Photoelectrochemical properties of iron (III)-doped TiO2 nanorods

Fe (iron)-doped TiO₂ nanorods were grown on fluorine doped tin oxide (FTO) substrates with various Fe doping concentrations using modified chemical bath deposition (M-CBD). We investigated the effects of Fe doping concentration on the morphological, structural, optical, and photoelectrochemical (PEC) properties of the TiO₂ nanorods. From this study, it was found that the PEC properties were mainly dependent on the morphological and optical properties of the Fe-doped TiO₂ nanorods. At low Fe doping concentration, the PEC properties were highly affected by the optical properties. On the other hand, the PEC properties were significantly affected by the morphological properties at high doping concentration. We observed a maximum photocurrent density of 0.48 mA/cm² at a Fe doping concentration of 2 at% from this study. In addition, the donor density and flat-band potential of the Fe doping concentration from the Mott–Schottky plot were analyzed.     

Conversion of benzoic acid during TiO2-mediated photocatalytic degradation in water

The photocatalytic degradation of benzoic acid in water over Degussa P-25 TiO₂ suspensions was studied. UVA irradiation at 365 nm was supplied by a medium pressure mercury lamp providing 25 mW cm⁻² light intensity. Experiments were conducted at benzoic acid initial concentrations between 25 and 150 mg L⁻¹, catalyst loadings between 0.2 and 1 g L⁻¹ and initial solution pH values between 2 and 10.6. Conversion increased with increasing catalyst loading up to about 0.6 g L⁻¹ and it was favored at alkaline or neutral conditions but impeded at extremely acidic conditions. Increasing initial substrate concentration led to decreased benzoic acid conversion, which was found to follow a Langmuir–Hinshelwood kinetic expression. High performance liquid chromatography (HPLC) was employed to follow benzoic acid concentration profiles as well as to identify reaction by-products, while chemical oxygen demand (COD) and total organic carbon (TOC) analyses were carried out to assess the extent of mineralization. Benzoic acid hydroxylation by-products, namely 2-, 3- and 4-hydroxybenzoic acids as well as phenol were identified as reaction intermediates, although these contributed only a small fraction of the residual organic content. Although benzoic acid at 50 mg L⁻¹ was not ecotoxic to marine photobacteria Vibrio fischeri, its photodegraded solution exhibited substantial toxicity, which, however, proved not to be due to the identified intermediates.     

Ultrasound assisted sol-gel TiO2 powders and thin films for photocatalytic removal of toxic pollutants

The paper presents a study on the structural, surface and photocatalytic properties of the ultrasound assisted sol-gel titanium dioxide particles, as part of stable photocatalytic ink formulations deposited on fabrics. The photocatalytic activity was validated using methylene blue as reference pollutant, under UV, VIS and combined UV+VIS radiation and allowed selecting the optimum TiO₂ samples for inks preparation. To minimize the particles agglomeration stabilizing agents were added and the stability was quantitatively evaluated considering the relative increase in the VIS transmittance for a pre-set period of 30 min. Further on, the ink(s) were deposited by cold spraying on cotton woven fabrics and a removal efficiency higher than 95% was observed in the degradation of the highly toxic mustard gas, after 30 min of UV irradiation.     

All-solid-state MoS2/WO3 photoelectrodes as high-efficiency catalysts for reductive/sorptive/recycling of hexavalent chromium

Photoelectrocatalysis (PEC) is an effective approach to eliminate carcinogen hexavalent chromium (Cr(VI)) in wastewater, in which high-performance catalysts are crucial. Herein, controlled growth of thin molybdenum disulphide (MoS₂) nanosheets on self-supported tungsten trioxide (WO₃) created an all-solid-state MoS₂/WO₃ heterojunction serving as electrode and catalyst simultaneously for removing Cr(VI). Countless small and thin MoS₂ nanoflakes build in a huge and porous interface for harvesting lights and adsorbing chromium species. And the highly conductive WO₃ substrate facilitates the transfer of those photoexcited-electron and therefore suppresses the recombination between electrons and holes. Furthermore, assisted by bias potential, electron streams from external circuit render an electron-rich interface at the MoS₂/WO₃ cathode, accelerating the Cr(VI) reduction by PEC. At −1.2 V, the PEC reduction efficiency of Cr(VI) reaches 100% within 30 min, surpassing the pristine WO₃ by 2.7 times. The generated Cr(III) ions can be immobilized on the porous MoS₂/WO₃ cathode through electrostatic attraction, enabling removal of total chromium. More importantly, the Cr(III) anchored to the catalyst can be effortlessly recovered by eluting with clean water, which also refreshes the MoS₂/WO₃ cathode. This study provides a new approach to fabricating photoelectrodes for sustainable PEC reduction and treatment of Cr(VI) containing wastewater.     

