Photocatalytic Oxidation Of Methanol Research Articles

Heterogeneous photocatalytic methanol oxidation coupled with oxygen reduction toward pyrimidines synthesis

Heterogeneous photocatalytic methanol oxidation coupled with oxygen reduction toward pyrimidines synthesis

Photocatalytic methanol oxidation to formaldehyde in a continuous laboratory plant over Aeroxide P25

We here report the photochemical synthesis of formaldehyde by gas phase methanol oxidation with oxygen in a sophisticated continuous laboratory setup.

Fabrication of nitrogen doped TiO2/Fe2O3 nanostructures for photocatalytic oxidation of methanol based wastewater

An important industrial process that often occurs on the surface of a heterogeneous catalyst using thermochemical or photochemical could help in the oxidation of methanol-based wastewater to formaldehyde. Titania-based photocatalysts have drawn a lot of interest from scientists because they are a reliable and affordable catalyst material for photocatalytic oxidation processes in the presence of light energy. In this study, a straight-forward hydrothermal method for producing n-TiO2@α-Fe2O3 composite photocatalysts and hematite (α-Fe2O3) nanocubes has been done. By adjusting the ratio of n-TiO2 in the prepared composite photocatalysts, the enhancing influence of the nitrogen-doped titania on the photocatalytic characteristics of the prepared materials was investigated. The prepared materials were thoroughly characterized using common physiochemical methods, such as transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), X-ray photoelectrons spectroscopy (XPS), physisorption (BET), and others, in order to learn more about the structure The results obtained showed that nitrogen-doped titania outperforms non-doped titania for methanol photooxidation. The addition of nitrogen-doped titania to their surfaces resulted in an even greater improvement in the photooxidation rates of the methanol coupled with hematite. The photooxidation of methanol in the aqueous solution to simulate its concentration in the wastewater has been occurred. After 3 h, the four weight percent of n-TiO2@α-Fe2O3 photocatalyst showed the highest rate of HCHO production.

Redox Dynamics of Pt and Cu Nanoparticles on TiO2 during the Photocatalytic Oxidation of Methanol under Aerobic and Anaerobic Conditions Studied by In Situ Modulated Excitation X-ray Absorption Spectroscopy

In situ modulated excitation X-ray absorption spectroscopy (ME-XAS) at the Pt L3- and Cu K-edges has been successfully used in this work to shed light on the controversial role that Pt and Cu nanoparticles (NPs) on TiO2 have in photocatalysis. TiO2 photocatalysts, either bare or modified by Pt and Cu NPs, synthesized in a single step by flame spray pyrolysis, were tested in the gas-phase photocatalytic oxidation of methanol to CO2 under both aerobic (CH3OH + 3/2O2 → CO2 + 2H2O) and anaerobic (CH3OH + H2O → CO2 + 3H2) conditions. Both Pt- and Cu-containing TiO2 showed lower activity than bare TiO2 under aerobic conditions, while higher H2 and CO2 production rates were attained under anaerobic conditions in the presence of the Pt co-catalyst, with copper-containing TiO2 having in this case an activity similar to that of bare titania. ME-XAS, coupled with phase-sensitive detection, proved in fact that Pt NPs efficiently capture the electrons photopromoted in the conduction band of TiO2 and are the active sites for H2 or H2O evolution under anaerobic or aerobic conditions, respectively. Much more complex is the role of Cu-NPs on titania, with ME-XAS revealing that copper is simultaneously present in different oxidations states, depending on the reaction conditions. Cu NPs are not the reaction active sites under anaerobic conditions, while a Cu(II)/Cu(I) redox switching occurs under chopped irradiation under aerobic conditions.

Semi-automated EPR system for direct monitoring the photocatalytic activity of TiO2 suspension using TEMPOL model compound.

