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Herein, in situ zirconium-doped hematite nanocoral (Zr–Fe2O3 (I) NC) photoanode was prepared via a specially designed diluted hydrothermal approach and modified with Al3+ co-doping and electrodeposited cobalt–phosphate (“Co–Pi”) cocatalyst. Firstly, an unintentional in situ Zr–Fe2O3 (I)) NC photoanode was synthesized, which achieved an optimum photocurrent density of 0.27 mA/cm2 at 1.0 V vs. RHE but possessed a more positively shifted onset potential than conventionally prepared hematite nanorod photoelectrodes. An optimized amount of aluminum co-doping suppresses the bulk as well as surface defects, which causes a negative shift in the onset potential from 0.85 V to 0.8 V vs. RHE and enhances the photocurrent density of Zr-Fe2O3(I) NC from 0.27 mA/cm2 to 0.7 mA/cm2 at 1.0 V vs. RHE. The electrodeposited Co–Pi modification further reduce the onset potential of Al co-doped Zr–Fe2O3(I) NC to 0.58 V vs. RHE and yield a maximum photocurrent of 1.1 mA/cm2 at 1.0 V vs. RHE (1.8 mA/cm2 at 1.23 V vs RHE). The improved photocurrent at low onset potential can be attributed to synergistic effect of Al co-doping and Co–Pi surface modification. Further, during photoelectrochemical water-splitting, a 137 and 67 μmol of hydrogen (H2) and oxygen (O2) evolution was achieved over the optimum Co–Pi-modified Al-co-doped Zr–Fe2O3(I) NC photoanode within 6 h. The proposed charge transfer mechanism in optimum Co–Pi-modified Alco-doped Zr–Fe2O3(I) NC photoanodes during the photoelectrochemical water splitting was also studied.

ZnFe2O4 nanorods (NR's) were prepared by a chemical conversion method from β-FeOOH NRs grown on FTO substrates. To activate their photoactivity of ZnFe2O4 NRs for solar water splitting, the surface passivation was achieved with SiO2 layer via facile and effective spray pyrolysis method. The presence of SiO2 layer enhances the photocurrent density of the Pristine ZnFe2O4 from 143 µA/cm2 to 212 µA/cm2 at 1.23 VRHE for 0.25 mM Si–ZnFe2O4, representing two time increment in the photocurrent density. The influences of amount of Si precursor (Tetraethyl orthosilicate) solutions on the physical properties and the passivation effect of SiO2/ZnFe2O4 interfaces were investigated. This improved photoresponse of the Si-treated ZnFe2O4 NRs was attributed to the excellent charge transfer electrode/electrolyte interface. The effectively improved charge transfer properties of the Si-treated ZnFe2O4 NRs were demonstrated by the electrochemical impedance spectroscopy (EIS), Mott–Schottky (MS) and intensity-modulated photocurrent spectroscopy (IMPS) analyses.

A highly three-dimensional CdIn2S4 deposited TiO2 (CdIS/TONR/FTO) heterostructured photoanode has been fabricated via a two-step hydrothermal process to enhance the photoelectrochemical (PEC) performance. In this work, bare TiO2 nanorods are grown successfully on the fluorine-doped tin oxide (FTO) substrate via a hydrothermal method (TONR/FTO), and a second-step hydrothermal synthesis is used to grow CdIn2S4 flower nanostructured layer over the top surface of the bare TONR/FTO. Structural, morphological, optical, and elemental analysis of CdIS/TONR/FTO heterostructure photoanode is investigated in detail. PEC performances are studied in 0.2 V versus Ag/AgCl in mixed sulfide-based electrolyte for various concentrations of CdIn2S4 deposited on photoanodes. The photocurrent density for optimized (×4)-CdIS/TONR/FTO heterostructure photoanode is observed to be three times higher than that of the bare TONR/FTO photoanode. This excellent PEC performance is ascribed to the way that the deposited CdIn2S4 layer and TiO2 nanorods synergistically allow the absorption of a wide portion of the solar spectrum under back illumination, and provide efficient separation of the electron-hole pairs in the photoanode architecture. The EIS and IMPS analysis also reveal the significance of CdIn2S4 layer that provides the lowest charge-transfer resistance at the interface and high electron-transfer rate in CdIS/TONR/FTO photoanode. Mainly, the deposited CdIn2S4 layer significantly broadens the optical absorption capacity, and provides efficient electrons-holes transfer that reduces the recombination losses of the charge carriers. The proposed charge transfer mechanism in CdIS/TONR/FTO heterojunction is well studied.

