C-doped TiO2 Research Articles

Importance of Surfaces and Many-Body Absorption Spectra for C-Doped TiO2 Photocatalysts

Heterogeneous photocatalytic processes, in which a photocatalyst absorbs light to produce redox-active electron–hole pairs, have strong prospects of application in light energy conversion and envir...

First-principles study of configurations, electronic and photocatalytic properties of carbon-doped anatase TiO2

C-Doping TiO2 could significantly enhance the photocatalytic activity, as found in experiments, but the mechanism behind is elusive. We systematically investigated the configurations, electronic and photocatalytic properties of C-doped anatase TiO2 by first-principles calculation. The results show that the structures for the C-anion (Ca) and C-cation (Cc) doped TiO2 could exist in different form, and the Ca and substitutional Cc doping are favored under O-poor and O-poor conditions, respectively. The calculated electric and optical properties demonstrate that the substitutional Cc doping play the vital role in narrowing the bandgap, responsible for enhanced visible-light absorption of the TiO2. Finally, the calculated band edges using the hybrid functional of Heyd, Scuseria and Ernzerhof (HSE) suggested that substitutional Cc doped TiO2 could exhibit the small band gap and appropriate band edges for visible-light photocatalytic water splitting. The findings could not only give new insights into atomistic origin of visible-light response and photocatalysis of the C-doped TiO2.

Controlled killing of human cervical cancer cells by combined action of blue light and C-doped TiO2 nanoparticles.

In this study, C-doped TiO2 nanoparticles (C-TiO2) were prepared and tested as a photosensitizer for visible-light-driven photodynamic therapy against cervical cancer cells (HeLa). X-ray diffraction and Transmission Electron Microscopy confirmed the anatase form of nanoparticles, spherical shape, and size distribution from 5 to 15nm. Ultraviolet-visible light spectroscopy showed that C doping of TiO2 enhances the optical absorption in the visible light range caused by a bandgap narrowing. The photo-cytotoxic activity of C-TiO2 was investigated in vitro against HeLa cells. The lack of dark cytotoxicity indicates good biocompatibility of C-TiO2. In contrast, a combination with blue light significantly reduced the survival of HeLa cells: illumination only decreased cell viability by 30% (15min of illumination, 120µW power), and 60% when HeLa cells were preincubated with C-TiO2. We have also confirmed blue light-induced C-TiO2-catalyzed generation of reactive oxygen species in vitro and intracellularly. Oxidative stress triggered by C-TiO2/blue light was the leading cause of HeLa cell death. Fluorescent labeling of treated HeLa cells showed distinct morphological changes after the C-TiO2/blue light treatment. Unlike blue light illumination, which caused the appearance of large necrotic cells with deformed nuclei, cytoplasm swelling, and membrane blebbing, a combination of C-TiO2/blue light leads to controlled cell death, thus providing a better outcome of local anticancer therapy.

Hierarchically Porous, Biphasic, and C-Doped TiO2 for Solar Photocatalytic Degradation of Dyes and Selective Oxidation of Benzyl Alcohol.

Macroporous TiO2 monoliths were synthesized by self-sustained combustion reactions of molded pellets made up of a mixture of TiCl4 as a precursor, urea as a fuel, ammonium nitrate as an oxidizer, and starch as a binder. The porous TiO2 monoliths were found to be a heterostructure of anatase and rutile phases, in addition to being doped with carbon. Variation in the amount of starch yielded porous monoliths of different anatase–rutile ratios (increasing rutile component from 0 to 40%) but comparable Brunauer–Emmett–Teller (BET) surface area (∼30 m2 g–1). The porous monoliths obtained, where the TiCl4/starch mass ratio was 2.17, exhibit exceptional photocatalytic activity in the degradation of dyes (methylene blue and methyl orange) and selective oxidation of benzyl alcohol to benzaldehyde under natural sunlight. The synergistic combination of high surface area, porous network, lowered band gap due to heterostructured anatase–rutile polymorphs, and the presence of doped carbon renders the macroporous TiO2 an efficient photocatalyst.

