Investigation of Structural Evolution of SnO2 Nanosheets towards Electrocatalytic CO2 Reduction

In‐depth understanding of the catalytic active sites is of paramount importance for the design of efficient electrocatalysts for CO₂ conversion. Here we highlight the structural evolution of SnO₂ nanosheets for electrocatalytic CO₂ reduction. The transformation of SnO₂ into metallic Sn would occur on the surface of catalyst during the catalytic process, followed by enhanced selectivity and activity for the conversion of CO₂ to HCOOH. Electrocatalytic characterization and structural analysis demonstrate that the metallic Sn derived from structural evolution plays a dominant role in the CO₂ reduction to HCOOH. This work deepens the understanding of the catalytic mechanism and provides a new pathway for the rational design of advanced electrocatalysts for CO₂ reduction.     

Transparent titania nanotubes of micrometer length prepared by anodization of titanium thin film deposited on ITO

Transparent TiO₂ nanotube arrays of micrometer lengths were prepared by anodization of titanium thin film RF sputtered on indium tin oxide (ITO) which was coated on glass substrate. The sputtering process took place at elevated temperature of 500 °C. The structures of the films were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD) while the optical properties of the films were investigated using UV-visible spectroscopy. Two types of electrolytes were used in this work: an aqueous mixture of acetic acid and HF solution and a mixture of NH₄F and water dissolved in ethylene glycol. The concentration of NH₄F, voltage and the thickness of the sputtered titanium film were varied to study their effect on the formation of TiO₂ nanotube arrays. It is demonstrated in this work that the nanoporous layer is formed on top of the ordered array of TiO₂ nanotubes. Furthermore, the optical transmittance of TiO₂ nanotubes annealed at 450 °C is much lower than the non annealed TiO₂ nanotubes in the visible wavelength region.     

Preparation and characterization of Ti0.7Sn0.3O2 as catalyst support for oxygen reduction reaction

Sn-doped TiO_2 nanoparticles with high surface area of 125.7 m~2·g~(-1) are synthesized via a simple one-step hydrothermai method and explored as the cathode catalyst support for proton exchange membrane fuel cells.The synthesized support materials are studied by X-ray diffraction analysis,energy dispersive X-ray spectroscopy and transmission electron microscopy.It is found that the conductivity has been greatly improved by the addition of 30 mol%Sn and Pt nanoparticles are well dispersed on Ti_(0.7)Sn_(0.3)O_2 support with an average size of 2.44 run.Electrochemical studies show that the Ti_(0.7)Sn_(0.3)O_2 nanoparticles have excellent electrochemical stability under a high potential compared to Vulcan XC-72.The as-synthesized Pt/Ti_(0.7)Sn_(0.3)O_2 exhibits high and stable electrocatalytic activity for the oxygen reduction reaction.The Pt/Ti_(0.7)Sn_(0.3)O_2 catalyst reserves most of its electrochemically active surface area(ECA),and its half wave potential difference is 11 mV,which is lower than that of Pt/XC-72(36 mV) under 10 h potential hold at 1.4 V vs.NHE.In addition,the ECA degradation of Pt/Ti_(0.7)Sn_(0.3)O_2is 1.9 times lower than commercial Pt/XC-72 under 500 potential cycles between 0.6 V and 1.2 V vs.NHE.Therefore,the as synthesized Pt/Ti_(0.7)Sn_(0.3)O_2 can be considered as a promising alternative cathode,catalyst for proton exchange membrane fuel cells.     

Platinum Complexes Containing Pyramidalized Germanium and Tin Dihalide Ligands Bound through σ,σ ME Multiple Bonds

We present the isolation of the first mononuclear dihalogermylene, and mono‐ and dinuclear stannylene complexes of transition metals. These exhibit exceptionally pyramidalized Group 14 centers. Additionally, removal of the halide substituents from the Ge/Sn atom was successfully performed in two ways, halide abstraction and reduction, leading to a variety of unusual structural motifs.     

