斜板液膜反应器光电催化降解罗丹明B

采用溶胶-凝胶法制备了TiO2/Ti电极,进行光电催化降解罗丹明B(RhB)试验。确定了最佳降解条件:外加偏压+0.8 V、废水流量7.7 L/h、初始pH=2.5和电解质质量浓度2.0 g/L。在最佳条件下,处理20 mg/L的RhB溶液1.5 h,脱色率和TOC去除率分别达到97.3%和76.2%。结果表明,由于同时强化了激发光源的利用率和溶液的传质效率,斜板液膜反应器可高效降解RhB。     

Graphite-supported TiO2 for 4-nitrophenol degradation in a photoelectrocatalytic reactor

Amorphous TiO₂, prepared at room temperature through a sol–gel method implementing hydrolysis of TiCl₄, has been supported on graphite rods and then annealed at 673 K. In this way graphite was completely covered by a porous anatase TiO₂ layer, with an external thickness of about 1 μm, with graphite pores completely filled by the semiconductor particles. The obtained electrode was structurally characterized by SEM microscopy coupled to EDAX mapping and by Raman spectroscopy. A Pyrex annular reactor was designed in order to test the prepared electrodes for the photoelectrocatalytic degradation of 4-nitrophenol, a target pollutant dissolved in aqueous conductive solution. The continuous reactor worked in total recirculation mode and the degradation runs were carried out by applying near UV-light, bias or both energy sources. The influence of flow rate, initial 4-nitrophenol concentration and applied potential on the degradation rate was studied.     

A novel photoelectrocatalytic system for organic contaminant degradation on a TiO2 nanotube (TNT)/Ti electrode

A novel degradation system, combined with photon-efficient thin-film photocatalysis, conventional bulk-phase photocatalysis and photocarrier-efficient electrocatalysis (TBPE), was developed on a vertically ordered one-dimensional (1D) TiO₂ nanotube (TNT)/Ti electrode for the purification of organics. The TBPE system possessed excellent optical, electrochemical, photoelectrochemical and photoelectrocatalytic properties as well as a high mass-transfer coefficient and interfacial activity. The combined degradation of methyl orange (MO) was optimized by varying the rotation angular velocity, applied bias and substrate concentration, and a photoelectrochemical synergetic effect of 62.2% was observed under the optimized conditions for TBPE compared to the individual electrocatalytic (EC) and photocatalytic (PC) systems. To explore the mechanisms, the combined thin-film degradation system of photon-efficient thin-film photocatalysis with photocarrier-efficient electrocatalysis (TPE), and the combined bulk-phase degradation system of conventional bulk-phase photocatalysis with photocarrier-efficient electrocatalysis (BPE), were comparatively estimated. A dramatic increase of 29.4-74.4% was observed in the MO removal efficiency via the thin-film TPE system compared to the bulk-phase BPE system. The results indicated that in the proposed TBPE system on the 1D TNT electrode, the predominant degradation occurred via the TPE system due to its excellent UV utilization efficiency and resultant interfacial photoactivity.     

Photoelectrocatalytic degradation of rhodamine B using Ti/TiO2 electrode prepared by laser calcination method

The method of Ti/TiO₂ photoelectrode prepared by using laser calcination method instead of oven calcination process was introduced. The prepared TiO₂ film was observed with AFM and XRD. Photoelectrocatalytic degradation of rhodamine B (RB) using this electrode was investigated, and anodic potential and pH were optimized. The laser power applied in this electrode preparation was also discussed, and it indicated that TiO₂ particle prepared with high laser power was crystallized adequately and the photoelectrocatalytic ability was satisfactory. RB degradation was investigated under different conditions, and it showed that photoelectrocatalytic degradation could achieve efficient and complete mineralization of organic pollutant. The photoelectrocatalytic oxidation using the Ti/TiO₂ electrode calcinated by laser was compared with that of the electrode calcinated by furnace, and it showed that the reaction rate of RB degradation using the electrode by laser was faster than that by furnace. Additionally, electrochemical impedance spectroscopy (EIS) was performed at the two different photoelectrodes, which verified the higher photocatalytic activity of the laser-treated electrode further.     