Improved photoelectrocatalytic degradation of methylene blue by Ti3C2Tx/Bi12TiO20 composite anodes

In order to effectively reduce the high recombination rate of photogenerated carriers when Bi₁₂TiO₂₀ (BTO) was excited by visible light, Ti₃C₂T_x/BTO/fluorine-doped tin oxide photoanodes were conveniently prepared with the aid of mechanical coating by gentle ultrasonic mixing. Systematic characterization and the degradation of methylene blue in a photoelectrochemical cell were performed. The results showed that the Ti₃C₂T_x/BTO composite exhibited a strong light absorption ability and the effective separation of photogenerated carriers. The optimal anode (6 wt% Ti₃C₂T_x/BTO) degraded 85.4% of methylene blue within 120 min at an applied electric field of 1 V, with a reaction rate that was 3.5 times that of BTO. It was proved that Ti₃C₂T_x, as a useful co-catalyst, creates an internal electric field at the contact interface with BTO and an external electric field, which are responsible for the enhanced photoelectrocatalytic degradation capacity of the composite anode materials.     

固体酸WO_3/TiO_2的制备及其催化合成正丁酸己酯

制备了WO3为活性组分、TiO2为载体的双金属固体酸酯化催化剂WO3/TiO2,用于正丁酸与正己醇酯化合成正丁酸己酯,考察了催化剂中WO3含量、焙烧温度、催化剂用量、n(正己醇)∶n(正丁酸)、反应时间和催化剂重复使用性等因素对酯化率的影响。实验结果表明,催化剂的适宜制备条件是WO350%、500℃焙烧2.0 h。催化合成正丁酸己酯的适宜反应条件为:n(正己醇)∶n(正丁酸)=2.0,催化剂用量2.0 g,环己烷10 mL,反应时间90 m in。在此条件下,酯化率为98.8%,催化剂使用5次后,酯化率仍可达87.6%。     

Mechanism of degradation of nitrilotriacetic acid by heterogeneous photocatalysis over TiO2 and platinized TiO2

TiO₂-heterogeneous photocatalysis of nitrilotriacetic acid (NTA) at pH 2.5 was studied to establish the kinetic regime and the reaction mechanism. Pure Degussa P-25 and Hombikat UV100 commercial samples were compared. A Langmuirian behavior was observed over P-25. Platinization of the Hombikat sample (0.5 wt.%) caused an important increase on the photocatalytic rate with a change in the kinetics from zero order in the pure precursors to first order in the platinized sample. The nature of the intermediates and their evolution with time were compared on all systems. Glycine, iminodiacetic and oxamic acids have been identified in different proportions, together with ammonium and glycolic acid, depending on the catalyst used. The rapid depletion of NTA was not accompanied by a corresponding total organic carbon (TOC) reduction, but 84% of TOC decrease was obtained on P25 after 24 h, a very reasonable result for refractory compounds. A detailed mechanism is proposed for the photocatalytic reaction, suggested to be the same over the three catalysts here tested.     

TiO2纳米管/UV/O3对腐殖酸的降解动力学

用自制的TiO₂纳米管（TNTs）作为催化剂,对腐殖酸进行TNTs/UV/O₃工艺降解研究.从动力学角度分析了光催化、臭氧化的协同作用及催化剂煅烧温度的影响,考察了反应温度、初始pH值、催化剂投加量和臭氧投加量对降解速率的影响,建立了新型动力学模型.结果表明,光催化和臭氧化有很强的协同作用,催化剂最佳煅烧温度为400℃,腐殖酸的TOC降解过程符合零级反应,模型显示当原水pH值为7.35,TNTs投加量0.806g·L^-1,O₃投加量0.49g·h^-1时TNTs/UV/O₃对腐殖酸TOC的降解取得最佳反应速率,当反应温度T为25℃时,最佳k为0.8095mg·L^-1·min^-1,当反应温度T为30℃时,最佳k为0.8231mg·L^-1·min^-1.试验结果和模型结果对比得出试验值基本符合动力学模型.     

