FTO Substrate Research Articles

Spray‐pyrolysis synthesis of CuMnO2 with the potential for photoelectrocatalysis

AbstractAmidst the global endeavor toward sustainable energy sources, photocatalysis appears as a promising gateway toward the production of solar fuels, in particular hydrogen. Hydrogen is currently a crucial reagent for vital industries such as petrol desulfurization, iron reduction and ammonia production, so the decarbonization of its production is a major challenge. CuMnO2 (CMO), a p‐type semiconductor, has been shown to enhance the efficiency of catalysts such as TiO2 for the photoelectrocatalytic water splitting reaction. However, since pure CMO thin films have never been reported, its potential and limitations remain elusive. We used spray pyrolysis as a low‐cost synthesis technique to simplify and accelerate the synthesis of CMO thin films directly on FTO substrates. CMO prepared in this manner exhibits activity toward photoeletrocatalytic water splitting and O2 reduction. The activity has been found to be highly dependent on synthesis conditions, especially on the ratio and volume of precursors.

Sol-Gel Derived ZnO Thin Films with Nonvolatile Resistive Switching Behavior for Future Memory Applications

Herein we report on a facile sol-gel spin-coating technique to fabricate ZnO thin films that grow preferentially along the (002) plane on FTO substrates. By employing the magnetron sputtering technique to deposit a tungsten (W) top metal electrode onto these ZnO thin films, we successfully realize a W/ZnO/FTO memory device that exhibits self-rectifying and forming-free resistive switching characteristics. Notably, the as-prepared device demonstrates impressive nonvolatile and bipolar resistive switching behavior, with a high resistance ratio (RHRS/RLRS) exceeding two orders of magnitude at a reading voltage of 0.1 V. Moreover, it exhibits ultralow set and reset voltages of approximately +0.5 V and −1 V, respectively, along with exceptional durability. In terms of carrier transport properties, the low resistance state of the device is dominated by ohmic conduction, whereas the high resistance state is characterized by trap-controlled space-charge-limited current conduction. This work highlights the potential of the ZnO-based W/ZnO/FTO memory device as a promising candidate for future high-density nonvolatile memory applications.

Design engineering of photoanode and counter electrode using lanthanum titanate infused natural dyes and activated carbon to enhance the performance of dye sensitized solar cells

Perovskite material of LaTiO3 has been synthesized by sol-gel technique and coated over TiO2 coated FTO substrate. Soxhlet extractor is used to extract the natural dyes from Cordyline Fruticosa and Clitoria Ternatea and perovskite material incorporated TiO2/FTO substrate is immersed in the dye solution to serve as photoanode material. The mixture of dye and perovskite material/TiO2 is characterized by UV–Visible, FTIR, XRD, SEM and Raman spectroscopy. The activated carbon prepared from coconut shell is served as counter electrode and sandwiched with Photoanode and electrolyte (I−/I3−) Redox couple to obtain the solar cell. The fabricated solar cells are subjected to JV characteristics and it is found that the cell with dyes from Cordyline Fruticosa with Perovskite/TiO2 has given highest efficiency of 0.494 % due to the rapid charge transfer from the dye to the semiconductor oxide material with decreased recombination of electrolyte.

Mullite-type Bi2Mn4O10 thin films prepared by a PVA-assisted sol–gel method

Mullite-type Bi2Mn4O10 is an attractive material for several potential applications, such as energy conversion and storage, data storage, batteries and photoelectrochemical devices. Bi2Mn4O10 thin films were prepared by sol–gel from a simple and highly stable precursor solution, based on the corresponding metal nitrate salts, acetic acid and polyvinyl alcohol. The films were deposited by dip-coating onto FTO substrates and dried at 350 °C; the dipping-drying cycle was repeated six times and the films were finally sintered at 600 °C. The films were characterized using GIXRD, revealing an excellent match with the ICDD database and previous studies. The UV–Vis measurements showed a direct band gap of 1.78 eV for the films. Raman spectroscopy permitted the identification of the Ag, B1g and B2g vibrational modes. The electrical properties via Hall effect measurements showed that the Bi2Mn4O10 thin films exhibit an n-type semiconductor behavior. Finally, the FESEM micrographs and AFM images revealed homogeneous, nanostructured thin films. In summary, through this comprehensive characterization, it was observed that high quality, nanocrystalline semiconductor thin films of Bi2Mn4O10 can be produced using this simple sol–gel method.

