Enhancement of thin film tin oxide negative electrodes for lithium batteries

Thin films of pure SnO₂, of the Sn/Li₂O layered structure, and of Sn/Li₂O were fabricated by sputtering method, while a `lithium-reacted tin oxide thin film' was assembled by the evaporation of lithium metal onto a SnO₂ thin film. Film structure and charge/discharge characteristics were compared. The lithium-reacted tin oxide thin film, the Sn/Li₂O layered structure, and the Sn/Li₂O co-sputtered thin films did not show any irreversible side reactions of forming Li₂O and metallic Sn near 0.8 V vs Li/Li⁺. The initial charge retention of the Sn/Li₂O layered structure and Sn/Li₂O co-sputtered thin films was about 50% and a similar value was found for the lithium-reacted tin oxide thin film (more than 60%). Sn/Li₂O layered structure and Sn/Li₂O co-sputtered thin films showed better cycling behavior over 500 cycles than the pure SnO₂ and lithium-reacted tin oxide thin film in the cut-off range from 1.2 to 0 V vs Li/Li⁺.     

Tin oxide dependence of the CO2 reduction efficiency on tin electrodes and enhanced activity for tin/tin oxide thin-film catalysts

The importance of tin oxide (SnO(x)) to the efficiency of CO(2) reduction on Sn was evaluated by comparing the activity of Sn electrodes that had been subjected to different pre-electrolysis treatments. In aqueous NaHCO(3) solution saturated with CO(2), a Sn electrode with a native SnO(x) layer exhibited potential-dependent CO(2) reduction activity consistent with previously reported activity. In contrast, an electrode etched to expose fresh Sn(0) surface exhibited higher overall current densities but almost exclusive H(2) evolution over the entire 0.5 V range of potentials examined. Subsequently, a thin-film catalyst was prepared by simultaneous electrodeposition of Sn(0) and SnO(x) on a Ti electrode. This catalyst exhibited up to 8-fold higher partial current density and 4-fold higher faradaic efficiency for CO(2) reduction than a Sn electrode with a native SnO(x) layer. Our results implicate the participation of SnO(x) in the CO(2) reduction pathway on Sn electrodes and suggest that metal/metal oxide composite materials are promising catalysts for sustainable fuel synthesis.     

Electrochemical synthesis and study of coordination compounds part 1: tin(II) catechol complexes

The electrochemical synthesis of tin(II) complexes of catechols, Sn(O₂Ar) (1a–9a), have carried out using tin metal as a sacrificial anode in acetonitrile, in the presence of catechol derivatives. The cyclic voltammetric characteristics of the synthesized complexes Sn(O₂Ar) (1a–9a) have been studied at glassy carbon electrode in dichloromethane. Anodic oxidation of Sn(O₂Ar) produces a single wave which shows irreversibility. Also, the electronic effects of ligands on the redox potential of complexes 1a–9a have been investigated. The synthesis of Sn(O₂Ar) species in high yields and purity has been successfully performed in an undivided cell using constant current conditions.     

Modification of a Pt surface by spontaneous Sn deposition for electrocatalytic applications

In the present communication we explored a simple dip-coating method for spontaneous (without applying an external current or additional reducing agents) modification of Pt surface by both tin oxy-species and tin metal based on hydrolysis of tin chloride complex and autocatalytic (electroless) deposition of tin for fabrication of the fuel cell catalysts with improved CO tolerance. It consisted of (i) Pt immersion into SnCl₂/HCl solution under open-circuit conditions; (ii) subsequent rinsing of the surface by pure water. The resulting Sn-modified Pt surfaces were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). Two types of tin species, namely, tin oxide/hydroxide species and metallic tin were identified at Pt surface. Tin oxide/hydroxide species were assumed to be derived as a result of Sn(II) chloride complex hydrolysis, while tin metal particles were most likely deposited spontaneously on Pt surface due to disproportionation of Sn(II) to Sn(IV) and metallic tin, competing with dissolution of the Sn deposit in strongly acidic medium. Modifying tin species show a satisfactory stability in 0.5-M H₂SO₄ solution at potentials relevant to low-temperature fuel cell operating conditions (below 0.6 V vs. a standard hydrogen electrode, SHE).     

