Black carbon-doped TiO2 films: Synthesis, characterization and photocatalysis

Facile synthesis of TiO2-carbon composite doped nitrogen for efficient photodegradation of noxious methylene blue dye

The present work shows that the degrading ability of TiO2 is significantly improved when exposed to light, particularly in relation to the organic dye methylene blue (MB), following the introduction of a carbon framework through sol-hydrothermal synthesis approach. The newly prepared TiO2-C@N composite had the ability to function as both an adsorbent and a photocatalyst to eliminate MB from contaminated wastewater. The outcomes show the removal efficiency of MB amounts to 99.87% upon the application of UV radiation, which is much higher than the rate achieved under dark conditions (28.9%). As ascertained by the kinetic study, the degradation of methylene blue (MB) under UV light through photocatalysis using the TiO2-C@N photocatalyst conformed to the widely recognized pseudo-first order (PFO) model. TiO2-C@N photocatalyst showed outstanding reliability and reusability, maintaining consistent degradation efficiency over five consecutive cycles without any obvious decline. The materials were characterized by XRD, XPS, FE-SEM, EDS, and N2 adsorption-desorption measurements. Nanometer-sized particles, a unique surface dominance, high surface area, large pore volume ratios, low band gap, high oxygen vacancies, increased pollution absorptivity, and reduced electron-hole pair recombination characterize the monolithic TiO2-C@N photocatalyst over TiO2. These unique features render TiO2-C@N a promising catalyst in effectively breaking down noxious MB organic pollutants through photodegradation.

Recent Progress of Ion-Modified TiO2 for Enhanced Photocatalytic Hydrogen Production

Harnessing solar energy to produce hydrogen through semiconductor-mediated photocatalytic water splitting is a promising avenue to address the challenges of energy scarcity and environmental degradation. Ever since Fujishima and Honda's groundbreaking work in photocatalytic water splitting, titanium dioxide (TiO2) has garnered significant interest as a semiconductor photocatalyst, prized for its non-toxicity, affordability, superior photocatalytic activity, and robust chemical stability. Nonetheless, the efficacy of solar energy conversion is hampered by TiO2's wide bandgap and the swift recombination of photogenerated carriers. In pursuit of enhancing TiO2's photocatalytic prowess, a panoply of modification techniques has been explored over recent years. This work provides an extensive review of the strategies employed to augment TiO2's performance in photocatalytic hydrogen production, with a special emphasis on foreign dopant incorporation. Firstly, we delve into metal doping as a key tactic to boost TiO2's capacity for efficient hydrogen generation via water splitting. We elaborate on the premise that metal doping introduces discrete energy states within TiO2's bandgap, thereby elevating its visible light photocatalytic activity. Following that, we evaluate the role of metal nanoparticles in modifying TiO2, hailed as one of the most effective strategies. Metal nanoparticles, serving as both photosensitizers and co-catalysts, display a pronounced affinity for visible light absorption and enhance the segregation and conveyance of photogenerated charge carriers, leading to remarkable photocatalytic outcomes. Furthermore, we consolidate perspectives on the nonmetal doping of TiO2, which tailors the material to harness visible light more efficiently and bolsters the separation and transfer of photogenerated carriers. The incorporation of various anions is summarized for their potential to propel TiO2's photocatalytic capabilities. This review aspires to compile contemporary insights on ion-doped TiO2, propelling the efficacy of photocatalytic hydrogen evolution and anticipating forthcoming advancements. Our work aims to furnish an informative scaffold for crafting advanced TiO2-based photocatalysts tailored for water-splitting applications.

