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Owing to the passivation of surface states, low surface-potential fluctuations, and low charge-transfer resistance, an in situ electrochemically passivated photoanode shows higher photoelectrochemical performance and outstanding stability for ∼100 h.

In the present research, we investigate the synergistic effects of Ru-doping and Ar/H2 reduction treatment on the photoelectrochemical water splitting performance and hydrogen evolution rate of TiO...

Graphene oxide flakes are considered as potential inhibitors for different pathogenic bacteria. However, the efficacy of inhibition changes for different types and strains of bacteria. In this work...

A new synergetic hybrid Ag/ZnO nanostructure was fabricated which is able to cause photocatalytic degradation (in high yields) of methylene blue under visible light as well as in the dark. In this nanostructure, ZnO was synthesized using the arc discharge method in water and was coupled with Ag via a chemical reduction method. X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy results confirmed the existence of defects in ZnO in the hybrid nanostructures; these defects act as electron traps and inhibit the recombination of electron-hole pairs. The absorption edge of the hybrid nanostructure shifts toward the visible region of the spectrum due to a combination of the Ag plasmonic effect and the defects in ZnO. Band-edge tuning causes effective visible light absorption and enhances the dye degradation efficiency of Ag/ZnO nanostructures. Silver oxidation in the hetero-structure changed the metal-semiconductor interface and suppressed the plasmonic enhancement. Nevertheless, the synthesized Ag/ZnO decomposed methylene blue in visible light, and the silver oxidation only affected the catalytic activity in the dark. This work provides insight into the design of a new and durable plasmonic-metal oxide nanocomposite with efficient dye degradation even without light illumination.

Supercapacitors store charge by ion adsorption or fast redox reactions on the surface of porous materials. One of the bottlenecks in this field is the development of biocompatible and high-rate supercapacitor devices by scalable fabrication processes. Herein, a Ti-rich anatase TiO2 material that addresses the above-mentioned challenges is reported. Tubular nanolettuces were fabricated by a cost-effective and fast anodization process of Ti foil. They attained a large potential window of 2.5 V in a neutral electrolyte owing to the high activation energy for water splitting of the (1 0 1) facet. Aqueous and all-solid-state devices showed diffusion time constants of 46 and 1700 ms, as well as high maximum energy (power) densities of 0.844 (0.858) and 0.338 μWh cm-2 (0.925 mW cm-2 ), respectively. The all-solid-state device showed ultrahigh stability of 96 % in capacitance retention after 20 000 galvanostatic charge/discharge cycles. These results open an avenue to fabricate biochemically inert supercapacitor devices.

RGO-α-Fe2O3/β-FeOOH ternary heterostructure composite has been developed as an active photocatalyst for photoelectrochemical water splitting. RGO-α-Fe2O3/β-FeOOH has been successfully synthesized through one-pot hydrothermal-ionic liquid assisted route using tetrabutyl ammonium L-methioninate [TBA][L-Met] and graphene oxide (GO). The electrochemical studies were carried out to demonstrate the oxygen evolution reaction (OER) and photocatalytic activities. The overpotential reduction by rGO-α-Fe2O3/β-FeOOH sample was higher than the nanobean α-Fe2O3/β-FeOOH and pristine α-Fe2O3 samples. The photocurrent density enhanced for rGO-α-Fe2O3/β–FeOOH urchin-like structure and obtained as 0.62 mA·cm−2. The data evidences the idea that the β–FeOOH layer in the modified morphology acts as an electron donor and the donor density increased substantially. Results from this study indicate that the rGO-α-Fe2O3/β-FeOOH can improve OER performance significantly with a peak shift of 0.13 V in the potential window, revealing its excellent potential as a higher rate and lower energy needed candidate.

Inkjet-printing (IJP) technology is recognized as a significant breakthrough in manufacturing high-performance electrochemical energy storage systems. In comparison to conventional fabrication protocols, this printing technique offers various advantages, such as contact-less high-resolution patterning capability; low-cost, controlled material deposition; process simplicity; and compatibility with a variety of substrates. Due to these outstanding merits, significant research efforts have been devoted to utilizing IJP technology in developing electrochemical energy storage devices, particularly in supercapacitors (SCs). These attempts have focused on fabricating the key components of SCs, including electrode, electrolyte, and current collector, through rational formulation and patterning of functional inks. In an attempt to further expand the material design strategy and accelerate technology development, it is urgent and essential to obtain an in-depth insight into the recent developments of inkjet-printed SCs. Toward this aim, first, a general introduction to the fundamental principles of IJP technology is provided. After that, the latest achievements in IJP of capacitive energy storage devices are systematically summarized and discussed with a particular emphasis on the design of printable functional materials, the printing process, and capacitive performance of inkjet-printed SCs. To close, existing challenges and future research trends for developing state-of-the-art inkjet-printed SCs are proposed.

Effective utilization of solar energy is an urgent global issue for solving current environmental problems and the energy crisis. A challenging issue in water splitting for solar fuel production is developing high performance and scalable photo/electro catalysts using low cost approach. Here, CoOx nanostructures were grown on anodized TiO2 nanotube arrays (TNAs) by amperostatic electrodeposition method as oxygen evolution reaction (OER) photoanodes. The effects of electrodeposition current density and deposition time on the growth of so-called nanostructures were investigated based on photoelectrochemical (PEC) measurements and structural characterizations. X-ray diffraction patterns of the photoanodes revealed formation of stoichiometric anatase TiO2 as well as cobalt oxide on the surface. Based on scanning electron microscope, by increasing the electrodeposition current, the morphology of CoOx nanostructures changed which makes electrodeposition current of 0.1 mA·cm−2 resulting in optimum distribution of cobalt oxide electrocatalysts with average size of 35 nm which exhibit the highest photocurrent density due to efficient and uniform distribution of electrocatalysts with no screening effect. Electrodeposition time was found to have a linear relationship with the surface coverage of TNAs by the electrocatalyst, and 2000s, having long charge carrier lifetime and successfully adjusted electrocatalyst to photocatalyst amount ratio turned out to be the optimum electrodeposition time. In this work, we achieved optimized electrodeposition conditions (current density and deposition time) which improve the PEC performance of CoOx-TNAs by 2 times higher than the pristine TNA photocatalyst. Photovoltage measurement and conductive atomic microscopy along with absorption spectra of the samples revealed formation of visible active p-type CoOx species in interface with n-type titania nanotube.

