Engineering of SnO2/TiO2 heterojunction compact interface with efficient charge transfer pathway for photocatalytic hydrogen evolution

Fabricating an efficient charge transfer pathway at the compact interface between two kinds of semiconductors is an important strategy for designing hydrogen production heterojunction photocatalysts. In this work, we prepared a compact, stable and oxygen vacancy-rich photocatalyst (SnO₂/TiO₂ heterostructure) via a simple and reasonable in-situ synthesis method. Briefly, SnCl₂–2H₂O is hydrolyzed on the TiO₂ precursor. After the pyrolysis process, SnO₂ nanoparticles (5 nm) were dispersed on the surface of ultrathin TiO₂ nanosheets uniformly. Herein, the heterojunction system can offer abundant oxygen vacancies, which can act as active sites for catalytic reactions. Meanwhile, the interfacial contact of SnO₂/TiO₂ grading semiconductor oxide is uniform and tight, which can promote the separation and migration of photogenerated carriers. As shown in the experimental results, the hydrogen production rate of SnO₂/TiO₂ is 16.7 mmol h^?1 g^?1 (4.4 times higher than that of TiO₂), which is owing to its good dynamical properties. This work demonstrates an efficient strategy of tight combining SnO₂/TiO₂ with abundant oxygen vacancies to improve catalytic efficiency.     

Improvement of interfacial adhesion performance of the kevlar fiber mat by depositing SiC/TiO2/Al2O3/graphene nanoparticles

Modern world seeks dramatic progress in composite materials use in numerous applications. Scientists worldwide are researching on fabricating new composites and attempting to have more applications using these materials. Serious attempts have also been taken to improve the properties of these materials. In this circumstance, a conscious attempt has been made in this present work that studies the effect of SiC/TiO₂/Al₂O₃/ graphene nanoparticles (NPs) deposition on Kevlar fiber. In this process, SiC/TiO₂/Al₂O₃/ graphene NPs have been deposited on Kevlar fiber by dip coating process. For the analysis, physical observation has been performed well at first which confirms nanoparticle deposition on the fiber and formation of adhesive bonding. SEM analysis followed by surface topography has been conducted to observe and further analysis of nanoparticle deposition. Atomic bonding mechanism shows how chemical bonding between fiber and nanoparticles. TGA analysis shows thermal improvement of the fiber by NPs deposition where graphene with binder makes 21.6% improvement in decomposition temperature. Tensile strength and young’s modulus of binder inclusion coated kevlar fabric are improved up to 26% and 5.7%, respectively. Finally, the IR-spectra confirms successful deposition of nanoparticles on the fiber.     

An experimental investigation of ionic transport properties in CuI-Ag2WO4 and CuI-Ag2CrO4 mixed systems

The phenomenon of ionic transport in the case of two different mixed systems (CuI)_(1−x)-(Ag₂WO₄)_x(0.15?x?0.6) and (CuI)_(1−y)-(Ag₂CrO₄)_y(0.15?y?0.5) has been investigated. Powder X-ray diffraction (XRD) analysis coupled with differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), FT-Raman and electrical transport studies involving ionic transport number and temperature-dependent electrical conductivity measurements have been carried out in order to identify the various phases responsible for the conduction process. The occurrence of typical ionic conductivity values of 4.5×10⁻³ Scm⁻¹ for the composition (CuI)_0.45-(Ag₂WO₄)_0.55 and 1.1×10⁻⁴ Scm⁻¹ in the case of (CuI)_0.55-(Ag₂CrO₄)_0.45 at room temperature has been discussed in terms of the observed characteristics.     

Enhancement of photovoltaic performance of polyaniline/graphene composite-based dye-sensitized solar cells by adding TiO2 nanoparticles

Polyaniline (PANi)-graphene composites and polyaniline-graphene/TiO₂ composites were prepared by ex-situ approach. Systematic investigation was carried out to explore photovoltaic (PV) properties of PANi-graphene and PANi-graphene/TiO₂ composite. The prepared composites were characterized using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Raman Spectroscopy and Ultraviolet–Visible (UV–Vis) Spectroscopy. The PV properties of dye-sensitized solar cells (DSSCs) prepared composites investigated by assembling materials in ITO/PANi-graphene/Al and ITO/PANi-graphene/TiO₂/Al architecture. Different PV parameters such as short circuit current, open circuit voltage, fill factor and power conversion efficiency were determined from the (Current-Voltage) IV characteristics of PV cell. The 15 wt% PANi loaded graphene composite based PV cell shows optimized power conversion efficiency of the order 6.47%. The main accomplishment of present work is that efficiency associated with 15 wt% PANi loaded graphene composite, improved further by addition of TiO₂ nanoparticles. The composite system between PANi-graphene/TiO₂ for 1 wt% of TiO₂ nanoparticles shows optimized power conversion efficiency of the order 8.63%.     