Single step electrosynthesis of Cu2ZnSnS4 (CZTS) thin films for solar cell application

The Cu₂ZnSnS₄ (CZTS) thin films have been electrodeposited onto the Mo coated and ITO glass substrates, in potentiostatic mode at room temperature. The deposition mechanism of the CZTS thin film has been studied using electrochemical techniques like cyclic voltammetery. For the synthesis of these CZTS films, tri-sodium citrate and tartaric acid were used as complexing agents in precursor solution. The structural, morphological, compositional, and optical properties of the CZTS thin films have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), EDAX and optical absorption techniques respectively. These properties are found to be strongly dependent on the post-annealing treatment. The polycrystalline CZTS thin films with kieserite crystal structure have been obtained after annealing as-deposited thin films at 550 in Ar atmosphere for 1 h. The electrosynthesized CZTS film exhibits a quite smooth, uniform and dense topography. EDAX study reveals that the deposited thin films are nearly stoichiometric. The direct band gap energy for the CZTS thin films is found to be about 1.50 eV. The photoelectrochemical (PEC) characterization showed that the annealed CZTS thin films are photoactive.     

SO4^2-／TiO2／La^3＋催化合成季戊四醇三丙烯酸酯

以自制的稀土改性固体超强酸SO4^2-／TiO2／La^3 为催化剂，通过酸醇直接酯化合成了季戊四醇三丙烯酸酯(PETA)，研究了反应条件对产率的影响、催化剂的制备条件对其催化活性的影响，得到较佳工艺条件，并简单探讨了催化剂的表面组成特征及催化机理。结果表明：当酸醇摩尔比为3．5：1，催化剂、阻聚剂用量分别为2％、1．5％(以酸、醇总质量计)，甲苯用量为55％(反应物总质量计)，120℃左右反应3h，产率可达78．5％；该固体酸催化剂可代替浓硫酸，是一种具有广泛应用前景的环境友好型催化剂。     

Photocatalytic degradation of malic acid using a thin coated TiO2‐film: Insights on the mechanism of photocatalysis

Decontamination of opaque fluids using photocatalysts and near Ultraviolet (UV) irradiation involves major technical challenges. This study considers a thin TiO₂ layer placed in a new Chemical Reactor Engineering Centre (CREC)‐photoreactor cell. This new photoreactor cell is used for the photocatalytic degradation of malic and malonic acids, typical apple juice components. Conversion of organic species can only proceed through the “dark side” of the TiO₂ layer, which is in direct contact with the fluid. Under the selected operating conditions both external mass‐transfer limitations and photolysis are found to be negligible. Macroscopic radiation balance shows that 92% of near UV radiation is absorbed by the ‘back side” of the TiO₂‐film. Photocatalytic degradation experiments with 10, 20, 30, and 40 ppm malic acid initial concentrations, show that malonic acid is a main intermediate. Complete malic acid conversion occurs after 5–8 h of irradiation. Kinetic modeling of malic and malonic acid photodegradation with kinetic parameter estimation is performed using both an “in series” and an “in series‐parallel” reaction networks. The “in series‐parallel” reaction network displays better ability for predicting CO₂ formation, showing maximum quantum yields of 14.2%. Given that in the CREC‐photoreactor cell with a thin TiO₂‐film, photocatalysis can only proceed via the transfer of mobile “h⁺” sites from the irradiated side to the “dark side', this study demonstrates the significance of this step on the overall photocatalysis mechanism. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3286–3299, 2014     