Ag-Functionalized CuWO 4 /WO 3 heterostructures were successfully prepared via a polyvinyl pyrrolidone (PVP)-assisted sol-gel (PSG) route. Thin films prepared via electrophoretic deposition were used as photoanodes for photoelectrochemical (PEC) water splitting. Compared to pristine CuWO 4 and WO 3 films, a significant enhancement of the photocurrent (3-4 times) at the thermodynamic potential for oxygen evolution (0.62 V vs. Ag/AgCl, pH 7) was obtained for the Ag-functionalized CuWO 4 /WO 3 photoanodes. The obtained enhancement is shown to be derived from a synergic contribution of heterostructure formation (CuWO 4 /WO 3 ) and improvements of light utilization by Ag-induced surface plasmon resonance (SPR) effects. Accordingly, a photocurrent of 0.205 mA cm -2 at 0.62 V vs. Ag/AgCl under neutral conditions (without hole scavengers) under front-side simulated AM1.5G illumination was achieved. A detailed analysis of the obtained PEC data alongside performed impedance measurements suggests that charge seperation is significantly improved for the prepared Ag-functionalized CuWO 4 /WO 3 photoanodes. Our work offers beneficial insights to design new plasmonic metal/heterostructured nanocomposites for energy conversion applications.

Hydrogen (H2) production via solar water splitting is one of the most ideal strategies for providing sustainable fuel because this requires only water and sunlight. In achieving high-yield production of hydrogen as a recyclable energy carrier, the nanoscale design of semiconductor (SC) materials plays a pivotal role in both photoelectrochemical (PEC) and photocatalytic (PC) water splitting reactions. In this context, the advent of two-dimensional (2D) materials with remarkable electronic and optical characteristics has attracted great attention for their application to PEC/PC systems. The elaborate design of combined 2D layered materials interfaced with other SCs can markedly enhance the PEC/PC efficiencies via bandgap alteration and heterojunction formation. Three classes of 2D materials including graphene, transition metal dichalcogenides (TMDs), and graphitic carbon nitride (g-C3N4), and their main roles in the photoelectrocatalytic production of H2, are discussed in detail herein. We highlight the various roles of these 2D materials, such as enhanced light harvesting, suitable band edge alignment, facilitated charge separation, and stability during the water splitting reaction, in various SC/2D photoelectrode and photocatalytic systems. The roles of emerging 2D nanomaterials, such as 2D metal oxyhalides, 2D metal oxides, and layered double hydroxides, in PEC H2 production are also discussed.

In this research, we investigate the effect of alkali metal cations including Li, Na and Cs in hydrothermal solution on the morphology, stability, and photoactivity of nanostructured TiO2 nanoflakes as a photoanode. The TiO2 nanoflakes are formed through hydrothermal treatment of Ti foil in 1.0 M LiOH, NaOH or CsOH at 100 °C for 3 h. By subsequent thermal reduction of the structure in an optimized Ar/H2 environment, conductive TiO2 nanoflakes were formed. The reduction treatment remarkably improves the photocurrent density of the TiO2 nanoflakes and has the highest impact on the sample treated in the NaOH alkali solution. For the nanoflakes produced in NaOH alkali solution, the bandgap is shifted to a lower value and the structure shows the most stable morphology after thermal treatment compared to nanoflakes formed in other alkali solutions. Such reduced hydrothermally treated nanoflakes formed in NaOH can generate a photocurrent density of approximately 1 mA/cm−2 vs. Ag/AgCl in 1.0 M KOH solution, which is six times higher than for pristine TiO2.

A nanocomposite of ZnV2O6 with hierarchical flower-like structure hybridized with reduced graphene oxide (rGO) was fabricated using a facile hydrothermal approach. The structure, morphology, optical and electronic properties were explored using comprehensive analytical techniques. The results revealed that the rGO sheets were decorated with the in situ-formed ZnV2O6 nanoparticles yielding a well-combined composite structure. The photocatalytic activity of as-prepared ZnV2O6/rGO hybrids is 2.48 times larger than that of pristine ZnV2O6 for the degradation of Rhodamine B (RhB). In parallel to the experimental results, the basic mechanisms of interfacial interaction, charge transfer/separation and subsequently their influence on the photocatalytic activity were theoretically studied by first-principles calculations. The photocatalytic enhancement is attributed to efficient interfacial electron transfer from ZnV2O6 to rGO, leading to a prolonged lifetime of photoinduced charge carriers. We anticipate that these results will lead to new insights in the judicious design of graphene-based semiconductor photocatalysts.

