Iyad Saadeddin

CdS-sensitized TiO2 in phenazopyridine photo-degradation: Catalyst efficiency, stability and feasibility assessment

Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO(2), TiO(2)/CdS, 2, as photo-catalysts. Despite that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd(2+) ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO(2)/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd(2+). This indicates limited future applicability of CdS-sensitized TiO(2) photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.

Electrochromic devices based on in situ polymerised EDOT and Prussian Blue: influence of transparent conducting oxide and electrolyte composition—towards up-scaling

Inorganic/organic (hybrid) complementary electrochromic devices (ECDs) of the type [transparent conducting oxide (TCO)//inorganic counter electrode/hydrophobic electrolytic membrane/polymeric working electrode//TCO] were assembled. The working electrodes consisted of spin-coated polymer films prepared by moderator-controlled in situ oxidative chemical polymerisation of 3,4-ethylene dioxythiophene (EDOT). Thin, galvanostatically deposited Prussian Blue (PB) films were employed as counter electrodes. Besides F : SnO2 (FTO)/glass and Sn : In2O3 (ITO)/glass, a flexible ITO/PET film was alternatively used for materials deposition. In order to attain the maximum device performance, the PB charge capacity was monitored and adapted to the capacity of the EDOT polymer films. The two electrochromic electrodes were separated by a novel hydrophobic polymer electrolyte based on a gel of 1-butyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide (BMI-TFSI) and poly(methylmethacrylate) (PMMA), with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the salt. The influence of two parameters—ITO sheet resistance and the PMMA content in the electrolyte—on the final device properties was investigated. The ITO sheet resistance value proved to be crucial for the switching kinetics. The variation of the weight ratio of PMMA in the electrolyte showed that the effect on the kinetics is small whereas the change in absorbance is highly affected. The properties of the complementary glass-based devices were eventually compared to the corresponding plastic-based electrochromic elements. First attempts to scale up the technology were made for flexible 12 × 15 cm2 (active area) devices.

EFFECT OF ANNEALING AND OF COOLING RATES ON n-GaAs ELECTRODE PHOTOELECTROCHEMICAL CHARACTERISTICS

The effect of annealing of the n-GaAs semiconductor on its characteristics in photoelectrochemical (PEC) systems has been investigated. The photocurrent densities vs. potential plots were improved by annealing. Cell efficiency and short-circuit current densities were enhanced for the annealed n-GaAs. The effect of the rate of cooling of heated n-GaAs wafers was also investigated. It was found that the slowly cooled electrodes gave better dark current density vs. potential plots, for samples annealed below 600 � C. For samples annealed at higher temperatures, quenching gave better dark-current density vs. potential plots. For n-GaAs, slowly cooled electrodes from temperatures below 600 � C showed better photocurrent density vs. potential plots and higher efficiency. n-GaAs samples, quenched from temperatures above 700 � C, showed better photocurrent density vs. potential plots and higher efficiency than their slowly cooled counterparts.