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In this work, a graphitic carbon nitride (g-C3N4) photocatalyst was synthesized by pyrolysis of melamine. The effect of different synthesis temperatures on the structural, morphological, and optical properties of the g-C3N4 photocatalyst was investigated. X-ray diffraction and Raman spectroscopic analyses confirmed the formation of the g-C3N4 photocatalyst. The elemental composition and valence states of the g-C3N4 photocatalyst were studied using X-ray photoelectron spectroscopy. A specific surface area of 25.45 m2/g was measured using the BET technique. UV–Vis spectroscopy showed that the g-C3N4 photocatalyst exhibited good absorbance in the ultraviolet and visible regions. The photocatalytic performance of the g-C3N4 photocatalyst was tested for the degradation of Rhodamine B under sunlight illumination.

Different types of organic impurities such as dyes, acids, and alcohols are discharged into potable water sources. The removal of these hazardous organic pollutants from wastewater is an important task globally. However, the conventional methods used to remove organic impurities suffer from low efficiency and recycling problems. Photocatalysis is a promising advanced oxidation process for the degradation of organic compounds in aqueous solution. Titanium dioxide (TiO2) is commonly used as a photocatalyst. However, the wide bandgap of TiO2 means that it is activated by ultraviolet light, which restrains its ability to harvest solar energy. In this study, a simple water-based precipitation method was used to synthesize TiO2@nanodiamond composites. The ability of the composites to degrade bisphenol A as a model organic pollutant was investigated. It was found that 10 ppm of bisphenol A was completely degraded in 100 min by the TiO2@nanodiamond photocatalyst under ultraviolet illumination.

In recent year, sonochemistry has fascinated some interest in the fabrication of nanostructured materials and functional nanoparticles because the chemical activity of ultrasound may cause different effects such as the generation of heat, mass transfer or intimate contact between materials, distribution of contaminated layers of chemicals and generation of free chemical radicals. In this work, Cu2ZnSnS4 (CZTS) photocatalyst is prepared by simple, cost effective, sonochemical method and used for photocatalytic degradation of phthalic acid. The ultrasonic treatment affects the structural, morphological, optical, contact angle properties of CZTS photocatalyst. The XRD and FT-Raman spectroscopy study shows the formation of a single phase CZTS with kesterite structure. SEM analysis reveals nano-spherical architecture with pinhole and crake free surface. The optical study shows that band gap energy lies in the visible region of the solar spectrum and useful for visible light assisted photocatalysis. The end results show that the CZTS photocatalyst exhibited about 56% degradation of phthalic acid under sunlight illumination. The mineralization study of phthalic acid is done by determining chemical oxygen demand (COD) values.

The nanostructure of metal oxides attracts great attention in the field of supercapacitors because of fast charge transport process. The hydrothermal method is used for development of NiCo2O4 nanostructure on carbon cloth as current collector backbone. The stepwise study of various structural, morphological and electrochemical properties of NiCo2O4 electrode is studied. The ultrasonic treatment is used to obtain nanowire-like morphology of NiCo2O4 which exhibits hierarchical nanostructure, which provides surface properties such as high surface area and appropriate pore capacity. NiCo2O4 nanostructure with specific capacitance of 1460 F g−1 with high electrochemical stability of 84% after 3000 cycles in 3 M KOH aqueous electrolyte at 100 mV s−1. The electrochemical property shows NiCo2O4 is one of the potential candidates for energy storage application. The specific capacitance and energy density for NiCo2O4@CC//NiCo2O4@CC symmetric supercapacitor device is of 124 F g−1 and 16.18 Wh.kg−1, respectively at current density of 5 mA.

Tetracycline (TC) is a persistent antibiotic used in many countries, including China, India, and the United States of America (USA), because of its low price and effectiveness in enhancing livestock production. However, such antibiotics can have toxic effects on living organisms via complexation with metals, and their accumulation leading to teratogenicity and carcinogenicity. In this study, two-dimensional molybdenum disulfide/titanium dioxide (MoS2/TiO2) composites with different amounts of molybdenum disulfide (MoS2) were prepared via a simple, cost-effective, and pollution-free hydrothermal route. The synthesized MoS2/TiO2 microstructures were thoroughly characterized and their performance for the photocatalytic degradation of antibiotics such as TC was investigated. In the degradation experiments, the photocatalytic activities of TiO2 and the MoS2/TiO2 composites were compared, and the effects of different parameters, such as catalyst dose and electrolyte solution pH, were investigated. Under irradiation, the MoS2/TiO2 composites possessed superior photodegradation activity toward TC because of their excellent adsorption abilities, suitable band positions, and large surface areas as well as the effective charge-transfer ability of MoS2. Kinetics studies revealed that the photocatalytic degradation process followed pseudo-first-order reaction kinetics. In addition, a degradation mechanism for TC was proposed.