Highly porous nanocomposites of graphitic-carbon nitride and tin oxide (g-C3N4/SnO2) were prepared through simple pyrolysis of urea molecules under microwave irradiation. The initial amount of tin was varied in order to investigate the effect of SnO2 content on preparation and properties of the composites. The synthesized nanocomposites were well-characterized by XRD, FE-SEM, HR-TEM, BET, FTIR, XPS, DRS, and PL. A homogeneous distribution of SnO2 nanoparticles with the size of less than 10 nm on the porous C3N4 sheets could be obtained, suggesting that in-situ synthesis of SnO2 nanoparticles was responsible for the formation of g-C3N4. The process likely occurred by the aid of the large amounts of OH groups formed on the surfaces of SnO2 nanoparticles during the polycondensation reactions of tin derivatives which could facilitate the pyrolysis of urea to carbon nitride. The porous nanocomposite prepared with initial tin amount of 0.175 g had high specific surface area of 195 m2 g−1 which showed high efficiency photoelectrochemical water-splitting ability. A maximum photocurrent density of 33 µA cm−2 was achieved at an applied potential of 0.5 V when testing this nanocomposite as photo-anode in water-splitting reactions under simulated visible light irradiation, introducing it as a promising visible light photoactive material.

Synthesis of colloidal metal oxides with controllable size and morphology is burgeoning field of research in nanoscience. Low band gap gray Zn/ZnO colloidal nanoparticles were fabricated by plasma-liquid interaction of DC arc discharge in water. Scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy were employed for morphology, crystal structure and optical characterizations respectively. Optical emission spectroscopy was used to investigate the plasma properties during the synthesis and formation mechanism of nanoparticles. Nanoparticles with different size and shape were fabricated only by adjusting discharge current during synthesis without introducing any chemical agent. Electric discharge current was set to 20, 50, 100 and 150 A during synthesis. Estimated values of plasma excitation energies were 2.41, 2.66, 2.86 and 3.04 eV and diameter size of nanoparticles were 63, 42, 37 and 29 nm for these applied currents respectively. Synthesized nanoparticles were dark gray as prepared and became more transparent gradually getting white color finally. XRD and UV–vis results revealed that the oxidation process was time dependent. The colloidal nanoparticles composed of two metal and metal-oxide phase and white crystalline ZnO was achieved after complete oxidation process. These results provided a flexible and versatile method to synthesize metal oxide nanoparticles with controlled composition.

We used first principles calculations based on density functional theory with generalized gradient approximation to investigate and compare the structural, electronic and optical properties of two photoanode materials, ZnV2O6 and Zn2V2O7, for use in photocatalytic water splitting. After geometry optimization, the calculated structural parameters evince a satisfactory agreement with the reported experimental results indicating that the used method and conditions are suitable. The electronic structures demonstrate that both photocatalysts possess favorable band gaps (2.31 and 2.52 eV) and appropriate band edge positions for oxygen evolution reaction under solar radiation. The relatively light effective masses at the valence band maximum and conduction band minimum are expected to result in enhanced photocatalytic activity due to lower recombination probability of the photogenerated electrons and holes. The analysis of electronic density of states reveal that the higher coordination number of vanadium in ZnV2O6 with respect to Zn2V2O7 causes more delocalisation of bands owning to lower V-V and O-O distances in conduction and valence bands, respectively. Moreover, the origins of features that appear in solar energy harvesting characteristics (dielectric function and optical absorption coefficient) have been discussed for solar water splitting in detail.

The necessity of research in food and nutrition and the emergence of diabetes mellitus call for fast and efficient glucose detection. Here, series of highly sensitive non-enzymatic photoelectrochemical glucose sensor based on engineered titanium dioxide nanotube arrays has been synthesized using a simple electrochemical approach to tune nanotubes morphology in a way that the highest sensitivity factor (525.5 µAmM−1cm−2) and saturation concentrations (0.18 mM) achieved in the photoelectrochemical sensor. The formation of oxygen-rich titanium oxide was confirmed by several techniques. Dependent on the growth condition, nanotube length changed from 1.9 to 8.4 µm while their inner diameter varied from 78 to 156 nm. According to the results, TiO2 nanotube arrays anodized for 4 h at 60 V presented the highest saturation concentration of 0.18 mM, which can be used for high glucose level demand cases. On the other hand, nanotubes anodized for 6 h at 50 V obtained the highest sensitivity factor of 525.5 µAmM−1cm−2 with an excellent detection limit and saturation level of 0.1 mM, which is beneficial for purposes involving slight changes in analyte amount. Both optimized sensors presented reasonable selectivity and stability providing optimum tubular TiO2 nanostructure morphology for developing non-enzymatic photoelectrochemical sensors.

To overcome recent energy and environment challenges, developing efficient and low cost photocatalysts are unavoidable. In this context, design of semiconductor nanostructures modified with earth abundant co-catalysts for water splitting reactions requires well engineered and controlled process to optimize surface interface and maximize nanocomposite system efficiency. Here, TiO 2 nanotube were synthesized electrochemically and decorated with cobalt based nanostructure co-catalyst for water oxidation reaction using low cost and scalable electro-deposition approach. By changing deposition parameters and complete studying on samples surface morphology and related statistical analysis data, correlation between all morphological parameters and photoelectrochamical activity of correspondence photoanode was illustrated for the first time. Based on SEM analysis and surface analysis data as well as catalytic performance investigation, nanotubes decorated with Co nanoparticles at 0.1 mA cm −2 deposited for 2000 s presented the best performance with most isotropic surface. Results suggested that by tuning deposition parameters surface structural parameters like fractal dimension, corner frequency, roughness and feature shape and size can be engineered completely. Moreover, X-ray diffraction data along with Rietveld method revealed coexistence of anatase, rutile and Ti 2 O 3 phases in the photoanode while poor crystallinity of grown cobalt based nanostructures was confirmed.

