TiO2@CdS core–shell nanorods films: Fabrication and dramatically enhanced photoelectrochemical properties

In this paper, we prepared TiO₂@CdS core–shell nanorods films electrodes using a simple and low-cost chemical bath deposition method. The core–shell nanorods films electrodes were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–vis spectrometry techniques. After applying these TiO₂@CdS core–shell nanorods electrodes in photovoltaic cells, we found that the photocurrent was dramatically enhanced, comparing with those of bare TiO₂ nanorods and CdS films electrodes. Moreover, TiO₂@CdS core–shell nanorods film electrode showed better cell performance than CdS nanoparticles deposited TiO₂ nanoparticles (P25) film electrode. A photocurrent of 1.31 mA/cm², a fill factor of 0.43, an open circuit photovoltage of 0.44 V, and a conversion efficiency of 0.8% were obtained under an illumination of 32 mW/cm², when the CdS nanoparticles deposited on TiO₂ nanorods film for about 20 min. The maximum quantum efficiency of 5.0% was obtained at an incident wavelength of 500 nm. We believe that TiO₂@CdS core–shell heterostructured nanorods are excellent candidates for studying some fundamental aspects on charge separation and transfer in the fields of photovoltaic cells and photocatalysis.     

Tuning crystal structure of iridium-incorporated titanium dioxide nanosupport and its influence on platinum catalytic performance in direct ethanol fuel cells

Titanium dioxide (TiO₂) has recently been used as a promising support for platinum (Pt)-based catalysts; however, its very low electrical conductivity and understanding the effect of the TiO₂ structure on Pt electrocatalytic performance for ethanol electro-oxidation reaction (EOR) are major challenges in direct ethanol fuel cells. This study reports an easy and green approach to control the crystal structures of a robust iridium-incorporated TiO₂ nanomaterial and its effect on the Pt electrocatalytic performance for EOR. A green hydrothermal route is used to fabricate iridium-modified TiO₂ nanosupports with different structures by controlling the reaction temperature and time as well as solution pH without using further calcination, followed by the anchoring of Pt nanoparticles (NPs) via a surfactant-free modified reduction route. The experimental results indicate that the pure structure of the iridium-modified TiO₂ nanosupport can easily be obtained by controlling the solution pH. In terms of EOR, all prepared catalysts show more effective performance than the commercial Pt/C catalyst. Among the prepared catalysts, the Pt anchored on the rutile iridium-incorporated TiO₂ exhibits higher EOR performance than on the anatase iridium-incorporated TiO₂ nanosupport, with negative onset potential, high current density, and electrochemical stability. The enhancement is assigned to the great adsorption and desorption ability as well as the high natural resistance to metal NPs ripening on (110) facets of the rutile structure compared with the (101) facets of the anatase structure. This exploration can offer an efficient route for tuning the structure of metal oxides and understanding the effect of the structure of the TiO₂-based support on the Pt catalytic performance.     

Platinum–titanium intermetallic nanoparticle catalysts for oxygen reduction reaction with enhanced activity and durability

A facile method to prepare Pt–Ti intermetallic nanoparticles supported on carbon was developed. Starting from a commercial Pt/C catalyst, TiO₂ layers were formed on the Pt/C then thermal annealing under a reducing condition successfully produced intermetallic Pt–Ti nanoparticles with an average size of 4.2 nm. The intermetallic Pt–Ti/C showed enhanced activity and durability for oxygen reduction reaction due to the change in electronic structure and less aggregation.     

Pt 改性的高结晶度 TiO2 晶须的光催化性能

 以二钛酸钾 (K₂Ti₂O₅) 为前驱体, 通过离子交换和 800^oC 焙烧制备了 TiO₂晶须 (TiO₂(800^oC)), 并采用乙二醇胶体法, 在 TiO₂(800^oC) 样品上负载 1% Pt 纳米颗粒制成了 Pt/TiO₂(800^oC 催化剂. 采用 X 射线衍射、扫描电镜、透射电镜、X 荧光光谱和低温 N2 吸附-脱附等技术对催化剂进行了表征, 并考察了该催化剂光催化降解苯酚活性及稳定性. 结果表明, TiO₂(800^oC)样品为结晶度较高的纯锐钛矿 TiO₂, 载 Pt 后催化活性提高到原来的 2.3 倍, 具有很高的单位比表面积活性. 催化剂经 10 次重复使用后, Pt 流失量仅为 6%, 活性为新鲜催化剂的 91%. 而低结晶度的纯锐钛矿或混晶的 TiO₂ 负载 Pt 催化剂的活性和稳定性均不及 Pt/TiO₂(800^oC).     