In this research work, we reported the synthesis of a spherical-shaped bismuth vanadate (BiVO4) photocatalyst using a cost-effective, simple, chemical hydrothermal method and studied the effect of deposition temperatures on the structural, morphological, optical properties, etc. The XRD result confirmed the monoclinic scheelite phase of BiVO4. An XPS study confirmed the occurrence of Bi, V, and O elements and also found that Bi and V exist in +3 and +5 oxidation states, respectively. SEM micrographs revealed the spherical-shaped morphology of the BiVO4 photocatalyst. Optical investigation showed that the bandgap of the BiVO4 photocatalyst varied between 2.25 and 2.32 eV. The as-synthesized BiVO4 photocatalyst was used to study the photocatalytic degradation of crystal violet (CV) dye under visible light illumination. The photocatalytic degradation experiment showed that the degradation percentage of crystal violet dye using BiVO4 reached 98.21% after 120 min. Mineralization of crystal violet dye was studied using a chemical oxygen demand analysis.

The study deals with the hydrothermal growth of a CuCo2O4 hierarchical 3D nanoflower–like array on carbon cloth (CuCo2O4@CC), which is a useful multifunctional electrode. The electrocatalytic oxygen evolution reaction (OER) study of the CuCo2O4@CC electrode shows high durability and good activity in 1 M KOH. As an energy storage electrode, it shows a high specific capacitance of 1438 Fg−1 at 10 mA cm−2 in a 3 M KOH electrolyte. The electrochemical stability of the CuCo2O4@CC electrode was tested for 5000 cycles at 10 mA cm−2, and it showed 98.6% stability. This CuCo2O4@CC electrode produces a capacitance of 10 mA cm−2 at an overpotential of 288 mV for the OER, with a Tafel slope of 64.2 mV dev-1. The electrochemical stability measured at an overpotential of 292 mV for 12 h at 10 mA cm−2 shows good electronic stability in an alkaline medium. The enhanced electrochemical performance of the CuCo2O4@CC electrode may be due to the Cu and Co counterparts in addition to the high surface area. The CuCo2O4@CC electrode is a simple, flexible, and cost-effectivive electrode in both electrocatalytic OER and energy storage applications.

A hexagonal ZnO thin films have been successfully synthesized by chemical spray pyrolysis technique. Photoelectrocatalytic activity of ZnO photoelectrode is tested for photoelectrocatalytic degradation of terephthalic acid as a model organic pollutant. The degradation percentage of terephthalic acid using ZnO photoelectrode has reached up to 91% under ultraviolet illumination after 400 min. ZnO thin films are used for detecting CO2 gas and getting maximum response for operating temperature of 350 °C and response and recovery time periods are 75 and 108 s, respectively for 400 ppm CO2 gas concentration. ZnO sensor has good repeatability along with a quick response time. Thus a multifunctional ZnO thin film is the potential candidate for both for photocatalytic and CO2 gas sensing applications.

In present work, Co3O4 nanowire is successfully prepared on stainless steel substrate by simple chemical bath deposition method and studied the supercapacitor application. The prepared Co3O4 nanowire is analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy and Brunauer–Emmett–Teller techniques. Co3O4 nanowire offers high specific surface area of 66.33 m2 g−1 for the intercalation of electrolyte ions. Co3O4 nanowires exhibit outstanding electrochemical performance with a high specific capacitance of 850 F g−1 at scan rate of 5 mV s−1, and excellent long-term cycling stability (86% over 5000 CV cycles). The symmetric solid-state supercapacitor device is fabricated by accumulating two electrodes of Co3O4 nanowire, which shows superior electrochemical performance with specific capacitance of 127 F g−1, specific energy of 24.18 Wh kg−1 and excellent cycling stability (85% over 3000 CV cycles).

The present study deals with the preparation of tetragonal barium titanate (BaTiO3) by hydrothermal technique and its use in the photocatalytic degradation of salicylic acid. The structural, morphological, and photocatalytic properties of the BaTiO3 nanoparticles are studied. The prepared samples are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM) and Ultraviolet–visible (UV–Vis) spectroscopy. The end result shows that the degradation percentage of salicylic acid using BaTiO3 photocatalyst has reached 51% under ultraviolet light illumination after 120 min. The amount of degradation is confirmed by COD analysis.

The present work deals with the preparation of WO3 and WO3-ZnO nanocomposites in presence of ultrasonic irradiation, and its use in the sonocatalytic degradation of brilliant blue dye. WO3-ZnO nanocomposite is prepared using one step in-situ ultrasound assisted method. The successfully prepared WO3 and WO3-ZnO nanocomposites were characterized using different characterization techniques such as XRD, Raman, BET, FE-SEM and EDS. The XRD pattern reveals that the formation of monoclinic and hexagonal crystal structures of WO3 and ZnO respectively. BET study shows that WO3-ZnO nanocomposite have maximum surface area than that of the WO3. EDS study confirms the formation of WO3-ZnO nanocomposites. Further the use of the prepared WO3 and WO3-ZnO nanocomposites as a sonocatalyst for the degradation of brilliant blue dye. The rate constant (k) was evaluated as a function of the initial concentration of brilliant blue dye. It is found that WO3-ZnO nanocomposites exhibits maximum sonocatalytic activity as compared to WO3 photocatalyst.

