Fabrication of CaFe2O4/TaON heterojunction photoanode for photoelectrochemical water oxidation.

Tantalum oxynitride photoanode is fabricated and modified with calcium ferrite to form a heterojunction anode for a photoelectrochemical water splitting cell. The synthesized powders are loaded sequentially to the transparent conducting glass by electrophoretic deposition, which is advantageous to form a uniform layer and a junction structure. X-ray diffraction, UV-vis diffuse reflectance spectroscopy, scanning electron microscopy, and impedance spectroscopy analysis are conducted to investigate the structural, morphological, and electrochemical characteristics of the anode. The introduction of CaFe2O4 overlayer onto TaON electrode increases the photocurrent density about five times at 1.23 V vs reversible hydrogen electrode without any co-catalyst. Impedance spectroscopy analysis indicates that the junction formation increased photocurrent density by reducing the resistance to the transport of charge carriers and thereby enhancing the electron-hole separation. This photocurrent generation is a result of the overall water splitting as confirmed by evolution of hydrogen and oxygen in a stoichiometric ratio. From the study of different junction configurations, it is established that the intimate contact between TaON and CaFe2O4 is critical for enhanced performance of the heterojunction anode for photoelectrochemical water oxidation under simulated sun light.

Morphology controlled fabrication and ferroelectric properties of vertically aligned one-dimensional lead titanate nanoarrays.

Vertically aligned nanowires and highly uniform nanoporous array thin films of PbTiO(3) are synthesized by varying anodic oxidation conditions of Ti foil followed by hydrothermal reaction in an aqueous Pb(II) acetate trihydrate solution. As-synthesized samples have single crystalline nanowire structure and polycrystalline nanoporous structure, although both are pure PbTiO(3) with a tetragonal phase. The structure of intermediate TiO(2) films obtained from different anodic oxidation conditions determines the structure of the product PbTiO(3). The relationships between these morphological structures and ferroelectric properties are investigated. Piezoresponse force microscopy reveals that both these films show ferroelectricity with clear phase contrast and well-defined hysteresis loops. The saturated longitudinal piezoelectric coefficient field (E(c)) of the nanowire sample is smaller than that of nanoporous thin film. Thus, polarization of nanowire thin film is larger in magnitude and easier to flip than that of nanoporous film.

The fabrication of highly uniform ZnO/CdS core/shell structures using a spin-coating-based successive ion layer adsorption and reaction method.

We developed a successive ion layer adsorption and reaction method based on spin-coating (spin-SILAR) and applied the method to the fabrication of highly uniform ZnO/CdS core/shell nanowire arrays. Because the adsorption, reaction, and rinsing steps occur simultaneously during spin-coating, the spin-SILAR method does not require rinsing steps between the alternating ion adsorption steps, making the growth process simpler and faster than conventional SILAR methods based on dip-coating (dip-SILAR). The ZnO/CdS core/shell nanowire arrays prepared by spin-SILAR had a denser and more uniform structure than those prepared by dip-SILAR, resulting in the higher power efficiency for use in photoelectrochemical cells.