Single TiO2 Research Articles

Enhanced visible light-driven photocathodic protection performance of CuBi2O4 modified TiO2 nanotube array S-type nano-heterojunction photoanodes for 316 stainless steel

CuBi2O4 (CBO) nanoparticle (NP)-sensitized TiO2 nanotube (NT) photoanodes have been prepared and optimized for high visible light utilization and photoconversion efficiency. The introduction of CBO significantly improved the charge generation/separation efficiency of the prepared photoanodes. The CBO-sensitized TiO2 NTs obtained with an electrodeposition time of 6 min had the best photocathodic protection (PCP) performance, and the photogeneration potential of CuBi2O4/TiO2 (CBOT) composites coupled to 316 stainless steel (SS) decreased by an additional 460 mV compared to that of TiO2. The CBO NPs were uniformly distributed on the TiO2 NTs to form tight interfacial bonds. Moreover, the one-dimensional TiO2 NTs act as direct electron channels, ensuring the fast collection of carriers generated by the system. The electronic lifetime of the 6CBOT composite is approximately 30 times that of the pure TiO2 material. In addition, the formation of S-type nano-heterojunction inside the CBOT not only promotes charge transfer in the system, but also retains a strong redox capacity compared to that of single TiO2 NTs. This work offers novel ideas in designing photoanode with efficient PCP property.

Oxidation cocatalyst/S-scheme junction cooperatively assists photocatalytic H2 production in ternary hybrid: The case of PdO@TiO2-Cu2O

Solar-driven photocatalytic hydrogen production from water splitting holds significant potential in addressing the energy crisis and environmental pollution. However, rapid recombination of photogenerated carriers and insufficient surface catalytic reaction kinetics hinder the photocatalytic process. Constructing the catalytic systems with multi-channel charge-separation can effectively alleviate those issues. In this work, ternary PdO@TiO2-Cu2O composites have been synthesized through precursor calcination and low-temperature reduction, where PdO and Cu2O nanoparticles couple with the TiO2 nanorods. Comparing to single TiO2, binary PdO@TiO2 and TiO2-Cu2O, the PdO@TiO2-Cu2O hybrid exhibits enhanced photocatalytic hydrogen production performance (5831μmol g-1h−1), with a hydrogen production rate more than three times that of single TiO2. Based on the band structures of TiO2 and Cu2O, along with the photochemical/electrochemical, in-situ EPR, Photoluminescence (PL) tests, and work function calculations, the formation of an S-scheme heterojunction at the TiO2-Cu2O interface under light illumination facilitates the recombination of electrons in the conduction band (CB) of TiO2 with holes in the valence band (VB) of Cu2O. In this regard, the established built-in electric field significantly accelerates the transfer of photogenerated charges while preserving their respective strong oxidation and reduction capabilities. Meanwhile, the introduction of PdO enriches the holes and further enhances the rate of charge separation. This S-scheme heterojunction with directional charge transfer and oxidation cocatalyst collectively form multi-channels of charge separation, optimizing charge migration and enabling efficient hydrogen production, thus improving the photocatalytic capability of pristine TiO2. This study provides a rational approach to construct efficient S-scheme heterojunction/oxidation cocatalyst multi-component catalytic systems for water splitting into hydrogen.

Semiconductor heterojunctions coated with reduced graphite oxide as electron transfer materials for high-performance perovskite solar cells

Exploring and insight into the relationship between the microstructure, light absorption performance, and carrier transport of perovskite light absorption layer materials and carrier transport layer materials is crucial for obtaining efficient and stable perovskite solar cells. We adopted a simple strategy to prepare a composite material known as reduced graphene oxide wrapped mesoporous hierarchical TiO2–CdS semiconductor heterojunctions (TiO2–CdS-RGO) as the electron transport layer in formamidine lead iodide perovskite solar cells. Compared with single TiO2 and binary composite, this composite material exhibits enhanced photoluminescence quenching, reduced photo generated carrier recombination rate, and improved electron transfer capability. Photovoltaic devices based on TiO2–CdS-RGO composite material showed a 14.5 % increase in short-circuit current density (JSC) and a 36.3 % increase in photoelectric conversion efficiency (PCE) compared to those with only TiO2. The improved optoelectronic properties observed with the TiO2–CdS-RGO as electron transfer layers can be attributed to several factors. On the one hand, mesoporous TiO2 with a high specific surface area is beneficial for perovskite infiltration and enhances electron transfer rate. On the other hand, the well-matching energy level structure among the three components aids in electrons extraction and reduces the recombination rate of photo generated charge carriers; In addition, RGO nanosheets with high conductivity serve as an efficient electron transfer network, providing a rapid charge transfer pathways, which is crucial for enhancing the photoelectric conversion performance of perovskite solar cells.