In present article, WO3 thin films have been successfully synthesized by chemical spray pyrolysis approach. The effect of spraying quantity of solution onto the photoelectrochemical (PEC), structural, morphological, and optical properties has been studied. Film prepared at 40 ml solution quantity shows the excellent photoelectrochemical performance (Isc= 0.69 mA/cm2 and Voc = 0.64 V) in 0.05 M concentrated H2SO4 electrolyte. X-ray diffraction studies reveal that the synthesized WO3 thin films are polycrystalline with monoclinic crystal structure. The chief vibrational modes of the WO3 sample, located at 712.64 and 804.28 cm−1 corresponding to the stretching and the bending of O W O bond respectively and are consistent with a monoclinic structure. The estimated band gap energy of WO3 thin films varies from 2.37 to 2.45 eV with respect to quantities of spraying solution and it exhibits absorption in visible region. Film shows a maximum specific surface area of 31.63 m2/g. Photoelectrocatalytic degradation of brilliant blue dye in aqueous solutions is studied. The end result shows that the degradation percentage of brilliant blue using WO3 photoelectrode has reached 92% under visible light illumination after 240 min. The enhancement in photoelectrocatalytic activity of optimized 40 ml WO3 sample is mainly due to the suppressed the recombination rate of photogenerated electron–hole pairs. This study provides an effective WO3 photoelectrode for removing of organic pollutants present in the water.

The need to utilize TiO2 based metal oxide hetero nanostructures for the degradation of environmental pollutants like Rhodamine B and reactive red 152 from the wastewater using stratified WO3/TiO2 catalyst under sunlight illumination. WO3, TiO2 and stratified WO3/TiO2 catalysts were prepared by a spray pyrolysis method. It was found that the stratified WO3/TiO2 heterostructure has high crystallinity, no mixed phase formation occurs, strong optical absorption in the visible region of the solar spectrum, and large surface area. The photocatalytic activity was tested for degradation of Rhodamine B (Rh B) and reactive red 152 in an aqueous medium. TiO2 layer in stratified WO3/TiO2 catalyst helps to extend its absorption spectrum in the solar light region. Rh B and Reactive red 152is eliminated up to 98 and 94% within the 30 and 40 min respectively at optimum experimental condition by stratified WO3/TiO2. Moreover, stratified WO3/TiO2 photoelectrode has good stability and reusability than individual TiO2 and WO3 thin film in the degradation of Rh B and reactive red 152. The photoelectrocatalytic experimental results indicate that stratified WO3/TiO2 photoelectrode is a promising material for dye removal.

TiO2 is one of the well-known multipurpose material for different applications such as gas sensors, catalysis, solar cells, optoelectronic devices, etc. TiO2 is widely used as photocatalyst due to interest optical and electrical properties. In the present work, TiO2 photocatalyst is used to study the degradation of phthalic acid under ultraviolet light illumination. The prepared TiO2 photocatalyst is characterized by different characterization techniques such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy. The end result shows that the degradation percentage of phthalic acid using TiO2 photocatalyst has reached 41.93% after 320 min. under ultraviolet light illumination. The amount of mineralization of phthalic acid is confirmed by chemical oxygen demand measurements.

The sluggish mechanism of oxygen evolution reaction (OER) inhibits the efficiencies of different energy storage systems. Thus, recent studies have mainly focused on designing highly active electrocatalysts to enhance OER. Here, a porous microsphere-like copper molybdate (CuMoO4) is synthesized via a simple hydrothermal route. Further, the crystalline nature of CuMoO4 is confirmed via X-ray diffraction (XRD). The chemical states of the designed sample are determined via X-ray photoelectron spectroscopy (XPS). The morphology and elemental composition of CuMoO4 are determined via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques, as well as energy-dispersive X-ray (EDX) analyses. The CuMoO4 microspheres exhibit interconnected nanoflake-like structures, which can improve the active surface area and efficiency of CuMoO4. Furthermore, the active surface area of the CuMoO4 microspheres is calculated via the Brunauer–Emmett–Teller (BET) method. The obtained catalytic performance of CuMoO4 is compared with those of its basic metal oxides, such as MoO3 and CuO. The obtained overpotentials (η) for CuO, MoO3, IrO2, and CuMoO4 were 286, 294, 267, and 247 mV with Tafel slope values of 65, 84, 58, and 53 mV/dec, respectively. The study for long-term stability of the CuMoO4 electrode reveals that it can sustain the electrochemical activity for 12 h.

The multiferroics with ferroelectric (FE) and ferromagnetic (FM) phases (x) [Co0.8Mn0.2Fe2O4] + (1−x) [PbZr0.52Ti0.48O3] composite samples with x = 0.25, 0.50 and 0.75, were prepared by ceramic route. X-ray diffraction (XRD) patterns of as-prepared samples exhibit the presence of lead zirconate titanate PbZr0.52Ti0.48O3 (PZT) and Co0.8Mn0.2Fe2O4 (CMFO) phases in the PZT-CMFO composites. The values of grain size were found to be decreased in the range of 680–390 nm with increasing the ferrite contents from x = 0.25 to 0.75. The temperature dependent dc resistivity (ρ) of the composites was reduced with increasing x contents. The values of dielectric constant (e′) 7x103-20 x103 were found to be increased at 30 Hz frequency. The variations in (e′) with frequency (20 Hz -1MHz) were caused by interfacial polarization occurred in the composites. The changes in AC conductivity (σac) of composite samples were found to be increased with the frequency. The higher value of magneto-electric (ME) coefficient (0.641μv/cm Oe) was obtained for x = 0.25 of composite sample.