Enhancement of solar light photocatalytic activity of TiO2-CeO2 composite by Er3+:Y3Al5O12 in organic dye degradation

The Er³⁺:Y₃Al₅O₁₂, as an upconversion luminescence agent which is able to transform the visible part of the solar light to ultraviolet light, was prepared by nitrate-citrate sol-gel method. A novel solar light photocatalyst, Er³⁺:Y₃Al₅O₁₂/TiO₂-CeO₂ composite was synthesized using ultrasonic treatment. The X-ray diffraction (XRD) and scanning election microscopy (SEM) were used to characterize the structural morphology of the Er³⁺:Y₃Al₅O₁₂/TiO₂-CeO₂ composite. In order to evaluate the solar light photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/TiO₂-CeO₂ composite, the Azo Fuchsine dye was used as a model organic pollutant. The progress of the degradation reaction was monitored by UV-Vis spectroscopy and ion chromatography. The key influences on the solar light photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/TiO₂-CeO₂ were studied, such as Ti/Ce molar ratio, heat-treatment temperature and heat-treatment time. Otherwise, the effects of initial dye concentration, Er³⁺:Y₃Al₅O₁₂/TiO₂-CeO₂ amount, solar light irradiation time and the nature of the dye on the solar light photocatalytic degradation process were investigated. It was found that the solar light photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/TiO₂-CeO₂ composite was superior to Er³⁺:Y₃Al₅O₁₂/TiO₂ and Er³⁺:Y₃Al₅O₁₂/CeO₂ powder in the similar conditions.     

Dependence of the mixed alkali effect on temperature and total alkali oxide content in y[xLi2O·(1−x)Na2O]·(1−y)B2O3 glasses

The complex conductivity spectra of mixed alkali borate glasses of compositions y [xLi₂O·(1−x)Na₂O]·(1−y)B₂O₃ (with x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0; y=0.1, 0.2, 0.3) in a frequency range between 10⁻² Hz and 3 MHz and at temperatures ranging from 298 to 573 K have been studied. For each glass composition the conductivities show a transition from the dc values into a dispersive regime where the conductivity is found to increase continuously with frequency, tending towards a linear frequency dependence at sufficiently low temperatures. Mixed alkali effects (MAEs) in the dc conductivity and activation energy are identified and discussed. It has been for the first time found that the strength of the MAE in the logarithm of the dc conductivity linearly increases with the total alkali oxide content, y, and the reciprocal temperature, 1/T.     

Synthesis and formation mechanism of TiO2/Al2O3 nanobelts by electrospinning

Poly(vinyl pyrrolidone) (PVP)/[Ti(SO₄)₂ + Al(NO₃)₃] composite nanobelts were prepared via electrospinning technology, and TiO₂/Al₂O₃ nanobelts were fabricated by calcination of the prepared composite nanobelts. The samples were characterized by thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). XRD results show that the composite nanobelts were amorphous in structure, and pure phase TiO₂/Al₂O₃ nanobelts were obtained by calcination of the relevant composite nanobelts at 950°C for 8 h. SEM analysis indicates that the surface of as-prepared composite nanobelts was smooth, the widths of the composite fibers were in narrow range, and the mean width was ca. 8.9 ± 2.1 μm, thickness was about 255 nm, and there is no cross-linking among nanobelts. The width of TiO₂/Al₂O₃ nanobelts was ca. 1.3 ± 0.1 μm and the thickness was about 105 nm. TG-DTA analysis reveals that the N,N-dimethylformamide (DMF), organic compounds and inorganic salts in the composite nanobelts were decomposed and volatilized totally, and the weight of the sample kept constant when sintering temperature was above 900°C, and the total weight loss percentage was 81%. FTIR analysis manifests that crystalline TiO₂/Al₂O₃ nanobelts were formed at 950°C. The possible formation mechanism of the TiO₂/Al₂O₃ nanobelts was preliminarily discussed.     