Facile Mechanochemical Synthesis of Nano SnO2/Graphene Composite from Coarse Metallic Sn and Graphite Oxide: An Outstanding Anode Material for Lithium‐Ion Batteries

A facile method for the large‐scale synthesis of SnO₂ nanocrystal/graphene composites by using coarse metallic Sn particles and cheap graphite oxide (GO) as raw materials is demonstrated. This method uses simple ball milling to realize a mechanochemical reaction between Sn particles and GO. After the reaction, the initial coarse Sn particles with sizes of 3–30 μm are converted to SnO₂ nanocrystals (approximately 4 nm) while GO is reduced to graphene. Composite with different grinding times (1 h 20 min, 2 h 20 min or 8 h 20 min, abbreviated to 1, 2 or 8 h below) and raw material ratios (Sn:GO, 1:2, 1:1, 2:1, w/w) are investigated by X‐ray diffraction, X‐ray photoelectron spectroscopy, field‐emission scanning electron microscopy and transmission electron microscopy. The as‐prepared SnO₂/graphene composite with a grinding time of 8 h and raw material ratio of 1:1 forms micrometer‐sized architected chips composed of composite sheets, and demonstrates a high tap density of 1.53 g cm^?3. By using such composites as anode material for LIBs, a high specific capacity of 891 mA h g^?1 is achieved even after 50 cycles at 100 mA g^?1.     

Organotin–Oxido Cluster‐Based Multiferrocenyl Complexes Obtained by Hydrolysis of Ferrocenyl‐Functionalized Organotin Chlorides

Three organotin–oxido clusters were formed by hydrolysis of ferrocenyl‐functionalized organotin chloride precursors in the presence of NaEPh (E=S, Se). [R^FcSnCl₃?HCl] ( C ; R^Fc = CMe₂CH₂C(Me)?N?N?C(Me)Fc) and [SnCl₆]^2? formed {(R^FcSnCl₂)₃[Sn(OH)₆]}[SnCl₃] ( 3 a ) and {(R^FcSnCl₂)₃[Sn(OH)₆]}[PhSeO₃] ( 3 b ), bearing an unprecedented [Sn₄O₆] unit, in a one‐pot synthesis or stepwise through [(R^FcSnCl₂)₂Se] ( 1 ) plus [(R^FcSnCl₂)SePh] ( 2 ). A one‐pot reaction starting out from FcSnCl₃ gave [(FcSn)₉(OH)₆O₈Cl₅] ( 4 ), which represents the largest Fc‐decorated Sn/O cluster reported to date.     

Reactivity of Liquid Ammonia Solutions of the Zintl Phase K12Sn17 towards Mesitylcopper(I) and Phosphinegold(I) Chloride

To gain more insight into the reactivity of intermetalloid clusters, the reactivity of the Zintl phase K₁₂Sn₁₇, which contains [Sn₄]^4? and [Sn₉]^4? cluster anions, was investigated. The reaction of K₁₂Sn₁₇ with gold(I) phosphine chloride yielded K₇[(η²‐Sn₄)Au(η²‐Sn₄)](NH₃)₁₆ ( 1 ) and K₁₇[(η²‐Sn₄)Au(η²‐Sn₄)]₂(NH₂)₃(NH₃)₅₂ ( 2 ), which both contain the anion [(Sn₄)Au(Sn₄)]^7? ( 1 a ) that consists of two [Sn₄]^4? tetrahedra linked through a central gold atom. Anion 1 a represents the first binary Au?Sn polyanion. From this reaction, the solvate structure [K([2.2.2]crypt)]₃K[Sn₉](NH₃)₁₈ ( 3 ; [2.2.2]crypt=4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) was also obtained. In the analogous reaction of mesitylcopper with K₁₂Sn₁₇ in the presence of [18]crown‐6 in liquid ammonia, crystals of the composition [K([18]crown‐6)]₂[K([18]crown‐6)(MesH)(NH₃)][Cu@Sn₉](thf) ( 4 ) were isolated ([18]crown‐6=1,4,7,10,13,16‐hexaoxacyclooctadiene, MesH=mesitylene, thf=tetrahydrofuran) and featured a [Cu@Sn₉]^3? cluster. A similar reaction with [2.2.2]crypt as a sequestering agent led to the formation of crystals of [K[2.2.2]crypt][MesCuMes] ( 5 ). The cocrystallization of mesitylene in 4 and the presence of [MesCuMes]^? ( 5 a ) in 5 provides strong evidence that the migration of a bare Cu atom into an Sn₉ anion takes place through the release of a Mes^? anion from mesitylcopper, which either migrates to another mesitylcopper to form 5 a or is subsequently protonated to give MesH.     

