A novel and facile route of ink-jet printing to thin film SnO2 anode for rechargeable lithium ion batteries

Thin film SnO₂ electrode has been prepared for the first time by using a novel facile and low-cost ink-jet printing technique. Wet ball-milling was employed to stabilize SnO₂ nano particles and conducting agent acetylene black (AB) using two kinds of polymeric hyperdispersants CH10B and CH12B, respectively, to prepare the stable colloid as “ink”. The morphology, structure, composition and electrochemical performance of SnO₂ thin film electrodes were investigated in detail by SEM, TEM, XRD, EDX, cyclic voltammograms (CV) and galvanostatic charge-discharge measurements. SEM images show uniform distribution of as-printed SnO₂ thin film electrodes. The thickness of monolayer thin film electrode was about 770-780 nm by TEM observation. The thickness of SnO₂ thin film could be increased by repeating the printing procedure on the Cu foil substrate. The average thickness of 10-layer SnO₂ thin-film electrode after compression for electrochemical measurement was about 2.3 μm. High initial discharge capacity about 812.7 mAh/g was observed at a constant discharge current density of 33 μA/cm² in a potential range of 0.05-1.2 V. It is expected that ink-jet printing is a very feasible, simple, convenient and inexpensive way to prepare thin film electrode for lithium ion batteries.     

Semiconductor oxide based electrodes for the label-free electrical detection of DNA hybridization: Comparison between Sb doped SnO2 and CdIn2O4

First results are reported regarding the design, fabrication and operation of a DNA biochip based on a semiconductor oxide electrode that employs label-free electrical detection of the DNA hybridization. The same process of DNA functionalisation, including hydroxylation and silanization steps, was performed on two types of semiconductor oxide: Sb doped SnO₂ and CdIn₂O₄ thin films. These oxide electrodes were laboratory-made films deposited on glass substrates using a chemical vapour deposition method, i.e. the aerosol pyrolysis technique. After having characterized some physico-chemical properties of the bare films, the label-free electrical DNA hybridization detection, without redox couple labelling, was performed using electrochemical impedance spectrometry (EIS) before and after hybridization. On both oxides, over a large frequency range, a significant increase in the impedance modulus was obtained. The increase in the case of CdIn₂O₄ was by a factor of 2.1 ± 0.5 and in the case of Sb doped SnO₂ was by a factor of 1.6 ± 0.1. This phenomenon was especially marked on CdIn₂O₄ thin films, which exhibit a higher sensitivity to the surface event. The DNA hybridization to complementary DNA targets labelled with fluorescent markers was confirmed using fluorescence microscopy.     

Graphene-supported SnO2 nanoparticles prepared by a solvothermal approach for an enhanced electrochemical performance in lithium-ion batteries

SnO₂ nanoparticles were dispersed on graphene nanosheets through a solvothermal approach using ethylene glycol as the solvent. The uniform distribution of SnO₂ nanoparticles on graphene nanosheets has been confirmed by scanning electron microscopy and transmission electron microscopy. The particle size of SnO₂ was determined to be around 5 nm. The as-synthesized SnO₂/graphene nanocomposite exhibited an enhanced electrochemical performance in lithium-ion batteries, compared with bare graphene nanosheets and bare SnO₂ nanoparticles. The SnO₂/graphene nanocomposite electrode delivered a reversible lithium storage capacity of 830 mAh g⁻¹ and a stable cyclability up to 100 cycles. The excellent electrochemical properties of this graphene-supported nanocomposite could be attributed to the insertion of nanoparticles between graphene nanolayers and the optimized nanoparticles distribution on graphene nanosheets.     