The photocatalytic activity of TiO2 nanoparticles in aqueous solutions is commonly evaluated by monitoring the rate of methylene blue bleaching and phenols degradation, but both substrates suffer from many drawbacks, e.g., the high capacity of dark adsorption, self-degradation, and photosensitization. Besides, filtration is always required to separate the particulate photocatalyst before the analysis. Herein, we investigated the potential use of electron paramagnetic resonance(EPR) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) to directly monitor the photocatalytic activity of TiO2 suspensions without the need for filtration. The results showed that TEMPOL aqueous solution is in the dark and under UV-A illumination, does not absorb UV-A and visible light, and has negligible dark adsorption. The influence of TEMPOL concentration, light intensity, and TiO2 loading on the photocatalytic deactivation rate has been investigated. The mechanisms of TEMPOL deactivation in the presence and absence of oxygen as well as in the presence of methanol •OH radicals' scavenger have been discussed. The photocatalytic deactivation products have been analyzed using EPR, 1H-NMR, and 13C-NMR spectroscopies. It is found that the deactivation of TEMPOL is initiated by •OH radicals and α-H abstraction from the 4-piperidine position followed by the formation of TEMPONE (4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl) and 4-oxo-2,2,6,6-tetramethylpiperidine). In the presence of methanol, the formed α-hydroxyl radicals (•CH2OH) attack the nitroxide side of TEMPOL and produce 4-hydroxy-tetramethylpiperidine. Same activity trends have been observed for the photocatalytic methanol oxidation and TEMPOL deactivation over different types of TiO2 photocatalysts evincing that the proposed method has a potential for direct monitoring of the activities of photocatalyst suspensions.

Atomic Fe sites doped two-dimensional (001) TiO2 nanosheets as an effective photo-response support in methanol electro-oxidation

The anode supports of direct methanol fuel cell (DMFC) directly affect the energy conversion efficiency between methanol fuel and electric energy. Semiconductor-based supports have nice photoelectric property for photo-assisted electrocatalytic methanol oxidation, making it be a kind of promising support of Pt. However, the rapid recombination of semiconductor photogenerated carriers limits the methanol oxidation ability of Pt. Herein, the two-dimensional (2D) (001) TiO2 nanosheets doped by a small amount of atomic iron were prepared by a reproducible impregnation method as the anode support to decrease the recombination rate. The atomic iron sites doped 2D (001) TiO2 nanosheets electrode has a high electrocatalytic performance for methanol oxidation under UV light-excitation, which is 2.7 times higher than that in dark and 4.8 times than that of non-doped electrode. The nice activities of atomic iron sites doped 2D (001) TiO2 nanosheets can be attributed to the introduction of atomic iron which are beneficial for the separation of photogeneration carriers and producing more photogenerated holes for the generation of strong oxidizing hydroxyl radicals (•OH). During the process of electrocatalytic methanol oxidation, •OH can not only promote the photocatalytic methanol oxidation, but also attenuate the inactivation of Pt poisoned by COads. These results provide a strategy to further ameliorate the photo-assisted electrocatalytic property for methanol oxidation.

Site Sensitivity of Interfacial Charge Transfer and Photocatalytic Efficiency in Photocatalysis: Methanol Oxidation on Anatase TiO2 Nanocrystals.

Photocatalytic oxidation of methanol on various anatase TiO2 nanocrystals was studied by in situ and time-resolved characterizations and DFT calculations. Surface site and resulting surface adsorbates affect the surface band bending/bulk-to-surface charge migration processes and interfacial electronic structure/interfacial charge transfer processes. TiO2 nanocrystals predominantly enclosed by the {001} facets expose a high density of reactive fourfold-coordinated Ti sites (Ti4c ) at which CH3 OH molecules dissociate to form the CH3 O adsorbate (CH3 O(a)Ti4c ). CH3 O(a)Ti4c localized density of states are almost at the valence band maximum of TiO2 surface, facilitating the interfacial hole transfer process; CH3 O(a)Ti4c with a high coverage promotes upward surface band bending, facilitating bulk-to-surface hole migration. CH3 O(a)Ti4c exhibits the highest photocatalytic oxidation rate constant. TiO2 nanocrystals enclosed by the {001} facets are most active in photocatalytic methanol oxidation.

