Thickness Of TiO2 Layer Research Articles

Optimizing Hybrid Perovskites for High-Efficiency Solar Energy

Our research explores hybrid perovskite solar cells, promising low-cost and high-efficiency photovoltaic solutions. Despite challenges, optimizations like interface engineering enhance performance for future commercial use. Study of different physical parameters with the help of SILVACO and MATLAB Simulink for cell modeling. Long-term stability and cost reductions are among the most significant challenges to broad commercialization Future research will be around trying different parameter values. There searcher said this project represents an important step forward in the development of hybrid perovskite solar cells, which could be a key partof a new wave of clean energy sources that are needed as global consumption levels continue to rise. The solar cells studied herein are detailed by the six-scan structure: Glass/Indium Tin Oxide (ITO) / Electron Transport Layer - (N layer) - Active Layer (Perovskite) - Hole transport_layer (Payer) - Metal Electrode; Glass/ITO/TiO2/Pero_Aardes Spiro-OMeTAD/Au. It delivers the energy conversion efficiency of 19.12% with a fill factor (FF) of 80.53%, an open-circuit voltage at Voc =1.14 Vandshort circuit current density Jsc=20.88 mA/cm²,respectively The active layer is a 0.25 -thick CH3NH3PbI3 perovskite, and the TiO2 layer thickness was set at 0.02

Histological and scanning electron microscopy investigation of the effects of titanium surface modifications on osseointegration in rabbits.

This study aimed to compare the novel Estaş Medical Anodization (EMA) surface treatment technique with the techniques commonly used in the literature and to examine their effects on osteointegration in the rabbit tibia. A total of 24 rabbits used in this study were divided into 3 groups, with 8 rabbits in each group. Using both tibias of all rabbits in the study, screws belonging to the control group were placed in the left tibia, and the right tibia belonging to the experimental group were placed. In the first 8 rabbits, a single experimental group in the right tibia were used; in the second 8 rabbits, 2 different experimental groups in the right tibia were used; and in the last 8 rabbits, 2 different experimental groups in the right tibia were used. Thus, 5 different experimental groups with 8 screws in each group and a separate control group were formed for each of them. EMA-treated surfaces were named 200-800 nm iris oxidation and 800-1200 nm gray oxidation according to the TiO2 layer thickness. Group 1 was implanted with mini-screws prepared with chemical etching+EMA iris oxidation, while group 2 was implanted with sandblasted, large-grit and acid-etched (SLA) mini screws treated with EMA gray oxidation. Group 3 was implanted with mini-screws treated with EMA gray oxidation, group 4 was implanted with mini-screws treated with chemical etching+micro-arc oxidation, and group 5 was implanted with mini-screws treated with chemical etching+EMA gray oxidation. The control group was implanted with mini-screws prepared with pure titanium. At the end of 6 weeks, osseointegration percentages were calculated and compared using histological and scanning electron microscope (SEM) analyses. The histological results confirmed the increase in osseointegration percentages in all experimental groups compared to those that received pure titanium implants (P values control group vs group 1=.005, control group vs group 2, 3, 4, 5=.001). The comparison between the groups revealed that the chemical etching+EMA gray oxidation modification technique (group 5) significantly increased osseointegration compared to the SLA+EMA gray oxidation technique (group 5 vs group 2 P=.016) and the chemical etching+EMA iris oxidation technique (group 5 vs group 1 Pp=.001). The EMA gray oxidation technique (group 3) significantly increased osseointegration compared to the chemical etching+EMA iris oxidation technique (group 1) (group 3 vs group 1 P=.043). The results of the SEM analysis showed that osseointegration was significantly increased in all experimental groups compared to that in the pure titanium (control) group (P values control group vs group 1, 2, 3=.001, control group vs Group 4,5=.006). The mean osseointegration percentage in the experimental groups was the highest in group 5, followed by group 4, group 3 and group 1 equally, and group 2. However, the differences among the experimental were not significant (group 1, group 2, group 3, group 4 vs group 5 P=.408). The EMA titanium surface modification techniques we developed significantly increased osseointegration compared to the pure titanium surface. The EMA gray oxidation technique seems to result in higher osseointegration rates than the EMA iris oxidation technique, and similar rates can be found with the SLA and chemical etching techniques. N/A.

