Black TiO2 Research Articles

Superior photothermal black TiO2 with random size distribution as flexible film for efficient solar steam generation

Black photothermal materials with broadband solar absorption have attracted great interest for efficient steam generation. However, the solar steam device composed of thermal insulators and water supply paths makes the device more intricate and problematic to operate. Herein, inspired by random close packing structure of beetle, black TiO2 (BTiO2) film with random size distribution is fabricated for simplifying the vapor generation device. The BTiO2 with random size distribution realized a broadband absorption in the full spectrum of solar light (250−2500 nm) due to the plenty of oxygen vacancies/surface disorders/surface defects after the reduction process. When BTiO2 film irradiated under 1 sun illumination, the temperature is quickly changed from 25.4 °C to 90 °C within 120 s which leads to a superior photothermal effect. This high solar thermal energy conversion surpasses other photothermal materials (PMs) reported before. At the same time, when used for steam generation, the solar steam efficiency of 77.14% is achieved under 1 sun solar light irradiation without any thermal insulating management and water supply path. Furthermore, the BTiO2 films presented remarkable flexibility and strong mechanical robustness, which provide a promising approach to design new black materials of different size structures with high mechanical stability/flexibility for developing solar energy-related applications.

(Invited) Black TiO2 Nanotubes As Functional Supports and Electrodes

TiO2 nanomaterials have over the last 30 years attracted tremendous scientific and technological interest. A main research direction for TiO2 in functional applications is its use in photocatalysis, e.g. for the direct splitting of water into H2 and O2 to generate the potential fuel of the future, hydrogen. In order to achieve a maximum reaction rate, high surface area substrates, usually nanoparticles are used either suspended or compacted to a photoelectrode. Over the past decades, various 1D and highly defined TiO2 morphologies were explored for the replacement of nanoparticle networks and were found in many cases superior to nanoparticles. However, in every case the kinetics of H2 generation is sluggish from a plain TiO2 surface and noble metal cocatalysts are needed to reach accelerated reaction rates. Only recently it has been shown that TiO2 can be intrinsically activated by generation of suitable surface defects. Such material of a “gray” or “black” color can be generated with various treatments of many titania polymorphs and morphologies. The presentation will focus on highly ordered nanotube arrays of TiO2 and discuss most recent progress in synthesis and modification for photocatalytic and photoelectrochemical H2 generation. Of special interest is the formation of black TiO2 nanotubes by various reductive treatments. Black titania produced by high pressure hydrogenation has been demonstrated to enable noble-metal-free photocatalytic H2 generation. TEM, EPR, and XPS investigations as well as photoelectrochemistry are used to characterize different degrees of surface hydrogenation, surface termination, electrical conductivity, and structural defects in the differently reduced titania nanotubes. These investigations find that the formation of intrinsic photocatalytic hydrogen evolution activity is induced by optimized and specific defect formation.

Enhanced acetone sensing performance in black TiO2 by Ag modification

The application of TiO2 acetone monitor is highly limited by the high operating temperature and poor sensitivity. In this work, black TiO2 (B-TiO2) is produced by Ti3+ self-doping and is followed by Ag modification to form B-TiO2@Ag. It is first demonstrated that the operating temperature and sensitivity of TiO2 to acetone can be promoted evidently. By introducing a Ti3+ self-doped layer on the surface of TiO2, as observed in TEM images, the band gap of TiO2 is reduced to 3.01 eV. Ag surface decoration is carried out for the enhancement of electron generation. Optical absorption and the Hall effect results prove that B-TiO2@Ag exhibits highest photoelectrical properties. As a result, the B-TiO2@Ag gas sensor with a low operating temperature at 250 °C and high response of 68.19 to 50 ppm acetone is realized. The low detection limit of B-TiO2@Ag sensor reaches 887 ppb, which provides an applicable way for non-invasive detection of blood glucose.