Site Sensitivity of Interfacial Charge Transfer and Photocatalytic Efficiency in Photocatalysis: Methanol Oxidation on Anatase TiO2 Nanocrystals

AbstractPhotocatalytic oxidation of methanol on various anatase TiO2 nanocrystals was studied by in situ and time‐resolved characterizations and DFT calculations. Surface site and resulting surface adsorbates affect the surface band bending/bulk‐to‐surface charge migration processes and interfacial electronic structure/interfacial charge transfer processes. TiO2 nanocrystals predominantly enclosed by the {001} facets expose a high density of reactive fourfold‐coordinated Ti sites (Ti4c) at which CH3OH molecules dissociate to form the CH3O adsorbate (CH3O(a)Ti4c). CH3O(a)Ti4c localized density of states are almost at the valence band maximum of TiO2 surface, facilitating the interfacial hole transfer process; CH3O(a)Ti4c with a high coverage promotes upward surface band bending, facilitating bulk‐to‐surface hole migration. CH3O(a)Ti4c exhibits the highest photocatalytic oxidation rate constant. TiO2 nanocrystals enclosed by the {001} facets are most active in photocatalytic methanol oxidation.

Multitarget Evaluation of the Photocatalytic Activity of P25-SiO2 Prepared by Atomic Layer Deposition

This work presents the evaluation of the photocatalytic activity of P25 TiO2 particles, coated with SiO2, using atomic layer deposition (ALD) for the photocatalytic removal of methylene blue, oxidation of methanol and inactivation of Escherichia coli bacteria in water and its comparative evaluation with bare P25 TiO2. Two different reactor configurations were used, a slurry reactor with the catalyst in suspension, and a structured reactor with the catalyst immobilized in macroporous foams, that enables the long-term operation of the process in continuous mode, without the necessity of separation of the particles. The results show that the incorporation of SiO2 decreases the efficiency of the photocatalytic oxidation of methanol, whereas a significant improvement in the removal of methylene blue is achieved, and no significant changes are observed in the photocatalytic inactivation of bacteria. Adsorption tests showed that the improvements, observed in the removal of methylene blue by the incorporation of SiO2, was mainly due to an increase in its adsorption. The improvement in the adsorption step as part of the global photocatalytic process led to a significant increase in its removal efficiency. Similar conclusions were reached for bacterial inactivation where the loss of photocatalytic efficiency, suggested by the methanol oxidation tests, was counteracted with a better adherence of bacteria to the catalyst that improved its elimination. With respect to the use of macroporous foams as support, a reduction in the photocatalytic efficiency is observed, as expected from the decrease in the available surface area. Nevertheless, this lower efficiency can be counteracted by the operational improvement derived from the easy catalyst reuse.

Excited-State Chemistry: Photocatalytic Methanol Oxidation by Uranyl@Zeolite through Oxygen-Centered Radicals.

We have elucidated the complex reaction network of partial methanol oxidation, H3COH + O2 → H2CO + H2O2, at a visible-light-activated actinide photocatalyst. The reaction inertness of C-H bonds and O═O diradicals at ambient conditions is overcome through catalysis by photoexcited uranyl units (*UO22+) anchored on a mesoporous silicate. The electronic ground- and excited-state energy hypersurfaces are investigated with quasirelativistic density-functional and ab initio correlated wave function approaches. Our study suggests that the molecular cluster can react on the excited energy surface due to the longevity of excited uranyl, typical for f-element compounds. The theoretically predicted energy profiles, chemical intermediates, related radicals, and product species are consistent with various experimental findings. The uranyl excitation opens various reaction pathways for the oxidation of volatile organic compounds (VOCs) by "hole-driven hydrogen transfer" (HDHT) through several exothermic steps over low activation barriers toward environmentally clean or chemically interesting products. Quantum-chemical modeling reveals the high efficiency of the uranyl photocatalysis and directs the way to further understanding and improvement of VOC degradation, chemical synthesis, and biologic photochemical interactions between uranyl and the environment.

Evaluating carbon dots as electron mediators in photochemical and photocatalytic processes of NiFe2O4

