Photocatalytic water splitting separates water into hydrogen and oxygen: 
The most prevalently investigated material,  , is inefficient.  Mixtures of  and nickel oxide (NiO) are more active. NiO allows a significant explоitation of the visible spectrum. One efficient photocatalyst in the UV range is based on sodium tantalite (NaTaO) doped with lanthanum and loaded with a nickel oxide cocatalyst. The surface is grooved with nanosteps from doping with lanthanum (3–15 nm range, see nanotechnology). The NiO particles are present on the edges, with the oxygen evolving from the grooves.