Photocatalytic Edge Growth of Conductive Gold Lines On Microstructured TiO2-ITO Substrates.

Titanium dioxide is well-known for its excellent photocatalytic properties. UV-controlled photodeposition of gold on TiO2 is achieved by photocatalytic reduction of precursor ions from a tetrachloroauric solution. During the growth process on the surface, clusters grow from nucleation centers and coalescence is observed for sufficiently long UV illumination times, resulting in gold structures with complex shapes. Here, we hypothesize and demonstrate that the growth process is altered by employing an ITO sublayer below the TiO2 layer. Photocatalytic gold growth experiments on a microstructured thin film stack of 6 nm ITO and 70 nm TiO2 lead to strongly localized gold growth along the edge of the patterned area. A conductive gold line with a height of 3.8 μm is achieved along the edge of the TiO2-coated region, while gold growth on the surface of TiO2 is effectively suppressed. For substrates coated only with ITO or TiO2, no edge growth is observed. Furthermore, for an 845 nm thick TiO2 layer, either with or without ITO sublayer, gold growth on the TiO2 surface is dominant. Thus, for the effective steering of electrons to the edge, both the ITO sublayer and a sufficiently thin TiO2 layer are necessary. This modified method of photocatalytic deposition─electrons photogeneration in a thin layer, collection in a dedicated conductive sublayer, and growth by reduction at a different position─opens opportunities for localized material deposition. We are in particular aiming at extending the toolbox of neuromorphic engineering by providing a technical implementation of stimulus-controlled dynamic formation of directional conductive interlinks.

TiO2‐Based Schottky Diodes as Bidirectional Switches for Bipolar Resistive Memories

This study presents TiO2‐based Schottky diodes designed as bidirectional switches for bipolar resistive memories. The TiO2 films in these Schottky diodes are prepared through an anodization process. The reverse current of these diodes exhibits an exponential increase with rising reverse voltage, ultimately matching the forward current. When two diodes are connected back‐to‐back, they demonstrate superior current–voltage symmetry and provide a wider off‐state voltage range compared to a single diode, reaching up to 3.65 V. The adjustable off‐state voltage range (0.40–3.65 V) of the switch, whether utilizing two diodes or a single diode, correlates well with the TiO2 layer thickness and oxygen partial pressure during Pt electrode sputtering. These diodes possess bidirectional switching characteristics and can serve as effective switch elements to address the sneak‐path issue in bipolar resistive memories.

The Effect of the TiO2 Anodization Layer in Pedicle Screw Conductivity: An Analytical, Numerical, and Experimental Approach.

The electrical stimulation of pedicle screws is a technique used to ensure its correct placement within the vertebrae pedicle. Several authors have studied these screws' electrical properties with the objective of understanding if they are a potential source of false negatives. As titanium screws are anodized with different thicknesses of a high electrical resistance oxide (TiO2), this study investigated, using analytical, numerical, and experimental methods, how its thickness may affect pedicle screw's resistance and conductivity. Analytical results have demonstrated that the thickness of the TiO2 layer does result in a significant radial resistance increase (44.21 mΩ/nm, for Ø 4.5 mm), and a decrease of conductivity with layers thicker than 150 nm. The numerical approach denotes that the geometry of the screw further results in a decrease in the pedicle screw conductivity, especially after 125 nm. Additionally, the experimental results demonstrate that there is indeed an effective decrease in conductivity with an increase in the TiO2 layer thickness, which is also reflected in the screw's total resistance. While the magnitude of the resistance associated with each TiO2 layer thickness may not be enough to compromise the ability to use anodized pedicle screws with a high-voltage electrical stimulator, pedicle screws should be the subject of more frequent electrical characterisation studies.

