This study explores the influence of various precursors including ammonium metatungstate (AMT) and peroxotungstic acid (PTA) in water, and tungsten hexachloride (WCl6 in MeOH or EtOH), as well as the role of ammonium chloride incorporation on the structural, morphological, and photoelectrochemical characteristics of WO3 layers synthesized by spray pyrolysis. X-ray diffraction (XRD) analysis revealed that films annealed at 550 °C crystallized in the monoclinic phase of WO3 with a polycrystalline structure without amorphous parts. Different morphological features of the samples were identified by scanning electron microscopy (SEM): dense grains for films formed using PTA, aggregated grains for films synthesized from AMT, smooth and uniform surfaces for films based on WCl6, and porous architectures resulting from NH4Cl incorporation. Photoelectrochemical measurements under UV and simulated solar illumination demonstrated that AMT/NH4Cl - derived WO3 films significantly enhanced the initial photocurrent density, reaching values of up to ∼3 mA cm-2 under UV light. Topological energy dispersive spectroscopy (EDS) revealed the existence of Cl rich areas responsible for this effect. With prolonged exposition to light and bias, Cl in these areas was oxidatively exhausted and average current densities as in samples obtained with other precursors were obtained. These findings highlight the critical role of precursor selection and doping in determining the photoelectrochemical performance of spray-deposited WO3 photoanodes.

Ag-doped CuWO₄ thin films with varying silver concentrations (0–4

WO3 thin films were synthesized on FTO (fluorine doped SnO2 on glass) by the hydrothermal method at 180 degrees C using different deposition times and subsequently annealed at 350 degrees C and 550 degrees C in air. The results of XRD and Raman showed complete phase transformation from WO3 hydrate into gamma-monoclinic WO3 after annealing at 550 degrees C. SEM analysis showed significant effects of deposition time and annealing on the surface morphology of the WO3 thin films. WO3 films were examined by the Scotch tape test and showed superior adhesion for samples synthetized for 2 h compared with samples synthesized for 15 h. The photoelectrochemical properties of the WO3 samples were measured. The highest photocurrent density of similar to 1.9 mA/cm(2) (E = 1.4 V vs. Ag/AgCl, 369 nm LED, irradiance 100 W/m(2)), IPCE = 0.69 at 369 nm, and 2 mA/cm(2) under simulated solar irradiation (AM1.5) was achieved for a layer thickness of 3.5 mu m.

Annealing of sprayed pure and Mg doped CuCrO _2 thin films by high intensity, short time light irradiation leads to a single delafossite phase at comparatively low temperatures compared with traditional furnace annealing. P-type crystalline undoped and Mg-doped CuCrO _2 films were obtained within few minutes by annealing with halogen lamp between 550 °C and 650 °C in Ar atmosphere. Transport properties of Mg-doped thin films were comparable to furnace annealed samples despite much shorter annealing time. The results demonstrate that post-annealing of chemically deposited samples using light irradiation is an effective and fast method for obtaining transparent conducting delafossite thin films.

One way to increase the solar cell efficiency is to increase the range of transmitted visible light throughout the window layer. This could be achieved via broadening its band gap; an aim that could be attained through doping and/or irradiation technique. In this way, cadmium sulfide (CdS) thin films have been successfully prepared on pre-heated glass substrates at 400 degrees C by spray pyrolysis technique and the effect of gamma radiation dose on the structural and optical properties of CdS thin films has been investigated in the range of 250 to 450 Gy. The XRD results manifest the formation of hexagonal phase of CdS with a crystallite size of 58.73 nm, which decreased to 47.26 nm after exposure to 350 Gy. Also, the SEM micrographs show the formation of some randomly oriented groups of nano-rods on the surface of highly condensed nanorods of CdS thin film. The optical investigation illustrates that a blue shift in the optical gap from 2.4 to 3.34 eV has been occurred as the radiation dose reached 350 Gy. The sensitivity of the films to the applied dose has approached 0.005 eV/Gy. Moreover, the shifted band gap exhibited less fading up to 74 days.