Herein, we report the surface treatment on Zr4+/Al3+ codoped α-Fe2O3 photoanode for high-performance photoelectrochemical water splitting. A high-temperature quenching exhibits the Zr4+/Al3+ codoping in α-Fe2O3 photoanode without damaging morphology. The presence of Zr4+/Al3+ codoping shows a cathodic shift in onset potential, but lack of increment in photocurrent reveals the major role of passivation and the minimum doping effect of aluminum. Additionally, CoOx cocatalyst exhibits increment in photocurrent with the greater cathodic shift in onset potential than the pristine α-Fe2O3 nanorods. The CoOx surface-reworked Zr4+/Al3+ codoped α-Fe2O3 photoanode displays the highest photocurrent of 1.5 mA/cm2 at 1.23 V vs. RHE (76% increment over the pristine α-Fe2O3) and 0.7 mA/cm2 at 1.0 V vs. RHE (102% increment over the pristine α-Fe2O3). The systematic characterization carried out using x-ray diffraction and scanning electron microscopy confirms that after Zr4+/Al3+ codoping, and surface treatment, the crystalline structure, and morphology of the photoanodes remains unchanged. X-ray photoelectron spectroscopy confirmed the existence of Zr4+/Al3+ codopants in the hematite nanostructure. The electrochemical properties of the photoanode suggest that Al3+ and Zr4+ codoping, as well as surface treatment with CoOx, cocatalyst lowers charge transfer resistance across the FTO/hematite interface, and hematite/electrolyte interface. This designs not only lowers onset potential but also offers the blueprint for the development of an efficient catalyst for solar water oxidation.

In this study, we have synthesized hierarchical TiO2@In2O3 heteroarchitecture photoanodes via a hydrothermal method and studied their interfacial charge carrier dynamics through water splitting and organic decomposition. Photoelectrochemical measurements show that the IN-0.4 exhibits an obvious enhancement in photocurrent density compared to the pristine TiO2. Electrochemical impendence spectroscopy (EIS) and Time-resolved photoluminescence (PL) have been employed to study the charge recombination in TiO2@In2O3 nanostructure. The surface passivation of TiO2 nanorods (NRs) with In2O3 nanostructures helps to the suppression of the surface defects. The surface-passivated photoanode (IN-0.4) has demonstrated the improved hydrogen generation activity (125 μmol∙h−1) of TiO2 nanorods (NRs) with In2O3 nanostructures during water splitting and organic decomposition. The probable causes of the enhancement in hydrogen evolution could be due to (i) enhanced photogenerated electron transport (ii) increased active surface area with In2O3 and/or (iii) catalytic activity of In2O3. Moreover, the photoelectrocatalytic activities of IN-0.4 were slight affect during degradation of Bisphenol A and methyl orange dye, which might be due to the lower hole mobility in TiO2@In2O3 heteroarchitecture photoelectrodes. These sightings and proposed schematic model can help to understand the charge transfer dynamics in hierarchical TiO2@In2O3 heteroarchitecture photoelectrodes as well as designing multifaceted photoelectrodes for solar energy conversion.

The surface modified tetravalent ions doped hematite nanorod photoanodes has been synthesized by successive hydrothermal and spin coating approaches. The effect of tetravalent ion (Sn, Ti, and Zr) doping and high temperature annealing on to the morphological, structural and photoelectrochemical properties has been investigated. Photoelectrochemical analyses indicate tetravalent doping (Sn, Ti, and Zr) and high-temperature annealing (800 °C) showed higher photocurrent and improved activity towards Orange-II dye degradation, compared to the pristine hematite film. Amongst tetravalent dopants, Zr4+ doped hematite can significantly enhance the photocurrent density (1.37 mA cm−2 at 1.23 V vs. RHE) as well as the Orange-II dye degradation activity (93% under one sun illumination in 270 min). Kinetic parameters are also investigated by first-order rate equation. Further, Zr–Fe2O3 photoanode modified with the appropriate composition of CoOx and specific structural features demonstrated improvement in photocurrent from 1.6 to 1.78 mA cm−2 (at 1.4 V vs. RHE). The efficient charge carrier separation and generated hydroxyl radicals led to enhancements of the Orange-II dye degradation efficiency up to 97% within 270 min. The significant decrease in chemical oxygen demand values suggests the removal of Orange-II dye. This work demonstrates that enhancement in photoelectrochemical activity is due to the combined effect of passivation of surface states and the formation of CoOx/Zr–Fe2O3 heterojunction.

In this work, the hydrothermal approach has been used to prepare and control the morphology of Bi2S3 nanosheet (NS)/Zr doped Fe2O3 nanorod (NR) heterojunction grown on fluorine doped tin oxide (FTO) phoptoelectrodes. The effect of morphology of Bi2S3 NS was examined by comparing the photocatalytic activity of Zr:Fe2O3 nanorod with synthesized heterojunctions. This novel heterojunction photoanode exhibits the light harvesting, the photoinduced electron–hole separation and yielding a maximum photocurrent density of ∼1.27 mA cm−2 at −0.4 V vs. Ag/AgCl under one sun illumination. Bi2S3 NS on surface of the Zr:Fe2O3 NR will act as the active material which shows the dramatic improvement in photocurrent generation. Further, effect of silver interlayer on the interface properties of Bi2S3 NS/Zr:Fe2O3 NR heterojunction was also studied. The results indicated that the silver interlayer reduces charge recombination at interface of Bi2S3 and Zr:Fe2O3. Also, the surface plasmon resonance of Ag and controlled morphology enhances the performance (1.5 mA cm−2 at −0.4 V) as well as improves the stability of Bi2S3/Zr:Fe2O3 heterojunction photoelectrode. This unique design of the nanoarchitecture provides an attractive pathway for the photogenerated electrons and the silver interlayers has great impact on enhancing charge separation and improving stability of photoanode.