Photoelectrochemical, all-soluble iron redox-flow battery for the direct conversion of solar energy

A photoelectrochemical redox-flow battery (RFB) employing an all-soluble, aqueous coordination chemistry of the element iron is developed. The system is based on the ferro/ferricyanide redox couple as posolyte, the iron-triethanolamine (TEOA) complex as negolyte and a Ge/GaAs/GaInP triple-junction solar cell (TJSC) as power source. Combining a discharging flow-cell with the photoelectrochemical unit, we enable an operando monitoring of degradation phenomena at the working electrode similar to a rotating ring-disc electrode (RRDE). In this manner, an irreversible deactivation of an unprotected TJSC is observed after 15 h of operation. In a post-mortem SEM/EDX analysis, this performance loss is identified to result from a dissolution of the top junctions of the photoabsorber. Mitigating this corrosion is achieved by introducing a 150 nm thick protection layer of TiO2 via reactive sputtering. In this manner, a stable performance for more than 120 h is obtained. In view of the fact that the iron species selected for this study are affordable, abundant, water-based and non-toxic our device is a prototype of a green photoelectrochemical RFB at laboratory scale.

In-Depth Analysis on the Fabry-Perot Effect of Cs2AgBiBr6 Double Perovskite-Based Solar Cells via Optical Path Length Modulation

Herein, the Fabry-Perot (F-P) interference of cesium silver bismuth bromide (Cs2AgBiBr6) double perovskite solar cells has been analyzed by modulating the optical path length of each layer step by step using the finite-difference time-domain (FDTD) method. The study was performed pass through three main steps. In step 1, for the fluorine-doped tin oxide (FTO)/Cs2AgBiBr6 double perovskite/gold (Au) architecture, we increased the absorption layer thickness from 150 to 600 nm at intervals of 150 nm and then predicted the optical performance including the absorption and reflection. In step 2, titanium dioxide (TiO2) layer was added between FTO electrode and Cs2AgBiBr6 double perovskite and then scaled from 20 to 200 nm at intervals of 20 nm. In the analysis process, short-circuit current density (Jsc) repeatedly fell and rose as the TiO2 layer thickness increased, and when TiO2 layer thickness is 100 nm, Jsc showed the highest value of 13.91 mA/cm2. In step 3, by applying a spiro-OMeTAD layer between the Cs2AgBiBr6 double perovskite absorption layer and Au electrode, the Jsc showed a continuous increase with slight decrease as the spiro-OMeTAD layer thickness increased from 110 to 200 nm, and when the spiro-OMeTAD layer thickness was 200 nm, Jscwas calculated as 14.57 mA/cm2, which is the highest value in the range. In the case of the optimal condition of full structure device, the Fabry-Perot resonance peaks were discovered at 477, 520, 572, 659, and 778 nm five wavelength regions, and the influence of the Fabry-Perot resonance on the generation rate inside the absorption layer on the 520, 572, and 659 nm monochromatic wavelength light was analyzed according to the position in the device. Our study approaches the Cs2AgBiBr6 double perovskite solar cell from an F-P cavity perspective and shows the light trapping phenomenon of the device according to the optical path length modulation.

Exploring the impact of electron transport layer thickness and morphology on perovskite infiltration and photoresponse in HTM-free self-powered photodetector

Methylammonium lead Iodide (MAPbI3) is emerging as the frontrunner for high-performance photo-detection due to its superior optoelectronic characteristics and ease of processing. Titanium dioxide (TiO2) is the commonly employed electron transport layer in conventional perovskite-based photodetectors. However, the fundamental understanding of the role of TiO2 morphology and its thickness on the photodetector performance is yet to be explored explicitly. This work systematically investigates the impact of morphology (mesoporous versus compact TiO2 layer) and thickness of the TiO2 layer (50 nm – 3000 nm) on the MAPbI3 photodetector performance. The devices have been fabricated in a hole transport material (HTM)-free architecture with carbon as the top contact. The heterojunction between MAPbI3 and TiO2 renders the device with self-powered capability. The influence of the perovskite sensitisation in the TiO2 electrodes, carrier recombination characteristics and charge-carrier transfer resistances have been studied using photoluminescence and impedance spectroscopy. The TiO2 layer morphology and thickness affected the MAPbI3 infiltration and film formation kinetics. Impedance and photoluminescence spectroscopies reveal that TiO2 layers, with thickness above 460 nm, negatively affected the device performance. An optimum thickness of 460 nm-mesoporous TiO2 layer exhibited a superior responsivity and rise time of 2.9 A/W and 21 ms, respectively. The poor performance at higher thicknesses is due to the increased interfacial charge transfer resistance and charge carrier recombination. This work is the first report of extensive optimisation and study on the impact of TiO2 film morphology and thickness on the MAPbI3 photodetectors. The present work will be a key for modelling and designing high-performance perovskite photodetectors.