In-situ nitrogen-doped black TiO2 with enhanced visible-light-driven photocatalytic inactivation of Microcystis aeruginosa cells: Synthesization, performance and mechanism

A series of nitrogen-doped black TiO2 nanocatalysts were successfully synthesized by a one-step method. It is novel to find that calcination in an N2 atmosphere completed N doping and oxygen vacancies production simultaneously. In contrast, the urea addition as N precursor inhibited the nitrogen incorporation and the oxygen vacancies production. However, it is the sample using urea as N precursor that had the higher visible-light absorption, the narrower bandgap, the more efficient excited charges separation and higher degradation efficiency for removing chlorophyll-a in Microcystis aeruginosa algae cells. Mechanism exploration indicated that the intermediate energy states existed within the bandgap of TiO2, and O2− and OH were the dominant radicals responsible for algae cell damage and organic matter degradation. This research will provide additional insight into the roles of N precursors and a calcining atmosphere to improve the photocatalytic activity of nitrogen-doped black TiO2 for algae inactivation and metabolites degradation.

Sol-gel derived TiO2–carbon composites with adsorption-enhanced photocatalytic activity and gas sensing performance

We report the in-situ sol-gel synthesis of TiO2–carbon composites (black TiO2) by carbonization of the gel. With ultra-fine anatase TiO2 nanoparticles dispersed homogeneously on amorphous carbon, the as-prepared black TiO2 possesses a BET surface area as high as 145.4 m2/g. Due to the synergy effect of adsorption and photocatalysis, the as-synthesized black TiO2 is demonstrated to exhibit enhanced photocatalytic activity. The gas sensing properties of black TiO2 have been rigorously investigated with and without UV illumination at room temperature. It is found that increased adsorption of gas molecules can effectively improve the sensor response. The mechanism of the adsorption-enhanced gas sensing performance of black TiO2 has been detailedly discussed.

Engineering black titanium dioxide by femtosecond laser filament

We propose an approach, by utilizing the propagation of femtosecond laser pulses in the filamentation region in air, to achieve black titanium dioxide (TiO2), a promising material for efficient photocatalysis. It is found that the black TiO2 engineered by femtosecond laser filament in both solution and air environments shows significantly improved absorption in a broad spectral range from 400 to 2500 nm. In addition, the engineered black TiO2 shows a certain degree of enhanced absorption in the microwave range. The structural and elemental analyses of the processed TiO2 suggest that the absorption enhancement is mainly ascribed to the filament-induced disorder and dopant impurity in the surface layer of crystalline TiO2. Our technique provides an alternative way to engineer black TiO2 with the capability of absorbing the solar energy across a broad spectrum that can be useful for various applications in optoelectronics and photochemistry.

Pulsed Laser Ablation in Water Synthesis of Black TiO2-Graphene Oxide Nanocomposites and the Enhanced Photocatalytic Performance

Black TiO₂-graphene oxide (GO) nanocomposites are synthesized via the pulsed laser ablating TiO₂ powders and GO in deionized water. The simple process enables the preparation of black TiO₂ nanoparticles and anchors them onto the GO sheet in one step. The TiO₂-GO nanocomposites exhibit greatly enhancement for photocatalytic degradation of Rhodamine B (RB) dye in comparison with the pristine and the ablated black TiO₂. The heterojunction structure plays an important role in efficient charge separation, which reduces the recombination of photogenerated electrons and holes. The unique two-dimensional structure of GO enables the composite to have a large specific surface area, and prevents the agglomeration of TiO₂ nanoparticles, which are beneficial to the photocatalytic performance of the composite.

