Titanate pyrochlores R2Ti2O7 (R = Y, rare earth) were synthesized by a polymerized complex (PC) technique and used as photocatalysts for the splitting of water into H-2 and O-2.NiOx-loaded Y2Ti2O7, the first example of an active photocatalyst with a pyrochlore structure, demonstrated efficient evolution of H-2 and O-2 in a stoichiometric ratio from pure water under UV-Iight irradiation, whereas R2Ti2O7 compounds with partly filled 4f orbitals showed quite low activity.