Properties Enhancement of Cu2O/TiO2 Heterostructure Film Using Two-step Hydrothermal and Potentiostatic Deposition Method

Two-steps hydrothermal were demonstrated to create a high efficiently interfacial layer of TiO2 thin film. The first hydrothermal was conducted to synthesize a well-aligned and compact structure of TiO2 nanorods on FTO substrate. Etching treatment in an acidic medium of hydrochloric acid (HCl) as a second hydrothermal favors increasing the surface area prior to any deposition to be a heterostructure film. The morphology of nanorods changed while the electrical resistivity decreased, demonstrating that the etching treatment had a substantial effect on the TiO2 thin film properties. Cyclic voltammetry (CV) was conducted prior deposition. The electrodeposition of Cu2O on the TiO2 thin film was fabricated by using copper acetate-based solution with pH value of 12.0 at bath temperature of 60°C. The finding revealed that the pyramidal structure of Cu2O film was deposited uniformly, which is believed that the properties of TiO2 interfacial layer were excellently improved.

Impact of Cu2+ precursor on physical and photoelectrochemical properties of electrodeposited nanostructured CuS thin films for biosensor applications

Nanostructured CuS films were synthesized on FTO substrates employing low-cost electro deposition technique. XRD, Raman, SEM, UV–visible spectroscopy, photocurrent, PL, Mott-Schottky, and electrochemical impedance spectroscopy (EIS) measurements were used to examine physical and photoelectrochemical properties of samples. XRD results indicated that CuS films have hexagonal crystal structure where the crystallite size raises from 32 to 53 nm with increasing the Cu2+ molarity. Raman results displayed two peaks at 270 and 450 cm−1 that related to A1g transverse optical mode (TO) and A1g longitudinal optical (LO) mode for the vibrations of the S–S stretching and Cu–S bonds, respectively. SEM images displayed that fabricated CuS cover the substrate surface entirely, where grains are distributed uniformly with increasing the Cu+2 molarity. UV–visible measurements exhibited an absorption band edge between 450 and 550 nm as a characteristic of CuS films direct band gap. PL results presented strong blue-green emission at about 500 nm for CuS thin films. The photocurrent studies demonstrated that the CuS films are p-type semiconductors where the current density increases from 0.8 mA/cm2 to 1.1 mA/cm2 with the Cu2+ molarity increasing. The EIS analysis confirmed that charge transfer resistance reduces with increasing molarity. Mott- Schottky measurements established that carrier concentrations and the flat band varied from 5 × 1019 to 6.7 × 1019 cm−3 and from 1.1 to 0.75V, respectively. The fabricated CuS film was tested as glucose biosensor where a fast response and higher stability were noticed. Our results indicated that nanostructured CuS films are gifted candidates for optoelectronics applications especially biosensors.

Photoelectrode FTO/ Anodized TiO2 Production and Characterization for Methylene Blue Affected Photoelectrochemical Decomposition

Background: The production of thin film TiO2 nanostructured systems for electrocatalytic, photocatalytic, and photoelectrocatalytic applications has been an essential topic in recent years. Due to the light-sensitive effect of TiO2, it can be produced by various methods and used as a photoelectrode to remove dye. Using magnetron sputtering, Ti thin films can be deposited on different substrates and converted into transparent TiO2 structures by electrochemical anodization. Methods: In this study, the thin Ti film was produced using a magnetic spraying technique on the FTO substrate, and then an anodic TiO2 structure was obtained by the anodization technique. TiO2 films produced by the anodizing technique were used as a photoelectrode for the degradation of MB. The reactor contained 400 mL of 20 mg/L MB solution at 20 °C. The produced photoelectrode was characterized by the SEM/EDS, FTIR, XRD, and UV-Vis Spectrophotometer analyses. Results: The EDS analysis confirmed the presence of titanium and oxygen in the FTO/ Anodized TiO2 photoelectrode. The XRD results showed that all the peaks of the produced FTO/ Anodic TiO2 were associated with the anatase phase of TiO2. According to the FTIR spectroscopy, the functional groups of the anodized TiO2 were obtained for the FTO/ Anodized TiO2. The electrocatalytic, photocatalytic, and photoelectrocatalytic degradation experiments were performed with the degradation of the dye solution of MB on the FTO/ Anodic TiO2 photoelectrode, and the rates of dye degradation were determined as 17.12%, 64.67%, and 82.12%, respectively. Conclusion: This study showed that the methylene blue dye of FTO/ Anodic TiO2 is a suitable photoelectrode for electrocatalytic, photocatalytic, and photoelectrocatalytic degradation.