Composite ZnO-ZnWO4 films were obtained by a cost-effective chemical spray pyrolysis approach on a glass substrate using zinc chloride and ammonium metatungstate as starting precursors. The X-ray diffraction investigation indicated that the crystal structure of the obtained films was a composition of ZnO and ZnWO4 phases with the predominant ZnWO4 phase. Scanning electron microscopy images for sprayed mixed ZnO-ZnWO4 layers exhibit a porous structure. Gas sensing performance was tested for detecting carbon monoxide (CO) at different operating temperatures. It was found that the sprayed composite ZnO-ZnWO4 layer shows a maximum sensitivity of 422.7% for 30 ppm CO at 250 degrees C with good sensor performance. This study suggests that the sprayed ZnO-ZnWO4 composite layer is a good candidate material for CO detection at a relatively low operating temperature.

AbstractExploiting low‐cost, highly active, and robust oxygen evolution reaction (OER) electrocatalysts based on earth‐abundant elements by a simple synthesis approach holds paramount importance for green hydrogen production through water electrolysis. In this work, the NiO, Co3O4 and NiCo2O4 nanoparticle layers with identical surface morphologies are prepared under same deposition conditions by a simple spray pyrolysis method and their OER activities are comparatively investigated. Among all these three electrocatalysts, NiCo2O4 shows the lowest overpotential of 420 mV to drive benchmark current density of 10 mA cm−2 and the smallest Tafel slope (84.1 mV dec−1), which are comparable to the OER performance of the benchmark commercial RuO2 electrocatalyst. The high OER activity of NiCo2O4 is attributed to the synergy effect and the modulation of electronic properties between Co and Ni atoms, which drastically reduces the overpotential required to drive OER activities. Therefore, it is believed that the NiCo2O4 synthesized by this simple method would be a competitive candidate as an industrial electrocatalyst with high‐efficiency and low cost for large‐scale green hydrogen production via water electrolysis.

NiO/ZnO core–shell nanoflakes structures were successfully fabricated using a unique strategy consisting of a simple chemical bath deposition (CBD) route followed by a metal-organic chemical vapor deposition (MOCVD) technique with different growth times. The XRD results combined with Raman measurements and X-ray photoelectron spectroscopy confirmed that the surface property and photocatalytic activity of NiO/ZnO core–shell nanostructures affected by varying the growth time of ZnO on the surface of NiO nanoflakes. The Scanning electron microscopy images exhibited that the NiO/ZnO samples have a porous core–shell architecture with high surface area and abundant open sites, resulting in enhanced photocatalytic activity. The photocatalytic activity was tested for the prepared samples by measuring the degradation of crystal violet (CV) dye under ultraviolet irradiation. NiO/ZnO core–shell nanostructures deposited at 30 min exhibits higher photodegradation efficiency toward CV dye compared to NiO/ZnO core–shell deposited at 60 min and NiO nanoflakes standing alone. The enhanced photocatalytic activity is due to the formation of p–n heterojunction between ZnO and NiO with a high specific area and more active site of core–shell nanoflakes architecture. The obtained results in this research suggest a new strategy for the fabrication of highly efficient photocatalytic activity semiconducting metal oxide with core–shell.

An antimony tri-sulfide Sb2S3 nanosphere photocatalyst was effectively deposited utilizing sodium thiosulfate and antimony chloride as the starting precursors in a chemical bath deposition process. This approach is appropriate for the large-area depositions of Sb2S3 at low deposition temperatures without the sulfurization process since it is based on the hydrolytic decomposition of starting compounds in aqueous solution. X-ray diffraction patterns and Raman spectroscopy analysis revealed the formation of amorphous Sb2S3 layers. The scanning electron microscopy images revealed that the deposited Sb2S3 has integrated small nanospheres into sub-microspheres with a significant surface area, resulting in increased photocatalytic activity. The optical direct bandgap of the Sb2S3 layer was estimated to be about 2.53 eV, making amorphous Sb2S3 appropriate for the photodegradation of organic pollutants in the presence of solar light. The possibility of using the prepared Sb2S3 layer in the photodegradation of methylene blue aqueous solutions was investigated. The degradation of methylene blue dye was performed to evaluate the photocatalytic property of Sb2S3 under visible light. The amorphous Sb2S3 exhibited photocatalytic activity for the decolorization of methylene blue solution under visible light. The mechanism for the photocatalytic degradation of methylene blue has been proposed. Our results suggest that the amorphous Sb2S3 nanospheres are valuable material for addressing environmental remediation issues.

