TiO2 Nanotube Arrays Electrode Research Articles

Photoelectrocatalytic activation of sulfate for sulfamethoxazole degradation and simultaneous H2 production by bifunctional N,P co-doped black-blue TiO2 nanotube array electrode

In recent years, sulfate radical (SO4•−)-based advanced oxidation processes and hybrid water electrolysis for hydrogen production have attracted widespread attention. However, the conventional electrochemical persulfate activation requires mass/expensive persulfate reagent, limiting its practical application due to high operation cost. In this work, using bifunctional N, P co-doped black-blue TiO2 nanotube arrays (N,P-BTNAs) as a wide-spectrum absorptive photoanode, we report the synergistic PEC sulfate activation for effective degrading sulfamethoxazole (SMX) antibiotic and simultaneous generating H2 at N,P-BTNAs cathode. With sulfate as h+ scavenger and SO4•− precursor, HO•, SO4•−, 1O2 and h+ are generated during PEC activation process. Detailed physicochemical characterization and density functional theory (DFT) calculations revealed that the Ti3+, P5+, N triple-doping induced a narrowed band gap (2.78 eV), a rapid separation/transfer of photo-induced carriers, an accelerated h+ extraction/utilization, and an optimized H binding/releasing ability, resulting in an outstanding PEC sulfate activation for SMX degradation (0.05368 min−1) and H2 evolution efficiency (132.3 μmol/cm2/h) under optimal conditions. This study provides a novel strategy for efficient contaminants removal and stable H2 production simultaneously, via the synergistic PEC activation of the coexisted sulfate using the bifunctional N,P-BTNAs electrode.

Effect of 3D titanium substrates with TiO2 nanotube arrays on photoelectrocatalysis degradation of phenol

TiO2 nanotube array electrodes are coated on 3D titanium foam and mesh by the anodic oxidation procedure to investigate the effect of electrode substrates. Distribution homogeneity, crystal shape, structure, and light absorption of TiO2 nanotube are the same, orientations are different due to the planar structure of the titanium foam and the non-planar structure of the titanium mesh. However, the performance of the photoelectrocatalysis, phenol degradation, and charge transfer significantly influences by anode substrates. Although the photocurrent density of titanium mesh is 3.29 mA·cm−2, which is 1.5% lower than that of titanium foam, 96.1% ± 2% of the phenol can be degraded by the titanium mesh anode in 120 min with a degradation efficiency of 86.5% ± 3% after 4 cycles, demonstrated titanium mesh substrate is better than titanium foam. The mechanism results show that·OH and photoelectric synergy play a primary role in phenol degradation, and electrocatalysis (29.8%) increased by anode substrates, is better than photocatalysis (17.9%). The electric field enhances by electrocatalysis, resulting in accelerating electron transfer and decreasing in the recombination of electron and hole. Due to its porous structure and large specific surface area, the 3D substrate improves mass transport, providing more photocatalysts, reactants, and reaction sites for photoelectrochemical reactions, further enhancing photoelectric synergy, and ultimately promoting phenol degradation. This study confirms the role of 3D anode titanium substrate and encourages electric field enhancement to solve the recombination of electrons and holes.

Facilitating light utilization and electron transfer of TiO2 nanotube arrays for catalyzing photoelectrochemical water reduction via acid etching and copper doping

Photoelectrochemical catalytic capability mainly relies on light absorption and charge transfer efficiency. TiO2 nanotube array (TNA) having suitable band edges and one-dimensional hollow structure is regarded as one of efficient photoelectrocatalysts toward water reduction. In this study, two strategies are firstly applied to modify TNA as the photocatalyst of water reduction. Ti foils are etched by acid to produce multiple light reflections planes for improving light absorption, and Cu is doped in TNA to enhance charge transfer efficiency. The optimal Cu-doped TNA electrode on the acid-etched Ti foil presents a much smaller overpotential of 91 mV at 10 mA/cm2 compared with that of the undoped TNA (524 mV). A smaller Tafel slope of 134 mV/dec is obtained for the optimal Cu-doped TNA electrode than that of the undoped TNA (167 mV/dec). After measuring the photoelectrochemical performance for 1000 cycles, overpotential and charge-transfer resistance of modified TNA are largely reduced owing to activation. Current retention of 96.7% is achieved after continuously illuminating for 10 h. Highly improved photoelectrochemical catalytic ability of TNA modified by acid etching and Cu doping provides new pages for material modifications on substrate and active material.

