Fluorine-doped Tin Oxide Substrate Research Articles

Properties of Electrosynthesized Cobalt Doped Zinc Selenide Thin Films Deposited at Varying Time

Time optimized cobalt-doped zinc selenide thin films have been successfully electrodeposited on fluorine-doped tin oxide substrates. The films were deposited at the varying time of 1 min, 3 mins, and 5 mins respectively. Film thickness, optical, structural, electrical, and morphological properties of the deposited thin films were evaluated. Film thickness estimated using the gravimetric method increased from 294.35 nm to 399.62 nm as deposition time increased. Optical properties showed that the absorbance of the films ranged from 13.58% to 83.15% and was found to increase as deposition time increased. Transmittance ranged from 24.40% to 73.15% and was found to decrease as deposition time increased. The reflectance of the films was found to be low while the energy band gap ranged between 2.10 eV and 2.85 eV. Structural properties confirmed the deposition of ZnSe thin film with crystallite size values that fall between 14.68 nm and 18.60 nm. Dislocation density is ranged from 4.66 × 1015 lines/m2 to 2.97 × 1015 lines/m2 while microstrain ranged between 8.53 × 10-3 and 5.83 × 10-3. Crystallite sizes of the films were found to increase as deposition time increased while dislocation density and microstrain were found to decrease as deposition time increased. Electrical properties showed that the deposited films are semiconducting films with electrical resistivity values of 1.54 × 105 Ω cm-1.83 × 104 Ω cm and electrical conductivity values of 6.30 × 10-6 S/cm-5.47 × 10-5 S/cm. The micrograph of the films showed that the films were made up of nanoparticles and nanofibres of different dimensions. Energy-Dispersive X-Ray Spectroscopy (EDS) spectra of the films confirmed the presence of cobalt, zinc, and selenium.

Evaluation of the Effect of Deposition pH on the Physico-chemical Properties of Electrochemically Deposited Cadmium Telluride for Photovoltaic Device Applications

Two-electrode (2E) configuration was successfully utilised in the electrochemical deposition of cadmium telluride (CdTe) on fluorine-doped tin oxide (FTO) substrate with the main emphasis on the electrolytic bath pH. The electrochemical deposition pH explored is within the range of (1.00 to 6.00)±0.02 for the aqueous electrolyte comprising of tellurium oxide (TeO2) and cadmium nitrate (Cd(NO3)2) which are the respective precursors of Te and Cd. The optical, structural, morphological, compositional, and electrical properties of the electroplated CdTe thin-films were respectively explored using UV-Vis spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and photoelectrochemical (PEC) cell measurements. The optical characterisation show that the CdTe samples exhibit dissimilar absorbance depending on the growth pH for both the as-deposited layers and post-growth treated CdTe layers. A decrease in the absorption edge slope and dip in the bandgap was observed away from pH2. The bandgap of the post-growth treated CdTe layers showed enhancement as it leans towards 1.45 eV, with the trend retention of absorption edge slope, similar to the as-deposited CdTe layers. The electrodeposited CdTe thin-films show a dominant orientation along the cubic (111) CdTe plane, while both the the calculated crystallite size and the XRD peak intensity Pi decreases with the electroplating pH outside the (2.00 to 3.00)±0.02 range. The EDX analyses depicts an alteration in the ratio of Cd to Te atomic percentage relative to the pH of the electrolyte. Comparatively high Te atomic ratio was observed at lower pH values and vice versa with increase alkalinity of the electrolyte. The obtained morphology depicts that the underlying FTO layers are well covered with a gradual reduction in the grain size of the CdTe observable away from pH value (2.00 and 3.00). The photoelectrochemical cell study depicts that the conduction type of the CdTe layers can also be attributed to the CdTe-electrolytic bath pH value.