Sulfonate-bonded tin complexes for the production of diphenyl carbonate

Various tin complexes including dibutyltin oxide and dibutyltin diacetate were tested for their activities in the transesterification between dimethyl carbonate (DMC) and phenol to produce diphenyl carbonate (DPC). The activities of tin complexes were significantly enhanced by the co-presence of alkyl or arylsulfonic acid, possibly due to the in situ formation of sulfonate-bonded tin complexes. Highly active triflate-bonded tin species, [Bu₂Sn(OH)(OTf)]₂ and [Bu₂Sn(OAc)(OTf)]₂, were isolated from the reaction of triflic acid with dibutyltin oxide and dibutyltin diacetate, and characterized by single crystal X-ray diffraction study.     

Alloying during codeposition of copper and tin out of silicofluoride electrolytes

A technique for obtaining binary Cu-Sn alloys containing 20–35 mol % Sn is proposed. The technique—the electrochemical deposition out of silicofluoride electrolytes—ensures a high deposition rate of coatings (25–50 μm h^?1). The formation of intermetallic compound Cu₁₀Sn₃ is found to occur at a high current density, in conditions of the tin reduction depolarization and the copper reduction superpolarization. The alloys consist of submicron grains. Apart from crystalline Cu₁₀Sn₃, they include x-ray-amorphous tin (2–12 mol %) and tin oxides (≤1–3 mol %). The alloys feature high hardness (4200 MPa), corrosion resistance, and solderability.     

A new way to prepare tin oxide precursor polymeric gels

Transparent tin oxide gels are elaborated in the isopropoxide/toluene/isopropanol system. The gelation occurs at room temperature without any acid or base additions. The formation of the SnO₂ precursor gels polymeric network is evidenced by Fourier transform infrared spectroscopy. The gelation time is studied as a function of the complexing ratio R = [acac]/[Sn(OR)₄], the hydrolysis ratio W = [H₂O]/[Sn(OR)₄], the concentration of tin oxide precursor C = [Sn(OR)₄], and the volume fraction of toluene P = (toluene volume) / (total solvent volume).     

Tin corrosion in highly acidic solutions containing ethylene glycol oligomers and halides: An electrochemical quartz crystal microbalance study

Tin corrosion in 1 M H₂SO₄ solutions containing 0.01 M Sn(II), 0.01 M ethylene glycol or its oligomers, and 30 μM of various halides is studied by the electrochemical quartz crystal microbalance method. The current density of the tin electrode corrosion is found to approach a few tens of μA cm^?2. In the presence of Sn(II), the current density is nearly half that in its absence. The corrosion potential steadily increases with time, approaching a certain limit. In solutions containing Sn(II), the limit practically corresponds to the equilibrium potential of the Sn/Sn²⁺ electrode. The corrosion rate barely depends on the oligomer nature even up to tetraethylene glycol. Halides accelerate the corrosion process. Their action intensifies at initial time instants (up to 15–20 min) in the series Cl^? < Br^? < I^?. The corrosion impedance equals ～1000 ohm cm². It may be ignored when analyzing the overall impedance of the tin electrode in the frequency region extending from 0.1 Hz to 50 kHz.     

