Cu∶CdS/TiO2的制备及其光电化学性能研究

采用水热法制备(001)晶面裸露的TiO2纳米片阵列薄膜,并采用水热法进行CdS纳米颗粒复合,探讨不同水热反应时长对复合薄膜结构及性能的影响.为了提高复合薄膜的光电化学性能,在水热反应过程中引入Cu前驱体,并探讨不同掺杂浓度对复合薄膜性能的影响.研究结果表明Cu元素掺杂有效拓宽了CdS复合TiO2纳米片阵列薄膜(CdS/TiO2)的光吸收范围,并且提高了CdS/TiO2的光电化学性能.当水热反应3h,Cu掺杂浓度为1∶1 000时,CdS/TiO2的光电性能达到最佳.     

Photoelectrochemical properties of Li2Pb(WO4)2

The photoelectrochemical (PEC) properties of lithium based mixed tungstate of Pb(II) prepared by ceramic technique. Its chemical composition was determined by estimating its metal contents. The electrode material was characterized by X-ray diffraction (XRD), electrical conductivity and diffuse reflectance spectroscopy. The photoelectrochemical property of lithium based mixed tungstates of Pb(II) is a good choice as photoanode in a PEC cell because of its 2.75 eV band-gap. The Flat - band potential is located at −0.15 Vs SCE. The conversion efficiency was found to be 0.41%.     

A ZnO/TiO2 composite nanorods photoanode with improved performance for dye‐sensitized solar cells

A dye‐sensitized solar cell (DSSC) based on ZnO/TiO₂ composite nanorods (NRs) photoanode is fabricated. The power conversion efficiency (PCE) of the ZnO/TiO₂ composite NRs film DSSC is 4.36%, which is obviously higher than that of DSSCs based on pure TiO₂ NRs (0.6%) and ZnO NRs (3.10%). The enhanced performance of ZnO/TiO₂ composite NRs film DSSC can be attributed to the combined effects of ZnO and TiO₂ NRs. In this architecture, the thick ZnO NRs overlayer offers a large surface area for enough dye absorption, while the thin TiO₂ NRs underlayer not only offers a direct and quick pathway for photoinjected electron transfer along the photoanode but also acts as a blocking layer, which effectively hinders the direct contact between the substrate and the electrolyte resulting in lower carrier recombination.     

不同形貌TiO2薄膜的可控制备及其光电化学性能研究

采用水热法在FTO(fluorine-doped tin oxide)基底上制备不同形貌的锐钛矿结构TiO2薄膜.通过不断增大反应前驱物中盐酸浓度,TiO2薄膜由球状颗粒薄膜逐渐演变生长成大面积高能(001)面裸露的TiO2纳米片阵列薄膜.通过对形貌演化规律及X射线衍射图谱变化规律进行分析,提出了不同形貌TiO2薄膜的...     

The effect of tourmaline additives in TiO2 photoanode for high-efficiency dye sensitized solar cells

Tourmaline is a kind of borosilicatemineral and has spontaneous polarization property. Due to this property, it can generate a feeble current around 0.06 mA[1 O'Regan, B., &; Grätzel, M. (1991). Nature 353, 737.[Crossref], [Web of Science ®] , [Google Scholar]]. We fabricated the TiO₂ photoanode with different wt.% ratio of tourmaline and investigated the effect of tourmaline additive on dye sensitized solar cells (DSSCs). We carried out electrochemical impedance spectroscopy (EIS) and current density-voltage (J-V) measurement. The results showed that the electron lifetime and the power conversion efficiency of the DSSCs with TiO₂ photoanode containing 3wt% tourmaline were enhanced by about 42% and 20%, respectively, as compared to the DSSCs using pristine TiO₂ photoanode.     

(Na1/2Bi1/2)TiO3-(Na1/2Bi1/2)(Zn1/3Nb2/3)O3无铅压电陶瓷的介电特性研究

采用固相合成法制备了(1-x)(Na1/2Bi1/2)TiO3-x(Na1/2Bi1/2)(Zn/23Nb2/3)O3(简写为(1-x)NBT-xNBZN)无铅压电陶瓷.研究了该体系陶瓷晶体结构、弥散相变特征与介电弛豫行为.X射线衍射分析表明,所研究的组成均能够形成纯钙钛矿(ABO3)型固溶体.当x≥0.5%摩尔分数时,该体系陶瓷具有三方、四方共存的晶体结构.材料的介电常数-温度曲线显示陶瓷具有两个介电反常峰Tf和Tm.修正的居里-外斯公式较好的描述了陶瓷弥散相变特征,弥散指数随x的增加而增加.x≤0.5%摩尔分数的陶瓷仅在低温介电反常峰Tf附近表现出明显的频率依赖性,随x的增加,陶瓷材料在室温和低温介电反常峰Tf之间都表现出明显的频率依赖性.根据有序-无序转变和宏畴.微畴转变理论探讨了该体系陶瓷介电弛豫特性的机理.     

