Photocatalytic decomposition of phenol over a novel kind of loaded photocatalyst of TiO2/activated carbon/silicon rubber film

A novel kind of loaded photocatalyst TiO₂/activated carbon/silicon rubber film that can photodegrade organic pollutants in dilute aqueous solution effectively is reported in this paper. Activated carbon is used as adsorbant and silicon rubber film as support. Compared with powdered TiO₂ catalyst this preparation procedure leads to a highly active and easily separable immobilized hybrid catalyst composed of 90 wt.% TiO₂ and 10 wt.% activated carbon in the photodegradation of phenol under UV irradiation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Plasma-Assisted Synthesis of TiO2 Nanorods by Gliding Arc Discharge Processing at Atmospheric Pressure for Photocatalytic Applications

The present study explores a new method of synthesis of TiO₂ nano-particles in an aqueous medium from TiCl₃ precursor by non-thermal plasma in humid air as feeding gas obtained at atmospheric pressure. The precursor solution, TiCl₃ is oxidized by strongly reactive species generated by gliding arc plasma (HO^· = 2.85 V/SHE) to produce titanium oxide powders. The synthesized powder was characterised by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, FTIR spectroscopy, nitrogen physisorption, and UV–Vis spectroscopy. The results obtained showed that the material consists of rod-shaped nanoparticles of rutile and anatase phases. The presence of TiO₂ phases was confirmed by FTIR spectrum and textural analyses showed that the material is mesoporous with specific surface area of 158 m² g^?1. UV–Visible spectrum of the plasma-synthesized TiO₂ sample showed that it absorbs in the UV–A region leading to effective use as a photocatalyst under visible light.     

A novel layered bismuth-based photocatalytic material LiBi3O4Cl2 with OH and h+ as the active species for efficient photodegradation applications

Developing new photocatalysts is of significant importance for their potential environmental and energetic applications. Herein, a novel layered bismuth-based photocatalytic material LiBi₃O₄Cl₂ was developed by a simple solid-state reaction. The morphology, microstructures and optical properties were investigated by XRD, SEM, TEM and DRS. The band gap of LiBi₃O₄Cl₂ has been determined to be 3.35 eV, and its E_CB and E_VB were also estimated. The photocatalytic property of LiBi₃O₄Cl₂ is surveyed by oxidative decomposition of rhodamine B (RhB), methyl orange (MO), methylene blue (MB) and phenol in aqueous solution. The results demonstrated that LiBi₃O₄Cl₂ is an efficient UV light active photocatalyst, which can destroy the contaminants with irradiation. It is also more effective in degrading pollutants than the related layered bismuth-based photocatalyst Bi₄NbO₈Br. The photocatalysis mechanism is detailedly investigated by active species trapping measurement and terephthalic acid photoluminescence probing technique (TA-PL). It revealed that powerful hydroxyl radicals (OH) and photogenerated holes (h⁺) are the two main active species and are responsible for the efficient degradation process. This study provides a new layered bismuth-based photocatalytic material for environmental and energetic applications.     

ZnO and TiO2 clusters as catalyst in the addition and abstraction reaction of acrylic acid with the OH radical

The present work displays the theoretical analysis on the role of metal oxide clusters as an effective catalyst in the reaction between acrylic acid and OH radical, which has an energy barrier of 12.4 kcal/mol. The formation of metal oxide cluster such as ZnO and TiO₂ with varying size from monomer to hexamer is analyzed using cohesive energy, which increases with cluster size. Adsorption of acrylic acid on clusters reveals that dimer ZnO and tetramer TiO₂ are good adsorbed entities. The dimer ZnO and tetramer TiO₂ clusters have reduced the barrier height. However, from the thermodynamical analysis of H-abstraction and OH addition reaction, the dimer ZnO cluster is found to be a good catalyst than a tetramer TiO₂ cluster. The favorable H abstraction and OH addition reactions are feasible at the active methylene group (–CH). OH addition reactions dominate over the H abstraction reaction. Further, the presence of metal oxide clusters enhances the rate of the reaction between acrylic acid and OH radical. The kinetics of the favorable reaction with a dimer ZnO cluster has a rate constant of 7.80 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, which is higher than the literature report (1.75 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹). Overall, ZnO and TiO₂ metal oxide clusters can be effectively utilized as catalyst.     