Flow injection analysis coupled with photoelectrochemical immunoassay for simultaneous detection of anti-SARS-CoV-2-spike and anti-SARS-CoV-2-nucleocapsid antibodies in serum samples

A thin-layer flow cell of low internal volume (12 μL) is incorporated in a flow injection analysis (FIA) system for simultaneous and real-time photoelectrochemical (PEC) immunoassay of anti-SARS-CoV-2 spike 1 (S1) and anti-SARS-CoV-2 nucleocapsid (N) antibodies. Covalent linkage of S1 and N proteins to two separate polyethylene glycol (PEG)-covered gold nanoparticles (AuNPs)/TiO2 nanotube array (NTA) electrodes affords 10 consecutive analyses with surface regenerations in between. An indium tin oxide (ITO) allows visible light to impinge onto the two electrodes. The detection limits for anti-S1 and anti-N antibodies were estimated to be 177 and 97 ng mL−1, respectively. Such values compare well with those achieved with other reported methods and satisfy the requirement for screening convalescent patients with low antibody levels. Additionally, our method exhibits excellent intra-batch (RSD = 1.3%), inter-batch (RSD = 3.4%), intra-day (RSD = 1.0%), and inter-day (RSD = 1.6%) reproducibility. The obviation of an enzyme label and continuous analysis markedly decreased the assay cost and duration, rendering this method cost-effective. The excellent anti-fouling property of PEG enables accuracy validation by comparing our PEC immunoassays of patient sera to those of ELISA. In addition, the simultaneous detection of two antibodies holds great potential in disease diagnosis and immunity studies.

Anodized TiO2 nanotubes arrays as microbial fuel cell (MFC) electrodes for wastewater treatment: An overview

This review discusses the main advances in electrodes based on TiO2 nanotube arrays (TNA) to improve the performance of microbial fuel cells (MFC), a sustainable technology for wastewater treatment and bioelectricity generation. The properties and synthesis of anodized TNA films are well-established in the literature. Contrary to the dye-sensitized solar cells, photoelectrochemical water-splitting, photocatalysts, biosensors, and implant applications, where they are widely explored, TNAs are still in the exploratory stage in fuel cells. The precise morphology control by the anodizing conditions, high surface area, low cost, chemical stability, and unidirectional orientation are their attractive properties. TNA-based electrodes have been explored mainly as bioanodes in conventional MFCs, and photoanodes in hybrid MFC systems and evaluated in terms of power and current generation and compared with Ti and carbon-based electrodes. The effects of nanotubular morphology, heat treatment conditions, and surface modification of TNA electrodes are addressed. Its utilization as a photoanode in photo-assisted MFCs is discussed as the strategies for improving MFC performance and turning it cost-effective by coupling other functions, like H2 production and CO2 conversion.

Effect of Zwitterionic Additive on Electrode Protection through Electrochemical Performances of Anatase TiO2 Nanotube Array Electrode in Ionic Liquid Electrolyte

In this work, a functionalized zwitterionic (ZI) compound 1-butylsulfonate-3-methylimidazole (C1C4imSO3) was synthesized and tested as an additive to LiTFSI/C2C2imTFSI ionic liquid-based electrolytes for lithium-ion batteries. The structure and purity of C1C4imSO3 were confirmed by NMR and FTIR spectroscopy. The thermal stability of the pure C1C4imSO3 was examined by simultaneous thermogravimetric-mass spectrometric (TG-MS) measurements and differential scanning calorimetry (DSC). The LiTFSI/C2C2imTFSI/C1C4imSO3 system was tested as a potential electrolyte for lithium-ion batteries by using anatase TiO2 nanotube array electrode as the anode material. This electrolyte with 3% C1C4imSO3 showed significant improvement of lithium-ion intercalation/deintercalation properties, such as capacity retention and Coulombic efficiency compared to electrolyte without additive.

Enhanced Visible Light-Driven Photoelectrocatalytic Degradation of Paracetamol at a Ternary z-Scheme Heterojunction of Bi2WO6 with Carbon Nanoparticles and TiO2 Nanotube Arrays Electrode.