Visible light driven Ti3+ self-doped TiO2 for adsorption-photocatalysis of aqueous U(VI)

The photocatalytic reduction of U(VI) is recognized as an economical and effective way for U(VI) removal/recovery from solutions. To improve the photocatalytic activity of TiO2 under visible light, TiO2 was hydrogenated by NaBH4 to generate Ti3+ self-doped black TiO2 (BTn). The self-doped Ti3+ alongside oxygen vacancies (Ov) could act as interband level to increase visible light capture and reduce the recombination of photogenerated carriers. The obtained BTn samples showed high performance for U(VI) elimination under near neutral conditions, and held an outstanding anti-interference for U(VI) over competing metal cations and anions. Methanol and ethanol could act as sacrificial donors, being favorable for the photocatalytic reduction of U(VI), while the presence of EDTA inhibited the photoreduction of U(VI). The BTn photocatalysts showed relatively high stability and reusability during the photocatalysis and elution processes. The XPS, TEM and XRD results revealed that U(VI) was photo-reduced to form UO2 on the surface of BTn. This work may serve as an important reference for improving the photocatalytic reactivity of TiO2 as well as for the efficient removal/recovery of U(VI) from aqueous solutions.

Photoelectrochemical Biosensor for DNA Formylation Detection in Genomic DNA of Maize Seedlings Based on Black Tio2-Enhanced Photoactivity of MoS2/WS2 Heterojunction.

5-Formylcytosine (5fC) is a rare base found in mammalian DNA, which is thought to be involved in the demethylation of DNA. As a stable epigenetic modification, 5fC participates in gene regulation and cell differentiation, and plays an important role in the growth and development of plants. However, the abundance of 5fC is only as low as 0.002-0.02% of cytosine. Therefore, to further understand the functions of 5fC, a rapid, highly sensitive, and efficient method is needed for detecting 5fC. Herein, a novel photoelectrochemical (PEC) biosensor was constructed for 5fC detection, where a MoS2/WS2 nanosheet heterojunction was employed as a photoactive material, amino-functionalized Fe3O4 and SMCC were used as a linker, 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole was adopted as 5fC recognition reagent, and black TiO2 (B-TiO2) was used as a signal amplification unit. Under the optimal experimental conditions, this PEC biosensor showed a wide linear range of 0.01-200 nM and a low detection limit of 2.7 pM (S/N = 3). Due to the specific covalent reaction between -NH2 and -CHO, the biosensor presented high detection sensitivity, even discriminating 5fC with 5-methylcytosine and 5-hydroxymethylcytosine. The biosensor was then applied to investigate the effect of heavy metal Cd2+ on 5fC content in the root, stem, and leaves of maize seedlings.

Polydopamine-sensitized WS2/black-TiO2 heterojunction for histone acetyltransferase detection with enhanced visible-light-driven photoelectrochemical activity

• Sensitive photoelectrochemical method was developed for histone acetyltransferase detection. • WS 2 and black TiO 2 heterojunction presented strong photoelectrochemical response. • Solid electron donor of polydopamine can effectively improve the photoactivity of WS 2 and black TiO 2 . • This method can also be applied for the inhibitor screening. A kind of novel heterojunction structure with black TiO 2 and WS 2 was prepared with matched energy band and significantly improved visible-light-driven photoelectrochemical activity. Then, to further improve the photoelectrochemical activity of this heterojunction, solid-state electron donor of polydopamine was employed with satisfactory result. The band gap, potential of conduction band and valence band was investigated using Mott-Schottky curve, VB-XPS and UV–vis diffuser reflectance techniques. These materials were also characterized by SEM, TEM, XRD, IR, Roman spectra, and EPR image. The improved photoactivity was confirmed by monitoring and comparing the photocurrent response of black TiO 2 , WS 2 and Black TiO 2 /WS 2 heterojunction. To explore the applicability of this novel heterojunction structure, a kind of photoelectrochemical biosensor was constructed for histone acetyltransferase p300 detection using black TiO 2 and WS 2 as photoactive material and polydopamine as electron donor. Under optimized conditions, the photoelectrochemical biosensor shows wide linear range from 0.01 to 500 nM for histone acetyltransferase p300 detection. The detection limit is 0.0033 nM (S/N = 3). The sensor has good selectivity, stability and reproducibility. The inhibition tests show that aminoglycoside antibiotics significantly inhibits the activity of histone acetyltransferase and the IC 50 of typical tobramycin, streptomycin sulfate and kanamycin sulfate were 10.41, 13.31 and 15.42 μM, respectively.