Tin oxide nanosensor fabrication using AC dielectrophoretic manipulation of nanobelts

Nanobelts are a new class of semiconducting metal oxide nanowires. The ribbon-like nanobelts are chemically pure and structurally uniform single crystals, with clean, sharp, smooth surfaces, and rectangular cross-sections. Positive and negative dielectrophoresis (DEP) was demonstrated for the first time on semiconducting oxide nanobelts. This effect was then used for the fabrication of a nanodevice, which consisted of SnO₂ nanobelts attached to castellated gold electrodes defined on a glass substrate, and covered by a microchannel. The SnO₂ nanobelts (width ∼ 100-300 nm, thickness ∼ 30-40 nm) were suspended in ethanol and introduced into the microchannel. An alternating (AC) voltage of ∼9.8 V peak to peak, with variable frequency, was applied between the electrodes (minimum electrode gap ∼ 20 μm), which corresponds to an average electric field strength of less than 2.5 × 10⁵ V/m. In the 10 Hz-1 kHz range, repulsion between the nanobelts and the electrodes occurred, while in the 1-10 MHz range, attraction was observed. Once the nanobelts touched the electrodes, those that were sufficiently long bridged the electrode gaps. The device was characterized and can potentially be used as a nanosensor.     

NiO-based composite electrode with RuO2 for electrochemical capacitors

NiO/RuO₂ composite materials were prepared for use in electrochemical capacitors (ECs) by co-precipitation method followed by heat treatment. X-ray diffraction (XRD) spectra indicated that no new structural materials were formed and ruthenium oxide particles were coated by NiO particles. RuO₂ partly introduced into NiO-based electrode had improved its electrochemical performance and capacitive properties by using electrochemical measurements. A maximum specific capacitance of 210 F/g was obtained for NiO-based composite electrode with 10 wt.% RuO₂ in the voltage range from −0.4 to 0.5 V in 1 mol/l KOH solution. By comparison of effect of modified modes on the specific capacitance, chemically modified composite electrodes had more stable cycling properties than those of physically modified electrodes. After 200 cycles, specific capacitance of NiO-based chemical composite electrode with 5 wt.% RuO₂ kept 95% above, while that of physical electrode was only 79% of initial specific capacitance.     

Synthesis of SnO2/Mg2SnO4 nanoparticles and their electrochemical performance for use in Li-ion battery electrodes

Uniform crystalline MgSn(OH)₆ nanocubes were synthesized by a hydrothermal method. The influences of reaction conditions were investigated and the results showed that the solvent constituents significantly affected the shape and size of MgSn(OH)₆·SnO₂/Mg₂SnO₄ has been obtained by thermal treatment at 850 °C for 8 h under a nitrogen atmosphere using MgSn(OH)₆ as the precursor. The electrochemical tests of SnO₂/Mg₂SnO₄ revealed that SnO₂/Mg₂SnO₄ has a higher capacity and better cyclability compared to pure SnO₂ or Mg₂SnO₄. The electrochemical performance of SnO₂/Mg₂SnO₄ was sensitive to the size of the nanoparticles. The lithium-driven structural and morphological changes of the electrode after cycling were also studied by the ex-situ XRD pattern and TEM tests. This work indicates that SnO₂/Mg₂SnO₄ is a promising anode material candidate for application in Li-ion batteries.     

Structure and properties of PbO2-CeO2 anodes on stainless steel

The lack of ideal anodes with excellent activity and stability is one of the critical problems in electrochemical oxidation for organic wastewater treatment. It is reported in this paper that the PbO₂-CeO₂ films electrodeposited on stainless steel were used as catalytic electrodes for treating antibiotic wastewater. The PbO₂-CeO₂ films on stainless steel were proved to be high stability, good activity and relatively low cost. Because of these properties, the films are more attractive than any other electrocatalytic materials among conventional dimensionally stable anodes (DSA). Experimental results showed that the PbO₂-CeO₂ electrode has a service life of 1100 h in 3 M H₂SO₄ solution under a current density of 1 A cm⁻² at 35 °C, compared with 300 h for PbO₂ under the same conditions. The X-ray diffraction (XRD) patterns and SEM images indicated that the PbO₂-CeO₂ films on stainless steel have a dense structure and the preferred crystalline orientation on the substrate surface was changed. Color and chemical oxygen demand (COD) of antibiotics wastewater were studied by electrolysis by using these electrodes as anode and stainless steel as cathode. The results indicated that the anodes have excellent activity in antibiotic wastewater treatment. The PbO₂-CeO₂ electrodes have high chemical stability which contributed by the superstable nature of the electrode, dense microstructure, good conductivity and the improvement of bonding with the stainless steel during electrodeposition.     