A high‐efficient rotating disk photoelectrocatalytic (PEC) reactor with macro light harvesting pyramid‐surface electrode

A series of pyramid‐surface TiO₂/Ti electrodes were proposed, fabricated, and used in a rotating disk photoelectrocatalytic (PEC) reactor to treat rhodamine B (RB) solution. Compared with conventional planar electrode, pyramid‐surface electrode exhibited much lower light reflectivity, larger photocurrent, and better treatment efficiency. For samples containing 20 to 150 mg L^?1 RB, 100– 98% color removal, and 87–30% COD removal were obtained in 150 min using 1/3 (h/w) pyramid‐surface electrode, much higher than 98–77% and 48–9% obtained by a conventional planer electrode. The excellent treatment performance attributed to two major reasons: (a) enhanced light harvest resulted from multiple reflections of irradiation light on the pyramid‐surface, and (b) enlarged electrode surface area enabling the electrode to carry more TiO₂ catalyst and pollutants for treatment. Experimental results also showed that the pyramid‐surface electrode consumed less power and exhibited superior performance when treating high concentration wastewater. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2448–2455, 2012     

Properties of sol-gel SnO2/TiO2 electrodes and their photoelectrocatalytic activities under UV and visible light illumination

A visible light active binary SnO₂-TiO₂ composite was successfully prepared by a sol-gel method and deposited on Ti sheet as a photoanode to degrade orange II dye. Titanium and SnO₂ can promote the development of rutile phase of TiO₂ and inhibit the formation of anatase phase of TiO₂. Formation of SnO₂ crystalline is insignificant even when the calcination temperature increases to 700 °C. Heterogenized interface between SnO₂ and TiO₂ inhibits growth of TiO₂ linkage and leads to the particle-filled surface morphology of SnO₂-containing films. The carbonaceous, Ti-O-C bonds and Ti³⁺ species are likely to account for the photoabsorption and photoelectrocatalytic (PEC) activity under visible light illumination. The electrode with 30% SnO₂ exhibits higher photocurrent when compared with those in the region of 0-50%. The 600 °C-calcined SnO₂-TiO₂ electrode indicates higher activity when compared with those at 400, 500, 700 and 800 °C. PEC degradation of orange II follows the Langmuir-Hinshelwood model and takes place much effectively in a solution of pH 3.0 than those in pH 7.0 and pH 11.0.     

The photoelectrocatalytic oxidation of aqueous nitrophenol using a novel reactor

This paper reports the oxidation of aqueous 4-nitrophenol solutions in a photo-electrochemical bubble column reactor (BCR) in which mass transfer has been shown not to be rate limiting. The work represents the first steps in the scale-up of active photoanodes and efficient reactors for the disinfection and detoxification of water. The preparation, optimization and application of two types of electrode are described and the results are compared with those for a TiO₂ electrode supplied by Ineos Chlor. Photocurrents measured in tap water and in aqueous methanol were used for the initial characterization of the electrodes. The methanol was employed for diagnostic purposes only, as discussed below; methanol can react either by direct hole transfer or by hydroxyl radical recombination, but the balance of these reactions depends upon the nature of the electrode surface. The most active thermal electrodes were fabricated by heating titanium metal in air at 750 °C for 10 min, whilst the most active sol–gel electrodes were heated at 600 °C for 10 min. Three of the central achievements of the work were to: (1) show that it is possible to design and fabricate photoelectrochemical reactors capable of effecting the mineralization of strongly absorbing organics; (2) confirm that the photocatalytic decomposition of 4-NP in reactors with a 4 dm³ capacity can be increased by the application of a small positive potential and (3) that the application of such a potential significantly enhances the mineralization of 4-NP. For the mineralization of 0.25 mM nitrophenol solutions the reactivity sequence is: Photoelectrocatalytic > Photocatalytic > Photochemical > Electrochemical. However, even at 3 V applied potential, charge recombination is not eliminated. The order of electrode activity was: Ineos > Sol Gel > Thermal. Differences between the activities of different electrodes were attributed to changes in the structure and morphology of the TiO₂. It is noteworthy that although, for nitrophenol oxidation, the thermal electrodes were the least active, for photoelectrocatalytic disinfection in the same type of reactor, thermal electrodes were the most active.     