Various solar conversion materials with 1D nanostructure have been developed and are being widely investigated for various solar fuel generation applications. In this study, aligned and non-aligned CdS nanowires (NWs) were synthesized on Cd foil or in solution via solvothermal processes. In the case of aligned CdS NWs, the relative intensity of the (0 0 2) diffraction peak was higher than that of the non-aligned CdS NWs, which indicated that the NWs grew preferentially in the (0 0 1) direction. The systematic comparison between the photoelectrochemical properties of both electrodes revealed that the aligned CdS NW electrode displayed markedly enhanced photocurrent (by a factor of 7), photoelectrochemical hydrogen production (by a factor of 10), and photostability in comparison with those of the non-aligned NWs electrode fabricated on FTO glass. Resistance (Rµ) through the inner part of the aligned CdS NWs was very small due to a low grain-boundary resistance (by a factor of 130). This low resistance induced efficient charge transfer, reducing the charge recombination loss and assisting the charge transport along the axial direction of the aligned NWs. Time-resolved photoluminescence spectroscopy confirmed that the charge separation in the aligned CdS NWs is longer than that in the non-aligned CdS NWs (by a factor of 1.6).

In present work, we synthesized ZnFe2O4 nanorods on a fluorine-doped tin oxide substrate using spray coating method followed by two-step high-temperature quenching (HTQ). X-ray photoelectron spectroscopy (XPS) results indicate that Sn4+ is diffused from the FTO substrate after the second quenching, which could help in minimizing the recombination of photogenerated carriers. Photoelectrochemical measurements of the ZnFe2O4 nanorod photoelectrodes quenched at 780 °C, 800 °C, and 820 °C indicate that among the studied samples (ZFO1, ZFO2 and ZFO3), the highest photocurrent density was observed for nanotextured ZFO3 photoelectrodes (130 µA cm−2 at 1.23 V vs RHE). The photoelectrochemical performances of the ZnFe2O4 nanorods after the second quenching were compared with those of the firstly quenched ZnFe2O4 nanorod samples; water-oxidation photocurrent density of the former (ZFO3) was increased by 6.9 times compared with that of the first quenching (PZFO). Intensity modulated photocurrent spectroscopy (IMPS) and photoluminescence (PL) results confirm the faster charge extraction was achieved for the ZFO3 photoelectrode. Thus, the overall photocurrent density during the second quenching process results from the effectively improved crystallinity, the reduced strain and suppressed charge–carrier recombination's on both the surface as well as in the bulk of the ZnFe2O4 nanorods. In terms of solar water splitting, these research findings provide an effective route for the synthesis of other nanostructures.

This work focuses on dependence of incident light illumination direction on the photoelectrochemical performance of hydrothermally prepared two dimensional ZnIn2S4 nanosheets/one dimensional rutile TiO2 nanorod arrays (2D ZIS NS's/1D R-TNR's) heterostructure photoelectrodes. The 2D ZIS NS's are grown on the 1D R-TNR's/FTO substrates by varying the concentration of ZIS precursor in the hydrothermal method, forming 2D ZIS NS's/1D R-TNR's heterostructure. One dimensional rutile TiO2 nanorod arrays (1D R-TNR's) provide excellent electron transfer pathway and role of the 2D ZIS NS's is to offer effective visible light absorbing surface onto the 1D R-TNR's and extended the absorbance spectrum from ultraviolet to visible region; bathochromic shift occurs. This binary heterostructure provides the lower resistance, shortest electron transport time and less recombination under the back side illumination (BSI) and effectively contributed to charge separation and transport in 2D ZIS NS's/1D R-TNR's heterostructure. However, the results demonstrate that the front side illumination (FSI) results in poor PEC performance; because of blockage of light at the surface of 2D ZIS NS's. Further, these results show that BSI could also be applicable for other heterostructures, where the low band gap sulfide materials need to be engineered on large band gap metal oxide for energy harvesting in future prospect.

The vertically aligned TiO2 nanorod arrays (NRA) with manipulated aspect ratio were hydrothermally synthesized by changing the amount of the titanium (Ti) precursor in the initial growth solution. FE-SEM images show the optimum morphology, density and aspect ratio of the well-aligned TB-1.2 NRs on the surface of the FTO substrate. The UV-vis-absorption measurements revealed that a sample prepared at TB-1.2 can provide an increased light trapping effect. PEC analyses demonstrated that the TiO2 nanorods deposited at TB-1.2 of Titanium butoxide show a relatively high PEC conversion efficiency (3.5 times) compared with the TB-0.8 prepared TiO2 at a 1.0 V versus RHE. The higher PEC performance is believed to be the result of an enhancement of the optimum aspect ratio, light trapping, an efficient charge separation, and the high carrier transport in the vertically aligned TiO2 NRs. Further, the PEC based organic dye degradation experiments showed 77% and 94% removal of Orange II and methylene blue respectively. Additionally, 109 μmol h−1 cm−2 hydrogen generations were attributed using optimized vertically aligned TiO2 NRA’s. Thus, the appropriate morphology manipulated the TiO2 NRAs are useful for solar conversion applications.

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.