Electrohydrodynamic-Jet-Printed SnO2-TiO2-Composite-Based Microelectromechanical Systems Sensor with Enhanced Ethanol Detection.

Ethanol sensors have found extensive applications across various industries, including the chemical, environmental, transportation, and healthcare sectors. With increasing demands for enhanced performance and reduced energy consumption, there is a growing need for developing new ethanol sensors. Micro-electromechanical system (MEMS) devices offer promising prospects in gas sensor applications due to their compact size, low power requirements, and seamless integration capabilities. In this study, SnO2-TiO2 nanocomposites with varying molar ratios of SnO2 and TiO2 were synthesized via ball milling and then printed on MEMS chips for ethanol sensing using electrohydrodynamic (EHD) printing. The study indicates that the two metal oxides dispersed evenly, resulting in a well-formed gas-sensitive film. The SnO2-TiO2 composite exhibits the best performance at a molar ratio of 1:1, with a response value of 25.6 to 50 ppm ethanol at 288 °C. This value is 7.2 times and 1.8 times higher than that of single SnO2 and TiO2 gas sensors, respectively. The enhanced gas sensitivity can be attributed to the increased surface reactive oxygen species and optimized material resistance resulting from the chemical and electronic effects of the composite.

Enhanced photocatalytic alkane production from fatty acid decarboxylation over sulfide-modified TiO2 under mild conditions

Photocatalytic decarboxylation of fatty acids derived from biomass is considered a sustainable approach for alkane production. In this study, a series of NiS2 co-catalyst-modified TiO2 (NiS2/TiO2) composites were successfully synthesized and employed for the photocatalytic decarboxylation of fatty acids. Under mild conditions, the optimized NiS2/TiO2 composite exhibited conversion of 60.2% and selectivity of 72.6% for converting chondritic acid to pentadecane, which was 6.56 times to single TiO2. The incorporation of the co-catalyst led to red shift of the absorption edge, and decrease in photoluminescence (PL) intensity, indicating enhanced light absorption and efficient separation of photogenerated charge in NiS2/TiO2. The lower work function of NiS2 compared with TiO2 and the differential charge density indicated that electrons tended to migrate from the S-atom to the O-atom, thus creating a built-in electric field that accelerated the reaction. The study on biofuel synthesized from biomass offered insights that can help mitigate future energy crises.

Exploring innovative antibacterial properties of porous ALT (Al2O3/TiO2) composite

Among all metallic materials, titanium is mostly employed in medical applications. In this study, single TiO2 layers on Ti as well as composite ALT(Al2O3/TiO2) layers on Ti for medical applications were synthesized using titanium and aluminum cathodic cages. SEM, EDX, XRD, PL, UV–Vis analyses of untreated and plasma-processed samples were used to determine the surface morphology, chemical content, microstructure, band gap, and photocatalytic behavior, respectively. E. coli and S. aureus immersion bacterial solutions were used to test the antibacterial performance of untreated and plasma-processed specimens. Comparing the composite to a single TiO2 and an untreated sample in PL spectra revealed a smaller band gap. When compared to untreated specimens, coatings made of TiO2 and composite ALT demonstrated significant antibacterial properties. The results showed that ALT-60min displayed unique antibacterial behavior because the band gap was reduced and antibacterial effectiveness was increased. This work explains the distinctive antibacterial activity of composite nanostructures made for medicinal use.