Evaluation of the Effect of Deposition pH on the Physico-chemical Properties of Electrochemically Deposited Cadmium Telluride for Photovoltaic Device Applications

Two-electrode (2E) configuration was successfully utilised in the electrochemical deposition of cadmium telluride (CdTe) on fluorine-doped tin oxide (FTO) substrate with the main emphasis on the electrolytic bath pH. The electrochemical deposition pH explored is within the range of (1.00 to 6.00)±0.02 for the aqueous electrolyte comprising of tellurium oxide (TeO2) and cadmium nitrate (Cd(NO3)2) which are the respective precursors of Te and Cd. The optical, structural, morphological, compositional, and electrical properties of the electroplated CdTe thin-films were respectively explored using UV-Vis spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and photoelectrochemical (PEC) cell measurements. The optical characterisation show that the CdTe samples exhibit dissimilar absorbance depending on the growth pH for both the as-deposited layers and post-growth treated CdTe layers. A decrease in the absorption edge slope and dip in the bandgap was observed away from pH2. The bandgap of the post-growth treated CdTe layers showed enhancement as it leans towards 1.45 eV, with the trend retention of absorption edge slope, similar to the as-deposited CdTe layers. The electrodeposited CdTe thin-films show a dominant orientation along the cubic (111) CdTe plane, while both the the calculated crystallite size and the XRD peak intensity Pi decreases with the electroplating pH outside the (2.00 to 3.00)±0.02 range. The EDX analyses depicts an alteration in the ratio of Cd to Te atomic percentage relative to the pH of the electrolyte. Comparatively high Te atomic ratio was observed at lower pH values and vice versa with increase alkalinity of the electrolyte. The obtained morphology depicts that the underlying FTO layers are well covered with a gradual reduction in the grain size of the CdTe observable away from pH value (2.00 and 3.00). The photoelectrochemical cell study depicts that the conduction type of the CdTe layers can also be attributed to the CdTe-electrolytic bath pH value.

Photoelectrochemical Degradation of Organic Pollutants on a La3+ Doped BiFeO3 Perovskite

Towards nonconventional wastewater treatment methods for the degradation of organic pollutants in wastewater, a perovskite-based photoelectrochemical system was developed. Bismuth ferrite doped with lanthanum (La-BiFeO3, La-BFO) perovskite was synthesised through a hydrothermal method with low calcination temperature for the photoelectrochemical degradation of orange II dye and other cocktails of dyes. Photoanodes were prepared by the deposition of the perovskites on a fluorine-doped tin oxide (FTO) substrate. The photoanodes were characterised using XRD, FESEM, FTIR and UV-vis diffuse reflectance. The photoelectrochemical properties of the synthesised photoanodes were investigated with chronoamperometry and electrochemical impedance spectroscopy (including Mott–Schottky analysis). The results show that all La3+-doped BFO photoanodes exhibited a higher absorption edge in the visible light region than the undoped BFO. The photocurrent response of 10% La-BFO (the best performing electrode) exhibited a three times higher current response than the pure BFO. In addition, the electrode exhibited a good degradation efficiency of 84.2% within 120 min with applied bias potential of 2 V at a pH of 7. EIS studies showed a significant enhancement of the interfacial electron transfer of the charge carriers. The enhancements in electrode performances were attributed to the synergistic effect of the applied bias potential and the introduction of La3+ into the BFO matrix. This study therefore shows that the photoelectrocatalytic performance of BFO for water treatment can be improved by the introduction of perovskites-doping ions such as La3+.

Study of structural, optical and electrochemical properties of GO/TiO2 nanostructures prepared by microwave-assisted technique for its application as a glucose sensor

The present work proposes a microwave-assisted technique for the synthesis of graphene oxide and titanium dioxide (GO/TiO2) nanocomposite. XRD, FESEM, EDS, UV, FTIR, Raman, and XPS spectroscopy were employed to study the elemental composition and surface morphology of the nanocomposite. FESEM revealed the spherical morphology of GO/TiO2 nanocomposite. It was observed that nanosized densely packed spherical TiO2 particles were attached to graphene sheets. A modified electrode was prepared using fluorine-doped tin oxide (FTO) substrate for electrochemical detection of the non-enzymatic glucose sensor. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were adopted for the electrochemical measurements of GO/TiO2/FTO electrodes. The high sensitivity of 426.5 μA mM−1.cm2, the linear detection range of 0.1 mM to 11 mM, the low detection threshold of 0.1 μM along with quick response time of 6 s towards glucose sensing are some highlights of the prepared electrode. Moreover, the microwave technique used for the preparation of GO/TiO2 composite is rapid and cost-effective.