Insight into conduction band density of states at c-Si/TiO2 interface for efficient heterojunction solar cell

Carrier selective solar cell has become one of the hot spots in the area of Si solar cell. The proposed architecture FTO/TiO2/c-Si/i-a-Si:H/Cu2O/back contact studied through simulation demonstrates a power conversion efficiency of 20.03%. This study is the first to report detailed exploration of effect of the conduction band density of states on the efficiency of Si solar cell. Through optimization, the conduction band density of state (1017 cm-3) drastically increases the power conversion efficiency from 18% (at 1021 cm-3) to 21.25% (at 1017 cm-3) i.e., an improvement of 18% relatively. Along with this, the parameters like absorber layer thickness, absorber’s defect density, thickness of electron transport layer and interface defect density are also optimized. Moreover, the charge transport properties and the impact of the Schottky barrier height at c-Si/TiO2 interface on band alignment is studied. After optimization of various physical parameters such as thickness (100 μm), conduction band density of states (1017 cm-3) and defect concentration (1010 cm−3) of c-Si layer, thickness of TiO2 layer (20 nm) and interface defect density at c-Si/TiO2 junction (1010 cm−2), a short-circuit current of 38.11 mA cm−2, open-circuit voltage of 0.84 V, fill factor of 85.99% is obtained, leading to an enhanced theoretical power conversion efficiency of 27.77%.

Tailoring crystallisation of anatase TiO2 ultra-thin films grown by atomic layer deposition using 2D oxides as growth template

TiO2 ultrathin films are required in many material research areas. The anatase phase was found to be more stable in case of atomic layer deposition growth, nevertheless a critical thickness of around 10 nm appears necessary to obtain crystallization on native silicon oxide on Si (001). This work focuses on direct liquid injection Atomic Layer Deposition (ALD) of TiO2 films with thicknesses about some nanometers, using titanium tetra-isopropoxide as precursor and H2O as oxidant. A particular care to the treatment of ellipsometric measurements is employed. Below the threshold value, films remain amorphous unless the growth starts onto a crystalized surface, a thick TiO2 layer in our case. Here we propose and show the efficiency of 2-dimensional (2D) [Ca2Nb3O10]− and [Ti0.865O2]0.54− nanosheets as seeds at the surface for the crystallization and epitaxy of ultra-thin films of TiO2 below the critical thickness. Furthermore, we show that the structure of the 2D nanosheets determines the growth orientation of the epitaxial anatase, namely (010) for [Ti0.865O2]0.54−, and (100) for [Ca2Nb3O10]−. These results, based on the tailoring of crystal anisotropy via adapted 2D seed nanosheets and low temperature ALD, opens the way for opto-electronics applications of titanium oxide layers of a few unit cells.

Efficiency performance of Ag-CdSe quantum dots nanocomposite sensitized solar cells

An in-depth analysis of a solar cell with a photoanode made of glass/FTO/TiO2, and Ag- CdSe quantum dots (QD) nanocomposite, an electrolyte of iodide and triiodide, and a Pt electrode is presented in this work. We looked at how CdSe QD filling factors and Ag nanoparticles affect the solar cell's ability to absorb light. Additionally, the effects of nanocomposite layer thicknesses, Iodide/triiodide layer thicknesses, and TiO2 layer thicknesses on the absorption are investigated. It has been discovered that the Ag nanoparticles have an effect on the absorbance around 700 nm, dropping around 800 nm while keeping the range from 400 nm to 600 nm constant as the fraction of silver increases. With the switch to CdSe, the solar cell's performance was only marginally altered. When the composite thickness is increased to 200 nm, the value of A has the highest values and is expanded to include longer wavelengths. While altering the thickness of the iodide/triiodide layer (di) causes the highest values of A to expand at di = 200 nm. However, the performance of the solar cell is unaffected by the TiO2 layer's thickness (dt). As a result, we gave a solar cell the variables that impacted its performance.