WO 3 films were chemically prepared by spray pyrolysis method using different starting tungsten precursors. The WO 3 layers were deposited at 450 °C and subsequently were heat treated at 500 °C in the air for 30 min. The effect of starting tungsten precursors on the physical properties and catalytic activity of WO 3 layers was investigated. The results of XRD show that the WO 3 films were crystalline and can be indexed to the monoclinic structure. The sample prepared using ammonium metatungstate precursor showed enhanced crystallinity and surface morphology. The diffuse reflection spectrophotometry shows that the obtained WO 3 films have a direct bandgap about of 2.7–2.9 eV. Chemical catalytic activity was evaluated through the reduction of 4-nitrophenol to 4-aminophenol. All prepared WO 3 thin films showed catalytic activity; however, the sample prepared using ammonium metatungstate precursor exhibited much higher catalytic activity when compared to the other precursors, which is consistent with other results. Furthermore, this sample demonstrated good stability and recyclability.

A facile spray pyrolysis processing of ternary Cu2SnS3 and Cu2Sn1_ xGexS3 absorbers is presented. The Cu2SnS3 and Cu2Sn1_xGexS3 thin films were sprayed onto both glass and Mo substrates at 350 degrees C and then annealed at 550 degrees C with S and SnS/GeS crystals. The impacts of germanium incorporation on the properties and solar cell device performance of the Cu2SnS3 layers were studied. X-ray diffraction and Raman measurements confirmed the monoclinic crystal structure of both Cu2SnS3 and Cu2Sn1_xGexS3 layers, with a slight peak shift observed in the Cu2Sn1_xGexS3 samples due to the substitutional incorporation of Ge into the Sn site in the Cu2SnS3 lattice. The introduction of Ge also increased the optical bandgap from 0.93 eV for Cu2SnS3 to 0.99 eV for Cu2Sn1_xGexS3 samples. Furthermore, Cu2Sn1_xGexS3 layers exhibited enhanced grain growth, leading to an improved device performance from 1% for Cu2SnS3 to 2.1% for Cu2Sn1_xGexS3 solar cells.

Two-step processes are used in the deposition of the Cu 2 ZnSnS 4 (CZTS) thin films. First, the CZTS precursors are deposited on Mo and soda-lime glass (SLG) substrates at different temperatures using the spray pyrolysis technique, followed by annealing in sulfur and tin atmosphere at 580 °C for 30 min. The impact of the substrate temperature and annealing step on structural, morphological, and optical properties of the prepared layers was studied. The annealing process improves the poor structural, morphological, and optical properties of as-deposited CZTS thin films by promoting grain size and crystallinity. The sprayed layers showed fine grains structure. A compact and large grains structure CZTS layers were formed upon annealing accompanied by improvement in crystallinity. The evaluated energy bandgap in the range of 1.5 eV indicates a suitable absorbing material for solar cell applications. The obtained results provide useful information and a better understanding of the influence of substrate temperature and the annealing process on the physical properties of sprayed CZTS layers.