Preparation of disk‐like Pt/CeO2‐p‐TiO2 catalyst derived from MIL‐125(Ti) for excellent catalytic performance

A feasible strategy is reported for the synthesis of a disk‐like Pt/CeO₂‐p‐TiO₂ catalyst derived from the titanium‐based metal–organic framework (MOF) MIL‐125(Ti) through a few valid steps. To verify the successful synthesis and structural features of the Pt/CeO₂‐p‐TiO₂ catalyst, as‐prepared samples were characterized using several techniques. The characterizations demonstrated that MOF‐derived porous TiO₂ was appropriate for application as a support owing to its moderate surface area (101 m² g^?1) and suitable pore size (6 nm). Moreover, to study the effect of calcination temperature on the catalytic performance, the obtained catalyst was calcined at various temperatures. It was found that Pt/CeO₂‐p‐TiO₂ calcined at 550 °C exhibited the highest catalytic performance, evaluated by means of the reduction of 4‐nitrophenol monitored by UV–visible spectra. Furthermore, this catalyst showed good reusability with a conversion of 94% even after six cycles. Finally, a possible reaction mechanism was proposed to explain the reduction of 4‐nitrophenol to 4‐aminophenol over the Pt/CeO₂‐p‐TiO₂ catalyst.     

Photovoltaic activity of Ti/MCM‐41

Ti/MCM‐41 is a well‐known heterogeneous catalyst for alkene epoxidation with organic peroxides. This titanosilicate contains isolated titanium atoms forming part of a framework of mesoporous silica whose structure is formed by parallel hexagonal channels 3.2 nm in diameter. The surface area and porosity of Ti/MCM‐41 are about 880 m² g^?1 and 0.70 cm³ g^?1, respectively. These values are among the highest for any material. Herein, we show that Ti/MCM‐41 exhibits photovoltaic activity. Dye‐sensitized solar cells using mesoporous Ti/MCM‐41 (2.8–5.7 % Ti content) as active layer, black dye N3 as photosensitizer and I₃^?/I^? in methoxyacetonitrile as electrolyte exhibit a V_OC, J_SC and FF of 0.44 V, 0.045 mA cm^?2 and 0.33, respectively. These values compare well against 0.75 V, 4.1 mA cm^?2 and 0.64, respectively, measured for analogous solar cells using conventional P‐25 TiO₂. However, the specific current density (J_SC/Ti atom) for the Ti/MCM‐41 is very similar to that of P25 TiO₂.     

Photoanode Based on Chain‐Shaped Anatase TiO2 Nanorods for High‐Efficiency Dye‐Sensitized Solar Cells

Anatase TiO₂ nanorods with large specific surface areas and high crystallinity have been synthesized by surfactant‐free hydrothermal treatment of water‐soluble peroxotitanium acid (PTA). X‐ray diffraction and TEM analysis showed that all TiO₂ nanorods derived from PTA in different hydrothermal processes were in the anatase phase, and high aspect ratio TiO₂ nanorods with chain‐shaped structures were formed at 150 °C for 24 h by oriented growth. The nanorods were fabricated as photoanodes for high‐efficiency dye‐sensitized solar cells (DSSCs). DSSCs fabricated from the chain‐shaped TiO₂ nanorods gave a highest short‐circuit current density of 14.8 mA cm^?2 and a maximum energy conversion efficiency of 7.28 %, as a result of the presence of far fewer surface defects and grain boundaries than are present in commercial P25 TiO₂ nanoparticles. Electrochemical impedance spectroscopy also confirmed that DSSCs based on the TiO₂ nanorods have enhanced electron transport properties and a long electron lifetime.     