Synthesis, structure and photoelectrochemical performance of micro/nano-textured ZnO/eosin Y electrodes

Micro/nano-textured ZnO thick films were synthesized through deposition and pyrolysis of layered hydroxide zinc acetate (LHZA), Zn₅(OH)₈(CH₃COO)₂·2H₂O. LHZA films having a unique, rose-like morphology were initially deposited on conducting glass sheets in a chemical bath composed of methanol and zinc acetate dihydrate at 60 °C under neutral conditions. Pyrolysis of the LHZA films resulted in formation of ZnO without destroying the original morphology. Pyrolysis temperatures were found to greatly influence grain sizes and specific surface areas of the ZnO films. Photoelectrochemical performance of the films as ZnO/eosin Y electrodes was investigated in dye-sensitized solar cells using an I⁻/I₃⁻ redox electrolyte solution. The cell using the ZnO film pyrolyzed at 150 °C exhibited overall light to electricity conversion efficiencies of 2.0 and 3.3% under an AM-1.5 illumination at 100 and 10 mW cm⁻², respectively. While microscale pores in the electrodes facilitated mass transfer of fluid electrolytes in the depth direction, nanoscale pores contributed to an increase in the amount of adsorbed dye. The maximum incident photon-to-current conversion efficiency (IPCE) of the electrode reached 84.9% at a wavelength of 530 nm.     

Solvothermal synthesis of SnO2/graphene nanocomposites for supercapacitor application

A facile solvent-based synthesis route based on the oxidation–reduction reaction between graphene oxide (GO) and SnCl₂·2H₂O has been developed to synthesize SnO₂/graphene (SnO₂/G) nanocomposites. The reduction of GO and the in situ formation of SnO₂ nanoparticles were achieved in one step. Characterization by X-ray diffraction (XRD), ultraviolet-visible (UV–vis) absorption spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FESEM) confirmed the feasibility of using the solvothermally treated reaction system to simultaneously reduce GO and form SnO₂ nanoparticles with an average particle size of 10 nm. The electrochemical performance of SnO₂/graphene showed an excellent specific capacitance of 363.3 F/g, which was five-fold higher than that of the as-synthesized graphene (68.4 F/g). The contributing factors were the synergistic effects of the excellent conductivity of graphene and the nanosized SnO₂ particles.     

Structural and electrochemical characterization of SnOx thin films for Li-ion microbattery

SnO_x thin films were prepared by reactive radio frequency magnetron sputtering with different sputtering powers. X-ray photoelectron spectroscopy suggested that all the films have similar chemical stoichiometry as SnO_1.5. X-ray diffraction and transmission electro microscopy results showed that crystal size of the SnO_x thin films gradually increases with increase of sputtering power from 50 to 150 W. Cyclic voltammetry and galvanostatic charge/discharge cycling measurements indicated that the electrochemical properties of SnO_x films strongly rely on their crystal sizes as well as surface morphologies. The SnO_x film deposited at sputtering power of 120 W exhibits the best electrochemical performances. It could deliver a reversible capacity of 670 μAh cm⁻² μm⁻¹ at 50 μA cm⁻² in the voltage range of 0.1-1.2 V up to 50 cycles.     