A new plasmonic Ag hybridized CuWO4/WO3 heterostructure was successfully synthesized via a ligand-assisted sol gel method. The as-prepared plasmonic nanohybrid was thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, photoluminescence (PL) spectrometry, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis and electrochemical impedance spectroscopy (EIS). Moreover, the photocatalytic activity was evaluated by photo-degradation of methylene blue (MB) under visible light irradiation. The results indicate that the as-prepared plasmonic Ag–CuWO4/WO3 nanohybrid (compared to pure WO3) with high surface area exhibits significant enhancement in photocatalytic behavior in the visible spectrum, which can be ascribed to combined effects, including the more effective absorption of visible light, lower bulk resistance, effective separation/transfer of photo-generated charge carriers and reduced electron/hole recombination which results from the contribution of hetero-junction and plasmonic Ag incorporation. In addition, a possible mechanism for the photo-degradation process of the hetero-structured Ag nanohybrid is proposed. Finally, the metal/semiconductor nanohybrid displayed sufficient recyclability with respect to photocatalytic activity, making it a promising candidate for pollutant degradation and energy conversion applications.

Bead-chain-like ZnO nanoparticles (NPs) formed in colloidal solution from oriented attachment (OA) of spherical nanoparticles. Arc discharge in liquid is a cost-effective method for quick mass production of nanostructured materials without considerable environmental footprints. Applying voltage across two zinc rods as electrodes, which were immersed in water cause explosion of electrodes and plasma generation. Zn/ZnO nanocomposites produced by interaction of different active species in high-pressure and high-temperature plasma at the solid-liquid interface. Different sized nanoparticles with diameters of 26, 35, 40 and 60 nm at applied discharge currents of 150, 100, 50 and 20 A respectively, were fabricated in water without any chemical additives. The results showed bead-like oriented attachments appeared with increasing the applied current during synthesis. Length of aggregates increases from 114 nm to 120 nm with the applied current of the arc discharge. The mechanism of OA of ZnO NPs was investigated by calculating the attractive and repulsive forces based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed for characterization of particle size, shape, and investigation of bead-like aggregates. X-ray diffraction (XRD) analysis was used to study the crystal structure and phase composition of the bead-chain like nanostructures. Finally, zeta potential analysis was used to measure surface charges and study the mechanism of oriented attachment. The results provide a simple and flexible method for synthesis of Zn/ZnO bead-chain like nanostructures.

Supercapacitors store charge by ion adsorption or fast redox reactions on the surface of porous materials. One of the bottlenecks in this field is the development of biocompatible and high-rate supercapacitor devices by scalable fabrication processes. Herein, a Ti-rich anatase TiO

Hematite is recognized as a promising photoanode for photoelectrochemical water oxidation to produce solar hydrogen due to its favorable properties. However, the high charge carrier recombination rate due to low electrical conductivity and sluggish oxygen reduction kinetics of pure hematite hinder its photocatalytic activity. This work proposed a new hematite-based heterostructure of Ti-Fe2O3/Fe2TiO5/FeOOH, synthesized through a hydrothermal method. The photoanode morphology was branched nanorods that expanded their surface area and improved charge transfer at the photoanode/electrolyte interface. In a novel and complement modification approach, a thin pseudobrookite interlayer was applied between β-FeOOH electrocatalyst and Ti-doped hematite to suppress charge recombination, and enhance charge separation, leading to 32% and 26% increase in photocurrent density and solar to current efficiency, respectively. The photoanode exhibited a great improvement with the photocurrent density of 1.63 mA/cm2 at V = 1.5 V vs. RHE and the total electrical resistance of 2.3 kΩ.cm2 compared to the pure hematite.

Providing solar hydrogen as a clean energy resource is one of the human challenges for future. Controlling oxygen vacancies as well as surface morphology in metal oxide semiconductors enables developing PEC H2 production in some understood ways. Here, the influence of simple change in annealing atmosphere, air and pure oxygen, on photoresponse of nanocrystalline WO3 has been studied completely. Results revealed that such slight change in annealing procedure increases effective surface interface and donor density by 77 and 72%, respectively. These effects and also retarding recombination of photogenerated electro-hole pair resulted in photocurrent enhancement under solar like illumination more than three times.

The controlled growth of metal oxide nanostructures within hierarchically porous conductive carbon-based frameworks is critically important to achieving high volumetric performance and appropriate channel size for energy storage applications. Herein, we grow cobalt oxide (Co3O4) nanoflakes, using a sequential-electrodeposition process, into spherically porous sponge-like few-layer partially reduced graphene oxide (SrGO) synthesized by template-directed ordered assembly. Maximum specific/volumetric capacitances of 1112 F gCo3O4−1 (at 3.3 A gCo3O4−1), 178 F cm−3 (at 2.6 A cm−2), and 406 F gtotal−1 (at 1 A gtotal−1) and sensible rate capability (80% retention by increasing the charge/discharge current from 1 A g−1 to 16 A g−1) are obtained for the Co3O4 nanoflakes@SrGO hybrid electrodes. Besides, an asymmetric supercapacitor is made with the Co3O4[63%]@SrGO[37%] hybrid and activated carbon as a positive and a negative electrode, respectively. Electrochemical results indicate an energy density of 23.3 W h kg−1 at a high power density of 2300 W kg−1 (discharge time of about 42 s) and 62% retention even at a remarkable power density of 36 600 W kg−1 (discharge time of 1.6 s). Moreover, it shows excellent cycling stability with no decay after 20 000 charge/discharge cycles. This performance is attributed to the unique pore-sizes for an ion to channel into the porous structures, conductivity, and mechanical stability of the SrGO framework, which makes it promising for next-generation supercapacitors.

