Photocatalytic hydrogen production

• Main Author: Almazroai, Layla S.
• Published: Cardiff University 2009
• Subjects: 541.39
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.584637

Due to the environmental problems arising from the combustion of fossil fuels and their depletion, the production and use of renewable fuels have grown rapidly in recent years. Hydrogen is among the promising fuels of the future as the only material that can be produced from the burning of hydrogen in air is water. The production of hydrogen by the photocatalytic water splitting method involving a semiconductor is a promising development in the field of energy and the environment, and this technique was employed in this work. TiO₂ and palladium were the main photoactive support and loaded metal used in this project, respectively. The hydrogen production, whether from water/methanol solution or water alone, was investigated by illumination of the catalyst by UV irradiation produced from an Xe arc lamp. The reactions were performed in liquid or gas phase under an argon atmosphere as an inert gas. The gaseous products were collected and analysed using gas chromatography. The main method used in Pd loading was the impregnation method. 0.5% and 0.1% wt Pd loading were the best in terms of hydrogen production rate in liquid and gas phase reactions respectively. 0.5% Pd/TiO₂ (P25) was used in the remaining experiments to investigate some of the variables, to maximize the rate of H₂ production. Glycerol displayed an activity and produced hydrogen and carbon dioxide, as in the case of methanol but in much higher quantities. Loading of mesoporous TiO₂ by a different weight of Pd, which had a high surface area, gave less hydrogen than Pd/P25 whether in liquid or gas phase reactions. The efficiency of Pd loaded titania (P25, pure anatase or anatase prepared by CHFS) doped by non-metals such as nitrogen, silver or strontium was low and less than Pd/TiO₂. Hydrogen produced over Pd/TiO₂, Au/TiO₂ and TiO₂ from water photolysis was also very low. The recombination between hydrogen and oxygen (back reaction) was studied over these catalysts and it was found that it was fastest on Pd/TiO₂ whether in the dark or in the presence of light. For Au/TiO₂, the light enhanced the hydrogen and oxygen reaction.