Highly crystalline Cu 2 ZnSnS 4 (CZTS) thin films have been deposited onto glass and FTO coated glass substrates by simple chemical spray-pyrolysis technique. It is an important material for solar energy conversion through the both photovoltaics and photocatalysis. The effect of substrate temperatures on the physico-chemical properties of the CZTS films is studied. The XRD study shows the formation of single phase CZTS with kesterite structure. FE-SEM analysis reveals nano flakes architecture with pin-hole and crake free surface with more adherent. The film deposited at optimized substrate temperature exhibits optical band gap energy of 1.90 eV, which lies in the visible region of the solar spectrum and useful for photocatalysis application. The photoelectrocatalytic activities of the large surface area (10 × 10 cm 2 ) deposited CZTS thin film photocatalysts were evaluated for the degradation of sugarcane factory wastewater under visible light irradiation. The results show that the CZTS thin film photocatalyst exhibited about 90% degradation of sugar cane factory wastewater. The mineralization of sugarcane factory wastewater is studied by measuring chemical oxygen demand (COD) values.

In the present work, layered WO3/ZnO thin films have been prepared by simple chemical spray pyrolysis method. As prepared films are characterized by photoelectrochemical (PEC) solar cell, X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM), Brunauer–Emmer–Teller (BET) and energy dispersive X-ray spectroscopy techniques. XRD analysis reveals the formation of hexagonal and monoclinic phases of ZnO and WO3 respectively. Raman analysis confirms the formation of layered WO3/ZnO thin films. FE-SEM images demonstrate that the surface morphology of layered WO3/ZnO consists of nano balls like morphology. The specific surface area of the layered WO3/ZnO thin film is found to be 65.12 m2 g−1. The photoelectrocatalytic degradation properties of layered WO3/ZnO thin films were investigated by studying degradation of sugarcane factory wastewater. The end result shows that the degradation percentage of sugarcane factory wastewater using layered WO3/ZnO photo electrode has reached 94.44% after 100 min. under sunlight illumination.

TiO2 thin films have been deposited onto glass and FTO coated glass substrates using spray pyrolysis method. The effect of substrate temperature on the structural, morphological and photoelectrocatalytic properties of TiO2 thin films are studied. The photoelectrochemical (PEC) study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Isc = 0.475 mA and Voc = 0.395 V) relatively higher at 400 °C substrate temperature. The structure and morphology of TiO2 thin films are studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM). XRD study reveals that the films are polycrystalline in nature with tetragonal crystal structure. FE-SEM images show that the substrate surface is well covered with a uniform grain like morphology. Photoelectrocatalytic degradation of reactive red 152 dye in aqueous solutions is studied. The end result shows that the degradation percentage of reactive red 152 using TiO2 photoelectrode has reached 70% under ultraviolet light illumination after 120 min.

In the present work, stratified WO 3 /ZnO thin films have been prepared by simple chemical spray pyrolysis technique. The structural, morphological, compositional and photoelectrocatalytic properties of the stratified WO 3 /ZnO thin films are studied. The photoelectrochemical (PEC) study shows that, both short circuit current (I sc ) and open circuit voltage (V oc ) are (I sc = 1.023 mA and V oc = 0.980 V) relatively high at 40 ml spraying quantity of ZnO solution on pre-deposited WO 3 thin films. XRD analysis reveals that stratified WO 3 /ZnO thin films are polycrystalline with monoclinic and hexagonal crystal structures for WO 3 and ZnO respectively. The specific surface area of the stratified WO 3 /ZnO thin film is found to be 48.12 m 2 g −1 . The enhanced photoelectrocatalytic activity of stratified WO 3 /ZnO is mainly due to the suppressing the recombination of photo generated electron-hole pairs. The end result shows that the degradation percentage of phthalic acid (PA) using stratified WO 3 /ZnO photo electrode has reached 63.63% after 320 min. under sunlight illumination. The amount of mineralization of phthalic acid is studied with the help of chemical oxygen demand (COD) measurement.

The stratified WO 3 /TiO 2 thin films have been deposited onto glass and FTO coated glass substrates using simple chemical a spray pyrolysis method. The structural, morphological, compositional and photoelectrocatalytic properties of the stratified WO 3 /TiO 2 thin films are studied. The photoelectrochemical (PEC) study shows that, both short circuit current (I sc ) and open circuit voltage (V oc ) are (I sc =1.192 mA and V oc =0.925 V) relatively high at 50 ml spraying quantity of TiO 2 solution on pre-deposited WO 3 . XRD analysis confirms that films are polycrystalline with monoclinic and tetragonal crystal structures for WO 3 and TiO 2 respectively. Specific surface area of 72.14 m 2 g −1 is measured by Brunauer-Emmett-Teller (BET) technique. Photoelectrocatalytic degradation of benzoic acid (BA) dye in aqueous solutions is studied. The end result shows that the degradation percentage of benzoic acid (BA) using stratified WO 3 /TiO 2 photoelectrode has reached 66% under sunlight illumination after 320 min. The amount of degradation is confirmed by COD analysis.