Spinel ferrites such as nickel ferrite are promising energy conversion photocatalysts as they are visible-light absorbers, chemically stable, earth abundant, and inexpensive. Nickel ferrite shows poor photocatalytic activity due to fast electron–hole recombination upon illumination. This study evaluates the capability of carbon dots (CDs) to improve charge-carrier separation in NiFe2O4. We report a facile solvothermal approach for synthesizing NiFe2O4 and CDs/NiFe2O4 nanoparticles at 200–215 °C. The photocatalysts were characterized using transmission and scanning electron microscopy, x-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV-VIS-NIR spectroscopy, photoelectrochemical analysis, and laser flash photolysis. Photocatalytic oxidation of methanol to formaldehyde under visible light was employed to test the effect of CDs on the photocatalytic efficacy of NiFe2O4. UV-VIS-NIR spectroscopy depicted a total quenching of NIR absorption and a diminished absorption of a peak at ∼745 nm in CDs/NiFe2O4 compared with NiFe2O4, indicating a transfer of electrons from NiFe2O4 to CDs. A 12-fold increment in the incident-photon-to-charge-efficiency was achievable with CDs/NiFe2O4 (0.36%) compared with NiFe2O4 (0.03%). Impedance spectroscopy exhibited a more efficient charge separation and faster interfacial charge transfer in CDs/NiFe2O4 compared with pure NiFe2O4. This was accounted for by the lower initial quantity of charge carrier upon irradiation in CDs/NiFe2O4 compared with NiFe2O4 as detected from laser flash photolysis, indicating that CDs acted as electron acceptors and reservoirs in CDs/NiFe2O4. Compared with NiFe2O4, CDs/NiFe2O4 showed an enhanced photocatalytic activity toward formaldehyde formation. Consequently, CDs are good electron mediators for NiFe2O4, capable of improving charge-carrier separation and the photocatalytic activity of NiFe2O4.

Ultrafast time-resolved quantum cascade laser diagnostic for revealing the role of surface formate species in the photocatalytic oxidation of methanol

QCL-assisted operando FT-IR spectroscopy revealed the role of surface formate species in the photocatalytic oxidation of methanol over TiO2.

Anchoring lead-free halide Cs3Bi2I9 perovskite on UV100–TiO2 for enhanced photocatalytic performance

Halide perovskites have shown great potential in photocatalytic applications. In order to enhance the charge transportation efficiency, the chemical stability, and the light absorption ability, we anchored a lead-free halide perovskite (Cs3Bi2I9) on UV100–TiO2 nanoparticles to build a visible-light active photocatalysts. The as-prepared material exhibited excellent stability and a remarkable yield for photocatalytic oxidation of methanol to formaldehyde under visible light irradiation. The photocatalyst was characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, Brunauer–Emmett–Teller surface area measurement, and photoelectrochemical properties. The analyses confirmed a remarkable improvement of visible-light absorption, a favorable decrease in the recombination of photoinduced charge carriers, and a suitable bandgap for visible-light photocatalytic applications. Recycle experiments showed that the composites still presented significant photocatalytic activity after three successive cycles. A possible underlying mechanism of the composite accounting for the enhanced photocatalytic activity under visible light irradiation was proposed.Our study aims to open new possibilities of using lead-free halide perovskites for photocatalytic applications.

Understanding the role of catalytic active sites for heterogeneous photocatalytic oxidation of methanol and thermal reduction of NOx

Identification and understanding the role of catalytic active sites are crucial to realize the performance of a catalyst. The conventional heterogeneous metal catalysts are still far away from the understanding of the nature of active sites. In this work, the solid solutions of Ti1-xPtxO2-δ (x = 0.01, 0.03, and 0.05) were synthesized by a microwave assisted hydrothermal method, where bivalent Pt was doped into the lattice of TiO2 in order to create the oxide ion vacancies. The as-prepared materials were reduced to leach out the substituted Pt in metallic state. Both the sets of materials were thoroughly characterized structurally and morphologically. The catalytic role of Pt was probed in these materials for two different and quite important reactions; room temperature photo-oxidation of methanol to hydrogen, and thermal reduction of NO to N2. The active sites of the catalysts were identified from the experimental observations. The elementary reaction mechanism over the active sites were proposed, and supported with modelling. The results revealed that the oxidized and the reduced catalyst behave in a completely different manner in the oxidation and reduction reactions chosen in this work.

Photocatalytic oxidation of methanol to formaldehyde on bismuth-based semiconductors.

