First Symposium in Allpied Chemistry, At Palestine Polytechnic University, Hebron

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Research Title: 
Solar Energy Processes with Nano-Materials: Enhancing Stability & Efficiency in PEC Processes
Hikmat S. Hilal, Ahed H. Zyoud
Palestine Polytechnic University, Hebron
Tue, 2013-12-24
Research Abstract: 

Under a prolonged history of occupation, Palestine has limited chances to build a sustainable economy. With severely limited natural resources and industrial infra-structure Palestine has only one way out to build its economy, simply establishing a knowledge-based industry. High-technologies, which demand no heavy industry or natural resources, should be adopted in Palestine. Starting with areas of high priority to Palestinian society, which lacks energy resources, healthy environment and water supplies, scientists should take initiatives to lay foundations for advanced material-based future technology targeting such priorities. Once achieved, such foundations could help establish commercial-scale production of advanced materials, such as advanced materials, electro-chromic devices, super-capacitors, super-batteries, and others. Based on this approach, a new generation of scientists has been created in the last 15 years whose research aspirations are focused on advanced materials and application in solar energy, environmental clean-up, water and health. One active area of research heavily involves modification of mono- and poly-crystalline semiconductor film electrodes for solar energy utilization. This presentation will give an account of what has been achieved by our research group, at An-Najah National University. A low-cost strategy to improve stability and conversion efficiency of semiconductor electrodes (monolithic n-GaAs and polycrystalline, CdS, CdSe and other films) is described. When coated with the electro-active species Tetra(-4-pyridyl)porphyrinatomanganeseIII/II sulfate embedded inside polysiloxane films (MnPyP/Polysil) the semiconductor electrodes showed remarkable stability and conversion efficiency enhancement under the photo-electrochemical (PEC) conditions. Additional heating of the coated semiconducting electrode at 120oC also enhanced its PEC characteristics. In monolithic electrodes, up to 8 fold enhancement in conversion efficiency was observed by coating. The techniques also showed remarkable enhancement in PEC characteristics of thin-film based electrodes. While the naked CBD prepared CdSe electrodes failed to show significant PEC activity and peeled out, the coated electrode showed significant efficiency and sound stability. The mode of action of the MnPyP/Polysil coating has been attributed to its ability to behave as a charge transfer catalyst at the solid/liquid interface. The positively charged metalloporphyrin complex ions, embedded inside the polymer matrix, resided in close proximity to the semiconductor surface. The metalloprphyrin ions caused shifting in flat band potentials within the semiconductor electrodes. Moreover, they behaved as mediators in transferring holes from the valence band of the semiconductor to the redox couple system in solution. Physical protection of the semiconductor surface, by preventing oxidation with oxygen and water, is another added value for using the MnPyP/Polysil matrix here. The new technique described here has been potentially valuable in stabilizing other types of semiconductor electrode materials.