Transition‐Metal‐Catalyzed Oxidation of Metallic Sn in NiO/SnO2 Nanocomposite

It is well accepted that metallic tin as a discharge (reduction) product of SnO_x cannot be electrochemically oxidized below 3.00 V versus Li⁺/Li⁰ due to the high stability of Li₂O, though a similar oxidation can usually occur for a transition metal formed from the corresponding oxide. In this work, nanosized Ni₂SnO₄ and NiO/SnO₂ nanocomposite were synthesized by coprecipitation reactions and subsequent heat treatment. Owing to the catalytic effect of nanosized metallic nickel, metallic tin can be electrochemically oxidized to SnO₂ below 3.00 V. As a result, the reversible lithium‐storage capacities of the nanocomposite reach 970 mAh g^?1 or above, much higher than the theoretical capacity (ca. 750 mAh g^?1) of SnO₂, NiO, or their composites. These findings extend the well‐known electrochemical conversion reaction to non‐transition‐metal compounds and may have important applications, for example, in constructing high‐capacity electrode materials and efficient catalysts.     

Synthesis,characterization and performance of nanosized Bi<Subscript>0.1</Subscript>Sn<Subscript>0.9</Subscript>O<Subscript>2</Subscript>–WPU organic–inorganic hybrid coatings

A series of organic–inorganic hybrid coatings consisting of organic waterborne polyurethane (WPU) and inorganic nanosized bismuth-doped tin dioxide were successfully synthesized by the in situ polymerization approach. Bi_0.1Sn_0.9O₂ nano-powders were prepared via a new route of sol–gel combustion hybrid method using acetylene black as the fuel. The formed nano-powders were characterized by transmission electron microscopy and X-ray diffraction (XRD). Bi_0.1Sn_0.9O₂–WPU was then fabricated with isophorone diisocyanate, 2,2-bis(hydroxymethyl) propionic acid and nano-Bi_0.1Sn_0.9O₂-poly(ε-caprolactone) (PCL) as the starting materials. Organic–inorganic hybrid coatings are always achieved with adjustable contents of Bi_0.1Sn_0.9O₂. The hybrid coatings with Bi_0.1Sn_0.9O₂ loading on the glass substrate exhibited good heat insulation efficiency. The tensile strength and breaking extensibility of nanocomposite film containing 1.0% of the nano-Bi_0.1Sn_0.9O₂ were measured as 9.35 MPa and 248%, respectively. The transmittance of visible light was above 80%. The heat insulation of glass coated with nano-Bi_0.1Sn_0.9O₂–WPU hybrid was over 60 °C in contrast to the commercial blank glass.     

The Si?Sn Chemical Bond: An Integrated Thermochemical and Quantum Mechanical Study of the SiSn Diatomic Molecule and Small Si–Sn Clusters

The silicon–tin chemical bond has been investigated by a study of the SiSn diatomic molecule and a number of new polyatomic Si_xSn_y molecules. These species, formed in the vapor produced from silicon–tin mixtures at high temperature, were experimentally studied by using a Knudsen effusion mass spectrometric technique. The heteronuclear diatomic SiSn, together with the triatomic Si₂Sn and SiSn₂ and tetratomic Si₃Sn, Si₂Sn₂, and SiSn₃ species, were identified in the vapor and studied in the overall temperature range 1474–1944 K. The atomization energy of all the above molecules was determined for the first time (values in kJ mol^?1): 233.0±7.8 (SiSn), 625.6±11.6 (Si₂Sn), 550.2±10.7 (SiSn₂), 1046.1±19.9 (Si₃Sn), 955.2±26.8 (Si₂Sn₂), and 860.2±19.0 (SiSn₃). In addition, a computational study of the ground and low‐lying excited electronic states of the newly identified molecules has been made. These electronic‐structure calculations were performed at the DFT‐B3LYP/cc‐pVTZ and CCSD(T)/cc‐pVTZ levels, and allowed the estimation of reliable molecular parameters and hence the thermal functions of the species under study. Computed atomization energies were also derived by taking into account spin–orbit corrections and extrapolation to the complete basis‐set limit. A comparison between experimental and theoretical results is presented. Revised values of (716.5±16) kJ mol^?1 (Si₃) and (440±20) kJ mol^?1 (Sn₃) are also proposed for the atomization energies of the Si₃ and Sn₃ molecules.