Oxygen vacancies induced band gap narrowing for efficient visible-light response in carbon-doped TiO2

The band gap of rutile TiO2 has been narrowed, via the formation of oxygen vacancies (OVs) during heat treatment in carbon powder (cHT) with embedding TiO2 coatings. The narrowed band gap efficiently improves the visible light response of TiO2 coatings, to further enhance the visible-light-driven photocatalytic activity. The change in OVs during cHT has been studied by manipulation of cHT temperature and time. The effect of OVs on the band structure of nonstoichiometric TiO2-x has been further calculated by first-principles calculations. With raising the temperature, SEM images show that the nano-size fiber-like structure forms on the surface of TiO2 coatings, and the amount of the fiber-like structure significantly increases and their size changes from nano to micro under 800 °C, contributing to cause an increase in accessible surface area. The UV-Vis results reveal that the band gap of TiO2 has been narrowed during cHT, due to the formed oxygen vacancies. The XPS results further confirm that the formation of surface defects including OVs, and the XPS depth profile further shows the decreased relative amount of O whereas increased relative amount of carbon. Notably, after cHT for TiO2 coatings, the photocatalytic activity first increases then decreases with raising the temperature, achieving approximately 3 times at 850 °C. The first-principles calculation suggest that the OVs in TiO2 coatings with localized electrons could facilitate the band gap narrowing, further favoring to enhance the photocatalytic activity under visible light.

Substantially boosted photocatalytic detoxification activity of TiO2 benefited from Eu doping

The wide energy band and high recombination rate of photogenerated carriers severely limit the photocatalytic activity of TiO₂. It has been demonstrated that ion doping can induce lattice defects, change the energy band structure, optimize the separation efficiency of photogenerated carrier, thus promoting the photocatalytic activity of the catalyst. In this work, Eu-doped TiO₂ was synthesized by a sol-gel method, and the composition and photogenerated carrier separation efficiency of the samples were analysed by various characterization methods. The results show that Eu-TiO₂ was successfully prepared and Eu-TiO₂ exhibits higher photogenerated carrier separation efficiency and generates more superoxide radicals compared to the bare TiO₂. Photocatalytic activity of the samples was evaluated by the degradation of Rhodamine B (RhB), and the results show that Eu doping improves the photocatalytic activity of the samples, the sample with Eu/Ti molar ratio of 0.2% displays 2.3-fold increase in photocatalytic activity compared to the blank TiO₂. The improved photocatalytic activity can be attributed to the fact that Eu doping facilitates the effective separation of photogenerated carriers.

Photocatalytic degradation of chlorazol yellow dye under sunlight irradiation using Ce, Bi, and N co-doped TiO2 photocatalyst in neutral medium

Chlorazol yellow (CY) is a commonly used anionic, toxic, mutagenic, and potentially carcinogenic azo dye, which is menacing to the environment, aquatic system, food chain, and human health as well. To remove CY dye molecules from an aqueous medium, a series of Ce, Bi, and N co-doped TiO₂ photocatalysts were prepared by varying the composition of the dopants. Under sunlight irradiation, the resultant 5 wt% (Ce-Bi-N) co-doped TiO₂ composite catalyst was found to show the best catalytic activity. Hence, the required characterization of this catalyst was performed systematically using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. From the thorough investigation, it is revealed that the CY molecules reached adsorption-desorption equilibrium onto the surface of the catalyst within 30 min following second-order kinetics. Herein, the catalyst attained 97% degradation when exposed to sunlight at neutral (pH ~ 7, [CY] = 5 mg L^-1) medium. The developed catalyst can destruct CY molecules with a maximum rate of 23.1 µg CY g^-1 min^-1 and the photodegradation kinetics follows first-order kinetics below 23.5 mg L^-1, a fractional order between 23.5 and 35.0 mg L^-1, and a zeroth order above 35.0 mg L^-1 of CY concentration. Finding from scavenging effect implies that [Formula: see text] and [Formula: see text] radicals have significant influence on the degradation. A suitable mechanism has been proposed with excellent stability and verified reusability of the proposed photocatalyst.