Enhanced Photocatalytic Activity of C-doped TiO2 under Visible Light Irradiation: A Comparison of Corn Starch, Honey, and Polyethylene Glycol as a Carbon Sources

Enhanced Photocatalytic Activity of C-doped TiO2 under Visible Light Irradiation: A Comparison of Corn Starch, Honey, and Polyethylene Glycol as a Carbon Sources

One-step preparation of C-doped TiO2 nanotubes with enhanced photocatalytic activity by a water-assisted method

In this paper, C-doped TiO2 nanotubes were prepared in one-step by adding sucrose to water-assisted crystallization solution. The photocatalytic activity was obviously enhanced due to the decrease of the energy band gap after doping.

Photodegradation of aqueous eosin yellow dye by carbon-doped TiO2 photocatalyst

In this study, a novel photocatalyst, carbon-doped TiO2 was prepared via a sol-gel technique with titanium (III) chloride as a precursor. The characterization of C-doped TiO2 was obtained by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and BET surface area analyses. The prepared catalyst’s photocatalytic activity was investigated using UV irradiation for the photo-oxidation of eosin yellow (EY) dye. The photocatalysis of EY dye was performed under various experimental parameters such as solution pH and oxidant dosage (H2O2). The prepared photocatalyst dosages were also taken separately to optimize process efficiency. About 77.43% of EY decolorization was obtained at an optimum pH of 3, and the performance was also observed by varying the oxidant concentration ranging from 5-10 mM. The % decolorization was higher for C-doped TiO2-200 photocatalyst (81.88%) compared to carbon-doped TiO2-400 photocatalyst (75.55%). It can be concluded that the carbon-doped TiO2, calcined at 200°C, can effectively decolorize EY dye in an aqueous medium.

Using C-doped TiO2 Nanoparticles as a Novel Sonosensitizer for Cancer Treatment.

Sonodynamic therapy is an effective treatment for eliminating tumor cells by irradiating sonosentitizer in a patient’s body with higher penetration ultrasound and inducing the free radicals. Titanium dioxide has attracted the most attention due to its properties among many nanosensitizers. Hence, in this study, carbon doped titanium dioxide, one of inorganic materials, is applied to avoid the foregoing, and furthermore, carbon doped titanium dioxide is used to generate ROS under ultrasound irradiation to eliminate tumor cells. Spherical carbon doped titanium dioxide nanoparticles are synthesized by the sol-gel process. The forming of C-Ti-O bond may also induce defects in lattice which would be beneficial for the phenomenon of sonoluminescence to improve the effectiveness of sonodynamic therapy. By dint of DCFDA, WST-1, LDH and the Live/Dead test, carbon doped titanium dioxide nanoparticles are shown to be a biocompatible material which may induce ROS radicals to suppress the proliferation of 4T1 breast cancer cells under ultrasound treatment. From in vivo study, carbon doped titanium dioxide nanoparticles activated by ultrasound may inhibit the growth of the 4T1 tumor, and it showed a significant difference between sonodynamic therapy (SDT) and the other groups on the seventh day of the treatment.

Water Disinfection Using Chitosan Microbeads With N-, C-, C-N/TiO2 By Photocatalysis Under Visible Light

Chitosan microbeads with C-doped TiO2, N-doped TiO2 and C,N-codoped TiO2 were prepared to obtain photocatalysts with higher photocatalytic efficiency, active under visible light and easy to removed from aqueous medium. TiO2 powders were synthesized by the sol–gel method and modified using glucose and ammonium nitrate as source of C and N, respectively. Scanning electron microscope (SEM), X-ray diffraction (XRD), DRUV–Vis spectra and Raman techniques, were used to characterize the modified TiO2 powders. The structural and physicochemical properties of the microbeads were analyzed by nitrogen physisorption, functional groups were identified by Fourier transform Infrared (FT-IR) spectroscopy and microbeads were observed by optical microscopy. The microbeads photocatalytic efficiency under visible light was evaluated monitoring the E. coli growth-inhibition, determined by colony count analysis (CFU—colony forming units). Results showed effectiveness in all tested composites to inhibit E. coli growth in 24 h under visible light. Furthermore chitosan microbeads with C,N-codoped TiO2 showed the best performance in the degradation test being the most effective composite to achieving 99.99% of E. coli growth inhibition in less than 4 h.