A novel self-powered aptasensor for digoxin monitoring based on the dual-photoelectrode membrane/mediator-free photofuel cell

Self-powered sensor is considered as a promising, rapid, portable and miniaturized detection device that can work without external power input. In this work, a novel dual-photoelectrode self-powered aptasensor for digoxin detection was designed on the basis of a photofuel cell (PFC) composed of a black TiO2 (B–TiO2) photoanode and a CuBr photocathode in a single-chamber cell. The sensing platform avoided the use of membrane, free mediator, bioactive components and costly metal Pt electrodes. The large inherent bias between the Fermi energy level of B–TiO2 and that of CuBr improved the electricity output of PFC that the open circuit potential (OCP) and the maximum power density (Pmax) reached 0.58 V and 6.78 μW cm-2 respectively. Based on the excellent output of PFC, digoxin aptamer was immobilized on photoanode as the recognition element to capture digoxin molecules, which realized the high sensitive and selective detection of digoxin. The self-powered aptasensor displayed a broad linear in the range from 10-12 M to 10-5 M with a detection limit (3 S/N) of 0.33 pM. This work paved a luciferous way for further rapid, portable, miniaturized and on-site self-powered sensors.

Black TiO2 Thin Films Production Using Hollow Cathode Hydrogen Plasma Treatment: Synthesis, Material Characteristics and Photocatalytic Activity

Black TiO2 materials have been quite widely explored due to their large solar absorption and superior photocatalytic activity. In this paper, the blackening process of titanium dioxide (TiO2) thin film using the hollow cathode hydrogen plasma (HCHP) technique is reported. First, pristine anatase TiO2 films were grown by magnetron sputtering onto silicon and cover glass substrates and then annealed at 450 °C for 2 h. Then, the as-grown TiO2 films were treated with HCHP for 15 min. The physical, chemical and morphological properties of the films were analyzed by profilometry, X-ray diffraction (XRD), UV-Vis spectrophotometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. Electrical and photocatalytic measurements were performed by four-point probe and methylene blue UV degradation assays, respectively. The results showed that the black TiO2 film is highly absorbent in the UV-visible region, has low electrical resistance and greater surface area compared to the non-treated TiO2 film. These properties of black TiO2 film, as well as its performance as a photocatalytic agent, were investigated, indicating the superior quality of this material in thin film form and the promising potential of the HCHP treatment to produce hydrogenated TiO2 in short process time.

Black TiO2: What are exact functions of disorder layer

AbstractAmong the substantial amount of photocatalyst materials, TiO2 has been enthusiastically studied for a few decades due to its outstanding photocatalytic activity and stability. Recently, black TiO2 consisting of approximately 2 nm of thin disorder layer around the surface showed surprisingly high solar hydrogen generation ability. The disorder layer of TiO2 can enhance its light absorption, charge separation, and surface reaction abilities, however exact fundamentals of photocatalytic water‐splitting pathways are still ambiguous. Herein, recent progress and investigations on exact functions of disorder layer and its application in photocatalytic CO2 reduction will be discussed. Throughout the comprehensive studies on disorder layer of TiO2, disorder engineering on photocatalyst materials will suggest the further extension of developing solar‐fuel production technologies.

Photoelectrochemical assay for DNA hydroxymethylation determination based on the inhibited photoactivity of black TiO2 nanosphere by ZnO.