C-TiO2+Ni and ZnO+Ni Magnetic Photocatalyst Powder Synthesis by Reactive Magnetron Sputtering Technique and Their Application for Bacteria Inactivation

In the current study, a bi-layered magnetic photocatalyst powder consisting of a Ni layer on one side and carbon-doped TiO2 or ZnO photocatalyst layers on the other side was synthesized by magnetron sputtering technique. SEM, XRD, and XPS analysis of powders revealed that the photocatalytic TiO2 layer had a mixed anatase-rutile structure, was doped by carbon to approximately 3 at. % and had a fraction of Ti(III) oxide. Meanwhile, the ZnO layer was crystalized in a wurtzite structure and had a considerable number of intrinsic defects, which are useful for visible light photocatalysis. The activity of magnetic photocatalyst powder was tested by photocatalytic bleaching of dyes, as well as performing photocatalytic inactivation of Salmonella bacteria under UV and visible light irradiation. It was observed, that C-TiO2+Ni magnetic photocatalyst had relatively high and stable activity under both light sources (for five consecutive cycles dye degradation reached approximately 95%), but ZnO+Ni was generally lacking in activity and stability (over five cycles under UV and visible light, dye degradation fell from approximately 60% to 55% and from 90% to 70%, respectively). Photocatalytic treatment of bacteria also provided mixed results. On one hand, in all tests bacteria were not inactivated completely. However, on the other hand, their susceptibility to antibiotics increased significantly.

Recent Advances in Black TiO2 Nanomaterials for Solar Energy Conversion

Titanium dioxide (TiO₂) nanomaterials have been widely used in photocatalytic energy conversion and environmental remediation due to their advantages of low cost, chemical stability, and relatively high photo-activity. However, applications of TiO₂ have been restricted in the ultraviolet range because of the wide band gap. Broadening the light absorption of TiO₂ nanomaterials is an efficient way to improve the photocatalytic activity. Thus, black TiO₂ with extended light response range in the visible light and even near infrared light has been extensively exploited as efficient photocatalysts in the last decade. This review represents an attempt to conclude the recent developments in black TiO₂ nanomaterials synthesized by modified treatment, which presented different structure, morphological features, reduced band gap, and enhanced solar energy harvesting efficiency. Special emphasis has been given to the newly developed synthetic methods, porous black TiO₂, and the approaches for further improving the photocatalytic activity of black TiO₂. Various black TiO₂, doped black TiO₂, metal-loaded black TiO₂ and black TiO₂ heterojunction photocatalysts, and their photocatalytic applications and mechanisms in the field of energy and environment are summarized in this review, to provide useful insights and new ideas in the related field.

Non-Conventional Synthesis and Repetitive Application of Magnetic Visible Light Photocatalyst Powder Consisting of Bi-Layered C-Doped TiO2 and Ni Particles

In the current study, a non-conventional application of the magnetron sputtering technique was proposed. A four-step synthesis procedure allowed us to produce a magnetic photocatalyst powder consisting of bi-layered particles with carbon-doped TiO2 on one side, and metallic Ni on the other side. XRD, SEM and EDS methods were used for sample characterization. It was determined, that after the sputtering process optimization, the bandgap of carbon-doped TiO2 was reduced to approximately 3.1 eV and its light adsorption increased over the whole visible light spectrum. The repetitive Rhodamine B solution bleaching with magnetic photocatalyst powder and visible light showed interesting evolvement of photocatalyst efficiency. After the first cycle, Rhodamine B concentration was reduced by just 35%. However, after the second cycle, the reduction had already reached nearly 50%. Photocatalytic bleaching efficiency continued to improve rapidly until higher than 95% of Rhodamine B concentration reduction was achieved (at tenth cycle). For the next ten cycles, photocatalytic bleaching efficiency remained relatively stable. The initial gain in efficiency was attributed to the magnetic photocatalyst particle size reduction from an initial diameter of 100–150 µm to 5 µm. Naturally, the 20–30 times size reduction resulted in a remarkably increased active surface area, which was a key factor for the increased performance.

Photocatalytic Treatment of Methyl Orange Dye Wastewater by Porous Floating Ceramsite Loaded with Cuprous Oxide

It is well known that water treatment of printing and dyeing wastewaters is problematic. In order to decompose dyes from dyestuff wastewater and convert them into almost harmless substances for the natural environment, an easily prepared, efficient, practical, and easy-to-regenerate composite material was produced from porous floating ceramsite loaded with cuprous oxide (PFCC). The PFCC samples were prepared and characterized by X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The material was applied for photocatalytic degradation of methyl orange (MO) in water. The results show that the maximal degradation rate of MO was 92.05% when the experimental conditions were as follows: cuprous oxide loading rate of 8%, PFCC dosage of 20 g/L, the reaction time of 2 h, pH value of 8, and solution initial concentration of 30 mg/L. The degradation processes of MO fits well with the Langmuir–Hinshelwood model in reaction kinetics, and the Freundlich model in reaction thermodynamics, respectively. The degradation mechanism of MO was considered from two perspectives—one was the synergetic effect of adsorption and photocatalytic oxidation, and the other was the strong oxidation of hydroxyl radicals produced by photocatalysts.