Activity Enhancement of Pt/Ba/Al2O3 Mixed with Mn/Ba/Al2O3 for NOx Storage-reduction by Hydrogen

The storage and reduction of nitrogen oxides has attracted much attention as an efficient way to reduce NOx emission of lean-burn gasoline and diesel engines1-5. At present, NOx storage and reduction (NSR) catalysts based on Pt and Ba have been extensivel…     

Ionic components dependence of the charge transfer reactions at the silicon/HF solution interface

The actual requirements for circuit miniaturization and production economy require obtaining smooth silicon surfaces using diluted chemicals, especially HF treatment. This fundamental research deals with the electrochemical corrosion of n- and p-type silicon substrates in 0.25 M dilute HF solutions, and examines the influence of fluoride ions or protons additives. All experiments were conducted both in the dark and under constant light flux, with solutions thoroughly degassed by high purity argon bubbling. Polarization resistance measurements near the open circuit potential lead to the value of the corrosion current. The kinetics of charge transfer reactions, studied by linear voltammetry, were interpreted as a function of the carrier density in the energy levels of the semiconductor and the concentration of acceptor species in the solution. The influence of these parameters on the surface roughening of the silicon samples was also studied by ex situ atomic force microscopy profile measurements. Received: 13 December 1998 / Accepted: 29 March 1999     

石墨烯修饰三氧化钨/二氧化钛S型异质结增强的光催化产氢活性（英文）

太阳光驱动的光催化分解水产氢是利用太阳能解决当前能源危机和环境问题的理想策略.二氧化钛由于其稳定、环境友好和成本低等优点受到广泛研究,在光催化领域具有不可或缺的作用.然而,纯二氧化钛光催化剂具有光生电子-空穴复合率高、太阳能利用率低等缺点,使其在光催化产氢领域的应用受到限制.迄今为止,人们探索了多种改性策略来提高二氧化钛的光催化活性,如贵金属负载、金属或非金属元素掺杂、构建异质结等.通过复合两个具有合适能带排布的半导体来构建异质结可以大大提高光生载流子的分离,被认为是一种有效的解决方案.最近提出了一种新的S型异质结概念,以解释不同半导体异质界面载流子转移分离的问题.S型异质结是在传统Ⅱ型和Z型(液相Z型、全固态Z型、间接Z型、直接Z型)基础上提出的,但又扬长避短,优于传统Ⅱ型和Z型.通常,S型异质结是由功函数较小、费米能级较高的还原型半导体光催化剂和功函数较大、费米能级较低的氧化型半导体光催化剂构建而成.三氧化钨禁带宽度较小(2.4-2.8 eV),功函数较大,是典型的氧化型光催化剂,也是构建S型异质结的理想半导体光催化剂.根据S型电荷转移机制,三氧化钨/二氧化钛复合物在光辐照下,三氧化钨导带上相对无用的电子与二氧化钛价带上相对无用的空穴复合,二氧化钛导带上还原能力较强的电子和三氧化钨价带上氧化能力较强的空穴得以保留,从而在异质界面上实现了氧化还原能力较强的光生电子-空穴对的分离.同时,石墨烯作为一种蜂窝状碳原子二维材料,是理想的电子受体,在异质结光催化剂中能及时转移电子.而且,石墨烯具有较好的导热性和电子迁移率,光吸收强,比表面积大,可为光催化反应提供丰富的吸附和活性位点,已经被认为是一种重要催化剂载体和光电分解水产氢的有效共催化剂.本文采用简便的一步水热法制备石墨烯修饰的三氧化钨/二氧化钛S型异质结光催化剂.光催化产氢性能测试表明,三氧化钨/二氧化钛/石墨烯复合材料的光催化产氢速率显著提高(245.8μmol g^-1 h^-1),约为纯TiO2的3.5倍.高分辨透射电子显微镜、拉曼光谱和X射线光电子能谱结果证明了TiO2和WO3纳米颗粒的紧密接触,并成功负载在还原氧化石墨烯(rGO)上.X射线光电子能谱中Ti 2p结合能的增加证实TiO2和WO3之间强的相互作用和S型异质结的形成.此外,复合材料中的rGO大大拓展了复合物的光吸收范围(紫外-可见漫反射光谱),增强了光热转换效应,而且rGO与TiO2之间形成肖特基结,促进了TiO2导带电子的转移和分离.总之,WO3和TiO2的S型异质结与TiO2和rGO之间的肖特基异质结的协同效应抑制了相对有用的电子和空穴的复合,有利于氧化还原能力较强的载流子的分离和进一步转移,加速了表面产氢动力学,于是增强了三元复合光催化剂的光催化产氢活性.     