Methanol is widely applied in photocatalysis as a scavenger of holes, and is also studied as a model system for heterogeneous photocatalysis for the production of formaldehyde. Compared to commercial processes for formaldehyde production via thermal catalytic methanol oxidation, photocatalytic oxidation of methanol to formaldehyde may be more promising when considering the following aspects: 1) lower reaction temperature and pressure (generally operated at room temperature and ambient pressure); 2) lower cost of the energy source (such as solar light) and 3) easy-to-design reactive system. Photocatalytic methanol oxidation was carried out using four different bismuth-based semiconductors (BBS), Bi2WO6, Bi2MoO6, BiOBr and BiVO4, under varying system temperature (5-50 °C), bubbling speed (0.1-1.0 LPM), catalyst dosage (0.2-2.0 g/L), and initial methanol concentration (12.5-250 mM). It was found that the formaldehyde formation rate for all photocatalysts increased as a function of each of these system parameters. Of these four BBS, it was found that Bi2WO6 had the highest formaldehyde formation rate (0.081 mM/h). This work provides a new approach to produce formaldehyde using photocatalysis, and future work has also been proposed.

Photocatalytic Methanol Oxidation by Supported Vanadium Oxide Species: Influence of Support and Degree of Oligomerization

Supported isolated vanadium oxide (VO4) species on silica have recently been shown to photocatalytically oxidize methanol selectively to formaldehyde. Insights into support effects and the reactivity of the different supported vanadium oxide species in photocatalytic methanol oxidation are obtained in the present study by varying the support, surface vanadium oxide loading, and synthesis procedure. Isolated and oligomeric surface vanadium oxide species supported on alumina can also photocatalytically oxidize methanol to formaldehyde. Crystalline V2O5 nanoparticles are inactive for photocatalytic conversion of methanol irrespective of the support, but they further convert the formaldehyde produced by the surface vanadium oxide species to surface formate species. The formation of surface formate species is also observed on the bare alumina support. Thermal catalyzed reactions take place at elevated temperatures, leading to product degradation, when attempting to desorb and quantify the photocatalysis products adsorbed on the alumina‐supported samples. This study is a step forward in the directed development of active and selective sites for photocatalysis, and highlights the importance of limitation by desorption in the kinetics of photoreactions.

Photoelectrochemical Methanol Oxidation on TiN@Au Core-Shell Nanoparticles Supported on TiO2

Refractory transition metal nitrides such as TiN and ZrN are a new class of plasmonic materials that exhibit plasmonic resonance in the visible and near-infrared regions [1, 2]. The similarity of optical appearance of TiN to gold makes one wonder whether inexpensive and chemically and mechanically robust TiN can replace Au in plasmon-mediated photocatalytic reactions. Prior research [3] has shown that cubic 50 nm TiN nanoparticles supported on TiO2 nanowires provide greater photocurrent enhancement for the photoelectrochemical water splitting compared to spherical Au nanoparticles. This has been attributed to more efficient hot carrier generation by TiN nanoparticles, followed by more efficient collection of hot electrons by TiO2. 50 nm TiN nanoparticles (NPs), however, proved to be inefficient in promoting photocatalytic activity of TiO2 towards methanol oxidation in the visible region [4]. This was likely due to a lack of catalytic activity of the TiN NPs’ surface for CH3OH oxidation. Here, we explore the plasmon-mediated photocatalytic methanol oxidation on hybrid core-shell nanoparticles consisting of a thin gold shell and TiN core and compare the effect of TiO2-supported TiN@Au nanoparticles to that of Au on the photon-to-electron conversion efficiency. The TiO2-supported TiN@Au photocatalysts were made by the deposition of a thin Au shell on 20 and 50 nm TiN NPs (PlasmaChem) followed by the dispersion of the TiN@Au NPs onto TiO2 nanoparticle support (Degussa). Electrochemical experiments were conducted in a three-electrode photoelectrochemical cell. The thin films of TiN@Au/TiO2 on FTO-coated glass served as working electrodes (WEs), while platinum foil and Ag/AgCl in 3 M NaCl (BioLogic, Inc) were used as counter and reference electrodes, respectively. LED lights were used as light sources. X-Ray Photoelectron Spectroscopy, Powder X-Ray Diffraction, and high resolution transmission electron microscopy were used for characterization of catalysts surface composition and morphology.