稀土元素(Ce/Nd/Eu/Gd)与N共掺金红石相TiO2的第一性原理研究

基于密度泛函理论的第一性原理平面波超软赝势计算方法,计算分析了纯金红石相TiO2,Ce、Nd、Eu和Gd四种稀土元素单掺杂金红石相TiO2,以及与N共掺金红石相TiO2的晶体结构、电子结构和光学性质.由掺杂前后的结果分析发现,掺杂后晶胞膨胀,晶格发生畸变;费米能级上移进入导带,导带底部引入杂质能级,提高了掺杂体系的电导率和对可见光的响应;光学性质、介电函数和吸收谱掺杂体系峰值比纯TiO2小,反射谱和能量损耗谱出现红移现象.     

Cu2O/ZnO异质结构纳米线阵列的光电化学性能

通过水热法和热还原法合成了Cu2O/ZnO异质结构纳米线阵列,研究了Cu2O/ZnO异质结构纳米线阵列的光电化学性能.与纯的ZnO纳米线阵列光阳极相比,这种Cu2O/ZnO异质结构光阳极在日光辐照时,展现出了更优异的光电化学性能.在1 V vs.Ag/AgCl偏压时,异质结构光阳极的光电流密度达到1.5 mA/cm2,是纯ZnO纳米线阵列的2倍多.这种光电化学性能的提高,一方面是由于Cu2O的加入,提高了光阳极对于可见光的吸收效率,增强了光生载流子的密度.另一方面,Cu2O和ZnO之间形成的空间电场加速了光生电子-空穴对的分离,从而提高了复合结构光阳极的光电化学性能.结果表明,用地球上储量丰富的元素合成的金属氧化物异质结,也可以实现利用太阳光分解水制备氢气.     

Photoelectrochemical solar cells: Stabilization of small band GAP semiconductor in aqueous solution by surface-attached organic conducting polymer

Surface-attached polypyrrole films have been shown to produce a marked improvement in the stability of n-type single-crystal and polycrystalline Si against oxidation in an aqueous electrolyte. The current production of n-type polycrystalline Si coated with polypyrrole deteriorates less than 30% during 122 hr of irradiation whereas the unprotected bare electrode stops producing photocurrent within 30 s. The polymer protection of the n-type single-crystal Si is significantly less than that of the polycrystalline material because of differences in the adhesion of the polymer film to the electrode surfaces. The adhesion strength is shown to depend on various surface properties of Si and other electrode materials. Moreover, the surface morphology of the electrode affects the topography of the growing surface of the polypyrrole film. Requirements are discussed for the applications of organic conducting polymers to photoelectrochemical devices utilized for solar energy conversion.     

Studies on the fabrication and characteristics of photoelectrochemical cells using IrO2-coated TiO2 photoanode for Z-scheme water splitting and perovskite solar cell bias

ABSTRACT

In the present work, to build a water splitting system using only a neutral electrolyte solution and light source, we investigated the photoelectrochemical properties and interface resistances of an IrO₂-coated TiO₂ photoanode in Z-scheme configuration. The photoelectrochemical cell was connected to the perovskite solar cell with to realize the system with no need for an external electrical bias. Photoanodes with IrO₂ were found to support hole transport and to reduce the overpotential, therefore increasing the current density of the system consisting of photoelectrochemical cells. A maximum solar-to-hydrogen efficiency of 8.2% was achieved in a neutral electrolyte.     

Growth,Structural Characteristics and Photoelectrochemical Behaviour of Tungsten Diselenide (WSe2) Single Crystals

Studies in regard to structural and photoelectrochemical (PEC) properties of tungsten diselenide (n-WSe₂) single crystals grown by vapour transport technique have been carried out. X-ray diffraction (oscillation) study reveals α curious two layer lines attributable to more than one a lattice parameters coexistence of nonstoichiometric phases is thought to lead to dual α lattice parameters (3.08 Å and 2.80 Å) observed. Surface studies with optical and scanning electron microscopic techniques revealed that the crystal surfaces possess varying density of surface steps. The photoelectrochemical behaviour of n-WSe₂ electrodes examined with stepped and stepfree surfaces reveals that the steps have significant influence on the PEC behaviour. Crystals with stepfree surfaces exhibited better photoresponse as evidenced by improved photopotential (520 mV) and photocurrent density (7.5 mA/cm²). Moreover, the improved photoresponse of n-WSe₂ crystal electrodes in the present study, as compared to the previous investigation, is expected to arise from the existence of different structural phases in the as-grown crystals (dual phases) which can lead to tandemization effect with consequent improvement in photoresponse.     

Tunable synthesis of hierarchical TiO2 spheres consisting of rutile nanowires for dye‐sensitized solar cells and photocatalysis

Hierarchical TiO₂ spheres consisting of rutile nanowires (HTS) are successfully prepared in the bulk solution via a non‐polar solvent/polar solution interfacial syntheses strategy. The effect of reaction temperature on the morphology, size, BET surface area and monodispersion of HTS is studied systematically. Increasing reaction temperature decreases the diameter of spheres in micro‐scale whereas increases the diameter of nanowires in nano‐scale for these HTS. Monodisperse HTS are formed at 230 °C for 20 h, which can suitably be served as light scattering structure for dye‐sensitized solar cell with the additional advantage of rapid electron transport rate. A high efficiency of 8.54% was achieved for the composite DSSC consisting of nanoparticles and monodispersed HTS (synthesized at 230 °C), showing 31.38% improvement compared with that (6.5%) of the DSSCs made from pure P25 nanoparticles at the similar thickness. Furthermore, the photocatalytic performances of HTS for the degradation of methyl orange were also investigated. Contrary to the effect on the performance of DSSC, the HTS synthesized at 150 °C show higher photocatalytic degradation efficiency due to larger BET surface area.     