Hydrothermal synthesis and characterization of carbon-doped TiO2 nanoparticles* *The authors would like to thank the Higher Education Commission of Pakistan for providing funding (NRPU project 5349/Federal/NRPU/R&D/HEC/2016).

We report the hydrothermal growth of pure and doped TiO2 nanoparticles with different concentrations of carbon. The microstructure of the as-synthesized samples is characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDX), and Raman spectroscopy to understand the structure and composition. The XRD patterns confirm the formation of anatase phase of TiO2 with the average crystallite size is calculated to be in the range of 13 nm to 14.7 nm. The functional groups of these nanostructures are characterized by Fourier transformed infrared (FT-IR) spectroscopy, which further confirms the single anatase phase of the synthesized nanostructures. UV-visible absorption spectroscopy is used to understand the absorption behavior, which shows modification in the optical bandgap from 3.13 eV (pure TiO2) to 3.74 eV (1.2 mol% C-doped TiO2). Furthermore, the Ti3+ centers associated with oxygen vacancies are identified using electron paramagnetic resonance spectroscopy (EPR).

A low-cost and stable Fe2O3/C-TiO2 system design for highly efficient photocatalytic H2 production from seawater

Photocatalytic seawater splitting for H2 production is extremely attractive in solar-to-fuel conversion areas toward achieving clean and renewable energy. In this study, we design a low-cost and robust Fe2O3/C-TiO2Z-scheme system by applying Fe2O3 nanosheets as electron donor and C-doped TiO2 nanosheets as H2 generation photocatalysts, achieving highly efficient seawater splitting for H2 evolution without any sacrificial reagents. The Fe2O3/C-TiO2Z-scheme system shows remarkable catalytic performance and high stability for H2 evolution in seawater. Under visible light illumination, the H2 generation rate reach 170.8 μmol g−1 h1 and remain unchanged in a 24 h cyclic test. This study may open avenues to designing low-price and stable photocatalysts for H2 extraction from seawater in future.

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 Kap 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.

Design and synthesis of ‘single-crystal-like’ C-doped TiO2 nanorods for high-performance supercapacitors

Although TiO2 is widely used as a promising electrode material for supercapacitors, its potential application suffers from a critical limitation due to its poor electrical conductivity and low rate capability. Here, we report a cost-effective hydrothermal strategy to design and construct a novel ‘single-crystal-like’ C-doped TiO2 electrode material. The as-synthesized electrode material combines the advantages of TiO2, ‘single-crystal-like’ features and carbon doping, considerably improving the electrical conductivity of TiO2. The electrochemical measurements demonstrate that the C-doped TiO2 material presents an excellent specific capacitance (449.8 F g−1 at 1 A g−1), which approaches six times more than the value (77.3 F g−1 at 1 A g−1) of P25 electrodes, and far beyond the value of many previously reported TiO2 electrodes. Therefore, this work explores a new method to design high performance electrochemical TiO2 electrode materials by incorporating other dopants into the TiO2 lattice.

C-doped TiO2 nanoparticles to detect alcohols with different carbon chains and their sensing mechanism analysis

C-TiO2 nanoparticles with the diameter of 30 ± 8 nm were prepared by using a facile template-free solvothermal method, in which the C was induced directly from the raw material itself. The sensor based on C-TiO2 showed excellent gas-sensing performance to alcohols at the optimal working temperature of 170 °C. Especially, the response increased with the carbon chain lengths increasing from C1 to C5. The response to 100 ppm n-pentanol was 11.12, which was 5.4 times higher than that of the pure anatase TiO2. Besides, the theoretical calculations, XPS, GC and GC–MS techniques were carried out to explore the gas-sensing mechanism of C-TiO2 to n-pentanol. The n-pentanol was speculated oxidization to aldehyde and decomposition into carbon dioxide and water eventually.