Comparison between the catalytic and photocatalytic activities of Cu/Al2O3 and TiO2 in the liquid–phase oxidation of methanol–ethanol mixtures: Development of a kinetic model for the preparation of catalyst

This work presents the preparation and characterization of copper supported on gamma alumina (γ–Al2O3) as a catalyst and compared with the photocatalytic activity of titania (TiO2) in the oxidation of methanol and ethanol mixtures; the ratio of both alcohols in the mixture was according to the commercial alcoholic beverages. In order to understand the thermal transformations of Cu/Al2O3 catalyst, a kinetic model of its synthesis has been developed and analyzed in terms of the oxidation of the precursor CuCl2∙2H2O impregnated onto Al2O3 to form CuO/Al2O3, and also its reduction to form the metallic copper supported on alumina (Cu/Al2O3) catalyst. The sequence of reactions was considered according to the X–ray diffraction (XRD) at different temperatures and thermal characterizations. The kinetic parameters revealed how the alumina support intervened in some steps to form the catalyst through chemical metal–support interactions. It was also verified that during the chemical changes that the active phase undergoes, its good dispersion is maintained on the support and the activation energy values of the model can predict that these metal–support chemical interactions were also preserved from the salt added to the formation of elementary copper. These kinetic model’s predictions were accurately demonstrated by High–resolution transmission electron microscopy (HRTEM) micrographs and X–ray photoelectron spectra (XPS) techniques, where the appearance of the copper aluminate phase (CuAl2O4) is an evidence of the metal–support interaction, which could have contributed to the elementary copper nanoparticles formation and the catalytic activity as an active phase in the oxidation of alcohols. Cu/Al2O3 catalyst showed a higher yield of acetic acid from ethanol than formic acid from methanol. In comparison, the TiO2 in the photocatalytic oxidation presented a higher yield of formic acid from methanol than acetic acid from ethanol. A similar behavior was observed in the oxidation tests of each alcohol separately, since, the photocatalytic oxidation of methanol, using TiO2, showed nearly the 100% of selectivity in the formation of formic acid from methanol, and the Cu/Al2O3 catalyst exhibited similar results but, in this case, the selectivity towards to acetic acid from ethanol. Stable acetate intermediates detected by FTIR in ethanol oxidation to acetic acid on Cu/Al2O3 showed that this oxidation proceeds via acetaldehyde intermediates.

An efficient photo-assisted BiOBr nanoplates support for electrocatalyst for methanol oxidation

Abstract Herein, visible-light driven BiOBr nanoplates with fully exposed (001) facet are for the first time adopted as Pt nanoparticles support for electrocatalytic methanol oxidation. We found that, as Pt nanoparticles support, high specific surface area of BiOBr (001) nanoplates not only can be driven by visible-light to produce photogenerated electrons and holes, but also benefit to the dispersion of Pt nanoparticles. When Pt–BiOBr (001) nanocomposites electrode exposed into the simulated solar light irradiation and visible-light irradiation, it exhibits 5.2 and 2.4 times higher electrocatalytic activities for methanol oxidation than dark condition, respectively. Synergistic effects between electrocatalytic and photocatalytic methanol oxidation as well as the efficient interfacial charger separation in Pt–BiOBr (001) electrode contribute to the enhanced electrocatalytic methanol oxidation activities. The present results suggest that BiOBr (001) nanoplates can be used as photo-assisted Pt nanoparticles support in direct methanol fuel cell.

Influence of anodization mode on the morphology and photocatalytic activity of TiO2-NTs array large size electrodes

Properties of nanotubular titania structures (TiO2-NTs) have been widely evaluated in small electrodes at lab scale. A novel experimental approach to overcome the limitations for the anodization of large size electrodes is presented. Several potentiostatic and galvanostatic anodization procedures have been tested, and their impact on the morphological features of the TiO2-NTs analyzed. A clear relationship between the applied voltage and current density and the NTs length and diameter is confirmed. Photocatalytic activity of the TiO2-NTs structures was evaluated in the methanol oxidation reaction. From these results, it was obtained that kinetic constant for the photocatalytic oxidation of methanol is higher when the reaction is carried out with NTs of higher length/diameter aspect ratio. This is related to a higher TiO2 active surface area available to generate photo-induced electron-hole pairs and for the adsorption of the reactants. This work confirms the viability of formation of photocatalytically active large size TiO2-NTs electrodes when high voltage or current density is applied under controlled conditions. Availability of fluoride in the electrolyte can be ensured by the use of a novel concept of continuous flow anodization reactor allowing the renovation of the electrolyte to keep under control not only the composition but also the temperature of the solution.