Influence of growth temperature on structural, optical, morphological and photoelectrochemical characteristics of vertically aligned hydrothermally synthesized TiO2 nanorods

Herein, vertically oriented TiO2 nanorods were prepared on FTO substrate using hydrothermal synthesis. The influence of growth temperature on structural, optical, morphological and photoelectrochemical characteristics were analyzed. The FESEM and AFM results validated the formation of TiO2 nanorods. XRD spectra revealed the formation TiO2 tetragonal crystal structure with the rutile phase. UV–vis data showed an increase in the visible light absorption and a narrowing of the energy band gap with increasing in reaction temperature. Based on PEC studies, all the samples showed good light response and pronounced photocurrent density under light conditions. The highest possible photocurrent density of 78.8 μA/cm2 at 1.2V vs Ag/AgCl was recorded from TiO2 film with hydrothermal growth temperature of 200°C for 3 h s. This performance is attributed to narrow bandgap (2.89eV) and longer lifetime of carriers (0.3s). This result was validated by data from EIS, whereby the fast separation and transfer of photogenerated charge carriers were demonstrated.

Improved charge kinetics of BiVO4/MoS2 photoanode by an TiO2 electron transport layer for photocatalytic fuel cell photodegradation and electricity generation

The poor contact between the photocatalyst and the FTO substrate are the main factors lead to the low performance of photocatalytic fuel cell (PFC). Herein, a FTO pre-treated with a TiO2 electron transport layer was used as a substrate for the synthesis of the MoS2/BiVO4/pre-FTO photoanode. The proposed MBV-4/pre-FTO photoanode with its enhances the visible light absorption and effectively delays the recombination of the photoexcited charge. The MBV-4/pre-FTO composite photoanode (6.02 mA/cm2) exhibited a photocurrent density that was 2.2 times higher than that of the BiVO4 photoanode (2.78 mA/cm2). This is attributed to the short charge migration length of the thin MoS2 layer, the fast photoexcited electron transport effect of the TiO2 seed layer, and the heterojunction structure of the proposed photoanode. The DFT calculation result indicated that the TiO2 electron transport layer showed an outstanding photoelectron attractive and transporting effect. The MoS2/Ni foam was employed as the photocathode to establish a mismatched Fermi level for driving PFC. The short-circuit current, open-circuit voltage, and maximum power density of the PFC were 0.578 mA/cm2, 0.632 V, and 0.125 mW/cm2, respectively. The main photodegradation active species are the superoxide anion (∙O2–) and the photoexcited hole (h+), and the degradation efficiency is 61.97 %.

Cu-doped NiO thin film's structural, optical, and electrical properties and its negative absorption behaviour in the Infra-Red region

NiO undoped and Cu-doped thin films on FTO-coated glass (fluorine-doped tin oxide) are prepared by employing the sol-gel spin coating method. The Cu-doping effect was observed in all the characterized reports such as absorption, transmittance, field emission scanning electron microscope (FESEM), Grazing Incidence X-ray Diffraction (GIXRD), photoluminescence (PL), Raman spectra, current-voltage measurement (IV), and X-ray photoelectron spectroscopy (XPS). Enhancement in electrical conductivity due to Cu doping and IR illumination has been found. Band gap can also be tuned by varying doping concentrations. One new phenomenon called negative absorption (NA) has been found while investigating the optical properties in the infrared (IR) region for both undoped and Cu-doped NiO on the FTO substrate, which opens a new door for advanced research. The multifarious properties of NiO thin films offer various applications in many different fields.