In this study, a ternary z-scheme heterojunction of Bi2WO6 with carbon nanoparticles and TiO2 nanotube arrays was used to remove paracetamol from water by photoelectrocatalysis. The materials and z-scheme electrode were characterised using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), EDS mapping, ultraviolet diffuse reflection spectroscopy (UV-DRS), photocurrent measurement, electrochemical impedance spectroscopy (EIS), uv-vis spectroscopy and total organic carbon measurement (TOC). The effect of parameters such as current density and pH were studied. At optimal conditions, the electrode was applied for photoelectrocatalytic degradation of paracetamol, which gave a degradation efficiency of 84% within 180 min. The total organic carbon removal percentage obtained when using this electrode was 72%. Scavenger studies revealed that the holes played a crucial role during the photoelectrocatalytic degradation of paracetamol. The electrode showed high stability and reusability therefore suggesting that the z-scheme Bi2WO6-CNP-TiO2 nanotube arrays electrode is an efficient photoanode for the degradation of pharmaceuticals in wastewater.

Efficient electrochemical oxidation of sulfamethoxazole by a novel reduced TiO2 nanotube arrays-based flow-through electrocatalytic membrane

The reduced TiO2 nanotube arrays (RTNA) electrode is a cost-effective anode, but its limited electrocatalytic activity is an obstacle for the application. To solve this problem, a reduced TiO2 nanotube arrays-based titanium membrane (RTNA/TM) was fabricated by a facile electrochemical method to promote the electrocatalytic performance. The one-dimensional nanostructure and reduction treatment increased the electrocatalytic capacity and reduced the energy consumption, resulting in the sulfamethoxazole (SMX) removal rate of 86.1% and electrical efficiency per order of 0.55 kWh/m3 for RTNA/TM. Compared with the batch mode, the SMX removal efficiency of the flow-through mode was significantly increased by 71%, verifying the superiority of a porous flow-through anode. The SMX degradation performances of RTNA/TM were strongly affected by the fluid velocity, current density and initial SMX concentration, except for pH. Both hydroxyl radicals and direct electron transfer were responsible for the SMX removal, while the contribution of sulfate radicals could be ignored. Furthermore, RTNA/TM displayed stable performances for five experimental cycles and showed remarkable degradation efficiencies of SMX spiked into the natural water (76.5%) and wastewater effluent (75.4%). Therefore, RTNA/TM has been proven to be a promising flow-through anode for electrochemical oxidation.

High-efficiency electrochemical decomposition of artificial sweetener aspartame using a Ti3+ self-doped TiO2 nanotube arrays anode

Artificial sweeteners have attracted growing concern considering their large usage, wide detection and ecological toxicity in the last decade. In this work, high-efficiency decomposition of artificial sweetener aspartame was investigated by using a Ti3+ self-doped TiO2 nanotube arrays electrode. Effects of current density, initial concentration and inorganic anions on the degradation kinetics were studied. Results showed that the electrochemical degradation of aspartame followed pseudo-first-order kinetics, and the rate constant was 0.039 min−1 at a current density of 2 mA cm−2. The electrochemical degradation was not susceptible to nitrate, and the degradation was significantly enhanced by chloridion. Twenty-four transformation products were identified by UPLC-Orbitrap-MS/MS, and possible electrochemical degradation pathway was proposed. The degradation process of aspartame mainly included hydroxylated, demethylation, dehydrogenation, dehydration condensation and side-chain cleavage. Quantitative structure-activity relationship model revealed that the potential risks in electrolysis process should not be ignored before complete mineralization of aspartame. Energy consumption was greatly reduced in the presence of Cl-, and the lowest value for 90% aspartame degradation was 0.07 Wh L−1. The findings presented here demonstrate that electrocatalysis exhibits high efficiency in degrading aspartame and is potentially suitable for eliminating artificial sweeteners from wastewaters.

Treatment of organic wastewater by a synergic electrocatalysis process with Ti3+ self-doped TiO2 nanotube arrays electrode as both cathode and anode

Electrochemical anodic oxidation (AO) is a promising technology for wastewater treatment due to its strong oxidation property and environmental compatibility. However, it suffers from high energy consumption for pollutants removal due to the side-reactions of hydrogen evolution reaction on cathode and oxygen evolution reaction on anode. Combining electro-Fenton (EF) with AO not only generated •OH for pollutants degradation but also increased current efficiency. This work investigated a synergic electrocatalysis process between EF and AO with Ti3+ self-doped TiO2 nanotube arrays (Ti3+/TNTAs) electrode as both cathode and anode for wastewater treatment. The pseudo-first-order kinetic rate constant of phenol degradation by EF+AO (0.107 min−1) was 9.7 or 6.3 times as much as that of only EF (0.011 min−1) or AO (0.017 min−1) process, respectively. Enhanced pollutants removal of EF+AO could be attributed to the coexistence of •OH oxidation and direct oxidation on Ti3+/TNTAs surface. The COD of secondary effluent of coking wastewater decreased from 159.3 mg L−1 to 47.0 mg L−1 by EF+AO within 120 min with low specific energy consumption (9.5 kWh kg−1 COD−1). This work provided a new insight into design of the energy-efficient synergic electrocatalysis process for refractory pollutants degradation.