旋转填充床中O_3/Fenton工艺处理聚丙烯酰胺污水的研究

在旋转填充床(RPB)中,研究了O_3/Fenton工艺处理模拟聚丙烯酰胺(PAM)污水的效果。考察了溶液p H值,Fe~(2+)浓度,H2O2浓度,O_3浓度,反应温度与RPB转速对PAM氧化降解率以及化学需氧量(COD)去除率的影响。结果表明,在pH值为4,Fe~(2+)浓度为0.25 mmol/L,H_2O_2浓度为0.8 mmol/L,O_3浓度为50 mg/L,反应温度为25℃,以及RPB转速为800 r/min的条件下,PAM氧化降解率和COD去除率可以达到96.82%与89.96%,表明采用RPB强化O_3/Fenton工艺处理PAM污水具有良好的效果。     

Growth of amorphous,anatase and rutile phase TiO2 thin films on Pt/TiO2/SiO2/Si (SSTOP) substrate for resistive random access memory (ReRAM) device application

Memory structures play a basic role in providing integrated circuits of powerful processing capabilities. Even most powerful processors have nothing to offer without an accompanying memory and importantly, the development of mobile devices is dependent on the continual improvement of memory technology. Herein, we report the synthesis of TiO₂ thin films on SSTOP (Pt/TiO₂/SiO₂/Si) substrate via physical vapour deposition process for the first time. The layers consisted of Si, SiO₂, TiO₂ and Pt, hence the SSTOP shorthand is used throughout the text. Three different phases of TiO₂ thin films were obtained, i.e. amorphous, anatase and rutile phases, by controlling the reaction parameters which were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM) and Raman-scattering spectroscopy in order to understand the crystallographic, morphological, compositional and scattering properties. The detailed studies confirmed the formation of various crystal phases of titania. The grown thin films on SSTOP substrates were further utilized to fabricate resistive random access memory (ReRAM) devices and the initial electrical screening was performed on capacitor-like structures which were prepared using platinum top electrodes (diameter = 250 μm) on a 14 × 14 array metal contact mask. Current-Voltage (I–V) measurements were implemented employing a range of current compliances (IC). The detailed electrical characterizations revealed that the forming field for a switchable unipolar device was found to be greatest on rutile titania and lowest on the amorphous titania phase. Similarity, the resistive contrast was greatest on the rutile titania phase and lowest on the anatase titania phase.     

Effect of aluminum chloride and Pt/ TiO2 on the thermal degradation of poly(vinyl chloride) in solution

The effect of two catalysts, Pt/TiO₂ and aluminum chloride, on the degradation of poly (vinyl chloride) (PVC) in solution was investigated at various temperatures. The molecular weight distribution of the polymer was obtained by analyzing the samples by gel permeation chromatography. Experimental data indicated that the catalysts enhanced the degradation rate of PVC compared to the thermal degradation of PVC. Continuous distribution kinetic models were used to evaluate the degradation rate coefficients. The activation energy, calculated from the temperature dependence of rate coefficients, was 26.5, 31.5, and 43.7 kcal/mol for the thermal degradation of PVC in solution, in the presence of Pt/TiO₂ and in the presence of AlCl₃, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3532–3535, 2003     

磁性光催化剂Fe3O4/SiO2/TiO2的制备及光催化降解苯酚

采用撞击流-旋转填料床辅助沉淀法连续制备Fe₃O₄磁性纳米颗粒,然后采用溶胶-凝胶法制备了具有磁性核壳结构Fe₃O₄/SiO₂/TiO₂颗粒,通过傅里叶变换红外光谱（FTIR）、X射线衍射仪（XRD）、透射电子显微镜（TEM）、热重分析仪（TGA）、振动样品磁强计（VSM）和紫外-可见漫反射光谱（UV-vis）等对材料的微观结构、形貌及性能进行了表征。考察了正硅酸乙酯添加量、铁钛比对Fe₃O₄/SiO₂/TiO₂磁性催化剂催化性能的影响。结果表明：制得的Fe₃O₄/SiO₂/TiO₂结晶度好,磁响应性高。当正硅酸乙酯添加量为20mL、铁钛比为1∶8时,制备的Fe₃O₄/SiO₂/TiO₂纳米光催化剂表现出较高的光催化活性和磁性能,紫外光照射2h后,苯酚水溶液降解效率高达86.7%。     