A photoelectrochemical method was proposed for DNA hydroxymethylation determination using black TiO2 (B-TiO2) nanosphere as photoactive material and ZnO as photoactivity inhibitor. After hydroxymethylated DNA (5hmC-DNA) was captured on the probe modified B-TiO2/ITO electrode surface through hybridization, a glycosyl can be then transferred from uridine diphosphoglucose to 5hmC-DNA and formed a covalent structure with -CH2OH in the presence of T4 β-glucosyltransferase (β-GT). Afterwards, based on a series of covalent reaction, amino functionalized ZnO nanoparticles are further immobilized to the surface of the electrode. Due to the capacity to expend the irradiation light and the photogenerated electron of electron donor, the modified ZnO nanoparticles can result in a decreased photocurrent. The developed method shows wide linear ranges from 0.05-200nM for hydroxymethylated DNA and 1-220 unit·mL-1 for T4-β-glucosyltransferase. The corresponding determination limits were 0.013nM and 0.24 unit·mL-1, respectively. The enzyme activity inhibited by 4-phenylimidazole was evaluated. This photoelectrochemical method shows high specificity for 5hmC-DNA (compared to 5fC, 5mC, m6A, control) and β-GT (compared to β-AGT, UGT2B7), and shows excellent stability for testing 5hmC (RSD = 2.75%). Graphical abstractSchematic representation of photoelectrochemical method for DNA hydroxymethylation and β-glucosyltransferase detection based on the glycosylation reaction of -CH2OH in 5-hydroxymethylcytosine and the inhibition activity of ZnO to the photoactivity of black TiO2 nanospheres.

Enhanced performance of dye-sensitized solar cells anodes modified with black phosphorus nanosheets

Black phosphorus (BP) has attracted increasing attention owing to its unique electronic and optoelectronic properties. In this account, BP nanosheets (BP-NS) with high concentration were prepared through organic salt trisodium citrate assisted exfoliation of BP crystal; then, an efficient photoanode for dye-sensitized solar cells (DSSCs) was developed using BP-NS/TiO2 composite. Compared to bare TiO2-based DSSC with power conversion efficiency of only 6.98%, the DSSCs assembled with BP-NS based photoanode showed enhanced performance by ca. 40%. Optimal values of photocurrent density (22.32 mA/cm2) and power conversion efficiency (9.73%) were achieved with DSSC comprising the BP nanosheets. The interaction at the interface between BP and TiO2 in BP/TiO2 played a crucial role in improving the performance, which benefit the charge separation and transfer. The interfacial interactions between black phosphorus and TiO2, and the corresponding chemical configurations were thoroughly investigated with TEM and XPS spectroscopy. Overall, the proposed route looks effective for enhancing DSSCs efficiencies and would hold potential prospects for future development of DSSCs anodes.

Heterojunction of vertically aligned MoS2 layers to Hydrogenated Black TiO2 and Rutile Based Inorganic Hollow Microspheres for the highly enhanced visible light arsenic photooxidation

In this research, Rutile Based Inorganic Hollow Microspheres (RBIHM) and hydrogenated anatase TiO2 nanoparticles decorated with MoS2 nanosheets (HBTiO2/RBIHM-MoS2 photocatalyst) using Pulsed Laser Ablation in Liquid (PLAL) followed by microwave irradiation. Formation of vertically aligned MoS2 nanosheets, RBIHM and HBTiO2 nanoparticles were confirmed by different characterization techniques. The spectroscopic analysis revealed phase transitions in HBTiO2/RBIHM nano and microstructures along with the formation of different crystal disorders such as amorphous layers, oxygen vacancies, trivalent titanium ions and formation of molybdenum oxide (MoO3-x) in MoS2. In addition, MoS2 films in HBTiO2/RBIHM-MoS2 nanocomposite showed both Mo5+ and Mo6+ oxidation state, which indicates that these films have a p-type conductive behavior. Furthermore, the interconnected layers of MoS2 nanosheets led to the formation of a porous like 3D nanostructure in HBTiO2/RBIHM-MoS2, which could significantly improve its photocatalytic performance. Arsenite photooxidation efficiencies of 70.3% and 96.6% and arsenate adsorption capacities of 1600 and 5200 μg g−1 were obtained for HBTiO2/RBIHM and HBTiO2/RBIHM-MoS2, respectively. The synergetic effects originated from making RBIHM-HBTiO2, RBIHM-MoS2 and MoS2–HBTiO2 heterojunctions along with the surface and morphology modification in MoS2 NSs and HBTiO2/RBIHM can explain the nanocomposite superior photocatalytic performance. The present work can trigger a broad interest in the cost-effective nanoarchitecture of visible light driven heterostructured photocatalysts.

