Abstract
Water splitting to produce hydrogen using abundantly available solar energy and water is a process of utmost importance and urgently required due to exponentially increasing global energy requirement, over-consumption and drying up of fossil fuels, as well as economic and environmental issues. Although first water splitting experiment with UV light was demonstrated on n-type TiO2 anode and Pt cathode in a photoelectrochemical cell on 1972 by Fujishima and Honda, there is no breakthrough results reported yet in terms of quantum efficiency more than 10% in visible light and sustainable activity without any sacrificial agent. Especially, catalysts that work with visible light and high efficiency are scarce, although many materials work efficiently in UV light. Nonetheless, there is some progress in this area in the last ten years, after the discovery of anion doping in semiconductor oxides. Especially, solid solution between an oxide and either nitride are emerging as promising materials. Present mini review is restricted to the above class of materials, which show electronic structural changes play a significant role in reducing the band gap to induce visible light absorption. Above solid solutions also demonstrate significant visible light driven photocatalytic activity and exhibiting high potential towards that.
