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The effects of electrolytes on the electrochemical performance of nickel cobaltite-titania nanotubes composites as electrochemical capacitors were evaluated. Four types of electrolytes were selected to assess their effects on the prepared composites, namely aqueous electrolytes of 1.0 M KCl, 1.0 M HCl, 1.0 M KOH; and an organic electrolyte, 0.27 M tetra-n-butylammonium tetrafluoroborate (TBATFB) ionic liquid salt in acetonitrile. The composites performed better in 1.0 M HCl and 1.0 M KOH, than in 1.0 M KCl and 0.27 M TBATFB, which suggested that aqueous electrolytes with non-neutral pH would improve the specific areal capacitance values of the composites. Results have shown optimal performance in 1.0 KOH, which endowed the composite with excellent rate capability up to 200 mV s−1. Cyclic voltammogram of the composite analysed in 1.0 M KOH produced a leaf-shaped like profile, with higher current densities towards more positive potentials. Charge-discharge analyses in 1.0 M KOH has shown that the composite possessed specific areal capacitance of up to 214.76 µF cm−2 when it was evaluated at the current density of 350 µA cm−2. The composite also retained up to 97.79% of its specific areal capacitance when current density was increased to 400 µA cm−2. This material has demonstrated potential application for electrochemical capacitors through its facile fabrication technique. [ABSTRACT FROM AUTHOR]

The self-organized titania nanotube arrays (NTAs) fabricated by anodisation has gained enormous interest due to its high spatial orientation, excellent charge transfer structure, and large internal surface area; all are crucial properties influencing the absorption and propagation of light. In this study, a composite material, CdSe nanoparticle/TiO nanotube arrays (CdSe/TiO NTAs) were assembled through the insertion of CdSe nanoparticles onto the anodized TiO nanotube arrays via electrochemical deposition. The annealing temperature of CdSe/TiO NTAs was varied from 200 to 350 °C and was found to play an important role in controlling the formation of CdSe nanoparticles on TiO NTAs. Characterizations of the films were performed by using field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, high resolution transmission electron microscopes, X-ray diffractometry and UV-visible diffuse reflectance spectroscopy. The transient photocurrent was examined in a three-electrode system under halogen illumination by using the prepared film as the photoanode. It was found that the CdSe nanoparticles were susceptible to spread through electrochemical deposition and formed on the nanotubes by annealing in nitrogen atmosphere. The increment in annealing temperature has resulted in greater amount of CdSe loaded onto TiO nanotube arrays. Therefore, a suitable annealing temperature can enhance the particle interaction, leading to considerable improvement in PEC performance. The sensitized CdSe/TiO NTAs annealed at 250 °C displayed 84 folds improvement in photoconversion efficiency than that of bare TiO NTAs counterparts. [ABSTRACT FROM AUTHOR]

CdS/ZnO nanorods composite nanofilms were successfully synthesized via hydrothermal method on indium doped tin oxide glass substrates. Sequentially deposited CdS formed cauliflower like nanostructures on vertically aligned ZnO nanorods. The morphological, compositional, structural and optical properties of the films were characterized by field emission scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction and ultraviolet-visible spectroscopy. Photoelectrochemical conversion efficiencies were evaluated by photocurrent measurements in a mixture of NaS and NaSO akaline aqueous solution. The amount of deposit, as well as the diameter and crystallinity of the CdS cauliflower were found to increase with growth time. CdS/ZnO nanorods composite exhibited greater photocurrent response than ZnO nanorod arrays. Besides, the composite film with 90 min of growth duration displayed the highest photocurrent density which is nearly four times greater than plain ZnO nanorods under the illumination of halogen light. The result exhibited remarkable photoconversion efficiency ( η) of 1.92 %. [ABSTRACT FROM AUTHOR]

Particular interest has been given to the self-organized titania nanotube TiO thin films prepared by using anodisation method followed by annealing in the air, while the CdSe layer was potentiostatically electrodeposited onto the TiO nanotube films at various pH. The resulting films were studied by using energy dispersive X-ray spectroscopy, X-ray diffraction, field emission scanning electron microscopy, UV-Vis spectroscopy and photoelectrochemical analysis to characterize their compositional, crystalline structure, surface morphological, optical, and photoconversion efficiency characteristics. The resulting CdSe/TiO nanotube exhibits significant enhancement in optical absorption, photocurrent density and photoconversion efficiency. CdSe/TiO nanotube prepared at pH 3 exhibited the highest photocurrent density of 2.13 mA cm and photoconversion efficiency of 1.02 % which is 51 times higher than TiO nanotube array. This may due to the formation of CdSe nanocrystals which were well crystallized and bonded with TiO NTAs contributing to the enhanced photoresponse and photostability of the overall performance of CdSe/TiO NTAs heterostructures. [ABSTRACT FROM AUTHOR]