Examining the dual effect of copper nanoparticles and nitrogen doping on Cu@N-TiO2

Abstract The study of six compositions of Cu@N-TiO2 with different amounts of copper and nitrogen synthesized using a sol–gel method is reported. X-ray diffraction patterns and Raman spectra indicated the formation of a single anatase TiO2 phase in all materials without evidence of secondary phases including copper or nitrogen. Electron microscopy images showed a homogeneous distribution of the copper particles around a TiO2 matrix, just as that the insertion of nitrogen did not have a significant effect on the morphology of the particles. X-ray photoelectron spectroscopy analysis confirmed that nitrogen was inserted in the atomic arrangement of titanium dioxide, while copper was presented mainly as metallic element on the TiO2 surface. Characterization of the optical properties and photoactivity test confirm that band gap strongly depends on the copper and nitrogen content phenomenon attributed to the combined presence of modifiers over the TiO2 surface and the promotion of a plasmonic effect, which displaced the absorption UV bands to higher wavelengths with respect to un-doped TiO2. The catalytic test performed using rhodamine-B as probe molecule, confirm that TiCuN2 and TiCuN3 samples exhibit the best decomposition percentages of 38 and 36 % respectively. Such results confirm the surface plasmon resonance effect associated to Cu particles on the TiO2 as main cause in the increase in current along synthesized samples and the use of cyclic voltammetry technique to identify these effects between 0.0 and 1.5 V.

Highly selective sensing of toxic NOx gases for environmental monitoring using Ru-doped single walled TiO2 nanotube: A density functional theory study

Applying density functional theory simulations, in this study, we examine the sensing properties of Ru-TNT surface towards NOx molecules such as NO and NO2. The obtained results show that Ru doping creates a large-spin density over the Ru-TNT surface, which hints at an increase in the adsorption energy of NOx molecules. The electronic properties of the Ru-TNT surface are significantly altered after NO and NO2 molecule adsorption, as proven by the larger change in the energy gap values. Moreover, the selectivity study indicates that the Ru-TNT is capable of selectively sensing the NOx molecules in the presence of other gases, e.g., CO2, CO, NH3 and H2O. Using an external positive electric field can resist the strong anchoring of NOx molecules over the Ru-TNT surface, suggesting that material recovery is feasible. Thus, the Ru-TNT structure can be applied as a selective, sensitive, and promising ambient temperature gas sensor for NOx molecules.

Photocatalytic degradation of sulfamethazine using g-C3N4/TiO2 heterojunction photocatalyst: Performance, mechanism insight and degradation pathway

In the present research, Z-scheme g-C3N4/TiO2 heterojunction composite photocatalysts with varied g-C3N4 content were successfully prepared using the sol-gel technique combined with calcination methods. The morphology, crystallinity, chemical composition, and optical properties of the synthesized catalysts were characterized employing a series of techniques. Sulfamethazine (SMZ) was selected as the model pollutant to evaluate the photocatalytic activity of the prepared catalysts employing a 500 W xenon lamp as the light source to simulate sunlight. The results demonstrated that within 180 min of irradiation, 94.8 % of SMZ was removed by using the optimal photocatalyst (0.4CN/TiO2 composite sample), affording an apparent first-order rate coefficient of 0.0152 min−1 which was 3.8 or 2.0 times as much as that involving single g-C3N4 or TiO2 catalyst, respectively. The effects of catalyst dosage, initial pH, different water matrices, different substrates, and inorganic ions on the performance of 0.4CN/TiO2 photocatalyst were explored. Furthermore, the 0.4CN/TiO2 composite also displayed satisfactory cyclic stability. The results of radical quenching experiments revealed that the key active species in SMZ degradation were hydroxyl radicals (•OH), superoxide radicals (O2•−), and holes (h+). The efficient separation of photo-generated electrons and holes originating in the formation of a Z-scheme g-C3N4/TiO2 heterojunction was evidenced by photoluminescence and electrochemical impedance spectroscopy determination and should be responsible for the enhanced catalytic activity of the 0.4CN/TiO2 sample. In addition, the plausible pathways for the aqueous degradation of SMZ were suggested according to the identified degradation intermediates employing the HPLC/MS technique. In summary, the current research provides a novel insight into the development of Z-scheme heterojunctions in the realm of organic pollutant treatment.

