Hydrogen Production through Sono-Photolysis of Water in the presence of Solid Solutions of Metal Oxides as Photocatalysts

Hydrogen is a promising energy carrier for the next future and, in order to favour a worldwide sustainable economy, it is necessary to produce it from an abundant material, such as water, and through a renewable energy source. Therefore, a compelling strategy entails splitting water by exploiting solar energy. Water does not absorb the frequencies of solar spectrum that have enough energy to fragment it, therefore the use of a photocatalyst is required. Since most of the solar radiation consists of visible wavelengths, coloured photocatalysts should be synthesized through a suitable band gap engineering. A way for reducing the waste of the longest wavelengths of solar radiation entails pursuing the upconversion phenomenon. To increase the production of hydrogen from water splitting, it is useful to combine the action of light and heterogeneous photocatalyst with that of ultrasounds. In fact, the hybrid action of light and ultrasounds favours a remarkable synergistic effect.