Energy and environment crises motivated scientists to develop sustainable, renewable, and clean energy resources mainly based on solar hydrogen. For this purpose, one main challenge is the low cost flexible substrates for designing earth abundant efficient cocatalysts to reduce required water oxidation overpotential. Here, a systematic morphological and electrochemical study has been reported for cobalt oxide/hydroxide nanoflakes simply electrodeposited on four different commercially available substrates, titanium, copper sheet, steel mesh, and nickel foam. Remarkable dependence between the used substrate, morphology, and electrocatalytic properties of nanoflakes introduced flexible porous steel layer as the best substrate for samples with 499 mV overpotential, 5.3 Ω charge transfer resistance, and 0.03 S–1 turnover frequency. Besides, carbonaceous paste including carbon nanotubes and graphene sheets as the middle layer increased turnover frequency by 33%, effective surface interface nearly three times wh...

Solar energy generation is one of the most efficient approach to solve emerging environment and energy challenges. In this context, solar assisted dissociation of water into oxygen and hydrogen utilizing scalable and high performance electrocatalysts plays key role since the produced hydrogen is a clean energy carrier. Here, cobalt based nanoflakes with metallic core and oxidized surface were grown on the designed carbonaceous layer for anodic oxygen evolution reaction (OER) using an electrochemical approach. Carbonaceous layers containing proper amount of carbon nanotubes (CNT) and reduced graphene oxide (rGO) species were used to optimize the system. Although higher weight percent of rGO led to a more effective surface on the CNT-rGO layer for depositing Co electrocatalytic sites, the lowest overpotential value and charge transfer resistance were obtained for carbonaceous hybrids containing 50 wt% rGO in both CNT-rGO (315 mV, 388 Ω) and Co-deposited CNT-rGO (289 mV, 20 Ω) electrodes. The optimized rGO concentration also influenced cobalt growth mechanism which produced starfish like surface morphology covered by nano sized flakes. This hierarchical surface roughness created more catalytic active sites providing high electrical conductivity in the overall structure leading to an optimum Co-deposited CNT-rGO electrocatalysts for efficient water oxidation process.

TiO2 nanotube arrays (TNA) have been modified by cobalt phosphate (CoPi) through potentiostatic electrodeposition method. Different samples have been prepared by changing the loaded CoPi through the deposition time from 10 to 960 min. Formed catalytic materials have been characterized by different methods. Although charge transfer resistance of the CoPi/TNA photoanodes have been decreased from 5.5 to 4.0 kΩ by increasing the deposition time from 5 to 60 min, the maximum photoresponse was obtained for 10 min CoPi deposition leading to 24% more photocurrent compare to bare TNA which proposed optimum value for cobalt phosphate decoration. Based on field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) results, by depositing the electrocatalyst, nanotube walls have been spread and holes have been covered by CoPi. Correlation between observed change in surface morphology and Raman spectra of the samples along with electrocatalytic tests revealed how decoration time can influence structural properties and photoelectrochemical performance of the final CoPi/TNA photoanodes in solar water splitting system.

A series of reduced graphene oxide/ZnxCd1−xS (RGO/ZnxCd1−xS) nanocomposites (0 < x < 1) with different ratios of Zn/Cd were synthesized via a facile hydrothermal route under optimized experimental conditions and were carefully characterized by various techniques. Because very little is known about the morphology, specific surface area, and crystal phase effects of RGO/ZnxCd1−xS crystals on their photoresponsivity, field-emission scanning electron microscopy (FE-SEM), BET surface area analysis and X-ray diffraction (XRD) data were studied to investigate their effects on photoactivity. Based on the results, a crystal phase transition from a cubic phase in RGO/Zn0.9Cd0.1S to a hexagonal wurtzite phase in RGO/Zn0.8Cd0.2S nanocomposites occurs and the crystalline phase is the main factor influencing the photoresponsivity of RGO/ZnxCd1−xS nanocomposites in photodegradation and photoelectrochemical (PEC) processes under visible light irradiation. According to the results, the RGO/Zn0.8Cd0.2S nanocomposite with the hexagonal crystal phase revealed better photocatalytic activity (k = 9.4 × 10−3 min−1) and PEC response (∼2.0 mA cm−2) in comparison with the cubic crystal phase.

This paper analyses the three-dimensional (3-D) surface texture of Co/CP/X (X = Cu, Ti, SM and Ni, CP: carbonaceous paste) nanoflakes prepared electrochemically using a conventional three electrode system. The surface chemical composition of the samples was investigated by X-ray photoelectron spectroscopy (XPS). Surface images were recorded using scanning electron microscopy (SEM) and analyzed by means of the fractal geometry. Statistical, fractal and functional surface properties of the prepared samples were computed. The statistical functions applied to the SEM data were employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of surface characteristics). The analysis of the 3-D surface texture of Co/CP/X nanoflakes is essential to control the surface topography and for the correct interpretation of surface topographic features as well as its functional role. It also provides a compact representation of complex micromorphology information.

Iron(III) oxide (hematite, Fe2O3) nanofibers, as visible light-induced photoanode for water oxidation reaction of a water splitting process, were fabricated through electrospinning method followed by calcination treatment. The prepared samples were characterized with scanning electron microscopy, and three-electrode galvanostat/potentiostat for evaluating their photoelectrochemical (PEC) properties. The diameter of the as-spun fibers is about 300 nm, and calcinated fibers have diameter less than 110 nm with mesoporous structure. Optimized multilayered electrospun α-Fe2O3 nanostructure mats showed photocurrent density of 0.53 mA/cm2 under dark and visible illumination conditions at voltage 1.23 V and constant intensity (900 mW/cm2). This photovoltaic performance of nanostructure mats makes it suitable choice for using in the PEC water splitting application as an efficient photoanode. This method, if combined with appropriate flexible conductive substrate, has the potential for producing flexible hematite solar fuel generators. Copyright © 2015 John Wiley & Sons, Ltd.