钕掺杂提高TiO2光催化活性的机制

采用X射线衍射(XRD), BET吸附, X射线光电子能谱(XPS)表征了溶胶凝胶法制备的Nd掺杂TiO2光催化剂的晶体结构、表面电子结构与化学组成. 以甲基橙为有机底物, 测试Nd掺杂对光催化剂吸附性能和光催化活性的影响. 结果表明, Nd掺杂可阻碍TiO2的晶相转变, 减小光催化剂的晶粒尺寸, 比表面积增大. Nd掺杂提高光催化剂表面三价钛(TiⅢ)的含量及其对甲基橙的吸附能力是其提高TiO2光催化降解甲基橙活性的主要原因. Nd掺杂量为1.2%时, 光催化剂活性最高.     

An evaluation of silver ionic transport in the mixed system (1−x)·CuI-x·Ag2MoO4 (0.15?x?0.6)

The origin and nature of correlation between silver ionic conduction and composition of various phases present in the case of the mixed system CuI-Ag₂MoO₄ were probed in terms of possible solid-state reactions. Detailed X-ray diffraction (XRD), differential scanning calorimetry, Fourier transform infrared, electrical transport studies involving ionic transport number data and electrical conductivity measurement were carried out in order to identify the reaction products. The feasible reaction products identified were found to determine the exact composition resulting from the completion of each solid-state reaction and hence the behavior of effective electric conduction.     

Effect of Screw-Dislocation on Electrical Properties of Spiral-Type Bi2Se3 Nanoplates

We systematically investigated the electrical properties of spiral-type and smooth Bi₂Se₃ nanoplates through field effect transistor and conductive atomic force microscopy (CAFM) measurement. It is observed that both nanoplates possess high conductivity and show metallic-like behavior. Compared to the smooth nanoplate, the spiral-type one exhibits the higher carrier concentration and lower mobility. CAFM characterization reveals that the conductance at the screw-dislocation edge is even higher than that on the terrace, implying that the dislocation can supply excess carriers to compensate the low mobility and achieve high conductivity. The unique structure and electrical properties make the spiral-type Bi₂Se₃ nanoplates a good candidate for catalysts and gas sensors.     

Er3+-Yb3+共掺纳米TiO2上转换光催化杀菌作用研究

采用溶胶凝胶法合成了稀土离子Er^3＋-Yb^3＋共掺杂的纳米TiO2晶体粉末,利用XRD,UV-VIS吸收光谱及上转换发射光谱对其结构和光学特性进行了表征．以致病性嗜水气单胞菌为实验菌株,以980nm激光为激发光源,考察了室温下Er^3＋-Yb^3＋共掺杂纳米TiO2的光催化杀菌性能．结果表明,稀土离子掺杂的纳米TiO2可以通过上转换发光的途径增加TiO2对可见光的利用率,从而实现TiO2在可见光和近红外光范围的光催化氧化杀菌作用．     

Study of the cold charge transfer state separation at the TQ1/PC71BM interface

Charge transfer (CT) state separation is one of the most critical processes in the functioning of an organic solar cell. In this article, we study a bilayer of TQ1 and PC₇₁BM molecules presenting disorder at the interface, obtained by means of Molecular Dynamics. The study of the CT state splitting can be first analyzed through the CT state splitting diagram, introduced in a previous work. Through this analysis, we identify the possibility of CT state splitting within Marcus Theory in function of the electric field. Once the right range of electric fields has been identified, we perform Kinetic Monte Carlo simulations to estimate percentages and times for the CT state splitting and the free charge carriers collection. Statistical information extracted from these simulations allows us to highlight the importance of polarization and to test the limits of the predictions given by the CT state splitting diagram. © 2017 Wiley Periodicals, Inc.     

Electronic reorganization triggered by electron transfer: The intervalence charge transfer of a Fe3+/Fe2+ bimetallic complex

The key role of the molecular orbitals in describing electron transfer processes is put in evidence for the intervalence charge transfer (IVCT) of a synthetic nonheme binuclear mixed‐valence Fe³⁺/Fe²⁺ compound. The electronic reorganization induced by the IVCT can be quantified by controlling the adaptation of the molecular orbitals to the charge transfer process. We evaluate the transition energy and its polarization effects on the molecular orbitals by means of ab initio calculations. The resulting energetic profile of the IVCT shows strong similarities to the Marcus' model, suggesting a response behaviour of the ensemble of electrons analogue to that of the solvent. We quantify the extent of the electronic reorganization induced by the IVCT process to be 11.74 eV, a very large effect that induces the crossing of states reducing the total energy of the transfer to 0.89 eV. © 2015 Wiley Periodicals, Inc.     