A novel inorganic-organic Se rich-ZnSe(en)0.5 red-brick (ZnSe(en)0.5 RB) was developed on Zinc (Zn) foil through a low-temperature solvothermal synthesis. The structure evolution and growth mechanism of ZnSe(en)0.5 RB were systematically proposed at 80 °C by varying the solvothermal times (2−12 h) . In the reaction system, adsorption of reduced Se2− in presence of ethylenediamine ((en)0.5) induced the red-brick (RB) color to ZnSe(en)0.5. Furthermore, Cd2+ ion-exchange strategy was adopted for converting ZnSe(en)0.5 RB into dual nanoarchitecture photoelectrode (ZnO-Zn1-xCdxSe). The optimum ZnO NR-Zn1-xCdxSe NP 160 photoelectrode converted from ZnSe(en)0.5 RB-12 exhibited a photocurrent density of 13.14 mA·cm-2 at -0.2 V vs. Ag/AgCl with 237.79 μmol·cm−2 hydrogen evolution over 3 h. The enhanced photocurrent performance was due to the effective light absorption, and the prolonged recombination lifetime. The charge separation and transport mechanisms during photoelectrochemical hydrogen production were also investigated in detail.

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.

Anatase/rutile TiO 2 nanorods composites were prepared by a facile hydrothermal method followed by dip coating method using titanium isopropoxide in acetic acid and ethanol solvent. The effects of the titanium isopropoxide precursor concentration, on the formation of dip coated anatase/rutile TiO 2 nanorods composite were systematically explored. The growth of anatase on rutile TiO 2 nanorods can be controlled by varying the titanium isopropoxide concentration. The morphological study reveals that anatase TiO 2 nanograins formed on the surface of rutile TiO 2 nanorod arrays through dip coating method. Photoelectrochemical analyses showed that the enhancement of the photocatalytic activities of the samples is affected by the anatase nanograins present on the rutile TiO 2 nanorods, which can induce the separation of electrons and holes. To interpret the photoelectrochemical behaviors, the prepared photoelectrodes were applied in photoelectrochemical solar hydrogen generation and orange II dye degradation. The optimized photocurrent density of 1.8 mA cm −2 and the 625 μmol hydrogen generation was observed for 10 mM anatase/rutile TiO 2 NRs composites. Additionally, 96% removal of the orange II dye was achieved within 5 h during oxidative degradation under solar light irradiation. One of the benefits of high specific surface area and the efficient photogenerated charge transport in the anatase/rutile TiO 2 nanorod composite improves the photoelectrochemical hydrogen generation and orange dye degradation compared to the rutile TiO 2 . Thus, our strategy provides a promising, stable, and low cost alternative to existing photocatalysts and is expected to attract considerable attention for industrial applications.

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.

Controlling the morphology of semiconductors at the nanoscale level is the key for efficient photoelectrochemical (PEC) water splitting systems. Herein, we report for the first time the fabrication of porous hematite nanoball array film on conducting FTO via a facile pulse reverse electrodeposition method using cetyltrimethylammonium bromide (CTAB) surfactant and a TiO2 underlayer (UL) on FTO. A prolonged low-temperature-annealing treatment is employed to convert iron into hematite (α-Fe2O3) and to remove the surfactant molecules gradually. Annihilation of surfactant molecules led to the creation of pores during crystallization of hematite nanoballs, thereby providing low-resistant diffusion pathways for the migration and incorporation of cations (Ti4+ from UL and Sn4+ from FTO) in hematite. The hematite photoanode with porous nanoball array exhibited significantly higher PEC performance than the flat hematite due to sixfold enrichment in the donor density, improved charge-transfer properties, and higher light absorption. The enhancement in photocurrent and water oxidation performance of porous hematite photoanode is also feasible when coupled with well-known Co and CoPi catalysts. Thus, our new approach allowed the simple fabrication of hematite films with nanoporous architecture for enabling high photon harvesting and maximized interfacial charge transfer to facilitate water oxidation reaction.

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 and effective strategy was used to fundamentally improve the performance of a heterostructured Ni(OH)2/CdS/ZnIn2S4/TiO2 photoanode. TiO2 nanorods grown hydrothermally on fluorine-doped tin oxide (FTO) and annealed at 500 °C yielded an optimal photocurrent density of ~988 μA cm–2 at 0.1 V vs. Ag/AgCl under simulated illumination conditions. The annealing process minimized the defects in TiO2 and assisted in the formation of close contacts between the FTO and TiO2 nanorods, which allowed for efficient electron transport. The stepwise introduction of ZnIn2S4 and CdS on annealed TiO2 enhanced absorption in the visible range and electron/hole separation in CdS/ZnIn2S4/TiO2. Additionally, the Ni(OH)2 cocatalyst functioned in hole trapping and improved the stability of the photoelectrode through timely consumption of the photogenerated charges, particularly the holes.

Synchronized surface modification and doping of hematite nanorod via sputtering is one of the impressive methods to develop photoanodes for practical application. In this paper, we report the role of Zr sputtering and 800 °C quenching on the structural and electrochemical properties of FeOOH NRs. The amount of ZrOx loading onto β-FeOOH NRs was controlled by varying the sputtering time. FESEM and TEM images revealed that high-temperature quenching of Zr-sputtered β-FeOOH NR’s confirms the Zr doping and non-uniform ZrO2 nanoparticles on vertically aligned Zr-doped hematite (Zr-Fe2O3 NRs). XPS analysis represented a tradeoff between extrinsic Zr doping and intrinsic Sn diffusion with increasing the thickness of deposited Zr layer in Zr-Fe2O3 NRs. A maximum achieved photocurrent density (1.23 mA/cm2 at 1.23 V vs RHE) for the 7 nm Zr-Fe2O3 sample is 48% higher than that of pristine photoanode (Fe2O3 NRs). The electrochemical impedance spectroscopy and Mott-Schottky analyses revealed that the charge transfer properties and donor densities were effectively improved for Zr-Fe2O3 NRs photoanode. The photoelectrochemical reactor consisted of an optimum 7 nm Zr-Fe2O3 based photoanode exhibits the 115 and 165 μmol, respectively O2 and H2 evolution over 10 h of 1 sun illumination. These results demonstrate the Zr sputtering approach followed by high-temperature quenching allows controlled Zr doping in vertically aligned Fe2O3 NRs for PEC water splitting applications.