Physical and Electrochemical Properties of Transition Metal Oxides with Hollow Structure As Sulfur Host Material for Lithium-Sulfur Batteries

INTRODUCTION Because of its high theoretical energy density, possibly low cost, and environmental friendliness, lithium-sulfur (Li-S) batteries have received a lot of interest. However, the principal disadvantage impeding the success of Li–S batteries lies in the severe leakage and migration of soluble lithium polysulfide intermediates out of cathodes upon cycling caused “shuttle effect”. The loss of active sulfur species incurs significant capacity decay and poor battery lifespans which has prevented it from commercial realization.Several researches have been conducted with an attempt to improve capacity of batteries while maintaining life of the Li-S cellใ including an introduction of nanostructured cathode host materials. Two main approaches have currently been explored a. chemical confinement and b. physical confinement to anchor the lithium poly-sulfide (LiPSs) reaction products durin the charging process. Transition metal oxides such as TiO2 and SnO2 has been studied with a potential material to anchor polysulfides via Lewis acid–base interactions and thus maybe able to chemically confine LiPSs within or on the transition metal oxide. Physical confinement may also be possible by trapping LiPSs within a transition metal oxide host structure e.g. hollow structure and thus help impedes polysulfide dissolution into the electrolyte. In this study, TiO2 and SnO2 are focused to understand the physical and electrochemical properties of sulfur host material with hollow structures. The in situ XAS is also conducted to understand the behavior of the dissolution and migration of long-chain LiPSs intermediates (Li2S x , 4 ≤ x ≤ 8) in the sulfur cathode upon discharge. EXPERIMENTAL The transition metal oxide, TiO2 and SnO2, were successfully synthesized by a templated method. The synthesis process involved four steps, preparation of SiO2 spheres, synthesis of SiO2@transition metal oxide core-shell structure by coating transition metal oxide shell on SiO2 and crystallization by calcination and etching the SiO2@transition metal oxide to form hollow transition metal oxide spheres. Structural properties of the synthesized samples were studied by X-ray diffraction (XRD) using Cu-Kα (λ=1.5418 Å) radiation. Particle morphologies and size of the resulting compounds were observed using a field emission scanning electron microscope. Composite electrodes for electrochemical studies were prepared by doctor blade coating of a slurry compound onto carbon-coated aluminium foil current-collectors. The transition metal oxide and sulfur composite, conductive carbon and PVDF binder were mixed in the ratio of 80:10:10 by weight. Electrochemical characterizations were performed by in 2032 coin cells and Galvanostatic charge-discharge cycling was done between 1.8-3.0 V at 0.1C using a MACCOR Series 4000 at room temperature. RESULTS AND DISCUSSIONS Based on the XRD results, single phase anatase TiO2 and tetragonal SnO2 were both successfully synthesized by the templated method. SEM images (Fig. 1a and 1b) demonstrate that TiO2 and SnO2 are generally spherical structures with nanometer scale dimensions ranging from 250-350 nm and 450-500 nm, respectively. The interior hollow region can be seen clearly in the images of broken spheres. The shelled surface of the synthesized powders is hierarchically made up of interconnected nanocrystals providing a possibly porous structure. Hence, the hierarchically porous and hollow structure has a large surface area for adsorbing the LiPSs distributed in the electrolyte.Fig. 1c shows the charge and discharge voltage profiles of SnO2 and sulfur composite electrode cathode in the first five cycles. Two discharge plateaus were clearly observed, which might be attributed to the two-step sulfur-lithium reaction process. The initial plateau, centered about 2.30 V, was commonly attributed to the reduction of the S8 ring and the formation of S8 2−. The second discharge plateau at 2.10 V was attributed to further reduction of the higher polysulfides (Li2S n , 4 ≤ n ≤ 8) to the lower polysulfides (Li2S n , n ≤ 3). There exhibited two plateaus in the charge process at about 2.25 and 2.35 V, respectively. Electrochemical performance in relations to capacity retention and the in situ XAS to understand the behavior of the dissolution and migration of LiPSs will be discussed in the meeting. Figure 1

Metal-organic framework [NH2-MIL-53(Al)] functionalized TiO2 nanotube photoanodes for highly stable and efficient photoelectrochemical cathodic protection of nickel-coated Mg alloy