Considering hydrogen as a future fuel, development of clean energy sources based on solar power is the main human challenge in recent years. Here, for the first time, Au:WO3 photoanodes are synthesized with different Au concentrations and then applied for photoelectrochemical (PEC) water splitting. A comprehensive statistical study on the prepared photoanode surface is conducted to understand the correlation between surface morphology and PEC activity, using atomic force microscopy (AFM). The results clearly justified the maximum surface area observed for the film containing 1 mol % Au. Additionally, X-ray diffraction (XRD) analysis determined that Au nanocrystals have been formed in cubic structure with the size of 29–52 nm. X-ray photoelectron spectroscopy (XPS) revealed that the presence of Au in a combined metal/oxide state strongly affects on the Au:WO3 photoanode performance. Photoresponse investigation of the synthesized films showed that the highest photocurrent was obtained for the sample contain...

Today, regarding the limitation and environmental side effects of fossil fuel resources, solar hydrogen production is one of the main interests in the energy research area. The development of visible light sensitized semiconductors based on non-toxic components, low cost and available bio-species is an ongoing approach for H2 generation based on water splitting reactions. Here, two different morphologies of TiO2 photoanodes, nanoparticulated and nanotubular, have been modified with simply extracted bacteriorhodopsin (bR) without any linker. Achieving a significant enhancement in photoconversion efficiency of TiO2 photoanodes, η% was increased from 2.9 to 16.5 by bR addition to the TiO2 nanoparticulate electrode, whereas it increased from 0.5 to 1.9 for the nanotubular system. This result indicated that because of the large size of the extracted purple membranes, nanoparticles showed a greater number of explosion sites for bR attachment, and they were more efficient than the nanotubes. Moreover, comparing these values with the ones reported for bR/TiO2 photoanodes before, the simple proposed decoration method displayed a remarkable improvement in the visible response of the TiO2 based photoanodes. This approach can be beneficial to the area of solar water splitting, photoelectrochemical sensing, and any other photoresponsive systems.

In this study, titanium dioxide (TiO2) nanotube array (TNA) films are fabricated via anodization of titanium (Ti) sheet. After annealing, the films consisted of well ordered, vertically oriented TNAs of 125 ± 6 nm diameter, 38 ± 3 nm wall thickness, and 2.9 ± 0.3 μm in length. Cadmium sulfide (CdS) nanoparticles are deposited on the synthesized TNAs by sequential-chemical bath deposition (S-CBD) method with different immersion cycle (n) to produce heterogeneous TNA/CdS-n (n = 10, 20 and 30) nanostructures. UV–visible absorption spectra of the samples revealed that the absorption edge of CdS modified TNAs was shifted to a higher wavelength with respect to the pure TNAs indicating band gap reduction of the TNA/CdS-n. Photocurrent response of the samples was changed with n, and the maximum photocurrent density (at steady state) of 28 ± 1 mA/cm2 (or 70 ± 2 mA/W) was obtained for the TNA/CdS-20 photoanode which is about 30 times higher than one for the pure TNA under similar condition.

There are some key requirements for a semiconductor employed as photo-catalyst in photoelectrochemical cells which can be predicted by density functional theory (DFT) calculations providing a robust framework to monitor electronic and optical properties. To explore the requiredcharacteristicsfor solar applications, we perform first-principles calculations based on DFT for Zn2V2O7structure. The results illustrate an upper valence band incorporating almost exclusively of O 2p orbitals, while V 3d states are the main constituents of the conduction band, with a moderate mobility of charge carriers. Furthermore, optical calculations display an indirect band gap with a value of 2.52 eV and a mean absorption coefficient about 7×104 cm-1 in the UV-Vis range.

In this work, the silver nanowires with an appropriate aspect ratio and plasmonic properties were successfully synthesized through a polyol process using PVP and characterized by UV-Visible Spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Density Functional Theory (DFT) calculations. UV-Visible spectra display a dual peak line shape which can be ascribed to the transverse dipole resonance (longer wavelength) and the transverse quadrupole resonance (shorter wavelength) of silver nanostructures, respectively. SEM image shows the morphologies and aspect ratios of the synthesized silver nanowires after purification by acetone centrifugation process. The diameters of most of the silver nanowires are in the range of 90–100 nm, and lengths of 1–3 μm. Consequently, asprepared Ag nanostructres with suitabe aspect ratio, satisfactory surface plasmon resonance (SPR) and conductive properties can be considered for designing new plasmonic-semiconductor composite to enhance solar energy conversion efficiency of Photoelectrochemical (PEC) and Photovoltaic (PV) cells.

Considering hydrogen as a future fuel, development of clean approaches based on solar energy conversion is the main human challenge. Here, for the first time, TiO2 photoanodes are decorated with Au–Ag alloy nanoparticles for efficient photoelectrochemical water splitting. The photoanodes were synthesized using a one-step co-sputtering method. The single surface plasmon resonance peak at 540 nm and also the observed shifts in photoelectron binding energies are fingerprints of homogenous alloyed nanoparticles. Scanning electron microscopy revealed the formation of nearly 40 nm particles on the surface, which was also verified by the simulation of the film's optical absorption. Photocurrent measurements showed a 30% increase in the presence of alloy nanoparticles, as well as a 50% reduction in charge transfer resistance of the electrodes. These observations are attributed to adjusting a suitable Schottky barrier in the junction of TiO2/metal particles, which introduces applying alloy noble metallic particles as a new effective strategy for energy and environmental purposes.