In this work, nanostructured α-Fe2O3 thin films have been deposited onto the glass and fluorine doped tin oxide coated glass substrates using simple chemical bath deposition method. The influence of bath temperature on the properties of α-Fe2O3 thin films are studied with the help of different characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Raman spectroscopy, Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and optical properties. XRD study reveals that films are polycrystalline in nature with rhombohedral crystal structure. Raman spectroscopy is used to study the structure and symmetry of α-Fe2O3 thin films. The SEM study reveals that substrate surface is well covered with small tiny grains. Specific surface area of 30.12 m2 g−1 is measured by BET technique. Optical study shows that the band gap energy of α-Fe2O3 film is varied from 2.19 to 2.35 eV. The synthesized α-Fe2O3 photoelectrode is used as a catalyst for the photoelectrocatalytic degradation of 4-chlorphenol in an aqueous medium. The photoelectrocatalytic degradation experiment shows that the degradation percentage of 4-chlorophenol (4-CP) has reached 50% under sunlight illumination after 240 min. The mineralization of 4-CP with reaction time is studied with the help of chemical oxygen demand (COD) measurement.

The WO 3 and stratified WO 3 /TiO 2 thin films are successfully prepared by the spray pyrolysis method. The structural, morphological, compositional and photoelectrocatalytic properties of WO 3 and stratified WO 3 /TiO 2 thin films are studied. XRD analysis confirms that films are polycrystalline with monoclinic and tetragonal crystal structures for WO 3 and TiO 2 respectively. The SEM images clearly show 3D sheeted porous structure of the as-prepared TiO 2 forms on WO 3 in stratified WO 3 /TiO 2 samples. The synthesized photoelectrodes was used as catalyst for photoelectrocatalytic degradation of oxalic acid in aqueous medium. The rate constant (k) was evaluated as a function of the initial concentration of species. A significant decrease in concentrations of organic species was observed from COD analysis. The photoelectrocatalytic degradation effect is relatively higher in the case of the stratified WO 3 /TiO 2 than WO 3 thin film photoelectrode in the degradation of oxalic acid and 83% removal efficiency of oxalic acid is obtained after 180 min. Based on the obtained experimental data, the possible photoelectrocatalytic reaction mechanism was proposed. The photoelectrocatalytic experimental results indicate that stratified WO 3 /TiO 2 photoelectrode is the promising material for removing of water pollutants.

A simple, cost-effective, ultrasound-assisted hydrothermal method was used to synthesize tungsten trioxide (WO3) and subsequently a tungsten trioxide/reduced graphene oxide (WO3/rGO) composite. The formation of the WO3/rGO composite was confirmed by XPS and Raman analyses. XPS analysis of the WO3/rGO composite revealed the presence of tungsten, carbon, and oxygen. Raman spectroscopy confirmed the presence of G and D bands in the WO3/rGO composite. The randomly arranged, interconnected, nanoplate-like morphology of WO3 was destroyed owing to the presence of rGO nanosheets and converted into a highly porous nanostructure. Multifunctional WO3 and WO3/rGO photocatalysts were used to study the sonocatalytic degradation of hazardous Congo red (CR) azo dye and photocatalytic hydrogen production. The surface area of the WO3/rGO composite (62.03 m2/g) was larger than that of WO3 (44.79 m2/g), thereby enhancing the efficiency of the sonocatalytic degradation and photocatalytic hydrogen production, which corresponds to the effective inter-charge transfer between WO3 and rGO. Platinum was used as a co-catalyst with WO3/rGO to promote hydrogen production. The incorporation of rGO enhanced the CR dye degradation efficiency from 56 to 94% and the hydrogen production activity from 424.5 to 825.8 µmol/h⋅g.

Rapid technological development requires sustainable, pure, and clean energy systems, such as hydrogen energy. It is difficult to fabricate efficient, highly active, and inexpensive electrocatalysts for the overall water splitting reaction: the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The present research work deals with a simple hydrothermal synthesis route assisted with ultrasound that was used to fabricate a 3D nanoflower-like porous CoMoS4 electrocatalyst. A symmetric electrolyzer cell was fabricated using a CoMoS4 electrode as both the anode and cathode, with a cell voltage of 1.51 V, to obtain a current density of 10 mA/cm2. Low overpotentials were observed for the CoMoS4 electrode (250 mV for OER and 141 mV for HER) at a current density of 10 mA/cm2.

Hydrogen produced from water splitting is a good alternative to conventional energy sources such as fossil fuels. A highly porous cobalt molybdenum sulfide (CoMoS4) electrocatalyst was fabricated using a simple chemical synthesis route. The porous CoMoS4 acts as an active electrocatalyst in alkaline medium for the oxygen evolution reaction with a low overpotential of 256 mV to reach a current density of 10 mA/cm2. CoMoS4 also acts as an active catalyst for the hydrogen evolution reaction at a current density of 10 mA/cm2 at an overpotential of 143 mV. An alkaline electrolyzer cell was constructed, where CoMoS4 was used as both the anode and cathode for the overall water splitting reaction with a current density of 10 mA/cm2 at a cell voltage of 1.65 V. This study confirms that CoMoS4 is a potential candidate as a bifunctional electrocatalyst for overall water splitting reaction.