Here, metal oxides/hydroxide (MO = (PdO)n·[Pd(OH)2]m, Co(OH)2, and (PdO)n·[Pd(OH)2]m/CoO, n > m) clusters were successfully co-loaded on the surface of acid-treated molten salt fluxed TiO2 nanorods (ATO-NRs) via conventional wet impregnation. The synergistic effect of palladium oxide/palladium hydroxide and cobalt oxide [((PdO)n·[Pd(OH)2]m/CoO)] co-loading on ATO-NR demonstrated by the photocatalytic degradation of Orange II dye, bisphenol A and S. typhimurium inactivation under mimicked and unfiltered solar light (Xe arc lamp) radiation. Optimum [((PdO)n·[Pd(OH)2]m/CoO)] co-loaded ATO-NRs exhibited significantly higher degradation efficiency (Orange II (91%) and BPA (97%) within 30 min of treatment) over (PdO)n·[Pd(OH)2]m (n > m) and CoO/ATO-NRs under Xe arc lamp light radiation. Also, optimal sample showed higher inactivation efficiency for S. typhimurium than (PdO)n·[Pd(OH)2]m (n > m)/ATO and CoO/ATO-NRs under UVA light radiation, however, the photocatalytic mechanisms for S. typhimurium inactivation was different than the BPA. Photoelectrochemical analyses demonstrated that the significantly accelerated charge-transfer process in metal oxides/hydroxide cluster [(PdO)n·[Pd(OH)2]m/CoO] co-loaded ATO-NRs leading to higher degradation efficiency than other studied samples. Radical trapping supports h+ and O2 − as major reactive species, with OH playing a secondary role in Orange II and BPA degradation. Cell membrane interruption by reactive oxygen species (ROS) and reactions of photocatalyst with the –NH and –COOH group of protein and metalloproteins, nucleic acid in bacterial cells could be the main cause in S. typhimurium disinfection. Plausible charge transport pathways were proposed for photocatalytic degradation of organic pollutants and bacterial inactivation over the (PdO)n·[Pd(OH)2]m/CoO/ATO-NR’s.

Herein, dual nanostructured ZnO nanorod (NR)-Zn1-xCdxS porous nanosheet (PNS) photoanodes were produced on a zinc foil through cation exchange reaction of inorganic–organic hybrid ZnS(en)0.5 nanosheets. ZnS(en)0.5 NS’s photoanodes have been synthesized via a facile solvothermal method followed by a series of cadmium (Cd2+) ion-exchange using various ion-exchange reaction times and temperatures. During Cd2+ ion-exchange, the Zn1-xCdxS PNS and a new type of vertically aligned ZnO NR were subsequently grown on the zinc foil substrate. The different exposed surfaces of the vertically aligned hexagonal ZnO NR and Zn1-xCdxS PNS photoanodes contribute to appropriate morphology, effective light harvesting, and efficient charge separation in ZnO-NR-Zn1-xCdxS PNS160C. The optimum ZnO NR-Zn1-xCdxS PNS160C photoanode contributed the highest photocurrent density of 6.60 mA·cm−2 and hydrogen production of 250.65 μmol·cm−2 at 0 V vs. Ag/AgCl. Finally, the charge transfer mechanism in the optimum photoanode is discussed in detail.

A nanocomposite heterojunction photoanode involving CdS nanoflowers (NFs) and one-dimensional TiO 2 nanotube (NT) arrays was reported. The self-assembled TiO 2 NT arrays were fabricated by an anodization method and the surface of TiO 2 NT arrays was decorated with CdS NFs by employing hydrothermal method for the first time. The CdS NF morphology was optimized by controlling the hydrothermal reaction time from 0 to 72 h. Field-emission scanning electron microscopy (FESEM) study of the CdS-NF/TiO 2 -NT photoanode revealed good coverage of hydrothermally grown CdS NFs on the surface of TiO 2 NT arrays. The photoelectrochemical measurements were performed under 100 mW cm −2 illumination using polysulfide electrolyte. A 5.5-fold photocurrent enhancement was observed for the CdS-NF/TiO 2 -NT array photoanode synthesized with a 48 h CdS hydrothermal reaction compared to a pristine TiO 2 NT array film. Annealing of TiO 2 NTs as well as CdS NFs led to further improvement in the photocurrent on account of greater crystallinity, significantly higher visible light photon absorption and improved interface properties between CdS and TiO 2 . These findings were supported by optical absorption, electrochemical impedance spectroscopy and Mott–Schottky analyses.