Dewetting of Pt Nanoparticles Boosts Electrocatalytic Hydrogen Evolution Due to Electronic Metal‐Support Interaction

AbstractSolid‐state dewetting is the heat‐induced agglomeration of thin metal films into defined nanoparticles (NPs). Dewetted Pt nanoparticles are investigated on F‐doped SnO2 (FTO) substrates as model binder‐free electrodes for the hydrogen evolution reaction (HER). Dewetting of Pt films into particles exposes the FTO substrate and the metal/support (Pt‐FTO) contact line. Despite the decrease in Pt electrochemical surface area (ECSA) upon dewetting, dewetted NPs show a >3‐fold increase in ECSA‐normalized HER activity compared to as‐deposited nanocrystalline Pt films. Electrodes designed with dewetted Pt NPs of different sizes show that the HER activity does not only correlate with the ECSA but also increases with increasing the Pt‐FTO contact line length. The smaller the NPs, the larger the Pt‐FTO contact line, and the higher the activity. This effect is ascribed to electronic metal‐support interaction (EMSI), due to electron transfer from FTO to Pt. It is proposed that EMSI effects alter the electronic structure of Pt sites near the Pt‐FTO contact line, facilitating the H2 evolution kinetics. When NPs are a few nm‐sized, a large mass fraction of Pt is affected by EMSI, resulting in a further increase of HER activity compared to NPs ≥10 nm despite the lower ECSA.

Investigating the synergistic effect of ZnO/GO nanocomposite films for methylene blue removal

AbstractThis study aims to reveal the growth kinetics of ZnO nanoflakes and ZnO/GO nanocomposite films obtained at different Zn precursor salt concentrations by electrochemical deposition method and to evaluate the catalytic performances of the obtained films. The films were grown on FTO substrate with Zn precursor salt concentrations of 0.1 M, 0.125 M, and 0.175 M. Characterization of the obtained films was performed by XRD, SEM, UV–vis–NIR, Raman, and XPS analyses. The strong photocatalytic capabilities of the synthesized ZnO nanoflakes and ZnO/GO nanocomposite films were demonstrated by comparative analyses with the existing literature. Accordingly, photocatalytic experiments carried out under UVA irradiation revealed the high performance of the synthesized samples in the degradation of MB dye. The reaction kinetics were investigated using the Langmuir‐Hinshelwood kinetic model, resulting in high kobs values and R2 coefficients. ZnO nanoparticles showed a kobs of 0.038 min−1 and an R2 value of 0.96, while ZnO/GO nanocomposite films showed a kobs of 0.055 min−1 and an R2 value of 0.92. The significant increase in the degradation percentage shows the significant improvement achieved by the integration of GO, despite a slightly lower R2 value for the ZnO/GO nanocomposite film compared with ZnO nanoflakes films.

Gold nanostructure-enhanced immunosensing: ultra-sensitive detection of VEGF tumor marker for early disease diagnosis

We present an advanced electrochemical immunosensor designed to detect the vascular endothelial growth factor (VEGF) precisely. The sensor is constructed on a modified porous gold electrode through a fabrication process involving the deposition of silver and gold on an FTO substrate. Employing thermal annealing and a de-alloying process, the silver is eliminated from the electrode, producing a reproducible porous gold substrate. Utilizing a well-defined protocol, we immobilize the heavy-chain (VHH) antibody against VEGF on the gold substrate, facilitating VEGF detection through various electrochemical methods. Remarkably, this immunosensor performs well, featuring an impressive detection limit of 0.05 pg/mL and an extensive linear range from 0.1 pg/mL to 0.1 µg/mL. This emphasizes it’s to measure biomarkers across a wide concentration spectrum precisely. The robust fabrication methodology in this research underscores its potential for widespread application, offering enhanced precision, reproducibility, and remarkable detection capabilities for the developed immunosensor.

Chiral Covalent Organic Framework Films with Enhanced Photoelectrical Performances.

