Photoelectrochemical Water Splitting: set up of an experimental device

The aim of our research is to produce hydrogen from water using sunlight as the energy source, with efficiencies high enough to allow commercial production of hydrogen on a large scale. Much research has been undertaken in the last three decades to engineer a suitable semiconducting photocatalyst materials for water splitting in an electrochemical cell. A good photocatalyst material must have; an energy band gap, which is optimum for water splitting (approximately 2 eV with conduction and valence band edges optimally placed with respect to the water redox potentials), strong optical absorption in the visible and ultraviolet spectral regions, good stability in strong electrolytes and efficient charge transfer properties between the semiconductor and the electrolyte. Titanium dioxide is used as a photocatalyst in this research; it is non-toxic, stable and inexpensive. Preliminary tests show hydrogen production. To determine the charge transfer resistance (Rct) of the reaction on electrode-solution interface, impedance spectroscopy measures in absence and in presence of light were carried out. The Rct decreases from 7310 to 1840 ohms when the light is turned on. In these preliminary experiments very low yield was obtained, but the use of additives with TiO2, inorganic (e.g. Fe2O3) or organic (anthocyanins) compounds will supply the desired improvements.