We designed metal oxide coated ZnIn 2 S 4 /TiO 2 (ZT) heterostructure photoanodes for enhanced photoelectrochemical performance via hydrothermal and dip-coating methods. The effects of thin metal oxide coating layers, such as TiO 2 , Al 2 O 3 , and SiO 2 , on the structural, morphological, optical, and photoelectrocatalytic activity of ZT photoanodes were investigated in detail. The metal oxide coating layers significantly enhanced the photoelectrochemical performance of ZT in the following order: SiO 2 /ZT > Al 2 O 3 /ZT > TiO 2 /ZT > ZT, all at pH 11.5 under simulated one sun illumination. A two-fold boost in the photocurrent density of ZT was recorded after a surface coating of a thin SiO 2 layer among the studied metal oxide layers. The charge transfer resistance measured from the electrochemical impedance spectroscopy (EIS) analysis was less for the SiO 2 /ZT photoanode, indicating enhanced charge separation between the oxide surface layer and electrolyte. The enhanced photoelectrochemical performance due to the thin SiO 2 coating was attributed to the improved interface properties that led to the effective charge transfer processes in the vicinity of the electrolyte.

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.

Herein, we synthesized porous Zn1-xCdxS nanosheets (PNS)/ZnO nanorod (NR) heterojunction photoanode via self-templated conversion using successively hydrothermal and Cd2+ ion exchange methods. Moreover, after conversion of ZnO to inorganic–organic hybrid ZnS-1,6-hexanediamine (HDA)0.5nanosheets/ZnO NR material, Cd2+ ion exchange was conducted. It was confirmed from X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM) analyses that the inorganic–organic hybrid ZnS(HDA)0.5 NS was transformed into Zn1-xCdxS PNS/ZnO NR heterojunction photoanode via the replacement of Zn2+ by Cd2+ ion. Zn1-xCdxS PNS/ZnO NR-160C3H heterojunction photoanode synthesized at 160 °C for 3 h showed the highest photocurrent density of 4.10 mA cm−2 (vs. RHE) under 1.5 G illumination, which was 7.9 times higher than that of bare ZnO NR photoanode. The porous nanostructured morphology and larger surface area of Zn1-xCdxS PNS/ZnO NR heterojunction photoanode fabricated by Cd2+ ion exchange result in efficient light absorption and effective charge transfer pathway. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) results show the shorter lifetime (37 ns) and reduced recombination in Zn1-xCdxS PNS/ZnO NR-160C3H heterojunction photoanode. During PEC analysis, the possible charge transfer mechanism in Zn1-xCdxS PNS/ZnO NR heterojunction photoanode was proposed. Surface passivated Zn1-xCdxS PNS/ZnO NR-160C3H photoanode shows improved photostability and exhibited 3.8 times higher H2 evolution (161 μmol) than the Zn1-xCdxS PNS/ZnO NR-160C3H (42 μmol) photoelectrode at 0.9 V vs. RHE.

To tackle the problem of bulk recombination and to solve the holes diffusion issue in hematite, the shape-guiding and in situ doping is an effective strategy. Herein, we developed a novel strategy for designing and fabricating zirconium-doped transparent hematite (Zr-Fe2O3(I)) photoanode through an in situ hydrothermal method and stoichiometric iron and zirconium dilution. The concentration of ZrO(NO3)2 and FeCl3·6H2O in the precursor solution effectively influenced the transparency and morphology of zirconium-doped Fe2O3. The XPS and TEM analyses confirms the co-existence of Zr doping and surface modification of Fe2O3 nanocoral diffused ZrO2 after high temperature quenching. Synergism between the Zr doping and ZrO2 layer facilizes the charge transfer in Zr-Fe2O3 nanocoral (NC) photoanodes. Among the photoanodes prepared by variously diluted concentrations of the iron and zirconium precursor, the in situ 1/32 Zr-Fe2O3 nanocoral (NC) photoanode achieved an excellent photocurrent density of 1.55 mA cm2 at 1.23 V vs. RHE, which is about doubles than that of the conventional pristine Fe2O3 (P-Fe2O3) NR. Additionally, as result of in situ Zr doping, favorable nanocoral morphology and ZrO2 surface modification exhibits the decreased changer transfer resistance and increased incident photon to current efficiency (IPCE) of 1/32 Zr-Fe2O3 NC upto 21.9%. This in situ Zr-doping and nanocoral morphology 1/32 Zr-Fe2O3 fulfills the requirements of both high charge separation efficiency and improved water oxidation kinetics. A novel 1/32 Zr-Fe2O3 (I) NC photoanode exhibits O2 and H2 evolution up to 69 and 138 μmol during 5 h of overall pure water splitting. This novel in situ hydrothermal dilution approach is feasible for fabricating a transparent hematite photoanode with NC morphology for practical PEC water splitting.

The Zr-doped ZnFe2O4 (Zr-ZFO) nanocorals photoanode have been synthesized from Zr-doped FeOOH (Zr–FeOOH) nanocorals on fluorine-doped tin oxide (FTO) substrate followed by Al2O3/Co–Pi surface modification for effective PEC water splitting. The hydrothermal method was adopted for the synthesis of in situ Zr doping in FeOOH, while Zr-ZFO nanocorals was fashioned by subsequent additional procedures, such as Zn(NO3)2 precursor dropping, first quenching, etching and second quenching. The Al2O3 layer decreases the over-potential of the Zr-ZFO photoanode‖electrolyte interface as well as lowers the charge transfer resistance which aids to increase in the photocurrent density from 0.24 mA/cm2 to 0.36 mA/cm2 at 1.23 V vs. RHE under 1 sun illumination condition. The subsequent loading of cobalt phosphate (Co–Pi) as a co-catalyst leads to an improved photocurrent density of 0.49 mA/cm2 at 1.23 V vs. RHE. These synergistic effects of Zr doping and surface modification led to remarkable improvement in photocurrent density from 0.19 mA/cm2 (at 1.4 V vs. RHE) for conventional ZFO nanorods to 0.65 mA/cm2 for the Zr-ZFO/Al2O3/CoPi photoanode. A systematic investigation into the effect of Zr doping and Al2O3/Co–Pi overlayer reveals the reduction of two distinct recombination processes (bulk and surface) in ZFO photoanode.

