Photolysis or photosplitting of w ater

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    31-May-2015

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1. Photolysis of WaterPrepared By : Yaseen Aziz Roll No : 23609Dept. Of Chemistry, Kashmir University 2. Water splitting-a general introduction : Water splitting is the general term for a chemical reaction in which water is separated intooxygen and hydrogen. This can be achieved through following ways:a) Electrolysisb) Thermal decomposition of waterc) Photobiological water splittingd) Photoelectrochemical water splittinge) Photocatalytic water splitting 3. Need for photosplitting of water: Hydrogen economy Hydrogen-a clean, pure fuel with very high calorific value (150 kJ/mol). We are at the peak of the oil age but the beginning of the hydrogen age.Anything else is an interim solution. The transition will be very messy, and willtake many technological paths .....but the future will be hydrogen fuel cells.- Herman Kuipers 4. Redox stability field of water: 5. Basic principle of overall water splitting on a Processes involved in photocatalytic overallsemiconductor particle. water splitting on a semiconductor particle. 6. Basic principle of photocatalytic reactions in the presence of sacrificial reagents. 7. The band gap in Metal oxide plays a crucial role in using them as photocatalysts. This can beillustrated by the following diagram: 8. Photoelectrochemical splitting of water: Water is broken down into H2 and O2 by electrolysis, but the electrical energy is obtainedby a photoelectrochemical cell (PEC) process, based on semiconductors. This is also named as artificial photosynthesis. The photoelectrochemical (PEC) path to water splitting involves separating the oxidationand reduction processes into half-cell reactions. Three methods are possible: PV approach i.e. using photovoltaic cells SCLJ approach i.e. semiconductor-liquid junctions Combination of the two (PV/SCLJ approach) 9. Schematic representation of a PV approach 10. Schematic representation of a SCLJ approach 11. Schematic representation of a PV/SCLJ approach 12. Photobiological water splitting: Produces H2 called as biological hydrogen, in algae bioreactors. Discovered in 1990s When algae are deprived of sulphur they produce H2 instead of O2 i.e. normalphotosynthesis is inhibited. Efficiency is 7-10 %, producing 10-12 ml H2 per culture litre per hour. 13. Conclusion: Hydrogen as fuel is a promising substitute to the non-renewable sources of energy. It is clean, pure and eco-friendly fuel. It can be obtained in large amounts provided a viable procedure of water splitting ismade available and the problem of H2 storage is overcomed. Photosplitting of water is a pure, clean, less energy consuming and easily availablesource of H2 production. The research field is wide open and challenging. 14. THANKS A LOT forListening Patiently!