Characterization of the patina formed on a low tin bronze exposed to aqueous hydrogen sulfide

The dark gray corrosion layer (patina) formed on the surface of a polished low tin bronze alloy following exposure to a deoxygenated and saturated aqueous solutions of H₂S has been characterized by X‐ray photoelectron spectroscopy, scanning electron microscopy‐energy dispersive spectroscopy and X‐ray diffraction. The system represents a model for bronze corrosion in reducing conditions where sulfate‐reducing bacteria in soils or deoxygenated seawater may generate H₂S during respiration. The initial surface was dominated by metallic copper together with Sn, Pb and Zn oxides and hydroxides. Surface enrichment of Pb and Zn was noted because of a smearing effect during polishing. At least some of the lead was crystalline. In contrast, the corrosion layer formed by H₂S(aq) exposure was dominated by polycrystalline Cu₂S (low and high chalcocite) and smaller concentrations of CuSO₄ · nH₂O. This surface was enriched with Zn as Zn(OH)₂. Lead was present as redeposited PbS (galena) crystallites in at least two different morphologies. Unlike bronzes exposed to oxidizing conditions, which develop protective SnO₂ layers, the H₂S(aq)‐exposed surface was considerably depleted in Sn. Copyright © 2014 John Wiley & Sons, Ltd.     

Hydrogen evolution reaction on Sn, In, and Sn–In alloys in carboxylic acids

The cathodic behavior of tin, indium, and tin–indium alloys in 0.5-M solutions of oxalic, malic, and citric acids has been investigated using potentiodynamic techniques at temperature range of 30–60 °C. The results showed that the corrosion rate (I _corr) is higher at lower indium percent (0.5% In) and starts to decrease gradually as increase of the In percent up to 5% In (although it is still higher than that of pure tin and lower than that of indium at 5% In) in all examined acids. The positive shift in corrosion potential with simultaneous increase in corrosion rate can be explained on the basis of the depolarizing action of β-InSn₄ phase compared with pure tin. The negative shift in the corrosion potential with much higher corrosion rate in case of alloys IV and V (10% and 20% In, respectively) can be ascribed to the formation of γ-In₃Sn phase which leads to the increase in the anodic to cathodic area ratio. The corrosion of the two investigated metals and their alloys is affected by the formation of soluble complex species with organic acid anions. The aggressiveness of the studied metals and their alloys decreases in the following order of the organic acids employed oxalic > malic > citric acid. The observed activation energy values support that the tested electrodes exhibit higher corrosion rates in oxalic acid solution than the corresponding values in the other investigated acids. X-ray diffraction and scanning electron microscopy photographs elucidated the types of phases formed in the prepared alloys. The presence of a definite amount of indium in tin alloy improves the hardness.     

Structure of hydrated tin dioxide doped with Sb(III) ions

The effect of antimony doping of tin dioxide at Sb/Sn = 0.2–2.5 on the physical properties and structure of air-dry samples of hydrous tin dioxide, SnO₂ ? nH₂O (HTD), was studied by IR and Raman spectroscopy, powder X-ray diffraction, impedance measurements, TGA, and electron microscopy. The doped materials retained the structure of undoped HTD materials if the Sb/Sn ratio did not exceed the threshold value of 1.0. When Sb/Sn > 1, crystalline antimony oxide admixture appeared. The data of IR spectroscopy attested to the presence of two types of water in HTD-Sb, namely, physisorbed and chemisorbed water. The major part of water of the former type can be removed by evacuation at room temperature. Chemisorption occurs upon coordination of water molecules by metal ions through the formation of metal–oxygen bonds. Water molecules of the latter type are retained in evacuated samples at room temperature and on heating above the boiling point of liquid water. By impedance spectroscopy, HTD-Sb samples were shown to possess fairly high proton conductivity at high humidity; however, the conductivity decreased by two orders of magnitude after partial removal of water molecules of the former type. This attests to the destruction of the loosely bound hydrogen bond network, across which proton transfer takes place. It was also found that under conditions of constant humidity, the proton conductivity successively decreases with increasing antimony concentration. This is attributable to the fact that Sb(III) ions polarize the local environment to a lesser extent than Sn(IV) ions.     