Impact of Solvent type on the Structural, Surface morphology and Optical energy gap of Kesterite Cu2ZnSnS4 thin films deposited by solvothermal method

In present work kesterite quaternary Cu2ZnSnS4 (CZTS) semiconductor thin films were prepared on fluorine-doped tin oxide (FTO) substrate by solvothermal method using different solvent types Ethylene glycol (EG), polyethylene glycol (PEG), and Ethylenediamine (ED). Crystal structure, surface morphology and optical characteristics of the prepared thin film were characterized by x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and UV–Vis absorption spectroscopies. X-ray diffraction results reveal that the deposited films have polycrystalline nature and in a kesterite phase (tetragonal structure). the crystallite size is in the rang (20-27) nm and the largest one is for the prepared by using PEG solvent. The films surface morphology shows smooth and uniform surface with well distributed spherical particles with largest particles for the films deposited by EG solvent. The EDS spectra confirmed the the existence of the elements Cu, Zn, Sn and S of the films composition. The direct optical energy gap shows different values caused by using different solvent type, where the lower band gap is about 1.56 eV and the largest is about 1.9 eV for the films using ED and EG respectively.

Modification of Ti-doped hematite nanowires with a NiOx buffer layer for improved photoelectrochemical performance

Hematite (α-Fe2O3) is a promising photoanode material for photoelectrochemical (PEC) water splitting due to its appropriate bandgap, good stability, and earth-abundance. However, the poor charge transfer property and sluggish kinetics of water oxidation limit the PEC performance of α-Fe2O3 photoanodes. Herein, a thin NiOx buffer layer was introduced between the Ti doped α-Fe2O3 (Fe2O3-Ti) layer and the fluorine-doped tin oxide (FTO) substrate without affecting the nanowire morphology and light absorption property of Fe2O3-Ti. This buffer layer can apparently suppress the charge recombination by mitigating the lattice mismatching between the Fe2O3-Ti film and the FTO substrate. In addition, the good conductivity of the NiOx film from the non-stoichiometric composition is also beneficial to the charge transfer. As a consequence, the photocurrent density was greatly improved by adding the NiOx layer in the Fe2O3-Ti photoanode, reaching 1.32 mA·cm−2 at 1.23 VRHE without any co-catalyst and sacrificial agent. This work gives a detailed analysis of the back contact in the hematite-based photoanode and provides an effective strategy for underlayer interface optimization.

Facile Fabrication of a Highly Crystalline and Well-Interconnected Hematite Nanoparticle Photoanode for Efficient Visible-Light-Driven Water Oxidation

Facile and scalable fabrication of α-Fe2O3 photoanodes using a precursor solution containing FeIII ions and 1-ethylimidazole (EIm) in methanol was demonstrated to afford a rigidly adhered α-Fe2O3 film with a controllable thickness on a fluorine-doped tin oxide (FTO) substrate. EIm ligation to FeIII ions in the precursor solution brought about high crystallinity of three-dimensionally well-interconnected nanoparticles of α-Fe2O3 upon sintering. This is responsible for the 13.6 times higher photocurrent density (at 1.23 V vs reference hydrogen electrode (RHE)) for photoelectrochemical (PEC) water oxidation on the α-Fe2O3 (w-α-Fe2O3) photoanode prepared with EIm compared with that (w/o-α-Fe2O3) prepared without EIm. The w-α-Fe2O3 photoanode provided the highest charge separation efficiency (ηsep) value of 27% among the state-of-the-art pristine α-Fe2O3 photoanodes, providing incident photon-to-current conversion efficiency (IPCE) of 13% at 420 nm and 1.23 V vs RHE. The superior ηsep for the w-α-Fe2O3 photoanode is attributed to the decreased recombination of the photogenerated charge carriers at the grain boundary between nanoparticles, in addition to the higher number of the catalytically active sites and the efficient bulk charge transport in the film, compared with w/o-α-Fe2O3.

