Researchesr at Penn State university are using highly ordered arrays of titanium nanotubes to increase the efficiency of photolysis- the breaking down of water to hydrogen and oxygen by sunlight.
“Basically we are talking about taking sunlight and putting water on top of this material, and the sunlight turns the water into hydrogen and oxygen. With the highly-ordered titanium nanotube arrays, under UV illumination you have a photoconversion efficiency of 13.1%. Which means, in a nutshell, you get a lot of hydrogen out of the system per photon you put in. If we could successfully shift its bandgap into the visible spectrum we would have a commercially practical means of generating hydrogen by solar energy. It beats fighting wars over middle-eastern oil.”
via Warren Ellis