Study by grazing incident diffraction and surface spectroscopy of amalgams from ancient mirrors

Characterization of four amalgam surfaces, with different alteration degrees from Andalusia historical mirrors, has been carried out by grazing-incidence X-ray diffraction (GIXRD), and other spectroscopic techniques (SEM/EDX, XPS, and REELS). The combination of all these techniques allows determining the corrosion state of the amalgams. The results show that the amalgams are composed in all cases of a binary alloy of tin and mercury. As mercury has high vapour pressure at RT, it slowly segregates and eventually evaporates, it leaves finely divided particles of tin that easily can be oxidize, forming tin monoxide (SnO) and tin dioxide (SnO₂). In one of the samples, most of the amalgam remains unoxidized, since Hg_0.1Sn_0.9 and metallic Sn phases are the major components; in two other samples, Hg_0.1Sn_0.9 and Sn phases are not detected while SnO₂ and SnO phases appear. Finally, in the last studied sample, only SnO₂ phase is detected. The surface analyses of these samples by XPS show that, for most of them an unique chemical species (Sn⁴⁺) is found.      

Interferences in the determination of trace elements in high-purity tin

Reactor neutron activation analysis of antimony, indium and cadmium in high-purity tin is interfered with by nuclear reactions on the tin matrix. For a number of interfering reactions the cross-sections were determined. The following results were obtained:¹²²Sn(n,γ)^123mSn:σ_th=0.145 barn, I=0.79 barn;¹²²Sn(n,γ)¹¹³Sn:σ_th=0.52, I=25.4 barn;¹¹²Sn(n, 2n)¹¹¹Sn: microbarn;¹¹⁸Sn(n, α)¹¹⁵Cd: microbarn; and¹¹⁴Sn(n, p)^114m1In: microbarn.     

Indium oxide co-doped with tin and zinc: A simple route to highly conducting high density targets for TCO thin-film fabrication

Indium oxide co-doped with tin and zinc (ITZO) ceramics have been successfully prepared by direct sintering of the powders mixture at 1300 °C. This allowed us to easily fabricate large highly dense target suitable for sputtering transparent conducting oxide (TCO) films, without using any cold or hot pressing techniques. Hence, the optimized ITZO ceramic reaches a high relative bulk density (∼ 92% of In₂O₃ theoretical density) and higher than the well-known indium oxide doped with tin (ITO) prepared under similar conditions. All X-ray diagrams obtained for ITZO ceramics confirms a bixbyte structure typical for In₂O₃ only. This indicates a higher solubility limit of Sn and Zn when they are co-doped into In₂O₃ forming a solid-solution. A very low value of electrical resistivity is obtained for [In₂O₃:Sn_0.10]:Zn_0.10 (1.7 × 10⁻³ Ω cm, lower than ITO counterpart) which could be fabricated to high dense ceramic target suing pressure-less sintering.     

Determination of oxygen in tin metal by the amalgam method

In vacuum, tin metal is completely separated from stannous oxide by mercury. The tin content of the stannous oxide is then determined colonmetrically by an improved blue phosphomolybdate solution technique; and from the tin result, the oxygen is calculated. The procedure is satisfactory for the determination of oxygen concentrations of 0.0001 % or less in tin metal samples weighing 2-5 mg.The apparatus developed for the vacuum preparation and treatment of the amalgam is described.     

Semiconducting tin oxide electrodes in molten sodium chloroaluminate at 175°C

Electrode behavior of Sb-doped poly-crystalline tin oxide electrodes has been investigated by means of current and differential capacity measurements in molten chloroaluminate melts (AlCl₃+NaCl) with different pCl values. The SnO₂ is stable in the melts consisting of near equimolar composition, being used as an indicator electrode possessing a polarizable potential region between chlorine evolution and its cathodic decomposition. The differential capacity is assigned to the space charge layer capacity of the electrode side and its potential dependence is explained by using the Mott-Schottky equation. It is found that the flat band potential does depend on pCl (=?log a_Cl^?) at a rate of 2(2.3kT/e) per pCl unit. This anomaly is attributed to the specific adsorption of Cl^? ions on the oxide electrode.     