Enhancing photoelectrocatalytic activity and stability of p-Cu2O photocathode through n-TiO2 coating for improved H2 evolution reaction

This article presents a novel approach to improve both the photoelectrocatalytic activity and stability of the p-Cu2O photocathode. The approach involves the coating of an n-type TiO2 layer using e-beam evaporation with precise controllability of the coating thickness onto the p-type Cu2O electrode, forming a TiO2/Cu2O p/n heterojunction. Such a p/n junction enhances the photoelectrocatalytic activity of the Cu2O electrode by promoting the separation of the photo-generated charge carriers. Additionally, the large bandgap TiO2 coating layer serves as protection, reducing the photocorrosion of Cu2O, thereby improving the stability of the electrode. The n-TiO2/p-Cu2O photocathode shows superior photoelectrochemical H2 evolution activity in comparison to the pristine p-Cu2O photocathode. We have found that the thickness and annealing temperature of TiO2 influence strongly the photocurrent and stability of the resultant TiO2/Cu2O photocathode. The best TiO2/Cu2O photocathode was achieved by coating a 50 nm thick TiO2 layer onto the Cu2O, followed by annealing at 350 °C. This configuration exhibited a large onset photovoltage of 0.58 V vs RHE and a catalytic current density of ∼0.9 mA·cm‒2 at 0 V vs RHE in a pH 7 phosphate buffer, under standard 1 Sunlight illumination.

Modelling TiO2 photoanodes for PEC water splitting: Decoupling the influence of intrinsic material properties and film thickness

Semiconductor metal oxides are intensively studied in electrodes for photoelectrochemical (PEC) water splitting. On a series of nanoparticulate TiO2 photoanodes, we analyze specific fabrication variables by means of data fitting. First, the experimental outcome is gathered using PEC characterization techniques, mostly cyclic voltammetry and transient photocurrent measurements. Subsequently, we apply models to gain insights into the involved charge trapping and transfer phenomena. We find that capacitance coefficients and the switch-on transient kinetics depend on the TiO2 layer thickness, respectively indicating surface mechanisms and stationary regimes that are mediated by light accessibility. On the contrary, exponential factors of capacitance are independent of thickness, but reflect changes in the density of electron states with different sintering atmospheres. Also, the transfer resistance in the electrolyte side is indirectly influenced by sintering. Through meticulous quantitative analysis of trends, we stablish simple mathematical relationships that connect thickness-dependent parameters. This knowledge delves into fundamental mechanisms governing the TiO2 photoelectrode behaviour, and aims to facilitate further improvements in the efficiency of materials and electrodes for green hydrogen production.

Device Simulation of a Thin-Layer CsSnI3-Based Solar Cell with Enhanced 31.09% Efficiency

In the last decade, perovskite-based solar cells (PSCs) have become the hotspot in photovoltaic (PV) research around the globe because of their excellent photovoltaic performance in terms of their high-power conversion efficiency. However, the stability and existence of lead in the perovskite absorber layer hindered their use in practical applications. In the present study, we evaluated the numerical simulation-based performance of oxide/perovskite/oxide-type PSCs using the one-dimensional solar cell capacitance program (SCAPS-1D). Initially, the effect of various oxide-based electron transport layers (ETLs; TiO2, SnO2, and ZnO) and hole transport layers (HTLs; NiO, Cu2O, and CuO) on PSC performance was evaluated. It was found that a solar cell with TiO2 as an ETL and NiO as an HTL (FTO/n-TiO2/CsSnI3/p-NiO) exhibited the highest PV performance in terms of power conversion efficiency (PCE ∼ 30.57%), and other parameters were open circuit voltage (VOC ∼ 0.98 V), short circuit current density (JSC ∼ 35.17 mA/cm2) and fill factor (FF ∼ 88.43%). Next, we evaluated the effect of the thickness of TiO2, NiO, and CsSnI3 layers of the above-benchmarked device, along with their bulk and interface defects in detail. It is successfully demonstrated that the PCE and FF can further reach values of 31.09 and 88.39%, respectively, at a 1.25 μm thick CsSnI3 absorber with a band gap of Eg ∼ 1.35 eV. The obtained results and detailed analysis will provide an important basis for the selection of CsSnI3 as an absorber with optimized defects.