Structure and Photocatalytic Activity of Copper and Carbon-Doped Metallic Zn Phase-Rich ZnO Oxide Films

ZnO is one of the most important industrial metal oxide semiconductors. However, in order to fully realise its potential, the electronic structure of ZnO has to be modified to better fit the needs of specific fields. Recent studies demonstrated that reactive magnetron sputtering under Zn-rich conditions promotes the formation of intrinsic ZnO defects and allows the deposition of metallic Zn phase-rich ZnO films. In photocatalytic efficiency tests these films were superior to traditional ZnO oxide, therefore, the purposeful formation of intrinsic ZnO defects, namely Zn interstitials and oxygen vacancies, can be considered as advantageous self-doping. Considering that such self-doped ZnO remains a semiconductor, the natural question is if it is possible to further improve its properties by adding extrinsic dopants. Accordingly, in the current study, the metallic Zn phase-rich ZnO oxide film formation process (reactive magnetron sputtering) was supplemented by simultaneous sputtering of copper or carbon. Effects of the selected dopants on the structure of self-doped ZnO were investigated by X-ray diffractometer, scanning electron microscope, X-ray photoelectron spectroscope and photoluminescence techniques. Meanwhile, its effect on photocatalytic activity was estimated by visible light activated bleaching of Methylene Blue. It was observed that both dopants modify the microstructure of the films, but only carbon has a positive effect on photocatalytic efficiency.

Incorporation of Ions into Nanostructured Anodic Oxides-Mechanism and Functionalities

Anodic oxidation of metals leads to the formation of ordered nanoporous or nanotubular oxide layers that contribute to numerous existing and emerging applications. However, there are still numerous fundamental aspects of anodizing that have to be well understood and require deeper understanding. Anodization of metals is accompanied by the inevitable phenomenon of anion incorporation, which is discussed in detail in this review. Additionally, the influence of anion incorporation into anodic alumina and its impact on various properties is elaborated. The literature reports on the impact of the incorporated electrolyte anions on photoluminescence, galvanoluminescence and refractive index of anodic alumina are analyzed. Additionally, the influence of the type and amount of the incorporated anions on the chemical properties of anodic alumina, based on the literature data, was also shown to be important. The role of fluoride anions in d-electronic metal anodizing is shown to be important in the formation of nanostructured morphology. Additionally, the impact of incorporated anionic species, such as ruthenites, and their influence on anodic oxides formation, such as titania, reveals how the phenomenon of anion incorporation can be beneficial.

Photocatalytic Inactivation of Salmonella typhimurium by Floating Carbon-Doped TiO2 Photocatalyst

Photocatalysis application is considered as one of the most highly promising techniques for the reduction in wastewater pollution. However, the majority of highly efficient photocatalyst materials are obtained as fine powders, and this causes a lot of photocatalyst handling and reusability issues. The concept of the floating catalyst proposes the immobilization of a photocatalytic (nano)material on relatively large floating substrates and is considered as an encouraging way to overcome some of the most challenging photocatalysis issues. The purpose of this study is to examine floating photocatalyst application for Salmonella typhimurium bacteria inactivation in polluted water. More specifically, high-density polyethylene (HDPE) beads were used as a photocatalyst support for the immobilization of carbon-doped TiO₂ films forming floating photocatalyst structures. Carbon-doped TiO₂ films in both amorphous and anatase forms were deposited on HDPE beads using the low-temperature magnetron sputtering technique. Bacteria inactivation, together with cycling experiments, revealed promising results by decomposing more than 95% of Salmonella typhimurium bacteria in five consecutive treatment cycles. Additionally, a thorough analysis of the deposited carbon-doped TiO₂ film was performed including morphology, elemental composition and mapping, structure, and depth profiling. The results demonstrate that the proposed method is a suitable technique for the formation of high-quality photocatalytic active films on thermal-sensitive substrates.