TiO2薄膜光催化氧化I-的研究

采用溶胶-凝胶法,在玻璃珠表面涂覆均匀透明的TiO     

Efficient and Robust Cu/TiO2 Nanorod Photocatalysts for Simultaneous Removal of Cr(VI) and Methylene Blue under Solar Light

Because of its large bandgap, TiO₂ can function only under UV light. TiO₂ surface modification with noble metal nanoparticles can extend the light absorption from UV to visible light region and enhance the photocatalytic quantum yield. In this work, TiO₂ nanorods (Cu/TiO₂) modified by copper nanoparticles were prepared by a one‐step solvothermal method at low cost. The resultant Cu/TiO₂ nanorods show excellent synergistic effect in the oxidation of methylene blue (MB) and the reduction of aqueous Cr(VI) under solar light irradiation. Mechanistic investigation suggests that the Cr(VI) species could effectively scavenge the electrons from MB in the presence of the as‐prepared photocatalyst, leading to the simultaneous removal of both pollutants. Being economically viable, environmentally sustainable, and highly efficient, the proposed photocatalyst holds promise for technologies involving simultaneous organic degradation and heavy metal removal in wastewater treatment.     

Synthesis,Characterisation of Novel Polyaniline Nanomaterials and Application in Amperometric Biosensors

Summary: Anthracene sulfonic acid doped polyaniline nanomaterials were prepared through the chemical oxidative polymerisation process. Ammonium peroxydisulfate (APS) was employed as oxidant. Scanning electron microscopy (SEM) results show the resultant polyaniline (PANi) materials exhibited nanofibrillar morphology with diameter sizes less than 300 nm. Using the nanofibrillar PANI, amperometric biosensors for H₂O₂ and erythromycin were constructed through the drop-coating technique. Anthracene sulfonic acid (ASA) doped PANi and the test enzymes horseradish peroxidase, (HRP), or cytochrome P₄₅₀ 3A4, (CYP₄₅₀3A4) were mixed in phosphate buffer solution before drop coating onto the electrode. The resultant biosensors displayed typical Michaelis-Menten behaviour. The apparent Michaelis-Menten constant obtained was 0.18 ± 0.01 mM and 0.80 ± 0.02 µM L⁻¹ for the peroxide and erythromycin biosensor respectively. The sensitivity for the peroxide sensor was 3.3 × 10⁻³ A · cm⁻² · mM⁻¹, and the detection limit was found to be 1.2 × 10⁻² mM respectively. Similarly, the sensitivity for the erythromycin sensor was in the same order at 1.57 × 10⁻³ A · cm⁻² · mM⁻¹ and detection limit was found to be 7.58 × 10⁻² µM.     

氮掺杂TiO2光催化剂的制备及可见光催化性能研究

在溶胶-凝胶法基础之上,以尿素为氮源,通过较温和的反应条件来制备氮掺杂TiO₂光催化剂。以亚甲基蓝为模型化合物、日光色镝灯为光源,探索了其可见光光催化性能;并用XRD、低温氮气吸附-脱附技术、UV-Vis等表征了其结构特征;同时以对苯二甲酸为探针分子,结合化学荧光技术研究了光催化体系中·OH自由基的变化规律,进一步验证了其光催化活性规律。结果表明：氮掺杂能引起TiO₂光催化剂的激发吸收光谱明显红移并具较好的可见光响应性;在不同煅烧温度和尿素/钛酸丁酯物质的量的比     

Treatment of TiO2 with COOH‐Functionalized Germanium Nanoparticles to Enhance the Photocurrent of Dye‐Sensitized Solar Cells

A dye‐sensitized solar cell (DSSC) containing a TiO₂ film treated with COOH‐functionalized germanium nanoparticles (Ge COOH Nps) exhibited a higher short‐circuit photocurrent density (J_sc; 15.4 mA cm⁻²) compared to the corresponding untreated DSSC (13.4 mA cm⁻²) using N719 and a 12 μm thick TiO₂ film at 100 mW cm⁻². The amount of N719 attached to the treated TiO₂ film was 21 % greater than that attached to the untreated TiO₂ film. Enhancement of the J_sc value by 15 % was attributed mostly to an intramolecular charge transfer from N719 attached to the Ge COOH Nps to the TiO₂ conduction band through the Ge COOH Nps.     