Properties of sol-gel SnO2/TiO2 electrodes and their photoelectrocatalytic activities under UV and visible light illumination

A visible light active binary SnO₂-TiO₂ composite was successfully prepared by a sol-gel method and deposited on Ti sheet as a photoanode to degrade orange II dye. Titanium and SnO₂ can promote the development of rutile phase of TiO₂ and inhibit the formation of anatase phase of TiO₂. Formation of SnO₂ crystalline is insignificant even when the calcination temperature increases to 700 °C. Heterogenized interface between SnO₂ and TiO₂ inhibits growth of TiO₂ linkage and leads to the particle-filled surface morphology of SnO₂-containing films. The carbonaceous, Ti-O-C bonds and Ti³⁺ species are likely to account for the photoabsorption and photoelectrocatalytic (PEC) activity under visible light illumination. The electrode with 30% SnO₂ exhibits higher photocurrent when compared with those in the region of 0-50%. The 600 °C-calcined SnO₂-TiO₂ electrode indicates higher activity when compared with those at 400, 500, 700 and 800 °C. PEC degradation of orange II follows the Langmuir-Hinshelwood model and takes place much effectively in a solution of pH 3.0 than those in pH 7.0 and pH 11.0.     

In situ fabrication of spherical porous tin oxide via a spray pyrolysis technique

Spherical porous tin oxide was fabricated via a spray pyrolysis technique. TEM revealed that the primary SnO₂ crystals had an average size of 5-10 nm. Good interconnection between SnO₂ crystals is also observed. The electrochemical measurements showed that the spherical porous SnO₂ samples have excellent cyclability, which can deliver a reversible capacity of 410 mAh/g for up to 50 cycles as a negative electrode for lithium batteries. Our approach for enhancing the structural stability of tin oxide is to incorporate spherical porous structures as a buffer zone to alleviate the volume expansion of the tin oxide anode during lithiation/delithiation.     

Enhanced inactivation of E. coli bacteria using immobilized porous TiO2 photoelectrocatalysis

Immobilized TiO₂ nanotube electrodes with high surface areas were grown via electrochemical anodization in aqueous solution containing fluoride ions for photocatalysis applications. The photoelectrochemical properties of the grown immobilized TiO₂ film were studied by potentiodynamic measurements (linear sweep voltammetry), in addition to the calculation of the photocurrent response. The nanotube electrode properties were compared to mesoporous TiO₂ electrodes grown by anodization in sulfuric acid at high potentials (above the microsparking potential) and to 1 g/l P-25 TiO₂ powder. Photocatalyst films were evaluated by high resolution SEM and XRD for surface and crystallographic characterization. Finally, photoelectrocatalytic application of TiO₂ was studied via inactivation of E. coli. The use of the high surface area TiO₂ nanotubes resulted in a high photocurrent and an extremely rapid E. coli inactivation rate of ∼10⁶ CFU/ml bacteria within 10 min. The immobilized nanotube system is proven to be the most potent electrode for water purification.     

Preparation of Ti/SnO2-Sb2O4 photoanode by electrodeposition and dip coating for PEC oxidations

Thin films of antimony-doped SnO₂ on titanium substrate with a doping range of 1.5-8 mol% were prepared by an electrodeposition and dip coating method. The prepared Ti/SnO₂-Sb₂O₄ thin films were tested as a photoanode in the photoelectrocatalytic(PEC) experiments to degrade phenol in aqueous solution in order to evaluate their PEC performance. The photocatalytic (PC), electrocatalytic (EC) and PEC activity of Ti/SnO₂-Sb₂O₄ thin films was compared in the degradation processes. And the effect of annealing temperature on their PEC activity was also investigated. The experimental results confirmed that the Sb-doped Ti/SnO₂ thin films enhanced the phenol degradation and the Ti/SnO₂-Sb₂O₄ film containing 6 mol% of Sb calcinated at 450 °C achieved the best performance for phenol degradation. The degradation experiments also demonstrated that the Ti/SnO₂-Sb₂O₄ film achieved faster degradation of phenol in the PEC process than in the PC and EC processes. Compared with Ti/TiO₂ and Ti/SnO₂ photoanodes, the Ti/SnO₂-Sb₂O₄ photoanode showed higher activity.     