Defective Indium Tin Oxide Forms an Ohmic Back Contact to an n-Type Cu2O Photoanode to Accelerate Charge-Transfer Kinetics for Enhanced Low-Bias Photoelectrochemical Water Splitting.

In significant contrast to the tremendous research efforts mostly geared to addressing the severe hole accumulation at the back contact of a p-type Cu2O photocathode with a fluorine-doped tin oxide (FTO) substrate, sluggish electron transfer from an n-type Cu2O photoanode to a tin-doped indium oxide (ITO) substrate has been largely overlooked. To tackle this issue that has been reported to largely limit the photoelectrochemical performance of n-type Cu2O photoanodes at a low bias, the present contribution puts forward a strategy to introduce oxygen vacancies into the ITO substrate via an unprecedented yet facile electrochemical approach. Such defect engineering turns out to decrease the work function of the ITO substrate, which in turn approaches the conduction band extremum of n-Cu2O to highly efficiently extract the photoexcited electrons therein. Moreover, the dendritic growth of n-Cu2O is, in the meantime, interfered by the oxygen vacancy manifested as pinholes distributed over the ITO substrate, which is thereby crystallized into several small grains with augmented surface roughness that is in favor of the injection of the photoexcited hole into the electrolyte. Such facile interfacial charge-transfer kinetics leads to a significant cathodic shift amounting to 200 mV of the onset potential to 0 VAg/AgCl, whereat the n-Cu2O photoanode deposited on the defective ITO substrate delivers the maximum photocurrent density reaching 2 mA cm-2 and, more significantly, its applied bias photon-to-current efficiency (ABPE) reaches 1.1%, which is among the highest performance reported to date for a variety of state-of-the-art metal oxide-based photoanodes in the literature.

Effect of Growth Time on the Structural, Optical and Electrical Properties of the 1%Fe doped TiO2 p-type Synthesized by Hydrothermal Technique

In this work, a hydrothermal technique is employed to prepare titanium dioxide films on fluorine-doped tin oxide (FTO) substrates. A low-cost homemade autoclave was used to fabricate iron-doped -TiO2 films (1at. %Fe) at different reaction times from 1 to 4 hours. X-ray diffraction (XRD) patterns showed that the predominant phase is rutile (R-TiO2) with peaks at (101), (002), and (112). The XRD results showed that with increasing reaction time the peaks become sharper and narrowed. The images of the field emission scanning electron microscope (FESEM) showed that with increasing reaction time the films appeared to have vertically aligned TiO2 nanorods. The atomic force microscope (AFM) results illustrated that surface roughness and the root means square was decreased with increasing the reaction time. UV-visible spectroscopy analysis revealed that the energy bandgap value (Eg) decreased with reaction time up to 3 hours. Urbach energy for the grown films was found to be decreased with increasing growth time. The electrical measurements indicated that all TiO2 films had p-type conductivity.

Effect of Electrosynthesis Potential on Nucleation, Growth, Adhesion, and Electronic Properties of Polypyrrole Thin Films on Fluorine-Doped Tin Oxide (FTO).

Polypyrrole (PPy) is one of the most attractive conducting polymers for thin film applications due to its good electrical conductivity, stability, optical properties, and biocompatibility. Among the technologies in which PPy has gained prominence are optoelectronics and solar energy conversion, where transparent electrodes such as fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) are frequently used. However, FTO substrates have the notable advantage that their components are widely available in nature, unlike those of ITO. Recognizing the importance that the FTO/polypyrrole system has gained in various applications, here, we studied for the first time the nucleation and growth mechanism of electro-synthesized PPy on FTO. Additionally, the effect of the synthesis potential (0.9, 1.0, 1.1, and 1.2 V vs. Ag/AgCl) on the homogeneity, adhesion, conductivity, and HOMO energy levels of PPy films was determined. From current–time transients and scanning electron microscopy, it was found that films synthesized at 0.9 and 1.0 V exhibit 3D growth with progressive nucleation (as well as lower homogeneity and higher adhesion to FTO). In contrast, films synthesized at 1.1 and 1.2 V follow 2D growth with instantaneous nucleation. It was also evident that increasing the polymerization potential leads to polymers with lower conductivity and more negative HOMO levels (versus vacuum). These findings are relevant to encourage the use of electro-synthesized PPy in thin film applications that require a high control of material properties.