Controlling the geometric design of anodic 1D TiO2 nanotubes for the electrochemical reduction of 2,4,6-trinitrotoluene in ambient conditions

In this study, we investigated how the geometric design of anodic one-dimensional (1D) TiO2 nanotube arrays affected their performance in the electrochemical reduction of 2,4,6-trinitrotoluene (2,4,6-TNT) in aqueous solutions and ambient conditions. Two main geometric parameters were considered: the inner diameter and length of TiO2 nanotubes. The various TiO2 nanotubes were fabricated using an anodization technique performed in four types of fluoride-containing organic solvents by adjusting various anodization parameters. All as-prepared samples successfully detected 2,4,6-TNT in an aqueous solution using cyclic voltammetry and linear sweep voltammetry. Three peaks corresponding to the reduction of each nitro group in 2,4,6-TNT were observed between − 0.5 and − 1.0 V (versus Ag/AgCl, 3 M KCl). Further, we discovered that nanotube length affected 2,4,6-TNT reduction performance. We also performed experiments at various concentrations of 2,4,6-TNT and determined the sensitivity to be 1.78 × 10-3 mA cm−2 ppm−1, the limit of detection to be 6.49 ppm, and the limit of quantitation to be 21.6 ppm 2,4,6-TNT over a linear range of 20 – 100 ppm using an electrode with nanotube inner diameter of 75 nm and length of 6 µm. A simple and fast fabricated composite-free 1D TiO2 nanotube arrays electrode can form the basis for future studies in enhancing the detection sensitivity. Electrochemical detection of other nitro-based compounds, such as nitroglycerin, nitrocellulose, picric acid, and their mixtures, require further investigation.

WO3 decorated TiO2 nanotube array electrode: Preparation, characterization and superior photoelectrochemical performance for rhodamine B dye degradation

An efficient photoelectrocatalyst was synthesized by electrochemical deposition of WO3 on the titanium nanotube (TNT) array by subsequent cycling the potential between -0.6 – 1.0 V vs Ag/AgCl. The structural and morphological properties of the electrode obtained (TNT-WO3) was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopic (SEM) techniques and it was revealed that TNT surfaces were successfully decorated by WO3 species without formation of another oxidation species. Then, the photoelectrocatalytic activity of the composite electrode set at 0.2 V (vs Ag/AgCl), was tested under UV light irradiation on the degradation of Methylene blue (MB), Orange G (OG) and Rhodamine B (RhB), as the model pollutants. Among the azo dyes studied, the electrode has given the best performance against RhB in comparison to the bare TNT electrode. The influence of the deposition conditions on the efficiency was examined and under optimal conditions and it was noted that efficient removal of the dye can be achieved within 10 min. Another advantage of the composite electrode is that PEC performance can be tuned by simply changing the parameters of deposition.

Treatment of Ni-EDTA containing wastewater by electrochemical degradation using Ti3+ self-doped TiO2 nanotube arrays anode

Ethylene diamine tetraacetic acid (EDTA) could form stable complexes with nickel due to its strong chelation. Ni-EDTA has significant impacts on human health because of its acute toxicity and low biodegradability, thus some appropriate approaches are required for its removal. In this research, a Ti3+ self-doped TiO2 nanotube arrays electrode (ECR-TiO2 NTA) was prepared and employed in electrochemical degradation of Ni-EDTA. The oxygen evolution potential of ECR-TiO2 NTA was 2.6 V vs. SCE. More than 96% Ni-EDTA and 88% TOC was removed after reaction for 120 min at current density 2 mA cm−2 at pH 4.34. The degradation of Ni-EDTA was mainly through the cleavage of amine group within Ni-EDTA and furthermore decomposed it into small molecular acids and inorganic ions including NH4+and NO3−. The electro-deposition of nickel ions at cathode was confirmed by XPS and was greatly affected by the pH of solution. The effects of current density, initial Ni-EDTA concentration, initial pH of solution and HCO3− concentration on Ni-EDTA degradation were investigated. The results exhibited that the ECR-TiO2 NTA had excellent efficiencies in electrochemical degradation of Ni-EDTA. The LSV analysis suggested that Ni-EDTA oxidation on ECR-TiO2 NTA anode and the production of hydroxyl radical (·OH) on the anode played an important role in the removal of Ni-EDTA.