The Multi-walled carbon nanotube (MWCNT)/WO{sub 3} nanocomposite thin films with different MWCNT’s weight percentages were prepared by sol–gel method as visible light induced photoanode in water splitting reaction. Weight percentage of MWCNT in the all nanocomposite thin films was confirmed by TGA/DSC analysis. According to XPS analysis, oxygenated groups at the surface of the MWCNT and stoichiometric formation of WO{sub 3} thin films were determined, while the crystalline structure of the nanocomposite samples was studied by XRD indicating (0 0 2) peak of MWCNT in the monoclinic phase of WO{sub 3}. The influence of different weight percentage (wt%) of MWCNT on WO{sub 3} photoactivity showed that the electron conductivity, charge transfer and electron life time had improved as compared with the pure WO{sub 3}. Based on linear sweep voltammetry and chronoamperometry measurements, the (1 wt%) MWCNT/WO{sub 3} nanocomposite thin films photoanode has a maximum photocurrent density of ∼4.5 A/m{sup 2} and electron life time of about 57 s. - Graphical abstract: Photocurrent density versus time at constant potential (0.7 V) for the WO{sub 3} films containing different MWCNT weight percentages annealed at 400 °C under 1000 Wm{sup −2} visible photo-illumination. Display Omitted - Highlights: • MWCNT/ WO{sub 3} nanocomposite thinmore » films were synthesized using sol–gel derived method. • TGA/DSC confirmed the weight percentage of MWCNT in the all nanocomposite thin films. • XPS analysis revealed that WO{sub 3} was attached on the oxygenated group of MWCNT surface. • The Highest Photoelectrochemical activity is achieved for (1 wt%)MWCNT/WO{sub 3} thin film.« less

WO3 thin film photoanodes containing different concentrations of Ag nanoparticles were synthesized by sol–gel method. Based on UV-visible spectra, presence of a surface plasmon resonance peak at 470 nm of wavelength indicated formation of silver nanoparticles in the WO3 films. According to atomic force microscopy (AFM) analysis, the highest value for surface roughness and the effective surface ratio was observed for the sample containing 2 mol% of Ag. X-ray diffraction (XRD) patterns revealed that WO3 nanocrystalline structure was formed in the monoclinic phase with the average size of about 18.2 nm while Ag nanocrystals were determined in cubic phase. X-ray photoelectron spectroscopy (XPS) showed that Ag exists in a combination of metal/oxide states on the surface. Photoresponse investigation of the synthesized films indicated that the highest photocurrent was obtained for the sample containing 2 mol% Ag with the maximum incident photon to current efficiency (IPCE) of about 20% at 360 nm wavelength. Moreover, measuring the amount of hydrogen produced during water splitting reactions verified that the highest hydrogen production rate (∼3 μmol/h) was obtained for the sample with 2 mol% Ag.

TiO 2 thin films containing different concentrations of Ag nanoparticles have been synthesized by sol-gel method. According to UV–visible spectra, presence of an intense surface plasmon resonance peak at 490 nm of wavelength indicated formation of silver nanoparticles in the TiO 2 films. Based on atomic force microscopy (AFM) analysis, the surface roughness and the effective surface ratio increased by increasing the Ag mol%. Moreover, scanning electron microscopy (SEM) images showed formation of Ag nanoparticles on the surface for the samples containing high Ag concentration. X-ray diffraction (XRD) patterns revealed that the size of Ag nanocrystals increased by increasing the Ag content in the films while the nanocrystalline size of TiO 2 reduced in the presence of silver nanoparticles. Based on x-ray photoelectron spectroscopy (XPS) data, a stoichiometric chemical composition was detected for TiO 2 while, Ag presented in a combination a metal/oxide states on the surface. Studying photoresponse of the samples showed that the highest photocurrent was obtained for the sample containing 1 mol% Ag. By measuring the photovoltage versus time, it was found that addition of silver nanoparticles to the TiO 2 layer resulted in reduction of the transient time of the photogenerated carriers in the samples. Impedance spectroscopy determined a slight decrease in charge transfer resistance by addition of Ag to the films. Moreover, measuring the amount of hydrogen produced during water splitting reactions verified that the highest quantum yield of 9.6% was obtained for the sample with 1 mol% Ag.

Chemical oxidation of produced water separated from gas stream of a gas refinery in Iran, has been attempted by use of hydrogen peroxide, ozone and calcium hypochlorite. All the experiments were carried out at 30 °C. The aim of the current work was improving the quality of produced water via degradation of soluble organic materials in order to be re-used as fire-fighting water supply source in the refinery. Produced water separated from natural gas at different stages of gas production process was collected and de-oiled in an API separator. The water effluent of API separator contained chemical oxygen demand (COD) and total dissolved solids (TDS) of 270 and 3450 mgL –1, respectively. The stoichiometry amount of hydrogen peroxide for complete COD removal of produced water (600 mgL –1) of hydrogen peroxide at pH of 7.2 decreased its COD to the level of 228 mgL–1 which corresponds to 15% degradation of organic materials. Ozonation of produced water for 1 hour at pH of 7.2 ended to COD value of 203 mgL–1 (i.e. 12% COD removal). Increasing pH of the water to 10, improved treated water quality (to COD of 192 mgL –1), which indicated higher ozonation efficiency of the produced water at higher pH values. Maximum COD removal was achieved for calcium hypochlorite oxidant. Employing concentrations of 300, 500, 1000 and 7100 mgL–1 of calcium hypochlorite showed COD removal in the range of 36-70%. The final COD values were obtained as 80-173 mgL –1. Kinetic studies of calcium hypochlorite oxidation of produced water revealed that the reaction was completed within 30 minutes at concentrations higher than 500 mgL–1. The results indicated that calcium hypochlorite was the most efficient oxidation agent among the three oxidants employed in this study. The drawback of using calcium hypochlorite is the high concentrations of residual active chlorine in the treated water which should be eliminated before using as fire-fighting water source.