The desirable superimposed stacking of two-dimensional covalent organic frameworks (2D COFs) benefits out-of-plane charge transfer, whereas the actual stacking deviation cannot leverage the potential of 2D COFs for optoelectrical applications. Herein, we report a chirality-induced strategy to control the parallel AA-stacking sequence for the β-ketoenamine-linked COF film supported on a FTO substrate. The resulting chiral modules are periodically distributed at the framework node, ensuring identical mirrored configurations of layers for parallel stacking. Such unique architectonics exhibit the prolonged charge carrier lifetime, fast charge-transfer dynamics, and ultrahigh electron collection efficiency, thereby allowing for the excellent photocurrent response of 38 μA/cm2 at 0.25 V (vs RHE). The origin of superior performances lies in the intensified exciton gradient distribution and electron density for photoinduced electron-hole dissociation and charge transfer, in stark contrast to achiral analogues. This study highlights the stacking sequence regulated by chiral nanoarchitectonics and promises great potential of chiral COFs in photoelectrical catalysis.

Synergetic effect of the SENSTIZER DERIVED from the flowers, leaves and stems of Senna auriculata for light HARVESTING and photogeneration in dye sensitized solar cell

Senna auriculata is a tolerant leguminous tree in drought and dry climatic condition and for the first time the leaves, leaf stems and flowers of Senna auriculata has been mixed to extract the dye using ethanol. Dye is enriched with the pigments of chlorophyll, anthraquinones, tannins, alkaloids, flavonoids, phenols, saponins, terpenoids, glycosides and triterpenoids which are indispensable for the sensitizer to be used in dye sensitized solar cell applications. Optical absorption wavelength, the chemical constituent's group and emission wavelength of the dye is studied using FTIR, UV–Visible and photoluminescence spectroscopy. The well-characterized dye is used as sensitizer in the photoanode which soaks the FTO substrate/TiO2 nanorods and sandwiched with the Graphite coated FTO counter electrode along with the electrolyte of iodide/triiodide of the solar cell. SEM photographs for the formation of randomly oriented TiO2 nanorods on the FTO substrate has been taken and confirmed. Two cells have been made with the dye of 5 g and 10 g in 50 ml of ethanol and tested for the better concentration on the performance of the cell. The cells have produced efficiency of 1.9656% and 1.8286% with fill factor of 0.7897 and 0.7840 which have light deviation from each other.

Activated carbon synthesized from Jack wood biochar for high performing biomass derived composite double layer supercapacitors

In this study, the electrochemical properties of bioderived activated carbon-based electrodes for supercapacitors formed using a sintered ceramic binder were investigated. Activated carbon derived from Jack wood tree (Artocarpus heterophyllus) with variable amounts of TiO2 nanoparticles as a binder, were used as electrodes in order to get good, activated carbon films on FTO substrates. No other binders were used in this study since most conventional binders devastate the electrical conductivity in the films. Furthermore, TiO2 has higher temperature tolerance compared to polymeric binders thus the electrode prepared can be used in wider applications. A series of electrochemical double-layer capacitors were fabricated and characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The supercapacitors prepared showed double-layer capacitive behavior. The electrodes that contain 90 % activated carbon and 10 % TiO2 show optimum performance along with an impressive specific capacitance of 147 F g−1 at 2 mV s−1 scan rate. This supercapacitor exhibits a power density of 68.5 W kg−1 while the energy density is 8.02 Wh kg−1. When the power density is as high as 1186.51 W kg−1 the energy density drops to 5.71 Wh kg−1. According to cyclic voltammetry measurements taken for 1000 cycles, the supercapacitor shows excellent cycle stability without any traces of capacitance drop.

Nanocone-substrated BiVO4-Mo/MOFs photoanodes for highly efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) performance of photoanode is limited by the cascade-dynamic processes, mainly including light absorption, charge separation, and surface reaction. This work adopted a strategy of nanocones modification on FTO substrate (FTO-NC) to enhance light utilization and photoelectrons collection for improved PEC water splitting. Comparative studies showed that FTO-NC enhanced the light scattering, promoting the conversion process of photon to electron/hole and enlarging the effective surface area of BiVO4 for surface reaction. Meanwhile, cooperative Mo-doping and Co-MOF decoration improved the bulk electron transportation in BiVO4, hole migration towards the electrode surface, and accelerated the water oxidation reaction of photogenerated holes. The photocurrent density of FTO-NC/BiVO4-Mo/MOFs reached 3.56 mA cm−2, 6.14 times that of pristine BiVO4. The IPCE of FTO-NC/BiVO4-Mo/MOFs photoanode achieve 60% at 1.23 V vs. RHE, demonstrating a significantly enhanced light utilization performance. This work presents new insight into boosting cascade-dynamic processes through collaborative strategies for highly efficient PEC water-splitting.

