TiO_2纳米管半导体特性与光电催化动力学研究

通过阳极氧化法在有机溶液中制备TiO2纳米管阵列,随着氧化时间的不同,TiO2纳米管阵列呈现各异的形貌。通过光电流测试,考察了不同氧化时间和施加不同电压下的Ti/TiO2纳米管阵列光电极的光电化学响应,阳极氧化6h表面规整纳米管阵列并施加偏压0.1V光电流响应最强。通过测试Mott-Schott-ky曲线,计算不同氧化时间的TiO2纳米管阵列的半导体载流子浓度、平带电位、空间电荷层宽度和能带弯曲量等特征参数,理论上提出了TiO2纳米管阵列生长机理。在光电催化降解无机氨氮的实验中,所得到的电化学阻抗谱(EIS)表明,外加偏压0.1V时,TiO2纳米管阵列电极的光电催化活性最强,同时通过拟合电路分析可知,光电催化降低了电极界面的反应阻抗,加速了光生载流子的转移,在TiO2纳米管阵列电极/溶液界面Helmholtz层中发生的氧化还原反应是整个光电催化反应的速率控制步骤。     

TiO2纳米管阵列催化降解甲基橙的性能研究

采用阳极氧化法制备了TiO2纳米管阵列电极,以甲基橙为目标降解物研究了TiO2纳米管阵列电极的光催化和光电催化性能.此外,还进行了超声辐射替代紫外光照探索性研究.结果表明,阳极氧化时间和热处理温度对TiO2纳米管阵列电极的光催化性能具有显著影响;在光催化过程中,施加一定外加电压可有效提高电极的光催化活性.尽管与紫外光照相比,超声辐射在TiO2纳米管阵列电极的催化氧化甲基橙分子过程中的促进作用具有一定的差距,但仍显示出替代紫外光照的可行性.     

阳极氧化法制备TiO2纳米管阵列及其光电性能研究

采用阳极氧化法在钛片上制备了TiO2纳米管阵列光电极，利用扫描电子显微镜（SEM）和X射线衍射仪（xRD）对TiO2纳米管的形貌和结构进行了表征，详细考察了氧化工艺参数对纳米管阵列形貌的影响，并通过稳态光电响应技术对TiO2纳米管电极的光电化学性能进行了研究．结果表明，在1wt％HF电解液中，控制氧化电压为20V，反应30min后，在Ti表面获得了垂直导向的TiO2纳米管阵列，孔径约为90nm，管壁厚度约为10nm．经600℃退火处理后，TiO2纳米管阵列为锐钛矿型与金红石型的混晶结构，此时电极的光电性能最佳，与TiO2纳米多孔膜电极相比，光电性能大幅提高．     

自持TiO2纳米管阵列薄膜与TiO2/FTO透明光电极制备工艺的研究

利用电化学阳极氧化法,采用三步氧化工艺,成功制备出大面积高度有序、孔洞分布均匀、孔道垂直取向且与金属钛基相分离的自持TiO2纳米管阵列膜。然后将其转移粘接至FTO导电玻璃上,形成高度有序的TiO2/FTO纳米管阵列透明光电极。利用场发射扫描电镜、X射线衍射仪、紫外-可见-近红外分光光度计分别对样品的形貌、晶相结构以及光学特性做了表征。研究表明,由三步阳极氧化工艺制备的自持TiO2纳米管阵列膜,其结构参数（如管径、管长及管壁厚度）在很大范围内可控,将其转移粘结至FTO导电玻璃上能制成多种用途的高质量透明光电极;另外,阳极氧化电压对TiO2纳米管阵列薄膜的光学能隙（Eg）也有较为明显的调制作用。显然,这项新工艺对基于TiO2纳米有序阵列复合结构的有机-无机光电器件的应用研究将是非常有益的。     

阳极氧化法制备二氧化钛纳米管阵列的形貌

采用阳极氧化法,以NH4F-乙二醇-水溶液为电解质,在钛片上制备了TiO2纳米管阵列,并研究了电解电压和电极距离对TiO2多孔薄膜形貌的影响。结果表明,通过优化电解电压,可以调控二氧化钛纳米管阵列的内径在20～145nm之间;通过调节两电极间的间距,在金属钛片上制备了完整的二氧化钛纳米孔阵列。并采用有限元模拟二氧化钛层中的电流密度分布,探讨了二氧化钛纳米管阵列和纳米孔阵列的形成。     