Ti3C2 MXene-derived carbon-doped TiO2 coupled with g-C3N4 as the visible-light photocatalysts for photocatalytic H2 generation

Photocatalytic hydrogen production is a fascinating clean energy technology to solve the environmental issues and energy crisis. Herein, Ti3C2, a member of MXene, is successfully designed as a precursor for preparing C-TiO2/g-C3N4 photocatalyst without extra carbon addition, and the C-TiO2/g-C3N4 photocatalysts exhibit drastically improved photocatalytic hydrogen generation activity. When the mass ratio of Ti3C2 to g-C3N4 is 10 wt% in the composite, the prepared C-TiO2/g-C3N4 composite photocatalyst shows the highest photocatalytic H2 production activity as high as of 1409 μmol/h/g, which is about 8 times and 24 times higher than the activity of pure g-C3N4 and C-TiO2, respectively. The possible mechanism is assumed that the achieved intimate heterojunction between the Ti3C2 MXene-derived C-doped TiO2 and g-C3N4 can efficiently facilitate the photogenerated charge transfer and inhibit the recombination of electronics and holes, which markedly enhanced photocatalytic hydrogen production activity of C-TiO2/g-C3N4 photocatalysts under visible light.

Hematite microcube decorated TiO2 nanorods as heterojunction photocatalyst with in-situ carbon doping derived from polysaccharides bio-templates hydrothermal carbonization

The novel in-situ formation of a heterojunction photocatalyst consisting of C-doped TiO2 nanorods decorated on the surface of C-doped α-Fe2O3 microcubes was successfully achieved using a one-pot hydrothermal carbonization synthesis. In this work, the treated kapok fibers (t-KF) used as a polysaccharide bio-template provided a dual function for crystal growth control and in-situ carbon doping of the heterojunction photocatalyst. It was found that the α-Fe2O3 precursor concentration plays an essential role in the unique and well-developed C-doped TiO2/α-Fe2O3 heterojunction formation. Assessment of photocatalytic activity of all samples indicated that the sample prepared with 0.25 M of α-Fe2O3 precursor concentration (BT-TF-0.25) exhibited the most efficient bisphenol A photodegradation in aqueous solution. The highest photocatalytic activity of BT-TF-0.25 under simulated solar irradiation was mainly associated with C-doping and favorable heterojunction formation between C-doped TiO2 and C-doped α-Fe2O3. Excellent charge carrier and separation were confirmed from the photocurrent response and photoluminescence spectroscopy analysis. Overall, this study is expected to contribute to the development of more efficient visible light active heterojunction photocatalyst systems, as well as demonstrating the versatility of polysaccharide materials as a green and low-cost bio-templates.

Synthesis of C-doped TiO2 by sol-microwave method for photocatalytic conversion of glycerol to value-added chemicals under visible light

C-doped TiO2 photocatalyst synthesized using a one-step sol-microwave method with microcrystalline cellulose as the carbon source to achieve TiO2 of desirable visible light absorption, cluster size, surface area and band gap was applied in the photocatalytic oxidation of glycerol under visible light to produce value-added chemicals, for the first time. An increase in microwave irradiation time from 0 to 20 min reduced the anatase crystal size but increased the surface area, pore volume and pore radius. Carbon coupled with microwave treatment produced Ti3+ and oxygen vacancies in the TiO2 lattice of the C-doped TiO2 which yielded improved performance of the photocatalysts. For example, a cellulose loading at 10 % (i.e. 10 % Cel-TiO2(4-MW)) provided the highest photo-conversion of glycerol (67.5 %) and highest yields of glyceraldehyde (10.0 %), dihydroxyacetone (7.4 %), formic acid (49.0 %) and acetic acid (1.8 %). On the other hand, excess residual carbon on TiO2 surface (e.g. 20 % Cel-TiO2(0-MW)) retarded the activity of the photocatalyst.