Reaction path dynamics and theoretical rate constants for the SiH3Cl+H→SiH2Cl+H2 reaction by ab initio direct dynamics method

Ab initio direct dynamics method has been used to study the title reaction. Electronic structure information including geometries, gradients and force constants (Hessians) are calculated at the UQCISD/6-311+G^** level. Energies along the minimum energy path are improved by a series of single-point G2//QCISD calculations. The changes of the geometries, vibratioanal frequencies, potential energies and total curvature along the reaction path are discussed. The rate constants in the temperature range 200–3000 K are calculated by canonical variational transition state theory with small-curvature tunneling correction (CVT/SCT) method. The results show that the variational effect is small and in the lower temperature range, the small curvature tunneling effect is important for the reaction.     

Synthesis and characterization of a NaSICON series with general formula Na2.8Zr2−ySi1.8−4yP1.2+4yO12 (0?y?0.45)

In this work, we present the synthesis and the characterization of ionic conducting ceramics of NaSICON-type (Natrium super ionic conductor). The properties of this ceramic make it suitable for use in electrochemical devices. These solid electrolytes can be used as sensors for application in the manufacturing of potentiometric gas sensors, for the detection of pollutant emissions and for environment control. The family of NaSICON that we studied has as a general formula Na_2.8Zr_2−ySi_1.8−4yP_1.2+4yO₁₂ with 0?y?0.45. The various compositions were synthesized by produced using the sol-gel method. The electric properties of these compositions were carried out by impedance spectroscopy. The results highlight the good conductivity of the Na_2.8Zr_1.775Si_0.9P_2.1O₁₂ composition.     

Thermally Conductive Study of Polyethylene/Al2O3 Composite Networks Cross-linked by Electron Beam Irradiation

The surface-modified Al₂O₃ particles were introduced into polyethylene(PE) to enhance the thermal conductivity, and PE/Al₂O₃ cross-linked networks with improved thermal and mechanical properties were prepared through electron beam(EB) irradiation technology. The incorporation of reactive irradiation sensitizer was useful in fabricating a high degree of cross-linking(DC) PE networks under a low irradiation dose. In the PE sample containing 2% sensitizer, DC ca.67.1% could be obtained under 60 kGy(1 kGy=1000 J/kg). EB-irradiation greatly improved the tensile stress of PE-based samples, and the tensile stresses of the samples with 0.2%-5% TMPTA(trimethylolpro-pane triacrylate) under 60 kGy were 24.61-27.77 MPa. All the EB-irradiated samples had higher Vicat softening temperatures than the samples without irradiation. After treatment at 120 kGy, the Vicat softening temperatures of PE-Al₂O₃-44/TMPTA-2 increased from 127℃ to 130.4℃. SEM images revealed that PE-Al₂O₃-50 samples with increased amount of Al₂O₃ particles showed a conduction "pathway," and thermal conductivity reached 0.67 W/(m·K). Thus, high-performance pipes were extruded, which could satisfy the static hydraulic blasting test and exhibit improved thermal conduction capability.     

Heavy doping of H ion in 12CaO·7Al2O3

12CaO·7Al₂O₃ (C12A7, mayenite), which has a nanoscale porous structure that can accommodate extraframework species such as hydride (H⁻), oxide (O²⁻), hydroxide (OH⁻) ions, and electrons, has been doped with H⁻ ions to investigate its effects as dominant extraframework species. Chemical doping with CaH₂ enables the concentration of H⁻ ions to reach almost the theoretical maximum. The concentration of H⁻ ions is characterized by optical absorption intensity ascribed to photoionization of H⁻ ions, and ¹H magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Persistent electron generation, which is accompanied by the formation of an F⁺ absorption band and electrical conductivity, by irradiation with ultraviolet light at room temperature increases as the H⁻ ion doping increases until it reaches half the theoretical maximum and then decreases as the H⁻ ion concentration increases further. This dependence indicates that both H⁻ and O²⁻ ions are necessary for the generation of persistent electrons.