Titanium oxide nanomaterials as an electron-selective contact in silicon solar cells for photovoltaic devices

To obtain high conversion efficiency, various carrier-selective contact structures are being applied to the silicon solar cell, and many related studies are being conducted. We conducted research on TiO2 to create an electron-selective contact structure that does not require a high-temperature process. Titanium metal was deposited using a thermal evaporator, and an additional oxidation process was conducted to form titanium oxide. The chemical compositions and phases of the titanium dioxide layers were analyzed by X-ray diffraction. The passivation effects of each titanium oxide layer were measured using the quasi-steady-state photoconductance. In this study, the layer properties were analyzed when TiO2 had a passivation effect on the silicon surface. The charge and interface defect densities of the layer were analyzed through CV measurements, and the passivation characteristics according to the TiO2 phase change were investigated. As a result, by applying optimized TiO2 layer thickness and annealing temperature conditions through the experiment for passivation to the cell-like structure, which is the structure before metal and electrode formation, an implied open-circuit voltage (iVoc) of 630 mV and an emitter saturation current density (J0) value of 60.4 fA/cm2 were confirmed.

Enhancing the photocatalytic properties of doped TiO2 nanowires grown by seed-assisted thermal oxidation

In the present paper, an investigation of the structural, optical, and photo-catalytical properties of TiO2 nanowires (NWs) was conducted. The NWs were synthesized on a Si substrate by thermal oxidation of a thick (4 µm) Ti film covered by a thin (∼ 5 nm) Au film. The annealing process at 750 °C produced a 1.7 μm thick NWs TiO2 layer over a 3 μm thick TiO2 film. Characterization techniques show that TiO2 NWs are in rutile phase and have gold nanoparticles on top. Fe-doped TiO2 NWs were synthesized to increase photoactivity in the visible range. The doping was performed using an unusual strategy, that is, implanting Fe+ ions into the Ti layers before the growth of the TiO2 NWs. The defectiveness introduced by the ion implantation is avoided and precise control of the doping is achieved. The photocatalytic properties were studied by following the degradation of methylene blue. In order to increase the photo-degradation rate under UV light of undoped NWs, two different strategies have been followed: 1) deposition of Pt nanoparticles on the front or on the rear side of the samples, and 2) thermal annealing in a reductive environment. A three-fold activity enhancement is obtained and discussed. Photocatalytic activity in the visible range was also measured for the Fe-doped samples, showing good activity, which was further improved by using the same strategies implemented under UV irradiation.

Effect of the TiO2 electron transport layer thickness on charge transfer processes in perovskite solar cells

Dense TiO2 thin films are widely used as electron transport layers in perovskite solar cells. TiO2 is a high band gap semiconductor with n-type conductivity showing excellent compatibility with metal-halide perovskites in terms of energy alignment providing efficient charge separation and less energy loss of electrons during electron transfer. In this work, TiO2 layers were deposited from TiO2 sol-gel solution by spin-coating methods. The optimization of TiO2 ETL thickness is a necessary procedure to reduce ETL resistance and minimize charge recombination. The thickness reduction leads to a decrease in resistance, however, also enhances charge recombination due to the formation of pin-holes and cracks. We found that TiO2 thickness reduction also causes the TiO2 defects density changes. By studying luminescence spectra of TiO2 with various thicknesses we found that the thickness reduction leads to the increase in the interstitial Ti+3 defects density, while the oxygen vacancies density decreases. Ti+3 species form deep levels trapping free electrons and as result increasing TiO2 resistance. TiO2 films with thicknesses in the range of 40–120 nm were deposited and used as ETL for PSCs with ITO/TiO2/CH3NH3I3PbClx/CuPc/MoOx/Ag structure. Our study revealed two competitive charge transport processes taking place in TiO2: electron transport through the TiO2 conduction band and electron trapping by deep trap levels formed by Ti+3 species. Therefore according to the IV and IS studies, the optimal TiO2 layer thickness at which there is a balance between the competitive charge transport processes is about 60 nm for our deposition condition.