ZnO/Fe2O3复合结构的制备及光电化学性能研究

采用水热法在FTO导电玻璃上制备出大面积高能面裸露的ZnO纳米片阵列.采用旋涂法在纳米片表面制备Fe2O3纳米颗粒形成ZnO/Fe2O3复合结构.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见光吸收光谱和三电极光电测试系统对复合薄膜的结构组成、形貌、光学性能和光电化学性质进行了表征和分析.研究结果表明,随着Fe2O3复合次数的增加薄膜的光吸收范围逐步拓宽到可见光区,ZnO/Fe2O3复合结构光电极的光电流明显高于单纯的ZnO纳米片阵列光电极.     

(Nb2O5)1-x(TiO2)x陶瓷的制备及其介电性能的研究

我们采用传统固态反应方法烧结制备(Nb2O5)1-x(TiO2)x陶瓷,给出了掺杂量x从0.01到0.13陶瓷的介电性能.在本工艺条件下,所有样品的介电系数均大于120.当样品中TiO2的掺杂量为5mol;时,陶瓷的介电性能最佳:介电系数和损耗分别为217和0.078.XRD测试实验给出,当x≤0.05时,陶瓷的主要相结构为Nb2O5;当x≥0.07时,主相为TiNb24O62.     

Photoemission Studies of Ultrathin Sn-Layers on TiO2—x (rutile)

A clearly reduced (111) surface of a rutile single crystal was coated in situ with monolayers of tin and investigated using soft X-ray photoelectron spectroscopy of core levels. Tin grows as an oxide in the first monolayer accompanied by a further reduction of TiO_2—x and in metal state for higher coverages.     

Ag/TiO2纳米复合材料的抑菌活性研究

用钛酸异丙酯水解的方法合成单分散性的锐钛矿型TiO2亚微球,直径约为400 nm.以TiO2球为模版,用光化学还原法在其表面沉积银,合成纳米复合材料Ag/TiO2,银粒子平均直径为11 nm.用金黄色葡萄球菌和大肠杆菌作为测试菌研究Ag/TiO2抑菌性能.结果表明,当Ag/TiO2的浓度为0.6 mg/mL时,对金黄色葡萄球菌的抑菌率为96;,对大肠杆菌为98;.由于Ag/TiO2具有高效的抑菌性能,该复合材料可以应用于生物材料,污水处理等领域.     

TiO2材料(100)典型晶面的形成与电子结构的研究

在超软赝势密度泛函理论基础上计算分析了TiO2基(100)晶面低维材料的形成、电子结构和光学性质.结果表明,TiO2基(100)晶面低维材料的形成焓大于TiO2块体材料的形成焓,其稳定性比TiO2块体材料低.TiO2基(100)晶面低维材料带隙为2.760 eV,高于其体材料,其带隙为间接型.其价带顶和导带底主要分别由O p电子和Ti d电子形成,并且Ti的d电子和O的p电子在-2.5 eV处有局域作用.TiO2基(100)晶面低维材料电子局域化程度增大,Ti和O之间的离子性结合程度增强.TiO2基(100)晶面低维材料在140.8 nm处有最强的反射峰,其反射系数达23.9;,其在34.5 nm处有强的选择性吸收,并且在33.3 nm和138.9 nm处有最强的能量损失.     

用MOCVD法在玻璃和Si(100)基片上制备TiO2薄膜

采用大气开放式金属有机化合物化学气相沉积方法(AP-MOCVD),以四异丙醇钛(TTIP)为原料,在不同的实验条件下分别在Si(100)和玻璃基片上制备TiO2薄膜.当气化室温度为140℃,基片温度为350℃时,玻璃基片上生长的薄膜XRD谱中只出现了锐钛矿相(200)晶面的衍射峰,表明此时薄膜高度取向,在Si(100)基片上生长的TiO2薄膜也有取向性.通过SEM观察高度取向的TiO2薄膜表面出现四边形的微结构.     

EXAFS and XANES Studies on 3d Transition Metal Intercalation Compounds M x TiS2

Abstract

EXAFS and XANES spectra of Ti K-edge have been measured for 3d transition metal intercalation compounds M _x TiS₂ (M = Mn, Fe, Co and Ni; x ≤ 0.33). We have found that the interatomic distance between Ti and the first nearest neighbor S atoms, R(Ti-S), increases with the guest concentration x. The variation in XANES spectra with x reveals the reduction of the valence state of Ti atoms upon intercalation of M. From these results as well as the M K-edge EXAFS data studied previously, we have proposed a simple model on the local structure of M _x TiS₂ to reproduce the observed values of R(Ti-S) by averaging local shift of S atoms caused by intercalation.