Efficient electrocatalysis for denitrification by using TiO2 nanotube arrays cathode and adding chloride ions

Electrocatalysis is emerging as a promising alternative to bacterial denitrification for removing nitrate and ammonia from sewage. The technology is highly efficient and robust in actual wastewater treatment scenarios; however, there may be the generation of harmful intermediates (such as nitrite) on the traditional cathode material. In this study, we demonstrated that TiO2 nanotube arrays can be used as an effective cathode to reduce nitrate to ammonia without generation of nitrite. Alongside this, the addition of chloride ions in the solution can further oxidize ammonia to N2. We looked into the key factors influencing the electrocatalytic denitrification, including the current density (2–10 mA/cm2), initial pH values (3–11), and types of anions (HCO3−, Cl−, SO42−). The results showed that 90.8% of nitrate and 59.4% of total nitrogen could be removed in 1.5 h under optimal conditions, with degradation kinetic constants of 1.61 h−1 and 0.79 h−1, respectively. Furthermore, we investigated the formation of intermediate products and explored the electrocatalytic denitrification mechanism: (a) the surface oxygen vacancies and high specific surface area of TiO2 nanotube arrays electrode promote the reduction of nitrate to ammonia and N2; (b) the active chlorine generated at the anode surface can effectively oxidize ammonium to N2.

Towards full cell potential utilization during water purification using Co/Bi/TiO2 nanotube electrodes

Here we report on a research effort towards full cell potential utilization during the elimination of organic pollutants under environmentally relevant conditions. Meropenem was selected as a representative recalcitrant antibiotic and a newly-developed Co and Bi co-doped TiO2 nanotube array (Co/Bi/TiO2 NTA) electrode was employed as both anode and cathode. While electrochemical reduction of Meropenem appeared to be much more energy efficient (0.042 kWh/m3) than electrochemical oxidation (0.813 kWh/m3) in synthetic electrolyte, the degradation was significantly inhibited in environmental matrices (secondary effluent/SE and RO concentrate) due to the competition and/or inhibition effects of other species present in the matrices as well as electrode fouling. Calcium carbonate and magnesium oxide were identified to be main mineral foulants. The elimination of Meropenem was then examined in coupled treatment schemes (e.g. sequential and simultaneous), taking advantages of the “self-regeneration” characteristic of TiO2 NTA based electrodes through cathodic polarization. While a simultaneous oxidation & reduction with regular polarity switching seems to be a preferred treatment scheme especially for challenging matrices such as RO concentrate, the bipolar stability of the nanostructured electrode may limit the electrode lifetime. A hybrid electrolysis system coupling anodic oxidation of organic pollutants and cathodic hydrogen generation as a renewable energy source was also tested in a flow-through reactor, where consistent and steady treatment performance was demonstrated for a period of 3 days. We think the results obtained from this study have underlined the importance of matrix characteristics on the design and selection of electrochemical treatment processes. It also provides insights into future development of coupled anodic and cathodic processes for water purification.

Zr4+-Doped Anatase TiO2 Nanotube Array Electrode for Electrocatalytic Reduction of L-cystine

A Zr4+-doped anatase TiO2 nanotube array electrode was prepared using a process that included Ti anodizing, chemical immersion, and heat treatment. The compositions, microstructure, and electrochemical properties of the prepared electrodes were characterized. The results show that Zr4+ was successfully introduced into the TiO2 nanotube array electrodes. Because Zr4+ was doped into the crystal structure of the TiO2and replaced a part of Ti4+ to form more oxygen vacancies and Ti3+, the electrocatalytic activity of the prepared electrodes, for the reduction of L-cystine, was significantly improved.

Sandwich structure MoO2/MoS2/TiO2 photocatalyst for superb hydrogen evolution

Abstract TiO2 has gained increasing interest because of its outstanding properties and promising applications in various fields. In this study, we report a novel MoO2/MoS2/TiO2 sandwich heterostructure that was prepared by chemical vapor deposition (CVD) for highly efficient photocatalytic H2 generation. The sandwich structure, consisting of a MoS2 nanoflake layer and a MoO2 nanoplate layer with large specific surface area, was grown on TiO2 nanotube array electrodes. The MoO2 acts as a fast hole transport layer that promotes efficient charge separation. Since the MoO2/MoS2/TiO2 heterostructure has a nearly full-solar-spectrum absorption range, its photocatalytic activity for water splitting is enhanced, resulting in a H2 production rate of 110 μmol h−1 cm−2. This work provides a bottom-up strategy for preparing highly efficient sandwich-type photocatalysts.

