by Dr. Xiaoxiang Xu
Solar energy is inexhaustible in nature and environmental benign. The almost homogeneous distribution of solar incidence worldwide on a daily basis ensures easy accessibility of solar source and wide applicability of solar techniques. Water splitting as well as CO2 reduction into fuels by solar energy is highly promising technology as all the products are now completely renewable and can be readily stored and transported. Unlike photovoltaic which includes expensive fabrication processes, photocatalysis is a very much “cheaper” means of utilising solar energy. It is normally performed in an aqueous solution with a photocatalyst, typically semicondutors in powder form and at ambient conditions. Hydrogen, oxygen, methane and carbon monoxide etc. can be produced gradually with an overall quantum efficiency as high as 56%.