Single-phase lanthanum ferrite oxides doped potassium (K) with various composition of La1-xKxFeO3 (0.0 <= x <= 0.3) were successfully prepared using cost-effective precursors via a solid-state reaction route. The influence of K substitution at La site of LaFeO3 on its structural, optical, and magnetic properties have been studied. X-ray diffraction (XRD) results indicated that all synthesized samples were a polycrystalline single-phase orthorhombic perovskite structure, with peaks shifting to higher Bragg angles by increasing K amount. Direct bandgap energy (E-g) of La1-xKxFeO3 samples was dramatically decreased from 2.28 eV to 1.22 eV with increasing the amount of K substitution in the LaFeO3 Lattice. Magnetic hysteresis loops show that the obtained samples have a ferromagnetic response at room temperature with enhanced magnetization from 0.16 to 1.72 emu/g with increasing the K concentration. The changes of the optical and magnetic properties attributed to the crystal structure defects resulting from the replacement of La-3+ by K-1+, which cerate oxygen vacancies due to the variation in the valence state ratio of Fe4+/Fe3+. The enhanced magnetization and tunable Eg in the visible region make La1-xKxFeO3 (0.0 <= x <= 0.3) promising materials for environmental applications such as solid oxides fuel cells (SOFC) and photocatalysis.

Balancing the stability and interfacial charge transfer (CT) ability of perovskite nanocrystals (PNCs) are the most challenging issue confronting their practical application in photoelectrochemistry (PEC) fields. Here, an efficient surface capping strategy is introduced relying on a set of air-stable nitroxide-based organic radical polymers with well-matched energy levels towards CsPbBr3 nanocrystals. The native ligand oleyl amine and oleic acid were readily replaced by radical polymers because of their high-affinity properties. The resulting radical polymer coated PNCs exhibit exceptional tolerance to water, thermal, and UV illumination with remarkable CT processes. The versatility and immense practical utility of such stable PNCs-radical core/shell structure are showcased by the halogen exchange between PNCs/radical and aryl chlorides at ambient temperature, demonstrating superb reduction ability of this complex. Besides, this strategy was also employed to improve the power conversion efficiency and stability of PNCs based solar cells. This approach imparts exceptional photoelectrochemical sta-bility and catalytic activity to the nanocrystals with excellent interfacial CT efficiency.

A single-phase and crystalline NiS2 nanoflake layer was produced by a facile and novel approach consisting of a two-step growth process. First, a Ni(OH)2 layer was synthesized by a chemical bath deposition approach using a nickel precursor and ammonia as the starting solution. In a second step, the obtained Ni(OH)2 layer was transformed into a NiS2 layer by a sulfurization process at 450 °C for 1 h. The XRD analysis showed a single-phase NiS2 layer with no additional peaks related to any secondary phases. Raman and X-ray photoelectron spectroscopy further confirmed the formation of a single-phase NiS2 layer. SEM revealed that the NiS2 layer consisted of overlapping nanoflakes. The optical bandgap of the NiS2 layer was evaluated with the Kubelka-Munk function from the diffuse reflectance spectrum (DRS) and was estimated to be around 1.19 eV, making NiS2 suitable for the photodegradation of organic pollutants under solar light. The NiS2 nanoflake layer showed photocatalytic activity for the degradation of phenol under solar irradiation at natural pH 6. The NiS2 nanoflake layer exhibited good solar light photocatalytic activity in the photodegradation of phenol as a model organic pollutant.

Nickel oxide thin films were obtained by a cost-effective chemical spray pyrolysis approach on glass sub-strates using nickel chloride as starting precursor with different deposition times. The X-ray diffraction investigation indicated that the obtained films were polycrystalline cubic structure with preferred or-ientation along (111) plane. Scanning electron microscopy images for sprayed NiO layers at deposition time of 5 and 10 min exhibit a porous structure with randomly oriented honeycomb like morphology. The optical direct band-gap energy E-g of sprayed NiO films was around 3.4-3.5 eV for all deposited samples and optical transmittance decreases with increasing the deposition time. Gas sensing performance was tested for the detection of nitrogen dioxide (NO2) at different operating temperatures and NO2 concentrations. It was found that the sprayed NiO thin film at deposition time of 5 min shows the maximum sensitivity of 57.3% for 20 ppm NO2 at 200 degrees C as operating temperature with good stability and selectivity. This study suggests that the sprayed NiO thin film is a good candidate material for NO2 detection at a relatively low operating temperature. (C) 2021 Elsevier B.V. All rights reserved.