Anodic passivation of tin in buffered phosphate electrolyte

The anodic behaviour of tin in buffered phosphate electrolyte (pH=3.1) has been studied by a variety of techniques. A number of anodic processes occur depending on potential and the conditions at the electrode/electrolyte interphase. On anodic polarisation the electrode, which is probably filmed with a phosphate layer, initially undergoes dissolution to form probably Sn(H₂PO₄·HPO₄)^? species. Impedance data indicate that this process has a corresponding Tafel slope of ～0.046 V/decade. At more positive potentials three consecutive passivating processes occur.The primary passivating process involves the blocking of the electrode by Sn₃(PO₄)₂ by a dissolution-precipitation mechanism. The formation of SnO by a slow three dimensional nucleation and growth process constitutes the second. It is formed as a result of the attainment of alkaline conditions at the electrode surface. There is also a parallel reaction path involving the formation of soluble Sn(II) species. The tertiary process consists of the oxidation of Sn to Sn(IV) species. Passivation occurs via a dissolution-precipitation mechanism when the electrode is blocked by SnO₂. The relative quantities of SnO and SnO₂ produced is a function of operating conditions.     

New tin(IV) complexes with sterically hindered o‐iminobenzoquinone ligand: Synthesis and structure

The reduction of 4,6‐di‐tert‐butyl‐N‐(2, 6‐di‐iso‐propylphenyl)‐o‐iminobenzoquinone (imQ) by tin amalgam in hexane solution leads to new six‐coordinated o‐iminoquinonato tin(IV) complex (iSQ)₂SnAP ( 1 ) (where iSQ and AP are o‐iminosemiquinolate and dianion o‐amidophenolate, respectively). Variable temperature magnetic susceptibility measurements of 1 have shown that this complex possesses a weak ferromagnetic exchange between o‐iminosemiquinonate ligands. The oxidation of 1 with air oxygen produces new o‐iminoquinonolate tin(IV) derivatives [(iSQ)Sn(AP)]₂O ( 2 ) and (iSQ)₂Sn(OH)₂ ( 3 ) containing μ‐oxo‐ and hydroxo‐ligands, respectively. The electronic structure of 1 was examined by DFT analysis. Complexes 1–3 have been investigated using single‐crystal X‐ray diffraction. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:332–340, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20555     

Electrochemical behaviour of tin in alkaline electrolyte

The electrochemical behaviour of two types of tin electrodes, Sn rod and electrodeposited Sn is investigated in 0.1 M KOH_aq in order to evaluate processes related to anodic Sn dissolution. Potential regions of formation of soluble Sn(II) and Sn(IV) are identified by means of a rotating ring disk electrode. An anodic reactivation peak observed for cathodic potential scans for partially passivated electrodes is accompanied by formation of soluble Sn(II) species and a minimum in the imaginary part of the impedance. This confirms that the reactivation peak is due to active dissolution of metallic Sn exposed to the electrolyte during rupture of the oxidised layer.     

Synthesis of radioactive tributyl[113Sn]tin of high specific activity for use in environmental fate studies

A method of synthesis of tributyl[¹¹³Sn]tin,­(n/C₄H₉)₃¹¹³Sn(IV), from commercially avail-­able inorganic ¹¹³Sn(IV) is presented. Inorganic tin is first extracted in diethyl ether and reacted with C₄H₉MgCl to produce tetrabutyltin, (C₄H₉)₄¹¹³Sn, which is then debutylated with HgCl₂. The resulting tributyl[¹¹³Sn]tin chloride is isolated from the reaction mixture by successive extractions with hexane and aqueous Na₂S₂O₃. The yield is 40–60% and the product obtained is >98% pure. It has the same specific activity as the starting ¹¹³Sn(IV), i.e. up to 550 MBq mg⁻¹ Sn, making it suitable for use in environmental fate and toxicology studies at concentrations relevant of those found in the aquatic environment. © 1998 John Wiley & Sons, Ltd.