Metal-organic framework [MOF, i.e., NH2-MIL-53(Al)] modified TiO2 (NMT) composite photoanodes were successfully prepared by hydrothermal synthesis and were used for the photoelectrochemical cathodic protection (PECCP) of nickel-plated magnesium alloy (Mg/Ni). Results showed that the synthesis temperature significantly impacted the morphology and PECCP performance of the NMT photoanodes. The NMT@150 photoanode prepared at a reaction temperature of 150 °C exhibited the best PECCP performance and produced a current density of 1980 μA cm−2 under visible light irradiation, which was 19.8 times higher than that of a single TiO2 photoanode. The composite photoanode could polarize the open circuit potential of the coupled Mg/Ni electrode to -876 mV and remain relatively stable within 35 h. XPS and EPR tests showed that a Z-scheme heterojunction was formed between the NH2-MIL-53(Al) and TiO2 nanotubes, allowing the photogenerated electrons to accumulate mainly on the conduction band of NH2-MIL-53(Al). The heterojunction greatly promoted the separation and transfer of photogenerated electron-hole in the NMT composite photoanode, significantly enhancing the PECCP performance for Mg/Ni.

Tailoring TiO2 finite nanotubes: Doping-induced modulation of electronic, optical, and hydrogen storage properties

In this study, we employ density functional theory calculations to investigate the properties of finite single walled TiO2 finite nanotubes (TiO2NTs). The constructed nanotubes demonstrate geometric stability, as evidenced by positive binding energy and real positive vibrational frequencies obtained from the infrared spectra. Substitutional doping with various atoms (B, N, C, Si, Li, Sc, Fe, and Cu) introduces intriguing effects on the electronic and optical properties of TiO2NTs. Doping with Fe slightly reduces the wide energy gap (∼5 eV) of unmodified TiO2NTs to 4.2 eV, while Si doping significantly decreases the energy gap by half. Furthermore, we investigate the impact of doping TiO2NTs with boron, carbon, nitrogen, iron, cesium, and silicon on their UV–Vis absorption spectra. The introduction of these dopants induces significant redshifts in the absorption peaks, indicating alterations in the electronic energy gap and transitions between specific states. These findings provide valuable insights into the structural and electronic modifications of TiO2NTs. Moreover, we explore the adsorption properties of TiO2NTs for H2 molecules. While unmodified TiO2NTs exhibit low adsorption energy, doping with a small number of C or Si atoms leads to a substantial enhancement in the adsorption energy. Specifically, Si doping achieves adsorption energy of approximately 0.2 eV, accompanied by a hydrogen storage capacity of 6.1 wt%, exceeding the standard capacity of 6.0 wt%. Importantly, the desorption temperature remains comparable to room temperature, ensuring long-term recyclability. These results highlight the potential of doped single-walled TiO2 nanotubes as efficient hydrogen storage devices.

Quaternized hollow TiO2-enhanced the dye adsorption capacity and photogenerated carrier separation for efficient reactive dye removal

Currently, titanium dioxide (TiO2) has been demonstrated as a significant photocatalyst for the efficient removal of reactive dyes in dyeing effluents. However, due to the easy recombination of photogenerated carriers and electrostatic repulsion with reactive dye, single TiO2 cannot achieve satisfactory removal efficiency to reactive dye which is commonly used in cellulose fibers dyeing. Therefore, we prepared hollow titanium dioxide (H-TiO2) by alkaline treatment etching method and introduced quaternary ammonium groups on the surface of H-TiO2 photocatalyst (QAS-H-TiO2) by nucleophilic addition reaction. Improving the adsorption capabilities of C. I. reactive red 2 (RR2) and simultaneously separating the photogenerated carriers via the nitrogen cation of the quaternary ammonium groups facilitated the enhancement of its RR2 removal. The experimental results indicated that the utilization of QAS-H-TiO2 substantially bolstered the removal efficiency of RR2. The impact of molecular structure of quaternary ammonium salts on the adsorption ability of RR2, and the mechanism of regulation for photogenerated carriers, were investigated. It was found that the grafting of the quaternary ammonium group enabled mass and electron transfer channels, resulting in faster adsorption of dyes and separation of photogenerated carriers. This study presents a novel approach for preparing efficient QAS-H-TiO2 for high-performance organic dye removal.