Dye-sensitized solar cell based on optically transparent TiO2 nanocrystalline electrode prepared by atomized spray pyrolysis technique

Preparation of crack-free thin films of interconnected and non-agglomerated TiO₂ nanoparticles on electronically conducting fluorine doped tin oxide surfaces is instrumental in designing and developing transparent dye-sensitized solar cells (DSCs). A novel technique called “Atomized Spray Pyrolysis” (ASP) has been designed and developed to achieve such perfectly transparent thin films. Optical transmittance of TiO₂ films produced on FTO surface by this ASP method has been compared with those obtained by doctor-blading and by hand spray methods and found that the atomized spray pyrolysis technique give films with high transparency. Dye adsorption per gram of TiO₂ is 2.16 times higher in the sample produced by the ASP method when compared to the film produced by the hand spray method and is 1.60 times higher than that produced by the doctor-blading method using a commercially available TiO₂ nanocrystalline paste. SEM studies show the presence of interconnected discrete particles in the film produced by the ASP method. The fill factor (ff) remains almost constant for the cells with thickness from 6 μm to 13 μm but the highest photovoltage and photocurrent were found in ∼10 μm film based DSC which gave 8.2% conversion efficiency at AM 1.5 irradiation for cells of 0.25 cm² active area.     

TiO2, TiO2/Ag and TiO2/Au photocatalysts prepared by spray pyrolysis

TiO₂, TiO₂/Ag and TiO₂/Au photocatalysts exhibiting a hollow spherical morphology were prepared by spray pyrolysis of aqueous solutions of titanium citrate complex and titanium oxalate precursors in one-step. Effects of precursor concentration and spray pyrolysis temperature were investigated. By subsequent heat treatment, photocatalysts with phase compositions from 10 to 100% rutile and crystallite sizes from 12 to 120 nm were obtained. A correlation between precursor concentration and size of the hollow spherical agglomerates obtained during spray pyrolysis was established. The anatase to rutile transformation was enhanced with metal incorporations and increased precursor concentration. The photocatalytic activity was evaluated by oxidation of methylene blue under UV-irradiation. As-prepared TiO₂ particles with large amounts of amorphous phase and organic residuals showed similar photocatalytic activity as the commercial Degussa P25. The metal incorporated samples showed comparable photocatalytic activity to the pure TiO₂ photocatalysts.     

Enhanced visible light-induced photoelectrocatalytic degradation of phenol by carbon nanotube-doped TiO2 electrodes

We used a modified sol-gel method to prepare titanium dioxide and multi-walled carbon nanotube (CNT) composites that we subsequently deposited onto indium tin oxide (ITO) conductive glass plates. We characterized these CNT-doped TiO₂ (CNT-TiO₂) films using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and diffuse reflectance UV-vis spectroscopy. The photoelectrocatalytic (PEC) activity of the composites was evaluated through their ability to mediate the degradation of phenol. XRD measurements indicated that the TiO₂ component existed solely in the anatase phase and that the crystallinity of the CNTs was low. XPS indicated that carbon atoms could substitute for both oxygen and titanium atoms in the TiO₂ lattice to form Ti-C and Ti-O-C structures, which were responsible for the extra photoabsorption and PEC activity under illumination with visible light, in addition to those provided by the CNTs and carbonaceous and Ti³⁺ species. An interphase interaction between TiO₂ and the CNTs elevated the photoabsorbance of the composites in the visible light region. A sample of TiO₂ doped with 10% CNTs and calcined at 400 °C exhibited the highest photocurrent and PEC efficiency. We systematically investigated the effects of several parameters of the PEC process, including the applied potential and pH, on the phenol conversion.     