Synthesis and characterization of highly stable optically passive CeO2-ZrO2 counter electrode

Transparent and adherent CeO₂-ZrO₂ thin films having film thicknesses ∼543-598 nm were spray deposited onto the conducting (fluorine doped tin oxide coated glass) substrates from a blend of equimolar concentrations of cerium nitrate hexahydrate and zirconium nitrate having different volumetric proportions (0-6 vol.% of Zr) in methanol. CeO₂-ZrO₂ films were polycrystalline with cubic fluorite crystal structure and the crystallinity was improved with increasing ZrO₂ content. Films were highly transparent (T ∼ 92%), showing decrease in band gap energy from 3.45 eV for pristine CeO₂ to 3.08-3.14 eV for CeO₂-ZrO₂ films. The different morphological features of the film obtained at various CeO₂-ZrO₂ compositions had pronounced effect on the ion storage capacity and electrochemical stability. CeO₂-ZrO₂ film prepared at 5 vol.% Zr concentration exhibited higher ion storage capacity of 24 mC cm⁻² and electrochemical stability of 10,000 cycles in 0.5 M LiClO₄ + PC electrolyte due to its film thickness (584 nm) coupled with relatively larger porosity (8%). The optically passive behavior of such CeO₂-ZrO₂ film (with 5 vol.% Zr) is affirmed by its negligible transmission modulation irrespective of repeated Li⁺ and electron insertion/extraction. The coloration efficiency of spray deposited WO₃ thin film is found to enhance from 47 to 107 cm² C⁻¹ when CeO₂-ZrO₂ is coupled as a counter electrode with WO₃ in an electrochromic device (ECD). These films can be used as stable ‘passive’ counter electrodes in electrochromic smart windows as they retain full transparency in both the oxidized and reduced states and ever-reported longevity.     

Design and electrochemical study of SnO2-based mixed oxide electrodes

For the electrochemical treatment of wastewater, it is critical to develop electrodes with a high activity for the oxidation of pollutants, long lifetimes, and low cost. In the present study, we have fabricated four different SnO₂-based electrodes (Ti/SnO₂-Sb₂O₅, Ti/SnO₂-Sb₂O₅-PtO_x, Ti/SnO₂-Sb₂O₅-RuO₂ and Ti/SnO₂-Sb₂O₅-IrO₂) using the thermal decomposition method and, for the first time, systemically studied their stability and electrocatalytic activity towards the degradation of 2-nitrophenol (2-NPh), 3-nitrophenol (3-NPh) and 4-nitrophenol (4-NPh). Scanning electron microscope (SEM) and X-ray energy dispersive spectrometry (EDS) were used to characterize the morphology and composition of the four different SnO₂-based electrocatalysts. Lifetime tests show that doping IrO₂ or RuO₂ greatly improves the stability of the SnO₂-based electrodes. The electrochemical activities of the prepared SnO₂-based electrodes were characterized using the degradation of 2-NPh, 3-NPh and 4-NPh. In situ UV/vis spectroscopy was used to monitor the concentration changes of the nitrophenols with time showing that the rate constants for the electrochemical oxidation of the nitrophenols decrease in the order of: 2-NPh > 4-NPh > 3-NPh. The effect of the applied current densities and initial concentrations of nitrophenols have also been investigated. Our study has shown that the fabricated Ti/SnO₂-Sb₂O₅-IrO₂ electrodes are very promising for the electrochemical treatment of wastewater.     

Preparation of micro-dot electrodes of LiCoO2 and Li4Ti5O12 for lithium micro-batteries

Fabrications of micro-dot electrodes of LiCoO₂ and Li₄Ti₅O₁₂ on Au substrates were demonstrated using a sol-gel process combined with a micro-injection technology. A typical size of prepared dots was about 100 μm in diameter, and the dot population on the substrate was 2400 dots cm⁻². The prepared LiCoO₂ and Li₄Ti₅O₁₂ micro-dot electrodes were characterized with scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy, and cyclic voltammetry. The prepared LiCoO₂ and Li₄Ti₅O₁₂ micro-dot electrodes were evaluated in an organic electrolyte as cathode and anode for lithium micro-battery, respectively. The LiCoO₂ micro-dot electrode exhibited reversible electrochemical behavior in a potential range from 3.8 to 4.2 V versus Li/Li⁺, and the Li₄Ti₅O₁₂ micro-dot electrode showed sharp redox peaks at 1.5 V.     

