Mahadeo A. Mahadik

Photoelectrocatalytic degradation of oxalic acid using WO3 and stratified WO3/TiO2 photocatalysts under sunlight illumination.

The WO3 and stratified WO3/TiO2 thin films are successfully prepared by the spray pyrolysis method. The structural, morphological, compositional and photoelectrocatalytic properties of WO3 and stratified WO3/TiO2 thin films are studied. XRD analysis confirms that films are polycrystalline with monoclinic and tetragonal crystal structures for WO3 and TiO2 respectively. The SEM images clearly show 3D sheeted porous structure of the as-prepared TiO2 forms on WO3 in stratified WO3/TiO2 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 WO3/TiO2 than WO3 thin film photoelectrode in the degradation of oxalic acid and 83% removal efficiency of oxalic acid is obtained after 180min. Based on the obtained experimental data, the possible photoelectrocatalytic reaction mechanism was proposed. The photoelectrocatalytic experimental results indicate that stratified WO3/TiO2 photoelectrode is the promising material for removing of water pollutants.

Fabrication of a ternary CdS/ZnIn2S4/TiO2 heterojunction for enhancing photoelectrochemical performance: effect of cascading electron–hole transfer

A novel, three-dimensional, ternary CdS/ZnIn2S4/TiO2 heterojunction has been fabricated via a three-step facile hydrothermal method. In this structure, one-dimensional TiO2 nanorods were directly grown on conductive fluorine-doped tin oxide (FTO) substrates. Next, to form a ternary heterojunction of CdS/ZnIn2S4/TiO2, ZnIn2S4 nanosheets were designed on the TiO2 nanorods and sensitized by CdS nanograins. A systematic photoelectrochemical study shows that the photocurrent density of the ternary heterojunction architecture is as high as 1.4 mA cm−2 at a potential of 0.1 V versus Ag/AgCl (under optimized conditions). A more detailed study shows that the photocurrent density is more than two times higher than that of a single CdS/TiO2 heterojunction (0.615 mA cm−2) and three times higher than that of ZnIn2S4/TiO2 (at 0.1 V vs. Ag/AgCl). This excellent photoelectrochemical performance is ascribed to the way that the band structure of TiO2 nanorods synergistically cascades with ZnIn2S4 and CdS, which allows for the absorption of a wider portion of the solar spectrum and improves the effective separation of the generated electron–hole pairs. Electrochemical impedance spectroscopy (EIS) studies also reveal the significant changes in both the interface resistance and the charge transfer resistance of the CdS/ZnIn2S4/TiO2 heterostructure. This can be attributed to the efficient hierarchical cascading that occurs during the electron–hole transfer from the excited CdS to TiO2 through the enlarged interface of ZnIn2S4 upon visible light illumination.

CdS/Zr:Fe2O3 Nanorod Arrays with Al2O3 Passivation Layer for Photoelectrochemical Solar Hydrogen Generation

CdS-sensitized 1 D Zr:Fe2 O3 nanorod arrays were synthesized on fluorine-doped tin oxide substrates by a two-step hydrothermal method. The photoelectrochemical results demonstrate that the current density (4.2 mA cm-2 at 0 V vs. Ag/AgCl) recorded under illumination for the CdS/1 D Zr:Fe2 O3 photoanodes is 2.8 time higher than the bare 1 D Zr:Fe2 O3 . The extended absorbance spectrum, the reduced recombination, and the effective transport of photogenerated holes in CdS to the electrolyte facilitate enhancement in the photoelectrochemical performance. From X-ray photoelectron spectroscopy and TEM observations of the bare and aluminum oxide-treated CdS/1 D Zr:Fe2 O3 photoanodes, we could confirm that the 1 D Zr:Fe2 O3 nanorods were covered by the CdS layer and Al2 O3 layer present on surface of CdS. Furthermore, the photocurrent and stability of the CdS/1 D Zr:Fe2 O3 nanorods was significantly enhanced by Al2 O3 compared to bare CdS/1 D Zr:Fe2 O3 heterojunction owing to its ability to act as an effective holetransport- as well as photocorrosion-protecting layer. These remarkable enhancements in light-energy harvesting, improvement in charge transport, and stability directly suggest the usefulness of photoanodes for solar hydrogen generation.

Boosting Photocatalytic Performance of Inactive Rutile TiO2 Nanorods under Solar Light Irradiation: Synergistic Effect of Acid Treatment and Metal Oxide Co-catalysts

In the present work, we accomplish the boosting of photocatalytic performance by the synergistic effect of acid treatment and transition metal oxide co-catalysts on molten salt rutile TiO2 nanorods. FT-IR and XPS (oxygen deconvolution) results confirmed that the amount of hydroxyl groups increased on the surface of rutile TiO2 nanorods (TO-NRs) after acid treatment. HR-TEM analysis revealed fine dispersion of metal oxide on the surface of acid treated TiO2 nanorods (ATO-NRs). The photocatalytic activities of as-prepared (TO-NRs), acid treated (ATO-NRs), metal oxide loaded (MTO-NRs), and both acid treated and metal oxide loaded (MATO-NRs) nanorods were compared based on the rate kinetics and dye degradation efficiencies. Cobalt oxide (1 wt %) loaded and 1.0 M acid treated TiO2 nanorods (Co/ATO-NR) exhibited the higher photocatalytic degradation efficiency for Orange-II dye degradation and inactivation of S. typhimurium pathogen compared to other photocatalysts under solar irradiation. Photoelectrochemical analysis demonstrated that the charge transfer process in Co/ATO-NR is significantly higher than that in the untreated samples. The improved photocatalytic activity of inactive TO-NRs might be due to enhanced charge transfer of finely dispersed metal oxides on the OH-rich surface of acid treated TiO2 nanorods.

Data on the effect of improved TiO2/FTO interface and Ni(OH)2 cocatalyst on the photoelectrochemical performances and stability of CdS cased ZnIn2S4/TiO2 heterojunction

This data article presents the experimental evidences of the effect of TiO2-fluorine doped tin oxide interface annealing and Ni(OH)2 cocatalysts on the photoelectrochemical, structural, morphological and optical properties of Ni(OH)2/CdS/ZnIn2S4/TiO2 heterojunction. The Raman spectroscopy exhibits the sharp features of the rutile phase of TiO2 and in agreement with the X-ray diffraction data. The band gap energy of the 500 °C sample was found to be 3.12 eV, further it was increased to 3.20, 3.22 eV for samples annealed at 600 and 700 °C respectively. The decrease in the band gap energy at 500 °C related to the oxygen vacancies and was analysed by photoluminescence spectroscopy analysis. The synthesis, characterization methods and other experimental details of TiO2 based heterostructure are also provided. The presence of CdS and ZnIn2S4 coating on surface of TiO2 electrodes providing a high surface area, extended visible absorption and helps to improve the change separation. This data article contains data related to the research article entitled “Highly efficient and stable 3D Ni(OH)2/CdS/ZnIn2S4/TiO2 heterojunction under solar light: Effect of an improved TiO2/FTO interface and cocatalyst” (Mahadik et al., 2017) [1].