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The photoreactivity of TiO2 nanotube arrays (TiNT) is mainly related to the light absorption and photogenerated charge carriers separation efficiencies. Recently, engineering of the crystal facets has gained increasing attention because of its exceptional ability to extend the photoresponse toward visible light and to separate photogenerated charges. Here, TiNT with high crystallinity and percentage of exposed {001} facets was synthesized using a two-step anodization process in ethylene glycol based electrolyte containing 2 wt% of water and 0.27 M NH4F. Decreasing the potential of the second anodization (from 50 to 20 V) resulted in an increase in crystallinity, crystallite size, and percentage of exposed {001} facets. Because trap states limit the photoreactivity performance of TiNT by facilitating the recombination of photogenerated electron/hole pairs, correlation between crystallinity, preferential crystalline orientation, gap states characteristics (density and location), and photoreactivity performance was investigated. TiNT with a high percentage of {001} exposed facets, consisting mainly of shallow gap states with low density, significantly improve photoelectrochemical water oxidation and photocatalytic efficiencies.

Electrodeposition of NiFe films, on hydrogen-terminated n-Si (111)-H from acidic dilute sulphate solution, was studied by electrochemical measurements at room temperature in the presence and absence of saccharin. The electroplating process kinetics was investigated by voltammetric study and the effect of Fe 2+ concentration on the deposit composition was studied as well with energy dispersive spectrometry analysis. The average composition of the Ni 45 Fe 55 film was obtained for Fe 2+ concentration in the range of [0.030-0.035] mol L −1 at a current density of −6 mA cm −2 . Correlation between Fe 2+ concentration in the NiFe deposit and electronic properties was examined by electrochemical impedance spectroscopy. Film roughness depends on Fe 2+ concentration and a smoother deposit was obtained for the Ni 45 Fe 55 film. Very low coercivity (less than 1.3 Oe) was measured in the Ni 45 Fe 55 film with a nominal thickness of 640 nm. The very soft magnetic properties of the NiFe films provide information about the low level of inhomogeneities present in these films.