Catalytically Active Rh Sub‐Nanoclusters on TiO2 for CO Oxidation at Cryogenic Temperatures

The discovery that gold catalysts could be active for CO oxidation at cryogenic temperatures has ignited much excitement in nanocatalysis. Whether the alternative Pt group metal (PGM) catalysts can exhibit such high performance is an interesting research issue. So far, no PGM catalyst shows activity for CO oxidation at cryogenic temperatures. In this work, we report a sub‐nano Rh/TiO₂ catalyst that can completely convert CO at 223 K. This catalyst exhibits at least three orders of magnitude higher turnover frequency (TOF) than the best Rh‐based catalysts and comparable to the well‐known Au/TiO₂ for CO oxidation. The specific size range of 0.4–0.8 nm Rh clusters is critical to the facile activation of O₂ over the Rh–TiO₂ interface in a form of Rh?O?O?Ti (superoxide). This superoxide is ready to react with the CO adsorbed on TiO₂ sites at cryogenic temperatures.     

Cobalt Doped Titanium Dioxide Nanoparticles: Synthesis,Characterization and Electrocatalytic Study

In this work, green synthesis of cobalt doped titanium dioxide (Co‐TiO₂) has been carried out in aqueous medium using gelatin. The Co‐TiO₂ particles have been characterized using transmission electron microscopy (TEM), X‐ray diffraction (XRD), energy dispersive X‐ray (EDAX), FT‐IR spectroscopy and voltammetry techniques. XRD results show pure Co‐TiO₂ and TiO₂ powders with average crystallite size about 12 nm and 15 nm, respectively. Co loaded in TiO₂ hasn't influence crystalline structure. Moreover, efficient Co‐TiO₂‐based anode was fabricated by casting of the Co‐TiO₂ solution on glassy carbon electrode (Co‐TiO₂/GCE). The electrocatalysis of oxygen evolution reaction (OER) at Co‐TiO₂/GCE has been examined using linear scanning voltammetry (LSV) in alkaline media. The OER is significantly enhanced at Co‐TiO₂/GCE, as demonstrated by a negative shift in the LSV curve at the Co‐TiO₂/GCE compared to that obtained at the unmodified one. The value of energy saving of oxygen gas at a current density of 5 mA cm^?2 is 12.6 kW h kg^?1. The low cost as well as the marked stability of the modified electrode make it promising candidate in industrial water electrolysis process.     

Single‐Nanoparticle Collision Events: Tunneling Electron Transfer on a Titanium Dioxide Passivated n‐Silicon Electrode

Single‐nanoparticle collisions were observed on an n‐type silicon electrode (600 μm diameter) passivated by a thin layer of amorphous TiO₂, where the current steps occurred by tunneling electron transfer. The observed collision frequency was in reasonable agreement with that predicted from theory. The isolated electrode, after a collision experiment, with a Pt/TiO₂/n‐Si architecture was shown to retain the photoelectrochemical properties of n‐Si without photocorrosion or current decay. The Pt/TiO₂/n‐Si electrode produced 19 mA cm^?2 of photocurrent density under 100 mW cm^?2 irradiation from a xenon lamp during oxygen evolution without current fading for over 12 h.     

Synthesis and In Vitro Bioactivity of TiO2 Nanorods

Titanium dioxide (TiO₂) powders were synthesized by the hydrothermal method. The TiO₂ powders were composed of nanorods with dimensions of 10–18 nm and 60–180 nm in diameter and length, respectively. The in vitro bioactivity of the TiO₂ powders was examined by evaluation of hydroxyapatite (HAp) formation ability in simulated body fluid (SBF). The results showed that TiO₂ nanorods induced the formation of nanocrystalline HAp after soaking in SBF after 1 day rapidly. Our study indicates that TiO₂ nanorods are bioactive and might be used for preparation of new biomaterials.     

Gold particles supported on self-organized nanotubular TiO2 matrix as highly active catalysts for electrochemical oxidation of glucose

Au/TiO₂/Ti electrode was prepared by a two-step process of anodic oxidation of titanium followed by cathodic electrodeposition of gold on resulted TiO₂. The morphology and surface analysis of Au/TiO₂/Ti electrodes was investigated using scanning electron microscopy and EDAX, respectively. The results indicated that gold particles were homogeneously deposited on the surface of TiO₂ nanotubes. The nanotubular TiO₂ layers consist of individual tubes of about 60–90 nm in diameter, and the electrode surface was covered by gold particles with a diameter of about 100–200 nm which are distributed evenly on the titanium dioxide nanotubes. This nanotubular TiO₂ support provides a high surface area and therefore enhances the electrocatalytic activity of Au/TiO₂/Ti electrode. The electrocatalytic behavior of Au/TiO₂/Ti electrodes in the glucose electro-oxidation was studied by cyclic voltammetry. The results showed that Au/TiO₂/Ti electrodes exhibit a considerably higher electrocatalytic activity toward the glucose oxidation than that of gold electrode.     