PEDOT-Type Conducting Polymers/Black TiO2 Composites for Electrochemical Determination of Cd2+ and Pb2+

In this paper, the PEDOT-type conducting polymers/black TiO2 composites were prepared by in situ polymerization method by varying the weight ratio of black TiO2 to monomer (3,4-ethylenedixoythiophene(EDOT) or 3,4-propylenedixoythiophene (ProDOT)). And, these composites (PEDOT/B-TiO2 and PProDOT/B-TiO2) were applied for the electrochemical determination of Cd2+ and Pb2+ by using differential pulse voltammetry (DPV). The relationship between the structure and electrochemical performances was studied systematically. The structural analysis revealed that the PEDOT-type conducting polymers could act with B-TiO2 by non-covalent bonding. The combination of polymers with B-TiO2 effectively enhanced adsorption and charge transfer ability of composites to heavy metal ions, which was favorable for enhancing the eletrcocatalytic ability of composites. The results showed that under optimized conditions, the limit of detection (LOD) of the PEDOT/B-TiO2 composite electrode from 50 wt% B-TiO2 are 0.00073 μM and 0.0816 μM, respectively, and the linear range of simultaneous detection of Pb2+ and Cd2+ is from 0.04 to 1.24 μM. In the case of PProDOT/B-TiO2, the LOD of composite electrode from 50 wt% B-TiO2 for Pb2+ are 0.00087 μM (0.04–0.4 μM) and 0.00186 μM (0.4–1.8 μM), respectively, and the LOD for Cd2+ are 0.01523 (linear range of 0.04–0.4 μM) and 0.03214 (linear range of 0.4–1.8 μM), respectively.

The Removal of Formaldehyde via Visible Photocatalysis Using the Black TiO2 Nanoparticles with Mesoporous

AbstractThe black TiO2 nanoparticles with plentiful mesoporous and active sites was synthesized by a simple calcination amorphous titanium hydroxide in vacuum. The photocatalytic and adsorption performance of the materials for removal of formaldehyde under visible light irradiation was investigated and compared with the white TiO2 nanoparticles according linear and nonlinear forms of pseudo‐first order and pseudo‐second order kinetic equations. The nonlinear of pseudo‐first order is suitable for the photocatalytic and adsorption performance. The reusability performance for formaldehyde shows that the removal rate constants of the black TiO2 in three cycles decline slowly while the white TiO2 declines sharply. The results imply that the black TiO2 nanoparticles have quickly removal rate for formaldehyde and reusability performance. The good photocatalytic and adsorption performance should be result from the mesoporous and oxygen vacancies as active sites. And, the close stacked structure nanoparticles can enhance separation of photogenerated holes and electrons to increase the photocatalytic performance for removal of formaldehyde.

A facile method for the preparation of black TiO2 by Al reduction of TiO2 and their visible light photocatalytic activity.

Black TiO2 has attracted widespread attention due to its visible light absorption and wide range of applications. However, the currently reported preparation methods for black TiO2 are not suitable for large-scale production due to its being prepared under high vacuum and over a long time. We have successfully prepared black TiO2 under normal pressure and short time conditions. The as-prepared black titanium dioxide was characterized by XRD, XPS, TEM, UV-visible absorption spectrum and other characterization methods. The result shows that the as prepared black titanium dioxide had a disordered structure and oxygen vacancy defects on the surface, and exhibits excellent visible and near infrared absorption performance. The black TiO2 sample was prepared under 650 °C 60 min exhibits excellent visible light photocatalytic performance, and can degrade 56% MO after visible light irradiation for 120 min.

Black TiO2 nanoparticles with efficient photocatalytic activity under visible light at low temperature: regioselective C–N bond cleavage toward the synthesis of thioureas, sulfonamides, and propargylamines

Several different colored forms of TiO2 were prepared through the easy treatment of white TiO2 and NaBH4 as a safe hydrogen source. Then, tertiary amines were harnessed toward the regioselective synthesis of three prominent scaffolds.