Improved photoelectrochemical hydrogen production over decorated titania with copper and nickel oxides by optimizing the photoanode and reaction characteristics

We optimized photocatalytic hydrogen production over TiO₂-based photocatalyst by varying the dopant (nickel and copper oxide), thin film active area, nature and concentration of sacrificial agents, and light intensity in a photoelectrochemical (PEC) cell/dye-sensitized solar cell (DSSC). Various characterization techniques have been used to investigate the structural, morphological, optical, and PEC behavior of single and codoped TiO₂. The TiO₂ decorated with both Cu and Ni oxides with active area of 1 cm² in a mixture of 5 vol % glycerol and 1 M KOH under light intensity of 100 mWcm^?2 produced the maximum hydrogen of 338.4 μmol cm^?2 for 2 h. The superior photocatalyst performance of this photocatalyst is attributed to its small crystallite size and large pore size, as confirmed by X-ray diffractometer, Transmission electron microscopy (TEM), and surface area of Brunauer-Emmet-Teller (S_BET). The absorption edges of this photocatalyst had the highest red shift compared with single doped and pure TiO₂ because of more indirect transitions of the photoexcited electrons, greater charge carrier separation, and lower recombination rate. The photoanode active area of 1 cm² with better photocatalytic performance correlated with the number of defects and grain boundaries. Glycerol shifted the conduction band of the photocatalyst to more negative flat potential compared with others. Increasing the concentration of glycerol further than 5 vol% saturated the photocatalyst active sites, increased photooxidation intermediates of glycerol, and reduced the hydrogen production. The light intensity had the maximum impact on the hydrogen production and could strongly control the number of charge carriers in both the PEC cell and the DSSC.     

Comparison of optical and structural properties of nanostructure TiO2 thin film doped by Sn and Nb

The thin films of TiO₂ doped by Sn or Nb were prepared by sol–gel method under process control. The effects of Sn and Nb doping on the structural, optical and photo-catalytic properties of applied thin films have been studied by X-ray diffraction (XRD) high resolution transmission electron microscopy and UV–Vis absorption spectroscopy. Surface chemical state of thin films was examined by atomic X-ray photoelectron spectroscopy. XRD results suggest that adding impurities has a great effect on the crystallinity and particle size of TiO₂. Titania rutile phase formation in thin film was promoted by Sn⁴⁺ addition but was inhibited by Nb⁵⁺ doping. The activity of the photocatalyst was evaluated by photocatalytic degradation kinetics of aqueous methylene blue under UV and Visible radiation. The results show that the photocatalytic activity of the Sn-doped TiO₂ thin film have a larger degradation efficiency than Nb-doped TiO₂ under visible light, but under UV light photocatalytic activity of the Nb-doped TiO₂ thin film is better.     

Synthesis,characterization and photocatalytic application of TiO2/magnetic graphene for efficient photodegradation of crystal violet

A magnetized nano‐photocatalyst based on TiO₂/magnetic graphene was developed for efficient photodegradation of crystal violet (CV). Scanning electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy and elemental mapping were used to characterize the prepared magnetic nano‐photocatalyst. The photocatalytic activity of the synthesized magnetic nano‐photocatalyst was evaluated using the decomposition of CV as a model organic pollutant under UV light irradiation. The obtained results showed that TiO₂/magnetic graphene exhibited much higher photocatalytic performance than bare TiO₂. Incorporation of graphene enhanced the activity of the prepared magnetic nano‐photocatalyst. TiO₂/magnetic graphene can be easily separated from an aqueous solution by applying an external magnetic field. Effects of pH, magnetized nano‐photocatalyst dosage, UV light irradiation time, H₂O₂ amount and initial concentration of dye on the photodegradation efficiency were evaluated and optimized. Efficient photodegradation (>98%) of the selected dye under optimized conditions using the synthesized nano‐photocatalyst under UV light irradiation was achieved in 25 min. The prepared magnetic nano‐photocatalyst can be used in a wide pH range (4–10) for degradation of CV. The effects of scavengers, namely methanol (OH^? scavenger), p‐benzoquinone (O₂^?? scavenger) and disodium ethylenediaminetetraacetate (hole scavenger), on CV photodegradation were investigated.     