A chemical spray pyrolysis technique was used to deposit a vanadium pentoxide (V2O5) thin films on glass substrate with a deposition temperature ranged from 300°C to 500°C in step of 50°C. From ammonium meta vanadate aqua precursor solution molarity of (0.1 M) was used as a source of vanadium. The effect of deposition temperature on structure, morphological, electrical conductivity and optical properties wasanalyzedat constant preparation time, solution molarity and the distance between spray nozzle and substrate.X-ray diffraction patterns shown that an orthorhombic cubic structure withgrowth along (001) plane. With increasing the substrate temperature, the electrical conductivity was increased, and the scanning electron microscopy clarified that the crystallinity of V2O5 thin films was effectively modified. The optical results revealed that energy band gap of V2O5 films deposited at 400oC, 450oC and 500oC is 2.38 eV for direct allowed transition. Based on the observed results the V2O5 phase can be well controlled by altering the substrate temperature. All prepared thin films up to 400oC show transparency in both visible and near IR region.

Chemical spray pyrolysis is utilized to deposit ZnO thin films with varied vanadium (V) contents, offering a simple, low cost and large-scale production deposition process. The effect of introducing V on structural, morphological, optical, electrical and magnetic properties of ZnO thin films is studied. XRD measurements reveal single phase ZnO polycrystalline layers with hexagonal wurtzite structure and high texturing along {002} plane. The incorporation of V into the ZnO lattice is confirmed through the XRD peaks shift towards a higher angle. Further, the SEM micrographs indicate morphological transformation from hexagonal nanoplates to spherical particles when increasing the V content from 2% to 10% nominally. All films are optically transparent in VIS and NIR spectral regions and the optical transmittance is strongly decreasing with increasing the V percentage. The magnetic measurement data shows paramagnetic behavior for the ZnO layer doped with 2% V while ZnO layer doped with 10% V shows a small ferromagnetic behavior. Additionally, the magnetoresistance measurement at 1.6 T shows positive values at room temperature and increased from 6% to 12% when increasing V amount.

Copper tin sulfide (CTS) has potential as solar cell absorber, and its photovoltaic properties can be enhanced for future energy applications. The CTS thin films were prepared by spray pyrolysis method at different deposition temperatures and time using single-step process. X-ray diffraction patterns of the samples confirmed polycrystalline structure at higher temperatures and shorter deposition time, while, secondary phases were formed at higher temperature and longer deposition time. Scanning electron microscope micrographs showed that the CTS films have a homogeneous and dense morphology. High optical absorption coefficient for all the samples determined from the absorption coefficient versus photon energy plot is above 3 × 104 cm−1 and near the fundamental absorption edge, making the CTS thin film suitable for solar cell applications. The band energy values of 1.51 eV observed in this study showed the potential application of this ternary material as an efficient absorber material for thin films used in photovoltaic industry.

Transparent and conducting cadmium oxide (CdO)thin films were deposited onto soda-lime glass substrate by simple chemical spray pyrolysis technique at different deposition temperatures.The influence of the deposition temperature on structural, morphological, electrical and optical properties of CdO films was investigated.X-ray diffraction patterns revealed that polycrystalline CdO phase with cubic crystal structure started to form at deposition temperature of 300 °C with secondary phase, while at lower deposition temperature the prepared layers showed amorphous structure.At deposition temperature higher than 300 °C, the prepared layers showed single CdO phase enhanced crystallinity.Enhanced grain growth of CdO films is observed with increasing the deposition temperature.Moreover, the electrical conductivity of the films was found to be increasing with increasing the deposition temperature, which is consistent with the enhanced grain growth.Additionally, the optical transmittance measurement of the CdO films showed around 90% transmission in the visible and near infrared regions, independently of deposition temperature.