组合型Pt/TiO_2催化剂用于低温催化甲苯完全氧化

将均匀分布的纳米Pt粒子直接吸附到TiO2载体上,即制得了组合型Pt/TiO2催化剂(Pt/TiO2-AS).与浸渍法制备的Pt/TiO2催化剂(Pt/TiO2-WI)比较,Pt/TiO2-AS催化剂在催化甲苯完全氧化反应中表现出了很好的催化性能,甲苯转化率为100%时的反应温度低至150°C,而且即使在较高甲苯浓度和较高气体空速下,该催化剂也能保持较好的催化性能.通过X射线衍射(XRD)、N2吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、氢气程序升温还原(H2-TPR)及傅里叶变换红外(FTIR)光谱等对两种Pt/TiO2催化剂的结构和表面性能进行了表征.结果表明组合型Pt/TiO2-AS催化剂粒径小(2.5 nm),活性组分主要以Pt0形式存在且分布在载体表面,而且载体表面Ti―O键活化使催化剂具有较强的催化氧化能力.另外,活性中心的价态变化(Pt0→Ptδ+)是导致Pt/TiO2-AS催化剂失活的主要原因.     

电镀法制备Pt/TiO2纳米管电极及其电催化析氢性能

采用阳极氧化法制备得到锐钛矿型二氧化钛(TiO₂)纳米管阵列,在其表面通过电镀法沉积Pt,得到了低铂的Pt/TiO₂纳米管电极(Pt/TiO₂-NTs)。通过扫描电子显微镜和透射电子显微镜对其进行形貌表征后发现,Pt较为均匀地分布于TiO₂纳米管阵列中。进一步的电催化析氢结果表明,Pb/TiO₂-NTs在10 m A·cm^-2时,过电位为0.079 V,塔菲尔斜率为42.7 m V·dec^-1,较Pt/TiO₂致密膜电极(Pt/TiO₂-F)以及商业Pt/C催化剂显示了更为优异的催化活性。同时,在长循环稳定性测试(3 000个周期)中,Pb/TiO₂-NTs相较于上述2种对比电极显示了更为优异的稳定性。     

Fabrication of a self‐doped TiO2 nanotube array electrode for electrochemical degradation of methyl orange

Self‐doped TiO₂ nanotube array (DTNA) electrodes were fabricated through anodic oxidation combined with cathodic reduction. The morphology and structural features of pristine TiO₂ nanotube arrays and DTNA electrodes were studied through scanning electron microscopy, X‐ray diffractometry, and X‐ray photoelectron spectroscopy. An accelerated life test was used to test the electrode service lifetime and thus the electrode's stability. The service lifetime of the DTNA electrode prepared at constant 40 V for 6 hr was approximately 338.7 hr at constant 1 mA/cm² in a 1 M NaClO₄ solution. Methyl orange (MO) was employed as the degradation probe for measuring electrochemical oxidation performance. The color removal rate of 200 mg/L MO of the DTNA electrode (85.2% at 1 mA/cm²) was greater than that of the Ti/IrO₂ electrode (31.1% at 1 mA/cm²). The larger the surface area of the DTNA electrode is, the more conductive the electrode is for the degradation of organic substances. Organic degradation on the DTNA electrode occurred primarily through an indirect pathway (producing [?OH]).     

低温吸附制备Au-TiO2复合薄膜及其光电化学性质

在低温条件下将预先合成的Au溶胶吸附到TiO₂薄膜上以制备纳米Au-TiO₂复合薄膜,以超高分辨率场发射扫描电镜(FESEM)、X射线衍射(XRD)及X射线光电子能谱(XPS)表征Au-TiO₂膜,并在UV辐照下测定了Au-TiO₂薄膜电极的光电化学性质。纳米Au呈金属态,平均粒径为(4.3±1.2) nm,负载量高,均匀地沉积于TiO₂薄膜表面。光电化学测试表明,沉积纳米Au后,TiO₂电极的光生电流提高近5倍,光生电压明显向负值增大,说明纳米Au可增强光生载流子的分离效率,促进电荷在电极与溶液界面间的转移。Au-TiO₂电极的电荷传递法拉第阻抗(R_ct)是TiO₂电极的一半,说明负载的纳米Au粒抑制了光生电子-空穴的复合,提高了电极中载流子浓度。     