Combined TiO2/SiO2 mesoporous photocatalysts with location and phase controllable TiO2 nanoparticles

Combined TiO₂/SiO₂ mesoporous materials were prepared by deposition of TiO₂ nanoparticles synthesised via the acid-catalysed sol–gel method. In the first synthesis step a titania solution is prepared, by dissolving titaniumtetraisopropoxide in nitric acid. The influences of the initial titaniumtetraisopropoxide concentration and the temperature of dissolving on the final structural properties were investigated. In the second step of the synthesis, the titania nanoparticles were deposited on a silica support. Here, the influence of the temperature during deposition was studied. The depositions were carried out on two different mesoporous silica supports, SBA-15 and MCF, leading to substantial differences in the catalytic and structural properties. The samples were analysed with N₂-sorption, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) to obtain structural information, determining the amount of titania, the crystal phase and the location of the titania particles on the mesoporous material (inside or outside the mesoporous channels). The structural differences of the support strongly determine the location of the nanoparticles and the subsequent photocatalytic activity towards the degradation of rhodamine 6G in aqueous solution under UV irradiation.     

Oxidation of CH4 over Pd supported on TiO2-doped SiO2: Effect of Ti(IV) loading and influence of SO2

Titania-modified silicas with different weight% of TiO₂ were prepared by sol–gel method and used as supports for Pd (1 wt%) catalysts. The obtained materials were tested in the oxidation of methane under lean conditions in absence and in presence of SO₂. Test reactions were consecutively performed in order to evaluate the thermal stability and poisoning reversibility. Increasing amounts of TiO₂ improved the catalytic activity, with an optimum of the performance for 10 wt% TiO₂ loading. Moreover, the titania-containing catalysts exhibited a superior tolerance towards SO₂ by either adding it to the reactants or feeding it as a pure pretreatment atmosphere at 350 °C. Catalysts were characterized by XPS, XRD, FT-IR and BET measurements. According to the structural and surface analyses, the mixed oxides contained Si–O–Ti linkages which were interpreted as being responsible for the enhanced intrinsic activity of supported PdO with respect to PdO on either pure SiO₂ or pure TiO₂. Moreover, the preferential interaction of the sulfur molecule with TiO₂ and the easy SO_x desorption from high surface area silica were the determining factors for the superior SO₂ tolerance of the TiO₂-doped catalysts.     

Photooxidation of anionic surfactant (sodium lauryl sulfate) in a three-phase fluidized bed reactor using TiO2/SiO2 photocatalyst

The photooxidation of sodium lauryl sulfate (=sodium dodecyl sulfate) in two different types of three-phase fluidized bed reactors was investigated. A low concentration of sodium lauryl sulfate (0.1–0.6 mM) in aqueous solution was photocatalytically decomposed by a TiO₂ photocatalyst immobilized on a porous SiO₂ support. In order to determine the optimum operating conditions in the fluidized beds, the effects of the air flow rate, amount of catalyst, initial concentration of surfactant, light source power, and pH on the photooxidation rate were investigated. From the experimental results, it was observed that the superficial air velocity was an important parameter in determining the reaction rate for both reactors. The photooxidation reaction rate increased with increasing UV lamp power and the experimentally obtained reaction rates showed good agreement with the Langmuir adsorption model. Also, a higher reaction rate was observed when the aqueous solution was acidic.     