具有光透性的超长TiO_2纳米管阵列/FTO的制备及表征

采用电子束蒸发方法在透明导电玻璃FTO上沉积Ti金属薄膜,室温条件下在C2H6O2+NH4F中通过恒压阳极氧化法制备出超长TiO2纳米管阵列/FTO电极,并通过场发射扫描电子显微镜(FESEM),透射电子显微镜(TEM),X光电子能谱(XPS),X射线衍射(XRD)及光谱分析等方法对纳米管阵列/FTO电极进行了表征.研究表明,制备出的TiO2纳米管阵列内径43nm,管长5.4μm,经退火处理后得到长度为5μm锐钛矿相TiO2纳米管阵列/FTO透明电极,在可见光波长段的透射率为45%,在400nm波长处有一明显吸收峰.     

CdS/TiO_2纳米管阵列的制备及其光电催化活性研究

利用阳极氧化法和电沉积法制备CdS修饰的TiO2纳米管阵列。应用FE-SEM、XRD、DRS和LSV(线性伏安扫描)对该阵列的形貌、晶型、光学性质和光电性能进行表征,并研究该阵列降解亚甲基蓝的光电催化活性。结果表明,CdS以颗粒形式存在于TiO2纳米管阵列表面,CdS/TiO2纳米管阵列在可见光处有较强吸收,有较大光响应电流,其光电催化活性优于纯TiO2纳米管阵列。     

TiO_2纳米管阵列电极染料敏化太阳能电池

采用电化学阳极氧化法在纯钛片表面制备了高度有序的TiO2纳米管阵列。利用SEM、XRD分别对TiO2纳米管阵列的形貌、晶型进行了表征,并通过线性扫描伏安法对N719染料敏化纳米管阵列电极的光电性能进行了研究。实验结果表明,纳米管阵列的管径和长度随着阳极氧化电压的升高和氧化时间的延长都分别相应增加。同时还发现,通过450℃热处理的TiO2纳米管阵列,具有较好的锐钛矿晶型结构,其光电转化效率为2.1%。     

载Pt-TiO2纳米管阵列制备及其光电催化性能

采用阳极氧化法在纯钛箔表面制备TiO2纳米管,再用直流电沉积法在纳米管内沉积Pt,制备出载Pt-TiO2纳米管电极.并采用场发射扫描电子显微镜(FESEM)、X射线衍射(XRD)对其进行表征.研究载Pt-TiO2纳米管阵列与TiO2纳米管阵列对有机磷农药敌敌畏(DDVP)的光电催化降解效果,并与光催化、电降解做了简单对比.结果表明:所制Pt-TiO2纳米管存在锐钛矿晶型TiO2,其饱合光电流比TiO2纳米管大.与单独光催化、电降解相比,载Pt-TiO2纳米管电极光电催化降解效果更显著.     

阳极氧化TiO_2纳米线生长研究

采用NH4F-乙二醇-H2O溶液体系的电化学阳极氧化法,在金属钛基板上形成厚度为0.9~36μm的TiO2纳米管阵列。研究了阳极氧化电压、氧化时间及电解液的组成对TiO2纳米管阵列结构的影响。结果表明,当醇水体积比为39∶1时,60V电压下氧化2h,TiO2纳米管顶部的氧化层在缺陷处发生二次击穿溶解,产生自组装的孔核,场助溶解驱动力使纳米管顶部在孔核处沿管轴向垂直劈裂,形成直径20nm、长度可达几微米的TiO2纳米线。     

方酸菁功能材料修饰纳米晶TiO2薄膜电极的光电转换性能研究

考察了三种方酸菁染料修饰的米晶ＴｉＯ２薄膜电极表面应用于光电化学太阳能电池进行光电转换的情况,发现它们的光电化学性能参数按照Ｓｑ３〉Ｓｑ２〉Ｓｑ１的顺序,随着染料在纳米晶ＴｉＯ２上吸附力的增强而提高,其中,Ｓｑ３的光电转换效率为２．１７％,它在６５０ｎｍ处的最高单色光光电流效率ＩＰＣＥ值达到６．２％,表明方酸菁是一类优良的光电转换功能材料。     

Effect of Substrate Pretreatment on Controllable Growthof TiO2 Nanorod Arrays

Well-aligned TiO2 nanorod arrays(TNAs) were prepared on the pretreated quartz substrates.The effect of the pretreatment conditions on the growth of TNAs was systematically investigated by X-ray diffraction(XRD),field-emission scanning electron microscopy(FE-SEM) and high-resolution transmission electron microscopy(HRTEM).It is demonstrated that the pre-coating TiO2 crystal seeds on the substrates can greatly improve the growth orientation of TNAs.Rutile TiO2 crystal seeds induce the nucleation and growth of TNAs more preferably than the anatase TiO2 seeds.The growth density and diameter distribution of TNAs strongly depend on the TiO2 crystal seeds density.It is proved that TNAs with different morphologies can be controllably synthesized by using hydrothermal approach by pretreating substrates.The photocatalytic activity of TNAs was investigated by measuring the photodegradation rate of methyl blue aqueous solution under UV irradiation(254 nm).And the results show that TNAs with large growth density and small diameter size exhibit relatively higher photocatalytic activity.     