NiFeOx decorated Ge-hematite/perovskite for an efficient water splitting system

To boost the photoelectrochemical water oxidation performance of hematite photoanodes, high temperature annealing has been widely applied to enhance crystallinity, to improve the interface between the hematite-substrate interface, and to introduce tin-dopants from the substrate. However, when using additional dopants, the interaction between the unintentional tin and intentional dopant is poorly understood. Here, using germanium, we investigate how tin diffusion affects overall photoelectrochemical performance in germanium:tin co-doped systems. After revealing that germanium is a better dopant than tin, we develop a facile germanium-doping method which suppresses tin diffusion from the fluorine doped tin oxide substrate, significantly improving hematite performance. The NiFeOx@Ge-PH photoanode shows a photocurrent density of 4.6 mA cm−2 at 1.23 VRHE with a low turn-on voltage. After combining with a perovskite solar cell, our tandem system achieves 4.8% solar-to-hydrogen conversion efficiency (3.9 mA cm−2 in NiFeOx@Ge-PH/perovskite solar water splitting system). Our work provides important insights on a promising diagnostic tool for future co-doping system design.

The Influence of the Thickness of Compact TiO2 Electron Transport Layer on the Performance of Planar CH3NH3PbI3 Perovskite Solar Cells.

In recent years, lead halide perovskites have attracted considerable attention from the scientific community due to their exceptional properties and fast-growing enhancement for solar energy harvesting efficiency. One of the fundamental aspects of the architecture of perovskite-based solar cells (PSCs) is the electron transport layer (ETL), which also acts as a barrier for holes. In this work, the influence of compact TiO2 ETL on the performance of planar heterojunction solar cells based on CH3NH3PbI3 perovskite was investigated. ETLs were deposited on fluorine-doped tin oxide (FTO) substrates from a titanium diisopropoxide bis(acetylacetonate) precursor solution using the spin-coating method with changing precursor concentration and centrifugation speed. It was found that the thickness and continuity of ETLs, investigated between 0 and 124 nm, strongly affect the photovoltaic performance of PSCs, in particular short-circuit current density (JSC). Optical and topographic properties of the compact TiO2 layers were investigated as well.

Thermal Evaporation Synthesis of Vertically Aligned Zn2SnO4/ZnO Radial Heterostructured Nanowires Array.

The construction of a heterostructured nanowires array allows the simultaneous manipulation of the interfacial, surface, charge transport, and transfer properties, offering new opportunities to achieve multi-functionality for various applications. Herein, we developed facile thermal evaporation and post-annealing method to synthesize ternary-Zn2SnO4/binary-ZnO radially heterostructured nanowires array (HNA). Vertically aligned ZnO nanowires array (3.5 μm in length) were grown on a ZnO-nanoparticle-seeded, fluorine-doped tin oxide substrate by a hydrothermal method. Subsequently, the amorphous layer consisting of Zn-Sn-O complex was uniformly deposited on the surface of the ZnO nanowires via the thermal evaporation of the Zn and Sn powder mixture in vacuum, followed by post-annealing at 550 °C in air to oxidize and crystallize the Zn2SnO4 shell layer. The use of a powder mixture composed of elemental Zn and Sn (rather than oxides and carbon mixture) as an evaporation source ensures high vapor pressure at a low temperature (e.g., 700 °C) during thermal evaporation. The morphology, microstructure, and charge-transport properties of the Zn2SnO4/ZnO HNA were investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and electrochemical impedance spectroscopy. Notably, the optimally synthesized Zn2SnO4/ZnO HNA shows an intimate interface, high surface roughness, and superior charge-separation and -transport properties compared with the pristine ZnO nanowires array.