Photocatalytic and Antibacterial Properties of a 3D Flower-Like TiO2 Nanostructure Photocatalyst

Flower-like titanium dioxide (TiO₂) nanostructures are successfully synthesized using a hybrid sol-gel and a simple hydrothermal method. The sample was characterized using various techniques to study their physicochemical properties and was tested as a photocatalyst for methyl orange degradation and as an antibacterial material. Raman spectrum and X-ray diffraction (XRD) pattern show that the phase structure of the synthesized TiO₂ is anatase with 80-100 nm in diameter and 150-200 nm in length of flower-like nanostructures as proved by field emission scanning electron microscope (FESEM). The energy-dispersive X-ray spectroscopy (EDS) analysis of flower-like anatase TiO₂ nanostructure found that only titanium and oxygen elements are present in the sample. The anatase phase was confirmed further by a high-resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) pattern analysis. The Brunauer-Emmett-Teller (BET) result shows that the sample had a large surface area (108.24 m²/g) and large band gap energy (3.26 eV) due to their nanosize. X-ray photoelectron spectroscopy (XPS) analysis revealed the formation of Ti⁴⁺ and Ti³⁺ species which could prevent the recombination of the photogenerated electron, thus increased the electron transportation and photocatalytic activity of flower-like anatase TiO₂ nanostructure to degrade the methyl orange (83.03%) in a short time (60 minutes). These properties also support the good performance of flower-like titanium dioxide (TiO₂) nanostructure as an antibacterial material which is comparable with penicillin which is 13.00 ± 0.02 mm inhibition zone against Staphylococcus aureus.

Tailoring Mesoporous Titania Features by Ultrasound-Assisted Sol-Gel Technique: Effect of Surfactant/Titania Precursor Weight Ratio

A mesoporous titania structure has been prepared using the ultrasound-assisted sol-gel technique in order to find out a way to tailor its structure. The TiO₂ obtained was compared to the same version of titania but synthesized by a conventional sol-gel method with the objective of understanding the effect of ultrasound in the synthesis process. All synthesis experiments were focused on the preparation of a titania photocatalyst. Thus, the anatase photocatalytic active phase of titania was proven by X-ray diffraction. Additionally, the ultrasonation treatment proved to increase the crystallinity of titania samples, being one of the requirements to having good photocatalytic activity for titania. The influence of surfactant/titania precursor weight ratio on the structural (XRD), textural (N₂-sorption measurements), morphological (TEM), surface chemistry (FTIR) and optical properties (UVDR) was investigated. It was observed that the crystallite size, specific surface area, band gap energy and even photocatalytic activity was affected by the synergism occurring between cavitation effect and the surfactant/titania precursor weight ratio. The study yielded interesting great results that could be considered for further application of ultrasound to tailor mesoporous titania features via sol-gel soft template synthesis, against conventional sol-gel process.

The effect of Cu dopants on electron transfer to O2 and the connection with acetone photocatalytic oxidations over nano-TiO2

Modifying TiO₂ with the Cu element has been shown to be useful for photocatalysis. Although it had been known that Cu species could trap electrons from TiO₂, whether they can affect the kinetics of electron transfer and how this can contribute to photocatalysis still remain unknown. In the current research, Cu-TiO₂ samples were firstly prepared with a hydrothermal reaction and characterized in detail. It was shown that Cu elements were doped in the TiO₂ lattice in +1/0 valence states and have a minor effect on the TiO₂ structure. By means of photoconductances, it is shown that the Cu dopants could catalyze the electron transfer from TiO₂ to O₂ by reducing the apparent activation energy (E_app) by about 2 times. The photocatalytic experiments conducted at different temperatures showed that the E_app of the acetone photocatalytic oxidations could be decreased by ∼2 times; this implies that the Cu dopants change the photocatalytic pathway. First-principles computation showed that the surface Cu dopants, along with the compensated oxygen vacancies, can mediate both of the electron and hole transfer. By combining other studies, we proposed that the Cu sites could act as Lewis acid and base pairs that could combine with acetone and O₂ molecules under UV light illumination; this allows electron transfer to O₂via the Cu sites that then react with acetone. As compared to pure TiO₂ surfaces, the different chemical environment of the Cu sites leads to the decrease in the E_app of photocatalysis.