Mn3O4 nanoparticles embedded into graphene nanosheets: Preparation, characterization, and electrochemical properties for supercapacitors

Mn₃O₄/graphene nanocomposites were synthesized by mixing graphene suspension in ethylene glycol with MnO₂ organosol, followed by subsequent ultrasonication processing and heat treatment. The as-prepared product consists of nanosized Mn₃O₄ particles homogeneously distributed on graphene nanosheets, which has been confirmed by field emission scanning electron microscopy and transmission electron microscopy analysis. Atomic force microscope analysis further identified the distribution of dense Mn₃O₄ nanoparticles on graphene nanosheets. When used as electrode materials in supercapacitors, Mn₃O₄/graphene nanocomposites exhibited a high specific capacitance of 175 F g⁻¹ in 1 M Na₂SO₄ electrolyte and 256 F g⁻¹ in 6 M KOH electrolyte, respectively. The enhanced supercapacitance of Mn₃O₄/graphene nanocomposites could be ascribed to both electrochemical contributions of Mn₃O₄ nanoparticles, functional groups attached to graphene nanosheets, and significantly increased specific surface area.     

Stable spinel type cobalt and copper oxide electrodes for O2 and H2 evolutions in alkaline solution

The stability of one material, Ti/Cu_xCo_3−xO₄, as anode and also cathode was investigated for electrolysis of alkaline aqueous solution. The electrodes were prepared by thermal decomposition method with x varied from 0 to 1.5. The accelerated life test illustrated that the electrodes with x = 0.3 nominally showed the best performance, with a total service life of 1080 h recorded in 1 M NaOH solution under alternating current direction at 1 A cm⁻² and 35 °C. The effects of copper content in electrode coating were examined in terms of electrode stability, surface morphology, coating resistivity and coating compositions. The presence of Cu in the spinel structure of Co₃O₄ could significantly enhance the electrochemical and physicochemical properties. The trends of crystallographic properties and surface morphology have been analyzed systemically before, during and after the electrodes were employed in alkaline electrolysis. The oxygen evolution would lead to the consumption of the coating material and the progressive cracking of the coating. Along with hydrogen evolution, cobalt oxide could be reduced to metal Co and Co(OH)₂ with particle sizes changed to smaller values in crystal and/or amorphous form at the cathode. The formation of Co is the key process for this electrode to serve as both anode and cathode. It is also the main reason leading to the eventual failure of the electrodes.     

Synthesis of Zn2SnO4 anode material by using supercritical water in a batch reactor

Zn₂SnO₄ anode powders were successfully synthesized using supercritical water (SCW) and metal salt solutions with 10 min reaction time. Effect of NaOH concentration, Zn to Sn ratio, and synthesis temperature were studied with a SCW batch reactor. X-ray diffraction (XRD), scanning electron microscopy (SEM), and charge/discharge cycling tests were employed to characterize the physical properties and electrochemical performance of the as-prepared samples. Alkaline solution concentration and synthesis temperature played a key role in the production of single-phase Zn₂SnO₄ powders. At a solution concentration of 0.3 M NaOH and a molar ratio of Zn:Sn = 2:1 at 400 °C and 30 MPa, the average size range of the pure Zn₂SnO₄ powders was 0.5-1.0 μm, and the morphology was nearly uniform and cubic-like in shape. The initial specific discharge capacity of the Zn₂SnO₄ powders prepared at this condition was 1526 mAh/g at a current density of 0.75 mA/cm² in 0.05-3.0 V, and their irreversible capacity loss was 433 mAh/g. The discharge capacities of the Zn₂SnO₄ powders decreased with cycling and remained at 856 mAh/g after 50 cycles, which was 56% of the initial capacity.