Optoelectronics applications of electrodeposited p- and n-type Al2Se3 thin films

Abstract In this paper, energy band gaps and electrical conductivity based on aluminum selenide (Al2Se3) thin films are synthesized electrochemically using cathodic deposition technique, with graphite and carbon as cathode and anode, respectively. Synthesis is done at 353 K from an aqueous solution of analytical grade selenium dioxide (SeO2), and aluminum chloride (AlCl2·7H2O). Junctions-based Al2Se3 thin films from a controlled medium of pH 2.0 are deposited on fluorine-doped tin oxide (FTO) substrate using potential voltages varying from 1,000 mV to 1,400 mV and 3 minutes −15 minutes respectively. The films were characterized for optical properties and electrical conductivity using UV-vis and photoelectrochemical cells (PEC) spectroscopy. The PEC reveals a transition in the conduction of the films from p-type to n-type as the potential voltage varies. The energy band gap reduces from 3.2 eV to 2.9 eV with an increase in voltage and 3.3 eV to 2.7 eV with increase in time. These variations indicate successful fabrication of junction-based Al2Se3 thin films with noticeable transition in the conductivity type and energy band gap of the materials. Consequently, the fabricated Al2Se3 can find useful applications in optoelectronic devices.

Facet controlled growth mechanism of SnO2 (101) nanosheet assembled film via cold crystallization

Cold crystallization of SnO2 was realized in aqueous solutions, where crystal growth was controlled to form SnO2 (101) nanosheet assembled films for devices such as chemical sensors. The nanosheets grew directly on a fluorine-doped tin oxide substrate without a seed layer or a buffer layer. The nanosheets had a thickness of 5–10 nm and an in-plane size of 100–1600 nm. Moreover, the large flat surface of the (101) facet was metastable. The thickness of the SnO2 (101) nanosheet assembled film was approximately 800 nm, and the film had a gradient structure that contained many connected nanosheets. TEM results revealed that the predominate branch angles between any two connected nanosheets were 90° and 46.48°, corresponding to type I and type II connections, respectively. These connections were consistent with the calculations based on crystallography. Crystallographic analysis clarified the characteristic crystal growth of the SnO2 (101) nanosheet assembled film in the aqueous solution. Furthermore, we demonstrate that the metastable (101) facet can be exploited to control the rate of crystal growth by adjusting the etching condition.

Novel TiO2/Bi4Ti3O12 nanorod arrays decorated with Co-Pi for boosted solar photoelectrochemical water splitting

We present a simple methodology to construct novel Co-Pi decorated TiO 2 /Bi 4 Ti 3 O 12 nanorod (TiO 2 /BTO@Co-Pi NR) arrays as photoanode for enhanced water splitting. By using successive ionic layer adsorption and reaction (SILAR) method, controllable amounts of BiOI nanoplates were uniformly immobilized on the hydrothermal grown TiO 2 NR arrays on Fluorine-doped tin oxide (FTO) substrate. TiO 2 /BTO NR heterojunction was conveniently obtained by partial conversion of TiO 2 to high crystallized Bi 4 Ti 3 O 12 through a solid-state reaction with BiOI nanoplates at high temperature. Afterwards, Co-Pi nanoparticles were deposited on TiO 2 /BTO by photoelectrical deposition to generate TiO 2 /BTO@Co-Pi composites. Photoelectrochemical (PEC) measurements have demonstrated that the prepared TiO 2 /BTO photoanode exhibits extremely enhanced performance than pristine TiO 2 for PEC water splitting thanks to the increased visible light absorption and photogenerated charge separation efficiency. Moreover, both the photocurrent density and incident photo-to-current conversion efficiency (IPCE) were further improved after the decoration of Co-Pi. This work provides a feasible and low-cost strategy to establish TiO 2 /Bi 4 Ti 3 O 12 based photoelectrode, therefore, is suitable for practical applications. • Novel TiO 2 /Bi 4 Ti 3 O 12 nanorod arrays were easily constructed by simple SILAR and solid-state reaction. • Controllable Bi 4 Ti 3 O 12 could be formed by adjusting the SILAR cycles to achieve a optimium photocurrent. • BTO can largely enhance the IPCE and photocurrent density, which were further improved by Co-Pi nanoparticles.