磁载光催化剂Fe3O4/C/TiO2的制备及对三氯苯酚的降解

以FeCl₃为铁源, 葡萄糖为碳源, 钛酸四丁酯为钛源, 采用水热法制备了磁载光催化剂Fe₃O₄/C/TiO₂, 用TEM、EDX、VSM、XRD和IR对Fe₃O₄/C/TiO₂的粒径、形貌和物相等进行了表征。研究了该催化剂对三氯苯酚的降解性能, 探讨了其重复使用的可能性, 用荧光光谱法推测了可能的反应机理。结果表明该材料结合了光催化与可再生的优点, 1 g·L^-1 Fe₃O₄/C/TiO₂在18 W紫外灯下, 50 min内可将三氯苯酚降解97.9%以上, 6次循环使用后降解率仍保持在95.1%, 降解过程中有羟基自由基生成。     

Electrochemical capacitors with KCl electrolyte

Potassium manganese dioxide K_xMnO_{2 + δ}·nH₂O and amorphous MnO₂ in a mild 2 M KCl aqueous electrolyte prove to be excellent electrodes for faradaic electrochemical capacitors. The K_xMnO_{2 + δ}·nH₂O materials were prepared by direct thermal decomposition of KMnO₄ and contained a large amorphous/crystalline ratio. A sample decomposed at 550 °C gave a specific cyclic capacitance between −0.2 and +1.0 V/SCE of 240 F·g⁻¹, which corresponds to nearly one-third of the Mn(IV) ions participating in the faradaic reaction. Excellent cyclability at 12 mA·cm⁻² was found for 100 cycles. On short-circuit, K_0,31MnO_2,12·0,63 H₂O in 2 M KCl and pH 10.6 aqueous solution gave an initial current density of 0.58 A·cm⁻² and a total released charge of 4.6 C·cm⁻² compared with 0.32 A·cm⁻² and 11.1 C·cm⁻² for RuOOH·nH₂O in 5.3 M H₂SO₄. Similar results obtained with amorphous MnO₂ demonstrate that alkali ions can be used as the working ion in a faradaic supercapacitor, which frees the search for new materials from the constraint of working in a strong-acid aqueous medium.     

Optimization of hydroxyl radical formation using TiO2 as photocatalyst by response surface methodology

The determination of the optimum parameters for hydroxyl radicals (OH) formation by a TiO₂ solution has been investigated by measuring the emitted fluorescence after the reaction with terephthalic acid has occurred. After UV irradiation, the terephthalic acid was transformed into 2-hydroxyterephthalic acid whose fluorescence is directly proportional to the generated OH. Optimization of hydroxyl radicals’ formation using TiO₂ as catalyst was carried out by studying the effects of irradiation time, TiO₂ concentration and terephthalic acid concentration on the production of the fluorescent HTA with an experimental design. The aim of our research was to apply response surface methodology as a chemometric method for the optimization of the reaction conditions. The combination of irradiation time, TiO₂ concentration and terephthalic acid concentration was varied at designed points of a central composite rotatable design. The three factors were found to have a significant effect upon the reaction. The optimum conditions for the reaction achievement were estimated to be 10 min for the irradiation time, 25 μg mL⁻¹ TiO₂ concentration and 0.1 mmol L⁻¹ terephthalic acid concentration. Afterwards, using these parameters the method was applied for the determination of the ability of several plant extract samples to scavenge the formed OH.     

Microwave‐Hydrothermal Preparation and Visible‐Light Photoactivity of Plasmonic Photocatalyst Ag‐TiO2 Nanocomposite Hollow Spheres

Visible‐light‐driven plasmonic photocatalyst Ag‐TiO₂ nanocomposite hollow spheres are prepared by a template‐free chemically‐induced self‐transformation strategy under microwave‐hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N₂ adsorption‐desorption isotherms, X‐ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of ?OH radicals on the surface of visible‐light illuminated TiO₂ was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as‐prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible‐light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO₂ hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag‐TiO₂ nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible‐light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO₂ and commercial Degussa P25 (P25) powders. Especially, the as‐prepared Ag‐TiO₂ nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium ( R ) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.     

