through the magnetic field-induced distillation precipitation polymerisation. Then, the liquid-phase seed-mediated growth method, together with subsequent calcination, was applied to introduce SnO2 shells and remove poly(ethyleneglycol dimethacrylate-co-methacrylic acid) shells, which led to the successful preparation of innovative core–shell Fe3O4@SnO2 nanochains. The unique microstructure and appropriate components endowed nanochains with multiple functional applications. The minimum reflection loss value was approximately −39.4 dB (5.67 GHz), exhibiting excellent microwave absorption performance. The possible microwave absorption mechanisms involve interfacial polarisation, space charge polarisation, natural resonance, and multiple reflections and scatterings. The optimal infrared reflectivity reached 0.64, 0.51, and 0.37 in three atmospheric windows, indicating outstanding infrared stealth performance, which was attributed to the intense infrared reflection of SnO2 shells. Furthermore, three nanochains showed different colours (dark green, brick red, and bright orange), revealing selection absorption for visible light. This can be attributed to the combined effect of visible responses of SnO2 shells along with Bragg diffraction from the periodic arrangement of Fe3O4 particles in a single nanochain. Thus, core-shell Fe3O4@SnO2 nanochains can be considered as promising radar-infrared-visible compatible stealth materials. This discovery opens a new means to exploit multiband-compatible stealth materials.

Selective CO gas sensing by Au-decorated WS2-SnO2 core-shell nanosheets on flexible substrates in self-heating mode

The effect of shell thickness and noble metal decoration on the gas-sensing characteristics of two-dimensional (2D) materials has not been reported yet. Herein, we synthesized 2D pristine and Au-decorated WS2-SnO2 core-shell nanosheets (Au NSs). SnO2 shells with various thicknesses (up to 60 nm) were deposited on the WS2 NSs. Subsequently, Au was deposited on the synthesized WS2-SnO2 core-shell NSs (WS2-SnO2 NSs) under UV irradiation. Flexible polyamide substrates were used to fabricate gas sensors, which operated in self-heating mode upon applying different voltages for CO detection. Bare and Au-decorated gas sensors with shell thicknesses of 15 and 30 nm revealed the highest CO sensing performance at a low voltage of 3.4 V. The flexibility of the gas sensors was demonstrated by the negligible degradation of the sensing performance after 10,000 bending cycles. We also evaluated the sensing characteristics under humid conditions. The developed gas sensors with very low applied voltage and high performance for CO gas sensing are very promising for commercial applications.

Synthesis of porous Fe3O4-SnO2 core-void-shell nanocomposites as high-performance microwave absorbers

Porous Fe3O4-SnO2 core-void-shell nanocomposites with a porous Fe3O4 core and urchin-like SnO2 shell have been fabricated through the combined processes of modified stobber method with hydrothermal deposition technique. These nanocomposites can be maximize the interface areas between the core and shell that consume higher microwave energy, with the goal of improving the microwave absorption performance, i.e., of achieving strong reflection loss and wide effective bandwidth. The surface area and pore width distribution confirmed the mesoporous morphology of the porous Fe3O4-SnO2 core-void-shell nanocomposites. The microwave absorption analysis shows that the present porous Fe3O4-SnO2 core-void-shell nanocomposites with lower amount (30 wt%) in paraffin wax matrix exhibit very strong reflection loss peak of −66.5 dB (6.8 GHz) with the 3 mm absorber thickness, and have a wide effective absorbing bandwidth of 5.6 GHz (10.2–15.8 GHz). The high performance of nanocomposites can be attributed to the porous core-shell structure together with the void space. The interspace between the core and the shell can induce multiple reflections, interfacial polarization and even microwave plasma. Thus, we believe that a controlled porous structure in Fe3O4-SnO2 core-void-shell nanocomposites constitutes a novel approach to attain high-performance microwave absorbers in the field of electromagnetic wave absorption.

Novel Doughnutlike Graphene Quantum Dot-Decorated Composites for High-Performance Li–S Batteries Displaying Dual Immobilization Toward Polysulfides

Emerging materials for high-performance Li–S batteries are of great significance. Here, we develop a unique doughnutlike graphene quantum dot (GQD)/Fe2O3@S@SnO2 composite for Li–S batteries. The GQDs are confined inside the yolk–shell structure, which could shorten the pathway for electron and ion transport, enhancing the utilization of sulfur and achieving an energy-storage performance. Both the Fe2O3 core and SnO2 shell display strong binding with Li2S4, Li2S6, and Li2S8, which is verified by using density functional theory calculations. The doughnutlike GQD/Fe2O3@S@SnO2-based Li–S battery displays a capacity of 923 mAh g–1 after cycling 100 times, an ≈100% Coulombic efficiency, and a recoverable rate performance after repeated measurements. The constructed battery possesses a good tolerance at a high temperature of 45 °C. These findings would enable the doughnutlike yolk–shell design to be broadly applied for developing other emerging high-performance materials and their secondary batteries.

Improved Photoresponse Characteristics of a ZnO-Based UV Photodetector by the Formation of an Amorphous SnO2 Shell Layer

Although ZnO nanostructure-based photodetectors feature a well-established system, they still present difficulties when being used in practical situations due to their slow response time. In this study, we report on how forming an amorphous SnO2 (a-SnO2) shell layer on ZnO nanorods (NRs) enhances the photoresponse speed of a ZnO-based UV photodetector (UV PD). Our suggested UV PD, consisting of a ZnO/a-SnO2 NRs core–shell structure, shows a rise time that is 26 times faster than a UV PD with bare ZnO NRs under 365 nm UV irradiation. In addition, the light responsivity of the ZnO/SnO2 NRs PD simultaneously increases by 3.1 times, which can be attributed to the passivation effects of the coated a-SnO2 shell layer. With a wide bandgap (~4.5 eV), the a-SnO2 shell layer can successfully suppress the oxygen-mediated process on the ZnO NRs surface, improving the photoresponse properties. Therefore, with a fast photoresponse speed and a low fabrication temperature, our as-synthesized, a-SnO2-coated ZnO core–shell structure qualifies as a candidate for ZnO-based PDs.

Engineering Bimetallic Copper‐Tin Based Core‐Shell Alloy@Oxide Nanowire as Efficient Catalyst for Electrochemical CO2 Reduction

AbstractPursuing both high effective and selective electrocatalysts is significant for efficient and low‐cost electrochemical carbon dioxide (CO2) reduction. Here, we design a novel bimetallic alloy/oxide nanowire catalyst with core‐shell configuration. A typical CuSn alloy core provides high electrical conductivity while the amorphous Cu doped SnO2 shell guarantees the catalytic activity and selectivity for CO2 reduction process. Computational studies further elucidate the important role of Cu doped SnO2 layer in the electrocatalytic selectivity for formate and the restraint of hydrogen production. Benefited from the well‐designed components and hierarchical configuration, the as‐prepared electrocatalyst displays a partial current density of 30 mA cm−2 with a Faradaic efficiency of 78 % at −0.9 V vs. reversible hydrogen electrode (RHE) for formate. This work provides a new pathway to design advanced electrocatalyst for CO2 electrochemical reduction.