An inorganic–organic CdSe(en)0.5/CdIn2S4/TiO2 complex heterostructure was successfully synthesized using a facile solvothermal method. The morphology of a CdSe(en)0.5/CdIn2S4/TiO2 heterostructure was controlled by varying the concentrations of cadmium nitrate and selenium precursors in ethylenediamine. Intentionally controlling the morphology enhances the absorption within the visible region compared to a ZnIn2S4/TiO2 photoanode. The photoelectrochemical (PEC) study shows that the CdSe(en)0.5/CdIn2S4/TiO2 photoanode complex heterostructure exhibits a photocurrent density of 2.43 mA cm−2 at 0 V versus Ag/AgCl, which is 180% higher than that of a ZnIn2S4/TiO2 photoanode. The extra-delayed lifetime and photostability of CdSe(en)0.5/CdIn2S4/TiO2 complex heterojunction is cause of efficient hole scavenging. During the PEC measurement, the Se and ethylenediamine leaches out into the electrolyte while S2− from the Na2S + Na2SO3 electrolyte reacts with surface of the CdSe(en)0.5/CdIn2S4/TiO2 complex heterojunction. Such structure can effectively separate the charge carrier and yields 100 µmol of hydrogen within 3 h. The possible charge transfer mechanism during solar hydrogen generation in an inorganic–organic CdSe(en)0.5/CdIn2S4/TiO2 complex heterojunction structure has also been proposed.

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

Transparent TiO 2 thin films have been sucessfully synthesized by chemical spray pyrolysis technique. The effect of substrate temperature on the photoelectrochemical (PEC), structural, morphological, optical and photoelectrocatalytic properties has been investigated. The PEC study shows that both short circuit current ( I sc ) and open circuit voltage ( V oc ) at the optimized substrate temperature (450 °C) are relatively maximum ( I sc =1.7 mA and V oc =770 mV). The tetragonal crystal structure has been confirmed from X-ray diffraction patterns. FE-SEM study reveals that the film surface is changed from nanogranular to nanorod like morphology. The films exhibit a transmittance of about 80% in the visible region and a sharp absorption edge at 375 nm corresponding to the fundamental absorption edge in UV region. Band gap energy varies from 3.33 to 3.43 eV with substrate temperature. Electron-phonon coupling present in TiO 2 films has been analyzed using Raman spectroscopy. The elemental composition and valence states of TiO 2 film are studied by using X-ray photoelectron spectroscopy. The effect on the photoelectrocatalytic behavior of the large surface area (64 cm 2 ) TiO 2 photocatalyst samples were studied by using photoelectrocatalytic degradation of benzoic acid under UV light illumination.

ZnFe 2 O 4 thin films are successfully deposited onto bare and fluorine doped tin oxide (FTO) coated quartz substrate using the spray pyrolysis method. The structure and morphology of ZnFe 2 O 4 photoelectrodes were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). The X-ray diffraction pattern confirms the polycrystalline nature of films with a spinel cubic crystal structure. The AFM micrographs shows the granular nature of the films. The dielectric constant and dielectric loss shows dispersion behavior as a function of frequency measured in the range from 20 Hz to 1 MHz. Photoelectrocatalysis degradation of salicylic acid using ZnFe 2 O 4 photoelectrode under sunlight illumination has been investigated. The result shows that the degradation percentage of salicylic acid on ZnFe 2 O 4 photoelectrodes is reached 49% under neutral conditions after 320 min illumination. The decrease in values of COD from 19.4 mg/L to 6.4 mg/L indicates there is mineralization of salicylic acid with time.

The Fe 2 O 3 , Au:Fe 2 O 3 , TiO 2 /Fe 2 O 3 and TiO 2 /Au:Fe 2 O 3 thin films are successfully prepared by the spray pyrolysis technique at an optimised substrate temperature of 400 °C and 470 °C, respectively onto amorphous and F:SnO 2 coated glass substrates. The effect of TiO 2 layer onto photoelectrochemical (PEC), structural, optical and morphological properties of Fe 2 O 3 , Au:Fe 2 O 3 , TiO 2 /Fe 2 O 3 and TiO 2 /Au:Fe 2 O 3 thin films is studied. The PEC characterization shows that, maximum values of short circuit current ( I sc ) and open circuit voltage ( V oc ) are ( I sc = 185 μA and V oc = 450 mV) are at 38 nm thickness of TiO 2 . Deposited films are polycrystalline with a rhombohedral and anatase crystal structure having (1 0 4) preferred orientation. SEM and AFM images show deposited thin films are compact and uniform with seed like grains. The photocatalytic activities of the large surface area (64 cm 2 ) TiO 2 /Au:Fe 2 O 3 thin film photocatalysts were evaluated by photoelectrocatalytic degradation of industrial wastewater under sunlight light irradiation. The results show that the TiO 2 /Au:Fe 2 O 3 thin film photocatalyst exhibited about 87% and 94% degradation of pollutant in sugarcane and textile industrial wastewater, respectively. The significant reduction in COD and BOD values from 95 mg/L to 13 mg/L and 75 mg/L to 11 mg/L, respectively was also observed.