P3HT及CTCHT修饰纳米TiO2的光电性能研究

用光电流作用谱、光电流-电势图等光电化学方法研究了聚3-己基噻吩(P3HT)及3-己基噻吩和2-噻吩甲酸共聚物(CTCHT)修饰纳米结构TiO2电极的光电转换性质。结果表明,经修饰后的纳米TiO2电极光电流明显增强,光电转换效率得到明显提高。在复合膜电极中存在p-n异质结,异质结的存在有利于光生电子-空穴对的分离,降低了电荷的反向复合几率,提高了光电转换效率。     

Fabrication of TiO2/Tin-doped indium oxide-based photoelectrode coated with overlayer materials and its photoelectrochemical behavior

The photoelectrochemical properties of TiO2-based photoelectrodes with metal oxide overlayers (e.g., ZnO, ZrO2, MgO, and Al2O3) were investigated. The metal oxides were deposited on TiO2/tin-doped indium oxide (ITO) films by spin-coating metal-alkoxide precursors. The formation of the overlayers was confirmed by energy dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscopy (HRTEM). Each overlayers were well-coated on the TiO2-based films and have approximately 2 nm thickness. The prepared films were used as photoanodes in a photoelectrochemical system with a Pt counter electrode to evaluate hydrogen production performance. Comparing with other overlayers, the ZnO-coated photoelectrode exhibits the highest rate of hydrogen evolution and which is better than the uncoated one. From the photoelectrochemical and spectroscopic study, the superior hydrogen production property of the ZnO-coated TiO2 photoelectrode was attributed to both the higher light absorbance of ZnO compared to TiO2 and the formation of hydroxyl groups at the ZnO surface.     

Fast fabrication of long TiO2 nanotube array with high photoelectrochemical property on flexible stainless steel

Oriented highly ordered long TiO2 nanotube array films with nanopore structure and high photoelectrochemical property were fabricated on flexible stainless steel substrate (50 microm) by anodization treatment of titanium thin films in a short time. The samples were characterized by means of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and photoelectrochemical methods, respectively. The results showed that Ti films deposited at the condition of 0.7 Pa Ar pressure and 96 W sputtering power at room temperature was uniform and dense with good homogeneity and high crystallinity. The voltage and the anodization time both played significant roles in the formation of TiO2 nanopore-nanotube array film. The optimal voltage was 60 V and the anodization time is less than 30 min by anodizing Ti films in ethylene glycerol containing 0.5% (w) NH4F and 3% (w) H2O. The growth rate of TiO2 nanotube array was as high as 340 nm/min. Moreover, the photocurrent-potential curves, photocurrent response curves and electrochemical impedance spectra results indicated that the TiO2 nanotube array film with the nanoporous structure exhibited a better photo-response ability and photoelectrochemical performance than the ordinary TiO2 nanotube array film. The reason is that the nanoporous structure on the surface of the nanotube array can separate the photo electron-hole pairs more efficiently and completely than the tubular structure.     

Nanostructured carbon-doping anodic TiO2 from TiC and its photoelectrochemical properties

In this paper, nanostructured carbon-doped titanium dioxide (TiO(2-x)Cx) has been fabricated from titanium carbide (TiC) thin film using electrochemical anodization in a solution containing fluorine ion. The resulting samples were characterized via scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and photoelectrochemistry. The SEM images and EDX analysis indicated that a nanostructured thin film of carbon-doped titanium dioxide had been formed. The XRD pattern showed the structural change from TiC to anatase type TiO2 after annealing. A series of photoelectrochemical measurement showed an increase in photovoltage and in photocurrent for the electrode of anodized TiC sample. The results demonstrated the feasibility to process carbon doped nanostructured TiO2 through anodization promising for applications in high efficient photoelectrochemical conversion.     