In this paper we report single step synthesis of ZnO - ZnWO4 nanocomposites using thermal plasma route, where thermal plasma plume having sufficiently high thermal flux was impinged onto zinc -tungsten precursor and the species so evaporated were made to interact with oxygen in gas phase to get the final product. X-ray diffraction and Raman spectroscopic techniques were used to ascertain the composite phases. X-Ray Diffraction and Raman Spectroscopic analysis witnessed the formation of ZnO-ZnWO4 nano-composites, with monoclinic wolframite structure of tungstate while wurtzite structure of ZnO. Optical properties of the as synthesized product were recorded and analyzed using UV–vis and Photo-luminescence spectroscopic techniques. Retarding field diode method was used to determine work function of the ZnO-ZnWO4 composites under investigation, where gold sample was used as a reference. Subsequently, the photocatalytic efficiency of such ZnO-ZnWO4 nano-composites was analyzed by assessing the degradation of Crystal Violet dye. Experimentally measured values of surface work-function of the composites were analyzed and corelated with photocatalytic response. The degradation of Crystal Violet up to 82.07 % was achieved for 5 wt. % of W in the composite as compared to a value of 25.14 % for the pure ZnO nanoparticles under the exposure to sunlight radiations.

Titanium dioxide (TiO2) has been widely used as a catalyst material in different applications such as photocatalysis, solar cells, supercapacitor, and hydrogen production, due to its better chemical stability, high redox potential, wide band gap, and eco-friendly nature. In this work TiO2 thin films have been deposited onto both glass and silicon substrates by the atmospheric pressure plasma jet (APPJ) technique. The structure and morphological properties of TiO2 thin films are studied using different characterization techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and field emission scanning electron microscopy. XRD study reveals the bronze-phase of TiO2. The XPS study shows the presence of Ti, O, C, and N elements. The FE-SEM study shows the substrate surface is well covered with a nearly round shaped grain of different size. The optical study shows that all the deposited TiO2 thin films exhibit strong absorption in the ultraviolet region. The oleic acid photocatalytic decomposition study demonstrates that the water contact angle decreased from 80.22 to 27.20° under ultraviolet illumination using a TiO2 photocatalyst.

In this study, spongy ball-like CuO and CuO/rGO photocatalysts were successfully synthesized by a simple hydrothermal method and further studied for photocatalytic hydrogen production activity. The CuO and CuO/rGO photocatalysts were analyzed by various structural, morphological, and optical characterization techniques. X-ray diffraction and Raman spectroscopy studies revealed that the CuO/rGO composite was formed without the presence of any secondary phase or impurities. The optical results demonstrated that the band gap lies in the visible range of the solar spectrum. The comparative study revealed that the CuO/rGO composite displays superior photocatalytic hydrogen production activity in comparison to CuO. Also, the CuO/rGO composite shows a hydrogen production rate of 19.2 mmol h−1 g−1 which was nearly 3 times higher than that of the CuO photocatalyst (6.8 mmol h−1 g−1).

The Ni0.4Zn0.6Fe2O4 ferrite, BaTiO3 ferroelectric and Ni0.4Zn0.6Fe2O4–BaTiO3 bilayered magnetoelectric thin films have been synthesized onto the quartz substrates at optimized substrate temperatures (400, 250 °C) using the simple spray pyrolysis technique. These films were characterized for their structural, morphological, dielectric and magnetic properties. The XRD studies reveal that the films are polycrystalline in nature with spinel cubic structure. The morphological study shows the formation of agglomerated cubes like grains. The dielectric constant and dielectric loss is measured as a function of frequency in the frequency range 20 Hz–1 MHz. Impedance spectroscopy is used to study the electrical behavior of these thin films. The saturation magnetization of Ni0.4Zn0.6Fe2O4 ferrite and Ni0.4Zn0.6Fe2O4–BaTiO3 bilayered thin films are 141 and 111 emu cm−3, respectively. The value of magnetoelectric voltage obtained for Ni0.4Zn0.6Fe2O4–BaTiO3 bilayered thin films is about 221 mV.

WO3 thin films have been deposited onto glass and FTO coated glass substrates using a simple chemical spray pyrolysis technique. The structural, morphological, optical and photocatalytic properties of WO3 thin films are studied. The photoelectrochemical (PEC) study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Isc=0.38 mA and Voc=0.59 V) relatively higher at 300 °C substrate temperature. The structure and morphology of WO3 thin films are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). XRD study reveals that the films are polycrystalline in nature with monoclinic crystal structure. SEM images show that the substrate surface is covered with a uniform and grain like morphology. The AFM images show the rough nature of the film. The structure and local symmetry of the film are studied with the help Raman spectroscopy. The chief vibrational modes of the WO3 sample, located at 805, 715 and 269 cm−1 corresponding to the stretching and the bending of O–W–O bond respectively and are consistent with a monoclinic structure and the low-frequency peaks are observed at 269 and 325 cm−1 can be assigned due to the bending δ (O\W\O) vibrations in monoclinic structure. Photoelectrocatalytic degradation of methyl orange (MO) dye in aqueous solutions is studied. The end result shows that the degradation percentage of methyl orange (MO) using WO3 photoelectrode has reached 98% under visible light illumination after 320 min. The amount of degradation is confirmed by COD and TOC analysis.