Synergetic effect of Sb ion implantation on the optical and structural properties of single crystal rutile TiO2 (110)

The present study investigates the synergetic influence of Sb ion implantation on the optical and structural properties of single crystal rutile TiO2 (110). The Implantation was carried out at various fluences using 2 MeV Sb ions. X-ray diffraction, X-ray photoelectron spectroscopy, and Photoluminescence studies reveal the occurrence of an ion-induced annealing process which is remarkably responsible for the healing of defect states in the absence of any thermal treatment. Surprisingly, the ion-induced annealing appears to get activated only for the fluences of 1 × 1015 ions/cm2 and higher. At the fluence of 5 × 1015 ions/cm2, reduction in defect states, increase in crystallinity, increase in the photo absorption response (130 % in visible and 165 % in ultraviolet range), improved band-edge luminescence, and bandgap reduction (by ∼0.26 eV) is observed. The ion-induced annealing process effectively improves photo absorption properties without any thermal treatment. These results can play a pivotal role in photocatalysis applications.

Efficiency enhancement and chrono-photoelectron generation in dye-sensitized solar cells based on spin-coated TiO2 nanoparticle multilayer photoanodes and a ternary iodide gel polymer electrolyte

The effect of the thickness of a multilayer TiO2 photoanode on the performance of a dye-sensitized solar cell (DSC) made with a polyethylene oxide-based gel polymer electrolyte containing ternary iodides and performance enhancer 4-tert-butylpyridine is studied. Multilayer photoanodes consisting of up to seven layers of TiO2 nano-particles (13 nm and 21 nm) are prepared by spin coating of successive layers. XRD results confirm the predominant presence of the anatase phase of TiO2 in the multilayer structure after sintering. The SEM images reveal the formation of a single TiO2 film upon sintering due to merging of individually deposited layers. The photocurrent density (JSC) and the efficiency increase with the number of TiO2 layers exhibiting the maximum efficiency and JSC of 5.5% and 12.5 mA cm−2, respectively, for the 5-layered electrode of total thickness 4.0 µm with a 9.66 × 10–8 mol cm−2 surface dye concentration. The present study introduces a method of determining the rate of effective photoelectron generation and the average time gap between two successive photon absorptions where the respective results are 1.34 molecule−1 s−1 and 0.74 s for the most efficient cell studied in this work.

Lab‐in‐a‐Bead: Magnetic Janus Bead Probe for the Detection of Biomarkers in Blood

AbstractRemotely handled miniaturized colorimetric sensor platforms with multiple functionalities are able to mimic conventional laboratory operations with reduced assets. The integration of a magnetic phase in a miniaturized hydrogel sensor system allows the manipulation of the sensor, under a magnetic field, in a programmable manner. However, dark color interferences from conventional magnetic phases (Fe3O4, Fe2O3, and Fe micro/nanoparticles) affect the signal readout, hindering the colorimetric response. Therefore, a novel Janus bead configuration is introduced and tested by the localized incorporation of ferromagnetic iron microparticles into a TiO2 nanotubes/alginate hydrogel bead biosystem, under an applied magnetic field. The so‐called hydrogel Janus bead shows both, magnetic translocation and biosensing properties in the same bead. These beads are used for the direct colorimetric analysis of biomarkers in blood. The surface of the Janus bead prevents the biofouling of red blood cells, keeping the sensor surface clean for accurate optical colorimetric analysis. Moreover, the external magnetic manipulation of the bead permits precise control of the time and position of the bead in the sample. Therefore, multiple functionalities are presented by a single magnetic TiO2 nanotubes/alginate Janus bead such as actuation, low biofouling, and sensing, positioning this technology as a truly Lab‐in‐a‐Bead System.

(Invited) In-Situ Time-Resolved Probe of Charge Carrier Dynamics at Planar Semiconductor Photoelectrode/Liquid Interface