H_3PW_(12)O_(40)/TiO_2催化合成对羟基苯甲酸丁酯的研究

采用溶胶-液相法制备了H3PW12O40/TiO2复合催化剂,用FT-IR分析方法对催化剂进行了结构表征。以对羟基苯甲酸和正丁醇为原料合成了对羟基苯甲酸丁酯,考察了反应物配比、催化剂用量、反应时间及催化剂的重复使用性能对产品收率的影响。实验结果表明,合成对羟基苯甲酸丁酯的较优反应条件为:对羟基苯甲酸0.1 mol,n(对羟基苯甲酸)∶n(正丁醇)=1.0∶5.0(摩尔比),催化剂的用量为1.2 g,反应时间4.0 h。上述条件下,对羟基苯甲酸丁酯的收率可达85.0%以上。     

固体超强酸SO2-4/TiO2催化合成乙酸环己酯

以乙酸和环己醇为原料，用不同晶型纳米TiO2制备的SO4^2-／TiO2超强酸为催化剂合成乙酸环己酯。考察了不同晶型纳米TiO2制备超强酸催化活性、催化剂活化温度、催化剂的用量、反应物摩尔比等因素对收率的影响。实验结果表明，较适宜条件为：锐钛型纳米TiO2制备超强酸，环己醇的用量在0．4mol的情况下，催化剂活化温度450℃、催化剂的用量1．50g，环己醇与乙酸的摩尔比1：2，酯收率达95．6％。     

Isothermal crystallization and melting behaviors of bionanocomposites from poly(lactic acid) and TiO2 nanowires

Two representative poly(lactic acid) (PLA) nanocomposites with 1% TiO₂ nanowires were prepared through in situ melt polycondensation and easy solution‐mixing approaches, respectively. The former was denoted as ISPLANC, and the latter as SMPLANC. The isothermal crystallization kinetics and melting behaviors of pure PLA, ISPLANC, and SMPLANC were comparatively investigated by differential scanning calorimetry in the temperature range of 80–115°C. Maximum crystallization growth rate (G_exp) was observed at 100°C for all three samples. The well dispersed TiO₂ nanowires acted as effective nucleation agents in ISPLANC, which exhibited much higher G_exp in compared to pure PLA and SMPLANC below 110°C. However, much smaller crystallization enthalpy of ISPLANC was obtained because of its restricted chain mobility in forming crystalline lamellar. The crystallization behavior of all three samples fit the Avrami equation quite well, with most of the R² values larger than 0.9990. Double‐melting behaviors were observed after heating the samples after isothermal crystallization at various temperatures, which was explained by the melt recrystallization of the smaller and imperfect crystals formed at lower isothermal crystallization temperatures. We also obtained the equilibrium melting temperatures of the three samples by carrying out Hoffman–Weeks plots. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Atmospheric pressure spatial ALD of Al2O3 thin films for flexible PEALD IGZO TFT application

Atmospheric pressure spatial atomic layer deposition (AP S-ALD)-derived Al₂O₃ films were investigated on the growth temperatures (100 °C ～ 200 °C) and demonstrated as the gate insulator for IGZO thin film transistor (TFT) applications. When the growth temperature increases to 200 °C, growth per cycle (GPC) and refractive index of the Al₂O₃ films were 1.33 Å/cycle and 1.63, respectively. The film density also increased from 2.55 g/cm³ to 2.79 g/cm³ on the growth temperature, which decreasing the carbon impurities of the Al₂O₃ film (100 °C: 3.57 at%, 150 °C: 1.73 at%, 200 °C: N/A). In addition, the impurity and low growth temperature may degrade not only film surface roughness, but also electrical characteristics. As the buffer and gate insulator Al₂O₃ layers, the IGZO TFT were fabricated on a polyimide substrate. The IGZO TFTs with the Al₂O₃ layers showed excellent device performances: 52.48 cm²/V.sec of field effect mobility, ?3.09 ± 0.14 of threshold voltage, and 0.14 ± 0.01 subthreshold swing. In addition, the TFT exhibited excellent bias reliability and mechanical bending stability. This highly stability will be attributed to AP S-ALD Al₂O₃ acting as an excellent insulator.