The current research work deals with the preparation of TiO2 and GO/TiO2 composite by simple, chemical, cost effective hydrothermal method. Graphene oxide (GO) is prepared by modified Hummer’s method. Dispersion of GO is achieved by an ultrasonic cleaning bath for 1 h. using a power of 200 W and at a frequency of 40 kHz. The prepared catalyst material is characterized by different characterization techniques. XRD study confirms the prepared material is polycrystalline in nature. The synthesized TiO2 and GO/TiO2 photocatalyst materials are used to study the photocatalytic degradation of salicylic acid under sunlight illumination. GO/TiO2 composite shows superior photocatalytic activity than TiO2. GO/TiO2 composite shows 57% degradation of salicylic acid. Mineralization of salicylic acid is studied using chemical oxygen demand.

Intensive research work has been carried out for the degradation of organic pollutants present in the environment using the metal oxide semiconductors For the same TiO ZnO semiconductor photocatalysts has been widely used but the main drawback of these materials is able to utilize the UV spectrum only due to its high band gap property Since solar spectrum contain a significant proportion of the visible light it is imperative that for an active and versatile utilization of the incident solar energy The visible light active photocatalysts with a relatively smaller band gap are developed However smaller band gap often results in rapid recombination and conversion of photonic energy into non usable heat The main aim of this review is provide different ways for utilization of solar spectrum using different catalyst with relatively smaller band gap

Barium titanate (BaTiO3) thin films have been prepared using the spray pyrolysis method. The films were deposited onto a glass substrate at varying substrate temperature ranging from 250 to 350 °C with the interval of 50 °C. The structural, morphological, electrical and dielectric properties of the deposited films have been studied. The X-ray diffraction pattern confirmed the polycrystalline nature of the films with a cubic crystal structure. X-ray photoelectron spectroscopy (XPS) showed a good agreement of the thin films stoichiometry with BaTiO3. A presence of Ba, Ti and O in the BaTiO3 thin films was observed by energy dispersive X-ray analysis. The scanning electron microscopy (SEM) showed the heterogeneous distribution of cubical grains all over the substrate. The grain size decreased with an increase in substrate temperature. The dielectric constant and dielectric loss showed the dispersion behaviour as a function of frequency, measured in the frequency range of 20 Hz to 1 MHz. The AC conductivity (σac) measurement showed the linear nature of obtained films, which confirms conduction mechanism due to small polarons. Impedance spectroscopy has been used to study the electrical behaviour of BaTiO3 ferroelectric thin films. The ferroelectric hysteresis loop has been recorded at room temperature.

WO3 thin films have been deposited using simple chemical spray pyrolysis technique and successfully applied as photoanode for photoelectrocatalytic degradation of methylene blue. The films were deposited on bare glass and fluorine doped tin oxide coated glass substrates to study photoelectrochemical (PEC) properties, crystal structure, surface morphology, chemical composition and optical studies. The PEC results indicate that, the films deposited at 300 °C show the improved the photocurrent response relative to other deposited thin films. The monoclinic crystal structure of WO3 has been confirmed from X-ray diffraction studies. The Raman spectra of optimized films show two strong peaks at 271.34 and 327.27 cm−1 can be assigned to the bending δ (O\W\O) vibrations in the monoclinic WO3 structure. Field emission scanning electron microscopy showed that the film surface constituted of aggregates of very small seed like nanoparticles. UV–vis spectrophotometry shows that the WO3 film deposited at the 300 °C shows a band gap of ~2.66 eV and has emerged as one of the visible light photocatalysts, which can absorb light below 520 nm wavelength. The photocatalytic degradation of methyl blue has been investigated in aqueous solution. The removal of the color and decrease of UV–Visible absorbance was simultaneously able to show the oxidation of methylene blue dye.

WO3 thin films have been deposited onto glass and FTO coated glass substrates using simple chemical spray pyrolysis technique. The effect of solution concentration on the photoelectrochemical (PEC), structural, morphological and photoelectrocatalytic properties has been investigated. The structure and morphology of WO3 photoelectrodes are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The PEC study shows that both open circuit voltage (Voc) and short circuit current (Isc) at the optimized solution concentration (0.125 M) are relatively maximum (Isc = 0.62 mA and Voc = 0.58 V). XRD study reveals that the films are polycrystalline in nature with monoclinic crystal structure. SEM images show that the substrate surface is well covered with uniform, compact and fine grain like morphology. The AFM image shows the rough nature of the film. Photoelectrocatalytic degradation of methyl red dye in aqueous solutions is studied. The end result shows that the degradation percentage of methyl red using WO3 photoelectrode has reached 97 % under visible light illumination after 160 min. The amount of mineralization is confirmed by COD and TOC analysis.