Excellent visible light responsive photocatalytic behavior of N-doped TiO2 toward decontamination of organic pollutants

In this work, N-doped TiO₂ (N-TiO₂) with ample and tunable OVs was successfully synthesized, deriving from facile hydrothermal method and baked in the NH₃ atmosphere. N-doping boosts the amount of surface hydroxyl and superoxide (O₂^-) of TiO₂, demonstrated by XPS and nitroblue tetrazolium (NBT)-O₂^- quantitative reaction. Rich and tunable OVs were confirmed by low temperature electron spin resonance (ESR) results, demonstrating that doping of N into TiO₂ can definitely construct higher OVs than the reference TiO₂. Surface photovoltage spectrum (SPS) test, fluorescence experiments and electrochemical measurements all display that N-TiO₂ photocatalysts with OVs have a higher severance efficiency of photogenerated e-/h⁺ pairs than the pristine TiO₂. Photocatalytic evaluation results exhibit that N-TiO₂ photocatalysts demonstrate better performance than the reference TiO₂ toward decontamination of rhodamine B and tetracycline. TiO₂ treated in ammonia atmosphere for 1 h shows the highest photocatalytic property. The visible light responsive catalytic behavior of TiO₂ treated in ammonia atmosphere for 1 h is much higher than that of commercial TiO₂ (P25) and the pristine TiO₂, separately. The ameliorated visible light behavior of N-TiO₂ photocatalysts is attributable to rich oxygen vacancies produced through introducing N into TiO₂ and the boosted severance of photoactivated e-/h⁺.

Recent Advances in Synthesis and Applications of Carbon-Doped TiO2 Nanomaterials

TiO2 has been widely used as a photocatalyst and an electrode material toward the photodegradation of organic pollutants and electrochemical applications, respectively. However, the properties of TiO2 are not enough up to meet practical needs because of its intrinsic disadvantages such as a wide bandgap and low conductivity. Incorporation of carbon into the TiO2 lattice is a promising tool to overcome these limitations because carbon has metal-like conductivity, high separation efficiency of photogenerated electron/hole pairs, and strong visible-light absorption. This review would describe and discuss a variety of strategies to develop carbon-doped TiO2 with enhanced photoelectrochemical performances in environmental, energy, and catalytic fields. Emphasis is given to highlight current techniques and recent progress in C-doped TiO2-based materials. Meanwhile, how to tackle the challenges we are currently facing is also discussed. This understanding will allow the process to continue to evolve and provide facile and feasible techniques for the design and development of carbon-doped TiO2 materials.

Functional Materials Based on Active Carbon and Titanium Dioxide in Fog Seal

Due to its ability to degrade nitrogen oxides under ultraviolet, titanium dioxide has been applied in asphalt concrete to degrade automobile exhaust in recent years. To highlight the protection of road traffic environmental quality and mitigate automobile exhaust on human health, this study proposes combining titanium dioxide and active carbon into Sand-fog seal to form a pavement coating material with a photocatalytic function. It uses active carbon to reinforce the material’s function, and the coupling agent for modification makes it well dispersed in the Sand-fog seal. The indoor experiments were carried out at 30 °C and relative humidity of 30%. It tested the composite material’s degradation efficiency on nitrogen dioxide in relation to component proportions, coupling agents, and dosages. The study concluded that the optimal photocatalytic efficiency could be achieved when the ratio of active carbon to titanium dioxide is 0.6. After being modified by the titanate coupling agent and through Scanning Electron Microscope tests, it can be seen that materials can be well dispersed into the Sand-fog seal. When the composite material accounts for 10% of the fog seal, it can achieve the optimal photocatalytic efficiency of about 23.9%. The British pendulum tests show it has good skid resistance performance. Half a kilometer of concrete roadway was sprayed with the material coating in Tianjin, China. The photocatalytic experimental road degrades nitrogen oxides better than the original road. The method is feasible for practical implementation.