Pseudocapacitive energy storage properties of rGO-WO3 electrode synthesized by electrodeposition

This article focuses on the eco-friendly and facile fabrication of well-defined hybrid electrode favorable in supercapacitor devices with the aim of studying its electrochemical properties. Reduced graphene oxide/tungsten trioxide (rGO-WO3) hybrid electrode has been fabricated by a constant potential of −0.6 V on fluorine-doped tin oxide (FTO) substrate using one-pot electrodeposition technique combined with a subsequent calcination at 450 °C. The fabricated electrodes are examined by energy dispersive X-rays spectroscopy (EDX), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis to confirm the existence of each composition in the active material. The crystalline nature of tetragonal WO3 phase is verified by XRD analysis. The porous structures of WO3 nanoparticles with uniformly dispersed onto the rGO sheet are observed from scanning electron microscopy (SEM) examinations. FT-IR and Raman spectra confirm the characteristic peaks of GO, rGO, and interaction of WO3 with rGO. Besides, the electrochemical behaviors of the fabricated electrodes/electrolyte interface are broadly studied by several methods such as cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and Mott-Schottky in 1 M H2SO4 aqueous solution. Based on CV analysis, the rGO-WO3 electrode acts as better redox behavior in the potential between (−0.7 V) and (+0.2 V) than that of bare WO3 electrode, resulting in maximum specific capacitance value of 60.3 F/g at 5 mV/s. The GCD measurement displays a maximum specific capacitance value of 58.3 and 42.6 F/g at a current density of 1 A/g for rGO-WO3 and WO3 electrode, respectively. The n-type conductive characteristic of both electrodes is confirmed by Mott-Schottky measurement. The calculated donor density is 3.64 × 1020 cm−3 and 7.03 × 1020 cm−3 for WO3 and rGO-WO3, respectively. An equivalent circuit model is designed according to the Nyquist plot, and RCT value of the rGO-WO3 electrode is found to be 12.57 Ω. The synergetic interaction between carbon-based material and metal oxides opens up a way for forming a promising electrode to be used in energy storage devices.

Enhanced performance of ultra-thin polyaniline supercapacitor via aniline blue-WS SAMs with rich nucleation site

We report the ultrathin supercapacitor’s superior performance via the vertically aligned one-dimensional polyaniline structure (1D PANI) growth on the fluorine-doped tin oxide (FTO) substrate. FTO electrodes were treated by the molecular-self assembly, and the effects of different self assembled monolayers (SAMs) on both the evolution of PANI and electrochemical performance were examined. We obtained 809.09 F g−1 specific capacitance from ∼120 nm thick PANI (at 20 mV s−1 scan rate of cyclic voltammetry) via aniline blue water soluble SAMs modification. The supercapacitor’s internal dynamics were clarified by a new equivalent circuit model developed from the Graham model. Through the new model, accurate information about double-layer capacitance, percolation capacitance, and bulk capacitance, which composes the electrode’s capacitive performance, could be obtained. This work provided novel knowledge to develop PANI deposition and hence to achieve greater capacitances.

Novel (CH6N3+, NH3+)-functionalized and nitrogen doped Co3O4 thin film electrochemical sensor for nanomolar detection of nitrite in neutral pH

The present work provides a soft chemical route for simultaneous nitrogen doping and (CH6N3+, NH3+)-functionalization of pre-deposited Co3O4 thin film. The Co3O4 thin film was prepared by metal-organic decomposition (MOD) on fluorine-doped tin oxide (FTO) substrate and hydrothermally treated in the presence of amino acid, L-Arginine. The L-Arginine-treated Co3O4 thin film (L-Arginine/Co3O4/FTO) was used for the electrochemical detection of nitrite under neutral pH condition. Various physical (i.e. XRD, XPS, SEM, and Raman spectroscopy) and electrochemical characterization (i.e. CV, CA, EIS, and Tafel slope) was conducted to elucidate the role and effect of L-Arginine on Co3O4 film and determine the sensor performance characteristics. L-Arginine/Co3O4/FTO electrode exhibited a low limit of detection of 1.95 nM, an ultrafast response time of <2 s, and a wide linear range of up to 16 mM in neutral pH. The sensor was nitrite selective in the presence of common interferants and showed chemical stability and reproducibility. The practical application of the proposed sensor was demonstrated using real samples for nitrite detection.