Graphical abstract: The Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} (where x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) thin films were prepared by spray pyrolysis technique onto the quartz substrates. The composition x = 0.4 shows the formation of the compact grain structure and highest saturation magnetization of 143 emu/cm{sup 3}. - Highlights: • Synthesis of nanocrystalline Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} thin films. • Influence of Ni substitution on physicochemical properties. • Electrical conductivity arises mainly from the grain boundary. • The highest saturation magnetization is 143 emu/cm{sup 3} for x = 0.4. - Abstract: The Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} thin films have been prepared using a simple spray pyrolysis technique. The X-ray diffraction studies reveal that, the films are polycrystalline with spinel structure. The lattice parameters vary in the range of 8.35–8.48 A with composition (x) obeying Vegard’s rule. SEM and AFM studies show that the surface of the films exhibit a smooth, compact and a pin hole free morphology. Raman spectra indicate first order Raman active modes; A{sub 1g} (λ = 334 cm{sup −1}); E{sub g} (λ = 148 cm{sup −1}) and T{sub 2g} (λ = 699) of the Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4}. The investigation onmore » dielectric constant, dielectric loss tangent and ac conductivity was carried out in the frequency range 20 Hz–1 MHz at room temperature. The linear nature of the AC conductivity shows small polaron type of hopping mechanism. The saturation magnetization increases up to x = 0.4 (143 emu/cm{sup 3}), which decreases for higher x.« less

Undoped and Al doped ZnO (AZO) thin films are successfully prepared by spray pyrolysis technique at optimised substrate temperature of 400 °C onto amorphous and F:SnO2 coated glass substrates. Effect of Al doping on structural, morphological and optical properties of ZnO thin films is studied. Deposited films are polycrystalline with a hexagonal (wurtzite) crystal structure having (0 0 2) preferred orientation. The PEC characterization shows that, short circuit current (Isc) and open circuit voltage (Voc) are (Isc = 0.38 mA and Voc = 421 mV) relatively higher at the 3 at.% Al doping. SEM images show deposited thin films are compact and uniform with seed like grains. All films exhibit average transmittance of about 82% in the visible region and a sharp absorption onset at 375 nm corresponding to 3.3 eV. The photocatalytic activities of the large surface area (64 cm2) Al-doped ZnO photocatalyst samples were evaluated by photoelectrocatalytic degradation of phthalic acid under UV light irradiation. The results show that the 3 at.% AZO thin film photocatalyst exhibited degradation of phthalic acid up to about 45% within 3 h with significant reduction in COD and TOC values.

To overcome problem of energy crises, and water pollution, multifunctional nanoflower-like FeCo2O4 is synthesized for energy storage and photocatalysis applications. The nanoflower-like FeCo2O4 possesses charge transportation ability. The nanoflower-like morphology of FeCo2O4 is designed by simple hydrothermal synthesis with use of probe sonicator. The systematic analysis is performed for verify relevance of surface characteristics with electrochemical and photocatalytic properties of FeCo2O4 electrode. FeCo2O4 exhibits hierarchical flower-like nanostructure with high surface area and appropriate pore volume, which increases specific capacitance (Cs) up to 1230 F g−1 with stability up to 5000 cycles. Degradation efficiency of crystal violet using FeCo2O4 photocatalyst is reached up to 94.19% under sunlight irradiation for 160 min.

In this investigation TiO2, nanogranules were synthesized by simple, cost effective hydrothermal route. The stepwise study of various structural, morphological and compositional properties of TiO2 photocatalyst is done. XRD study reveals that the TiO2 thin films are polycrystalline in nature with the tetragonal crystal structure. SEM images show that the substrate surface is covered with a uniform, nanogranule like morphology. Optical band gap lies in the ultraviolet region. Hydrothermally prepared TiO2 nanogranules show a good photocatalytic H2 evolution activity. The photocatalytic hydrogen production rate for TiO2 nanogranules found to be 79.1 µmol g−1 h−1 after each 9 h cycle.

Highly transparent pure and Au doped TiO2 thin films are successfully deposited by using simple chemical spray pyrolysis technique. The effect of Au doping onto the structural and physicochemical properties has been investigated. The PEC study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Isc=1.81mA and Voc=890mV) relatively higher at 3at.% Au doping percentage. XRD study shows that the films are nanocrystalline in nature with tetragonal crystal structure. FESEM images show that the film surface covered with a smooth, uniform, compact and rice shaped nanoparticles. The Au doped thin films exhibit indirect band gap, decreases from 3.23 to 3.09eV with increase in Au doping. The chemical composition and valence states of pure and Au doped TiO2 films are studied by using X-ray photoelectron spectroscopy. The photocatalytic degradation effect is 49% higher in case 3at.% Au doped TiO2 than the pure TiO2 thin film photoelectrodes in the degradation of benzoic acid. It is revealed that Au doped TiO2 can be reused for five cycles of experiments without a requirement of post-treatment while the degradation efficiency was retained.

Highly transparent and preferential c-axis oriented nanocrystalline undoped and Al doped zinc oxide (AZO) thin films have been deposited onto amorphous glass substrate by spray pyrolysis. The XRD studies reveal that AZO with a hexagonal (wurtzite) crystal structure having (002) preferred orientation is formed. The atomic force microscope (AFM) shows uniform surface topography. The optical band gap values of undoped and AZO thin films were changed from 3.34 to 3.35 eV. The band gap energy and photoluminescence are found to depend on the Al doping. Thermoelectric power measurement shows film having n-type in nature. Dielectric constant and loss (tan δ) were found to be frequency dependent. Interparticle interactions in the deposited films are studied by complex impendence spectroscopy.