Enhanced degradation of organic pollutant 4-chlorophenol in water by non-thermal plasma process with TiO2

The combined application of TiO₂ photocatalyst and pulsed high-voltage electrical discharge process for the degradation of organic pollutant parachlorophenol (4-CP) in aqueous solution was tentatively investigated. The optimum conditions for 4-CP removal were applied voltage at 14 kV, electrode distance at 2 cm, pH at 6.5 (close to neutral solution), TiO₂ concentration at 50 mg/L, gas source O₂ at 100 L/h, and hybrid corona-streamer discharge mode. Introduced TiO₂ into pulsed discharge plasma process under such optimum condition, the rate constant of 4-CP degradation (k _cp) was greatly promoted, from 1.56×10⁻³ to 2.81×10⁻³ s⁻¹, and energy efficiency for 4-CP removal was greatly enhanced by approximately one time, and it was attributed to more amounts of chemically active species (e.g., ozone and hydrogen peroxide, especially hydroxyl radicals) produced in pulsed discharge plasma process in combination with TiO₂ photocatalyst.     

TiO<Subscript>2</Subscript> nanotube arrays: a study on the surface electrochemical reactions during the photoelectrochemical process

The surface electrochemical reactions of TiO₂ nanotube arrays (NTAs) corresponding to different active species of TiO₂ NTAs (·OH, h⁺, and ·O₂ ^?) play key roles during the photoelectrochemical process. Effect of the active species and surface electrochemical reactions are studied by adding capture agents of isopropyl alcohol (IPA) for ·OH, ammonium oxalate ((NH₄)₂C₂O₂) for h⁺, and benzoquinone (BQ) for ·O₂ ^? radicals. The changes of photocurrent with addition of capture agents confirm the existence of ·OH, h⁺, and ·O₂ ^? during photoelectrochemical process. IPA and (NH₄)₂C₂O₂ additions are found to enhance the photocurrent by accelerating the consumption velocity of h⁺ indirectly and directly and restricting the chargers recombination. BQ can decrease the photocurrent stepwise to 0 due to the indirect consumption of e^? on surface of TiO₂ NTAs. The consumption of h⁺ by forming ·OH is 38% that of the whole consumption of h⁺. The ratio of chargers recombination is higher than 80.8% that of the whole photogenerated chargers.     

Conversion of spent coffee grounds to biochar as promising TiO2 support for effective degradation of diclofenac in water

A novel composite, biochar derived from spent coffee grounds with immobilized TiO₂ (biochar–TiO₂) was prepared, characterized, and applied as an alternative, effective, and sustainable photocatalyst for degrading diclofenac from aqueous solution. Composites with different mass ratios between TiO₂ and biochar were prepared by mechanical mixing and subsequent pyrolysis in an inert atmosphere of N₂ at 650°C. The sample with biochar–TiO₂ ratio of 1:1 presented a degradation efficiency of 90% at just 120 min versus 40% for TiO₂ used as reference. This fact is associated with a set of intrinsic characteristics obtained during the formation of the composite, such as superior pore size, avoiding the recombination of the ē/h⁺ pair, bandgap reduction, and promotion of reactive oxygen species due to phenolic groups present on the biochar surface. The dominant reactive species involved during the photocatalytic degradation of diclofenac were h⁺ and ^•OH. The diclofenac degradation pathways were determined based on the identification of intermediates and nonpurgeable organic carbon (NPOC) analysis. The novel biochar–TiO₂ composite prepared in this work showed high physical–chemical stability and efficiency over five consecutive cycles of reuse, proving to be a highly promising photocatalyst for degrading diclofenac in water.     

N‐Doped Yellow TiO2 Hollow Sphere‐Mediated Visible‐Light‐Driven Efficient Esterification of Alcohol and N‐Hydroxyimides to Active Esters

Herein we report a simple synthetic protocol for N‐doped yellow TiO₂ (N‐TiO₂) hollow spheres as an efficient visible‐light‐active photocatalyst using aqueous titanium peroxocarbonate complex (TPCC) solution as precursor and NH₄OH. In the developed strategy, the ammonium ion of TPCC and NH₄OH acts as nitrogen source and structure‐directing agent. The synthesized N‐TiO₂ hollow spheres are capable of promoting the synthesis of active esters of N‐hydroxyimide and alcohol through simultaneous selective oxidation of alcohol to aldehyde followed by cross‐dehydrogenative coupling (CDC) under ambient conditions upon irradiation of visible light. It is possible to develop a novel and cost‐effective one‐pot strategy for the synthesis of important esters and amides on gram scale using the developed strategy. The catalytic activity of N‐TiO₂ hollow spheres is much superior to that of other reported N‐TiO₂ samples as well as TiO₂ with varying morphology.