Threatening nature of childhood cancer and the aggressiveness of prescribed treatments place enormous stress on the family of children suffering from cancer. This study was conducted to better understand the lived experiences of parents of children suffering from cancer and to document their account of such experiences. The aim of this research was to describe the lived experiences of parents of children diagnosed with cancer in Iran. This hermeneutic phenomenological study was conducted between June 2008 and May 2009. Data were generated from 15 parents using in-depth interviews to capture their experiences of having children with cancer. Analysis is based on the framework of Diekelmann enabled data interpretation and elaboration of shared themes. One constitutive pattern 'Feeling trapped in the cancer dead end' and four related themes, namely 'Contradiction in reconciliation with situation', 'Doomed to accept', 'Isolation from others' and 'Devastated life', were identified. The results of this study showed that parents feel as if they are trapped by their child's disease. They are affected by several mental, social and familial issues while trying to tolerate their child's illness and conform to the new order of life.

WO3 thin films were fabricated by sol–gel method using polyethylene glycol (PEG) as dispersing agent. Physical and photoelectrochemical properties of the synthesized nanocrystalline films were studied by varying weight ratio of PEG to tungsten precursor (x). Based on AFM observations and statistical modeling of the WO3 surface, the thickness of the films increased by increasing the amount of x with a nearly linear fashion while the surface roughness reached to a saturated value. However, the film synthesized with x = 4 showed a chaotic surface behavior. Optical analysis revealed that by increasing the x, transmittance of the films decreased while their band gap energies remained unchanged. According to XRD results, variation of x did not change structure of the nanocrystalline film while XPS analysis indicated a better stoichiometry for the films with higher x values. A less charge transport life time was obtained for films with higher x values, but an enhanced photoresponse of the films and also hydrogen production via water splitting reaction were observed by increasing the amount of x. On the other hand, the charge transfer resistance of the samples reduced from 6.5 kΩ to 1.2 kΩ by addition of PEG to the sol from x = 0 to x = 2.

TiO2/ZnO and ZnO/TiO2 nanolayer thin films were synthesized using sol–gel method. Optical analysis revealed high transmittance of the films in the visible range with almost the same bandgap energy for the both systems. XPS technique shows stoichiometric formation of TiO2 and ZnO on the surface of TiO2/ZnO and ZnO/TiO2 layers, respectively. According to AFM observations and its data analysis, the TiO2/ZnO films exhibited a higher surface roughness and more effective interfaces with electrolyte during redox reactions. Based on photoelectrochemical measurements, TiO2/ZnO nanolayer photoanode possesses a lower charge transfer resistance and higher transient time for charge carriers (e− and h+) and hence a higher photocurrent density under visible light irradiation as compared with the ZnO/TiO2 nanolayer system.

In this study, the effects of TiO2 addition on the physical and photoelectrochemical properties of ZnO thin films have been investigated. The (TiO2)x–(ZnO)1−x nanocomposite thin films were dip-coated on both glass and indium tin oxide (ITO)-coated conducting glass substrates with various values of x, specifically 0, 0.05, 0.1, 0.25 and 0.5. Optical properties of the samples were studied by UV–vis spectrophotometry in the range of 300–1100 nm. The optical spectra of the nanocomposite thin films showed high transparency in the visible region. The optical bandgap energy of the (TiO2)x–(ZnO)1−x films increased slightly with increasing values of x. The crystalline structure of the nanocomposite films was investigated by X-ray diffraction, which indicated the formation of ZnO nanocrystals in the thin films with x

In this study, pure TiO2 and Au:TiO2 nanocomposite thin films are both synthesized using sol–gel and RF reactive co-sputtering methods. Physical and photoelectrochemical properties of the thin films deposited by each method are compared. The optical density spectra and scanning electron microscopy images of the Au:TiO2 films reveal formation of gold nanoparticles in the all nanocomposite films synthesized by two methods. Moreover, the optical bandgap energy of the thin films decreases with addition of Au nanoparticles. X-ray photoelectron spectroscopy indicates that the presence of gold in metallic state and the formation of TiO2 is stoichiometric. The photoelectrochemical properties of the TiO2 and Au:TiO2 thin films are characterized by using a compartment cell containing KOH solution as electrolyte. It is found that in the pure systems, TiO2 sputtered films shows a higher photocurrent under visible light illumination while a reverse result is obtained for the Au:TiO2 systems. In addition, photoirradiation on electrode/electrolyte (EE) and substrate/electrode (SE) interfaces for the sputtered samples reveals the EE illumination enhances the photoresponse of the layers as compared to SE case.

In this investigation, the effect of gold nanocrystals on the electrochromical properties of sol–gel Au doped WO3 thin films has been studied. The Au–WO3 thin films were dip-coated on both glass and indium tin oxide coated conducting glass substrates with various gold concentrations of 0, 3.2 and 6.4 mol%. Optical properties of the samples were studied by UV–visible spectrophotometry in a range of 300–1100 nm. The optical density spectra of the films showed the formation of gold nanoparticles in the films. The optical bandgap energy of Au–WO3 films decreased with increasing the Au concentration. Crystalline structure of the doped films was investigated by X-ray diffractometry, which indicated formation of gold nanocrystals in amorphous WO3 thin films. X-ray photoelectron spectroscopy (XPS) was used to study the surface chemical composition of the samples. XPS analysis indicated the presence of gold in metallic state and the formation of stoichiometric WO3. The electrochromic properties of the Au–WO3 samples were also characterized using lithium-based electrolyte. It was found that doping of Au nanocrystals in WO3 thin films improved the coloration time of the layer. In addition, it was shown that variation of Au concentration led to color change in the colored state of the Au–WO3 thin films.