Photoelectrochemistry is a promising approach for converting solar energy to storable chemical energy in chemical fuels. The efficiency of photoelectrochemcial devices depends critically on efficient transfer of charge carrier across the electrode liquid interface and the efficiency and selectivity of the catalytic reaction on electrode surface. Although transient absorption spectroscopy is a powerful tool for probing interfacial dynamics in high surface area electrodes, it is often not applicable on planar electrodes because the observed signal is often dominated by carrier dynamics in the bulk. In this talk, we discuss our recent effort in developing in situ time-resolved linear and nonlinear spectroscopic tools that can be used to probe carrier dynamics and reactions at planar electrode/liquid interfaces, focusing on transient reflection spectroscopy and electric field induced second harmonic generation (EFISH) spectroscopy. Compared to transient absorption, transient reflection spectroscopy is more sensitive to surface carrier density that can be more directly correlated to catalysis. We showed that transient reflectance change can be used to follow charge carrier dynamics and their amplitude can be directly correlated to efficiency of initial interfacial charge separation on p-GaP single crystals protected by TiO2 ALD layer. Our finding suggests that IPCE is determined by the product of the efficiency of initial ultrafast (< hundreds of ps) charge separation across the GaP/TiO2 interface and the efficiency of water reduction reaction on the slower time scale. Key loss pathways that limit these efficiencies are discussed. In a second approach, we showed the EFISH signal in a n-doped single crystal TiO2 can be used to probe the accumulation of photogenerated carriers at surface states and these trapped carriers are responsible for the water oxidation reaction.

Ultra-low power resistive random-access memory based on VO2/TiO2 nanotubes composite film

In this study, a resistive random access memory (RRAM) based on VO2/TiO2 nanotubes was prepared. Compared with single VO2-based RRAM or TiO2 nanotube-based RRAM, the Ag/VO2/TiO2 nanotube/FTO RRAM device has advantages such as low power consumption (∼0.154 pJ), excellent stability (3000 DC cycles), and high switching rate (300 times). It still shows certain advantages compared with TiO2-based low-power RRAM (0.5 pJ). The device can also exhibit 20 consecutive long-term enhancement/suppression behaviors, which can be used to simulate brain-like activity and achieve recognition accuracy of 95% (8 × 8 pixels) and 88% (28 × 28 pixels) in artificial neural network identification field.

Oxygen vacancy self-doped single crystal-like TiO 2 nanotube arrays for efficient light-driven methane non-oxidative coupling

Photocatalytic non-oxidative coupling of methane (PNOCM) is a mild and cost-effective method for the production of multicarbon compounds.&nbsp;However, the separation of photogenerated charges and activation of methane are the main challenges for this reaction. Here, single crystal-like TiO₂&nbsp;nanotubes (V_O-p-TNT) with oxygen vacancies (V_O) and preferential orientation were prepared and applied to PNOCM. The results demonstrate that the&nbsp;significantly enhanced photocatalytic performance is mainly related to the strong synergistic effect between preferential orientation and V_O. The preferential orientation of V_O-p-TNT along [001] direction reduces the formation of complex centers at grain boundaries as the form of interfacial states and potential barriers, which improves the separation and transport of photogenerated carriers. Meanwhile, V_O&nbsp;provides abundant coordination unsaturated sites for methane chemisorption and also acts as electron traps to hinder the recombination of electrons and holes, establishing an effective electron transfer channel between adsorbed CH₄&nbsp;molecule and photocatalyst, thus weakening C–H bond. In addition, the introduction of V_O&nbsp;broadens the light absorption range. As a result, V_O-p-TNT exhibits excellent PNOCM performance and provides new insights into catalyst design for CH₄&nbsp;conversion.

Synthesis of uniformly ordered single-crystalline TiO2 nanorods on flexible Ti substrate

With high conductivity and ionic mobility, one-dimensional (1D) titanium dioxide (TiO2) nanoarrays have attracted great interest in the photoanode of solar cells and the cathode of lithium-ion/sodium-ion batteries. However, the synthesis of TiO2 nanoarrays often requires highly toxic or corrosive solution circumstances. Meanwhile, the case that most TiO2 nanoarrays are grown on rigid conductive substrate can’t satisfy the demand for application in the space of complex shape. In this work, we developed a simple method to prepare highly ordered single crystalline rutile TiO2 nanorod arrays with high density on flexible metal Ti substrate in relatively weak acid solution, and the orientation of the nanorods were more uniform than those by other means ever before. Based on detailed analysis, an ion-assisted and concentration-limited epitaxial growth mechanism by H+ and is proposed for this uniformly ordered rutile TiO2 nanorod array. This work can promote the research and application of flexible solar cells and lithium-ion batteries, especially their integration.