Enhancement of photovoltaic performance in dye-sensitized solar cells with the spin-coated TiO2 blocking layer

The TiO2 thin film layers were introduced with the spin-coating method between FTO electrode and TiO2 photoanode in dye sensitized solar cell (DSSC) to prevent electron back migration from the FTO electrode to electrolyte. The DSSC containg different thickness of TiO2 thin film (10-30, 40-60 and 120-150 nm) were prepared and photovoltaic performances were analysed with /-Vcurves and electrochemical impedance spectroscopy. The maximum cell performance was observed in DSSC with 10-30 nm of TiO2 thin film thickness (11.92 mA/cm2, 0.74 V, 64%, and 5.62%) to compare with that of pristine DSSC (11.09 mA/cm2, 0.65 V, 62%, and 4.43%). The variation of photoelectric conversion efficiency of the DSSCs with different TiO2 thin film thickness was discussed with the analysis of crystallographic and microstructural properties of TiO2 thin films.     

Poly(3-hexylthiophene)/TiO2 nanoparticle-functionalized electrodes for visible light and low potential photoelectrochemical sensing of organophosphorus pesticide chlopyrifos

A dramatic visible light photoelectrochemical sensing platform for the detection of pesticide molecules at zero potential (versus saturated calomel electrode) was first constructed using poly(3-hexylthiophene)-functionalized TiO(2) nanoparticles. Poly(3-hexylthiophene) (P3HT) was synthesized via chemical oxidative polymerization with anhydrous FeCl(3) as the oxidant, 3-hexylthiophene as the monomer, and chloroform as the solvent, and the functional TiO(2) nanoparticles were facilely prepared by blending TiO(2) nanoparticles and P3HT in chloroform solution. The resulting photoelectrocatalysts were characterized by scanning electron microscopy, Raman spectroscopy, and X-ray diffractometry. Under visible light irradiation, P3HT generated the transition from the valence band to the conduction band, delivering the excited electrons into the conduction band of TiO(2) and then to the glassy carbon electrode. Simultaneously, a positive charged hole (h(+)) of TiO(2) may form and migrate to the valence band of P3HT, which can react with H(2)O to generate (?)OH, and then it converted chlopyrifos into chlopyrifos(?) that promoted the amplifying photocurrent response. On the basis of the proposed photoelectrochemical mechanism, a methodology for sensitive photoelectrochemical sensing for chlopyrifos at zero potential was thus developed. Under optimal conditions, the proposed photoelectrochemical method could detect chlopyrifos ranging from 0.2 to 16 μmol L(-1) with a detection limit of 0.01 μmol L(-1) at a signal-to-noise ratio of 3. The photoelectrochemical sensor had an excellent specificity against the other pesticides and could be successfully applied to the detection of reduced chlopyrifos in green vegetables, showing a promising application in photoelectrochemical sensing.     

平整二钛酸钾薄膜的制备及其气相光催化活性

采用溶胶-凝胶法制备了K2Ti2O5薄膜并进行表征;在K2Ti2O5薄膜表面上形成致密的十八烷基三氯硅烷(C18H37SiCl3,OTS)单层自组装膜(SAMs);用OTS SAMs 水接触角变化研究薄膜的气相光催化活性;测量了薄膜的光电流响应.研究发现:K2Ti2O5薄膜表面平整、均匀、致密、在玻璃基片上透明;在紫外和可见光区都有光吸收;K2Ti2O5薄膜上OTS SAMs在空气中用254nm的紫外光照射时降解速度比在TiO2薄膜上快;K2Ti2O5薄膜产生阳极光电流,比TiO2薄膜具有更强的光激发和更稳定的光电流响应.结果表明,K2Ti2O5薄膜在空气中用紫外光照射能很有效的分解OTS SAMs,是一种很好的治理气相有机污染物的光催化剂.     

Single wall carbon nanotube scaffolds for photoelectrochemical solar cells. Capture and transport of photogenerated electrons

Single wall carbon nanotube (SWCNT) architecture when employed as conducting scaffolds in a TiO2 semiconductor based photoelectrochemical cell can boost the photoconversion efficiency by a factor of 2. Titanium dioxide nanoparticles were dispersed on SWCNT films to improve photoinduced charge separation and transport of carriers to the collecting electrode surface. The shift of approximately 100 mV in apparent Fermi level of the SWCNT-TiO2 system as compared to the unsupported TiO2 system indicates the Fermi level equilibration between the two systems. The interplay between the TiO2 and SWCNT of attaining charge equilibration is an important factor for improving photoelectrochemical performance of nanostructured semiconductor based solar cells. The feasibility of employing a SWCNT-TiO2 composite to drive the water photoelectrolysis reaction has also been explored.