Recent Developments of TiO2-Based Photocatalysis in the Hydrogen Evolution and Photodegradation: A Review

The growth of industrialization, which is forced to use non-renewable energy sources, leads to an increase in environmental pollution. Therefore, it is necessary not only to reduce the use of fossil fuels to meet energy needs but also to replace it with cleaner fuels. Production of hydrogen by splitting water is considered one of the most promising ways to use solar energy. TiO₂ is an amphoteric oxide that occurs naturally in several modifications. This review summarizes recent advances of doped TiO₂-based photocatalysts used in hydrogen production and the degradation of organic pollutants in water. An intense scientific and practical interest in these processes is aroused by the fact that they aim to solve global problems of energy conservation and ecology.

Solvothermal synthesis of C doped Co-Cu/TiO2 based nanocomposite to study their photocatalytic activity

The solvothermal approach is applied to produce doped titanium dioxide nanoparticles in the mesoporous form using Pluronic F127 as a delicate mold. The formulated samples are investigated successfully via x-ray diffraction, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, scanning electron microscope, energy dispersive x-ray, transmission electron microscope, nitrogen adsorption-desorption analysis, and Fourier-transform infrared spectroscopy. Analysis of XRD, SEM, and TEM demonstrates the existence of a nanocrystalline size range of the particles. Methylene blue, congo red, and malachite green dyes are used to evaluate the photocatalytic competence of the samples. The results verified that the TiO2 including a peak quantity of copper (4%) shows maximum photocatalysis caused by the declined bandgap energy including effective charge separation of photoinduced charge carrier with a maximum surface area as revealed by ultraviolet-visible, photoluminescence spectroscopy & nitrogen adsorption-desorption analysis respectively.

Floating TiO2 photocatalyst for efficient inactivation of E. coli and decomposition of methylene blue solution

The anatase phase TiO₂ films with nanocrystalline structure were successfully deposited on a water-floating non-expanded polystyrene (PS) beads via magnetron sputtering. The combination of UVB light and PS beads with TiO₂ film was used for decomposition of methylene blue as well as inactivation tests for intact and EDTA-treated Escherichia coli bacteria. Crystal structure, elemental composition, elemental mapping, surface morphology and chemical bonds of TiO₂ film were investigated. E. coli inactivation experiments showed that such floating photocatalyst could destroy >90% bacteria in 45 min under UVB irradiation. Results demonstrated that combination of TiO₂ and UVB light leads to disruption of the outer membrane which causes effective inactivation of E. coli bacteria.

Adsorption and Photocatalytic Study of Phenol Using Composites of Activated Carbon Prepared from Onion Leaves (Allium fistulosum) and Metallic Oxides (ZnO and TiO2)

The aim of this study was to evaluate and compare the adsorption and photocatalytic activity of activated carbon-based photocatalysts. Titanium dioxide (TiO2) and zinc oxide (ZnO) were chosen as semiconductors to prepare composites with activated carbon by the wet impregnation method. Activated carbon was prepared using as starting material onion leaves (Allium fistulosum) and as activating agent phosphoric acid (H3PO4). Photooxidation and batch adsorption of phenol was studied to compare the efficiency of the materials prepared. The results showed that the composite AC–TiO2 has a greater photocatalytic activity and a better adsorption capacity compared to AC–ZnO composite.

Carbon Black-Doped Anatase TiO2 Nanorods for Solar Light-Induced Photocatalytic Degradation of Methylene Blue