Microwave treated dye from seeds of Syzygium cumini for the photogeneration of charge carriers and consistency of the fabricated dye sensitized solar cell

In this work, aid of microwaves has been used for the ethanolic extract of the dyes from the seeds of syzygiumcumini. The dye served as a good sensitizer in the photoanode of dye sensitized solar cell as it has greater affinity to have anchoring effect with the TiO2 coated over FTO substrate. The photoexcitation of the anthocyanin present in the dye has engendered electronic excited states to promote the electron transfer into the semiconductor oxide (TiO2) material. The key lead of the dye is the production of electronic excited states with the energy equal to that of the conduction band of TiO2. Basic characterization of FTIR and UV–Visible spectroscopy for the dye has been done and SEM photograph has been taken for the photoanode of the fabricated DSSC. The fabricated solar cell with the photoanode, graphite-based counter electrode and I−/I3− electrolyte has been tested for JV characteristics. The cell has given efficiency of 1.85 % with fill factor, open circuit voltage, short circuit current density, maximum voltage and maximum current of 0.808219, 0.9921V, 2.314 mA/cm2 0.8865V and 2.093 mA/cm2.

Optical and electronic properties of MgPc-Ch-diisoQ blend organic thin film as an active layer for photovoltaic cells.

Organic photovoltaic cells are a promising technology for generating renewable energy from sunlight. These cells are made from organic materials, such as polymers or small molecules, and can be lightweight, flexible, and low-cost. Here, we have created a novel mixture of magnesium phthalocyanine (MgPc) and chlorophenyl ethyl diisoquinoline (Ch-diisoQ). A coating unit has been utilized in preparing MgPc, Ch-diisoQ, and MgPc-Ch-diisoQ films onto to FTO substrate. The MgPc-Ch-diisoQ film has a spherical and homogeneous surface morphology with a grain size of 15.9 nm. The optical absorption of the MgPc-Ch-diisoQ film was measured, and three distinct bands were observed at 800-600 nm, 600-400 nm, and 400-250 nm, with a band gap energy of 1.58 eV. The current density-voltage and capacitance-voltage measurements were performed to analyze the photoelectric properties of the three tested cells. The forward current density obtained from our investigated blend cell is more significant than that for each material by about 22%. The photovoltaic parameters (Voc, Isc, and FF) of the MgPc-Ch-diisoQ cell were found to be 0.45 V, 2.12 μA, and 0.4, respectively. We believe that our investigated MgPc-Ch-diisoQ film will be a promising active layer in organic solar cells.

Deposition of Fe2O3:Sn semiconducting thin films by reactive pulsed HiPIMS + ECWR co-sputtering from Fe and Sn targets

Semiconducting Fe2O3 thin films were deposited on SnO2:F (FTO) and Pt substrates by reactive high-power impulse magnetron sputtering combined with electron cyclotron wave resonance plasma (HiPIMS + ECWR). Fe2O3 films were fabricated either by sputtering from a single Fe target or by co-sputtering from an additional Sn target. Plasma parameters during co-sputtering were measured by an RF probe system enabling the comparison between HiPIMS + ECWR and only HiPIMS conditions used for the film deposition. As deposited Fe2O3 films were post-annealed in air at 450 °C and 650 °C, respectively. It was shown that as deposited Fe2O3 films were amorphous but became crystalline after post-annealing at 450 °C. Further increase of annealing temperature to 650 °C did not improve significantly the crystalline structure of the Fe2O3 film. All post-annealed Fe2O3 films exhibited photocurrents in the anodic region; generally, hematite films annealed at 650 °C exhibited higher photocurrents than those annealed at 450 °C. Films doped by Sn co-sputtering had higher photocurrents than films only doped by Sn diffusion during post-annealing from the FTO substrate. Hematite films on Pt substrate doped by Sn co-sputtering and post-annealed at 650 °C exhibited the highest photocurrents. It was verified by XPS analysis with ion sputtering depth profiling that Pt atoms also diffuse from the Pt substrate into the Fe2O3 film during the post-annealing at 650 °C and can, similar to Sn in the case of an FTO substrate, act as a dopant.