ML-WO3/TiO2异质结的制备及其对罗丹明B的光催化降解

采用空间限域法制备了单层三氧化钨纳米片(ML-WO₃),然后将其与TiO₂复合得到ML-WO₃/TiO₂纳米材料,被用来在模拟太阳光下对罗丹明B进行光催化降解。ML-WO₃/TiO₂的组成和光学特性通过扫描电镜、透射电镜、高分辨透射电镜、X射线衍射、紫外-可见吸收光谱和光致发光光谱手段进行表征。结果证实,纳米ML-WO₃/TiO₂克服了纯TiO₂带隙较大的缺陷,在全波段太阳光表现出比ML-WO₃和TiO₂更强的吸收性能,ML-WO₃与TiO₂之间具有明显的协同效应。活性物种捕获实验表明.OH和.O_2^-自由基是RhB降解的主要活性物种。ML-WO₃和TiO₂之间构建的Z型异质结电荷转移路径能够保证光生载流子的高效分离和重组。在5次循环实验后ML-WO₃/TiO₂的光催化活性仍能接近80%,具有良好的光化学稳定性。通过高效液相色谱-质谱检测RhB的中间产物,推测了RhB可能的降解路径。     

Degradation of azo dye from aqueous solutions using nano-SnO2/Ti electrode prepared by electrophoretic deposition method: Experimental Design

In this work, degradation of C.I. Acid Red 33 (AR33) in aqueous solutions was investigated. The combined electrolysis–ozone (ECO) process optimized based on SnO₂ nanoparticles electrode (nano-SnO₂/Ti) as anode using response surface methodology (RSM) involving a five-level central composite design (CCD). The nano-SnO₂/Ti electrode was prepared using electrophoretic deposition (EPD) method. The electrode was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV). The initial pH, current density, reaction time and electrolyte concentration were selected as independent variables in central composite design while color removal efficiency was considered as the response function. Based on analysis of variance (ANOVA), the coefficient of determination value (R² = 0.981) was high. In optimum conditions, maximum color removal efficiency (93.2%) was obtained after 16 min; and the removal of chemical oxygen demand (COD) was reduced to 57.1% after 60 min.     

Al2O3-coated SnO2/TiO2 composite electrode for the dye-sensitized solar cell

A novel Al₂O₃-coated SnO₂/TiO₂ composite electrode has been applied to the dye-sensitized solar cell. In such an electrode, two kinds of energy barriers (SnO₂/TiO₂ and TiO₂/Al₂O₃) were designed to suppress the recombination processes of the photo-generated electrons and holes. After the SnO₂ was modified by colloid TiO₂, the photoelectric conversion efficiency of the SnO₂/TiO₂ composite cell increased to 2.08% by a factor of 2.8 comparing with that of the SnO₂ cell. The Al₂O₃ layer on the SnO₂/TiO₂ composite electrode further suppressed the generation of the dark current, resulting in 37% improvement in device performance comparing with the SnO₂/TiO₂ cell.     

Efficient decomposition of organic compounds with FeTiO3/TiO2 heterojunction under visible light irradiation

FeTiO₃/TiO₂, a new heterojunction-type photocatalyst working at visible light, was prepared by a simple sol–gel method. Not only did FeTiO₃/TiO₂ exhibit greatly enhanced photocatalytic activity in decomposing 2-propanol in gas phase and 4-chlorophenol in aqueous solution, but also it induced efficient mineralization of 2-propanol under visible light irradiation (λ ≥ 420 nm). Furthermore, it showed a good photochemical stability in repeated photocatalytic applications. FeTiO₃ showed a profound absorption over the entire visible range, and its valence band (VB) position is close to that of TiO₂. The unusually high photocatalytic efficiency of the FeTiO₃/TiO₂ composite was therefore deduced to be caused by hole transfer between the VB of FeTiO₃ and TiO₂.     

Synthesis and electrochemiluminescence of the CeO2/TiO2 composite

CeO₂/TiO₂ composite with kernel–shell structure was synthesized by a sol–gel process. The characterization results show that the composite is made up of anatase phase TiO₂ and cubic system CeO₂. The electrochemiluminescence (ECL) behavior of the CeO₂/TiO₂ composite was studied by a cyclic voltammetry in the presence of persulfate, and the effect factors on ECL emission were discussed. Based on a series of experiments, it is proposed that the strong dual ECL emission produced by the CeO₂/TiO₂ composite resulted from the benefit ECL effect of interface heterojunction in composite.