Advanced ceramics in radical filtration: TiO2 layer thickness effect on the photocatalytic membrane performance

Membranes with advanced oxidation processes (AOPs) are a promising combination to separate and degrade organic pollutants in a single system. In this work, we describe the fabrication and characteristics of nine membranes with different TiO2 top layer thicknesses (from 0.26 to 21.9 μm), giving attention to the critical catalyst thickness and the formation of defects. We also report the optimum photocatalyst thickness for our single-layer membranes (∼2.74 μm), after which more titanium dioxide does not improve the degradation. However, an increase in degradation for membranes with multiple TiO2 layers was still possible. These results and the comparisons with the literature suggested that the optimal catalyst thickness is closely related to the material morphology. We obtained a maximum degradation at the lower filtration rate (1.6 L m−2 h−1) of 72% with a single layer membrane of 3.4 μm and 82% with a membrane with six layers of 21.9 μm. Furthermore, a 1D mass transport and reaction model that describes the coating thickness effect was developed and fitted with the experimental data. Other parameters are also discussed, such as light penetration limitations, surface area, and surface reaction rate constant. These results and analysis provide a better understanding of the fabrication and optimization of photocatalytic membranes.

Surface and interface properties of TiO2/CuO thin film bilayers deposited by rf reactive magnetron sputtering

Thin film bilayers of TiO2/CuO with intentionally varied thickness of the top layer of TiO2(25–150 nm) were grown by means of sequential rf magnetron reactive sputtering from Cu and Ti metallic targets in a flow rate-controlled Ar + O2 gas mixture. XRD diffraction in GID configuration, SEM top and cross-sectional images, EDS combined with SEM, XRR profiles, UV–VIS-NIR spectrophotometry and synchrotron soft radiation XAS in TEY mode were used to characterize crystal structure, morphology, the mode of growth, chemical composition, density and roughness as well as the optical and electronic properties of the synthesized thin film bilayers. CuO bottom layer turned out to crystallize in a monoclinic structure while TiO2 top layer remained amorphous. Film roughness of CuO decreased from about 12 nm with the increasing thickness of TiO2 thin film to about 1–2 nm. X-ray absorption spectroscopy demonstrated a presence of Cu+ and Cu2+ in TiO2 top layer of TiO2/CuO heterostructure. The photoelectrochemical measurements revealed that thin film bilayers of TiO2/CuO behaved as photocathodes in the process of water splitting. The photocurrent density was found to be an increasing function of the top TiO2 layer thickness.

Heterostructured and Mesoporous Nb2O5@TiO2 Core-Shell Spheres as the Negative Electrode in Li-Ion Batteries

Niobium pentoxides have received considerable attention and are promising anode materials for lithium-ion batteries (LIBs), due to their fast Li storage kinetics and high capacity. However, their cycling stability and rate performance are still limited owing to their intrinsic insulating properties and structural degradation during charging and discharging. Herein, a series of mesoporous Nb2O5@TiO2 core-shell spherical heterostructures have been prepared for the first time by a sol-gel method and investigated as anode materials in LIBs. Mesoporosity can provide numerous open and short pathways for Li+ diffusion; meanwhile, heterostructures can simultaneously enhance the electronic conductivity and thus improve the rate capability. The TiO2 coating layer shows robust crystalline skeletons during repeated lithium insertion and extraction processes, retaining high structural integrity and, thereby, enhancing cycling stability. The electrochemical behavior is strongly dependent on the thickness of the TiO2 layer. After optimization, a mesoporous Nb2O5@TiO2 core-shell structure with a ∼13 nm thick TiO2 layer delivers a high specific capacity of 136 mA h g-1 at 5 A g-1 and exceptional cycling stability (88.3% retention over 1000 cycles at 0.5 A g-1). This work provides a facile strategy to obtain mesoporous Nb2O5@TiO2 core-shell spherical structures and underlines the importance of structural engineering for improving the performance of battery materials.