Cu2O on anodised TiO2 nanotube arrays: A heterojunction photoanode for visible light assisted electrochemical degradation of pharmaceuticals in water

A visible-light active p-n heterojunction photoanode was synthesised via electrodeposition of Cu2O on anodised TiO2 nanotube arrays (NTAs). The photoanode was characterised with XRD, FESEM, EDX and diffusive reflectance UV–Vis, and evaluated by the degradation of ciprofloxacin in water. Mott-Shottky plots were carried out to confirm the formation of the p-n heterojunctions between the two electrodes. Photoelectrochemical properties of the synthesised photoanode were also examined with linear sweep voltammetry, photocurrent response and electrochemical impedance spectroscopy. The linear sweep voltammetry showed that the TiO2 NTA/Cu2O photoanode gave the highest current as compared to the pristine TiO2 NTA. In addition, photocurrent response study showed that the TiO2 NTA/Cu2O gave an improved response three times (0.169 mA cm−2) larger than the pure TiO2 NTA (0.05 mA cm−2). The as-prepared photoanodes were applied in the photoelectrocatalytic degradation of ciprofloxacin an antibiotic. An overall percentage degradation of 73% over a period of 4 h. Trapping experiment revealed that the degradation occurred majorly through the holes on the semiconductor. The photoanodes displayed high stability and reusability and therefore suggests the electrodeposited Cu2O anodised TiO2 NTA electrode as an efficient photoanode for degrading other emerging pharmaceutical pollutants from wastewater.

Fabrication of TiO2-Nanotube-Array-Based Supercapacitors.

In this work, a simple and cost-effective electrochemical anodization technique was adopted to rapidly grow TiO2 nanotube arrays on a Ti current collector and to utilize the synthesized materials as potential electrodes for supercapacitors. To accelerate the growth of the TiO2 nanotube arrays, lactic acid was used as an electrolyte additive. The as-prepared TiO2 nanotube arrays with a high aspect ratio were strongly adhered to the Ti substrate. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results confirmed that the TiO2 nanotube arrays were crystallized in the anatase phase. TEM images confirmed the nanotublar-like morphology of the TiO2 nanotubes, which had a tube length and a diameter of ~16 and ~80 nm, respectively. The electrochemical performance of the TiO2 nanotube array electrodes was evaluated using the cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) measurements. Excellent electrochemical response was observed for the electrodes based on the TiO2 nanotube arrays, as the cells delivered a high specific capacitance of 5.12 mF/cm2 at a scan rate of 100 mV/s and a current density of 100 µA/cm2. The initial capacity was maintained for more than 250 cycles. Further, a remarkable rate capability response was observed, as the cell retained 88% of the initial areal capacitance when the scan rate was increased from 10 to 500 mV/s. The results suggest the suitability of TiO2 nanotube arrays as electrode materials for commercial supercapacitor applications.

Research Synthesis of La3+ Doped TiO2 Nanoparticles by Hydrothermal Method, Study on Photocatalytic Activity of Decomposition of Methylene Blue under Ultraviolet Irradiation

In this study, with the aim of improving the photocatalytic efficiency of TiO2, we studied the synthesis of La3+ doped TiO2 (with doped rates 1%, 2.5%, 5% mol/mol compared to Ti4+) by hydrothermal method. The hydrothermal condition was set at 180 °C for 12 hours. Material characteristics were investigated by XRD, SEM and solid UV-Vis methods. The results show that, all prepared materials have a crystal particle size of about nano-meters, small and smooth (4.5¸6.5 nm). La3+ doped TiO2 samples had a shift towards longer wavelengths (l» 400¸500 nm) compared to non-doped TiO2 sample (l£ 380 nm). The band gap energy (Eg) of La3+ doped TiO2 samples was reduced to 3.04¸3.10 eV . The yield of MB degradation of La3+ doped TiO2 at 5% mol/mol reached the highest ~93% after 60 minutes under ultraviolet irradiation.
 Keywords
 Anatase TiO2, photocatalysis, La3+ doped TiO2, hydrothermal method, ultraviolet irradiation. 
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