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.

The Fe 2 O 3 thin films have been deposited using ferric trichloride precursor at an optimized substrate temperature and concentration by simple chemical spray pyrolysis technique. Effect of quantity of the spraying solution on physicochemical properties of Fe 2 O 3 thin films has been studied. Photoelectrochemical technique was used to optimize the quantity of a spraying solution. The PEC study shows that, Fe 2 O 3 films are photoactive with relatively higher values of I sc =34.2 μA and V oc =190 mV respectively at 50 ml quantity (thickness ~239 nm). Effects of thickness on crystalline structure, morphology and optical properties have been studied. X-ray diffraction study confirms that the films are polycrystalline with rhombohedral crystal structure. The SEM and AFM micrographs depicts that the films are compact and needle shaped grains with grain size ~160–250 nm. The direct band gap energy of Fe 2 O 3 thin films is found to be in the range of 2.16–2.47 eV. Four characteristic luminescence peaks having near band-edge, violet, blue and green emission are observed in the photoluminescence spectra. Photocatalytic degradation of benzoic acid by using Fe 2 O 3 photoelectrode under visible light illumination has been investigated. The amount of mineralization is confirmed by COD and TOC analysis.

Ni x Zn 1− x Fe 2 O 4 ferrite has been synthesized by the ceramic method using Ni CO 3 , ZnO, Fe 2 O 3 precursors. The influence of Ni content on the structural, morphological, electrical and magnetic properties of Ni x Zn 1− x Fe 2 O 4 ferrites is studied. The X-ray diffraction (XRD) analysis reveals that the samples are polycrystalline with spinel cubic structure. The SEM images of Ni x Zn 1− x Fe 2 O 4 ferrite show that the grain size decreases with an increase in the Ni content. The tetrahedral and octahedral vibrations in the samples are studied by IR spectra. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell–Wagner type of interfacial polarization. Conduction mechanism due to polarons has been analyzed by measuring the AC conductivity. Impedance spectroscopy is used to study the electrical behavior. Magnetic properties of Ni x Zn 1− x Fe 2 O 4 are studied by using hysteresis loop measurement. The maximum value of saturation magnetization of 132.8 emu/g obtained for the composition, x =0.8, is attributed to magnetic moment of Fe 3+ ions.

The photoelectrocatalytic degradation of selected aromatic phenols and acids, amongst them substances of environmental concern like bisphenol-A (BPA), ethyl-paraben and phthalic acid, was studied on thin layers of semiconducting titanium dioxide deposited on transparent, electrically conducting substrates. A module of nine backside solar illuminated flow-through parallel plate photoelectrochemical reactors was used and electrical bias for suppressing charge carrier recombination was applied. The progress of oxidative degradation on the illuminated semiconductor electrode was followed by UV/vis absorption and COD (chemical oxygen demand) analysis. From the latter, kinetic data were calculated and compared on the basis of apparent first-order rate constants, related to current efficiencies which reflect the competition between solute and solvent (water) oxidation. The efficiencies (COD based) for 4-chlorophenol, salicylic acid, benzoic acid, phthalic acid, ethyl-paraben, BPA, p-cresol and 4-methoxyphenol as well as model compounds for aliphatic transient species in the course of the degradations – acetate, oxalic acid and maleic acid, lie between 10 and 70 M−1, a rather narrow range illustrating the rather unspecific oxidation on TiO2, which can be ascribed to the high redox potential of light generated oxidizing species. In many cases, these values are close to values obtained from the decrease of UV absorption of bands characteristic for the aromatic system. Long time irradiation experiments using solar light yielded conversion efficiencies of up to 90 percent in batch recirculation mode.

Thin films of iron oxide are synthesized by spray pyrolysis technique using ferric chloride as precursor in non-aqueous medium. The effect of solution concentration onto photochemical, structural, morphological, optical, luminescence and thermal properties has been investigated. Structural analysis confirms the rhombohedral crystal structure with strong (1 1 0) orientation. Raman spectrum reveals that the deposited films contain α-phase of Fe 2 O 3 (hematite). The SEM images of optimized Fe 2 O 3 thin films show microneedle like structure with varying grain size from 75 to 120 nm. The observed direct band gap is about 2.0 eV for Fe 2 O 3 thin film. Room temperature photoluminescencespectra showed three pronounced emission peaks for all concentrations. The photocatalytic oxidation of Rhodamine B with hematite Fe 2 O 3 thin films under solar illumination is investigated. The first order rate constants for this heterogeneousphotocatalysis are evaluated as a function of the initial concentration of Rhodamine B (RhB). The extent of mineralization of degraded sample is confirmed by total organic carbon (TOC) andchemical oxygen demand (COD)analysis. This work suggests that prepared iron oxide photoelectrodes demonstrate an excellent ability to remove toxic dyes from industrial wastewater.