In this work, C-doped TiO₂ nanorods were synthesized through doping carbon black into hydrothermally synthesized solid-state TiO₂ nanowires (NWs) via calcination. The effects of carbon content on the morphology, phase structure, crystal structure, and photocatalytic property under both UV and solar light by the degradation of methylene blue (MB) were explored. Besides, the photoelectrochemical property of C-TiO₂ was systematically studied to illustrate the solar light degradation mechanism. After doping with C, TiO₂ NWs were reduced into nanorods and the surface became rough with dispersed particles. Results showed that C has successfully entered the TiO₂ lattice, resulting in the lattice distortion, reduction of band gap, and the formation of C-Ti-O, which expands TiO₂ to solar light activation. Comparing with P25 and anatase TiO₂ NWs, doping with carbon black showed much higher UV light and solar light photocatalytic activity. The photocatalytic activity was characterized via the degradation of MB, showing that K _ap was 0.0328 min^-1 under solar light, while 0.1634 min^-1 under UV irradiation. The main free radicals involved in methylene blue degradation are H⁺ and OH^•-. Doping with carbon black led to the reduction of photocurrent in a long-term operation, while C-doping reduced the electron-hole recombination and enhanced the carrier migration.

Influence of Mg, Cu, and Ni Dopants on Amorphous TiO2 Thin Films Photocatalytic Activity

The present study investigates Mg (0 ÷ 17.5 wt %), Cu (0 ÷ 21 wt %) and Ni (0 ÷ 20.2 wt %) dopants (M-doped) influence on photocatalytic activity of amorphous TiO₂ thin films. Magnetron sputtering was used for the deposition of M-doped TiO₂ thin films. According to SEM/EDS surface analysis, the magnetron sputtering technique allows making M-doped TiO₂ thin films with high uniformity and high dopant dispersion. Photocatalysis efficiency analysis was set in oxalic acid under UV irradiation. In accordance with the TOC (total organic carbon) measurements followed by the apparent rate constant (k_app) results, the dopants’ concentration peak value was dopant-dependent; for Mg/TiO₂, it is 0.9% (k_app—0.01866 cm⁻¹), for Cu/TiO₂, it is 0.6% (k_app—0.02221 cm⁻¹), and for Ni/TiO₂, it is 0.5% (k_app—0.01317 cm⁻¹). The obtained results clearly state that a concentration of dopants in TiO₂ between 0.1% and 0.9% results in optimal photocatalytic activity.

Effect of the Titanium Isopropoxide:Acetylacetone Molar Ratio on the Photocatalytic Activity of TiO2 Thin Films

TiO₂ thin films with different titanium isopropoxide (TTIP):acetylacetone (AcacH) molar ratios in solution were prepared by the chemical spray pyrolysis method. The TTIP:AcacH molar ratio in spray solution varied from 1:3 to 1:20. TiO₂ films were deposited onto the glass substrates at 350 °C and heat-treated at 500 °C. The morphology, structure, surface chemical composition, and photocatalytic activity of the obtained TiO₂ films were investigated. TiO₂ films showed a transparency of ca 80% in the visible spectral region and a band gap of ca 3.4 eV irrespective of the TTIP:AcacH molar ratio in the spray solution. TiO₂ films consist of the anatase crystalline phase with a mean crystallite size in the range of 30-40 nm. Self-cleaning properties of the films were estimated using the stearic acid (SA) test. A thin layer of 8.8-mM SA solution was spin-coated onto the TiO₂ film. The degradation rate of SA as a function of irradiation time was monitored by Fourier-transform infrared spectroscopy (FTIR). An increase in the TTIP:AcacH molar ratio from 1:4 to 1:8 resulted in a ten-fold increase in the photodegradation reaction rate constant (from 0.02 to the 0.2 min^-1) under ultraviolet light and in a four-fold increase under visible light.

Recent Advances in TiO2 Films Prepared by Sol-gel Methods for Photocatalytic Degradation of Organic Pollutants and Antibacterial Activities

Photocatalysis has recently emerged as an advanced, green, and eco-friendly process for the treatment of wastewater and air, and antimicrobial disinfection applications. In this context, TiO2 nanostructures have been shown to be the prominent photocatalyst candidates due to their low cost, non-toxicity, and ease of fabrication. This review highlights the investigation and development of TiO2 photocatalyst film by sol-gel method with special emphasis on the photodecolorization of synthetic dyes and antibacterial activities. Furthermore, various synthesis methods for the preparation of TiO2 films and their advantages, as well as limitations, are summarized. Finally, recent advances in TiO2 films by sol-gel method for dye degradation and antibacterial activities, challenges, and future perspective are discussed.