Photocatalytic and biological activities of undoped and doped TiO2 prepared by Green method for water treatment

The present study reports an eco-friendly, rapid and easy method for the synthesis of TiO2, C-doped TiO2(C-TiO2), S-doped TiO2 (S-TiO2) and C, S co-doped TiO2(C,S-TiO2) nanoparticles (NPs) via Eichhornia aqueous extract using the sol-gel method. The prepared samples were characterized by XRD, SEM, FTIR, EDX, XPS, Photoluminescence (PL), photoelectric current (PEC) and UV–vis absorption techniques. Under visible lamination, the synthesized NPs have a great photocatalytic activity for the degradation of the Reactive Blue 19 (RB19) and the Reactive Red 76 (RR76) organic dyes pollutant present in textile wastewater. The C-TiO2 showed the highest photocatalytic efficiency. The degradation of RB19 and RR76 dyes were studied via applying of different experimental conditions such as pH, amount of catalyst, dye concentration, shaking speed, and irradiation time as well as the recover possibility of catalyst. Under optimum conditions, the photocatalytic degradation efficiency of the C-TiO2 sample for textile wastewater, containing RB 19 and RR 76 dyes, attained 100% after 1 h reaction time with catalyst dose 0.08 g and pH 1. The chemical oxygen demand (COD) values were investigated before treatment and after irradiation treatment. Marine aquatic organisms’ rotifer, artemia, and Vibrio parahaemolyticus were used to study biological effects and Toxicity of resultant degraded material form the irradiation treatment of RB 19 and RR 76 dyes in wastewater.

Enhanced Electrocatalytic N2 Reduction via Partial Anion Substitution in Titanium Oxide-Carbon Composites.

The electrochemical conversion of N2 at ambient conditions using renewably generated electricity is an attractive approach for sustainable ammonia (NH3 ) production. Considering the chemical inertness of N2 , rational design of efficient and stable catalysts is required. Therefore, in this work, it is demonstrated that a C-doped TiO2 /C (C-Tix Oy /C) material derived from the metal-organic framework (MOF) MIL-125(Ti) can achieve a high Faradaic efficiency (FE) of 17.8 %, which even surpasses most of the established noble metal-based catalysts. On the basis of the experimental results and theoretical calculations, the remarkable properties of the catalysts can be attributed to the doping of carbon atoms into oxygen vacancies (OVs) and the formation of Ti-C bonds in C-Tix Oy . This binding motive is found to be energetically more favorable for N2 activation compared to the non-substituted OVs in TiO2 . This work elucidates that electrochemical N2 reduction reaction (NRR) performance can be largely improved by creating catalytically active centers through rational substitution of anions into metal oxides.

A C-Doped TiO2/Fe3O4 Nanocomposite for Photocatalytic Dye Degradation under Natural Sunlight Irradiation

Magnetically recyclable C-doped TiO2/Fe3O4 (C-TiO2/Fe3O4) nanocomposite was successfully synthesized via a sol–gel method. The synthesized samples were characterized using SEM, energy-dispersive X-ray spectroscopy (EDS), FTIR, and UV-VIS diffuse reflectance spectroscopy (DRS) techniques. The results clearly showed that a C-TiO2/Fe3O4 nanocomposite was produced. The photocatalytic activities of the prepared pristine (TiO2), C-doped TiO2 (C-TiO2) and C-TiO2/Fe3O4 were evaluated by the photodegradation of methyl orange (MO) under natural sunlight. The effect of catalyst loading and MO concentration were studied and optimized. The C-TiO2/Fe3O4 nanocomposite exhibited an excellent photocatalytic activity (99.68%) that was higher than the TiO2 (55.41%) and C-TiO2 (70%) photocatalysts within 150 min. The magnetic nanocomposite could be easily recovered from the treated solution by applying external magnetic field. The C-TiO2/Fe3O4 composite showed excellent photocatalytic performance for four consecutive photocatalytic reactions. Thus, this work could provide a simple method for the mass production of highly photoactive and stable C-TiO2/Fe3O4 photocatalyst for environmental remediation.