Ti/TiO2 indicator electrodes formed by plasma electrolytic oxidation for potentiometric analysis

Ti/TiO₂ indicator electrodes were prepared by plasma electrolytic oxidation (PEO) method in the tetraborate electrolyte and were used for potentiometric indication of chemical reactions of different types and for analysis of surface and industrial wastewaters on the example of potentiometric determination of alkalinity and chloride. The electrodes formed at current densities of 0.05, 0.1, 0.15 and 0.2 A/cm² are different in composition, surface morphology and electroanalytical properties. The electrodes formed at a current density of 0.05 A/cm² exhibit the highest pH-sensitivity and generate the highest analytical signal at the equivalence point in the acid–base and precipitation titrations. The maximum analytical signal at the equivalence point, exceeding in magnitude the analytical signal, obtained by classical Pt electrode in oxidation–reduction and complexometric titrations generates PEO layers formed at a current density of 0.05 A/cm² and a platinum-modified nanoparticles. The results of the potentiometric titration of the surface and technogenic waters using as indicator Ti/TiO₂ electrodes are comparable with the conventionally used glass electrode (to determine alkalinity) and Ag electrode (to the determine chloride) and the results of visual titration. The advantage of the obtained metal oxide systems is the ability to determine two hydrochemical parameters due to their multifunctionality and opportunity to work with a single electrode. In addition, these sensors offer some analytical characteristics such as sensitivity, good reproducibility, high mechanical stability and a simple preparation procedure.     

A self-cleaning nonenzymatic glucose detection system based on titania nanotube arrays modified with platinum nanoparticles

In the present work, we show how TiO₂ nanotube layers that are decorated with a Pt-nanoparticle coating can be fabricated and operated as a reusable glucose sensing system. A critical amount of Pt coating is essential not only to provide an effective catalyst for glucose oxidation but also to establish a sufficient conductivity along TiO₂ nanotube walls to allow an efficient amperometric operation of the electrode. On such an electrode the self-cleaning photocatalytic features of TiO₂ can be maintained and used to re-establish poisoned activity of the Pt particles.     

Visible Light Photocatalytic Activity of Pt/N‐TiO2 towards Enhanced H2 Production from Water Splitting

Present work mainly focuses on experimental investigation to improvement of hydrogen production by water photoelectrolysis. An experimental facility was designed and constructed for visible light photocatalysis. A series of N‐TiO₂ photocatalysts impregnated with platinum on the surface of N‐TiO₂ were prepared. Hydrogen production upon irradiating aqueous Pt/N‐TiO₂ suspension with visible light was investigated. The shift in excitation wavelength of TiO₂ was 380 nm improved the yield of hydrogen production by N‐TiO₂ and Pt/N‐TiO₂. We used a 400 W mercury arc lamp combined with a 400 nm cutoff filter eliminating all the wavelengths under 400 nm. Pt/N‐TiO₂ material was characterized with TPR, reflective UV/Visible spectroscopy and TEM. The best hydrogen production rate obtained for this setup for N/Ti = 10, 0.05 wt% Pt/N‐TiO₂, through water splitting was about 772 μmolh^?1g^?1.     

Compositing Amorphous TiO2 with N‐Doped Carbon as High‐Rate Anode Materials for Lithium‐Ion Batteries

Compositing amorphous TiO₂ with nitrogen‐doped carbon through Ti? N bonding to form an amorphous TiO₂/N‐doped carbon hybrid (denoted a‐TiO₂/C? N) has been achieved by a two‐step hydrothermal–calcining method with hydrazine hydrate as an inhibitor and nitrogen source. The resultant a‐TiO₂/C? N hybrid has a surface area as high as 108 m² g^?1 and, when used as an anode material, exhibits a capacity as high as 290.0 mA h g^?1 at a current rate of 1 C and a reversible capacity over 156 mA h g^?1 at a current rate of 10 C after 100 cycles; these results are better than those found in most reports on crystalline TiO₂. This superior electrochemical performance could be ascribed to a combined effect of several factors, including the amorphous nature, porous structure, high surface area, and N‐doped carbon.